Histone Deacetylase Inhibitor Alleviates the Neurodegenerative Phenotypes and Histone Dysregulation in Presenilins-Deficient Mice

Exploring environmental exposomes and the gut-brain nexus: Unveiling the impact of pesticide exposure

This review delves into the escalating concern of environmental pollutants and their profound impact on human health in the context of the modern surge in global diseases. The utilisation of chemicals in food production, which results in residues in food, has emerged as a major concern nowadays. By exploring the intricate relationship between environmental pollutants and gut microbiota, the study reveals a dynamic bidirectional interplay, as modifying microbiota profile influences metabolic pathways and subsequent brain functions. This review will first provide an overview of potential exposomes and their effect to gut health. This paper is then emphasis the connection of gut brain function by analysing microbiome markers with neurotoxicity responses. We then take pesticide as example of exposome to elucidate their influence to biomarkers biosynthesis pathways and subsequent brain functions. The interconnection between neuroendocrine and neuromodulators elements and the gut-brain axis emerges as a pivotal factor in regulating mental health and brain development. Thus, manipulation of gut microbiota function at the onset of stress may offer a potential avenue for the prevention and treatment for mental disorder and other neurodegenerative illness.

Short-chain fatty acids: Important components of the gut-brain axis against AD

Alzheimer's disease (AD) comprises a group of neurodegenerative disorders with some changes in the brain, which could lead to the deposition of certain proteins and result in the degeneration and death of brain cells. Patients with AD manifest primarily as cognitive decline, psychiatric symptoms, and behavioural disorders. Short-chain fatty acids (SCFAs) are a class of saturated fatty acids (SFAs) produced by gut microorganisms through the fermentation of dietary fibre ingested. SCFAs, as a significant mediator of signalling, can have diverse physiological and pathological roles in the brain through the gut-brain axis, and play a positive effect on AD via multiple pathways. Firstly, differences in SCFAs and microbial changes have been stated in AD cases of humans and mice in this paper. And then, mechanisms of three main SCFAs in treating with AD have been summarized, as well as differences of gut bacteria. Finally, functions of SCFAs played in regulating intestinal flora homeostasis, modulating the immune system, and the metabolic system, which were considered to be beneficial for the treatment of AD, have been elucidated, and the key roles of gut bacteria and SCFAs were pointed out. All in all, this paper provides an overview of SCFAs and gut bacteria in AD, and can help people to understand the importance of gut-brain axis in AD.

Histone deacetylase-3 regulates the expression of the amyloid precursor protein and its inhibition promotes neuroregenerative pathways in Alzheimer's disease models

HDAC3 inhibition has been shown to improve memory and reduce amyloid-β (Aβ) in Alzheimer's disease (AD) models, but the underlying mechanisms are unclear. We investigated the molecular effects of HDAC3 inhibition on AD pathology, using in vitro and ex vivo models of AD, based on our finding that HDAC3 expression is increased in AD brains. For this purpose, N2a mouse neuroblastoma cells as well as organotypic brain cultures (OBCSs) of 5XFAD and wild-type mice were incubated with various concentrations of the HDAC3 selective inhibitor RGFP966 (0.1-10 μM) for 24 h. Treatment with RGFP966 or HDAC3 knockdown in N2a cells was associated with an increase on amyloid precursor protein (APP) and mRNA expressions, without alterations in Aβ42 secretion. In vitro chromatin immunoprecipitation analysis revealed enriched HDAC3 binding at APP promoter regions. The increase in APP expression was also detected in OBCSs from 5XFAD mice incubated with 1 μM RGFP966, without changes in Aβ. In addition, HDAC3 inhibition resulted in a reduction of activated Iba-1-positive microglia and astrocytes in 5XFAD slices, which was not observed in OBCSs from wild-type mice. mRNA sequencing analysis revealed that HDAC3 inhibition modulated neuronal regenerative pathways related to neurogenesis, differentiation, axonogenesis, and dendritic spine density in OBCSs. Our findings highlight the complexity and diversity of the effects of HDAC3 inhibition on AD models and suggest that HDAC3 may have multiple roles in the regulation of APP expression and processing, as well as in the modulation of neuroinflammatory and neuroprotective genes.

Microbiota-Gut-Brain Axis Dysregulation in Alzheimer's Disease: Multi-Pathway Effects and Therapeutic Potential

An essential regulator of neurodegenerative conditions like Alzheimer's disease (AD) is the gut microbiota. Alterations in intestinal permeability brought on by gut microbiota dysregulation encourage neuroinflammation, central immune dysregulation, and peripheral immunological dysregulation in AD, as well as hasten aberrant protein aggregation and neuronal death in the brain. However, it is unclear how the gut microbiota transmits information to the brain and how it influences brain cognition and function. In this review, we summarized the multiple pathways involved in the gut microbiome in AD and provided detailed treatment strategies based on the gut microbiome. Based on these observations, this review also discusses the problems, challenges, and strategies to address current therapeutic strategies.

Increasing histone acetylation improves sociability and restores learning and memory in KAT6B-haploinsufficient mice

Mutations in genes encoding chromatin modifiers are enriched among mutations causing intellectual disability. The continuing development of the brain postnatally, coupled with the inherent reversibility of chromatin modifications, may afford an opportunity for therapeutic intervention following a genetic diagnosis. Development of treatments requires an understanding of protein function and models of the disease. Here, we provide a mouse model of Say-Barber-Biesecker-Young-Simpson syndrome (SBBYSS) (OMIM 603736) and demonstrate proof-of-principle efficacy of postnatal treatment. SBBYSS results from heterozygous mutations in the KAT6B (MYST4/MORF/QFK) gene and is characterized by intellectual disability and autism-like behaviors. Using human cells carrying SBBYSS-specific KAT6B mutations and Kat6b heterozygous mice (Kat6b+/-), we showed that KAT6B deficiency caused a reduction in histone H3 lysine 9 acetylation. Kat6b+/- mice displayed learning, memory, and social deficits, mirroring SBBYSS individuals. Treatment with a histone deacetylase inhibitor, valproic acid, or an acetyl donor, acetyl-carnitine (ALCAR), elevated histone acetylation levels in the human cells with SBBYSS mutations and in brain and blood cells of Kat6b+/- mice and partially reversed gene expression changes in Kat6b+/- cortical neurons. Both compounds improved sociability in Kat6b+/- mice, and ALCAR treatment restored learning and memory. These data suggest that a subset of SBBYSS individuals may benefit from postnatal therapeutic interventions.

Unlocking the epigenetic symphony: histone acetylation's impact on neurobehavioral change in neurodegenerative disorders

Recent genomics and epigenetic advances have empowered the exploration of DNA/RNA methylation and histone modifications crucial for gene expression in response to stress, aging and disease. Interest in understanding neuronal plasticity's epigenetic mechanisms, influencing brain rewiring amid development, aging and neurodegenerative disorders, continues to grow. Histone acetylation dysregulation, a commonality in diverse brain disorders, has become a therapeutic focus. Histone acetyltransferases and histone deacetylases have emerged as promising targets for neurodegenerative disorder treatment. This review delves into histone acetylation regulation, potential therapies and future perspectives for disorders like Alzheimer's, Parkinson's and Huntington's. Exploring genetic-environmental interplay through models and studies reveals molecular changes, behavioral insights and early intervention possibilities targeting the epigenome in at-risk individuals.

Post-translational protein lactylation modification in health and diseases: a double-edged sword

As more is learned about lactate, it acts as both a product and a substrate and functions as a shuttle system between different cell populations to provide the energy for sustaining tumor growth and proliferation. Recent discoveries of protein lactylation modification mediated by lactate play an increasingly significant role in human health (e.g., neural and osteogenic differentiation and maturation) and diseases (e.g., tumors, fibrosis and inflammation, etc.). These views are critically significant and first described in detail in this review. Hence, here, we focused on a new target, protein lactylation, which may be a "double-edged sword" of human health and diseases. The main purpose of this review was to describe how protein lactylation acts in multiple physiological and pathological processes and their potential mechanisms through an in-depth summary of preclinical in vitro and in vivo studies. Our work aims to provide new ideas for treating different diseases and accelerate translation from bench to bedside.

Early changes of fecal short-chain fatty acid levels in patients with mild cognitive impairments

AIMS

To compare the fecal levels of short-chain fatty acids (SCFAs) in patients with mild cognitive impairment (MCI) and normal controls (NCs) and to examine whether fecal SCFAs could be used as the biomarker for the identification of patients with MCI. To examine the relationship between fecal SCFAs and amyloid-β (Aβ) deposition in the brain.

METHODS

A cohort of 32 MCI patients, 23 Parkinson's disease (PD) patients, and 27 NC were recruited in our study. Fecal levels of SCFAs were measured using chromatography and mass spectrometry. Disease duration, ApoE genotype, body mass index, constipation, and diabetes were evaluated. To assess cognitive impairment, we used the Mini-Mental Status Examination (MMSE). To assess brain atrophy, the degree of medial temporal atrophy (MTA score, Grade 0-4) was measured by structural MRI. Aβ positron emission tomography with 18 F-florbetapir (FBP) was performed in seven MCI patients at the time of stool sampling and in 28 MCI patients at an average of 12.3 ± 0.4 months from the time of stool sampling to detect and quantify Aβ deposition in the brain.

RESULTS

Compared with NC, MCI patients had significantly lower fecal levels of acetic acid, butyric acid, and caproic acid. Among fecal SCFAs, acetic acid performed the best in discriminating MCI from NC, achieved an AUC of 0.752 (p = 0.001, 95% CI: 0.628-0.876), specificity of 66.7%, and sensitivity of 75%. By combining fecal levels of acetic acid, butyric acid, and caproic acid, the diagnostic specificity was significantly improved, reaching 88.9%. To better verify the diagnostic performance of SCFAs, we randomly assigned 60% of participants into training dataset and 40% into testing dataset. Only acetic acid showed significantly difference between these two groups in the training dataset. Based on the fecal levels of acetic acid, we achieved the ROC curve. Next, the ROC curve was evaluated in the independent test data and 61.5% (8 in 13) of patients with MCI, and 72.7% (8 in 11) of NC could be identified correctly. Subgroup analysis showed that reduced fecal SCFAs in MCI group were negatively associated with Aβ deposition in cognition-related brain regions.

CONCLUSION

Reductions in fecal SCFAs were observed in patients with MCI compared with NC. Reduced fecal SCFAs were negatively associated with Aβ deposition in cognition-related brain regions in MCI group. Our findings suggest that gut metabolite SCFAs have the potential to serve as early diagnostic biomarkers for distinguishing patients with MCI from NC and could serve as potential targets for preventing AD.

Reduction of class I histone deacetylases ameliorates ER-mitochondria cross-talk in Alzheimer's disease

Several molecular mechanisms have been described in Alzheimer's disease (AD), including repressed gene transcription and mitochondrial and endoplasmic reticulum (ER) dysfunction. In this study, we evaluate the potential efficacy of transcriptional modifications exerted by inhibition or knockdown of class I histone deacetylases (HDACs) in ameliorating ER-mitochondria cross-talk in AD models. Data show increased HDAC3 protein levels and decreased acetyl-H3 in AD human cortex, and increased HDAC2-3 in MCI peripheral human cells, HT22 mouse hippocampal cells exposed to Aβ1-42 oligomers (AβO) and APP/PS1 mouse hippocampus. Tacedinaline (Tac, a selective class I HDAC inhibitor) counteracted the increase in ER-Ca2+ retention and mitochondrial Ca2+ accumulation, mitochondrial depolarization and impaired ER-mitochondria cross-talk, as observed in 3xTg-AD mouse hippocampal neurons and AβO-exposed HT22 cells. We further demonstrated diminished mRNA levels of proteins involved in mitochondrial-associated ER membranes (MAM) in cells exposed to AβO upon Tac treatment, along with reduction in ER-mitochondria contacts (MERCS) length. HDAC2 silencing reduced ER-mitochondria Ca2+ transfer and mitochondrial Ca2+ retention, while knockdown of HDAC3 decreased ER-Ca2+ accumulation in AβO-treated cells. APP/PS1 mice treated with Tac (30 mg/kg/day) also showed regulation of mRNA levels of MAM-related proteins, and reduced Aβ levels. These data demonstrate that Tac normalizes Ca2+ signaling between mitochondria and ER, involving the tethering between the two organelles in AD hippocampal neural cells. Tac-mediated AD amelioration occurs through the regulation of protein expression at MAM, as observed in AD cells and animal models. Data support transcriptional regulation of ER-mitochondria communication as a promising target for innovative therapeutics in AD.

Epigenetic effects of short-chain fatty acids from the large intestine on host cells

Adult humans harbor at least as many microbial cells as eukaryotic ones. The largest compartment of this diverse microbial population, the gut microbiota, encompasses the collection of bacteria, archaea, viruses, and eukaryotic organisms that populate the gastrointestinal tract, and represents a complex and dynamic ecosystem that has been increasingly implicated in health and disease. The gut microbiota carries ∼100-to-150-times more genes than the human genome and is intimately involved in development, homeostasis, and disease. Of the several microbial metabolites that have been studied, short-chain fatty acids emerge as a group of molecules that shape gene expression in several types of eukaryotic cells by multiple mechanisms, which include DNA methylation changes, histone post-translational modifications, and microRNA-mediated gene silencing. Butyric acid, one of the most extensively studied short-chain fatty acids, reaches higher concentrations in the colonic lumen, where it provides a source of energy for healthy colonocytes, and its concentrations decrease towards the bottom of the colonic crypts, where stem cells reside. The lower butyric acid concentration in the colonic crypts allows undifferentiated cells, such as stem cells, to progress through the cell cycle, pointing towards the importance of the crypts in providing them with a protective niche. In cancerous colonocytes, which metabolize relatively little butyric acid and mostly rely on glycolysis, butyric acid preferentially acts as a histone deacetylase inhibitor, leading to decreased cell proliferation and increased apoptosis. A better understanding of the interface between the gut microbiota metabolites and epigenetic changes in eukaryotic cells promises to unravel in more detail processes that occur physiologically and as part of disease, help develop novel biomarkers, and identify new therapeutic modalities.

Transcriptome Profiling of Hippocampus After Cerebral Hypoperfusion in Mice

Chronic cerebral hypoperfusion (CCH) is considered to be one of the major mechanism in the pathogenesis of vascular cognitive impairment (VCI). Increased inflammatory cells, particularly microglia, often parallel hypoperfusion-induced gray matter damage such as hippocampal lesions, but the exact mechanism remains largely unknown. To understand the pathological mechanisms, we analyzed hippocampus-specific transcriptome profiles after cerebral hypoperfusion. The mouse hypoperfusion model was induced by employing the 0.16/0.18 mm bilateral common carotid artery stenosis (BCAS) procedure. Cerebral blood flow (CBF) was assessed after 3-week hypoperfusion. Pathological changes were evaluated via hematoxylin staining and immunofluorescence staining. RNA-sequencing (RNA-seq) was performed using RNA samples of sham- or BCAS-operated mice, followed by quantitative real-time PCR (qRT-PCR) validation. We found that the 0.16/0.18 mm BCAS induced decreased CBF, hippocampal neuronal loss, and microglial activation. Furthermore, GSEA between sham and BCAS mice showed activation of interferon-beta signaling along with inflammatory immune responses. In addition, integrative analysis with published single-cell RNA-seq revealed that up-regulated differentially expressed genes (DEGs) were enriched in a distinct cell type of "microglia," and down-regulated DEGs were enriched in "CA1 pyramidal," not in "interneurons" or "S1 pyramidal." This database of transcriptomic profiles of BCAS-hypoperfusion will be useful for future studies to explore potential targets for vascular cognitive dysfunction.

Short-Chain Fatty Acids in the Microbiota-Gut-Brain Axis: Role in Neurodegenerative Disorders and Viral Infections

The gut-brain axis (GBA) is the umbrella term to include all bidirectional communication between the brain and gastrointestinal (GI) tract in the mammalian body. Evidence from over two centuries describes a significant role of GI microbiome in health and disease states of the host organism. Short-chain fatty acids (SCFAs), mainly acetate, butyrate, and propionate that are the physiological forms of acetic acid, butyric acid, and propionic acid respectively, are GI bacteria derived metabolites. SCFAs have been reported to influence cellular function in multiple neurodegenerative diseases (NDDs). In addition, the inflammation modulating properties of SCFAs make them suitable therapeutic candidates in neuroinflammatory conditions. This review provides a historical background of the GBA and current knowledge of the GI microbiome and role of individual SCFAs in central nervous system (CNS) disorders. Recently, a few reports have also identified the effects of GI metabolites in the case of viral infections. Among these viruses, the flaviviridae family is associated with neuroinflammation and deterioration of CNS functions. In this context, we additionally introduce SCFA based mechanisms in different viral pathogenesis to understand the former's potential as agents against flaviviral disease.

Cortex-specific transcriptome profiling reveals upregulation of interferon-regulated genes after deeper cerebral hypoperfusion in mice

Background: Chronic cerebral hypoperfusion (CCH) is commonly accompanied by brain injury and glial activation. In addition to white matter lesions, the intensity of CCH greatly affects the degree of gray matter damage. However, little is understood about the underlying molecular mechanisms related to cortical lesions and glial activation following hypoperfusion. Efforts to investigate the relationship between neuropathological alternations and gene expression changes support a role for identifying novel molecular pathways by transcriptomic mechanisms.

Methods: Chronic cerebral ischemic injury model was induced by the bilateral carotid artery stenosis (BCAS) using 0.16/0.18 mm microcoils. Cerebral blood flow (CBF) was evaluated using laser speckle contrast imaging (LSCI) system. Spatial learning and memory were assessed by Morris water maze test. Histological changes were evaluated by Hematoxylin staining. Microglial activation and neuronal loss were further examined by immunofluorescence staining. Cortex-specific gene expression profiling analysis was performed in sham and BCAS mice, and then validated by quantitative RT-PCR and immunohistochemistry (IHC).

Results: In our study, compared with the sham group, the right hemisphere CBF of BCAS mice decreased to 69% and the cognitive function became impaired at 4 weeks postoperation. Besides, the BCAS mice displayed profound gray matter damage, including atrophy and thinning of the cortex, accompanied by neuronal loss and increased activated microglia. Gene set enrichment analysis (GSEA) revealed that hypoperfusion-induced upregulated genes were significantly enriched in the pathways of interferon (IFN)-regulated signaling along with neuroinflammation signaling. Ingenuity pathway analysis (IPA) predicted the importance of type I IFN signaling in regulating the CCH gene network. The obtained RNA-seq data were validated by qRT-PCR in cerebral cortex, showing consistency with the RNA-seq results. Also, IHC staining revealed elevated expression of IFN-inducible protein in cerebral cortex following BCAS-hypoperfusion.

Conclusion: Overall, the activation of IFN-mediated signaling enhanced our understanding of the neuroimmune responses induced by CCH. The upregulation of IFN-regulated genes (IRGs) might exert a critical impact on the progression of cerebral hypoperfusion. Our improved understanding of cortex-specific transcriptional profiles will be helpful to explore potential targets for CCH.

Leptin differentially regulate cell apoptosis and cycle by histone acetylation in tibial and vertebral epiphyseal plates

Leptin showed different apoptosis regulation effects on the chondrocytes from tibial and vertebral epiphyseal plates. However, the mechanism is still unclear. In this study, we tested the protein profile of tibial and vertebral epiphyseal plate chondrocytes with and without leptin stimulation by mass spectrometry and found that the histone acetylation level of tibial chondrocytes was decreased after leptin treatment, while increased in vertebral epiphyseal plates. COIP assay showed that leptin promoted H3, H4 histone acetylation by recruiting CREB binding protein (CBP)/P300 to activate histone acetyl transferases (HATs) activity in vertebral disc chondrocytes. But in tibial plate cartilage cells, leptin did not recruit CBP and p300, thus differently affect the apoptosis of epiphyseal plate chondrocytes. Through explored the mechanism of histone acetylation modulated by leptin, and its effect on cartilage cell apoptosis and cell cycle regulation, This provides a novel target therapy possibility therapeutic approach to for the related disease.

A mechanistic perspective on the health promoting effects of alcohol - A focus on epigenetics modification

While the detrimental effects of binge drinking are well recognized, low-to-moderate alcohol consumption may be beneficial to health, although the underlying mechanism(s) remains elusive. In this opinion article, we will examine the effects of low dose alcohol consumption from the perspective of epigenetic modulation. Biochemically, alcohol is metabolized into acetate and subsequently to acetyl-coA, which can modulate histone acetylation levels. While elevated levels of acetyl-CoA are detrimental for longevity, we argue that diminished acetyl-CoA also negatively affects fatty acid biosynthesis and histone acetylation, which play a critical role in gene expression and, ultimately, health span. Since mitochondrial function and glucose metabolism, which provide the main source of nucleocytoplasmic acetyl-CoA, are compromised with age, alcohol-derived acetate could be an alternative source of acetyl-CoA to compensate. Hence, the health benefits of low ethanol consumption may be more pronounced after midlife, since mitochondrial function and/or glucose metabolism are diminished in this phase of the life course. Indeed, various clinical alcohol consumption studies concur with this notion, and have shown that a low dose of regular alcohol intake after midlife brings about various health and survival benefits. The requirement for regular alcohol intake may also reflect the transient nature of ethanol-induced histone acetylation. Conversely, ethanol may also stimulate carcinogenesis by inhibiting DNA methylation, as it was shown to reduce various pathways leading to DNA and histone methylation. However, unlike acetylation, where ethanol directly increases the substrate for acetylation, this effect was only observed in the high alcohol exposure cohort. While alcohol-derived acetate may be beneficial for health after midlife, various detrimental effects of alcohol consumption remain, and hence, we do not advocate excessive drinking to increase acetate. This opinion article establishes a possible role of ethanol-derived acetate in achieving homeostasis and sustaining an organism's health span.

Caloric restriction induced epigenetic effects on aging

Aging is the subject of many studies, facilitating the discovery of many interventions. Epigenetic influences numerous life processes by regulating gene expression and also plays a crucial role in aging regulation. Increasing data suggests that dietary changes can alter epigenetic marks associated with aging. Caloric restriction (CR)is considered an intervention to regulate aging and prolong life span. At present, CR has made some progress by regulating signaling pathways associated with aging as well as the mechanism of action of intercellular signaling molecules against aging. In this review, we will focus on autophagy and epigenetic modifications to elaborate the molecular mechanisms by which CR delays aging by triggering autophagy, epigenetic modifications, and the interaction between the two in caloric restriction. In order to provide new ideas for the study of the mechanism of aging and delaying aging.

Spatiotemporal patterns of gliosis and neuroinflammation in presenilin 1/2 conditional double knockout mice

Increasing evidence indicates that neuroinflammation contributes to and exacerbates the pathogenesis of Alzheimer’s disease (AD). Neuroinflammation is thought to be primarily driven by glial cells (microglia and astrocytes) and escalates with neurodegenerative progression in AD. However, the spatiotemporal change patterns of glial reactivity and neuroinflammatory response during different stages of neurodegeneration, especially early in disease, remain unknown. Here we found that gliosis and the up-regulation of substantial neuroinflammatory genes were primarily initiated in the cortex of presenilin 1/2 conditional double knockout (cDKO) mice, rather than in the hippocampus. Specifically, astrocyte activation preceding microglial activation was found in the somatosensory cortex (SS) of cDKO mice at 6 weeks of age. Over time, both astrocyte and microglial activation were found in the whole cortex, and age-related increases in gliosis activation were more pronounced in the cortex compared to hippocampus. Moreover, the age-associated increase in glial activation was accompanied by a gradual increase in the expression of cell chemokines Ccl3 and Ccl4, complement related factors C1qb, C3 and C4, and lysosomal proteases cathepsin S and Z. These findings suggest that astrocyte and microglial activation with a concurrent increase in inflammatory mediators such as chemokines might be an early event and contribute to the pathogenesis of neurodegeneration due to presenilin deficiency.

Mechanisms of Short-Chain Fatty Acids Derived from Gut Microbiota in Alzheimer's Disease

Short-chain fatty acids (SCFAs) are important metabolites derived from the gut microbiota through fermentation of dietary fiber. SCFAs participate a number of physiological and pathological processes in the human body, such as host metabolism, immune regulation, appetite regulation. Recent studies on gut-brain interaction have shown that SCFAs are important mediators of gut-brain interactions and are involved in the occurrence and development of many neurodegenerative diseases, including Alzheimer's disease. This review summarizes the current research on the potential roles and mechanisms of SCFAs in AD. First, we introduce the metabolic distribution, specific receptors and signaling pathways of SCFAs in human body. The concentration levels of SCFAs in AD patient/animal models are then summarized. In addition, we illustrate the effects and mechanisms of SCFAs on the cognitive level, pathological features (Aβ and tau) and neuroinflammation in AD. Finally, we analyze the translational value of SCFAs as potential therapeutic targets for the treatment of AD.

Chasing a Breath of Fresh Air in Cystic Fibrosis (CF): Therapeutic Potential of Selective HDAC6 Inhibitors to Tackle Multiple Pathways in CF Pathophysiology

Compelling new support has been provided for histone deacetylase isoform 6 (HDAC6) as a common thread in the generation of the dysregulated proinflammatory and fibrotic phenotype in cystic fibrosis (CF). HDAC6 also plays a crucial role in bacterial clearance or killing as a direct consequence of its effects on CF immune responses. Inhibiting HDAC6 functions thus eventually represents an innovative and effective strategy to tackle multiple aspects of CF-associated lung disease. In this Perspective, we not only showcase the latest evidence linking HDAC(6) activity and expression with CF phenotype but also track the new dawn of HDAC(6) modulators in CF and explore potentialities and future perspectives in the field.

Fecal Calprotectin in Parkinson's Disease and Multiple System Atrophy

Objective

Converging evidence suggests that intestinal inflammation is involved in the pathogenesis of neurodegenerative diseases. Previous studies on fecal calprotectin in Parkinson’s disease (PD) were limited by small sample sizes, and literature regarding intestinal inflammation in multiple system atrophy (MSA) is very scarce. We investigated the levels of fecal calprotectin, a marker of intestinal inflammation, in PD and MSA.

Methods

We recruited 169 subjects (71 PD, 38 MSA, and 60 age-similar nonneurological controls). Clinico-demographic data were collected. PD and MSA were subtyped and the severity assessed using the MDS-UPDRS and UMSARS, respectively. Fecal calprotectin and blood immune markers were analyzed.

Results

Compared to controls (median: 35.7 [IQR: 114.2] μg/g), fecal calprotectin was significantly elevated in PD (median: 95.6 [IQR: 162.1] μg/g, p = 0.003) and even higher in MSA (median: 129.5 [IQR: 373.8] μg/g, p = 0.002). A significant interaction effect with age was observed; between-group differences were significant only in older subjects (i.e., ≥ 61 years) and became more apparent with increasing age. A total of 28.9% of MSA and 18.3% of PD patients had highly abnormal fecal calprotectin levels (≥ 250 μg/g); however, this difference was only significant for MSA compared to controls. Fecal calprotectin correlated moderately with selected blood immune markers in PD, but not with clinical features of PD or MSA.

Conclusions

Elevated fecal calprotectin suggests a role for intestinal inflammation in PD and MSA. A more complete understanding of gut immune alterations could open up new avenues of research and treatment for these debilitating diseases.

Noncognitive species-typical and home-cage behavioral alterations in conditional presenilin 1/presenilin 2 double knockout mice

Impairments in activities of daily living (ADL) are common clinical symptoms of human Alzheimer's disease (AD). Describing the ADL in AD animal models might provide more insights into the mechanism/treatment of the disease. Here, we demonstrated that the forebrain presenilin 1(Psen1)/presenilin 2 (Psen2) conditional double knockout (DKO) mice exhibited deficits in nest building, marble burying and food burrowing starting at 3 months old and worsening at later ages. At 4 months of age, spontaneous activities in the home cage were also impaired in DKO mice, including physically demanding activities, habituation-like behaviors, and nourishment behaviors during the first two hours in the dark phase. These results indicated that loss of function of Psen1 and Psen2 in mice impaired a series of noncognitive behaviors in the early phase of neurodegeneration. This observation suggests that DKO mice are an ideal model for further mechanistic studies of Psen1 and Psen2 functions in regulating noncognitive behaviors.

Selective expression of the neurexin substrate for presenilin in the adult forebrain causes deficits in associative memory and presynaptic plasticity

Presenilins (PS) form the active subunit of the gamma-secretase complex, which mediates the proteolytic clearance of a broad variety of type-I plasma membrane proteins. Loss-of-function mutations in PSEN1/2 genes are the leading cause of familial Alzheimer's disease (fAD). However, the PS/gamma-secretase substrates relevant for the neuronal deficits associated with a loss of PS function are not completely known. The members of the neurexin (Nrxn) family of presynaptic plasma membrane proteins are candidates to mediate aspects of the synaptic and memory deficits associated with a loss of PS function. Previous work has shown that fAD-linked PS mutants or inactivation of PS by genetic and pharmacological approaches failed to clear Nrxn C-terminal fragments (NrxnCTF), leading to its abnormal accumulation at presynaptic terminals. Here, we generated transgenic mice that selectively recreate the presynaptic accumulation of NrxnCTF in adult forebrain neurons, leaving unaltered the function of PS/gamma-secretase complex towards other substrates. Behavioral characterization identified selective impairments in NrxnCTF mice, including decreased fear-conditioning memory. Electrophysiological recordings in medial prefrontal cortex-basolateral amygdala (mPFC-BLA) of behaving mice showed normal synaptic transmission and uncovered specific defects in synaptic facilitation. These data functionally link the accumulation of NrxnCTF with defects in associative memory and short-term synaptic plasticity, pointing at impaired clearance of NrxnCTF as a new mediator in AD.

Effects of exercise and pharmacological inhibition of histone deacetylases (HDACs) on epigenetic regulations and gene expressions crucial for neuronal plasticity in the motor cortex

The objective of this study was to examine the effect of epigenetic treatment using an histone deacetylases (HDAC) inhibitor in addition to aerobic exercise on the epigenetic markers and neurotrophic gene expressions in the motor cortex, to find a more enriched brain pre-conditioning for motor learning in neurorehabilitation. ICR mice were divided into four groups based on two factors: HDAC inhibition and exercise. Intraperitoneal administration of an HDAC inhibitor (1.2 g/kg sodium butyrate, NaB) and treadmill exercise (approximately at 10 m/min for 60 min) were conducted five days a week for four weeks. NaB administration inhibited total HDAC activity and enhanced acetylation level of histones specifically in histone H4, accompanying the increase of transcription levels of immediate-early genes (IEGs) (c-fos and Arc) and neurotrophins (BDNF and NT-4) crucial for neuroplasticity in the motor cortex. However, exercise enhanced HDAC activity and acetylation level of histone H4 and H3 without the modification of transcription levels. In addition, there were no synergic effects between HDAC inhibition and the exercise regime on the gene expressions. This study showed that HDAC inhibition could present more enriched condition for neuroplasticity to the motor cortex. However, exercise-induced neurotrophic gene expressions could depend on exercise regimen based on the intensity, the term etc. Therefore, this study has a novelty suggesting that pharmacological HDAC inhibition could be an alternative potent approach to present a neuronal platform with enriched neuroplasticity for motor learning and motor recovery, however, an appropriate exercise regimen is expected in this approach.

Cognitive epigenetic priming: leveraging histone acetylation for memory amelioration

Multiple studies have found that increasing histone acetylation by means of histone deacetylase inhibitor (HDACi) treatment can ameliorate memory and rescue cognitive impairments, but their mode of action is not fully understood. In particular, it is unclear how HDACis, applied systemically and devoid of genomic target selectivity, would specifically improve memory-related molecular processes. One theory for such specificity is called cognitive epigenetic priming (CEP), according to which HDACis promote memory by facilitating the expression of neuroplasticity-related genes that have been stimulated by learning itself. In this review, we summarize the experimental evidence in support of CEP, describe newly discovered off-target effects of HDACis and highlight similarities between drug-induced and naturally occurring CEP. Understanding the underlying mechanisms of CEP is important in light of the preclinical premise of HDACis as cognitive enhancers.

The ageing epigenome and its rejuvenation

Ageing is characterized by the functional decline of tissues and organs and the increased risk of ageing-associated disorders. Several 'rejuvenating' interventions have been proposed to delay ageing and the onset of age-associated decline and disease to extend healthspan and lifespan. These interventions include metabolic manipulation, partial reprogramming, heterochronic parabiosis, pharmaceutical administration and senescent cell ablation. As the ageing process is associated with altered epigenetic mechanisms of gene regulation, such as DNA methylation, histone modification and chromatin remodelling, and non-coding RNAs, the manipulation of these mechanisms is central to the effectiveness of age-delaying interventions. This Review discusses the epigenetic changes that occur during ageing and the rapidly increasing knowledge of how these epigenetic mechanisms have an effect on healthspan and lifespan extension, and outlines questions to guide future research on interventions to rejuvenate the epigenome and delay ageing processes.

The Hyperactivity-Impulsivity-Irritiability-Disinhibition-Aggression-Agitation Domain in Alzheimer's Disease: Current Management and Future Directions

Behavioral and psychological symptoms of dementia (BPSD) afflict the vast majority of patients with dementia, especially those with Alzheimer's disease (AD). In clinical settings, patients with BPSD most often do not present with just one symptom. Rather, clusters of symptoms commonly co-occur and can, thus, be grouped into behavioral domains that may ultimately be the result of disruptions in overarching neural circuits. One major BPSD domain routinely identified across patients with AD is the hyperactivity-impulsivity-irritiability-disinhibition-aggression-agitation (HIDA) domain. The HIDA domain represents one of the most difficult sets of symptoms to manage in AD and accounts for much of the burden for caregivers and hospital staff. Although many studies recommend non-pharmacological treatments for HIDA domain symptoms as first-line, they demonstrate little consensus as to what these treatments should be and are often difficult to implement clinically. Certain symptoms within the HIDA domain also do not respond adequately to these treatments, putting patients at risk and necessitating adjunct pharmacological intervention. In this review, we summarize the current literature regarding non-pharmacological and pharmacological interventions for the HIDA domain and provide suggestions for improving treatment. As epigenetic changes due to both aging and AD cause dysfunction in drug-targeted receptors, we propose that HIDA domain treatments could be enhanced by adjunct strategies that modify these epigenetic alterations and, thus, increase efficacy and reduce side effects. To improve the implementation of non-pharmacological approaches in clinical settings, we suggest that issues regarding inadequate resources and guidance for implementation should be addressed. Finally, we propose that increased monitoring of symptom and treatment progression via novel sensor technology and the "DICE" (describe, investigate, create, and evaluate) approach may enhance both pharmacological and non-pharmacological interventions for the HIDA domain.

3D cellular reconstruction of cortical glia and parenchymal morphometric analysis from Serial Block-Face Electron Microscopy of juvenile rat

With the rapid evolution in the automation of serial electron microscopy in life sciences, the acquisition of terabyte-sized datasets is becoming increasingly common. High resolution serial block-face imaging (SBEM) of biological tissues offers the opportunity to segment and reconstruct nanoscale structures to reveal spatial features previously inaccessible with simple, single section, two-dimensional images. In particular, we focussed here on glial cells, whose reconstruction efforts in literature are still limited, compared to neurons. We imaged a 750,000 cubic micron volume of the somatosensory cortex from a juvenile P14 rat, with 20 nm accuracy. We recognized a total of 186 cells using their nuclei, and classified them as neuronal or glial based on features of the soma and the processes. We reconstructed for the first time 4 almost complete astrocytes and neurons, 4 complete microglia and 4 complete pericytes, including their intracellular mitochondria, 186 nuclei and 213 myelinated axons. We then performed quantitative analysis on the three-dimensional models. Out of the data that we generated, we observed that neurons have larger nuclei, which correlated with their lesser density, and that astrocytes and pericytes have a higher surface to volume ratio, compared to other cell types. All reconstructed morphologies represent an important resource for computational neuroscientists, as morphological quantitative information can be inferred, to tune simulations that take into account the spatial compartmentalization of the different cell types.

Epigenetics of the Synapse in Neurodegeneration

PURPOSE OF REVIEW

In the quest for understanding the pathophysiological processes underlying degeneration of nervous systems, synapses are emerging as sites of great interest as synaptic dysfunction is thought to play a role in the initiation and progression of neuronal loss. In particular, the synapse is an interesting target for the effects of epigenetic mechanisms in neurodegeneration. Here, we review the recent advances on epigenetic mechanisms driving synaptic compromise in major neurodegenerative disorders.

RECENT FINDINGS

Major developments in sequencing technologies enabled the mapping of transcriptomic patterns in human postmortem brain tissues in various neurodegenerative diseases, and also in cell and animal models. These studies helped identify changes in classical neurodegeneration pathways and discover novel targets related to synaptic degeneration. Identifying epigenetic patterns indicative of synaptic defects prior to neuronal degeneration may provide the basis for future breakthroughs in the field of neurodegeneration.

Regulation of Chemokines and Cytokines by Histone Deacetylases and an Update on Histone Decetylase Inhibitors in Human Diseases

Histone acetyltransferases (HATs) and histone deacetylases (HDACs) counteract with each other to regulate gene expression by altering chromatin structure. Aberrant HDAC activity was reported in many human diseases including wide range of cancers, viral infections, cardiovascular complications, auto-immune diseases and kidney diseases. HDAC inhibitors are small molecules designed to block the malignant activity of HDACs. Chemokines and cytokines control inflammation, immunological and other key biological processes and are shown to be involved in various malignancies. Various HDACs and HDAC inhibitors were reported to regulate chemokines and cytokines. Even though HDAC inhibitors have remarkable anti-tumor activity in hematological cancers, they are not effective in treating many diseases and many patients relapse after treatment. However, the role of HDACs and cytokines in regulating these diseases still remain unclear. Therefore, understanding exact mechanisms and effector functions of HDACs are urgently needed to selectively inhibit them and to establish better a platform to combat various malignancies. In this review, we address regulation of chemokines and cytokines by HDACs and HDAC inhibitors and update on HDAC inhibitors in human diseases.