足细胞自噬调控在肝细胞生长因子保护糖尿病肾病中作用机制的实验研究

Autophagy is an essential mechanism to maintain podocyte homeostasis under physiological and pathological conditions. Impaired autophagy led to severe oxidative stress in podocytes. Oxidative stress, a common pathogenetic mechanism underlying diabetes and its complications, mediates high glucose-induced podocyte injury via multiple pathways. Podocyte injury is a key initial event in pathogenesis of diabetic nephropathy (DN) and presented in all the stages of development of DN. Hepatocyte growth factor (HGF) is a putative renotrophic and renoprotective factor. In the previous study, we found that HGF could prevent high glucose-induced oxidative stress in rat mesangial cells. Next, in this project, we want to investigate how HGF affects autophagy and oxidative stress in high glucose-stimulated podocytes, explore the involved signal pathways, and elucidate the cross talk among these signaling. These should help in revealing the mechanism of HGF to regulate autophagy in podocytes as well as to function as an antioxidant and protective factor in kidney, thus providing novel insights into therapeutic approaches for the treatment of diabetic nephropathy.

自噬是肾脏足细胞在生理和病理情况下，赖以维持细胞内环境稳态和应对各种损伤应激的重要生存调节机制之一。自噬不济会导致足细胞内严重的氧化应激。氧化应激作为糖尿病及其并发症的共同病理机制之一，可通过多种途径介导高血糖对足细胞的损伤。足细胞损伤在糖尿病肾病（DN）的发病机制中占有非常重要的始动地位，且贯穿DN发生发展的始终。肝细胞生长因子（HGF）对肾脏具有良好的营养保护作用。基于我们的前期研究发现：HGF可抑制高糖刺激下的大鼠系膜细胞内的氧化应激，本项目拟通过体内外研究观察HGF对高糖环境下足细胞内自噬和氧化应激的影响，探讨足细胞自噬调控在HGF防治DN中发挥的作用及其与HGF抗氧化效应的联系，并阐明这些作用涉及的信号通路及互相之间的影响机制（Cross Talk），以明确HGF调控足细胞自噬的机理，完善HGF的抗氧化机制和HGF保护肾脏的机制，为糖尿病肾病的治疗研究提供新的思路和实验依据。

研究糖尿病肾病中HGF对足细胞自噬水平的影响及其调节机制。首先，我们在探索莱菔硫烷（Sulforaphane）抗氧化保护糖尿病肾病的研究中发现，GSK3β是高糖介导肾脏氧化应激损伤的重要作用靶点。而后我们通过体外自噬流的观察证实，高糖刺激下足细胞内自噬流的受阻与其内GSK3β/活性的增高和溶酶体数量的锐减有关。HGF则能增强Akt和GSK3β（活性抑制性位点Ser9）的磷酸化水平，恢复溶酶体数量和自噬流，并对高糖刺激下的足细胞产生抗凋亡和抗氧化的保护作用。因此，激活PI3K/Akt通路，抑制GSK3β活性，促进TFEB核转位，进而增加溶酶体数量是HGF改善高糖刺激下足细胞内自噬流的具体作用机制。最后，我们通过体内糖尿病肾病模型的研究，进一步验证了HGF对糖尿病肾病的显著防治效果和PI3K/Akt/GSK3β/TFEB信号通路在HGF调节足细胞自噬和保护肾脏中所发挥的重要作用。