Molecular Mechanisms of Nitrofurantoin-Induced Hepatocyte Toxicity in Aerobic versus Hypoxic Conditions

We have previously reported that incubation of isolated rat hepatocytes with the antimicrobial drug nitrofurantoin causes toxic oxidative stress as a result of oxygen activation by futile one-electron redox cycling. In continuation of this work nitrofurantoin was found to cause rapid glutathione-protein mixed disulfide formation before GSSG had completely effluxed from the hepatocytes. Furthermore, the disulfide reductant dithiothreitol added up to 60 min later restored protein thiols and prevented cytotoxicity. In contrast, under hypoxic conditions nitrofurantoin-induced hepatocyte toxicity was associated with [14C]nitrofurantoin irreversible binding to protein, protein thiol depletion without glutathione-protein mixed disulfide formation, and GSH depletion. Furthermore, dithiothreitol did not have any antidotal properties and did not reverse covalent binding though some binding was prevented. These results suggest that under aerobic conditions nitrofurantoin-induced hepatocyte toxicity is due to the formation of glutathione-protein mixed disulfides, while under hypoxic conditions toxicity is associated with protein alkylation.