Purpose: Use of medication during pregnancy is increasingly prevalent with 40-80% of women taking at least one drug throughout pregnancy and about 50% taking at least one drug in the first trimester1 . To date, very little is known about fetal drug exposure at different gestational ages. However, determining such exposure is logistically and ethically challenging. Therefore alternative methods are required to predict fetal drug exposure. One such alternative is Physiologically Based Pharmacokinetic (PBPK) modeling and simulation. To utilize this approach, the abundance of placental transporters and drug metabolizing enzymes in human placentae of different gestational age is needed. Therefore, we chose to quantify and compare the protein expression of BCRP, Pg-p, SERT, NET, OAT4, OATP2B1, OCT3, CYP19 and CYP reductase in human placentae of different gestational ages. These proteins were chosen because they have previously been shown to be expressed in the human placenta and are involved in the transport or metabolism of drugs in the placenta2. Methods: Total cellular membrane fractions from end of first trimester (T1-end), mid second trimester (T2-mid) and term human placentae were isolated by ultracentrifugation and analyzed by quantitative proteomics using LC-MS/MS and surrogate peptides as calibrators. Data were analyzed using Kruskal-Wallis test. Results: Placentae were of the following gestational ages (mean±SD): T1-end, 91.3±6.0 days (n=5), T2-mid, 136.2±3.4 days (n=6) and term (n=6). Total membrane protein yield in µg per gram of tissue was not significantly different (p>0.05, Kruskall-Wallis test) between T1-end (23.4±6.0), T2-mid (27.2±4.0), and term (22.5±11.5) placentae. The following proteins showed no significant changes in abundance (p>0.05) with gestational age (all abundance data below are stated in picomoles per gram of tissue, mean±SD): SERT (6.4±2.4), NET (7.6±3.6), OAT4 (12.1±5.0), OCT3 (15.3±4.9), CYP reductase (79.6±28.5), CYP19 (172.7±77.2). P-gp abundance significantly (p=0.042) increased between T1-end (8.0±1.6) and term placentae (29.1±19.3). In contrast, there was a significant decrease (p=0.007) in BCRP abundance between T2-mid (13.2±4.5) and term (6.2±1.4) placentae. OATP2B1 could be quantified in only term placentae (2.8±1.5, n=4). Significance: The above data as well as future assessment of abundance of the corresponding proteins in T1 placentae and fetal livers of various gestational ages (including other CYP enzymes) will provide us with the information necessary to predict fetal drug exposure throughout pregnancy. Such predictions will inform fetal risks due to medication use during pregnancy. Supported by NIH PO1DA32507.
- Scaffidi, J., et al. (2017). "The pregnant women as a drug orphan: a global survey of registered clinical trials of pharmacological interventions in pregnancy." BJOG 124(1): 132-140.
- Syme, M. R., et al. (2004). "Drug transfer and metabolism by the human placenta." Clin Pharmacokinet 43(8): 487-514