Protein tyrosine kinase is downstream of protein kinase C for ischemic preconditioning's anti-infarct effect in the rabbit heart.
The present study tested the hypothesis that one or more tyrosine kinase(s) are downstream of protein kinase C (PKC) in the signal transduction pathway responsible for the cardioprotective effect of ischemic preconditioning (PC). Isolated rabbit hearts were subjected to 30 min of regional ischemia followed by 2 h of reperfusion. Infarct size was measured by triphenyltetrazolium staining and expressed as a percentage of the area at risk. Infarction in control hearts was 32.9+/-1.8%. Ischemic PC with 5-min ischemia/10-min reperfusion reduced infarct size to 11.5+/-1.5% (P<0.05). Infusion of the tyrosine kinase inhibitors, genistein (50 microM) or lavendustin A (0.5 microM), alone did not affect the level of infarction. When infused around the 5-min PC ischemia genistein failed to block protection (13.7+/-1.0%). However, when present at the onset of the 30-min ischemia both genistein and lavendustin A completely aborted protection (31.4+/-2.0 and 28.1+/-1.5%, respectively). Activation of PKC by phorbol 12-myristate 13-acetate (PMA, 0.05 nmol) was as protective is ischemic PC (14.9+/-3.0%; P<0. 05). Similar to PC, PMA-induced protection was completely prevented by both genistein and lavendustin A. Conversely, anisomycin (50 ng/ml), an activator of MAP kinase kinases (dual tyrosine and threonine kinases), was very protective (7.5+/-1.6%; P<0.05) and this protection was still present when PKC was inhibited by 5 microM chelerythrine (12.1+/-1.6%; P<0.05). In conclusion, activation of a tyrosine kinase during the long ischemia appears to be required for cardioprotection in the rabbit heart. Furthermore, the ability of tyrosine kinase inhibitors to block PMA-induced protection in conjunction with the failure of PKC inhibition to prevent anisomycin-induced protection suggests that the tyrosine kinase is downstream of PKC and that the tyrosine kinase may be a MAP kinase kinase.
Baines
C P
CP
Departments of Physiology and Medicine, College of Medicine, University of South Alabama, Mobile 36688, USA.
Wang
L
L
Cohen
M V
MV
Downey
J M
JM
D000470:Alkaloids; D000818:Animals; D000841:Anisomycin / Q000494:pharmacology; D053119:Benzophenanthridines; D004789:Enzyme Activation / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D019833:Genistein / Q000494:pharmacology; D006439:Hemodynamics; D019157:Ischemic Preconditioning, Myocardial; D008297:Male; D020929:Mitogen-Activated Protein Kinase Kinases; D009203:Myocardial Infarction / Q000201:enzymology* / Q000503:physiopathology / Q000517:prevention & control*; D015428:Myocardial Reperfusion Injury / Q000201:enzymology* / Q000503:physiopathology / Q000517:prevention & control*; D010617:Phenanthridines / Q000494:pharmacology; D010636:Phenols / Q000494:pharmacology; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism*; D011494:Protein Kinases / Q000378:metabolism; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D011817:Rabbits; D015398:Signal Transduction; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
D000470:Alkaloids; D053119:Benzophenanthridines; D004791:Enzyme Inhibitors; D010617:Phenanthridines; D010636:Phenols; C062898:lavendustin A; D000841:Anisomycin; D019833:Genistein; C016299:chelerythrine; D011494:Protein Kinases; D011505:Protein-Tyrosine Kinases; D011493:Protein Kinase C; D020929:Mitogen-Activated Protein Kinase Kinases; D013755:Tetradecanoylphorbol Acetate