Inhibition of the expression of inducible nitric oxide synthase and cyclooxygenase-2 in macrophages by 7HQ derivatives: involvement of I kappa B-alpha stabilization

Nitric oxide is an important biological mediator associated with multiple p athophysiological phenomena, such as platelet aggregation, vasodilation, se ptic shock, and autoimmune diseases. Prostaglandins, derived from cyclooxyg enases, play prominent roles in homeostasis and inflammation. In this study , we characterized the effects of 7HQ derivatives (7-[(4-methylene-5-oxo-2- R-2-tetrahydrofuranyl)methoxy]-3,4-dihydrocarbostyril, where R is methyl, p henyl, p-fluorophenyl and p-phenylphenyl; 7HQ-1,-2,-3 and-if, respectively) in murine RAW 264.7 cells, a macrophage-like cell line. Lipopolysaccharide . the active component of endotoxin, significantly induced the expression o f inducible nitric oxide synthase and cyclooxygenase-2, leading to the accu mulation of nitrite and prostaglandin E-2, respectively. These actions of l ipopolysaccharide wen inhibited by 7HQ derivatives; additionally, the inhib ition of the expression, rather than the activity, of inducible nitric oxid e synthase correlated well with that of nitric oxide formation. Western blo tting and electrophoretic mobility shift assay results demonstrated that th e 7HQ derivatives could effectively inhibit I kappaB-alpha degradation and nuclear factor kappaB (NF-kappaB) translocation. At higher concentrations, 7HQ derivatives also inhibited cyclooxygenase-2 enzyme activity. These resu lts suggest that 7HQ derivatives exhibit inhibitory effects on lipopolysacc haride-induced nitric oxide production and expression of inducible nitric o xide synthase and cyclooxygenase-2 through inhibition of I kappaB-alpha deg radation and NF-kappaB activation. (C) 2001 Elsevier Science B.V. All right s reserved.