RESUMO
Increased circulating and cardiac TNF-alpha levels during myocardial ischemia have been found in both experimental animals and patients with ischemic heart disease and advanced heart failure. Soluble TNF-alpha receptor 1 (sTNFR1) is an antagonist to TNF-alpha. In the present study, we examined whether sTNFR1 improves cardiac function in rats after myocardial infarction. Male Wistar rats were subjected to left coronary artery (LCA) ligation. Immediately after the ligation, a total of 200 microg of either the sTNFR1 or LacZ plasmid was injected into three different sites in the left ventricular wall. From 1 to 21 days after LCA ligation, TNF-alpha bioactivity in the heart was higher in rats receiving LacZ plasmid than in sham-operated rats, whereas sTNFR1 plasmid significantly suppressed the increase. The LV diastolic dimension was significantly lower, and the fractional shortening was significantly higher in rats treated with the sTNFR1 plasmid than in those treated with the LacZ plasmid. At 21 days after LCA ligation, the LV end-diastolic pressure was also significantly lower in the rats treated with the sTNFR1 plasmid. In addition, the sTNFR1 expression plasmid had significantly reduced the infarct size. In conclusion, TNF-alpha bioactivity in the heart increased during the early stage of infarction and remained elevated. This elevation seemed partially responsible for the impairment of LV function and the increased infarct size. Suppression of TNF-alpha bioactivity from the early stage of infarction with the sTNFR1 plasmid improved cardiac function and reduced infarct size.