Nonalcoholic fatty liver disease is a serious liver disorder associated with oxidative stress. Black radish (Raphanus sativus L. var. niger) extract (BRE) can lower the risk of this disease. The hepatoprotective effect of BRE containing 3-(E)-(methylthio)methylene-2-pyrrolidinethione was evaluated in human hepatocyte carcinoma (HepG2) cells and in rat livers with carbon tetrachloride (CCl4)-induced hepatic injury. BRE was administered at 125, 250, 500, and 1000 μg/mL to the oleic acid-induced HepG2 cells. Male Sprague-Dawley rats were randomly divided into seven groups: the control group, BRE group, CCl4 group, and BRE + CCl4 group. BRE was administered orally at 125, 250, 500, and 1000 mg/kg/day once daily for 7 consecutive days, followed by a single oral treatment of 1.5 mL/kg CCl4. Inhibition of lipid accumulation, serum markers of liver injury, histological evaluations, levels of oxidative stress related enzymatic and nonenzymatic antioxidants in HepG2 cells and liver tissue were investigated. The protein expression of main liver P450 isoenzymes such as cytochrome p450(CYP)2E1, the expression of nuclear factor erythroid 2-related factor-2(Nrf-2) and heme oxygenase-1(HO-1) were also studied. BRE has an inhibitory effect on lipid accumulation and caused acute hepatotoxicity manifested by increased levels of lipid peroxidation, serum alanine aminotransferase, and aspartate aminotransferase with corresponding histopathological changes and high levels of oxidative stress. BRE treatment significantly increased the level of CYP2E1, Nrf-2, and HO-1 in a dose-dependent manner. Besides, 3-(E)-(methylthio)methylene-2-pyrrolidinethione significantly increased radical-scavenging effects and the expression of Nrf-2 in oleic acid-treated HepG2 cells. These results suggest that BRE treatment reduces lipid accumulation in oleic acid-induced steatosis of HepG2 cells, and has a hepatoprotective effect against CCl4-induced liver injury in rats, possibly through Nrf-2/HO-1-mediated antioxidant effects.
Keywords: black radish extract; carbon tetrachloride; hepatoprotection; nonalcoholic fatty liver.