In Vitro Characterization of the Cytochrome P450 Isoforms Involved in the Metabolism of 6-Methoxy-2-napthylacetic Acid, an Active Metabolite of the Prodrug Nabumetone

Abstract

Nabumetone, 4-(6-methoxy-2-naphthyl)-butan-2-one, is a nonsteroidal anti-inflammatory drug (NSAID) that has proved effective in the treatment of rheumatoid and osteoarthritis.1) Nabumetone is a prodrug that undergoes extensive first-pass metabolism to 6-methoxy-2-naphthylacetic acid (6-MNA), the major circulating metabolite. 6-MNA is largely responsible for the therapeutic efficacy of nabumetone. It decreases prostaglandin synthesis via inhibition of cyclooxygenase, an enzyme involved in the arachidonic acid conversion pathway.2)The metabolism of 6-MNA has been studied in rats, the major experimental animal, and humans. The primary metabolite of 6-MNA, namely, 6-hydroxy-2-naphthylacetic acid (6-HNA), was detected in urine. About 70% of a radiolabeled dose of nabumetone was recovered within 48 h in urine, mainly as 6-MNA, 6-HNA and their conjugates.3) The 6-O-demethylation of 6-MNA to 6-HNA is known to be a major metabolic pathway (Fig. 1). Although it may be obvious that the cytochrome P450 (CYP) system is involved in this pathway, actual CYP isoforms that are involved have not been identified. Their identification is of considerable clinical importance with regard to potential drug interactions and genetically based individual variations of drug metabolism. To our knowledge, no in vitro study has been conducted with respect to the metabolism of 6-MNA or to obtain specific data on the enzyme(s) involved in its metabolic pathway in vitro using human and rat liver microsomes.The purpose of this study was to elucidate CYP isoforms with regard to the 6-O-demethylase activity, a major metabolic pathway of 6-MNA, in human/rat microsomes and recombinant human CYP enzymes expressed in insect cells in which both human/rat CYP and reduced nicotinamide adenine dinucleotide phosphate (NADPH)-P450 reductase cDNAs had been incorporated. We also examined the inhibition or activation of 6-MNA metabolism by chemical substrates and antibodies. MATERIALS AND METHODSChemicals and Reagents 6-MNA and 6-HNA were supplied by Sanwa Kagaku Kenkyusho (SKK) Co., Ltd. (Nagoya, Japan). Glucose-6-phosphaste and glucose-6-dehydrogenase were obtained from Oriental Yeast (Tokyo, Japan). NADPH and nicotinamide adenine dinucleotide phosphate (NADP) were purchased from Alexis (San Diego, CA, U.S.A.). Mefenamic acid and naproxen were purchased from Tokyo Kasei Kogyo Co. (Tokyo, Japan). Acetonitrile, methanol and cimetidine were purchased from Wako Pure Chemical Industries Ltd. (Tokyo, Japan). Furafylline, troleandomycin, ketoconazole, sulfaphenazole and S-mephenytoin were purchased from Daiichi Pure Chemicals (Tokyo, Japan). Diethyldithiocarbamate and quinidine were pur- The cytochrome P450 (CYP) isoforms that catalyze the oxidation metabolism of 6-methoxy-2-napthylacetic acid (6-MNA), an active metabolite of nabumetone, were studied in rats and humans. Using an extractive reversed-phase HPLC assay with fluorescence detection, monophasic Michaelis-Menten kinetics was obtained for the formation of 6-hydroxy-2-naphthylacetic acid (6-HNA) in liver micr...

Unimolecular and Bimolecular Binding System for the Prediction of CYP2D6-Mediated Metabolism

“…at ASPET Journals on May 12, 2018 dmd.aspetjournals.org troanisole, 4-nitroanisole, and 6-methoxy-2-naphthylacetic acid (Matsumoto et al, 2011) (Fig. 8).…”

Pharmacokinetic and Pharmacodynamic Interaction of Andrographolide and Standardized Extract of Andrographis paniculata (Nees) with Nabumetone in Wistar Rats

“…6‐MNA is a close structural analog of naproxen which is more potent and more selective inhibitor of cyclooxygenase‐2 compared with the parent drug (Dahl, ; Davies, ). CYP1A2 plays an important role in the metabolism of NAB to the active metabolite 6‐MNA along with other enzymes like CYP2C6, CYP2C11 in rats and CYP2A6, CYP2C9, CYPC19, CYP2D6, CYP3A4 in human, (Turpeinen et al , ; Matsumoto et al , , Varfaj et al , ). So any substance influencing the CYP1A2 enzyme may affect the metabolism of NAB.…”

Effect of nabumetone on humoral immune responses in mice

“…Vet. Zootec., v.72, n.3, p.915-920, 2020 reaches the joint fluid (Klebanoff et al, 2005;Muneer et al, 2005). It has been found that Nabumetone has very few undesired health effects.…”