Valproic acid-induced DNA damage increases embryonic p27(KIP1) and caspase-3 expression: a mechanism for valproic-acid induced neural tube defects.

Valproic acid is a commonly prescribed antiepileptic agent that causes birth defects including neural tube defects. The purpose of this study was to measure DNA damage and downstream changes in cell cycle inhibitors and apoptosis to further elucidate the molecular changes that occur following VPA exposure. Pregnant CD-1 mice were administered a teratogenic dose of VPA (400mg/kg) on gestational day 9 (plug=day 1) and embryos extracted 0.5, 1, 3, 6, and 24h after injection. Western blotting and immunohistochemistry were performed for γH2A.X, p21(WAF1/CIP1), p27(KIP1), and cleaved caspase-3. A rapid increase in γH2A.X expression was observed a half hour following VPA exposure, followed by a subsequent decrease. p27(KIP1)and cleaved caspase-3 expression was significantly increased 3 and 6h following VPA exposure. Immunohistochemistry revealed increased staining for γH2A.X, p27(KIP1), and cleaved caspase 3 in the head, confirming our hypothesis that DNA damage, cell cycle inhibition, and apoptosis are induced by VPA.