Catestatin-induced cardioprotection involves a PI3K-Akt-GSK3ß pathway converging on the mithocondrial membrane potential preservation

Introduction: Catestatin (CST) is a short 21-amino acid peptide deriving from the proteolytic cleavage of its precursor chromogranin A (CgA). In mammalian heart, CgA is stored in non-adrenergic myoendocrine atrial cells in association with atrial natriuretic peptide, in Purkinje fibers and in both atrial and ventricular cells. Although CST affects several cardiovascular parameters, the mechanisms underlying CST action in the heart has not completely elucidated. CST antagonizes catecholamine secretion and exerts a negative myocardial inotropism, acting via a nitric oxide-dependent mechanism. Recently, we have demonstrated that CST contributes to limiting ischemia/reperfusion (I/R) injury. By virtue of its negative inotropic activity, this peptide improves post-ischemic cardiac function and cardiomyocyte survival. Aims: To define the cardioprotective signalling pathways activated by CST against I/R injury on isolated adult rat cardiomyocytes. The protective effect of CST was studied by evaluating cell viability rate with propidium iodide labeling (IP) and mitochondrial membrane potential (MMP) with JC-1 fluorescence probe. In addition, we performed immunofluorescence experiments to study the involvement of Akt, GSK3β and phospholamban (PLN) cascade. The role of PI3K-Akt pathway was investigated by using the pharmacological blocker of PI3K wortmannin (Wm). Results: In isolated cardiomyocytes undergoing simulated I/R injury CST increased by about 65% cell viability rate. The cardioprotective effect of CST was related to its ability to maintain MMP and to increase Akt, PLN and GSK3β phosphorylation level. Wm pretreatment abolished the CST-induced cardioprotection. Conclusions: These results elucidate a molecular mechanism involved in the cardioprotective role of CST, highlighting the PI3K pathway as the trigger and the MMP preservation as the end point.