Licorice (Glycyrrhiza glabra) Root Extract Alleviated TCDD-Induced Toxicity in Primary Rat Hepatocytes

2, 3, 7, 8-Tetrachlorodibenzo-p-dioxin (TCDD) is the most toxic member of a class of planar, halogenated aromatic hydrocarbons. Recently it raises great public concern about its impact on human health. It has been suggested that TCDD induce hepatocyte toxicity by a mechanism involving the generation of ROS through CYP1A1 (cytochrome P450 1A1) activation. Many studies indicated that Licorice (Glycyrrhiza glabra) Root Extract (LRE) exhibits chemopreventive and detoxicative properties. The aim of this study was to assess the effect of ethanolic LRE against TCDD induced toxicity in a primary culture of rat hepatocytes. Primary cultured hepatocytes were treated with TCDD (10nM) with or without LRE (0-400μg/ml) for 24 and 48 hours. Treatment with TCDD alone lowered hepatocyte viability, but the toxic effect of TCDD on cell viability was ameliorated by the treatment of LRE dose dependently. Free radical scavenging activity by DPPH assay showed that LRE has a strong antioxidant activity. RT-PCR and Western Blot analysis, both showed that TCDD toxicity related genes (AhR, ARNT and CYP1A1) were subsequently down-regulated by LRE treatment in a dose dependent manner. DNA fragmentation assay also showed the protective effect of LRE against TCDD mediated DNA damage. These data suggested that LRE can alleviate the toxic effects of TCDD in cultured hepatocytes by its strong antioxidant activity as well as the down regulation of CYP1A1 expression followed by the suppression of AhR and ARNT genes. In conclusion, LRE can be used as a potential toxicity alleviating agent against TCDD induced hepatocyte toxicity.