Protective Effect Of Apigenin On Acetaminophen-induced Acute Liver Injury And Its Mechanisms

Objective：To examine the protective effect of apigenin on acetaminophen-inducedacute liver injury and to probe into the possible mechanisms.Methods: Male Kunming mice were used and randomly divided into the control,model, apigenin100,200mg/kg groups and positive drug reduced glutathione sodium240mg/kg group. A mouse model with acute liver injury was induced byintraperitoneally given acetaminophen350mg/kg after oral administration for7days.The levels of serum alanine aminotransferase (ALT) and aspartate aminotransferase(AST)，hepatic glutathione and its metabolism-related enzymes, superoxide dismutase(SOD) and malondialdehyde (MDA) were measured with the colorimetric methods, andthe hepatic histopathologic changes were evaluated under a light microscope. Thecultured hepatocytes were divided into control, DMSO, model, apigenin (3.125,6.25,12.5μmol/l), normal with apigenin12.5μmol/l, and reduced glutathione sodium1mmol/l groups, respectively. After incubation with drugs for2h, the levels of culturedsupernatant ALT, AST and MDA, activity of glutathione reductase (GR) in intracellularwere measured with the colorimetric methods. In order to determine whether themechanisms of apigenin hepatoprotective effect were associated with increment ofhepatic reduced glutathione (GSH) via enhancing GR activity, the cultured hepatocyteswere pretreated with BCNU (a GR inhibitor) for2h, then incubated with12.5μmol/lapigenin for2h, changes of cultured supernatant ALT, AST and MDA levels wereexamined.Results: In vivo, after pretreatment with apigenin for7days, the levels of serumALT and AST were dose-dependently decreased, and the severity of liver injury wasimproved, especially in apigenin200mg/kg group (P<0.05or P<0.01). The hepaticGSH content in apigenin groups was increased in different degrees, and was obviouslyincreased in apigenin200mg/kg group (P<0.05). Though the ratio of GSH/oxidized glutathione (GSSG) was no significantly difference, there was a tendency to increasewith increasing dose of apigenin. Hepatic GR and SOD activities also were significantlyincreased in apigenin200mg/kg group (P<0.01). In vitro, after treatment with apigenin3.125-12.5μmol/l for2h, cultured supernatant ALT and AST activities as well as MDAcontent were decreased in dose-dependent manner, while the intracellular GR activitywas gradually increased, especially in apigenin12.5μmol/l (P<0.05or P<0.01). Afterpretreatment with GR inhibitor BCNU for2h, the apigenin-reduced effects on the ALT,AST and MDA were decreased in varying degree, especially in ALT level (P<0.01).Conclusion：Apigenin had a good protective effect on acetaminophen-inducedacute liver injury, and its mechanisms might firstly be associated with increment ofhepatic GSH via enhancing GR activity, and secondly with scavenging reactive oxygenspecies of acetaminophen-generation via increment of SOD activity.