Metabolic Activation of Benzodiazepines by CYP3A4

Abstract

ABSTRACT:Cytochrome P450 3A4 is the predominant isoform in liver, and it metabolizes more than 50% of the clinical drugs commonly used. However, CYP3A4 is also responsible for metabolic activation of drugs, leading to liver injury. Benzodiazepines are widely used as hypnotics and sedatives for anxiety, but some of them induce liver injury in humans. To clarify whether benzodiazepines are metabolically activated, 14 benzodiazepines were investigated for their cytotoxic effects on HepG2 cells treated with recombinant CYP3A4. By exposure to 100 M flunitrazepam, nimetazepam, or nitrazepam, the cell viability in the presence of CYP3A4 decreased more than 25% compared with that of the control. In contrast, in the case of other benzodiazepines, the changes in the cell viability between CYP3A4 and control Supersomes were less than 10%.These results suggested that nitrobenzodiazepines such as flunitrazepam, nimetazepam, and nitrazepam were metabolically activated by CYP3A4, which resulted in cytotoxicity. To identify the reactive metabolite, the glutathione adducts of flunitrazepam and nimetazepam were investigated by liquid chromatography-tandem mass spectrometry. The structural analysis for the glutathione adducts of flunitrazepam indicated that a nitrogen atom in the side chain of flunitrazepam was conjugated with the thiol of glutathione. Therefore, the presence of a nitro group in the side chain of benzodiazepines may play a crucial role in the metabolic activation by CYP3A4. The present study suggested that metabolic activation by CYP3A4 was one of the mechanisms of liver injury by nitrobenzodiazepines.

In vitro studies on flubromazolam metabolism and detection of its metabolites in authentic forensic samples

“…[3,[10][11][12] Midazolam, alprazolam and triazolam ( Fig. 1) are mainly excreted in urine as glucuronides of the hydroxylated metabolites, where the α-hydroxy-metabolite predominates the 4-hydroxylation.…”

Hyaluronic acid–nimesulide conjugates as anticancer drugs against CD44-overexpressing HT-29 colorectal cancer in vitro and in vivo

“…64 The toxicity of nimesulide to hepatocytes has been previously observed 65,66 which is attributed mainly to the nitro group in its structure. 67 After reduction, NiNH 2 exhibits reduced toxicity than nimesulide in hepatocytes because nimesulide is a powerful protonophoretic uncoupler and NAD(P)H oxidant.…”

Development of a Highly Sensitive Cytotoxicity Assay System for CYP3A4-Mediated Metabolic Activation

“…Vignati et al (2005) demonstrated, using HepG2 cells transiently transfected with CYP3A4, that reactive metabolites of various hepatotoxic drugs such as albendazole, flutamide, and troglitazone were produced by CYP3A4. Our previous study showed that benzodiazepines such as flunitrazepam and nimetazepam were metabolically activated by CYP3A4 by coincubation with HepG2 cells and CYP3A4 Supersomes (Mizuno et al, 2009). Thus, several in vitro studies demonstrated that P450 enzymes, especially CYP3A4, are involved in the cytotoxicities of various kinds of drugs.…”