Pregnancy decreases rat CYP1A2 activity and expression

Pregnancy-Related Hormones Increase Nifedipine Metabolism in Human Hepatocytes by Inducing CYP3A4 Expression

Pregnancy-related hormones (PRH) have emerged as key regulators of hepatic cytochrome P450 (CYP) enzyme expression and function. The impact of PRH on protein levels of CYP3A4 and other key CYP enzymes, and the metabolism of nifedipine (a CYP3A4 substrate commonly prescribed during pregnancy), was evaluated in primary human hepatocytes. Sandwich-cultured human hepatocytes (SCHH) from female donors were exposed to PRH (estradiol, estriol, estetrol, progesterone, and cortisol), individually or in combination as a cocktail. Absolute protein concentrations of twelve CYP isoforms in SCHH membrane fractions were quantified by nanoLC-MS/MS, and metabolism of nifedipine to dehydronifedipine in SCHH was evaluated. PRH significantly increased CYP3A4 protein concentrations and nifedipine metabolism to dehydronifedipine in a concentration-dependent manner. CYP3A4 mRNA levels in hepatocyte-derived exosomes positively correlated with CYP3A4 protein levels and dehydronifedipine formation in SCHH. PRH also increased CYP2B6, CYP2C8 and CYP2A6 levels. Our findings demonstrate that PRH increase nifedipine metabolism in SCHH by inducing CYP3A4 expression and alter expression of other key CYP proteins in an isoform-specific manner, and suggest that hepatocyte-derived exosomes warrant further investigation as biomarkers of hepatic CYP3A4 metabolism. Together, these results offer mechanistic insight into the increases in nifedipine metabolism and clearance observed in pregnant women.

Alteration of the expression of pesticide-metabolizing enzymes in pregnant mice: potential role in the increased vulnerability of the developing brain

Studies on therapeutic drug disposition in humans have shown significant alterations as the result of pregnancy. However, it is not known whether pesticide metabolic capacity changes throughout pregnancy, which could affect exposure of the developing brain. We sought to determine the effect of pregnancy on the expression of hepatic enzymes involved in the metabolism of pesticides. Livers were collected from virgin and pregnant C57BL/6 mice at gestational days (GD)7, GD11, GD14, GD17, and postpartum days (PD)1, PD15, and PD30. Relative mRNA expression of several enzymes involved in the metabolism of pesticides, including hepatic cytochromes (Cyp) P450s, carboxylesterases (Ces), and paraoxonase 1 (Pon1), were assessed in mice during gestation and the postpartum period. Compared with virgin mice, alterations in the expression occurred at multiple time points, with the largest changes observed on GD14. At this time point, the expression of most of the Cyps involved in pesticide metabolism in the liver (Cyp1a2, Cyp2d22, Cyp2c37, Cyp2c50, Cyp2c54, and Cyp3a11) were downregulated by 30% or more. Expression of various Ces isoforms and Pon1 were also decreased along with Pon1 activity. These data demonstrate significant alterations in the expression of key enzymes that detoxify pesticides during pregnancy, which could alter exposure of developing animals to these chemicals.

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

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.