Post-ischaemic activation of kinases in the pre-conditioning-like cardioprotective effect of the platelet-activating factor.
OBJECTIVE
Platelet-activating factor (PAF) triggers cardiac pre-conditioning against ischemia/reperfusion injury. The actual protection of ischaemic pre-conditioning occurs in the reperfusion phase. Therefore, we studied in this phase the kinases involved in PAF-induced pre-conditioning.


METHODS
Langendorff-perfused rat hearts underwent 30 min of ischaemia and 2 h of reperfusion (group 1, control). Before ischaemia, group 2 hearts were perfused for 19 min with PAF (2 x 10(-11) M); groups 3-5 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. Left ventricular pressure and infarct size were determined.


RESULTS
PAF pre-treatment reduced infarct size (33 +/- 4% vs. 64 +/- 5% of the area at risk of control hearts) and improved pressure recovery. PAF pre-treatment 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 pre-treatment were abolished by post-ischaemic infusion of either chelerythrine, LY294002 or atractyloside.


CONCLUSIONS
The cardioprotective effect exerted by PAF pre-treatment involves activation of PKC and PI3K in post-ischaemic phases and might be mediated by the prevention of mPTP opening in reperfusion via GSK-3beta inactivation.
Laboratories of Physiology and Pharmacology, Department of Clinical and Biological Sciences, University of Torino, Torino, Italy.
C
C
Penna
B
B
Mognetti
F
F
Tullio
D
D
Gattullo
D
D
Mancardi
F
F
Moro
P
P
Pagliaro
G
G
Alloatti
D000818:Animals; D015153:Blotting, Western; D004789:Enzyme Activation; D038362:Glycogen Synthase Kinase 3 / Q000378:metabolism; D000071679:Glycogen Synthase Kinase 3 beta; D019157:Ischemic Preconditioning, Myocardial; D008297:Male; D033681:Mitochondrial Membrane Transport Proteins / Q000378:metabolism; D000083162:Mitochondrial Permeability Transition Pore; D009203:Myocardial Infarction / Q000201:enzymology; D015428:Myocardial Reperfusion Injury / Q000201:enzymology*; D009924:Organ Culture Techniques; D010972:Platelet Activating Factor / Q000378:metabolism*; D011494:Protein Kinases / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar
D033681:Mitochondrial Membrane Transport Proteins; D000083162:Mitochondrial Permeability Transition Pore; D010972:Platelet Activating Factor; D011494:Protein Kinases; D000071679:Glycogen Synthase Kinase 3 beta; C000605508:Gsk3b protein, rat; D038362:Glycogen Synthase Kinase 3