VPA Inhibits P19 Neural Differentiation through Redox Dysregulation and Oxidative Stress

Abstract

Valproic acid (VPA), a common anti-epileptic drug and migraine reducer, causes deficiencies in developing nervous systems and can be manifested as neural tube defects (NTDs). The appearance of these defects is believed to be due to the disruption of the redox state of differentiating cells. P19 cells are embryo carcinoma cells and are an established model for neurogenesis. Preliminary work in P19 cells shows that during neural differentiation, the glutathione (GSH) redox potential (Eh) shifts from a reducing state to a more oxidizing one. The effects of VPA exposure during distinct stages of neural differentiation are unknown. The purpose of this study was to determine if specific states of neural differentiation are more susceptible to redox disruption. In undifferentiated cells, GSH Eh were much more easily disrupted with VPA treatment than differentiated cells, suggesting earlier periods of development are more susceptible to redox dysregulation. Cellular proteins in undifferentiated P19 cells also demonstrate a greater degree of redox dysregulation, where VPA altered protein redox states to a greater extent in undifferentiated cells. Furthermore, P19 cells treated early in pro-differentiation conditions with VPA decreased the expression of neurogenic terminal differentiation markers (B III tubulin) compared to control, untreated cultures. Interestingly, pretreatment with D3T, a Nrf2 inducer, prior to VPA exposure, diminished GSH Eh oxidative shifts, increased differentiation and reduced alterations to protein redox states. Together, these data suggest that VPA-induced oxidative stress is a critical factor regulating P19 neurogenesis and may serve as an important mediator in VPA-induced NTDs. Clearly, VPA-induced oxidative stress in the embryo elicits further study.