Objective:To explore the impact and mechanism of the thrombospondin-1 in septic liver injury by application of RNA interference.Methods:The model for sepsis was developed by cecal ligation and puncture(CLP) in male Balb/c mice.Then the general anatomical feature of abdominal cavity and liver was observed.Serum aminotransferase,expression level of liver TSP-1 mRNA and TSP-1 protein were detected.The pattern of liver TSP-1 in sepsis was investigated.By application of RNA interference targeted degradation of TSP-1 mRNA to induce post transcriptional gene silencing(PTGS),the downregulation of liver TSP-1 mRNA and protein was achieved.Serum aminotransferase and serum TNF-αcontents were detected.Apoptosis of liver cell was observed.The change of liver p38 mitogen activated protein kinase was detected.The role and mechanism of TSP-1 in septic liver injury were investigated.Results:In comparison with control group,the expression of liver TSP-1 mRNA and TSP-1 protein was significantly increased accompanied with more severe liver inflammation as well as dramatically increasing serum ALT and AST contents 6 hours after the CLP model for sepsis.TSP-1 maintained a relatively high level during 24 hours observation period.Through hydrodynamic tail vein injection effective fragments of siRNA specific for TSP-1 were deliveried to make RNA inference,and then the CLP model for sepsis was developed.Serum ALT,AST and TNF-αcontents were significantly decreased,apoptosis of liver cell reduced markedly,and the expression of liver phospho-p38 MAPK was decreased.Conclusion:In sepsis the expression of liver TSP-1 is increased which may induce septic liver injury as a mediator of inflammation.This results in increased serum aminotransferase,serum TNF-αcontents and increased apoptosis of liver cell,with the activation of phospho-p38 MAPK.TSP-1 may induce liver injury by the activation of p38MAPK signal transduction pathway.