Signal transduction pathways involved in rheumatoid arthritis synovial fibroblast interleukin-18-induced vascular cell adhesion molecule-1 expression

Anti-angiogenic effect of YuXueBi tablet in experimental rheumatoid arthritis by suppressing LOX/Ras/Raf-1 signaling

ETHNOPHARMACOLOGICAL RELEVANCE

A Chinese patent medicine derived from a classical traditional Chinese medicine formula, Yu-Xue-Bi tablet (YXB) is widely used in the clinic to treat rheumatoid arthritis (RA). During the progression of RA, angiogenesis plays a central role in fostering the production of inflammatory cells, leading to synovial hyperplasia and bone destruction. However, whether YXB attenuates the angiogenesis during RA progression remains to be defined.

AIM OF THE STUDY

We aimed to evaluate the anti-angiogenic activity of YXB and explore its mechanism of action in collagen-induced arthritis (CIA) rats and VEGF-induced HUVECs.

MATERIALS AND METHODS

Transcriptional regulatory network analysis and a network pharmacology approach were employed to explore mechanism of YXB in RA angiogenesis. The antiarthritic effect of YXB was evaluated by determining the arthritis incidence, and score, and by micro-CT analysis. The anti-angiogenic effect of YXB in vivo was assessed by histological and immunohistochemical analyses. The anti-angiogenic effect of YXB in vitro was assessed by wound healing, Transwell migration, Transwell invasion, and tube formation assays. Western-blotting and immunohistochemical analysis were employed to explore the molecular mechanisms of YXB.

RESULTS

YXB reduced disease severity and ameliorated pathological features in CIA rats. YXB markedly decreased bone destruction and synovial angiogenesis. Consistently, we also demonstrated that YXB effectively suppressed angiogenesis marker CD31 and VEGF expression. In vitro, YXB effectively inhibited HUVEC migration, invasion, and tube formation. Following the identification of transcriptional expression profiles, "YXB putative targets-known RA-related genes-genes associated with the therapeutic effect of YXB" interaction network was constructed and analyzed. After that, the LOX/Ras/Raf-1 signaling axis, which is involved in RA angiogenesis, was identified as one of the candidate mechanisms of YXB against RA. Experimentally, YXB dose-dependently decreased the expression levels of LOX, Ras, and Raf-1, as well as the phosphorylation of MEK and ERK in CIA rats, and these effects were better than the inhibitory effects of methotrexate (MTX), an FDA approved drug used for some autoimmune diseases such as RA. In addition, YXB may function as a potent angiogenesis inhibitor and significantly suppress the VEGF-induced activation of LOX/Ras/Raf-1 signaling in vitro.

CONCLUSIONS

We provide evidence that YXB may decrease the disease severity of RA and reduce bone erosion by suppressing angiogenesis via inhibition of LOX/Ras/Raf-1 signaling.

Interleukin-18 cytokine in immunity, inflammation, and autoimmunity: Biological role in induction, regulation, and treatment

Interleukin-18 (IL-18) is a potent pro-inflammatory cytokine involved in host defense against infections and regulates the innate and acquired immune response. IL-18 is produced by both hematopoietic and non-hematopoietic cells, including monocytes, macrophages, keratinocytes and mesenchymal cell. IL-18 could potentially induce inflammatory and cytotoxic immune cell activities leading to autoimmunity. Its elevated levels have been reported in the blood of patients with some immune-related diseases, including rheumatoid arthritis, systemic lupus erythematosus, type I diabetes mellitus, atopic dermatitis, psoriasis, and inflammatory bowel disease. In the present review, we aimed to summarize the biological properties of IL-18 and its pathological role in different autoimmune diseases. We also reported some monoclonal antibodies and drugs targeting IL-18. Most of these monoclonal antibodies and drugs have only produced partial effectiveness or complete ineffectiveness in vitro, in vivo and human studies. The ineffectiveness of these drugs targeting IL-18 may be largely due to the loophole caused by the involvement of other cytokines and proteins in the signaling pathway of many inflammatory diseases besides the involvement of IL-18. Combination drug therapies, that focus on IL-18 inhibition, in addition to other cytokines, are highly recommended to be considered as an important area of research that needs to be explored.

Thousands of CpGs Show DNA Methylation Differences in ACPA-Positive Individuals

High levels of anti-citrullinated protein antibodies (ACPA) are often observed prior to a diagnosis of rheumatoid arthritis (RA). We undertook a replication study to confirm CpG sites showing evidence of differential methylation in subjects positive vs. negative for ACPA, in a new subset of 112 individuals sampled from the population cohort and biobank CARTaGENE in Quebec, Canada. Targeted custom capture bisulfite sequencing was conducted at approximately 5.3 million CpGs located in regulatory or hypomethylated regions from whole blood; library and protocol improvements had been instituted between the original and this replication study, enabling better coverage and additional identification of differentially methylated regions (DMRs). Using binomial regression models, we identified 19,472 ACPA-associated differentially methylated cytosines (DMCs), of which 430 overlapped with the 1909 DMCs reported by the original study; 814 DMRs of relevance were clustered by grouping adjacent DMCs into regions. Furthermore, we performed an additional integrative analysis by looking at the DMRs that overlap with RA related loci published in the GWAS Catalog, and protein-coding genes associated with these DMRs were enriched in the biological process of cell adhesion and involved in immune-related pathways.

A comprehensive pathway map of IL-18-mediated signalling

Interleukin-18 (IL-18) is a member of the IL-1 family of cytokines and was initially described as an IFN-γ-inducing factor derived from anti-CD3-stimulated T-helper (Th)1 cells. IL-18 plays a significant role in the activation of hematopoietic cell types mediating both Th1 and Th2 responses and is the primary inducer of interferon-γ in these cells. The biological activity of IL-18 is mediated through its binding to the IL-18 receptor complex and activation of nuclear factor-κB (NF-κB), culminating in the production and release of several cytokines, chemokines, and cellular adhesion molecules. In certain cell types, IL-18 also activates mitogen-activated protein kinases (MAPKs) and phosphoinositide 3-kinase/ AKT serine/threonine kinase (PI3K/AKT) signaling modules leading to the production and release of proinflammatory cytokines. IL-18-mediated signaling acts as one of the vital components of the immunomodulatory cytokine networks involved in host defense, inflammation, and tissue regeneration. Albeit its biomedical importance, a comprehensive resource of IL-18 mediated signaling pathway is currently lacking. In this study, we report on the development of an integrated pathway map of IL-18/IL-18R signaling. The pathway map was developed through literature mining from published literature based on manual curation guidelines adapted from NetPath and includes information on 16 protein-protein interaction events, 38 enzyme-catalysis events, 12 protein translocation events, 26 activations/inhibition events, transcriptional regulators, 230 gene regulation events and 84 induced protein expression events. The IL-18 signaling pathway can be freely accessed through the WikiPathways database (https://www.wikipathways.org/index.php/Pathway:WP4754).

Redox-sensitive transcription factors play a significant role in the development of rheumatoid arthritis

Rheumatoid arthritis (RA) is a chronic autoimmune disease which is associated with significant morbidity. Redox sensitive transcription factors including NF-κB, HIF, AP-1, and Nrf2 are intimately involved in the pathogenesis of RA. The treatment of this disease is limited by the elusive nature of the pathogenesis of RA. NF-κB is crucial for the maturation of immune cells as well as production of TNFα and MMPs, which escalate RA. HIF is essential for activation of inflammatory cells, angiogenesis and pannus formation in RA. AP-1 regulates cytokine and MMP production as well as synovial hyperplasia which are key processes in RA. Nrf2 is involved with chondrogenesis, osteoblastogenesis, prostaglandin secretion and ROS production in RA. Targeting two or more of these transcription factors may result in increased efficacy than either therapy in isolation. This review will highlight the control specific mediators on these transcription factors, the subsequent effect of these transcription factors once activated, and then mesh this with the pathogenesis of RA. The elucidation of key transcription factor regulation in the pathogenesis of RA may highlight the novel therapy interventions which may prove to have a greater efficacy than those therapies currently available.

Immunoselected STRO-3+ mesenchymal precursor cells reduce inflammation and improve clinical outcomes in a large animal model of monoarthritis

BACKGROUND

The purpose of this study was to investigate the therapeutic efficacy of intravenously administered immunoselected STRO-3 + mesenchymal precursor cells (MPCs) on clinical scores, joint pathology and cytokine production in an ovine model of monoarthritis.

METHODS

Monoarthritis was established in 16 adult merino sheep by administration of bovine type II collagen into the left hock joint following initial sensitization to this antigen. After 24 h, sheep were administered either 150 million allogeneic ovine MPCs (n = 8) or saline (n = 8) intravenously (IV). Lameness, joint swelling and pain were monitored and blood samples for leukocytes and cytokine levels were collected at intervals following arthritis induction. Animals were necropsied 14 days after arthritis induction and gross and histopathological evaluations were undertaken on tissues from the arthritic (left) and contralateral (right) joints.

RESULTS

MPC-treated sheep demonstrated significantly reduced clinical signs of lameness, joint pain and swelling compared with saline controls. They also showed decreased cartilage erosions, synovial stromal cell activation and angiogenesis. This was accompanied by decreased infiltration of the synovial tissues by CD4+ lymphocytes and CD14+ monocytes/macrophages. Over the 3 days following joint arthropathy induction, the numbers of neutrophils circulating in the blood and plasma concentrations of activin A were significantly reduced in animals administered MPCs.

CONCLUSIONS

The results of this study have demonstrated the capacity of IV-administered MPCs to mitigate the clinical signs and some of the inflammatory mediators responsible for joint tissue destruction in a large animal model of monoarthritis.

Hmox1 Deficiency Sensitizes Mice to Peroxynitrite Formation and Diabetic Glomerular Microvascular Injuries

OBJECTIVE

Indirect evidence suggests a role for heme oxygenase-1 (HO-1) in limiting diabetic vasculopathy. The goal of this study was to assess the role of HO-1 in the development of microvascular lesions within glomeruli during diabetes mellitus using a mouse model with specific alteration of the Hmox1 gene.

APPROACH AND RESULTS

The effects of Hmox1 haploinsufficiency were studied as a means of assessing the intrinsic contribution of HO-1 in the development of renal microvascular lesions during diabetes. Renal function and histology were analyzed 10 weeks after diabetes induction with streptozotocin. Diabetic Hmox1^+/- mice showed higher levels of albuminuria and blood urea compared to their wild-type diabetic littermates. More severe glomerular microvascular lesions were also observed in the diabetic Hmox1^+/- mice. This was associated with a renal increase in the expression of the oxidative stress marker, nitrotyrosine.

CONCLUSIONS

Genetic Hmox1 partial deficiency is sufficient to sensitize mice to the development of diabetic glomerular microvascular lesions. HO-1 exerts antioxidant effects in the kidney during diabetes mellitus. These have protective effects on the development of glomerular endothelial injury.

Inflammation induced loss of skeletal muscle

Inflammation is an important contributor to the pathology of diseases implicated in skeletal muscle dysfunction. A number of diseases and disorders including inflammatory myopathies and Chronic Obstructive Pulmonary Disorder (COPD) are characterized by chronic inflammation or elevation of the inflammatory mediators. While these disease states exhibit different pathologies, all have in common the loss of skeletal muscle mass and a deregulated skeletal muscle physiology. Pro-inflammatory cytokines are key contributors to chronic inflammation found in many of these diseases. This section of the review focuses on some of the known inflammatory disorders like COPD, Rheumatoid Arthritis (RA) and inflammatory myopathies that display skeletal muscle atrophy and also provides the reader an overview of the mediators of inflammation, their signaling pathways, and mechanisms of action. This article is part of a Special Issue entitled "Muscle Bone Interactions".

Interleukin-18 expression increases in response to neurovascular damage following soman-induced status epilepticus in rats

Background

Status epilepticus (SE) can cause neuronal cell death and impaired behavioral function. Acute exposure to potent acetylcholinesterase inhibitors such as soman (GD) can cause prolonged SE activity, micro-hemorrhage and cell death in the hippocampus, thalamus and piriform cortex. Neuroinflammation is a prominent feature of brain injury with upregulation of multiple pro-inflammatory cytokines including those of the IL-1 family. The highly pleiotropic pro-inflammatory cytokine interleukin-18 (IL-18) belongs to the IL-1 family of cytokines and can propagate neuroinflammation by promoting immune cell infiltration, leukocyte and lymphocyte activation, and angiogenesis and helps facilitate the transition from the innate to the adaptive immune response. The purpose of this study is to characterize the regional and temporal expression of IL −18 and related factors in the brain following SE in a rat GD seizure model followed by localization of IL-18 to specific cell types.

Methods

The protein levels of IL-18, vascular endothelial growth factor and interferon gamma was quantified in the lysates of injured brain regions up to 72 h following GD-induced SE onset using bead multiplex immunoassays. IL-18 was localized to various cell types using immunohistochemistry and transmission electron microscopy. In addition, macrophage appearance scoring and T-cell quantification was determined using immunohistochemistry. Micro-hemorrhages were identified using hematoxylin and eosin staining of brain sections.

Results

Significant increases in IL-18 occurred in the piriform cortex, hippocampus and thalamus following SE. IL-18 was primarily expressed by endothelial cells and astrocytes associated with the damaged neurovascular unit. The increase in IL-18 was not related to macrophage accumulation, neutrophil infiltration or T-cell appearance in the injured tissue.

Conclusions

These data show that IL-18 is significantly upregulated following GD-induced SE and localized primarily to endothelial cells in damaged brain vasculature. IL-18 upregulation occurred following leukocyte/lymphocyte infiltration and in the absence of other IL-18-related cytokines, suggesting another function, potentially for angiogenesis related to GD-induced micro-hemorrhage formation. Further studies at more chronic time points may help to elucidate this function.

Distinct effects of soluble and membrane-bound fas ligand on fibroblast-like synoviocytes from rheumatoid arthritis patients

OBJECTIVE

Injection of agonistic anti-Fas antibody has been shown to decrease disease symptoms in mouse models of arthritis. Additionally, membrane-bound FasL (mFasL) has been shown to induce cell death in fibroblast-like synoviocytes (FLS) from rheumatoid arthritis (RA) patients. However, levels of soluble FasL (sFasL) are increased in the joints of RA patients and have been associated with disease severity, indicating that mFasL and sFasL play opposing roles in RA. The purpose of this study was to analyze the effects of FasL on RA FLS responses.

METHODS

The responses of FLS from RA and osteoarthritis (OA) patients to soluble and oligomeric FasL, the latter mimicking mFasL, were analyzed by fluorescence-activated cell sorting and proliferation assays, using 3 different FasL variants. The signaling pathways that trigger FasL responses were characterized by Western blotting.

RESULTS

We found that mFasL and sFasL have distinct roles in RA FLS. Crosslinked FasL preferentially induced apoptosis, whereas sFasL stimulated proliferation. Moreover, sFasL activated several signaling pathways in RA FLS, such as ERK-1/2, phosphatidylinositol 3-kinase, caspase 8, and JNK, with a prominent role of JNK, since only the blockade of this pathway rendered FLS more susceptible to FasL-induced apoptosis. Crosslinked FasL induced apoptosis in FLS from OA patients, but sFasL failed to stimulate their proliferation.

CONCLUSION

Our findings suggest that sFasL is a disease promoter in RA, a finding consistent with previous reports describing a tumor-promoting role of FasL. Therefore, blocking of sFasL could be a therapeutic strategy for RA.

The CO donor CORM-2 inhibits LPS-induced vascular cell adhesion molecule-1 expression and leukocyte adhesion in human rheumatoid synovial fibroblasts

BACKGROUND AND PURPOSE

Infection with Gram-negative bacteria has been recognized as an initiator of rheumatoid arthritis, which is characterized by chronic inflammation and infiltration of immune cells. Carbon monoxide (CO) exhibits anti-inflammatory properties. Here we have investigated the detailed mechanisms of vascular cell adhesion molecule-1 (VCAM-1) expression induced by LPS and if CO inhibited LPS-induced leukocyte adhesion to synovial fibroblasts by suppressing VCAM-1 expression.

EXPERIMENTAL APPROACH

Human rheumatoid arthritis synovial fibroblasts (RASFs) were incubated with LPS and/or the CO-releasing compound CORM-2. Effects of LPS on VCAM-1 levels were determined by analysing mRNA expression, promoter activity, protein expression, and immunohistochemical staining. The molecular mechanisms were investigated by determining the expression, activation, and binding activity of transcriptional factors using target signal antagonists.

KEY RESULTS

CORM-2 significantly inhibited inflammatory responses in LPS-treated RASFs by down-regulating the expression of adhesion molecule VCAM-1 and leukocyte infiltration. The down-regulation of LPS-induced VCAM-1 expression involved inhibition of the expression of phosphorylated-NF-κB p65 and AP-1 (p-c-Jun, c-Jun and c-Fos mRNA levels). These results were confirmed by chromatin immunoprecipitation assay to detect NF-κB and AP-1 DNA binding activity.

CONCLUSIONS AND IMPLICATIONS

LPS-mediated formation of the TLR4/MyD88/TRAF6/c-Src complex regulated NF-κB and MAPKs/AP-1 activation leading to VCAM-1 expression and leukocyte adhesion. CORM-2, which liberates CO to elicit direct biological activities, attenuated LPS-induced VCAM-1 expression by interfering with NF-κB and AP-1 activation, and significantly reduced LPS-induced immune cell infiltration of the synovium.

Interleukin 18 activates MAPKs and STAT3 but not NF-κB in hippocampal HT-22 cells

Interleukin (IL)-18 is a cytokine previously demonstrated to participate in neuroinflammatory processes. Since the components of the IL-18 receptor complex are expressed in neurons throughout the brain, IL-18 is also believed to directly influence neuronal function. Here we tested this hypothesis on mouse hippocampal neurons by measuring the effects of IL-18 on three pathways previously shown to be regulated by this cytokine in non-neuronal cells: the MAPK pathways, p38 and ERK1/2 MAPKs, STAT3 and NF-κB. Experiments were carried out in vitro using the immortalized hippocampal neuronal line HT-22 or in vivo following i.c.v. injection with recombinant mouse IL-18. We showed that IL-18 did not activate NF-κB in HT-22 cells whereas it induced a rapid (within 15min) activation of the MAPK pathways. Moreover, we demonstrated that IL-18 treatment enhanced P-STAT3 (Tyr705)/STAT3 ratio in the nucleus of HT-22 cells after 30-60min of exposure. A similar increase in P-STAT3 (Tyr705)/STAT3 ratio was observed in the whole hippocampus one hour after i.c.v. injection. These data demonstrate that IL-18 can act directly on neuronal cells affecting the STAT3 pathway; therefore, possibly regulating the expression of specific genes within the hippocampus. This effect may help to explain some of the IL-18-induced effects on synaptic plasticity and functionality within the hippocampal system.

Blocking the janus-activated kinase pathway reduces tumor necrosis factor alpha-induced interleukin-18 bioactivity by caspase-1 inhibition

Introduction

Our objective was to examine the role of the janus-activated kinase (JAK) pathway in the modulation of tumor necrosis factor-α (TNF)-induced-IL-18 bioactivity by reduction of caspase-1 function.

Methods

Caspase-1 expression in rheumatoid arthritis (RA) synovial fibroblasts treated with TNF was assessed by qRT-PCR and Western blot. Interleukin (IL)-18 was assessed by enzyme-linked immunosorbent assay (ELISA) in cell lysates and conditioned media and detected by immunofluorescence (IF) staining in RA synovial fibroblasts. The critical pathways for TNF-induced caspase-1 expression were determined by using chemical inhibitors of signaling followed by TNF stimulation. IL-18 bioactivity was assessed using human myelomonocytic KG-1 cells.

Results

TNF induced RA synovial fibroblast caspase-1 expression at the protein level in a time-dependant manner (P < 0.05). Blocking the JAK pathway reduced TNF-induced-caspase-1 expression at the transcriptional and protein levels by approximately 60% and 40%, respectively (P < 0.05). Blocking the JAK pathway reduced TNF-induced-caspase-1 expression at the transcriptional, protein, and activity levels by approximately 60%, 40%, and 53%, respectively (P < 0.05). We then confirmed by IF that TNF-induced IL-18 and investigated roles of the ERK1/2 and JAK pathways. Blocking the JAK pathway, TNF induced intracytoplasmic granular IL-18 expression suggesting a defect of caspase-1. Finally, blocking the JAK pathway, we observed a reduction of IL-18 bioactivity by 52% in RA synovial fibroblasts (P < 0.05).

Conclusions

These results provide a new way to regulate TNF-induced-IL-18 bioactivity by blocking capase-1. These data present a novel role for JAK inhibition in RA patients and emphasize JAK inhibition use as a new therapeutic option in RA management.

IL-18 in inflammatory and autoimmune disease

Inflammation serves as the first line of defense in response to tissue injury, guiding the immune system to ensure preservation of the host. The inflammatory response can be divided into a quick initial phase mediated mainly by innate immune cells including neutrophils and macrophages, followed by a late phase that is dominated by lymphocytes. Early in the new millennium, a key component of the inflammatory reaction was discovered with the identification of a number of cytosolic sensor proteins (Nod-like receptors) that assembled into a common structure, the 'inflammasome'. This structure includes an enzyme, caspase-1, which upon activation cleaves pro-forms of cytokines leading to subsequent release of active IL-1 and IL-18. This review focuses on the role of IL-18 in inflammatory responses with emphasis on autoimmune diseases.

IL-18 upregulates the production of key regulators of osteoclastogenesis from fibroblast-like synoviocytes in rheumatoid arthritis

Recent data have demonstrated the importance of IL-18 in the induction and perpetuation of chronic inflammation in experimental arthritis. The aim of the present study was to elucidate whether IL-18 has any indirect effects on osteoclastogenesis by regulating the production of molecules from fibroblast-like synoviocytes (FLS) in rheumatoid arthritis (RA). Human FLS were isolated from RA synovial tissue and cultured in vitro for three to five passages. The expression of IL-18 receptor was determined by RT-PCR. The levels of soluble receptor activator of nuclear factor κB ligand (RANKL), osteoprotegerin (OPG), macrophage colony-stimulating factor (M-CSF), and granulocyte-macrophage colony-stimulating factor (GM-CSF) in culture supernatants were determined by ELISA. Membrane-bound RANKL expression was analyzed by flow cytometry. Both α and β chains of IL-18 receptor were confirmed in cultured FLS. IL-18 upregulated membrane-bound RANKL expression and soluble RANKL production by FLS in both time- and dose-dependent manners. In addition, IL-18 enhanced production of M-CSF, GM-CSF, and OPG from cultured FLS in a dose-dependent manner. IL-18 also increased the ratio of RANKL/OPG, suggesting that the net effect of IL-18 on FLS favors for the induction of osteoclast formation and bone resorption. In conclusion, IL-18 upregulates the production of key regulators of osteoclastogenesis from FLS in RA.

NLRP1 gene polymorphism influences gene transcription and is a risk factor for rheumatoid arthritis in han chinese

OBJECTIVE

The inflammasome-related protein NLRP1/NALP1 has been implicated in the onset and progression of some autoimmune diseases. This study was undertaken to determine whether a polymorphism in the NLRP1 gene is associated with susceptibility to rheumatoid arthritis (RA) in Han Chinese and to assess the functional implications of this association.

METHODS

RA patients (n = 190) and matched healthy controls (n = 190) residing in the city of Chengdu were genotyped for the NLRP1 promoter polymorphisms rs6502867 and rs878329. Genotyping for rs878329 was performed in a second set of subjects (n = 1,514) residing in the city of Chongqing. The effect of each polymorphism on NLRP1 transcription was evaluated by dual-luciferase assay, while the effect on DNA protein interaction was determined by electrophoretic mobility shift assay. Differential expression of NLRP1 in individuals with different genotypes was investigated by real-time quantitative polymerase chain reaction.

RESULTS

The polymorphism rs878329, but not rs6502867, was associated with RA (odds ratio [OR] 0.83, P = 0.02 for the C allele; OR 0.42, P = 0.01 for the CC genotype). The GG genotype of rs878329 was the risk genotype for RA (OR 2.38) and had a runt-related transcription factor 1 binding site that up-regulated NLRP1 transcription. Individuals with the RA risk genotype GG had significantly higher NLRP1 messenger RNA levels than those with the CC genotype among the Han Chinese population.

CONCLUSION

Our findings indicate that NLRP1 is associated with RA in Han Chinese. The G allele of rs878329 in the NLRP1 promoter up-regulates gene transcription and confers the risk of RA.

Serum IL-18 is closely associated with renal tubulointerstitial injury and predicts renal prognosis in IgA nephropathy

BACKGROUND

IgA nephropathy (IgAN) was thought to be benign but recently found it slowly progresses and leads to ESRD eventually. The aim of this research is to investigate the value of serum IL-18 level, a sensitive biomarker for proximal tubule injury, for assessing the histopathological severity and disease progression in IgAN.

METHODS

Serum IL-18 levels in 76 IgAN patients and 36 healthy blood donors were measured by ELISA. We evaluated percentage of global and segmental sclerosis (GSS) and extent of tubulointerstitial damage (TID). The correlations between serum IL-18 levels with clinical, histopathological features and renal prognosis were evaluated.

RESULTS

The patients were 38.85 ± 10.95 years old, presented with 2.61 (1.43∼4.08) g/day proteinuria. Serum IL-18 levels were significantly elevated in IgAN patients. Baseline serum IL-18 levels were significantly correlated with urinary protein excretion (r = 0.494, P = 0.002), Scr (r = 0.61, P < 0.001), and eGFR (r = -0.598, P < 0.001). TID scores showed a borderline significance with serum IL-18 levels (r = 0.355, P = 0.05). During follow-up, 26 patients (34.21%) had a declined renal function. Kaplan-Meier analysis found those patients with elevated IL-18 had a significant poor renal outcome (P = 0.03), and Cox analysis further confirmed that serum IL-18 levels were an independent predictor of renal prognosis (β = 1.98, P = 0.003).

Anti-inflammatory activities of Chinese herbal medicine sinomenine and Liang Miao San on tumor necrosis factor-α-activated human fibroblast-like synoviocytes in rheumatoid arthritis

AIM OF THE STUDY

Sinomenine, an alkaloid isolated from the root of Sinomenium acutum, has been used to alleviate the symptoms of rheumatic diseases. Liang Miao San (LMS), composed of the herbs Rhizoma Atractylodis (Cangzhu) and Cotex Phellodendri (Huangbai), is another traditional Chinese medicine formula for rheumatoid arthritis (RA) treatment. Although numerous studies have demonstrated the potential anti-inflammatory activities of sinomenine and LMS, the underlying intracellular mechanisms regulating the anti-inflammatory activities of sinomenine and LMS on human primary fibroblast-like synoviocytes (FLS) from RA patients and normal control subjects have not been elucidated.

MATERIALS AND METHODS

We investigated the in vitro anti-inflammatory activity of sinomenine and LMS on inflammatory cytokine tumor necrosis factor (TNF)-α-mediated activation of human normal and RA-FLS. The underlying intracellular signaling molecules were analyzed quantitatively using flow cytometry.

RESULTS

Sinomenine was found to significantly inhibit TNF-α induced cell surface expression of vascular cell adhesion molecule (VCAM)-1 and release of inflammatory cytokine and chemokine IL-6, CCL2 and CXCL8 from both normal and RA-FLS (all p<0.05). Moreover, the suppression of sinomenine on TNF-α induced VCAM-1 expression and IL-6 release of RA-FLS was significantly higher than that of normal FLS (p<0.05). LMS significantly inhibited TNF-α-induced inflammatory chemokines CXCL10 and CCL5 release from both normal and RA-FLS, with significantly higher suppression on CXCL10 secretion in RA-FLS than that of normal FLS (all p<0.05). Further investigations showed that sinomenine and LMS could significantly suppress TNF-α-induced phosphorylation of inhibitor κBα and extracellular signal-regulated protein kinase, the central signaling molecules mediating TNF-α-induced VCAM-1 expression and chemokine production.

CONCLUSION

Our results therefore provide a new insight into the differential anti-inflammatory activities of sinomenine and LMS through the suppression of TNF-α-activated FLS by modulating distinct intracellular signaling pathways in RA.

Bambusae caulis in Liquamen Suppresses the Expression of Thymus and Activation-Regulated Chemokine and Macrophage-Derived Chemokine in Human Keratinocytes due to Antioxidant Effect

Bambusae caulis in Liquamen (BCL), traditional herbal medicine used in East Asia, is known to have antioxidative and immune-regulating properties. We hypothesized that the potential antioxidant effects of BCL might suppress the production of thymus and activation-regulated chemokine (TARC) and macrophage-derived chemokine (MDC) in human keratinocytes (HaCaT cell). The immune-regulating effect of BCL was demonstrated by antioxidant capacity using DPPH analysis and DCFH-DA analysis. We found that BCL had strong ROS scavenge effect in HaCaT cell. BCL also showed suppression of IFN-γ-induced expression of TARC and MDC, activation of NF-κB, and, moreover, significant block of IFN-γ-induced degradation and phosphorylation of IκB. However, it had no effects on phosphorylation of p38 MAPK. Collectively, these results suggest that BCL may have a therapeutic potential on skin disease such as atopic dermatitis by inhibiting Th2 chemokines which is due, at least in part, to its antioxidant capacities.

Proinflammatory cytokines in heart failure: double-edged swords

Increased circulating and intracardiac levels of proinflammatory cytokines have been associated with chronic heart failure. Following an initial insult, the increased production of proinflammatory cytokines, including TNF-α, IL-6, IL-1, and IL-18, jeopardizes the surrounding tissue through propagation of the inflammatory response and direct effects on the cardiac myocyte structure and function. Cardiac myocyte hypertrophy, contractile dysfunction, cardiac myocyte apoptosis, and extracellular matrix remodeling contribute enormously to the development and progression of chronic heart failure. Despite the identification of efficacious pharmacological regimens and introduction of mechanical interventions, chronic heart failure remains among the leading causes of mortality worldwide. To introduce novel therapeutic strategies that modulate the inflammatory response in the context of the failing heart, it is of prime importance to determine the contributions of TNF-α, IL-6, IL-1, and IL-18 in mediating cardiac adaptive and maladaptive responses, as well as delineating their downstream intracellular signaling pathways and their potential therapeutic implications.

Macrophage migration inhibitory factor: a multifunctional cytokine in rheumatic diseases

Macrophage migration inhibitory factor (MIF) was originally identified in the culture medium of activated T lymphocytes as a soluble factor that inhibited the random migration of macrophages. MIF is now recognized to be a multipotent cytokine involved in the regulation of immune and inflammatory responses. Moreover, the pivotal nature of its involvement highlights the importance of MIF to the pathogenesis of various inflammatory disorders and suggests that blocking MIF may be a useful therapeutic strategy for treating these diseases. This paper discusses the function and expressional regulation of MIF in several rheumatic diseases and related conditions.

Effects of inflammatory cytokine IL-27 on the activation of fibroblast-like synoviocytes in rheumatoid arthritis

Introduction

Interleukin (IL)-27 is a novel member of the IL-6/IL-12 family cytokines that are produced early by antigen-presenting cells in T helper (Th)1-mediated inflammation. Elevated expression of IL-27 has been detected in the synovial membranes and fluid of rheumatoid arthritis (RA).

Methods

We investigated the in vitro effects of IL-27, alone or in combination with inflammatory cytokine tumor necrosis factor (TNF)-α or IL-1 β on the pro-inflammatory activation of human primary fibroblast-like synoviocytes (FLS) from RA patients and normal control subjects, and the underlying intracellular signaling molecules were determined by intracellular staining using flow cytometry.

Results

Significantly higher plasma concentration of IL-27 was found in RA patients (n = 112) than control subjects (n = 46). Both control and RA-FLS constitutively express functional IL-27 receptor heterodimer, gp130 and WSX-1, with more potent IL-27-mediated activation of signal transducers and activators of transcription (STAT)1 in RA-FLS. IL-27 was found to induce significantly higher cell surface expression of intercellular adhesion molecule (ICAM)-1 and vascular cell adhesion molecule (VCAM)-1 and release of inflammatory chemokine IL-6, CCL2, CXCL9, CXCL10 and matrix metalloproteinase-1 of RA-FLS than that of control FLS (all P < 0.05). Moreover, an additive or synergistic effect was observed in the combined treatment of IL-27 and TNF-α or IL-1 β on the surface expression of ICAM-1 and VCAM-1 and the release of CXCL9 and CXCL10 of RA-FLS. Further investigations showed that the expression of ICAM-1, VCAM-1 and chemokines stimulated by IL-27 was differentially regulated by intracellular activation of phosphatidylinositol 3-OH kinase-AKT, c-Jun amino-terminal kinase and Janus kinase pathways.

Conclusions

Our results therefore provide a new insight into the IL-27-activated immunopathological mechanisms mediated by distinct intracellular signal transductions in joint inflammation of RA.

Interleukin-18 as an in vivo mediator of monocyte recruitment in rodent models of rheumatoid arthritis

Introduction

The function of interleukin-18 (IL-18) was investigated in pertinent animal models of rodent rheumatoid arthritis (RA) to determine its proinflammatory and monocyte recruitment properties.

Methods

We used a modified Boyden chemotaxis system to examine monocyte recruitment to recombinant human (rhu) IL-18 in vitro. Monocyte recruitment to rhuIL-18 was then tested in vivo by using an RA synovial tissue (ST) severe combined immunodeficient (SCID) mouse chimera. We defined monocyte-specific signal-transduction pathways induced by rhuIL-18 with Western blotting analysis and linked this to in vitro monocyte chemotactic activity. Finally, the ability of IL-18 to induce a cytokine cascade during acute joint inflammatory responses was examined by inducing wild-type (Wt) and IL-18 gene-knockout mice with zymosan-induced arthritis (ZIA).

Results

We found that intragraft injected rhuIL-18 was a robust monocyte recruitment factor to both human ST and regional (inguinal) murine lymph node (LN) tissue. IL-18 gene-knockout mice also showed pronounced reductions in joint inflammation during ZIA compared with Wt mice. Many proinflammatory cytokines were reduced in IL-18 gene-knockout mouse joint homogenates during ZIA, including macrophage inflammatory protein-3α (MIP-3α/CCL20), vascular endothelial cell growth factor (VEGF), and IL-17. Signal-transduction experiments revealed that IL-18 signals through p38 and ERK½ in monocytes, and that IL-18-mediated in vitro monocyte chemotaxis can be significantly inhibited by disruption of this pathway.

Conclusions

Our data suggest that IL-18 may be produced in acute inflammatory responses and support the notion that IL-18 may serve a hierarchic position for initiating joint inflammatory responses.

Blocking ERK-1/2 reduces tumor necrosis factor alpha-induced interleukin-18 bioactivity in rheumatoid arthritis synovial fibroblasts by induction of interleukin-18 binding protein A

OBJECTIVE

To examine the mechanism of regulation of interleukin-18 (IL-18) bioactivity by IL-18 binding protein (IL-18BP) induction.

METHODS

Levels of IL-18 and IL-18BPa in synovial fluid samples from patients with osteoarthritis (OA) or rheumatoid arthritis (RA) were determined by enzyme-linked immunosorbent assays (ELISAs), followed by calculation of free IL-18. IL-18 and IL-18BPa synthesis in RA synovial fibroblasts that had been treated with proinflammatory and antiinflammatory cytokines were assessed by quantitative real-time polymerase chain reaction and ELISA, respectively, followed by IL-18 bioactivity determination using KG-1 cells. Chemical signaling inhibitors were used for determination of the signal transduction pathways involved in IL-18BPa/IL-18 regulation. Tumor necrosis factor alpha (TNFalpha)-induced caspase 1 activity was determined by a colorimetric assay.

RESULTS

IL-18BPa was lower in RA synovial fluid than in OA synovial fluid (P < 0.05; n = 8), and free IL-18 was higher in RA synovial fluid than in OA synovial fluid. TNFalpha induced RA synovial fibroblast IL-18BPa and IL-18 in a time-dependent manner (P < 0.05). Evaluation of signaling pathways suggested that TNFalpha induced IL-18 production through the ERK-1/2, protein kinase Cdelta (PKCdelta), and Src pathways, whereas IL-18BPa synthesis was mediated through the NFkappaB, PKC, Src, and JNK pathways. Furthermore, addition of exogenous IL-18BPa-Fc reduced the RA synovial fibroblast phosphorylation of ERK-1/2 induced by TNFalpha.

CONCLUSION

These results suggest that IL-18BPa reduces IL-18 bioactivity induced by TNFalpha, by regulating the ERK-1/2 pathway in RA synovial fibroblasts. Targeting IL-18 bioactivity by induction or addition of IL-18BPa may provide another therapeutic option in the management of RA.

Idiopathic inflammatory myopathies

The idiopathic inflammatory myopathies are a group of systemic autoimmune syndromes characterized by striated muscle inflammation. Here, we discuss the clinical features of this group of conditions and review the recent developments in the understanding of the pathogenesis and immunogenetics of the idiopathic inflammatory myopathies. The role of myositis-specific autoantibodies and their clinical significance and an overview of management are also provided.

Cytokines in idiopathic inflammatory myopathies

Recent findings suggest cytokines as important key molecules in the pathogenic mechanisms of idiopathic inflammatory myopathies, myositis. In this review, we focus on cytokines with a potential role in disease mechanisms in myositis and present some general information on individual cytokines and an updated summary from the literature concerning cytokines in these disorders. The idiopathic inflammatory myopathies is a heterogeneous group of disorders clinically characterized by symmetric proximal muscle weakness and by certain defined histolopathological findings, including inflammatory infiltrates in muscle tissue. Other prominent findings in the target tissue of these patients are defined molecular changes of blood vessels and muscle fibers, including reformation to high endothelial venule (HEV)-like blood vessels and intensive MHC class I expression in muscle fibers. The predominant clinical symptoms of muscle weakness and decreased muscle endurance are shared by all subsets of inflammatory myopathies and indicate that some pathogenic mechanisms related to muscle function may be shared by the different disease groups. Studies on cytokine gene, RNA and protein expression in muscle tissue from patients with various forms of the disease also indicate similar profiles, despite different phenotypes of the inflammatory cells present in muscle tissue from the different subsets of myositis. There is a pronounced expression of various cytokines in muscle tissue, among which the proinflammatory cytokines TNF-alpha and IL-1 are most widely explored in the inflammatory myopathies, which has made them into potential therapeutic targets. The use of targeted cytokine therapy has been successful in several other chronic inflammatory diseases and although the exact role of cytokines in chronic idiopathic inflammatory myopathies remains to be delineated their potential role as targets for new therapies in this disorder will be discussed in this review.

Fluvastatin inhibits expression of the chemokine MDC/CCL22 induced by interferon-gamma in HaCaT cells, a human keratinocyte cell line

BACKGROUND AND PURPOSE

The macrophage-derived chemokine (MDC/CCL22) is a prototypic Th2-type chemokine intimately involved in Th2-skewed allergic diseases, such as atopic dermatitis and asthma. The statins (3-hydroxy-3-methyl glutaryl coenzyme A reductase inhibitors) have been demonstrated to relieve allergic inflammation. However, the immunological effects and mechanisms of statins against atopic dermatitis remain unknown, at least in vitro. This study aimed to define how different statins affect MDC expression in HaCaT cells, a human keratinocyte cell line.

EXPERIMENTAL APPROACH

To measure the effects of statins on MDC expression in HaCaT cells, we used a cell viability assay, reverse transcription-polymerase chain reaction, enzyme-linked immunosorbent assay and Western blotting analyses.

KEY RESULTS

Fluvastatin, but not atorvastatin or simvastatin, inhibited MDC expression induced by interferon (IFN)-gamma and NF-kappaB activation. A NF-kappaB inhibitor, but not a STAT1 inhibitor, suppressed MDC expression in HaCaT cells. Further, inhibition of p38 mitogen-activated protein kinases (MAPKs) significantly suppressed IFN-gamma-induced MDC expression and NF-kappaB activation. Interestingly, fluvastatin suppressed IFN-gamma-induced NF-kappaB activation in parallel with p38 MAPK phosphorylation.

CONCLUSIONS AND IMPLICATIONS

These results indicate that fluvastatin inhibited expression of the CC chemokine MDC induced by IFN-gamma in HaCaT cells, by inhibiting NF-kappaB activation via the p38 MAPK pathway. This blockade of a Th2 chemokine by fluvastatin may suppress the infiltration of Th2 cells into skin lesions and lessen the skin inflammation seen in atopic dermatitis, suggesting a potential therapeutic use of fluvastatin for this condition.

The pleiotropic effect of TRAIL on tumor-like synovial fibroblasts from rheumatoid arthritis patients is mediated by caspases

The tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) has gained much attention as a possible therapeutic reagent for the treatment of tumors, as TRAIL was originally described to induce apoptosis specifically in cancer cells, but not in normal cells. Fibroblast-like synoviocytes (FLS) in rheumatoid arthritis (RA) patients exhibit tumor-like features and we have described earlier that TRAIL induces apoptosis only in a subset of RA FLS, but an induction of proliferation in the surviving cells. This observation corresponds to the pleiotropic effects of TRAIL observed on primary human tumor cells. Here, we describe that the PI3 kinase/Akt-signaling pathway, but not that of the MAP kinases ERK and p38, protects RA FLS from TRAIL-induced apoptosis by modulating the expression of the cell survival regulators p21, XIAP, Mcl-1 and RIP. Moreover, we found that not only TRAIL-induced apoptosis, but also TRAIL-triggered proliferation in RA FLS is mediated by caspases with a crucial role for caspase 8. TRAIL was found to induce degradation of p21 and p27 that was caspase-dependent, but independent of the ERK, p38 and PI3 kinase/Akt-signaling pathways. The finding that TRAIL-triggered proliferation and apoptosis share intracellular routes has to be taken in consideration in defining therapeutic strategies on the basis of the administration of TRAIL.

The adenylyl cyclase-cAMP system suppresses TARC/CCL17 and MDC/CCL22 production through p38 MAPK and NF-kappaB in HaCaT keratinocytes

Patients with atopic dermatitis (AD) have significantly reduced plasma cAMP levels, and the cAMP level is correlated with the immunopathogenesis of AD. The production of thymus and activation-regulated chemokine (TARC/CCL17) and macrophage-derived chemokine (MDC/CCL22) in keratinocytes is significantly enhanced in patients with AD. In the present study, we investigated the in vitro effects of the adenylyl cyclase-cAMP system on IFN-gamma and TNF-alpha-stimulated production of TARC and MDC in human HaCaT keratinocytes. Both forskolin (a direct activator of adenylyl cyclase) and dibutyryl-cAMP (DBcAMP, a permeable analog of cAMP) suppressed production of TARC and MDC in parallel with the activation of NF-kappaB in IFN-gamma and TNF-alpha-stimulated HaCaT cells. Moreover, inhibition of NF-kappaB suppressed TARC and MDC production induced by IFN-gamma plus TNF-alpha. However, dideoxyforskolin, a forskolin derivative that does not activate cAMP, failed to suppress the secretion of these chemokines. An inhibitor of p38 MAPK suppressed the production of TARC and MDC in parallel to the activation of NF-kappaB in HaCaT cells. Of note, the IFN-gamma plus TNF-alpha-stimulated activation of p38 MAPK was suppressed following incubation with forskolin or DBcAMP alone. These results indicate that the adenylyl cyclase-cAMP system has an inhibitory role in IFN-gamma plus TNF-alpha-stimulated production of TARC and MDC in HaCaT keratinocytes by inhibiting NF-kappaB activation through p38 MAPK pathway, implying that the adenylyl cyclase-cAMP system could be a candidate therapeutic target of Th2-skewed skin inflammation such as AD.

All-trans retinoic acid suppresses interleukin-6 expression in interleukin-1-stimulated synovial fibroblasts by inhibition of ERK1/2 pathway independently of RAR activation

INTRODUCTION

Interleukin-6 (IL-6) is thought to play a pathogenic role in rheumatoid arthritis and synovium is a major source of IL-6 release. We investigated the ability of retinoids to suppress IL-6 expression in IL-1-stimulated synovial fibroblasts, with special care to the contribution of retinoic acid receptor (RAR) and retinoid X receptor (RXR) subtypes, and the implication of the mitogen-activated protein kinase (MAPK) pathway.

METHODS

RAR-alpha, -beta, and -gamma and RXR-alpha, -beta, and -gamma levels were determined by reverse transcription-quantitative polymerase chain reaction (RT-qPCR) or Western blot in rat synovial fibroblasts stimulated with 10 ng/mL of IL-1beta. Stimulated levels of IL-6 were assessed by RT-qPCR or immunoassays in the presence or absence of 1 microM all-trans retinoic acid (ATRA) (RAR agonist) or 0.3 microM BMS-649 (RXR agonist). The contribution of RAR subtypes was checked with selective agonists or small interfering RNAs. The effect of ATRA on upstream MAPK (p38 MAPK, c-Jun N-terminal kinase [JNK], and extracellularly regulated kinase 1/2 [ERK1/2]) was assessed by Western blot, and the contribution of the ERK1/2 pathway to the activation of pro-inflammatory transcription factors was studied by TransAm assays.

RESULTS

Synovial fibroblasts expressed all RAR and RXR subtypes except RXR-gamma. In IL-1-stimulated cells, ATRA, but not BMS-649, reduced IL-6 expression whereas selective RAR agonists were inactive. The inhibitory effect of ATRA on IL-6 was not affected by the silencing of RAR subtypes. ATRA also reduced the phosphorylation of ERK1/2, but not of p38 MAPK or of JNK. The suppressive effect of ATRA on the activation of activator protein-1 (AP-1) and nuclear factor-IL-6 (NF-IL-6) was reproduced by the MEK1 (mitogen-activated protein extracellularly regulated kinase kinase 1) inhibitor PD-98059, whereas ATRA and PD-98059 had no effect on NF-kappaB activation.

CONCLUSIONS

Among RAR and RXR agonists, only ATRA inhibited IL-1-induced IL-6 expression in rat synovial fibroblasts by inhibiting ERK1/2 pathway and subsequent activation of AP-1 and NF-IL-6 independently of RAR.

The effects of ketorolac tromethamine and baicalein on the levels of inflammatory factors in human synoviocytes

This study examined the effects of ketorolac tromethamine (KT) and baicalein (BE) on the levels of inflammatory factors in human synoviocytes. The fibroblast-like synoviocytes (FLS) cells were used to determine the possible regulatory effects of KT and BE (KTBE) on the levels of inflammatory factors in FLS cells. In addition, the levels of TNF-alpha, IL-6, and IL-1beta mRNA expression in FLS cells induced by a TNF-alpha and IL-1beta co-treatment were largely inhibited by a KTBE treatment. The level of FLS cells proliferation was increased by IL-1beta and TNF-alpha, and strongly inhibited by KTBE treatment. The production of oxygen species (ROS) was inhibited by KTBE in FLS cells. KTBE appears to regulate the levels of mRNA that are important for regulating RA progression.

Leptin enhances human beta-defensin-2 production in human keratinocytes

Leptin, an adipocyte-derived cytokine/hormone, modulates innate and adaptive immunity. Human beta-defensin-2 (hBD-2) produced by epidermal keratinocytes promotes cutaneous antimicrobial defense, inflammation, and wound repair. We examined the in vitro effects of leptin on hBD-2 production in human keratinocytes. hBD-2 secretion and mRNA expression were analyzed by ELISA and RT-PCR, respectively. Although leptin alone was ineffective, it enhanced IL-1beta-induced hBD-2 secretion and mRNA expression in keratinocytes. IL-1beta- and IL-1beta plus leptin-induced hBD-2 production both were suppressed by antisense oligonucleotides against nuclear factor-kappaB (NF-kappaB) p50 and p65; the latter was also suppressed by antisense signal transducer and activator of transcription (STAT)1 and STAT3. IL-1beta enhanced the transcriptional activity of NF-kappaB, whereas leptin enhanced STAT1 and STAT3 activity. The p38 MAPK inhibitor SB202190 suppressed IL-1beta- and IL-1beta plus leptin-induced hBD-2 production, IL-1beta-induced NF-kappaB activity, and leptin-induced STAT1 and STAT3 activity; contrastingly, the Janus kinase (JAK) 2 inhibitor AG490 suppressed IL-1beta plus leptin-induced hBD-2 production and leptin-induced STAT1 and STAT3 activity. IL-1beta induced serine phosphorylation of inhibitory kappaBalpha, STAT1, and STAT3. Leptin induced tyrosine and serine phosphorylation of STAT1 and STAT3, both of which were suppressed by AG490, and serine phosphorylation was also suppressed by SB202190. IL-1beta or leptin individually induced threonine/tyrosine phosphorylation of p38 MAPK, whereas only leptin induced tyrosine phosphorylation of JAK2, suggesting that leptin may enhance hBD-2 production in keratinocytes by activating STAT1 and STAT3 via JAK2 and p38 MAPK in cooperation with NF-kappaB, which is activated by IL-1beta. Leptin may promote cutaneous antimicrobial defense, inflammation, and wound repair via hBD-2.

IL-18 contributes to renal damage after ischemia-reperfusion

IL-18 is a proinflammatory cytokine produced by macrophages and other cell types present in the kidney during ischemia-reperfusion injury (IRI), but its role in this injury is unknown. Here, compared with wild-type mice, IL-18(-/-) mice subjected to kidney IRI demonstrated better kidney function, less tubular damage, reduced accumulation of neutrophils and macrophages, and decreased expression of proinflammatory molecules that are downstream of IL-18. For determination of the relative contributions of leukocytes and parenchymal cells to IL-18 production and subsequent kidney damage during IRI, bone marrow-chimeric mice were generated. Wild-type mice engrafted with IL-18(-/-) hemopoietic cells showed less kidney dysfunction and tubular damage than IL-18(-/-) mice engrafted with wild-type bone marrow. In vitro, macrophages produced IL-18 mRNA and protein in response to ischemia. These data suggest bone marrow-derived cells are the key contributors to IL-18-mediated effects of renal IRI. Finally, similar to IL-18(-/-) mice, pretreatment of wild-type mice with IL-18-binding protein was renoprotective in this model of IRI. In conclusion, IL-18, derived primarily from cells of bone marrow origin, contributes to the renal damage observed during IRI. IL-18-binding protein may have potential as a renoprotective therapy.

Interleukin 18 in the heart

IL-18, originally termed as interferon gamma (IFN-gamma) inducing factor, is a proinflammatory cytokine that belongs to the IL-1 cytokine superfamily. IL-18 plays an important role in immune, infectious, and inflammatory diseases due to its induction of IFN-gamma. However, accumulated evidence has demonstrated that other effects of IL-18 are independent of IFN-gamma. Here, we reviewed the current literatures regarding the role of IL-18 in the heart and cardiovascular system. Infiltrated neutrophils, resident macrophages, endothelial cells, smooth muscle cells, and cardiomyocytes in the heart are able to produce IL-18 in response to injury. IL-18 is produced as a biologically inactive precursor (pro-IL-18) that is activated by caspase 1 (the IL-1beta converting enzyme). Elevated IL-18 levels have been observed in cardiac tissue and circulation after myocardial I/R and sepsis. The possible cellular and molecular mechanisms concerning IL-18-induced myocardial injury include induction of inflammation, increased apoptosis, a cardiac hypertrophy effect, modulation of mitogen activated protein kinase activation, and changes in intracellular calcium. Finally, we briefly reviewed the therapeutic strategies for inhibiting IL-18's biological activity to protect cardiac tissue from injury.

Role of adhesion molecules in synovial inflammation

PURPOSE OF REVIEW

The ability of cells to adhere to other cells and extracellular matrix (ECM) through cellular adhesion molecules (CAMs) is central to tissue remodeling and inflammation. This review discusses the potential role of CAMs in development of synovial inflammation through regulating the recruitment of inflammatory cells via endothelial-leukocyte interactions, the organization and activation of leukocytes in the synovial sublining, and the formation and behavior of the hyperplastic synovial lining.

RECENT FINDINGS

Over the past several years valuable insight has been gained into the role of cell-cell and cell-ECM adhesive interactions in synovial organization and inflammation. Recently, cadherin-11 was identified on fibroblast-like synoviocytes and has been demonstrated to play a central role in synovial lining organization. Furthermore, studies using animal models of inflammatory arthritis have demonstrated critical roles for E- and P-selectins, CD11a/CD18 [lymphocyte function-associated antigen (LFA)-1], alpha4beta1 integrin, and cadherin-11 in the development of synovial inflammation.

SUMMARY

Cell-cell and cell-ECM interactions through CAMs play an important role in synovial inflammation. Future studies of CAMs are needed to define more thoroughly their role in synovial inflammation and their potential as therapeutic targets in the treatment of rheumatoid arthritis and related inflammatory arthritic conditions.

Interleukin 18 stimulates release of soluble lectin-like oxidized LDL receptor-1 (sLOX-1)

Lectin-like oxidized LDL receptor-1 (LOX-1) appears to play crucial roles in atherosclerotic plaque rupture. We previously reported that circulating soluble LOX-1 (sLOX-1) levels are elevated in acute coronary syndrome (ACS) and that sLOX-1 can be a specific and sensitive biomarker for ACS. A proinflammatory cytokine interleukin 18 (IL-18) and its receptor are prominently expressed in atherosclerotic plaques. In addition, circulating IL-18 levels were reported to be high in ACS. In this study, we have examined if IL-18 can stimulate shedding of LOX-1 and subsequent release of sLOX-1. After transfection with LOX-1 cDNA, HEK-293T cells were incubated with or without IL-18. Cell-conditioned media and total cell lysates were subjected to immunoblot analyses with an anti-LOX-1 monoclonal antibody. In addition, ADAM10 cDNA, ADAM10 siRNA or control vector were also co-transfected into HEK-293T cells, and the cell-conditioned media and total cell lysates were subjected to LOX-1 immunoblotting after treatment with or without IL-18. The cell-conditioned medium/total cell lysate ratios in the amounts of LOX-1 or sLOX-1 were determined as sLOX-1 cleavage ratios. IL-18 (10-100ng/mL) stimulation increased the sLOX-1 cleavage by 3-4-fold in a concentration- and time-dependent manner. ADAM10 overexpression alone similarly enhanced the sLOX-1 cleavage. ADAM10 inhibition by ADAM10 siRNA transfection significantly suppressed IL-18-induced sLOX-1 cleavage. IL-18 similarly enhanced sLOX-1 cleavage in TNF-alpha-activated cultured endothelial cells, as well as LOX-1 transgenic mice in vivo. IL-18 appears one of the stimuli that enhance sLOX-1 release in ACS and ADAM10 may be involved in this process.

Synergism between AT1 receptor and hyperhomocysteinemia during vascular remodeling

BACKGROUND

Hyperhomocysteinemia (HHcy) is an independent risk factor of cardiovascular diseases. Extracellular signal-regulated kinase-1/2 (ERK-1/2) and the JAK/STAT pathway kinase, signal transducer and activator of transcription 3 (STAT3), are involved in matrix metalloproteinase-9 (MMP-9) induction and matrix remodeling. However, their role in homocysteine (Hcy)-mediated MMP-9 induction and matrix remodeling is unclear. Clinical and experimental evidence indicates that HHcy and activation of the renin-angiotensin system, mediated by angiotensin II type 1 (AT1) receptor, are involved in a variety of vascular pathologies. Despite this fact, the relationship between HHcy and activation of the renin-angiotensin system has not been comprehensively characterized. Therefore, we hypothesized that Hcy activates AT1 receptor that potentiates STAT3 via ERK-1/2 phosphorylation. STAT3 modulates target MMP-9 and collagen, resulting in vascular remodeling.

METHODS

Mouse aortic endothelial cells (MAEC) were treated with various doses of Hcy for different time periods. The levels of AT1 receptor, ERK-1/2, STAT3, MMP-9 and collagen type-1 were measured by immunoblot analyses. The activation of ERK-1/2 and STAT3 were determined by measuring ERK-1/2 phosphorylation and phosphoserine (727) STAT3.

RESULTS

Although Hcy dose-dependently induced AT1 receptor expression in the endothelial cells, a significant induction was observed at 100 microM at 48 h. We investigated Hcy-induced ERK-1/2 and STAT3 phosphorylation through AT1 receptor induction, and our results suggest that Hcy activated AT1 receptor which led to ERK-1/2 and STAT3 phosphorylation. In addition, findings of this study suggest that Hcy-mediated STAT3 activation regulated MMP-9 and collagen type-1. However, AT1 receptor blocker, valsartan, and the specific STAT3 inhibitor peptide attenuated MMP-9 and collagen type-1 induction.

CONCLUSIONS

These findings demonstrate for the first time the contribution of AT1 receptor in HHcy-induced atherosclerotic diseases; Hcy-induced activation of AT1 receptor involves MMP-9 and collagen type-1 modulation using ERK-1/2 and STAT3 signaling cascades.

Apoptosis is not the major death mechanism induced by celecoxib on rheumatoid arthritis synovial fibroblasts

Synovial hyperplasia in rheumatoid arthritis (RA) has been associated with apoptosis deficiency of RA fibroblast-like synoviocytes (FLSs). Celecoxib is a non-steroidal anti-inflammatory drug that has been demonstrated to induce apoptosis in some cellular systems. We have therefore examined the dose- and time-dependent effects of celecoxib on RA FLS viability. Treatment of RA FLSs with celecoxib for 24 hours reduced their viability in a dose-dependent manner. Analysis of celecoxib-treated RA FLSs for their content of apoptotic and necrotic cells by Annexin V staining and TO-PRO-3 uptake displayed only few apoptotic cells. Caspase 3, a key mediator of apoptosis, was not activated in celecoxib-treated RA FLSs, and the presence of specific caspase 3 or pan-caspase inhibitors did not affect celecoxib-induced cell death. Moreover, we could not detect other signs of apoptosis, such as cleavage of poly(ADP-ribose) polymerase, caspase 8 or 9, or DNA fragmentation. We therefore conclude that apoptosis is not the major death pathway in celecoxib-treated RA FLSs.

Interleukin-18 suppresses adiponectin expression in 3T3-L1 adipocytes via a novel signal transduction pathway involving ERK1/2-dependent NFATc4 phosphorylation

An inverse correlation between the pro-inflammatory cytokine interleukin-18 and the anti-atherogenic adipokine adiponectin has been reported in the chronic pathological conditions obesity, insulin resistance, coronary artery disease, and metabolic syndrome. We investigated whether this relationship is coincidental or has a causal basis. Here we show that interleukin-18 (IL-18) suppresses adiponectin transcription, mRNA expression, and secretion by 3T3-L1 adipocytes. IL-18 suppresses adiponectin promoter-reporter activity, an effect reversed by deletion or mutation of the NFATc4 core DNA-binding site. IL-18 induces NFATc4 phosphorylation (Ser(676)), nuclear translocation, and in vivo DNA binding. IL-18 induces ERK1/2 phosphorylation and enzyme activity, and pretreatment with the MEK inhibitor U0126, ERK1/2 inhibitor PD98059, or small interference RNA targeted to ERK1/2 attenuates ERK1/2 activation and NFATc4 phosphorylation. Finally, inhibition of ERK1/2 or NFATc4 knockdown reverses IL-18-mediated adiponectin suppression. In contrast to its inhibitory effects on adiponectin expression, IL-18 potently stimulates PAI-1 secretion. These data demonstrate for the first time that IL-18 selectively suppresses adiponectin expression via ERK1/2-dependent NFATc4 activation and suggest that the inverse relationship observed between IL-18 and adiponectin in various chronic pathological conditions is causally related. Thus, targeting IL-18 expression may enhance adiponectin expression and mitigate disease progression.

[Therapeutic potential of phosphoinositide 3-kinase inhibitors in rheumatoid arthritis]

Activation of PI3K is a key step of intracellular signaling involved in many cellular functions. PI3K inhibitors have shown anti-rheumatic effects on arthritis model in mice. PI3K is a potential therapeutic target of rheumatoid arthritis.

In vivo inhibition of angiogenesis by interleukin-13 gene therapy in a rat model of rheumatoid arthritis

OBJECTIVE

Interleukin-13 (IL-13) is a pleiotropic cytokine that can affect vessel formation, an important component of the rheumatoid arthritis (RA) synovial tissue pannus. The purpose of this study was to use a gene therapy approach to investigate the role of IL-13 in angiogenesis in vivo, using a rat adjuvant-induced arthritis model of RA.

METHODS

Ankle joints of female rats were injected preventatively with an adenovirus vector containing human IL-13 (AxCAIL-13), a control vector with no insert (AxCANI), or phosphate buffered saline (PBS). Joints were harvested at the peak of arthritis, and histologic and biochemical features were evaluated.

RESULTS

AxCAIL-13-treated joint homogenates had lower hemoglobin levels, suggesting reduced joint vascularity, and both endothelial cell migration and tube formation were significantly inhibited (P < 0.05). Similarly, AxCAIL-13 inhibited capillary sprouting in the rat aortic ring assay and vessel growth in the Matrigel plug in vivo assay. IL-13 gene delivery resulted in up-regulation and association of phosphorylated ERK-1/2 and protein kinase Calpha/betaII, suggesting a novel pathway in IL-13-mediated angiostasis. The angiostatic effect of AxCAIL-13 was associated with down-regulation of proangiogenic cytokines (IL-18, cytokine-induced neutrophil chemoattractant 1/CXCL1, lipopolysaccharide-induced CXC chemokine/CXCL5) and up-regulation of the angiogenesis inhibitor endostatin. The expression and activity of matrix metalloproteinases 2 and 9, which participate in angiogenesis, was impaired in response to IL-13 as compared with AxCANI and PBS treatment.

CONCLUSION

Our findings support a role for IL-13 as an in vivo antiangiogenic factor and provide a rationale for its use in RA to control pathologic neovascularization.

Interleukin-18 induces angiogenic factors in rheumatoid arthritis synovial tissue fibroblasts via distinct signaling pathways

OBJECTIVE

Interleukin-18 (IL-18) is a proinflammatory cytokine implicated in the pathogenesis of rheumatoid arthritis (RA). This study was undertaken to examine the role of IL-18 in up-regulating secretion of the angiogenic factors stromal cell-derived factor 1alpha (SDF-1alpha)/CXCL12, monocyte chemoattractant protein 1 (MCP-1)/CCL2, and vascular endothelial growth factor (VEGF) in RA synovial tissue (ST) fibroblasts, and the underlying signaling mechanisms involved.

METHODS

We used enzyme-linked immunosorbent assays, Western blotting, and chemical inhibitors/antisense oligodeoxynucleotides to signaling intermediates to assess the role of IL-18.

RESULTS

IL-18 significantly enhanced the production of SDF-1alpha/CXCL12, MCP-1/CCL2, and VEGF in RA ST fibroblasts, in a time- and concentration-dependent manner. IL-18-induced SDF-1alpha/CXCL12 up-regulation was dependent on JNK, p38 MAPK, phosphatidylinositol 3-kinase (PI3K), and NFkappaB. While IL-18-induced production of SDF-1alpha/CXCL12 was also dependent on protein kinase Cdelta (PKCdelta), production of MCP-1/CCL2 was dependent on PKCalpha, not PKCdelta. Additionally, RA ST fibroblast IL-18-induced MCP-1/CCL2 production was mediated by JNK, PI3K, and NFkappaB. In contrast, IL-18 did not induce secretion of RA ST fibroblast MCP-1/CCL2 or VEGF via p38 MAPK. IL-18-induced RA ST fibroblast production of VEGF was mediated mainly by JNK-2, PKCalpha, and NFkappaB. IL-18 induced phosphorylation of JNK, PKCdelta, p38 MAPK, and activating transcription factor 2 (ATF-2) in RA ST fibroblasts in a time-dependent manner, with JNK-2 being upstream of PKCdelta, ATF-2, and NFkappaB.

CONCLUSION

These data support the notion that IL-18 has a unique role in inducing the secretion of angiogenic SDF-1alpha/CXCL12, MCP-1/CCL2, and VEGF in RA ST fibroblasts, via distinct signaling intermediates.

Cellular targets of interleukin-18 in rheumatoid arthritis

Recent data are presented which indicate a critical role for interleukin (IL)-18 in rheumatoid arthritis (RA). The T cells and macrophages invading the synovium or in the synovial fluid are the chief cellular targets of IL-18 in RA. Neutrophils, dendritic cells and endothelial cells may also be cellular mediators of IL-18. The direct effect of IL-18 on fibroblast-like synoviocytes or chondrocytes may not be essential or important. In RA, IL-18, which is mainly produced by macrophages, activates T cells and macrophages to produce proinflammatory cytokines, chemokines, adhesion molecules and RANKL which, in turn, perpetuate chronic inflammation and induce bone and cartilage destruction.