Neuroprotective effects of valproic acid on brain ischemia are related to its HDAC and GSK3 inhibitions

BML-281 promotes neuronal differentiation by modulating Wnt/Ca2+ and Wnt/PCP signaling pathway

Histone deacetylase (HDAC) inhibitors promote differentiation through post-translational modifications of histones. BML-281, an HDAC6 inhibitor, has been known to prevent tumors, acute dextran sodium sulfate-associated colitis, and lung injury. However, the neurogenic differentiation effect of BML-281 is poorly understood. In this study, we investigated the effect of BML-281 on neuroblastoma SH-SY5Y cell differentiation into mature neurons by immunocytochemistry (ICC), reverse transcriptase PCR (RT-PCR), quantitative PCR (qPCR), and western blotting analysis. We found that the cells treated with BML-281 showed neurite outgrowth and morphological changes into mature neurons under a microscope. It was confirmed that the gene expression of neuronal markers (NEFL, MAP2, Tuj1, NEFH, and NEFM) was increased with certain concentrations of BML-281. Similarly, the protein expression of neuronal markers (NeuN, Synaptophysin, Tuj1, and NFH) was upregulated with BML-281 compared to untreated cells. Following treatment with BML-281, the expression of Wnt5α increased, and downstream pathways were activated. Interestingly, both Wnt/Ca2+ and Wnt/PCP pathways activated and regulated PKC, Cdc42, RhoA, Rac1/2/3, and p-JNK. Therefore, BML-281 induces the differentiation of SH-SY5Y cells into mature neurons by activating the non-canonical Wnt signaling pathway. From these results, we concluded that BML-281 might be a novel drug to differentiation into neuronal cells through the regulation of Wnt signaling pathway to reduce the neuronal cell death.

Valproic acid treatment attenuates cisplatin-induced kidney injury by suppressing proximal tubular cell damage

Cisplatin treatment is effective against several types of carcinomas. However, it frequently leads to kidney injury, which warrants effective prevention methods. Sodium valproic acid is a prophylactic drug candidate with a high potential for clinical application against cisplatin-induced kidney injury. Therefore, in this study, we aimed to elucidate the mechanism underlying the prophylactic effect of valproic acid on cisplatin-induced kidney injury in a mouse model and HK2 and PODO cells with cisplatin-induced toxicity. In the mouse model of cisplatin-induced kidney injury, various renal function parameters and tubular damage scores were worsened by cisplatin, but they were significantly improved upon combination with valproic acid. No difference was observed in cisplatin accumulation between the cisplatin-treated and valproic acid-treated groups in whole blood and the kidneys. The mRNA expression levels of proximal tubular damage markers, apoptosis markers, and inflammatory cytokines significantly increased in the cisplatin group 72 h after cisplatin administration but significantly decreased upon combination with valproic acid. In HK2 cells, a human proximal tubular cell line, the cisplatin-induced decrease in cell viability was significantly suppressed by co-treatment with valproic acid. Valproic acid may inhibit cisplatin-induced kidney injury by suppressing apoptosis, inflammatory responses, and glomerular damage throughout the kidneys by suppressing proximal tubular cell damage. However, prospective controlled trials need to evaluate these findings before their practical application.

Transient plasticity response is regulated by histone deacetylase inhibitor in oxygen-glucose deprivation condition

BACKGROUND

The pathological form of synaptic plasticity, ischemic long-term potentiation (iLTP), induced by oxygen and glucose deprivation (OGD), is implicated in the acute phase of stroke with the potentiation of N-methyl-D-aspartate receptor (NMDAR). While there has been widespread attention on the excitatory system, a recent study reported that γ-aminobutyric acid (GABA)ergic system is also involved in iLTP. Valproic acid (VPA), a histone deacetylase inhibitor, protects against ischemic damage. However, whether VPA regulates early phase plasticity in ischemic stroke remains unknown. The present study aims to investigate the potential role and mechanism of VPA in ischemic stroke.

METHODS

A brief exposure of OGD on the hippocampal slices and the induction of photothrombotic ischemia (PTI) were used as ex vivo and in vivo models of ischemic stroke, respectively.

RESULTS

Using extracellular recordings, iLTP was induced in the hippocampal Schaffer collateral pathway following OGD exposure. VPA treatment abolished hippocampal iLTP via GABAA receptor enhancement and extracellular signal-regulated kinase (ERK) phosphorylation. Administration of VPA reduced brain infarct volume and motor dysfunction in mice with PTI. Moreover, VPA protected against ischemic injury by upregulating the GABAergic system and ERK phosphorylation, as well as by reducing of matrix metalloproteinase in a PTI-induced ischemic stroke model.

CONCLUSIONS

Together, this study revealed the protection of VPA in ex vivo OGD-induced pathological form of neuroplasticity and in vivo PTI-induced brain damage and motor dysfunction through rescuing GABAergic deficiency and the pathological hallmarks of ischemia.

Valproate reduces retinal ganglion cell apoptosis in rats after optic nerve crush

The retinal ganglion cells of the optic nerve have a limited capacity for self-repair after injury. Valproate is a histone deacetylase inhibitor and multitarget drug, which has been demonstrated to protect retinal neurons. In this study, we established rat models of optic nerve-crush injury and injected valproate into the vitreous cavity immediately after modeling. We evaluated changes in the ultrastructure morphology of the endoplasmic reticulum of retinal ganglion cells over time via transmission electron microscope. Immunohistochemistry and western blot assay revealed that valproate upregulated the expression of the endoplasmic reticulum stress marker glucose-regulated protein 78 and downregulated the expression of transcription factor C/EBP homologous protein, phosphorylated eukaryotic translation initiation factor 2α, and caspase-12 in the endoplasmic reticulum of retinal ganglion cells. These findings suggest that valproate reduces apoptosis of retinal ganglion cells in the rat after optic nerve-crush injury by attenuating phosphorylated eukaryotic translation initiation factor 2α-C/EBP homologous protein signaling and caspase-12 activation during endoplasmic reticulum stress. These findings represent a newly discovered mechanism that regulates how valproate protects neurons.

Epidrugs in the Therapy of Central Nervous System Disorders: A Way to Drive on?

The polygenic nature of neurological and psychiatric syndromes and the significant impact of environmental factors on the underlying developmental, homeostatic, and neuroplastic mechanisms suggest that an efficient therapy for these disorders should be a complex one. Pharmacological interventions with drugs selectively influencing the epigenetic landscape (epidrugs) allow one to hit multiple targets, therefore, assumably addressing a wide spectrum of genetic and environmental mechanisms of central nervous system (CNS) disorders. The aim of this review is to understand what fundamental pathological mechanisms would be optimal to target with epidrugs in the treatment of neurological or psychiatric complications. To date, the use of histone deacetylases and DNA methyltransferase inhibitors (HDACis and DNMTis) in the clinic is focused on the treatment of neoplasms (mainly of a glial origin) and is based on the cytostatic and cytotoxic actions of these compounds. Preclinical data show that besides this activity, inhibitors of histone deacetylases, DNA methyltransferases, bromodomains, and ten-eleven translocation (TET) proteins impact the expression of neuroimmune inflammation mediators (cytokines and pro-apoptotic factors), neurotrophins (brain-derived neurotropic factor (BDNF) and nerve growth factor (NGF)), ion channels, ionotropic receptors, as well as pathoproteins (β-amyloid, tau protein, and α-synuclein). Based on this profile of activities, epidrugs may be favorable as a treatment for neurodegenerative diseases. For the treatment of neurodevelopmental disorders, drug addiction, as well as anxiety disorders, depression, schizophrenia, and epilepsy, contemporary epidrugs still require further development concerning a tuning of pharmacological effects, reduction in toxicity, and development of efficient treatment protocols. A promising strategy to further clarify the potential targets of epidrugs as therapeutic means to cure neurological and psychiatric syndromes is the profiling of the epigenetic mechanisms, which have evolved upon actions of complex physiological lifestyle factors, such as diet and physical exercise, and which are effective in the management of neurodegenerative diseases and dementia.

A comprehensive review on pharmacological applications and drug-induced toxicity of valproic acid

Valproic acid, a branching short chain fatty acid, is a popular drug to treat epilepsy and acts as a mood-stabilizing drug. The obstruction of ion channels and Gamma Amino Butyrate transamino butyrate GABA has been linked to antiepileptic effects. Valproic acid has been characterized as a Histone deacetylase inhibitor, functioning directly transcription of gene levels by blocking the deacetylation of histones and increasing the accessibility of transcription sites. Study has been extensively focused on pharmaceutical activity of valproic acid through various pharmacodynamics activity from absorption, distribution and excretion particularly in patients who are resistant to or intolerant of lithium or carbamazepine, as well as those with mixed mania or rapid cycling.

Cross-reactivity between histone demethylase inhibitor valproic acid and DNA methylation in glioblastoma cell lines

Currently, valproic acid (VPA) is known as an inhibitor of histone deacetylase (epigenetic drug) and is used for the clinical treatment of epileptic events in the course of glioblastoma multiforme (GBM). Which improves the clinical outcome of those patients. We analyzed the level of 5-methylcytosine, a DNA epigenetic modulator, and 8-oxodeoxyguanosine, an cellular oxidative damage marker, affected with VPA administration, alone and in combination with temozolomide (TMZ), of glioma (T98G, U118, U138), other cancer (HeLa), and normal (HaCaT) cell lines. We observed the VPA dose-dependent changes in the total DNA methylation in neoplastic cell lines and the lack of such an effect in a normal cell line. VPA at high concentrations (250-500 μM) induced hypermethylation of DNA in a short time frame. However, the exposition of GBM cells to the combination of VPA and TMZ resulted in DNA hypomethylation. At the same time, we observed an increase of genomic 8-oxo-dG, which as a hydroxyl radical reaction product with guanosine residue in DNA suggests a red-ox imbalance in the cancer cells and radical damage of DNA. Our data show that VPA as an HDAC inhibitor does not induce changes only in histone acetylation, but also changes in the state of DNA modification. It shows cross-reactivity between chromatin remodeling due to histone acetylation and DNA methylation. Finally, total DNA cytosine methylation and guanosine oxidation changes in glioma cell lines under VPA treatment suggest a new epigenetic mechanism of that drug action.

GSK3 Is a Central Player in Retinal Degenerative Diseases but a Challenging Therapeutic Target

Glycogen synthase kinase 3 (GSK3) is a key regulator of many cellular signaling processes and performs a wide range of biological functions in the nervous system. Due to its central role in numerous cellular processes involved in cell degeneration, a rising number of studies have highlighted the interest in developing therapeutics targeting GSK3 to treat neurodegenerative diseases. Although recent works strongly suggest that inhibiting GSK3 might also be a promising therapeutic approach for retinal degenerative diseases, its full potential is still under-evaluated. In this review, we summarize the literature on the role of GSK3 on the main cellular functions reported as deregulated during retinal degeneration, such as glucose homeostasis which is critical for photoreceptor survival, or oxidative stress, a major component of retinal degeneration. We also discuss the interest in targeting GSK3 for its beneficial effects on inflammation, for reducing neovascularization that occurs in some retinal dystrophies, or for cell-based therapy by enhancing Müller glia cell proliferation in diseased retina. Together, although GSK3 inhibitors hold promise as therapeutic agents, we highlight the complexity of targeting such a multitasked kinase and the need to increase our knowledge of the impact of reducing GSK3 activity on these multiple cellular pathways and biological processes.

β-Hydroxybutyrate Attenuates Painful Diabetic Neuropathy via Restoration of the Aquaporin-4 Polarity in the Spinal Glymphatic System

Waste removal is essential for maintaining homeostasis and the normal function of the central nervous system (CNS). The glymphatic system based on aquaporin-4 (AQP4) water channels on the endfeet of astrocytes is recently discovered as the excretion pathway for metabolic waste products of CNS. In the CNS, α-syntrophin (SNTA1) directly or indirectly anchors AQP4 in astrocyte membranes facing blood vessels. Studies have indicated that β-hydroxybutyrate (BHB) can raise the expression of SNTA1 and thus restoring AQP4 polarity in mice models with Alzheimer’s disease. The study aims to evaluate the neuroprotective mechanism of BHB in rats with painful diabetic neuropathy (PDN). PDN rats were modeled under a high-fat and high-glucose diet with a low dose of streptozotocin. Magnetic resonance imaging (MRI) was applied to observe the clearance of contrast to indicate the functional variability of the spinal glymphatic system. Mechanical allodynia was assessed by paw withdrawal threshold. The expressions of SNTA1 and AQP4 were tested, and the polarity reversal of AQP4 protein was measured. As demonstrated, PDN rats were manifested with deceased contrast clearance of the spinal glymphatic system, enhanced mechanical allodynia, lower expression of SNTA1, higher expression of AQP4, and reversed polarity of AQP4 protein. An opposite change in the above characteristics was observed in rats being treated with BHB. This is the first study that demonstrated the neuroprotective mechanism of BHB to attenuate PDN via restoration of the AQP4 polarity in the spinal glymphatic system and provides a promising therapeutic strategy for PDN.

GSK-3β inhibition elicits a neuroprotection by restoring lysosomal dysfunction in neurons via facilitation of TFEB nuclear translocation after ischemic stroke

Lysosomal dysfunction is an essential pathogenesis of autophagic neuronal injury after ischemic stroke. As a result of cerebral ischemia, transcription factor EB (TFEB) is greatly phosphorylated by prominently activated glycogen synthase kinase-3β (GSK-3β). This increased TFEB phosphorylation decreases its nuclear translocation and subsequently leads to reduced lysosomal biosynthesis, which ultimately results in lysosomal dysfunction. The present study is to investigate whether the lysosomal dysfunction in neurons can be restored to alleviate post-stroke damage by GSK-3β inhibition. The GSK-3β activity was inhibited by pre-treatment with CHIR-99021 (CHIR) for 3 days before middle cerebral artery occlusion (MCAO) surgery in rats. Besides, the lysosomal capacity was altered by pre-administration with Bafilomycin A1 (Baf-A1) and EN6, respectively. Twenty-four hours after MCAO/reperfusion, the penumbral tissues were obtained to detect the GSK-3β, cytoplasmic and nuclear TFEB, and proteins in autophagic/lysosomal pathway by western blot and immunofluorescence, respectively. Meanwhile, the infarct volume, neurological deficits and neuron survival were assessed to evaluate the neurological outcomes elicited by GSK-3β inhibition. The results demonstrated that the neurological injury could be significantly mitigated by GSK-3β inhibition in MCAO+CHIR group, compared with that in MCAO group. Moreover, CHIR-facilitated TFEB nuclear translocation in neurons was coupled with reinforced lysosomal activities and attenuated autophagic substrates. However, GSK-3β inhibition-induced neuroprotection was greatly counteracted by Baf-A1-weakened lysosomal capacity. Conversely, EN6-reinforced lysosomal activities further ameliorated the autophagic/lysosomal signaling, and synergistically alleviated the neurological damage upon GSK-3β inhibition after MCAO/reperfusion. Our data suggests that GSK-3β inhibition-augmented neuroprotection against ischemic stroke is elicited by restoring the lysosomal dysfunction in neurons.

HDAC9 in the Injury of Vascular Endothelial Cell Mediated by P38 MAPK Pathway

Ischemic stroke caused by atherosclerosis (AS) poses a serious threat to human life expectancy and quality. With the development of genome-wide association studies, the association of histone deacetylase 9 (HDAC9) expression of atheromatous plaques with ischemic stroke in large arteries has been revealed, but the molecular mechanisms behind this phenomenon have not been elucidated. In this study, we explored the effect of HDAC9 on the P38 mitogen activated protein kinase (P38 MAPK), a classic cellular inflammation-related pathway, by knocking down HDAC9 in vascular endothelial cells with short hairpin RNA (shRNA) and found that HDAC9 may mediate oxidized low density lipoprotein (ox-LDL)-induced inflammatory injury in vascular endothelial cells by regulating the phosphorylation level of P38 MAPK to lead to AS. It can be seen that HDAC9 may be a target to control the formation of atherosclerotic plaques. In follow-up experiments, it was verified that sodium valproate (SVA), as a HDAC9 inhibitor, can indeed antagonize the inflammatory damage of vascular endothelial cells, as well as SB203580, which is a P38 MAPK inhibitor. It proves that SVA may be a potential drug for the prevention and treatment of ischemic stroke.

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.

Improved Visual Function in a Case of Ultra-low Vision following Ischemic Encephalopathy Using Transcranial Electrical Stimulation; A Brief Report

OBJECTIVES

Cerebral visual impairment is amongst the key pathological causes of pediatric visual abnormalities often resulted from hypoxic-ischemic brain injury. Such an injury results in profound visual impairments which severely impairs patients' quality of life. Given the nature of the pathology, treatments are currently limited to rehabilitation strategies such as transcranial electrical stimulation and visual rehabilitation therapy.

CASE DESCRIPTION

Here, we discussed an 11-year-old girl with cerebral visual impairment who underwent concurrent visual rehabilitation therapy, transcranial electrical stimulation, and pharmacological therapy resulting in her improved visual function.

CONCLUSION

Given its beneficial effects, transcranial electrical stimulation may be sought as a potential add-on modality when strategizing visual rehabilitation therapy.

Valproic Acid and Its Amidic Derivatives as New Antivirals against Alphaherpesviruses

Herpes simplex viruses (HSVs) are neurotropic viruses with broad host range whose infections cause considerable health problems in both animals and humans. In fact, 67% of the global population under the age of 50 are infected with HSV-1 and 13% have clinically recurrent HSV-2 infections. The most prescribed antiherpetics are nucleoside analogues such as acyclovir, but the emergence of mutants resistant to these drugs and the lack of available vaccines against human HSVs has led to an imminent need for new antivirals. Valproic acid (VPA) is a branched short-chain fatty acid clinically used as a broad-spectrum antiepileptic drug in the treatment of neurological disorders, which has shown promising antiviral activity against some herpesviruses. Moreover, its amidic derivatives valpromide and valnoctamide also share this antiherpetic activity. This review summarizes the current research on the use of VPA and its amidic derivatives as alternatives to traditional antiherpetics in the fight against HSV infections.

Updating a Strategy for Histone Deacetylases and Its Inhibitors in the Potential Treatment of Cerebral Ischemic Stroke

BACKGROUND

Cerebral ischemic stroke is one of the severe diseases with a pathological condition that leads to nerve cell dysfunction with seldom available therapy options. Currently, there are few proven effective treatments available for improving cerebral ischemic stroke outcome. However, recently, there is increasing evidence that inhibition of histone deacetylase (HDAC) activity exerts a strong protective effect in in vivo and vitro models of ischemic stroke. Review Summary. HDAC is a posttranslational modification that is negatively regulated by histone acetyltransferase (HATS) and histone deacetylase. Based on function and DNA sequence similarity, histone deacetylases (HDACs) are organized into four different subclasses (I-IV). Modifications of histones play a crucial role in cerebral ischemic affair development after translation by modulating disrupted acetylation homeostasis. HDAC inhibitors (HDACi) mainly exert neuroprotective effects by enhancing histone and nonhistone acetylation levels and enhancing gene expression and protein modification functions. This article reviews HDAC and its inhibitors, hoping to find meaningful therapeutic targets.

CONCLUSIONS

HDAC may be a new biological target for cerebral ischemic stroke. Future drug development targeting HDAC may make it a potentially effective anticerebral ischemic stroke drug.

Selenium and L-carnitine protects from valproic acid-Induced oxidative stress and mitochondrial damages in rat cortical neurons

Oxidative stress and mitochondrial dysfunction have been associated with valproic acid (VPA) induced neurotoxicity. Mitochondria are vulnerable to oxidative damage and are also a major source of superoxide free radicals. Therefore, the need for mitochondrial protective and antioxidant agents for reducing valporic acid toxicity in central nerve system (CNS) is essential. In the present study, we investigated the potential beneficial effects of sodium selenite (SS) and L-carnitine (LC) against valproic acid -induced oxidative stress and mitochondrial dysfunction in isolated rat cortical neurons. Valproic acid (50, 100 and 200 µM) treatment caused a significant decrease in cellular viability, which was accompanied by increases in reactive oxygen species (ROS) generation, GSSG and GSH content, lipid peroxidation and lysosomal and mitochondrial damages. Sodium selenite (1 µM) and L-carnitine (1 mM) pretreatment attenuated valproic acid-induced decrease in cell viability. In addition, sodium selenite (1 µM) and L-carnitine (1 mM) pretreatment significantly protected against valproic acid-induced raise in oxidative stress, mitochondrial and lysosomal dysfunction, lipid peroxidation levels and depletion of GSH content. Our results in the current study provided insights into the protective mechanism by L-carnitine and sodium selenite, which is liked, to neuronal ROS generation and mitochondrial and lysosomal damages.

Effect of valproic acid on oxidative stress parameters of glutamate-induced excitotoxicity in SH-SY5Y cells

Glutamate-induced excitotoxicity has been reported to be involved in the pathophysiology of neurodegenerative disorders. It has been proposed that valproic acid (VPA), which is used in epileptic and bipolar disorders, may be protective against excitotoxic insult. The aim of the present study was to investigate the effects of VPA against the glutamate excitotoxicity in the SH-SY5Y human neuroblastoma cell line and determine its anti-oxidant capacity by measuring oxidative and anti-oxidant biochemical parameters. SH-SY5Y human neuroblastoma cells were pre-treated with 1, 5 or 10 mM VPA prior to exposure to 15 mM glutamate. The MTT assay was performed to determine cell viability. To detect oxidative insult in glutamate toxicity and the potential anti-oxidant effect of VPA, the cell catalase (CAT), superoxide dismutase (SOD), malondialdehyde and hydrogen peroxide (H₂O₂) activity was determined. A progressive decline in cell viability was observed with increasing glutamate concentrations (1-50 mM). Treatment with 1 mM VPA was revealed to be effective in increasing the viability of cells exposed to glutamate for 24 h. Oxidative damage, including an increase in H₂O₂ and MDA, was observed in SH-SY5Y cells treated with glutamate and was reduced by pre-treatment with VPA. CAT activity was decreased following glutamate exposure, but VPA did not prevent this decrease. SOD activity was increased by treatment with VPA alone and was not affected by glutamate exposure. Overall, the present results confirmed the critical role of oxidative stress in glutamate-induced excitotoxicity. They also suggested that VPA may exert an anti-oxidant effect against glutamate-induced excitotoxicity by decreasing oxidative parameters, including H₂O₂ and MDA, but only had a slight effect on CAT and SOD activity, which have an anti-oxidant capacity.

Histone Deacetylase Inhibitors: A Novel Strategy for Neuroprotection and Cardioprotection Following Ischemia/Reperfusion Injury

Ischemia/reperfusion injury is a complex molecular cascade that causes deleterious cellular damage and organ dysfunction. Stroke, sudden cardiac arrest, and acute myocardial infarction are the most common causes of ischemia/reperfusion injury without effective pharmacologic therapies. Existing preclinical evidence suggests that histone deacetylase inhibitors may be an efficacious, affordable, and clinically feasible therapy that can improve neurologic and cardiac outcomes following ischemia/reperfusion injury. In this review, we discuss the pathophysiology and epigenetic modulations of ischemia/reperfusion injury and focus on the neuroprotective and cardioprotective effects of histone deacetylase inhibitors. We also summarize the protective effects of histone deacetylase inhibitors for other vital organs and highlight the key research priorities for their successful translation to the bedside.

Contribution of neuronal calcium sensor 1 (Ncs-1) to anxiolytic-like and social behavior mediated by valproate and Gsk3 inhibition

Peripheral biomarker and post-mortem brains studies have shown alterations of neuronal calcium sensor 1 (Ncs-1) expression in people with bipolar disorder or schizophrenia. However, its engagement by psychiatric medications and potential contribution to behavioral regulation remains elusive. We investigated the effect on Ncs-1 expression of valproic acid (VPA), a mood stabilizer used for the management of bipolar disorder. Treatment with VPA induced Ncs-1 gene expression in cell line while chronic administration of this drug to mice increased both Ncs-1 protein and mRNA levels in the mouse frontal cortex. Inhibition of histone deacetylases (HDACs), a known biochemical effect of VPA, did not alter the expression of Ncs-1. In contrast, pharmacological inhibition or genetic downregulation of glycogen synthase kinase 3β (Gsk3β) increased Ncs-1 expression, whereas overexpression of a constitutively active Gsk3β had the opposite effect. Moreover, adeno-associated virus-mediated Ncs-1 overexpression in mouse frontal cortex caused responses similar to those elicited by VPA or lithium in tests evaluating social and mood-related behaviors. These findings indicate that VPA increases frontal cortex Ncs-1 gene expression as a result of Gsk3 inhibition. Furthermore, behavioral changes induced by Ncs-1 overexpression support a contribution of this mechanism in the regulation of behavior by VPA and potentially other psychoactive medications inhibiting Gsk3 activity.

Cerebral ischemia-reperfusion causes a down regulation of HCN1 expression via enhancing the nuclear NRSF-HDAC4 gathering that contributes to neuron damage

Cerebral ischemia-reperfusion (I/R) can trigger neuronal death through several biologically plausible pathways, but its underlying neurobiological mechanisms remain unclear. In this study, we tested whether hyperpolarization-activated cyclic nucleotide-gated channel 1 (HCN1) is altered in I/R that contributes to neuron damage and further clarified the mechanisms underlying this process. Cerebral I/R injury was induced by middle cerebral artery occlusion (MCAO) surgery followed by reperfusion in rats or simulated by oxygen-glucose deprivation/reoxygenation (OGD/R) in cultured cell. After reperfusion, the mRNA and protein levels of HCN1 were tested by RT-PCR and Western blot (WB). The histone deacetylases 4 (HDAC4) shuttling and the nuclear neuron-restrictive silencer factor (NRSF) expression were evaluated by WB and immunohistochemistry. Our data showed that I/R caused a strong decrease of HCN1 subunit in both hippocampus and cortex of rat. Additionally, the nuclear expression of HDAC4 and NRSF were significantly increased. In vitro OGD/R model, the gathering of HDAC4 and NRSF to nuclei was further confirmed. Valproic acid (VPA), a HDAC4 inhibitor, could reverse the decreased HCN1 and protect neuron damage from OGD/R injury. Collectively, these results demonstrated that I/R cause a decrease of HCN1 expression via enhancing nuclear HDAC4-NRSF gathering and might contribute to neuron damage.

Sodium valproate ameliorates memory impairment and reduces the elevated levels of apoptotic caspases in the hippocampus of diabetic mice

Learning and memory deficits appear in chronic diabetes and valproic acid has been proved to be beneficial in neurodegenerative diseases. Hence, the current study investigated the effectiveness of chronic valproate treatment for diabetes-induced memory impairment and increased levels of hippocampal apoptotic caspases. This study was conducted in adult male C57B15/J mice. Diabetes, which was induced by alloxan (150 mg/kg; i.p.), was confirmed when fasting blood sugar (FBS) was > 200 mg/dl. Sodium valproate (100 mg/kg; i.p.) was administrated to the diabetic and non-diabetic groups, every 72 h for 2 months. Next, all groups were evaluated for memory performance using the radial maze and shuttle box. After FBS measurement, animals were killed and the hippocampus was extracted and prepared for ELISA to assess caspase levels. Diabetic animals had significantly high FBS and memory impairment 2 months after the alloxan injection. Hippocampal levels of caspases 3, 6, and 8 were significantly higher in the diabetic group than in the control group. However, valproate treatment of diabetic animals significantly improved memory performance in both the radial maze and shuttle box and reduced the elevated levels of hippocampal apoptotic caspases, in comparison with diabetic animals. Chronic administration of valproate seems to have beneficial effects on diabetic neuropathy.