内毒素预处理对内毒素血症大鼠肝TLR-4、NF-κB和ICAM-1表达的影响

Protective Effects of Endotoxin Pretreatment on Expression of TLR-4,NF-κB and ICAM-1 in Hepatic Tissue of Rats with Endotoxemia

目的观察内毒素预处理对内毒素血症大鼠肝Toll样受体4(TLR-4)、核因子-κB(NF-κB)和白细胞间粘附分子-1(ICAM-1)表达的影响,探讨内毒素预处理对内毒素血症肝损伤的保护作用及机制。方法采用直接注射内毒素脂多糖(LPS,10mg/kg体重)的方法建立大鼠急性内毒素血症模型,实验动物随机分成3组:生理盐水对照组(N组);内毒素脂多糖(LPS)组(L组)和LPS预处理组(P组),其中P组在制模前分别经腹腔注射LPS 0.25、0.50mg/kg体重。逆转录聚合酶链反应(RT-PCR)检测肝组织TLR-4mRNA表达,免疫印迹法(Western blot)检测肝组织NF-κB表达,免疫组化法检测肝组织ICAM-1表达,取肝脏(肝左上叶)用10%的中性甲醛固定观察肝脏病理形态。结果内毒素血症时,肝脏组织TLR-4、NF-κB和ICAM-1水平明显增加,显著高于N组(P<0.05),而经内毒素预处理的模型动物肝脏组织TLR-4、NF-κB和ICAM-1水平明显降低(P<0.05),P组肝脏组织病理学改变较L组减轻。结论内毒素预处理能够减轻内毒素血症导致的肝损伤,其机制可能与抑制TLR-4信号传导通路及减少单核巨噬细胞内NF-κB和ICAM-1的表达有关。

Objective To study the effects of endotoxin pretreatment on the expression of TLR-4,NF-κB and ICAM-1 in hepatic tissue of rats with endotoxemia and the protective effects of endotoxin pretreatment on the hepatic injury induced by endotoxemia and the mechanism.Methods The models of acute endotoxemia in rats were established by the method of injecting lipopolysaccharide（LPS）directly.Seventy-two male Wistar rats were randomly divided into three groups：saline control group（N）,LPS-treated group（L）,LPS-pretreated group（P）.The last two groups were divided into four subgroups：LPS-treated 2 h,4 h,6 h,12 h subgroups and LPS-pretreated 2 h,4 h,6 h,12 h subgroups.Rats in P group were first introperitoneally injected with 0.25 mg/kg LPS.After 24 h,they were subjected to the injection of 0.50 mg/kg LPS.Rats in N and L groups received an equivalent amount of saline.After 72 h,rats in L and P groups were challenged with intravenous injection of 10 mg/kg LPS,otherwise saline in N group.Six rats were killed at 2,4,6 and 12 h after injection of LPS in L and P groups.The livers were removed for detecting TLR-4 by RT-PCR,NF-κB by Western blot,and ICAM-1 by immunohistochemistry respectively.The pathological changes of the liver were also examined.Results The levels of TLR-4,NF-κB and ICAM-1 in the hepatic tissues in L group were higher than those in N group.After endotoxin pretreatment,the levels of TLR-4,NF-κB and ICAM-1 in the hepatic tissues in P group were significantly reduced as compared with L group.Conclusion Endotoxin pretreatment can eliminate the progress of hepatic injury in rats with endotoxemia,which may be correlated to inhibition of the signal transduction pathway of TLR-4 and down-regulation of the expression of NF-κB and ICAM-1 in mononuclear phagocyte system.