Inhibition of acetaminophen-induced hepatotoxicity in mice by exogenous thymosinβ4 treatment

Objective: To study the effects of exogenous thymosinβ4 (Tβ4) treatment in acetaminophen (APAP)-induced hepatotoxicity.

Methods: Liver injury was induced in mice by a single intraperitoneal injection of APAP (500 mg/kg). Exogenous Tβ4 was intraperitoneally administrated at 0 h, 2 h and 4 h after APAP injection. Chloroquine (CQ) (60 mg/kg) was intraperitoneally injected 2 h before APAP administration to inhibit Autophagy. Six hours after APAP injection liver injury was evaluated by histological examinations, biochemical measurements and Enzyme linked immunosorbent assay (ELISAs). Western blots were performed to detect proteins expression.

Results: Serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) activities were significantly increased 6 h after APAP administration, but were significantly reduced by co-administration of Tβ4. Histological examinations demonstrated that Tβ4 reduced necrosis and inflammation induced by APAP. Immunofluorescence showed that Tβ4 suppressed APAP-induced translocation of high mobility group box-1 protein (HMGB1) from the nucleus to cytosol and intercellular space. Hepatic glutathione (GSH) depletion, malondialdehyde (MDA) formation and decreased superoxide dismutase (SOD) activities induced by APAP were all attenuated by Tβ4. APAP-induced increases in hepatic nuclear factor-κB (NF-κB) p65 protein expression and inflammatory cytokines production including interleukin-1β (IL-1β) and tumor necrosis factor-α (TNF-α) were reduced by Tβ4 treatment. Increased LC3 and p62 proteins in the liver tissues of APAP-treated mice were decreased by Tβ4 treatment, which indicated the enhancement of Autophagy flux by Tβ4. Furthermore, inhibiting Autophagy by CQ abrogated the protective effects of Tβ4 against APAP hepatotoxicity.

Conclusion: Exogenous Tβ4 treatment exerts protective effects against APAP-induced hepatotoxicity in mice. The underneath molecular mechanisms may involve Autophagy enhancement and inhibition of oxidative stress by Tβ4.