Atorvastatin-induced cardioprotection is mediated by increasing inducible nitric oxide synthase and consequent S- nitrosylation of cycloxygenase-2

Objectives: We determined the effects of cycloxygenase-1 (COX1)(Sc560), COX2 (Sc58125) and inducible nitric oxide synthase (iNOS)(1400w) inhibitors on atorvastatin (ATV)-induced myocardial protection and whether iNOS mediates the ATV-induced increases in COX2. Methods: Sprague-Dawley rats received ATV 10 mg/kg/d added to the drinking water or water alone for 3 days. Rats received IV Sc58125, Sc560, 1400W or vehicle alone. Anesthesia was induced with ketamine and xylazine and maintained with isofluorane. Fifteen minutes after IV injection rats underwent 30min myocardial ischemia followed by 4h reperfusion [infarct size (IS) protocol], or the hearts were explanted for biochemical analysis and immunoblotting. Results: Left ventricular weight and the area at risk were comparable among groups. ATV reduced IS to 12.7% (SD 3.1%) of AR, a reduction of 64% vs. 35.1% (SD 7.6) in the sham-treated group, P<0.001). Sc58125 and 1400W attenuated the protective effect without affecting IS in the non-ATV treated rats. ATV increased calcium independent NOS (iNOS) (11.9 (SD 0.8) vs. 3.9 (SD 0.1) X 1000cpm; P<0.001) and COX2 (46.7 (SD 1.1) vs. 6.5 (SD 1.4) pg/ml of 6-keto-PGF1α; P<0.001) activity. Both Sc58125 and 1400W attenuated this increase. Sc58125 did not affect iNOS activity, whereas 1400W blocked iNOS activity. COX2 was S-nitrosylated in the ATV-treated but not in the sham-treated rats or rats pretreated with 1400W. COX2 immuno-precipitated with iNOS, but not with eNOS. Conclusions: ATV reduced IS by increasing the activity of iNOS and COX2. iNOS is upstream to COX2. iNOS activates COX2 by S-nitrosylation. These results are consistent with the hypothesis that preconditioning effects are mediated via prostaglandin.