Mou Kuanhou, Liu Wei, Han Dan, Li Pan
Department of Dermatology, the Frist Affiliated Hospital of Xi'an Jiaotong University, 277 West Yanta Road, Xi'an, Shaanxi 710061, People's Republic of China.
Center for Translational Medicine, the Frist Affiliated Hospital of Xi'an Jiaotong University, 277 West Yanta Road, Xi'an, Shaanxi 710061, People's Republic of China.
J Dermatol Sci. 2017 Mar;85(3):162-169. doi: 10.1016/j.jdermsci.2016.12.011. Epub 2016 Dec 14.
The primary cause of skin cancer is ultraviolet (UV) light from the sun. Keratinocytes are the predominant cell type in the epidermis and form a barrier against environmental damage, especially from UV light irradiation. Autophagy is a self-digestion mechanism for energy homeostasis at critical times during development and as a response to stress. High-mobility group protein 1 (HMGB1) is a highly conserved nuclear protein that is associated with cell autophagy.
We investigated the role of HMGB1 in keratinocytes exposed to UV irradiation and its regulation of keratinocyte autophagy.
Specimens of UV-exposed human skin were assayed immunohistochemically for HMGB1. HaCaT immortalized human keratinocytes were used to investigate the mechanism of HMGB1 translocation induced by UV irradiation. Levels of cytosolic reactive oxygen species (ROS) were determined by HDCF assay, apoptosis was assayed by flow cytometry and western-blot after lentivirus-mediated shRNA targeting of HMGB1 in keratinocytes by UV irradiation. Phosphorylated-Erk1/2 expression was assayed by western blotting.
HMGB1 and its receptor (receptor for advanced glycation end products, RAGE) were both expressed by HaCaT cells, and HMGB1 was transferred from the nucleus to the cytoplasm after UV irradiation in both HaCaT and human skin keratinocytes. Knockdown of HMGB1 expression by lentivirus-mediated shRNA limited UV-induced autophagy and led to increased apoptosis of HaCaT cells. Pharmacological inhibition of HMGB1 cytoplasmic translocation by agents such as ethyl pyruvate limits starvation-induced autophagy. UV irradiation led to phosphorylation of Erk1/2 in HaCaT cells. Inhibition of RAGE and Erk1/2 limited HaCaT cell autophagy.
Autocrine HMGB1 modulated HaCaT autophagy via a RAGE/HMGB1/extracellular signal-regulated Erk1/2-dependent pathway to protect keratinocytes from apoptosis during UV irradiation.
皮肤癌的主要病因是来自太阳的紫外线（UV）。角质形成细胞是表皮中的主要细胞类型，形成抵御环境损伤的屏障，尤其是抵御紫外线照射。自噬是一种在发育关键时期维持能量稳态以及作为对应激反应的自我消化机制。高迁移率族蛋白1（HMGB1）是一种与细胞自噬相关的高度保守的核蛋白。
我们研究了HMGB1在暴露于紫外线照射的角质形成细胞中的作用及其对角质形成细胞自噬的调节。
对紫外线照射的人皮肤标本进行HMGB1免疫组织化学检测。使用HaCaT永生化人角质形成细胞研究紫外线照射诱导HMGB1易位的机制。通过HDCF法测定细胞溶质活性氧（ROS）水平，通过流式细胞术和蛋白质免疫印迹法检测慢病毒介导的针对紫外线照射的角质形成细胞中HMGB1的短发夹RNA（shRNA）后的细胞凋亡。通过蛋白质免疫印迹法检测磷酸化的细胞外信号调节激酶1/2（Erk1/2）表达。
HaCaT细胞同时表达HMGB1及其受体（晚期糖基化终产物受体，RAGE），在HaCaT细胞和人皮肤角质形成细胞中，紫外线照射后HMGB1从细胞核转移至细胞质。慢病毒介导的shRNA敲低HMGB1表达限制了紫外线诱导的自噬，并导致HaCaT细胞凋亡增加。诸如丙酮酸乙酯等药物抑制HMGB1细胞质易位可限制饥饿诱导的自噬。紫外线照射导致HaCaT细胞中Erk1/2磷酸化。抑制RAGE和Erk1/2可限制HaCaT细胞自噬。
自分泌HMGB1通过RAGE/HMGB1/细胞外信号调节的Erk1/2依赖性途径调节HaCaT自噬，以保护角质形成细胞在紫外线照射期间免于凋亡。
