Inhibition of type 2A secretory phospholipase A₂ reduces death of cardiomyocytes in acute myocardial infarction

During acute myocardial infarction (AMI), ischemia leads to necrotic areas surrounded by border zones of reversibly damaged cardiomyocytes, showing membrane flip-flop. During reperfusion type IIA secretory phopholipase A₂ (sPLA₂-IIA) induces direct cell-toxicity and facilitates binding of other inflammatory mediators on these cardiomyocytes. Therefore, we hypothesized that the specific sPLA₂-IIA-inhibitor PX-18 would reduce cardiomyocyte death and infarct size in vivo. Wistar rats were treated with PX-18 starting minutes after reperfusion, and at day 1 and 2 post AMI. After 28 days hearts were analyzed. Furthermore, the effect of PX-18 on membrane flip-flop and apoptosis was investigated in vitro. PX-18 significantly inhibited sPLA₂-IIA activity and reduced infarct size (reduction 73 ± 9%, P < 0.05), compared to the vehicle-treated group, without impairing wound healing. In vitro, PX-18 significantly reduced reversible membrane flip-flop and apoptosis in cardiomyocytes. However, no sPLA₂-IIA activity could be detected, suggesting that PX-18 also exerted a protective effect independent of sPLA₂-IIA. In conclusion, PX-18 is a potent therapeutic to reduce infarct size by inhibiting sPLA₂-IIA, and possibly also by inhibiting apoptosis of cardiomyocytes in a sPLA₂-IIA independent manner.