Leski M L, Valentine S L, Coyle J T
Consolidated Department of Psychiatry, Harvard Medical School, Massachusetts General Hospital-East, 115 Mill Street, Belmont, MA 02178, USA.
Brain Res. 1999 May 15;828(1-2):27-40. doi: 10.1016/s0006-8993(99)01270-6.
This study reports on the regulation of kainate neurotoxicity in cerebellar granule cells by calcium entry through voltage-gated calcium channels and by calcium release from internal cellular stores. Kainate neurotoxicity was prevented by the AMPA selective antagonist LY 303070 (10 microM). Kainate neurotoxicity was potentiated by cadmium, a general voltage-gated calcium channel blocker, and the L-type voltage-gated calcium channel blocker nifedipine. The antagonists of intracellular Ca2+ ([Ca2+]i) release, thapsigargin and ryanodine, were also able to potentiate kainate neurotoxicity. Kainate treatment elevated [Ca2+]i concentration with a rapid initial increase that peaked at 1543 nM and then declined to plateau at approximately 400 nM. Nifedipine lowered the peak response to 764 nM and the plateau response to approximately 90 nM. Thapsigargin also lowered the kainate-induced increase in [Ca2+]i (640 nM peak, 125 nM plateau). The ryanodine receptor agonist caffeine eliminated the kainate-induced increase in [Ca2+]i, and reduced kainate neurotoxicity. Kainate neurotoxicity potentiated by nifedipine was not prevented by RNA or protein synthesis inhibitors, nor by the caspase inhibitors YVAD-CHO and DEVD-CHO. Neither DNA laddering nor the number of apoptotic nuclei were increased following treatment with kainate and nifedipine. Increased nuclear staining with the membrane impermeable dye propidium iodide was observed immediately following kainate treatment, indicating a loss of plasma membrane integrity. Thus, kainate neurotoxicity is prevented by calcium entry through L-type calcium channels.
本研究报告了通过电压门控钙通道的钙内流以及细胞内钙库的钙释放对小脑颗粒细胞中红藻氨酸神经毒性的调节作用。AMPA选择性拮抗剂LY 303070（10微摩尔）可预防红藻氨酸神经毒性。镉（一种通用的电压门控钙通道阻滞剂）和L型电压门控钙通道阻滞剂硝苯地平可增强红藻氨酸神经毒性。细胞内Ca2+（[Ca2+]i）释放的拮抗剂毒胡萝卜素和ryanodine也能够增强红藻氨酸神经毒性。红藻氨酸处理可提高[Ca2+]i浓度，最初迅速升高，峰值达到1543纳摩尔，然后下降至约400纳摩尔的平台期。硝苯地平将峰值反应降低至764纳摩尔，平台期反应降低至约90纳摩尔。毒胡萝卜素也降低了红藻氨酸诱导的[Ca2+]i升高（峰值640纳摩尔，平台期125纳摩尔）。ryanodine受体激动剂咖啡因消除了红藻氨酸诱导的[Ca2+]i升高，并降低了红藻氨酸神经毒性。硝苯地平增强的红藻氨酸神经毒性不能被RNA或蛋白质合成抑制剂以及半胱天冬酶抑制剂YVAD-CHO和DEVD-CHO所预防。用红藻氨酸和硝苯地平处理后，DNA梯状条带和凋亡细胞核数量均未增加。红藻氨酸处理后立即观察到用膜不透性染料碘化丙啶进行的核染色增加，表明质膜完整性丧失。因此，通过L型钙通道的钙内流可预防红藻氨酸神经毒性。
