HMGB1激活脑内肥大细胞对BBB的影响在POCD中的作用及机制探讨

Postoperative cognitive dysfunction（POCD）is a common complication in aged patients. Neuro-inflammation is involved in the pathogenesis of POCD.The increased permeability of blood-brain barrier (BBB) following peripheral surgery is highly likely linked with neuro-inflammation. Our previous study found that activated brain mast cells (MCs) induced by surgery could disrupt BBB to mediate neuro-inflammation and POCD. Furthermore, it has been known that high mobility group box-1 protein (HMGB-1) releasing after surgery leads to the disruption of BBB and the pathogenesis of POCD. But whether HMGB-1 is able to evoke brain MCs has not been elucidated. Our preliminary experiment demonstrated that HMGB-1 promoted MCs degranulation in vitro. In addition, HMGB-1 antibody injection in mice inhibited the increasing number of MCs in hippocampal, protected the integrity of BBB and ameliorated the cognitive function after surgery. Based on these data, we hypothesized that HMGB-1 might induce MCs degranulation, which participated in the damage of BBB and developing of POCD. To test our hypothesis, we will use dividual animal model, cytological and molecular biological methods to investigate the role and mechanism of HMGB-1-induced MCs degranulation in the BBB disruption and POCD. This study will help us to further understand the molecular mechanism of POCD and provide a novel potential target for the prevention and treatment of POCD.

术后认知功能障碍（POCD）是老年患者术后常见的神经并发症。现认为POCD与中枢炎症有关。外周手术为何引起中枢炎症？血脑屏障（BBB）通透性的增加值得重视。我们前期研究发现外周手术会激活脑内肥大细胞，破坏BBB的完整性，致中枢炎症和动物学习记忆能力下降。已知外周手术释放的高迁移率族蛋白1（HMGB-1）也可破坏BBB，但脑内肥大细胞和HMGB-1之间的关联机制不详。我们提出假说：HMGB-1致脑内肥大细胞脱颗粒，破坏BBB完整性。预试验提示HMGB-1可刺激离体的肥大细胞脱颗粒，腹腔提前注射HMGB-1中和抗体可有效预防骨折小鼠术后海马区肥大细胞增多，保护BBB完整性，改善动物学习记忆能力。本课题拟采用脑内肥大细胞缺陷小鼠从行为学、细胞学和分子生物学层面，观察HMGB1致脑内肥大细胞脱颗粒对BBB的影响与POCD的关系，探讨外周手术致中枢炎症的新机制，为老年患者术后康复提供潜在的防治途径。

术后认知功能障碍（POCD﹑现称PND）是老年患者术后常见的神经并发症、受到临床工作者和神经免疫研究者的关注。现认为中枢炎症是POCD发生的主要病理机制，但有许多环节仍不清楚。我们前期研究发现外周手术会激活脑内肥大细胞（MCs），破坏BBB的完整性，致中枢炎症和动物学习记忆能力下降。本课题主要探讨外周手术释放的高迁移率族蛋白1（HMGB-1）是否通过激活脑内肥大细胞脱颗粒，破坏BBB完整性引起中枢炎症及此作用是否与与RAGE/NF-κB途径有关。我们从离体和在体试验证实HMGB-1可刺激肥大细胞脱颗粒，促进炎性细胞因子TNF和IL-1b的释放，破坏BBB，引起海马区域炎症反应和动物学习记忆能力的下降。在离体细胞学实验中证实HMGB-1上调肥大细胞株的RAGE表达。这些结果提示HMGB-1可通过激活MCs导致中枢炎症，这一作用与RAGE/NF-κB途径有关。.我们还探讨了LPS刺激MCs后24小时内的动态变化。大鼠海马区MCs数量于2h显著上升，在4h达峰值；至24h时未恢复到刺激前水准。预先使用TM诱发轻度内质网应激，离体和在体试验可部分抑制LPS激活星形胶质细胞释放炎症因子的作用；同时抑制大鼠海马区炎症和相应的认知损伤。在离体实验发现组胺可上调星形胶质细胞组胺受体，释放GDNF，发挥神经保护作用。这一作用与H1R和H3R有关。在大鼠胫骨骨折模型上，我们发现术前睡眠障碍可增强术后24h的神经炎症、神经元损伤、BBB破坏和记忆障碍。. 我们的研究结果丰富了POCD的中枢炎症学说内容，为防治POCD提供了有益的试验依据和新的思路。