Characterization of mouse flavin-containing monooxygenase transcript levels in lung and liver, and activity of expressed isoforms

Siddens, Lisbeth K.; Henderson, Marilyn C.; VanDyke, Jonathan; Williams, David E.; Krueger, Sharon K.

doi:10.1016/j.bcp.2007.09.006

Cited by 26 publications

(23 citation statements)

References 31 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…To determine the breadth of the FMO response to TCDD, in the current project we measured mRNA levels for the five most prominent FMOs in mouse liver. As recently reported by Siddens et al (2008), the most abundant hepatic mRNA under basal (untreated) conditions in adult C57BL/6J mice is FMO5. At a dose of 30 g/kg for 24 h, TCDD significantly suppressed FMO5 mRNA levels in both male ( Fig.…”

Section: Resultssupporting

confidence: 71%

“…Because of a lack of specificity and high cross-reactivity with other proteins, it was not possible to distinguish FMO3 from other protein bands (data not shown). Unfortunately, suitable antibodies are currently not available for immunological characterization of mouse FMO proteins (Siddens et al, 2008). Thus, as an alternative index to the effect of TCDD on FMO protein, we measured FMO catalytic activity with methimazole, a substrate that is metabolized by multiple species of FMO , FIG.…”

Section: Resultsmentioning

confidence: 99%

See 1 more Smart Citation

Aryl Hydrocarbon Receptor-Dependent Induction of Flavin-Containing Monooxygenase mRNAs in Mouse Liver

Celius¹,

Roblin²,

Harper³

et al. 2008

Drug Metab Dispos

View full text Add to dashboard Cite

ABSTRACT:Flavin-containing monooxygenases (FMOs) are important in detoxication but generally are considered not to be inducible by xenobiotics. Our recent microarray studies revealed induction of FMO2 and FMO3 mRNAs by 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) in liver of mice with wild-type aryl hydrocarbon receptor (AHR) but not in Ahr-null mice. The aim of the present study was to delineate mechanisms of FMO regulation. In adult male mice, basal FMO3 mRNA is low but was induced 6-fold at 4 h and 6000-fold at 24 h. The ED50 was approximately 1 g/kg for FMO2 and FMO3, similar to that for the classic AHR-regulated gene, Cyp1a1. In adult female mice basal FMO3 mRNA is high and was not induced at 4 h but was elevated 8-fold at 24 h. FMO5 mRNA was significantly downregulated by TCDD in both male and female adult mice. Juvenile mice show no sex difference in response to TCDD; FMO3 was induced 4 to 6-fold by TCDD in both sexes. Chromatin immunoprecipitation demonstrated recruitment of AHR and aryl hydrocarbon nuclear translocator proteins to Fmo3 regulatory regions, suggesting that induction by TCDD is a primary AHR-mediated event. Although FMO2 and FMO3 mRNAs were highly induced by TCDD in adult males, overall FMO catalytic activity increased only modestly. In contrast to the striking up-regulation of FMO2 and FMO3 in mouse liver, TCDD has little effect on FMO mRNA in rat liver. However, FMO2 and FMO3 mRNAs were highly induced in transgenic mice that express wild-type rat AHR, indicating that lack of induction in rat is not due to an incompetent AHR in this species.

show abstract

Section: Resultssupporting

confidence: 71%

Section: Resultsmentioning

confidence: 99%

Aryl Hydrocarbon Receptor-Dependent Induction of Flavin-Containing Monooxygenase mRNAs in Mouse Liver

Celius¹,

Roblin²,

Harper³

et al. 2008

Drug Metab Dispos

View full text Add to dashboard Cite

show abstract

“…Thus, this is the first study to show that CYP2A5, which is one of the most abundant P450 isoforms in the mouse OM (Gu et al, 1998) and is known to be active toward a number of nasal toxicants and procarcinogens (Jalas and Hecht, 2003;Xie et al, 2010), is able to metabolize MMZ, as indicated by the decreased MMZ metabolism in Cyp2a5-null OM microsomes. Previous studies have shown that several isoforms of FMO are active in metabolizing MMZ (Siddens et al, 2008). Furthermore, NADPH-supported formation of N-methylimidazole from MMZ by rat hepatic microsomes was largely dependent on the P450 system (Lee and Neal, 1978).…”

Section: Downloaded Frommentioning

confidence: 97%

The Tissue-Specific Toxicity of Methimazole in the Mouse Olfactory Mucosa Is Partly Mediated through Target-Tissue Metabolic Activation by CYP2A5

Xie¹,

Zhou²,

Genter³

et al. 2011

Drug Metab Dispos

View full text Add to dashboard Cite

ABSTRACT:The antithyroid drug methimazole (MMZ) can cause severe, tissuespecific toxicity in mouse olfactory mucosa (OM), presumably through a sequential metabolic activation of MMZ by cytochrome P450 (P450) and flavin monooxygenases (FMO). The aims of this study were to determine whether CYP2A5, one of the most abundant P450 enzymes in the mouse OM, is involved in MMZ metabolic activation, by comparing Cyp2a5-null with wild-type (WT) mice, and whether hepatic microsomal P450 enzymes, including CYP2A5, are essential for MMZ-induced OM toxicity, by comparing liver-Cpr-null (LCN) mice, which have little P450 activity in hepatocytes, with WT mice. We showed that the loss of CYP2A5 expression did not alter systemic clearance of MMZ (at 50 mg/kg, i.p.); but it did significantly decrease the rates of MMZ metabolism in the OM, whereas FMO expression in the OM was not reduced. MMZ induced depletion of nonprotein thiols, as well as pathological changes, in the OM of WT mice; the extent of these changes was much reduced in the Cyp2a5-null mice. Thus, CYP2A5 plays an important role in mediating MMZ toxicity in the OM. In contrast, the rate of systemic clearance of MMZ was significantly reduced in the LCN mice, compared to WT mice, whereas the MMZ-induced OM toxicity was not prevented. Therefore, hepatic P450 enzymes are essential for systemic MMZ clearance, but they are not required for MMZ-induced OM toxicity. We conclude that the tissue-specific toxicity of MMZ is mediated by target tissue metabolic activation, and the reaction is partly catalyzed by CYP2A5 in the OM.

show abstract

“…FMO1 is the major FMO in adult human kidney and intestine (Hines, 2006; Koukouritaki et al, 2002; Yeung et al, 2000). This pattern differs from most laboratory animals in that FMO1 is the major hepatic FMO; one exception is the mouse where there is a gender-specific expression of FMO3 in female liver (Janmohamed et al, 2004; Siddens et al, 2008). A number of mutations in FMO3 result in the heritable disease known as trimethylaminuria, in which patients have reduced capacity to N-oxygenate trimethylamine resulting in excretion of high levels of this noxious odorant in urine and sweat (Phillips and Shephard, 2008; Yeung et al, 2007; Zhang et al, 2003).…”

Section: Introductionmentioning

confidence: 69%

Flavin-containing monooxygenase S-oxygenation of a series of thioureas and thiones

Henderson¹,

Siddens²,

Krueger³

et al. 2014

Toxicology and Applied Pharmacology

Self Cite

View full text Add to dashboard Cite

Mammalian flavin-containing monooxygenase (FMO) is active towards many drugs with a heteroatom having the properties of a soft nucleophile. Thiocarbamides and thiones are S-oxygenated to the sulfenic acid which can either react with glutathione and initiate a redox-cycle or be oxygenated a second time to the unstable sulfinic acid. In this study, we utilized LC-MS/MS to demonstrate that the oxygenation by hFMO of the thioureas under test terminated at the sulfenic acid. With thiones, hFMO catalyzed the second reaction and the sulfinic acid rapidly lost sulfite to form the corresponding imidazole. Thioureas are often pulmonary toxicants in mammals and, as previously reported by our laboratory, are excellent substrates for hFMO2. This isoform is expressed at high levels in the lung of most mammals, including non-human primates. Genotyping to date indicates that individuals of African (up to 49%) or Hispanic (2–7%) ancestry have at least one allele for functional hFMO2 in lung, but not Caucasians nor Asians. In this study the major metabolite formed by hFMO2 with thioureas from Allergan, Inc. was the sulfenic acid that reacted with glutathione. The majority of thiones were poor substrates for hFMO3, the major form in adult human liver. However, hFMO1, the major isoform expressed in infant and neonatal liver and adult kidney and intestine, readily S-oxygenated thiones under test, with Kms ranging from 7–160 μM and turnover numbers of 30–40 min−1. The product formed was identified by LC-MS/MS as the imidazole. The activities of the mouse and human FMO1 and FMO3 orthologs were in good agreement with the exception of some thiones for which activity was much greater with hFMO1 than mFMO1.

show abstract

Characterization of mouse flavin-containing monooxygenase transcript levels in lung and liver, and activity of expressed isoforms

Cited by 26 publications

References 31 publications

Aryl Hydrocarbon Receptor-Dependent Induction of Flavin-Containing Monooxygenase mRNAs in Mouse Liver

Aryl Hydrocarbon Receptor-Dependent Induction of Flavin-Containing Monooxygenase mRNAs in Mouse Liver

The Tissue-Specific Toxicity of Methimazole in the Mouse Olfactory Mucosa Is Partly Mediated through Target-Tissue Metabolic Activation by CYP2A5

Flavin-containing monooxygenase S-oxygenation of a series of thioureas and thiones

Contact Info

Product

Resources

About