Interstrain differences in the expression and activity of Cyp2a5 in the mouse liver

• Published in: BMC research notes Vol. 10; no. 1; p. 125
• Main Authors: Poça, Katia S, Parente, Thiago E M, Chagas, Lucas F, Leal, Bruna S, Leal, Hellen S, Paumgartten, Francisco J R, De-Oliveira, Ana C A X
• Format: Journal Article
• Language: English
• Published: England BioMed Central 15.03.2017
• Subjects: Aflatoxin B1; Animal models; Animals; Aryl Hydrocarbon Hydroxylases - metabolism; Background levels; Body weight; Coumarin; Cytochrome; Cytochrome P450; Cytochrome P450 Family 2 - metabolism; Dehydrogenases; Endoplasmic reticulum; Enzymes; Female; Gene expression; Glucose; Heme; Heme oxygenase (decyclizing); Hydroxylase; Liver; Metabolism; Mice; Nicotine; Oxygenase; Phenobarbital; RNA-protein interactions; Rodents; Species Specificity; Studies; Toxicants; Transcription; Transcription factors; Xenografts; Cyp2a4; Cyp2a5; Liver toxicity; Coumarin 7-hydroxylase; Heme oxygenase
• ISSN: 1756-0500; 1756-0500
• DOI: 10.1186/s13104-017-2435-x

Cytochrome P450 2A5 (Cyp2a5), a mouse enzyme orthologous of human CYP2A6, catalyzes a number of toxicologically important reactions, including the metabolism of nicotine, aflatoxin B1, and several other xeno- and endobiotics. Cyp2a5 expression is complex and not yet fully understood. We investigated inter-strain differences in the activity and mRNA expression of hepatic Cyp2a5. Cyp1a1/2 and Cyp2b9/10 activities were evaluated for comparative purposes. Data on the interstrain differences in the expression and activity of Cyp2a5 are important to select a suitable mouse model for studying CYP2A6-mediated metabolism. Activity of Cyp2a5 (coumarin 7-hydroxylase) was highest in DBA-2 and DBA-1, intermediate in B6D2F1 (hybrid) and low in the remaining strains (C57BL/6, C57BL/10, CBA, BALB/cAn, SW). Contrasting with the activity, background levels of Cyp2a4/5 mRNA did not differ between high- and low-activity murine strains. Phenobarbital (PB, 80 mg/kg body weight/day × 3 days, i.p.) increased Cyp2a5, Cyp1a1/2 (ethoxyresorufin-O-deethylase) and Cyp2b9/10 (bezyloxyresorufin-O-debenzylase) activities while only Cyp2a5 was enhanced by pyrazole (PYR, 100 mg/kg body weight/day × 3 days, i.p.). Inductions of Cyp2a5 activity by PYR and PB were accompanied by increases of Cyp2a4/5 mRNA. PYR and PB did not upregulate heme oxygenase-1 (hmox-1) mRNA expression in any strain, a finding that is apparently at odds with the notion that Cyp2a5 and hmox-1 inductions are coordinated events. Since background levels of Cyp2a4/5 gene transcripts of high-activity strains did not differ from those of low-activity mice, distinct constitutive activities did not result from different transcription rates and/or mRNA half-lives. Results therefore suggested that interstrain differences in constitutive activity of Cyp2a5 possibly arise from distinct translation efficiencies, protein half-lives and/or enzyme kinetics toward the substrate. Data from this study indicated that all tested strains are suitable models for studying toxicants that are substrates for human CYP2A6; DBA-2, DBA-1 and the hybrid B62DF1, however, have the advantage of presenting high constitutive activities of Cyp2a5.