Protective effects of protein kinase C during myocardial ischemia require activation of phosphatidyl-inositol specific phospholipase C.
BACKGROUND
Protein kinase C (PKC) activation during myocardial ischemia is thought to be cardioprotective. However, the mechanism of ischemia-induced PKC activation remains unclear. We hypothesized that ischemic PKC activation occurs through activation of phosphatidyl-inositol specific phospholipase C (PI-PLC) and protects the heart from ischemic injury.


METHODS
Isolated rabbit hearts were subjected to 20 minutes of normothermic ischemia and reperfusion. The PI-PLC inhibitor U73122 (0.5 micromol/L), its inactive analogue U73343 (0.5 micromol/L), or the PKC inhibitor chelerythrine (2 micromol/L) were given just before ischemia. Another group received U73122 plus the direct PKC activator phorbol 12-myristate-13-acetate (PMA, 10 pmol/L). Measurements included contractile function, intracellular calcium, PI-PLC activity, and translocation of PKC isoforms.


RESULTS
PI-PLC activity increased during myocardial ischemia and was inhibited by U73122. PI-PLC inhibition prevented the ischemic translocation of PKC-alpha, PKC-epsilon, and PKC-eta, and impaired cardiac recovery and cytosolic calcium regulation without significant changes in energy metabolism. PMA restored both contractile function and PKC translocation pattern in U73122-treated hearts. Direct PKC inhibition with chelerythrine mimicked the effects of U73122.


CONCLUSIONS
PI-PLC mediates PKC translocation during myocardial ischemia. Inhibition of PI-PLC or PKC activation, or both, during ischemia significantly impairs postischemic myocardial recovery.
Munakata
Mamoru
M
Department of Pediatric Cardiac Surgery, Children's Hospital and Harvard Medical School, Boston, Massachusetts 02115, USA.
Stamm
Christof
C
Friehs
Ingeborg
I
Zurakowski
David
D
Cowan
Douglas B
DB
Cao-Danh
Hung
H
McGowan
Francis X
FX
del Nido
Pedro J
PJ
D000255:Adenosine Triphosphate / Q000378:metabolism; D000470:Alkaloids; D000818:Animals; D053119:Benzophenanthridines; D015153:Blotting, Western; D002118:Calcium / Q000378:metabolism; D003326:Coronary Circulation; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004963:Estrenes / Q000494:pharmacology; D007527:Isoenzymes / Q000378:metabolism; D019344:Lactic Acid / Q000378:metabolism; D009200:Myocardial Contraction; D017202:Myocardial Ischemia / Q000378:metabolism / Q000503:physiopathology*; D009206:Myocardium / Q000378:metabolism*; D010101:Oxygen Consumption; D010617:Phenanthridines / Q000494:pharmacology; D010716:Phosphatidylinositols / Q000378:metabolism*; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism*; D011760:Pyrrolidinones / Q000494:pharmacology; D011817:Rabbits; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D010738:Type C Phospholipases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D016277:Ventricular Function, Left
D000470:Alkaloids; D053119:Benzophenanthridines; D004791:Enzyme Inhibitors; D004963:Estrenes; D007527:Isoenzymes; D010617:Phenanthridines; D010716:Phosphatidylinositols; D011760:Pyrrolidinones; C060229:1-(6-((3-methoxyestra-1,3,5(10)-trien-17-yl)amino)hexyl)-1H-pyrrole-2,5-dione; D019344:Lactic Acid; D000255:Adenosine Triphosphate; C016299:chelerythrine; D011493:Protein Kinase C; D010738:Type C Phospholipases; D013755:Tetradecanoylphorbol Acetate; D002118:Calcium