Targeted Disruption of the Olfactory Mucosa-Specific<i>Cyp2g1</i>Gene: Impact on Acetaminophen Toxicity in the Lateral Nasal Gland, and Tissue-Selective Effects on<i>Cyp2a5</i>Expression

Zhuo, Xianlu; Gu, Jun; Behr, Melissa; Swiatek, Pamela J.; Cui, Huadong; Zhang, Qing Yu; Xie, Yingqiu; Collins, Doris N.; Ding, Xinxin

doi:10.1124/jpet.103.060301

Cited by 28 publications

(40 citation statements)

References 30 publications

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“…For example, a reduction was seen in the expression of the Cyp2a5 gene in Cyp2g1 knockout animals (Zhuo et al, 2004), and bidirectional transcriptional activity of PGK-neo resulted in embryonic lethality in heterozygote multiple endocrine neoplasia type 1 chimeric knockout mice (Scacheri et al, 2001). Most often, the PGK-neo cassette was found to affect neighboring genes when inserted within gene clusters or locus control regions, such as the myogenic regulator factor genes (Olson et al, 1996), ␤-like globin locus control region , the Hox gene cluster (Ren et al, 2002), and the granzyme B gene cluster (Pham et al, 1996).…”

Section: Arylamine N-acetyltransferase Nat3(ϫ/ϫ) Knockout Micementioning

confidence: 99%

Effect of Arylamine AcetyltransferaseNat3Gene Knockout onN-Acetylation in the Mouse

Sugamori¹,

Brenneman²,

Wong³

et al. 2007

Drug Metab Dispos

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ABSTRACT:Arylamine N-acetyltransferases (NAT) catalyze the biotransformation of many important arylamine drugs and procarcinogens. NAT can either detoxify or activate procarcinogens, complicating the manner in which these enzymes may participate in enhancing or preventing toxic responses to particular agents. Mice possess three NAT isoenzymes: Nat1, Nat2, and Nat3. Whereas Nat1 and Nat2 can efficiently acetylate many arylamines, few substrates appear to be appreciably metabolized by Nat3. We generated a Nat3 knockout mouse strain and used it along with our double Nat1/2(؊/؊) knockout strain to further investigate the functional role of Nat3. Nat3(؊/؊) mice showed normal viability and reproductive capacity. Nat3 expression was very low in wild-type animals and completely undetectable in Nat3(؊/؊) mice. In contrast, greatly elevated expression of Nat3 transcript was observed in Nat1/2(؊/؊) mice. We used a transcribed marker polymorphism approach to establish that the increased expression of Nat3 in Nat1/2(؊/؊) mice is a positional artifact of insertion of the phosphoglycerate kinase-neomycin resistance cassette in place of the Nat1/Nat2 gene region and upstream of the intact Nat3 gene, rather than a biological compensatory mechanism. Despite the increase in Nat3 transcript, the N-acetylation of p-aminosalicylate, sulfamethazine, 2-aminofluorene, and 4-aminobiphenyl was undetectable either in vivo or in vitro in Nat1/2(؊/؊) animals. In parallel, no difference was observed in the in vivo clearance or in vitro metabolism of any of these substrates between wild-type and Nat3(؊/؊) mice. Thus, Nat3 is unlikely to play a significant role in the N-acetylation of arylamines either in wild-type mice or in mice lacking Nat1 and Nat2 activities.

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Section: Arylamine N-acetyltransferase Nat3(ϫ/ϫ) Knockout Micementioning

confidence: 99%

Effect of Arylamine AcetyltransferaseNat3Gene Knockout onN-Acetylation in the Mouse

Sugamori¹,

Brenneman²,

Wong³

et al. 2007

Drug Metab Dispos

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“…In mice and several other mammalian species, CYP2G1 is uniquely expressed in OM, and mouse CYP2G1 has been found to be active toward both endogenous (e.g., testosterone) and exogenous substrates (e.g., the olfactory toxicant dichlobenil) (Hua et al, 1997;Gu et al, 1998Zhuo et al, 2004. However, humans no longer have a functional CYP2G gene (Sheng et al, 2000).…”

Section: Mousementioning

confidence: 99%

“…Testosterone is a known substrate for multiple P450 enzymes. The roles of CYP2A5/2G1 in testosterone hydroxylation in OM (Zhuo et al, 2004) and the role of CYP2A5 in testosterone hydroxylation in liver and lateral nasal gland have been studied previously using Cyp2a5-null and Cyp2g1-null mice, but the contributions of the CYP2A(4/5)BGS enzymes to testosterone metabolism in the lung and brain have not been examined until now. Our results showed that, in the lung, they play an important role in the formation of 15a-OH-T (the most abundant metabolite detected in lung), 15b-OH-T, 2b-OH-T [presumably all formed by CYP2A5 , and 16b-OH-T [presumably formed by CYP2B (Sonderfan et al, 1987)]; these enzymes do not appear to play a role, however, in the formation of 16a-OH-T [preferentially formed by CYP2D9 (Ichikawa et al, 1989)].…”

Section: Mousementioning

confidence: 99%

“…Among genes of the Cyp2 cluster, single-gene knockout models have been generated previously for Cyp2a5, Cyp2g1, and Cyp2f2, and used to study the specific roles of these P450 enzymes in the metabolism and toxicity of numerous xenobiotics, including nicotine, naphthalene, coumarin, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone, dichlobenil, methimazole, and 3-methylindole (Zhou et al, , 2012aZhuo et al, 2004;Xie et al, 2010Xie et al, , 2011Li et al, 2011). However, the single-Cyp knockout mouse models are often unsatisfactory due to the multiplicity of Cyp genes in many of the mouse Cyp subfamilies and to the overlapping substrate specificity of the corresponding P450 enzymes.…”

Section: Introductionmentioning

confidence: 99%

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Generation and Characterization of a Novel Cyp2a(4/5)bgs-Null Mouse Model

Wei

Zhou

et al. 2012

Drug Metab Dispos

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Knockout mouse models targeting various cytochrome P450 (P450 or CYP) genes are valuable for determining P450's biologic functions, including roles in drug metabolism and chemical toxicity. In this study, a novel Cyp2a(4/5)bgs-null mouse model was generated, in which a 1.2-megabase pair genomic fragment containing nine Cyp genes in mouse chromosome 7 (including, sequentially, Cyp2a5, 2g1, 2b19, 2b23, 2a4, 2b9, 2b13, 2b10, and 2s1) are deleted, through Cre-mediated recombination in vivo. The resultant mouse strain was viable and fertile, without any developmental deficits or morphologic abnormalities. Deletion of the constitutive genes in the cluster was confirmed by polymerase chain reaction analysis of the genes and the mRNAs in tissues known to express each gene. The loss of this gene cluster led to significant decreases in microsomal activities toward testosterone hydroxylation in various tissues examined, including olfactory mucosa (OM), lung, liver, and brain. In addition, systemic clearance of pentobarbital was decreased in Cyp2a(4/5)bgs-null mice, as indicated by >60% increases in pentobarbital-induced sleeping time, compared with wild-type (WT) mice. This novel Cyp2a(4/5) bgs-null mouse model will be valuable for in vivo studies of drug metabolism and chemical toxicities in various tissues, including the liver, lung, brain, intestine, kidney, skin, and OM, where one or more of the targeted Cyp genes are known to be expressed in WT mice. The model will also be valuable for preparation of humanized mice that express human CYP2A6, CYP2A13, CYP2B6, or CYP2S1, and as a knockout mouse model for five non-P450 genes (Vmn1r184, Nalp9c, Nalp4a, Nalp9a, and Vmn1r185) that were also deleted.

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“…In mice, APAP causes toxicity in several organs, including the liver, kidney, lung, the nasal olfactory mucosa and respiratory mucosa, and the lateral nasal gland (LNG) (Zhuo et al, 2004;Gu et al, 2005). The LNG, found in most mammalian species, including humans, is one of the largest anterior nasal glands (Moe and Bojsen-Moller, 1971).…”

Section: Introductionmentioning

confidence: 99%

A Novel Defensive Mechanism against Acetaminophen Toxicity in the Mouse Lateral Nasal Gland: Role of CYP2A5-Mediated Regulation of Testosterone Homeostasis and Salivary Androgen-Binding Protein Expression

Zhou¹,

Wei²,

Xie³

et al. 2011

Mol Pharmacol

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To identify novel factors or mechanisms that are important for the resistance of tissues to chemical toxicity, we have determined the mechanisms underlying the previously observed increases in resistance to acetaminophen (APAP) toxicity in the lateral nasal gland (LNG) of the male Cyp2g1-null/Cyp2a5-low mouse. Initial studies established that Cyp2a5-null mice, but not a newly generated strain of Cyp2g1-null mice, were resistant to APAP toxicity in the LNG; therefore, subsequent studies were focused on the Cyp2a5-null mice. Compared with the wild-type (WT) male mouse, the Cyp2a5-null male mouse had intact capability to metabolize APAP to reactive intermediates in the LNG, as well as unaltered circulating levels of APAP, APAP-GSH, APAP-glucuronide, and APAP-sulfate. However, it displayed reduced tissue levels of APAP and APAP-GSH and increased tissue levels of testosterone and salivary androgen-binding protein (ABP) in the LNG. Furthermore, we found that ABP was able to compete with GSH and cellular proteins for adduction with reactive metabolites of APAP in vitro. The amounts of APAP-ABP adducts formed in vivo were greater, whereas the amounts of APAP adducts formed with other cellular proteins were substantially lower, in the LNG of APAP-treated male Cyp2a5-null mice compared with the LNG of APAP-treated male WT mice. We propose that through its critical role in testosterone metabolism, CYP2A5 regulates 1) the bioavailability of APAP and APAP-GSH (presumably through modulation of the rates of xenobiotic excretion from the LNG) and 2) the expression of ABP, which can quench reactive APAP metabolites and thereby spare critical cellular proteins from inactivation.

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Targeted Disruption of the Olfactory Mucosa-SpecificCyp2g1Gene: Impact on Acetaminophen Toxicity in the Lateral Nasal Gland, and Tissue-Selective Effects onCyp2a5Expression

Cited by 28 publications

References 30 publications

Effect of Arylamine AcetyltransferaseNat3Gene Knockout onN-Acetylation in the Mouse

Effect of Arylamine AcetyltransferaseNat3Gene Knockout onN-Acetylation in the Mouse

Generation and Characterization of a Novel Cyp2a(4/5)bgs-Null Mouse Model

A Novel Defensive Mechanism against Acetaminophen Toxicity in the Mouse Lateral Nasal Gland: Role of CYP2A5-Mediated Regulation of Testosterone Homeostasis and Salivary Androgen-Binding Protein Expression

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