严重烧伤后肠道微生态失衡在屏障功能损害中的作用与分子机制

The disruption of intestinal mucosa barrier plays a critical role in the pathophysiological disturbance following severe burn injury, however the mechanisms involved in the burn-induced intestinal mucosa barrier disruption are still incompletely clarified. Based on our previous studies showing that the changes of tight junction (TJ) proteins in intestinal epithelial cells are involved in the intestinal mucosa barrier dysfunction caused severe burn injury, here we hypothesize that severe burn injury may cause the disturbance of intestinal microflora and induce the dysbiosis of intestinal microbiota, leading to the reduction of short chain fatty acids (SCFA), which in turn disrupt the intestinal mucosa barrier function by causing the the changed expression and/or localization of TJ proteins in intestinal epithelial cells. Therefore, the current proposed research project aims to investigate the changes of intestinal microbiota and its effects on lumenal SCFA, the expression and/or localization of TJ proteins in intestinal epithelial cells, the mucosa barrier function and permeability after severe burn injury by employing conventional mice, germ-free mice, transplantation of lumenal microflora, induction of intestinal dysbiotic microbiota, and LPS stimulation of intestinal epithelial cells in vivo or in vitro. By the time these proposed studies are completed, we, for the first time, will prove the noval idea that the dysbiotic microbiota is involved in the intestinal epithelial barrier disruption caused by severe burn injury, and define the underlying molecular mechanism. It is expected that these studies will be very meaningful to further understanding the molecular mechanisms of intestinal epithelial barrier dysruption following severe burn injury.

肠道黏膜屏障损害在严重烧伤后病理生理紊乱中扮演着极其重要的角色，但其发生机制仍不完全清楚。在原基金项目发现肠上皮细胞紧密连接（TJ）蛋白变化参与了严重烧伤后肠黏膜屏障损害发生的基础上，根据文献资料并结合动物预实验结果，率先提出严重烧伤后肠道微生物群发生改变，以致微生态失衡，短链脂肪酸（SCFA）产生减少，从而引起肠黏膜上皮细胞TJ蛋白表达和/或分布改变，导致肠黏膜上皮屏障功能损害的科学假说。拟通过体内外实验，分别采用普通小鼠、无菌小鼠、肠腔内微生物移植、诱导肠道微生态失衡及LPS刺激肠上皮细胞等研究策略，探索严重烧伤后肠道微生态的变化及其对肠腔内SCFA、肠上皮细胞TJ蛋白表达和/或分布、肠粘膜上皮屏障功能与通透性等的影响，从而首次阐明肠道微生态失衡参与了严重烧伤后肠上皮屏障损害发生的新观点，并揭示其相关分子机制。对进一步深入阐明严重烧伤后肠上皮屏障功能损害的分子机制具有极其重要的意义。

肠道黏膜屏障损害在严重烧伤后病理生理紊乱中扮演着极其重要的角色，但其发生机制仍不完全清楚。本项目提出严重烧伤后肠道微生物群发生改变，以致微生态失衡，短链脂肪酸（SCFA）产生减少，从而引起肠黏膜上皮细胞紧密连接（TJ）蛋白表达和/或分布改变，导致肠黏膜上皮屏障功能损害的科学假说。通过体内外实验，分别采用普通小鼠、无菌小鼠、肠腔内微生物移植、诱导肠道微生态失衡及LPS刺激肠上皮细胞等研究策略，研究了严重烧伤后肠道微生态的变化及其对肠腔内SCFA、肠上皮细胞TJ蛋白表达和/或分布、肠粘膜上皮屏障功能与通透性等的影响，以期明确肠道微生态失衡参与了严重烧伤后肠上皮屏障损害的发生，并揭示其相关分子机制。主要研究结果表明：严重烧伤后肠黏膜屏障功能受到明显损害，TJ蛋白表达与分布均发生明显改变；烧伤后肠道屏障功能损害可能与肠道菌群结构改变、肠腔内SCFA含量降低、促炎细胞因子表达增加以及抗炎细胞因子表达降低有关；广谱抗生素可诱导肠道菌群失衡，降低肠腔内SCFA含量，改变肠黏膜TJ蛋白的表达与分布，损害屏障功能，可能与NLRP3炎症小体及自噬活化有关；SCFA可促进单层肠上皮细胞屏障的形成，保护LPS所引起的肠上皮细胞屏障功能损害，SCFA对肠上皮细胞屏障的保护作用与其抑制NLRP3炎症小体及细胞自噬的激活有关。本项目的上述研究结论明确了肠道微生态失衡参与了严重烧伤后肠上皮屏障损害的发生，对进一步深入阐明严重烧伤后肠上皮屏障功能损害的分子机制具有极其重要的意义。