Department of Gastroenterology, Tongji Hospital, Tongji University, Shanghai, China.
Department of Gastroenterology, Tongji Hospital, Tongji University, Shanghai, China
Clin Sci (Lond). 2018 Aug 14;132(15):1645-1667. doi: 10.1042/CS20180177. Print 2018 Aug 16.
High-mobility group box-1 (HMGB1) plays a context-dependent role in autophagy, which is required for hepatic stellate cells (HSCs) activation. However, the significance of HMGB1-induced HSCs autophagy in liver fibrosis has not been elucidated. Here, we first documented an enrichment of peripheral and intrahepatic HMGB1 signal in hepatitis B virus (HBV)-related liver fibrosis progression, and presented a direct evidence of anatomic proximity of HMGB1 with a-SMA (a marker for HSCs activation) in cirrhotic liver specimens. Then, we demonstrated the autophagy-inducing effects by serum-sourced HMGB1 in both primary murine HSCs and human HSCs cell line (LX-2), reflected by increased number of autophagic vacuoles (AVs) under the transmission electron microscope (TEM) and up-regulated protein expression of lipidated microtubule-associated light chain 3 (LC3-II) (a marker for autophagosome) in Western blot analysis. Intriguingly, there is a possible translocation of endogenous HMGB1 from the nucleus to cytoplasm to extracellular space, during exogenous HMGB1-induced HSCs autophagy. Meanwhile, the dose- and time-dependent effects by recombinant HMGB1 (rHMGB1) in enhancing LX-2 autophagy and fibrogenesis have been revealed with activated extracellular regulated protein kinase (ERK)/c-Jun N-terminal kinase (JNK) mitogen-activated protein kinase (MAPK) and restrained mammalian target of rapamycin (mTOR)/STAT3 signaling pathways. Additionally, the ERK or JNK inhibitor could not only inhibit rHMGB1-induced autophagy and fibrogenesis in LX-2 cells, but also restore the suppressed mTOR and STAT3 pathways. Furthermore, using LC3-siRNA transfected LX-2, we found HMGB1-induced fibrogenesis is dependent on its autophagy-inducing effects. Finally, we elucidated the involvement of extracellular HMGB1-receptor for advenced glycation end product (RAGE) axis and endogenous HMGB1 in exogenous HMGB1-induced effects. Our findings could open new perspectives in developing an antifibrotic therapy by targetting the HSCs autophagy.
高迁移率族蛋白 B1（HMGB1）在自噬中发挥着依赖于上下文的作用，这对于肝星状细胞（HSCs）的激活是必需的。然而，HMGB1 诱导的 HSCs 自噬在肝纤维化中的意义尚未阐明。在这里，我们首先记录了乙型肝炎病毒（HBV）相关肝纤维化进展中外周和肝内 HMGB1 信号的富集，并在肝硬化肝组织标本中直接证明了 HMGB1 与 a-SMA（HSCs 激活的标志物）的解剖接近性。然后，我们通过血清来源的 HMGB1 在原代小鼠 HSCs 和人 HSCs 细胞系（LX-2）中证明了自噬诱导作用，透射电子显微镜（TEM）下自噬小体（AV）数量增加，Western blot 分析中脂质化微管相关轻链 3（LC3-II）（自噬体的标志物）的蛋白表达上调。有趣的是，在外源 HMGB1 诱导的 HSCs 自噬过程中，内源性 HMGB1 可能从核转移到细胞质到细胞外空间。同时，通过重组 HMGB1（rHMGB1）在增强 LX-2 自噬和纤维化方面的剂量和时间依赖性作用，揭示了激活细胞外调节蛋白激酶（ERK）/c-Jun N 端激酶（JNK）有丝分裂原激活蛋白激酶（MAPK）和抑制哺乳动物雷帕霉素靶蛋白（mTOR）/信号转导和转录激活因子 3（STAT3）信号通路。此外，ERK 或 JNK 抑制剂不仅可以抑制 rHMGB1 诱导的 LX-2 细胞自噬和纤维化，还可以恢复受抑制的 mTOR 和 STAT3 途径。此外，通过 LC3-siRNA 转染的 LX-2，我们发现 HMGB1 诱导的纤维化依赖于其自噬诱导作用。最后，我们阐明了细胞外 HMGB1-晚期糖基化终产物受体（RAGE）轴和内源性 HMGB1 在体外 HMGB1 诱导作用中的作用。我们的研究结果为通过靶向 HSCs 自噬开发抗纤维化疗法开辟了新的视角。
