HSP70-HSF1-Atg5/Atg12通路调控自噬：白癜风黑素细胞氧化损伤的新机制

Oxidative stress induced melanocytes destruction has been demonstrated to play a key role in the pathogenesis of vitiligo. Autophagy is the an important way for cells to reduce the damage from oxidative stress. In our previous studies, we have found that the activation of autophagy was blocked in melanocytes of vitiligo, which is a key factor leading to apopotosis in melanocytes of vitiligo under oxidative stress, but its upstream regulation mechanism is unclear. Recently, we compared the different expression of all the autophagy related genes in melanocytes from healthy and vitiligo patients using microarray, we found both Atg5 and Atg12 are significantly reduced in vitiligo patients. Based on literature review, HSP70 is an important molecule in the pathogenesis of vitiligo,and is highly expressed in vitiligo melanocytes. It can resulted in reduced transcriptional activity of HSF1 which is bioinformatic predicted to transcript both Atg5 and Atg12. Based on these findings, our study is to find the key molecules resulting in autophagy blocking, and to discuss the pathway HSP70-HSF1-Atg5/Atg12 in regulating autophagy. The implementation of this project will expand upstream regulation mechanisms of autophagy, and discover a new mechanism of oxidative damage in vitiligo melanocytes. It is expected to provide a new theoretical basis for the prevention and treatment of vitiligo.

氧化应激诱导黑素细胞凋亡是白癜风发病的关键事件，自噬是细胞抵抗氧化损伤的重要途径。我们前期发现，氧化应激下，白癜风黑素细胞自噬激活存在障碍，是促进其凋亡的重要原因，但导致自噬障碍的关键分子及调控机制不清。我们最近利用表达谱芯片对比了氧化应激下正常和患者黑素细胞自噬相关基因的表达差异，结果提示Atg5和Atg12可能是自噬障碍的关键分子。结合文献，HSP70可抑制HSF1磷酸化，降低其转录活性，我们发现白癜风黑素细胞中，HSP70呈显著高表达，生物信息学预测HSF1可调控Atg5和Atg12转录。据此推测，氧化应激反应性激活黑素细胞中HSP70-HSF1-Atg5/12通路，负向调控自噬，促进白癜风发病。本项目拟在前期研究基础上，明确导致自噬障碍的关键分子并阐明上游的分子调控机制。项目的顺利实施有望拓展对自噬上游调控机制的认识，揭示白癜风黑素细胞氧化损伤的新机制，为治疗提供新靶点。

自噬在氧化应激诱导的黑素细胞死亡中起保护作用。我们之前的研究表明，自噬失调会增加白癜风黑素细胞对氧化损伤的敏感性，从而促进黑素细胞凋亡及白癜风的发展。但是，该过程的分子机制尚未完全阐明。本课题首先在皮损组织中证实了白癜风黑素细胞自噬水平障碍这一现象，随后利用RNA-seq技术，对正常和白癜风黑素细胞在氧化应激条件下转录组的表达变化进行了分析，并重点关注了目前人类自噬基因库中的基因的表达差异。结果发现：氧化应激条件下，自噬小体形成过程中的两个重要分子，Atg5和Atg12的表达降低是造成白癜风黑素细胞自噬激活障碍的关键分子。进一步对Atg5和Atg12缺失的上游机制进行探讨，结果显示：热休克因子1（HSF1），作为Atg5和Atg12的主要转录因子，在白癜风黑素细胞应对氧化应激损伤时的表达显著不足，进而抑制了黑素细胞在应激条件下自噬的正常发生，干预HSF1可有效改变黑素细胞对氧化应激诱导的细胞凋亡情况。最后，通过回复实验，我们证明，HSF1对氧化应激下黑素细胞的保护作用依赖于自噬激活的。总的来说，本课题证明了HSF1-Atg5/12轴调控自噬激活可保护氧化应激诱导的黑素细胞死亡，可能成为白癜风治疗的新靶点。