Abstract
Human arylamine N-acetyltransferase 2 (NAT2) mediates the biotransformation of arylamine drugs and procarcinogens into either innocuous or reactive DNA-damaging metabolites and is expressed predominantly in liver. Interspecies differences and incongruous results between in vitro, in vivo, and epidemiological studies make it difficult to extrapolate animal results to human risk. We have generated human NAT2 transgenic mice on both C57BL/6 (hNAT2tg) and Nat1/2 null backgrounds [hNAT2tgNat1/2(−/−)], in which liver-selective expression of human NAT2 is driven by the mouse albumin promoter. We detected expression of the human NAT2 transcript and protein in mouse liver by real-time PCR and Western blot analysis. NAT2 enzyme activity, measured using the human NAT2-selective substrate sulfamethazine (SMZ), was 40- to 80-fold higher in liver cytosols from hNAT2tgNat1/2(−/−) mice than in wild-type mice. An unexpected gender difference was observed, with males displaying 2-fold higher activity than females. Transgenic mice also had an increased in vivo plasma clearance of SMZ and higher levels of N-acetylated SMZ than wild-type mice. Liver expression of human NAT2 did not affect the disposition of the human NAT1-selective substrate p-aminosalicylic acid (PAS), because hNAT2tgNat1/2(−/−) mice displayed in vivo PAS pharmacokinetic profiles similar to those of Nat1/2(−/−) mice. The metabolism of 4-aminobiphenyl was similar between hNAT2tgNat1/2(−/−) and wild-type mice with the exception of a more liver-restricted pattern in hNAT2tgNat1/2(−/−) mice and lower activity in females. Overall, the hNAT2tgNat1/2(−/−) mouse mimics human expression of NAT2 and may thus be of value in clarifying the role of human NAT2 in arylamine clearance, detoxification, and bioactivation.
Footnotes
This research was supported by the National Cancer Institute of Canada; and the Canadian Institutes of Health Research.
Article, publication date, and citation information can be found at http://dmd.aspetjournals.org.
doi:10.1124/dmd.111.038216.
-
ABBREVIATIONS:
- NAT
- N-acetyltransferase
- ABP
- 4-aminobiphenyl
- OAT
- O-acetyltransferase
- SMZ
- sulfamethazine
- PCR
- polymerase chain reaction
- ASMZ
- N-acetyl-sulfamethazine
- PAS
- p-aminosalicylic acid
- APAS
- N-acetyl-p-aminosalicylic acid
- AABP
- N-acetyl-4-aminobiphenyl
- kb
- kilobase
- SV
- simian virus
- h
- human
- bp
- base pair
- BLAST
- Basic Local Alignment Search Tool
- Pde
- phosphodiesterase
- GAPDH
- glyceraldehyde-3-phosphate dehydrogenase
- HPLC
- high-performance liquid chromatography
- AUC
- area under the curve
- ANOVA
- analysis of variance
- qPCR
- quantitative polymerase chain reaction
- PhIP
- 2-amino-1-methyl-6-phenyl[4,5-b]pyridine.
- Received January 13, 2011.
- Accepted February 11, 2011.
- Copyright © 2011 by The American Society for Pharmacology and Experimental Therapeutics
DMD articles become freely available 12 months after publication, and remain freely available for 5 years.Non-open access articles that fall outside this five year window are available only to institutional subscribers and current ASPET members, or through the article purchase feature at the bottom of the page.
|