Department of Pharmacology, Basic Medical School of Wuhan University, Wuhan 430071, China; Department of Clinical Pharmacology, PLA General Hospital of Central Theater Command, Wuhan 430061, China.
Department of Pharmacology, Basic Medical School of Wuhan University, Wuhan 430071, China.
Toxicology. 2020 Feb 28;432:152381. doi: 10.1016/j.tox.2020.152381. Epub 2020 Jan 22.
Chronic glutamate excitotoxicity has been thought to be involved in numerous neurodegenerative disorders. A small but significant loss of membrane cholesterol has been reported following a short stimulation of ionotropic glutamate receptors (iGluRs). We investigated the alteration of brain cholesterol following chronic glutamate treatment. The alteration of cholesterol levels was evaluated in the hippocampus from the adult rats that received the subcutaneous injection with monosodium l-glutamate at 1, 3, 5, and 7 days of age. The regulation of CYP46A1, LXRα, and ApoE levels were assayed following subtoxic glutamate treatment in SH-SY5Y cells as well as HT-22 cells lacking iGluRs. The ratio of 24S-hydroxycholesterol to cholesterol was elevated in the adult rats exposed to monosodium l-glutamate before the weaning age, compared to the control. The blockers of NMDA receptor (MK801) and mGluR5 (MPEP) attenuated the glutamate-induced loss of cholesterol and elevation of 24S-hydroxycholesterol level in SH-SY5Y cells. The induction of the mRNA levels of CYP46A1, LXRα, and ApoE by glutamate was observed in both SH-SY5Y cells and HT-22 cells; additionally, MK801 and MPEP attenuated the increases in these genes in SH-SY5Y cells. The increase in the binding of LXRα proteins with ApoE promoter following glutamate treatment was attenuated by MK801. The luciferase assay indicated the binding of CREB protein with CYP46A1 promoter, and the glutamate-induced CREB expression was inhibited by MK801. The results suggest that glutamate, the major excitatory neurotransmitter, may affect the metabolism and redistribution of cholesterol in the neuronal cells via its specific receptors during chronic exposure.
慢性谷氨酸兴奋性毒性被认为与许多神经退行性疾病有关。已有报道称，短暂刺激离子型谷氨酸受体（iGluRs）后，膜胆固醇会出现少量但显著的损失。我们研究了慢性谷氨酸处理后大脑胆固醇的变化。在接受单谷氨酸钠皮下注射的成年大鼠的海马体中评估了胆固醇水平的变化，注射年龄为 1、3、5 和 7 天。在 SH-SY5Y 细胞和缺乏 iGluRs 的 HT-22 细胞中，检测了亚毒性谷氨酸处理后 CYP46A1、LXRα 和 ApoE 水平的调节。与对照组相比，在断奶前暴露于单谷氨酸钠的成年大鼠中，24S-羟胆固醇与胆固醇的比值升高。NMDA 受体（MK801）和 mGluR5（MPEP）的阻滞剂可减轻谷氨酸诱导的 SH-SY5Y 细胞中胆固醇损失和 24S-羟胆固醇水平升高。谷氨酸在 SH-SY5Y 细胞和 HT-22 细胞中诱导 CYP46A1、LXRα 和 ApoE 的 mRNA 水平升高；此外，MK801 和 MPEP 可减轻 SH-SY5Y 细胞中这些基因的增加。MK801 可减轻谷氨酸处理后 LXRα 蛋白与 ApoE 启动子结合的增加。荧光素酶测定表明 CREB 蛋白与 CYP46A1 启动子结合，MK801 抑制谷氨酸诱导的 CREB 表达。结果表明，谷氨酸作为主要的兴奋性神经递质，可能通过其在慢性暴露期间的特定受体影响神经元细胞中胆固醇的代谢和重新分布。
