INDUCTION OF NITRIC-OXIDE SYNTHASE GENE BY INTERLEUKIN IN VASCULAR SMOOTH-MUSCLE CELLS

To elucidate whether cytokines induce nitric oxide synthase in vascular smooth muscle cells, we studied the effects of human recombinant interleukin-1beta on the synthesis and release of nitric oxide in cultured rat vascular smooth muscle cells by measurement of NO2-/NO3- levels. Furthermore, we performed Northern blot analysis using subcloned polymerase chain reaction products as probes for constitutive and inducible nitric oxide synthase. Interleukin-1beta dose dependently (1 to 20 ng/mL) stimulated NO2-/NO3-production as a function of time. Northern blotting demonstrated the interleukin-1beta-induced expression of messenger RNA for an inducible but not for the constitutive nitric oxide synthase after 3 hours. N(G)-Monomethyl L-arginine completely blocked the interleukin-1beta-induced NO2-/NO3- production, the effect of which was reversed by L-arginine but not by D-arginine. Dexamethasone inhibited the interleukin-1beta-induced NO2-/NO3- production in a dose-dependent manner (10(-9) to 10(-7) M) and the interleukin-1beta-inducible nitric oxide synthase messenger RNA levels. Neither a calmodulin inhibitor (W-7) nor a protein kinase C inhibitor (staurosporine) showed any effects on the induction of nitric oxide synthase transcripts or production of NO2-/NO3- stimulated by interleukin-1beta, whereas cycloheximide and actinomycin D completely inhibited the basal and stimulated NO2-/NO3- production. These data demonstrate for the first time that interleukin-1beta induces gene expression of inducible nitric oxide synthase and its de novo protein synthesis in rat vascular smooth muscle cells, thereby leading to generation of nitric oxide via Ca2+/calmodulin-independent and protein kinase C-independent mechanisms.