query: The density of cytokine receptor bearing cells has no effect on the distance over which cytokines act.

title: A Tunable Diffusion‐Consumption Mechanism of Cytokine Propagation Enables Plasticity in Cell‐to‐Cell Communication in the Immune System

text: &NA; Immune cells communicate by exchanging cytokines to achieve a context‐appropriate response, but the distances over which such communication happens are not known. Here, we used theoretical considerations and experimental models of immune responses in vitro and in vivo to quantify the spatial extent of cytokine communications in dense tissues. We established that competition between cytokine diffusion and consumption generated spatial niches of high cytokine concentrations with sharp boundaries. The size of these self‐assembled niches scaled with the density of cytokine‐consuming cells, a parameter that gets tuned during immune responses. In vivo, we measured interactions on length scales of 80–120 &mgr;m, which resulted in a high degree of cell‐to‐cell variance in cytokine exposure. Such heterogeneous distributions of cytokines were a source of non‐genetic cell‐to‐cell variability that is often overlooked in single‐cell studies. Our findings thus provide a basis for understanding variability in the patterning of immune responses by diffusible factors. Graphical Abstract Figure. No caption available. HighlightsCytokine penetration in tissues is governed by a diffusion‐consumption mechanismSpherical cytokine niches are generated around cytokine‐producing cellsThe characteristic niche size depends on the density of cytokine consumersCytokine niches are a source of variability in otherwise identical cells &NA; Cytokine‐mediated communication allows immune cells to achieve a context‐appropriate response, but the distance over which this communication happens is unclear. Oyler‐Yaniv et al. (2017) show that a simple diffusion‐consumption mechanism quantitatively describes the spatial spread of cytokines in vivo and results in localized niches of high cytokine concentrations that contribute to cell‐to‐cell variability.

title: Cytokine control of memory T-cell development and survival

text: Evidence has accumulated that cytokines have a fundamental role in the differentiation of memory T cells. Here, we follow the CD8+ T cell from initial activation to memory-cell generation, indicating the checkpoints at which cytokines determine the fate of the T cell. Members of the common cytokine-receptor γ-chain (γc)-cytokine family — in particular, interleukin-7 (IL-7) and IL-15 — act at each stage of the immune response to promote proliferation and survival. In this manner, a stable and protective, long-lived memory CD8+ T-cell pool can be propagated and maintained.

title: Keeping your senescent cells under control

text: Cellular senescence is a stable form of cell-cycle arrest which is thought to limit the proliferative potential of premalignant cells [1]. The senescence phenotype was initially described by Hayflick and Moorhead in 1961 on human fibroblasts undergoing replicative exhaustion in culture [2]. It has been shown that senescence can be triggered in different cell types in response to diverse forms of cellular damage or stress (for review see [1]). Importantly, while senescence was denounced as a tissue culture phenomenon for many years, recent in vivo studies demonstrated that cellular senescence represents a potent failsafe mechanism against tumorigenesis and contributes to the cytotoxicity of certain anticancer agents (see for example [3-7]). Interestingly, senescent cells have also been observed in certain aged or damaged tissues and there is growing evidence that senescence checkpoints can affect the regenerative reserve of tissues and organismal aging [8-11]. However, senescence may also have positive effects on organ maintenance by limiting pathological responses to acute forms of injury such as fibrotic scarring in response to chemical induced liver injury [12].     Over the past years it was also shown that senescent cells can communicate with their environment by secreting a myriad of cytokines and growth factors. Interestingly, this "senescence associated secretory phenotype (SASP)" seems to be a double edged sword regarding tumor initiation and maintenance:    i)    On the one hand, it has been shown that the SASP can have pro-tumorigenic effects. In an experimental system it was shown that senescent mesenchymal cells can enhance the tumorigenicity of surrounding breast cancer cells [13].     ii)    Similarly, it is possible that the SASP enhances selection of transformed cell clones in aged organ systems. It has been shown that loss of proliferative competition of non-transformed cells can accelerate leukemogenesis [14]. It remains to be seen whether aberrant secretion of cytokines and growth factors by the SASP can accelerated this process in aged and chronically damage organ systems.     iii)    In contrast to its pro-tumorigenic aspect, the SASP could also have anti-tumor effects. A recent study showed that in a mosaic liver cancer mouse model the activation of p53 induced senescence, an upregulation of inflammatory cytokines, and activation of innate immune responses leading to tumour cell clearance [15].     iv)    In further support that the SASP could have anti-tumor activities, a series of recent papers showed that components of the SASP can stabilize the senescence cell cycle arrest via an autoregulatory feedback loop [16,17] or induces apoptosis of tumor cells [18].     In addition to its effects on tumorigenesis, the SASP could also influence tissue aging. Studies on aging telomere dysfunctional mice have provided direct experimental evidence for an in vivo activation of the SASP in response to telomere dysfunction [19]. Interestingly, this in vivo SASP provoked alterations in stem cell differentiation (skewing of hematopoiesis towards reduction in lymphopoiesis and enhancement of myelopoiesis) that are also characteristic signs of human aging.         Figure 1.     Different cellular stresses can induce senescence including telomere shortening, DNA damage, and oncogene activation. Senescence of tumor cells ...         In light of the many possible roles o the SASP in aging and carcinogenesis, it appears to be of utmost importance to decipher regulatory pathways controlling the SASP. In a current publication, Bhaumik et al. have identified 2 microRNAs (miR-146a/b) that negatively regulate the secretion of IL-6 and IL-8 - two of the SASP [20]. The authors show that these microRNAs are up-regulated at late stages of senescence, many days after a permanent cell cycle arrest has been established. Interestingly, the inhibitory miRs are most strongly up-regulated in senescence of cell lines that show a strong SASP but not in cell lines characterized by a weak SASP. The authors propose a new concept indicating that miRs 146a and b function in a negative feedback loop preventing an over-activation of the SASP in senescent cells. The authors present some initial data suggesting that activation of this negative feedback loop involves IL-1 receptor, IRAK-1, and NFκB signalling leading to an up-regulation of miRs-146a and b. A direct proof that this proposed feedback loop suppresses over-activation of the SASP remains to be demonstrated in future studies. The authors show that blockage of IL-1-receptor signalling prevents both the up-regulation of miRs-146a and b as well as Il-6 secretion. To confirm their new concept, it would be important to show that a selective blockage of miRs-146a and b results in over-activation of the SASP.     The work by Bhaumik et al. places mir-146a/b as central players to control IL-6 and IL-8 expression within the SASP. MicroRNAs are emerging therapeutic targets because their expression levels can be effectively modulated via the use of antagomirs (see for example [21]). Also, for increasing microRNA expression, microRNAs can be delivered into cellsin vivo (see for example [22]). Therefore, it will be interesting to functionally test the impact of mir-146 inhibition on tumorigenesis and aging in relevant mouse models. Such studies will be of particular interest, as recent work showed that IL-6 secretion by senescent cells is relevant for initiating and maintaining the senescene response via an autocrine loop [17]. A reduction of miR-146 could increase IL-6 levels in senescent cells, which should stabilize the senescence program and reduce the risk of malignant transformation. Furthermore, it can be speculated that reduction of mir-146 a/b will increase NfκB activation via IRAK1. As NfκB is modulating the expression of various inflammation associated genes, this may also lead to increased clearance of senescent tumor cells by the innate immune system. However, it should be mentioned that Il-6 secreted by senescent cells can also act as a mitogen for surrounding cells, thus potentially increasing the risk of malignant transformation [13,17]. Besides its function in SASP modulation, miR-146 was also reported to target the mRNAs of the BRCA1 and BRCA2 tumor suppressors. In a recent study a G to C polymorphism in miR-146, which leads to an increased processing and release of the mature microRNA, can predict an early onset of breast cancer [23].     Taken together, the study of Bhaumik et al. opens an interesting new research area dealing with the gene regulatory mechanisms that control activation of the SASP. Given the diverse roles of the SASP in modulating tumor progression, immune surveillance of damaged cells, and the stabilization of the senescence arrest itself, it will be of great interest to analyse the influence of SASP regulatory pathways during aging and cancer.

title: Induction of myelodysplasia by myeloid-derived suppressor cells.

text: Myelodysplastic syndromes (MDS) are age-dependent stem cell malignancies that share biological features of activated adaptive immune response and ineffective hematopoiesis. Here we report that myeloid-derived suppressor cells (MDSC), which are classically linked to immunosuppression, inflammation, and cancer, were markedly expanded in the bone marrow of MDS patients and played a pathogenetic role in the development of ineffective hematopoiesis. These clonally distinct MDSC overproduce hematopoietic suppressive cytokines and function as potent apoptotic effectors targeting autologous hematopoietic progenitors. Using multiple transfected cell models, we found that MDSC expansion is driven by the interaction of the proinflammatory molecule S100A9 with CD33. These 2 proteins formed a functional ligand/receptor pair that recruited components to CD33’s immunoreceptor tyrosine-based inhibition motif (ITIM), inducing secretion of the suppressive cytokines IL-10 and TGF-β by immature myeloid cells. S100A9 transgenic mice displayed bone marrow accumulation of MDSC accompanied by development of progressive multilineage cytopenias and cytological dysplasia. Importantly, early forced maturation of MDSC by either all-trans-retinoic acid treatment or active immunoreceptor tyrosine-based activation motif–bearing (ITAM-bearing) adapter protein (DAP12) interruption of CD33 signaling rescued the hematologic phenotype. These findings indicate that primary bone marrow expansion of MDSC driven by the S100A9/CD33 pathway perturbs hematopoiesis and contributes to the development of MDS.

title: Urban spatial development in the land policy reform era: evidence from Beijing

text: This paper examines the characteristics of urban spatial development in Beijing and identifies the extent to which these characteristics can be attributed to the emerging land market in Beijing as well as the impact of land policy reform. Based on the observations of land use rights granted from 1993 to the first half of 2000 in the built-up area of Beijing, empirical analyses illustrate that both land prices and land development density decrease with distance to the city core. It further provides evidence that the slope of the land rent curve also depends on land use types. This leads to the conclusion that the land market influences land development decisions and urban form. Finally, it shows that the slope of the land rent curve and the elasticity of land-capital substitution change over time. The former declines, as expected. This is because Beijing's massive investments in transport have reduced transport costs, which in turn has shifted the land rent curve. The latter rises, implying the price effect on land development density. Both changesâ€”in land rent function and the elasticity of land-capital substitution-point to the maturing of the Beijing land market. It should be mentioned that there are enormous land developments outside the land market (land development on administratively allocated land). These developments can significantly distort urban land use patterns portrayed through this study.

title: IL-17 promotes tumor development through the induction of tumor promoting microenvironments at tumor sites and myeloid-derived suppressor cells.

text: The role of immune responses in tumor development is a central issue for tumor biology and immunology. IL-17 is an important cytokine for inflammatory and autoimmune diseases. Although IL-17-producing cells are detected in cancer patients and tumor-bearing mice, the role of IL-17 in tumor development is controversial, and mechanisms remain to be fully elucidated. In the current study, we found that the development of tumors was inhibited in IL-17R-deficient mice. A defect in IFN-gammaR increased tumor growth, whereas tumor growth was inhibited in mice that were deficient in both IL-17R and IFN-gammaR compared with wild-type animals. Further experiments showed that neutralization of IL-17 by Abs inhibited tumor growth in wild-type mice, whereas systemic administration of IL-17 promoted tumor growth. The IL-17R deficiency increased CD8 T cell infiltration, whereas it reduced the infiltration of myeloid-derived suppressor cells (MDSCs) in tumors. In contrast, administration of IL-17 inhibited CD8 T cell infiltration and increased MDSCs in tumors. Further analysis indicated that IL-17 was required for the development and tumor-promoting activity of MDSCs in tumor-bearing mice. These data demonstrate that IL-17-mediated responses promote tumor development through the induction of tumor-promoting microenvironments at tumor sites. IL-17-mediated regulation of MDSCs is a primary mechanism for its tumor-promoting effects. The study provides novel insights into the role of IL-17 in tumor development and has major implications for targeting IL-17 in treatment of tumors.

title: Interaction of TNF with TNF receptor type 2 promotes expansion and function of mouse CD4+CD25+ T regulatory cells.

text: Although TNF is a major proinflammatory cytokine, increasing evidence indicates that TNF also has immunosuppressive feedback effects. We have demonstrated in this study that, in both resting and activated states, mouse peripheral CD4(+)CD25(+) T regulatory cells (Tregs) expressed remarkably higher surface levels of TNFR2 than CD4(+)CD25(-) T effector cells (Teffs). In cocultures of Tregs and Teffs, inhibition of proliferation of Teffs by Tregs was initially transiently abrogated by exposure to TNF, but longer exposure to TNF restored suppressive effects. Cytokine production by Teffs remained continually suppressed by Tregs. The profound anergy of Tregs in response to TCR stimulation was overcome by TNF, which expanded the Treg population. Furthermore, in synergy with IL-2, TNF expanded Tregs even more markedly up-regulated expression of CD25 and FoxP3 and phosphorylation of STAT5, and enhanced the suppressive activity of Tregs. Unlike TNF, IL-1beta and IL-6 did not up-regulate FoxP3-expressing Tregs. Furthermore, the number of Tregs increased in wild-type mice, but not in TNFR2(-/-) mice following sublethal cecal ligation and puncture. Depletion of Tregs significantly decreased mortality following cecal ligation and puncture. Thus, the stimulatory effect of TNF on Tregs resembles the reported costimulatory effects of TNF on Teffs, but is even more pronounced because of the higher expression of TNFR2 by Tregs. Moreover, our study suggests that the slower response of Tregs than Teffs to TNF results in delayed immunosuppressive feedback effects.

title: Inflammatory T cells rapidly induce differentiation of human bone marrow stromal cells into mature osteoblasts.

text: Activated T cells secrete multiple osteoclastogenic cytokines which play a major role in the bone destruction associated with rheumatoid arthritis. While the role of T cells in osteoclastogenesis has received much attention recently, the effect of T cells on osteoblast formation and activity is poorly defined. In this study, we investigated the hypothesis that in chronic inflammation activated T cells contribute to enhanced bone turnover by promoting osteoblastic differentiation. We show that T cells produce soluble factors that induce alkaline phosphatase activity in bone marrow stromal cells and elevated expression of mRNA for Runx2 and osteocalcin. This data indicate that T cell derived factors have the capacity to stimulate the differentiation of bone marrow stromal cells into the osteoblast phenotype. RANKL mRNA was undetectable under any conditions in highly purified bone marrow stromal cells. In contrast, RANKL was constitutively expressed in primary osteoblasts and only moderately up-regulated by activated T cell conditioned medium. Interestingly, both bone marrow stromal cells and osteoblasts expressed mRNA for RANK, which was strongly up-regulated in both cell types by activated T cell conditioned medium. Although, mRNA for the RANKL decoy receptor, osteoprotegerin, was also up-regulated by activated T cell conditioned medium, it's inhibitory effects may be mitigated by a simultaneous rise in the osteoprotegerin competitor TNF-related apoptosis-inducing ligand. Based on our data we propose that during chronic inflammation, T cells regulate bone loss by a dual mechanism involving both direct stimulation of osteoclastogenesis, by production of osteoclastogenic cytokines, and indirectly by induction of osteoblast differentiation and up-regulation of bone turnover via coupling.

title: Ancient Hybridization and an Irish Origin for the Modern Polar Bear Matriline

text:
BACKGROUND Polar bears (Ursus maritimus) are among those species most susceptible to the rapidly changing arctic climate, and their survival is of global concern. Despite this, little is known about polar bear species history. Future conservation strategies would significantly benefit from an understanding of basic evolutionary information, such as the timing and conditions of their initial divergence from brown bears (U. arctos) or their response to previous environmental change.
 RESULTS We used a spatially explicit phylogeographic model to estimate the dynamics of 242 brown bear and polar bear matrilines sampled throughout the last 120,000 years and across their present and past geographic ranges. Our results show that the present distribution of these matrilines was shaped by a combination of regional stability and rapid, long-distance dispersal from ice-age refugia. In addition, hybridization between polar bears and brown bears may have occurred multiple times throughout the Late Pleistocene.
 CONCLUSIONS The reconstructed matrilineal history of brown and polar bears has two striking features. First, it is punctuated by dramatic and discrete climate-driven dispersal events. Second, opportunistic mating between these two species as their ranges overlapped has left a strong genetic imprint. In particular, a likely genetic exchange with extinct Irish brown bears forms the origin of the modern polar bear matriline. This suggests that interspecific hybridization not only may be more common than previously considered but may be a mechanism by which species deal with marginal habitats during periods of environmental deterioration.

title: Alkylating agent melphalan augments the efficacy of adoptive immunotherapy using tumor-specific CD4+ T cells.

text: In recent years, the immune-potentiating effects of some widely used chemotherapeutic agents have been increasingly appreciated. This provides a rationale for combining conventional chemotherapy with immunotherapy strategies to achieve durable therapeutic benefits. Previous studies have implicated the immunomodulatory effects of melphalan, an alkylating agent commonly used to treat multiple myeloma, but the underlying mechanisms remain obscure. In the present study, we investigated the impact of melphalan on endogenous immune cells as well as adoptively transferred tumor-specific CD4(+) T cells in tumor-bearing mice. We showed that melphalan treatment resulted in a rapid burst of inflammatory cytokines and chemokines during the cellular recovery phase after melphalan-induced myelodepletion and leukodepletion. After melphalan treatment, tumor cells exhibited characteristics of immunogenic cell death, including membrane translocation of the endoplasmic reticulum-resident calreticulin and extracellular release of high-mobility group box 1. Additionally, there was enhanced tumor Ag uptake by dendritic cells in the tumor-draining lymph node. Consistent with these immunomodulatory effects, melphalan treatment of tumor-bearing mice led to the activation of the endogenous CD8(+) T cells and, more importantly, effectively drove the clonal expansion and effector differentiation of adoptively transferred tumor-specific CD4(+) T cells. Notably, the combination of melphalan and CD4(+) T cell adoptive cell therapy was more efficacious than either treatment alone in prolonging the survival of mice with advanced B cell lymphomas or colorectal tumors. These findings provide mechanistic insights into melphalan's immunostimulatory effects and demonstrate the therapeutic potential of combining melphalan with adoptive cell therapy utilizing antitumor CD4(+) T cells.

title: Chimeric antigen receptor-modified T cells for acute lymphoid leukemia.

text: Chimeric antigen receptor-modified T cells with specificity for CD19 have shown promise in the treatment of chronic lymphocytic leukemia (CLL). It remains to be established whether chimeric antigen receptor T cells have clinical activity in acute lymphoblastic leukemia (ALL). Two children with relapsed and refractory pre-B-cell ALL received infusions of T cells transduced with anti-CD19 antibody and a T-cell signaling molecule (CTL019 chimeric antigen receptor T cells), at a dose of 1.4×10(6) to 1.2×10(7) CTL019 cells per kilogram of body weight. In both patients, CTL019 T cells expanded to a level that was more than 1000 times as high as the initial engraftment level, and the cells were identified in bone marrow. In addition, the chimeric antigen receptor T cells were observed in the cerebrospinal fluid (CSF), where they persisted at high levels for at least 6 months. Eight grade 3 or 4 adverse events were noted. The cytokine-release syndrome and B-cell aplasia developed in both patients. In one child, the cytokine-release syndrome was severe; cytokine blockade with etanercept and tocilizumab was effective in reversing the syndrome and did not prevent expansion of chimeric antigen receptor T cells or reduce antileukemic efficacy. Complete remission was observed in both patients and is ongoing in one patient at 11 months after treatment. The other patient had a relapse, with blast cells that no longer expressed CD19, approximately 2 months after treatment. Chimeric antigen receptor-modified T cells are capable of killing even aggressive, treatment-refractory acute leukemia cells in vivo. The emergence of tumor cells that no longer express the target indicates a need to target other molecules in addition to CD19 in some patients with ALL.

title: Enterovirus-induced gene expression profile is critical for human pancreatic islet destruction

text: Virally induced inflammatory responses, beta cell destruction and release of beta cell autoantigens may lead to autoimmune reactions culminating in type 1 diabetes. Therefore, viral capability to induce beta cell death and the nature of virus-induced immune responses are among key determinants of diabetogenic viruses. We hypothesised that enterovirus infection induces a specific gene expression pattern that results in islet destruction and that such a host response pattern is not shared among all enterovirus infections but varies between virus strains. The changes in global gene expression and secreted cytokine profiles induced by lytic or benign enterovirus infections were studied in primary human pancreatic islet using DNA microarrays and viral strains either isolated at the clinical onset of type 1 diabetes or capable of causing a diabetes-like condition in mice. The expression of pro-inflammatory cytokine genes (IL-1-α, IL-1-β and TNF-α) that also mediate cytokine-induced beta cell dysfunction correlated with the lytic potential of a virus. Temporally increasing gene expression levels of double-stranded RNA recognition receptors, antiviral molecules, cytokines and chemokines were detected for all studied virus strains. Lytic coxsackievirus B5 (CBV-5)-DS infection also downregulated genes involved in glycolysis and insulin secretion. The results suggest a distinct, virus-strain-specific, gene expression pattern leading to pancreatic islet destruction and pro-inflammatory effects after enterovirus infection. However, neither viral replication nor cytotoxic cytokine production alone are sufficient to induce necrotic cell death. More likely the combined effect of these and possibly cellular energy depletion lie behind the enterovirus-induced necrosis of islets.

title: Cocoa flavonols and procyanidins promote transforming growth factor-beta1 homeostasis in peripheral blood mononuclear cells.

text: Evidence suggests that certain flavan-3-ols and procyanidins (FP) can have a positive influence on cardiovascular health. It has been previously reported that FP isolated from cocoa can potentially modulate the level and production of several signaling molecules associated with immune function and inflammation, including several cytokines and eicosanoids. In the present study, we examined whether FP fractions monomers through decamers modulate secretion of the cytokine transforming growth factor (TGF)-beta(1) from resting human peripheral blood mononuclear cells (PBMC). A total of 13 healthy subjects were studied and grouped according to their baseline production of TGF-beta(1). When cells from individuals with low baseline levels of TGF-beta(1) (n = 7) were stimulated by individual FP fractions (25 microg/ml), TGF-beta(1) release was enhanced in the range of 15%-66% over baseline (P < 0.05; monomer, dimer, and tetramer). The low-molecular-weight FP fractions (<or=pentamer) were more effective at augmenting TGF-beta(1) secretion than their larger counterparts (>or=hexamer), with the monomer and dimer inducing the greatest increases (66% and 68%, respectively). In contrast to the above, TGF-beta(1) secretion from high TGF-beta(1) baseline subjects (n = 6) was inhibited by individual FP fractions (P < 0.05; trimer through decamer). The inhibition was most pronounced with trimeric through decameric fractions (28%-42%), and monomers and dimers moderately inhibited TGF-beta(1) release (17% and 23%, respectively). Given the vascular actions associated with TGF-beta(1), we suggest that in healthy individuals, homeostatic modulation of its production by FP offers an additional mechanism by which FP-rich foods can potentially benefit cardiovascular health.


query: The deregulated and prolonged activation of monocytes has deleterious effects in chronic infectious conditions.

title: The myeloid transcription factor KLF2 regulates the host response to polymicrobial infection and endotoxic shock.

text: Precise control of myeloid cell activation is required for optimal host defense. However, this activation process must be under exquisite control to prevent uncontrolled inflammation. Herein, we identify the Kruppel-like transcription factor 2 (KLF2) as a potent regulator of myeloid cell activation in vivo. Exposure of myeloid cells to hypoxia and/or bacterial products reduced KLF2 expression while inducing hypoxia inducible factor-1α (HIF-1α), findings that were recapitulated in human septic patients. Myeloid KLF2 was found to be a potent inhibitor of nuclear factor-kappaB (NF-κB)-dependent HIF-1α transcription and, consequently, a critical determinant of outcome in models of polymicrobial infection and endotoxemia. Collectively, these observations identify KLF2 as a tonic repressor of myeloid cell activation in vivo and an essential regulator of the innate immune system.

title: Kruppel-like factor 2 is a transcriptional regulator of chronic and acute inflammation.

text: Although myeloid cell activation is requisite for an optimal innate immune response, this process must be tightly controlled to prevent collateral host tissue damage. Kruppel-like factor 2 (KLF2) is a potent regulator of myeloid cell proinflammatory activation. As an approximately 30% to 50% reduction in KLF2 levels has been observed in human subjects with acute or chronic inflammatory disorders, we studied the biological response to inflammation in KLF2(+/-) mice. Herein, we show that partial deficiency of KLF2 modulates the in vivo response to acute (sepsis) and subacute (skin) inflammatory challenge. Mechanistically, we link the anti-inflammatory effects of KLF2 to the inhibition of NF-κB transcriptional activity. Collectively, the observations provide biologically relevant insights into KLF2-mediated modulation of these inflammatory processes that could potentially be manipulated for therapeutic gain.

title: CCR2 and CXCR4 regulate peripheral blood monocyte pharmacodynamics and link to efficacy in experimental autoimmune encephalomyelitis

text:
BACKGROUND CCR2 plays a key role in regulating monocyte trafficking to sites of inflammation and therefore has been the focus of much interest as a target for inflammatory disease.
 METHODS Here we examined the effects of CCR2 blockade with a potent small molecule antagonist to determine the pharmacodynamic consequences on the peripheral blood monocyte compartment in the context of acute and chronic inflammatory processes.
 RESULTS We demonstrate that CCR2 antagonism in vivo led to a rapid decrease in the number of circulating Ly6Chi monocytes and that this decrease was largely due to the CXCR4-dependent sequestration of these cells in the bone marrow, providing pharmacological evidence for a mechanism by which monocyte dynamics are regulated in vivo. CCR2 antagonism led to an accumulation of circulating CCL2 and CCL7 levels in the blood, indicating a role for CCR2 in regulating the levels of its ligands under homeostatic conditions. Finally, we show that the pharmacodynamic changes due to CCR2 antagonism were apparent after chronic dosing in mouse experimental autoimmune encephalomyelitis, a model in which CCR2 blockade demonstrated a dramatic reduction in disease severity, manifest in a reduced accumulation of monocytes and other cells in the CNS.
 CONCLUSION CCR2 antagonism in vivo has tractable pharmacodynamic effects that can be used to align target engagement with biologic effects on disease activity.

title: A role for interleukin-1β in determining the lineage fate of embryonic rat hippocampal neural precursor cells.

text: Neurogenesis occurs in the hippocampus of the developing and adult brain due to the presence of multipotent stem cells and restricted precursor cells at different stages of differentiation. It has been proposed that they may be of potential benefit for use in cell transplantation approaches for neurodegenerative disorders and trauma. Prolonged release of interleukin-1β (IL-1β) from activated microglia has a deleterious effect on hippocampal neurons and is implicated in the impaired neurogenesis and cognitive dysfunction associated with aging, Alzheimer's disease and depression. This study assessed the effect of IL-1β on the proliferation and differentiation of embryonic rat hippocampal NPCs in vitro. We show that IL-1R1 is expressed on proliferating NPCs and that IL-1β treatment decreases cell proliferation and neurosphere growth. When NPCs were differentiated in the presence of IL-1β, a significant reduction in the percentages of newly-born neurons and post-mitotic neurons and a significant increase in the percentage of astrocytes was observed in these cultures. These effects were attenuated by IL-1 receptor antagonist. These data reveal that IL-1β exerts an anti-proliferative, anti-neurogenic and pro-gliogenic effect on embryonic hippocampal NPCs, which is mediated by IL-1R1. The present results emphasise the consequences of an inflammatory environment during NPC development, and indicate that strategies to inhibit IL-1β signalling may be necessary to facilitate effective cell transplantation approaches or in conditions where endogenous hippocampal neurogenesis is impaired.

title: Toll-like receptor 7 agonist GS-9620 induces prolonged inhibition of HBV via a type I interferon-dependent mechanism.

text:
BACKGROUND & AIMS GS-9620, an oral agonist of toll-like receptor 7 (TLR7), is in clinical development for the treatment of chronic hepatitis B (CHB). GS-9620 was previously shown to induce prolonged suppression of serum viral DNA and antigens in the woodchuck and chimpanzee models of CHB. Herein, we investigated the molecular mechanisms that contribute to the antiviral response to GS-9620 using in vitro models of hepatitis B virus (HBV) infection.
 METHODS Cryopreserved primary human hepatocytes (PHH) and differentiated HepaRG (dHepaRG) cells were infected with HBV and treated with GS-9620, conditioned media from human peripheral blood mononuclear cells treated with GS-9620 (GS-9620 conditioned media [GS-9620-CM]), or other innate immune stimuli. The antiviral and transcriptional response to these agents was determined.
 RESULTS GS-9620 had no antiviral activity in HBV-infected PHH, consistent with low level TLR7 mRNA expression in human hepatocytes. In contrast, GS-9620-CM induced prolonged reduction of HBV DNA, RNA, and antigen levels in PHH and dHepaRG cells via a type I interferon (IFN)-dependent mechanism. GS-9620-CM did not reduce covalently closed circular DNA (cccDNA) levels in either cell type. Transcriptional profiling demonstrated that GS-9620-CM strongly induced various HBV restriction factors - although not APOBEC3A or the Smc5/6 complex - and indicated that established HBV infection does not modulate innate immune sensing or signaling in cryopreserved PHH. GS-9620-CM also induced expression of immunoproteasome subunits and enhanced presentation of an immunodominant viral peptide in HBV-infected PHH.
 CONCLUSIONS Type I IFN induced by GS-9620 durably suppressed HBV in human hepatocytes without reducing cccDNA levels. Moreover, HBV antigen presentation was enhanced, suggesting additional components of the TLR7-induced immune response played a role in the antiviral response to GS-9620 in animal models of CHB.    LAY SUMMARY GS-9620 is a drug currently being tested in clinical trials for the treatment of chronic hepatitis B virus (HBV) infection. GS-9620 has previously been shown to suppress HBV in various animal models, but the underlying antiviral mechanisms were not completely understood. In this study, we determined that GS-9620 does not directly activate antiviral pathways in human liver cells, but can induce prolonged suppression of HBV via induction of an antiviral cytokine called interferon. However, interferon did not destroy the HBV genome, suggesting that other parts of the immune response (e.g. activation of immune cells that kill infected cells) also play an important role in the antiviral response to GS-9620.

title: Association of NOD2 leucine-rich repeat variants with susceptibility to Crohn's disease.

text: Crohn's disease and ulcerative colitis, the two main types of chronic inflammatory bowel disease, are multifactorial conditions of unknown aetiology. A susceptibility locus for Crohn's disease has been mapped to chromosome 16. Here we have used a positional-cloning strategy, based on linkage analysis followed by linkage disequilibrium mapping, to identify three independent associations for Crohn's disease: a frameshift variant and two missense variants of NOD2, encoding a member of the Apaf-1/Ced-4 superfamily of apoptosis regulators that is expressed in monocytes. These NOD2 variants alter the structure of either the leucine-rich repeat domain of the protein or the adjacent region. NOD2 activates nuclear factor NF-kB; this activating function is regulated by the carboxy-terminal leucine-rich repeat domain, which has an inhibitory role and also acts as an intracellular receptor for components of microbial pathogens. These observations suggest that the NOD2 gene product confers susceptibility to Crohn's disease by altering the recognition of these components and/or by over-activating NF-kB in monocytes, thus documenting a molecular model for the pathogenic mechanism of Crohn's disease that can now be further investigated.

title: TLR activation triggers the rapid differentiation of monocytes into macrophages and dendritic cells

text: Leprosy enables investigation of mechanisms by which the innate immune system contributes to host defense against infection, because in one form, the disease progresses, and in the other, the infection is limited. We report that Toll-like receptor (TLR) activation of human monocytes induces rapid differentiation into two distinct subsets: DC-SIGN+ CD16+ macrophages and CD1b+ DC-SIGN− dendritic cells. DC-SIGN+ phagocytic macrophages were expanded by TLR-mediated upregulation of interleukin (IL)-15 and IL-15 receptor. CD1b+ dendritic cells were expanded by TLR-mediated upregulation of granulocyte-macrophage colony-stimulating factor (GM-CSF) and its receptor, promoted T cell activation and secreted proinflammatory cytokines. Whereas DC-SIGN+ macrophages were detected in lesions and after TLR activation in all leprosy patients, CD1b+ dendritic cells were not detected in lesions or after TLR activation of peripheral monocytes in individuals with the progressive lepromatous form, except during reversal reactions in which bacilli were cleared by T helper type 1 (TH1) responses. In tuberculoid lepromatous lesions, DC-SIGN+ cells were positive for macrophage markers, but negative for dendritic cell markers. Thus, TLR-induced differentiation of monocytes into either macrophages or dendritic cells seems to crucially influence effective host defenses in human infectious disease.

title: Differential expression of bcl-2 and susceptibility to anti-Fas-mediated cell death in peripheral blood lymphocytes, monocytes, and neutrophils.

text: The recently identified Fas antigen (Ag) is a cell surface molecule that can mediate apoptosis. The cytoplasmic product of proto-oncogene bcl-2 has been shown to prolong the cellular survival by inhibiting apoptosis. To elucidate the physiologic significance of expression of both molecules, we examined the expression of Fas Ag and bcl-2 on blood leukocyte populations and evaluated their sensitivity to the cytolytic action of anti-Fas antibody. Although Fas Ag was expressed on a fraction of lymphocytes, both neutrophils and monocytes expressed Fas Ag constitutively. In contrast, there was marked difference among these leukocytes regarding bcl-2 expression. Lymphocytes expressed bcl-2 intensely, but monocytes showed weaker bcl-2 expression, and neutrophils were essentially absent for bcl-2 expression. Seemingly reflecting this lack of bcl-2-expression, neutrophils more easily underwent apoptotic cell death in vitro as compared with monocytes and lymphocytes. We showed that anti-Fas antibody affectively accelerated apoptotic cell death in neutrophils. However, the apoptosis-inducing effect of anti-Fas antibody was minimal on monocytes, and lymphocytes were resistant to this antibody. These results suggest that anti-Fas-mediated cell death may, in part, be determined by bcl-2 expression status in Fas+ lymphoid and hematopoietic cells.

title: Dasatinib inhibits both osteoclast activation and prostate cancer PC-3-cell-induced osteoclast formation.

text:
PURPOSE Therapies to target prostate cancer bone metastases have only limited effects. New treatments are focused on the interaction between cancer cells, bone marrow cells and the bone matrix. Osteoclasts play an important role in the development of bone tumors caused by prostate cancer. Since Src kinase has been shown to be necessary for osteoclast function, we hypothesized that dasatinib, a Src family kinase inhibitor, would reduce osteoclast activity and prostate cancer (PC-3) cell-induced osteoclast formation.
 RESULTS Dasatinib inhibited RANKL-induced osteoclast differentiation of bone marrow-derived monocytes with an EC(50) of 7.5 nM. PC-3 cells, a human prostate cancer cell line, were able to differentiate RAW 264.7 cells, a murine monocytic cell line, into osteoclasts, and dasatinib inhibited this differentiation. In addition, conditioned medium from PC-3 cell cultures was able to differentiate RAW 264.7 cells into osteoclasts and this too, was inhibited by dasatinib. Even the lowest concentration of dasatinib, 1.25 nmol, inhibited osteoclast differentiation by 29%. Moreover, dasatinib inhibited osteoclast activity by 58% as measured by collagen 1 release.    EXPERIMENTAL DESIGN We performed in vitro experiments utilizing the Src family kinase inhibitor dasatinib to target osteoclast activation as a means of inhibiting prostate cancer bone metastases.
 CONCLUSION Dasatinib inhibits osteoclast differentiation of mouse primary bone marrow-derived monocytes and PC-3 cell-induced osteoclast differentiation. Dasatinib also inhibits osteoclast degradation activity. Inhibiting osteoclast differentiation and activity may be an effective targeted therapy in patients with prostate cancer bone metastases.

title: Chronic variable stress activates hematopoietic stem cells

text: Exposure to psychosocial stress is a risk factor for many diseases, including atherosclerosis. Although incompletely understood, interaction between the psyche and the immune system provides one potential mechanism linking stress and disease inception and progression. Known cross-talk between the brain and immune system includes the hypothalamic-pituitary-adrenal axis, which centrally drives glucocorticoid production in the adrenal cortex, and the sympathetic-adrenal-medullary axis, which controls stress-induced catecholamine release in support of the fight-or-flight reflex. It remains unknown, however, whether chronic stress changes hematopoietic stem cell activity. Here we show that stress increases proliferation of these most primitive hematopoietic progenitors, giving rise to higher levels of disease-promoting inflammatory leukocytes. We found that chronic stress induced monocytosis and neutrophilia in humans. While investigating the source of leukocytosis in mice, we discovered that stress activates upstream hematopoietic stem cells. Under conditions of chronic variable stress in mice, sympathetic nerve fibers released surplus noradrenaline, which signaled bone marrow niche cells to decrease CXCL12 levels through the β3-adrenergic receptor. Consequently, hematopoietic stem cell proliferation was elevated, leading to an increased output of neutrophils and inflammatory monocytes. When atherosclerosis-prone Apoe(-/-) mice were subjected to chronic stress, accelerated hematopoiesis promoted plaque features associated with vulnerable lesions that cause myocardial infarction and stroke in humans.

title: Subpopulations of mouse blood monocytes differ in maturation stage and inflammatory response.

text: Blood monocytes are well-characterized precursors for macrophages and dendritic cells. Subsets of human monocytes with differential representation in various disease states are well known. In contrast, mouse monocyte subsets have been characterized minimally. In this study we identify three subpopulations of mouse monocytes that can be distinguished by differential expression of Ly-6C, CD43, CD11c, MBR, and CD62L. The subsets share the characteristics of extensive phagocytosis, similar expression of M-CSF receptor (CD115), and development into macrophages upon M-CSF stimulation. By eliminating blood monocytes with dichloromethylene-bisphosphonate-loaded liposomes and monitoring their repopulation, we showed a developmental relationship between the subsets. Monocytes were maximally depleted 18 h after liposome application and subsequently reappeared in the circulation. These cells were exclusively of the Ly-6C(high) subset, resembling bone marrow monocytes. Serial flow cytometric analyses of newly released Ly-6C(high) monocytes showed that Ly-6C expression on these cells was down-regulated while in circulation. Under inflammatory conditions elicited either by acute infection with Listeria monocytogenes or chronic infection with Leishmania major, there was a significant increase in immature Ly-6C(high) monocytes, resembling the inflammatory left shift of granulocytes. In addition, acute peritoneal inflammation recruited preferentially Ly-6C(med-high) monocytes. Taken together, these data identify distinct subpopulations of mouse blood monocytes that differ in maturation stage and capacity to become recruited to inflammatory sites.

title: Influence of DNA on the activities and inhibition of neutrophil serine proteases in cystic fibrosis sputum.

text: Uncontrolled proteolysis by neutrophil serine proteases (NSPs) in lung secretions is a hallmark of cystic fibrosis (CF). We have shown that the active neutrophil elastase, protease 3, and cathepsin G in CF sputum resist inhibition in part by exogenous protease inhibitors. This resistance may be due to their binding to neutrophil extracellular traps (NETs) secreted by the activated neutrophils in CF sputum and to genomic DNA released from senescent and dead neutrophils. Treating CF sputum with DNase dramatically increases its elastase activity, which can then be stoichiometrically inhibited by exogenous elastase inhibitors. However, DNase treatment does not increase the activities of protease 3 and cathepsin G, indicating their different distribution and/or binding in CF sputum. Purified blood neutrophils secrete NETs when stimulated by the opportunistic CF bacteria Pseudomonas aeruginosa and Staphylococcus aureus. The activities of the three proteases were unchanged in these conditions, but subsequent DNase treatment produced a dramatic increase in all three proteolytic activities. Neutrophils activated with a calcium ionophore did not secrete NETs but released huge amounts of active proteases whose activities were not modified by DNase. We conclude that NETs are reservoirs of active proteases that protect them from inhibition and maintain them in a rapidly mobilizable status. Combining the effects of protease inhibitors with that of DNA-degrading agents could counter the deleterious proteolytic effects of NSPs in CF lung secretions.

title: Hypothermic preservation up-regulates calpain expression and increases ubiquitination in cultured vascular endothelial cells: influence of dopamine pretreatment.

text:
BACKGROUND Prolonged hypothermia, as occurs during solid organ transplantation, negatively influences transplantation outcome. Proteolysis is one of the deleterious events implicated in preservation injury of organ allografts. This strongly affects graft quality and hence immediate organ function. Since donor catecholamine treatment improves transplantation outcome after renal transplantation, the present study was conducted to examine the influence of dopamine (DA) pretreatment on hypothermia induced proteolysis in endothelial cells subjected to prolonged cold storage.    MATERIALS AND METHODS Lactate dehydrogenase (LDH) assay, two-dimensional electrophoresis, ubiquitination analysis, intracellular calcium measurement, and Western blot analysis were performed on human umbilical vein endothelial cells (HUVEC) subjected to hypothermic preservation or not.
 RESULTS HUVEC were highly susceptible to cold storage, which was reflected by morphological changes, loss of viability, and by significant changes in cellular proteome. DA pretreatment prevented cell death during cold storage. Western blot analysis demonstrated a time dependent up-regulation of calpain 1 and 2 during cold storage, which could be prevented by addition of EDTA. DA pretreatment abolished autoproteolysis of calpain 1. Analysis of ubiquitination revealed a significant increase in ubiquitinated conjugates after cold storage. This was not prevented by DA pretreatment. Neither proteasome nor calpain inhibitors prevented cell death during cold storage.
 CONCLUSION In endothelial cells subjected to cold preservation, activation of the calpain pathway and the ubiquitin proteasome system occur. Although DA pretreatment inhibits the former, calpain inhibition did not protect endothelial cells during cold storage. DA pretreatment might influence proteolysis, but proteolysis is not the major cause of endothelial cell death.

title: Another Barrier to Regeneration in the CNS: Activated Macrophages Induce Extensive Retraction of Dystrophic Axons through Direct Physical Interactions

text: Injured axons of the adult CNS undergo lengthy retraction from the initial site of axotomy after spinal cord injury. Macrophage infiltration correlates spatiotemporally with this deleterious phenomenon, but the direct involvement of these inflammatory cells has not been demonstrated. In the present study, we examined the role of macrophages in axonal retraction within the dorsal columns after spinal cord injury in vivo and found that retraction occurred between days 2 and 28 after lesion and that the ends of injured axons were associated with ED-1+ cells. Clodronate liposome-mediated depletion of infiltrating macrophages resulted in a significant reduction in axonal retraction; however, we saw no evidence of regeneration. We used time-lapse imaging of adult dorsal root ganglion neurons in an in vitro model of the glial scar to examine macrophage-axon interactions and observed that adhesive contacts and considerable physical interplay between macrophages and dystrophic axons led to extensive axonal retraction. The induction of retraction was dependent on both the growth state of the axon and the activation state of the macrophage. Only dystrophic adult axons were susceptible to macrophage "attack. " Unlike intrinsically active cell line macrophages, both primary macrophages and microglia required activation to induce axonal retraction. Contact with astrocytes had no deleterious effect on adult dystrophic axons, suggesting that the induction of extensive retraction was specific to phagocytic cells. Our data are the first to indicate a direct role of activated macrophages in axonal retraction by physical cell-cell interactions with injured axons.

title: Characterization of Programmed Death-1 Homologue-1 (PD-1H) Expression and Function in Normal and HIV Infected Individuals

text: Chronic immune activation that persists despite anti-retroviral therapy (ART) is the strongest predictor of disease progression in HIV infection. Monocyte/macrophages in HIV-infected individuals are known to spontaneously secrete cytokines, although neither the mechanism nor the molecules involved are known. Here we show that overexpression of the newly described co-stimulatory molecule, PD1 homologue (PD-1H) in human monocyte/macrophages is sufficient to induce spontaneous secretion of multiple cytokines. The process requires signaling via PD-1H as cytokine secretion could be abrogated by deletion of the cytoplasmic domain. Such overexpression of PD-1H, associated with spontaneous cytokine expression is seen in monocytes from chronically HIV-infected individuals and this correlates with immune activation and CD4 depletion, but not viral load. Moreover, antigen presentation by PD-1H-overexpressing monocytes results in enhanced cytokine secretion by HIV-specific T cells. These results suggest that PD-1H might play a crucial role in modulating immune activation and immune response in HIV infection.

title: Infralimbic BDNF/TrkB enhancement of GluN2B currents facilitates extinction of a cocaine-conditioned place preference.

text: Brain-derived neurotrophic factor (BDNF) regulates synaptic activity and behavioral flexibility, and reduction of BDNF strongly predicts psychiatric disorders and cognitive dysfunction. Restoration of BDNF-dependent activity could alleviate these impairments, but BDNF has limited clinical utility due to its pharmacokinetics. Here we demonstrate that activation of a primary BDNF target, the tropomyosin-related kinase B (TrkB) receptor, enhances the amplitude and prolongs the decay kinetics of N-methyl-d-aspartate receptor (NMDAR) currents in male rat infralimbic prefrontal pyramidal neurons. Moreover, these effects were prevented and reversed by blockade of NMDARs containing the GluN2B subunit. Our results show that this signaling cascade bidirectionally regulates extinction of a cocaine-induced conditioned place preference (CPP), a task that requires behavioral flexibility. Blockade of infralimbic TrkB receptors or GluN2B-containing NMDARs disrupted consolidation of extinction of the CPP. In contrast, extinction was strengthened by potentiation of TrkB receptor activity with infralimbic infusions of BDNF or systemic injections of 7,8 dihydroxyflavone (7,8DHF), the newly synthesized TrkB receptor agonist. The 7,8DHF-induced enhancement of extinction was prevented by infralimbic infusions of a GluN2B-specific receptor antagonist, demonstrating that TrkB receptor activation enhances extinction of cocaine-CPP via GluN2B-containing NMDARs. Together, infralimbic TrkB receptor activation strengthens GluN2B-containing NMDAR currents to support extinction learning. TrkB receptor agonists would therefore be useful as pharmacological adjuncts for extinction-based therapies for treatment of psychiatric disorders associated with reduced BDNF activity.

title: Atm-deficient mice exhibit increased sensitivity to dextran sulfate sodium-induced colitis characterized by elevated DNA damage and persistent immune activation.

text: The role of ataxia telangiectasia mutated (ATM), a DNA double-strand break recognition and response protein, in inflammation and inflammatory diseases is unclear. We have previously shown that high levels of systemic DNA damage are induced by intestinal inflammation in wild-type mice. To determine the effect of Atm deficiency in inflammation, we induced experimental colitis in Atm(-/-), Atm(+/-), and wild-type mice via dextran sulfate sodium (DSS) administration. Atm(-/-) mice had higher disease activity indices and rates of mortality compared with heterozygous and wild-type mice. Systemic DNA damage and immune response were characterized in peripheral blood throughout and after three cycles of treatment. Atm(-/-) mice showed increased sensitivity to levels of DNA strand breaks in peripheral leukocytes, as well as micronucleus formation in erythroblasts, compared with heterozygous and wild-type mice, especially during remission periods and after the end of treatment. Markers of reactive oxygen and nitrogen species-mediated damage, including 8-oxoguanine and nitrotyrosine, were present both in the distal colon and in peripheral leukocytes, with Atm(-/-) mice manifesting more 8-oxoguanine formation than wild-type mice. Atm(-/-) mice showed greater upregulation of inflammatory cytokines and significantly higher percentages of activated CD69+ and CD44+ T cells in the peripheral blood throughout treatment. ATM, therefore, may be a critical immunoregulatory factor dampening the deleterious effects of chronic DSS-induced inflammation, necessary for systemic genomic stability and homeostasis of the gut epithelial barrier.

title: Grass plants bind, retain, uptake, and transport infectious prions.

text: Prions are the protein-based infectious agents responsible for prion diseases. Environmental prion contamination has been implicated in disease transmission. Here, we analyzed the binding and retention of infectious prion protein (PrP(Sc)) to plants. Small quantities of PrP(Sc) contained in diluted brain homogenate or in excretory materials (urine and feces) can bind to wheat grass roots and leaves. Wild-type hamsters were efficiently infected by ingestion of prion-contaminated plants. The prion-plant interaction occurs with prions from diverse origins, including chronic wasting disease. Furthermore, leaves contaminated by spraying with a prion-containing preparation retained PrP(Sc) for several weeks in the living plant. Finally, plants can uptake prions from contaminated soil and transport them to aerial parts of the plant (stem and leaves). These findings demonstrate that plants can efficiently bind infectious prions and act as carriers of infectivity, suggesting a possible role of environmental prion contamination in the horizontal transmission of the disease.

title: Gender-dependent differences in outcome after the treatment of infection in hospitalized patients.

text:
CONTEXT While it is established that management strategies and outcomes differ by gender for many diseases, its effect on infection has not been adequately studied.
 OBJECTIVE To investigate the role of gender among hospitalized patients treated for infection.
 DESIGN Observational cohort study conducted during a 26-month period from December 1996 through January 1999.
 SETTING University-affiliated hospital.
 PARTICIPANTS A total of 892 patients in the surgical units of the hospital with 1470 consecutive infectious episodes (782 in men and 688 in women).
 MAIN OUTCOME MEASURES Mortality during hospitalization by gender for infection episodes overall and for specific infectious sites, including lung, peritoneum, bloodstream, catheter, urine, surgical site, and skin/soft tissue.
 RESULTS Among all infections, there was no significant difference in mortality based on gender (men, 11.1% vs women, 14.2%; P = .07). After logistic regression analysis, factors independently associated with mortality included higher APACHE (Acute Physiology and Chronic Health Evaluation) II score, older age, malignancy, blood transfusion, and diagnosis of infection more than 7 days after admission, but not gender (female odds ratio [OR] for death, 1.32; 95% confidence interval [CI], 0.90-1.94; P = .16). Mortality was higher in women for lung (men, 18% vs women, 34%; P = .002) and soft tissue (men, 2% vs women, 10%; P < or = .05) infection; for other infectious sites, mortality did not differ by gender. Factors associated with mortality due to pneumonia by logistic regression included higher APACHE II score, malignancy, diabetes mellitus, diagnosis of infection more than 7 days after admission, older age, transplantation, and female gender (OR for death, 2.25; 95% CI, 1.17-4.32; P = .02).
 CONCLUSIONS Although gender may not be predictive of mortality among all infections, women appear to be at increased risk for death from hospital-acquired pneumonia, even after controlling for other comorbidities.

title: Myeloid Cells Expressing VEGF and Arginase-1 Following Uptake of Damaged Retinal Pigment Epithelium Suggests Potential Mechanism That Drives the Onset of Choroidal Angiogenesis in Mice

text: Whilst data recognise both myeloid cell accumulation during choroidal neovascularisation (CNV) as well as complement activation, none of the data has presented a clear explanation for the angiogenic drive that promotes pathological angiogenesis. One possibility that is a pre-eminent drive is a specific and early conditioning and activation of the myeloid cell infiltrate. Using a laser-induced CNV murine model, we have identified that disruption of retinal pigment epithelium (RPE) and Bruch's membrane resulted in an early recruitment of macrophages derived from monocytes and microglia, prior to angiogenesis and contemporaneous with lesional complement activation. Early recruited CD11b(+) cells expressed a definitive gene signature of selective inflammatory mediators particularly a pronounced Arg-1 expression. Accumulating macrophages from retina and peripheral blood were activated at the site of injury, displaying enhanced VEGF expression, and notably prior to exaggerated VEGF expression from RPE, or earliest stages of angiogenesis. All of these initial events, including distinct VEGF (+) Arg-1(+) myeloid cells, subsided when CNV was established and at the time RPE-VEGF expression was maximal. Depletion of inflammatory CCR2-positive monocytes confirmed origin of infiltrating monocyte Arg-1 expression, as following depletion Arg-1 signal was lost and CNV suppressed. Furthermore, our in vitro data supported a myeloid cell uptake of damaged RPE or its derivatives as a mechanism generating VEGF (+) Arg-1(+) phenotype in vivo. Our results reveal a potential early driver initiating angiogenesis via myeloid-derived VEGF drive following uptake of damaged RPE and deliver an explanation of why CNV develops during any of the stages of macular degeneration and can be explored further for therapeutic gain.

title: Brief Internet-Based Intervention Reduces Posttraumatic Stress and Prolonged Grief in Parents after the Loss of a Child during Pregnancy: A Randomized Controlled Trial

text: Background: The loss of a child during pregnancy causes significant psychological distress for many women and their partners, and may lead to long-lasting psychiatric disorders. Internet-based interventions using exposure techniques and cognitive restructuring have proved effective for posttraumatic stress disorder (PTSD) and prolonged grief. This study compared the effects of an Internet-based intervention for parents after prenatal loss with a waiting list condition (WLC). Methods: The Impact of Event Scale - Revised assessed symptoms of PTSD; the Inventory of Complicated Grief and the Brief Symptom Inventory assessed depression, anxiety, and general mental health. The 228 participants (92% female) were randomly allocated to a treatment group (TG; n = 115) or a WLC group (n = 113). The TG received a 5-week cognitive behavioral intervention including (1) self-confrontation, (2) cognitive restructuring, and (3) social sharing. Results: The TG showed significantly reduced symptoms of posttraumatic stress, prolonged grief, depression, and anxiety relative to the WLC control group. Intention-to-treat analysis revealed treatment effects of between d = 0.84 and d = 1.02 for posttraumatic stress and prolonged grief from pre- to posttreatment time points. Further significant improvement in all symptoms of PTSD and prolonged grief was found from the posttreatment evaluation to the 12-month follow-up. The attrition rate of 14% was relatively low. Conclusions: The Internet-based intervention proved to be a feasible and cost-effective treatment, reducing symptoms of posttraumatic stress, grief, depression, anxiety, and general mental health after pregnancy loss. Low-threshold e-health interventions should be further evaluated and implemented routinely to improve psychological support after pregnancy loss.


query: The deregulated and prolonged activation of monocytes improves inflammatory disease outcomes.

title: The myeloid transcription factor KLF2 regulates the host response to polymicrobial infection and endotoxic shock.

text: Precise control of myeloid cell activation is required for optimal host defense. However, this activation process must be under exquisite control to prevent uncontrolled inflammation. Herein, we identify the Kruppel-like transcription factor 2 (KLF2) as a potent regulator of myeloid cell activation in vivo. Exposure of myeloid cells to hypoxia and/or bacterial products reduced KLF2 expression while inducing hypoxia inducible factor-1α (HIF-1α), findings that were recapitulated in human septic patients. Myeloid KLF2 was found to be a potent inhibitor of nuclear factor-kappaB (NF-κB)-dependent HIF-1α transcription and, consequently, a critical determinant of outcome in models of polymicrobial infection and endotoxemia. Collectively, these observations identify KLF2 as a tonic repressor of myeloid cell activation in vivo and an essential regulator of the innate immune system.

title: Myeloid-specific Krüppel-like factor 2 inactivation increases macrophage and neutrophil adhesion and promotes atherosclerosis.

text:
RATIONALE Hemizygous deficiency of the transcription factor Krüppel-like factor 2 (KLF2) has been shown previously to augment atherosclerosis in hypercholesterolemic mice. However, the cell type responsible for the increased atherosclerosis due to KLF2 deficiency has not been identified. This study examined the consequence of myeloid cell-specific KLF2 inactivation in atherosclerosis.
 METHODS AND RESULTS Cell-specific knockout mice were generated by Cre/loxP recombination. Macrophages isolated from myeloid-specific Klf2 knockout (myeKlf2(-/-)) mice were similar to myeKlf2(+/+) macrophages in response to activation, polarization, and lipid accumulation. However, in comparison to myeKlf2(+/+) macrophages, myeKlf2(-/-) macrophages adhered more robustly to endothelial cells. Neutrophils from myeKlf2(-/-) mice also adhered more robustly to endothelial cells, and fewer myeKlf2(-/-) neutrophils survived in culture over a 24-hour period in comparison with myeKlf2(+/+) neutrophils. When myeKlf2(-/-) mice were mated to Ldlr(-/-) mice and then fed a high fat and high cholesterol diet, significant increase in atherosclerosis was observed in the myeKlf2(-/-)Ldlr(-/-) mice compared with myeKlf2(+/+)Ldlr(-/-) littermates. The increased atherosclerosis in myeKlf2(-/-)Ldlr(-/-) mice was associated with elevated presence of neutrophils and macrophages, with corresponding increase of myeloperoxidase as well as chlorinated and nitrosylated tyrosine epitopes in their lesion areas compared with myeKlf2(+/+)Ldlr(-/-) mice.
 CONCLUSIONS This study documents a role for myeloid KLF2 expression in modulating atherosclerosis. The increased neutrophil accumulation and atherosclerosis progression with myeloid-specific KLF2 deficiency also underscores the importance of neutrophils in promoting vascular oxidative stress and atherosclerosis. Collectively, these results suggest that elevating KLF2 expression may be a novel strategy for prevention and treatment of atherosclerosis.

title: Human SNP Links Differential Outcomes in Inflammatory and Infectious Disease to a FOXO3-Regulated Pathway

text: The clinical course and eventual outcome, or prognosis, of complex diseases varies enormously between affected individuals. This variability critically determines the impact a disease has on a patient's life but is very poorly understood. Here, we exploit existing genome-wide association study data to gain insight into the role of genetics in prognosis. We identify a noncoding polymorphism in FOXO3A (rs12212067: T > G) at which the minor (G) allele, despite not being associated with disease susceptibility, is associated with a milder course of Crohn's disease and rheumatoid arthritis and with increased risk of severe malaria. Minor allele carriage is shown to limit inflammatory responses in monocytes via a FOXO3-driven pathway, which through TGFβ1 reduces production of proinflammatory cytokines, including TNFα, and increases production of anti-inflammatory cytokines, including IL-10. Thus, we uncover a shared genetic contribution to prognosis in distinct diseases that operates via a FOXO3-driven pathway modulating inflammatory responses.

title: Oncogenic pathway signatures in human cancers as a guide to targeted therapies

text: The development of an oncogenic state is a complex process involving the accumulation of multiple independent mutations that lead to deregulation of cell signalling pathways central to the control of cell growth and cell fate. The ability to define cancer subtypes, recurrence of disease and response to specific therapies using DNA microarray-based gene expression signatures has been demonstrated in multiple studies. Various studies have also demonstrated the potential for using gene expression profiles for the analysis of oncogenic pathways. Here we show that gene expression signatures can be identified that reflect the activation status of several oncogenic pathways. When evaluated in several large collections of human cancers, these gene expression signatures identify patterns of pathway deregulation in tumours and clinically relevant associations with disease outcomes. Combining signature-based predictions across several pathways identifies coordinated patterns of pathway deregulation that distinguish between specific cancers and tumour subtypes. Clustering tumours based on pathway signatures further defines prognosis in respective patient subsets, demonstrating that patterns of oncogenic pathway deregulation underlie the development of the oncogenic phenotype and reflect the biology and outcome of specific cancers. Predictions of pathway deregulation in cancer cell lines are also shown to predict the sensitivity to therapeutic agents that target components of the pathway. Linking pathway deregulation with sensitivity to therapeutics that target components of the pathway provides an opportunity to make use of these oncogenic pathway signatures to guide the use of targeted therapeutics.

title: CCR2 and CXCR4 regulate peripheral blood monocyte pharmacodynamics and link to efficacy in experimental autoimmune encephalomyelitis

text:
BACKGROUND CCR2 plays a key role in regulating monocyte trafficking to sites of inflammation and therefore has been the focus of much interest as a target for inflammatory disease.
 METHODS Here we examined the effects of CCR2 blockade with a potent small molecule antagonist to determine the pharmacodynamic consequences on the peripheral blood monocyte compartment in the context of acute and chronic inflammatory processes.
 RESULTS We demonstrate that CCR2 antagonism in vivo led to a rapid decrease in the number of circulating Ly6Chi monocytes and that this decrease was largely due to the CXCR4-dependent sequestration of these cells in the bone marrow, providing pharmacological evidence for a mechanism by which monocyte dynamics are regulated in vivo. CCR2 antagonism led to an accumulation of circulating CCL2 and CCL7 levels in the blood, indicating a role for CCR2 in regulating the levels of its ligands under homeostatic conditions. Finally, we show that the pharmacodynamic changes due to CCR2 antagonism were apparent after chronic dosing in mouse experimental autoimmune encephalomyelitis, a model in which CCR2 blockade demonstrated a dramatic reduction in disease severity, manifest in a reduced accumulation of monocytes and other cells in the CNS.
 CONCLUSION CCR2 antagonism in vivo has tractable pharmacodynamic effects that can be used to align target engagement with biologic effects on disease activity.

title: Programmed death-1–induced interleukin-10 production by monocytes impairs CD4+ T cell activation during HIV infection

text: Viral replication and microbial translocation from the gut to the blood during HIV infection lead to hyperimmune activation, which contributes to the decline in CD4+ T cell numbers during HIV infection. Programmed death-1 (PD-1) and interleukin-10 (IL-10) are both upregulated during HIV infection. Blocking interactions between PD-1 and programmed death ligand-1 (PD-L1) and between IL-10 and IL-10 receptor (IL-10R) results in viral clearance and improves T cell function in animal models of chronic viral infections. Here we show that high amounts of microbial products and inflammatory cytokines in the plasma of HIV-infected subjects lead to upregulation of PD-1 expression on monocytes that correlates with high plasma concentrations of IL-10. Triggering of PD-1 expressed on monocytes by PD-L1 expressed on various cell types induced IL-10 production and led to reversible CD4+ T cell dysfunction. We describe a new function for PD-1 whereby microbial products inhibit T cell expansion and function by upregulating PD-1 levels and IL-10 production by monocytes after binding of PD-1 by PD-L1.

title: Blood monocytes consist of two principal subsets with distinct migratory properties

text: Peripheral blood monocytes are a heterogeneous population of circulating leukocytes. Using a murine adoptive transfer system to probe monocyte homing and differentiation in vivo, we identified two functional subsets among murine blood monocytes: a short-lived CX(3)CR1(lo)CCR2(+)Gr1(+) subset that is actively recruited to inflamed tissues and a CX(3)CR1(hi)CCR2(-)Gr1(-) subset characterized by CX(3)CR1-dependent recruitment to noninflamed tissues. Both subsets have the potential to differentiate into dendritic cells in vivo. The level of CX(3)CR1 expression also defines the two major human monocyte subsets, the CD14(+)CD16(-) and CD14(lo)CD16(+) monocytes, which share phenotype and homing potential with the mouse subsets. These findings raise the potential for novel therapeutic strategies in inflammatory diseases.

title: Kruppel-like factor 2 (KLF2) regulates monocyte differentiation and functions in mBSA and IL-1β-induced arthritis.

text: Kruppel-like factor 2 (KLF2) plays an important role in the regulation of a variety of immune cells, including monocytes. We have previously shown that KLF2 inhibits proinflammatory activation of monocytes. However, the role of KLF2 in arthritis is yet to be investigated. In the current study, we show that recruitment of significantly greater numbers of inflammatory subset of CD11b(+)F4/80(+)Ly6C+ monocytes to the inflammatory sites in KLF2 hemizygous mice compared to the wild type littermate controls. In parallel, inflammatory mediators, MCP-1, Cox-2 and PAI-1 were significantly up-regulated in bone marrow-derived monocytes isolated from KLF2 hemizygous mice, in comparison to wild-type controls. Methylated-BSA and IL-1β-induced arthritis was more severe in KLF2 hemizygous mice as compared to the littermate wild type controls. Consistent with this observation, monocytes isolated from KLF2 hemizygous mice showed an increased number of cells matured and differentiated towards osteoclastic lineage, potentially contributing to the severity of cartilage and bone damage in induced arthritic mice. The severity of arthritis was associated with the higher expression of proteins such as HSP60, HSP90 and MMP13 and attenuated levels of pPTEN, p21, p38 and HSP25/27 molecules in bone marrow cells of arthritic KLF2 hemizygous mice compared to littermate wild type controls. The data provide new insights and evidences of KLF2-mediated transcriptional regulation of arthritis via modulation of monocyte differentiation and function.

title: Local proliferation dominates lesional macrophage accumulation in atherosclerosis

text: During the inflammatory response that drives atherogenesis, macrophages accumulate progressively in the expanding arterial wall. The observation that circulating monocytes give rise to lesional macrophages has reinforced the concept that monocyte infiltration dictates macrophage buildup. Recent work has indicated, however, that macrophage accumulation does not depend on monocyte recruitment in some inflammatory contexts. We therefore revisited the mechanism underlying macrophage accumulation in atherosclerosis. In murine atherosclerotic lesions, we found that macrophages turn over rapidly, after 4 weeks. Replenishment of macrophages in these experimental atheromata depends predominantly on local macrophage proliferation rather than monocyte influx. The microenvironment orchestrates macrophage proliferation through the involvement of scavenger receptor A (SR-A). Our study reveals macrophage proliferation as a key event in atherosclerosis and identifies macrophage self-renewal as a therapeutic target for cardiovascular disease.

title: Inflammatory monocyte/macrophage modulation by liposome-entrapped spironolactone ameliorates acute lung injury in mice.

text:
AIM To examine the therapeutic/preventive potential of liposome-encapsulated spironolactone (SP; Lipo-SP) for acute lung injury (ALI) and fibrosis.    MATERIALS & METHODS Lipo-SP was prepared by the film-ultrasonic method, and physicochemical and pharmacokinetic characterized for oral administration (10 and 20 mg/kg for SP-loaded liposome; 20 mg/kg for free SP) in a mouse model bleomycin-induced ALI.
 RESULTS Lipo-SP enhanced bioavailability of SP with significant amelioration in lung pathology. Mechanistically, SP-mediated mineralocorticoid receptor antagonism contributes to inflammatory monocyte/macrophage modulation via an inhibitory effect on Ly6C(hi) monocytosis-directed M2 polarization of alveolar macrophages. Moreover, Lipo-SP at lower dose (10 mg/kg) exhibited more improvement in body weight gain.
 CONCLUSION Our data highlight Lipo-SP as a promising approach with therapeutic/preventive potential for ALI and fibrosis.

title: Bile acid receptor TGR5 agonism induces NO production and reduces monocyte adhesion in vascular endothelial cells.

text:
OBJECTIVE TGR5 is a G-protein-coupled receptor for bile acids. So far, little is known about the function of TGR5 in vascular endothelial cells.    APPROACH AND RESULTS In bovine aortic endothelial cells, treatment with a bile acid having a high affinity to TGR5, taurolithocholic acid (TLCA), significantly increased NO production. This effect was abolished by small interfering RNA-mediated depletion of TGR5. TLCA-induced NO production was also observed in human umbilical vein endothelial cells measured via intracellular cGMP accumulation. TLCA increased endothelial NO synthase(ser1177) phosphorylation in human umbilical vein endothelial cells. This response was accompanied by increased Akt(ser473) phosphorylation and intracellular Ca(2+). Inhibition of these signals significantly decreased TLCA-induced NO production. We next examined whether TGR5-mediated NO production affects inflammatory responses of endothelial cells. In human umbilical vein endothelial cells, TLCA significantly reduced tumor necrosis factor-α-induced adhesion of monocytes, vascular cell adhesion molecule-1 expression, and activation of nuclear factor-κB. TLCA also inhibited lipopolysaccharide-induced monocyte adhesion to mesenteric venules in vivo. These inhibitory effects of TLCA were abrogated by NO synthase inhibition.
 CONCLUSIONS TGR5 agonism induces NO production via Akt activation and intracellular Ca(2+) increase in vascular endothelial cells, and this function inhibits monocyte adhesion in response to inflammatory stimuli.

title: IL-6 as a keystone cytokine in health and disease

text: Interleukin 6 (IL-6) has a broad effect on cells of the immune system and those not of the immune system and often displays hormone-like characteristics that affect homeostatic processes. IL-6 has context-dependent pro- and anti-inflammatory properties and is now regarded as a prominent target for clinical intervention. However, the signaling cassette that controls the activity of IL-6 is complicated, and distinct intervention strategies can inhibit this pathway. Clinical experience with antagonists of IL-6 has raised new questions about how and when to block this cytokine to improve disease outcome and patient wellbeing. Here we discuss the effect of IL-6 on innate and adaptive immunity and the possible advantages of various antagonists of IL-6 and consider how the immunobiology of IL-6 may inform clinical decisions.

title: Morin Attenuates Ovalbumin-Induced Airway Inflammation by Modulating Oxidative Stress-Responsive MAPK Signaling.

text: Asthma is one of the most common inflammatory diseases characterized by airway hyperresponsiveness, inflammation, and remodeling. Morin, an active ingredient obtained from Moraceae plants, has been demonstrated to have promising anti-inflammatory activities in a range of disorders. However, its impacts on pulmonary diseases, particularly on asthma, have not been clarified. This study was designed to investigate whether morin alleviates airway inflammation in chronic asthma with an emphasis on oxidative stress modulation. In vivo, ovalbumin- (OVA-) sensitized mice were administered with morin or dexamethasone before challenge. Bronchoalveolar lavage fluid (BALF) and lung tissues were obtained to perform cell counts, histological analysis, and enzyme-linked immunosorbent assay. In vitro, human bronchial epithelial cells (BECs) were challenged by tumor necrosis factor alpha (TNF-α). The supernatant was collected for the detection of the proinflammatory proteins, and the cells were collected for reactive oxygen species (ROS)/mitogen-activated protein kinase (MAPK) evaluations. Severe inflammatory responses and remodeling were observed in the airways of the OVA-sensitized mice. Treatment with morin dramatically attenuated the extensive trafficking of inflammatory cells into the BALF and inhibited their infiltration around the respiratory tracts and vessels. Morin administration also significantly suppressed goblet cell hyperplasia and collagen deposition/fibrosis and dose-dependently inhibited the OVA-induced increases in IgE, TNF-α, interleukin- (IL-) 4, IL-13, matrix metalloproteinase-9, and malondialdehyde. In human BECs challenged by TNF-α, the levels of proteins such as eotaxin-1, monocyte chemoattractant protein-1, IL-8 and intercellular adhesion molecule-1, were consistently significantly decreased by morin. Western blotting and the 2',7'-dichlorofluorescein assay revealed that the increases in intracellular ROS and MAPK phosphorylation were abolished by morin, implying that ROS/MAPK signaling contributes to the relief of airway inflammation. Our findings indicate for the first time that morin alleviates airway inflammation in chronic asthma, which probably occurs via the oxidative stress-responsive MAPK pathway, highlighting a novel profile of morin as a potent agent for asthma management.

title: Translocated LPS Might Cause Endotoxin Tolerance in Circulating Monocytes of Cystic Fibrosis Patients

text: Cystic Fibrosis (CF) is an inherited pleiotropic disease that results from abnormalities in the gene codes of a chloride channel. The lungs of CF patients are chronically infected by several pathogens but bacteraemia have rarely been reported in this pathology. Besides that, circulating monocytes in CF patients exhibit a patent Endotoxin Tolerance (ET) state since they show a significant reduction of the inflammatory response to bacterial stimulus. Despite a previous description of this phenomenon, the direct cause of ET in CF patients remains unknown. In this study we have researched the possible role of microbial/endotoxin translocation from a localized infection to the bloodstream as a potential cause of ET induction in CF patients. Plasma analysis of fourteen CF patients revealed high levels of LPS compared to healthy volunteers and patients who suffer from Chronic Obstructive Pulmonary Disease. Experiments in vitro showed that endotoxin concentrations found in plasma of CF patients were enough to induce an ET phenotype in monocytes from healthy controls. In agreement with clinical data, we failed to detect bacterial DNA in CF plasma. Our results suggest that soluble endotoxin present in bloodstream of CF patients causes endotoxin tolerance in their circulating monocytes.

title: Transcriptome analysis reveals human cytomegalovirus reprograms monocyte differentiation toward an M1 macrophage.

text: Monocytes are primary targets for human CMV (HCMV) infection and are proposed to be responsible for hematogenous dissemination of the virus. Monocytes acquire different functional traits during polarization to the classical proinflammatory M1 macrophage or the alternative antiinflammatory M2 macrophage. We hypothesized that HCMV induced a proinflammatory M1 macrophage following infection to promote viral dissemination because, biologically, a proinflammatory state provides the tools to drive infected monocytes from the blood into the tissue. To test this hypothesis of monocyte conversion from a normal quiescent phenotype to an inflammatory phenotype, we used Affymetrix Microarray to acquire a transcriptional profile of infected monocytes at a time point our data emphasized is a key temporal regulatory point following infection. We found that HCMV significantly up-regulated 583 (5.2%) of the total genes and down-regulated 621 (5.5%) of the total genes>or=1.5-fold at 4 h postinfection. Further ontology analysis revealed that genes implicated in classical M1 macrophage activation were stimulated by HCMV infection. We found that 65% of genes strictly associated with M1 polarization were up-regulated, while only 4% of genes solely associated with M2 polarization were up-regulated. Analysis of the monocyte chemokinome at the transcriptional level showed that 44% of M1 and 33% of M2 macrophage chemokines were up-regulated. Proteomic analysis using chemokine Ab arrays confirmed the secretion of these chemotactic proteins from HCMV-infected monocytes. Overall, the results identify that the HCMV-infected monocyte transcriptome displayed a unique M1/M2 polarization signature that was skewed toward the classical M1 activation phenotype.

title: Kruppel-like factor 4 is essential for inflammatory monocyte differentiation in vivo.

text: Several members of the Kruppel-like factor (KLF) family of transcription factors play important roles in differentiation, survival, and trafficking of blood and immune cell types. We demonstrate in this study that hematopoietic cells from KLF4(-/-) fetal livers (FL) contained normal numbers of functional hematopoietic progenitor cells, were radioprotective, and performed as well as KLF4(+/+) cells in competitive repopulation assays. However, hematopoietic "KLF4(-/-) chimeras" generated by transplantation of KLF4(-/-) fetal livers cells into lethally irradiated wild-type mice completely lacked circulating inflammatory (CD115(+)Gr1(+)) monocytes, and had reduced numbers of resident (CD115(+)Gr1(-)) monocytes. Although the numbers and function of peritoneal macrophages were normal in KLF4(-/-) chimeras, bone marrow monocytic cells from KLF4(-/-) chimeras expressed lower levels of key trafficking molecules and were more apoptotic. Thus, our in vivo loss-of-function studies demonstrate that KLF4, previously shown to mediate proinflammatory signaling in human macrophages in vitro, is essential for differentiation of mouse inflammatory monocytes, and is involved in the differentiation of resident monocytes. In addition, inducible expression of KLF4 in the HL60 human acute myeloid leukemia cell line stimulated monocytic differentiation and enhanced 12-O-tetradecanoylphorbol 13-acetate induced macrophage differentiation, but blocked all-trans-retinoic acid induced granulocytic differentiation of HL60 cells. The inflammation-selective effects of loss-of-KLF4 and the gain-of-KLF4-induced monocytic differentiation in HL60 cells identify KLF4 as a key regulator of monocytic differentiation and a potential target for translational immune modulation.

title: Macrophages in the Pathogenesis of Atherosclerosis

text: In atherosclerosis, the accumulation of apolipoprotein B-lipoproteins in the matrix beneath the endothelial cell layer of blood vessels leads to the recruitment of monocytes, the cells of the immune system that give rise to macrophages and dendritic cells. Macrophages derived from these recruited monocytes participate in a maladaptive, nonresolving inflammatory response that expands the subendothelial layer due to the accumulation of cells, lipid, and matrix. Some lesions subsequently form a necrotic core, triggering acute thrombotic vascular disease, including myocardial infarction, stroke, and sudden cardiac death. This Review discusses the central roles of macrophages in each of these stages of disease pathogenesis.

title: Regulation of myeloid cell function through the CD200 receptor.

text: Myeloid cells play pivotal roles in chronic inflammatory diseases through their broad proinflammatory, destructive, and remodeling capacities. CD200 is widely expressed on a variety of cell types, while the recently identified CD200R is expressed on myeloid cells and T cells. CD200 deletion in vivo results in myeloid cell dysregulation and enhanced susceptibility to autoimmune inflammation, suggesting that the CD200-CD200R interaction is involved in immune suppression. We demonstrate in this study that CD200R agonists suppress mouse and human myeloid cell function in vitro, and also define a dose relationship between receptor expression and cellular inhibition. IFN-gamma- and IL-17-stimulated cytokine secretion from mouse peritoneal macrophages was inhibited by CD200R engagement. Inhibitory effects were not universal, as LPS-stimulated responses were unaffected. Inhibition of U937 cell cytokine production correlated with CD200R expression levels, and inhibition was only observed in low CD200R expressing cells, if the CD200R agonists were further cross-linked. Tetanus toxoid-induced human PBMC IL-5 and IL-13 secretion was inhibited by CD200R agonists. This inhibition was dependent upon cross-linking the CD200R on monocytes, but not on cross-linking the CD200R on CD4+ T cells. In all, we provide direct evidence that the CD200-CD200R interaction controls monocyte/macrophage function in both murine and human systems, further supporting the potential clinical application of CD200R agonists for the treatment of chronic inflammatory diseases.