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

Sodium valproate exposure influences the expression of pparg in the zebrafish model

Valproic acid (VPA) is an anti-epileptic drug used alone or in combination with other medications to treat seizures, mania, and bipolar disorder. VPA recognized as a teratogenic chemical can cause severe birth defects mainly affecting the brain and spinal cord when administered during pregnancy. However, the potential mechanisms of developmental toxicity are still less studied, and in the present study, the influence of VPA exposure was evaluated on zebrafish early-life stages. Zebrafish were exposed to two sublethal concentrations of sodium valproate (SV) (0.06 mM and 0.15 mM) from 24 hours post-fertilization (hpf) to 96 hpf and the SV teratogenic potential was investigated through morphometric analysis of zebrafish larvae combined with the evaluation of cartilage profile. Moreover, the effect of SV on the transcription level of pparg was also performed. The results of the study showed the teratogenic potential of SV, which disrupts the morphometric signature of the head and body. The marked distortion of cartilage structures was paralleled to a malformation of telencephalon and optic tectum in both concentrations suggesting a high teratogen effect of SV on the brain. These data were further confirmed by the increased expression of pparg in the zebrafish head. Overall, the present study confirms the teratogenic activity of SV in the zebrafish model and, for the first time, points out the potential protective role of pparg in the SV dose-dependent toxicity.

Direct β- and γ-C(sp3 )-H Alkynylation of Free Carboxylic Acids*

In this study we report the identification of a novel class of ligands for palladium-catalyzed C(sp3 )-H activation that enables the direct alkynylation of free carboxylic acid substrates. In contrast to previous synthetic methods, no introduction/removal of an exogenous directing group is required. A broad scope of acids including both α-quaternary and challenging α-non-quaternary can be used as substrates. Additionally, the alkynylation in the distal γ-position is reported. Finally, this study encompasses preliminary findings on an enantioselective variant of the title transformation as well as synthetic applications of the products obtained.

Valproic acid stimulates proliferation of glial precursors during cortical gliogenesis in developing rat

Valproic acid (VPA) is a neurotherapeutic drug prescribed for seizures, bipolar disorder, and migraine, including women of reproductive age. VPA is a well-known teratogen that produces congenital malformations in many organs including the nervous system, as well as later neurodevelopmental disorders, including mental retardation and autism. In developing brain, few studies have examined VPA effects on glial cells, particularly astrocytes. To investigate effects on primary glial precursors, we developed new cell culture and in vivo models using frontal cerebral cortex of postnatal day (P2) rat. In vitro, VPA exposure elicited dose-dependent, biphasic effects on DNA synthesis and proliferation. In vivo VPA (300 mg/kg) exposure from P2 to P4 increased both DNA synthesis and cell proliferation, affecting primarily astrocyte precursors, as >75% of mitotic cells expressed brain lipid-binding protein. Significantly, the consequence of early VPA exposure was increased astrocytes, as both S100-β+ cells and glial fibrillary acidic protein were increased in adolescent brain. Molecularly, VPA served as an HDAC inhibitor in vitro and in vivo as enhanced proliferation was accompanied by increased histone acetylation, whereas it elicited changes in culture in cell-cycle regulators, including cyclin D1 and E, and cyclin-dependent kinase (CDK) inhibitors, p21 and p27. Collectively, these data suggest clinically relevant VPA exposures stimulate glial precursor proliferation, though at higher doses can elicit inhibition through differential regulation of CDK inhibitors. Because changes in glial cell functions are proposed as mechanisms contributing to neuropsychiatric disorders, these observations suggest that VPA teratogenic actions may be mediated through changes in astrocyte generation during development. © 2015 Wiley Periodicals, Inc. Develop Neurobiol 76: 780-798, 2016.

Prenatal exposures associated with neurodevelopmental delay and disabilities

Neurobehavioral teratology refers to the study of the abnormal development of the structure and the behavioral functions of the central nervous system, which result from exposure to exogenous agents during prenatal development. The focus of this review is the effects of various prenatal exposures on human neurodevelopment. Studies that deal with the adverse effects of infectious agents (rubella, cytomegalovirus, and toxoplasma), teratogenic drugs (e.g., antiepileptic drugs such as phenytoin, valproate, and carbamazepine, coumarin derivatives, and retinoids), alcohol, and other substances of abuse will be reviewed. Additionally, prenatal exposure to industrial or environmental chemicals (e.g., lead, methylmercury, and polycarbonated biphenyls) as well as exposure of the embryo or fetus to high amounts of ionizing radiation will be addressed. Possible mechanisms of selected neurobehavioral teratogens will also be discussed.

Enantioselective apoptosis induction in histiocytic lymphoma cells and acute promyelocytic leukemia cells

The aim of this study was to identify valproic acid (VPA) analogs with a broad spectrum of anti-cancer activities and an increased apoptosis-inducing potential compared with the parent VPA, which is enrolled as histone deacetylase (HDAC) inhibitor in a large number of clinical trials. We identified a chiral VPA derivative, (S)-2-pentyl-4-pentynoic acid, previously characterized as HDAC inhibitor that induced massive programmed cell death in a strongly enantioselective manner in U937 histiocytic lymphoma cells and NB4 acute promyelocytic leukemia cells. By performing fluorescence-activated cell sorting and Western blotting analyses, we established that enantiomer (S)-2-pentyl-4-pentynoic acid has higher apoptosis-inducing potential than VPA itself. The optic antipode (R)-2-pentyl-4-pentynoic acid and VPA caused under the same conditions only a weak growth inhibition without inducing cell differentiation and apoptosis. (S)-2-pentyl-4-pentynoic acid is more apoptogenic than VPA and displays enantioselective anti-cancer properties that warrant further research regarding the mechanistic basis of its activity and its potential use in cancer therapy.

Antiepileptic drugs and pregnancy outcomes

The treatment of epilepsy in women of reproductive age remains a clinical challenge. While most women with epilepsy (WWE) require anticonvulsant drugs for adequate control of their seizures, the teratogenicity associated with some antiepileptic drugs (AEDs) is a risk that needs to be carefully addressed. Antiepileptic medications are also used to treat an ever broadening range of medical conditions such as bipolar disorder, migraine prophylaxis, cancer, and neuropathic pain. Despite the fact that the majority of pregnancies of WWE who are receiving pharmacological treatment are normal, studies have demonstrated that the risk of having a pregnancy complicated by a major congenital malformation is doubled when comparing the risk of untreated pregnancies. Furthermore, when AEDs are used in polytherapy regimens, the risk is tripled, especially when valproic acid (VPA) is included. However, it should be noted that the risks are specific for each anticonvulsant drug. Some investigations have suggested that the risk of teratogenicity is increased in a dose-dependent manner. More recent studies have reported that in utero exposure to AEDs can have detrimental effects on the cognitive functions and language skills in later stages of life. In fact, the FDA just issued a safety announcement on the impact of VPA on cognition (Safety Announcement 6-30-2011). The purpose of this document is to review the most commonly used compounds in the treatment of WWE, and to provide information on the latest experimental and human epidemiological studies of the effects of AEDs in the exposed embryos.

Epigenetics of psychoactive drugs

Objectives

Epigenetics refers to the heritable, but reversible regulation of various biological functions. Changes in DNA methylation and chromatin structure derived from histone modifications are involved in the brain development, pathogenesis and pharmacotherapy of brain disorders.

Key findings

Evidence suggests that epigenetic modulations play key roles in psychiatric diseases such as schizophrenia and bipolar disorder. The analysis of epigenetic aberrations in the mechanisms of psychoactive drugs helps to determine dysfunctional genes and pathways in the brain, to predict side effects of drugs on human genome and identify new pharmaceutical targets for treatment of psychiatric diseases.

Summary

Although numerous studies have concentrated on epigenetics of psychosis, the epigenetic studies of antipsychotics are limited. Here we present epigenetic mechanisms of various psychoactive drugs and review the current literature on psychiatric epigenomics. Furthermore, we discuss various epigenetic modulations in the pharmacology and toxicology of typical and atypical antipsychotics, methionine, lithium and valproic acid.

Chromatin remodeling, cell proliferation and cell death in valproic acid-treated HeLa cells

Background

Valproic acid (VPA) is a potent anticonvulsant that inhibits histone deacetylases. Because of this inhibitory action, we investigated whether VPA would affect chromatin supraorganization, mitotic indices and the frequency of chromosome abnormalities and cell death in HeLa cells.

Methodology/Principal Findings

Image analysis was performed by scanning microspectrophotometry for cells cultivated for 24 h, treated with 0.05, 0.5 or 1.0 mM VPA for 1–24 h, and subjected to the Feulgen reaction. TSA-treated cells were used as a predictable positive control. DNA fragmentation was investigated with the TUNEL assay. Chromatin decondensation was demonstrated under TSA and all VPA treatments, but no changes in chromosome abnormalities, mitotic indices or morphologically identified cell death were found with the VPA treatment conditions mentioned above, although decreased mitotic indices were detected under higher VPA concentration and longer exposure time. The frequency of DNA fragmentation identified with the TUNEL assay in HeLa cells increased after a 24-h VPA treatment, although this fragmentation occurred much earlier after treatment with TSA.

Conclusions/Significance

The inhibition of histone deacetylases by VPA induces chromatin remodeling in HeLa cells, which suggests an association to altered gene expression. Under VPA doses close to the therapeutic antiepileptic plasma range no changes in cell proliferation or chromosome abnormalities are elicited. The DNA fragmentation results indicate that a longer exposure to VPA or a higher VPA concentration is required for the induction of cell death.