title: Mode of action: inhibition of histone deacetylase, altering WNT-dependent gene expression, and regulation of beta-catenin--developmental effects of valproic acid.
abstract: Valproic acid (VPA) has long been known to cause spina bifida, a neural tube defect, and other effects in fetuses of women treated with this drug. Toxicological tests in laboratory mice and rats at human therapeutic doses also show neural tube and other defects. Studies show that VPA alters Wnt signaling in human and animal cells, inducing Wnt-dependent gene expression at doses that cause developmental effects. Structural analogues of VPA that do not have this effect on Wnt signaling do not cause developmental effects. Similarly, Trichostatin A, a compound that mimics VPA in its effects on Wnt gene expression, also causes similar developmental effects. Alteration of Wnt signaling is empirically well supported as the postulated mode of action (MOA) for VPA's developmental effects in animals. VPA causes alteration of Wnt signaling in both human and animal cells systems at the same dose levels. The correspondence of effects on signaling and of effects on development in animals and humans supports the view that alteration of Wnt signaling is a relevant MOA in humans.
authors.affiliation: US Environmental Protection Agency, Washington, DC, USA. dpatton@ilsi.org
authors.forename: Jeanette
authors.initials: J
authors.lastname: Wiltse
mesh_terms: D000818:Animals; D000927:Anticonvulsants / Q000633:toxicity*; D004791:Enzyme Inhibitors / Q000633:toxicity*; D005260:Female; D015870:Gene Expression / Q000187:drug effects*; D056572:Histone Deacetylase Inhibitors; D006801:Humans; D011247:Pregnancy; D015398:Signal Transduction / Q000187:drug effects; D013045:Species Specificity; D013723:Teratogens; D014635:Valproic Acid / Q000633:toxicity*; D051153:Wnt Proteins / Q000235:genetics / Q000502:physiology*; D051176:beta Catenin / Q000096:biosynthesis* / Q000235:genetics
chemical_list: D000927:Anticonvulsants; D004791:Enzyme Inhibitors; D056572:Histone Deacetylase Inhibitors; D013723:Teratogens; D051153:Wnt Proteins; D051176:beta Catenin; D014635:Valproic Acid