Post-ischaemic activation of kinases in the preconditioning-like cardioprotective effect of the platelet activating factor.

Aim. Platelet activating factor (PAF) triggers cardiac preconditioning against ischemia/reperfusion injury. The actual protection of ischaemic-preconditioning occurs in the reperfusion phase. Therefore, we studied in this phase the kinases involved in PAF-induced preconditioning. Methods. Langendorff-perfused rat hearts underwent 30-minutes ischaemia and 2-hours of reperfusion (Group 1, control). Before ischaemia, Group 2 hearts were perfused for 19-min with PAF (2x10(-11) M); Groups 3,4 and 5 hearts were co-infused during the initial 20-min of reperfusion, with the protein kinase C (PKC) inhibitor chelerythrine (5 x 10(-6) M) or the phosphoinositide 3-kinase (PI3K) inhibitor LY294002 (5 x 10(-5) M), and Atractyloside (2 x 10(-5) M), a mitochondrial permeability transition pore (mPTP) opener, respectively. Phosphorylation of PKCepsilon, PKB/Akappat, GSK-3beta and ERK1/2 at the beginning of reperfusion was also checked. Results. Left ventricular pressure and infarct size were determined. PAF-pretreatment reduced infarct size (33+/-4 vs 64+/-5% of the area at risk of control hearts) and improved pressure recovery. PAF-pretreatment enhanced the phosphorylation/activation of PKCepsilon, PKB/Akappat and the phosphorylation/inactivation of GSK-3beta at reperfusion. Effects on ERK1/2 phosphorylation were not consistent. Infarct-sparing effect and post-ischaemic functional improvement induced by PAF-pretreatment were abolished by post-ischaemic infusion of either chelerythrine, LY294002, or Atractyloside. Conclusions. The cardioprotective effect exerted by PAF-pretreatment involves activation of PKC and PI3K in post-ischaemic phases, and might be mediated by prevention of mPTP opening in reperfusion via GSK-3beta inactivation.