虫草素通过CAPS1-ERS途径调控星形胶质细胞表型转化抑制Aβ诱导神经毒性的机制研究

Neuro-immune microenvironment mediated by astrocyte(AS) phenotype transformation contributes to maintain the normal function of neurons. It was found that cordycepin (CCS) inhibited the neuronal apoptosis and improved learning and memory impairment in AD mice, accompanied by inhibiting AS-M1 polarization and promoting AS-M2 polarization. Further in vitro studies also found that CCS inhibited the M1 polarization and promoted AS-M2 polarization in SVGP12 cell line. Bioinformatics predicted that CCS can combine with the active pocket of CASP1 at the site of Arg179, His237 and Ser339. Furthermore, CASP1 was also inhibited by CCS treatment, and the markers of ER stress such as GRP78 and CHOP were down-regulated simultaneously. The results suggested that AS-M1/M2 phenotype transformation play an important role in the anti-AD efficacy after CCS treatment via CASP1-ERS pathway. In the present study, based on the correlation between the CASP1-ERS signaling and astroglial polarization induced by CCS, the key binding site and the action mechanism of CCS and CASP1 are investigated, and the molecular mechanism of inhibiting Aβ-induced neurotoxicity after CCS treatment via CASP1-ERS pathway mediated AS-M1/M2 transformation is further clarified. This project will provide the evidences for discovering new targets of anti-AD drug and for establishing new therapeutic strategies for AD treatment.

星形胶质细胞（AS）表型转化介导神经免疫微环境进而影响神经元活性。申请者发现虫草素（CCS）改善学习记忆障碍与降低Aβ诱导神经元毒性、抑制AD鼠神经元凋亡相关；同时发现CCS可下调CASP1及ERS标记物GRP78/CHOP表达、使SVGP12细胞的M1极化阻抑及M2极化激活；进一步预测发现CCS与CASP1活性口袋中Arg179、His237及Ser339位点结合，提示CCS通过阻滞CASP1介导的ERS通路调控AS-M1/M2转化发挥抗Aβ神经毒性作用。本项目拟通过：1）明确CASP1在CCS调控AS表型转化介导Aβ诱导神经毒性中的作用；2）明确CCS与CASP1活性口袋中关键位点的结合作用与功能；3）阐明CCS通过CASP1-ERS途径调控AS-M1/M2表型转化、进而发挥抗Aβ神经毒性分子机制。本项目为研究炎性微环境对Aβ诱导神经毒性的影响、为发现抗AD作用新靶点提供实验依据。

神经胶质细胞是中枢神经系统中的一种巨噬细胞样免疫细胞，也是调节神经元免疫微环境的主要参与者。阿尔茨海默病(AD)是一种的中枢神经系统退行性疾病，AD脑区常出现异常活化的胶质细胞，影响周围神经元免疫微环境，这与AD的发生和发展密切相关。胶质细胞有M1型和M2型两种典型的活化模式：M1型胶质细胞参与促进炎性反应具有神经毒性作用，而M2型胶质细胞参与抑制炎性反应具有神经保护作用。调控胶质细胞M1/M2表型转化介导的神经免疫微环境，可能成为治疗AD的新手段和新思路。因此，迫切需要开发和研究新的基于调控小胶质细胞M1/M2转化改善神经免疫微环境的神经保护性药物，并对其机制进行深入探讨，具有重要的科学意义和潜在的临床应用价值。虫草素是从蛹虫草中分离出来的第一个核苷类抗菌素，因其具有抗自由基、耐缺氧、增强记忆、抗炎、提高免疫力等作用而备受关注。有报道证实AD中炎性小体激活的CASP1导致脑内炎症反应，而引起神经元的损伤和死亡。因此，本课题首先从离体和在体两方面明确虫草素具有抗AD作用的基础上，从CASP1调控胶质细胞表性转化的新角度，进一步深入探讨了虫草素发挥神经保护作用的机制，发现虫草素分别通过减少CASP1活性抑制Aβ诱导的胶质细胞向M1极化并激活STAT6促进其向M2极化，从而改变了炎性微环境发挥抗AD的神经保护作用，以上研究结果为抗AD药物机制的研究提供新的思路和作用靶点，并提示虫草素可作为新的效果显著的有临床应用价值的抗AD候选药物进行深入研究。