Nrf2/Hx/LRP1信号通路调控小胶质细胞M2型转化在脑出血后血红素清除中的作用及机制研究

Hematoma is the initial factor causing intracerebral hemorrhage(ICH) -induced brain injury, so the timely removal of hematoma products is essential to prevent and alleviate cerebral insults in early stage following ICH. Heme is a major neurotoxic component from the lysis of hematoma within the first days after ICH. In our previous study, we found that hemopexin (Hx) and Low density lipoprotein receptor related protein-1(LRP1)- the only heme scavenger receptor, which facilitated heme scavenging after ICH in mice. And Hx/LRP1 is the convergent signaling pathway for heme removal following ICH. Nuclear factor erythroid-2-related factor-2 (Nrf2) activation induced Hx mRNA transcription. Nrf2/Hx/LRP1 pathway can regulate phagocytosis of microglia – which is the key to scavenge the products of hematoma. So we speculate that activation of Nrf2/Hx/LRP1 pathway promote transformation of the activated microglia to M2 phenotype, then enhance orientational phagocytosis of microglia, and facilitate heme scavenging following ICH. In this research, we will explore the endogenous mechanism of heme removal in vitro and in vivo by regulating Nrf2/ Hx/ LRP1 signaling pathways then observe M2 microglia transformation. ①In vitro studies (Murine microglial cell line): To assess the effect of Nrf2/Hx/LRP1 by using their siRNA and agonists on M2 microglia and heme induced injured neurons. ②In vivo studies(Animal ICH models): To assess the role of Hx/LRP1 by murine Hx-/-, LRP1-/-, agonists of Nrf2/Hx/LRP1 pathway and M2 microglia in ICH. Verify the endogenous mechanism of heme scavenging after ICH. This study evaluated the pharmacological effect of activated Nrf2/Hx/LRP1 pathway on ICH, which provides a potential new avenues for the treatment of ICH derived from the endogenous mechanism of hematoma removal.

血红素是脑出血后血肿主要的毒性产物，也是诱发早期脑损伤的重要始动因素。我们前期研究发现，血红素结合蛋白（Hx）及血红素清除受体-低密度脂蛋白受体相关蛋白1（LRP1）是介导脑出血后血红素清除的信号通路。核转录因子E2相关因子（Nrf2）可促进Hx转录。Nrf2/Hx/LRP1通路可调控小胶质细胞（MG）的吞噬功能。我们推测激活该通路可促进MG向M2型转化，增强定向吞噬，加速血红素清除。本研究结合离体及在体实验，从Hx/LRP1入手，观察干预该通路与M2型MG的关系，明确脑出血后血红素清除的内在机制。①离体细胞：通过抑制/激活Nrf2/Hx/LRP1通路观察其对于M2型MG及血红素损伤神经元的影响；②动物实验：借助小鼠脑出血模型、基因敲除鼠及药理学方法抑制/激活上述通路并评价干预药物效果，明确该通路与M2型MG转化、血红素清除及继发脑损伤的关系；拟从机制水平建立一个新的治疗脑出血的临床策略。

背景：血肿作为脑出血后脑损害的始动因素，有效清除血肿成分对于预防或减轻早期脑损伤至关重要；血红素作为血肿主要早期毒性产物，我们前期研究已证实血红素结合蛋白（Hx）及血红素清除受体-低密度脂蛋白受体相关蛋白1（LRP1）是介导脑出血后血红素清除的信号通路；活化小胶质细胞作为清除血肿产物的关键环节，其调控机制尚不明确；.主要研究内容：结合离体细胞及在体动物实验，从Hx/LRP1入手，通过激活该通路与调控M2型小胶质细胞关系的研究，明确脑出血后血红素清除的内在机制。 ①离体细胞：通过抑制及激活Nrf2/Hx/LRP1通路观察其对于活化不同表型小胶质细胞及血红素损伤神经元的影响；②动物实验：借助小鼠脑出血模型、Hx/LRP1基因敲除鼠及药理学方法激活Nrf2/Hx/ LRP1通路并评价干预药物效果，明确上述通路与活化小胶质细胞M2型转化、血红素清除及继发脑损伤的关系；.重要结果：小胶质细胞功能转化与脑出血后的血肿清除有关。Nrf2激活导致小胶质细胞功能转化并强化其吞噬功能，在脑出血后发挥神经保护作用。Nrf2激活剂（红曲素/血脂康）通过调节脑出血后的小胶质细胞功能改变促进血肿清除并减轻神经炎症反应。Nrf2可能通过强化血管周围小胶质细胞Hx及LRP1 的表达促进血肿清除，同时减轻脑出血后水肿形成。提示Nrf2可能通过调控Heme-Hx-LRP1 通路参与脑出血后血肿清除；头颅MRI测定脑组织血肿及水肿与脑组织检测血红蛋白及脑水含量所得出的结论一致。.关键数据：脑出血后Nrf2/Hx/LRP1通路通过调控小胶质细胞功能转换促进血肿清除，进而发挥神经保护作用。.科学意义：从机制水平为脑出血患者提供全新的治疗方向；对于脑出血患者临床治疗指导意义重大。