组胺及其受体在脑内肥大细胞调节小胶质细胞活化及POCD中的作用及机制研究

Postoperative cognitive dysfunction (POCD) is a common complication in aged patients. Neuroinflammation is involved in the pathogenesis of POCD. Brain mast cells (MCs) are first responders, acting as catalysts and recruiters to initiate and amplify neuroinflammation. Our previous studies found that activated MCs contribute to POCD by evoking microglial activation; H1R, H2R, H3R, and H4R are expressed in primary cultured microglia and histamine could induce microglial activation. Then, whether brain MCs are involved in POCD by the release of histamine from its degranulation. Further studies have shown that inhibition of histamine production by α-FMH, an antagonist of histidine decarboxylase, could improve tibial surgery-induced memory impairment. Based on these data, we hypothesized that brain MCs participate in the developing of POCD by releasing histamine, which combine with histamine receptors on microglia and activate microglia. To test our hypothesis, we will use chimeric animal model, behavior, cytological and molecular biological methods to investigate the role and mechanism of histamine and its receptors in the genesis of POCD. This study will help us to further understand the molecular mechanism of POCD and provide a new insight for better prevention and treatment of POCD.

老年患者术后易发生认知功能障碍（POCD）。已知中枢炎症与POCD发生有关，而脑内肥大细胞是中枢炎症的催化剂。我们在胫骨骨折动物模型发现脑内肥大细胞脱颗粒可活化小胶质细胞进而影响动物的认知行为，离体实验证实小胶质细胞表达有组胺四类亚型受体，外源性组胺可激活小胶质细胞。那么，组胺作为脱颗粒物质的主要组份是否直接介入POCD？预实验示，使用组氨酸脱羧酶特异性拮抗剂α-FMH抑制肥大细胞的组胺生成，可使上述动物模型的认知功能得以改善，即组胺参与POCD进程。据此，我们提出假说：手术创伤应激下脑内肥大细胞脱颗粒释放的组胺与小胶质细胞上的组胺受体结合并促后者活化诱发中枢炎症致POCD 发生。为验证此假说，我们拟采用肥大细胞缺陷小鼠和嵌合体小鼠从行为学、细胞学及分子生物学层面，探讨脑内肥大细胞释放的组胺及其受体在POCD中的作用及机制。该项目将揭示POCD发病的新机制，为POCD的防治提供新思路。

老年患者术后易发生认知功能障碍（POCD）。已知中枢炎症与POCD发生有关，而脑内肥大细胞是中枢炎症的催化剂。我们在胫骨骨折动物模型发现脑内肥大细胞脱颗粒可活化小胶质细胞进而影响动物的认知行为，离体实验证实小胶质细胞表达有组胺四类亚型受体，外源性组胺可激活小胶质细胞。那么，组胺作为脱颗粒物质的主要组份是否直接介入POCD？为此，我们进行了相关实验。首先在动物实验水平发现组胺酸脱羧酶抑制剂可抑制LPS引起的大鼠海马区组胺表达升高，小胶质细胞活化和中枢炎症，并改善LPS引起的认知功能损害，说明脑内组胺水平的升高可加剧中枢炎症。其次在动物实验发现H2R和H3R受体激动剂可抑制手术引发的大脑海马区小胶质细胞激活和中枢炎症，并改善术后认知功能；同时发现小胶质细胞上TLR4受体表达增加，而H2R和H3R受体激动剂可抑制其表达水平；在细胞实验我们发现，LPS可抑制小胶质细胞上组胺2、3受体的表达，组胺2、3受体激动剂可通过H2R/H3R-PI3K/AKT-FoxO1信号通路抑制LPS导致的小胶质细胞TLR4表达和小胶质细胞的活化及炎症因子的释放。这些实验结果为研发POCD相关药物提供新靶标，为临床防治POCD提供新策略。