Inhibition of inducible nitric oxide synthase expression by novel nonsteroidal anti-inflammatory derivatives with gastrointestinal-sparing properties

The effects of novel nitric oxide-releasing nonsteroidal anti-inflammatory compounds (NO-NSAIDs) on induction of nitric oxide (NO) synthase by bacterial lipopolysaccharide (LPS) were examined in a murine cultured macrophage cell line, J774. 2 LPS-induced nitrite production was markedly attenuated by the nitroxybutylester derivatives of flurbiprofen (FNBE), aspirin, ketoprofen, naproxen, diclofenac and ketorolac, with each compound reducing accumulated nitrite levels by >40% at the maximum concentrations (100 mu g mi)used. 3 Further examination revealed that nitrite production was inhibited in a concentration-dependent (1-100 mu g ml(-1)) manner by FNBE which at 100 mu g ml(-1) decreased LPS-stimulated levels by 63.3+/-8.6% (n=7). The parent compound flurbiprofen was relatively ineffective over the same concentration-range, inhibiting nitrite accumulation by 24+/-0.9% (n=3) at the maximum concentration used (100 mu g ml(-1)). 4 FNBE reduced LPS-induced nitrite production when added to cells up to 4 h after LPS. Thereafter, FNBE caused very little or no reduction in nitrite levels. Furthermore NO-NSAIDs (100 mu g ml(-1)) did not inhibit the metabolism of L-[H-3]-arginine to citrulline by NO synthase isolated from LPS-activated macrophages. 5 Western blot analysis demonstrated that NO synthase expression was markedly attenuated following co-incubation of J774 cell with LPS (1 mu g ml(-1) 24 h) and FNBE (100 mu g ml 24 h). Thus taken together, these findings indicate that NO-NSAIDs inhibit induction of NO synthase without directly affecting enzyme activity. 6 In conclusion our results indicate that NO-NSAIDs can inhibit the inducible L-arginine-NO pathway, and are capable of suppressing NO synthesis by inhibiting expression of NO synthase. The clinical implications of these findings remain to be established.