Sphingosine Kinase Activation Mediates Ischemic Preconditioning in Murine Heart

Abstract

Background— Phosphorylation of sphingosine by sphingosine kinase (SK) is the rate-limiting step in the cellular synthesis of sphingosine 1-phosphate (S1P). The monoganglioside GM 1 , which stimulates SK, is cardioprotective in part through increased generation of S1P that protects myocytes by diverse mechanisms. Because protein kinase C (PKC)ε activation is necessary for myocardial ischemic preconditioning (IPC) and PKC activators increase SK activity, we tested the hypothesis that SK may be a central mediator of IPC. Methods and Results— In adult murine hearts, IPC sufficient to reduce infarct size significantly increased cardiac SK activity, induced translocation of SK protein from the cytosol to membranes, and enhanced cardiac myocyte survival. IPC did not increase SK activity in PKCε-null mice. The SK antagonist N,N -dimethylsphingosine inhibited PKCε activation and directly abolished the protective effects of IPC and the enhanced SK activity induced by IPC. Conclusions— These findings demonstrate that PKCε is thus recruited by IPC and induces activation of SK that then mediates IPC-induced cardioprotection in murine heart.