Cytochrome P450 & Pregnancy

1. PHM142 Fall 2013 Coordinator: Dr. Jeffrey Henderson Instructor: Dr. David Hampson Cytochrome P450 & Pregnancy Han Pham  Jana Kharboutly Seiwon Park November 4, 2013

2. What is Cytochrome P450? Essential enzymes for the metabolism of many medications Catalyze the oxidation of a variety of hydrophobic substrates More than 50 enzymes in this class 6 of them metabolize 90 percent of drugs Most significant enzymes: CYP3A4 and CYP2D6 Mostly expressed in the liver, but also present in the small intestine, lungs, placenta, and kidneys

3. Effects of pregnancy • Generally decrease the contents and activities of P450 and other enzymes that metabolize drugs • Decreased expression of Cyp1a2, Cyp2c37, Cyp2d22, Cyp2e1, and Cyp3a11 • Unchanged expression of Cyp2a5 • Elevated expression of Cyp3a41

4. Mechanism • Unknown underlying mechanisms for the global down-regulation • Possible factors from pregnancy-related physiological changes: 1) increased inflammatory response 2) changes in activity of key transcription factors that regulate P450 expression 3) rising levels of pregnancy hormones

5. P450 expression • Regulated by immunomodulators and nuclear receptors: • Cytokines released during systemic inflammation (eg: interleukin, tumor necrosis factor, interferon) decrease expression of major P450 isoforms • Hepatic transcription factors (eg: pregnaneX receptor, peroxisome proliferator-activated receptor-PPARα, etc) increase P450 expression

6. Transcription factor • Pregnancy has been shown to decrease expression of PPARα & CAR (nuclear receptor proteins that up-regulate P450) • Decreased PPARα expression is strongly correlated with the reduced expression levels of Cyp2d22 and Cyp2e1

7. Effect of Pregnancy on P450 and Anti-HIV Protease Inhibitors

8. Function of Anti-HIV Protease Inhibitors • http://www.dnatube.com/video/12230/Protease-inhibitors-animation

9. Metabolism of Anti-HIV Protease Inhibitorsby P450 • Example: Indinavir • Seven metabolites have been identified, one glucuronide conjugate and six oxidative metabolites. • In vitro studies indicate that cytochrome P450 (CYP3A4) is the major enzyme responsible for formation of the oxidative metabolites.

10. Effect of Pregnancy on P450 Pregnancy hormones: • Increased Placental growth hormone concentrations enhance the expression of HNF6 • The hepatic expression of HNF6 transcripts is +: Cyp3a44, Cyp3a41 -: Cyp3a11 and Cyp3a25

11. Effect of Pregnancy on P450 Pregnancy hormones: • Increased estradiol hormone  increase in hepatic mRNA expression of ERα  + : Cyp3a44, Cyp3a41 - : Cyp3a11

12. Conclusion • Hepatic transcripts of Cyp3a41 and Cyp3a44 were significantly increased • Cyp3a11 and Cyp3a25 were significantly decreased • Net result: increase in Cyp3a protein expression and activity in the liver • The plasma concentrations of orally administered anti-HIV PIs are significantly reduced

13. Inhibition of P450 by Herbs • Increasing consumption of herbs • Herbal products often used to treat pregnancy-related problems in women • Herbs often consumed include: Black elderberry, cranberry, fennel, ginger, horsetail, and raspberry leaf • It is estimated that 80% of pregnant women use drugs • These herbs can be pharmacologically active • When taking drugs with herbs, there is potential for drug-herb interactions because herbs can alter P450 cytochrome metabolizing activity

14. Inhibition of P450 by Herbs Experiment: • Measured metabolite formation of CYP by using LCMS/MS or HPLC methodologies • Tested the recommended dosing of the different commercial herbal products (black elderberry, cranberry, fennel, ginger, horsetail, and raspberry leaf) and its inhibitory effect on P450 isozymes CYP1A2, 2D6, and 3A4

15. Inhibition of P450 by Herbs Results: • The most potent inhibition was shown for: • Fennel towards CYP2D6 and 3A4 • Horsetail towards CYP1A2 • Raspberry leaf towards CYP1A2, 2D6, and 3A4 Conclusion: These herbs are potentially place pregnant women under risk of P450 inhibition. These herbs should be further investigated

16. Summary • Pregnancy generally decreases expression of major P450 isoforms in mice but the effect is isoform-specific • Possible involved factors: inflammatory response, changes in transcription factors, and pregnancy hormones • Increase in Cyp3a protein expression and activity in the liver • The plasma concentrations of orally administered anti-HIV PIs are significantly reduced • Herbs such as fennel, horsetail, raspberry leaf have the potential to inhibit P450 isozymes CYP1A2, 2D6, and 3A4

17. References • Aitken AE, Richardson TA, and Morgan ET. (2006). Regulation of drug-metabolizing enzymes and transporters in inflammation. Annu Rev PharmacolToxicol. 46:123–149. • Zhang H, Wu X, Wang H, Mikheev AM, Mao Q, and UnadkatJD. (2008). Effect of pregnancy on cytochrome P450 3a and P-glycoprotein expression and activity in the mouse: mechanisms, tissue specificity, and time course. MolPharmacol 74:714–723. • KwiHyeKoh, HuiXie, Ai-Ming Yu, HyunyoungJeong. (2011). Altered Cytochrome P450 Expression in Mice during Pregnancy. Drug MetabDispos. 39(2): 165–169. • Langhammer, A. J. and Nilsen, O. G. (2013).In vitro Inhibition of Human CYP1A2, CYP2D6, and CYP3A4 by Six Herbs Commonly Used in Pregnancy. Phytother. Res. doi: 10.1002/ptr.5037