Aldehyde Oxidase-Catalyzed Metabolism of N¹-Methylnicotinamide in Vivo and in Vitro in Chimeric Mice with Humanized Liver

Abstract

ABSTRACT:Aldehyde oxidase-mediated oxidation of N 1 -methylnicotinamide to N 1 -methyl-2-pyridine-5-carboxamide (2-PY) and N 1 -methyl-4-pyridone-5-carboxamide (4-PY) in chimeric mice constructed by transplanting human hepatocytes into urokinase-type plasminogen activator-transgenic severe combined immunodeficient mice was examined in vivo and in vitro. The activity in liver cytosol of chimeric mice with a high replacement index was approximately 4-fold higher than that in control mice. Furthermore, the oxidation products in control mice were 2-PY and 4-PY, whereas, in chimeric mice, the major product was 2-PY, as in humans. The aldehyde oxidase in chimeric mouse liver was confirmed to be of human type by immunoblotting analysis. The ratio of pyridones (2-PY/4-PY) excreted in the urine of chimeric mice was closer to that of humans than to that of control mice. Thus, the aldehyde oxidase in chimeric mice has human-type functional characteristics. Tateno et al. (2004) established chimeric mice in which the liver was almost completely repopulated with human hepatocytes. Such mice should be an excellent in vivo model for predicting drug metabolism, drug-drug interactions, drug induction, and inhibition of drug-metabolizing enzymes in humans. Katoh et al. (2004Katoh et al. ( , 2005b reported that the patterns of cytochrome P450 isoforms and phase II enzymes, such as UDP-glucuronosyltransferase, sulfotransferase, N-acetyltransferase, and glutathione S-transferase, in chimeric mice having a nearly 90% replacement rate with human hepatocytes were almost identical with those in human liver, and they used these mice to estimate the in vivo induction of cytochrome P450 enzymes in humans (Katoh et al., 2005a). Nishimura et al. (2005) reported that hepatocytes from chimeric mice with nearly completely humanized liver are useful for predictive screening of the induction potency of new drugs on drug-metabolizing enzymes in humans. We were interested in knowing whether drug metabolism by a cytosolic drugmetabolizing enzyme, aldehyde oxidase, in these mice is also similar to that in humans.Aldehyde oxidase (EC 1.2.3.1) contains flavin adenine dinucleotide, molybdenum, and iron-sulfur centers. It has been suggested to be relevant to the pathophysiology of a number of clinical disorders (Berger et al., 1995;Wright et al., 1995;Moriwaki et al., 1997). The enzyme in liver of various species catalyzes the oxidation of various aldehydes and nitrogenous heterocyclic xenobiotics, such as methotrexate and cyclophosphamide (Beedham, 1985;Kitamura et al., 2006), and also catalyzes the metabolism of physiological compounds, such as retinaldehyde (Huang and Ichikawa, 1994). However, there are marked species differences and strain differences of the enzyme activities for oxidative reaction in rats and mice (Beedham, 1985;Schofield et al., 2000;Kitamura et al., 2006;Sugihara et al., 2006). This has presented problems in preclinical studies. Many aldehyde oxidase substrates, such as methotrexate and phthalazine, show similar metabolic profiles ...

CYP2C9-Catalyzed Metabolism ofS-Warfarin to 7-Hydroxywarfarin in Vivo and in Vitro in Chimeric Mice with Humanized Liver

“…In those reports, it was demonstrated that isoforms of P450 and phase II enzymes in chimeric mouse liver behaved similarly to those in human liver in in vitro experiments. In a recent study, we showed that aldehyde oxidase in chimeric mice functions as a human-type aldehyde oxidase in vivo and in vitro (Kitamura et al, 2008). In this study, we extended the studies in chimeric mice to in vivo and in vitro metabolism of S-warfarin by CYP2C9.…”

“…They also showed that the chimeric mice are a useful animal model to estimate the inductive effect on P450 in humans (Katoh et al, 2005b). We have shown that aldehyde oxidase, a cytosolic drugmetabolizing enzyme, in chimeric mice has functional characteristics almost identical to those of human aldehyde oxidase (Kitamura et al, 2008). Furthermore, Nishimura et al (2005) reported that hepatocytes from chimeric mice with nearly completely humanized liver are a useful tool for screening the potency of new drugs to induce drug-metabolizing enzymes in human.…”

Predictability of Metabolism of Ibuprofen and Naproxen Using Chimeric Mice with Human Hepatocytes

“…These mice are transplanted with approximately 80% of human hepatocytes, and the expression levels and activities of P450 and non-P450 in the liver of h-PXB mice are similar to those of humans (Katoh et al, 2004(Katoh et al, , 2005Nishimura et al, 2005;Katoh and Yokoi, 2007;Kitamura et al, 2008).…”

Prediction of Human Metabolism of FK3453 by Aldehyde Oxidase Using Chimeric Mice Transplanted with Human or Rat Hepatocytes

“…The expression and activity of AO in liver of h-PXB mice have been reported (Kitamura et al, 2008). In contrast, the AO activity of r-PXB mice seems to be low, probably because rat hepatocytes for r-PXB mice were derived from Crj:SD rats, which show lower AO activity than other strains of rats (Moriyasu et al, 2006;Sugihara et al, 2006;Itoh et al, 2007).…”