The Teratogenic Potencies of Valproic Acid Derivatives and Their Effects on Biological End‐points are Related to Changes in Histone Deacetylase and Erk1/2 Activities

Abstract

Valproic acid (VPA) is a known teratogen. In the present study, the effects of VPA and seven VPA derivatives with different teratogenic potencies were investigated in L929 cells in vitro. Evaluated end-points included changes in cell proliferation, growth, cell cycle distribution, morphology, speed, glycogen synthase kinase-3b (GSK-3b) and Erk1 ⁄ 2 phosphorylation, and histone H3 acetylation. Changes in proliferation, growth, speed, Erk1 ⁄ 2 and GSK-3b-Tyr216 phosphorylation, and H3 acetylation were significantly associated with the teratogenic potencies of the VPA derivatives. However, in contrast to changes in Erk1 ⁄ 2 phosphorylation and H3 acetylation, significant changes in GSK-3b phosphorylation could only be obtained in response to prolonged incubation at high drug concentration. There was an association between changes in H3 acetylation and GSK-3b-Tyr216 phosphorylation, whereas none of these end-points were associated with changes in Erk1 ⁄ 2 phosphorylation. These results suggest that the teratogenic potencies of VPA and VPA derivatives are related to effects on both Erk1 ⁄ 2 and histone deacetylase activities, whereas changes in GSK-3b activity are possibly a secondary effect.Valproic acid (VPA) is a widely used antiepileptic drug [1] that is also used for the treatment of migraine, mood disorders and cancer [2,3]. Adverse effects associated with VPA treatment include weight gain, hair loss and hepatotoxicity. Additionally, the drug is a teratogen that induces various malformations, including neural tube defects, in human foetuses exposed to the compound during early pregnancy [2].In addition to effects related to its antiepileptic function, VPA affects many cellular and biochemical processes, including cell proliferation, morphology, differentiation, survival, apoptosis and the activity of Erk1 ⁄ 2, glycogen synthase kinase-3b (GSK-3b) and histone deacetylases (HDACs) [4,5]. The teratogenic potencies of VPA and VPA derivatives have been correlated with drug-induced changes in the proliferation [6-9], area and motility of L929 cells [10,11] and the aggregation of primary neurons in culture [12]. Moreover, the HDAC inhibitory activity of VPA and VPA derivatives has been related to the teratogenic potencies of the compounds [13][14][15]. The HDAC inhibitory activity of VPA has also been proposed to account for the anticancer effects and other potentially beneficial effects of the drug [3,16].In the present study, VPA and seven VPA derivatives with different in vivo teratogenic potencies were tested in vitro in L929 cells for their effects on proliferation, growth, cell cycle distribution, area, speed, GSK-3b and Erk1 ⁄ 2 phosphorylation, and HDAC activity (reflected by histone H3 acetylation).Several of the estimated drug-induced changes in the cellular and biochemical end-points correlated with the teratogenic potencies of the respective VPA derivatives. However, relative to changes in Erk1 ⁄ 2 phosphorylation and H3 acetylation, significant changes in GSK-3b phosphorylation required longer ...

Chromatin Remodeling, Cell Proliferation and Cell Death in Valproic Acid-Treated HeLa Cells

“…Maximum histone H4 acetylation in HeLa cells appears nearly 12-16 h after VPA addition [6]. Acetylation of histone H3 also significantly increases in HeLa and L929 cells after VPA treatment [16], [17].…”

“…On the other hand, the hyperacetylation of histones induced by a class I-specific HDAC inhibitor (HDACi) like VPA or by a pan-HDACi such as trichostatin A (TSA) [11] has been considered totally or at least partly responsible for the similar teratogenic side-effects in vertebrate embryos [1], [17], [22].…”

Antiepileptic Drugs and Pregnancy Outcomes

“…It was found the three strongest teratogens (i.e. butyl-, pentyl-and hexyl-4-yn-VPA) significantly increased the degree of histone H3 acetylation [Gotfryd et al, 2011]. These investigators observed a highly significant linear correlation between the teratogenic potencies of the test compounds and their effects on histone H3 acetylation (n = 42, R2 = 0.…”

“…These investigators observed a highly significant linear correlation between the teratogenic potencies of the test compounds and their effects on histone H3 acetylation (n = 42, R2 = 0. 5080, p < 0.0001) [Gotfryd et al, 2011].…”

Epigenetics of psychoactive drugs

“…The attention given to epigenetic mechanisms of VPA action arose from various studies demonstrating that VPA is a human teratogen. [98,99] Recently, it has been shown that VPA induces apoptosis and neural tube defects in postimplantation embryos. [100] A severe foetal valproate syndrome has also been documented.…”