In Vivo Assessment of Drug-Induced Hepatotoxicity Using Xenopus Embryos

Abstract

Failure to predict drug-induced toxicity reactions is a major problem contributing to a high attrition rate and tremendous cost in drug development. Drug screening in X. laevis embryos is high-throughput relative to screening in rodents, potentially making them an ideal model organism for this use. Xenopus embryos have been used as a toxicity model in the frog teratogenesis assay-Xenopus (FETAX assay) for the early stages of drug safety evaluation. We have previously developed compound-screening methods using Xenopus embryos and believe they could be used for in vitro druginduced toxicity safety assessment prior to expensive preclinical trials in mammals. Specifically, Xenopus embryos could help predict drug-induced hepatotoxicity and consequently aid lead candidate prioritization. Here we present methods, which we have modified for use on Xenopus embryos, to help measure the potential for a drug to induce liver toxicity. One such method is the release of the liver-specific micro-RNA (miRNA), miR-122, from the liver into the vasculature as a result of hepatocellular damage, which could be due to drug-induced acute liver injury. Paracetamol, a known hepatotoxin at high doses, was a positive control. We have previously shown that some of the phenotypes of mammalian paracetamol overdose are reflected in Xenopus embryos. Consequently, we have also included a method that measures the concentration of free glutathione (GSH), which is an indicator of paracetamol-induced liver injury. These methods can be used as part of a panel of protocols to help predict the hepatoxicity of a drug at an early stage in drug development.