Myocardial protection during reperfusion by administration of caspase-3 inhibitor is mediated via PI3 kinase survival pathway

Abstract

Apoptosis contributes significantly to cardiomyocyte death during ischaemia reperfusion injury. Caspase family proteases play an essential role in the execution of apoptosis. Caspase inhibitors have been found to be cardioprotective, although there is a question as to the specificity of these class of compounds. Adult cardiac myocytes were subjected to 6 h simulated ischaemia and 18 h reoxygenation (SIR). The broad spectrum caspase inhibitor (z-VAD.fmk, 0.1 μM) was administered at reoxygenation in the absence or presence of Wortmannin (Wort, 5 nM, PI3-kinase inhibitor). Cell viability (using flow cytometry) was determined by annexin-V and sytox green as a measure of apoptosis and necrosis, respectively, caspase 3 activity was also assessed. Results are summarised in the table below. z-VAD.fmk significantly reduced apoptosis and necrosis after 18 h reoxygenation compared to the SIR control. To examine whether the anti-apoptotic effects of the caspase-3 inhibitor involved activation of PI3-kinase, z-VAD.fmk was simultaneously administered with the PI3-kinase inhibitor Wort to the adult rat myocytes during reoxygenation. Wort completely abolished the anti-apoptotic effects of z-VAD.fmk and also reversed the reduction in caspase-3 activity induced by z-VAD.fmk back to control SIR levels. These studies are the first to show that the caspase inhibitor z-VAD.fmk reduces apoptosis through a PI3-kinase-dependent cell survival pathway.