Phospholipase A1 Member A Activates Fibroblast-like Synoviocytes through the Autotaxin-Lysophosphatidic Acid Receptor Axis.

Lysophosphatidylserine (lysoPS) is known to regulate immune cell functions. Phospholipase A1 member A (PLA1A) can generate this bioactive lipid through hydrolysis of sn-1 fatty acids on phosphatidylserine (PS). PLA1A has been associated with cancer metastasis, asthma, as well as acute coronary syndrome. However, the functions of PLA1A in the development of systemic autoimmune rheumatic diseases remain elusive. To investigate the possible implication of PLA1A during rheumatic diseases, we monitored PLA1A in synovial fluids from patients with rheumatoid arthritis and plasma of early-diagnosed arthritis (EA) patients and clinically stable systemic lupus erythematosus (SLE) patients. We used human primary fibroblast-like synoviocytes (FLSs) to evaluate the PLA1A-induced biological responses. Our results highlighted that the plasma concentrations of PLA1A in EA and SLE patients were elevated compared to healthy donors. High concentrations of PLA1A were also detected in synovial fluids from rheumatoid arthritis patients compared to those from osteoarthritis (OA) and gout patients. The origin of PLA1A in FLSs and the arthritic joints remained unknown, as healthy human primary FLSs does not express the PLA1A transcript. Besides, the addition of recombinant PLA1A stimulated cultured human primary FLSs to secrete IL-8. Preincubation with heparin, autotaxin (ATX) inhibitor HA130 or lysophosphatidic acid (LPA) receptor antagonist Ki16425 reduced PLA1A-induced-secretion of IL-8. Our data suggested that FLS-associated PLA1A cleaves membrane-exposed PS into lysoPS, which is subsequently converted to LPA by ATX. Since primary FLSs do not express any lysoPS receptors, the data suggested PLA1A-mediated pro-inflammatory responses through the ATX-LPA receptor signaling axis.

Mechanosensitive TRPV4 is required for crystal-induced inflammation.

Crystal structures activate innate immune cells, especially macrophages and initiate inflammatory responses. We aimed to understand the role of the mechanosensitive TRPV4 channel in crystal-induced inflammation. Real-time RT-PCR, RNAscope in situ hybridisation, and Trpv4eGFP mice were used to examine TRPV4 expression and whole-cell patch-clamp recording and live-cell Ca2+ imaging were used to study TRPV4 function in mouse synovial macrophages and human peripheral blood mononuclear cells (PBMCs). Both genetic deletion and pharmacological inhibition approaches were used to investigate the role of TRPV4 in NLRP3 inflammasome activation induced by diverse crystals in vitro and in mouse models of crystal-induced pain and inflammation in vivo. TRPV4 was functionally expressed by synovial macrophages and human PBMCs and TRPV4 expression was upregulated by stimulation with monosodium urate (MSU) crystals and in human PBMCs from patients with acute gout flares. MSU crystal-induced gouty arthritis were significantly reduced by either genetic ablation or pharmacological inhibition of TRPV4 function. Mechanistically, TRPV4 mediated the activation of NLRP3 inflammasome by diverse crystalline materials but not non-crystalline NLRP3 inflammasome activators, driving the production of inflammatory cytokine interleukin-1ß which elicited TRPV4-dependent inflammatory responses in vivo. Moreover, chemical ablation of the TRPV1-expressing nociceptors significantly attenuated the MSU crystal-induced gouty arthritis. In conclusion, TRPV4 is a common mediator of inflammatory responses induced by diverse crystals through NLRP3 inflammasome activation in macrophages. TRPV4-expressing resident macrophages are critically involved in MSU crystal-induced gouty arthritis. A neuroimmune interaction between the TRPV1-expressing nociceptors and the TRPV4-expressing synovial macrophages contributes to the generation of acute gout flares.

Tanshinones inhibit NLRP3 inflammasome activation by alleviating mitochondrial damage to protect against septic and gouty inflammation.

Tanshinones, the active ingredients derived from the roots of Salvia miltiorrhiza, have been widely used as traditional medicinal herbs for treating human diseases. Although tanshinones showed anti-inflammatory effects in many studies, large knowledge gaps remain regarding their underlying mechanisms. Here, we identified 15 tanshinones that suppressed the activation of NLRP3 inflammasome and studied their structure-activity relationships. Three tanshinones (tanshinone IIA, isocryptotanshinone, and dihydrotanshinone I) reduced mitochondrial reactive-oxygen species production in lipopolysaccharide (LPS)/nigericin-stimulated macrophages and correlated with altered mitochondrial membrane potentials, mitochondria complexes activities, and adenosine triphosphate and protonated-nicotinamide adenine dinucleotide production. The tanshinones may confer mitochondrial protection by promoting autophagy and the AMP-activated protein kinase pathway. Importantly, our findings demonstrate that dihydrotanshinone I improved the survival of mice with LPS shock and ameliorated inflammatory responses in septic and gouty animals. Our results suggest a potential pharmacological mechanism whereby tanshinones can effectively treat inflammatory diseases, such as septic and gouty inflammation.

The Anti-Inflammatory and Uric Acid Lowering Effects of Si-Miao-San on Gout.

Background: Si-Miao-San (SMS) is a well-known traditional Chinese medicine. This study aims to evaluate the anti-inflammatory effects of SMS on gouty arthritis and its potential mechanism of action. Methods: The effects and mechanism of SMS were evaluated in monosodium urate (MSU)-treated mice or macrophages. The expression of cytokines and PI3K/Akt was analyzed using real-time PCR and Western blotting analyses. Macrophage polarization was assessed with immunofluorescence assays, real-time PCR, and Western blotting. Mass spectrometry was used to screen the active ingredients of SMS. Results: Pretreatment with SMS ameliorated MSU-induced acute gouty arthritis in mice with increased PI3K/Akt activation and M2 macrophage polarization in the joint tissues. In vitro, SMS treatment significantly inhibited MSU-triggered inflammatory response, increased p-Akt and Arg-1 expression in macrophages, and promoted M2 macrophage polarization. These effects of SMS were inhibited when PI3K/Akt activation was blocked by LY294002 in the macrophages. Moreover, SMS significantly reduced serum uric acid levels in the hyperuricemia mice. Using mass spectrometry, the plant hormones ecdysone and estrone were detected as the potentially effective ingredients of SMS. Conclusion: SMS ameliorated MSU-induced gouty arthritis and inhibited hyperuricemia. The anti-inflammatory mechanism of SMS may exert anti-inflammatory effects by promoting M2 polarization via PI3K/Akt signaling. Ecdysone and estrone might be the potentially effective ingredients of SMS. This research may provide evidence for the application of SMS in the treatment of gout.

Efficacy of Rebixiao Chinese herbal tablets and Chinese formula granules in acute gout arthritis patients: a randomized, multicenter, double-blind, controlled trial.

OBJECTIVE: To evaluate the clinical efficacy and safety of Rebixiao (RBX) Chinese herbal tablets (CHT) and Chinese formula granules (CFG) in the treatment of acute gout arthritis (AGA). METHODS: This randomized, multicenter, double-blind, controlled trial included 165 AGA patients with the damp-heat symptom pattern who were randomly divided into an RBX CHT group and an RBX CFG group and treated for 7 d at three centers. The total effective rates of the joint symptom score, Traditional Chinese Medicine (TCM) symptoms score, erythrocyte sedimentation rate (ESR), and C-reactive protein (CRP) were used to evaluate the clinical efficacy. Safety assessments were also performed. RESULTS: Of the 165 enrolled patients, 147 completed the clinical observation. There was no difference in baseline between the two groups. The total effective rates of the joint symptom score were 94.36% and 97.36%, and the total effective rates of the TCM symptoms score were 95.77% and 97.36% in the CFG group and CHT group, respectively. No statistical difference was found between the two groups (P > 0.05). Additionally, ESR and CRP were similar in both groups (P > 0.05). Furthermore, treatment efficacy regarding TCM and joint symptoms, the ESR, and CRP were consistent within each center and among the different centers (P > 0.05). In addition, the incidence of adverse events was 4.22% and 2.63% in the CFG group and CHT group, respectively, and no difference was observed between the two groups (P > 0.05). CONCLUSION: RBX CFG and CHT have significant and similar efficacy in the treatment of AGA, and CFG did not increase adverse side effects.

Differential DNA Methylation of Networked Signaling, Transcriptional, Innate and Adaptive Immunity, and Osteoclastogenesis Genes and Pathways in Gout.

OBJECTIVE: In gout, autoinflammatory responses to urate crystals promote acute arthritis flares, but the pathogeneses of tophi, chronic synovitis, and erosion are less well understood. Defining the pathways of epigenomic immunity training can reveal novel pathogenetic factors and biomarkers. The present study was undertaken to seminally probe differential DNA methylation patterns utilizing epigenome-wide analyses in patients with gout. METHODS: Peripheral blood mononuclear cells (PBMCs) were obtained from a San Diego cohort of patients with gout (n = 16) and individually matched healthy controls (n = 14). PBMC methylome data were processed with ChAMP package in R. ENCODE data and Taiji data analysis software were used to analyze transcription factor (TF)-gene networks. As an independent validation cohort, whole blood DNA samples from New Zealand Maori subjects (n = 13 patients with gout, n = 16 control subjects without gout) were analyzed. RESULTS: Differentially methylated loci clearly separated gout patients from controls, as determined by hierarchical clustering and principal components analyses. IL23R, which mediates granuloma formation and cell invasion, was identified as one of the multiple differentially methylated gout risk genes. Epigenome-wide analyses revealed differential methylome pathway enrichment for B and T cell receptor signaling, Th17 cell differentiation and interleukin-17 signaling, convergent longevity regulation, circadian entrainment, and AMP-activated protein kinase signaling, which are pathways that impact inflammation via insulin-like growth factor 1 receptor, phosphatidylinositol 3-kinase/Akt, NF-κB, mechanistic target of rapamycin signaling, and autophagy. The gout cohorts overlapped for 37 (52.9%) of the 70 TFs with hypomethylated sequence enrichment and for 30 (78.9%) of the 38 enriched KEGG pathways identified via TFs. Evidence of shared differentially methylated gout TF-gene networks, including the NF-κB activation-limiting TFs MEF2C and NFATC2, pointed to osteoclast differentiation as the most strongly weighted differentially methylated pathway that overlapped in both gout cohorts. CONCLUSION: These findings of differential DNA methylation of networked signaling, transcriptional, innate and adaptive immunity, and osteoclastogenesis genes and pathways suggest that they could serve as novel therapeutic targets in the management of flares, tophi, chronic synovitis, and bone erosion in patients with gout.

Anti-Nociceptive Effect and Standardization from Mixture of Agrimonia pilosa Ledeb and Salvia miltiorrhiza Bunge Extracts.

Agrimonia pilosa Ledeb has been previously reported to produce an anti-nociceptive effect in ICR mice in both tail-flick and hot-plate tests. Studies have shown that Salvia miltiorrhiza Bunge, also renowned in traditional Chinese medicine, is an effective anti-inflammatory treatment. Among the extraction solvents investigated, a 50% ethanol (EtOH) extract of A. pilosa produced the highest anti-nociceptive effect in monosodium uric acid-induced gout pain models and the greatest yield. The 80% EtOH extract of S. miltiorrhiza moderately inhibited lipopolysaccharide-induced nitric oxide release from RAW 264.7 murine macrophages and exhibited outstanding yield. The mixture of optimized A. pilosa and S. miltiorrhiza extracts were evaluated for enhanced anti-nociceptive effects in gout arthritis treatment. To control extract quality, four marker compounds were determined using an HPLC-DAD method. A 1:1 mixture of A. pilosa 50 and S. miltiorrhiza 80% EtOH extracts of produced better results than when the extracts were administered individually.

Mechanisms of unconventional secretion of IL-1 family cytokines.

One of the most poorly understood processes in cell biology is the peculiar ability of specific leaderless proteins to be secreted via ER/Golgi-independent mechanisms ('unconventional protein secretion'). One such leaderless protein is the major immune-activating cytokine, interleukin-1ß (IL-1ß). Unusual amongst cytokines, IL-1ß is expressed in the cytosol as an inactive precursor protein. It requires maturation by the caspase-1 protease, which itself requires activation upon immune cell sensing of infection or cell stress. Despite 25 years of intensive research into IL-1ß secretory mechanisms, how it exits the cell is still not well understood. Here we will review the various mechanisms by which macrophages have been proposed to secrete IL-1 family cytokines, and the potential involvement of caspase-1 therein. Since aberrant IL-1ß production drives inherited and acquired human diseases (e.g. autoinflammatory diseases, arthritic diseases, gout, Alzheimer's disease), elucidation of the IL-1ß secretory pathway may offer new therapeutic opportunities for treatment across this wide range of human conditions.

Lipid-associated rheumatologic syndromes.

Rheumatologic manifestations of hyperlipidemia and lipid-associated arthritis are rarely seen in the rheumatologist's office. On the other hand, a rheumatologist may be the clinician who identifies and initiates proper therapy for disorders related to hyperlipidemia when the musculoskeletal manifestations of these syndromes are recognized. In this article both the joint and tendon manifestations are reviewed, including the lesser known lipid liquid crystal form of arthritis. The relationship between gout and hyperuricemia is briefly discussed, as are the autoimmune manifestations of lipid-lowering therapy.

Anti-nociceptive and anti-edematogenic effects of glibenclamide in a model of acute gouty attack in rats.

OBJECTIVE AND DESIGN: We investigated the effect of glibenclamide on inflammatory parameters in a model of acute gouty attack in rats. TREATMENT: Intra-articular injection of 50 µl of monosodium urate (MSU) crystals (1.25 mg/site) was used to induce gout-related inflammation. The effects of glibenclamide (1-10 mg/kg, s.c.) or dexamethasone (8 mg/kg, s.c., positive control) were assessed on several inflammation parameters. METHODS: Spontaneous nociception assessment, edema measurement, total and differential leucocyte counts, interleukin (IL)-1ß release, prostaglandin E2 production and determination of blood glucose levels were analyzed. Peritoneal macrophages were incubated with MSU and levels of IL-1ß were measured. Statistical significance was assessed by one- or two-way analysis of variance. RESULTS: Glibenclamide (3 mg/kg) or dexamethasone (8 mg/kg) prevented nociception and edema induced by MSU injection in rats. Glibenclamide did not affect leukocyte infiltration, IL-1ß release and PGE2 production, but only reduced IL-1ß production by MSU-stimulated macrophages at very high concentration (200 µM). Dexamethasone significantly reduced leukocyte infiltration, IL-1ß release and PGE2 production. Glibenclamide reduced whereas dexamethasone increased blood glucose levels of MSU-injected rats. CONCLUSIONS: Glibenclamide reduced nociception and edema, but not leukocyte infiltration, IL-1ß release and PGE2 production. However, its substantial effect on nociception and edema suggests that glibenclamide can be an interesting option as an adjuvant treatment for pain induced by acute attacks of gout.

The role of uric acid as an endogenous danger signal in immunity and inflammation.

Gout is an ancient disease that still plagues us. Its pathogenic culprit, uric acid crystal deposition in tissues, is a strong inflammatory stimulant. In recent years, the mechanisms through which uric acid crystals promote inflammation have been a subject of increasing interest among rheumatologists and immunologists. Uric acid has been identified as an endogenous adjuvant that drives immune responses in the absence of microbial stimulation. Because uric acid is a ubiquitous metabolite that is produced in high quantities upon cellular injury, the ramifications of its effects may be considerable in health and in disease. Uric acid crystals also have been shown to trigger interleukin-1ß-mediated inflammation via activation of the NOD-like receptor protein (NLRP)3 inflammasome, a multimolecular complex whose activation appears to be central to many pathological inflammatory conditions. In this article, we review the possible mechanisms of uric acid-mediated inflammation and offer some historical perspectives on what has been learned about the complex effects of a relatively simple substance.

Kinetic study on the inhibition of xanthine oxidase by extracts from two selected Algerian plants traditionally used for the treatment of inflammatory diseases.

In order to further understand and assess the validity of herbal medicine, we investigated the potential inhibitory effect of various extracts from Fraxinus angustifolia and Pistacia lentiscus, two plants used traditionally in Algeria against several inflammatory diseases such as rheumatism, arthritis, and gout, on purified bovine milk xanthine oxidase (XO) activity. The total phenolic contents of the leaves and bark of F. angustifolia and the leaves and seeds of P. lentiscus were estimated. P. lentiscus aqueous fractions from hexane and chloroform extractions and F. angustifolia aqueous fraction from ethyl acetate extraction inhibited XO activity by 72.74 +/- 2.63% (50% inhibitory concentration [IC(50)] = 27.52 microg/mL), 68.97 +/- 3.89% (IC(50) = 42.46 microg/mL) and 53.92 +/- 3.17% (IC(50) = 58.84 mmicroug/mL), respectively, at 100 microg/mL, compared to that of reference drug, allopurinol (98.18% [IC(50) = 6.34 microg/mL]). Moreover, at a concentration of 50 microg/mL, both P. lentiscus extracts showed inhibition rates higher than 50%. F. angustifolia leaf extracts showed only mild inhibition. Lineweaver-Burk analysis showed that the inhibitory activity exerted by F. angustifolia bark aqueous extract and P. lentiscus aqueous extracts is of mixed type, whereas the leaf extracts from F. angustifolia inhibited XO noncompetitively. Positive correlations were established between XO inhibition and total phenols (r = 0.89) and flavonoids (r = 0.93) for P. lentiscus and with total phenols (r = 0.72) and tannins (r = 0.54) for F. angustifolia. Our findings suggest that the therapeutic use of these plants may be due to the observed XO inhibition, thereby supporting their use in traditional folk medicine against inflammatory-related diseases, in particular, gout.

A role of IgM antibodies in monosodium urate crystal formation and associated adjuvanticity.

Uric acid is released from injured cells and can act as an adjuvant signal to the immune system. Uric acid crystals invoke strong inflammatory responses in tissues. Although their biological effects are evident and the associated signaling mechanisms are becoming clear, it remains unexplained as to why uric acid precipitates rapidly in vivo, in sharp contrast to the minimal crystallization in vitro. We report in this study that a group of IgM Abs is able to bind to these crystals, which is interesting in light that B cell-deficient mice do not sense the proinflammatory adjuvant effect of uric acid. The titers of these Abs increase upon immunization with uric acid crystals. We have produced large quantities of such mAbs. The purified IgM Abs can significantly facilitate uric acid precipitation to form the inflammatory crystals in vitro. Infusion of these Abs into B cell-deficient mice significantly increases the basal level of inflammation in these recipients and restores the host's ability to sense uric acid's adjuvanticity. Therefore, we have identified a factor in determining uric acid precipitation and possibly its ability to function as an endogenous adjuvant. This finding suggests a new mechanism of the pathogenesis of gouty arthritis and uric acid-induced immune activation.

Diabetes and rheumatic diseases.

PURPOSE OF REVIEW: This review summarizes recent advances in the field of diabetes and rheumatic disease. These conditions exert a significant healthcare burden on our society and much remains to be learned regarding their pathophysiology and treatment. RECENT FINDINGS: We summarize new insights into diabetes and its association with osteoarthritis, rheumatoid arthritis, carpal tunnel syndrome, osteoporosis, diffuse idiopathic skeletal hyperostosis, crystalline arthropathy, neuropathic arthropathy, and tendinopathy. Diabetes has major effects on connective tissues, which have significant impact on both the development and outcome of these diseases of cartilage, bone, ligament, and tendon. An improved understanding of the mechanisms through which diabetes alters connective tissue metabolism should lead to better preventive and therapeutic interventions. SUMMARY: Incremental progress has been made in understanding the interactions between diabetes and common musculoskeletal syndromes. Although this review highlights exciting areas of future interest, more work in this field is certainly warranted.

Update on the management of hyperuricemia and gout.

Gout is the most common inflammatory arthritis in the United States, with more than three million sufferers. Management of gout has changed relatively little in the past 50 years, despite the fact that many gout patients have contraindications to one or more currently available gout therapies. However, recent insights into gout pathophysiology suggest that time is ripe for a change. This article reviews recent updates in the management of gout, including new insights into dietary management that may permit better control of hyuperuricemia. Also reviewed are the biological and clinical data behind newly-developed drugs for gout that are likely to receive serious consideration for FDA approval, and clinical use, in the foreseeable future.

TLR2 signaling in chondrocytes drives calcium pyrophosphate dihydrate and monosodium urate crystal-induced nitric oxide generation.

Microcrystals of calcium pyrophosphate dihydrate (CPPD) and monosodium urate (MSU) deposited in synovium and articular cartilage initiate joint inflammation and cartilage degradation in large part by binding and directly activating resident cells. TLRs trigger innate host defense responses to infectious pathogens, and the expression of certain TLRs by synovial fibroblasts has revealed the potential for innate immune responses to be triggered by mesenchymally derived resident cells in the joint. In this study we tested the hypothesis that chondrocytes also express TLRs and that one or more TLRs centrally mediate chondrocyte responsiveness to CPPD and MSU crystals in vitro. We detected TLR2 expression in normal articular chondrocytes and up-regulation of TLR2 in osteoarthritic cartilage chondrocytes in situ. We demonstrated that transient transfection of TLR2 signaling-negative regulator Toll-interacting protein or treatment with TLR2-blocking Ab suppressed CPPD and MSU crystal-induced chondrocyte release of NO, an inflammatory mediator that promotes cartilage degeneration. Conversely, gain-of-function of TLR2 in normal chondrocytes via transfection was associated with increased CPPD and MSU crystal-induced NO release. Canonical TLR signaling by parallel pathways involving MyD88, IL-1R-associated kinase 1, TNF receptor-associated factor 6, and IkappaB kinase and Rac1, PI3K, and Akt critically mediated NO release in chondrocytes stimulated by both CPPD and MSU crystals. We conclude that CPPD and MSU crystals critically use TLR2-mediated signaling in chondrocytes to trigger NO generation. Our results indicate the potential for innate immunity at the level of the articular chondrocyte to directly contribute to inflammatory and degenerative tissue reactions associated with both gout and pseudogout.

Excitatory amino acids, TNF-alpha, and chemokine levels in synovial fluids of patients with active arthropathies.

The aim of this study was to assess the synovial fluid (SF) neurotransmitter excitatory amino acid (EAA) levels, including glutamate (Glu) and aspartate (Asp), in the context of SF levels of other amino acids, TNF-alpha and chemokines from patients with active arthropathies. The SF was collected from patients with active rheumatoid arthritis (RA), gout, or osteoarthritis (OA). The SF samples were analysed for levels of neurotransmitters glutamate and aspartate, tumour necrosis factor-alpha (TNF-alpha), Regulated upon Activation Normally T-cell Expressed and Secreted (RANTES), macrophage inhibitory factor-1 alpha (MIP-1alpha) and interleukin 8 (IL-8). SF WBC counts were also determined. Correlations between SF EAA, TNF-alpha and chemokines were determined by the Pearson product-moment correlation. Primary cultures derived from SF from active RA and gout patients were incubated with added l-glutamate, to assess if exposure to Glu could increase TNF-alpha levels. There were significant elevations in SF EAA, SF TNF-alpha and SF RANTES in RA patients compared to gout or OA patients. Significant correlations between SF EAA and SF RANTES, MIP-1alpha and IL-8 levels were seen, and SF EAA and SF TNF-alpha or SF WBC levels approached significance. Addition of exogenous neurotransmitter glutamate significantly increased TNF-alpha levels in primary cell cultures derived from RA and gout patients. The SF neurotransmitter EAA levels significantly correlated to selected SF chemokine levels, in clinically active RA, gout and OA patients, independent of disease. Added Glu resulted in significantly increased TNF-alpha levels in primary synovial cell cultures. These data expand the relationship of SF neurotransmitter EAA levels to SF cytokines and chemokines in patients with clinically active arthritis, and suggest that neurotransmitters Glu and Asp contribute to peripheral inflammatory processes.

Inflammatory properties of IgG modified by oxygen radicals and peroxynitrite.

In inflammatory arthritis, there is evidence indicating that the affected tissues produce large amounts of oxygen-free radicals and NO. Herein, we examine the biologic effects of exposure of IgG to hypochlorous acid (HOCl) and peroxynitrite (ONOO). The concentrations of IgG modified by chlorination and nitrosation were measured in synovial fluids from inflammatory and noninflammatory arthritis. Human IgG was exposed to increasing concentrations of HOCl and ONOO, and the resulting products were tested for complement component binding; binding to FcgammaRI; activation of polymorphonuclear neutrophils; effect on the Ab-combining site of Abs; and in vivo inflammatory activity in a rabbit model of acute arthritis. Rheumatoid synovial fluids contained significantly greater concentrations of nitrosated and chlorinated IgG compared with ostearthritic specimens. In vitro exposure of human IgG to HOCl and ONOO resulted in a concentration-dependent decrease in C3 and C1q fixation. The decrease in Fc domain-dependent biologic functions was confirmed by competitive binding studies to the FcgammaRI of U937 cells. HOCl-treated IgG monomer was 10 times less effective in competing for binding compared with native IgG, and ONOO-treated IgG was 2.5 times less effective. The modified IgGs were also ineffective in inducing synthesis of H(2)O(2) by human PMN. The Ag-binding domains of IgG also showed a concentration-dependent decrease in binding to Ag. The ability of the modified IgGs to induce acute inflammation in rabbit knees decreased 20-fold as gauged by the intensity of the inflammatory cell exudates. These studies clarify the modulating role of biological oxidants in inflammatory processes in which Ag-autoantibody reactions and immune complex pathogenesis may play an important role.

Tryptophan catabolism in synovial fluid of various arthropathies and its relationship with inflammatory cytokines.

Synovial fluids (SF) from patients with rheumatoid arthritis (RA), psoriatic arthritis (PsA), gout, and osteoarthritis (OA) were investigated for the levels of interleukin (IL)-1 beta, IL-6 and IL-8, tryptophan (Trp) and indoleamine 2,3-dioxygenase (IDO) activity. Significant differences exist in the levels of IL-1 beta between inflammatory arthritides RA, PsA and gout and non inflammatory arthritis, such as OA. The highest concentration of IL-1 beta was found in RA, that showed high levels also of IL-6 and IL-8. In the same disease we also found the highest IDO activity and the lowest Trp concentration. In addition, IDO activity seems to be related with the decrease in Trp, as demonstrated by the inverse correlation found between these two substances in the SF of all patients.

Immunochemical and ultrastructural characterization of serum proteins associated with monosodium urate crystals (MSU) in synovial fluid cells from patients with gout.

Immunoelectron microscopic (IEM) analysis of the surface coats of intracellular and extracellular monosodium urate (MSU) crystals in synovial fluid (SF) in gouty arthritis was performed using the ferritin-bridge method. Cells from patients with acute gout were fixed in 1% glutaraldehyde containing 0.05% saponin to permeabilize membranes for access of immunochemicals to intracellular antigens. Intracellular MSU crystals were observed in phagosomes of greater than 75% of both polymorphonuclear (PMNs) and mononuclear cells. Coating of crystals with IgG was more prominent than with IgM or IgA. Other proteins such as C3, and fibrinogen were also found to a lesser extent. Albumin was not detected in appreciable amounts on MSU crystals. Extracellular crystals also showed IgG to be bound more prominently than other proteins. The various proteins, shown here for the first time to be clearly associated with intracellular crystals by EM, and other materials associated with MSU crystals may influence the phlogistic properties of these crystals.