bluuebunny/crossref_metadata_2025 huggingface dataset:
Multinutrient undernutrition dysregulates the resident macrophage proinflammatory cytokine network, nuclear factor-κB activation, and nitric oxide production
Authors: Anstead Gregory M , Chandrasekar Bysani , Zhang Qiong , Melby Peter C
Published: September 2003

We have described previously a murine model of multinutrient undernutrition that reproduced the features of moderate human malnutrition and led to increased early dissemination of Leishmania donovani. Peritoneal cells from these malnourished mice produced decreased NO after stimulation with IFN-γ/LPS. We hypothesized that malnutrition may cause a deficit in NF-κB activation, a principal transcription pathway for inducible NO synthase and proinflammatory cytokines. Macrophages from malnourished mice, stimulated with IFN-γ/LPS, showed increased IL-6 production and decreased IL-10 and TNF-α production. Neutralization of TNF-α in macrophage cultures from the control mice mimicked the effect of malnutrition on NO and IL-10 production, whereas supplemental TNF-α added to cultures of macrophages from malnourished mice increased NO secretion. NF-κB nuclear binding activity in macrophages from the malnourished mice was reduced early after stimulation, but increased to supranormal values by 16- or 24-h poststimulation. Blocking NO production in the macrophages from the control mice reproduced the effect of malnutrition on the late activation of NF-κB, whereas supplemental NO decreased the late NF-κB activation in the malnourished mice. Thus, in macrophages from the malnourished mice, initial deficits in NF-κB activity probably lead to decreased TNF-α, which results in decreased NO; however, IL-6 is regulated independently from NF-κB and TNF-α. The late activation of NF-κB in the macrophages from malnourished mice is due to absence of negative feedback from NO.
Artificially controlled aggregation of proteins and targeting in hematopoietic cells
Authors: Rosén Hanna , Gao Ying , Johnsson Ellinor , Olsson Inge
Published: September 2003

The targeting mechanisms for granule proteins in hematopoietic cells are largely unknown. Aggregation is believed to be important for protein sorting-for-entry and sorting-by-retention in endocrine and neuroendocrine cells. We asked whether artificially induced multimerization/aggregation of chimeric proteins could affect their sorting in hematopoietic cells. A system was used that permits ligand-controlled intracellular oligomerization of hybrid proteins containing the FK506-binding protein (FKBP). The hybrid proteins ELA-(FKBP)3 with neutrophil elastase (ELA) and (FKBP∗)4-FCS-hGH with a furin cleavage site (FCS) and human growth hormone (hGH) were expressed in the myeloblastic 32D and the rat basophilic leukemia (RBL-1) hematopoietic cell lines. ELA alone is normally targeted to secretory lysosomes. However, the hybrid proteins and ligand-induced aggregates of them were constitutively secreted and not targeted. The hGH that was released at the FCS in (FKBP∗)4-FCS-hGH was also constitutively secreted. We conclude that protein multimerization/aggregation per se is not enough to facilitate sorting-for-entry to secretory lysosomes in hematopoietic cells and that improperly folded proteins may be eliminated from sorting by constitutive secretion.
Expression of the c-ErbB-2/HER2 proto-oncogene in normal hematopoietic cells
Authors: Leone Francesco , Perissinotto Eliana , Cavalloni Giuliana , Fonsato Valentina , Bruno Stefania , Surrenti Nadia , Hong Dengli , Capaldi Antonio , Geuna Massimo , Piacibello Wanda , Aglietta Massimo
Published: September 2003

The HER2/c-ErbB-2 proto-oncogene is overexpressed in 25–30% of human breast cancers. We previously reported the c-ErbB-2 transcript in mononuclear cells (MNC) from bone marrow (BM), peripheral blood (PB), and mobilized PB (MPB). Here, we describe extensively the expression pattern of c-ErbB-2 mRNA and protein in normal adult hematopoietic tissue and cord blood (CB)-derived cells. Quantitative reverse transcriptase-polymerase chain reaction shows that the c-ErbB-2 transcript is expressed in hematopoietic cells at low levels if compared with normal epithelial and breast cancer cells. The c-ErbB-2 protein was detected predominantly in MNC from PB and CB by Western blot analysis. Flow cytometry revealed that CD15+, CD14+, and glycophorin A+ subpopulations express c-ErbB-2 protein, whereas lymphocytes are c-ErbB-2-negative. The c-ErbB-2 expression is higher in CB MNC. More than 90% of BM- and MPB-derived CD34+ progenitors are c-ErbB-2-negative; by contrast, 5–40% of CB-derived CD34+ progenitors express c-ErbB-2. We found that c-ErbB-2 protein is up-regulated during cell-cycle recruitment of progenitor cells. Similarly, it increases in mature, hematopoietic proliferating cells. This study reports the first evidence that the c-ErbB-2 receptor is correlated to the proliferating state of hematopoietic cells. Studies in progress aim to clarify the role of c-ErbB-2 in regulation of this process in hematopoietic tissues.
How we detect microbes and respond to them: the Toll-like receptors and their transducers
Authors: Beutler B , Hoebe K , Du X , Ulevitch R J
Published: September 2003

Macrophages and dendritic cells are in the front line of host defense. When they sense host invasion, they produce cytokines that alert other innate immune cells and also abet the development of an adaptive immune response. Although lipolysaccharide (LPS), peptidoglycan, unmethylated DNA, and other microbial products were long known to be the primary targets of innate immune recognition, there was puzzlement as to how each molecule triggered a response. It is now known that the Toll-like receptors (TLRs) are the principal signaling molecules through which mammals sense infection. Each TLR recognizes a restricted subset of molecules produced by microbes, and in some circumstances, only a single type of molecule is sensed (e.g., only LPS is sensed by TLR4). TLRs direct the activation of immune cells near to and far from the site of infection, mobilizing the comparatively vast immune resources of the host to confine and defeat an invasive organism before it has become widespread. The biochemical details of TLR signaling have been analyzed through forward and reverse genetic methods, and full elucidation of the molecular interactions that transpire within the first minutes following contact between host and pathogen will soon be at hand.
Developmental markers of B cells are superior to those of T cells for identification of stages with distinct gene expression profiles
Authors: Hoffmann Reinhard , Seidl Thomas , Bruno Ludovica , Dugas Martin
Published: September 2003

B and T lymphocytes develop through a series of cellular stages, which are defined by recombination status of the immunoglobulin and T cell receptor loci and can be separated by analysis of cell-surface markers. We evaluated how well 26 and 41 samples from five and eight developmental stages of B and T cell development, respectively, could be correctly assigned to their lineage of origin and developmental stage by analysis of the expression of 13,026 genes and expressed sequence tags (ESTs). The RNA expression patterns of eight genes correctly classified all 67 samples as belonging to the B cell or to the T cell lineage. Ninety-two to 100% of B-lineage samples could be correctly assigned to the protein-defined developmental stage by the RNA expression pattern of 29 genes. By contrast, RNA expression patterns of 39 genes were necessary to correctly assign 85–100% of T-lineage samples to the correct developmental stage. The sets of genes used for these classifications contain ESTs as well as known genes that have not previously been associated with lymphocyte development. Graphical display of the classifications shows that B-lineage samples are well separated from T-lineage samples, and samples from the five stages of B cell development are well separated from each other. By contrast, samples from the eight stages of T cell development cannot be separated precisely. We conclude that the protein markers currently widely used for separating stages of B cell development better identify molecularly distinct stages than those used for separating stages of T cell development.
Expression of glucocorticoid resistance following social stress requires a second signal
Authors: Avitsur Ronit , Padgett David A , Dhabhar Firdaus S , Stark Jennifer L , Kramer Kari A , Engler Harald , Sheridan John F
Published: September 2003

Stimulation of splenocytes from socially stressed mice [social disruption (SDR)] with Gram-negative bacterial lipopolysaccharide (LPS) revealed a state of functional glucocorticoid (GC) resistance. LPS-stimulated splenocytes were less sensitive to the inhibitory effects of corticosterone. This study demonstrated that activation signals were required for the expression of splenic GC resistance. The results demonstrated that six cycles of SDR induced splenomegaly and increased the number of CD11b-positive monocytes. SDR also increased the viability of cultured, nonstimulated splenocytes, and addition of corticosterone reduced the viability of these cells in a dose-dependent manner. However, following stimulation with LPS, the sensitivity of SDR splenocytes to GC was reduced. Similar results were obtained using lipid A, a fraction of the LPS molecule that binds to Toll-like receptor (TLR)4. Furthermore, C3H/HeJ mice that do not possess a functional TLR4 molecule responded to SDR with an increased number of CD11b-positive monocytes in the spleen and increased viability of nonstimulated splenocytes. However, neither LPS nor lipid A stimulation resulted in the expression of GC resistance. Together, these findings suggest that the expression of GC resistance in response to SDR requires a second signal that can be provided by ligation of TLR4.
CD44, α4 integrin, and fucoidin receptor-mediated phagocytosis of apoptotic leukocytes
Authors: Johnson Jacob D , Hess Krista L , Cook-Mills Joan M
Published: September 2003

Various types of phagocytes mediate the clearance of apoptotic cells. We previously reported that human and murine high endothelial venule (HEV) cells ingest apoptotic cells. In this report, we examined endothelial cell fucoidin receptor-mediated phagocytosis using a murine endothelial cell model mHEV. mHEV cell recognition of apoptotic leukocytes was blocked by fucoidin but not by other phagocytic receptor inhibitors such as mannose, fucose, N-acetylglucosamine, phosphatidylserine (PS), or blocking anti-PS receptor antibodies. Thus, the mHEV cells used fucoidin receptors for recognition and phagocytosis of apoptotic leukocytes. The fucoidin receptor-mediated endothelial cell phagocytosis was specific for apoptotic leukocytes, as necrotic cells were not ingested. This is in contrast to macrophages, which ingest apoptotic and necrotic cells. Endothelial cell phagocytosis of apoptotic cells did not alter viable lymphocyte migration across these endothelial cells. Antibody blocking of CD44 and α4 integrin on the apoptotic leukocyte inhibited this endothelial cell phagocytosis, suggesting a novel function for these adhesion molecules in the removal of apoptotic targets. The removal of apoptotic leukocytes by endothelial cells may protect the microvasculature, thus ensuring that viable lymphocytes can successfully migrate into tissues.
The cannabinoid system and immune modulation
Authors: Klein Thomas W , Newton Cathy , Larsen Kellie , Lu Lily , Perkins Izabella , Nong Liang , Friedman Herman
Published: September 2003

Studies on the effects of marijuana smoking have evolved into the discovery and description of the endocannabinoid system. To date, this system is composed of two receptors, CB1 and CB2, and endogenous ligands including anandamide, 2-arachidonoyl glycerol, and others. CB1 receptors and ligands are found in the brain as well as immune and other peripheral tissues. Conversely, CB2 receptors and ligands are found primarily in the periphery, especially in immune cells. Cannabinoid receptors are G protein-coupled receptors, and they have been linked to signaling pathways and gene activities in common with this receptor family. In addition, cannabinoids have been shown to modulate a variety of immune cell functions in humans and animals and more recently, have been shown to modulate T helper cell development, chemotaxis, and tumor development. Many of these drug effects occur through cannabinoid receptor signaling mechanisms and the modulation of cytokines and other gene products. It appears the immunocannabinoid system is involved in regulating the brain-immune axis and might be exploited in future therapies for chronic diseases and immune deficiency.
Divergence in NK cell and cyclic AMP regulation of T cell CD40L expression in asthmatic subjects
Authors: Wingett Denise , Nielson Christopher P
Published: September 2003

T cells are central in the pathogenesis of asthma, and the associated ligand, CD40L, plays an important role by increasing production of immunoglobulin E and inflammatory mediators. β-Adrenoceptor agonists are commonly used in asthma, although little is known regarding effects on CD40L expression and T cell activation. Here, we demonstrate that cyclic adenosine monophosphate (cAMP) and β-adrenoceptor agonists differentially regulate CD40L in asthma. cAMP increased naïve T cell CD40L expression in asthmatics (9.8±8.5 increase in percent CD40L-positive cells), and expression in control subjects was inhibited (7.1±6.0 decrease in percent CD40L-positive cells; P< 0.05). Cell depletion and reconstitution experiments were used to determine that cAMP enhancement of CD40L required cell-to-cell contact with an asthma-associated natural killer (NK) cell subset. The NK cell subset expressed elevated levels of CD95, and in vitro-generated CD95+ NK2 cells also produced similar effects on CD40L expression. Our findings suggest that a subset of NK cells with elevated CD95 expression is associated with asthma and can reverse cAMP inhibitory effects on T cell CD40L with the potential to increase disease exacerbation.
Antibiotic cyclic AMP signaling by “primed” leukocytes confers anti-inflammatory cytoprotection
Authors: Abeyama Kazuhiro , Kawahara Ko-ichi , Iino Satoshi , Hamada Takashi , Arimura Shin-ichiro , Matsushita Kenji , Nakajima Toshihiro , Maruyama Ikuro
Published: September 2003

The mechanism underlying anti-inflammatory effects of macrolide antibiotics remains uncertain. In this study, we first show the evidences concerning the possible link between leukocytic cyclic adenosine monophosphate (cAMP) signaling and the mechanism of anti-inflammatory, cytoprotective actions of macrolides. The clinical range of macrolides (i.e., erythromycin, roxithromycin, and clarithromycin) preferentially inhibited nuclear factor-κB activation mediated by reactive oxygen intermediates, inducing cAMP-dependent signaling [i.e., cAMP and cAMP-responsive element-binding protein (CREB)] by “primed” but not “resting” leukocytes. In this context, cAMP/CREB inhibition with adenosine 3′:5′-cyclic monophosphothioate, rp-isomer (rp-cAMPs) and CREB decoy oligonucleotides reduced the anti-inflammatory actions of macrolides. These results thus indicate that macrolide-induced cAMP/CREB signaling, selectively by primed leukocytes, plays a major role in the mechanism of anti-inflammatory actions of macrolides.
Sepsis-induced SOCS-3 expression is immunologically restricted to phagocytes
Authors: Grutkoski P S , Chen Y , Chung C S , Ayala A
Published: September 2003

We have shown that immune cells from septic mice exhibit a suppressed response to exogenous stimuli in vitro. The suppressors of the cytokine signaling (SOCS) family are proteins that block intracellular signaling and can be induced by inflammatory mediators. Therefore, we hypothesized that SOCS-3 is up-regulated in immune cells in response to a septic challenge induced by cecal ligation and puncture (CLP). Mice were subjected to CLP or sham-CLP, and 2–48 h later, the blood, thymus, spleen, lung, and peritoneal leukocytes were harvested and examined. SOCS-3 was undetectable in thymocytes or blood leukocytes. In contrast, SOCS-3 was up-regulated in the spleen, lung, and peritoneal leukocytes in a time-dependent manner. Further examination revealed that only the macrophages and neutrophils expressed SOCS-3. These data suggest that cytokines and bacterial toxins present during sepsis have the ability to suppress the cytokine and/or lipopolysaccharide response and the function of immune cells by up-regulating SOCS-3.
Regulation of TCR-mediated T cell activation by TNF-RII
Authors: Aspalter Rosa Maria , Eibl Martha Marianne , Wolf Hermann Maximilian
Published: September 2003

In the present study, we investigated the role of tumor necrosis factor receptor II (TNF-RII) in human T cell activation induced via the T cell receptor (TCR) in an antigen-presenting cell-independent system. Our results confirm that interaction of TNF-α with TNF-RII but not TNF-RI is directly costimulatory to TCR-mediated T cell activation, thereby augmenting T cell proliferation, expression of T cell activation markers (CD25, human leukocyte antigen-DR, TNF-RII), and secretion of cytokines such as interferon-γ and TNF-α. In contrast to the well-defined costimulatory molecule CD28, costimulation via TNF-RII showed significant differences in kinetics, requirement for cross-linking, redundancy of intracellular signaling pathways involved, and the capacity to induce interleukin (IL)-2, IL-10, and IL-13 secretion. In addition, cross-linking TNF-RII had the capacity to down-regulate TCR/CD28-induced Ca++ mobilization, IL-2 mRNA expression, and IL-2 and IL-10 secretion. Taken together, our findings demonstrate that TNF-RII plays a unique role among the T cell costimulatory molecules, as TNF-RII ligation can have positive and negative effects on TCR-dependent signaling. TNF-RII cross-linking has an inhibitory effect on early TCR signaling events proximal to induction of Ca++ flux, which ultimately leads to modulation of the T cell cytokine pattern expressed.
Prostaglandin E2 inhibits production of the inflammatory chemokines CCL3 and CCL4 in dendritic cells
Authors: Jing Huie , Vassiliou Evros , Ganea Doina
Published: September 2003

Dendritic cells bridge innate and adaptive immunity and participate in both responses. Upon capture of pathogens, dendritic cells release inflammatory cytokines and chemokines, attracting other immune cells to the infection site. Anti-inflammatory cytokines, glucocorticoids, anti-inflammatory neuropeptides, and lipid mediators such as prostaglandin E2 (PGE2) limit and control the inflammatory response. In this study we report that exogenous PGE2 inhibits CCL3 (MIP-1α) and CCL4 (MIP-1β) expression and release from dendritic cells stimulated with either lipopolysaccharide (LPS), a TLR4 ligand, or peptidoglycan, a TLR2 ligand. The inhibition is dose-dependent and occurs at both the mRNA and protein levels. The inhibitory effect is mediated through EP2 and EP4 receptors and requires the presence of PGE2 at the time of LPS stimulation. Intraperitoneal administration of PGE2 together with LPS results in a reduction in the levels of CCL3 and CCL4 released in the peritoneal fluid, a reduction in the number of dendritic cells accumulating in the peritoneal cavity, and a reduction in CCL3 amount per cell in the peritoneal cell population. These results suggest that one of the mechanisms by which endogenous PGE2 acts as an anti-inflammatory agent, is the inhibition of inflammatory chemokine release from activated dendritic cells, preventing the excess accumulation of activated immune cells.
A key role of C5a/C5aR activation for the development of sepsis
Authors: Riedemann Niels C , Guo Ren-Feng , Ward Peter A
Published: September 2003

In recent studies, evidence has been provided for complement activation early during the onset of experimental sepsis. Excessive production of the anaphylatoxin C5a thereby appears to elicit various harmful effects. Blockade of C5a or C5a receptor (C5aR) at the start of experimental sepsis has been demonstrated to greatly improve survival in rodents. There is evidence that C5a, during the onset of sepsis, enhances the production of various proinflammatory mediators in different cell types. Besides its known, other proinflammatory effects, recent work suggested an inhibitory role of C5a for innate-immune functions of phagocytic cells (phagocytosis, reactive oxygen species production, chemotaxis) during experimental sepsis. This review article provides an overview of the important role of C5a/C5aR activation for the onset and development of sepsis.
Tumor cell-induced deactivation of human monocytes
Authors: Mytar Bożenna , Wołoszyn Maria , Szatanek Rafał , Baj-Krzyworzeka Monika , Siedlar Maciej , Ruggiero Irena , Więckiewicz Jerzy , Zembala Marek
Published: September 2003

Although blood monocytes exhibit significant cytotoxic activity against tumor cells, the function of tumor infiltrating macrophages (TIM) is depressed in cancer patients. This study addresses the question of how the antitumor response of human monocytes, assessed by production of cytokines (tumor necrosis factor α, TNF; IL-10; IL-12p40) and cytotoxicity, is altered by exposure to cancer cells. Tumor cell−pre-exposed monocytes restimulated with tumor cells showed significantly decreased production of TNF, IL-12, increased IL-10 (mRNA and release) and inhibition of IL-1 receptor-associated kinase-1 (IRAK-1) expression. This down-regulation of cytokine production was selective, as the response of pre-exposed monocytes to lipopolysaccharide (LPS) was unaffected. Treatment of tumor cell−pre-exposed monocytes with hyaluronidase (HAase) improved their depressed production of TNF, while HAase-treated cancer cells did not cause monocyte dysfunction. The response of hyaluronan (HA)−pre-exposed monocytes to stimulation with tumor cells was also inhibited. Cytotoxic activity of monocytes pretreated with cancer cells was also decreased. This study shows that tumor cells selectively deactivate monocytes and suggests that tumor cell-derived HA by blocking CD44 on monocytes inhibits their antitumor response. These observations may provide some explanation for the depressed function of TIM in human malignancy.
Phosphatidylinositol 3-kinase is essential for kit ligand-mediated survival, whereas interleukin-3 and flt3 ligand induce expression of antiapoptoticBcl-2family genes
Authors: Karlsson Richard , Engström Maria , Jönsson Maria , Karlberg Peter , Pronk Cornelis J H , Richter Johan , Jönsson Jan-Ingvar
Published: September 2003

Cytokines such as interleukin 3 (IL-3), kit ligand (KL), and flt3 ligand (FL) promote survival of hematopoietic stem cells and myeloid progenitor cells. In many cell types, members of the Bcl-2 gene family are major regulators of survival, but the mediating mechanisms are not fully understood. Using two myeloid progenitor cell lines, FDCP-mix and FDC-P1, as well as primary mouse bone marrow progenitors, we demonstrate that KL-mediated survival is dependent on the activation of phosphatidylinositol-3 (PI-3) kinase. The inhibitor LY294002 was able to completely abolish survival mediated by KL, whereas IL-3 and FL were only partially affected. Although all three cytokines induced phosphorylation of protein kinase B (PKB), only KL required PI-3 kinase activity to elicit survival in hematopoietic progenitors. In contrast, pretreatment of cells with inhibitors to the MAP kinase pathway did not affect the survival. We next established if IL-3 and FL activated antiapoptotic Bcl-2 and the related genes Bcl-XL and Mcl-1. By RNA protection assay and Western blot analysis, we show that all three genes are induced by IL-3, whereas FL induces Bcl-2 and to some extent Bcl-XL. Importantly, KL could not sustain their expression. Moreover, use of inhibitors implied that IL-3 was mainly exerting its effect on Bcl-2 at the level of transcription. The addition of LY294002 did not affect the expression of Bcl-2 and Bcl-XL, and thus, we conclude that expression of antiapoptotic Bcl-2 family member genes is not dependent on PI-3 kinase activity. Our results indicate that cytokines exert distinct survival effects and that FL and IL-3 are capable of sustaining progenitor survival by up-regulating the expression of Bcl-2 and related genes.
Cathelicidins, multifunctional peptides of the innate immunity
Authors: Zanetti Margherita
Published: September 2003

Cathelicidins comprise a family of mammalian proteins containing a C-terminal cationic antimicrobial domain that becomes active after being freed from the N-terminal cathelin portion of the holoprotein. Many other members of this family have been identified since the first cathelicidin sequences were reported 10 years ago. The mature peptides generally show a wide spectrum of antimicrobial activity and, more recently, some of them have also been found to exert other biological activities. The human cathelicidin peptide LL-37 is chemotactic for neutrophils, monocytes, mast cells, and T cells; induces degranulation of mast cells; alters transcriptional responses in macrophages; stimulates wound vascularization and re-epithelialization of healing skin. The porcine PR-39 has also been involved in a variety of processes, including promotion of wound repair, induction of angiogenesis, neutrophils chemotaxis, and inhibition of the phagocyte NADPH oxidase activity, whereas the bovine BMAP-28 induces apoptosis in transformed cell lines and activated lymphocytes and may thus help with clearance of unwanted cells at inflammation sites. These multiple actions provide evidence for active participation of cathelicidin peptides in the regulation of the antimicrobial host defenses.
Serum inactivation contributes to the failure of stromal-derived factor-1 to block HIV-I infection in vivo
Authors: Villalba Sabrina , Salvucci Ombretta , Aoki Yoshiyasu , Sierra Maria De La Luz , Gupta Ghanshyam , Davis David , Wyvill Kathleen , Little Richard , Yarchoan Robert , Tosato Giovanna
Published: September 2003

The chemokine stromal-derived factor-1 (SDF-1) can block human immunodeficiency virus type 1 (HIV-1) infection in vitro by binding to the CXC chemokine receptor, CXCR-4, which serves as a coreceptor for T cell tropic HIV-1. In spite of being constitutively expressed in vivo, SDF-1 does not appear to block HIV-1 infection and spread in vivo. We report that SDF-1 is consistently measured in normal serum (15.4±3.0 ng/ml; mean±sd) and in serum from AIDS patients (16.6±3.7 ng/ml). However, we find that circulating SDF-1 is modified to an inactive form. When exposed to serum, recombinant SDF-1 is specifically and rapidly altered to yield an apparently smaller chemokine that does not bind to SDF-1 receptor-expressing cells, does not have chemoattractive or pre-B cell stimulatory activity, and does not block HIV-1 infection. Thus, serum modification and inactivation contribute to the failure of SDF-1 to block HIV-1 infection and spread in man. The inactivation of circulating SDF-1 may be critical in permitting local gradients to develop and direct cell trafficking.
Antimicrobial polypeptides
Authors: Ganz Tomas
Published: September 2003

The respiratory tract presents a large and potentially vulnerable surface to inhaled microbes. It is coated by a thin layer of secretions generated by airway epithelial cells, submucosal glands, resident and recruited phagocytes (neutrophils, eosinophils, monocytes, and macrophages) and alveolar epithelial cells, as well as substances that enter from blood plasma. More than 80 years ago, Alexander Fleming observed that respiratory secretions have microbicidal and microbistatic properties [1]. He described the activity of lysozyme, one of the principal polypeptides of these secretions. Since then, a number of additional antimicrobial components have been identified, and there is increasing insight into their complex interactions. This review is an update of my previous summary of this area [2].
Drug-loaded red blood cell-mediated clearance of HIV-1 macrophage reservoir by selective inhibition of STAT1 expression
Authors: Magnani Mauro , Balestra Emanuela , Fraternale Alessandra , Aquaro Stefano , Paiardini Mirko , Cervasi Barbara , Casabianca Anna , Garaci Enrico , Perno Carlo-Federico
Published: September 2003

Current highly active antiretroviral therapy (HAART) cannot eliminate HIV-1 from infected persons, mainly because of the existence of refractory viral reservoir(s). Beyond latently-infected CD4+-T lymphocytes, macrophages (M/M) are important persistent reservoirs for HIV in vivo, that represent a major obstacle to HIV-1 eradication. Therefore, a rational therapeutic approach directed to the selective elimination of long-living HIV-infected M/M may be relevant in the therapy of HIV infection. Here we report that HIV-1 chronic infection of human macrophages results in the marked increase of expression and phosphorylation of STAT1, a protein involved in the regulation of many functions such as cell growth, differentiation, and maintenance of cellular homeostasis, thereby providing a new molecular target for drug development. A single and brief exposure to 9-(β-D-arabinofuranosyl)-2-fluoroadenine 5′-monophosphate (FaraAMP, Fludarabine), a potent antileukemic nucleoside analog active against STAT1 expressing cells, selectively kills macrophage cultures infected by HIV-1 without affecting uninfected macrophages. Furthermore, encapsulation of Fludarabine into autologous erythrocytes (RBC) and targeting to macrophages through a single-18 h treatment with drug-loaded RBC, not only abolishes the Fludarabine-mediated toxic effect on non-phagocytic cells, but also enhances the selective killing of HIV-infected macrophages. As a final result, a potent (>98%) and long-lasting (at least 4 weeks without rebound) inhibition of virus release from drug-loaded RBC-treated chronically-infected macrophages was achieved. Taken together, the evidence of HIV-1-induced increase of STAT1, and the availability of a selective drug targeting system, may prove useful in the design of new pharmacological treatments to clear the HIV-1 macrophage reservoir.
Biology of Toll receptors: lessons from insects and mammals
Authors: Imler Jean-Luc , Zheng Liangbiao
Published: September 2003

Toll receptors are type I transmembrane proteins that play important roles in development and immunity in animals. Comparison of the genomes of mouse and human on one side and of the fruitfly Drosophila and the mosquito Anopheles (two dipteran insects) on the other, revealed that the four species possess a similar number of Toll receptors (∼10). However, phylogenetic analyses indicate that the families of Toll receptors expanded independently in insects and mammals. We review recent results on these receptors, which point to differences in the activation and signaling between Tolls in insects and Toll-like receptors (TLRs) in mammals. Whereas mammalian TLRs appear to be solely dedicated to host-defense, insect Tolls may be predominantly linked to other functions, probably developmental.
Human immunodeficiency virus type 1 (HIV-1) Nef activates STAT3 in primary human monocyte/macrophages through the release of soluble factors: involvement of Nef domains interacting with the cell endocytotic machinery
Authors: Percario Zulema , Olivetta Eleonora , Fiorucci Gianna , Mangino Giorgio , Peretti Silvia , Romeo Giovanna , Affabris Elisabetta , Federico Maurizio
Published: September 2003

Increasing evidence indicates that the expression of the human immunodeficiency virus-1 (HIV-1) Nef protein significantly influences the activation state of the host cell. Here we report that Nef specifically activates STAT3 in primary human monocyte-derived macrophages (MDM). This was demonstrated by both single-cycle infection experiments driven by Vesicular Stomatitis virus glycoprotein (VSV-G) pseudotyped HIV-1 and treatment with exogenous recombinant Nef. The analysis of the effects of Nef mutants revealed that domains of the C-terminal flexible loop interacting with the cell endocytotic machinery are involved in the STAT3 activation. In particular, our data suggest that the Nef-dependent STAT3 activation relies on the targeting of Nef to the late endosome/lysosome compartment. In addition, we found that Nef activates STAT3 through a mechanism mediated by the release of soluble factor(s), including MIP-1α, that requires de novo protein synthesis but appears independent from the activation of src tyrosine kinases. The results presented here support the idea that the first intervention of Nef in the intracellular signaling of monocyte-macrophages could generate, by means of the release of soluble factor(s), a secondary wave of activation that could be of a potential pathogenetic significance.
Human circulating CD14+ monocytes as a source of progenitors that exhibit mesenchymal cell differentiation
Authors: Kuwana Masataka , Okazaki Yuka , Kodama Hiroaki , Izumi Keisuke , Yasuoka Hidekata , Ogawa Yoko , Kawakami Yutaka , Ikeda Yasuo
Published: September 2003

Circulating CD14+ monocytes are precursors of phagocytes, such as macrophages and dendritic cells. Here we report primitive cells with a fibroblast-like morphology derived from human peripheral blood CD14+ monocytes that can differentiate into several distinct mesenchymal cell lineages. We named this cell population monocyte-derived mesenchymal progenitor (MOMP). MOMPs were obtained in vitro from human peripheral blood mononuclear cells cultured on fibronectin in the presence of fetal bovine serum alone as a source of growth factors. MOMPs had a unique molecular phenotype–CD14+CD45+CD34+ type I collagen+–and showed mixed morphologic and molecular features of monocytes and endothelial and mesenchymal cells. MOMPs were found to be derived from a subset of circulating CD14+ monocytes, and their differentiation required that they bind fibronectin and be exposed to one or more soluble factors derived from peripheral blood CD14− cells. MOMPs could be expanded in culture without losing their original phenotype for up to five passages. The induction of MOMPs to differentiate along multiple limb-bud mesodermal lineages resulted in the expression of genes and proteins specific for osteoblasts, skeletal myoblasts, chondrocytes, and adipocytes. Our findings represent the first evidence that human circulating CD14+ monocytes are a source of progenitors that exhibit mesenchymal cell differentiation.
Role of CD40 Ligand dysregulation in HIV-associated dysfunction of antigen-presenting cells
Authors: Chougnet Claire
Published: September 2003

Cellular interactions between antigen-presenting cells and activated CD4+ T cells are central to the regulation of adaptive immunity. Among the many receptor–ligand pairs involved, the critical importance of CD40−CD40 Ligand (CD40L) interactions has been demonstrated in many experimental systems. Dysregulation of antigen-presenting cell function is a hallmark of HIV-associated defects in cell-mediated immunity. Much evidence suggests a mechanistic role for defective CD40−CD40L interactions in such a defect. Consistent with this hypothesis, the capacity to upregulate CD40L on purified CD4+ T cells becomes progressively impaired in HIV infection, in parallel with the progression of clinical immunosuppression. The mechanisms underlying CD40L dysregulation in HIV infection remain unknown. Because CD40L expression is tightly regulated (transcriptionally, post-transcriptionally and post-translationally), HIV may interfere at several levels. However, a transcriptional defect in CD40L expression, mediated by the engagement of CD4 by HIV gp120, appears to play a primary role. Clear elucidation of mechanism may well lead to the development of novel immunotherapeutic approaches to HIV infection.
Monocyte/macrophage-derived CC chemokines and their modulation by HIV-1 and cytokines: A complex network of interactions influencing viral replication and AIDS pathogenesis
Authors: Fantuzzi Laura , Belardelli Filippo , Gessani Sandra
Published: September 2003

Monocytes/macrophages are cells of the innate arm of the immune system and exert important regulatory effects on adaptive immune response. These cells also represent major targets of HIV infection and one of the main reservoirs. Notably, macrophage-tropic viruses are responsible for the initial infection, predominate in the asymptomatic phase, and persist throughout infection, even after the emergence of dual-tropic and T-tropic variants. Functional impairment of HIV-infected macrophages plays an important role in the immune dysregulation typical of AIDS. Recent studies have underlined the pivotal role of chemokines, cytokines, and their receptors in HIV pathogenesis. It is becoming increasingly apparent that the expression level of chemokine receptors, serving as HIV coreceptors, influences the susceptibility of a CD4+ cell to viral infection and to certain HIV envelope-induced alterations in cellular functions. Numerous pathogens, including HIV, can stimulate the production of chemokines and cytokines, which in turn can modulate coreceptor availability, resulting in differential replication potential for R5 and X4 strains, depending on the microenvironment milieu. Thus, a complex network of interactions involving immune mediators produced by monocytes/macrophages and other cell types as a direct/indirect consequence of HIV infection is operative at all stages of the disease and may profoundly influence the extent of viral replication, dissemination, and pathogenesis.
The role of urokinase-type plasminogen activator (uPA)/uPA receptor in HIV-1 infection
Authors: Alfano Massimo , Sidenius Nicolai , Blasi Francesco , Poli Guido
Published: September 2003

The binding of urokinase-type plasminogen activator (uPA) to its glycosyl-phosphatidyl-inositol (GPI) anchored receptor (uPAR) mediates a variety of functions in terms of vascular homeostasis, inflammation and tissue repair. Both uPA and uPAR, as well as their soluble forms detectable in plasma and other body fluids, represent markers of cancer development and metastasis, and they have been recently described as predictors of human immunodeficiency virus (HIV) disease progression, independent of CD4+ T cell counts and viremia. A direct link between the uPA/uPAR system and HIV infection was earlier proposed in terms of cleavage of gp120 envelope by uPA. More recently, a negative regulatory effect on both acutely and chronically infected cells has been linked to the noncatalytic portion of uPA, also referred to as the amino-terminal fragment (ATF). ATF has also been described as a major CD8+ T cell soluble HIV suppressor factor. In chronically infected promonocytic U1 cells this inhibitory effect is exerted at the very late stages of the virus life cycle, involving virion budding and entrapment in intracytoplasmic vacuoles, whereas its mechanism of action in acutely infected cells remains to be defined. Since uPAR is a GPI-anchored receptor it requires association with a signaling-transducing component and different partners, which include CD11b/CD18 integrin and a G-protein coupled receptor homologous to that for the bacterial chemotactic peptide formyl-methionyl-leucyl-phenylalanine. Which signaling coreceptor(s) is(are) responsible for uPA-dependent anti-HIV effect remains currently undefined.
Specific CD4 down-modulating compounds with potent anti-HIV activity
Authors: Vermeire Kurt , Schols Dominique
Published: September 2003

Despite the availability of the current clinically approved anti-HIV drugs, new classes of effective antiviral agents are still urgently needed to combat AIDS. A promising approach for drug development and vaccine design involves targeting research on HIV-1 entry, a multistep process that comprises viral attachment, coreceptor interactions, and fusion. Determination of the viral entry process in detail has enabled the design of specific agents that can inhibit each step in the HIV entry process. Therapeutic agents that interfere with the binding of the HIV envelope glycoprotein gp120 to the CD4 receptor (e.g., PRO 542, PRO 2000, and CV-N) or the coreceptors CCR5 and CXCR4 (e.g., SCH-C and AMD3100) are briefly outlined in this review. The anti-HIV activity of cyclotriazadisulfonamides, a novel class of compounds with a unique mode of action by down-modulating the CD4 receptor in lymphocytic and monocytic cells, is especially highlighted. On the basis of the successful results of T-20, the first approved entry inhibitor, the development of effective antiretrovirals that block HIV entry will certainly be further encouraged.
Immunodeficiency virus exploitation of dendritic cells in the early steps of infection
Authors: Teleshova Natalia , Frank Ines , Pope Melissa
Published: September 2003

The unique capacity of dendritic cells (DCs) to capture and process pathogens for presentation to the immune system, combined with their capacity to express costimulatory and adhesion molecules as well as cytokines and chemokines, renders them powerful antigen-presenting cells. However, immunodeficiency viruses hijack DCs to facilitate virus dissemination while subverting effective immune activation. Depending on the activation level of the DC subset, human immunodeficiency virus can use different receptors (CD4, chemokine, and C-type lectin receptors) to bind to DCs. These aspects likely impact whether a DC is productively infected by or simply carries virus for transmission to more permissive targets. DCs efficiently transmit virus to CD4+ T cells, driving virus growth as well as providing signals to trigger virus expansion in virus-bearing CD4+ T cells. There is accumulating evidence that viral determinants (nef, tat) selectively modulate immature DC biology, fostering DC–T cell interactions and virus replication without up-regulating costimulatory molecules for effective immune function. In addition, virus-loaded, immature DCs activate CD4+ virus-specific T cells, and mature DCs stimulate CD4+ and CD8+ T cells. Thus, even if immature DCs entrap virus as it crosses the mucosae and initiate a CD4+ T cell response, this is likely insufficient to control infection. Appreciating how virus modulates DC function and what determines whether virus is processed for immune stimulation or transmitted between cells will unveil the exact role of these cells in the onset of infection and advance preventative microbicide and vaccine/therapeutic approaches.
Regulation of HIV-1 gene transcription: from lymphocytes to microglial cells
Authors: Rohr Olivier , Marban Céline , Aunis Dominique , Schaeffer Evelyne
Published: September 2003

Transcription is a crucial step for human immunodeficiency virus type 1 (HIV-1) expression in all infected host cells, from T lymphocytes, thymocytes, monocytes, macrophages, and dendritic cells in the immune system up to microglial cells in the central nervous system. To maximize its replication, HIV-1 adapts transcription of its integrated proviral genome by ideally exploiting the specific cellular environment and by forcing cellular stimulatory events and impairing transcriptional inhibition. Multiple cell type-specific interplays between cellular and viral factors perform the challenge for the virus to leave latency and actively replicate in a great diversity of cells, despite the variability of its long terminal repeat region in different HIV strains. Knowledge about the molecular mechanisms underlying transcriptional regulatory events helps in the search for therapeutic agents that target the step of transcription in anti-HIV strategies.
HIV-1 fitness and macrophages
Authors: Goodenow Maureen M , Rose Stephanie L , Tuttle Daniel L , Sleasman John W
Published: September 2003

HIV-1 comprises a collection of closely related, but not identical, viruses or quasispecies. Fitness represents a selective advantage for propagation among populations of organisms competing in a particular environment and is an important characteristic of viruses because of a link between fitness and pathogenesis. Environmental differences based on the type of cell that is targeted for infection or the cell type that produces virus, impact fitness. CD4-expressing cells of lymphocyte or macrophage lineage are the principal host cells for HIV-1, although the milieu in lymphocytes is distinct from the macrophage environment from the perspective of cell half-life and activation, signal transduction and expression of coreceptors, and bioavailability of antiretroviral drugs. Multiple viral determinants, including entry via envelope glycoproteins, replication by reverse transcriptase, and virion maturation by protease activity, contribute to fitness in different cells and provide targets for current antiretroviral therapies. This review focuses on fitness of HIV-1 in macrophages and examines the impact of protease inhibitors on fitness of quasispecies and an unexplained discordance between fitness and pathogenesis.
Macrophages and lymphocytes differentially modulate the ability of RANTES to inhibit HIV-1 infection
Authors: Gross Eleanore , Amella Carol A , Pompucci Lorena , Franchin Giovanni , Sherry Barbara , Schmidtmayerova Helena
Published: September 2003

The β-chemokines MIP-1α, MIP-1β, and RANTES inhibit HIV-1 infection of CD4+ T cells by inhibiting interactions between the virus and CCR5 receptors. However, while β-chemokine-mediated inhibition of HIV-1 infection of primary lymphocytes is well documented, conflicting results have been obtained using primary macrophages as the virus target. Here, we show that the β-chemokine RANTES inhibits virus entry into both cellular targets of the virus, lymphocytes and macrophages. However, while virus entry is inhibited at the moment of infection in both cell types, the amount of virus progeny is lowered only in lymphocytes. In macrophages, early-entry restriction is lost during long-term cultivation, and the amount of virus produced by RANTES-treated macrophages is similar to the untreated cultures, suggesting an enhanced virus replication. We further show that at least two distinct cellular responses to RANTES treatment in primary lymphocytes and macrophages contribute to this phenomenon. In lymphocytes, exposure to RANTES significantly increases the pool of inhibitory β-chemokines through intracellular signals that result in increased production of MIP-1α and MIP-1β, thereby amplifying the antiviral effects of RANTES. In macrophages this amplification step does not occur. In fact, RANTES added to the macrophages is efficiently cleared from the culture, without inducing synthesis of β-chemokines. Our results demonstrate dichotomous effects of RANTES on HIV-1 entry at the moment of infection, and on production and spread of virus progeny in primary macrophages. Since macrophages serve as a reservoir of HIV-1, this may contribute to the failure of endogenous chemokines to successfully eradicate the virus.
The contribution of monocyte infection and trafficking to viral persistence, and maintenance of the viral reservoir in HIV infection
Authors: Crowe Suzanne , Zhu Tuofu , Muller William A
Published: September 2003

Cellular viral reservoirs and anatomic sanctuary sites allow continuing HIV-1 replication in patients with suppressed plasma viremia who are receiving highly active antiretroviral therapy and prevent eradication of HIV-1 by these regimens. Cells of macrophage lineage, including monocytes subsets within the blood, play a role in HIV-1 persistence. Evidence of sequence evolution in blood monocytes, in comparison to resting CD4+ T cells, demonstrates their distinct contribution to plasma viremia. There is evidence to suggest that a specific monocyte subset, of CD14loCD16hi phenotype, is more susceptible to HIV-1 infection than the majority of blood monocytes. Trafficking of monocytes through various tissues following their emigration from the bloodstream allows these cells to differentiate into tissue macrophages, or potentially to egress from the tissues as migratory dendritic cells. This review provides an evaluation of the contribution of monocytes to HIV-1 persistence and the HIV-1 reservoir, essential for the effective design of therapeutic eradication strategies.