Inhibition of Apoptosis After Ischemia-reperfusion in Rat Myocardium by Cycloheximide,

Macromolecular synthesis inhibitors protect cells from apoptosis in many systems. To determine whether the protein synthesis inhibitor cycloheximide (CHX) might inhibit apoptosis and protect the myocardium during ischemia-reperfusion, we subjected isovolumic isolated perfused rat hearts to 25 min of normothermic global ischemia followed by reperfusion. We monitored coronary flow, end-diastolic pressure and rate-pressure product (RPP) throughout and assessed apoptosis by terminal deoxynucleotidyl transferase mediated dUTP nick end labeling (TUNEL). Regardless of the treatment regimen (only before ischemia; only during reperfusion; or both before ischemia and during reperfusion), CHX significantly improved functional recovery during reperfusion. These effects were most pronounced when CHX was present during reperfusion. When hearts were treated with CHX only during reperfusion the recovery of sinus rhythm was more frequent in the CHX-treated hearts than control hearts (80%v53%) and earlier for CHX-treated than control hearts: 6.4±2v19.4±4.7 min of reperfusion. The maximal RPP recoveries for the CHX-treated hearts were 45±4.0% (P=0.005) of pre-ischemic values, compared to 26±3% for controls. In control hearts reperfused for 2 h, TUNEL identified 49.5±10 intact nuclei and 7.5±2 fragmented nuclei per 1000 nuclei counted. A significantly lower incidence of labeled nuclei with or without fragmentation was observed in CHX treated hearts: 7.6±3.4 (P=0.009) intact labeled nuclei and 1.8±0.7/103fragmented labeled nuclei. Our results suggest that CHX-induced inhibition of apoptosis in reperfused myocardium is cardioprotective and promotes functional recoveryin vitro.