Furukawa K, Smith-Swintosky V L, Mattson M P
Sanders-Brown Research Center on Aging, University of Kentucky, Lexington 40536-0230, USA.
Exp Neurol. 1995 Jun;133(2):153-63. doi: 10.1006/exnr.1995.1018.
Calcium influx through glutamate receptors and voltage-dependent channels mediates an array of functional and structural responses in neurons. However, unrestrained Ca2+ influx can injure and kill neurons; a mechanism implicated in both acute and chronic neurodegenerative disorders. Data reported here indicate that depolymerization of actin filaments can stabilize intracellular free calcium levels ([Ca2+]i) and protect hippocampal neurons against excitotoxic injury. Studies with fluorescein-labeled phalloidin showed that cytochalasin D and glutamate each induced actin filament depolymerization. The microfilament-disrupting agent cytochalasin D protected cultured rat hippocampal neurons against glutamate toxicity, whereas the actin filament-stabilizing agent jasplakinolide potentiated glutamate toxicity. The microtubule-disrupting agent colchicine was ineffective in protecting neurons against glutamate toxicity. Cytochalasin D did not protect neurons against calcium ionophore toxicity or iron toxicity, indicating that its actions were not due to nonspecific effects on Ca2+ or free radical metabolism. Cytochalasin D markedly attenuated kainate-induced damage to hippocampus of adult rats, suggesting an excitoprotective role for actin depolymerization in vivo. Elevations of [Ca2+]i induced by glutamate were attenuated in cultured hippocampal neurons pretreated with cytochalasin D and potentiated in neurons pretreated with jasplakinolide. The [Ca2+]i response to a Ca2+ ionophore was unaffected by cytochalasin D, suggesting that actin depolymerization reduced Ca2+ influx through membrane channels. Taken together with previous patch clamp data, our findings suggest that depolymerization of actin in response to Ca2+ influx may serve as a feedback mechanism to attenuate potentially toxic levels of Ca2+ influx.
通过谷氨酸受体和电压依赖性通道的钙内流介导了神经元中的一系列功能和结构反应。然而，不受控制的Ca2+内流会损伤并杀死神经元；这一机制与急性和慢性神经退行性疾病均有关联。此处报告的数据表明，肌动蛋白丝的解聚可以稳定细胞内游离钙水平（[Ca2+]i），并保护海马神经元免受兴奋性毒性损伤。用荧光素标记的鬼笔环肽进行的研究表明，细胞松弛素D和谷氨酸各自诱导肌动蛋白丝解聚。破坏微丝的药物细胞松弛素D保护培养的大鼠海马神经元免受谷氨酸毒性，而稳定肌动蛋白丝的药物茉莉酸甲酯增强了谷氨酸毒性。破坏微管的药物秋水仙碱在保护神经元免受谷氨酸毒性方面无效。细胞松弛素D不能保护神经元免受钙离子载体毒性或铁毒性，表明其作用并非由于对Ca2+或自由基代谢的非特异性影响。细胞松弛素D显著减轻了成年大鼠海马体中由红藻氨酸诱导的损伤，表明肌动蛋白解聚在体内具有兴奋性保护作用。在用细胞松弛素D预处理的培养海马神经元中，由谷氨酸诱导的[Ca2+]i升高减弱，而在用茉莉酸甲酯预处理的神经元中则增强。对Ca2+离子载体的[Ca2+]i反应不受细胞松弛素D的影响，表明肌动蛋白解聚减少了通过膜通道的Ca2+内流。结合先前的膜片钳数据，我们的研究结果表明，响应Ca2+内流的肌动蛋白解聚可能作为一种反馈机制，以减弱潜在毒性水平的Ca2+内流。
