Catestatin (CST) limits myocardial ischaemia/reperfusion (I/R) injury with unknown mechanisms. Clearly phosphoinositide-3-kinase (PI3K),
protein kinase C (PKC)
isoforms, including intra-mitochondrial PKCε, mitochondrial KATP (
mitoKATP) channels and subsequent
reactive oxygen species (ROS)-signalling play important roles in postconditioning cardioprotection, preventing
mitochondrial permeability transition pore (mPTP) opening. Therefore, we studied the role of these extra- and intra-mitochondrial factors in CST-induced protection. Isolated rat hearts and H9c2 cells underwent I/R and oxidative stress, respectively. In isolated hearts CST (75nM, CST-Post) given in early-reperfusion significantly reduced
infarct size, limited post-ischaemic
contracture, and improved recovery of developed left ventricular pressure. PI3K inhibitor,
LY-294002 (LY), large spectrum PKC inhibitor,
Chelerythrine (CHE), specific PKCε inhibitor (εV1-2),
mitoKATP channel blocker,
5-Hydroxydecanoate (5HD) or ROS scavenger,
2-mercaptopropionylglycine (MPG) abolished the
infarct-sparing effect of CST. Notably the CST-induced
contracture limitation was maintained during co-infusion of 5HD, MPG or εV1-2, but it was lost during co-infusion of LY or CHE. In H9c2 cells challenged with H2O2, mitochondrial depolarization (an index of
mPTP opening studied with JC1-probe) was drastically limited by CST (75nM). Our results suggest that the protective signalling pathway activated by CST includes
mitoKATP channels, ROS signalling and prevention of
mPTP opening, with a central role for upstream PI3K/Akt and
PKCs. In fact, all inhibitors completely abolished CST-
infarct-sparing effect. Since CST-anti-
contracture effect cannot be explained by intra-mitochondrial mechanisms (PKCε activation and
mitoKATP channel opening) or ROS signalling, it is proposed that these downstream signals are part of a reverberant loop which re-activates upstream
PKCs, which therefore play a pivotal role in CST-induced protection.