HDAC1 Regulates Neuronal Differentiation

Histone Deacetylases in Metabolism: the Known and the Unexplored

Histone deacetylases (HDACs) are enzymes that catalyze the removal of acetyl groups from key lysine residues on histone and nonhistone proteins and thereby regulate gene transcription. They have been implicated in several biological processes in both healthy and pathological settings. This review discusses the role of HDACs in multiple metabolically active tissues and highlights their contribution to the pathogenesis of tissue-specific maladaptation and diseases. We also summarize the current knowledge gaps and potential ways to address them in future studies.

HDAC1 Promotes Hippocampal Neuronal Pyroptosis in Epileptic Mice Through the miR-15a-5p/Caspase-1 Axis

Status epilepticus (SE) is a life-threatening disorder associated with neuronal pyroptosis. This study aims to explore the mechanism of HDAC1 in hippocampal neuronal pyroptosis induced by kainic acid in mice, providing a theoretical basis for SE treatment. A mouse model of SE was established by kainic acid. After sh-HDAC1 injection, the severity of SE and hippocampal neuronal damage were assessed. Cell model was established using kainic acid-induced HT22, followed by detection of HDAC1, miR-15a-5p, Caspase-1, cleaved Caspase-1, H3K9ac, and GSDMD-N using qRT-PCR and Western blot assays. Levels of IL-1β, IL-18, and LDH were measured. The enrichment of HDAC1 on the miR-15a-5p promoter was detected. The binding of miR-15a-5p to Caspase-1 was validated. We found that HDAC1 was highly expressed in kainic acid-induced SE. HDAC1 knockdown alleviated the symptoms of SE, inhibited cleaved Caspase-1, GSDMD-N, IL-1β, and IL-18, and suppressed hippocampal neuronal pyroptosis. HDAC1 bound to the miR-15a-5p promoter and reduced H3K9ac, thereby inhibiting miR-15a-5p expression. miR-15a-5p bound to Caspase-1 and inhibited Caspase-1 expression. Inhibiting miR-15a-5p or overexpressing Caspase-1 partially reversed the inhibitory effect of si-HDAC1 on kainic acid-induced cell pyroptosis. In conclusion, HDAC1 aggravates hippocampal neuronal pyroptosis in SE via the miR-15a-5p/Caspase-1 axis through deacetylation of H3K9.

Maternal immune activation imprints translational dysregulation and differential MAP2 phosphorylation in descendant neural stem cells

Alterations induced by maternal immune activation (MIA) during gestation impact the subsequent neurodevelopment of progeny, a process that in humans, has been linked to the development of several neuropsychiatric conditions. To undertake a comprehensive examination of the molecular mechanisms governing MIA, we have devised an in vitro model based on neural stem cells (NSCs) sourced from fetuses carried by animals subjected to Poly I:C treatment. These neural progenitors demonstrate proliferative capacity and can be effectively differentiated into both neurons and glial cells. Transcriptomic, proteomic, and phosphoproteomic analyses conducted on these cellular models, in conjunction with counterparts from control treatments, revealed discernible shifts in the expression levels of a specific subset of proteins implicated in neuronal function. Furthermore, the phosphoproteomic data highlighted a discernible discrepancy in the basal phosphorylation of proteins between differentiated cells from both experimental groups, particularly within proteins associated with cytoskeletal architecture and synaptic functionality, notably those belonging to the MAP family. Observed alterations in MAP phosphorylation were found to potentially have functional consequences as they correlate with changes in neuronal plasticity and the establishment of neuronal synapses. Our data agrees with previous published observations and further underscore the importance of MAP2 phosphorylation state on its function and the impact that this protein has in neuronal structure and function.

Induction of neuronal differentiation in glioma cells by histone deacetylase inhibitors based on Connectivity Map discovery

Neuron conversion leads to proliferation inhibition of glioma cells and may be an effective strategy to combat glioma and prevent recurrence. In this study, drug repositioning based on Connectivity Map (CMap) was conducted to discover drugs that could induce the differentiation of glioma cells into neuron-like cells, complemented by in vitro experimental validation. Downregulated neuronal genes in glioma were identified by the Human Protein Atlas database and the GeneCards database, and enrichment analysis and Gene Expression Profiling Interactive Analysis (GEPIA) were performed to ensure their reliability before they were uploaded to CMap for drug screening. The potential drug targets were screened through GEPIA and validated by the Chinese Glioma Genome Atlas database. Cell morphology, proliferation, and neuronal marker expression were detected to evaluate the differentiation-inducing effect of the selected drugs. The bioinformatics analysis identified histone deacetylase (HDAC) inhibitors as potential drugs. HDAC1/3/7 showed the relationship with neuronal genes, and HDAC1 showed the highest level of inverse correlation with neuronal gene expression and had the highest hazard ratio. In vitro study showed that both the pan-HDAC inhibitor belinostat, class I and class IIa HDAC inhibitor valproic acid, and selective HDAC1 inhibitor parthenolide induce morphology alteration, proliferation inhibition, expression of neuronal markers including microtubule-associated protein 2, neuronal nuclei antigen, and synaptophysin in U87 cells. This study suggests that the HDAC inhibitors belinostat, valproic acid, and parthenolide can induce glioma cells to differentiate into neuron-like cells, with HDAC1/3/7 being the likely drug targets and HDAC1 potentially playing an important role in this.

BET activity plays an essential role in control of stem cell attributes in Xenopus

Neural crest cells are a stem cell population unique to vertebrate embryos that retains broad multi-germ layer developmental potential through neurulation. Much remains to be learned about the genetic and epigenetic mechanisms that control the potency of neural crest cells. Here, we examine the role that epigenetic readers of the BET (bromodomain and extra terminal) family play in controlling the potential of pluripotent blastula and neural crest cells. We find that inhibiting BET activity leads to loss of pluripotency at blastula stages and a loss of neural crest at neurula stages. We compare the effects of HDAC (an eraser of acetylation marks) and BET (a reader of acetylation) inhibition and find that they lead to similar cellular outcomes through distinct effects on the transcriptome. Interestingly, loss of BET activity in cells undergoing lineage restriction is coupled to increased expression of genes linked to pluripotency and prolongs the competence of initially pluripotent cells to transit to a neural progenitor state. Together these findings advance our understanding of the epigenetic control of pluripotency and the formation of the vertebrate neural crest.

Influence of the brain‑gut axis on neuroinflammation in cerebral ischemia‑reperfusion injury (Review)

Stroke, a debilitating cerebrovascular ailment, poses significant threats to human life and health. The intricate interplay between the gut‑brain‑microbiota axis (GBMA) and cerebral ischemia‑reperfusion has increasingly become a focal point of scientific exploration, emerging as a pivotal research avenue in stroke pathophysiology. In the present review, the authors delved into the nexus between the GBMA and neuroinflammation observed post‑stroke. The analysis underscored the pivotal roles of histone deacetylase 3 and neutrophil extracellular traps subsequent to stroke incidents. The influence of gut microbial compositions and their metabolites, notably short‑chain fatty acids and trimethylamine N‑oxide, on neuroinflammatory processes, was further elucidated. The involvement of immune cells, especially regulatory T‑cells, and the intricate signaling cascades including cyclic GMP‑AMP synthase/stimulator of interferon genes/Toll‑like receptor, further emphasized the complex regulatory mechanisms of GBMA in cerebral ischemia/reperfusion injury (CI/RI). Collectively, the present review offered a comprehensive perspective on the metabolic, immune and inflammatory modulations orchestrated by GBMA, augmenting the understanding of its role in neuroinflammation following CI/RI.

Emerging Neuroprotective Strategies: Unraveling the Potential of HDAC Inhibitors in Traumatic Brain Injury Management

Traumatic brain injury (TBI) is a significant global health problem, leading to high rates of mortality and disability. It occurs when an external force damages the brain, causing immediate harm and triggering further pathological processes that exacerbate the condition. Despite its widespread impact, the underlying mechanisms of TBI remain poorly understood, and there are no specific pharmacological treatments available. This creates an urgent need for new, effective neuroprotective drugs and strategies tailored to the diverse needs of TBI patients. In the realm of gene expression regulation, chromatin acetylation plays a pivotal role. This process is controlled by two classes of enzymes: histone acetyltransferase (HAT) and histone deacetylase (HDAC). These enzymes modify lysine residues on histone proteins, thereby determining the acetylation status of chromatin. HDACs, in particular, are involved in the epigenetic regulation of gene expression in TBI. Recent research has highlighted the potential of HDAC inhibitors (HDACIs) as promising neuroprotective agents. These compounds have shown encouraging results in animal models of various neurodegenerative diseases. HDACIs offer multiple avenues for TBI management: they mitigate the neuroinflammatory response, alleviate oxidative stress, inhibit neuronal apoptosis, and promote neurogenesis and axonal regeneration. Additionally, they reduce glial activation, which is associated with TBI-induced neuroinflammation. This review aims to provide a comprehensive overview of the roles and mechanisms of HDACs in TBI and to evaluate the therapeutic potential of HDACIs. By summarizing current knowledge and emphasizing the neuroregenerative capabilities of HDACIs, this review seeks to advance TBI management and contribute to the development of targeted treatments.

Sub-Chronic Aluminum Exposure in Rats' Learning-Memory Capability and Hippocampal Histone H4 Acetylation Modification: Effects and Mechanisms

Aluminum has been found to be closely related to the pathogenesis of neurodegenerative diseases and damage learning and memory functions. Many changes in epigenetics may be one of the mechanisms of aluminum neurotoxicity. The purpose of this study is to further investigate the mechanism of action of sub-chronic aluminum exposure on learning memory and histone H4 acetylation modification in Wistar rats, and the correlation between learning memory impairment and histone H4 acetylation in aluminum-exposed rats. Rats in each dose group were given 0.0 g/L, 2.0 g/L, 4.0 g/L, and 8.0 g/L of AlCl3 distilled water daily for 12 weeks. The learning and memory ability of rats was measured by the Morris water maze test; the neuronal morphology of rat hippocampus was observed by Nissl staining and transmission electron microscope; real-time PCR, and Western blot were used to detect mRNA expression and protein content in hippocampus of rats. The results suggest that aluminum may affect the gene and protein expression of HAT1 and HDAC2, and then affect histone H4 and the acetylation of H4K12 (acH4K12), which may lead to learning and memory dysfunction in rats.

5-Methylcytosine and 5-Hydroxymethylcytosine in Scrapie-Infected Sheep and Mouse Brain Tissues

Scrapie is a neurodegenerative disorder belonging to the group of transmissible spongiform encephalopathies or prion diseases, which are caused by an infectious isoform of the innocuous cellular prion protein (PrP^C) known as PrP^Sc. DNA methylation, one of the most studied epigenetic mechanisms, is essential for the proper functioning of the central nervous system. Recent findings point to possible involvement of DNA methylation in the pathogenesis of prion diseases, but there is still a lack of knowledge about the behavior of this epigenetic mechanism in such neurodegenerative disorders. Here, we evaluated by immunohistochemistry the 5-methylcytosine (5mC) and 5-hydroxymethylcytosine (5hmC) levels in sheep and mouse brain tissues infected with scrapie. Expression analysis of different gene coding for epigenetic regulatory enzymes (DNMT1, DNMT3A, DNMT3B, HDAC1, HDAC2, TET1, and TET2) was also carried out. A decrease in 5mC levels was observed in scrapie-affected sheep and mice compared to healthy animals, whereas 5hmC displayed opposite patterns between the two models, demonstrating a decrease in 5hmC in scrapie-infected sheep and an increase in preclinical mice. 5mC correlated with prion-related lesions in mice and sheep, but 5hmC was associated with prion lesions only in sheep. Differences in the expression changes of epigenetic regulatory genes were found between both disease models, being differentially expressed Dnmt3b, Hdac1, and Tet1 in mice and HDAC2 in sheep. Our results support the evidence that DNA methylation in both forms, 5mC and 5hmC, and its associated epigenetic enzymes, take part in the neurodegenerative course of prion diseases.

The role of histone modifications: from neurodevelopment to neurodiseases

Epigenetic regulatory mechanisms, including DNA methylation, histone modification, chromatin remodeling, and microRNA expression, play critical roles in cell differentiation and organ development through spatial and temporal gene regulation. Neurogenesis is a sophisticated and complex process by which neural stem cells differentiate into specialized brain cell types at specific times and regions of the brain. A growing body of evidence suggests that epigenetic mechanisms, such as histone modifications, allow the fine-tuning and coordination of spatiotemporal gene expressions during neurogenesis. Aberrant histone modifications contribute to the development of neurodegenerative and neuropsychiatric diseases. Herein, recent progress in understanding histone modifications in regulating embryonic and adult neurogenesis is comprehensively reviewed. The histone modifications implicated in neurodegenerative and neuropsychiatric diseases are also covered, and future directions in this area are provided.