Effects of aspirin-like drugs on nitric oxide synthesis in rat vascular smooth muscle cells

The purpose of this study was to investigate the effects of aspirin-like drugs on nitric oxide (NO) synthesis in rat vascular smooth muscle cells (VSMCs). We measured the accumulation of nitrite, a stable oxidation product of NO, and the expression of inducible NO synthase (iNOS) mRNA and protein in rat cultured VSMCs. Sodium salicylate, aspirin, and indomethacin dose-dependently enhanced nitrite production by interleukin (IL)-1 beta-stimulated VSMCs at therapeutic plasma concentration ranges. Increased nitrite production by aspirin-like drugs was accompanied by increased iNOS mRNA and protein accumulation in VSMCs. Addition of IL-1 beta activated nuclear factor kappa B (NF-kappa B) in VSMCs, but sodium salicylate did not affect IL-1 beta-induced NF-kappa B activation. The nonselective lipoxygenase (LO) inhibitor nordihydroguaiaretic acid inhibited sodium salicylate-induced nitrite production, whereas the selective 5-LO inhibitor caffeic acid did not influence production of nitrite. The 12-LO product 12-HETE dose-dependently enhanced nitrite production by IL-1 beta-stimulated VSMCs, whereas the 15-LO product 15-HETE did not. Our study demonstrates that aspirin and the aspirin-like drugs, sodium salicylate and indomethacin, increase NO synthesis in IL-1 beta-stimulated VSMCs by upregulation of iNOS transcription via a 12-LO pathway. These effects were independent of NF-kappa B activation. In addition to the direct inhibition of platelet function, aspirin-like drugs may contribute to the reduction of atherothrombotic risk in myocardial ischemia via enhancing NO production by VSMCs.