ABSTRACT

The mechanism underlying the biological effects caused by an extremely low-frequency electromagnetic field (ELF-EMF) is still unclear. Previously, we found that L-type calcium channel and sphingosine kinase 1 (SK1) were involved in 50-Hz MF exposure-induced cell proliferation. In the present study, the role of intracellular Ca²⁺ and signal molecules related to SK1 in cell proliferation induced by 50-Hz MF was investigated in human amniotic epithelial (FL) cells. Results showed that the intracellular Ca²⁺ chelator, BAPTA, could completely inhibit 50-Hz MF-induced cell proliferation, whereas NIF, the inhibitor of L-type calcium channel, only partly blocked it. When cells were cultured in calcium-free medium, MF exposure also increased intracellular Ca²⁺, activated SK1 and promoted cell proliferation although all of those increasing levels were lower than those in complete medium. Moreover, MF-activated SK1 could be completely inhibited by BAPTA, and MF-induced cell proliferation was abolished by SKI II, the specific inhibitor of SK1. Additionally, a 50-Hz MF exposure did not affect the activation of ERK and PKCα under the condition of calcium-free medium, but activated the Akt, which could be precluded entirely by BAPTA, but not be inhibited by NIF. Treatment of FL cells with LY294002, the inhibitor of Akt, could delete the MF-induced SK1 activation under the condition of calcium-free medium. Based on the data from the present experiment, it is concluded that endogenous Ca²⁺ release was involved in 50-Hz MF-induced cell proliferation via Akt-SK1 signal cascade.

摘要

极低频电磁场（ELF-EMF）引起生物效应的机制尚不清楚。以前，我们发现 L 型钙通道和鞘氨醇激酶 1 (SK1) 参与 50-Hz MF 暴露诱导的细胞增殖。在本研究中，在人羊膜上皮 (FL) 细胞中研究了细胞内 Ca ²⁺和与 SK1 相关的信号分子在 50-Hz MF 诱导的细胞增殖中的作用。结果表明，细胞内Ca ²⁺螯合剂BAPTA可以完全抑制50-Hz MF诱导的细胞增殖，而L型钙通道抑制剂NIF只能部分阻断它。当细胞在无钙培养基中培养时，MF 暴露也会增加细胞内 Ca ²⁺，激活SK1并促进细胞增殖，尽管所有这些增加的水平都低于完全培养基中的水平。此外，MF 激活的 SK1 可以被 BAPTA 完全抑制，并且 MF 诱导的细胞增殖被 SK1 的特异性抑制剂 SKI II 消除。此外，在无钙培养基条件下，50-Hz MF 暴露不影响 ERK 和 PKCα 的激活，但激活了 Akt，这可以被 BAPTA 完全排除，但不受 NIF 抑制。在无钙培养基条件下，用 Akt 抑制剂 LY294002 处理 FL 细胞可以消除 MF 诱导的 SK1 活化。根据本实验的数据，可以得出结论，内源性 Ca ²⁺释放通过 Akt-SK1 信号级联参与 50-Hz MF 诱导的细胞增殖。