EXAMINATION OF CBP/P300/AKT, NF-ΚB AND STAT3 SIGNALING FOLLOWING IN UTERO VALPROIC ACID EXPOSURE IN CD-1 MOUSE EMBRYOS WITH NEURAL TUBE DEFECTS
Valproic acid (VPA), an antiepileptic drug and effective treatment for mood disorders is teratogenic with an increased risk of congenital malformations including neural tube defects (NTDs) following in utero exposure. The mechanisms of the VPA-induced NTDs are not yet fully understood. Studies in this thesis investigated the role of three key signaling pathways, the Cbp/p300/Akt, the nuclear factor kappa B (NF-κB), and the signal transducer and activator of transcription3 (Stat3) in VPA-induced NTDs using the CD-1 mouse model. Following in utero exposure to a teratogenic dose of VPA (400 mg/kg) during the critical period of the neural tube (NT) closure at gestational day (GD)9, mouse embryos were harvested on GD9, GD10, and GD13. At GD9 and GD10 whole embryos were analyzed, while at GD13, the heads of control, non-exencephalic, and exencephalic embryos were used for analysis. The first study showed that Cbp, p300, and Akt mRNA expression was downregulated, Cbp/p300 protein levels remained unchanged, while Akt protein levels were upregulated in GD9 embryos. The second study investigated the effects of VPA exposure on the key components of the NF-κB signaling pathway including p65, p50, and Pim-1. A decrease was observed in p65, p105/p50, and Pim-1 mRNA expression in GD9 embryos. Furthermore, upregulated p65 and downregulated p50 protein levels were noted in GD13 embryos. The nuclear levels of total p65 and p50 protein levels remained unchanged in VPA-exposed non-exencephalic and exencephalic GD13 nuclear extracts from embryonic heads. The third study characterized the effects of VPA on the transcription factor Stat3. Stat3 mRNA expression remained stable while total Stat3 protein levels were increased in GD9 embryos and GD13 embryonic heads. In contrast, phosphorylated Stat3 protein levels were downregulated in GD9 embryos with an overall trend of downregulation in the GD10 and GD13 groups. In conclusion, the studies described in this thesis indicate that the perturbations in the Cbp/p300/Akt, NF-κB, and Stat3 signaling pathways following in utero VPA exposure might contribute towards VPA-induced NTDs.