IL-32, a proinflammatory cytokine in rheumatoid arthritis

Interactive cytokine regulation of synoviocyte lubricant secretion

Cytokine regulation of synovial fluid (SF) lubricants, hyaluronan (HA), and proteoglycan 4 (PRG4) is important in health, injury, and disease of synovial joints, and may also provide powerful regulation of lubricant secretion in bioreactors for articulating tissues. This study assessed lubricant secretion rates by human synoviocytes and the molecular weight (MW) of secreted lubricants in response to interleukin (IL)-1beta, IL-17, IL-32, transforming growth factor-beta 1 (TGF-beta1), and tumor necrosis factor-alpha (TNF-alpha), applied individually and in all combinations. Lubricant secretion rates were assessed using ELISA and binding assays, and lubricant MW was assessed using gel electrophoresis and Western blotting. HA secretion rates were increased approximately 40-fold by IL-1beta, and increased synergistically to approximately 80-fold by the combination of IL-1beta + TGF-beta1 or TNF-alpha + IL-17. PRG4 secretion rates were increased approximately 80-fold by TGF-beta1, and this effect was counterbalanced by IL-1beta and TNF-alpha. HA MW was predominantly <1 MDa for controls and individual cytokine stimulation, but was concentrated at >3 MDa after stimulation by IL-1beta + TGF-beta1 + TNF-alpha to resemble the distribution in human SF. PRG4 MW was unaffected by cytokines and similar to that in human SF. These results contribute to an understanding of the relationship between SF cytokine and lubricant content in health, injury, and disease, and provide approaches for using cytokines to modulate lubricant secretion rates and MW to help achieve desired lubricant composition of fluid in bioreactors.

Downregulation of immune response by the human cytokines Interleukin-32alpha and beta in cell-mediated rejection

Xenotransplantation of porcine organs has the potential to help overcome the severe shortage of human tissues and organs available for human transplantation. However, numerous hurdles such as immune-mediated xenograft rejection remain before clinical xenotransplantation. In this study, we elucidated the role of human TNF-alpha-inducing factor, Interleukin-32 (IL-32), in porcine kidney cells (PK-15) during cell-mediated rejection by examining host cell responses. CD8+ and CD4+ T cells numbers were reduced in the lymph nodes of PK-15/IL-32beta injected mice. CD3+ Tcells were in mice injected with control cells but PK-15/IL-32alpha- and PK-15/IL-32beta-injected cell numbers were lower in lymph nodes than un transfected controls. In Mixed lymphocyte reaction cultures, the rates of cell proliferation were increased in both PK-15/IL-32alpha- and PK-15/IL-32beta-injected groups compared to the untransfected control groups. The Stable porcine PK-15 cells expression IL-32alpha and IL-32beta inhibited cytotoxic T lymphocyte (CTLs) after cellular xenograft. Our results suggest that human IL-32alpha and IL-32beta regulates on xenograft rejection in cellular xenotransplantation.

Semi-permeable membrane retention of synovial fluid lubricants hyaluronan and proteoglycan 4 for a biomimetic bioreactor

Synovial fluid (SF) contains lubricant macromolecules, hyaluronan (HA), and proteoglycan 4 (PRG4). The synovium not only contributes lubricants to SF through secretion by synoviocyte lining cells, but also concentrates lubricants in SF due to its semi-permeable nature. A membrane that recapitulates these synovium functions may be useful in a bioreactor system for generating a bioengineered fluid (BF) similar to native SF. The objectives were to analyze expanded polytetrafluoroethylene membranes with pore sizes of 50 nm, 90 nm, 170 nm, and 3 microm in terms of (1) HA and PRG4 secretion rates by adherent synoviocytes, and (2) the extent of HA and PRG4 retention with or without synoviocytes adherent on the membrane. Experiment 1: Synoviocytes were cultured on tissue culture (TC) plastic or membranes +/- IL-1beta + TGF-beta1 + TNF-alpha, a cytokine combination that stimulates lubricant synthesis. HA and PRG4 secretion rates were assessed by analysis of medium. Experiment 2: Bioreactors were fabricated to provide a BF compartment enclosed by membranes +/- adherent synoviocytes, and an external compartment of nutrient fluid (NF). A solution with HA (1 mg/mL, MW ranging from 30 to 4,000 kDa) or PRG4 (50 microg/mL) was added to the BF compartment, and HA and PRG4 loss into the NF compartment after 2, 8, and 24 h was determined. Lubricant loss kinetics were analyzed to estimate membrane permeability. Experiment 1: Cytokine-regulated HA and PRG4 secretion rates on membranes were comparable to those on TC plastic. Experiment 2: Transport of HA and PRG4 across membranes was lowest with 50 nm membranes and highest with 3 microm membranes, and transport of high MW HA was decreased by adherent synoviocytes (for 50 and 90 nm membranes). The permeability to HA mixtures for 50 nm membranes was approximately 20 x 10(-8) cm/s (- cells) and approximately 5 x 10(-8) cm/s (+ cells), for 90 nm membranes was approximately 35 x 10(-8) cm/s (- cells) and approximately 19 x 10(-8) cm/s (+ cells), for 170 nm membranes was approximately 74 x 10(-8) cm/s (+/- cells), and for 3 microm membranes was approximately 139 x 10(-8) cm/s (+/- cells). The permeability of 450 kDa HA was approximately 40x lower than that of 30 kDa HA for 50 nm membranes, but only approximately 2.5x lower for 3 microm membranes. The permeability of 4,000 kDa HA was approximately 250x lower than that of 30 kDa HA for 50 nm membranes, but only approximately 4x lower for 3 microm membranes. The permeability for PRG4 was approximately 4 x 10(-8) cm/s for 50 nm membranes, approximately 48 x 10(-8) cm/s for 90 nm membranes, approximately 144 x 10(-8) cm/s for 170 nm membranes, and approximately 336 x 10(-8) cm/s for 3 microm membranes. The associated loss across membranes after 24 h ranged from 3% to 92% for HA, and from 3% to 93% for PRG4. These results suggest that semi-permeable membranes may be used in a bioreactor system to modulate lubricant retention in a bioengineered SF, and that synoviocytes adherent on the membranes may serve as both a lubricant source and a barrier for lubricant transport.

IL-32 is expressed by human primary keratinocytes and modulates keratinocyte apoptosis in atopic dermatitis

BACKGROUND

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSION

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

Interleukin-32beta propagates vascular inflammation and exacerbates sepsis in a mouse model

Background

Inflammation is associated with most diseases, which makes understanding the mechanisms of inflammation vitally important.

Methodology/Principal Findings

Here, we demonstrate a critical function of interleukin-32β (IL-32β) in vascular inflammation. IL-32β is present in tissues from humans, but is absent in rodents. We found that the gene is highly expressed in endothelial cells. Three isoforms of IL-32, named IL-32α, β, and ε, were cloned from human endothelial cells, with IL-32β being the major isoform. Pro-inflammatory cytokines (TNFα and IL-1β) induced IL-32β expression through NF-κB. Conversely, IL-32β propagated vascular inflammation via induction of vascular cell adhesion molecules and inflammatory cytokines. Accordingly, IL-32β increased adhesion of inflammatory cells to activated endothelial cells, a paramount process in inflammation. These results illustrate a positive feedback regulation that intensifies and prolongs inflammation. Importantly, endothelial/hematopoietic expression of IL-32β in transgenic mice elevated inflammation and worsened sepsis. This was demonstrated by significant elevation of leukocyte infiltration and serum levels of TNFα and IL-1β, increased vascular permeability and lung damage, and accelerated animal death. Together, our results reveal an important function of IL-32 in vascular inflammation and sepsis development.

Conclusions/Significance

Our results reveal an important function of IL-32 in vascular inflammation and sepsis development.

Genome-based expression profiling study of Hunner's ulcer type interstitial cystitis: an array of 40-gene model

INTRODUCTION AND HYPOTHESIS

The aim of this study was to explore potential molecular mechanisms contributing to the pathogenesis of Hunner's ulcer type interstitial cystitis (IC).

METHODS

Dataset acquisitions from Gene Expression Omnibus under platform accession no GSE 11783. We compared global gene expression profiles in bladder epithelial cells from IC patients with Hunner's ulcer corresponding to normal controls. We re-sampling and exploit the correlation structure presented in the dataset through the transcriptional response. For each patient, two bladder biopsies were studied, one from an ulcer area and one from a non-ulcer area. RNA was extracted, and all labeled samples were hybridized to Human Genome U133 Plus 2.0 Array (Affymetrix, CA, USA).

RESULTS

The Mahalanobis distance in hierarchical cluster analysis revealed a model of 40 genes expression which is increased in IC and ulcerated IC. Our results can be summarized as follows: First, the expressions of major histocompatibility complex (MHC) class IF and II molecules, leukocyte immunoglobulin-like receptors, hepatitis A virus cellular receptor 2, and interleukin 32 were increased in bladder epithelial from IC and ulcerative IC area. Next, there is an indication of antigen-mediated aggregation of the high-affinity Fc epsilon and gamma RI leading to allergic inflammation through the disease status. Third, the high-affinity Fc gamma RI subunit facilitated T-cell-mediated immune response through the disease status. Such changes, jointly termed "bladder remodeling," can constitute an important long-term consequence of Hunner's ulcer type IC.

CONCLUSIONS

Our results indicate that genome-based expression profiling can be used for the diagnostic tests of Hunner's ulcer type IC in clinical practice.

IL-32 is a host protective cytokine against Mycobacterium tuberculosis in differentiated THP-1 human macrophages

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

Interleukin-32gamma enhances the production of IL-6 and IL-8 in fibroblast-like synoviocytes via Erk1/2 activation

INTRODUCTION

In the present study, we examined the effect of the pro-inflammatory cytokine IL-32gamma, the most biologically active isoform, and its related molecules in fibroblast-like synoviocytes (FLS).

MATERIALS AND METHODS

FLS were isolated from synovial tissues of rheumatoid arthritis (RA) patients. The secretion and expression of IL-6 and IL-8 were examined by ELISA and real-time PCR, and the activation of signaling molecules was evaluated by Western blot, electrophoretic mobility shift assay (EMSA), real-time PCR, and siRNA transfection.

RESULTS

By IL-32gamma stimulation in RA FLS, the expressions of IL-6 and IL-8 were increased significantly, and the phosphorylated Erk1/2 and AP-1 were expressed prominently in Western blot and EMSA. In the Erk1/2 inhibited cells, IL-32gamma stimulation did not increase the mRNA expression of IL-6 and IL-8.

CONCLUSION

Our results suggest that IL-32gamma stimulation can induce the production of IL-6 and IL-8 from RA FLS via Erk1/2 activation.

Oral administration of curcumin suppresses production of matrix metalloproteinase (MMP)-1 and MMP-3 to ameliorate collagen-induced arthritis: inhibition of the PKCdelta/JNK/c-Jun pathway

We investigated whether oral administration of curcumin suppressed type II collagen-induced arthritis (CIA) in mice and its effect and mechanism on matrix metalloproteinase (MMP)-1 and MMP-3 production in CIA mice, RA fibroblast-like synoviocytes (FLS), and chondrocytes. CIA in mice was suppressed by oral administration of curcumin in a dose-dependent manner. Macroscopic observations were confirmed by histological examinations. Histological changes including infiltration of immune cells, synovial hyperplasia, cartilage destruction, and bone erosion in the hind paw sections were extensively suppressed by curcumin. The histological scores were consistent with clinical arthritis indexes. Production of MMP-1 and MMP-3 were inhibited by curcumin in CIA hind paw sections and tumor necrosis factor (TNF)-alpha-stimulated FLS and chondrocytes in a dose-dependent manner. As for the mechanism, curcumin inhibited activating phosphorylation of protein kinase Cdelta (PKCdelta) in CIA, FLS, and chondrocytes. Curcumin also suppressed the JNK and c-Jun activation in those cells. This study suggests that the suppression of MMP-1 and MMP-3 production by curcumin in CIA is mediated through the inhibition of PKCdelta and the JNK/c-Jun signaling pathway.

Utility of synovial biopsy

Synovial biopsies, gained either by blind needle biopsy or minimally invasive arthroscopy, offer additional information in certain clinical situations where routine assessment has not permitted a certain diagnosis. In research settings, synovial histology and modern applications of molecular biology increase our insight into pathogenesis and enable responses to treatment with new therapeutic agents to be assessed directly at the pathophysiological level. This review focuses on the diagnostic usefulness of synovial biopsies in the light of actual developments.

Suppressing IL-32 in monocytes impairs the induction of the proinflammatory cytokines TNFalpha and IL-1beta

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

Lessons from animal models of arthritis over the past decade

This review summarizes the major developments in animal models of arthritis in the past decade. It focuses on novel transgenic models, addresses the involvement of cytokines and discusses novel findings in cartilage and bone erosion. It is clear that interest has been raised in the direct arthritogenic role of autoantibodies, apart from T cell involvement, and their interaction with cells through Fcgamma receptors. In addition, a role for IL-6 and IL-17 and Th17 cells seems apparent in most T cell-driven arthritis models, with environmental triggering through Toll-like receptors contributing to this process. Further insights into enzymes involved in cartilage proteoglycan loss in arthritis, as well as mediators regulating bone erosion and bone apposition, have been gained.

Anti-proline-glycine-proline or antielastin autoantibodies are not evident in chronic inflammatory lung disease

RATIONALE

In patients with chronic inflammatory lung disease, pulmonary proteases can generate neoantigens from elastin and collagen with the potential to fuel autoreactive immune responses. Antielastin peptide antibodies have been implicated in the pathogenesis of tobacco-smoke-induced emphysema. Collagen-derived peptides may also play a role.

OBJECTIVES

To determine whether autoantibodies directed against elastin- and collagen-derived peptides are present in plasma from three groups of patients with chronic inflammatory lung disease compared with a nonsmoking healthy control group and to identify whether autoimmune responses to these peptides may be an important component of the disease process in these patients.

METHODS

A total of 124 patients or healthy control subjects were recruited for the study (Z-A1AT deficiency, n = 20; cystic fibrosis, n = 40; chronic obstructive pulmonary disease, n = 31; healthy control, n = 33). C-reactive protein, IL-32, and antinuclear antibodies were quantified. Antielastin and anti-N-acetylated-proline-glycine-proline autoantibodies were measured by reverse ELISA.

MEASUREMENTS AND MAIN RESULTS

All patients were deemed stable and noninfective on the basis of the absence of clinical or radiographic evidence of recent infection. There were no significant differences in the levels of autoantibodies or IL-32 in the patients groups compared with the healthy control subjects.

CONCLUSIONS

Antielastin or anti-N-acetylated proline-glycine-proline autoantibodies are not evident in chronic inflammatory lung disease.

Interleukin-32 positively regulates radiation-induced vascular inflammation

PURPOSE

To study the role of interleukin-32 (IL-32), a novel protein only detected in human tissues, in ionizing radiation (IR)-induced vascular inflammation.

METHODS AND MATERIALS

Irradiated (0-6 Gy) human umbilical vein endothelial cells treated with or without various agents--a cytosolic phospholipase A2 (cPLA2) inhibitor, a cyclooxygenase-2 (Cox-2) inhibitor, or lysophosphatidylcholines (LPCs)--were used to assess IL-32 expression by Northern blot analysis and quantitative reverse transcriptase-polymerase chain reaction. Expression of cell adhesion molecules and leukocyte adhesion to endothelial cells using human acute monocytic leukemia cell line (THP-1) cells was also analyzed.

RESULTS

Ionizing radiation dramatically increased IL-32 expression in vascular endothelial cells through multiple pathways. Ionizing radiation induced IL-32 expression through nuclear factor kappaB activation, through induction of cPLA2 and LPC, as well as induction of Cox-2 and subsequent conversion of arachidonic acid to prostacyclin. Conversely, blocking nuclear factor kappaB, cPLA2, and Cox-2 activity impaired IR-induced IL-32 expression. Importantly, IL-32 significantly enhanced IR-induced expression of vascular cell adhesion molecules and leukocyte adhesion on endothelial cells.

CONCLUSION

This study identifies IL-32 as a positive regulator in IR-induced vascular inflammation, and neutralization of IL-32 may be beneficial in protecting from IR-induced inflammation.

Expression of IL-32 in human lung cancer is related to the histotype and metastatic phenotype

RATIONALE

A strong link has been recently demonstrated between inflammation and lung cancer. Thus, we investigated whether the proinflammatory cytokine IL-32 may be involved in lung carcinogenesis and hence provide a novel therapeutic target.

OBJECTIVES

Lung cancer subtypes display different clinical outcomes. We have set out to clarify the role of IL-32 in the physiopathology of the main histotypes.

METHODS

IL-32 expression, as visualized by immunohistochemistry on 23 premalignant and 148 malignant lesions, was correlated with clinicopathological and survival data. Confocal microscopy, microdissection, and real-time reverse transcription-polymerase chain reaction were used to identify cell sources and expression levels of IL-32.

MEASUREMENTS AND MAIN RESULTS

IL-32 expression was lacking in the majority of squamous-cell carcinomas (SCC) (76%) and their precursor lesions, but strongly up-regulated in most adenocarcinomas (AC) (73%) and their precursors, 64% of large-cell carcinomas, and 77% of small-cell lung cancers. Lymph node metastases frequently developed from IL-32-expressing lung cancers, and especially (82%) from those endowed with an IL-32-expressing leukocyte infiltrate (TIL) mainly composed of CD68(+) macrophages, CD4(+) T lymphocytes, and DC-SIGN(+) dendritic cells. Expression levels of IL-32 by both TIL and tumor cells (TC), particularly in AC and SCC, were paralleled by those of IL-6, IL-8, and vascular endothelial growth factor in the same cell population and correlated with high intratumor microvessel density and poor clinical outcome.

CONCLUSIONS

IL-32 is probably implicated in the pathogenesis of most lung cancer histotypes but unlikely in that of SCC. Its TIL and TC expression are both associated with acquisition of an invasive and metastatic phenotype and may be a useful prognostic indicator.

Microarray analysis of lymphatic tissue reveals stage-specific, gene expression signatures in HIV-1 infection

Untreated HIV-1 infection progresses through acute and asymptomatic stages to AIDS. Although each of the three stages has well-known clinical, virologic, and immunologic characteristics, much less is known of the molecular mechanisms underlying each stage. In this study, we report lymphatic tissue microarray analyses, revealing for the first time stage-specific patterns of gene expression during HIV-1 infection. We show that although there is a common set of key genes with altered expression throughout all stages, each stage has a unique gene expression signature. The acute stage is most notably characterized by increased expression of hundreds of genes involved in immune activation, innate immune defenses (e.g., RIG-1, MDA-5, TLR7 and TLR8, PKR, APOBEC3B, 3F, 3G), adaptive immunity, and in the proapoptotic Fas-Fas ligand pathway. Yet, quite strikingly, the expression of nearly all acute stage genes return to baseline levels in the asymptomatic stage, accompanying partial control of infection. This transition from acute to asymptomatic stage is tied to increased expression of a diverse array of immunosuppressive genes (e.g., CLEC12B, ILT4, galectin-3, CD160, BCMA, FGL2, LAG3, GPNMB). In the AIDS stage, decreased expression of numerous genes involved in T cell signaling identifies genes contributing to T cell dysfunction. These common and stage-specific gene expression signatures identify potential molecular mechanisms underlying the host response and the slow, natural course of HIV-1 infection.

Cartilage homeostasis in health and rheumatic diseases

As the cellular component of articular cartilage, chondrocytes are responsible for maintaining in a low-turnover state the unique composition and organization of the matrix that was determined during embryonic and postnatal development. In joint diseases, cartilage homeostasis is disrupted by mechanisms that are driven by combinations of biological mediators that vary according to the disease process, including contributions from other joint tissues. In osteoarthritis (OA), biomechanical stimuli predominate with up-regulation of both catabolic and anabolic cytokines and recapitulation of developmental phenotypes, whereas in rheumatoid arthritis (RA), inflammation and catabolism drive cartilage loss. In vitro studies in chondrocytes have elucidated signaling pathways and transcription factors that orchestrate specific functions that promote cartilage damage in both OA and RA. Thus, understanding how the adult articular chondrocyte functions within its unique environment will aid in the development of rational strategies to protect cartilage from damage resulting from joint disease. This review will cover current knowledge about the specific cellular and biochemical mechanisms that regulate cartilage homeostasis and pathology.

Tumor necrosis factor alpha-induced interleukin-32 is positively regulated via the Syk/protein kinase Cdelta/JNK pathway in rheumatoid synovial fibroblasts

OBJECTIVE

Interleukin-32 (IL-32) is a recently discovered cytokine that appears to play a critical role in human rheumatoid arthritis (RA). It is highly expressed in synovium and fibroblast-like synoviocytes (FLS) from RA patients, but not in patients with osteoarthritis (OA). This study was undertaken to assess IL-32 levels in RA synovial fluid (SF) and to investigate the secretion and regulation of IL-32 in RA FLS.

METHODS

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

RESULTS

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

CONCLUSION

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

Interleukin-32 expression in the pancreas

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

Molecular characterization of IL-32 in human endothelial cells

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

IL-32-dependent effects of IL-1beta on endothelial cell functions

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

Evidence that cytokines play a role in rheumatoid arthritis

A large number of cytokines are active in the joints of patients with rheumatoid arthritis (RA). It is now clear that these cytokines play a fundamental role in the processes that cause inflammation, articular destruction, and the comorbidities associated with RA. Following the success of TNF-alpha blockade as a treatment for RA, other cytokines now offer alternative targets for therapeutic intervention or might be useful as predictive biomarkers of disease. In this Review, we discuss the biologic contribution and therapeutic potential of the major cytokine families to RA pathology, focusing on molecules contained within the TNF-alpha, IL-1, IL-6, IL-23, and IL-2 families.

Interleukin-32 promotes osteoclast differentiation but not osteoclast activation

Background

Interleukin-32 (IL-32) is a newly described cytokine produced after stimulation by IL-2 or IL-18 and IFN-γ. IL-32 has the typical properties of a pro-inflammatory mediator and although its role in rheumatoid arthritis has been recently reported its effect on the osteoclastogenesis process remains unclear.

Methodology/Principal Findings

In the present study, we have shown that IL-32 was a potent modulator of osteoclastogenesis in vitro, whereby it promoted the differentiation of osteoclast precursors into TRAcP+ VNR+ multinucleated cells expressing specific osteoclast markers (up-regulation of NFATc1, OSCAR, Cathepsin K), but it was incapable of inducing the maturation of these multinucleated cells into bone-resorbing cells. The lack of bone resorption in IL-32-treated cultures could in part be explain by the lack of F-actin ring formation by the multinucleated cells generated. Moreover, when IL-32 was added to PBMC cultures maintained with soluble RANKL, although the number of newly generated osteoclast was increased, a significant decrease of the percentage of lacunar resorption was evident suggesting a possible inhibitory effect of this cytokine on osteoclast activation. To determine the mechanism by which IL-32 induces such response, we sought to determine the intracellular pathways activated and the release of soluble mediators in response to IL-32. Our results indicated that compared to RANKL, IL-32 induced a massive activation of ERK1/2 and Akt. Moreover, IL-32 was also capable of stimulating the release of IL-4 and IFN-γ, two known inhibitors of osteoclast formation and activation.

Conclusions/Significance

This is the first in vitro report on the complex role of IL-32 on osteoclast precursors. Further clarification on the exact role of IL-32 in vivo is required prior to the development of any potential therapeutic approach.

A human dendritic cell subset receptive to the Venezuelan equine encephalitis virus-derived replicon particle constitutively expresses IL-32

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

Mucosal cytokine network in inflammatory bowel disease

Inflammatory bowel disease (IBD), ulcerative colitis (UC) and Crohn’s disease (CD) are characterized by ongoing mucosal inflammation in which dysfunction of the host immunologic response against dietary factors and commensal bacteria is involved. The chronic inflammatory process leads to disruption of the epithelial barrier, and the formation of epithelial ulceration. This permits easy access for the luminal microbiota and dietary antigens to cells resident in the lamina propria, and stimulates further pathological immune cell responses. Cytokines are essential mediators of the interactions between activated immune cells and non-immune cells, including epithelial and mesenchymal cells. The clinical efficacy of targeting TNF-α clearly indicates that cytokines are the therapeutic targets in IBD patients. In this manuscript, we focus on the biological activities of recently-reported cytokines [Interleukin (IL)-17 cytokine family, IL-31 and IL-32], which might play a role through interaction with TNF-α in the pathophysiology of IBD.

Identification of the most active interleukin-32 isoform

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

Endogenous IL-32 controls cytokine and HIV-1 production

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

Lymphocyte-derived cytokines in inflammatory arthritis

Inflammatory bone loss is observed in a number of disorders including rheumatoid arthritis (RA), osteoporosis and periodontal disease. Lymphocytes are key components in the onset and exacerbation of autoimmune diseases and the cytokines produced by these cells have a powerful impact on disease progression. Many cytokines implicated in inflammation impact upon osteoclast (OCL) differentiation and function either directly or indirectly by modulating the relative expression of RANKL and OPG. This review highlights the contribution of lymphocyte-derived cytokines to the bone loss observed in RA and other autoimmune disorders. A greater understanding of the cytokines involved in these disorders will ultimately lead to the identification of novel therapeutic strategies for the prevention of bone loss in these diseases.

Activation of interleukin-32 pro-inflammatory pathway in response to influenza A virus infection

Background

Interleukin (IL)-32 is a recently described pro-inflammatory cytokine that has been reported to be induced by bacteria treatment in culture cells. Little is known about IL-32 production by exogenous pathogens infection in human individuals.

Methods and Findings

In this study, we found that IL-32 level was increased by 58.2% in the serum samples from a cohort of 108 patients infected by influenza A virus comparing to that of 115 healthy individuals. Another pro-inflammatory factor cyclooxygenase (COX)-2-associated prostaglandin E2 was also upregulated by 2.7-fold. Expression of IL-32 in influenza A virus infected A549 human lung epithelial cells was blocked by either selective COX-2 inhibitor NS398 or Aspirin, a known anti-inflammatory drug, indicating IL-32 was induced through COX-2 in the inflammatory cascade. Interestingly, we found that COX-2-associate PGE₂ production activated by influenza virus infection was significantly suppressed by over-expression of IL-32 but increased by IL-32-specific siRNA, suggesting there was a feedback mechanism between IL-32 and COX-2.

Conclusions

IL-32 is induced by influenza A virus infection via COX-2 in the inflammatory cascade. Our results provide that IL-32 is a potential target for anti-inflammatory medicine screening.

Cells of the synovium in rheumatoid arthritis. Chondrocytes

Rheumatoid arthritis (RA) is one of the inflammatory joint diseases in a heterogeneous group of disorders that share features of destruction of the extracellular matrices of articular cartilage and bone. The underlying disturbance in immune regulation that is responsible for the localized joint pathology results in the release of inflammatory mediators in the synovial fluid and synovium that directly and indirectly influence cartilage homeostasis. Analysis of the breakdown products of the matrix components of joint cartilage in body fluids and quantitative imaging techniques have been used to assess the effects of the inflammatory joint disease on the local remodeling of joint structures. The role of the chondrocyte itself in cartilage destruction in the human rheumatoid joint has been difficult to address but has been inferred from studies in vitro and in animal models. This review covers current knowledge about the specific cellular and biochemical mechanisms that account for the disruption of the integrity of the cartilage matrix in RA.

Pro-inflammatory cytokine-induced SAPK/MAPK and JAK/STAT in rheumatoid arthritis and the new anti-depression drugs

BACKGROUND

Adult rheumatoid arthritis (RA) patients are frequently clinically depressed. Peripheral inflammation in RA may influence neurotransmitter metabolism, neuroendocrine function, synaptic plasticity, as well as growth factor production, which can modify neural circuitry and contribute to depression.

OBJECTIVE

A convergence between pro-inflammatory cytokine-induced synovial joint inflammation in RA and the effects of pro-inflammatory cytokines on the brain may occur through activation of the stress-activated/mitogen-activated protein kinases (SAPK/MAPK) and/or Janus kinase/signal transducers and activators of transcription (JAK/STAT) pathways.

METHODS

The PubMed and Medlines databases were critically evaluated for evidence of SAPK/MAPK and/or JAK/STAT pathway activation in RA and depression.

RESULTS/CONCLUSION

Some novel anti-depression drugs that were employed in animal models of 'sickness behavior' and in human depression clinical trials suppressed clinical markers of inflammation, as well as SAPK/MAPK and/or JAK/STAT signaling in vitro. Modifying pro-inflammatory cytokine signaling pathways in the brain with antidepressants may also be useful in ameliorating peripheral inflammation in RA.

Phosphatidylinositol 3-kinase/Akt signaling mediates interleukin-32alpha induction in human pancreatic periacinar myofibroblasts

Interleukin (IL)-32 is a recently described proinflammatory cytokine, characterized by the induction of nuclear factor (NF)-kappaB activation. We studied IL-32alpha expression in human pancreatic periacinar myofibroblasts, which play important roles in the regulation of extracellular matrix metabolism and inflammatory responses in the pancreas. IL-32alpha protein expression was evaluated by Western blot analyses, and IL-32alpha mRNA expression was analyzed by Northern blot and real-time PCR analyses. IL-32alpha mRNA was weakly expressed without a stimulus, and its expression was markedly enhanced by IL-1beta, IFN-gamma, and TNF-alpha. IL-1beta, IFN-gamma, and TNF-alpha enhanced intracellular accumulation of IL-32alpha protein, but IL-32alpha was not detected in supernatants. Each cytokine dose and time dependently induced IL-32alpha mRNA expression. An inhibitor of phosphatidylinositol 3-kinase (LY294002) significantly suppressed IL-1beta-, IFN-gamma-, and TNF-alpha-induced IL-32alpha mRNA expression, although MAPK inhibitors had no effect. Akt activation in response to these cytokines was confirmed by Western blot. Furthermore, LY294002 suppressed both IL-1beta- and TNF-alpha-induced NF-kappaB activation and IL-1beta-, TNF-alpha-, and IFN-gamma-induced activated protein-1 (AP-1) activation. Blockade of NF-kappaB and AP-1 activation by an adenovirus expressing a stable mutant form of IkappaBalpha and a dominant negative mutant of c-Jun markedly suppressed IL-1beta-, IFN-gamma-, and/or TNF-alpha-induced IL-32alpha mRNA expression. Human pancreatic periacinar myofibroblasts expressed IL-32alpha in response to IL-1beta, TNF-alpha, and IFN-gamma. IL-32alpha mRNA expression is dependent on interactions between the phosphatidylinositol 3-kinase/Akt-pathway and the NF-kappaB/AP-1 system.

Interleukin-32 induces the differentiation of monocytes into macrophage-like cells

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

Dysregulation of IL-32 in myelodysplastic syndrome and chronic myelomonocytic leukemia modulates apoptosis and impairs NK function

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

Increased level of IL-32 during human immunodeficiency virus infection suppresses HIV replication

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

Mannose-capped lipoarabinomannan- and prostaglandin E2-dependent expansion of regulatory T cells in human Mycobacterium tuberculosis infection

We evaluated the role of regulatory T cells (CD4(+) CD25(+) Foxp3(+) cells, Tregs) in human Mycobacterium tuberculosis infection. Tregs were expanded in response to M. tuberculosis in healthy tuberculin reactors, but not in tuberculin-negative individuals. The M. tuberculosis mannose-capped lipoarabinomannan (ManLAM) resulted in regulatory T cell expansion, whereas the M. tuberculosis 19-kDa protein and heat shock protein 65 had no effect. Anti-IL-10 and anti-TGF-beta alone or in combination, did not reduce expansion of Tregs. In contrast, the cyclooxygenase enzyme-2 inhibitor NS398 significantly inhibited expansion of Tregs, indicating that prostaglandin E2 (PGE2) contributes to Treg expansion. Monocytes produced PGE2 upon culturing with heat-killed M. tuberculosis or ManLAM, and T cells from healthy tuberculin reactors enhanced PGE2 production by monocytes. Expanded Tregs produced significant amounts of TGF-beta and IL-10 and depletion of Tregs from PBMC of these individuals increased the frequency of M. tuberculosis-responsive CD4(+) IFN-gamma cells. Culturing M. tuberculosis-expanded Tregs with autologous CD8(+) cells decreased the frequency of IFN-gamma(+)cells. Freshly isolated PBMC from tuberculosis patients had increased percentages of Tregs, compared to healthy tuberculin reactors. These findings demonstrate that Tregs expand in response to M. tuberculosis through mechanisms that depend on ManLAM and PGE2.

Alteration in the activation state of new inflammation-associated targets by phospholipase A2-activating protein (PLAA)

Phospholipase A(2) (PLA(2))-activating protein (PLAA) is a novel signaling molecule that regulates the production of prostaglandins (PGE(2)) and tumor necrosis factor (TNF)-alpha. To characterize the function of native PLAA in situ, we generated HeLa (Tet-off) cells overexpressing plaa (plaa(high)) and control (plaa(low)) cells, with the plaa gene in opposite orientation in the latter construct. The plaa(high) cells produced significantly more PGE(2) and interleukin (IL)-6 compared to plaa(low) cells in response to TNF-alpha. There was an increased activation and/or expression of cytosolic PLA(2), cyclooxgenase-2, and NF-kappaB after induction of plaa(high) cells with TNF-alpha compared to the respective plaa(low) cells. Microarray analysis of plaa(high) cells followed by functional assays revealed increased production of proinflammatory cytokine IL-32 and a decrease in the production of annexin A4 and clusterin compared to plaa(low) cells. We demonstrated the role of annexin A4 as an inhibitor of PLA(2) and showed that addition of exogeneous clusterin limited the production of PGE(2) from plaa(high) cells. To understand regulation of plaa gene expression, we used a luciferase reporter system in HeLa cells and identified one stimulatory element, with Sp1 binding sites, and one inhibitory element, in exon 1 of the plaa gene. By using decoy DNA oligonucleotides to Sp1 and competitive binding assays, we showed that Sp1 maintains basal expression of the plaa gene and binds to the above-mentioned stimulatory element. We demonstrated for the first time that the induction of native PLAA by TNF-alpha can perpetuate inflammation by enhancing activation of PLA(2) and NF-kappaB.

Historical insights into cytokines

Cytokines affect nearly every biological process; these include embryonic development, disease pathogenesis, non-specific response to infection, specific response to antigen, changes in cognitive functions and progression of the degenerative processes of aging. In addition, cytokines are part of stem cell differentiation, vaccine efficacy and allograft rejection. This short insight focuses on the milestones in cytokine biology and how the various and often contradictory activities of these small, non-structural proteins affected the fields of inflammation and immunology. Multiple biological properties or pleiotropism is the hallmark of a cytokine. Today, the term "cytokine" encompasses interferons, the interleukins, the chemokine family, mesenchymal growth factors, the tumor necrosis factor family and adipokines. As of this writing, 33 cytokines are called interleukins, but many are part of families of related but distinct gene products. There are certainly over 100 separate genes coding for cytokine-like activities, many with overlapping functions and many still unexplored. Also discussed in this overview are the failures and successes of cytokines as therapeutic targets. A recent advance in the field has been that of differential cytokine production, which can be used to classify human disease as being "autoimmune" or "autoinflammatory" thus impacting on therapeutic interventions.

Developments in the synovial biology field 2006

Synovial pathophysiology is a complex and synergistic interplay of different cell populations with tissue components, mediated by a variety of signaling mechanisms. All of these mechanisms drive the affected joint into inflammation and drive the subsequent destruction of cartilage and bone. Each cell type contributes significantly to the initiation and perpetuation of this deleterious concert, especially in rheumatoid arthritis. Rheumatoid arthritis synovial fibroblasts and macrophages, both cell types with pivotal roles in inflammation and destruction, but also T cells and B cells are crucial for complex network in the inflamed synovium. An even more complex cellular crosstalk between these key players maintains a process of chronic inflammation. As outlined in the present review, in the past year substantial progress has been made to elucidate further details of the rich pathophysiology of rheumatoid arthritis, which may also facilitate the identification of novel targets for future therapeutic strategies.

[Rheumatoid arthritis and interleukin-32]

Inflammatory cytokine cascade plays a pivotal role in the pathogenesis of rheumatoid arthritis. Recently, a novel human cytokine, interleukin-32, was reported to induce TNF-alpha. Interleukin-32 is expressed mainly in lymphoid tissues and leukocytes, but also in stimulated epithelial cells and synovial fibroblasts. Although the interleukin-32 receptor has not been reported, interleukin-32 can induce other inflammatory cytokines, such as TNF-alpha, interleukin-1beta, and interleukin-6 from monocytes/macrophages in vitro and in vivo, and synergizes with signals from pattern-recognition receptors. Notably, in the inflamed synovial tissues from rheumatoid arthritis patients, interleukin-32 is prominently expressed and correlates with the severity of arthritis and the expression of other cytokines, including TNF-alpha and interleukin-1. In experimental mice models of arthritis, joint injection of interleukin-32 induces joint inflammation, and overexpression of interleukin-32beta in haematopoietic cells exacerbates collagen-induced arthritis. Herein, interleukin-32 plays an important role in the pathogenesis of rheumatoid arthritis.