Low dose N,N-dimethylsphingosine is cardioprotective and activates cytosolic sphingosine kinase by a PKCε dependent mechanism

Objective: N, N-Dimethylsphingosine (DMS) is recognized as an inhibitor of sphingosine kinase (SphK), a key enzyme responsible for the formation of sphingosine-1-phosphate (SIP). We previously showed that SIP was cardioprotective and that SphK was critical for myocardial ischemic preconditioning. Although DMS is an endogenous sphingolipid, its effect on cardiac function and cardioprotection at low concentration has not been studied. Methods: In Langendorff-perfused wild-type and protein kinase C (PKC)epsilon-null mouse hearts, cardiac function, infarction size, and SphK activity were measured. Results: Pretreatment with 0.3 mu M and 1 mu M DMS for 10 min protected against ischemia/reperfusion injury. Cardiac function (LVDP, +/- dP/dtmax) was improved and infarction size was reduced. The cardiac protection induced by DMS was abolished in PKC epsilon-null mouse hearts. Administration of 1 mu M DMS ex vivo increased cytosolic SphK activity. This enhanced SphK activity was abolished in PKC epsilon-null mouse hearts. DMS also increased PKC epsilon translocation from the particulate to the cytosolic fraction with no effect on PKC alpha distribution. Co-immunoprecipitation showed that SphK1 interacted with PKC epsilon phosphorylated on Ser729. DMS also increased cytosolic Akt phosphorylation (Ser 473) and Akt translocation from a Triton-insoluble fraction to the cytosol. Conclusions: DMS has a biphasic effect on cardioprotection. Higher concentrations (10 mu M) are inhibitory, whereas a low concentration (0.3 mu M and 1 mu M) of DMS protects murine hearts against ischemia/reperfusion injury. DMS activates SphK in the cytosol via a PKC epsilon dependent mechanism. The PKC epsilon-SphK-S1P-Akt pathway is involved in the cardiac protection induced by DMS. (c) 2006 European Society of Cardiology. Published by Elsevier B.V. All rights reserved.