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The study for new regulating mechanism of neuronal nicotinic acetylcholine receptor and the development of new therapeutics for psycho-neurological disorders

神经烟碱型乙酰胆碱受体调控新机制研究及精神神经疾病新疗法开发

基本信息

批准号：
18590234
负责人：
MATSUBAYASHI Hiroaki
金额：
$ 2.52万
依托单位：
Hiroshima Institute of Technology
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2006
资助国家：
日本
起止时间：
2006 至 2007
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-18590234/
关键词：
nicotinic receptor microglia PLC activity ion channel RT-PCR 細胞内カルシウム PKC

项目摘要

The alpha7 type of nicotinic acetylcholine receptors (nAChRs) are homopentameric ion channels with high Ca^<2+> permeability. Although the nAChRs were thought to be expressed mainly in neuronal cells, recent evidence indicates that these receptors also function in some non-neuronal cell types. I have found that in rat primary culture microglia, nicotine elicits a transient increase in intracellular Ca^<2+> levels, which is abolished by specific blockers of nAChRs, methyllycaconitine and alpha-bungarotoxin. However, this response is not affected by the absence of extracellular Ca^<2+> and is blocked by U73122, an inhibitor of phospholipase C (PLC), and xestospongin C, a blocker of the IP_3 receptor. Extensive electrophysiological measurements failed to reveal any nicotine-induced currents in microglia. These results suggest that microglial nAChRs drive a signaling process involving the activation of PLC and Ca^<2+> release from 1P_3-sensitive stores, rather than operating as ion channels. Furthermore, the activation of nAChRs enhanced BzATP-stimulated TNF release (P2X_7 receptor activation), but suppressed lipopolysaccahride (LPS)-induced TNF release (Toll-like receptor 4 activation), without affecting the expression of TNF mRNA. In LPS-stimulated microglia, the decreased TNF release induced by nicotine was associated with the suppression of the activation of JNK and p38 MAP kinases, which regulate the post-transcriptional steps of TNF synthesis. On the other hand, nicotine had no effect on the activation of either MAP kinase induced by BzATP, but enhanced BzATP-elicited Ca^<2+> influx. It still remains to study why the microglial nAChRs have no ion channel activities, although their cDNA sequences are as same as those of neurons.

α7型烟碱乙酰胆碱受体(nAChR)是具有高Ca 2+ 渗透性的同五聚体离子通道。尽管人们认为 nAChR 主要在神经元细胞中表达，但最近的证据表明这些受体也在一些非神经元细胞类型中发挥作用。我发现在大鼠原代培养的小胶质细胞中，尼古丁引起细胞内Ca 2+ 水平的短暂增加，这种增加被nAChR、甲基lycaconitine和α-银环蛇毒素的特异性阻断剂所消除。然而，该反应不受细胞外Ca 2+ 缺乏的影响，并且被U73122(磷脂酶C(PLC)抑制剂)和xestospongin C(IP_3受体阻断剂)阻断。广泛的电生理学测量未能揭示小胶质细胞中任何尼古丁诱导的电流。这些结果表明，小胶质细胞nAChR驱动涉及PLC激活和Ca 2+ 从1P_3敏感存储中释放的信号传导过程，而不是作为离子通道操作。此外，nAChRs的激活增强了BzATP刺激的TNF释放（P2X_7受体激活），但抑制脂多糖（LPS）诱导的TNF释放（Toll样受体4激活），而不影响TNF mRNA的表达。在 LPS 刺激的小胶质细胞中，尼古丁诱导的 TNF 释放减少与抑制 JNK 和 p38 MAP 激酶的激活有关，这些激酶调节 TNF 合成的转录后步骤。另一方面，尼古丁对BzATP诱导的任一MAP激酶的激活没有影响，但增强了BzATP引起的Ca 2+ 流入。尽管小胶质细胞nAChRs的cDNA序列与神经元相同，但其为何没有离子通道活性仍有待研究。