Potential roles of HDAC inhibitors in mitigating ischemia-induced brain damage and facilitating endogenous regeneration and recovery

Sodium acetate prevents testicular damage in Wistar rats subjected to testicular ischaemia/reperfusion injury

AIMS

The aim of this study was to investigate the potential antioxidant, anti-inflammatory, and sperm function-preserving properties of sodium acetate (ACE), a histone deacetylase (HDAC) inhibitor, in a rat model of testicular torsion/detorsion (T/D).

MAIN METHODS

Littermate Wistar rats of identical weight were subjected to sham surgery or testicular T/D by rotating the left testis at 720° around its axis along the spermatic cord clockwise and fixing it in this position for two and a half hours. 1 h before detorsion, T/D + ACE-treated rats were treated with ACE (200 mg/kg/day, per os) while T/D rats were vehicle-treated by administering 0.5 mL of distilled water. After 72 h, animals were euthanized, and the left testes were harvested for bio-molecular and histological analysis.

KEY FINDINGS

Acetate administration attenuated T/D-induced rises in serum and testicular HDAC and testicular xanthine oxidase, uric acid, MDA, GSSG, MPO, TNF-α, IL-1β, IL-6, NFkB, HIF-1α, and VCAM-1. In addition, acetate treatment alleviated T/D-induced decline in sperm quality (count, motility, viability, and normal morphology) and testicular 3β-HSD, 17β-HSD, testosterone, GSH, GSH/GSSG, SOD, catalase, GPx, GST, Nrf2, and HO-1. Furthermore, acetate prevented T/D-distorted testicular histoarchitecture and spermatogenic germ cell loss.

SIGNIFICANCE

Sodium acetate during the post-ischaemic phase of testicular T/D may be beneficial in preventing I/R injury and maintaining fertility.

Butyrate as a potential therapeutic agent for neurodegenerative disorders

Maintaining an optimum microbial community within the gastrointestinal tract is intricately linked to human metabolic, immune and brain health. Disturbance to these microbial populations perturbs the production of vital bioactive compounds synthesised by the gut microbiome, such as short-chain fatty acids (SCFAs). Of the SCFAs, butyrate is known to be a major source of energy for colonocytes and has valuable effects on the maintenance of intestinal epithelium and blood brain barrier integrity, gut motility and transit, anti-inflammatory effects, and autophagy induction. Inducing endogenous butyrate production is likely to be beneficial for gut-brain homeostasis and for optimal neuronal function. For these reasons, butyrate has gained interest as a potential therapy for not only metabolic and immunological disorders, but also conditions related to the brain, including neurodegenerative diseases. While direct and indirect sources of butyrate, including prebiotics, probiotics, butyrate pro-drugs and glucosidase inhibitors, offer a promising therapeutic avenue, their efficacy and dosage in neurodegenerative conditions remain largely unknown. Here, we review current literature on effects of butyrate relevant to neuronal function, the impact of butyrate in a range of neurodegenerative diseases and related treatments that may have potential for the treatment of neurodegenerative diseases.

HAT and HDAC: Enzyme with Contradictory Action in Neurodegenerative Diseases

In view of the increasing risk of neurodegenerative diseases, epigenetics plays a fundamental role in the field of neuroscience. Several modifications have been studied including DNA methylation, histone acetylation, histone phosphorylation, etc. Histone acetylation and deacetylation regulate gene expression, and the regular activity of histone acetyltransferases (HATs) and histone deacetylases (HDACs) provides regulatory stages for gene expression and cell cycle. Imbalanced homeostasis in these enzymes causes a detrimental effect on neurophysiological function. Intriguingly, epigenetic remodelling via histone acetylation in certain brain areas has been found to play a key role in the neurodegenerative diseases such as Alzheimer's disease, Parkinson's disease, and Huntington's disease. It has been demonstrated that a number of HATs have a role in crucial brain processes such regulating neuronal plasticity and memory formation. The most recent therapeutic methods involve the use of small molecules known as histone deacetylase (HDAC) inhibitors that antagonize HDAC activity thereby increase acetylation levels in order to prevent the loss of HAT function in neurodegenerative disorders. The target specificity of the HDAC inhibitors now in use raises concerns about their applicability, despite the fact that this strategy has demonstrated promising therapeutic outcomes. The aim of this review is to summarize the cross-linking between histone modification and its regulation in the pathogenesis of neurological disorders. Furthermore, these findings also support the notion of new pharmacotherapies that target particular areas of the brain using histone deacetylase inhibitors.

Histone deacetylase inhibition by suberoylanilide hydroxamic acid during reperfusion promotes multifaceted brain and vascular protection in spontaneously hypertensive rats with transient ischaemic stroke

Hypertension is the most prevalent modifiable risk factor for stroke and is associated with worse functional outcomes. Pharmacological inhibition of histone deacetylases by suberoylanilide hydroxamic acid (SAHA) modulates gene expression and has emerged as a promising therapeutic approach to reduce ischaemic brain injury. Here, we have tested the therapeutic potential of SAHA administered during reperfusion in adult male spontaneously hypertensive (SHR) rats subjected to transient middle cerebral artery occlusion (tMCAO; 90 min occlusion/24 h reperfusion). Animals received a single dose of SAHA (50 mg/kg) or vehicle i.p. at 1, 4, or 6 h after reperfusion onset. The time-course of brain histone H3 acetylation was studied. After tMCAO, drug brain penetrance and beneficial effects on behavioural outcomes, infarct volume, oedema, angiogenesis, blood-brain barrier integrity, cerebral artery oxidative stress and remodelling, and brain and vascular inflammation were evaluated. SAHA increased brain histone H3 acetylation from 1 to 6 h after injection, reaching the ischaemic brain administered during reperfusion. Treatment given at 4 h after reperfusion onset improved neurological score, reduced infarct volume and oedema, attenuated microglial activation, prevented exacerbated MCA angiogenic sprouting and blood-brain barrier breakdown, normalised MCA oxidative stress and remodelling, and modulated brain and cerebrovascular cytokine expression. Overall, we demonstrate that SAHA administered during early reperfusion exerts robust brain and vascular protection after tMCAO in hypertensive rats. These findings are aligned with previous research in ischaemic normotensive mice and help pave the way to optimise the design of clinical trials assessing the effectiveness and safety of SAHA in ischaemic stroke.

Multi-omics Data Reveal the Effect of Sodium Butyrate on Gene Expression and Protein Modification in Streptomyces

Streptomycetes possess numerous gene clusters and the potential to produce a large amount of natural products. Histone deacetylase (HDAC) inhibitors play an important role in the regulation of histone modifications in fungi, but their roles in prokaryotes remain poorly understood. Here, we investigated the global effects of the HDAC inhibitor, sodium butyrate (SB), on marine-derived Streptomycesolivaceus FXJ 8.021, particularly focusing on the activation of secondary metabolite biosynthesis. The antiSMASH analysis revealed 33 secondary metabolite biosynthetic gene clusters (BGCs) in strain FXJ 8.021, among which the silent lobophorin BGC was activated by SB. Transcriptomic data showed that the expression of genes involved in lobophorin biosynthesis (ge00097-ge00139) and CoA-ester formation (e.g., ge02824), as well as the glycolysis/gluconeogenesis pathway (e.g., ge01661), was significantly up-regulated in the presence of SB. Intracellular CoA-ester analysis confirmed that SB triggered the biosynthesis of CoA-ester, thereby increasing the precursor supply for lobophorin biosynthesis. Further acetylomic analysis revealed that the acetylation levels on 218 sites of 190 proteins were up-regulated and those on 411 sites of 310 proteins were down-regulated. These acetylated proteins were particularly enriched in transcriptional and translational machinery components (e.g., elongation factor GE04399), and their correlations with the proteins involved in lobophorin biosynthesis were established by protein-protein interaction network analysis, suggesting that SB might function via a complex hierarchical regulation to activate the expression of lobophorin BGC. These findings provide solid evidence that acetylated proteins triggered by SB could affect the expression of genes involved in the biosynthesis of primary and secondary metabolites in prokaryotes.

Novel small molecules inhibit proteotoxicity and inflammation: Mechanistic and therapeutic implications for Alzheimer's Disease, healthspan and lifespan- Aging as a consequence of glycolysis

Inflammation drives many age-related, especially neurological, diseases, and likely mediates age-related proteotoxicity. For example, dementia due to Alzheimer's Disease (AD), cerebral vascular disease, many other neurodegenerative conditions is increasingly among the most devastating burdens on the American (and world) health system and threatens to bankrupt the American health system as the population ages unless effective treatments are developed. Dementia due to either AD or cerebral vascular disease, and plausibly many other neurodegenerative and even psychiatric conditions, is driven by increased age-related inflammation, which in turn appears to mediate Abeta and related proteotoxic processes. The functional significance of inflammation during aging is also supported by the fact that Humira, which is simply an antibody to the pro-inflammatory cytokine TNF-a, is the best-selling drug in the world by revenue. These observations led us to develop parallel high-throughput screens to discover small molecules which inhibit age-related Abeta proteotoxicity in a C. elegans model of AD AND LPS-induced microglial TNF-a. In the initial screen of 2560 compounds (Microsource Spectrum library) to delay Abeta proteotoxicity, the most protective compounds were, in order, phenylbutyrate, methicillin, and quetiapine, which belong to drug classes (HDAC inhibitors, beta lactam antibiotics, and tricyclic antipsychotics, respectably) already robustly implicated as promising to protect in neurodegenerative diseases, especially AD. RNAi and chemical screens indicated that the protective effects of HDAC inhibitors to reduce Abeta proteotoxicity are mediated by inhibition of HDAC2, also implicated in human AD, dependent on the HAT Creb binding protein (Cbp), which is also required for the protective effects of both dietary restriction and the daf-2 mutation (inactivation of IGF-1 signaling) during aging. In addition to methicillin, several other beta lactam antibiotics also delayed Abeta proteotoxicity and reduced microglial TNF-a. In addition to quetiapine, several other tricyclic antipsychotic drugs also delayed age-related Abeta proteotoxicity and increased microglial TNF-a, leading to the synthesis of a novel congener, GM310, which delays Abeta as well as Huntingtin proteotoxicity, inhibits LPS-induced mouse and human microglial and monocyte TNF-a, is highly concentrated in brain after oral delivery with no apparent toxicity, increases lifespan, and produces molecular responses highly similar to those produced by dietary restriction, including induction of Cbp inhibition of inhibitors of Cbp, and genes promoting a shift away from glycolysis and toward metabolism of alternate (e.g., lipid) substrates. GM310, as well as FDA-approved tricyclic congeners, prevented functional impairments and associated increase in TNF-a in a mouse model of stroke. Robust reduction of glycolysis by GM310 was functionally corroborated by flux analysis, and the glycolytic inhibitor 2-DG inhibited microglial TNF-a and other markers of inflammation, delayed Abeta proteotoxicity, and increased lifespan. These results support the value of phenotypic screens to discover drugs to treat age-related, especially neurological and even psychiatric diseases, including AD and stroke, and to clarify novel mechanisms driving neurodegeneration (e.g., increased microglial glycolysis drives neuroinflammation and subsequent neurotoxicity) suggesting novel treatments (selective inhibitors of microglial glycolysis).

Myc beyond Cancer: Regulation of Mammalian Tissue Regeneration

Myc is one of the most well-known oncogenes driving tumorigenesis in a wide variety of tissues. From the brain to blood, its deregulation derails physiological pathways that grant the correct functioning of the cell. Its action is carried out at the gene expression level, where Myc governs basically every aspect of transcription. Indeed, in addition to its role as a canonical, chromatin-bound transcription factor, Myc rules RNA polymerase II (RNAPII) transcriptional pause-release, elongation and termination and mRNA capping. For this reason, it is evident that minimal perturbations of Myc function mirror malignant cell behavior and, consistently, a large body of literature mainly focuses on Myc malfunctioning. In healthy cells, Myc controls molecular mechanisms involved in pivotal functions, such as cell cycle (and proliferation thereof), apoptosis, metabolism and cell size, angiogenesis, differentiation and stem cell self-renewal. In this latter regard, Myc has been found to also regulate tissue regeneration, a hot topic in the research fields of aging and regenerative medicine. Indeed, Myc appears to have a role in wound healing, in peripheral nerves and in liver, pancreas and even heart recovery. Herein, we discuss the state of the art of Myc's role in tissue regeneration, giving an overview of its potent action beyond cancer.

Sirtuins: Promising Therapeutic Targets to Treat Ischemic Stroke

Stroke is a major cause of mortality and disability globally, with ischemic stroke (IS) accounting for over 80% of all stroke cases. The pathological process of IS involves numerous signal molecules, among which are the highly conserved nicotinamide adenine dinucleotide (NAD+)-dependent enzymes known as sirtuins (SIRTs). SIRTs modulate various biological processes, including cell differentiation, energy metabolism, DNA repair, inflammation, and oxidative stress. Importantly, several studies have reported a correlation between SIRTs and IS. This review introduces the general aspects of SIRTs, including their distribution, subcellular location, enzyme activity, and substrate. We also discuss their regulatory roles and potential mechanisms in IS. Finally, we describe the current therapeutic methods based on SIRTs, such as pharmacotherapy, non-pharmacological therapeutic/rehabilitative interventions, epigenetic regulators, potential molecules, and stem cell-derived exosome therapy. The data collected in this study will potentially contribute to both clinical and fundamental research on SIRTs, geared towards developing effective therapeutic candidates for future treatment of IS.

Mechanisms of Blood-Brain Barrier Protection by Microbiota-Derived Short-Chain Fatty Acids

Impairment of the blood-brain barrier (BBB) integrity is implicated in the numerous neurological disorders associated with neuroinflammation, neurodegeneration and aging. It is now evident that short-chain fatty acids (SCFAs), mainly acetate, butyrate and propionate, produced by anaerobic bacterial fermentation of the dietary fiber in the intestine, have a key role in the communication between the gastrointestinal tract and nervous system and are critically important for the preservation of the BBB integrity under different pathological conditions. The effect of SCFAs on the improvement of the compromised BBB is mainly based on the decrease in paracellular permeability via restoration of junctional complex proteins affecting their transcription, intercellular localization or proteolytic degradation. This review is focused on the revealed and putative underlying mechanisms of the direct and indirect effects of SCFAs on the improvement of the barrier function of brain endothelial cells. We consider G-protein-coupled receptor-mediated effects of SCFAs, SCFAs-stimulated acetylation of histone and non-histone proteins via inhibition of histone deacetylases, and crosstalk of these signaling pathways with transcriptional factors NF-κB and Nrf2 as mainstream mechanisms of SCFA's effect on the preservation of the BBB integrity.

Inflammatory bowel disease: A potential pathogenic factor of Alzheimer's disease

Alzheimer's disease (AD) is a central nervous system disease characterised by degenerative cognitive dysfunction and memory loss. In a society where the global population is gradually ageing, the health threats and financial burdens caused by AD are becoming increasingly severe since AD often occurs in old age. With the in-depth study of AD, many new pathogenic mechanisms have been proposed, among which bidirectional communication between intestinal microbes and the brain has attracted widespread attention. The aetiology of inflammatory bowel disease (IBD) is related to the imbalance of the gut microbiota. Epidemiological investigations have shown that patients with IBD are more likely to suffer from AD. Targeting IBD as a potential AD treatment target has attracted considerable interest. Here, we reviewed the link between chronic intestinal inflammation and central nervous system inflammation and found that IBD patients had a higher risk of AD than non-IBD patients. Preclinical models based on AD also showed that IBD aggravated the condition of AD. We discussed possible biological links between AD and IBD, including the gut-brain axis, autoimmunity, and the gut microbiota. In addition, IBD-induced changes in intestinal microbial metabolites, such as short-chain fatty acids, bile acids, and tryptophan, which aggravate the development of AD, were also discussed.

Effects of MgSO4 Alone or Associated with 4-PBA on Behavior and White Matter Integrity in a Mouse Model of Cerebral Palsy: A Sex- and Time-Dependent Study

Cerebral palsy (CP) is defined as permanent disorders of movement and posture. Prematurity and hypoxia-ischemia (HI) are risk factors of CP, and boys display a greater vulnerability to develop CP. Magnesium sulfate (MgSO₄) is administered to mothers at risk of preterm delivery as a neuroprotective agent. However, its effectiveness is only partial at long term. To prolong MgSO₄ effects, it was combined with 4-phenylbutyrate (4-PBA). A mouse model of neonatal HI, generating lesions similar to those reported in preterms, was realized. At short term, at the behavioral and cellular levels, and in both sexes, the MgSO₄/4-PBA association did not alter the total prevention induced by MgSO₄ alone. At long term, the association extended the MgSO₄ preventive effects on HI-induced motor and cognitive deficits. This might be sustained by the promotion of oligodendrocyte precursor differentiation after HI at short term, which led to improvement of white matter integrity at long term. Interestingly, at long term, at a behavioral level, sex-dependent responses to HI were observed. This might partly be explained by early sex-dependent pathological processes that occur after HI. Indeed, at short term, apoptosis through mitochondrial pathways seemed to be activated in females but not in males, and only the MgSO₄/4-PBA association seemed to counter this apoptotic process.

Advancement of epigenetics in stroke

A wide plethora of intervention procedures, tissue plasminogen activators, mechanical thrombectomy, and several neuroprotective drugs were reported in stroke research over the last decennium. However, against this vivid background of newly emerging pieces of evidence, there is little to no advancement in the overall functional outcomes. With the advancement of epigenetic tools and technologies associated with intervention medicine, stroke research has entered a new fertile. The stroke involves an overabundance of inflammatory responses arising in part due to the body's immune response to brain injury. Neuroinflammation contributes to significant neuronal cell death and the development of functional impairment and even death in stroke patients. Recent studies have demonstrated that epigenetics plays a key role in post-stroke conditions, leading to inflammatory responses and alteration of the microenvironment within the injured tissue. In this review, we summarize the progress of epigenetics which provides an overview of recent advancements on the emerging key role of secondary brain injury in stroke. We also discuss potential epigenetic therapies related to clinical practice.

Neuroprotective Effect of Polyherbal Recipe Containing Ginger, Chinese Date, and Wood Ear Mushroom against Ischemic Stroke with Metabolic Syndrome Condition via Epigenetic Modification of Inflammation and Oxidative Stress

Currently, the prevalence of stroke with metabolic syndrome (MetS) is increasing and the current therapeutic efficiency is still limited. Therefore, the applications of herbal recipes have gained much attention. The polyherbal recipe containing ginger, Chinese date, and wood ear mushroom is reputed for atherosclerosis and stroke prevention. It has been long-term consumed without scientific support. Therefore, this study was carried out to determine the neuroprotective effect and its mechanisms in animal model of ischemic stroke with MetS. Male Wistar rats weighing 180-220 g were exposed to a 16-week high-fat high-carbohydrate feeding. The rats with the MetS characteristic were exposed to a temporary occlusion of the right middle cerebral artery (MCAO) for 90 minutes. They were orally fed with the polyherbal recipe (GCJ) at the doses of 100, 200, and 300 mg/kg BW for 21 days and assessed the neurological deficit, ion volume, cortical neuron density in the cerebral cortex, oxidative stress status, inflammation, and expressions of histone deacetylase 3 (HDAC3) and DNA methyltransferase 1 (DNMT1). The results showed that GCJ significantly improved all mentioned parameters. Therefore, GCJ is the potential neuroprotectant against ischemic stroke with MetS. The underlying mechanisms may involve the reduction of oxidative stress, inflammation, and the modification of epigenetic mechanism via the reduction of HDAC3 and DNMT1. However, further clinical investigation is essential to confirm this positive modulation effect.

miR-383-5p Regulated by the Transcription Factor CTCF Affects Neuronal Impairment in Cerebral Ischemia by Mediating Deacetylase HDAC9 Activity

Stroke, the leading cause of long-term disability worldwide, is caused by the blockage or hemorage of cerebral arteries. The resultant cerebral ischemia causes local neuronal death and brain injury. Histone deacetylase 9 (HDAC9) has been reported to be elevated in ischemic brain injury, but its mechanism in stroke is still enigmatic. The present study aimed to unveil the manner of regulation of HDAC9 expression and the effect of HDAC9 activation on neuronal function in cerebral ischemia. MicroRNAs (miRNAs) targeting HDAC9 were predicted utilizing bioinformatics analysis. We then constructed the oxygen glucose deprivation (OGD) cell model and the middle cerebral artery occlusion (MCAO) rat model, and elucidated the expression of CCCTC binding factor (CTCF)/miR-383-5p/HDAC9. Targeting between miR-383-5p and HDAC9 was verified by dual-luciferase reporter assay and RNAi. After conducting an overexpression/knockdown assay, we assessed neuronal impairment and brain injury. We found that CTCF inhibited miR-383-5p expression via its enrichment in the promoter region of miR-383-5p, whereas the miR-383-5p targeted and inhibited HDAC9 expression. In the OGD model and the MCAO model, we confirmed that elevation of HDAC9 regulated by the CTCF/miR-383-5p/HDAC9 pathway mediated apoptosis induced by endoplasmic reticulum stress, while reduction of HDAC9 alleviated apoptosis and the symptoms of cerebral infarction in MCAO rats. Thus, the CTCF/miR-383-5p/HDAC9 pathway may present a target for drug development against ischemic brain injury.

The function of gut microbiota in immune-related neurological disorders: a review

This review provides an overview of the importance of microbiota in the regulation of gut–brain communication in immune-related neurological disorders. The gastrointestinal (GI) tract hosts a diverse abundance of microbiota, referred to as gut microbiota. The gut microbiota plays a role in the maintenance of GI tract homeostasis and is likely to have multiple effects on brain development and function. The bidirectional communication between the gut microbiota and the brain is termed the microbiota–gut–brain axis. This communication between the intestine and the brain appears to affect human health and behavior, as certain animal studies have demonstrated the association between alterations in the gut microbiota and neurological disorders. Most insights about the microbiota–gut–brain axis come from germ-free animal models, which reveal the importance of gut microbiota in neural function. To date, many studies have observed the impact of the gut microbiota in patients with neurological disorders. Although many studies have investigated the microbiota–gut–brain axis, there are still limitations in translating this research to humans given the complexities of the relationship between the gut microbiota and the brain. In this review, we discuss emerging evidence of how the microbiota–gut–brain axis regulates brain development and function through biological networks, as well as the possible contribution of the microbiota–gut–brain axis in immune-related neurological disorders.

The Role of the Gut Microbiota in the Development of Ischemic Stroke

An increasing number of studies have focused on the gut microbiota and its relationship with various neurological diseases. The gut microbiota can affect the metabolic status of the body, in addition to having an important impact on blood pressure, blood glucose, and atherosclerosis, all of which are risk factors for ischemic stroke. In this review, we summarized studies that included the physiological function of the gut microbiota and gut microbiota disorders related to the central nervous system, thus providing novel ideas for the prevention and treatment of ischemic stroke.

HDAC inhibition as neuroprotection in COVID-19 infection

The SARS-CoV-2 virus is responsible of COVID-19 affecting millions of humans around the world. COVID-19 shows diverse clinical symptoms (fever, cough, fatigue, diarrhea, body aches, headaches, anosmia and hyposmia). Approximately 30% of the patients with COVID-19 showed neurological symptoms, these going from mild to severe manifestations including headache, dizziness, impaired consciousness, encephalopathy, anosmia, hypogeusia, hyposmia, psychology and psychiatry among others. The neurotropism of SARS-CoV-2 virus explains its neuroinvasion provoking neurological damage as acute demyelination, neuroinflammation etc. At molecular level, the COVID-19 patients had higher levels of cytokines and chemokines known as cytokines storms which disrupt the blood brain barrier allowing the entrance of monocytes and lymphocytes causing neuroinflammation, neurodegeneration and demyelination. In addition, ischemic, hemorrhagic strokes, seizures and encephalopathy have been observed due to the proinflammatory cytokines. In this sense, to avoid or decrease neurological damage due to SARS-CoV-2 infection, an early neuroprotective management should be adopted. Several approaches can be used; one of them includes the use of HDAC inhibitors (HDACi) due to their neuroprotective effects. Also, the HDACi down regulates the pro-inflammatory cytokines (IL-6 and TNF- decreasing the neurotoxicity. HDACi can also avoid and prevent the entrance of the virus into the Central nervous System (CNS) as well as decrease the virus replication by downregulating the virus receptors. Here we review the mechanisms that could explain how the SARS-CoV-2 virus could reach the CNS, induce the neurological damage and symptoms, as well as the possibility to use HDACi as neuroprotective therapy.

Butyrate Rescues Oxidative Stress-Induced Transport Deficits of Tryptophan: Potential Implication in Affective or Gut-Brain Axis Disorders

INTRODUCTION

Butyrate is a short-chain fatty acid metabolite produced by microbiota in the colon. With its antioxidant properties, butyrate has also been shown to alter the neurological functions in affective disorder models, suggesting it as a key mediator in gut-brain interactions.

OBJECTIVE

Here, we evaluated the negative effect of oxidative stress on the transport of the serotonin precursor tryptophan as present in affective disorders. Butyrate was hypothesized to be able to rescue these deficits due to its antioxidative capacities and its effect on transmembrane transport of tryptophan. Human skin-derived fibroblasts were used as cellular models to address these objectives.

METHODS

Human fibroblasts were treated with hydrogen peroxide to induce oxidative stress. Stressed as well as control cells were treated with different concentrations of butyrate. Tryptophan (3H) was used as a tracer to measure the transport of tryptophan across the cell membranes (n = 6). Furthermore, gene expression profiles of different amino acid transporters were analyzed (n = 2).

RESULTS

As hypothesized,oxidative stress significantly decreased the uptake of tryptophan in fibroblast cells, while butyrate counteracted this effect. Oxidative stress did not alter the gene expression profile of amino acid transporters. However, treatment of stressed and control cells with different concentrations of butyrate differentially regulated the gene expression of large amino acid transporters 1 and 2, which are the major transporters of tryptophan.

CONCLUSIONS

Gut microbiota-derived butyrate may have therapeutic potential in affective disorders characterized by either aberrant serotonergic activity or neuroinflammation due to its role in rescuing the oxidative stress-induced perturbations of tryptophan transport.

Histone Deacetylases and Their Isoform-Specific Inhibitors in Ischemic Stroke

Cerebral ischemia is the second leading cause of death in the world and multimodal stroke therapy is needed. The ischemic stroke generally reduces the gene expression due to suppression of acetylation of histones H3 and H4. Histone deacetylases inhibitors have been shown to be effective in protecting the brain from ischemic damage. Histone deacetylases inhibitors induce neurogenesis and angiogenesis in damaged brain areas promoting functional recovery after cerebral ischemia. However, the role of different histone deacetylases isoforms in the survival and death of brain cells after stroke is still controversial. This review aims to analyze the data on the neuroprotective activity of nonspecific and selective histone deacetylase inhibitors in ischemic stroke.

The Role of Post-Translational Acetylation and Deacetylation of Signaling Proteins and Transcription Factors after Cerebral Ischemia: Facts and Hypotheses

Histone deacetylase (HDAC) and histone acetyltransferase (HAT) regulate transcription and the most important functions of cells by acetylating/deacetylating histones and non-histone proteins. These proteins are involved in cell survival and death, replication, DNA repair, the cell cycle, and cell responses to stress and aging. HDAC/HAT balance in cells affects gene expression and cell signaling. There are very few studies on the effects of stroke on non-histone protein acetylation/deacetylation in brain cells. HDAC inhibitors have been shown to be effective in protecting the brain from ischemic damage. However, the role of different HDAC isoforms in the survival and death of brain cells after stroke is still controversial. HAT/HDAC activity depends on the acetylation site and the acetylation/deacetylation of the main proteins (c-Myc, E2F1, p53, ERK1/2, Akt) considered in this review, that are involved in the regulation of cell fate decisions. Our review aims to analyze the possible role of the acetylation/deacetylation of transcription factors and signaling proteins involved in the regulation of survival and death in cerebral ischemia.

The Emerging Role of HDACs: Pathology and Therapeutic Targets in Diabetes Mellitus

Diabetes mellitus (DM) is one of the principal manifestations of metabolic syndrome and its prevalence with modern lifestyle is increasing incessantly. Chronic hyperglycemia can induce several vascular complications that were referred to be the major cause of morbidity and mortality in DM. Although several therapeutic targets have been identified and accessed clinically, the imminent risk of DM and its prevalence are still ascending. Substantial pieces of evidence revealed that histone deacetylase (HDAC) isoforms can regulate various molecular activities in DM via epigenetic and post-translational regulation of several transcription factors. To date, 18 HDAC isoforms have been identified in mammals that were categorized into four different classes. Classes I, II, and IV are regarded as classical HDACs, which operate through a Zn-based mechanism. In contrast, class III HDACs or Sirtuins depend on nicotinamide adenine dinucleotide (NAD+) for their molecular activity. Functionally, most of the HDAC isoforms can regulate β cell fate, insulin release, insulin expression and signaling, and glucose metabolism. Moreover, the roles of HDAC members have been implicated in the regulation of oxidative stress, inflammation, apoptosis, fibrosis, and other pathological events, which substantially contribute to diabetes-related vascular dysfunctions. Therefore, HDACs could serve as the potential therapeutic target in DM towards developing novel intervention strategies. This review sheds light on the emerging role of HDACs/isoforms in diabetic pathophysiology and emphasized the scope of their targeting in DM for constituting novel interventional strategies for metabolic disorders/complications.

The Effect of Histone Deacetylase Inhibitors Panobinostat or Entinostat on Motor Recovery in Mice After Ischemic Stroke

Using rigorous and clinically relevant experimental design and analysis standards, in this study, we investigated the potential of histone deacetylase (HDAC) inhibitors panobinostat and entinostat to enhance recovery of motor function after photothrombotic stroke in male mice. Panobinostat, a pan-HDAC inhibitor, is a FDA-approved drug for certain cancers, whereas entinostat is a class-I HDAC inhibitor in late stage of clinical investigation. The drugs were administered every other day (panobinostat-3 or 10 mg/kg; entinostat-1.7 or 5 mg/kg) starting from day 5 to 15 after stroke. To imitate the current standard of care in stroke survivors, i.e., physical rehabilitation, the animals run on wheels (2 h daily) from post-stroke day 9 to 41. The predetermined primary end point was motor recovery measured in two tasks of spontaneous motor behaviors in grid-walking and cylinder tests. In addition, we evaluated the running distance and speed throughout the study, and the number of parvalbumin-positive neurons in medial agranular cortex (AGm) and infarct volumes at the end of the study. Both sensorimotor tests revealed that combination of physical exercise with either drug did not substantially affect motor recovery in mice after stroke. This was accompanied by negligible changes of parvalbumin-positive neurons recorded in AGm and comparable infarct volumes among experimental groups, while dose-dependent increase in acetylated histone 3 was observed in peri-infarct cortex of drug-treated animals. Our observations suggest that add-on panobinostat or entinostat therapy coupled with limited physical rehabilitation is unlikely to offer therapeutic modality for stroke survivors who have motor dysfunction.

Therapeutic effectiveness of a single exercise session combined with WalkAide functional electrical stimulation in post-stroke patients: a crossover design study

A growing body of evidence has suggested that the imbalance of epigenetic markers and oxidative stress appears to be involved in the pathophysiology and progression of stroke. Thus, strategies that modulate these biomarkers might be considered targets for neuroprotection and novel therapeutic opportunities for these patients. Physical exercise has been reported to induce changes in these epigenetic markers and improve clinical outcomes in different populations. However, little is reported on this in post-stroke patients. The purpose of this study was to investigate the effect of a single exercise session with WalkAide functional electrical stimulation (FES) on cognitive performance, clinical functional parameters, oxidative stress and epigenetic modulation in post-stroke individuals. In this crossover design study, 12 post-stroke individuals aged 54–72 years of either sexes were included and subjected to a single session of exercise (45 minutes) without WalkAide functional electrical stimulation (EXE alone group), followed by another single session of exercise (45 minutes) with WalkAide functional electrical stimulation (EXE + FES group). The clinical functional outcome measures, cognitive performance and blood collections for biomarker measurements were assessed pre- and post-intervention. After intervention, higher Berg Balance Scale scores were obtained in the EXE + FES group than in the EXE alone group. There was no significant difference in the Timed Up and Go test results post-intervention between EXE alone and EXE + FES groups. After intervention, a better cognitive performance was found in both groups compared with before the intervention. After intervention, the Timed Up and Go test scores were higher in the EXE + FES group than in the EXE alone group. In addition, the intervention induced lower levels of lipid peroxidation. After intervention, carbonyl level was lower, superoxide dismutase activity and superoxide dismutase/catalase activity ratio were higher in the EXE + FES group, compared with the EXE group alone. In each group, both histone deacetylase (HDAC2) and histone acetyltransferase activities were increased after intervention compared with before the intervention. These findings suggest that a single exercise session with WalkAide FES is more effective on balance ability and cognitive performance compared with conventional exercise alone in post-stroke patients. This is likely to be related to the regulation of oxidative stress markers. The present study was approved by the Research Ethics Committee of the Methodist University Center-IPA (approval No. 2.423.376) on December 7, 2017 and registered in the Brazilian Registry of Clinical Trials—ReBEC (RBR-9phj2q) on February 11, 2019.

HDAC1 Expression, Histone Deacetylation, and Protective Role of Sodium Valproate in the Rat Dorsal Root Ganglia After Sciatic Nerve Transection

Nerve injury is an important reason of human disability and death. We studied the role of histone deacetylation in the response of the dorsal root ganglion (DRG) cells to sciatic nerve transection. Sciatic nerve transection in the rat thigh induced overexpression of histone deacetylase 1 (HDAC1) in the ipsilateral DRG at 1-4 h after axotomy. In the DRG neurons, HDAC1 initially upregulated at 1 h but then redistributed from the nuclei to the cytoplasm at 4 h after axotomy. Histone H3 was deacetylated at 24 h after axotomy. Deacetylation of histone H4, accumulation of amyloid precursor protein, a nerve injury marker, and GAP-43, an axon regeneration marker, were observed in the axotomized DRG on day 7. Neuronal injury occurred on day 7 after axotomy along with apoptosis of DRG cells, which were mostly the satellite glial cells remote from the site of sciatic nerve transection. Administration of sodium valproate significantly reduced apoptosis not only in the injured ipsilateral DRG but also in the contralateral ganglion. It also reduced the deacetylation of histones H3 and H4, prevented axotomy-induced accumulation of amyloid precursor protein, which indicated nerve injury, and overexpressed GAP-43, a nerve regeneration marker, in the axotomized DRG. Therefore, HDAC1 was involved in the axotomy-induced injury of DRG neurons and glial cells. HDAC inhibitor sodium valproate demonstrated the neuroprotective activity in the axotomized DRG.

Astroglial Connexin43 as a Potential Target for a Mood Stabiliser

Mood disorders remain a major public health concern worldwide. Monoaminergic hypotheses of pathophysiology of bipolar and major depressive disorders have led to the development of monoamine transporter-inhibiting antidepressants for the treatment of major depression and have contributed to the expanded indications of atypical antipsychotics for the treatment of bipolar disorders. In spite of psychopharmacological progress, current pharmacotherapy according to the monoaminergic hypothesis alone is insufficient to improve or prevent mood disorders. Recent approval of esketamine for treatment of treatment-resistant depression has attracted attention in psychopharmacology as a glutamatergic hypothesis of the pathophysiology of mood disorders. On the other hand, in the last decade, accumulated findings regarding the pathomechanisms of mood disorders emphasised that functional abnormalities of tripartite synaptic transmission play important roles in the pathophysiology of mood disorders. At first glance, the enhancement of astroglial connexin seems to contribute to antidepressant and mood-stabilising effects, but in reality, antidepressive and mood-stabilising actions are mediated by more complicated interactions associated with the astroglial gap junction and hemichannel. Indeed, several depressive mood-inducing stress stimulations suppress connexin43 expression and astroglial gap junction function, but enhance astroglial hemichannel activity. On the other hand, monoamine transporter-inhibiting antidepressants suppress astroglial hemichannel activity and enhance astroglial gap junction function, whereas several non-antidepressant mood stabilisers activate astroglial hemichannel activity. Based on preclinical findings, in this review, we summarise the effects of antidepressants, mood-stabilising antipsychotics, and anticonvulsants on astroglial connexin, and then, to establish a novel strategy for treatment of mood disorders, we reveal the current progress in psychopharmacology, changing the question from "what has been revealed?" to "what should be clarified?".

Clinacanthus nutans Mitigates Neuronal Death and Reduces Ischemic Brain Injury: Role of NF-κB-driven IL-1β Transcription

Neuroinflammation has been shown to exacerbate ischemic brain injury, and is considered as a prime target for the development of stroke therapies. Clinacanthus nutans Lindau (C. nutans) is widely used in traditional medicine for treating insect bites, viral infection and cancer, due largely to its anti-oxidative and anti-inflammatory properties. Recently, we reported that an ethanol extract from the leaf of C. nutans could protect the brain against ischemia-triggered neuronal death and infarction. In order to further understand the molecular mechanism(s) for its beneficial effects, two experimental paradigms, namely, in vitro primary cortical neurons subjected to oxygen-glucose deprivation (OGD) and in vivo rat middle cerebral artery (MCA) occlusion, were used to dissect the anti-inflammatory effects of C. nutans extract. Using promoter assays, immunofluorescence staining, and loss-of-function (siRNA) approaches, we demonstrated that transient OGD led to marked induction of IL-1β, IL-6 and TNFα, while pretreatment with C. nutans suppressed production of inflammatory cytokines in primary neurons. C. nutans inhibited IL-1β transcription via preventing NF-κB/p65 nuclear translocation, and siRNA knockdown of either p65 or IL-1β mitigated OGD-mediated neuronal death. Correspondingly, post-ischemic treatment of C. nutans attenuated IκBα degradation and decreased IL-1β, IL-6 and TNFα production in the ischemic brain. Furthermore, IL-1β siRNA post-ischemic treatment reduced cerebral infarct, thus mimicking the beneficial effects of C. nutans. In summary, our findings demonstrated the ability for C. nutans to suppress NF-κB nuclear translocation and inhibit IL-1β transcription in ischemic models. Results further suggest the possibility for using C. nutans to prevent and treat stroke patients.

The Impact of Gut Microbiota Disorders on the Blood-Brain Barrier

The gut microbiota is symbiotic with the human host and has been extensively studied in recent years resulting in increasing awareness of the effects of the gut microbiota on human health. In this review, we summarize the current evidence for the effects of gut microbes on the integrity of the cerebral blood-brain barrier (BBB), focusing on the pathogenic impact of gut microbiota disorders. Based on our description and summarization of the effects of the gut microbiota and its metabolites on the nervous, endocrine, and immune systems and related signaling pathways and the resulting destruction of the BBB, we suggest that regulating and supplementing the intestinal microbiota as well as targeting immune cells and inflammatory mediators are required to protect the BBB.

A Working Hypothesis Regarding Identical Pathomechanisms between Clinical Efficacy and Adverse Reaction of Clozapine via the Activation of Connexin43

Clozapine (CLZ) is an approved antipsychotic agent for the medication of treatment-resistant schizophrenia but is also well known as one of the most toxic antipsychotics. Recently, the World Health Organization’s (WHO) global database (VigiBase) reported the relative lethality of severe adverse reactions of CLZ. Agranulocytosis is the most famous adverse CLZ reaction but is of lesser lethality compared with the other adverse drug reactions of CLZ. Unexpectedly, VigiBase indicated that the prevalence and relative lethality of pneumonia, cardiotoxicity, and seizures associated with CLZ were more serious than that of agranulocytosis. Therefore, haematological monitoring in CLZ patients monitoring system provided success in the prevention of lethal adverse events from CLZ-induced agranulocytosis. Hereafter, psychiatrists must amend the CLZ patients monitoring system to protect patients with treatment-resistant schizophrenia from severe adverse CLZ reactions, such as pneumonia, cardiotoxicity, and seizures, according to the clinical evidence and pathophysiology. In this review, we discuss the mechanisms of clinical efficacy and the adverse reactions of CLZ based on the accumulating pharmacodynamic findings of CLZ, including tripartite synaptic transmission, and we propose suggestions for amending the monitoring and medication of adverse CLZ reactions associated with pneumonia, cardiotoxicity, and seizures.

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.

Overexpression of HDAC6, but not HDAC3 and HDAC4 in the penumbra after photothrombotic stroke in the rat cerebral cortex and the neuroprotective effects of α-phenyl tropolone, HPOB, and sodium valproate

Epigenetic processes play important roles in brain responses to ischemic injury. We studied effects of photothrombotic stroke (PTS, a model of ischemic stroke) on the intracellular level and cellular localization of histone deacetylases HDAC3, HDAC4 and HDAC6 in the rat brain cortex, and tested the potential neuroprotector ability of their inhibitors. The background level of HDAC3, HDAC4 and HDAC6 in the rat cerebral cortex was relatively low. HDAC3 localized in the nuclei of some neurons and few astrocytes. HDAC4 was found in the neuronal cytoplasm. After PTS, their levels in penumbra did not change, but HDAC4 appeared in the nuclei of some cells. Its level in the cytoplasmic, but not nuclear fraction of penumbra decreased at 24, but not 4 h after PTS. HDAC6 was upregulated in neurons and astrocytes in the PTS-induced penumbra, especially in the nuclear fraction. Unlike HDAC3 and HDAC4, HDAC6 co-localized with TUNEL-positive apoptotic cells. Inhibitory analysis confirmed the involvement of HDAC6, but not HDAC3 and HDAC4 in neurodegeneration. HDAC6 inhibitor HPOB, HDAC2/8 inhibitor α-phenyl tropolone, and non-specific histone deacetylase inhibitor sodium valproate, but not HDAC3 inhibitor BRD3308, or HDAC4 inhibitor LMK235, decreased PTS-induced infarction volume in the mouse brain, reduced apoptosis, and recovered the motor behavior. HPOB also restored PTS-impaired acetylation of α-tubulin. α-phenyl tropolone restored acetylation of histone H4 in penumbra cells. These results suggest that histone deacetylases HDAC6 and HDAC2 are the possible molecular targets for anti-ischemic therapy, and their inhibitors α-phenyl tropolone, HBOP and sodium valproate can be considered as promising neuroprotectors.

The Chemical Biology of Ferroptosis in the Central Nervous System

Over the past five decades, thanatology has come to include the study of how individual cells in our bodies die appropriately and inappropriately in response to physiological and pathological stimuli. Morphological and biochemical criteria have been painstakingly established to create clarity around definitions of distinct types of cell death and mechanisms for their activation. Among these, ferroptosis has emerged as a unique, oxidative stress-induced cell death pathway with implications for diseases as diverse as traumatic brain injury, hemorrhagic stroke, Alzheimer's disease, cancer, renal ischemia, and heat stress in plants. In this review, I highlight some of the formative studies that fostered its recognition in the nervous system and describe how chemical biological tools have been essential in defining events necessary for its execution. Finally, I discuss emerging opportunities for antiferroptotic agents as therapeutic agents in neurological diseases.

Activation of Astroglial Connexin is Involved in Concentration-Dependent Double-Edged Sword Clinical Action of Clozapine

Clozapine (CLZ) is a gold-standard antipsychotic against treatment-refractory schizophrenia, but is one of the most toxic antipsychotic agents. Pharmacological mechanisms of the double-edged sword clinical action of CLZ remain to be clarified. To explore the mechanisms of CLZ, the present study determined the astroglial transmission associated with connexin43 (Cx43), which is the most principal expression in astrocytes and myocardial cells, and expression of Cx43 in primary cultured astrocytes. Both acute and subchronic administrations of CLZ concentration-dependently increased Cx43-associated astroglial release of l-glutamate and d-serine, whereas therapeutic-relevant concentration of CLZ acutely did not affect but subchronically increased astroglial release. In contrast, after the subchronic administration of therapeutic-relevant concentration of valproate (VPA), acute administration of therapeutic-relevant concentration of CLZ drastically increased Cx43-associated astroglial releases. VPA increased Cx43 expression in cytosol fraction without affecting plasma membrane fraction, whereas CLZ increased Cx43 expression in both fractions. Acute administration of therapeutic-relevant concentration of CLZ drastically increased Cx43 expression in the plasma membrane fraction of astrocytes subchronically treated with VPA. The present findings suggest that CLZ-induced the activation of Cx43-associated channel activity and transported Cx43 to plasma membrane, probably contribute to the double-edged sword clinical action of CLZ, such as improvement of cognitive dysfunction and CLZ-induced myocarditis.

Effect of the Histone Deacetylases Inhibitors on the Differentiation of Stem Cells in Bone Damage Repairing and Regeneration

Tissue damage repairing and regeneration is a research hot topic. Tissue engineering arises at the historic moment which is a defect repair compound composed of seed cells, tissue engineering scaffolds, and inducing factors. Stem cells have a limited growth period in vitro culture, and they have a pattern of replicating ageing, and these disadvantages are limiting the applications of stem cells in basic research and clinical treatment. The enhancement of stem cell differentiation ability is a difficult problem to overcome, and it is possible to enhance the differentiation ability of stem cells through histone modification so as to provide a more robust foundation for damage repairing and regeneration. Studies have shown that Histone Deacetylases (HDAC) inhibitors can improve mesenchymal stem cells in vitro induced in different directions, conversion efficiency, increasing the feasibility and safety of stem cell therapy and tissue engineering, to offer reference to promote the stem cell therapy in clinical application. Therefore, this paper mainly focusing on the usage and achievements of the deacetylase inhibitors in stem cell differentiation studies and their use and prospects in repair of bone tissue defects.

Epigenetic Alterations Induced by Photothrombotic Stroke in the Rat Cerebral Cortex: Deacetylation of Histone h3, Upregulation of Histone Deacetylases and Histone Acetyltransferases

Ischemic penumbra that surrounds a stroke-induced infarction core is potentially salvageable; however, mechanisms of its formation are not well known. Covalent modifications of histones control chromatin conformation, gene expression and protein synthesis. To study epigenetic processes in ischemic penumbra, we used photothrombotic stroke (PTS), a stroke model in which laser irradiation of the rat brain cortex photosensitized by Rose Bengal induces local vessel occlusion. Immunoblotting and immunofluorescence microscopy showed decrease in acetylation of lysine 9 in histone H3 in penumbra at 1, 4 or 24 h after PTS. This was associated with upregulation of histone deacetylases HDAC1 and HDAC2, but not HDAC4, which did not localize in the nuclei. HDAC2 was found in cell nuclei, HDAC4 in the cytoplasm and HDAC1 both in nuclei and cytoplasm. Histone acetyltransferases HAT1 and PCAF (p300/CBP associated factor) that acetylated histone H3 synthesis were also upregulated, but lesser and later. PTS increased localization of HDAC2 and HAT1 in astroglia. Thus, the cell fate in PTS-induced penumbra is determined by the balance between opposite tendencies leading either to histone acetylation and stimulation of gene expression, or to deacetylation and suppression of transcriptional processes and protein biosynthesis. These epigenetic proteins may be the potential targets for anti-stroke therapy.

Neuronal susceptibility to beta-amyloid toxicity and ischemic injury involves histone deacetylase-2 regulation of endophilin-B1

Histone deacetylases (HDACs) catalyze acetyl group removal from histone proteins, leading to altered chromatin structure and gene expression. HDAC2 is highly expressed in adult brain, and HDAC2 levels are elevated in Alzheimer's disease (AD) brain. We previously reported that neuron-specific splice isoforms of Endophilin-B1 (Endo-B1) promote neuronal survival, but are reduced in human AD brain and mouse models of AD and stroke. Here, we demonstrate that HDAC2 suppresses Endo-B1 expression. HDAC2 knockdown or knockout enhances expression of Endo-B1. Conversely, HDAC2 overexpression decreases Endo-B1 expression. We also demonstrate that neurons exposed to beta-amyloid increase HDAC2 and reduce histone H3 acetylation while HDAC2 knockdown prevents Aβ induced loss of histone H3 acetylation, mitochondrial dysfunction, caspase-3 activation, and neuronal death. The protective effect of HDAC2 knockdown was abrogated by Endo-B1 shRNA and in Endo-B1-null neurons, suggesting that HDAC2-induced neurotoxicity is mediated through suppression of Endo-B1. HDAC2 overexpression also modulates neuronal expression of mitofusin2 (Mfn2) and mitochondrial fission factor (MFF), recapitulating the pattern of change observed in AD. HDAC2 knockout mice demonstrate reduced injury in the middle cerebral artery occlusion with reperfusion (MCAO/R) model of cerebral ischemia demonstrating enhanced neuronal survival, minimized loss of Endo-B1, and normalized expression of Mfn2. These findings support the hypothesis that HDAC2 represses Endo-B1, sensitizing neurons to mitochondrial dysfunction and cell death in stroke and AD.

Leaky brain in neurological and psychiatric disorders: Drivers and consequences

BACKGROUND

The blood-brain barrier acts as a highly regulated interface; its dysfunction may exacerbate, and perhaps initiate, neurological and neuropsychiatric disorders.

METHODS

In this narrative review, focussing on redox, inflammatory and mitochondrial pathways and their effects on the blood-brain barrier, a model is proposed detailing mechanisms which might explain how increases in blood-brain barrier permeability occur and can be maintained with increasing inflammatory and oxidative and nitrosative stress being the initial drivers.

RESULTS

Peripheral inflammation, which is causatively implicated in the pathogenesis of major psychiatric disorders, is associated with elevated peripheral pro-inflammatory cytokines, which in turn cause increased blood-brain barrier permeability. Reactive oxygen species, such as superoxide radicals and hydrogen peroxide, and reactive nitrogen species, such as nitric oxide and peroxynitrite, play essential roles in normal brain capillary endothelial cell functioning; however, chronically elevated oxidative and nitrosative stress can lead to mitochondrial dysfunction and damage to the blood-brain barrier. Activated microglia, redox control of which is mediated by nitric oxide synthases and nicotinamide adenine dinucleotide phosphate (NADPH) oxidases, secrete neurotoxic molecules such as reactive oxygen species, nitric oxide, prostaglandin, cyclooxygenase-2, quinolinic acid, several chemokines (including monocyte chemoattractant protein-1 [MCP-1], C-X-C motif chemokine ligand 1 [CXCL-1] and macrophage inflammatory protein 1α [MIP-1α]) and the pro-inflammatory cytokines interleukin-6, tumour necrosis factor-α and interleukin-1β, which can exert a detrimental effect on blood-brain barrier integrity and function. Similarly, reactive astrocytes produce neurotoxic molecules such as prostaglandin E2 and pro-inflammatory cytokines, which can cause a 'leaky brain'.

CONCLUSION

Chronic inflammatory and oxidative and nitrosative stress is associated with the development of a 'leaky gut'. The following evidence-based approaches, which address the leaky gut and blood-brain barrier dysfunction, are suggested as potential therapeutic interventions for neurological and neuropsychiatric disorders: melatonin, statins, probiotics containing Bifidobacteria and Lactobacilli, N-acetylcysteine, and prebiotics containing fructo-oligosaccharides and galacto-oligosaccharides.

Valproate is protective against 6-OHDA-induced dopaminergic neurodegeneration in rodent midbrain: A potential role of BDNF up-regulation

BACKGROUND/PURPOSE

The main purpose of this study was to extend previously reported showing potent neuroprotective effect of valproic acid (VPA) in primary midbrain neuro-glial cultures to investigate whether VPA could protect dopamine (DA) neurons in vivo against 6-hydroxydopamine (6-OHDA)-induced neurodegeneration and to determine the underlying mechanism.

METHODS

Male adult rats received a daily intraperitoneal injection of VPA or saline for two weeks before and after injection of 5, 10, or 15 μg of 6-OHDA into the brain. All rats were evaluated for motor function by rotarod performance. Brain samples were prepared for immunohistochemical staining and for determination of levels of dopamine, dopamine metabolites, and neurotrophic factors.

RESULTS

6-OHDA injection showed significant and dose-dependent damage of dopaminergic neurons and decrease of striatal dopamine content. Rats in the VPA-treated group were markedly protected from the loss of dopaminergic neurons and showed improvements in motor performance, compared to the control group at the moderate 6-OHDA dose (10 μg). VPA-treated rats also showed significantly increased brain-derived neurotrophic factor (BDNF) levels in the striatum and substantia nigra compared to the levels in control animals.

CONCLUSION

Our studies demonstrate that VPA exerts neuroprotective effects in a rat model of 6-OHDA-induced Parkinson's disease (PD), likely in part by up-regulation BDNF.

The Role of Astrocytes in Multiple Sclerosis

The role traditionally assigned to astrocytes in the pathogenesis of multiple sclerosis (MS) lesions has been the formation of the glial scar once inflammation has subsided. Astrocytes are now recognized to be early and highly active players during lesion formation and key for providing peripheral immune cells access to the central nervous system. Here, we review the role of astrocytes in the formation and evolution of MS lesions, including the recently described functional polarization of astrocytes, discuss prototypical pathways for astrocyte activation, and summarize mechanisms by which MS treatments affect astrocyte function.

The role of histone deacetylase inhibitors in regulation of Akt/GSK-3β signaling pathway in mice following transient focal cerebral ischemia

PURPOSE

To investigate whether the neuroprotective effect of TSA on cerebral ischemia reperfusion injury is mediated by the activation of Akt/GSK-3β signaling pathway.

METHODS

Mice were randomly divided into four groups (n=15): sham group (S); ischemia reperfusion group (IR); ischemia reperfusion and pretreated with TSA group (IR+T); ischemia reperfusion and pretreated with TSA and LY294002 group (IR+T+L). The model of cerebral ischemia reperfusion was established by 1h of MCAO following 24h of reperfusion. TSA (5mg/kg) was intraperitoneally given for 3 days before MCAO, Akt inhibitor, LY294002 (15 nmol/kg) was injected by tail vein 30 min before the MCAO.

RESULTS

TSA significantly increased the expression of p-Akt, p-GSK-3β proteins and the levels of SOD, Bcl-2, reduced the infarct volume and the levels of MDA, ROS, TNF-α, IL-1β, Bax, Caspase-3, TUNEL and attenuated neurological deficit in mice with transient MCAO, LY294002 weakened such effect of TSA dramatically.

CONCLUSIONS

TSA could significantly decrease the neurological deficit and reduce the cerebral infarct volume, oxidative stress, inflammation, as well as apoptosis during cerebral ischemia reperfusion injury, which was achieved by activation of the Akt/GSK-3β signaling pathway.

Histone acetylation of oligodendrocytes protects against white matter injury induced by inflammation and hypoxia-ischemia through activation of BDNF-TrkB signaling pathway in neonatal rats

The major pathological damage in encephalopathy of prematurity is white matter injury (WMI). Perinatal hypoxic-ischemia (HI) and inflammation are two major risk factors in the development of WMI. To study the cellular and molecular mechanisms of WMI, we set up a WMI model using lipopolysaccharide-sensitized HI injury in 2-day postnatal rats. Immunofluorescence staining was used to measure the expression of acetylated histone H3 (AH3) in oligodendrocytes, the target cells of WMI; the oligodendrocyte protein markers, NG2, O4, MBP, PLP, and MAG, were detected at different developmental stages. 5-bromo-2'-deoxyuridine (BrdU) was used to detect the proliferation of oligodendrocytes. We found that the expression of AH3 was markedly decreased in oligodendrocytes at 7 days after WMI. The differentiation and maturation of oligodendrocytes were inhibited in the WMI group. After inducing histone acetylation in oligodendrocytes by treatment with sodium butyrate, the inhibition of differentiation and maturation of oligodendrocytes was reversed. Furthermore, we found that these protective effects of histone acetylation were associated with the upregulation of brain-derived neurotrophic factor (BDNF) and its receptor, tyrosine kinase B (TrkB). In conclusion, histone acetylation protects oligodendrocytes from WMI through activation of the BDNF-TrkB signaling pathway in immature brains.

Genome-Wide Dynamics of Nascent Noncoding RNA Transcription in Porcine Heart After Myocardial Infarction

Background—

Microarrays and RNA sequencing are widely used to profile transcriptome remodeling during myocardial ischemia. However, the steady-state RNA analysis lacks in sensitivity to detect all noncoding RNA species and does not provide separation between transcriptional and post-transcriptional regulations. Here, we provide the first comprehensive analysis of nascent RNA profiles of mRNAs, primary micro-RNAs, long noncoding RNAs, and enhancer RNAs in a large animal model of acute infarction.

Methods and Results—

Acute infarction was induced by cardiac catheterization of domestic swine. Nuclei isolated from healthy, border zone, and ischemic regions of the affected heart were subjected to global run-on sequencing. Global run-on sequencing analysis indicated that half of affected genes are regulated at the level of transcriptional pausing. A gradient of induction of inflammatory mediators and repression of peroxisome proliferator-activated receptor signaling and oxidative phosphorylation was detected when moving from healthy toward infarcted area. In addition, we interrogated the transcriptional regulation of primary micro-RNAs and provide evidence that several arrhythmia-related target genes exhibit repression at post-transcriptional level. We identified 450 long noncoding RNAs differently regulated by ischemia, including novel conserved long noncoding RNAs expressed in antisense orientation to myocardial transcription factors GATA-binding protein 4, GATA-binding protein 6, and Krüppel-like factor 6. Finally, characterization of enhancers exhibiting differential expression of enhancer RNAs pointed a central role for Krüppel-like factor, MEF2C, ETS, NFY, ATF, E2F2, and NRF1 transcription factors in determining transcriptional responses to ischemia.

Conclusions—

Global run-on sequencing allowed us to follow the gradient of gene expression occurring in the ischemic heart and identify novel noncoding RNAs regulated by oxygen deprivation. These findings highlight potential new targets for diagnosis and treatment of myocardial ischemia.

4-Phenylbutyrate Benefits Traumatic Hemorrhagic Shock in Rats by Attenuating Oxidative Stress, Not by Attenuating Endoplasmic Reticulum Stress

OBJECTIVE

Vascular dysfunction such as vascular hyporeactivity following severe trauma and shock is a major cause of death in injured patients. Oxidative stress and endoplasmic reticulum stress play an important role in vascular dysfunction. The objective of the present study was to determine whether or not 4-phenylbutyrate can improve vascular dysfunction and elicit antishock effects by inhibiting oxidative and endoplasmic reticulum stress.

DESIGN

Prospective, randomized, controlled laboratory experiment.

SETTING

State key laboratory of trauma, burns, and combined injury.

SUBJECTS

Five hundred and fifty-two Sprague-Dawley rats.

INTERVENTIONS

Rats were anesthetized, and a model of traumatic hemorrhagic shock was established by left femur fracture and hemorrhage. The effects of 4-phenylbutyrate (5, 20, 50, 100, 200, and 300 mg/kg) on vascular reactivity, animal survival, hemodynamics, and vital organ function in traumatic hemorrhagic shock rats and cultured vascular smooth muscle cells, and the relationship to oxidative stress and endoplasmic reticulum stress was observed.

MEASUREMENTS AND MAIN RESULTS

Lower doses of 4-phenylbutyrate significantly improved the vascular function, stabilized the hemodynamics, and increased the tissue blood flow and vital organ function in traumatic hemorrhagic shock rats, and markedly improved the survival outcomes. Among all dosages observed in the present study, 20 mg/kg of 4-phenylbutyrate had the best effect. Further results indicated that 4-phenylbutyrate significantly inhibited the oxidative stress, decreased shock-induced oxidative stress index such as the production of reactive oxygen species, increased the antioxidant enzyme levels such as superoxide dismutase, catalase, and glutathione, and improved the mitochondrial function by inhibiting the opening of the mitochondrial permeability transition pore in rat artery and vascular smooth muscle cells. In contrast, 4-phenylbutyrate did not affect the changes of endoplasmic reticulum stress markers following traumatic hemorrhagic shock. Furthermore, 4-phenylbutyrate increased the nuclear levels of nuclear factor-E2-related factor 2, and decreased the nuclear levels of nuclear factor κB in hypoxic vascular smooth muscle cells.

CONCLUSIONS

4-phenylbutyrate has beneficial effects for traumatic hemorrhagic shock including improving animal survival and protecting organ function. These beneficial effects of 4-phenylbutyrate in traumatic hemorrhagic shock result from its vascular function protection via attenuation of the oxidative stress and mitochondrial permeability transition pore opening. Nuclear factor-E2-related factor 2 and nuclear factor-κB may be involved in 4-phenylbutyrate-mediated inhibition of oxidative stress.

4-phenylbutyrate Mitigates Fluoride-Induced Cytotoxicity in ALC Cells

Chronic fluoride over-exposure during pre-eruptive enamel development can cause dental fluorosis. Severe dental fluorosis is characterized by porous, soft enamel that is vulnerable to erosion and decay. The prevalence of dental fluorosis among the population in the USA, India and China is increasing. Other than avoiding excessive intake, treatments to prevent dental fluorosis remain unknown. We previously reported that high-dose fluoride induces endoplasmic reticulum (ER) stress and oxidative stress in ameloblasts. Cell stress induces gene repression, mitochondrial damage and apoptosis. An aromatic fatty acid, 4-phenylbutyrate (4PBA) is a chemical chaperone that interacts with misfolded proteins to prevent ER stress. We hypothesized that 4PBA ameliorates fluoride-induced ER stress in ameloblasts. To determine whether 4PBA protects ameloblasts from fluoride toxicity, we analyzed gene expression of Tgf-β1, Bcl2/Bax ratio and cytochrome-c release in vitro. In vivo, we measured fluorosis levels, enamel hardness and fluoride concentration. Fluoride treated Ameloblast-lineage cells (ALC) had decreased Tgf-β1 expression and this was reversed by 4PBA treatment. The anti-apoptotic Blc2/Bax ratio was significantly increased in ALC cells treated with fluoride/4PBA compared to fluoride treatment alone. Fluoride treatment induced cytochrome-c release from mitochondria into the cytosol and this was inhibited by 4PBA treatment. These results suggest that 4PBA mitigates fluoride-induced gene suppression, apoptosis and mitochondrial damage in vitro. In vivo, C57BL/6J mice were provided fluoridated water for six weeks with either fluoride free control-chow or 4PBA-containing chow (7 g/kg 4PBA). With few exceptions, enamel microhardness, fluorosis levels, and fluoride concentrations of bone and urine did not differ significantly between fluoride treated animals fed with control-chow or 4PBA-chow. Although 4PBA mitigated high-dose fluoride toxicity in vitro, a diet rich in 4PBA did not attenuate dental fluorosis in rodents. Perhaps, not enough intact 4PBA reaches the rodent ameloblasts necessary to reverse the effects of fluoride toxicity. Further studies will be required to optimize protocols for 4PBA administration in vivo in order to evaluate the effect of 4PBA on dental fluorosis.

Loss of GCN5 leads to increased neuronal apoptosis by upregulating E2F1- and Egr-1-dependent BH3-only protein Bim

Cellular acetylation homeostasis is a kinetic balance precisely controlled by histone acetyl-transferase (HAT) and histone deacetylase (HDAC) activities. The loss of the counterbalancing function of basal HAT activity alters the precious HAT:HDAC balance towards enhanced histone deacetylation, resulting in a loss of acetylation homeostasis, which is closely associated with neuronal apoptosis. However, the critical HAT member whose activity loss contributes to neuronal apoptosis remains to be identified. In this study, we found that inactivation of GCN5 by either pharmacological inhibitors, such as CPTH2 and MB-3, or by inactivation with siRNAs leads to a typical apoptosis in cultured cerebellar granule neurons. Mechanistically, the BH3-only protein Bim is transcriptionally upregulated by activated Egr-1 and E2F1 and mediates apoptosis following GCN5 inhibition. Furthermore, in the activity withdrawal- or glutamate-evoked neuronal apoptosis models, GCN5 loses its activity, in contrast to Bim induction. Adenovirus-mediated overexpression of GCN5 suppresses Bim induction and apoptosis. Interestingly, the loss of GCN5 activity and the induction of Egr-1, E2F1 and Bim are involved in the early brain injury (EBI) following subarachnoid haemorrhage (SAH) in rats. HDAC inhibition not only significantly rescues Bim expression and apoptosis induced by either potassium deprivation or GCN5 inactivation but also ameliorates these events and EBI in SAH rats. Taken together, our results highlight a new mechanism by which the loss of GCN5 activity promotes neuronal apoptosis through the transcriptional upregulation of Bim, which is probably a critical event in triggering neuronal death when cellular acetylation homeostasis is impaired.