丙戊酸保护严重烧伤后肠屏障的作用和机制研究

The protection of gut barrier from damage caused by major burn injury is of great importance in the prevention and treatment of sepsis and multiple organ failure. Emerging evidence suggests that hypoxia-inducible factor-1(HIF-1) is a critical regulator in gut barrier functions via regulating vascular endothelial growth factor (VEGF) and myosin light chain kinase (MLCK) expression. Hypoxia activates the HIF-1 signaling pathway and promotes the transcription of downstream genes VEGF and MLCK which have been demonstrated to be strong regulators involved in intestinal permeability. Valproic acid (VPA),a histone deacetylase inhibitor (HDACI), has recently been showed to be able to repress HIF-1. Our recent study also found that VPA treatment significantly attenuated the burn-induced HIF-1α, VEGF, MLCK accumulation, and prevents the increase in intestinal permeability. However,the mechanism remains unknown. The objectives of this research are: 1. to confirm whether or not valproic acid can repress HIF-1 function and protect gut barrier function from hypoxia-induced injury in an intestinal sac model. 2. to investigate the mechanism of the repressive effects of VPA on HIF-1 and its protective effects on gut barrier function in vitro. 3. to explore the therapeutic potential of valproic acid in treating burn-induced gut barrier dysfunction.

保护肠上皮屏障功能，对于防治严重烧伤引起的脓毒症和多器官衰竭有重要意义。研究表明，缺氧诱导因子1（HIF-1）对于维护肠屏障功能起重要作用，低氧能激活HIF-1信号通路，增强其下游靶基因血管内皮生长因子（VEGF）和肌球蛋白轻链激酶（MLCK）的转录，促进肠上皮细胞间紧密连接蛋白（TJPs）降解和再分布。丙戊酸（VPA）是组蛋白去乙酰化酶（HDAC）抑制剂，以往文献和我们的前期研究均表明VPA能抑制HIF-1的功能，降低VEGF及MLCK的蛋白水平，保护肠屏障功能，但其具体作用机制尚不清楚。本研究目标：1.制作肠袋缺血模型确认丙戊酸肠内给药对肠上皮HIF-1和TJPs的调节作用；2.采用肠上皮细胞低氧培养模型研究丙戊酸通过调节HIF-1α及其共刺激分子的乙酰化水平，降低HIF-1α的活性和含量，抑制肠上皮TJPs降解和重分布的机制；3.采用烧伤休克模型进一步验证VPA防治肠屏障损害的效果。

保护肠上皮屏障功能，对于防治严重烧伤引起的脓毒症和多器官衰竭有重要意义。研究表明，缺氧诱导因子1（HIF-1）对于维护肠屏障功能起重要作用，低氧能激活HIF-1信号通路，增强其下游靶基因血管内皮生长因子（VEGF）和肌球蛋白轻链激酶（MLCK）的转录，促进肠上皮细胞间紧密连接蛋白（TJPs）降解和再分布。丙戊酸（VPA）是组蛋白去乙酰化酶（HDAC）抑制剂，以往文献和我们的前期研究均表明VPA能丙戊酸钠能够抑制多种细胞间紧密连接（tight junction）蛋白的降解，保护细胞屏障。本项目通过建立大鼠55%TBSAⅢ度烫伤模型和体外单层Caco2肠上皮细胞模型研究丙戊酸对严重烧伤后肠屏障的保护作用及其机制。结果发现：严重烧伤后肠粘膜组织组蛋白乙酰化及ZO-1水平降低，并引起肠屏障功能损害；丙戊酸钠能提高组蛋白乙酰化及ZO-1水平，保护肠上皮屏障功能，其作用机制与丙戊酸钠对HIF-1α及其下游靶基因VEGF和MLCK的抑制作用有关。