CRH-IRE1/XBP1失衡启动肠粘膜应激损伤及其逆向调理研究

Stressful challenges of intestinal immune barrier, resulting in the gut-derived bacterial translocation, are associated with internal infections for the trauma patients. However, the single anti-inflammatory procedure is difficult to reconstrunt the intestinal homostasis. One current of modulation in intestinal immune chaos invokes brain-gut feedback axis. Hence, based on our recent findings that CRH knockout could deteriorate the intestinal stress injury in trauma, we choose corticotropin-releasing hormone (CRH) as the hinge molecule of the neuroendocrine network. Concerning its direct immunostimilatoy and indirect immunosrpressive effects, endoplasmic reticulum (ER) stress responses, and the sharing of critical signals between CRH and ER stress, we propose the hypothesis that CRH modulates the intestinal stress injury via the high conserved ER stress pathway, IRE1/XBP1. To test the hypotheses, we will conduct studies in a novel rodent model, a genetically modified CRH deficient mice, which will be succumbed to acute traumatic stress and a co-culture model of intestinal epithelial cells and mast cells stimulated with CRH and glucocorticoid. In this project we propose the following specific aims: 1. Using an animal model of single traumatic stress, to confirm the differential responses of CRH induced intestinal stress injury via double pathway (HPA axis and CRH receptors). 2. In vitro and in vivo to determine the imblanced mechanism of CRH-IRE1/XBP1 signals. 3. To determine the protetive effects of the reversing modulation of CRH-IRE1/XBP1 on the intestinal stress injury. Thus, the research aims to primarily elucidate the initiate mechanism of CRH in intestinal stress injury, and disclose the checkpoint that could turn round the vicious cycle of brain-gut axis and alleviate the intestinal injury. It is of widespread significance for the promotion of intestinal immune equilibrium via neuroencocrine immune network for the trauma patients.

肠道应激损伤致体内共栖细菌移位是创伤患者感染的重要途径，但单纯拮抗肠道过度炎症难以重建肠道稳态。项目基于脑肠轴反馈调节肠道免疫功能紊乱设想，以神经内分泌网络枢纽分子-促肾上腺皮质激素释放激素(CRH)为切入点，在证实CRH敲除影响肠道应激损伤基础上，从CRH直接免疫刺激和间接炎症抑制活性、内质网应激效应以及CRH与IRE1/XBP1共享下游信号分子角度，提出CRH经保守内质网应激IRE1/XBP1通路调控肠道应激反应。故以CRH敲除小鼠和小肠细胞-肥大细胞共培养模型，将研究创伤致肠粘膜应激损伤时：①CRH经双重途径对肠粘膜差异性调控作用；②肠粘膜CRH-IRE1/XBP1信号失衡机制；③逆向调理CRH-IRE1/XBP1对肠粘膜的保护效应，旨在初步阐明CRH启动肠道应激损伤机制，探寻扭转脑肠恶性循环、改善肠道应激损伤的关键点，以转化医学视角为从神经内分泌免疫网络恢复肠道免疫平衡提供新依据。

肠道应激损伤致体内共栖细菌移位是创伤患者感染的重要途径，但单纯拮抗肠道过度炎症难以重建肠道稳态。项目基于脑肠轴反馈调节肠道免疫功能紊乱设想，以神经内分泌网络枢纽分子-促肾上腺皮质激素释放激素(corticotropin-releasing hormone,CRH)为切入点，认为CRH以双重途径经IRE1/XBP1通路启动肠粘膜应激反应：即CRH一方面通过HPA轴途径调控炎症级联，遏制肠道过度炎症反应；另一方面通过肠道CRH受体途径增强免疫防御功能。当应激反应强度和时程超过肠道稳态域限时，CRH-IRE1/XBP1失衡，肠粘膜损伤并对继发性感染失控，形成脑-肠恶性循环。为此，本项目通过CRH基因工程小鼠烧伤等模型研究发现，烧伤应激早期，小鼠腹腔巨噬细胞趋化、吞噬功能显著增强，CRH基因敲除显著抑制腹腔巨噬细胞的趋化和吞噬功能。小鼠肝脏、肺脏和肠系膜淋巴结可见细菌移位，CRH基因敲除进一步促进该细菌移位过程，且随观察时间延长，肠系膜淋巴结细菌菌落数和移位率均有增多。同时，CRH基因敲除加剧小鼠肠粘膜炎性细胞浸润，水肿，粘膜厚度增加。CRH基因敲除小鼠血浆TNFα分泌水平明显升高。以上变化从内质网应激机制角度，揭示了CRH基因敲除显著抑制烧伤小鼠巨噬细胞在转录和翻译水平GRP78、XBP1、ATF6表达。此外，项目从脑内Glutamate、 GABA和糖皮质激素角度，探讨了创伤应激条件下脑内神经内分泌免疫相关核团(海马、前额叶、杏仁核)的功能联系，提出上述核团递质失衡引起脑内核团网络功能异常，与CRH协同参与创伤早期肠道应激损伤过程。因此，本项目神经内分泌免疫网络角度证实CRH敲除影响肠道应激损伤，从CRH直接免疫刺激和间接炎症抑制活性、内质网应激效应以及CRH与IRE1/XBP1共享下游信号分子角度，提出中枢性神经内分泌递质网络参与下，CRH经保守内质网应激IRE1/XBP1通路调控肠道应激反应。研究初步阐明了CRH启动肠道应激损伤机制，为探寻扭转脑肠恶性循环、改善肠道应激损伤的关键点，以转化医学视角为从神经内分泌免疫网络恢复肠道免疫平衡提供了新依据。