RT Journal Article
SR Electronic
T1 Metabolic Activation of Benzodiazepines by CYP3A4
JF Drug Metabolism and Disposition
JO Drug Metab Dispos
FD American Society for Pharmacology and Experimental Therapeutics
SP 345
OP 351
DO 10.1124/dmd.108.024521
VO 37
IS 2
A1 Katsuhiko Mizuno
A1 Miki Katoh
A1 Hirotoshi Okumura
A1 Nao Nakagawa
A1 Toru Negishi
A1 Takanori Hashizume
A1 Miki Nakajima
A1 Tsuyoshi Yokoi
YR 2009
UL http://dmd.aspetjournals.org/content/37/2/345.abstract
AB 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 μM 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. The American Society for Pharmacology and Experimental Therapeutics