Intralipid Induces Cardioprotection against Ischemia-Reperfusion Injury by Inhibiting the Mitochondrial Permeability Transition Pore Opening Via the PI3K/AKT Pathway

Abstract

Acute myocardial infarction is a major cause of mortality, and the best hope of salvaging viable myocardium is by rapid cardiac reperfusion. A novel cardioprotective drug which could be applied at the time of reperfusion after acute infarction would be ideal. Here we tested the hypothesis that administration of Intralipid at the onset of reperfusion protects the heart against ischemia reperfusion (I/R) injury. Isolated hearts (Langendorff) from male mice were subjected to 20 minutes of global normothermic (37°C) ischemia followed by 40 minutes of reperfusion with Krebs Henseleit buffer (CTRL) or with additional 1% Intralipid (ILP). Postischemic treatment with Intralipid significantly improved the cardiac function; the rate pressure product (RPP) was increased from 3432±334mmHg∗beats/min in CTRL to 15405±1011mmHg∗beats/min in ILP. Consistent with the higher functional recovery in ILP, the infarct size was markedly smaller in ILP (19±3%,n=8) compared to CTRL (55.6±3.4%,n=10). The inhibition of mitochondria permeability transition pore (mPTP) opening during reperfusion has been shown to induce cardioprotection. To investigate whether intralipid-induced cardioprotection occurs by inhibition of the mPTP opening, we compared the viability of isolated mitochondria by calcium overload. Postischemic administration of Intralipid inhibited the opening of the mPTP as calcium retention capacity was higher in the ILP group compared to control (2.7±0.06 vs. 1.5±0.11 μM/mg-mitochondrial protein, p<0.05). To identifiy the key signaling molecules involved in regulating mPTP opening, Western Blot analyis of heart lysates was performed. The activity of AKT/ERK1/GSK were respectively 2.3, 5 and 2.7 fold higher in ILP compared to CTRL. The involvement of PI3K/AKT pathway was further investigated by LY294002, a specific inhibitor of PI3K. The Intralipid-induced cardioprotection was fully abolished in the presence of LY294002, indicating the cardioprotective action of Intralipid is mediated via PI3K/AKT pathway.