Involvement of mitochondria on neuroprotective effect of sphingosine-1-phosphate in cell death in an in vitro model of brain ischemia

Sphingosine-1-phosphate (S1P) has been demonstrated to be an important regulator of cell death and survival. Although it has been suggested that the sphingolipid may act as a neuroprotector in the cell apoptosis induced by traumatic brain injury, the mechanisms involved in this action are unknown. In this study, the relationship between SIP and neuroprotective effect was studied in an in vitro model of ischemia, maintaining SH-SY5Y human neuroblastoma cells under oxygen-glucose deprivation (OGD). When cells were treated with 1 mu M S1P simultaneously with OGD and recovery, cell viability increases in a dose-response manner. SI P treatment reduces significantly both necrosis and apoptosis cell death. On the other hand, the treatment with specific PKC epsilon (V1-2), prevents S1P protective effect of OGD/recovery-induced necrosis. Moreover, SIP treatment provokes the translocation of PKC epsilon to the mitochondria. From these results, it is reasonable to assume that SIP protection from necrosis is mediated by PKC epsilon. We also studied the action of SIP on mitochondrial inner membrane potential and mitochondrial Ca2+ levels during ischemia. In this regard, we must point out that S1P treatment reduces the OGD-induced membrane depolarization and also reduces the increase of Ca2+ in mitochondria during OGD. Results also indicate that mitochondria from OGD treated cells have significantly less ability to resist swelling on Ca2+ loading than those obtained in presence of oxygen and glucose. Nevertheless, when SI P was added, this resistance increases considerably. These findings suggest that SIP may have a potential role as a neuroprotective agent in brain injury. (C) 2009 Elsevier Ireland Ltd. All rights reserved.