FoxO介导的自噬通路抑制内质网应激缓解肾小球微循环障碍的研究

Glomerular microcirculation impairment has contributed much to pathophysiology mechanism in process of glomerular sclerosis. Endoplasmic reticulum stress(ERS) is involved in a variety of renal disease, and inhibition of endoplasmic reticulum stress may ameliorate impairment of glomerular microcirculation. Promotion autophagy may remove production of ERS and alleviate damage. In recent years, more and more studies have focused on the O subfamily of forkhead transcription factors (FoxO),which regulate autophagy in many tissues. However, the fact FoxO mediated autophagy pathway in renal disease is still undiscoved. Our previous studies have found that promote autophagy can alleviate endoplasmic reticulum stress injury in renal disease. In cultured glomerular endothelial cells(GENCs), the autophagic level was suppressed by pretreatment with FoxO1 siRNA, whereas ER stress was enhanced at the same time. So we hypothesis that FoxO might promote autophagy, and ameliorate glomerular microcirculation damage induced by endoplasmic reticulum stress. In this study, we first examine whether expression of FoxO, autophagy and glomerular microcirculation had altered under ERS injury condition in vivo and vitro. Furthermore, we detected whether blocking and overexpression FoxO could mediate autophagy and renal ERS injury. To identify other FoxO target genes, we performe microarray analysis of expression profile in glomerular endothelial cells and podocytes transfected with FoxO plasmids or FoxO siRNA. Lastly, we establish a transgenic mice of foxo specific knockout in glomerular endothelial cells and podocytes, and discuss the effect of autophagy depended on FoxO to inhibit endoplasmic reticulum stress and ameliorate impairment of glomerular microcirculation. Our study provide new insights into the role of FoxO factors in adjusting autophagy and egulation glomerular microcirculation.

肾小球微循环障碍是肾小球硬化的主要病理学基础。内质网应激（ERS）参与了多种肾脏病进程、抑制过度ERS可缓解肾小球微循环障碍。自噬持续激活可清除ERS产物、缓解细胞损伤。FoxO是近年倍受关注的自噬调控因子，在肾脏病中关于其调控自噬的研究仅刚刚起步。我们前期研究发现激活自噬可缓解肾脏ERS损伤，阻断FoxO1明显降低自噬水平且ERS损伤加重。因此我们推测FoxO可能通过调控自噬、抑制ERS损伤而缓解肾小球微循环障碍。本课题在体内外ERS损伤模型中确认FoxO表达、自噬和肾脏血管生成变化的基础上；以肾小球内皮/足细胞为研究对象，通过过表达或沉默FoxO，明确其对自噬及内质网应激的影响，并用基因芯片技术探索其调控自噬的分子机制；最后应用FoxO肾小球内皮/足细胞条件敲除小鼠，阐明FoxO依赖的自噬对ERS及肾小球微循环的影响，揭示FoxO作为自噬调控靶点在肾小球ERS损伤及微循环障碍中的作用。

近年来慢性肾脏病(chronic kidney disease，CKD)已成为威胁人类健康与生命的世界性公共卫生问题，其发生发展呈潜隐缓慢趋势，并最终导致慢性肾功能衰竭（ESRD）。肾小球毛细血管襻毁损、微血管网闭塞丧失、血管生成障碍与肾小球硬化、慢性肾脏病进展密切相关。内质网应激（ERS）参与了多种肾脏病进程、抑制过度ERS可缓解肾小球微循环障碍。自噬持续激活可清除ERS产物、缓解细胞损伤。Forkhead转录因子（FoxO）是近年倍受关注的自噬调控因子，在肾脏病中关于其调控自噬的研究仅刚刚起步。本研究结果提示了醛固酮以及血管紧张素II可引起FoxO蛋白的磷酸化，通过mTOR信号通路调节Atg7影响自噬，从而调控内质网应激相关蛋白BIP/ATF4/CHOP信号轴，从而造成肾脏组织损伤的一系列信号通路。同时，本课题组还开展了横向研究，观察了高脂饮食对动物肾功能的影响，结果发现饱和脂肪酸导致小鼠肾小球硬化，肾小管上皮细胞凋亡，纤维化和ERS，足细胞凋亡，自噬水平增加和Glut4转位受阻。而GLP-1可通过减轻胰岛素抵抗，促进Glut4转位，抑制高脂导致的过度自噬，从而减轻饱和脂肪酸导致的肾脏损伤。GLP-1减轻饱和脂肪酸导致的肾小管细胞ERS和凋亡，其机制可能通过抑制AT1R表达。本研究结果不仅验证了一种转录因子在肾病疾病可能发挥的重要作用，并初步探讨了其致病的分子机制，为肾脏病的干预提供了一个潜在的新靶点。