HMGB1介导的自噬在脑出血后炎症损伤中的作用机制研究

Intracerebral hemorrhage (ICH) causes a high lethality and morbidity. After ICH, a large number of cells die and the inflammatory reaction is recruited and enhanced. Recently, autophagy has been widely studied in many fields of neuroscience, but the interaction between the autophagy on cell survival and the inflammatory responses after ICH remains controversial. In addition to the functions in extracellular inflammation and nuclear transcription, high-mobility group box 1 (HMGB1) has been reported to be an important regulator of autophagy in tumor. Extracellular HMGB1 can be activated by RAGE axis and induce autophagy. Our previous study showed that after ICH, HMGB1 aggravated inflammatory injury in acute phase. During recovery phase, HMGB1 promoted the regeneration of neural precursor cells and the angiogenesis around the periventricular and perihematomal tissue via the activation of RAGE receptors. In acute phase, the inhibition of HMGB1 release and the antagonism of RAGE reduced the inflammatory cytokines and helped the recovery of neurological function. The trend of HMGB1 release over time was reported to be consistent with the trend of autophagy after ICH. In the rat model of ICH, does HMGB1 affect the inflammatory responses after ICH through autophagy and then help the recovery of neurological function? Does the upregulation or inhibition of HMGB1 affect the autophagy, or vice versa? How do they affect the inflammation after ICH? This study will explore how HMGB1 mediates autophagy and plays a role in inflammation after ICH. It may provide a new therapeutic target for ICH and lay a new theoretical foundation.

脑出血具有较高的致死率､致残率｡脑出血后细胞大量死亡,炎症反应发生｡近年来自噬已被广泛研究,但自噬对脑出血后细胞存活和与炎症反应的相互作用目前仍存在争议｡高迁移率族蛋白1(HMGB1)除具有胞外致炎､核内转录等功能外,有研究发现HMGB1是细胞自噬的重要调节因子,胞外HMGB1可以通过晚期糖基化终末产物受体RAGE诱导自噬,我们的前期研究证实大鼠脑出血后HMGB1急性期加重炎症损伤,恢复期可以通过RAGE促进神经修复。HMGB1释放随时间变化趋势与文献中报道脑出血后自噬变化趋势较一致｡在脑出血后HMGB1是否通过自噬的相互作用而影响脑出血后的炎症反应进而影响神经功能恢复?是否上调或者抑制HMGB1的表达会影响自噬,或上调或抑制自噬影响HMGB1的释放以及如何影响脑出血炎症的发生?本研究旨在探索脑出血后HMGB1如何介导自噬对炎症起到调节作用,为脑出血提供新的治疗靶点和奠定新的理论基础。

我们的研究观察到大鼠脑出血后不同时间点（1d、3d、7d、14d）血肿周围细胞自噬相关蛋白及HMGB1表达的变化情况。在脑出血发生后，随着时间的推移HMGB1的表达量及位置均发生明显变化。在脑出血的急性期，血肿处大量细胞死亡，残存的细胞HMGB1表达量差异较小且有胞浆转移趋势；Western Blot结果显示在脑出血急性期自噬表达较对照组降低，结合细胞实验及我们前期的研究结果提示，在脑出血的急性期大量细胞死亡，其释放出的HMGB1抑制了血肿周围残存细胞的自噬。随着时间的推移尤其是7d、14d我们观察到HMGB1的表达逐渐增加，同时表达位置由细胞核转移至细胞浆，同时自噬相关蛋白表达也逐渐升高，其趋势与HMGB1基本一致，提示在脑出血的恢复期HMGB1通过转移至细胞浆与相关蛋白结合从而促进自噬。在体外实验中，我们发现通过外源性HMGB1干预星型胶质细胞可以抑制其自噬，同时增加其凋亡及炎症相关蛋白的表达水平。同时HMGB1的下游受体TLR4及NF-kb表达增加，提示HMGB1可能通过该通路发挥作用。本研究提示在脑出血的急性期细胞死亡释放出的HMGB1会抑制周围细胞的自噬，而在恢复期胞内的HMGB1通过核转移的方式促进自噬从而改善预后。