糖皮质激素抵抗介导的小胶质细胞过度激活在脑外伤后CIRCI发病中的作用机制研究

Critical illness related corticosteroids insufficiency in the acute phase of traumatic brain injury significantly increases mortality, and thus far no effective pharmacotherapies and practically diagnostic methods are available. Our previous studies (2011Brain Res,165,298) suggest that primary/secondary HPA axis injury and severe glucocorticoid resistance are two distinct characteristics in TBI-related-CIRCI. Also, extensive microglia over-activation occurred simultaneously with CIRCI after TBI. This proposal is aiming to develop a systematic diagnosis by comprehensively analyzing the clinical manifestation, MR spectrometry of hypothalamus and pituitary, neuroinflammatory biomarkers, and small dose dexamethasone suppression test. By using TBI model of genetically modified mice and in vitro cytological platform, we are also planning to investigate the relationship between injury severity and the extent of hypothalamic microglia activation and the incidence of CIRCI. Additionally, we will examine the effect of microglia with different activation on the function and structural integrity of CRH neuron and blood-brain-barrier in hypothalamus. Finally, we will compare VEGI with glucocorticoids sensitizer on regulating microglia activation to potentially prevent and treat CIRCI, with the purpose of exploring the underlying mechanism of VEGI/VEGF on the regulation of microglial activation and glucocorticoids resistance, and developing pharmacotherapies based on reverting glucocorticoids resistance and normalizing microglia overactivation.

TBI后危重症相关皮质类固醇不足（CIRCI）诊治困难，致死率高。本课题组系列研究（2011年BrainRes,165,298）提示：CIRCI发病与HPA轴原发/继发损害和糖皮质激素抵抗密切相关且发病高峰期小胶质细胞广泛激活。内皮生长抑制因子（VEGI）与VEGF相互拮抗和补充，具有神经保护功能。本研究拟通过分析患者临床表现、下丘脑垂体MRS检查、体液神经炎性标志物检查、小剂量地塞米松抑制实验，探索TBI后CIRCI的诊断方案。利用VEGI转基因小鼠TBI模型和体外细胞学研究平台，观察TBI与下丘脑小胶质细胞激活、糖皮质激素抵抗和CIRCI发病的关系，利用扫描离子电导显微镜、膜片钳和分子生物学技术，探究不同激活程度的小胶质细胞对下丘脑CRH细胞和血脑屏障结构和功能的影响及作用机理，探索VEGI/VEGF在调控小胶质细胞激活和糖皮质激素抵抗中的作用机制，为TBI后CIRCI的诊疗奠定基础。

脑外伤（TBI）后危重症相关皮质类固醇不足(Critical Illness-Related Corticosteroid Insufficiency, CIRCI)发病率高，是TBI致残致死的重要原因之一。本课题组在国家自然科学基金的系列资助下，通过临床与基础研究，初步探明了CIRCI的发病机制及诊断方法，具体研究结果如下：（1）明确了TBI后急性期CIRCI的发病、临床表现及在预后判断中的意义。研究发现：亚急性期轻、中、重型TBI患者CIRCI发病率分别为7.1%、25%、52.1%。CIRCI的发病与院内获得性肺炎、消化道出血以及28天死亡率呈正相关。休克、TBI损伤程度、TBI损伤类型（脑挫裂伤、弥漫性轴索损伤）、脑疝是TBI后发生CIRCI的独立危险因素。建立了基于外周血皮质醇检测及地塞米松抑制试验综合诊断1型和2型CIRCI的临床检测方法；（2）通过神经细胞、脑组织以及转基因动物系列研究，证实了TBI后糖皮质激素抵抗介导的小胶质细胞过度激活可导致下丘脑BBB结构和功能破坏、局部神经细胞凋亡，进而引发CIRCI的实验假设。研究发现下丘脑室旁核（PVN）小胶质细胞的激活程度与CIRCI发病、BBB结构和功能的破坏显著正相关。伴随下丘脑小胶质细胞GCs受体的表达显著下调，小胶质细胞的持续激活水平显著提高。VEGI可显著抑制小胶质细胞的激活，上调GCs受体表达水平，减少BBB的渗漏及PVN细胞的凋亡，并显著减少CIRCI的发生。上述实验结果已先后发表在：J Neurol Sci，Brain Struct Funct，Cell Mol Neurobiol，Front Cell Neurosci和中华神经外科、中华神经医学杂志上。基于上述研究结果，课题负责人晋升副教授，并成为硕士研究生导师，入选天津市“131”第二层次人才及天津市高校“中青年骨干创新人才培养计划”。

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