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

microRNAs: critical targets for treating rheumatoid arthritis angiogenesis

Vascular neogenesis, an early event in the development of rheumatoid arthritis (RA) inflammation, is critical for the formation of synovial vascular networks and plays a key role in the progression and persistence of chronic RA inflammation. microRNAs (miRNAs), a class of single-stranded, non-coding RNAs with approximately 21-23 nucleotides in length, regulate gene expression by binding to the 3' untranslated region (3'-UTR) of specific mRNAs. Increasing evidence suggests that miRNAs are differently expressed in diseases associated with vascular neogenesis and play a crucial role in disease-related vascular neogenesis. However, current studies are not sufficient and further experimental studies are needed to validate and establish the relationship between miRNAs and diseases associated with vascular neogenesis, and to determine the specific role of miRNAs in vascular development pathways. To better treat vascular neogenesis in diseases such as RA, we need additional studies on the role of miRNAs and their target genes in vascular development, and to provide more strategic references. In addition, future studies can use modern biotechnological methods such as proteomics and transcriptomics to investigate the expression and regulatory mechanisms of miRNAs, providing a more comprehensive and in-depth research basis for the treatment of related diseases such as RA.

Unveiling Novel Drug Targets and Emerging Therapies for Rheumatoid Arthritis: A Comprehensive Review

Rheumatoid arthritis (RA) is a chronic debilitating autoimmune disease, that causes joint damage, deformities, and decreased functionality. In addition, RA can also impact organs like the skin, lungs, eyes, and blood vessels. This autoimmune condition arises when the immune system erroneously targets the joint synovial membrane, resulting in synovitis, pannus formation, and cartilage damage. RA treatment is often holistic, integrating medication, physical therapy, and lifestyle modifications. Its main objective is to achieve remission or low disease activity by utilizing a "treat-to-target" approach that optimizes drug usage and dose adjustments based on clinical response and disease activity markers. The primary RA treatment uses disease-modifying antirheumatic drugs (DMARDs) that help to interrupt the inflammatory process. When there is an inadequate response, a combination of biologicals and DMARDs is recommended. Biological therapies target inflammatory pathways and have shown promising results in managing RA symptoms. Close monitoring for adverse effects and disease progression is critical to ensure optimal treatment outcomes. A deeper understanding of the pathways and mechanisms will allow new treatment strategies that minimize adverse effects and maintain quality of life. This review discusses the potential targets that can be used for designing and implementing precision medicine in RA treatment, spotlighting the latest breakthroughs in biologics, JAK inhibitors, IL-6 receptor antagonists, TNF blockers, and disease-modifying noncoding RNAs.

Can pyroptosis be a new target in rheumatoid arthritis treatment?

Rheumatoid arthritis (RA) is a chronic systemic autoimmune disease of undefined etiology, with persistent synovial inflammation and destruction of articular cartilage and bone. Current clinical drugs for RA mainly include non-steroidal anti-inflammatory drugs (NSAIDs), glucocorticoids, disease modifying anti-rheumatic drugs (DMARDs) and so on, which can relieve patients' joint symptoms. If we want to have a complete cure for RA, there are still some limitations of these drugs. Therefore, we need to explore new mechanisms of RA to prevent and treat RA radically. Pyroptosis is a newly discovered programmed cell death (PCD) in recent years, which is characterized by the appearance of holes in cell membranes, cell swelling and rupture, and the release of intracellular pro-inflammatory factors into the extracellular space, resulting in a strong inflammatory response. The nature of pyroptosis is pro-inflammatory, and whether it is participating in the development of RA has attracted a wide interest among scholars. This review describes the discovery and mechanism of pyroptosis, the main therapeutic strategies for RA, and the role of pyroptosis in the mechanism of RA development. From the perspective of pyroptosis, the study of new mechanisms of RA may provide a potential target for the treatment of RA and the development of new drugs in the clinics.

Autocitrullination confers monocyte chemotactic properties to peptidylarginine deiminase 4

Peptidylarginine deiminase 4 (PAD4) contributes to the production of citrullinated proteins as autoantigens for anti-citrullinated protein antibodies (ACPAs) in rheumatoid arthritis (RA). PAD4 can also self-deiminate via autocitrullination. However, the role of this process in RA pathogenesis has not been elucidated. This study aimed to clarify PAD4 function before and after autocitrullination and identify citrullinated PAD4 in the synovial fluid of patients with RA. The autocitrullination of recombinant human PAD4 (rhPAD4) was catalyzed in vitro and determined using anti-modified citrulline immunoblotting. Monocyte chemotaxis was evaluated using Boyden chambers, and citrullinated rhPAD4's ability to induce arthritis was assessed in a C57BL/6J mouse model. Citrullinated PAD4 levels were measured in the synovial fluid of patients with RA and osteoarthritis using a novel enzyme-linked immunosorbent assay. Chemotactic findings showed that citrullinated rhPAD4 recruited monocytes in vitro, whereas unmodified rhPAD4 did not. Compared to unmodified rhPAD4, citrullinated rhPAD4 induced greater inflammation in mouse joints through monocyte migration. More citrullinated PAD4 was found in the synovial fluid of patients with RA than in those with osteoarthritis. Citrullinated PAD4 was even detected in ACPA-negative patients with RA. The autocitrullination of PAD4 amplified inflammatory arthritis through monocyte recruitment, suggesting an ACPA-independent role of PAD4 in RA pathogenesis.

Atherogenic oxoaldehyde of cholesterol induces innate immune response in monocytes and macrophages

Cholesterol oxidation product, 3β-hydroxy-5-oxo-5,6-secocholestan-6-al (cholesterol 5,6-secosterol, ChSeco or Atheronal-A), formed at inflammatory sites, has been shown to promote monocyte differentiation into macrophages and cause elevated expression of macrophage scavenger receptors. Since inflammation is a key event at all stages of atherosclerotic plaque formation, the pro-inflammatory actions of ChSeco in human THP-1 monocytes and mouse J774 macrophages were investigated in the present study by employing ELISA, qRT-PCR, and functional assays. An increase in the secretion of interleukin-8 and platelet-derived growth factor (PDGF) isoform AA and, to a limited extent, PDGF isoform BB was observed into the culture medium of THP-1 monocytes exposed to ChSeco. However, no changes were seen in the secretion of tumor necrosis factor-alpha. In J774 macrophages treated with ChSeco, there was an upregulation of gene expression of several pro-inflammatory cytokines and their receptors. Concomitantly, there was down-regulation of gene expression of interleukin-1ß, interleukin-10, and lymphotoxin-beta. An increase in the release of interleukin-18 and chemokine (C-C motif) ligand-20 from J774 macrophages (which corroborated well with their gene expression profiles) and increased binding of THP-1 monocytes to ChSeco-exposed human aortic endothelial cells were observed. The results of the present study, for the first time, demonstrate the pro-inflammatory action of ChSeco and suggest the underlying pro-atherogenic mechanisms. These could be mediated through enhanced monocyte recruitment into the sub-endothelial space and subsequent proliferation of smooth muscle cells under the influence of monocyte-derived PDGF.

Promising Therapeutic Targets for Treatment of Rheumatoid Arthritis

Rheumatoid arthritis (RA) is a systemic poly-articular chronic autoimmune joint disease that mainly damages the hands and feet, which affects 0.5% to 1.0% of the population worldwide. With the sustained development of disease-modifying antirheumatic drugs (DMARDs), significant success has been achieved for preventing and relieving disease activity in RA patients. Unfortunately, some patients still show limited response to DMARDs, which puts forward new requirements for special targets and novel therapies. Understanding the pathogenetic roles of the various molecules in RA could facilitate discovery of potential therapeutic targets and approaches. In this review, both existing and emerging targets, including the proteins, small molecular metabolites, and epigenetic regulators related to RA, are discussed, with a focus on the mechanisms that result in inflammation and the development of new drugs for blocking the various modulators in RA.

Traditional Chinese medicine formula Bi-Qi capsule alleviates rheumatoid arthritis-induced inflammation, synovial hyperplasia, and cartilage destruction in rats

BACKGROUND

Traditional Chinese medicine (TCM) formula Bi-Qi capsule (Bi-Qi) is a commonly prescribed drug to treat rheumatoid arthritis (RA). However, the mechanism of Bi-Qi-mediated amelioration of RA pathogenesis is still a mystery. Collagen induced arthritis (CIA) in rats is an established model that shares many similarities with RA in humans. In this study we investigated the effect of Bi-Qi on the pathogenesis of CIA in rats.

METHODS

CIA was developed in Sprague-Dawley (S.D) rats (n = 60, female) and used as a model resembling RA in humans. Rats were treated with a high or moderate dose of Bi-Qi, or methotrexate (MTX). Effects of the treatment on local joint and systemic inflammation, synovial hyperplasia, cartilage destruction, and other main features in the pathogenesis of CIA were analyzed.

RESULTS

Inflamed and swollen ankles and joints were observed in arthritic rats, while Bi-Qi or MTX treatment alleviated these symptoms. Only the Bi-Qi moderate dose decreased RA-induced serum levels of tumor necrosis factor-alpha (TNF-α). Both Bi-Qi and MTX reduced the interleukin (IL)-18 serum level. Protein levels of cartilage oligomeric matrix protein and osteopontin in serum, synovium, and cartilage were elevated in arthritic rats, while Bi-Qi alleviated these effects. Synovial hyperplasia, inflammatory cell infiltration in synovium and a high degree of cartilage degradation was observed in RA, and Bi-Qi or MTX alleviated this effect. Bi-Qi at the moderate dose was the most effective in mitigating CIA-related clinical complications.

CONCLUSIONS

Our findings showed that Bi-Qi alleviates CIA-induced inflammation, synovial hyperplasia, cartilage destruction, and the other main features in the pathogenesis of CIA. This provides fundamental evidence for the anti-arthritic properties of Bi-Qi and corroborates the use of Bi-Qi TCM formula for the treatment of RA.

Therapeutic effect of erythroid differentiation regulator 1 (Erdr1) on collagen-induced arthritis in DBA/1J mouse

Rheumatoid arthritis (RA) is a chronic inflammatory autoimmune disease, and multiple inflammatory cytokines are involved in RA pathogenesis. Interleukin (IL)-18, in particular, has a significant positive correlation with RA. In this study, we investigated the effect of erythroid differentiation regulator 1 (Erdr1), which is negatively regulated by IL-18, in an animal model of inflammatory arthritis, collagen-induced arthritis (CIA) in DBA/1J mice. Treatment of mice with recombinant (r)Erdr1 significantly suppressed the severity of arthritis, histologic features of arthritic tissue, and serum levels of anti-collagen autoantibodies (IgG, IgG1, IgG2a and IgM) in CIA. In addition, IL-18 expression was reduced in the affected synovium of rErdr1-treated mice. Interestingly, Erdr1 treatment suppressed migration in contrast to the pro-migratory effect of IL-18, indicating the therapeutic effects of Erdr1 on CIA through inhibiting synovial fibroblast migration. In addition, Erdr1 inhibited activation of ERK1/2, a key signaling pathway in migration of various cell types. Taken together, these data show that rErdr1 exerts therapeutic effects on RA by inhibiting synovial fibroblast migration, suggesting that rErdr1 treatment might be an effective therapeutic approach for RA.

A unique role for galectin-9 in angiogenesis and inflammatory arthritis

Background

Galectin-9 (Gal-9) is a mammalian lectin secreted by endothelial cells that is highly expressed in rheumatoid arthritis synovial tissues and synovial fluid. Roles have been proposed for galectins in the regulation of inflammation and angiogenesis. Therefore, we examined the contribution of Gal-9 to angiogenesis and inflammation in arthritis.

Methods

To determine the role of Gal-9 in angiogenesis, we performed human dermal microvascular endothelial cell (HMVEC) chemotaxis, Matrigel tube formation, and mouse Matrigel plug angiogenesis assays. We also examined the role of signaling molecules in Gal-9-induced angiogenesis by using signaling inhibitors and small interfering RNA (siRNA). We performed monocyte (MN) migration assays in a modified Boyden chamber and assessed the arthritogenicity of Gal-9 by injecting Gal-9 into mouse knees.

Results

Gal-9 significantly increased HMVEC migration, which was decreased by inhibitors of extracellular signal-regulating kinases 1/2 (Erk1/2), p38, Janus kinase (Jnk), and phosphatidylinositol 3-kinase. Gal-9 HMVEC-induced tube formation was reduced by Erk1/2, p38, and Jnk inhibitors, and this was confirmed by siRNA knockdown. In mouse Matrigel plug assays, plugs containing Gal-9 induced significantly higher angiogenesis, which was attenuated by a Jnk inhibitor. Gal-9 also induced MN migration, and there was a marked increase in MN ingress when C57BL/6 mouse knees were injected with Gal-9 compared with the control, pointing to a proinflammatory role for Gal-9.

Conclusions

Gal-9 mediates angiogenesis, increases MN migration in vitro, and induces acute inflammatory arthritis in mice, suggesting a novel role for Gal-9 in angiogenesis, joint inflammation, and possibly other inflammatory diseases.

Insulin regulates multiple signaling pathways leading to monocyte/macrophage chemotaxis into the wound tissue

Wound healing is a complex process that involves sequential phases that overlap in time and space and affect each other dynamically at the gene and protein levels. We previously showed that insulin accelerates wound healing by stimulating faster and regenerative healing. One of the processes that insulin stimulates is an increase in monocyte/macrophage chemotaxis. In this study, we performed experiments in vivo and in vitro to elucidate the signaling transduction pathways that are involved in insulin-induced monocyte/macrophage chemotaxis. We found that insulin stimulates THP-1 cell chemotaxis in a dose-dependent and insulin receptor-dependent manner. We also show that the kinases PI3K-Akt, SPAK/JNK, and p38 MAPK are key molecules in the insulin-induced signaling pathways that lead to chemoattraction of the THP-1 cell. Furthermore, both PI3K-Akt and SPAK/JNK signaling involve Rac1 activation, an important molecule in regulating cell motility. Indeed, topical application of Rac1 inhibitor at an early stage during the healing process caused delayed and impaired healing even in the presence of insulin. These results delineate cell and molecular mechanisms involved in insulin-induced chemotaxis of monocyte/macrophage, cells that are critical for proper healing.

Summary: Insulin regulates multiple signaling pathways leading to monocyte/macrophage chemotaxis into the wound tissue, involving -Akt, SPAK/JNK, and p38 MAPK which in turn are involved in Rac1 activation. Furthermore, these results augment our understanding of the insulin-regulated wound inflammatory response.

YKL-40-Induced Inhibition of miR-590-3p Promotes Interleukin-18 Expression and Angiogenesis of Endothelial Progenitor Cells

YKL-40, also known as human cartilage glycoprotein-39 or chitinase-3-like-1, is a pro-inflammatory protein that is highly expressed in rheumatoid arthritis (RA) patients. Angiogenesis is a critical step in the pathogenesis of RA, promoting the infiltration of inflammatory cells into joints and providing oxygen and nutrients to RA pannus. In this study, we examined the effects of YKL-40 in the production of the pro-inflammatory cytokine interleukin-18 (IL-18), and the stimulation of angiogenesis and accumulation of osteoblasts. We observed that YKL-40 induces IL-18 production in osteoblasts and thereby stimulates angiogenesis of endothelial progenitor cells (EPCs). We found that this process occurs through the suppression of miR-590-3p via the focal adhesion kinase (FAK)/PI3K/Akt signaling pathway. YKL-40 inhibition reduced angiogenesis in in vivo models of angiogenesis: the chick embryo chorioallantoic membrane (CAM) and Matrigel plug models. We report that YKL-40 stimulates IL-18 expression in osteoblasts and facilitates EPC angiogenesis.

Tripterygium wilfordii Inhibiting Angiogenesis for Rheumatoid Arthritis Treatment

Rheumatoid arthritis (RA) is a chronic inflammatory disease with a serious pre-vascular inflammatory phase, followed by significant increase in vessel growth. Inhibition of angiogenesis is a novel therapeutic strategy against RA. The Chinese herbal remedy Tripterygium wilfordii, Hook. f. (TwHf) has been reported to be therapeutically efficacious in the treatment of RA. Recent studies have revealed that treatment with TwHf extracts inhibit angiogenesis of RA, thereby elaborately attenuation RA symptom. This review mainly addresses the anti-angiogenesis effect of TwHf in treatment of RA.

DEK-targeting DNA aptamers as therapeutics for inflammatory arthritis

Novel therapeutics are required for improving the management of chronic inflammatory diseases. Aptamers are single-stranded RNA or DNA molecules that have recently shown utility in a clinical setting, as they can specifically neutralize biomedically relevant proteins, particularly cell surface and extracellular proteins. The nuclear chromatin protein DEK is a secreted chemoattractant that is abundant in the synovia of patients with juvenile idiopathic arthritis (JIA). Here, we show that DEK is crucial to the development of arthritis in mouse models, thus making it an appropriate target for aptamer-based therapy. Genetic depletion of DEK or treatment with DEK-targeted aptamers significantly reduces joint inflammation in vivo and greatly impairs the ability of neutrophils to form neutrophil extracellular traps (NETs). DEK is detected in spontaneously forming NETs from JIA patient synovial neutrophils, and DEK-targeted aptamers reduce NET formation. DEK is thus key to joint inflammation, and anti-DEK aptamers hold promise for the treatment of JIA and other types of arthritis.

Targeting the inflammasome in rheumatic diseases

Activation of the inflammasome, a protein complex responsible for many cellular functions, including the activation of the proinflammatory cytokines interleukin (IL)-1β and IL-18, has been identified as a key participant in many rheumatic diseases including autoimmune, inflammatory, and autoinflammatory syndromes. This review will discuss the recent advances in understanding the role of this complex in various rheumatic diseases. Furthermore, it will focus on available therapies, which directly and indirectly target the inflammasome and its downstream cytokines to quiet inflammation and possibly dampen autoimmune processes.

The Interplay Between Monocytes/Macrophages and CD4(+) T Cell Subsets in Rheumatoid Arthritis

Rheumatoid arthritis (RA) is a chronic inflammatory disease characterized by inflammation of the synovial lining (synovitis). The inflammation in the RA joint is associated with and driven by immune cell infiltration, synovial hyperproliferation, and excessive production of proinflammatory mediators, such as tumor necrosis factor α (TNFα), interferon γ (IFNγ), interleukin (IL)-1β, IL-6, and IL-17, eventually resulting in damage to the cartilage and underlying bone. The RA joint harbors a wide range of immune cell types, including monocytes, macrophages, and CD4(+) T cells (both proinflammatory and regulatory). The interplay between CD14(+) myeloid cells and CD4(+) T cells can significantly influence CD4(+) T cell function, and conversely, effector vs. regulatory CD4(+) T cell subsets can exert profound effects on monocyte/macrophage function. In this review, we will discuss how the interplay between CD4(+) T cells and monocytes/macrophages may contribute to the immunopathology of RA.

The pathogenic role of angiogenesis in rheumatoid arthritis

Angiogenesis is the formation of new capillaries from pre-existing vasculature, which plays a critical role in the pathogenesis of several inflammatory autoimmune diseases such as rheumatoid arthritis (RA), spondyloarthropathies, psoriasis, systemic lupus erythematosus, systemic sclerosis, and atherosclerosis. In RA, excessive migration of circulating leukocytes into the inflamed joint necessitates formation of new blood vessels to provide nutrients and oxygen to the hypertrophic joint. The dominance of the pro-angiogenic factors over the endogenous angiostatic mediators triggers angiogenesis. In this review article, we highlight the underlying mechanisms by which cells present in the RA synovial tissue are modulated to secrete pro-angiogenic factors. We focus on the significance of pro-angiogenic factors such as growth factors, hypoxia-inducible factors, cytokines, chemokines, matrix metalloproteinases, and adhesion molecules on RA pathogenesis. As pro-angiogenic factors are primarily produced from RA synovial tissue macrophages and fibroblasts, we emphasize the key role of RA synovial tissue lining layer in maintaining synovitis through neovascularization. Lastly, we summarize the specific approaches utilized to target angiogenesis. We conclude that the formation of new blood vessels plays an indispensable role in RA progression. However, since the function of several pro-angiogenic mediators is cross regulated, discovering novel approaches to target multiple cascades or selecting an upstream cascade that impairs the activity of a number of pro-angiogenic factors may provide a promising strategy for RA therapy.

A disintegrin and metalloprotease-10 is correlated with disease activity and mediates monocyte migration and adhesion in rheumatoid arthritis

A disintegrin and metalloproteases (ADAMs) are a family of proteins that have been reported to be involved in several inflammatory conditions. We examined the secretion of ADAM-10 in biological fluids from patients with rheumatoid arthritis (RA) and the role it plays in monocyte migration. ADAM-10 levels were measured using enzyme-linked immunosorbent assays and immunofluorescence. To examine the role of ADAM-10 in RA synovial fluids (SFs), we studied THP-1 (human acute monocyte leukemia cell line) and monocyte chemotaxis. To determine whether ADAM-10 plays a role in cell proliferation in the RA synovium, we assayed the proliferation of ADAM-10 small interfering RNA (siRNA)-transfected RA fibroblast-like synoviocytes (FLSs). The ADAM-10 level in RA serum was significantly higher than that in normal serum and was correlated with a disease activity score of 28. ADAM-10-depleted RA SFs showed a decrease in THP-1 and monocyte migratory activity compared with that of sham-depleted controls. ADAM-10 siRNA inhibited monocyte adhesion to RA FLSs. Finally, blocking ADAM-10 secretion in RA FLSs resulted in decreased production of fractalkine/CX3CL1 and vascular endothelial cell growth factor. These data indicate that ADAM-10 plays a role in monocyte migration in RA and suggest that targeting ADAM-10 may provide a method of decreasing inflammation and potentially treating other inflammatory diseases.

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.

The inflammasome adaptor ASC contributes to multiple innate immune processes in the resolution of otitis media

This study was designed to understand the contribution of the inflammasome and IL-1β activation in otitis media (OM). We examined the middle ear (ME) response to non-typeable Haemophilus influenzae (NTHi) in wild type (WT) mice using gene microarrays and a murine model of acute OM. Expression of members of the NOD domain-like receptor family of inflammasome genes was significantly up-regulated early in NTHi infection of the ME, potentially activating specific downstream regulatory cascades that contribute to the proliferative inflammatory response observed during OM. Expression of the pro-forms of the inflammasome targets IL-1β and IL-18 were also up-regulated. To evaluate the role of inflammasome-mediated cytokine maturation, NTHi-induced OM was examined in Asc(-/-)-deficient mice and compared with that seen in WT mice. Mice lacking the Asc gene showed near absence of IL-1β maturation in the ME and a reduction in leukocyte recruitment and infiltration to the cavity, and their macrophages exhibited reduced phagocytosis of NTHi. These inflammatory defects were linked to an increase in the degree and duration of mucosal epithelial hyperplasia in the ME of Asc(-/-) mice, as well as a delay in bacterial clearance from their MEs. These data demonstrate an important role for the inflammasome and cytokine processing in the course and resolution of OM.

Systemic toll-like receptor and interleukin-18 pathway activation in patients with acute ST elevation myocardial infarction

Acute myocardial infarction (AMI) is accompanied by increased expression of Toll like receptors (TLR)-2 and TLR4 on circulating monocytes. In animal models, blocking TLR2/4 signaling reduces inflammatory cell influx and infarct size. The clinical consequences of TLR activation during AMI in humans are unknown, including its role in long-term cardiac functional outcome Therefore, we analyzed gene expression in whole blood samples from 28 patients with an acute ST elevation myocardial infarction (STEMI), enrolled in the EXenatide trial for AMI patients (EXAMI), both at admission and after 4-month follow-up, by whole genome expression profiling and real-time PCR. Cardiac function was determined by cardiac magnetic resonance (CMR) imaging at baseline and after 4-month follow-up. TLR pathway activation was shown by increased expression of TLR4 and its downstream genes, including IL-18R1, IL-18R2, IL-8, MMP9, HIF1A, and NFKBIA. In contrast, expression of the classical TLR-induced genes, TNF, was reduced. Bioinformatics analysis and in vitro experiments explained this noncanonical TLR response by identification of a pivotal role for HIF-1α. The extent of TLR activation and IL-18R1/2 expression in circulating cells preceded massive troponin-T release and correlated with the CMR-measured ischemic area (R=0.48, p=0.01). In conclusion, we identified a novel HIF-1-dependent noncanonical TLR activation pathway in circulating leukocytes leading to enhanced IL-18R expression which correlated with the magnitude of the ischemic area. This knowledge may contribute to our mechanistic understanding of the involvement of the innate immune system during STEMI and may yield diagnostic and prognostic value for patients with myocardial infarction.

IL-18 regulates melanoma VLA-4 integrin activation through a Hierarchized sequence of inflammatory factors

Very late antigen-4 (VLA-4) is frequently overexpressed on melanoma cells contributing to inflammation-dependent metastasis. Melanoma cell adhesion to endothelium via VLA-4-vascular cell adhesion molecule-1 (VCAM-1) interaction was used to study VLA-4 activation during melanoma cell response to inflammation. Cooperation among major inflammatory mediators was analyzed in melanoma cells exposed to single inflammatory factors in the presence of inhibitors for other assayed mediators. A stepwise cascade of hierarchized molecules heterogeneously made and used during melanoma response to IL-18, induced hydrogen peroxide (H2O2), in turn activating VLA-4 and melanoma cell adhesion to endothelium. The cascade involved prostaglandin E2 (PGE2) production from melanoma induced by IL-18-dependent tumor necrosis factor-α (TNFα); next, PGE2-induced IL-1β via vascular endothelial growth factor (VEGF) secretion, which in turn induced VLA-4 activation via cyclooxygenase 2-dependent H2O2. This sequence operated in IL-18R/VLA-4/VEGF-expressing murine (B16) and human (A375 and 883) melanomas, but not in those without this phenotype. Separation of active VLA-4-expressing B16 melanoma cells through immobilized VCAM-1 verified their higher IL-18R/TNFR1/VEGFR2 expression and metastatic growth than inactive VLA-4-expressing cells. However, cooperation among melanoma cell sub-populations with heterogeneous cytokine receptor levels may occur through VLA-4-stimulating factors, leading to intratumoral amplification of metastatic potential. Therefore, expression of the VLA-4-stimulating factor sequence may help to predict melanoma prometastatic risk, and offers therapeutic targets for metastatic melanoma deactivation through VLA-4 activation blockade.

Mediators of inflammation-induced bone damage in arthritis and their control by herbal products

Rheumatoid arthritis (RA) is an autoimmune disease characterized by chronic inflammation of the synovial joints leading to bone and cartilage damage. Untreated inflammatory arthritis can result in severe deformities and disability. The use of anti-inflammatory agents and biologics has been the mainstay of treatment of RA. However, the prolonged use of such agents may lead to severe adverse reactions. In addition, many of these drugs are quite expensive. These limitations have necessitated the search for newer therapeutic agents for RA. Natural plant products offer a promising resource for potential antiarthritic agents. We describe here the cellular and soluble mediators of inflammation-induced bone damage (osteoimmunology) in arthritis. We also elaborate upon various herbal products that possess antiarthritic activity, particularly mentioning the specific target molecules. As the use of natural product supplements by RA patients is increasing, this paper presents timely and useful information about the mechanism of action of promising herbal products that can inhibit the progression of inflammation and bone damage in the course of arthritis.

Increased expression of interleukin-18 receptor in blood cells of subjects with mild cognitive impairment and Alzheimer's disease

Inflammation has been proposed as a leading force in neurodegeneration and Interleukin (IL)-18 is a pro-inflammatory cytokine which is suggested to be implicated in Alzheimer's disease (AD). However, the meaning of the IL-18 participation in this disease is still unclear. Since IL-18 activity is mediated by its heterodimeric receptor complex IL-18Rα/β, we evaluated the presence of both IL-18R chains on peripheral blood cells of AD patients, as well as in individuals with Mild Cognitive Impairment (MCI), at increased risk to develop AD. More specifically, we compared the levels of CD14(+) monocytes and CD3(+) T-lymphocytes bearing IL-18Rα and β chains in the two groups of patients with those in healthy control subjects, both before and after in vitro cell treatment with lipopolysaccharide (LPS). While no differences in the levels of monocytes and T-lymphocytes bearing IL-18Rα chain were found among the three groups, either in untreated and LPS-treated conditions, the IL-18Rβ chain expression appeared differently regulated in MCI and AD patients, as compared to controls. In particular, the amount of IL-18Rβ-bearing monocytes was similar among the three groups at unstimulated conditions, while after LPS treatment it was increased in MCI vs. controls. A significant increase of IL-18Rβ-bearing T-lymphocytes was also observed in MCI and AD vs. controls, both in untreated and LPS-stimulated conditions. Our findings indicate that the expression of IL-18R complex on blood cells is perturbed in AD and even more markedly in its preclinical state of MCI, confirming that an increased peripheral activity of IL-18 may be involved in the early phase of AD pathophysiology.

Immunoregulatory natural killer cells suppress autoimmunity by down-regulating antigen-specific CD8+ T cells in mice

Natural killer (NK) cells belong to the innate immune system. Besides their role in antitumor immunity, NK cells also regulate the activity of other cells of the immune system, including dendritic cells, macrophages, and T cells, and may, therefore, be involved in autoimmune processes. The aim of the present study was to clarify the role of NK cells within this context. Using two mouse models for type 1 diabetes mellitus, a new subset of NK cells with regulatory function was identified. These cells were generated from conventional NK cells by incubation with IL-18 and are characterized by the expression of the surface markers CD117 (also known as c-Kit, stem cell factor receptor) and programmed death (PD)-ligand 1. In vitro analyses demonstrated a direct lysis activity of IL-18-stimulated NK cells against activated insulin-specific CD8(+) T cells in a PD-1/PD-ligand 1-dependent manner. Flow cytometry analyses revealed a large increase of splenic and lymphatic NK1.1(+)/c-Kit(+) NK cells in nonobese diabetic mice at 8 wk of age, the time point of acceleration of adaptive cytotoxic immunity. Adoptive transfer of unstimulated and IL-18-stimulated NK cells into streptozotocin-treated mice led to a delayed diabetes development and partial disease prevention in the group treated with IL-18-stimulated NK cells. Consistent with these data, mild diabetes was associated with increased numbers of NK1.1(+)/c-Kit(+) NK cells within the islets. Our results demonstrate a direct link between innate and adaptive immunity in autoimmunity with newly identified immunoregulatory NK cells displaying a potential role as immunosuppressors.

Signalling profiles of circulating leucocytes in patients recovered from reactive arthritis

OBJECTIVES

Reactive arthritis (ReA) is a sterile joint inflammation triggered by a remote infection and associated with human leucocyte antigen (HLA)-B27. Its pathogenesis is unknown, but abnormal response to microbial structures or endogenous inflammatory mediators may be involved. We studied responses in leucocyte signalling profiles in patients with previous ReA after a full recovery.

METHOD

The study comprised 10 HLA-B27-positive healthy subjects with a history of Yersinia enterocolitica-triggered ReA (B27+ReA+) and 20 healthy reference subjects, of whom 10 carried HLA-B27 (B27+ReA-) and 10 did not (B27-ReA-). Phosphospecific fluorescent monoclonal antibodies and flow cytometry were used to determine activation of nuclear factor kappa B (NF-κB), signal transducers and activators of transcription (STATs) 1, 3, 5, and 6, and two mitogen-activated protein (MAP) kinases, p38 and extracellular signal-regulated kinase (ERK)1/2, in monocytes, lymphocytes, lymphocyte subsets, and neutrophils. B27+ReA+ and B27-ReA- whole-blood samples were incubated with Yersinia with or without infliximab to study the role of tumour necrosis factor (TNF) in lymphocyte subset activation. Samples of the three subject groups were studied using soluble bacterial or endogenous stimuli. Fluorescence levels were determined as relative fluorescence units (RFU) and the proportion of positively fluorescing cells.

RESULTS

The intracellular activation of circulating leucocytes in response to soluble stimuli was consistently comparable in B27+ReA+, B27+ReA-, and B27-ReA- subjects. Infliximab inhibited Yersinia-induced lymphocyte NF-κB phosphorylation similarly in B27+ReA+ and B27-ReA- groups.

CONCLUSIONS

ReA susceptibility is not reflected in leucocyte signalling profiles elicited by phlogistic stimuli. However, the possibility remains that aberrations occur in response to combinations of stimuli, such as those associated with leucocyte adhesion.

Advances in rheumatoid arthritis animal models

Experimental models of rheumatoid arthritis have contributed immensely to our understanding of the pathogenesis as well as the treatment of this debilitating autoimmune disease. Significant progress has been made in the past few years in defining the role of newer cytokines and regulatory T cells, of inflammation-mediated bone and cartilage damage, and of the cholinergic anti-inflammatory pathway in modulating the disease process in arthritis. Furthermore, new therapeutic targets, including specific tyrosine kinases and proteasome subunits, have been explored. These advances offer renewed optimism for continued improvements in the management of rheumatoid arthritis.

A cytokine-centric view of the pathogenesis and treatment of autoimmune arthritis

Cytokines are immune mediators that play an important role in the pathogenesis of rheumatoid arthritis (RA), an autoimmune disease that targets the synovial joints. The cytokine environment in the peripheral lymphoid tissues and the target organ (the joint) has a strong influence on the outcome of the initial events that trigger autoimmune inflammation. In susceptible individuals, these events drive inflammation and tissue damage in the joints. However, in resistant individuals, the inflammatory events are controlled effectively with minimal or no overt signs of arthritis. Animal models of human RA have permitted comprehensive investigations into the role of cytokines in the initiation, progression, and recovery phases of autoimmune arthritis. The discovery of interleukin-17 (IL-17) and its association with inflammation and autoimmune pathology has reshaped our viewpoint regarding the pathogenesis of arthritis, which previously was based on a simplistic T helper 1 (Th1)-Th2 paradigm. This review discusses the role of the newer cytokines, particularly those associated with the IL-17/IL-23 axis in arthritis. Also presented herein is the emerging information on IL-32, IL-33, and IL-35. Ongoing studies examining the role of the newer cytokines in the disease process would improve understanding of RA as well as the development of novel cytokine inhibitors that might be more efficacious than the currently available options.

Interleukin-18: a mediator of inflammation and angiogenesis in rheumatoid arthritis

Interleukin-18 (IL-18) is a highly regulated inflammatory cytokine that is elevated in synovial tissues and synovial fluids of patients with rheumatoid arthritis (RA) compared with patients with osteoarthritis (OA) and patients with other arthropathies. Within the RA joint, IL-18 can contribute to the inflammatory process by inducing leukocyte extravasation through upregulation of endothelial cell adhesion molecules, the release of chemokines from RA synovial fibroblasts, and directly as a monocytes, lymphocyte, and neutrophil chemoattractant. IL-18 can also help maintain and develop the inflammatory pannus by inducing endothelial cell migration and angiogenesis. IL-18 does this directly by binding and activating endothelial cells and indirectly by inducing RA synovial fibroblasts to produce angiogenic chemokines and vascular endothelial growth factor. IL-18 is present in RA synovial fluid in high levels, where it functions as an angiogenic mediator and leukocyte chemoattractant. IL-18 mediates all these inflammatory processes by binding to its receptor, IL-18 receptor, and initiating the activation of different signaling cascades leading to changes in target cells gene expression and behavior. IL-18 has been identified as a potential therapeutic target in the treatment of RA.

Near eradication of clinically relevant concentrations of human tumor cells by interferon-activated monocytes in vitro

We have previously reported that low concentrations of interferon (IFN)-activated monocytes exert near-eradicative cytocidal activity against low concentrations of several human tumor cells in vitro. In the present study, we examined 7 human tumor cell lines and 3 diploid lines in the presence or absence of 10 ng/mL IFNα2a and monocytes. The results confirmed strong cytocidal activity against 4 of 7 tumor lines but none against 3 diploid lines. To model larger in vivo tumors, we increased the target cell concentration and determined the concentration of IFNα2a and monocytes, required for cell death. We found that increasing the tumor cell concentration from 10- to 100-fold (10(5) cells/well) required an increase in the concentration of IFNs by over 100-fold and monocytes by 10-fold. High concentrations of monocytes could sometimes kill tumor or diploid cells in the absence of IFN. We may conclude that killing of high concentrations of tumor or diploid cells required high concentrations of monocytes that could sometimes kill in the absence of IFN. Thus, high concentrations of tumor cells required high concentrations of IFN and monocytes to cause near eradication of tumor cells. These findings may have clinical implications.

T-bet controls severity of hypersensitivity pneumonitis

Hypersensitivity Pneumonitis (HP) is an interstitial lung disease that develops following repeated exposure to inhaled environmental antigens. The disease is characterized by alveolitis, granuloma formation and in some patients' fibrosis. IFNγ plays a critical role in HP; in the absence of IFNγ granuloma formation does not occur. However, recent studies using animal models of HP have suggested that HP is a Th17 disease calling into question the role of IFNγ. In this study, we report that initially IFNγ production is dependent on IL-18 and the transcription factor T-bet, however as the disease continues IFNγ production is IL-18-independent and partially T-bet dependent. Although IFNγ production is required for granuloma formation its role is distinct from that of T-bet. Mice that are deficient in T-bet and exposed to S. rectivirgula develop more severe disease characterized by an exacerbated Th17 cell response, decreased Th1 cell response, and increased collagen production in the lung. T-bet-mediated protection does not appear to be due to the development of a protective Th1 response; shifting the balance from a Th17 predominant response to a Th1 response by inhibition of IL-6 also results in lung pathology. The results from this study suggest that both Th1 and Th17 cells can be pathogenic in this model and that IFNγ and T-bet play divergent roles in the disease process.