Gene therapy with iNOS provides long-term protection against myocardial infarction without adverse functional consequences

Previous studies have shown that gene therapy with inducible nitric oxide synthase ( iNOS) protects against myocardial infarction at 3 days after gene transfer. However, the long-term effects of iNOS gene therapy on myocardial ischemic injury and cardiac function are unknown. To address this issue, we used a recombinant adenovirus 5 ( Ad5) vector ( Av3) with deletions of the E1, E2a, and E3 regions, which enables long-lasting recombinant gene expression for at least 2 mo due to lack of inflammation. Mice received intramyocardial injections in the left ventricular ( LV) anterior wall of Av3/LacZ ( LacZ group) or Av3/iNOS ( iNOS group); 1 or 2 mo later, they were subjected to myocardial infarction ( 30-min coronary occlusion followed by 4 h of reperfusion). Cardiac iNOS gene expression was confirmed by immunoblotting and activity assays at 1 and 2 mo after gene transfer. In the iNOS group, infarct size ( percentage of risk region) was significantly reduced ( P < 0.05) both at 1 mo ( 24.2 +/- 3.4%, n = 6, vs. 48.0 +/- 3.6%, n = 8, in the LacZ group) and at 2 mo ( 23.4 +/- 3.1%, n = 8, vs. 36.6 +/- 2.4%, n = 7). The infarct-sparing effects of iNOS gene therapy were as powerful as those observed 24 h after ischemic preconditioning ( 23.1 +/- 3.4%, n = 10). iNOS gene transfer had no effect on LV function or dimensions up to 8 wk later ( echocardiography). These data demonstrate that iNOS gene therapy mediated by the Av3 vector affords long-term ( 2 mo) cardioprotection without inflammation or adverse functional consequences, a finding that provides a rationale for further preclinical testing of this therapy.