Abstract 604: Atorvastatin Activates Cycloxygenase-2 in the Heart via S-Nitrosylation by Inducible Nitric Oxide Synthase
Background: Atorvastatin (AT) increases myocardial expression of phophorylated Ser-1777 endothelial nitric oxide synthase (P-eNOS), inducible NOS (iNOS) and Cycloxygenase-2 (COX2). Although AT increases the expression of COX2 in eNOS−/ − mice, there is no increase in COX2 activity as occurs in wild-type (WT) mice. In the rat, COX2 activation occurs by iNOS mediated S-nitrosylation.
Aim: To investigate whether the difference in COX2 activity between the AT-treated WT and eNOS−/ − is related to S-nitrosylation.
Methods: WT, eNOS−/ −, and iNOS−/ − mice received AT 10 mg/kg/d (AT+) or water alone (AT-) for 3 days. Hearts were harvested and subjected to ELISA and immunoblotting. Snitrosylation of COX2 was assessed by the “Biotin Switch” assay. To verify that the immunoprecipitates contained COX2, membranes were stripped and blots with anti-COX2 antibodies.
Results: COX2 expression in the AT- groups was very low. AT increased COX2 expression in WT (4,287±104%) and eNOS−/ − (4,354±101%), but not iNOS−/ − mice (101±3%). However, myocardial 6- keto-PGF1α levels (81.4±0.2 vs. 15.7±0.1 pg/ml; p<0.001) were increased by AT only in WT mice, but not in eNOS−/ − (16.5±0.1 vs. 15.6±0.1 pg/ml) or iNOS−/ − (15.9±0.2 vs. 15.3±0.1 pg/ml) mice. The “Biotin Switch” assay shows that COX2 was S-nitrosylated only in WT mice. Although eNOS is activated by AT in the iNOS−/ − mice, there is no S-nitrosylation and activation of COX2.
Conclusions: COX2 is activated by S-nitrosylation only in WT mice. Although iNOS is intact in eNOS−/ − mice, it is not activated and therefore, does not S-nitrosylate the AT-induced upregulated COX2.