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

Abstract

We determined the effects of cyclooxygenase-1 (COX-1; SC-560), COX-2 (SC-58125), and inducible nitric oxide synthase (iNOS; 1400W) inhibitors on atorvastatin (ATV)-induced myocardial protection and whether iNOS mediates the ATV-induced increases in COX-2. Sprague-Dawley rats received 10 mg ATV.kg(-1).day(-1) added to drinking water or water alone for 3 days and received intravenous SC-58125, SC-560, 1400W, or vehicle alone. Anesthesia was induced with ketamine and xylazine and maintained with isoflurane. Fifteen minutes after intravenous injection rats underwent 30-min myocardial ischemia followed by 4-h reperfusion [infarct size (IS) protocol], or the hearts were explanted for biochemical analysis and immunoblotting. Left ventricular weight and area at risk (AR) 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). SC-58125 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 1,000 counts/min; P < 0.001] and COX-2 [46.7 (SD 1.1) vs. 6.5 (SD 1.4) pg/ml of 6-keto-PGF(1alpha); P < 0.001] activity. Both SC-58125 and 1400W attenuated this increase. SC-58125 did not affect iNOS activity, whereas 1400W blocked iNOS activity. COX-2 was S-nitrosylated in ATV-treated but not sham-treated rats or rats pretreated with 1400W. COX-2 immunoprecipitated with iNOS but not with endothelial nitric oxide synthase. We conclude that ATV reduced IS by increasing the activity of iNOS and COX-2, iNOS is upstream to COX-2, and iNOS activates COX-2 by S-nitrosylation. These results are consistent with the hypothesis that preconditioning effects are mediated via PG.

Pioglitazone protects the myocardium against ischemia-reperfusion injury in eNOS and iNOS knockout mice

“…Subcutaneous 0.1 mg/kg buprenorphine was administered, the chest was closed, and the mice were recovered from anesthesia. Four hours after reperfusion, the mice were reanesthetized, the coronary artery was reoccluded, Evans blue dye (3%) was injected into the right ventricle, and the mice were euthanized under deep anesthesia (2,7,54,69).…”

“…Scalia et al (49) has shown that simvastatin does not limit IS in iNOS Ϫ/Ϫ mice. Our laboratory showed that 1400W, a specific iNOS inhibitor, abrogated the IS-limiting effects of atorvastatin in the rat without affecting eNOS (2) and, more recently, that atorvastatin failed to decrease IS in iNOS Ϫ/Ϫ mice (71). The cardioprotection by preconditioning diminishes with age (17,20,30), hypertension (17,20), diabetes (20), and atherosclerosis (20).…”

“…The 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors (statins) have been shown to decrease cardiovascular morbidity and mortality when administered before elective surgery or percutaneous coronary interventions (39), and recently, the American College of Cardiology/American Heart Association guidelines gave class IIa recommendation for the initiation of statin therapy before vascular surgery and class IIb recommendation for the initiation of statin therapy in patients with risk factors scheduled for intermediate risk surgery (21). Animal studies have shown that statins protect against ischemia-reperfusion injury and when administered before ischemia (2,5,7,31,32,46,48,49,54,55,59,62,63,68,69), or immediately upon reperfusion (4,18,62), limit myocardial infarct size (IS). The activation of eNOS is essential for the IS-limiting effects of late ischemic preconditioning (8,9,53,66).…”

“…Thus it seems that statins and Pio activate cPLA 2 and COX2 by different mechanisms. Moreover, Snitrosylation of COX2 (2,6,34,71) and cPLA 2 (65) by iNOS is needed for the activation of these enzymes. Thus it is unclear whether Pio can activate COX2 and/or cPLA 2 in the iNOS Ϫ/Ϫ mice.…”

The effect of acute simvastatin administration on the severity of arrhythmias resulting from ischaemia and reperfusion in the canine: Is there a role for nitric oxide?

“…Perhaps, the most likely mechanism by which statins provide protection against ischaemia and reperfusion-induced arrhythmias is their ability to increase NO synthesis (Mital et al, 2000;Lefer et al, 2001;Atar et al 2006). We have substantial previous evidence that NO plays an essential role in both the early and delayed anti-arrhythmic effects of preconditioning, induced either by brief periods of coronary artery occlusion (Végh et al, 1992b), cardiac pacing (Kis et al, 1999) or heavy physical exercise (Babai et al, 2002).…”