Effect Of Toll-Like Receptor 4 On Liver Regeneration During APAP-Induced Liver Injury In Mice

Objective To observe whether toll-like receptor 4(TLR4)affects liver regeneration during acetaminophen(APAP)-induced liver injury in mice,and preliminarily explore the mechanism of TLR4 involved in liver regeneration.Methods ICR mice were randomly divided into control group,model groups(APAP 24 h group,APAP 48 h group,APAP 72 h group),and inhibitor groups(TAK-242+APAP 24 h group,TAK-242+APAP 48 h group,TAK-242+APAP 72 h group).Mice in model groups were given intraperitoneal injection of APAP(300mg/kg).Mice in inhibitor groups were given intraperitoneal injection of TLR4 inhibitor(TAK-242)at a dose of 3mg/kg,and then injected with APAP 3 hours later.Serum and liver tissues were collected at 0h,24 h,48h and 72 h,respectively.The serum ALT level of mice was detected by biochemical method,and the pathological changes of liver tissue were detected by HE staining.The expressions of Cyclin D1,PCNA,Ki-67,STAT3 and p-STAT3 in liver tissue were detected by RT-PCR,Western Blot and immunohistochemistry.Results Compared with normal control group,serum ALT levels in APAP 24 h group and APAP 48 h group were significantly higher(P< 0.05);Serum ALT levels in TAK-242+APAP group at 24 h and 48 h were significantly higher than those in APAP group at the same time point(P< 0.05).HE staining showed that the size and morphology of liver cells in normal control group were normal,and typical lobular central necrosis was observed in APAP-treated mice.The necrotic area of liver in the TAK-242+APAP group at 24 h and 48 h was significantly greater than that in the APAP group at the same time point(P < 0.05).RT-PCR results showed that the m RNA expression levels of Cyclin D1,Ki-67 and PCNA in APAP 48 h and 72 h groups were higher than those in the normal control group(P< 0.05);Cyclin D1 and PCNA m RNA expression levels in TAK-242+APAP 24 h,TAK-242+APAP 48 h and TAK-242+APAP 72 h groups were lower than those in APAP group at the same time point(P< 0.05).The m RNA expression level of Ki-67 in liver tissue of TAK-242+APAP 24 h and TAK-242+72 h groups was lower than that of APAP group at the same time point(P< 0.05).Western Blot results showed that the Cyclin D1 and PCNA protein expression levels in TAK-242+APAP 24 h and TAK-242+APAP 48 h groups were lower than those in APAP group at the same time point(P < 0.05).Immunohistochemical results showed that Ki-67 expression in APAP 48 h group and APAP 72 h group was higher than that in normal control group(P< 0.05);Compared with the APAP group at the same time point,the positive expression of Ki-67 in TAK-242+APAP 24 h,TAK-242+APAP 48 h and TAK-242+APAP 72 h groups was weaker(all P < 0.05).In addition,the expression level of STAT3 phosphorylated protein in liver tissue of APAP 24 h group and APAP 48 h group was higher than that of normal control group(P< 0.05),and the expression level of STAT3 phosphorylated protein in liver tissues of TAK-242+APAP 24 h and TAK-242+APAP 48 h groups were lower than those of APAP group at the same time point(P< 0.05).Conclusion TLR4 may play a role in promoting liver regeneration during APAPinduced liver injury in mice by regulating STAT3 signaling pathway.