REGULATION OF COLLAGENASE 3 GENE EXPRESSION BY CYTOKINES

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The overall goal of this proposal is to study the cytokine-mediated regulation of collagenase-3 gene expression in order to better understand the mechanisms involved in the degradation of articular cartilage in rheumatic diseases such as rheumatoid arthritis (RA) and osteoarthritis ( OA). OA is the most common form of joint disease and is second only to cardiovascular disease as a cause of early retirement and disability. The destruction of hyaline articular cartilage is the hallmark of OA and disabling RA. Although various therapeutic regiment can cause symptom relief, no regiment has been proven to retard progression of articular cartilage degradation. In disease there is either a suppression of normal chondrocyte functions or in the constitutive inability of these cells to match the rate of repair with the increased rate of degradation of the matrix. Various cytokines and inflammatory mediators have been shown to either derange the synthetic functions of the chondrocytes of increase cartilage matrix catabolism by regulating various matrix-degrading enzymes, including the collagenases. Collagenase-3 is specifically expressed in skeletal cells including chondrocytes and has been shown to have an additional cleavage site when compared to other collagenases. It has aggrecanase and gelatinase activity as well. It's expression is response to IL-1 and other inflammatory cytokines. Thus it may play a significant role in physiological skeletal remodeling and destruction of cartilage in disease. The collagenase-3 gene has been recently cloned, but the role of various cytokines in the transcriptional regulation of this gene is yet to be elucidated. We have cloned the collagenase-3 promoter from a human genomic DNA library. We will prepare reporter gene constructs (CAT) containing collagenase-3 promoter and transfect immortalized human cell lines and analyze the effects of selected cytokines/ligands e.g. IL- 1beta, TNF-alpha and TGF1-beta. The cis-elements and trans-acting factors will also be characterized employing transfection and DNA-binding assays. We will also develop transgenic mice containing the collagenase promoter- beta-galactosidase fusion gene to analyze the expression and role of collagenase in development of arthritis in vivo. Transgenic mice will be treated with IL-1ra, TNFR1-IgG1 fusion protein, and dexamethasone after induction of arthritis and the role of cytokines/ligands in the control of expression of collagenase and its role in development of arthritis will be elucidated. This proposal will provide insight into the mechanisms involved in the expression of collagenase-3 by cytokines and thereby may provide targets for developing novel therapeutic measures to inhibit cartilage destruction in joint disease.