ABSTRACT
Nitrofurans (5-nitro-2-hydrazonylfuran as pharmacophore) are a group of widely used antimicrobial drugs but also associated to a variety of side effects. The molecular mechanisms that underlie the cytotoxic effects of nitrofuran drugs are not yet clearly understood. One-electron reduction of 5-nitro group by host enzymes and ROS production via redox cycling have been attributed as mechanisms of cell toxicity. However, the current evidence suggests that nitrofuran ROS generation by itself is uncapable to explain the whole toxic effects associated to nitrofuran consumption, proposing a nitro-reduction independent mechanism of toxicity. In the present work, a series of nitrated and non-nitrated derivatives of nitrofuran drugs were synthesized and evaluated in vitro for their cytotoxicity, ROS-producing capacity, effect on GSH-S-transferase and antibacterial activity. Our studies showed that in human cells non-nitrated derivatives were less toxic than parental drugs but, unexpectedly preserved the ability to generate intracellular ROS in similar amounts to nitrofurans despite not entering into a redox cycle mechanism. In addition, some non-nitrated derivatives although being uncapable to generate ROS exhibited the highest cell toxicity among all derivatives. Inhibition of cytosolic glutathione-S-transferase activity by some derivatives was also observed. Finally, only nitrofuran derivatives displayed antibacterial effect. Results suggest that the combined 2-hydrazonylfuran moiety, redox cycling of 5-nitrofuran, and inhibitory effects on antioxidant enzymes, would be finally responsible for the toxic effects of the studied nitrofurans on mammalian cells.
Subject(s)
Anti-Bacterial Agents/toxicity , Microsomes, Liver/drug effects , Microsomes, Liver/metabolism , Nitrofurans/toxicity , Reactive Oxygen Species/metabolism , A549 Cells , Animals , Anti-Bacterial Agents/chemistry , HCT116 Cells , HEK293 Cells , HL-60 Cells , Hep G2 Cells , Humans , Male , Nitrofurans/chemistry , Oxidation-Reduction/drug effects , Rats , Rats, Sprague-DawleyABSTRACT
Nifurtimox (Nfx) and benznidazole (Bz) have serious toxic side effects. Manufacturers warn about significant adverse effects when simultaneous alcohol consumption is being made, but its mechanism is not known. The levels and toxicity of these drugs are linked to their liver microsomal nitroreduction to reactive metabolites. In this study, we analyzed whether alcohol drinking enhanced those nitroreductive processes. Male and female Sprague-Dawley rats, 5-6 weeks old (125-150 g body weight) were used. They were fed ad libitum for 28 days with Lieber and De Carli control or alcohol regular liquid diets. The rats were separated into two dietary groups: ethanol and control group. Both were pair fed with the respective diet. Their liver microsomes were isolated and the nicotinamide adenine dinucleotide phosphate-dependent nitroreduction of Nfx and Bz were determined. Alcohol drinking significantly induced microsomal nitroreduction of these drugs in male rats (11% for Nfx and 41% for Bz) but not in females. The activity observed in the alcohol-induced male rats was 100% inhibited by diphenyleneiodonium and attributable to P450 reductase. Inductive effects of alcohol drinking on nitroreductive activation of both drugs might be only partially involved in the harmful interactions described.
Subject(s)
Alcohol Drinking/adverse effects , Microsomes, Liver/drug effects , Nifurtimox/toxicity , Nitroimidazoles/toxicity , Nitroreductases/metabolism , Trypanocidal Agents/toxicity , Animals , Drug Interactions , Female , Male , Microsomes, Liver/metabolism , Rats , Rats, Sprague-DawleyABSTRACT
Benznidazole (Bz) and Nifurtimox (Nfx) have been used to treat Chagas disease. As recent studies have de-monstrated cardiotoxic effects of Nfx, we attempted to determine whether Bz behaves similarly. Bz reached the heart tissue of male rats after intragastric administration. No cytosolic Bz nitroreductases were detected, although microsomal NADPH-dependent Bz nitroreductase activity was observed, and appeared to be mediated by P450 reductase. No ultrastructurally observable deleterious effects of Bz were detected, in contrast to the overt cardiac effects previously reported for Nfx. In conclusion, when these drugs are used in chagasic patients, Bz may pose a lesser risk to heart function than Nfx when any cardiopathy is present.