Abstracts

Rationale: In utero exposure to AEDs has been associated with fetal loss, intrauterine growth restriction, and dose-dependent major congenital malformations, impaired postnatal cognitive and behavioral development in children and with an increased risk of ASD and ADHD in offspring. The mechanisms of the adverse fetal effects of valproic acid (VPA) are not clearly understood. We have recently shown in a human trophoblast cell line that VPA alters the expression of carriers for hormones and nutrients. Here, our aim was to study the effects VPA on placental transport mechanisms for folate, an essential nutrient for fetal development: folate uptake carriers (the reduced folate carrier, RFC; folate receptor a, FRa) and the efflux carrier breast cancer resistance protein (BCRP), which removes folate from cells. Methods: Placental tissue of gestational age 7-10 weeks was collected from elective pregnancy terminations in women without known epilepsy. Villous explant cultures were incubated with VPA (42, 83, 166 µg/mL) or the vehicle, for 5 days. Carrier protein expression was evaluated using Western blot analysis. Quantitative real-time PCR assays were carried out in order to evaluate effects of VPA on Carrier mRNA levels. Placental folate levels were measured by the Hadassah Medical Center's Biochemistry Laboratories using a chemiluminescence-based assay. Results: Great intra-subject and inter-subject variability was observed with regard to the expression of placental carriers and placental folate concentrations. Compared with controls, at 42 µg/mL, VPA reduced BCRP expression (P=0.03, n=9). No clear trend of change in BCRP expression was observed at 83 µg/mL (n=9) and 166 µg/mL (n=12) VPA and in FRa expression at all VPA concentrations (P>0.05). A tendency towards decreased expression was additionally observed for RFC, but the reduction was not statistically significant. Folate concentrations were elevated by a mean of 25% (SD 105%, P>0.05, n=10) following incubation with 42 µg/mL VPA. Conclusions: Our results suggest that VPA affects the expression of a carrier important for cellular folate kinetics and fetal protection against xenobiotics. The reduction in BCRP expression translates into a trend towards greater placental folate concentrations, but the variability between the placentas is high. It is currently unknown whether the potential alteration in placental folate handling reflects changes in the amount delivered to the fetus. If validated, these results may point at a novel mechanism through which VPA affects fetal development. The knowledge gained through these studies will hopefully contribute to improved outcome of children born to mothers with epilepsy. Funding: This study was funded by the European Comission FP7-PEOPLE-2011-CIG grant 293800 and by the Israel Science Foundation (ISF) Grant #506/13.