Characterizing the effects of in utero valproic acid exposure on murine fetoplacental development

A Narrative Review on the Effect of Valproic Acid on the Placenta

BACKGROUND

Valproic acid (VPA) is an antiepileptic and mood-stabilizing drug with well-established teratogenic risks when taken during pregnancy. While its harmful effects on fetal development are well known, less attention has been given to its impact on placental development and function, despite the placenta's critical role in pregnancy.

AIM

This narrative review examines how VPA exposure affects placental growth, morphology, nutrient transport, and epigenetic modifications. It also considers whether placental dysfunction may contribute VPA's teratogenic effects.

RESULTS

Evidence suggests that VPA disrupts placental structure and growth, alters the expression of nutrient transporters, such as those for folate, glucose, and amino acids, and modifies the placental epigenome, including globally decreased DNA methylation and increased histone acetylation.

DISCUSSION

It is hypothesized that these epigenetic changes may influence chromatin remodelling and trophoblast gene expression, though this connection has not been fully established. Such epigenetic dysregulation may result in aberrant gene expression that underlies the structural and functional impairments observed in the placenta, potentially compromising its ability to support fetal development and contributing to VPA's teratogenic effects. Findings across studies, however, are inconsistent, varying with dose, timing of exposure, and model system. Furthermore, there is a lack of research examining sex-specific differences in placental responses to VPA, despite evidence that male and female placentas exhibit distinct growth patterns, gene expression profiles, and susceptibilities to environmental insults.

CONCLUSION

Addressing these knowledge gaps through targeted research will improve our understanding of how VPA affects the placenta and its role in teratogenesis.

Modulation of VEGF/eNOS/TGF-β Axis by Piracetam as a New Avenue to Ameliorate Valproic Acid-Induced Placental Toxicity and Teratogenicity in Rats

Valproic acid (VPA) is a very effective therapy used to treat generalized epilepsy, but it must be avoided during pregnancy as it leads to a high risk of teratogenesis. Its teratogenic effect is believed to be due to its placental toxic effect, altering angiogenesis and inducing oxidative stress. Piracetam (PIRA) is a derivative of the neurotransmitter γ-aminobutyric acid (GABA) and has anti-oxidative and pro-angiogenic features. However, its effects against Valproic acid-evoked placental toxicity and abnormal fetal development have not been mechanistically examined. Herein, the present study targets angiogenesis and oxidative stress by Piracetam to investigate the potential modulation of Valproic acid-induced placental toxicity and abnormal fetal development in rats. After administration of Valproic acid (500 mg/kg/day, orally) and/or piracetam (500 mg/kg/day, orally) from the 6th to 15th of gestation, fetuses and placenta were obtained for analysis. The present findings revealed that Piracetam improved the histopathological lesions in the placenta and restored the labyrinth zone area percent. Moreover, it improved the intra-uterine growth retardation (IUGR) via restoring fetal body weight and length and also ameliorated all external malformations (subcutaneous hemorrhage, fore limb, and hind limb anomalies) and additionally amended the skeletal lack of ossification. These favorable effects of Piracetam were mediated by the enhancement of placental angiogenesis via the VEGF/eNOS/TGF-β pathway and attenuating placental oxidative stress, which appeared as decreased MDA content and increased GSH and TAC levels. In conclusion, activation of placental angiogenesis via the VEGF/eNOS/TGF-β axis alongside inhibition of oxidative stress by Piracetam can ameliorate Valproic acid-evoked placental toxicity and, subsequently, fetal malformations in rats.

PLGA nanocarriers biomimetic of platelet membranes and their interactions with the placental barrier

This study focuses on the preparation and characterization of platelet membrane biomimetic nanocarriers (P-PLGA NPs) and investigates their interactions with the transplacental barrier. Poly (lactic-co-glycolic acid) nanoparticles (PLGA NPs) were coated with platelet membrane (PLTM) to construct P-PLGA NPs. Additionally, fluorinated polyethylenimine (F-PEI) was grafted onto PLGA NPs to prepare F-PEI-PLGA NPs, which were compared with PLGA NPs. In vitro placental barrier cell models using human choriocarcinoma cells (BeWo b30) and in vivo pregnancy animal models using ICR mice were utilized to evaluate the transplacental barrier efficiency of the PLGA NPs with different surface modifications. The results demonstrated that all three types of nanoparticles could accumulate in the uterus and placenta. The transplacental barrier efficiency of F-PEI-PLGA NPs was found to be the highest at 4 h, while P-PLGA NPs exhibited the highest transplacental barrier efficiency at 12 and 24 h. Furthermore, there were no significant effects on the main organs, structure, and quantity of uterine spiral arteries, indicating the safety of the nanoparticles (NPs). P-PLGA NPs are expected to be a safe and effective nano-delivery system for perinatal drug delivery. This study provides insights into the transplacental barrier mechanism of NPs with different surface characteristics.

Investigating the effects of valproic acid on placental epigenetic modifications and development in the CD-1 mouse model

Gestational exposure to the anticonvulsant drug valproic acid (VPA) is associated with congenital malformations and neurodevelopmental disorders through its action as a histone deacetylase inhibitor. VPA can elicit placental toxicity and affect placental growth and development. The objective of this study was to evaluate the impact of maternal exposure to VPA on the mouse placenta following exposure on gestational day (GD) 13 since previous studies have shown that mice exposed at this time during gestation give birth to offspring with an autism spectrum disorder-like phenotype. We exposed CD-1 dams to a teratogenic dose (600 mg/kg) of VPA or saline on GD13 and assessed fetoplacental growth and development on GD18. We evaluated epigenetic modifications, including acetylated histone H4 (H4ac), methylated H3K4 (H3K4me2) using immunohistochemistry, and global DNA methylation in the placenta at 1, 3, and 24 h following maternal exposure on GD13. In utero exposure to VPA on GD13 significantly decreased placental weight and increased fetal resorptions. Moreover, VPA significantly increased the staining intensity of histone H4 acetylation and H3K4 di-methylation across the placenta at 1 and 3 h post maternal dose. Our results also demonstrate that VPA significantly decreased global DNA methylation levels in placental tissue. These results show that gestational exposure to VPA interferes with placental growth and elicits epigenetic modifications, which may play a vital role in VPA-induced developmental toxicity.

Pharmacokinetic characterisation of a valproate Autism Spectrum Disorder rat model in a context of co-exposure to α-Hexabromocyclododecane

Assessing the role of α-hexabromocyclododecane α-HBCDD as a factor of susceptibility for Autism Spectrum disorders by using valproic acid-exposed rat model (VPA) required characterizing VPA pharmacokinetic in the context of α-HBCDD-co-exposure in non-pregnant and pregnant rats. The animals were exposed to α-HBCDD by gavage (100 ng/kg/day) for 12 days. This was followed by a single intraperitoneal dose of VPA (500 mg/kg) or a daily oral dose of VPA (500 mg/kg) for 3 days. Exposure to α-HBCDD did not affect the pharmacokinetics of VPA in pregnant or non-pregnant rats. Surprisingly, VPA administration altered the pharmacokinetics of α-HBCDD. VPA also triggered higher foetal toxicity and lethality with the PO than IP route. α-HBCDD did not aggravate the embryotoxicity observed with VPA, regardless of the route of exposure. Based on this evidence, a single administration of 500 mg/kg IP is the most suitable VPA model to investigate α-HBCDD co-exposure.

Exposure to Valproic acid (VPA) resulted in alterations in the expression of angiogenic genes (NRP-1, VEGFA, VEGFR-2 and sFlt1) and histological modifications in the placenta of mice (Mus musculus)

Valproic acid (VPA), an anti-epileptic drug (AED), has been reported to exhibit anti-angiogenic properties. This study aimed to examine the impact of VPA on the expression of NRP-1 and additional angiogenic factors, as well as angiogenesis, in mouse placenta. Pregnant mice were divided into four groups: control (K), solvent control (KP), VPA treatment at a dose of 400 mg/kg body weight (BW) (P1), and VPA treatment at a dose of 600 mg/kg BW (P2). The mice were subjected to daily treatment via gavage from embryonic day (E) 9 to E14 and E9 to E16. Histological analysis was performed to evaluate Microvascular Density (MVD) and percentage of the placental labyrinth area. In addition, a comparative analysis of Neuropilin-1 (NRP-1), vascular endothelial growth factor (VEGFA), vascular endothelial growth factor receptor (VEGFR-2), and soluble (sFlt1) expression was conducted in relation to glyceraldehyde-3-phosphate dehydrogenase (GAPDH). The results of the MVD analysis and percentage of labyrinth area in the E14 and E16 placentas indicated that the treated groups were significantly lower than the control group. The relative expression levels of NRP-1, VEGFA, and VEGFR-2 in the treated groups were lower than those in the control group at E14 and E16. Meanwhile, the relative expression of sFlt1 in the treated groups at E16 was significantly higher than in the control group. Changes in the relative expression of these genes inhibit angiogenesis regulation in the mouse placenta, as evidenced by reduced MVD and a smaller percentage of the labyrinth area.