Metabolic and Functional Protection by Selective Inhibition of Nitric Oxide Synthase 2 During Ischemia-Reperfusion in Isolated Perfused Hearts

BACKGROUND: Drugs that selectively block nitric oxide synthase (NOS) 2 enzyme activity by inhibiting dimerization of NOS2 monomers have recently been developed. METHODS AND RESULTS: To investigate whether selective inhibition of NOS2 is cardioprotective, rats were pretreated for 2 days with BBS2, an inhibitor of NOS2 dimerization, at 15 mg/kg SC. Isolated buffer-perfused hearts from treated (n=9) and control (n=7) hearts were subjected to 20 minutes of ischemia followed by 60 minutes of reperfusion. NOS2 protein was upregulated in all hearts at the end of ischemia and of reperfusion; NOS2 enzyme activity was 60% lower in hearts from the treated animals. In the treated hearts, the increase in end-diastolic pressure was significantly attenuated at the end of ischemia, and the return of developed pressure at reperfusion was greater (P<0.05). Creatine kinase release at reperfusion was lower in treated hearts than in controls (P=0.02). At the end of ischemia and of reperfusion, myocardial ATP levels were significantly higher in the treated hearts than in controls (P<0.05). In the treated hearts under ischemic conditions, lactate content was higher and the lactate/pyruvate ratio was lower than in controls (P<0.05); GAPDH activity was higher; and G-3-P and aldose reductase activity were lower. At reperfusion, in the treated hearts, there was less histological damage and less apoptosis of cardiac muscle cells. CONCLUSIONS: Pretreatment with BBS2, a selective inhibitor of NOS2, improves contractile performance, preserves myocardial ATP, and reduces damage and death of cardiac myocytes during ischemia and reperfusion of isolated buffer-perfused rat hearts.