Co-location of HDAC2 and insulin signaling components in the adult mouse hippocampus

Modulation of the Inflammatory Response in Polycystic Ovary Syndrome (PCOS)-Searching for Epigenetic Factors

Polycystic ovary syndrome (PCOS) is the most common endocrine disorder in women of reproductive age. Despite its incidence, the syndrome is poorly understood and remains underdiagnosed, and female patients are diagnosed with a delay. The heterogenous nature of this complex disorder results from the combined occurrence of genetic, environmental, endocrine, and behavioral factors. Primary clinical manifestations of PCOS are derived from the excess of androgens (anovulation, polycystic ovary morphology, lack of or scanty, irregular menstrual periods, acne and hirsutism), whereas the secondary manifestations include multiple metabolic, cardiovascular, and psychological disorders. Dietary and lifestyle factors play important roles in the development and course of PCOS, which suggests strong epigenetic and environmental influences. Many studies have shown a strong association between PCOS and chronic, low-grade inflammation both in the ovarian tissue and throughout the body. In the vast majority of PCOS patients, elevated values of inflammatory markers or their gene markers have been reported. Development of the vicious cycle of the chronic inflammatory state in PCOS is additionally stimulated by hyperinsulinemia and obesity. Changes in DNA methylation, histone acetylation and noncoding RNA levels are presented in this review in the context of oxidative stress, reactive oxygen species, and inflammatory signaling in PCOS. Epigenetic modulation of androgenic activity in response to inflammatory signaling is also discussed.

Effects of dexmedetomidine on cognitive dysfunction and neuroinflammation via the HDAC2/HIF-1α/PFKFB3 axis in a murine model of postoperative cognitive dysfunction

Inhibition of histone deacetylase (HDAC) may be a useful approach in the treatment of disorders characterized by cognitive dysfunction. Dexmedetomidine (DEX), an α2-adrenoceptor (α2-AR) agonist, has demonstrated neuroprotective effects. Here, we attempted to investigate the protective effects of DEX on postoperative cognitive dysfunction (POCD) involving HDAC2. Male C57BL/6 mice were selected to develop a POCD model, where HDAC2, HIF-1α, and PFKFB3 expression was quantified. DEX was administered before POCD modeling. Then the cognitive function of POCD mice was evaluated with the open field and Y-maze tests. Meanwhile, lipopolysaccharide (LPS) was employed to induce BV-2 microglial cells to simulate the inflammatory response. The contents of TNF-α, IL-6, and IL-10 were measured by enzyme-linked immunosorbent assay (ELISA) in mouse serum and BV-2 cell supernatant. Abundant expression of HDAC2, HIF-1α, and PFKFB3 was confirmed in POCD mice (p < 0.05). Cognitive dysfunction in POCD mice could be alleviated following pharmacological inhibition of HDAC2 by FK228 (p < 0.05). Mechanistically, HDAC2 upregulated HIF-1α and PFKFB3 and promoted the secretion of inflammatory factors in LPS-exposed BV-2 cells (p < 0.05). DEX attenuated neuroinflammation and the resulting cognitive dysfunction by decreasing HDAC2 expression and HIF-1α-dependent PFKFB3 upregulation in POCD mice (p < 0.05). In conclusion, DEX-regulated HDAC2 may play an inhibitory role in mice with POCD through regulation of the HIF-1α/PFKFB3 axis.

Targeting Insulin-Like Growth Factor-I in Management of Neurological Disorders

The degradation of neurons marks as the pathological reason for onset of most of the neurological diseases although the functional deficiencies and symptoms may vary. Insulin-like growth factor-I (IGF-I) boosts regeneration of both motor and sensory neurons and thus presents as a potential treatment in management of neurological disorders. IGF-I is a pleiotropic agent which stimulates the survival and outgrowth of neurons accompanied by their motility as well as myelination by glial cells. This hormone has been found to possess neuroprotective properties which is in association with its antioxidant and mitochondrial protection activity. Studying and exploring the signaling pathways which mediate pleotropic responses intracellularly have elucidated significant therapeutic approach in treatment and management of neurological disorders by IGF-I. The current review highlights the role of IGF-I in management of major neurological disorders such as depression, Parkinson's disease, and Alzheimer's disease and also covers the mechanisms involved in the process.

The Role of Glucagon-Like Peptide-1 Receptor Agonists (GLP-1 RA) in Diabetes-Related Neurodegenerative Diseases

Recent clinical guidelines have emphasized the importance of screening for cognitive impairment in older adults with diabetes, however, there is still a lack of understanding about the drug therapy. Glucagon-like peptide 1 receptor agonists (GLP-1 RAs) are widely used in the treatment of type 2 diabetes and potential applications may include the treatment of obesity as well as the adjunctive treatment of type 1 diabetes mellitus in combination with insulin. Growing evidence suggests that GLP-1 RA has the potential to treat neurodegenerative diseases, particularly in diabetes-related Alzheimer’s disease (AD) and Parkinson’s disease (PD). Here, we review the molecular mechanisms of the neuroprotective effects of GLP-1 RA in diabetes-related degenerative diseases, including AD and PD, and their potential effects.

Maternal Separation-Induced Histone Acetylation Correlates with BDNF-Programmed Synaptic Changes in an Animal Model of PTSD with Sex Differences

Maternal separation (MS) causes long-lasting epigenetic changes in the brain and increases vulnerability to traumatic events in adulthood. Of interest, there may be sex-specific differences in these epigenetic changes. In this study, the extent of histone acetylation in the hippocampus (HIP) and the expression of BDNF were measured to determine whether BDNF influences risk of PTSD following MS in early life. Rat offspring were separated from their dams (3 h/day or 6 h/day from PND2~PND14). Then, pups were treated with a single prolonged stress (SPS) procedure when they reached adulthood (PND80). In animals stressed with the SPS procedure in adulthood, those that had increased MS intensity in childhood demonstrated more significant changes in performance on tests of anxiety, depression, and contextual fear memory. Reduced levels of total BDNF mRNA and protein were observed after SPS treatment and further declined in groups with greater MS time in childhood. Interestingly, these changes were correlated with decreased H3K9ac levels and increased HDAC2 levels. Additional MS also led to more severe ultrastructural synaptic damage in rats that experienced the SPS procedure, particularly in the CA1 and CA3 region of the HIP, reflecting impaired synaptic plasticity in these regions. Interestingly, male rats in the MS3h-PTSD group showed decreased anxiety, but no similar changes were found in female rats, suggesting a degree of gender specificity in coping with stress after mild MS. In summary, this study suggests that the epigenetic signatures of the BDNF genes can be linked to HIP responses to stress, providing insights that may be relevant for people at risk of stress-related psychopathologies.

Regulatory Roles of Histone Deacetylases 1 and 2 in Pb-induced Neurotoxicity

Lead (Pb) prevails among the environmental hazards against human health. Although increasing evidence highlights the epigenetic roles underlying the Pb-induced neurotoxicity, the exact mechanisms concerning histone acetylation and its causative agents are still at its infancy. In the present study, the roles of histone deacetylases 1 and 2 (HDAC1/2), as well as acetylation of Lys9 on histone H3 (Ac-H3K9), in Pb-induced neurotoxicity were investigated. Pb was administered to PC12 cells at 10 μM for 24 h. And Sprague Dawley rats were chronically exposed to Pb through drinking water containing 250 ppm Pb for 2 months. Owing to Pb exposure, it indicated that HDAC2 was up-regulated accompanied by Ac-H3K9 down-regulation. Meanwhile, chromatin immunoprecipitation assay revealed that the changes in HDAC2 were attributed to histone H3 Lys27 trimethylation occupancy on its promoter. Blockade of HDAC2 with either Trichostatin A or HDAC2-knocking down construct (shHDAC2) resulted in amelioration of neurite outgrowth deficits via increasing Ac-H3K9 levels. It implied that HDAC2 plays essential regulatory roles in Pb-induced neurotoxicity. And, coimmunoprecipitation trials revealed that HDAC2 colocalized with HDAC1, forming a so-called HDAC1/2 complex. Subsequently, it was shown that HDAC1/2 repression could markedly prevent neurite outgrowth impairment and rescue the spatial memory deficits caused by Pb exposure, unequivocally implicating this complex in the studied toxicological process. Furthermore, Notch2 maybe the functional target of the HDAC1/2 and Ac-H3K9 alterations. Our study provided insight into the precise roles of HDAC1/2 in Pb-induced neurotoxicity, and thereby provided a promising molecular target for medical intervention of neurological disorders with environmental etiology.

The development prospection of HDAC inhibitors as a potential therapeutic direction in Alzheimer's disease

Alzheimer’s disease (AD) is a chronic neurodegenerative disease, which is associated with learning and memory impairment in the elderly. Recent studies have found that treating AD in the way of chromatin remodeling via histone acetylation is a promising therapeutic regimen. In a number of recent studies, inhibitors of histone deacetylase (HDACs) have been found to be a novel promising therapeutic agents for neurological disorders, particularly for AD and other neurodegenerative diseases. Although HDAC inhibitors have the ability to ameliorate cognitive impairment, successful treatments in the classic AD animal model are rarely translated into clinical trials. As for the reduction of unwanted side effects, the development of HDAC inhibitors with increased isoform selectivity or seeking other directions is a key issue that needs to be addressed. The review focused on literatures on epigenetic mechanisms in recent years, especially on histone acetylation in terms of the enhancement of specificity, efficacy and avoiding side effects for treating AD.

Histone deacetylase-2 is involved in stress-induced cognitive impairment via histone deacetylation and PI3K/AKT signaling pathway modification

Exposure to chronic stress upregulates blood glucocorticoid levels and impairs cognition via diverse epigenetic mechanisms, such as histone deacetylation. Histone deacetylation can lead to transcriptional silencing of many proteins involved in cognition and may also cause learning and memory dysfunction. Histone deacetylase-2 (HDAC2) has been demonstrated to epigenetically block cognition via a reduction in the histone acetylation level; however, it is unknown whether HDAC2 is involved in the cognitive decline induced by chronic stress. To the best of authors' knowledge, this is the first study to demonstrate that the stress hormone corticosteroid upregulate HDAC2 protein levels in neuro-2a cells and cause cell injuries. HDAC2 knockdown resulted in a significant amelioration of the pathological changes in N2a cells via the upregulation of histone acetylation and modifications in the phosphoinositide 3-kinase/protein kinase B signaling pathway. In addition, the HDAC2 protein levels were upregulated in 12-month-old female C57BL/6J mice under chronic stress in vivo. Taken together, these findings suggested that HDAC2 may be an important negative regulator involved in chronic stress-induced cognitive impairment.

Natural Selection and Functional Potentials of Human Noncoding Elements Revealed by Analysis of Next Generation Sequencing Data

Noncoding DNA sequences (NCS) have attracted much attention recently due to their functional potentials. Here we attempted to reveal the functional roles of noncoding sequences from the point of view of natural selection that typically indicates the functional potentials of certain genomic elements. We analyzed nearly 37 million single nucleotide polymorphisms (SNPs) of Phase I data of the 1000 Genomes Project. We estimated a series of key parameters of population genetics and molecular evolution to characterize sequence variations of the noncoding genome within and between populations, and identified the natural selection footprints in NCS in worldwide human populations. Our results showed that purifying selection is prevalent and there is substantial constraint of variations in NCS, while positive selectionis more likely to be specific to some particular genomic regions and regional populations. Intriguingly, we observed larger fraction of non-conserved NCS variants with lower derived allele frequency in the genome, indicating possible functional gain of non-conserved NCS. Notably, NCS elements are enriched for potentially functional markers such as eQTLs, TF motif, and DNase I footprints in the genome. More interestingly, some NCS variants associated with diseases such as Alzheimer's disease, Type 1 diabetes, and immune-related bowel disorder (IBD) showed signatures of positive selection, although the majority of NCS variants, reported as risk alleles by genome-wide association studies, showed signatures of negative selection. Our analyses provided compelling evidence of natural selection forces on noncoding sequences in the human genome and advanced our understanding of their functional potentials that play important roles in disease etiology and human evolution.

Spatiotemporal expression of HDAC2 during the postnatal development of the rat hippocampus

BACKGROUND

Histone acetylation, which is a chromatin modification of histone tails, can dynamically regulate the expression of various genes in normal development. HDAC2 is a negative regulatory factor of acetylation and closely related to learning and memory. NSE is a nerve marker and vital for maintaining physiological functions in nervous system. Currently, few studies associated with the expression pattern of HDAC2 in postnatal rat hippocampus have been reported. This study aimed to explore the temporal and spatial expression pattern of HDAC2, helping to reveal the expression characteristics of HDAC2 during postnatal neuronal maturation.

MATERIALS AND METHODS

With NSE as a biomarker of neuronal maturation at postnatal days 1, 3, 7 and weeks 2, 4, and 8 (P1D, P3D, P7D, P2W, P4W, P8W), the expression patterns of HDAC2 in rat hippocampus were examined using real-time PCR and western blotting. Additionally, the subcellular distribution of HDAC2 was analysed by immunofluorescence.

RESULTS

We found that HDAC2 was highly expressed in the neonatal period and decreased gradually. HDAC2 expression was widely distributed in neurons of hippocampal CA1, CA3 and DG regions and gradually shifted from the nucleus to the cytoplasm during postnatal development. Altogether, the expression of HDAC2 decreased gradually with different subcellular localizations throughout development.

CONCLUSIONS

The observed results indicate that the expression levels of HDAC2 become lower and with different subcellular localizations in neurons during hippocampal neuronal maturation, suggesting the specific expression characteristics of HDAC2 might play an important role during postnatal learning-memory function and development.

Folate and epigenetic mechanisms in neural tube development and defects

INTRODUCTION

Multiple genetic and epigenetic factors involved in central nervous system (CNS) development influence the incidence of neural tube defects (NTDs).

DISCUSSION

The beneficial effect of periconceptional folic acid on NTD prevention denotes a vital role for the single-carbon biochemical pathway in NTD genesis. Indeed, NTDs are associated with polymorphisms in a diversity of genes that encode folate pathway enzymes. Recent evidence suggests that CNS development and function, and consequently NTDs, are also associated with epigenetic mechanisms, many of which participate in the folate cycle and its input and output pathways. We provide an overview with select examples drawn from the authors' research.