Statin treatment upregulates vascular neuronal nitric oxide synthase through Akt/NF-κB pathway

OBJECTIVE - Three-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors (statins) are known to enhance vascular expression of endothelial (eNOS) and inducible nitric oxide synthase (iNOS). In this study, we examined whether statins also upregulate vascular expression of neuronal NOS (nNOS). METHODS AND RESULTS - In cultured rat aortic smooth muscle cells, treatment with atorvastatin significantly increased nNOS expression, associated with activation of Akt and NF-κB. Inhibition of Akt by dominant-negative Akt suppressed atorvastatin-induced nNOS expression as well as Akt and NF-κB activation. Inhibition of NF-κB by dominant-negative IκB also attenuated atorvastatin-induced nNOS expression and NF-κB activation, but not Akt activation. We further examined whether atorvastatin also enhances nNOS expression in isolated mouse aorta, and if so, how much nNOS-derived NO accounts for atorvastatin-induced NOx production. In isolated aortas of wild-type mice, atorvastatin significantly increased all three NOS isoform expression and NOx production. In isolated aortas of doubly i/eNOS, n/eNOS, and n/iNOS mice, which express only nNOS, iNOS, and eNOS, respectively, atorvastatin-induced NOx production was approximately 25%, 25%, and 50% to that of wild-type mice, respectively, suggesting that nNOS accounts for 25% of the atorvastatin-mediated NOx production. CONCLUSIONS - These results indicate that atorvastatin upregulates vascular nNOS through Akt/NF-κB pathway, demonstrating a novel nNOS-mediated vascular effect of the statin.