Oxygen/ozone protects the heart from acute myocardial infarction through local increase of eNOS activity and endothelial progenitor cells recruitment

Abstract

The purpose of this study is to investigate whether an oxygen/ozone (O(2)/O(3)) mixture protects the heart from acute myocardial infarction through local involvement of endothelial nitric oxide synthase (eNOS) and endothelial progenitor cells (EPCs). Male Sprague-Dawley rats were subject to 25-min occlusion and 2-h reperfusion of the left descending coronary artery. O(2)/O(3) mixture was insufflated i.p. 30 min prior to ischemia/reperfusion (I/R) procedure at doses of 100, 150, and 300 microg/kg. Myocardial infarct size (IS) measurement and myocardial immunohistochemistry for EPCs were done. For these latter cells, immunoreactivities for CD34, and CD117/c-kit were assessed within the infarcted tissue. Moreover, cardiac eNOS was monitored. I/R in rats treated with O(2) produced an IS as a percentage of the area at risk (IS/AR) equal to 51 +/- 5%. I/R in rats treated with the O(2)/O(3) mixture showed reduced IS (for example, IS/AR for 150 microg/kg O(2)/O(3) was 35 +/- 2.1%; P < 0.01 vs. O(2)). The O(2)/O(3) cardio-protection was paralleled by an increased number of immunopositive particles per area for CD34 and CD117/c-kit. The increase of these markers was associated with an increase of cardiac eNOS expression as assayed by immunohistochemistry. Interestingly, N5-(1-Iminoethyl)-L-ornithine dihydrochloride (L-NIO), a selective eNOS activity inhibitor (30 mg/kg s.c.), prior to O(2)/O(3) and I/R almost abolished the cardio-protection exerted by the O(2)/O(3) mixture. L-NIO also abolished the increase in immunostaining for CD-34 and CD117/c-kit as compared with the rats receiving O(2)/O(3) and I/R only. O(2)/O(3) mixture protects the heart from acute myocardial infarction through local increase of eNOS expression/activity and consequent EPCs recruitment.