SQ-28603

We have shown earlier that cardiomyocyte apoptosis continues at a high level late after myocardial infarction and contributes to adverse cardiac remodeling. Here we studied whether this process can be inhibited by the vasopeptidase inhibitor omapatrilat, a drug which causes simultaneous inhibition of both angiotensin converting enzyme and neutral endopeptidase. Our hypothesis was that omapatrilat-treated rats would have less cardiomyocyte apoptosis, and less adverse cardiac remodeling compared to rats treated with selective inhibitors of angiotensin converting enzyme, neutral endopeptidase or placebo. Myocardial infarction was produced by ligation of the left anterior descending coronary artery. Rats were randomized to receive omapatrilat, captopril, neutral endopeptidase inhibitor SQ-28603 or vehicle. Rats treated with omapatrilat and captopril had reduced cardiac BNP mRNA levels and less myocardial fibrosis by comparison with the vehicle-treated rats. However, omapatrilat was more effective than captopril in attenuating hypertrophy as measured by relative cardiac weight (3.0+/-0.2 vs. 3.8+/-0.2 mg/g, P<0.01) or by echocardiographically determined left ventricular mass (0.61+/-0.05 vs. 0.83+/-0.06 g, P<0.01). Myocardial apoptosis was elevated both in the infarction border zone (0.129+/-0.017%) and in the remote area (0.035+/-0.005%) still 4 weeks after myocardial infarction. Angiotensin converting enzyme inhibition proved to be important in the prevention of apoptosis since both omapatrilat and captopril reduced the number of apoptotic myocytes whereas selective neutral endopeptidase inhibitor SQ-28603 had no effect. In conclusion, myocardial apoptosis, remaining increased 4 weeks after myocardial infarction, was reduced by angiotensin converting enzyme inhibition. Vasopeptidase inhibition was more effective than selective angiotensin converting enzyme inhibition in preventing adverse cardiac remodeling after myocardial infarction.