NO Inhibits Cytokine-Induced iNOS Expression and NF-κB Activation by Interfering With Phosphorylation and Degradation of IκB-α

Abstract—Nitric oxide (NO) is known to have antiatherogenic and anti-inflammatory properties, but its effects on the cytokine-induced nuclear factor-kappa B (NF-κB) activation pathway in relation to the regulation of inducible nitric oxide synthase (iNOS) gene in vascular smooth muscle cells (VSMCs) remain elusive. To elucidate the roles of NO in the regulation of cytokine-induced NF-κB activation and consequent iNOS gene expression, we studied the effects of NO donors [(±)-(E)-ethyl-2-[(E)-hydroxyamino]-5-nitro-3-hexeneamide (NOR3) and sodium nitroprusside] on interleukin (IL)-1β–induced NF-κB activation and IκB-α degradation and subsequent iNOS expression in rat VSMCs. Northern blot and Western blot analyses demonstrated that NO donors decreased IL-1β–induced iNOS mRNA and protein expression. Electrophoretic mobility shift assay using synthetic oligonucleotide corresponding to the downstream NF-κB site of rat iNOS promoter as a probe showed that NOR3 inhibited IL-1β–induced NF-κB activation and its nucl...