FGF-2-induced negative inotropism and cardioprotection are inhibited by chelerythrine: involvement of sarcolemmal calcium-independent protein kinase C.
Fibroblast growth factor-2 (FGF-2), administered to the isolated rat heart by perfusion and under constant pressure, is protective against ischemia-reperfusion (I-R). Here we have investigated whether FGF-2 cardioprotection: (a) is dependent on flow modulation; (b) is linked to effects on contractility; (c) is mediated by protein kinase C (PKC); and (d) is linked to PKC and/or mitogen activated protein kinase (MAPK) associated with the sarcolemma. The isolated rat heart was used as a model. Under conditions of constant flow FGF-2 induced significant improvement in recovery of contractile function during I-R. Under constant perfusion pressure, FGF-2 induced a negative inotropic effect (15% decrease in developed pressure). Chelerythrine, a specific PKC inhibitor, prevented both the FGF-2-induced negative inotropic effect before ischemia, and cardioprotection during I-R. FGF-2 induced a chelerythrine-preventable, five-fold increase in sarcolemmal calcium-independent PKC activity. It also increased the association of PKC subtypes -epsilon and -delta with sarcolemmal membranes, detected by Western blotting, as well as, for PKC delta, by immunolocalization. FGF-2 increased the association of PKC epsilon with the membrane fraction of adult cardiomyocyte in culture, confirming that it can affect PKC signaling in cardiomyocytes directly and in a manner similar to its effects in situ. Finally, FGF-2 induced increased active MAPK at sarcolemmal as well as cytosolic sites. Active sarcolemmal MAPK remained elevated when the FGF-2-induced protection was prevented by chelerythrine. In conclusion, we have provided evidence that cardioprotection by FGF-2 is independent of flow modulation. PKC activation mediates both the FGF-2-induced negative inotropic effect before ischemia and the cardioprotective effect assessed during reperfusion, suggesting a cause and effect relationship. Furthermore, FGF-2 cardioprotection is linked to targeting of sarcolemmal sites by calcium-independent PKC.
Padua
R R
RR
Institute of Cardiovascular Sciences, St Boniface General Hospital Research Centre, Winnipeg, Manitoba, Canada.
Merle
P L
PL
Doble
B W
BW
Yu
C H
CH
Zahradka
P
P
Pierce
G N
GN
Panagia
V
V
Kardami
E
E
D000470:Alkaloids; D000818:Animals; D053119:Benzophenanthridines; D015153:Blotting, Western; D002118:Calcium / Q000494:pharmacology; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000187:drug effects; D002478:Cells, Cultured; D003600:Cytosol / Q000187:drug effects; D003720:Densitometry; D004791:Enzyme Inhibitors / Q000494:pharmacology; D016222:Fibroblast Growth Factor 2 / Q000037:antagonists & inhibitors* / Q000494:pharmacology / Q000502:physiology; D005455:Fluorescent Antibody Technique; D008297:Male; D008566:Membranes / Q000187:drug effects; D009200:Myocardial Contraction / Q000187:drug effects*; D010477:Perfusion; D010617:Phenanthridines / Q000494:pharmacology*; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D015427:Reperfusion Injury / Q000188:drug therapy / Q000517:prevention & control; D012508:Sarcolemma / Q000201:enzymology*; D013997:Time Factors; D016277:Ventricular Function, Left / Q000187:drug effects