The Protection And Mechanisms Of Glycine Against Liver Injury Induced By Lipopolysaccharide

Endotoxemia (ETM) refers to systemic inflammatory responsesyndroum (SIRS) caused by endotoxin. Endotoxin is also named aslipopolysaccharide (LPS), which is the main component on the outermembrane of Gram-negative bacteria, and is the most important pathogenicfactor of this kind of bacteria. Endotoxin can activate mononuclearphagocytic system (MPS) and lead to the release of multiplepro-inflammatory mediators including tumor necrosis factor alpha (TNF-α).As a result, SIRS and multiple organs damage occurred. As the largestpopulation of fixed tissue macrophages in the body, Kupffer cells (KCs)constituting 80-90% of MPS, so KCs and liver are the targets of endotoxinwhen ETM occurs. Today, ETM is still a nodus in clinical treatment. In recent years,scholars have been looking for effective antagonists of endotoxin, but theresult is unsatisfying. Substantial evidences showed that glycine (Gly)could protect liver injury caused by multiple insulting factors, such asischemia-reperfusion injury, hypoxia and so on. So the animal model ofendotoxin-induced liver injury was used to investigate the protective effectof Gly on the liver, and to explore its protective mechanisms. On the basisof the reaserch above, we attempt to provide a new method for the clinicaltreatment of endotoxin-induced liver injury. Objective: To investigate the protective effect of Gly on endotoxin-induced liver injury, and to explore its protective mechanisms. Methods: The experimetal mice were randomly divided into LPSgroup in which animals were intraperitoneally injected with 10mg/kg LPSand Gly group in which animal were intraperitoneally injected with thesame dose of LPS after pretreatment with 5% Gly-containing diet. KCswere isolated from the mouse liver by in situ collangenase digestion. Allcells were also randomly divided into LPS group in which KCs wereincubated in 100ng/ml LPS-containing DMEM with 10% FBS and Glygroup in which KCs were incubated in 100ng/ml LPS-containing DMEMwith 10% FBS and 4mmol/l Gly. The liver samples were collected toobserve histopathological changes. The TNF-α levels in plasma and culturemedium were measured by ELISA analysis, so were the interleukin-10(IL-10) levels. The mRNA expression of TNF-α, IL-10 and toll likereceptor4 (TLR4) in hepatic tissue and KCs was detected by RT-PCR analysis. TheTLR4 protein expression in liver and KCs was detected withimmunohistochemistry immunocytochemistry. Results: 5% Gly pretreatment improved survival rate and attenuatedLPS-induced liver injury in BABL/c mouse, the pathological changes ofthe liver tissues were remarkably milder than that of LPS group. Glypretreatment also decreased the TNF-α levels in plasma and culturemedium, as well as the expression of TNF-α mRNA and TLR4 mRNA inliver tissues and KCs. Simultaneously, the levels of plasma interleukin-10and its mRNA expression in liver tissues were significantly increased andthe peaking time advanced. Conclusions: Gly pretreatment could attenuate endotoxic liver injury,which may be associated with its role in down-regulating TLR4 expressionin hepatic cells (especially KCs) and in increasing IL-10 production.