TLR4信号激活负调控CD36表达影响脑出血血肿吸收及机制

The timely removal of the hematoma is one of key measures in treatment of intrcerebral hemorrhage, the unavoidable complications of surgical removal of the hematoma dampen its clinical effect.In view of brain tissue with hematoma absorption ability, thus promote the absorption of hematoma is the new direction for intracerebral hemorrhage treatment, but the mechanism of intracerebral hematoma absorption is still unknown. We found that TLR4 activation initiated the intracerebral hemorrhage inflammatory damage, Interesting,we also found the TLR4 knockout mouse cerebral absorption of hematoma increased, but its mechanism is not clear. Previous studies suggested that CD36 expressed on microglial cells may play an important role in the cerebral hematoma absorption. We also found that CD36 expression was significantly higher in cerebral hemorrhage TLR4 knockout mice,We further hypothesize that TLR4 signal activation down-regulate CD36 expression may affects the brain hematoma absorption. Futher,The specific aims of this study are; (1) to explore the function of CD36 in cerebral hematoma absorption ; (2) to study TLR4 signal activation and negative regulation of CD36 expression on microglia in intracerebral hemorrhage and effect to hematoma absorption; (3) to explore whether TLR4 inhibitors could promote the absorption of hematoma of intacerebral hemorrhage. This study not only can elucidate mechanism of cerebral hematoma absorption, also provide the experimental basis and new concept for treatment of intracerebral hemorrhage by promote the absorption of hematoma.

及时清除血肿是治疗脑出血的关键措施，现有外科血肿清除的方法存在难以避免的并发症，影响了其临床效果。鉴于脑组织自身具有血肿吸收能力，因此促进自身血肿吸收是治疗脑出血的新方向，但脑血肿吸收的机制至今仍不明了。我们发现TLR4信号激活启动了脑出血炎症损伤，而且意外地发现TLR4敲除鼠脑出血血肿吸收异常增加，但其机制不清楚。有研究提示小胶质细胞CD36可能在脑出血血肿吸收中起重要作用。我们还发现TLR4敲除脑出血鼠，CD36表达显著上调，据此提出TLR4信号激活下调CD36的表达影响了脑出血血肿吸收的假说。为此本项目拟进行：（1）明确CD36在脑出血血肿吸收中的作用；（2）探讨脑出血TLR4信号激活负调控CD36表达影响脑出血血肿吸收及机制；（3）探索TLR4抑制剂促进脑出血血肿吸收对脑出血的治疗效果。该研究不仅可阐明脑出血血肿吸收的机制，同时为通过促进血肿吸收治疗脑出血这一全新理念提供实验依据。

ICH后血肿的机械压迫及其代谢产物是导致脑出血神经功能缺损、致死、致残的主要原因，近年来如何促进内源性血肿吸收成为ICH治疗的新方向。我们首先收集了209例临床ICH患者，发现与CD36表达正常的患者相比，CD36缺陷患者血肿吸收显著减慢，神经功能缺损明显加重。强烈提示CD36在介导内源性血肿吸收中具有重要的作用。为进一步探讨CD36在ICH血肿吸收中的作用及调控机制，我们利用在体及离体ICH模型，发现ICH后血肿周围组织CD36表达显著增加，并且主要表达在小胶质细胞。进一步采用CD36敲除鼠ICH模型，发现CD36敲除后，血肿吸收显著减慢，脑水肿明显加重，神经功能缺损明显加重。利用活细胞工作站，采用三维动态激光共聚焦观察，发现CD36敲除或应用CD36抗体后，小胶质细胞吸收RBCs明显减少。提示促进CD36表达，可以促进内源性血肿吸收。为进一步研究脑出血后CD36表达的调控机制，我们发现TLR4敲除后，血肿周围组织CD36表达显著上调，并且离体ICH模型发现高剂量IL-1、TNF-α能显著抑制小胶质细胞CD36的表达，抑制细胞对RBCs的吸收。证实了ICH后TLR4介导的炎症反应通过调控CD36表达影响血肿的吸收。为此，我们在前期发现TLR4抑制剂TAK242对ICH显著治疗作用的基础上，进一步利用细胞及小鼠模型，发现TAK242能明显增加血肿吸收。该部分的研究结果发表在J Immunol [J Immunol. 2014;192: 5984-92.]。该研究结果不仅揭示了ICH后血肿吸收的调控机制，同时也进一步揭示了ICH后炎症级联反应的机制。因此，调控TLRs介导的炎症反应，不仅可抑制炎症损伤，还可以促进血肿吸收,可望为ICH提供切实可行的治疗效果。