Vol. 289, Issue 3, 1634-1640, June 1999

Induction of Stromelysin Gene Expression by Tumor Necrosis Factor  Is Inhibited by Dexamethasone, Salicylate, and N-Acetylcysteine in Synovial Fibroblasts¹

Isabelle Morin, Wen Qing Li, Suming Su, Mushtaq Ahmad and Muhammad Zafarullah

Louis-Charles Simard Research Centre, Centre Hospitalier de L'Université de Montréal Campus Notre-Dame, and Department of Medicine, University of Montreal, Montreal, Quebec, Canada (I.M., W.Q.L., S.S., M.Z.); and Department of Medicine, Division of Cardiology, Emory University School of Medicine, Atlanta, Georgia (M.A.)

Proinflammatory cytokines, altered connective tissue metabolism, and overexpression of matrix metalloproteinases (MMPs) such as stromelysin compared to tissue inhibitors of metalloproteinases (TIMPs) result in synovial inflammation and erosion of arthritic cartilage. Tumor necrosis factor  (TNF-) is a major synovial inflammatory mediator responsible for inhibiting extracellular matrix (ECM) synthesis and stimulating degradation of cartilage ECM by activated MMPs in arthritic joints. To suppress these effects and to gain insight into the mechanism of TNF- action, we identified the inhibitors of TNF- stimulation of stromelysin gene expression. In bovine synovial fibroblasts, TNF- did not affect a recently identified inhibitor, TIMP-3, but induced stromelysin mRNA expression in a dose- and time-dependent fashion (3- to 5-fold) which required de novo protein synthesis. Stimulation by TNF- was potently inhibited (99-100%) by the synthetic glucocorticoid, dexamethasone. Sodium salicylate dose-dependently inhibited (100%) the TNF- action. Indomethacin and ibuprofen were partially inhibitory. Free radical scavenger antioxidant, N-acetylcysteine (but not other antioxidants) also suppressed the TNF- induction (36-100%) of stromelysin suggesting involvement of reactive oxygen species in the induction process. TNF- induction of stromelysin gene expression can therefore be inhibited at the gene expression level by several pharmacological agents which are likely to function via arachidonic acid metabolites, free radical scavenging or interference with the activator protein 1, polyoma virus enhancer A-binding protein 3, and nuclear factor B classes of transcription factors. Our results may help to elucidate the mechanism of TNF- action and explain the beneficial role of these agents in the treatment of inflammatory diseases.