p107 and p130 Coordinately regulate proliferation, Cbfa1 expression, and hypertrophic differentiation during endochondral bone development.
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During endochondral bone development, both the chondrogenic differentiation of mesenchyme and the hypertrophic differentiation of chondrocytes coincide with the proliferative arrest of the differentiating cells. However, the mechanisms by which differentiation is coordinated with cell cycle withdrawal, and the importance of this coordination for skeletal development, have not been defined. Through analysis of mice lacking the pRB-related p107 and p130 proteins, we found that p107 was required in prechondrogenic condensations for cell cycle withdrawal and for quantitatively normal alpha1(II) collagen expression. Remarkably, the p107-dependent proliferative arrest of mesenchymal cells was not needed for qualitative changes that are associated with chondrogenic differentiation, including production of Alcian blue-staining matrix and expression of the collagen IIB isoform. In chondrocytes, both p107 and p130 contributed to cell cycle exit, and p107 and p130 loss was accompanied by deregulated proliferation, reduced expression of Cbfa1, and reduced expression of Cbfa1-dependent genes that are associated with hypertrophic differentiation. Moreover, Cbfa1 was detected, and hypertrophic differentiation occurred, only in chondrocytes that had undergone or were undergoing a proliferative arrest. The results suggest that Cbfa1 links a p107- and p130-mediated cell cycle arrest to chondrocyte terminal differentiation. (+info)
Predominant selection of T cells specific for the glycosylated collagen type II epitope (263-270) in humanized transgenic mice and in rheumatoid arthritis.
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Rheumatoid arthritis (RA) is associated with certain MHC class II alleles and is characterized by a chronic autoimmune response in the joints. Using transgenic mice expressing human DR4 (DRB1*0401) and human CD4, but lacking endogenous MHC class II, we show that posttranslational glycosylation of type II collagen (CII) influences the level of T cell tolerance to this candidate cartilage-specific autoantigen. In such mice, the expression of human CII resulted in a tolerized murine T cell response to human CII. However, tolerance induction remained incomplete, preferentially deleting responses to the nonmodified CII 263-270 epitope, whereas T cell recognition of a glycosylated variant of this epitope was affected to a lesser degree. A similar dominance of T cell responses to CII-glycopeptides was recorded in a cohort of severely affected RA-patients (n = 14). Thus, RA T cells predominantly recognize the immunodominant CII peptide in its glycosylated form and may explain why previously it has been difficult to detect T cell responses to CII in RA patients. (+info)
Regional quantification of cartilage type II collagen and aggrecan messenger RNA in joints with early experimental osteoarthritis.
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OBJECTIVE: Accurate assessment of chondrocyte metabolism is a potentially valuable indicator of cartilage health in osteoarthritis (OA). This study was conducted to explore the anabolic metabolism of chondrocytes early in the natural history of an experimental canine model of OA. METHODS: Competitive reverse transcription-polymerase chain reaction was used to calculate the copy number of type II collagen and the messenger RNA (mRNA) levels of aggrecan core protein in articular cartilage samples obtained from different regions of the femorotibial joint 12 and 39 weeks after cruciate transection. RESULTS: Gene expression of both type II collagen and aggrecan in cartilage samples obtained from experimental joints at both intervals after surgery was elevated significantly compared with that in samples from contralateral control joints. The number of mRNA copies per microgram of DNA of aggrecan exceeded that of type II collagen in control cartilage, but the copy number of type II collagen mRNA exceeded that of aggrecan in OA cartilage. Thus, the ratio of type II collagen-to-aggrecan mRNA copy number (normalized to DNA) was shown to be characteristically altered in cartilage with experimental OA. CONCLUSION: Accurate assessment of multiple gene products in small samples of cartilage taken from focal areas of a joint can be used diagnostically for monitoring chondrocyte metabolism and possibly for staging at least the early phases of this joint disease. (+info)
Pathologic indicators of degradation and inflammation in human osteoarthritic cartilage are abrogated by exposure to n-3 fatty acids.
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OBJECTIVE: To determine if n-3 polyunsaturated fatty acid (PUFA) supplementation (versus treatment with n-6 polyunsaturated or other fatty acid supplements) affects the metabolism of osteoarthritic (OA) cartilage. METHODS: The metabolic profile of human OA cartilage was determined at the time of harvest and after 24-hour exposure to n-3 PUFAs or other classes of fatty acids, followed by explant culture for 4 days in the presence or absence of interleukin-1 (IL-1). Parameters measured were glycosaminoglycan release, aggrecanase and matrix metalloproteinase (MMP) activity, and the levels of expression of messenger RNA (mRNA) for mediators of inflammation, aggrecanases, MMPs, and their natural tissue inhibitors (tissue inhibitors of metalloproteinases [TIMPs]). RESULTS: Supplementation with n-3 PUFA (but not other fatty acids) reduced, in a dose-dependent manner, the endogenous and IL-1-induced release of proteoglycan metabolites from articular cartilage explants and specifically abolished endogenous aggrecanase and collagenase proteolytic activity. Similarly, expression of mRNA for ADAMTS-4, MMP-13, and MMP-3 (but not TIMP-1, -2, or -3) was also specifically abolished with n-3 PUFA supplementation. In addition, n-3 PUFA supplementation abolished the expression of mRNA for mediators of inflammation (cyclooxygenase 2, 5-lipoxygenase, 5-lipoxygenase-activating protein, tumor necrosis factor alpha, IL-1alpha, and IL-1beta) without affecting the expression of message for several other proteins involved in normal tissue homeostasis. CONCLUSION: These studies show that the pathologic indicators manifested in human OA cartilage can be significantly altered by exposure of the cartilage to n-3 PUFA, but not to other classes of fatty acids. (+info)
Suppression of tumor necrosis factor alpha-induced matrix metalloproteinase 9 production in human salivary gland acinar cells by cepharanthine occurs via down-regulation of nuclear factor kappaB: a possible therapeutic agent for preventing the destruction of the acinar structure in the salivary glands of Sjogren's syndrome patients.
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OBJECTIVE: Our previous results suggested that suppression of tumor necrosis factor alpha (TNFalpha)-induced matrix metalloproteinase 9 (MMP-9) could prevent the destruction of acinar tissue in the salivary glands of patients with Sjogren's syndrome (SS). The present study was undertaken to investigate the effect of cepharanthine on the suppression of TNFalpha-induced MMP-9 production in NS-SV-AC, an SV40-immortalized normal human acinar cell clone. METHODS: After pretreatment with or without cepharanthine, NS-SV-AC cells were treated with TNFalpha alone or with a combination of TNFalpha and cepharanthine. The expression of MMP-9 was then examined at the protein and messenger RNA levels. In addition, the effect of cepharanthine on the morphogenetic behavior of NS-SV-AC cells cultured on type IV collagen-coated dishes in the presence of TNFalpha was examined. RESULTS: Although TNFalpha induced the production of MMP-9 in NS-SV-AC cells, this production was greatly suppressed when cells were pretreated with cepharanthine, followed by treatment with both TNFalpha and cepharanthine. In addition, cepharanthine suppressed the TNFalpha-stimulated NF-kappaB activity by partly preventing the degradation of IkappaBalpha protein in NS-SV-AC cells. When NS-SV-AC cells were seeded on type IV collagen-coated dishes in the presence of both TNFalpha and plasmin, type IV collagen interaction with the cells was lost and the cells entered apoptosis. However, pretreatment with cepharanthine restored the aberrant in vitro morphogenesis of the NS-SV-AC cells. CONCLUSION: These results may indicate a molecular mechanism by which cepharanthine is able to protect against the destruction of the acinar structure in salivary glands from patients with SS. (+info)
Interleukin 17 induces cartilage collagen breakdown: novel synergistic effects in combination with proinflammatory cytokines.
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OBJECTIVE: To investigate whether interleukin 17 (IL17), derived specifically from T cells, can promote type II collagen release from cartilage. The ability of IL17 to synergise with other proinflammatory mediators to induce collagen release from cartilage, and what effect anti-inflammatory agents had on this process, was also assessed. METHODS: IL17 alone, or in combination with IL1, IL6, oncostatin M (OSM), or tumour necrosis factor alpha (TNFalpha), was added to bovine nasal cartilage explant cultures. Proteoglycan and collagen release were determined. Collagenolytic activity was determined by bioassay. Chondroprotective effects of IL4, IL13, transforming growth factor beta1 (TGFbeta1) and insulin-like growth factor-1 (IGF1) were assessed by inclusion in the explant cultures. RESULTS: IL17 alone stimulated a dose dependent release of proteoglycan and type II collagen from bovine nasal cartilage explants. Suboptimal doses of IL17 synergised potently with TNFalpha, IL1, OSM, and IL6 to promote collagen degradation. This collagen release was completely inhibited by tissue inhibitor of metalloproteinase-1 and BB-94 (a synthetic metalloproteinase inhibitor), and was significantly reduced by IL4, IL13, TGFbeta1, and IGF1. In IL17 treated chondrocytes, mRNA expression for matrix metalloproteinase (MMP)-1, MMP-3, and MMP-13 was detected. Moreover, a synergistic induction of these MMPs was seen when IL17 was combined with other proinflammatory cytokines. CONCLUSIONS: IL17 can, alone and synergistically in combination with other proinflammatory cytokines, promote chondrocyte mediated MMP dependent type II collagen release from cartilage. Because levels of all these proinflammatory cytokines are raised in rheumatoid synovial fluids, this study suggests that IL17 may act as a potent upstream mediator of cartilage collagen breakdown in inflammatory joint diseases. (+info)
The importance of IL-1 beta and TNF-alpha, and the noninvolvement of IL-6, in the development of monoclonal antibody-induced arthritis.
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Injection of anti-type II collagen Ab and LPS induces arthritis in mice. The levels of IL-1 beta, IL-6, and chemokines (macrophage inflammatory protein (MIP)-1 alpha, MIP-2, and monocyte chemoattractant protein-1) in the hind paws increased with the onset of arthritis and correlated highly with arthritis scores. The level of TNF-alpha was also elevated, but only transiently. Quantitative real-time PCR analysis revealed increases in cytokine and chemokine mRNA. To elucidate the contribution of inflammatory cytokines and chemokines in arthritis development more directly, recombinant proteins, neutralizing Abs, and knockout mice were used. The injection of rIL-1 beta or TNF-alpha, but not IL-6 or chemokines, induced arthritis when mice were i.v. preinjected with anti-type II collagen Ab. However, a single injection of recombinant cytokines or chemokines into the hind paws did not induce swelling. Arthritis development was inhibited by neutralizing Ab against IL-1 beta, TNF-alpha, or MIP-1 alpha. In contrast, the inhibitory effect by anti-MIP-2 Ab was partial and, surprisingly, Abs to IL-6 and monocyte chemoattractant protein-1 showed no inhibitory effect. Furthermore, arthritis development in IL-1R(-/-) mice and TNFR(-/-) mice was not observed at all, but severe arthritis was developed in IL-6(-/-) mice. These results suggest that IL-1 beta and TNF-alpha play more crucial roles than IL-6 or chemokines in this model. Because arthritis was also developed in SCID mice, the development of arthritis in the Ab-induced mice model is due to a mechanism that does not involve T or B cells. (+info)
Continuous nasal administration of antigen is critical to maintain tolerance in adoptively transferred autoimmune arthritis in SCID mice.
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Mucosal tolerance is a natural mechanism that prevents immunological reactions to antigens by altering the activity of immune cells of pathogenic clones without modulating the entire immune system. This 'natural immune suppression' can be exploited when antigen(s) of the target organ in an autoimmune disease is used for mucosal treatment. Being inspired by the experimental results in animal models, clinical trials using type II collagen for mucosal treatment have been conducted in rheumatoid arthritis. High-density proteoglycan (aggrecan) is another major macromolecular component in articular cartilage, and may be a candidate autoantigen for provoking immune reactions in patients with rheumatoid arthritis. Indeed, like type II collagen, systemic immunization of genetically susceptible mice with proteoglycan (PG) aggrecan induces progressive autoimmune polyarthritis. Here, we investigated whether intranasally applied PG can be effective in suppressing PG-induced arthritis (PGIA) in BALB/c mice. We found that nasal administration of 100 microg PG exerted a strong suppressive effect on both the incidence and severity of the disease, most probably by reducing responsiveness towards the immunizing PG antigen. When we transferred PGIA into genetically matched but immunodeficient SCID mice, we were able to establish a tolerized state, but only if the recipient SCID mice received lymphocytes from tolerized animals and intranasal treatment with PG was continued. Without nasally administered antigen, the transferred anergic cells recovered and arthritis rapidly developed in a severe form. Intranasal PG treatment of recipient SCID mice was ineffective when cells from non-tolerized arthritic donors were transferred, in which case the regular weekly 'tolerizing' dose of PG made the disease worse. Our results suggest that mucosal treatment in an already existing disease may result in paradoxical outcomes. (+info)