脂多糖诱发肝损伤机理的初步研究

目的:探讨LPS肝损伤的信号转导途径及LPS诱导肝细胞凋亡的规律。方法:Balb/c小鼠腹腔注射LPS建立内毒素血症模型,在不同时间点取其肝脏,HE染色观察病理改变,RT-PCR法检测肝组织TLR4的表达。TUNEL法检测肝细胞凋亡,免疫组化法检测bax、bcl-2、Fas、Fasl表达。结果:LPS注入腹腔后24h小鼠肝脏开始出现明显病理改变;3～6h肝细胞凋亡达高峰,12h后明显减少;肝脏TLR4在LPS注射3h后显著下调,6～12h明显受抑制,24h后则基本恢复;LPS刺激后3～6h肝脏bax、Fas表达达高峰,而bcl-2、Fasl表达在6～12h达到高峰,随后都逐渐下降。结论:LPS刺激肝脏后,肝损伤呈时间依从性,凋亡是其细胞死亡方式之一。LPS刺激后,肝脏TLR4表达呈时间依从性,TLR4表达下调可能是对LPS产生的耐受现象,是机体抗损伤的一种保护性的下调。LPS所致肝细胞凋亡是多因素作用的结果。

Basic mechanism study on lipopolysaccharide-induced murine liver injury

Objective: To observe signaling for LPS transduction ,mechanism of LPS-induced liver injury and LPS-induced hepatocyte apoptosis.Methods:LPS-induced endotoxin mouse was sacrificed at 3 hours,6 hours,12 hours,24 hours and 30 hours respectively. The liver tissue was stained with hematoxylun and eosin for histopathologic analyses. Hepatocyte apoptosis ,hepatic bax,bcl-2,Fas,Fasl were detected by use of immunohistochemistry technology.The expression of TLR4 were detected by use of semi-quantitative RT-PCR.Results:A large number of cells infiltrated portal areas with additional focal hepatocellular necrosis 24 hours after i.p. LPS. Hepatic TLR4 expression was significantly depressed from 6 to 12 hours after i.p. LPS,but recover at 24 hours. Hepatocyte apoptosis increased significantly at 3~6 hours after i.p. LPS,while returned to normal at 12 hours. At the same time,the expression peak of bax and Fas were at 3 hours after i.p.LPS,while the expression peak of bcl-2 and Fasl at 12 hours after i.p. LPS.Conclusion:1,LPS-induced liver injury was time-dependent. Hepatocyte apoptosis play a important role in its cell death. 2,The expression of TLR4 was time-dependent.The depression of TLR4 may be the protection of cells to LPS tolerance.3,Many kinds of factors result in LPS-induced hepatocyte apoptosis.