The Biology and Role of Interleukin-32 in Tuberculosis

Tuberculosis, caused by Mycobacterium tuberculosis, remains a leading cause of morbidity and mortality globally, with nearly 10.4 million new cases of incidence and over 1.7 million deaths annually. Drug-resistant M. tuberculosis strains, especially multidrug-resistant or extensively drug-resistant strains, have further intensified the problem associated with tuberculosis control. Host-directed therapy is a promising alternative for tuberculosis control. IL-32 is increasingly recognized as an important host molecule against tuberculosis. In this review, we highlight the proinflammatory properties of IL-32 and the mode of action of IL-32 in mycobacterial infections to inspire the development of novel immunity-based countermeasures and host-directed therapies against tuberculosis.

Related papers:

title: Multidrug-resistant and extensively drug-resistant Mycobacterium tuberculosis: epidemiology and control
abstract: The emergence of multidrug-resistant (MDR)-TB and, more recently, of extensively drug-resistant (XDR)-TB is a real threat to achieve TB control and elimination. Over 400,000 new cases of MDR-TB occur each year and, although their number is currently unknown, XDR cases are recognized in every setting where there has been the capacity to detect them. The long-term vision for the full control of MDR-TB requires the scaling-up of culture and drug-susceptibility testing capacity, which is very limited in disease-endemic countries, and the expanded use of high-technology assays for rapid determination of resistance. MDR cases are treatable and well designed regimens, largely based on second-line anti-TB drugs, can considerably improve cure rates. However, treatment regimens need to be markedly improved through the introduction of less toxic and more powerful drugs, thus reducing duration of treatment and tolerability. This is of utmost importance for XDR-TB cases. The prevalence of MDR-TB and XDR-TB are inversely correlated with the quality of TB control and the proper use of second-line anti-TB drugs. Adherence to proper standards of care and control is imperative and a top priority of all TB control efforts. However, the risk of an uncontrollable epidemic of MDR- and XDR-TB is real considering current levels of financing and commitment to care.

title: Identification of a novel gene expressed in activated natural killer cells and T cells.
abstract: We have isolated a cDNA clone from a human activated NK cell-derived cDNA library that identifies a transcript (NK4) that is selectively expressed in lymphocytes. The expression of this transcript is increased after activation of T cells by mitogens or activation of NK cells by IL-2 (lymphokine-activated killer cells). The transcript levels demonstrated by Northern blot analysis increase by 12 h after activation, remain high for at least 48 h, and require protein synthesis for expression. Southern blot analysis of B lymphoblastoid lines derived from 18 unrelated individuals reveal variable banding patterns suggestive of polymorphism within the NK4 gene. No homology was found between the sequence of the coding region of this transcript and any sequences in the GenBank data base. Sequence homology to the U1 small nuclear RNA was found within the 3' untranslated region immediately upstream of the site of polyadenylation, suggesting a possible role for U1 in the polyadenylation process. Sequence analysis indicates the transcript would encode a protein having a mass of 27 kDa. The presence of a signal sequence and lack of a transmembrane region suggests that the protein is secreted. In addition, the protein contains an RGD sequence that may be involved in cellular adhesion. This transcript appears to encode a novel product common to the activation pathways of both NK cells and T cells.

title: Interleukin-32: a cytokine and inducer of TNFalpha.
abstract: We describe the gene structure, regulation, signal transduction. and functions of a cytokine, interleukin (IL)-32. An IL-18 unresponsive cell was converted to a responsive cell by transfection of the IL-18 receptor beta chain, and IL-18-induced microarray revealed high expression of a cytokine-like gene. Although IL-32 does not share sequence homology with known cytokine families, IL-32 induces various cytokines, human TNFalpha, and IL-8 in THP-1 monocytic cells as well as mouse TNFalpha and MIP-2 in Raw macrophage cells. IL-32 activates typical cytokine signal pathways of nuclear factor-kappa B (NF-kappaB) and p38 mitogen-activated protein kinase. IL-32 mRNA is highly expressed in immune tissue rather than other tissues. Human IL-32 exists as four splice variants, and IL-32 from other species were found as expressed sequence tag clones in the databank. Induced in human peripheral lymphocyte cells after mitogen stimulation, in human epithelial cells by IFNgamma, and in NK cells after exposure to the combination of IL-12 plus IL-18, IL-32 may play a role in inflammatory/autoimmune diseases.

title: The newest interleukins: recent additions to the ever-growing cytokine family.
abstract: Cytokines play a critical role in the control of the innate and adaptive immune responses. The most recent additions to the ever-growing family of cytokines include interleukin (IL)-27, IL-28A, IL-28B, IL-29, IL-31, IL-32, and IL-33. Many of the newly identified cytokines and/or their specific receptors have been identified using bioinformatics. The coming of age of this discipline has coincided with completion of the sequencing of the human genome thus enabling the identification of new uncharacterized proteins. The latest additions to the interleukin family have shed new light on the intricacies of immune system regulation. These novel cytokines have pleiotrophic actions ranging from antiviral immunity to the regulation of Th2 immune responses. For example, the discovery of IL-27 has greatly improved our understanding of the factors regulating the polarization of the T helper cell responses and IL-31 appears to be an important regulator of Th2 responses. On the other hand, IL-28 and IL-29 are considered to be critical for mounting an efficient antiviral response and IL-32 and IL-33, which are yet to be fully characterized, are emerging as important components of the inflammatory response in allergy and autoimmunity. These new cytokine/receptor combinations may therefore serve as novel targets for the treatment and control of allergy, autoimmune diseases, and some cancers.

title: Molecular characterization of IL-32 in human endothelial cells.
abstract: IL-32 is a newly discovered protein found in human and certain primates, but absent in rodent. Various reports suggest its role as a proinflammatory mediator. Since vascular endothelium is critical in inflammation, we investigate IL-32 in endothelial cells. We found that the gene is expressed in human endothelial cells and Akt strongly induces its expression. Sequence analysis indicates IL-32 beta as the major isoform in endothelial cells. Surprisingly, we did not detect any secretion of IL-32 beta in human endothelial cells; instead we observed co-localization of IL-32 beta with endoplasmic reticulum, suggesting IL-32 beta is an intracellular protein in these cells. Promoter analysis identified a minimum required region for IL-32 transcription at -0.1 to +0.5 kb around the initially identified transcription start site. We also defined a transcriptional suppressor-binding site at -2.0 to -1.5 kb. Importantly, RNA ligase mediated rapid amplification of cDNA ends in endothelial cells determined the transcription start site at the 328 bp downstream from the original identified site. Finally, we found a positive correlation of IL-32 levels with human breast cancer and glioblastoma multiforme (GBM). These findings improve our understanding of IL-32 in vascular endothelium. IL-32 expression might be valuable as a biomarker for cancer.

title: A Human Dendritic Cell Subset Receptive to the Venezuelan Equine Encephalitis Virus-Derived Replicon Particle Constitutively Expresses IL-321
abstract: Dendritic cells (DCs) are a diverse population with the capacity to respond to a variety of pathogens. Because of their critical role in pathogenesis and Ag-specific adaptive immune responses, DCs are the focus of extensive study and incorporation into a variety of immunotherapeutic strategies. The diversity of DC subsets imposes a substantial challenge to the successful development of DC-based therapies, requiring identification of the involved subset(s) and the potential roles each contributes to the immunologic responses. The recently developed and promising Venezuelan equine encephalitis replicon particle (VRP) vector system has conserved tropism for a subset of myeloid DCs. This immunotherapeutic vector permits in situ targeting of DCs; however, it targets a restricted subset of DCs, which are heretofore uncharacterized. Using a novel technique, we isolated VRP-receptive and -nonreceptive populations from human monocyte-derived DCs. Comparative gene expression analysis revealed significant differential gene expression, supporting the existence of two distinct DC populations. Further analysis identified constitutive expression of the proinflammatory cytokine IL-32 as a distinguishing characteristic of VRP-receptive DCs. IL-32 transcript was exclusively expressed (>50 fold) in the VRP-receptive DC population relative to the background level of expression in the nonreceptive population. The presence of IL-32 transcript was accompanied by protein expression. These data are the first to identify a subset of immature monocyte-derived DCs constitutively expressing IL-32 and they provide insights into both DC biology and potential mechanisms employed by this potent vector system.

title: Interleukin-32 induces the differentiation of monocytes into macrophage-like cells
abstract: After emigration from the bone marrow to the peripheral blood, monocytes enter tissues and differentiate into macrophages, the prototype scavenger of the immune system. By ingesting and killing microorganisms and removing cellular debris, macrophages also process antigens as a first step in mounting a specific immune response. IL-32 is a cytokine inducing proinflammatory cytokines and chemokines via p38-MAPK and NF-κB. In the present study, we demonstrate that IL-32 induces differentiation of human blood monocytes as well as THP-1 leukemic cells into macrophage-like cells with functional phagocytic activity for live bacteria. Muramyl dipepide (MDP), the ligand for the intracellular nuclear oligomerization domain (NOD) 2 receptor, has no effect on differentiation alone but augments the monocyte-to-macrophage differentiation by IL-32. Unexpectedly, IL-32 reversed GM-CSF/IL-4-induced dendritic cell differentiation to macrophage-like cells. Whereas the induction of TNFα, IL-1β, and IL-6 by IL-32 is mediated by p38-MAPK, IL-32-induced monocyte-to-macrophage differentiation is mediated through nonapoptotic, caspase-3-dependent mechanisms. Thus, IL-32 not only contributes to host responses through the induction of proinflammatory cytokines but also directly affects specific immunity by differentiating monocytes into macrophage-like cells.

title: Interleukin-32 Promotes Osteoclast Differentiation but Not Osteoclast Activation
abstract: (IL-32) is a newly described cytokine produced after stimulation by IL-2 or IL-18 and IFN-γ. IL-32 has the typical properties of a pro-inflammatory mediator and although its role in rheumatoid arthritis has been recently reported its effect on the osteoclastogenesis process remains unclear.  In the present study, we have shown that IL-32 was a potent modulator of osteoclastogenesis in vitro, whereby it promoted the differentiation of osteoclast precursors into TRAcP+ VNR+ multinucleated cells expressing specific osteoclast markers (up-regulation of NFATc1, OSCAR, Cathepsin K), but it was incapable of inducing the maturation of these multinucleated cells into bone-resorbing cells. The lack of bone resorption in IL-32-treated cultures could in part be explain by the lack of F-actin ring formation by the multinucleated cells generated. Moreover, when IL-32 was added to PBMC cultures maintained with soluble RANKL, although the number of newly generated osteoclast was increased, a significant decrease of the percentage of lacunar resorption was evident suggesting a possible inhibitory effect of this cytokine on osteoclast activation. To determine the mechanism by which IL-32 induces such response, we sought to determine the intracellular pathways activated and the release of soluble mediators in response to IL-32. Our results indicated that compared to RANKL, IL-32 induced a massive activation of ERK1/2 and Akt. Moreover, IL-32 was also capable of stimulating the release of IL-4 and IFN-γ, two known inhibitors of osteoclast formation and activation.  This is the first in vitro report on the complex role of IL-32 on osteoclast precursors. Further clarification on the exact role of IL-32 in vivo is required prior to the development of any potential therapeutic approach.

title: IL-32 Is a Host Protective Cytokine against Mycobacterium tuberculosis in Differentiated THP-1 Human Macrophages
abstract: Macrophages provide a first line of defense against Mycobacterium tuberculosis. However, in instances where macrophage activation for killing is suboptimal, M. tuberculosis is capable of surviving intracellularly. IL-32 is a recently described cytokine induced by M. tuberculosis in a variety of cell types including human monocytes and macrophages. In this study, we investigated the biological significance of IL-32 in an in vitro model of M. tuberculosis infection in differentiated THP-1 human macrophages in which IL-32 expression was silenced using stable expression of short hairpin RNA (shRNA). Inhibition of endogenous IL-32 production in THP-1 cells that express one of three distinct shRNA-IL-32 constructs significantly decreased M. tuberculosis induction of TNF-α by ∼60%, IL-1β by 30–60%, and IL-8 by 40–50% and concomitantly increased the number of cell-associated M. tuberculosis bacteria compared with THP-1 cells stably expressing a scrambled shRNA. In THP-1 cells infected with M. tuberculosis and stimulated with rIL-32, a greater level of apoptosis was observed compared with that with M. tuberculosis infection alone. Obversely, there was significant abrogation of apoptosis induced by M. tuberculosis and a concomitant decrease in caspase-3 activation in cells depleted of endogenous IL-32. rIL-32γ significantly reduced the number of viable intracellular M. tuberculosis bacteria, which was modestly but significantly abrogated with a caspase-3 inhibitor. We conclude that IL-32 plays a host defense role against M. tuberculosis in differentiated THP-1 human macrophages.

title: IL-32, a proinflammatory cytokine in rheumatoid arthritis.
abstract: IL-32 is a recently discovered cytokine that induces TNFalpha, IL-1beta, IL-6, and chemokines. We investigated whether IL-32 is expressed in the synovia of patients with rheumatoid arthritis (RA) and studied associations with disease severity and the presence of other cytokines. Immunohistochemistry revealed that IL-32 is highly expressed in RA synovial tissue biopsies, whereas IL-32 was not observed in synovial tissues from patients with osteoarthritis. Moreover, in synovial biopsies from 29 RA patients with active disease, the level of IL-32 staining correlated with erythrocyte sedimentation rate, a marker of systemic inflammation (R = 0.63 and P < 0.0003). Synovial staining of IL-32 also correlated with indices of synovial inflammation (R = 0.80 and P < 0.0001) as well as synovial presence of TNFalpha (R = 0.68 and P < 0.004), IL-1beta (R = 0.79 and P < 0.0001), and IL-18 (R = 0.82 and P < 0.001). IL-32 was a potent inducer of prostaglandin E(2) release in mouse macrophages and human blood monocytes, an important property for inflammation. After the injection of human IL-32gamma into the knee joints of naïve mice, joint swelling, with pronounced influx of inflammatory cells and cartilage damage, was observed. In TNFalpha-deficient mice, IL-32-driven joint swelling was absent and cell influx was markedly reduced, but loss of proteoglycan was unaffected, suggesting that IL-32 activity is, in part, TNFalpha-dependent. IL-32, strongly associated with TNFalpha, IL-1beta, and IL-18, appears to play a role in human RA and may be a novel target in autoimmune diseases.

title: Innate immunity triggers IL-32 expression by fibroblast-like synoviocytes in rheumatoid arthritis
abstract: IntroductionInterleukin-32 (IL-32) is a recently described cytokine that is a strong inducer of pro-inflammatory cytokines such as tumor necrosis factor (TNF)-α, IL-1β, IL-6, and IL-8. The expression of this cytokine is highly increased in the rheumatoid synovium and correlated with the severity of joint inflammation. Little is known regarding the innate immune-related regulation of IL-32 by fibroblast-like synoviocytes (FLSs). We therefore investigated the effect of innate immune stimulation by ligands of Toll-like receptor (TLR)2, TLR3, and TLR4, and cytokines such as TNF-α and interferon (IFN)-γ, on IL-32 expression by FLSs.MethodsFLSs were isolated from patients with rheumatoid arthritis (RA) according to the ACR criteria. Quantitative RT-PCR, confocal analysis, and ELISA were performed to evaluate IL-32 mRNA induction and IL-32 release by FLSs stimulated with TLR2 (BLP), TLR3 (poly I:C), and TLR4 (lipopolysaccharide) ligands, TNF-α and IFN-γ.ResultsTLR2, -3, and -4 ligands as well as IFN-γ and TNF-α induced IL-32 β, γ and δ mRNA expression by RA FLSs. Mature IL-32 was expressed intracellularly and released by cells stimulated with the various activators. The IL-32α isoform was expressed intracellularly in response to TNF-α and poly I:C and not released in culture supernatants. Stimulation of FLS with TNF-α, BLP, lipopolysaccharide, or poly I:C concomitant with IFN-γ increased IL-32 expression compared with stimulation with IFN-γ alone.ConclusionsIL-32 synthesis by FLSs is tightly regulated by innate immunity in rheumatoid arthritis. Thus TNF-α, IFN-γ, double-strand RNA, hyaluronic acid, or other damage-associated molecular patterns (DAMPs), highly secreted in synovial tissues of RA patients, might trigger IL-32 secretion by FLSs. IL-32 might therefore represent a relevant therapeutic target in RA.

title: IL‐32 up‐regulation is associated with inflammatory cytokine production in allergic rhinitis
abstract: IL‐32 is a described pro‐inflammatory cytokine produced by T lymphocytes, natural killer cells, monocytes, and epithelial cells. However, the specific mechanism of IL‐32 on allergic rhinitis (AR) has not been elucidated. Here, we report a significant increase of IL‐32 protein and mRNA in the nasal mucosa of AR patients. In addition, in nasal mucosa tissue from AR patients, the level of IL‐32 production correlated with inflammation, IL‐1β, IL‐18, and granulocyte‐macrophage colony‐stimulating factor (GM‐CSF). In an AR animal model, IL‐32 significantly increased IgE and inflammatory cytokine levels. IL‐32 expression was induced by recombinant human GM‐CSF via activation of caspase‐1 in eosinophils. In addition, depletion of IL‐32 prevents the production of inflammatory cytokines in eosinophils. In conclusion, IL‐32 is an important cytokine involved in the inflammation of AR. The regulation of IL‐32 expression may form the basis of a new strategy for the treatment of AR.

title: Inhibition of IL-32 signaling by bamboo salt decreases pro-inflammatory responses in cellular models of allergic rhinitis.
abstract: Previously, we showed the antiallergic effect of bamboo salt (BS) in allergic rhinitis (AR). We also demonstrated that interleukin (IL)-32 is an important mediator of AR. The aim of this study was to evaluate the effect and specific underlying mechanism of BS, NaCl, and the mineral mixture (components of BS other than NaCl, including zinc, magnesium, and potassium, Mix) on IL-32 signaling using the human monocyte cell line, THP-1. Here, we documented for the first time that BS significantly decreased IL-32-induced thymic stromal lymphopoietin protein and mRNA expression in THP-1 cells. BS treatment significantly inhibited IL-32-induced proinflammatory cytokine production including IL-1β, IL-8, and tumor necrosis factor (TNF)-α by suppressing nuclear factor-κB, p38 mitogen-activated kinase, and caspase-1 pathways. The presence of BS or Mix effectively suppressed IL-32-induced macrophage-like cell differentiation but NaCl exhibited no effect on monocyte-to-macrophage-like cell differentiation. In IL-32-induced macrophages, the production of IL-1β, IL-6, IL-8, and TNF-α, and expression of inducible nitric oxide synthase and cyclooxygenase-2, induced by lipopolysaccharide was dramatically decreased in a dose-dependent manner after BS treatment. BS also significantly decreased IL-32-induced nitric oxide, IL-8, and TNF-α production. Furthermore, BS inhibited granulocyte-macrophage colony-stimulating factor-induced IL-32 and IL-8 protein and mRNA expression in EOL-1 cells. Taken together, BS suppressed inflammatory activity by inhibiting the IL-32 signaling pathway in AR.

title: Increased Plasma Interleukin-32 Expression in Patients with Neuromyelitis Optica
abstract: PurposeNeuromyelitis optica (NMO) is a chronic inflammatory demyelinating disease of the central nervous system (CNS). The pathogenesis of NMO remains unclear. IL-32 is emerging as a critical molecule in the pathophysiology of immune-mediated chronic inflammatory diseases. Whether IL-32 levels are elevated in NMO patients is unclear. We aimed to determine whether IL-32 levels are elevated in NMO patients and explore its relationship with IL-6, IL-17, and Expanded Disability Status Scale (EDSS) scores.MethodsPlasma IL-32α, IL-6 and IL-17A were measured by enzyme-linked immunosorbent assay in NMO (n = 26), MS (n = 23) and 22 healthy controls.ResultsWe found IL-32α levels were higher in NMO patients compared with MS (p = 0.020) and healthy controls (p = 0.00001). IL-32α levels were increased in MS patients compared with controls (p = 0.009). IL-32α positively correlated with IL-6 and IL-17A levels and EDSS scores in NMO patients.ConclusionsIn summary, plasma IL-32α levels are associated with inflammatory responses in NMO patients.

title: Differential expression of interleukin‐32 in chronic rhinosinusitis with and without nasal polyps
abstract: To cite this article: Keswani A, Chustz RT, Suh L, Carter R, Peters AT, Tan BK, Chandra R, Kim S‐H, Azam T, Dinarello CA, Kern RC, Schleimer RP, Kato A. Differential expression of interleukin‐32 in chronic rhinosinusitis with and without nasal polyps. Allergy 2012;

title: Interleukin-32 Gamma Stimulates Bone Formation by Increasing miR-29a in Osteoblastic Cells and Prevents the Development of Osteoporosis
abstract: Interleukin-32 gamma (IL-32γ) is a recently discovered cytokine that is elevated in inflamed tissues and contributes to pathogenic features of bone in human inflammatory rheumatic diseases. Nevertheless, the role of IL-32γ and its direct involvement in bone metabolism is unclear. We investigated the molecular mechanism of IL-32γ in bone remodeling and the hypothetical correlation between IL-32γ and disease activity in osteoporosis patients. Transgenic (TG) mice overexpressing human IL-32γ showed reduced bone loss with advancing age, increased bone formation, and high osteogenic capacity of osteoblast compared to wild-type (WT) mice through the upregulation of miR-29a, which caused a reduction of Dickkopf-1 (DKK1) expression. IL-32γ TG mice were protected against ovariectomy (OVX)induced osteoporosis compared with WT mice. Decreased plasma IL-32γ levels were associated with bone mineral density (BMD) in human patients linked to increased DKK1 levels. These results indicate that IL-32γ plays a protective role for bone loss, providing clinical evidence of a negative correlation between IL-32γ and DKK1 as bone metabolic markers.

title: Interleukin-32 promotes lipid accumulation through inhibition of cholesterol efflux.
abstract: Interleukin-32 (IL-32) is a pro-inflammatory cytokine and its effects in various inflammatory diseases have been investigated. However, the role of IL-32 on atherosclerosis, an inflammatory disease, remains unknown. The present study examined the use of IL-32α, the most abundant transcript of IL-32, in the treatment of oxidized low-density lipoprotein (ox-LDL)-stimulated THP-1 macrophages for 24 h, which simulates a foam cell formation model. The effect of IL-32α (20, 50 and 100 ng/ml) on lipid deposition in the macrophages was analyzed using Oil Red O staining, while the cholesterol efflux on apolipoprotein A-I was also measured. The mRNA and protein expression levels of peroxisome proliferator-activated receptor γ (PPARγ), liver X receptor α (LXRα), ATP-binding cassette transporter A1 (ABCA1) and ABCG1 were quantified by reverse transcription-quantitative polymerase chain reaction and western blot analysis, respectively. The results indicated that IL-32α exposure enhanced the lipid deposition and attenuated the cholesterol efflux from ox-LDL-stimulated THP-1 macrophages in a dose-dependent manner. Furthermore, the expression levels of ABCA1, LXRα and PPARγ were dose-dependently decreased by IL-32α at the mRNA and protein levels. Addition of the PPARγ agonist 15d-PGJ2 or overexpression of PPARγ in THP-1 macrophages abrogated the IL-32α-mediated inhibition of cholesterol efflux and reversed the IL-32α-mediated downregulation of ABCA1 and LXRα. In conclusion, IL-32α enhances lipid accumulation and inhibits cholesterol efflux from ox-LDL-exposed THP-1 macrophages by regulating the PPARγ-LXRα-ABCA1 pathway.

title: Interleukin-32 in chronic inflammatory conditions is associated with a higher risk of cardiovascular diseases.
abstract: Cardiovascular diseases (CVD) are the most frequent cause of death in developed countries. Their prevalence is higher in several chronic inflammatory conditions. This is likely due to the substantial contribution of the inflammatory status of the patients to the development and stability of atherosclerotic plaques. Recent evidence suggests that interleukin (IL)-32 may be involved in the conditions that contribute to CVD. IL-32 not only modulates important inflammatory pathways known to contribute to the pathogenesis of both inflammatory diseases and atherosclerosis, including tumor necrosis factor (TNF)α, IL-6 or IL-1β, but it has been also suggested to modulate endothelial cell function and the serum concentration of high-density lipoprotein (HDL). In this review, we highlight the recent advances in the field of IL-32 in relation to chronic inflammatory disorders and argue for a role of IL-32 in the increased prevalence of CVD in these patients.

title: IL-32, a novel proinflammatory cytokine in chronic obstructive pulmonary disease.
abstract: Chronic obstructive pulmonary disease (COPD) is a chronic inflammatory disorder of the lung, yet the mechanisms that regulate this immune-inflammatory response are not fully understood.



We investigated whether IL-32, a newly discovered cytokine, was related to markers of inflammation and clinical progression in COPD.



Using immunohistochemistry, expression of IL-32 was examined in surgically resected specimens from 40 smokers with COPD (FEV(1) = 39 +/- 4% predicted), 11 smokers with normal lung function, and 9 nonsmoking control subjects. IL-32 was quantified in alveolar macrophages, alveolar walls, bronchioles, and arterioles, and confirmed by molecular analysis. The levels of IL-32 were correlated with the cellular infiltrates, markers of inflammation, and clinical data.



Macrophage staining for IL-32 was increased in smokers with COPD compared with control smokers and nonsmokers (P = 0.0014 and P < 0.0001, respectively), and similar differences were observed in alveolar walls (P = 0.0004 and P = 0.0005) and bronchiolar epithelium (P = 0.004 and P = 0.0009). This increase was also detected at the mRNA level (P = 0.007 vs. control smokers and P = 0.029 vs. nonsmokers) and was mainly due to non-alpha isoforms. Moreover, IL-32 expression was positively correlated with tumor necrosis factor-alpha (P = 0.004, r(s)=0.70), CD8(+)cells (P = 0.02, r(s)=0.46), phospho p38MAPK (P < 0.01, r(s)=0.60) and negatively with FEV(1) values (P = 0.004, r(s)= -0.53).



This is the first study to demonstrate increased expression of IL-32 in lung tissue of patients with COPD, where it was colocalized with tumor necrosis factor-alpha and correlated with the degree of airflow obstruction. These results suggest that IL-32 is implicated in the characteristic immune response of COPD, with a possible impact on disease progression.

title: IL-32 synergizes with nucleotide oligomerization domain (NOD) 1 and NOD2 ligands for IL-1beta and IL-6 production through a caspase 1-dependent mechanism.
abstract: The activation of innate immunity requires the amplification of signals induced by pattern-recognition receptors for bacterial products. We have investigated the role of the newly described cytokine IL-32 in the amplification of cytokine production induced by the two most clinically relevant families of microbial receptors, the cell-surface Toll-like receptors (TLRs) and the intracellular nuclear oligomerization domain (NOD) receptor family. IL-32 synergized with the NOD1- and NOD2-specific muropeptides of peptidoglycans for the release of IL-1beta and IL-6 (a 3- to 10-fold increase). In contrast, IL-32 did not influence the cytokine production induced via TLRs. The synergistic effect of IL-32 and synthetic muramyl dipeptide (MDP) on cytokine production was absent in the cells of patients with Crohn's disease bearing the NOD2 frameshift mutation 3020insC, demonstrating that the IL-32/MDP synergism depends on NOD2. This in vitro synergism between IL-32 and NOD2 ligands was consistent with a marked constitutive expression of IL-32 in human colon epithelial tissue. In addition, the potentiating effect of IL-32 on the cytokine production induced by the synthetic muropeptide FK-156 was absent in NOD1-deficient macrophages, supporting the interaction between IL-32 and NOD1 pathways. When specific caspase inhibitors were used, the synergism between IL-32 and MDP/NOD2 depended on the activation of caspase 1. Only additive effects of IL-32 and muropeptides were observed for TNF-alpha production. The modulation of intracellular NOD2 pathways by IL-32, but not cell-surface TLRs, and the marked expression of IL-32 in colon mucosa suggest a role of IL-32 in the pathogenesis of Crohn's disease.

title: Increased serum interleukin‐32 levels in patients with Behçet's disease
abstract: Interleukin (IL)‐32 is known to act as a proinflammatory cytokine and is likely involved in several chronic inflammatory diseases. The aims of this study were to investigate whether serum IL‐32 levels are elevated in patients with Behçet's disease (BD) and to identify the correlation between IL‐32 levels and disease activity.

title: Interleukin‐32 is highly expressed in lesions of hidradenitis suppurativa
abstract: Hidradenitis suppurativa (HS) is a chronic inflammatory skin disease. Its immunopathogenic mechanisms are still poorly understood. Previous studies demonstrated that the proinflammatory cytokine interleukin (IL)‐32 is implicated in the pathogenesis of other inflammatory diseases.

title: Alternatively spliced isoforms of IL-32 differentially influence cell death pathways in cancer cell lines.
abstract: Alternative splicing is a biological mechanism that enables the synthesis of several isoforms with different or even opposite functions. This process must be tightly regulated to prevent unwanted isoform expression favoring pathological processes. Some isoforms of interleukin 32 (IL-32) are reported to be more potent in inducing inflammation, however the role in cell death remains to be investigated. This study demonstrates that IL-32γ and IL-32β can induce caspase-8-dependent cell death whereas this was not observed for IL-32α. Overexpression of IL-32β or IL-32γ but not IL-32α, resulted in enhanced expression of the survival cytokine IL-8. Furthermore, restoring the IL-8 signaling pathway by overexpressing CXCR1 in HEK293 cells, rescued IL-32β but not IL-32γ-induced cell death. Interestingly, IL-32γ was able to downregulate CXCR1 and thereby induce cell death. Subsequent studies into the role of IL-32 in thyroid cancer (TC) revealed that several IL-32 isoforms, IL-8, and CXCR1 are expressed in TC cell lines and specimens. Remarkably, TC cell lines were found to produce high concentrations of IL-8, indicating an important role for IL-8 in the survival-signaling pathway in these cells. Intriguingly, a significant correlation between the IL-8 receptor CXCR1 and IL-32γ was observed in TC specimens, while this was not observed for the other IL-32 splice variants. Blocking IL-32 alternative splicing by Isoginkgetin resulted in predominant expression of IL-32γ splice variants and cell death in TC cell lines. All together, modulation of IL-32 alternative splicing could represent a novel strategy for the treatment of malignancies, in particular thyroid cancer.

title: IL-32θ gene expression in acute myeloid leukemia suppresses TNF-α production
abstract: The proinflammatory cytokine TNF-α is highly expressed in patients with acute myeloid leukemia (AML) and has been demonstrated to induce rapid proliferation of leukemic blasts. Thus suppressing the production of TNF-α is important because TNF-α can auto-regulate own expression through activation of NF-κB and p38 mitogen-activated protein kinase (MAPK). In this study, we focused on the inhibitory effect of IL-32θ on TNF-α production in acute myeloid leukemia. Approximately 38% of patients with AML express endogenous IL-32θ, which is not expressed in healthy individuals. Furthermore, plasma samples were classified into groups with or without IL-32θ; then, we measured proinflammatory cytokine TNF-α, IL-1β, and IL-6 levels. TNF-α production was not increased in patients with IL-32θ expression than that in the no-IL-32θ group. Using an IL-32θ stable expression system in leukemia cell lines, we found that IL-32θ attenuated phorbol 12-myristate 13-acetate (PMA)-induced TNF-α production. IL-32θ inhibited phosphorylation of p38 MAPK, inhibitor of κB (IκB), and nuclear factor κB (NF-κB), which are key positive regulators of TNF-α expression, and inhibited nuclear translocation of NF-κB. Moreover, the presence of IL-32θ attenuated TNF-α promoter activity and the binding of NF-κB with the TNF-α promoter. In addition, IL-32γ-induced TNF-α production has no correlation with inhibition of TNF-α via IL-32θ expression. Thus, IL-32θ may serve as a potent inhibitor of TNF-α in patients with AML.

title: IL-32: a newly-discovered proinflammatory cytokine.
abstract: IL-32, a newly-discovered proinflammatory cytokine that activates the p38MAPK and NF-kappaB pathways, is an important player in innate and adaptive immune response. IL-32, a cytokine produced mainly by T, natural killer, and epithelial cells induces significant amounts of TNFalpha and MIP-2 and increases the production of both cytokines in a dose-dependent manner. IL-32 has been implicated in inflammatory disorders, mycobacterium tuberculosis infections, inflammatory bowel disease, and influenza A virus infection, as well as in some autoimmune diseases, such as rheumatoid arthritis, ulcerative colitis and Crohn?s disease and in human stomach cancer, human lung cancer and breast cancer tissues. Moreover, it has been reported that IL-32 has pro-inflammatory effects on myeloid cells and causes the differentiation of osteoclast precursors into multinucleated cells expressing specific osteoclast markers. We recently found that human IL-32 has the capacity to provoke histamine release in human-derived cord blood mast cells (HDCBMC), but not in LAD 2 cells nor in rat peritoneal mast cells (RPMC), showing that IL-32 may be specie specific and act more in mature human mast cells (HDCBMC) than in transformed mast cells (LAD 2 cells). Certainly, IL-32 is another potent proinflammatory cytokine, however, the specific role of this newly-discovered protein in the network of cytokine biology remains to be determined.

title: Interleukin 32, inflammation and cancer
abstract: &NA; Interleukin‐32 (IL‐32) is a novel cytokine involved in inflammation and cancer development. IL‐32 gene consists of eight small exons, and IL‐32 mRNA has nine alternative spliced isoforms, and was thought to be secreted because it contains an internal signal sequence and lacks a transmembrane region. IL‐32 is initially expressed selectively in activated T cells by mitogen and activated NK cells and their expression is strongly augmented by microbes, mitogens, and other cytokines. The IL‐32 is induced mainly by pathogens and pro‐inflammatory cytokines, but IL‐32 is more prominent in immune cells than in non‐immune tissues. The IL‐32 transcript is expressed in various human tissues and organs such as the spleen, thymus, leukocyte, lung, small intestine, colon, prostate, heart, placenta, liver, muscle, kidney, pancreas, and brain. Cytokines are critical components of cell signaling pathways that are involved in the regulation of cell growth, metabolism, hormone signaling, immune regulation and a variety of other physiological functions. Earlier studies have demonstrated that IL‐32 regulates cell growth, metabolism and immune regulation and is therefore involved in the pathologic regulator or protectant of inflammatory diseases. Previous studies defined that IL‐32 is upregulated in the patients with several inflammatory diseases, and is induced by inflammatory responses. However, several reports suggested that IL‐32 is downregulated in several inflammatory diseases including asthma, HIV infection disease, neuronal diseases, metabolic disorders, experimental colitis and metabolic disorders. IL‐32 is also involved in various cancer malignancies including renal cancer, esophageal cancer and hepatocellular carcinoma, lung cancer, gastric cancer, breast cancer, pancreatic cancer, lymphoma, osteosarcoma, breast cancer, colon cancer and thyroid carcinoma. Other studies suggested that IL‐32 decreases tumor development including cervical cancer, colon cancer and prostate cancer, melanoma, pancreatic cancer, liver cancer and chronic myeloid leukemia. Nevertheless, review articles that discuss the roles and its mechanism of IL‐32 isoforms focusing on the therapeutic approaches have not yet been reported. In this review article, we will discuss recent findings regarding IL‐32 in the development of diseases and further discuss therapeutic approaches targeting IL‐32. Moreover, we will suggest that IL‐32 could be the target of several diseases and the therapeutic agents for targeting IL‐32 may have potential beneficial effects for the treatment of inflammatory diseases and cancers. Future research should open new avenues for the design of novel therapeutic approaches targeting IL‐32.

title: Interleukin 32: a novel player in the control of infectious diseases
abstract: Interleukin 32 (IL‐32) is a proinflammatory cytokine, expressed as 9 distinct isoforms. The most active isoform is the predominantly intracellular‐functioning IL‐32γ. Involvement of IL‐32 in infectious diseases is increasingly being appreciated. Production of IL‐32 promotes pathways that serve to control bacterial infection, especially those caused by mycobacteria. A similar role for this cytokine is observed in the cellular response to viral infections. In addition to its protective effects against microorganisms, IL‐32 is involved in immunopathogenesis of some infectious diseases. In parasitic diseases, it has been demonstrated that this cytokine is induced by Leishmania infection. In this review, we summarize the present data on the role of IL‐32 in infectious diseases, highlighting this cytokine as new target for control of infections.

title: Characterizing antiviral mechanism of interleukin-32 and a circulating soluble isoform in viral infection.
abstract: Interleukin-32 (IL-32) is an inflammatory cytokine, and its activity is associated with various auto-inflammatory disorders as well as infectious pathogens such as Mycobacterium tuberculosis, and viral infections. However, the precise antiviral mechanism of IL-32 remains unclear. We assessed the IL-32 level in the sera of H1N1 influenza A patients and IL-32 level was significantly elevated. Next we examined the antiviral activity of recombinant IL-32γ (rIL-32γ) with WISH cells infected by vesicular stomatitis virus (VSV) but no antiviral activity was observed. Therefore we investigated the supernatant of rIL-32-treated THP-1 cells since this cell line effectively responded to rIL-32γ. The supernatant of rIL-32-treated THP-1 cell possessed an antiviral effect and in addition, an agonistic monoclonal antibody further enhanced a specific antiviral activity of rIL-32γ. The fractionation and mass spectrometer analysis of the THP-1 cell supernatant revealed that the antiviral activity of rIL-32γ is via a THP-1 cell-produced factor, transferrin, rather than the direct effects of rIL-32γ on epithelial cells. We also characterized a secreted soluble IL-32γ protein in serum of IL-32γ transgenic mouse (TG), but not in that of IL-32α TG. The present results suggest that IL-32γ expression and its genetic variation in individual could be an important aspect of viral infections.

title: Endogenous IL-32 Controls Cytokine and HIV-1 Production1
abstract: IL-32, a proinflammatory cytokine that activates the p38MAPK and NF-κB pathways, induces other cytokines, for example, IL-1β, IL-6, and TNF-α. This study investigated the role of endogenous IL-32 in HIV-1 infection by reducing IL-32 with small interfering (si)RNA in freshly infected PBMC and in the latently infected U1 macrophage cell line. When PBMC were pretreated with siRNA to IL-32 (siIL-32), IL-6, IFN-γ, and TNF-α were reduced by 57, 51, and 36%, respectively, compared with scrambled siRNA. Cotransfection of NF-κB and AP-1 reporter constructs with siIL-32 decreased DNA binding of these transcription factors by 42 and 46%, respectively. Cytokine protein array analysis revealed that the inhibitory activity of siIL-32 primarily targeted Th1 and proinflammatory cytokines and chemokines, e.g., MIP-1α/β. Unexpectedly, HIV-1 production (as measured by p24) increased 4-fold in these same PBMC when endogenous IL-32 was reduced. Because IFN-γ was lower in siIL-32-treated PBMC, we blocked IFN-γ bioactivity, which enhanced the augmentation of p24 by siIL-32. Furthermore, siIL-32 reduced the natural ligands of the HIV-1 coreceptors CCR5 (MIP-1α/β and RANTES) and CXCR4 (SDF-1). Inhibition of endogenous IL-32 in U1 macrophages also increased HIV-1. When rhIL-32γ was added to these cells, p24 levels fell by 72%; however, in the same cultures IFN-α increased 4-fold. Blockade of IFN-α/β bioactivity in IL-32γ-stimulated U1 cells revealed that IFN-α conveys the anti-HIV-1 effect of rhIL-32γ. In summary, depletion of endogenous IL-32 reduced the levels of Th1 and proinflammatory cytokines but paradoxically increased p24, proposing IL-32 as a natural inhibitor of HIV-1.

title: Increased level of IL-32 during human immunodeficiency virus infection suppresses HIV replication.
abstract: Interleukin-32 was recently identified as a pro-inflammatory cytokine produced by T-lymphocytes, natural killer cells, epithelial cells, and blood monocytes. IL-32 is induced by IFN-gamma in a time-dependent manner suggesting a role for IL-32 in innate and adaptive immune responses. In this study we present evidence that Human immunodeficiency virus promotes interleukin-32 production at both mRNA and protein levels. Our results showed that there is a 74% increase in the serum levels of IL-32 among HIV patients as compared to healthy individuals. There was a three-fold increase in the promoter activity of the IL-32 in the present infections HIV clone. This increase in IL-32 promoter activity was substantiated by increased IL-32 mRNA and protein levels. We have also demonstrated that IL-32 suppresses HIV replication. Our results show that HIV LTR activity was increased by more than six-folds when endogenous IL-32 was knocked down by IL-32-specific siRNA whereas it decreased by one-fold when IL-32 was over expressed in the cells. Similarly a more than two-fold increase and a 50% decrease in HIV p24 values were noted when IL-32 was knocked down and when IL-32 was over expressed in the cells, respectively. Our present work shows that raised IL-32 levels in HIV infection may in turn hamper HIV replication; one of the protective mechanisms of nature.

title: The Immunosuppressive Role of IL-32 in Lymphatic Tissue during HIV-1 Infection
abstract: One pathological hallmark of HIV-1 infection is chronic activation of the immune system, driven, in part, by increased expression of proinflammatory cytokines. The host attempts to counterbalance this prolonged immune activation through compensatory mediators of immune suppression. We recently identified a gene encoding the proinflammatory cytokine IL-32 in microarray studies of HIV-1 infection in lymphatic tissue (LT) and show in this study that increased expression of IL-32 in both gut and LT of HIV-1–infected individuals may have a heretofore unappreciated role as a mediator of immune suppression. We show that: 1) IL-32 expression is increased in CD4+ T cells, B cells, macrophages, dendritic cells, and epithelial cells in vivo; 2) IL-32 induces the expression of immunosuppressive molecules IDO and Ig-like transcript 4 in immune cells in vitro; and 3) in vivo, IL-32-associated IDO/Ig-like transcript 4 expression in LT macrophages and gut epithelial cells decreases immune activation but also may impair host defenses, supporting productive viral replication, thereby accounting for the correlation between IL-32 levels and HIV-1 replication in LT. Thus, during HIV-1 infection, we propose that IL-32 moderates chronic immune activation to avert associated immunopathology but at the same time dampens the antiviral immune response and thus paradoxically supports HIV-1 replication and viral persistence.

title: Negative feedback regulation of IL‐32 production by iNOS activation in response to dsRNA or influenza virus infection
abstract: iNOS plays an important role in mediating inflammation. In this study, we found that iNOS‐derived NO was increased 2.4‐fold in the serum samples of 101 patients infected with influenza A virus in comparison with samples of 105 healthy individuals. In A549 human lung epithelial cells, infection with influenza A virus or stimulation with poly(I:C)+IFN‐γ resulted in increased mRNA and protein levels of both IL‐32 and iNOS, with subsequent release of NO. Over‐expression of IL‐32 resulted in upregulated iNOS expression with subsequent NO production. Knock down of IL‐32 by IL‐32‐specific siRNA resulted in the inhibition of dsRNA‐induced expression of iNOS and NO release, indicating that IL‐32 is an upstream regulatory factor of dsRNA‐triggered iNOS production. Surprisingly, over‐expression of iNOS resulted in the reduction of IL‐32 expression, and suppression of iNOS by the selective iNOS inhibitor S‐methylisothiourea sulfate stimulated IL‐32 expression, indicating that a negative feedback mechanism operates between the iNOS/NO and IL‐32 systems. These findings suggest that influenza A virus infection activates IL‐32 and iNOS expression by a heretofore unrecognized complex mechanism, in which the two pro‐inflammatory factors regulate each other, involving positive and negative feedback regulatory loops.

title: The expression of interleukin-32 is activated by human cytomegalovirus infection and down regulated by hcmv-miR-UL112-1
abstract: BackgroundInterleukin-32 (IL-32) is an important factor in innate and adaptive immune responses, which activates the p38MAPK, NF-kappa B and AP-1 signaling pathways. Recent reports have highlighted that IL-32 is regulated during viral infection in humans.MethodsEnzyme-linked immunosorbent assays (ELISA) were carried out to detect IL-32 levels in serum samples. Detailed kinetics of the transcription of IL-32 mRNA and expression of IL-32 protein during human cytomegalovirus (HCMV) infection were determined by semi-quantitative RT-PCR and western blot, respectively. The expression levels of hcmv-miR-UL112-1 were detected using TaqMan® miRNA assays during a time course of 96 hours. The effects of hcmv-miR-UL112-1 on IL-32 expression were demonstrated by luciferase assay and western blot, respectively.ResultsSerum levels of IL-32 in HCMV-IgM positive patients (indicating an active HCMV infection) were significantly higher than those in HCMV-IgM negative controls. HCMV infection activated cellular IL-32 transcription mainly in the immediately early (IE) phase and elevated IL-32 protein levels between 6 and 72 hours post infection (hpi) in the human embryonic lung fibroblast cell line, MRC-5. The expression of hcmv-miR-UL112-1 was detected at 24 hpi and increased gradually as the HCMV-infection process was prolonged. In addition, it was demonstrated that hcmv-miR-UL112-1 targets a sequence in the IL-32 3′-UTR. The protein level of IL-32 in HEK293 cells could be functionally down-regulated by transfected hcmv-miR-UL112-1.ConclusionsIL-32 expression was induced by active HCMV infection and could be functionally down-regulated by ectopically expressed hcmv-miR-UL112-1. Our data may indicate a new strategy of immune evasion by HCMV through post-transcriptional regulation.

title: [Interleukin-32 expression is induced by hepatitis B virus].
abstract: To investigate whether hepatitis B virus (HBV) can induce the expression of the host-encoded cytokine interleukin-32 (IL-32) and its effects on host signaling mechanisms related to HBV pathogenesis.



A eukaryotic expression vector harboring an enhanced green fluorescent protein was constructed with HBV genomic sequences (pIRES2-HBV-EGFP) and transfected into HepG2 cells. In addition, the nuclear factor-kappa B (NF-kB) subunits, p50 and p65, were transfected respectively into HepG2 cells. In both cases, 48 hrs after transfection, IL-32 expression was determined at the mRNA and protein levels using real-time PCR and ELISA and western blot, respectively. The HepG2 cells transfected with pIRES2-HBV-EGFP were also treated with the NF-kB inhibitor SN50 at various concentrations, and the effects on IL-32 protein expression 48 hrs later were evaluated by western blot. Significance of between-group differences was assessed by the Student's t-test.



Transfection with pIRES2-HBV-EGFP led to significantly higher IL-23 expression than transfection with empty vector (mRNA: 2.8-fold higher and protein: 4.5-fold higher; both P less than 0.05). Transfection of p50 and p65 proteins led to significantly higher IL-32 expression (both P less than 0.05), and NF-kB activation was found to be required for HBV-induced IL-32 expression.



IL-32 expression is induced by HBV in HepG2 cells. This host-encoded cytokine, and its downstream activation of NF-kB, may be involved in the pathogenesis of HBV, especially in the subsequent liver inflammation that accompanies HBV infection.

title: IL-32γ promotes the healing of murine cutaneous lesions caused by Leishmania braziliensis infection in contrast to Leishmania amazonensis
abstract: BackgroundInterleukin 32 (IL-32) is a pro-inflammatory cytokine induced in patients with American tegumentary leishmaniasis (ATL) caused by Leishmania braziliensis. Here, we investigated whether IL-32 is also expressed in patient lesions caused by L. amazonensis. In addition, we evaluated experimental L. amazonensis and L. braziliensis infections in C57BL/6 transgenic mice for human IL-32γ (IL-32γTg) in comparison with wild-type (WT) mice that do not express the IL-32 gene.ResultsHuman cutaneous lesions caused by L. amazonensis express higher levels of IL-32 than healthy control skin. In mice, the presence of IL-32γ promoted the control of cutaneous lesions caused by L. braziliensis, but not lesions caused by L. amazonensis in an ear dermis infection model. In addition, IL-32γTg mice displayed less tissue parasitism and inflammation in IL-32γTg than WT mice during the healing phase of L. braziliensis infection. Production of antigen-specific pro-inflammatory cytokines was higher in IL-32γTg mice than in WT mice during L. braziliensis infection but not during L. amazonensis infection.ConclusionsHuman cutaneous lesions caused by L. amazonensis express high levels of IL-32. In mice, the presence of IL-32γ contributes to the lesion healing caused by L. braziliensis but not by L. amazonensis. Data suggest that despite the ability for both species to induce IL-32 in humans, the connections between this cytokine and other immune players induced by related species of parasites can lead to distinct outcomes of the murine infections.

title: Cytokines and microbicidal molecules regulated by IL-32 in THP-1-derived human macrophages infected with New World Leishmania species
abstract: (IL-32) is expressed in lesions of patients with American Tegumentary Leishmaniasis (ATL), but its precise role in the disease remains unknown.  In the present study, silencing and overexpression of IL-32 was performed in THP-1-derived macrophages infected with Leishmania (Viannia) braziliensis or L. (Leishmania) amazonensis to investigate the role of IL-32 in infection. We report that Leishmania species induces IL-32γ, and show that intracellular IL-32γ protein production is dependent on endogenous TNFα. Silencing or overexpression of IL-32 demonstrated that this cytokine is closely related to TNFα and IL-8. Remarkably, the infection index was augmented in the absence of IL-32 and decreased in cells overexpressing this cytokine. Mechanistically, these effects can be explained by nitric oxide cathelicidin and β-defensin 2 production regulated by IL-32.  Thus, endogenous IL-32 is a crucial cytokine involved in the host defense against Leishmania parasites.

title: IL-32 expression in the airway epithelial cells of patients with Mycobacterium avium complex lung disease.
abstract: Lung disease due to Mycobacterium avium complex (MAC) organisms is increasing. A greater understanding of the host immune response to MAC organisms will provide a foundation to develop novel therapies for these recalcitrant infections. IL-32 is a newly described pro-inflammatory cytokine that enhances host immunity against various microbial pathogens. Cytokines that induce IL-32 such as interferon-gamma, IL-18, IL-12 and tumor necrosis factor-alpha are of considerable importance to mycobacterial immunity. We performed immunohistochemistry and morphometric analysis to quantify IL-32 expression in the lungs of 11 patients with MAC lung disease and 10 controls with normal lung tissues. After normalizing for basement membrane length, there was a profound increase in IL-32 expression in the airway epithelial cells of the MAC-infected lungs compared with controls. Following normalization for alveolar surface area, there was a trend toward increased IL-32 expression in type II alveolar cells and alveolar macrophages in the lungs of MAC patients. Human airway epithelial cells (BEAS-2B) infected with M. avium produced IL-32 by a nuclear factor-kappa B-dependent mechanism. In both BEAS-2B cells and human monocyte-derived macrophages, exogenous IL-32γ significantly reduced the growth of intracellular M. avium. This finding was corroborated by an increase in the number of intracellular M. avium recovered from THP-1 monocytes silenced for endogenous IL-32 expression. The anti-mycobacterial effect of IL-32 may be due, in part, to increased apoptosis of infected cells. These findings indicate that IL-32 facilitates host defense against MAC organisms but may also contribute to the airway inflammation associated with MAC pulmonary disease.

title: Human IL-32 expression protects mice against a hypervirulent strain of Mycobacterium tuberculosis
abstract: Significance Interleukin-32 (IL-32) is induced by IL-1β, Toll-like receptor agonists, and nucleotide oligomerization domain as well as by Mycobacterium tuberculosis (MTB). Expression of human IL-32γ in the lungs of mice reduced the burden of MTB in both the lungs but also in the spleen and was associated with increased survival. Mechanistically, increased numbers of host-protective innate and adaptive immune cells were present in the IL-32 transgenic mice. Alveolar macrophages from the transgenic mice were also better able to control MTB infection and had increased colocalization of MTB with lysosomes. IL-32 expression was increased in the surgically resected lungs of tuberculosis patients, particularly in macrophages, airway epithelial cells, B cells, and T cells. Thus, IL-32 enhances host immunity against MTB. Silencing of interleukin-32 (IL-32) in a differentiated human promonocytic cell line impairs killing of Mycobacterium tuberculosis (MTB) but the role of IL-32 in vivo against MTB remains unknown. To study the effects of IL-32 in vivo, a transgenic mouse was generated in which the human IL-32γ gene is expressed using the surfactant protein C promoter (SPC-IL-32γTg). Wild-type and SPC-IL-32γTg mice were infected with a low-dose aerosol of a hypervirulent strain of MTB (W-Beijing HN878). At 30 and 60 d after infection, the transgenic mice had 66% and 85% fewer MTB in the lungs and 49% and 68% fewer MTB in the spleens, respectively; the transgenic mice also exhibited greater survival. Increased numbers of host-protective innate and adaptive immune cells were present in SPC-IL-32γTg mice, including tumor necrosis factor-alpha (TNFα) positive lung macrophages and dendritic cells, and IFN-gamma (IFNγ) and TNFα positive CD4+ and CD8+ T cells in the lungs and mediastinal lymph nodes. Alveolar macrophages from transgenic mice infected with MTB ex vivo had reduced bacterial burden and increased colocalization of green fluorescent protein-labeled MTB with lysosomes. Furthermore, mouse macrophages made to express IL-32γ but not the splice variant IL-32β were better able to limit MTB growth than macrophages capable of producing both. The lungs of patients with tuberculosis showed increased IL-32 expression, particularly in macrophages of granulomas and airway epithelial cells but also B cells and T cells. We conclude that IL-32γ enhances host immunity to MTB.

title: The role of interleukin-32 against tuberculosis.
abstract: IL-32 is increasingly recognized to be an important host-protective molecule against tuberculosis. In this commentary, we highlight some of the potential mechanisms by which the immunomodulatory effect of IL-32 occurs against mycobacterial infections but also areas where mechanistic clarifications are needed.

title: Generation of secretable and nonsecretable interleukin 15 isoforms through alternate usage of signal peptides.
abstract: Two isoforms of human interleukin 15 (IL-15) exist. One isoform has a shorter putative signal peptide (21 amino acids) and its transcript shows a tissue distribution pattern that is distinct from that of the alternative IL-15 isoform with a 48-aa signal peptide. The 21-aa signal isoform is preferentially expressed in tissues such as testis and thymus. Experiments using different combinations of signal peptides and mature proteins (IL-2, IL-15, and green fluorescent protein) showed that the short signal peptide regulates the fate of the mature protein by controlling the intracellular trafficking to nonendoplasmic reticulum sites, whereas the long signal peptide both regulates the rate of protein translation and functions as a secretory signal peptide. As a consequence, the IL-15 associated with the short signal peptide is not secreted, but rather is stored intracellularly, appearing in the nucleus and cytoplasmic components. Such production of an intracellular lymphokine is not typical of other soluble interleukin systems, suggesting a biological function for IL-15 as an intracellular molecule.

title: Interaction network mapping among IL-32 isoforms.
abstract: IL-32 has been studied for its pleiotropic effects ranging from host immune responses to cell differentiation. Although several IL-32 isoforms have been characterized for their effects on cells, the roles of the others remain unclear. We previously reported that IL-32δ interacted with IL-32β and inhibited IL-32β-mediated IL-10 production. Thus, we performed comprehensive analyses to reveal more interactions between IL-32 isoforms in this study. We screened the interactions of 81 combinations of nine IL-32 isoforms by using a yeast two-hybrid assay, which identified 13 heterodimeric interactions. We verified these results by using reciprocal immunoprecipitation assays and reconfirmed 10 interactions, and presented the interaction network map between IL-32 isoforms. Our data suggest that IL-32 may have diverse intracellular effects through the interactions with its different isoforms.

title: Inflammation-dependent secretion and splicing of IL-32γ in rheumatoid arthritis
abstract: Different splice variants of the proinflammatory cytokine IL-32 are found in various tissues; their putative differences in biological function remain unknown. In the present study, we report that IL-32γ is the most active isoform of the cytokine. Splicing to one less active IL-32β appears to be a salvage mechanism to reduce inflammation. Adenoviral overexpression of IL-32γ (AdIL-32γ) resulted in exclusion of the IL-32γ–specific exon in vitro as well as in vivo, primarily leading to expression of IL-32β mRNA and protein. Splicing of the IL-32γ–specific exon was prevented by single-nucleotide mutation, which blocked recognition of the splice site by the spliceosome. Overexpression of splice-resistant IL-32γ in THP1 cells or rheumatoid arthritis (RA) synovial fibroblasts resulted in a greater induction of proinflammatory cytokines such as IL-1β, compared with IL-32β. Intraarticular introduction of IL-32γ in mice resulted in joint inflammation and induction of several mediators associated with joint destruction. In RA synovial fibroblasts, overexpression of primarily IL-32β showed minimal secretion and reduced cytokine production. In contrast, overexpression of splice-resistant IL-32γ in RA synovial fibroblasts exhibited marked secretion of IL-32γ. In RA, we observed increased IL-32γ expression compared with osteoarthritis synovial tissue. Furthermore, expression of TNFα and IL-6 correlated significantly with IL-32γ expression in RA, whereas this was not observed for IL-32β. These data reveal that naturally occurring IL-32γ can be spliced into IL-32β, which is a less potent proinflammatory mediator. Splicing of IL-32γ into IL-32β is a safety switch in controlling the effects of IL-32γ and thereby reduces chronic inflammation.

title: Tumour necrosis factor alpha-driven IL-32 expression in rheumatoid arthritis synovial tissue amplifies an inflammatory cascade
abstract: To investigate the interplay between IL-32 and tumour necrosis factor alpha (TNFα) during the chronic inflammation of rheumatoid arthritis (RA) and to assess whether anti-TNFα treatment of RA patients modulates synovial IL-32 expression.  Induction of IL-32γ by Pam3Cys, lipopolysaccharide, IL-1β or TNFα was investigated in human fibroblast-like synoviocytes (FLS). Stimulation of TNFα production by IL-32γ was studied by adenoviral overexpression of IL-32γ (AdIL-32γ) and lipopolysaccharide stimulation of THP1 cells. Silencing of endogenous IL-32 was employed to study cytokine regulation in FLS. AdIL-32γ followed by TNFα stimulation was performed in FLS to investigate cytokine induction. Immunohistochemistry was applied to study IL-32 expression in synovial biopsies from RA patients.  TNFα potently induced IL-32γ expression in FLS. Increased TNFα, IL-1β, IL-6 and CXCL8 production was observed after IL-32γ overexpression and lipopolysaccharide stimulation of THP1 cells. TNFα stimulation of FLS after silencing IL-32γ resulted in diminished IL-6 and CXCL8 production, whereas IL-32γ overexpression resulted in enhanced IL-6 and CXCL8 levels. Remarkably, the mechanism through which IL-32γ overexpression induced TNFα, IL-1β and CXCL8 was by counteracting messenger RNA decay. Importantly, treatment of RA patients with anti-TNFα resulted in significant reduction of IL-32 protein in synovial tissue.  TNFα is a potent inducer of endogenous IL-32 expression and IL-32 itself contributes to prolonged TNFα production, thus inducing an important auto-inflammatory loop. Treatment of RA patients with anti-TNFα antibodies diminished IL-32 expression in synovial tissue. The potent anti-inflammatory effect of TNFα blockade in RA patients may be partly due to the reduction of synovial IL-32 expression.

title: IL-32 is expressed by human primary keratinocytes and modulates keratinocyte apoptosis in atopic dermatitis.
abstract: Keratinocyte (KC) apoptosis is an important mechanism of eczema and spongiosis in patients with atopic dermatitis (AD) and is mediated by IFN-gamma, which is secreted by T(H)1 cells. IL-32 is a proinflammatory cytokine that is involved in the inflammatory processes of rheumatoid arthritis, chronic obstructive pulmonary disease, and Crohn disease. Recently, it was shown that upregulation of IL-32 induces apoptosis.



The aim of the study was to investigate the expression and function of IL-32 in patients with AD.



The expression of IL-32 in KCs was analyzed by means of RT-PCR, ELISA, and flow cytometry. Transfections of small interfering RNA were performed in primary KCs, and apoptosis was analyzed by means of terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling, annexin-V, and 7-amino actinomycin D stainings. Immunofluorescence stainings were used to detect IL-32 in skin biopsy specimens, and serum levels of IL-32 were analyzed by means of ELISA.



We report that IL-32 is expressed in human primary KCs on stimulation with IFN-gamma, TNF-alpha, and T(H)1 cells in contrast to T(H)2, regulatory T (Treg), or T(H)17 cells, which showed no effect. Transfection of primary KCs and artificial skin equivalents with small interfering RNA to IL-32, which resulted in a clear decrease in IL-32 expression, significantly reduced KC apoptosis. Immunofluorescence staining demonstrated that IL-32 was expressed in AD lesional skin, whereas it was present in neither skin biopsy specimens from healthy donors nor in lesional skin from patients with psoriasis. Serum levels of IL-32 from patients with AD correlated with disease severity, but increased serum levels of IL-32 were also detected in asthmatic patients.



The present study demonstrates KCs as a source of IL-32, which modulates KC apoptosis and contributes to the pathophysiology of AD.

title: Interleukin-32α expression in human colonic subepithelial myofibroblasts.
abstract: Interleukin (IL)-32 is a recently described proinflammatory cytokine, characterized by induction of nuclear factor (NF)-κB activation. We studied IL-32α expression in human colonic subepithelial myofibroblasts (SEMFs). Colonic SEMFs were isolated from normal human colon tissue. IL-32α protein expression was evaluated by Western blot analyses, and IL-32α mRNA expression was analyzed by real-time PCR. IL-32α mRNA was weakly expressed without a stimulus, and its expression was markedly enhanced by IL-1ß and TNF-α. IL-1ß and TNF-α enhanced intracellular accumulation of IL-32α protein, but IL-32α was not detected in supernatants. Each cytokine dose- and time-dependently induced IL-32α mRNA expression. An inhibitor of phosphatidylinositol 3-kinase (LY294002) significantly suppressed IL-1ß- and TNF-α-induced IL-32α mRNA expression, although MAPK inhibitors had no effect. Akt activation in response to these cytokines was confirmed by Western blotting. Blockade of NF-κB activation by an adenovirus expressing a stable mutant form of IκBα markedly suppressed IL-1ß- and TNF-α-induced IL-32α mRNA expression. Human colonic SEMFs expressed IL-32α in response to IL-1ß and TNF-α. IL-32α mRNA expression depends on the phosphatidylinositol 3-kinase and the NF-κB system.

title: Proteinase 3 is an IL-32 binding protein.
abstract: IL-32, a recently discovered proinflammatory cytokine with four isoforms, induces IL-1beta, TNF-alpha, IL-6, and chemokines. Here, we used ligand (IL-32alpha) affinity chromatography in an attempt to isolate an IL-32alpha soluble receptor or binding protein. Recombinant IL-32alpha was covalently immobilized on agarose, and preparations of concentrated crude human urinary proteins were applied for chromatographic separation. A specific 30-kDa protein eluted from the column during acid washing and was identified by mass spectrometry as proteinase 3 (PR3) and confirmed by N-terminal microsequencing. PR3, a neutrophil granule serine protease, exists in a soluble or membrane form and is the major autoantigen for autoantibodies in the systemic vasculitic disease, Wegener's granulomatosis. The affinity of IL-32alpha to PR3 was determined by surface plasmon resonance. The dissociation constants were 2.65 +/- 0.4 nM for urinary PR3 and 1.2 +/- 0.05 nM for neutrophil-derived PR3. However, irreversible inactivation of PR3 enzymatic activity did not significantly change binding to the cytokine. Nevertheless, limited cleavage of IL-32 yielded products consistent with PR3 enzyme activity. Moreover, after limited cleavage by PR3, IL-32alpha was more active than intact IL-32alpha in inducing macrophage inflammatory protein-2 in mouse macrophages and IL-8 in human peripheral blood mononuclear cells. We suggest that PR3 is a specific IL-32alpha binding protein, independent of its enzymatic activity. However, limited cleavage of IL-32alpha by PR3 enhances activities of the cytokine. Therefore, specific inhibition of PR3 activity to process IL-32 or neutralization of IL-32 by inactive PR3 or its fragments may reduce the consequences of IL-32 in immune regulated diseases.

title: Intracellular Interaction of Interleukin (IL)-32α with Protein Kinase Cϵ (PKCϵ) and STAT3 Protein Augments IL-6 Production in THP-1 Promonocytic Cells*
abstract: IL-32α is known to interact with FAK1, and IL-32α overexpression in chronic myeloid leukemia cells increases natural killer cell-mediated killing.  IL-32α interacted with PKCϵ and STAT3, mediated STAT3 phosphorylation, and thereby augmented IL-6 production.  IL-32α elevated IL-6 production through interaction with PKCϵ and STAT3.  The interaction of IL-32α with PKCϵ and STAT3 reveals a new intracellular mediatory role of IL-32α. IL-32α is known as a proinflammatory cytokine. However, several evidences implying its action in cells have been recently reported. In this study, we present for the first time that IL-32α plays an intracellular mediatory role in IL-6 production using constitutive expression systems for IL-32α in THP-1 cells. We show that phorbol 12-myristate 13-acetate (PMA)-induced increase in IL-6 production by IL-32α-expressing cells was higher than that by empty vector-expressing cells and that this increase occurred in a time- and dose-dependent manner. Treatment with MAPK inhibitors did not diminish this effect of IL-32α, and NF-κB signaling activity was similar in the two cell lines. Because the augmenting effect of IL-32α was dependent on the PKC activator PMA, we tested various PKC inhibitors. The pan-PKC inhibitor Gö6850 and the PKCϵ inhibitor Ro-31-8220 abrogated the augmenting effect of IL-32α on IL-6 production, whereas the classical PKC inhibitor Gö6976 and the PKCδ inhibitor rottlerin did not. In addition, IL-32α was co-immunoprecipitated with PMA-activated PKCϵ, and this interaction was totally inhibited by the PKCϵ inhibitor Ro-31-8220. PMA-induced enhancement of STAT3 phosphorylation was observed only in IL-32α-expressing cells, and this enhancement was inhibited by Ro-31-8220, but not by Gö6976. We demonstrate that IL-32α mediated STAT3 phosphorylation by forming a trimeric complex with PKCϵ and enhanced STAT3 localization onto the IL-6 promoter and thereby increased IL-6 expression. Thus, our data indicate that the intracellular interaction of IL-32α with PKCϵ and STAT3 promotes STAT3 binding to the IL-6 promoter by enforcing STAT3 phosphorylation, which results in increased production of IL-6.

title: Interleukin 32 (IL-32) Contains a Typical α-Helix Bundle Structure That Resembles Focal Adhesion Targeting Region of Focal Adhesion Kinase-1*
abstract: IL-32 is involved in several cell processes, most likely through integrin signaling.  Modeling of IL-32 revealed a structure similar to FAT and binds to integrins, paxillin, and FAK-1, all members of the integrin-signaling pathway.  IL-32 interacts with members of the focal adhesion protein complex.  IL-32 might be a key protein in integrin signaling and downstream processes. IL-32 can be expressed in several isoforms. The amino acid sequences of the major IL-32 isoforms were used to predict the secondary and tertiary protein structure by I-TASSER software. The secondary protein structure revealed coils and α-helixes, but no β sheets. Furthermore, IL-32 contains an RGD motif, which potentially activates procaspase-3 intracellular and or binds to integrins. Mutation of the RGD motif did not result in inhibition of the IL-32β- or IL-32γ-induced cytotoxicity mediated through caspase-3. Although IL-32α interacted with the extracellular part of αVβ3 and αVβ6 integrins, only the αVβ3 binding was inhibited by small RGD peptides. Additionally, IL-32β was able to bind to αVβ3 integrins, whereas this binding was not inhibited by small RGD peptides. In addition to the IL-32/integrin interactions, we observed that IL-32 is also able to interact with intracellular proteins that are involved in integrin and focal adhesion signaling. Modeling of IL-32 revealed a distinct α-helix protein resembling the focal adhesion targeting region of focal adhesion kinase (FAK). Inhibition of FAK resulted in modulation of the IL-32β- or IL-32γ-induced cytotoxicity. Interestingly, IL-32α binds to paxillin without the RGD motif being involved. Finally, FAK inhibited IL-32α/paxillin binding, whereas FAK also could interact with IL-32α, demonstrating that IL-32 is a member of the focal adhesion protein complex. This study demonstrates for the first time that IL-32 binds to the extracellular domain of integrins and to intracellular proteins like paxillin and FAK, suggesting a dual role for IL-32 in integrin signaling.

title: Interleukin-32: a predominantly intracellular proinflammatory mediator that controls cell activation and cell death.
abstract: In this review, we will discuss the current knowledge on IL-32 and provide new insights regarding the biological function of IL-32. IL-32 is seen as a cytokine that can induce a range of proinflammatory mediators and contribute to autoimmune diseases, such as rheumatoid arthritis, however present knowledge demonstrates that IL-32 is not a classical cytokine. We present the history of this cytokine, the role of IL-32 in several diseases and discuss a possible novel role of intracellular IL-32 in cell homeostasis. Taken into account the observed biological functions of IL-32, it may belong to a class of cytokines, like IL-1α, IL-33, and IL-37, with both intracellular and extracellular functions.

title: Interleukin (IL)-32β-mediated CCAAT/Enhancer-binding Protein α (C/EBPα) Phosphorylation by Protein Kinase Cδ (PKCδ) Abrogates the Inhibitory Effect of C/EBPα on IL-10 Production*
abstract: IL-32β promotes IL-10 production in myeloid cells.  IL-32β-mediated C/EBPα serine 21 phosphorylation by PKCδ induced the dissociation of C/EBPα from IL-10 promoter, thereby promoting IL-10 production.  IL-32β suppressed the inhibitory effect of C/EBPα on IL-10 production by mediating C/EBPα serine 21 phosphorylation by PKCδ.  Our data suggest that IL-32β functions as an intracellular regulator of IL-10 production. We previously reported that IL-32β promotes IL-10 production in myeloid cells. However, the underlying mechanism remains elusive. In this study, we demonstrated that IL-32β abrogated the inhibitory effect of CCAAT/enhancer-binding protein α (C/EBPα) on IL-10 expression in U937 cells. We observed that the phosphorylation of C/EBPα Ser-21 was inhibited by a PKCδ-specific inhibitor, rottlerin, or IL-32β knockdown by siRNA and that IL-32β shifted to the membrane from the cytosol upon phorbol 12-myristate 13-acetate treatment. We revealed that IL-32β suppressed the binding of C/EBPα to IL-10 promoter by using ChIP assay. These data suggest that PKCδ and IL-32β may modulate the effect of C/EBPα on IL-10 expression. We next demonstrated by immunoprecipitation that IL-32β interacted with PKCδ and C/EBPα, thereby mediating C/EBPα Ser-21 phosphorylation by PKCδ. We showed that IL-32β suppressed the inhibitory effect of C/EBPα on IL-10 promoter activity. However, the IL-10 promoter activity was reduced to the basal level by rottlerin treatment. When C/EBPα serine 21 was mutated to glycine (S21G), the inhibitory effect of C/EBPα S21G on IL-10 promoter activity was not modulated by IL-32β. Taken together, our results show that IL-32β-mediated C/EBPα Ser-21 phosphorylation by PKCδ suppressed C/EBPα binding to IL-10 promoter, which promoted IL-10 production in U937 cells.

title: Identification of the most active interleukin‐32 isoform
abstract: Cytokines are crucial in host defence against pathogens such as bacteria, viruses, fungi and parasites. A newly described cytokine, interleukin‐32 (IL‐32), induces various proinflammatory cytokines (tumour necrosis factor‐α, IL‐1β, IL‐6) and chemokines in both human and mouse cells through the nuclear factor‐κB and p38 mitogen‐activated protein kinase inflammatory signal pathway. The IL‐32 primarily acts on monocytic cells rather than T cells. In an attempt to isolate the IL‐32 soluble receptor, we used an IL‐32 ligand‐affinity column to purify neutrophil proteinase 3, which is a serine proteinase involved in many inflammatory diseases. IL‐32 has biological activity associated with Mycobacterium tuberculosis and chronic proinflammatory diseases such as rheumatoid arthritis. IL‐32 is transcribed as six alternative splice variants and the biological activity of each individual isoform remains unknown. Here, we cloned the complementary DNA of the four IL‐32 isoforms (α, β, γ and δ) that are the most representative IL‐32 transcripts. To produce recombinant protein with a high yield, the amino acids of two cysteine residues were mutated to serine residues, because serine residues are not conserved among different species. The multi‐step purified recombinant IL‐32 isoform proteins were assessed for their biological activities with different cytokine assays. The γ isoform of IL‐32 was the most active, although all isoforms were biologically active. The present study will provide a specific target to neutralize endogenous IL‐32, which may contribute to basic and clinical immunology.

title: Mycobacterium tuberculosis Induces Interleukin-32 Production through a Caspase- 1/IL-18/Interferon-γ-Dependent Mechanism
abstract: (IL)–32 is a newly described proinflammatory cytokine that seems likely to play a role in inflammation and host defense. Little is known about the regulation of IL-32 production by primary cells of the immune system.  In the present study, freshly obtained human peripheral blood mononuclear cells were stimulated with different Toll-like receptor (TLR) agonists, and gene expression and synthesis of IL-32 was determined. We demonstrate that the TLR4 agonist lipopolysaccharide induces moderate (4-fold) production of IL-32, whereas agonists of TLR2, TLR3, TLR5, or TLR9, each of which strongly induced tumor necrosis factor α and IL-6, did not stimulate IL-32 production. However, the greatest amount of IL-32 was induced by the mycobacteria Mycobacterium tuberculosis and M. bovis BCG (20-fold over unstimulated cells). IL-32-induced synthesis by either lipopolysaccharide or mycobacteria remains entirely cell-associated in monocytes; moreover, steady-state mRNA levels are present in unstimulated monocytes without translation into IL-32 protein, similar to other cytokines lacking a signal peptide. IL-32 production induced by M. tuberculosis is dependent on endogenous interferon-γ (IFNγ); endogenous IFNγ is, in turn, dependent on M. tuberculosis–induced IL-18 via caspase-1.  In conclusion, IL-32 is a cell-associated proinflammatory cytokine, which is specifically stimulated by mycobacteria through a caspase-1- and IL-18-dependent production of IFNγ.

title: Protein sulfation analysis--A primer.
abstract: The aim of this review is to present an overview of protein sulfation in the context of 'modificomics', i.e. post-translational modification-specific proteome research. In addition to a short introduction to the biology of protein sulfation (part 1), we will provide detailed discussion regarding (i) methods and tools for prediction of protein tyrosine sulfation sites (part 2), (ii) biochemical techniques used for protein sulfation analysis (part 3.1), and (iii) mass spectrometric strategies and methods applied to protein sulfation analysis (part 3.2). We will highlight strengths and limitations of different strategies and approaches (including references), providing a primer for newcomers to protein sulfation analysis.

title: Native IL-32 is released from intestinal epithelial cells via a non-classical secretory pathway as a membrane-associated protein.
abstract: Although IL-32 has been shown to be induced under various pathological conditions, a detailed understanding of native IL-32 intracellular distribution and mechanism of release from cells has not been reported. We examined the expression of IL-32 in the intestinal epithelial cell line HT-29 following TNFα and IFNγ co-stimulation. The subcellular localization of induced IL-32 was associated with the membrane of lipid droplet-like structures and vacuolar structures that co-localized with markers of endosomes and lysosomes. Prolonged co-stimulation resulted in cell death and appearance of IL-32 in the culture medium. IL-32 released from co-stimulated HT-29 cells was found in a detergent-sensitive particulate fraction, and in a step density gradient the IL-32 particulate was buoyant, suggesting association with a membrane-bound vesicle. Upon Triton X-114 partitioning, most of the IL-32 partitioned to the detergent phase, suggesting hydrophobic characteristics. When IL-32-containing vesicles were subjected to protease K treatment, a protease resistant ∼12kDa fragment was generated from ∼24kDa IL-32. We propose that under these conditions, native IL-32 is released via a non-classical secretory route perhaps involving multi-vesicular bodies and exosomes. Demonstration of membrane association for both intracellular and released IL-32 suggests this unique cytokine may have a complex biosynthetic pathway and mechanism of action.

title: Interactions between IL-32 and tumor necrosis factor alpha contribute to the exacerbation of immune-inflammatory diseases
abstract: IL-32 is a newly described cytokine in the human found to be an in vitro inducer of tumor necrosis factor alpha (TNFα). We examined the in vivo relationship between IL-32 and TNFα, and the pathologic role of IL-32 in the TNFα-related diseases – arthritis and colitis. We demonstrated by quantitative PCR assay that IL-32 mRNA was expressed in the lymphoid tissues, and in stimulated peripheral T cells, monocytes, and B cells. Activated T cells were important for IL-32 mRNA expression in monocytes and B cells. Interestingly, TNFα reciprocally induced IL-32 mRNA expression in T cells, monocyte-derived dendritic cells, and synovial fibroblasts. Moreover, IL-32 mRNA expression was prominent in the synovial tissues of rheumatoid arthritis patients, especially in synovial-infiltrated lymphocytes by in situ hybridization. To examine the in vivo relationship of IL-32 and TNFα, we prepared an overexpression model mouse of human IL-32β (BM-hIL-32) by bone marrow transplantation. Splenocytes of BM-hIL-32 mice showed increased expression and secretion of TNFα, IL-1β, and IL-6 especially in response to lipopolysaccharide stimulation. Moreover, serum TNFα concentration showed a clear increase in BM-hIL-32 mice. Cell-sorting analysis of splenocytes showed that the expression of TNFα was increased in resting F4/80+ macrophages, and the expression of TNFα, IL-1β and IL-6 was increased in lipopolysaccharide-stimulated F4/80+ macrophages and CD11c+ dendritic cells. In fact, BM-hIL-32 mice showed exacerbation of collagen-antibody-induced arthritis and trinitrobenzen sulfonic acid-induced colitis. In addition, the transfer of hIL-32β-producing CD4+ T cells significantly exacerbated collagen-induced arthritis, and a TNFα blockade cancelled the exacerbating effects of hIL-32β. We therefore conclude that IL-32 is closely associated with TNFα, and contributes to the exacerbation of TNFα-related inflammatory arthritis and colitis.

title: Dendritic Cell–Derived IL-32α: A Novel Inhibitory Cytokine of NK Cell Function
abstract: Cytokines produced by dendritic cells (DCs) can largely determine the direction of immunity. Transcriptional analysis revealed that besides IL-15, IL-32 was the only other cytokine expressed by human Langerhans cells. IL-32 is a human cytokine that exists in four main isoforms. Currently, little is known about the regulation and function of the various IL-32 isoforms. In this study, we found that IL-15 is a potent inducer of IL-32α in DCs. Because IL-15 promotes NK cell activation, we investigated the interplay between IL-32 and IL-15 and their role in NK cell activity. We show that IL-32α acts on NK cells to inhibit IL-15–mediated STAT5 phosphorylation and to suppress their IL-15–induced effector molecule expression and cytolytic capacity. IL-32α also acted on DCs by downregulating IL-15–induced IL-18 production, an important cytokine in NK cell activity. Blocking IL-32α during DC:NK cell coculture enhanced NK cell effector molecule expression as well as their cytolytic capacity. Taken together, our findings suggest a feedback inhibition of IL-15–mediated NK cell activity by IL-32α.

title: Interleukin‐32: A new proinflammatory cytokine involved in hepatitis C virus‐related liver inflammation and fibrosis
abstract: Interleukin 32 (IL‐32) is a recently described proinflammatory cytokine that activates p38 mitogen‐activated protein kinase (MAPK) and nuclear factor kappa B (NF‐κB), thereby inducing proinflammatory cytokines such as IL‐1β and tumor necrosis factor alpha (TNF‐α). We investigated the role of IL‐32 in patients with chronic hepatitis C virus (HCV) infection. Steady‐state hepatic messenger RNA (mRNA) levels of IL‐32 were determined in a cohort of 90 subjects; anti‐IL‐32 staining was used in a second cohort of 132 consecutive untreated chronic HCV patients. Correlations with histological features of steatosis, inflammation, and fibrosis were made. In vitro, endogenous IL‐32 in monocytes and in the human hepatoma cell line Huh‐7.5 were examined. The effects of IL‐32‐overexpression and IL‐32‐silencing on HCV replication were studied using HCV luciferase reporter viruses. There were highly significant positive associations between hepatic IL‐32 mRNA expression and liver steatosis, inflammation, fibrosis, smooth muscle actin (SMA) area, and serum alanine aminotransferase (ALT) levels. IL‐32 protein expression was positively associated with portal inflammation, SMA area, and ALT. In vitro, IL‐1β and TNF‐α significantly induced IL‐32 expression in human Huh‐7.5 cells. Alone, stimulation with interferon alpha (IFN‐α) did not induce IL‐32 expression in Huh‐7.5. However, IFN‐α exerted a significant additive effect on TNF‐α‐induced but not IL‐1β‐induced IL‐32 expression, particularly in CD14+ monocytes. This effect was dependent both on NF‐κB and Jak/STAT signaling. Viral infection of Huh‐7.5 cells resulted in a significant (11‐fold) induction of IL‐32 mRNA expression. However, modulation of IL‐32 in Huh‐7.5 cells by overexpression or silencing did not influence HCV virus replication as determined by luciferase assays.  IL‐32 is a novel proinflammatory cytokine involved in HCV‐associated liver inflammation/fibrosis. IL‐32 is expressed by human hepatocytes and hepatoma cells and its expression is regulated by proinflammatory stimuli. (HEPATOLOGY 2011;)

title: Effects of 30 min of aerobic exercise on gene expression in human neutrophils.
abstract: Relatively brief bouts of exercise alter gene expression in peripheral blood mononuclear cells (PBMCs), but whether exercise changes gene expression in circulating neutrophils (whose numbers, like PBMCs, increase) is not known. We hypothesized that exercise would activate neutrophil genes involved in apoptosis, inflammation, and cell growth and repair, since these functions in leukocytes are known to be influenced by exercise. Blood was sampled before and immediately after 30 min of constant, heavy ( approximately 80% peak O(2) uptake) cycle ergometer exercise in 12 healthy men (19-29 yr old) of average fitness. Neutrophils were isolated using density gradients; RNA was hybridized to Affymetrix U133+2 Genechip arrays. With false discovery rate (FDR) <0.05 with 95% confidence, a total of 526 genes were differentially expressed between before and after exercise. Three hundred and sixteen genes had higher expression after exercise. The Jak/STAT pathway, known to inhibit apoptosis, was significantly activated (EASE score, P < 0.005), but 14 genes were altered in a way likely to accelerate apoptosis as well. Similarly, both proinflammatory (e.g., IL-32, TNFSF8, and CCR5) and anti-inflammatory (e.g., ANXA1) were affected. Growth and repair genes like AREG and FGF2 receptor genes (involved in angiogenesis) were also activated. Finally, a number of neutrophil genes known to be involved in pathological conditions like asthma and arthritis were altered by exercise, suggesting novel links between physical activity and disease or its prevention. In summary, brief heavy exercise leads to a previously unknown substantial and significant alteration in neutrophil gene expression.

title: Synthetic double-stranded RNA induces interleukin-32 in bronchial epithelial cells
abstract: Interleukin (IL)-32 is a novel cytokine and is involved in the pathogenesis of various inflammatory diseases, including asthma and COPD. However, the regulatory mechanisms of IL-32 expression and its precise pathogenic role remain to be defined. Given that viral infections are known to potentially cause and exacerbate airway inflammation, in this study, we investigated the expression of IL-32 induced by synthetic double-stranded (ds) RNA, and its signaling mechanisms involved.  Bronchial epithelial cells were stimulated with synthetic dsRNA poly I:C. The levels of IL-32 expression were analyzed using real-time PCR and ELISA. The involvement of transforming growth factor β-activated kinase 1 (TAK1) and a subunit of nuclear factor-κB (NF-κB), p65 was determined by western blot analyses. TAK1 inhibitor, 5Z-7-Oxozeaenol and NF-κB inhibitor, BAY 11-7082 were added to the culture to identify key signaling events leading to the expression of IL-32. Finally, the effect of short interfering RNAs (siRNAs) targeting TAK1 and p65 was investigated.  dsRNA significantly induced IL-32 gene and protein expression, concomitant with activation of TAK1 and p65. Pretreatment of 5Z-7-Oxozeaenol diminished dsRNA-induced phosphorylation of NF-κB. Both 5Z-7-Oxozeaenol and BAY 11-7082 significantly abrogated dsRNA-induced IL-32 production. Moreover, transfection of the cells with siRNAs targeting TAK1 and p65 inhibited the expression of IL-32.  The expression of IL-32 is induced by dsRNA via the TAK1-NF-κB signaling pathway in bronchial epithelial cells. IL-32 is involved in the pathogenesis of airway inflammation, and may be a novel therapeutic target for airway inflammatory diseases.

title: IL-32–dependent effects of IL-1β on endothelial cell functions
abstract: Increasing evidence demonstrates that interleukin (IL)–32 is a pro-inflammatory cytokine, inducing IL-1α, IL-1β, IL-6, tumor necrosis factor (TNF)–α, and chemokines via nuclear factor (NF)–κB, p38 mitogen-activated protein kinase (MAPK), and activating protein (AP)-1 activation. Here we report that IL-32 is expressed and is also functional in human vascular endothelial cells (EC) of various origins. Compared with primary blood monocytes, high levels of IL-32 are constitutively produced in human umbilical vein EC (HUVEC), aortic macrovascular EC, and cardiac as well as pulmonary microvascular EC. At concentrations as low as 0.1 ng/ml, IL-1β stimulated IL-32 up to 15-fold over constitutive levels, whereas 10 ng/ml of TNFα or 100 ng/ml of lipopolysaccharide (LPS) were required to induce similar quantities of IL-32. IL-1β–induced IL-32 was reduced by inhibition of the IκB kinase-β/NF-κB and ERK pathways. In addition to IL-1β, pro-coagulant concentrations of thrombin or fresh platelets increased IL-32 protein up to 6-fold. IL-1β and thrombin induced an isoform-switch in steady-state mRNA levels from IL-32α/γ to β/ε. Adult EC responded in a similar fashion. To prove functionality, we silenced endogenous IL-32 with siRNA, decreasing intracellular IL-32 protein levels by 86%. The knockdown of IL-32 resulted in reduction of constitutive as well as IL-1β–induced intercellular adhesion molecule–1 (ICAM-1) (of 55% and 54%, respectively), IL-1α (of 62% and 43%), IL-6 (of 53% and 43%), and IL-8 (of 46% and 42%). In contrast, the anti-inflammatory/anti-coagulant CD141/thrombomodulin increased markedly when IL-32 was silenced. This study introduces IL-32 as a critical regulator of endothelial function, expanding the properties of this cytokine relevant to coagulation, endothelial inflammation, and atherosclerosis.

title: Tumor necrosis factor alpha-induced interleukin-32 is positively regulated via the Syk/protein kinase Cdelta/JNK pathway in rheumatoid synovial fibroblasts.
abstract: Interleukin-32 (IL-32) is a recently discovered cytokine that appears to play a critical role in human rheumatoid arthritis (RA). It is highly expressed in synovium and fibroblast-like synoviocytes (FLS) from RA patients, but not in patients with osteoarthritis (OA). This study was undertaken to assess IL-32 levels in RA synovial fluid (SF) and to investigate the secretion and regulation of IL-32 in RA FLS.



FLS and SF were obtained from the joints of RA patients. The secretion and expression of IL-32 and activation of signaling molecules were examined by enzyme-linked immunosorbent assay, immunoblotting, immunoprecipitation, reverse transcriptase-polymerase chain reaction, and small interfering RNA (siRNA) transfection.



IL-32 levels were high in RA SF compared with OA SF. Furthermore, RA FLS expressed and secreted IL-32 when stimulated with tumor necrosis factor alpha (TNFalpha). TNFalpha-induced expression of IL-32 was significantly suppressed, in a dose-dependent manner, by inhibitors of Syk, protein kinase Cdelta (PKCdelta), and JNK and by knockdown of these kinases and c-Jun with siRNA. We also observed that PKCdelta mediated the activation of JNK and c-Jun, and experiments using specific inhibitors and siRNA demonstrated that Syk was the upstream kinase for the activation of PKCdelta.



The present findings suggest that IL-32 may be a newly identified prognostic biomarker in RA, thereby adding valuable knowledge to the understanding of this disease. The results also demonstrate that the production of IL-32 in RA FLS is regulated by Syk/PKCdelta-mediated signaling events.

title: Unique expression of a small IL-32 protein in the Jurkat leukemic T cell line.
abstract: Interleukin (IL)-32 was recently identified as a new cytokine which induces various proinflammatory cytokines in human monocytes and macrophages. Therefore, IL-32 has been primarily studied in inflammatory models such as rheumatoid arthritis and inflammatory bowel diseases. The regulation of endogenous IL-32 in other immune cells remains unknown. In the present study, we stimulated Jurkat T cells with phytohaemagglutinin (PHA) and phorbol myristate acetate (PMA) and examined IL-32 expression at both the mRNA and protein levels. All mRNAs of the four IL-32 isoforms and the 12-15 kDa IL-32 protein were independent of PHA and PMA stimulation, however a 9 kDa molecular weight IL-32 protein in the cell culture supernatant was induced by PHA and PMA after 16 h of stimulation. Compared to other human cell lines, the Jurkat cell line constitutively expressed a 12-15 kDa molecule of IL-32, which is smaller than the known IL-32 isoforms. We used IL-32 shRNA to examine the specificity of the 12-15 kDa molecule. Upon IL-32 shRNA transfection, the 12-15 kDa band was decreased specifically as compared to the control scrambled clone. Thus, the constitutive expression of IL-32 mRNA as well as the predominant production of a smaller sized IL-32 isoform in Jurkat cells may implicate a role for IL-32 in human T cell leukemia.

title: Activation of Interleukin-32 Pro-Inflammatory Pathway in Response to Influenza A Virus Infection
abstract: Interleukin (IL)-32 is a recently described pro-inflammatory cytokine that has been reported to be induced by bacteria treatment in culture cells. Little is known about IL-32 production by exogenous pathogens infection in human individuals.  In this study, we found that IL-32 level was increased by 58.2% in the serum samples from a cohort of 108 patients infected by influenza A virus comparing to that of 115 healthy individuals. Another pro-inflammatory factor cyclooxygenase (COX)-2-associated prostaglandin E2 was also upregulated by 2.7-fold. Expression of IL-32 in influenza A virus infected A549 human lung epithelial cells was blocked by either selective COX-2 inhibitor NS398 or Aspirin, a known anti-inflammatory drug, indicating IL-32 was induced through COX-2 in the inflammatory cascade. Interestingly, we found that COX-2-associate PGE2 production activated by influenza virus infection was significantly suppressed by over-expression of IL-32 but increased by IL-32-specific siRNA, suggesting there was a feedback mechanism between IL-32 and COX-2.  IL-32 is induced by influenza A virus infection via COX-2 in the inflammatory cascade. Our results provide that IL-32 is a potential target for anti-inflammatory medicine screening.

title: IL-32: A Host Proinflammatory Factor against Influenza Viral Replication Is Upregulated by Aberrant Epigenetic Modifications during Influenza A Virus Infection
abstract: Our previous studies with clinical data analysis have shown that the proinflammatory factor IL-32 is activated in response to influenza virus infection. However, little is known about how influenza virus induces IL-32 production, and the role of IL-32 in the host immune responses during viral infection remains unclear. In this study, we show that IL-32 production is stimulated by influenza A virus or dsRNA in human PBMCs from healthy volunteers. We demonstrate that the NF-κB and CREB pathways play key roles in the activation of IL-32 production in response to influenza virus infection in A549 human lung epithelial cells. We then show that aberrant epigenetic modifications in the IL32 promoter are important in the transcriptional regulation of IL-32 expression. Interestingly, one CpG demethylation within the CREB binding site increases the binding of CREB to the promoter, which is followed by IL32 transcriptional activation in influenza A virus-infected cells. Overexpression assays combined with RNA interference show that DNA methyltransferases DNMT1 and DNMT3b are critical for IL32 promoter methylation and gene silencing before viral infection. We have demonstrated the anti-influenza virus function of IL-32. Assays for each of the six IL-32 isoforms (α, β, γ, δ, ε, and ζ) during influenza virus infection indicated that all the isoforms have antiviral activity, with different inhibitory rates, and that the effect of IL-32γ is strongest. Our results indicate that the elevated IL-32 levels triggered by influenza virus infection in turn hamper viral replication.

title: Interleukin-32 Expression in the Pancreas
abstract: Interleukin (IL)-32 is a recently described proinflammatory cytokine characterized by the induction of nuclear factor (NF)-κB activation. We studied IL-32 expression in human pancreatic tissue and pancreatic cancer cell lines. Tissue samples were obtained surgically. IL-32 expression was evaluated by standard immunohistochemical procedures. IL-32 mRNA expression was analyzed by Northern blotting and real time PCR analyses. IL-32 was weakly immunoexpressed by pancreatic duct cells. In the inflamed lesions of chronic pancreas, the ductal expression of IL-32 was markedly increased. A strong expression of IL-32α was detected in the pancreatic cancer cells. In pancreatic cancer cell lines (PANC-1, MIA PaCa-2, and BxPC-3 cells), the expression of IL-32 mRNA and protein was enhanced by IL-1β, interferon (IFN)-γ, and tumor necrosis factor (TNF)-α. An inhibitor of phosphatidylinositol 3-kinase (LY294002) significantly suppressed the IL-1β-, IFN-γ- and TNF-α-induced IL-32 mRNA expression. The blockade of NF-κB and activated protein-1 activation markedly suppressed the IL-1β-, IFN-γ-, and/or TNF-α-induced IL-32 mRNA expression. Furthermore, IL-32-specific small interfering RNA significantly decreased the uptake of [3H]thymidine and increased the annexin V-positive population (apoptotic cells) in PANC-1 cells. IL-32 knockdown also suppressed the mRNA expression of antiapoptotic proteins (Bcl-2, Bcl-xL, and Mcl-1). Pancreatic duct cells are the local source of IL-32, and IL-32 may play an important role in inflammatory responses and pancreatic cancer growth.

title: Dysregulation of IL-32 in myelodysplastic syndrome and chronic myelomonocytic leukemia modulates apoptosis and impairs NK function
abstract: TNFα levels are elevated in the marrows of patients with myelodysplastic syndrome (MDS) and are associated with high rates of apoptosis, which contributes to hematopoietic failure. We observed that exposure of human marrow stroma cell lines HS5 and HS27a to TNFα increases levels of IL-32 mRNA. IL-32, in turn, induces TNFα. Marrow stroma from patients with MDS expressed 14- to 17-fold higher levels of IL-32 mRNA than healthy controls. In contrast, cells from patients with chronic myelomonocytic leukemia (CMML) expressed only one tenth the level of IL-32 measured in healthy controls. Human KG1a leukemia cells underwent apoptosis when cocultured with HS5 stromal cells, but knockdown of IL-32 in the stromal cells by using siRNA abrogated apoptosis in the leukemia cells. IL-32 knockdown cells also showed dysregulation of VEGF and other cytokines. Furthermore, CD56+ natural killer cells from patients with MDS and CMML expressed IL-32 at lower levels than controls and exhibited reduced cytotoxic activity, which was unaffected by IL-2 treatment. We propose that IL-32 is a marrow stromal marker that distinguishes patients with MDS and CMML. Furthermore, IL-32 appears to contribute to the pathophysiology of MDS and may be a therapeutic target.

title: The effects of IL-32 on the inflammatory activation of cultured rat primary astrocytes.
abstract: A new family of cytokine IL-32 has been implicated in pro-inflammatory immune responses several human diseases such as rheumatoid arthritis, inflammatory bowel diseases and vasculitis. In this study, we investigated the role of IL-32 in the inflammatory activation of cultured rat primary astrocytes. Treatment of IL-32 increased ROS production and augmented lipopolysaccharide-induced increased production of nitric oxide as well as the expression of iNOS. IL-32 also induced the expression of MMP-9 but not MMP-2 in rat primary astrocytes. The increased expression of these inflammatory mediators was accompanied by the increased mRNA expression encoding iNOS, MMP-9 and TNF-α. ERK1/2 and p38, two essential regulators of pro-inflammatory signaling in rat primary astrocytes were activated by IL-32 as evidenced by increased phosphorylation. The results from the present study suggest that IL-32 may play a role in the regulation of neuroinflammatory responses in several neurological disease conditions such as ischemia and Alzheimer's disease.

title: Suppressing IL-32 in monocytes impairs the induction of the proinflammatory cytokines TNFalpha and IL-1beta.
abstract: Targeting major proinflammatory cytokines such as IL-1beta and TNFalpha is of great interest in patients with chronic inflammatory diseases, including rheumatoid arthritis, colitis, and psoriasis. The cytokine Interleukin (IL)-32 induces proinflammatory cytokines such as TNFalpha, IL-1beta, IL-6, and chemokines. We previously used an IL-32 ligand-affinity column to purify proteinase 3, which is abundantly expressed in neutrophil and monocytic leukocytes but not in other cell types, and found that IL-32 is mainly produced by monocytic leukocytes. This evidence suggested that silencing endogenous IL-32 by short hairpin RNA (shRNA) in monocytic cells might reveal the precise function of endogenous IL-32. Indeed, lipopolysaccharide (LPS)- or phorbol myristate acetate (PMA)-induced proinflammatory cytokine production was significantly inhibited in shRNA/IL-32 stable clones as compared to control clones. Furthermore, macrophages in PMA-differentiated shRNA/IL-32 stable clones displayed remarkably impaired LPS- and IL-1beta-induced proinflammatory cytokine production. These data suggest that IL-32 is not only involved in host defense against pathogens, but also might play a role in chronic inflammatory diseases. IL-32 production leads to major proinflammatory cytokine production during the initial immune response.

title: Cloning and characterization of bovine interleukin-32 beta isoform.
abstract: Interleukin-32 (IL-32) is a new cytokine produced mainly by T-cells, natural killer cells, and epithelial cells after stimulation with IL-2, IL-12 plus IL-18, and IFNgamma, respectively. IL-32 induces various proinflammatory cytokines such as TNFalpha, IL-1beta, IL-6, and IL-8 in monocytes and macrophages. In this study, we cloned bovine IL-32 cDNA from peripheral blood mononuclear cells (PBMC) of a Holstein (Bos Taurus). The bovine IL-32 cDNA has an entire open reading frame, encoding 171 amino acid residues and the deduced amino acid sequence has 27.5% identity with human IL-32 beta isoform. Recombinant bovine IL-32 protein was produced in E. coli and its molecular weight was approximately 26kDa. The biological activity of the bovine IL-32 was examined for cytokine induction using human monocytic THP-1 cells and bovine PBMC. The THP-1 cells responded to stimulation by recombinant bovine IL-32 and produced IL-8. Stimulation by recombinant bovine IL-32 induced mRNA for TNFalpha and IL-6 in bovine PBMC suggesting conservation of the biological activity and function in cattle.

title: IL-32θ downregulates CCL5 expression through its interaction with PKCδ and STAT3.
abstract: Interleukin-32 (IL-32) exists in several isoforms and plays an important role in inflammatory response. Recently, we identified a new isoform, IL-32θ, and performed a microarray analysis to identify IL-32θ-regulated genes in THP-1 myelomonocytic cells. Upon stimulating IL-32θ-expressing THP-1 cells with phorbol myristate acetate (PMA), we found that the CCL5 transcript level was significantly reduced. We confirmed the downregulation of CCL5 protein expression by using an enzyme-linked immunosorbent assay (ELISA). Because STAT3 phosphorylation on Ser727 by PKCδ is reported to suppress CCL5 protein expression, we examined whether IL-32θ-mediated STAT3 Ser727 phosphorylation occurs through an interaction with PKCδ. In this study, we first demonstrate that IL-32θ interacts with PKCδ and STAT3 using co-immunoprecipitation (Co-IP) and pulldown assay. Moreover, STAT3 was rarely phosphorylated on Ser727 in the absence of IL-32θ, leading to the binding of STAT3 to the CCL5 promoter. These results indicate that IL-32θ, through its interaction with PKCδ, downregulates CCL5 expression by mediating the phosphorylation of STAT3 on Ser727 to render it transcriptionally inactive. Therefore, similar to what we have reported for IL-32α and IL-32β, our data from this study suggests that the newly identified IL-32θ isoform also acts as an intracellular modulator of inflammation.

title: Human cathelicidin LL‐37 and its derivative IG‐19 regulate interleukin‐32‐induced inflammation
abstract: Human cathelicidin LL‐37 protects against infections and endotoxin‐induced inflammation. In a recent study we have shown that IG‐19, an LL‐37‐derived peptide, protects in a murine model of arthritis. Cytokine interleukin‐32 (IL‐32) is elevated and directly associated with the disease severity of inflammatory arthritis. Therefore, in this study we examined the effects of LL‐37 and IG‐19 on IL‐32‐induced responses in human peripheral blood‐derived mononuclear cells (PBMC) and macrophages. We showed that CD14+ monocytes are the primary cells that produce pro‐inflammatory tumour necrosis factor‐α (TNF‐α) following stimulation of PBMC with IL‐32. We demonstrated that LL‐37 and IG‐19 significantly suppress IL‐32‐induced production of pro‐inflammatory cytokines, e.g. TNF‐α and IL‐1β, without altering chemokine production. In contrast, LL‐37 and IG‐19 enhance the production of the anti‐inflammatory cytokine IL‐1RA. Further mechanistic studies revealed that LL‐37 and IG‐19 suppress IL‐32‐mediated phosphorylation of Fyn (Y420) Src kinase. In contrast, IL‐32‐mediated phosphorylation of AKT‐1 (T308) and MKP‐1 (S359) is not suppressed by the peptides. LL‐37 and IG‐19 alone induce the phosphorylation of MKP‐1 (S359), which is a known negative regulator of inflammation. Furthermore, the peptides induce the activity of p44/42 mitogen‐activated protein kinase, which is known to phosphorylate MKP‐1 (S359). This is the first study to demonstrate the regulation of IL‐32‐induced inflammation by LL‐37 and its derivative peptide IG‐19. The mechanistic results from this study suggest that regulation of immune‐mediated inflammation by these peptides may be controlled by the dual phosphatase MKP‐1. We speculate that LL‐37 and its derivatives may contribute to the control of immune‐mediated inflammatory diseases.

title: Inflammatory Cytokines IL-32 and IL-17 Have Common Signaling Intermediates despite Differential Dependence on TNF-Receptor 1
abstract: Cytokines IL-32 and IL-17 are emerging as critical players in the pathophysiology of immune-mediated chronic inflammatory diseases. It has been speculated that the molecular mechanisms governing IL-32– and IL-17–mediated cellular responses are differentially dependent on the TNF pathway. In this study, kinome analysis demonstrated that following stimulation with cytokine IL-32, but not IL-17, there was increased phosphorylation of a peptide target corresponding to TNF-R1. Consistent with this observation, blocking TNF-R1 resulted in a suppression of IL-32–induced downstream responses, indicating that IL-32–mediated activity may be dependent on TNF-R1. In contrast, blocking TNF-R1 did not affect IL-17–induced downstream responses. Kinome analysis also implicated p300 (transcriptional coactivator) and death-associated protein kinase-1 (DAPK-1) as signaling intermediates for both IL-32 and IL-17. Phosphorylation of p300 and DAPK-1 upon stimulation with either IL-32 or IL-17 was confirmed by immunoblots. The presence of common targets was supported by results demonstrating similar downstream responses induced in the presence of IL-32 and IL-17, such as transcriptional responses and the direct activation of NF-κB. Furthermore, knockdown of p300 and DAPK-1 altered downstream responses induced by IL-32 and IL-17, and impacted certain cellular responses induced by TNF-α and IL-1β. We hypothesize that p300 and DAPK-1 represent nodes where the inflammatory networks of IL-32 and IL-17 overlap, and that these proteins would affect both TNF-R1–dependent and –independent pathways. Therefore, p300 and DAPK-1 are viable potential therapeutic targets for chronic inflammatory diseases.

title: IL-32-PAR2 axis is an innate immunity sensor providing alternative signaling for LPS-TRIF axis
abstract: Interleukin (IL)-32 is known to exert adujvant effects on innate immune response, however, receptors and downstream signaling pathways remain to be clarified. Here we found that IL-32γ upregulated serine protease activity of proteinase-3 (PR3), in turn triggering protease-activated receptor 2 (PAR2) signaling. Interestingly, silencing of PR3 or PAR2 using siRNA markedly diminished IL-32γ-induced TNFα and IFN-β mRNA expression. IL-32γ-PAR2 axis utilized TRIF and Ras-Raf-1 pathways. On stimulation with lipopolysaccharide (LPS), differential activation of protein kinase C isoforms modulated the balance between LPS-TLR4-TRIF and IL-32-PAR2-TRIF axes, because LPS was a strong inducer of IL-32γ. IL-32-PAR2-TRIF axis might serve not only as an extracellular sensor of bacterial and autologous proteases, but also as a modulator of innate and adaptive immunity during infection.

title: Decreased severity of collagen antibody and lipopolysaccharide-induced arthritis in human IL-32β overexpressed transgenic mice
abstract: Interleukin (IL)-32, mainly produced by T-lymphocytes, natural killer cells, epithelial cells, and blood monocytes, is dominantly known as a pro-inflammatory cytokine. However, the role of IL-32 on inflammatory disease has been doubtful according to diverse conflicting results. This study was designed to examine the role of IL-32β on the development of collagen antibody (CAIA) and lipopolysaccharide (LPS)-induced inflammatory arthritis. Our data showed that the paw swelling volume and clinical score were significantly reduced in the CAIA and LPS-treated IL-32β transgenic mice compared with non-transgenic mice. The populations of cytotoxic T, NK and dendritic cells was inhibited and NF-κB and STAT3 activities were significantly lowered in the CAIA and LPS-treated IL-32β transgenic mice. The expression of pro-inflammatory proteins was prevented in the paw tissues of CAIA and LPS-treated IL-32β transgenic mice. In addition, IL-32β altered several cytokine levels in the blood, spleen and paw joint. Our data indicates that IL-32β comprehensively inhibits the inflammation responses in the CAIA and LPS-induced inflammatory arthritis model.

title: Interleukin-32α Inhibits Endothelial Inflammation, Vascular Smooth Muscle Cell Activation, and Atherosclerosis by Upregulating Timp3 and Reck through suppressing microRNA-205 Biogenesis
abstract: Interleukin-32 (IL-32) is a multifaceted cytokine that promotes inflammation and regulates vascular endothelial cell behavior. Although some IL-32 isoforms have been reported to contribute to vascular inflammation and atherosclerosis, the functional role of IL-32α in vascular inflammation and atherogenesis has not been studied.  IL-32α function was assessed in cells with transient IL-32α overexpression or treated with recombinant human IL-32α by western blotting and mRNA expression analysis. Vascular smooth muscle cell (VSMC) proliferation and migration was examined by BrdU incorporation and wound healing assays, respectively. In addition, the participation of IL-32α on vascular inflammation, arterial wall thickening, and atherosclerosis in vivo was monitored in human IL-32α transgenic (hIL-32α-Tg) mice with or without ApoE knockout (ApoE-/-/hIL-32α-Tg).  Our analyses showed that IL-32α suppresses genes involved in the inflammatory and immune responses and cell proliferation, and by limiting matrix metalloproteinase (MMP) function. In vivo, administration of hIL-32α inhibited vascular inflammation and atherosclerosis in hIL-32α-Tg and ApoE-/-/hIL-32α-Tg mice. Subsequent microarray and in silico analysis also revealed a marked decreased in inflammatory gene expression in hIL-32α-Tg mice. Collectively, our studies demonstrated that IL-32α upregulates the atheroprotective genes Timp3 and Reck by downregulating microRNA-205 through regulation of the Rprd2-Dgcr8/Ddx5-Dicer1 biogenesis pathway.  Our findings provide the first direct evidence that IL-32α is an anti-inflammatory and anti-atherogenic cytokine that may be useful as a diagnostic and therapeutic protein in atherosclerosis.

title: Inhibition of PTEN Gene Expression by Oncogenic miR-23b-3p in Renal Cancer
abstract: However, the functional significance of miR-23b-3p in renal cell carcinoma (RCC) has not been reported.  We measured miR-23b-3p levels in 29 pairs of renal cell carcinoma and their normal matched tissues using real-time PCR. The expression level of miR-23b-3p was correlated with the 5 year survival rate of renal cancer patients. In 15 cases (52%), miR-23b-3p expression was found to be high. All patients with moderate to low miR-23b-3p expression survived 5 years, while those with high miR-23b-3p expression, only 50% survived. After knocking down miRNA-23b-3p expression in RCC cell lines, there was an induction of apoptosis and reduced invasive capabilities. MiR-23b-3p was shown to directly target PTEN gene through 3′UTR reporter assays. Inhibition of miR-23b-3p induces PTEN gene expression with a concomitant reduction in PI3-kinase, total Akt and IL-32. Immunohistochemistry showed the lack of PTEN protein expression in cancerous regions of tissue samples where the expression of miR-23b-3p was high. We studied the in vitro effects of the dietary chemo preventive agent genistein on miR-23b-3p expression and found that it inhibited expression of miR-23b-3p in RCC cell lines.  The current study shows that miR-23b-3p is an oncogenic miRNA and inhibits PTEN tumor suppressor gene in RCC. Therefore, inhibition of miR-23b-3p may be a useful therapeutic target for the treatment of renal cell carcinoma.

title: Caspase-3-independent apoptotic pathways contribute to interleukin-32γ-mediated control of Mycobacterium tuberculosis infection in THP-1 cells
abstract: BackgroundMacrophages are the primary effector cells responsible for killing Mycobacterium tuberculosis (MTB) through various mechanisms, including apoptosis. However, MTB can evade host immunity to create a favorable environment for intracellular replication. MTB-infected human macrophages produce interleukin-32 (IL-32). IL-32 is a pro-inflammatory cytokine and has several isoforms. We previously found that IL-32γ reduced the burden of MTB in human macrophages, in part, through the induction of caspase-3-dependent apoptosis. However, based on our previous studies, we hypothesized that caspase-3-independent death pathways may also mediate IL-32 control of MTB infection. Herein, we assessed the potential roles of cathepsin-mediated apoptosis, caspase-1-mediated pyroptosis, and apoptosis-inducing factor (AIF) in mediating IL-32γ control of MTB infection in THP-1 cells.ResultsDifferentiated human THP-1 macrophages were infected with MTB H37Rv alone or in the presence of specific inhibitors to caspase-1, cathepsin B/D, or cathepsin L for up to four days, after which TUNEL-positive cells were quantified; in addition, MTB was quantified by culture as well as by the percentage of THP-1 cells that were infected with green fluorescent protein (GFP)-labeled MTB as determined by microscopy. AIF expression was inhibited using siRNA technology. Inhibition of cathepsin B/D, cathepsin L, or caspase-1 activity significantly abrogated the IL-32γ-mediated reduction in the number of intracellular MTB and of the percentage of GFP-MTB-infected macrophages. Furthermore, inhibition of caspase-1, cathepsin B/D, or cathepsin L in the absence of exogenous IL-32γ resulted in a trend toward an increased proportion of MTB-infected THP-1 cells. Inhibition of AIF activity in the absence of exogenous IL-32γ also increased intracellular burden of MTB. However, since IL-32γ did not induce AIF and because the relative increases in MTB with inhibition of AIF were similar in the presence or absence of IL-32γ, our results indicate that AIF does not mediate the host-protective effect of IL-32γ against MTB.ConclusionsThe anti-MTB effects of IL-32γ are mediated through classical caspase-3-dependent apoptosis as well as caspase-3-independent apoptosis.

title: Mycobacterium tuberculosis PPE32 promotes cytokines production and host cell apoptosis through caspase cascade accompanying with enhanced ER stress response
abstract: Tuberculosis, caused by Mycobacterium tuberculosis (MTB) infection, remains a grave global public health burden which claims the lives around two to three million annually. PE and PPE proteins, featured by the Pro-Glu (PE) or Pro-Pro-Glu (PPE) motifs at the conserved N-terminal domain, are abundant in the MTB genome. PPE32 can increase intracellular survival of mycobacteria through abnormally increase in cytokines production. PPE32 might subvert the macrophage immune response and thwart its bactericidal effect. THP-1 macrophages treated with PPE32 or infected with Mycobacterium smegmatis (MS) expression PPE32 showed increase of cytokines production and multiple hallmarks of apoptosis. We found that PPE32 significantly increases the expression of IL-12p40 and IL-32 through ERK1/2 signaling pathway. In addition, the cell viability of macrophage was inhibited after PPE32 stimulation. We noted that PPE32 induces cleavage of caspase-3 and caspase-9, while inhibition of caspase activity significantly abrogates the PPE32-induced cell apoptosis. Moreover, PPE32 treatment promotes endoplasmic reticulum stress related gene expression, suggesting ER stress might be responsible for PPE32-induced cell apoptosis.

title: Tricks to translating TB transcriptomics.
abstract: Transcriptomics and other high-throughput methods are increasingly applied to questions relating to tuberculosis (TB) pathogenesis. Whole blood transcriptomics has repeatedly been applied to define correlates of TB risk and has produced new insight into the late stage of disease pathogenesis. In a novel approach, authors of a recently published study in Science Translational Medicine applied complex data analysis of existing TB transcriptomic datasets, and in vitro models, in an attempt to identify correlates of protection in TB, which are crucially required for the development of novel TB diagnostics and therapeutics to halt this global epidemic. Utilizing latent TB infection (LTBI) as a surrogate of protection, they identified IL-32 as a mediator of interferon gamma (IFNγ)-vitamin D dependent antimicrobial immunity and a marker of LTBI. Here, we provide a review of all TB whole-blood transcriptomic studies to date in the context of identifying correlates of protection, discuss potential pitfalls of combining complex analyses originating from such studies, the importance of detailed metadata to interpret differential patient classification algorithms, the effect of differing circulating cell populations between patient groups on the interpretation of resulting biomarkers and we decipher weighted gene co-expression network analysis (WGCNA), a recently developed systems biology tool which holds promise of identifying novel pathway interactions in disease pathogenesis. In conclusion, we propose the development of an integrated OMICS platform and open access to detailed metadata, in order for the TB research community to leverage the vast array of OMICS data being generated with the aim of unraveling the holy grail of TB research: correlates of protection.

title: IL-32 is a molecular marker of a host defense network in human tuberculosis
abstract: IL-32 links the microbicidal peptide pathway with resistance to disease progression in clinical tuberculosis. TB Sunny Side Up Interleukin-32 (IL-32) could be a correlate of protection against tuberculosis. Montoya et al. report that IL-32 is a potential candidate marker of host defense against tuberculosis. Mycobacterium tuberculosis causes a sometimes deadly infection that nonetheless only develops to disease in about 10% of individuals. The authors performed gene expression profiles of human macrophages and found an association between IL-32 and the vitamin D antimicrobial pathway. Moreover, analysis of five different clinical data sets suggested that IL-32 can serve as a molecular marker of latent tuberculosis and may be activated in response to signaling by IL-15. These data suggest that IL-32 may not only serve as a putative correlate of protection but also contribute directly to host response to tuberculosis. Tuberculosis is a leading cause of infectious disease–related death worldwide; however, only 10% of people infected with Mycobacterium tuberculosis develop disease. Factors that contribute to protection could prove to be promising targets for M. tuberculosis therapies. Analysis of peripheral blood gene expression profiles of active tuberculosis patients has identified correlates of risk for disease or pathogenesis. We sought to identify potential human candidate markers of host defense by studying gene expression profiles of macrophages, cells that, upon infection by M. tuberculosis, can mount an antimicrobial response. Weighted gene coexpression network analysis revealed an association between the cytokine interleukin-32 (IL-32) and the vitamin D antimicrobial pathway in a network of interferon-γ– and IL-15–induced “defense response” genes. IL-32 induced the vitamin D–dependent antimicrobial peptides cathelicidin and DEFB4 and to generate antimicrobial activity in vitro, dependent on the presence of adequate 25-hydroxyvitamin D. In addition, the IL-15–induced defense response macrophage gene network was integrated with ranked pairwise comparisons of gene expression from five different clinical data sets of latent compared with active tuberculosis or healthy controls and a coexpression network derived from gene expression in patients with tuberculosis undergoing chemotherapy. Together, these analyses identified eight common genes, including IL-32, as molecular markers of latent tuberculosis and the IL-15–induced gene network. As maintaining M. tuberculosis in a latent state and preventing transition to active disease may represent a form of host resistance, these results identify IL-32 as one functional marker and potential correlate of protection against active tuberculosis.

title: Mechanisms of Defense against Intracellular Pathogens Mediated by Human Macrophages.
abstract: The key question our work has sought to address has been, "What are the necessary and sufficient conditions that engender protection from intracellular pathogens in the human host?" The origins of this work derive from a long-standing interest in the mechanisms of protection against two such paradigmatic intracellular pathogens, Mycobacterium tuberculosis and Mycobacterium leprae, that have brilliantly adapted to the human host. It was obvious that these pathogens, which cause chronic diseases and persist in macrophages, must have acquired subtle strategies to resist host microbicidal mechanisms, yet since the vast majority of individuals infected with M. tuberculosis do not develop disease, there must be some potent human antimicrobial mechanisms. What follows is not a comprehensive review of the vast literature on the role of human macrophages in protection against infectious disease, but a summary of the research in our two laboratories with collaborators that we hope has contributed to some understanding of mechanisms of resistance and pathogenesis. While mouse models revealed some necessary conditions for protection, e.g., innate immunity, Th1 cells and their cytokines, and major histocompatibility complex class I-restricted T cells, here we emphasize multiple antimicrobial mechanisms that exist in human macrophages that differ from those of most experimental animals. Prominent here is the vitamin D-dependent antimicrobial pathway common to human macrophages activated by innate and acquired immune responses, mediated by antimicrobial peptides, e.g., cathelicidin, through an interleukin-15- and interleukin-32-dependent common pathway that is necessary for macrophage killing of M. tuberculosis in vitro.

title: Differential potentiation of anti‐mycobacterial activity and reactive nitrogen intermediate‐producing ability of murine peritoneal macrophages activated by interferon‐gamma (IFN‐γ) and tumour necrosis factor‐alpha (TNF‐α)
abstract: The anti‐mycobacterial activities of IFN‐γ and TNF‐α‐treated murine peritoneal macrophages were determined. Resident macrophages pretreated with IFN‐γ or TNF‐α for 2 days were infected with test organisms and subsequently cultured for up to 7 days. First, the early‐phase growth of Mycobacterium tuberculosis (days 0–3) was strongly suppressed in IFN‐γ‐treated macrophages, and progressive bacterial elimination was subsequently observed. Although TNF‐α treatment of macrophages did not affect the early phase growth of organisms, bacterial killing was observed in the later phase of cultivation. Second, although IFN‐γ‐treated macrophages killed M. avium during the first 3 days of culture, regrowth of the intracellular organisms was subsequently observed. TNF‐α treatment of macrophages did not influence the mode of intracellular growth of M. avium. Third, IFN‐γ but not TNF‐α enhanced production of reactive nitrogen intermediates (RNI) by macrophages infected with M. tuberculosis or M. avium, whereas both cytokines increased macrophage release of reactive oxygen intermediates (ROI). The present findings therefore show that IFN‐γ and TNF‐α potentiated the anti‐mycobacterial activity of murine peritoneal macrophages in different fashions. They also suggest that RNI played more important roles than did ROI in the expression of macrophage anti‐mycobacterial, particularly anti‐M. avium, activity.

title: NADPH Oxidase 2 Interaction with TLR2 Is Required for Efficient Innate Immune Responses to Mycobacteria via Cathelicidin Expression1
abstract: Gp91phox/NADPH oxidase (NOX) 2 is the main catalytic component of NOX, which mediates the phagocytic killing of ingested pathogens via the production of reactive oxygen species (ROS). However, Mycobacterium tuberculosis (Mtb) is relatively resistant to the microbicidal effects of ROS. Thus, the exact roles of NOX2 in the innate immune control against Mtb infection are not fully resolved. In this study, we show that NOX2 is essential for TLR2-dependent inflammatory responses and 1,25-dihydroxyvitamin D3 (1,25D3)-mediated antimicrobial activity against Mtb via cathelicidin expression. NOX2-null macrophages prominently abrogated Mtb-induced ROS production and inflammatory signaling activation in a TLR2-dependent manner. Mtb triggered a physical association between NOX2 and TLR2. In addition, the knockdown of NOX2 inhibited 1,25D3-triggered antimicrobial activity against viable Mtb through the modulation of cathelicidin expression in human macrophages. Treatment of NOX2 knocked down cells with cathelicidin restored the 1,25D3-induced antimicrobial effect, suggesting that the NOX2-dependent induction of cathelicidin in macrophages is part of a defensive strategy against Mtb. Furthermore, cathelicidin expression was required for the Mtb-induced release of ROS and the production of proinflammatory cytokines/chemokines, indicating a positive circuit of inflammation in response to Mtb. Our data collectively demonstrate a novel regulatory mechanism for TLR2-dependent innate responses to Mtb involving crosstalk between NOX2 and TLR2 and the expression of cathelicidin.

title: Mycobacterium tuberculosis-induced expression of granulocyte-macrophage colony stimulating factor is mediated by PI3-K/MEK1/p38 MAPK signaling pathway
abstract: Members of the colony stimulating factor cytokine family play important roles in macrophage activation and recruitment to inflammatory lesions. Among them, granulocyte-macrophage colony stimulating factor (GM-CSF) is known to be associated with immune response to mycobacterial infection. However, the mechanism through which Mycobacterium tuberculosis (MTB) affects the expression of GM-CSF is poorly understood. Using PMA-differentiated THP-1 cells, we found that MTB infection increased GM-CSF mRNA expression in a dosedependent manner. Induction of GM-CSF mRNA expression peaked 6 h after infection, declining gradually thereafter and returning to its basal levels at 72 h. Secretion of GM-CSF protein was also elevated by MTB infection. The increase in mRNA expression and protein secretion of GM-CSF caused by MTB was inhibited in cells treated with inhibitors of p38 MAPK, mitogen-activated protein kinase kinase (MEK-1), and PI3-K. These results suggest that up-regulation of GM-CSF by MTB is mediated via the PI3-K/MEK1/p38 MAPK-associated signaling pathway.

title: Keratinocyte Growth Factor Administration Attenuates Murine Pulmonary Mycobacterium tuberculosis Infection through Granulocyte-Macrophage Colony-stimulating Factor (GM-CSF)-dependent Macrophage Activation and Phagolysosome Fusion*
abstract: Mycobacterium tuberculosis is a major cause of morbidity and mortality worldwide, and chemotherapeutic treatments are not always effective.  Keratinocyte growth factor (KGF) administration results in an epithelium-dependent, GM-CSF-mediated induction of microbicidal programs in alveolar macrophages.  KGF induces GM-CSF and enhances clearance of M. tuberculosis from the lungs of mice.  KGF may be a useful adjunctive strategy for treatment of infection with M. tuberculosis. Augmentation of innate immune defenses is an appealing adjunctive strategy for treatment of pulmonary Mycobacterium tuberculosis infections, especially those caused by drug-resistant strains. The effect of intranasal administration of keratinocyte growth factor (KGF), an epithelial mitogen and differentiation factor, on M. tuberculosis infection in mice was tested in prophylaxis, treatment, and rescue scenarios. Infection of C57BL6 mice with M. tuberculosis resulted in inoculum size-dependent weight loss and mortality. A single dose of KGF given 1 day prior to infection with 105 M. tuberculosis bacilli prevented weight loss and enhanced pulmonary mycobacterial clearance (compared with saline-pretreated mice) for up to 28 days. Similar effects were seen when KGF was delivered intranasally every third day for 15 days, but weight loss and bacillary growth resumed when KGF was withdrawn. For mice with a well established M. tuberculosis infection, KGF given every 3 days beginning on day 15 postinoculation was associated with reversal of weight loss and an increase in M. tuberculosis clearance. In in vitro co-culture experiments, M. tuberculosis-infected macrophages exposed to conditioned medium from KGF-treated alveolar type II cell (MLE-15) monolayers exhibited enhanced GM-CSF-dependent killing through mechanisms that included promotion of phagolysosome fusion and induction of nitric oxide. Alveolar macrophages from KGF-treated mice also exhibited enhanced GM-CSF-dependent phagolysosomal fusion. These results provide evidence that administration of KGF promotes M. tuberculosis clearance through GM-CSF-dependent mechanisms and enhances host defense against M. tuberculosis infection.

title: NOD2 triggers an interleukin-32–dependent human dendritic cell program in leprosy
abstract: It is unclear whether the ability of the innate immune system to recognize distinct ligands from a single microbial pathogen via multiple pattern recognition receptors (PRRs) triggers common pathways or differentially triggers specific host responses. In the human mycobacterial infection leprosy, we found that activation of monocytes via nucleotide-binding oligomerization domain-containing protein 2 (NOD2) by its ligand muramyl dipeptide, as compared to activation via heterodimeric Toll-like receptor 2 and Toll-like receptor 1 (TLR2/1) by triacylated lipopeptide, preferentially induced differentiation into dendritic cells (DCs), which was dependent on a previously unknown interleukin-32 (IL-32)-dependent mechanism. Notably, IL-32 was sufficient to induce monocytes to rapidly differentiate into DCs, which were more efficient than granulocyte-macrophage colony–stimulating factor (GM-CSF)-derived DCs in presenting antigen to major histocompatibility complex (MHC) class I–restricted CD8+ T cells. Expression of NOD2 and IL-32 and the frequency of CD1b+ DCs at the site of leprosy infection correlated with the clinical presentation; they were greater in patients with limited as compared to progressive disease. The addition of recombinant IL-32 restored NOD2-induced DC differentiation in patients with the progressive form of leprosy. In conclusion, the NOD2 ligand–induced, IL-32–dependent DC differentiation pathway contributes a key and specific mechanism for host defense against microbial infection in humans.