Picroside II ameliorates acute liver injury induced by LPS/D-GalN in mice

Background: Acute liver injury (ALI) due to massive hepatocyte death can lead to hepatic metabolic dysfunction and high mortality. Picroside II (Picro II), an iridoid compound extracted from the roots of Picrorhiza, has been demonstrated to possess anti-inflammatory and anti-apoptotic activities. Objective: To determine whether Picro II could protect against ALI by inhibiting hepatocytic apoptosis and pyroptosis in a lipopolysaccharide (LPS) and D-galactosamine (GalN)-induced ALI mouse model. Methods: Male C57BL/6 mice aged 6-8 weeks were randomized into three groups: a control group, a LPS/D-GalN group, and a LPS/D-GalN+ 20 mg/kg Picro II group. The ALI model was established by intraperitoneal (i.p.) injection of 700 mg/kg D-GalN/10 ug LPS. Picro II (20 mg/kg) was injected i.p. at 1, 6, 12 and 24 h prior to LPS/D-GalN exposure. HE staining was used to determine the liver injury level. AST, ALT levels in plasma and IL-6, TNF-alpha, IL-1 beta, IL-18 in serum or supernatant were examined by ELISA. Besides, RNA levels in liver tissue were detected by RT-qPCR. To assay cell death rate, flow cytometry was used by double staining with Annexin V-PE and 7-AAD. To detect whether caspase-1 and caspase-3 were activated, western blot was used. Results: The results showed that pretreatment with Picro II decreased the mortality and alleviated liver injury of the ALI mice, as demonstrated by a significant decrease in alanine aminotransferase (ALT) and aspartate transaminase (AST) levels and amelioration of the histological changes as represented by less hemorrhage and inflammatory cell infiltration. In addition, Picro II protected hepatocytes against apoptosis by inhibiting the expression of Bax and increasing the expression of Bcl-2, protected hepatocytes against pyroptosis by inhibiting the expression of caspase-1, and prevented inflammatory response by inhibiting the activation of NF-kappa B. Conclusion: Our results suggest that Picro II could protect the liver in LPS/D-GalN-induced ALI. This finding may provide a new therapeutic option for the clinical treatment of human septic liver injury.