FTY720 Protects Against Acetaminophen-induced Liver Injury In Mice

Background:Acetaminophen(APAP)overdose induces acute liver failure in humans and hepatocyte necrosis,which is followed by the activation of the innate immune system,further aggravating liver injury.The development and implementation of successful therapeutic intervention strategies,due to the limitations associated with the use of current treatment for acetaminophen-induced liver injury(AILI),have been difficult.FTY720(fingolimod)is an immunomodulatory drug that was shown to have many biological functions.Objective:To explore the mechanism underlying the protective effects of FTY720 in a murine model of AILI.Methods:Mice were injected with FTY720(5 mg/kg,i.p.)at 0.5 h after APAP challenge(250 mg/kg,i.p.).Blood and liver tissue samples were collected at 6 and 24 h,respectively,after the APAP injection for serum AST and ALT determination,and histological examination.ELISA was performed to assess the levels of TNF-α,IL-1β and IL-6 in both serum and cell culture supernatants.The expressions of TNF-α,IL-1β and IL-6 were evaluated using real-time PCR.Hematoxylin and eosin(H&E)and TUNEL staining were used for hepatocyte necrosis analysis.In order to detect the populations of APAP-stimulated macrophages and neutrophils in livers,non-parenchymal cells were isolated from mouse livers after APAP/PBS and APAP/FTY720 treatment,and analyzed by flow cytometry.Western blotting analysis was performed in order to detect the expression of high-mobility group box 1(HMGB1 and JNK activation.Result:Compared with those in the APAP-treated group,the levels of serum AST and ALT in APAP/FTY720 co-treatment group were significantly reduced(p<0.001).APAP-induced hepatocyte necrosis was considerably decreased in APAP/FTY720 group,compared with that in the APAP group.Furthermore,the mortality of mice induced by a lethal dose of APAP was significantly reduced following the administration of FTY720.FTY720 reduced the expression levels of TNF-α,IL-1βand IL-6 in the sera of mice,compared with those determined in the APAP treatment group(p<0.01)and in the liver tissue samples(p<0.05).A large number of macrophages and neutrophils were shown to infiltrate into mouse livers after APAP challenge,but after FTY720 treatment the infiltration of inflammatory cells was markedly reduced.In vitro experiments showed that HMGB1 expression levels were significantly increased and JNK was activated after APAP challenge,while FTY720 markedly suppressed the expression levels of HMGB1 and the activation of JNK.Conclusion:Collectively,the obtained data indicate that FTY720 shows a direct protective effect on hepatocytes through the inhibition of APAP metabolism,decreasing the liver infiltration of APAP-induced macrophages and neutrophils,thereby providing the protection against AILI.Taken together,our results demonstrate a significant therapeutic potential of FTY720 for the treatment of AILI.