Nitrofurantoin-mediated oxidative stress cytotoxicity in isolated rat hepatocytes

Freshly isolated rat hepatocytes were used to study the mechanism(s) of toxicity of the antimicrobial drug nitrofurantoin. This 5-nitrofuran derivative stimulated hepatocyte oxygen uptake in the presence of the mitochondrial respiration inhibitors KCN or antimycin A. This could indicate the formation of O 2 − and H 2O 2, following intracellular nitrofurantoin reduction. Addition of nitrofurantoin to suspensions of isolated rat hepatocytes produced a dose- and time-dependent decrease of cell viability. H 2O 2 probably plays a significant role in the cytotoxic effects of nitrofurantoin as the catalase inhibitors azide or aminotriazole markedly enhanced cytotoxicity. The loss of cell viability was preceded by glutathione (GSH) depletion and a concomitant and nearly stoichiometric formation of oxidised glutathione (GSSG) that did not occur in hepatocytes lacking glutathione peroxidase activity isolated from rats fed a low-selenium diet. This indicates that H 2O 2 and the seleno-enzyme glutathione peroxidase are responsible for GSH oxidation. Furthermore, addition of nitrofurantoin to isolated rat hepatocytes produced a reversible inactivation of hepatocyte glutathione reductase activity and explains the maintenance of high GSSG levels. The compromised hepatocytes were also highly susceptible to H 2O 2. The hepatocyte toxicity of nitrofurantoin may, therefore, be attributed to oxidative stress caused by redox-cycling mediated oxygen activation.