Hepatic Cyp2d and Cyp26a1 mRNAs and activities are increased during mouse pregnancy

Abstract

There is considerable evidence that drug disposition is altered during human pregnancy and based on probe drug studies, CYP2D6 activity increases during human pregnancy. The aim of this study was to determine whether the changes of CYP2D6 activity observed during human pregnancy could be replicated in the mouse, and explore possible mechanisms of increased CYP2D6 activity during pregnancy. Cyp2d11, Cyp2d22, Cyp2d26 and Cyp2d40 mRNA was increased (P < 0.05) on gestational days (GD) 15 and 19 compared with the non-pregnant controls. There was no change (P > 0.05) in Cyp2d9 and Cyp2d10 mRNA. In agreement with the increased Cyp2d mRNA, Cyp2d-mediated dextrorphan formation from dextromethorphan was increased 2.7-fold (P < 0.05) on GD19 (56.8±39.4 pmol/min/mg protein) when compared with the non-pregnant controls (20.8±11.2 pmol/min/mg protein). An increase in Cyp26a1 mRNA (10-fold) and retinoic acid receptor (Rar)β mRNA (2.8-fold) was also observed during pregnancy. The increase in Cyp26a1 and Rarβ mRNA during pregnancy indicates increased retinoic acid signaling in the liver during pregnancy. A putative retinoic acid response element was identified within the Cyp2d40 promoter and the mRNA of Cyp2d40 correlated (P < 0.05) with Cyp26a1 and Rarβ. These results show that Cyp2d mRNA is increased during mouse pregnancy the and mouse may provide a suitable model to investigate the mechanisms underlying the increased clearance of CYP2D6 probes observed during human pregnancy. Our findings also suggest that retinoic acid signaling in the liver is increased during pregnancy, which may have broader implications to energy homeostasis in the liver during pregnancy.

Fig. 1.

(A) The fold change in Cyp2d mRNA on GD 15 (n = 6, blue bars), and GD 19 (n = 6, green bars) in comparison with non-pregnant mice (n = 4, yellow bars). The measured dextrorphan formation velocity at 50 µM (B) and 1 µM (C) concentration of dextromethorphan is shown at two gestational ages and in non-pregnant controls using MLH from a separate group of animals. The panels show box and whiskers plots of dextrorphan formation velocity in non-pregnant (n = 5), GD 15 (n = 3) and GD 19 (n = 3) mice. The line shows the median, the box the 75th and 25th percentile and the error bar the range of the measurements in each group. The Michaelis-Menten parameters of dextrorphan formation from dextromethorphan were measured in MLHs from individual animals (D) using three control (open circles), two GD15 (closed circles) and two GD19 (closed triangles) MLHs. The lines indicate the fit of Michaelis-Menten equation to the average data from all animals on that gestational age and the error bars show the range of formation velocities observed at a given concentration of dextromethorphan in the different animals. The Eadie-Hofstee plots for each GD are shown in Supplemental Fig. 1. The K_m and V_max values are listed in Table 1. Significant changes in comparison with nonpregnant controls are indicated as **P < 0.01 and *P < 0.05.

Fig. 2.

(A) The fold change in Cyp26a1, Rarα and Rarβ mRNA in GD 15 (n = 6, blue bars) and GD 19 (n = 6, green bars) mice in comparison to non-pregnant (n=4, yellow bars) mice. The fold differences were calculated relative to non-pregnant values. (B) A box and whiskers plot of 4-OH-RA + 4-oxo-RA formation from atRA (1 µM) in MLHs in non-pregnant (n = 5), GD 15 (n = 3) and GD 19 (n = 3) mice. (C) The relative quantification of 16-OH-RA formation from atRA in MLHs from non-pregnant (n = 5), GD 15 (n = 3) and GD 19 (n = 3) mice. Significant changes in comparison with non-pregnant controls are indicated as **P < 0.01 and *P < 0.05.

Fig. 3.

(A) The orientation of the Cyp2d genes in the Cyp2d gene locus. The promoter region of Cyp2d40 gene is enlarged in (B) and the identified RARE is shown. The promoters of Cyp26a1 and Rarβ with the RAREs identified are shown in (C and D). Panel (E) shows sequences of the identified RAREs in the respective genes.