Abstract

Our previous studies have shown that rat pulmonary microvascular smooth muscle cells (RPMSMC) upregulate inducible nitric oxide synthase (iNOS) and produce nitric oxide (NO) when treated with interleukin-1 beta (IL-1 beta). We now report that an additional effect of IL-1 beta stimulation in RPMSMC is an increase in production of superoxide (O2-) that results in the formation of peroxynitrite (ONOO-). IL-1 beta produced a rapid (within 1 h) concentration-dependent increase in O2-, as detected by ferricytochrome c reduction and lucigenin-enhanced chemiluminescence. O2- production was sensitive to quinacrine and diphenyliodinium, suggesting that NADH and NADPH oxidoreductases were responsible. After induction of iNOS and production of iNOS-derived NO, ONOO- was detected by luminol-enhanced chemiluminescence and was found to cause lipid peroxidation and to form nitrotyrosine in the cytoskeleton, detected by immunostaining. Cell viability, however, appeared to be unaffected. IL-1 beta-mediated induction of RPMSMC-derived ONOO- may have significant effects on pulmonary vascular function in sepsis and inflammatory states.