Identification and hepatic expression profiles of cytochrome P450 1–4 isozymes in common minke whales ( Balaenoptera acutorostrata)

• Published in: Comparative Biochemistry and Physiology Part B: Biochemistry and Molecular Biology Vol. 147; no. 4; pp. 667 - 681
• Main Authors: Niimi, Satoko, Kim, Eun-Young, Iwata, Hisato, Watanabe, Michio X., Yasunaga, Genta, Fujise, Yoshihiro, Tanabe, Shinsuke
• Format: Journal Article
• Language: English
• Published: England Elsevier Inc 01-08-2007
• Subjects: Amino Acid Sequence; Animals; Balaenoptera acutorostrata; Base Sequence; Cetacea; Common minke whale; CYP2C; CYP2E; CYP3A; CYP4A; CYP4V; Cytochrome P-450 CYP1A1 - genetics; Cytochrome P-450 CYP1A1 - metabolism; Cytochrome P-450 CYP1A2 - genetics; Cytochrome P-450 CYP1A2 - metabolism; Cytochrome P-450 CYP2E1 - genetics; Cytochrome P-450 CYP2E1 - metabolism; Cytochrome P-450 CYP3A - genetics; Cytochrome P-450 CYP3A - metabolism; Cytochrome P-450 CYP4A - genetics; Cytochrome P-450 CYP4A - metabolism; Cytochrome P-450 Enzyme System - genetics; Cytochrome P-450 Enzyme System - metabolism; Gene Expression Profiling; Isoenzymes - genetics; Isoenzymes - metabolism; Liver - metabolism; Male; Marine; Minke Whale - genetics; Minke Whale - metabolism; Molecular Sequence Data; mRNA expression; Phylogeny; IN, North Pacific; CYP3A; CYP2C; CYP2E; CYP4V; Common minke whale; CYP4A; mRNA expression
• ISSN: 1096-4959; 1879-1107
• DOI: 10.1016/j.cbpb.2007.04.005

Full-length cDNA sequences of cytochrome P450 (CYP) 2C78, 2E1, 3A72, 4A35 and 4V6 isozymes were isolated from a hepatic cDNA library of common minke whale (
Balaenoptera acutorostrata). The deduced amino acid sequences of minke whale CYP2C78, 2E1, 3A72, 4A35 and 4V6 showed high identities with cattle CYP2C86 (83%), pig CYP2E1 (85%), sheep CYP3A24 (82%), pig CYP4A21 (80%), and human CYP4V2 (76%), respectively. To investigate whether or not these CYP expression levels are altered by contamination of organochlorine contaminants (OCs), mRNA levels of these CYPs in the liver of common minke whale were measured using a quantitative real-time RT-PCR method, and the quantified mRNA levels were employed for the statistical analysis with the residue levels of OCs including PCBs, DDTs (
p,p′-DDT,
p,p′-DDD and
p,p′-DDE), chlordanes (
cis-chlordane,
trans-chlordane,
cis-nonachlor,
trans-nonachlor and oxychlordane), HCHs (α-, β- and γ-isomers) and hexachlorobenzene that have already been reported elsewhere. Spearman's rank correlation analyses showed no significant correlation between CYP expression levels and each OC level in the common minke whale liver, implying that these environmental chemicals have no potential to alter the expression levels of these CYPs or the residue levels encountered in the whale livers may not reach their transcriptional regulation levels. This suggests that the expression of individual CYPs in the whale liver may be at basal level. Relationships among hepatic mRNA expression levels of these CYP2–4 isozymes together with CYP1A1 and CYP1A2 were also examined. Significant positive correlations were detected among mRNA expression levels of individual CYP isozymes in most cases. These associations indicate that the transcriptional regulation of these CYPs examined in this study may be reciprocally related. CYP1A1 levels showed a positive correlation with CYP1A2 levels (
r
=
0.64,
p
<
0.01) indicating that both CYP isozymes were regulated by aryl hydrocarbon receptor activated by endogenous ligands. A strong positive correlation between CYP2C78 and 3A72 (
r
=
0.90,
p
<
0.001) suggests that expression of these CYP isozymes may be under a regulation mechanism of cross-talk in which specific nuclear receptors such as constitutive androstane receptor and pregnane X receptor are involved. The present study indicates that minke whale from the North Pacific may be a model species to investigate the mechanism of basal regulation of these CYPs.