Activation of SphK1 by K6PC-5 Inhibits Oxygen-Glucose Deprivation/Reoxygenation-Induced Myocardial Cell Death

In the current study, we evaluated the potential effect of a novel sphingosine kinase 1 (SphK1) activator, K6PC-5, on oxygen-glucose deprivation (OGD)/reoxygenation-induced damages to myocardial cells. We demonstrated that K6PC-5 increased intracellular sphingosine-1-phosphate (S1P) content and remarkably inhibited OGD/reoxygenation-induced death of myocardial cells (H9c2/HL-1 lines and primary murine myocardiocytes). SphK1 inhibitors, B-5354c and SKI-II, or SphK1-siRNA knockdown not only aggregated OGD/reoxygenation-induced cytotoxicity but also nullified the cytoprotection by K6PC-5. On the other hand, overexpression of SphK1 alleviated H9c2 cell death by OGD/reoxygenation, and K6PC-5-mediated cytoprotection was also enhanced in SphK1 overexpressed cells. Molecularly, OGD/reoxygenation activated the mitochondrial death pathway, evidenced by reactive oxygen species (ROS) production, mitochondrial membrane potential reduction, and p53-cyclophilin D (Cyp-D) association, which were all alleviated by K6PC-5 or overexpression of SphK1, but exacerbated by SphK1 knockdown. Furthermore, OGD/reoxygenation induced prodeath ceramide production in myocardial cells, which was largely suppressed by K6PC-5. In the meantime, adding a cell-permeable short-chain ceramide (C6) mimicked OGD/reoxygenation actions and induced ROS production and the mitochondrial death pathway in myocardial cells. Together, we conclude that K6PC-5 inhibits OGD/reoxygenation-induced myocardial cell death probably through activating SphK1. The results of the study indicate a potential benefit of K6PC-5 on ischemic heart disease.