Comparison of Drug Metabolism and Its Related Hepatotoxic Effects in HepaRG, Cryopreserved Human Hepatocytes, and HepG2 Cell Cultures.

Differentiated HepaRG cells maintain liver-specific functions such as drug-metabolizing enzymes. In this study, the feasibility of HepaRG cells as a human hepatocyte model for in vitro toxicity assessment was examined using selected hepatotoxic compounds. First, basal drug-metabolizing enzyme activities (CYP1A2, CYP2B6, CYP2C9, CYP2C19, CYP2D6, CYP3A4, uridine 5'-diphospho-glucuronosyltransferase [UGT], and sulfotransferases [SULT]) were measured in HepaRG, human hepatocytes, and HepG2 cells. Enzyme activities in differentiated HepaRG cells were comparable to those in human hepatocytes and much higher than those in HepG2 cells, except for SULT activity. Second, we examined the cytotoxicity of hepatotoxic compounds, acetaminophen (APAP), aflatoxin B1 (AFB1), cyclophosphamide (CPA), tamoxifen (TAM), and troglitazone (TGZ) in HepaRG cells and human hepatocytes. AFB1- and CPA-induced cytotoxicities against HepaRG cells were comparable to those against human hepatocytes. Furthermore, the cytotoxicities of these compounds were inhibited by 1-aminobenzotriazole (ABT), a broad CYP inhibitor, in both cells and were likely mediated by metabolic activation by CYP. Finally, toxicogenomics analysis of HepG2 and HepaRG cells after exposure to AFB1 and CPA revealed that numerous p53-related genes were upregulated- and the expression of these genes was greater in HepaRG than in HepG2 cells. These results suggest that gene expression profiles of HepaRG cells were affected more considerably by the toxic mechanisms of AFB1 and CPA than the profiles of HepG2 cells were. Therefore, our investigation shows that HepaRG cells could be useful human hepatic cellular models for toxicity studies.

Twenty-six week carcinogenicity study of ampicillin in CB6F1-TgrasH2 mice.

As a part of the ILSI-HESI Alternative to Carcinogenicity Testing (ACT) program, we performed a 26-week carcinogenetic study of nonmutagenic drug, ampicillin (ABPC) in Tg-rasH2 mice. ABPC was given to Tg-rasH2 mice (0, 350, 1000, 3000 mg/kg, p.o.) and Non-Tg mice (0, 3000 mg/kg, p.o.) daily for 26 weeks. As a positive control, a single dose of MNU was administered once to Tg-rasH2 mice (75 mg/kg, i.p.). In this study, Tg-rasH2 mice did not demonstrate any increases in tumor development in response to ABPC. Thus, ABPC had no carcinogenicity in the 26-week carcinogenesis study in Tg-rasH2 mice or in a 2-year carcinogenesis study in B6C3F1 mice.