Liver microsomal biotransformation of nitro-aryl drugs: mechanism for potential oxidative stress induction

• Published in: Journal of applied toxicology Vol. 24; no. 6; pp. 519 - 525
• Main Authors: Letelier, M. E., Izquierdo, P., Godoy, L., Lepe, A. M., Faúndez, M.
• Format: Journal Article
• Language: English
• Published: Chichester, UK John Wiley & Sons, Ltd 01.11.2004; Wiley
• Subjects: Animals; Anti-Infective Agents, Urinary - toxicity; Antibacterial agents; Antibiotics. Antiinfectious agents. Antiparasitic agents; Antiseptics; Biological and medical sciences; Biotransformation; Catalysis; Drug toxicity and drugs side effects treatment; Lipid Peroxidation; liver microsomes; Male; Medical sciences; microsomal reduction; Microsomes, Liver; Miscellaneous (drug allergy, mutagens, teratogens...); NADPH-Ferrihemoprotein Reductase - pharmacology; Nifurtimox - toxicity; nitro-aryl drug reduction; nitro-aryl drugs; Nitrofurantoin - toxicity; nitrofurantoin/nifurtimox; Oxidative Stress; Oxygen Consumption; Pharmacology. Drug treatments; Rats; Rats, Wistar; Drug; Nitro compound; Oxidative stress; nitro-aryl drugs; nitrofurantoin/nifurtimox; Nitrofurantoin; Toxicity; Liver; Nifurtimox; Furan derivatives; Metabolism toxicity relation; Microsome; microsomal reduction; Chemical reduction; Tissue; Biotransformation; nitro-aryl drug reduction; Enzymatic reaction; liver microsomes
• ISSN: 0260-437X; 1099-1263
• DOI: 10.1002/jat.999

Toxic effects of several nitro‐aryl drugs are attributed to the nitro‐reduction that may be suffered in vivo, a reaction that may be catalysed by different reductases. One of these enzymes is NADPH–cytochrome P450 reductase, which belongs to the cytochrome P450 oxidative system mainly localized in the endoplasmic reticulum of the hepatic cell. This system is responsible for the biotransformation of oxidative lipophilic compounds, so that oxidative and reductive metabolic pathways of lipophilic nitro‐aryl drugs can take place simultaneously. Because of the affinity of nitro‐aryl drugs (xenobiotics) for the endoplasmic reticulum, we propose this subcellular organelle as a good biological system for investigating the toxicity induced by the biotransformation of these or another compounds. In this work we used rat liver microsomes to assess the oxidative stress induced by nitro‐aryl drug biotransformation. Incubation of microsomes of rat liver with nifurtimox and nitrofurantoin in the presence of NADPH induced lipoperoxidation, UDP‐glucuronyltransferase activation and an increase in the basal microsomal oxygen consumption. Nitro‐aryl‐1,4‐dihydropyridines did not elicit these prooxidant effects; furthermore, they inhibited lipoperoxidation and oxygen consumption induced by Fe3+/ascorbate. Nifurtimox and nitrofurantoin modified the maximum absorption of cytochrome P450 oxidase and inhibited p‐nitroanisole O‐demethylation, an oxidative reaction catalysed by the cytochrome P450 system, signifying that oxidation may proceed in a similar way to that described for nitro‐aryl‐1,4‐dihydropyridines. Thus the balance between lipophilic nitro‐aryl drug oxidation and reduction may be involved in the potential oxidative stress induced by biotransformation. Copyright © 2004 John Wiley & Sons, Ltd.