软骨复合物对小鼠类风湿性关节炎的预防作用

目的观察口服软骨复合物对类风湿性关节炎（rheumatoid arthritis,RA）的预防作用。方法口服软骨复合物两周后,再注射弗氏完全佐剂（Freund’s complete adjuvant,FCA）诱发小鼠RA模型,通过观察小鼠关节炎分数的变化,测定小鼠各器官的指数,检测小鼠血清中一氧化氮（nitric oxide,NO）和肿瘤坏死因子-α（TNF-α）水平以及关节组织病理学的变化来评价口服软骨复合物对类风湿性关节炎的预防作用。结果软骨复合物能较有效的改善关节的肿胀度,并显著地提高小鼠的胸腺指数（P〈0．01）,显著地提高脾指数（P〈0．05）,明显降低NO和TNF-α水平;组织病理学显示给药组关节的变形破坏得到减轻。结论软骨复合物能有效地起到预防佐剂性关节炎的作用,然而其治疗作用还有待进一步研究。     

Adiponectin associates with markers of cartilage degradation in osteoarthritis and induces production of proinflammatory and catabolic factors through mitogen-activated protein kinase pathways

Introduction  

Adiponectin is an adipokine that regulates energy metabolism and insulin sensitivity, but recent studies have pointed also to a role in inflammation and arthritis. The purpose of the present study was to investigate the association and effects of adiponectin on inflammation and cartilage destruction in osteoarthritis (OA).     

Lessons from animal models of arthritis over the past decade

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

Articular cartilage destruction in experimental inflammatory arthritis: insulin-like growth factor-1 regulation of proteoglycan metabolism in chrondrocytes

Summary Rheumatoid arthritis, a disease of unknown aetiology, is characterized by joint inflammation and, in its later stages, cartilage destruction. Inflammatory mediators may exert not only suppression of matrix synthesis but also cartilage degradation, which eventually leads to severe cartilage depletion. Systemically and locally produced growth factors and hormones regulate cartilage metabolism. Alterations in levels of these factors or in their activity can influence the pathogenesis of articular cartilage destruction in arthritic joints. The main topic of the present review is the role of the anabolic factor insulin-like growth factor-1 in the regulation of chondrocyte metabolic functions in normal and in diseased cartilage. This is the most important growth factor that balances chondrocyte proteoglycan synthesis and catabolism to maintain a functional cartilage matrix. A brief overview of how chondrocytes keep the cartilage matrix intact, and how catabolic and anabolic vactors are thought to be involved in pathological cartilage destruction precedes the review of the role of this growth factor in proteoglycan metabolism in cartilage.     

Zymosan-induced arthritis in rats II. Effects of anti-inflammatory drugs

As zymosan-induced arthritis in rats combines dual activation of early prostaglandindependent processes (edema, fever, pain) and IL-1 related effects on cartilage metabolism, we compared the respective influences of indomethacin (IMT) and dexamethasone (DEX) on its course. Different parameters were assessed: knee swelling, febrile response, loss of activity, cartilage metabolism and histology. DEX improved all these parameters, while IMT exerted only light beneficial effects on fever and knee swelling without obvious beneficial influence on cartilage metabolism and histological lesions. These results suggest that anti-inflammatory activities of DEX and IMT are due to interferences with different pathways during zymosan-induced arthritis in rats.     

Active matrix metalloproteinases are present in cartilage during immune complex-mediated arthritis: a pivotal role for stromelysin-1 in cartilage destruction.

The involvement of immune complexes during experimental arthritis in induction of metalloproteinases (MMP)-induced neoepitopes in aggrecan in cartilage, as well as the role of stromelysin-1 (SLN-1) in the induction of this neoepitope, was investigated. Passive immune complex arthritis was induced, and generation of the MMP-specific cleavage product (VDIPEN) was studied by immunolocalization. The role of SLN-1 was studied with use of SLN-1-deficient (SLN-1KO) mice. VDIPEN expression was studied in vitro by exposing the cartilage to IL-1 and subsequent activation of latent MMPs. Immune complex arthritis was characterized by an acute inflammation, with influx of mainly polymorphonuclear cells into the joint cavity. Expression of VDIPEN neoepitopes was consistently found in areas extensively depleted from proteoglycans. SLN-1KO mice did not show expression of the VDIPEN neoepitope, although inflammation and proteoglycan depletion was comparable to wild-type mice. In addition, erosions of cartilage were absent in SLN-1KO mice, but were present in wild-type mice, suggesting an important role for SLN-1 in cartilage destruction. In vitro studies showed that SLN-1 is also pivotally involved in IL-1-induced MMP activity. Stimulated polymorphonuclear neutrophils were able to activate latent MMPs present in the cartilage. Neutrophil elastase was also capable of activating IL-1-induced latent MMPs, which identifies elastase as a possible activator for latent VDIPEN-inducing MMPs. This study suggests that IC are important in the activation of latent MMPs in cartilage, possibly through polymorphonuclear neutrophil activation on the cartilage edge. SLN-1 is a pivotal enzyme in overall MMP-activity in cartilage during immune complex-mediated arthritis.     

Nitric oxide mediates interleukin-1 induced inhibition of glycosaminoglycan synthesis in rat articular cartilage

Interleek-1beta (IL-1) is a key mediator of cartilage matrix degradation in osteoarthritis and rheumatoid arthritis. It was found that the IL-1-induced suppression of glycosaminoglycan (GAG) synthesis in rat articular cartilage occurred simultaneously with the accumulation of nitrite (a metabolite of nitric oxide (NO) in aqueous milieu) in the culture medium. NO-synthase inhibitors, L-NMMA and L-NIO, inhibited both these IL-1 effects. Dexamethasone suppressed GAG synthesis additively to IL-1, but did not alter nitrite accumulation. Three NO-donors (GEA 3175, SNAP and SIN-1) also had an inhibitory effect on cartilage GAG synthesis. Therefore, it is concluded that IL-1 induced suppression of GAG synthesis in rat articular cartilage is mediated by the production of NO.     

In vitro model for the analysis of synovial fibroblast-mediated degradation of intact cartilage

Introduction  

Activated synovial fibroblasts are thought to play a major role in the destruction of cartilage in chronic, inflammatory rheumatoid arthritis (RA). However, profound insight into the pathogenic mechanisms and the impact of synovial fibroblasts in the initial early stages of cartilage destruction is limited. Hence, the present study sought to establish a standardised in vitro model for early cartilage destruction with native, intact cartilage in order to analyse the matrix-degrading capacity of synovial fibroblasts and their influence on cartilage metabolism.     

Diazeniumdiolates: pro- and antioxidant applications of the "NONOates"

Diazeniumdiolates are compounds containing the X-[N(O)NO](-) structural unit that as a class offer many advantages as tools for probing the roles of nitric oxide (NO) in biological redox processes. Available examples in which X is a secondary amine group spontaneously generate up to two molecules of NO per [N(O)NO](-) unit when dissolved in aqueous media; their half-lives range from 2 s (for X = L-prolyl) to 20 h [for X = (H(2)NCH(2)CH(2))(2)N] at pH 7. 4 and 37 degrees C, and are in general relatively little influenced by medium effects or metabolism. When X = O(-) (Angeli's salt), first-order dissociation produces NO(-) rather than NO, but the ion becomes an NO source on 1-electron oxidation; diazeniumdiolate-derived NO can also be used to generate reactive nitrogen/oxygen species with higher nitrogen oxidation states (+3 and +4) in the presence of selected oxidizing agents. The advantages of diazeniumdiolates in biomedical research are briefly illustrated with examples from the recent literature probing NO's role in inhibiting oxidative drug metabolism, radical-induced lipid oxidation, the cytotoxicity of reactive oxygen species, and ischemia-induced vascular reoxygenation injury. Future work with this compound class should provide further insight into the mechanisms of NO's involvement in pro- and antioxidant processes, and may well lead to important medicinal advances, including reversal of cerebral vasospasm and radiosensitization of hypoxic tumors.     

Keratan sulfate suppresses cartilage damage and ameliorates inflammation in an experimental mice arthritis model

Proteoglycans bearing keratan sulfate (KS), such as aggrecan, are components of the human cartilage extracellular matrix (ECM). However, the role of KS in influencing cartilage degradation associated with arthritis remains to be completely understood. KS side chains of the length found in human cartilage are not found in murine skeletal tissues. Using a murine model of inflammatory polyarthritis and cartilage explants exposed to interleukin-1α (IL-1α), we examined whether administering KS could influence intraarticular inflammation and cartilage degradation. Acute arthritis was induced by intravenous administration of an anti-type II collagen antibody cocktail, followed by an intraperitoneal injection of lipopolysaccharide. This treatment was followed by an intraperitoneal KS administration in half of the total mice to evaluate the therapeutic potential of KS for ameliorating arthritis. To investigate the therapeutic potential ex vivo, we examined cartilage fragility by measuring IL-1α-induced aggrecan release from cartilage explants treated with or without KS. Intraperitoneal KS administration ameliorated arthritis in DBA/1J mice. The aggrecan release induced by IL-1α was less in cartilage explants containing media with KS than in those without KS. Our data indicate that exogenous KS ameliorated arthritis in vivo and suppressed cartilage degradation ex vivo. KS may have important therapeutic potential in the treatment of inflammatory arthritis. The mechanism responsible for this requires further investigation, but KS may become a novel therapeutic agent for treating inflammatory diseases such as rheumatoid arthritis.     

Is there NO help for leptin?

Since the initial identification of leptin as the product of the ob gene in 1994, the signaling pathways by which this hormone alters cell physiology have been the subject of extensive investigations. The fact that leptin can induce nitric oxide (NO) production was first demonstrated in studies of the pituitary gland and pancreatic islets. A large number of additional studies further showed that this adipokine stimulates NO synthesis in multiple tissues. This review article discusses the role of leptin in NO production and its pathophysiological consequences. The role of this gaseous messenger in cell physiology depends on the cell type, the concentration of NO and the duration of exposure. It can be either a potent oxidant or a protector of cell integrity against the formation of reactive oxygen species. Leptin plays two opposing roles on arterial pressure. It exerts a hypertensive effect due to sympathetic activation and a vasorelaxant effect due to NO production. This adipokine acts via NO to produce pro-inflammatory factors in cartilage pathology, potentially contributing to an increased risk for osteoarthritis. Another well-documented role of leptin-induced NO, acting either directly or via the hypothalamus, concerns lipid metabolism in muscle and adipose tissue. In adipocytes, the direct and rapid action of leptin is to activate the nitric oxide synthase III, which favors lipolysis. In contrast, in the long-term, leptin reduces lipolysis. However, both in the short-term and in the long-term, glyceroneogenesis and its key enzyme, the cytosolic phosphoenolpyruvatecarboxykinase (PEPCK-C), are down-regulated by the adipokine, thus favoring fatty acid release. Hence, leptin-induced NO production plays a crucial role in fatty acid metabolism in adipose tissue. The resulting effects are to prevent lipid storage and to improve energy expenditure, with possible improvements of the obese state and its associated diseases.     

Pathways by which interleukin 17 induces articular cartilage breakdown in vitro and in vivo.

Overexpression of interleukin (IL-)17 has recently been shown to be associated with a number of pathological conditions. Because IL-17 is found at high levels in the synovial fluid surrounding cartilage in patients with inflammatory arthritis, the present study determined the direct effect of IL-17 on articular cartilage. As shown herein, IL-17 was a direct and potent inducer of matrix breakdown and an inhibitor of matrix synthesis in articular cartilage explants. These effects were mediated in part by leukemia inhibitory factor (LIF), but did not depend on interleukin-1 activity. The mechanism whereby IL-17 induced matrix breakdown in cartilage tissue appeared to be due to stimulation of activity of aggrecanase(s), not matrix metalloproteinase(s). However, IL-17 upregulated expression of matrix metalloproteinase(s) in chondrocytes cultured in monolayer. In vivo, IL-17 induced a phenotype similar to inflammatory arthritis when injected into the intra-articular space of mouse knee joints. Furthermore, a related protein, IL-17E, was found to have catabolic activity on human articular cartilage. This study characterizes the mechanism whereby IL-17 acts directly on cartilage matrix turnover. Such findings have important implications for the treatment of degenerative joint diseases such as arthritis.     

Intra-articular injection of recombinant TRAIL induces synovial apoptosis and reduces inflammation in a rabbit knee model of arthritis

We demonstrated previously that local, intra-articular injection of an adenoviral vector expressing human tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) in a rabbit knee model of inflammatory arthritis stimulated synovial apoptosis and reduced inflammation. To examine whether intra-articular injection of recombinant chimeric human TRAIL protein (rTRAIL) also induces apoptosis of proliferating rabbit synovium and reduces inflammation, we used an experimental rabbit arthritis model of rheumatoid arthritis, induced by intra-articular introduction of allogeneic fibroblasts genetically engineered to secrete human IL-1β. Analysis of synovium isolated from the rabbits treated with intra-articular injection of rTRAIL, relative to saline control, showed areas of extensive acellular debris and large fibrous regions devoid of intact cells, similar to adenoviral mediated TRAIL gene transfer. Extensive apoptosis of the synovial lining was demonstrated using TUNEL analysis of the sections, corresponding to the microscopic findings in hematoxylin and eosin staining. In addition, leukocyte infiltration into the synovial fluid of the inflamed knee joints following rTRAIL treatment was reduced more than 50% compared with the saline control. Analysis of the glycosaminoglycan synthetic rate by cultured cartilage using radiolabeled sulfur and cartilage histology demonstrated that rTRAIL did not adversely affect cartilage metabolism and structure. Analysis of serum alanine aminotransferase showed that intra-articular injection of rTRAIL did not have adverse effects on hepatic function. These results demonstrate that intra-articular injection of rTRAIL could be therapeutic for treating pathologies associated with rheumatoid arthritis.     

Efficacy of treatment with glycosaminoglycans on experimental collagen-induced arthritis in rats

To evaluate the antioxidant activity of the glycosaminoglycans hyaluronic acid (HYA) and chondroitin-4-sulphate (C4S), we used a rat model of collagen-induced arthritis (CIA). Arthritis was induced in Lewis rats by multiple intradermal injections of 250 μl of emulsion containing bovine type II collagen in complete Freund's adjuvant at the base of the tail and into three to five other sites on the back. Rats were challenged again with the same antigen preparation 7 days later. Disease developed about 11 days after the second immunization. The effects of treatment in the rats were monitored by biochemical parameters and by macroscopic and histological evaluations in blood, synovial tissue and articular cartilage. Arthritis produced the following symptoms: severe periarticular erythema, edema and inflammation in the hindpaws; membrane peroxidation in the cartilage of the joints; endogenous antioxidant wasting; high tumour necrosis factor-α (TNF-α) plasma levels; and synovial neutrophil accumulation. Treatment with HYA and C4S, starting at the onset of arthritis for 10 days, limited the erosive action of the disease in the articular joints of knee and paw, reduced lipid peroxidation, restored the endogenous antioxidants reduced glutathione (GSH) and superoxide dismutase, decreased plasma TNF-α levels, and limited synovial neutrophil infiltration. These data confirm that erosive destruction of the joint cartilage in CIA is due at least in part to free radicals released by activated neutrophils and produced by other biochemical pathways. The beneficial effects obtained with the treatment suggest that HYA and C4S could be considered natural endogenous macromolecules to limit erosive damage in CIA or as a useful tool with which to study the involvement of free radicals in rheumatoid arthritis.     

(Auto)immunity to cartilage matrix proteins - a time bomb?

Geng and colleagues consolidate and detail the role of cartilage oligomeric matrix protein (COMP) as a (potential) autoantigen in experimental and human arthritis, a finding also supported by the detection of COMP fragments and anti-COMP antibodies in rheumatoid arthritis serum and/or synovial fluid and by synovial B-cell responses against COMP. The reactivity to COMP is yet another example of how, in addition to collagen II and the large aggregating proteoglycan, cartilage-specific proteins can induce arthritis and contribute to autoimmunity. Progression of cartilage damage and degradation in disease is believed to promote the autoimmune reaction to cartilage components. However, Geng and colleagues show that anti-COMP mAbs bind in vivo to undamaged cartilage, as previously also observed for anti-collagen II antibodies. Whether this autoimmunity also involves modifications of cartilage matrix proteins, such as citrullination, remains to be further investigated. Latent, subpathogenic (auto)immune reactions directed against cartilage matrix proteins may thus eventually contribute to the outbreak of human arthritis.     

The Peculiar Facets of Nitric Oxide as a Cellular Messenger: From Disease-Associated Signaling to the Regulation of Brain Bioenergetics and Neurovascular Coupling

In this review, we address the regulatory and toxic role of ^·NO along several pathways, from the gut to the brain. Initially, we address the role on ^·NO in the regulation of mitochondrial respiration with emphasis on the possible contribution to Parkinson’s disease via mechanisms that involve its interaction with a major dopamine metabolite, DOPAC. In parallel with initial discoveries of the inhibition of mitochondrial respiration by ^·NO, it became clear the potential for toxic ^·NO-mediated mechanisms involving the production of more reactive species and the post-translational modification of mitochondrial proteins. Accordingly, we have proposed a novel mechanism potentially leading to dopaminergic cell death, providing evidence that NO synergistically interact with DOPAC in promoting cell death via mechanisms that involve GSH depletion. The modulatory role of NO will be then briefly discussed as a master regulator on brain energy metabolism. The energy metabolism in the brain is central to the understanding of brain function and disease. The core role of ^·NO in the regulation of brain metabolism and vascular responses is further substantiated by discussing its role as a mediator of neurovascular coupling, the increase in local microvessels blood flow in response to spatially restricted increase of neuronal activity. The many facets of NO as intracellular and intercellular messenger, conveying information associated with its spatial and temporal concentration dynamics, involve not only the discussion of its reactions and potential targets on a defined biological environment but also the regulation of its synthesis by the family of nitric oxide synthases. More recently, a novel pathway, out of control of NOS, has been the subject of a great deal of controversy, the nitrate:nitrite:NO pathway, adding new perspectives to ^·NO biology. Thus, finally, this novel pathway will be addressed in connection with nitrate consumption in the diet and the beneficial effects of protein nitration by reactive nitrogen species.

     

Interleukin-34 as a promising clinical biomarker and therapeutic target for inflammatory arthritis

Interleukin-34 (IL-34), recently identified as a novel inflammatory cytokine and the second ligand for colony-stimulating factor-1 receptor, is known to play regulatory roles in the development, maintenance, and function of mononuclear phagocyte lineage cells – especially osteoclasts. Regarding its primary effect on osteoclasts, IL-34 has been shown to stimulate formation and activation of osteoclasts, which in turn magnifies osteoclasts-resorbing activity. In addition to its role in osteoclastogenesis, IL-34 has been implicated in inflammation of synovium via augmenting production of inflammatory mediators, in which altered IL-34 expression is regulated by pro-inflammatory cytokines responsible for cartilage degradation. Indeed, IL-34 has been documented to be highly expressed in inflamed synovium of rheumatoid arthritis (RA) and knee osteoarthritis (OA) patients, which are recognized as inflammatory arthritis. Furthermore, a number of clinical studies demonstrated that IL-34 levels were significantly increased in the circulation and synovial fluid of patients with RA and knee OA. Its levels were also found to be positively associated with disease severity – especially radiographic severity of both RA and knee OA patients. Interestingly, emerging evidence has accumulated that functional blockage of IL-34 with specific antibody can alleviate the severity of inflammatory arthritis. It is therefore reasonable to speculate that IL-34 may be developed as a potential biomarker and a new therapeutic candidate for inflammatory arthritis. To date, there are numerous studies showing IL-34 involvement and association with many aspects of inflammatory arthritis. Herein, this review aimed to summarize the recent findings regarding regulatory role of IL-34 in synovial inflammation-mediated cartilage destruction and update the current comprehensive knowledge on usefulness of IL-34-based treatment in inflammatory arthritis – particularly RA and knee OA.     

Effects of interleukin-6 on proliferation and proteoglycan metabolism in articular chondrocyte cultures.

Interleukin-6 (IL-6) levels are markedly increased in the synovial fluid of patients with rheumatoid arthritis or osteoarthritis. However, the effects of IL-6 on proliferation and proteoglycan metabolism in articular cartilage are not known. We demonstrated here the effects of human recombinant (hr) IL-6 on proliferation and proteoglycan metabolism in rabbit articular chondrocyte cultures. In vitro, these cells proliferated and produced abundant extracellular matrices. We found that 1-10 ng/ml of hrIL-6 inhibited proliferation to approximately 65% of control levels and suppressed colony formation induced by bFGF in soft agarose. The same concentration of hrIL-6 depressed proteoglycan synthesis to approximately 60% of control levels. Moreover, hrIL-6 significantly enhanced proteoglycan degradation induced by hrIL-1beta, although hrIL-6 alone did not affect proteoglycan degradation. These findings suggest that IL-6 is a negative regulator for chondrocyte proliferation and articular cartilage metabolism.     

Characterization of zymosan-induced arthritis in the rat: Effects on joint inflammation and cartilage metabolism

A single intra-articular (ia) injection of 2 mg zymosan on D0 led to the production of acute periarticular edema followed by subacute erosive synovitis. The development of the zymosan-induced arthritis was associated with an initial loss of running activity and with an initial decrease of proteoglycan synthesis. Febrile response was present only on D1. In addition, on D20 synovial pannus led to a marked depletion of the proteoglycan content in the articular cartilage. When injected ia, IL1β (1 μg) provoked similar fever and similar changes in cartilage anabolism, but did not affect cartilage proteoglycan content (D20). These results suggest that zymosan-induced synovitis in the rat combines early prostaglandin-dependent processes (edema, pain, fever) with IL1-related effects on cartilage metabolism, thus allowing evaluation of chondroprotective drugs.