Neuroinformatics analyses reveal GABAt and SSADH as major proteins involved in anticonvulsant activity of valproic acid

Clinical side-effects based drug repositioning for anti-epileptic activity

Several generations of anti-epileptic drugs (AEDs) are available but have several associated side effects apart from a limited success rate. Drug repositioning strategies have gained importance in the last two decades owing to lower failure rates and economic burden. Drugs with similar side effect profiles may share a common mechanism of action and thus can be linked to other disease treatments. The present study was carried out to identify the newly approved drug candidate(s) as AEDs using clinical side-effects drug repositioning strategy. The clinical side effect similarity of drugs available in the SIDER v4.1 database was estimated against common side effects of 5 major marketed AEDs, using the 'dplyr' package library in the R. Further drugs were filtered based on Blood Brain Barrier permeability prediction and FDA-approval status. Molecular docking studies were performed for selected 26 hits (drugs) against previously identified epilepsy target receptors: Voltage-gated sodium channel α2 (Nav1.2), GABA receptor α1-β1 (GABAr α1-β1), and Voltage-gated calcium channel α-1 G (Cav3.1). Only 2 drugs (Ziprasidone and Paroxetine) showed better binding affinities against studied epilepsy receptors Nav1.2, GABAr α1-β1, and Cav3.1, than their corresponding standard AEDs, i.e. Carbamazepine, Clonazepam, and Pregabalin, respectively. Ziprasidone reportedly showed seizure-like symptoms in ∼3% of patients and was hence omitted from further study. The MDS study of docked complexes of Paroxetine with selected epilepsy target receptors showed stable RMSD values and better interaction energies. The study reveals Paroxetine as a potential candidate to be repurposed for 1st line epileptic seizure medication.Communicated by Ramaswamy H. Sarma.

Design and evaluation of pharmacological properties of a new 1,3,4-thiadiazolylamide derivative of 2-propylpentanoic acid

Introduction: The use of the pharmacophoric approach is a promising direction for modifying the chemical structure of 2-propylpentanoic (valproic) acid in order to obtain new drugs.

Materials and methods: In the experiments on mice, acute toxicity, neurotoxicity, antiepileptic activity and analgesic effect of N-(5-ethyl-1,3,4-thiadiazol-2-yl)-2-propylpentanamide (valprazolamide) were evaluated. LD50 was determined by probit analysis. Neurotoxicity was determined in a rotarod test and a bar test in mice. The effects of valprazolamide on the exploratory behavior of mice in open field test and in a light/dark transition test were evaluated. Its antiepileptic activity was tested in mice against seizures induced by maximal electroshock, pentylenetetrazole (scPTZ); isoniazid, thiosemicarbazide, pilocarpine, and camphor. The analgesic effect was studied in a hot plate test.

Results and discussion: N-(5-ethyl-1,3,4-thiadiazol-2-yl)-2-propylpentanamide was obtained by introducing pharmacophores into the structure of 2-propylpentanoic acid: a substituted amide group and an electron-donor domain of 1,3,4-thiadiazole. The LD50 value for intraperitoneal administration of a new 2-propylpentanoic acid: derivative to mice was 924.8 mg/kg, and the TD50 value in the rotarod test and the bar test were 456.7 mg/kg and 546.7 mg/kg, respectively. The suppression of orienting responses in the animals was noted when it was administered in neurotoxic doses. Valprazolamide showed the most antiepileptic activity on models of MES, scPTZ and isoniazid antagonism tests. The ED50 values were 138.4 mg/kg, 74.5 mg/kg, and 126.8 mg/kg, respectively. The therapeutic indices for these models of epilepsy were 6.7; 12.4; 7.3, and protective index – 3.3; 6.1 and 3.6, respectively. In the hot plate test, valprazolamide increased the latency period before a defensive response to a thermal stimulus (ED50 165 mg/kg).

Conclusion: N-(5-ethyl-1,3,4-thiadiazol-2-yl)-2-propylpentanamide is a new 1,3,4-thiadiazolylamide derivative of 2-propylpentanoic acid with antiepileptic and analgesic activities, which belongs to the group of low-toxic agents.

Graphic abstract

N-(5-ethyl-1,3,4-thiadiazol-2-yl)-2-propylpentanamide (3D)

LD50=924.8 mg/kg (mice, intraperitoneally)

TD50=456.7 mg/kg (rotarod, mice, intraperitoneally)

ED50=138.4 mg/kg (MES, mice, intraperitoneally)

ED50=74.5 mg/kg (scPTZ, mice, intraperitoneally)

Dihydrolipoamide dehydrogenase, pyruvate oxidation, and acetylation-dependent mechanisms intersecting drug iatrogenesis

In human metabolism, pyruvate dehydrogenase complex (PDC) is one of the most intricate and large multimeric protein systems representing a central hub for cellular homeostasis. The worldwide used antiepileptic drug valproic acid (VPA) may potentially induce teratogenicity or a mild to severe hepatic toxicity, where the underlying mechanisms are not completely understood. This work aims to clarify the mechanisms that intersect VPA-related iatrogenic effects to PDC-associated dihydrolipoamide dehydrogenase (DLD; E3) activity. DLD is also a key enzyme of α-ketoglutarate dehydrogenase, branched-chain α-keto acid dehydrogenase, α-ketoadipate dehydrogenase, and the glycine decarboxylase complexes. The molecular effects of VPA will be reviewed underlining the data that sustain a potential interaction with DLD. The drug-associated effects on lipoic acid-related complexes activity may induce alterations on the flux of metabolites through tricarboxylic acid cycle, branched-chain amino acid oxidation, glycine metabolism and other cellular acetyl-CoA-connected reactions. The biotransformation of VPA involves its complete β-oxidation in mitochondria causing an imbalance on energy homeostasis. The drug consequences as histone deacetylase inhibitor and thus gene expression modulator have also been recognized. The mitochondrial localization of PDC is unequivocal, but its presence and function in the nucleus were also demonstrated, generating acetyl-CoA, crucial for histone acetylation. Bridging metabolism and epigenetics, this review gathers the evidence of VPA-induced interference with DLD or PDC functions, mainly in animal and cellular models, and highlights the uncharted in human. The consequences of this interaction may have significant impact either in mitochondrial or in nuclear acetyl-CoA-dependent processes.

Hidden pharmacological activities of valproic acid: A new insight

Valproic acid (VPA) is an approved drug for managing epileptic seizures, bipolar disorders, and migraine. VPA has been shown to elevate the level of gamma-aminobutyric acid (GABA) in the brain through competitive inhibition of GABA transaminase, thus promoting the availability of synaptic GABA and facilitating GABA-mediated responses. VPA, which is a small chain of fatty acids, prevents histone deacetylases (HDACs). HDACs play a crucial role in chromatin remodeling and gene expression through posttranslational changes of chromatin-associated histones. Recent studies reported a possible effect of VPA against particular types of cancers. This effect was partially attributed to its role in regulating epigenetic modifications through the inhibition of HDACs, which affect the expression of genes associated with cell cycle control, cellular differentiation, and apoptosis. In this review, we summarize the current information on the actions of VPA in diseases such as diabetes mellitus, kidney disorders, neurodegenerative diseases, muscular dystrophy, and cardiovascular disorders.

Waggle needling wields preferable neuroprotective and anti-spastic effects on post-stroke spasticity rats by attenuating γ-aminobutyric acid transaminase and enhancing γ-aminobutyric acid

Waggle needling, a classical anti-spastic needling technique characterized by combination of acupuncture with joint movement, has gained increasing popularity of spasticity treatment in China. This study was designed to compare the anti-spastic effect of waggle needling to the routine needling and to explore its underlying mechanism. We established post-stroke spasticity model based on ischemia stroke operation (middle cerebral artery occlusion). Rats were divided into six groups: normal control group, sham-operated control group, ischemia stroke model group, waggle needling group, routine needling group and baclofen group. Neurological function and muscle tone were assessed by the Zea Longa score and modified Ashworth scale, respectively. Indirect muscle tone was testified with electrophysiological recording. Cerebral infarction was measured by 2,3,5-triphenyltetrazolium chloride staining. The concentrations and expressions of γ-aminobutyric acid transaminase (GABAT) and γ-aminobutyric acid (GABA) were detected by enzyme-linked immunosorbent assay and western blot assay. Waggle needling markedly alleviated neurological deficits, decreased cerebral infarction and eased muscle tone; simultaneously, attenuated GABAT and enhanced GABA expression in the cortical infarct regions in comparison with the routine needling (P < 0.01), yet showed similar therapeutic effect to the baclofen group (P > 0.05). These results preliminary supported that waggle needling as a potential promising non-pharmacological intervention for the treatment of cerebral ischemia and spasticity.

Longitudinal Effects of Bumetanide on Neuro-Cognitive Functioning in Drug-Resistant Epilepsy

Antiepileptic drugs (AEDs) have repeatedly shown inconsistent and almost contradictory effects on the neurocognitive system, from substantial impairments in processing speed to the noticeable improvement in working memory and executive functioning. Previous studies have provided a novel insight into the cognitive improvement by bumetanide as a potential antiepileptic drug. Through the current investigation, we evaluated the longitudinal effects of bumetanide, an NKCC1 co-transporter antagonist, on the brain microstructural organization as a probable underlying component for cognitive performance. Microstructure assessment was completed using SPM for the whole brain assay and Freesurfer/TRACULA for the automatic probabilistic tractography analysis. Primary cognitive operations including selective attention and processing speed, working memory capacity and spatial memory were evaluated in 12 patients with a confirmed diagnosis of refractory epilepsy. Participants treated with bumetanide (2 mg/ day) in two divided doses as an adjuvant therapy to their regular AEDs for 6 months, which followed by the re-assessment of their cognitive functions and microstructural organizations. Seizure frequency reduced in eight patients which accompanied by white matter reconstruction; fractional anisotropy (FA) increased in the cingulum-cingulate gyrus (CCG), anterior thalamic radiation (ATR), and temporal part of the superior longitudinal fasciculus (SLFt) in correlation with the clinical response. The voxel-based analysis in responder patients revealed increased FA in the left hippocampus, right cerebellum, and right medial temporal lobe, while mean diffusivity (MD) values reduced in the right occipital lobe and cerebellum. Microstructural changes in SLFt and ATR accompanied by a reduction in the error rate in the spatial memory test. These primary results have provided preliminary evidence for the effect of bumetanide on cognitive functioning through microstructural changes in patients with drug-resistant epilepsy.

2-Pyrrolidinone and Succinimide as Clinical Screening Biomarkers for GABA-Transaminase Deficiency: Anti-seizure Medications Impact Accurate Diagnosis

Broad-scale untargeted biochemical phenotyping is a technology that supplements widely accepted assays, such as organic acid, amino acid, and acylcarnitine analyses typically utilized for the diagnosis of inborn errors of metabolism. In this study, we investigate the analyte changes associated with 4-aminobutyrate aminotransferase (ABAT, GABA transaminase) deficiency and treatments that affect GABA metabolism. GABA-transaminase deficiency is a rare neurodevelopmental and neurometabolic disorder caused by mutations in ABAT and resulting in accumulation of GABA in the cerebrospinal fluid (CSF). For that reason, measurement of GABA in CSF is currently the primary approach to diagnosis. GABA-transaminase deficiency results in severe developmental delay with intellectual disability, seizures, and movement disorder, and is often associated with death in childhood. Using an untargeted metabolomics platform, we analyzed EDTA plasma, urine, and CSF specimens from four individuals with GABA-transaminase deficiency to identify biomarkers by comparing the biochemical profile of individual patient samples to a pediatric-centric population cohort. Metabolomic analyses of over 1,000 clinical plasma samples revealed a rich source of biochemical information. Three out of four patients showed significantly elevated levels of the molecule 2-pyrrolidinone (Z-score ≥2) in plasma, and whole exome sequencing revealed variants of uncertain significance in ABAT. Additionally, these same patients also had elevated levels of succinimide in plasma, urine, and CSF and/or homocarnosine in urine and CSF. In the analysis of clinical EDTA plasma samples, the levels of succinimide and 2-pyrrolidinone showed a high level of correlation (R = 0.73), indicating impairment in GABA metabolism and further supporting the association with GABA-transaminase deficiency and the pathogenicity of the ABAT variants. Further analysis of metabolomic data across our patient population revealed the association of elevated levels of 2-pyrrolidinone with administration of vigabatrin, a commonly used anti-seizure medication and a known inhibitor of GABA-transaminase. These data indicate that anti-seizure medications may alter the biochemical and metabolomic data, potentially impacting the interpretation and diagnosis for the patient. Further, these data demonstrate the power of combining broad scale genotyping and phenotyping technologies to diagnose inherited neurometabolic disorders and support the use of metabolic phenotyping of plasma to screen for GABA-transaminase deficiency.

Lack of evidence for synaptic high-affinity γ-hydroxybutyric acid (GHB) transport in rat brain synaptosomes and 11 Na+ -dependent SLC neurotransmitter transporters

γ-Hydroxybutyric acid (GHB) is an endogenous compound proposed to act as a neurotransmitter. Na⁺ -dependent, high-affinity GHB transport has long been considered important evidence supporting this hypothesis. However, the molecular identity of such a high-affinity transporter remains unknown. In this study, we sought to identify and characterize GHB synaptic transport through a series of studies using both native and recombinant systems with the ultimate aim of providing evidence to clarify the proposed role of GHB as a neurotransmitter in the mammalian brain. Native [³ H]GHB transport was studied in isolated rat brain synaptosomes and compared to synaptic membranes. As a targeted approach, GHB was also screened against a panel of Na⁺ -dependent SLC6 neurotransmitter transporters recombinantly expressed in Xenopus laevis oocytes or tsA201 cells. Finally, the low-affinity GHB transporters, MCT1/2 and SMCT1, were probed as GHB transporters in L-[¹⁴ C]lactate uptake assays in synaptosomes. We found no evidence of high-affinity [³ H]GHB transport in purified rat brain cortical or striatal synaptosomes or at any of the 11 SLC6 transporters tested. Instead, our results indicate the binding of [³ H]GHB to an unidentified membrane component, distinct from any of the known GHB targets. In accordance with others, we found that GHB and the analog 3-hydroxycyclopent-1-enecarboxylic acid (HOCPCA) can, in millimolar concentrations, inhibit L-[¹⁴ C]lactate uptake at MCT1 and/or MCT2 and that this also can occur in synaptosomes. In conclusion, through a variety of in vitro pharmacological studies, we were unsuccessful in identifying a specific synaptic high-affinity transporter for GHB. Our findings emphasize the need to reevaluate GHB's role as a potential neurotransmitter. OPEN SCIENCE BADGES: This article has received a badge for *Open Materials* because it provided all relevant information to reproduce the study in the manuscript. The complete Open Science Disclosure form for this article can be found at the end of the article. More information about the Open Practices badges can be found at https://cos.io/our-services/open-science-badges/.

Meta-analysis of central and peripheral γ-aminobutyric acid levels in patients with unipolar and bipolar depression

BACKGROUND

Many studies have measured central and peripheral γ-aminobutyric acid (GABA) levels in patients with depression. We performed a meta-analysis to provide an objective overview of GABA changes in those with unipolar or bipolar depression.

METHODS

After a systematic database search, original data were extracted with the help of seminal authors to calculate standardized mean differences. We compared GABA levels between patients with current major depressive episodes and controls, between euthymic patients and controls, and in patients before and after treatment. We performed meta-regressions to explore the influence of demographic and clinical variables on GABA significant mean differences.

RESULTS

For unipolar depression, central and peripheral GABA levels were diminished in currently depressed patients, but normal in euthymic patients, compared with the healthy controls. For bipolar disorder, GABA levels were diminished in medication-free patients, but seemed to be normalized in medicated patients, compared with the healthy controls. We found no significant association with demographic or clinical variables.

LIMITATIONS

There was a great heterogeneity across studies, probably because of the substantial variation of clinical characteristics in the included samples. Many subanalyses were performed to assess how the diagnosis, medications, or the type of measurements of peripheral or central GABA levels may affect the main results.

CONCLUSION

The GABA levels evolved differentially in patients with unipolar and bipolar disorders. Our results suggest that GABA levels could represent a biomarker of symptomatic states in patients with unipolar disorder and would be normalized by mood stabilizers in those with bipolar disorder.

Identification of suitable reference genes during the formation of chlamydospores in Clonostachys rosea 67-1

Clonostachys rosea is a potential biocontrol fungus that can produce highly resistant chlamydospores under specific conditions. To investigate the genes related to chlamydospore formation, we identified reliable reference genes for quantification of gene expression in C. rosea 67-1 during sporulation. In this study, nine reference genes, actin (ACT), elongation factor 1 (EF1), glyceraldehyde-3-phosphate dehydrogenase (GAPDH), histone (HIS), RNA polymerase II CTD phosphatase Fcp1 (RPP), succinate-semialdehyde dehydrogenase (SSD), TATA-binding protein (TBP), ubiquitin (UBQ), and ubiquitin-conjugating enzyme (UCE), were selected and cloned from 67-1, and their expression stability during chlamydospore formation was determined using reverse transcription quantitative PCR and assessed using the software geNorm, NormFinder and BestKeeper. The Ct values of the candidates ranged from 19.9 to 29.7, among which HIS, ACT and SSD exhibited high expression levels. The statistical analysis showed that ACT and SSD were most stably expressed, while UBQ and GAPDH showed relatively large variations under different culture conditions. Calculation of pairwise variation value indicated that two reference genes were required for precise quantification. Finally, ACT and SSD were selected to normalize gene expression during chlamydospore production in C. rosea 67-1. To the best of our knowledge, this is the first report of SSD as a reference gene. This study will facilitate the accurate quantification of differentially expressed genes during the generation of chlamydospores and contribute to the investigation of the molecular mechanism underlying chlamydospore formation in C. rosea.