肌苷对脂多糖诱导的急性肺损伤大鼠的肺保护作用及机制探讨

Protective effect and mechanism of inosine on acute lung injury induced by lipopolysaccharide in rats

目的探讨肌苷对急性肺损伤(ALI)大鼠的肺保护作用及其相关机制。方法20只SD大鼠随机分为4组:空白(NC)组、模型(LPS)组、肌苷低剂量干预(IN-L)组、肌苷高剂量干预(IN-H)组,每组5只。气管内滴入脂多糖(LPS)完成建模的大鼠在1、6、12 h后采用腹腔注射法给予100 mg/kg肌苷(IN-L组),200 mg/kg肌苷(IN-H组)和生理盐水(LPS组)。NC组在建模和干预阶段均使用等体积生理盐水。在诱导ALI 24 h后采集动脉血测定氧分压(PaO2);取肺组织,计算湿/干质量比(W/D)并进行病理检查;取血清和支气管肺泡灌洗液(BALF)测定多聚ADP核糖聚合酶(PARP)-1、诱导型一氧化氮合酶(iNOS)、肿瘤坏死因子(TNF)-α和白细胞介素(IL)-1β含量。制备肺组织匀浆,检测Toll样受体4(TLR4)、髓样分化蛋白88(MYD88)、核因子κB(NF-κB)蛋白表达。结果LPS诱导大鼠肺组织损伤,造成严重的低氧血症,PARP-1、iNOS水平升高,促进炎性因子TNF-α和IL-1β分泌,肺组织中TLR4、MYD88、p-NF-κB p65蛋白表达上调(P<0.05)。肌苷干预后可使肺组织TLR4、MYD88和p-NF-κB p65蛋白表达下降,PARP-1、iNOS、TNF-α和IL-1β的产生减少,肺组织损伤程度减轻,大鼠低氧血症得到改善(P<0.05)。IN-H组上述改变较IN-L组更加明显(均P<0.05)。结论肌苷可减轻LPS诱导的肺部炎症,减少炎性细胞因子的产生,其机制可能与肌苷下调TLR4/MYD88/NF-κB信号通路,抑制PARP-1活性,减少NF-κB核易位有关。

Objective To investigate the lung protective effect of inosine on acute lung injury(ALI)rats and its associated mechanism.Methods Twenty SD rats were randomly divided into 4 group:the control(NC)group,the model(LPS)group,the inosine low-dose intervention(IN-L)group and the inosine high-dose intervention(IN-H)group.Rats challenged with intratracheal lipopolysaccharide(LPS)were treated after 1,6,and 12 hours with 100 mg/kg inosine(IN-L group),200 mg/kg inosine(IN-H group)and normal saline(LPS group).The NC group received equal volume normal saline during the modeling and intervention phases.After 24 hours of the induction of ALI,the arterial blood was used to detect partial pressure of oxygen(PaO2),the lung tissue sample was collected for the wet/dry weight(W/D)value and pathological examination.Serum and bronchoalveolar lavage fluid(BALF)were obtained to measure polyadp ADP-ribose polymerase(PARP)-1,inducible nitric oxides(iNOS),tumor necrosis factor(TNF)-αand interleukin(IL)-1β.Lung tissue homogenate was prepared to determine the toll-like receptor 4(TLR4),myeloid differentiation primary response 88(MYD88)and nuclear factor kappa-B(NF-κB)proteins.Results LPS induced lung tissue injury in rats,resulting in severe hypoxemia,increased levels of PARP-1 and iNOS,promoted the secretion of inflammatory factors TNF-αand IL-1β,and up-regulated expression levels of TLR4,MYD88,NF-κB proteins in lung tissue(P<0.05).Inosine intervention down-regulated expression levels of TLR4,MYD88 and NF-κB in lung tissue,decreased the production of PARP-1,iNOS,TNF-αand IL-1β,alleviated the degree of lung tissue injury and improved hypoxemia(P<0.05).The above changes were more obvious in the IN-H group than those in the IN-L group(all P<0.05).Conclusion Inosine inhibits LPS-induced lung inflammation and reduces inflammatory cytokines,which may be related in part to the inosine down-regulation of TLR4/MYD88/NF-κB signaling pathway,the inhibition of PARP-1 activity and the reduction of NF-κB nuclear translocation.