Gender Differences in the Hepatotoxicity and Toxicokinetics of Emodin: The Potential Mechanisms Mediated by UGT2B7 and MRP2.

Emodin is a main anthraquinone compound which exists in Chinese traditional medicines including Polygonum multiflorum and Rhubarb. It is documented to have obvious liver and kidney toxicity. This study aims to (a) estimate gender differences of the hepatotoxicity and toxicokinetics in rats after oral administration of emodin (60 and 150 mg/kg/d) for a consecutive 28 days and (b) clarify relative mechanisms caused by glucuronidation and disposition. Hepatotoxicity was significantly higher in female rats than that in male rats, as evidenced by histopathological and biochemical tests. Similarly, the toxicokinetic profiles of emodin have time and gender differences, which could cause time and gender differences in hepatotoxicity. The metabolic and transcriptomics data of 55 human liver and 36 human kidney samples demonstrated that UDP-glucuronosyltransferase 2B7 (UGT2B7) was the predominant enzyme for emodin glucuronidation. A genome-wide association study (GWAS) identified that rs11726899 located within ∼50 kb of the transcript of UGT2B could significantly affect emodin metabolism. Knockdown of UGT2B7 in HepG2 cells significantly decreased emodin glucuronidation and increased cytotoxicity of emodin. The gene expression and protein levels of UGT2B7 were decreased, but those of the multidrug-resistant-protein 2 (MRP2) were increased in HepG2 cells after being treated with 50 μM emodin for 48 h. Long-term use of emodin could decrease the intrinsic clearance (CL, decreased by 18.5%-35.4%) values of zidovidue (UGT2B7 substrate) glucuronide in both male and female liver microsomes from rats administrated with emodin for 28 days, thus causing the accumulation of emodin. However, higher self-induced MRP2 expression and lower hepatotoxicity were observed in emodin-treated male rats compared to that in female rats. Therefore, gender differences in the hepatotoxicity and toxicokinetics of emodin are potentially mediated by the coupling of UGT2B7 and MRP2 in vivo.