Estradiol Inhibits Depolarization-Evoked Exocytosis in PC12 Cells via N-Type Voltage-Gated Calcium Channels
Estradiol Inhibits Depolarization-Evoked Exocytosis in PC12 Cells via N-Type Voltage-Gated Calcium Channels
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DOI：
10.1007/s10571-010-9570-4
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发表时间：
2010-11-01
影响因子：
4
通讯作者：
Ewing, Andrew G.
中科院分区：
文献类型：
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作者：
Adams, Kelly L.;Maxson, Marc M.;Ewing, Andrew G.
17-β-雌二醇（E2）对胞浆钙浓度（[Ca 2 +]（i））的快速神经调节作用已在许多细胞类型中报道，但对其对囊泡神经递质分泌（胞吐作用）的直接作用知之甚少。我们用荧光法检测了E2对去极化诱发的PC 12细胞[Ca ~（2+）]（i）的影响。[Ca 2 +]（i）与FURA-2的成像显示，暴露于10 nM和10 μ M E2后，去极化诱发的钙离子内流受到抑制。暴露于50 μ M E2后钙进入略有下降，但不显著。为了将E2诱导的[Ca 2 +]（i）变化与功能效应联系起来，我们使用电流分析法测量胞吐作用。据观察，E2在某些细胞中激发胞吐作用。此外，E2以复杂的浓度依赖性抑制去极化诱发的胞吐作用，在生理和药理浓度下均具有抑制作用。这种快速抑制在接近生理水平（10 nM E2）时达到45%，在可能的药理学浓度50 μ M时达到50%。一小部分（22%）的细胞在E2暴露期间显示胞吐作用（“雌激素刺激”），因此囊泡耗竭可能（至少部分）解释E2诱导的去极化诱发的胞吐作用抑制。在不表现出E2刺激的释放（“雌激素安静”）的细胞中，E2诱导的胞吐抑制通过消除N型电压门控钙通道（VGCC）对胞吐作用的贡献的处理而消除。总的来说，数据表明E2可以作用于N型VGCC以影响神经递质的分泌。这为类固醇调节神经元通讯和可塑性提供了另一种机制。
Fast neuromodulatory effects of 17-beta-estradiol (E2) on cytosolic calcium concentration ([Ca2+](i)) have been reported in many cell types, but little is known about its direct effects on vesicular neurotransmitter secretion (exocytosis). We examined the effects of E2 on depolarization-evoked [Ca2+](i) in PC12 cells using fluorescence measurements. Imaging of [Ca2+](i) with FURA-2 revealed that depolarization-evoked calcium entry is inhibited after exposure to 10 nM and 10 mu M E2. Calcium entry after exposure to 50 mu M E2 decreases slightly, but insignificantly. To relate E2-induced changes in [Ca2+](i) to functional effects, we measured exocytosis using amperometry. It was observed that E2 in some cells elicits exocytosis upon exposure. In addition, E2 inhibits depolarization-evoked exocytosis with a complex concentration dependence, with inhibition at both physiological and pharmacological concentrations. This rapid inhibition amounts to 45% at a near physiological level (10 nM E2), and 50% at a possible pharmacological concentration of 50 mu M. A small percentage (22%) of cells show exocytosis during E2 exposure ("Estrogen stimulated"), thus vesicle depletion could possibly account (at least partly) for the E2-induced inhibition of depolarization-evoked exocytosis. In cells that do not exhibit E2-stimulated release ("Estrogen quiet"), the E2-induced inhibition of exocytosis is abolished by a treatment that eliminates the contribution of N-type voltage-gated calcium channels (VGCCs) to exocytosis. Overall, the data suggest that E2 can act on N-type VGCCs to affect secretion of neurotransmitters. This provides an additional mechanism for the modulation of neuronal communication and plasticity by steroids.