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 -ηand -δwith sarcolemmal membranes, detected by Western blotting, as well as, for PKCδ, by immunolocalization. FGF-2 increased the association of PKCηwith 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 effectsin 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.