Objective:To observe the synthesis of Toll-like receptor (TLR)4 protein and its mRNA expression in Kupffer cells (KCs) and evaluate the role of TLR 4 in the liver injury in the rats with alcohol-induced liver disease (ALD).Methods:Twenty eight Wistar rats were divided into two groups: ethanol-fed group(group E) and control group (group C). Group E were fed with ethanol (dose of 5～12g/kg/d) and group C received dextrose instead of ethanol. Rats of the two groups were sacrificed at 4 wk and 8 wk. KCs were isolated and incubated.TLR 4 protein in KCs was determined by laser scanning confocal microscopy (LSCM).TLR 4 mRNA in KCs was determined by the reverse transcription polymerase chain reaction (RT-PCR).Plasma endotoxin levels were measured using the Limulus Amebocyte Lysate test kit.The liver pathology was observed under light and electronic microscopy.Results:The fluorescence intensity of TLR 4 protein in KCs by LSCM was stronger in group E than those in group C. Ethanol administration led to a significant increase in TLR 4 mRNA expression compared with group C ( P< 0.01).Plasma endotoxin levels increased significantly in group E ( 129±21)ng/L and (187±35 )ng/L at than in control rats (48±9)ng/L and (53±11)ng/L

respectively at 4 wk and 8 wk ( P <0.01). In liver section from group E

there was marked pathological changes including steatosis

cell infiltration and necrosis. None of the rats in group C developed marked pathological changes in liver. Conclusion: Ethanol administration can markedly lead to the synthesis of TLR 4 protein and its gene expression in KCs

and TLR 4 may play a role in the development of alcohol-induced liver injury.