SALICYLATE IS A TRANSCRIPTIONAL INHIBITOR OF THE INDUCIBLE NITRIC-OXIDE SYNTHASE IN CULTURED CARDIAC FIBROBLASTS

We have previously reported that salicylate inhibits the inducible NO synthase (NOS 2) in cytokine-induced cardiac fibroblasts (Farivar, R. S., Chobanian, A. V., and Brecher, P. (1996) Circ. Res. 78, 759-768). To define further the mechanism of inhibition of NOS 2 by salicylate, we investigated NOS 2 mRNA induction by cytokines and determined the k inetics of inhibition by salicylate as compared to dexamethasone. Inte rferon-gamma plus tumor necrosis factor-alpha induced NOS 2 mRNA syner gistically in a time- and dose-dependent manner. Both dexamethasone an d salicylate equally inhibited the induction of NOS 2 mRNA in a time a nd dose-dependent fashion, both before and after cytokine induction. S alicylate also inhibited interferon-gamma plus interleukin-1 beta-indu ced NOS 2 mRNA After 24 h of cytokine stimulation, salicylate stopped the induction of NOS 2 mRNG whereas dexamethasone delayed the accumula tion of transcript. In half-life experiments of NOS 2 mRNA, we found t hat dexamethasone reduced the half-life of NOS 2 mRNA from 7 to 4 h, w hereas salicylate had no effect on mRNA stability. Tumor necrosis fact or-alpha and interferon-gamma induced NF-kappa B (p50/p65) and STAT-1, respectively, as assessed by gel shift assays. Salicylate did not inh ibit the cytokine induction of NF-kappa B or STAT-1. This study sugges ts that the anti-inflammatory mechanism of salicylate involves inhibit ion of NOS 2 transcription and shows that the effect is independent of NF-kappa B activation.