BACKGROUND
Acetaminophen (APAP) is commonly used for treatment of pain and fever. In overdose the potential risk of a patient having significant liver injury is directly proportional to the amount of APAP ingested. Rice is widely consumed in many countries worldwide and rice bran is the pericarp of Oryza sativa, a good source of protein, fat, vitamin as well as antioxidants. It has been reported to exhibit various pharmacological effects, including anti-oxidant, anti-microbial, strong in vitro α-amylase, β-glucosidase, dipeptidyl peptidase-IV and ACE-inhibition activities. In this study, we evaluated the hepatoprotective effects and antioxidants activities of protein rice bran extract against acetaminophen (APAP)-induced liver damaged in vitro using HepG2 cells as a cell model.
METHODS
Protein rice bran extract was screened for reactive oxygen species (ROS) scavenging effect using the TBARS assay, thereafter hepatoprotective effects against APAP-induced HepG2 cell injury was performed. HepG2 cells were pre-treated with various concentrations of protein rice bran extract (0.00001-1 mg/mL) for 12 h prior to incubation with 20 mM of APAP for 24 h. Cell viability and ROS generation were assessed by MTT and DCFH-DA assays, respectively. Aspartate aminotransferase (AST) and alanine aminotransferase (ALT) in the culture medium were analyzed to determine the degree of liver injury. Oxidative defense mechanisms were investigated by measuring glutathione levels and activities of antioxidant enzymes.
RESULTS AND DISCUSSION
The results showed that APAP at concentration of 20 mM significantly decreased cell viability of HepG2 cells while increased ROS generation, enhancement in hepatic lipid peroxidation, leakage of AST and ALT and marked depletion in GSH level. Protein rice bran extract (0.0001-1 mg/mL), when administered prior to APAP, increased cell viability, prevented ROS generation and decreased leakage of liver enzymes and lipid peroxidation in a dose-dependent manner in HepG2 cells against APAP-induced hepatotoxicity. The extract increased the activities of antioxidant enzymes (CAT, GPx, GR and SOD), total GSH, GSH and the GSH/GSSG ratio, but decreased GSSG level. Thus, this study demonstrated that protein rice bran extract possessed hepatoprotective effect against APAP-induced liver injury in HepG2 cells. Attenuation of ROS production, modulation of GSH level and activation of antioxidant enzymes including CAT, GPx, GR and SOD could contribute to this effect.
