Human group IIA secretory phospholipase A2 potentiates Ca2+ influx through L-type voltage-sensitive Ca2+ channels in cultured rat cortical neurons

Mammalian group IIA secretory phospholipase A(2) (sPLA(2)-IIA) generates prostaglandin D-2 (PGD(2)) and triggers apoptosis in cortical neurons. However, mechanisms of PGD(2) generation and apoptosis have not yet been established. Therefore, we examined how second messengers are involved in the sPLA(2)-IIA-induced neuronal apoptosis in primary cultures of rat cortical neurons. sPLA(2)-IIA potentiated a marked influx of Ca2+ into neurons before apoptosis. A calcium chelator and a blocker of the L-type voltage-sensitive Ca2+ channel (L-VSCC) prevented neurons from sPLA(2)-IIA-induced neuronal cell death in a concentration-dependent manner. Furthermore, the L-VSCC blocker ameliorated sPLA(2)-IIA-induced morphologic alterations and apoptotic features such as condensed chromatin and fragmented DNA. Other blockers of VSCCs such as N type and P/Q types did not affect the neurotoxicity of sPLA(2)-IIA. Blockers of L-VSCC significantly suppressed sPLA(2)-IIA-enhanced Ca2+ influx into neurons. Moreover, reactive oxygen species (ROS) were generated prior to apoptosis. Radical scavengers reduced not only ROS generation, but also the sPLA(2) -IIA-induced Ca2+ influx and apoptosis. In conclusion, we demonstrated that sPLA(2)-IIA potentiates the influx of Ca2+ into neurons via L-VSCC. Furthermore, the present study suggested that eicosanoids and ROS generated during arachidonic acid oxidative metabolism are involved in sPLA(2)-IIA-induced apoptosis in cooperation with Ca2+ .