Role of enzymatic N-hydroxylation and reduction in flutamide metabolite-induced liver toxicity
| Autor: | Yasushi Yamazoe, Daichi Nagai, Kouichi Yoshinari, Miki Shimada, Masato Ohbuchi, Masaaki Miyata |
|---|---|
| Rok vydání: | 2008 |
| Předmět: |
Male
medicine.medical_specialty Metabolite Blotting Western Pharmaceutical Science Allopurinol Hydroxylation Flutamide chemistry.chemical_compound Mice Internal medicine medicine Animals Xanthine oxidase Chromatography High Pressure Liquid Pharmacology Liver injury virus diseases Androgen Antagonists Glutathione medicine.disease respiratory tract diseases Mice Inbred C57BL Endocrinology chemistry Liver Toxicity Microsome Spectrophotometry Ultraviolet medicine.drug |
| Zdroj: | Drug metabolism and disposition: the biological fate of chemicals. 37(1) |
| ISSN: | 1521-009X |
| Popis: | Flutamide is used for prostate cancer therapy but occasionally induces severe liver injury. Flutamide is hydrolyzed in the body into 5-amino-2-nitrobenzotrifluoride (FLU-1) and then further oxidized. In our previous study, N-hydroxy FLU-1 (FLU-1 N-OH) was detected in the urine of patients and exhibited cytotoxicity in rat primary hepatocytes. In the present study, we have assessed the roles of FLU-1 N-oxidation and hepatic glutathione (GSH) depletion in liver injury. FLU-1 (200 mg/kg p.o.) was administered to C57BL/6 mice for 5 days together with 1,4-bis[2-(3,5-dichloropyridyloxy)]benzene (TCPOBOP) (3 mg/kg i.p.) for the first 3 days. Mice were fasted for the last 2 days to deplete hepatic GSH. Administration of FLU-1 alone did not affect serum alanine aminotransferase activities (ALT), whereas coadministration of FLU-1 and TCPOBOP significantly increased ALT in fasted mice but not in nonfasted mice. Microsomal FLU-1 N-hydroxylation was enhanced approximately 5 times by TCPOBOP treatment. Flutamide metabolite-protein adducts were detected in liver microsomes incubated with FLU-1 N-OH, but not with FLU-1 and flutamide, by immunoblotting using antiflutamide antiserum. In the presence of mouse liver cytosol, FLU-1 N-OH was reduced back into FLU-1. This enzymatic reduction required NAD(P)H as a cofactor. The reduction was enhanced by the coexistence of NAD(P)H and GSH, whereas it was markedly inhibited by allopurinol (20 microM). By using purified bovine xanthine oxidase, the reduction was observed in the presence of NAD(P)H. These results suggest that FLU-1 N-OH is involved in flutamide-induced hepatotoxicity and that cytosolic reduction of FLU-1 N-OH plays a major role in protection against flutamide-induced hepatotoxicity. |
| Databáze: | OpenAIRE |
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