Involvement of calcium in 50-Hz magnetic field-induced activation of sphingosine kinase 1 signaling pathway.

Previously, we found that exposure to a 50-Hz magnetic field (MF) could induce human amniotic epithelial (FL) cell proliferation and sphingosine kinase 1 (SK1) activation, but the mechanism was not clearly understood. In the present study, the possible signaling pathways which were involved in SK1 activation induced by 50-Hz MF exposure were investigated. Results showed that MF exposure increased intracellular Ca2+ which was dependent on the L-type calcium channel, and induced Ca2+-dependent phosphorylation of extracellular regulated protein kinase (ERK), SK1, and protein kinase C alpha (PKC alpha). Also, treatment with U0126, an inhibitor of ERK, could block MF-induced SK1 phosphorylation, but had no effect on PKC alpha phosphorylation. Also, the inhibitor of PKC alpha, Go6976, had no effect on MF-induced SK1 activation in FL cells. In addition, the activation of ERK and PKC alpha could be abolished by SKI II, the inhibitor of SK1. In conclusion, the intracellular Ca2+ mediated the 50-Hz MF-induced SK1 activation which enhanced PKC alpha phosphorylation, and there might be a feedback mechanism between SK1 and ERK activation in responding to MF exposure in FL cells. Bioelectromagnetics. 9999:XX-XX, 2019. (c) 2019 Bioelectromagnetics Society.