Cdk5 and aberrant cell cycle activation at the core of neurodegeneration

OSMR is a potential driver of inflammation in amyotrophic lateral sclerosis

JOURNAL/nrgr/04.03/01300535-202419110-00031/figure1/v/2024-03-08T184507Z/r/image-tiff Amyotrophic lateral sclerosis is a neurodegenerative disease, and the molecular mechanism underlying its pathology remains poorly understood. However, inflammation is known to play an important role in the development of this condition. To identify driver genes that affect the inflammatory response in amyotrophic lateral sclerosis, as well as potential treatment targets, it is crucial to analyze brain tissue samples from patients with both sporadic amyotrophic lateral sclerosis and C9orf72-related amyotrophic lateral sclerosis. Therefore, in this study we used a network-driven gene analysis tool, NetBID2.0, which is based on SJARACNe, a scalable algorithm for the reconstruction of accurate cellular networks, to experimentally analyze sequencing data from patients with sporadic amyotrophic lateral sclerosis. The results showed that the OSMR gene is pathogenic in amyotrophic lateral sclerosis and participates in the progression of amyotrophic lateral sclerosis by mediating the neuroinflammatory response. Furthermore, there were differences in OSMR activity and expression between patients with sporadic amyotrophic lateral sclerosis and those with C9orf72-related amyotrophic lateral sclerosis. These findings suggest that OSMR may be a diagnostic and prognostic marker for amyotrophic lateral sclerosis.

CDK5 as a therapeutic tool for the treatment of Alzheimer's disease: A review

Alzheimer's disease (AD) remains one of the most challenging and prevalent neurodegenerative disorders worldwide. Despite extensive research efforts, effective treatments for AD are lacking, emphasising the need for a deeper understanding of its underlying molecular mechanisms. Cyclin-dependent kinase 5 (CDK5), a serine/threonine kinase primarily associated with cell cycle regulation and neuronal development, has emerged as a key player in AD pathology. This review article comprehensively explores the multifaceted roles of CDK5 in the pathogenesis of AD. We begin by elucidating the physiological functions of CDK5 in normal brain development and neuronal maintenance, highlighting its involvement in synaptic plasticity, neurotransmitter release, and cytoskeletal dynamics. Subsequently, we delve into the dysregulation of CDK5 activity observed in AD, encompassing aberrant hyperactivation, and dysregulated protein interactions. Moreover, we discuss the intricate interplay between CDK5 and AD-related proteins, including amyloid-beta precursor protein (APP) and tau protein, elucidating their collective impact on disease progression. Finally, we described various approaches available for the inhibition of CDK-5, which can be explored as future therapeutic intervention for AD. Through synthesizing evidence from in vitro studies, animal models, and clinical investigations, this review provides a comprehensive overview of the intricate relationship between CDK5 dysregulation and AD pathogenesis, offering insights that may inform future therapeutic interventions strategies.

Antineoplastics for treating Alzheimer's disease and dementia: Evidence from preclinical and observational studies

As the world population ages, there will be an increasing need for effective therapies for aging-associated neurodegenerative disorders, which remain untreatable. Dementia due to Alzheimer's disease (AD) is one of the leading neurological diseases in the aging population. Current therapeutic approaches to treat this disorder are solely symptomatic, making the need for new molecular entities acting on the causes of the disease extremely urgent. One of the potential solutions is to use compounds that are already in the market. The structures have known pharmacokinetics, pharmacodynamics, toxicity profiles, and patient data available in several countries. Several drugs have been used successfully to treat diseases different from their original purposes, such as autoimmunity and peripheral inflammation. Herein, we divulge the repurposing of drugs in the area of neurodegenerative diseases, focusing on the therapeutic potential of antineoplastics to treat dementia due to AD and dementia. We briefly touch upon the shared pathological mechanism between AD and cancer and drug repurposing strategies, with a focus on artificial intelligence. Next, we bring out the current status of research on the development of drugs, provide supporting evidence from retrospective, clinical, and preclinical studies on antineoplastic use, and bring in new areas, such as repurposing drugs for the prion-like spreading of pathologies in treating AD.

De Novo Rational Design of Peptide-Based Protein-Protein Inhibitors (Pep-PPIs) Approach by Mapping the Interaction Motifs of the PP Interface and Physicochemical Filtration: A Case on p25-Cdk5-Mediated Neurodegenerative Diseases

Protein-protein interactions, or PPIs, are a part of every biological activity and have been linked to a number of diseases, including cancer, infectious diseases, and neurological disorders. As such, targeting PPIs is considered a strategic and vital approach in the development of new medications. Nonetheless, the wide and flat contact interface makes it difficult to find small-molecule PP inhibitors. An alternative strategy would be to use the PPI interaction motifs as building blocks for the design of peptide-based inhibitors. Herein, we designed 12-mer peptide inhibitors to target p25-inducing-cyclin-dependent kinase (Cdk5) hyperregulation, a PPI that has been shown to perpetuate neuroinflammation, which is one of the major causal implications of neurodegenerative disorders such as Alzheimer's disease, Parkinson's disease, and frontotemporal dementia. We generated a library of 5 062 500 peptide combination sequences (PCS) derived from the interaction motif of Cdk5/p25 PP interface. The 20 amino acids were differentiated into six groups, namely, hydrophobic (aliphatic), aromatic, basic, acidic, unique, and polar uncharged, on the basis of their physiochemical properties. To preserve the interaction motif necessary for ideal binding, de novo modeling of all possible peptide sequence substitutions was considered. A set of filters, backed by the Support Vector Machine (SVM) algorithm, was then used to create a shortlisted custom peptide library that met specific bioavailability, toxicity, and therapeutic relevance, leading to a refined library of 15 PCS. A greedy algorithm and coarse-grained force field were used to predict peptide structure and folding before subsequent modeling studies. Molecular docking was performed to estimate the relative binding affinities, and out of the top hits, Pep15 was subjected to molecular dynamics simulations and binding free-energy calculations in comparison to a known peptide inhibitor with experimental data (template peptide). Interestingly, the identified peptide through our protocol, Pep15, was found to show a significantly higher binding affinity than the reference template peptide (-48.10 ± 0.23 kcal/mol and -17.53 ± 0.27 kcal/mol, respectively). In comparison to the template peptide, Pep15 was found to possess a more compact and buried surface area, tighter binding landscape, and reduced conformational variability, leading to enhanced structural and kinetic stability of the Cdk5/p25 complex. Notably, both peptide inhibitors were found to have a minimal impact on the architectural integrity of the Cdk5/p25 secondary structure. Herein, we propose Pep15 as a novel and potentially disruptive peptide drug for Cdk5/p25-mediated neurodegenerative phenotypes that require further clinical investigation. The systematic protocol and findings of this report would serve as a valuable tool in the identification of critical PPI interface reactive residues, designing of analogs, and identification of more potent peptide-based PPI inhibitors.

Mechanisms of autophagy-lysosome dysfunction in neurodegenerative diseases

Autophagy is a lysosome-based degradative process used to recycle obsolete cellular constituents and eliminate damaged organelles and aggregate-prone proteins. Their postmitotic nature and extremely polarized morphologies make neurons particularly vulnerable to disruptions caused by autophagy-lysosomal defects, especially as the brain ages. Consequently, mutations in genes regulating autophagy and lysosomal functions cause a wide range of neurodegenerative diseases. Here, we review the role of autophagy and lysosomes in neurodegenerative diseases such as Alzheimer disease, Parkinson disease and frontotemporal dementia. We also consider the strong impact of cellular ageing on lysosomes and autophagy as a tipping point for the late-age emergence of related neurodegenerative disorders. Many of these diseases have primary defects in autophagy, for example affecting autophagosome formation, and in lysosomal functions, especially pH regulation and calcium homeostasis. We have aimed to provide an integrative framework for understanding the central importance of autophagic-lysosomal function in neuronal health and disease.

Neuronal double-stranded DNA accumulation induced by DNase II deficiency drives tau phosphorylation and neurodegeneration

BACKGROUND

Deoxyribonuclease 2 (DNase II) plays a key role in clearing cytoplasmic double-stranded DNA (dsDNA). Deficiency of DNase II leads to DNA accumulation in the cytoplasm. Persistent dsDNA in neurons is an early pathological hallmark of senescence and neurodegenerative diseases including Alzheimer's disease (AD). However, it is not clear how DNase II and neuronal cytoplasmic dsDNA influence neuropathogenesis. Tau hyperphosphorylation is a key factor for the pathogenesis of AD. The effect of DNase II and neuronal cytoplasmic dsDNA on neuronal tau hyperphosphorylation remains unclarified.

METHODS

The levels of neuronal DNase II and dsDNA in WT and Tau-P301S mice of different ages were measured by immunohistochemistry and immunolabeling, and the levels of DNase II in the plasma of AD patients were measured by ELISA. To investigate the impact of DNase II on tauopathy, the levels of phosphorylated tau, phosphokinase, phosphatase, synaptic proteins, gliosis and proinflammatory cytokines in the brains of neuronal DNase II-deficient WT mice, neuronal DNase II-deficient Tau-P301S mice and neuronal DNase II-overexpressing Tau-P301S mice were evaluated by immunolabeling, immunoblotting or ELISA. Cognitive performance was determined using the Morris water maze test, Y-maze test, novel object recognition test and open field test.

RESULTS

The levels of DNase II were significantly decreased in the brains and the plasma of AD patients. DNase II also decreased age-dependently in the neurons of WT and Tau-P301S mice, along with increased dsDNA accumulation in the cytoplasm. The DNA accumulation induced by neuronal DNase II deficiency drove tau phosphorylation by upregulating cyclin-dependent-like kinase-5 (CDK5) and calcium/calmodulin activated protein kinase II (CaMKII) and downregulating phosphatase protein phosphatase 2A (PP2A). Moreover, DNase II knockdown induced and significantly exacerbated neuron loss, neuroinflammation and cognitive deficits in WT and Tau-P301S mice, respectively, while overexpression of neuronal DNase II exhibited therapeutic benefits.

CONCLUSIONS

DNase II deficiency and cytoplasmic dsDNA accumulation can initiate tau phosphorylation, suggesting DNase II as a potential therapeutic target for tau-associated disorders.

MicroRNA-based interventions in aberrant cell cycle diseases: Therapeutic strategies for cancers, central nervous system disorders and comorbidities

Malignant tumors and central nervous system (CNS) disorders are intricately linked to a process known as "aberrant cell cycle re-entry," which plays a critical role in the progression of these diseases. Addressing the dysregulation in cell cycles offers a promising therapeutic approach for cancers and CNS disorders. MicroRNAs (miRNAs) play a crucial role as regulators of gene expression in cell cycle transitions, presenting a promising therapeutic avenue for treating these disorders and their comorbidities. This review consolidates the progress made in the last three years regarding miRNA-based treatments for diseases associated with aberrant cell cycle re-entry. It encompasses exploring fundamental mechanisms and signaling pathways influenced by miRNAs in cancers and CNS disorders, particularly focusing on the therapeutic effects of exosome-derived miRNAs. The review also identifies specific miRNAs implicated in comorbidity of cancers and CNS disorders, discusses the future potential of miRNA reagents in managing cell cycle-related diseases.

Targeting Abnormal Tau Phosphorylation for Alzheimer's Therapeutics

Alzheimer's disease (AD) is a widespread neurodegenerative disorder characterized by progressive memory and cognitive decline, posing a formidable public health challenge. This review explores the intricate interplay between two pivotal players in AD pathogenesis: β-amyloid (Aβ) and tau protein. While the amyloid cascade theory has long dominated AD research, recent developments have ignited debates about its centrality. Aβ plaques and tau NFTs are hallmark pathologies in AD. Aducanumab and lecanemab, monoclonal antibodies targeting Aβ, have been approved, albeit amidst controversy, raising questions about the therapeutic efficacy of Aβ-focused interventions. On the other hand, tau, specifically its hyperphosphorylation, disrupts microtubule stability and contributes to neuronal dysfunction. Various post-translational modifications of tau drive its aggregation into NFTs. Emerging treatments targeting tau, such as GSK-3β and CDK5 inhibitors, have shown promise in preclinical and clinical studies. Restoring the equilibrium between protein kinases and phosphatases, notably protein phosphatase-2A (PP2A), is a promising avenue for AD therapy, as tau is primarily regulated by its phosphorylation state. Activation of tau-specific phosphatases offers potential for mitigating tau pathology. The evolving landscape of AD drug development emphasizes tau-centric therapies and reevaluation of the amyloid cascade hypothesis. Additionally, exploring the role of neuroinflammation and its interaction with tau pathology present promising research directions.

Dual-specificity protein phosphatase 6 (DUSP6) overexpression reduces amyloid load and improves memory deficits in male 5xFAD mice

Introduction

Dual specificity protein phosphatase 6 (DUSP6) was recently identified as a key hub gene in a causal VGF gene network that regulates late-onset Alzheimer's disease (AD). Importantly, decreased DUSP6 levels are correlated with an increased clinical dementia rating (CDR) in human subjects, and DUSP6 levels are additionally decreased in the 5xFAD amyloidopathy mouse model.

Methods

To investigate the role of DUSP6 in AD, we stereotactically injected AAV5-DUSP6 or AAV5-GFP (control) into the dorsal hippocampus (dHc) of both female and male 5xFAD or wild type mice, to induce overexpression of DUSP6 or GFP.

Results

Barnes maze testing indicated that DUSP6 overexpression in the dHc of 5xFAD mice improved memory deficits and was associated with reduced amyloid plaque load, Aß1-40 and Aß1-42 levels, and amyloid precursor protein processing enzyme BACE1, in male but not in female mice. Microglial activation, which was increased in 5xFAD mice, was significantly reduced by dHc DUSP6 overexpression in both males and females, as was the number of "microglial clusters," which correlated with reduced amyloid plaque size. Transcriptomic profiling of female 5xFAD hippocampus revealed upregulation of inflammatory and extracellular signal-regulated kinase pathways, while dHc DUSP6 overexpression in female 5xFAD mice downregulated a subset of genes in these pathways. Gene ontology analysis of DEGs (p < 0.05) identified a greater number of synaptic pathways that were regulated by DUSP6 overexpression in male compared to female 5xFAD.

Discussion

In summary, DUSP6 overexpression in dHc reduced amyloid deposition and memory deficits in male but not female 5xFAD mice, whereas reduced neuroinflammation and microglial activation were observed in both males and females, suggesting that DUSP6-induced reduction of microglial activation did not contribute to sex-dependent improvement in memory deficits. The sex-dependent regulation of synaptic pathways by DUSP6 overexpression, however, correlated with the improvement of spatial memory deficits in male but not female 5xFAD.

The pathogenic mechanism of TAR DNA-binding protein 43 (TDP-43) in amyotrophic lateral sclerosis

The onset of amyotrophic lateral sclerosis is usually characterized by focal death of both upper and/or lower motor neurons occurring in the motor cortex, basal ganglia, brainstem, and spinal cord, and commonly involves the muscles of the upper and/or lower extremities, and the muscles of the bulbar and/or respiratory regions. However, as the disease progresses, it affects the adjacent body regions, leading to generalized muscle weakness, occasionally along with memory, cognitive, behavioral, and language impairments; respiratory dysfunction occurs at the final stage of the disease. The disease has a complicated pathophysiology and currently, only riluzole, edaravone, and phenylbutyrate/taurursodiol are licensed to treat amyotrophic lateral sclerosis in many industrialized countries. The TAR DNA-binding protein 43 inclusions are observed in 97% of those diagnosed with amyotrophic lateral sclerosis. This review provides a preliminary overview of the potential effects of TAR DNA-binding protein 43 in the pathogenesis of amyotrophic lateral sclerosis, including the abnormalities in nucleoplasmic transport, RNA function, post-translational modification, liquid-liquid phase separation, stress granules, mitochondrial dysfunction, oxidative stress, axonal transport, protein quality control system, and non-cellular autonomous functions (e.g., glial cell functions and prion-like propagation).

New molecular mechanisms to explain the neuroprotective effects of insulin-like growth factor II in a cellular model of Parkinson's disease

INTRODUCTION

One of the hallmarks of Parkinsońs Disease (PD) is oxidative distress, leading to mitochondrial dysfunction and neurodegeneration. Insulin-like growth factor II (IGF-II) has been proven to have antioxidant and neuroprotective effects in some neurodegenerative diseases, including PD. Consequently, there isgrowing interest in understanding the different mechanisms involved in the neuroprotective effect of this hormone.

OBJECTIVES

To clarify the mechanism of action of IGF-II involved in the protective effect of this hormone.

METHODS

The present study was carried out on a cellular model PD based on the incubation of dopaminergic cells (SN4741) in a culture with the toxic 1-methyl-4-phenylpyridinium (MPP+), in the presence of IGF-II. This model undertakes proteomic analyses in order to understand which molecular cell pathways might be involved in the neuroprotective effect of IGF-II. The most important proteins found in the proteomic study were tested by Western blot, colorimetric enzymatic activity assay and immunocytochemistry. Along with the proteomic study, mitochondrial morphology and function were also studied by transmission electron microscopy and oxygen consumption rate. The cell cycle was also analysed using 7AAd/BrdU staining, and flow cytometry.

RESULTS

The results obtained indicate that MPP+, MPP++IGF-II treatment and IGF-II, when compared to control, modified the expression of 197, 246 proteins and 207 respectively. Some of these proteins were found to be involved in mitochondrial structure and function, and cell cycle regulation. Including IGF-II in the incubation medium prevents the cell damage induced by MPP+, recovering mitochondrial function and cell cycle dysregulation, and thereby decreasing apoptosis.

CONCLUSION

IGF-II improves mitochondrial dynamics by promoting the association of Mitofilin with mitochondria, regaining function and redox homeostasis. It also rebalances the cell cycle, reducing the amount of apoptosis and cell death by the regulation of transcription factors, such as Checkpoint kinase 1.

Effects of PM2.5 exposure on clock gene BMAL1 and cell cycle in human umbilical vein endothelial cells

Background

Fine particulate matter (PM2.5) exposure has been closely associated with cardiovascular diseases, which are relevant to cell cycle arrest. Brain and muscle aryl-hydrocarbon receptor nuclear translocator-like protein 1 (BMAL1) not only participates in regulating the circadian clock but also plays a role in modulating cell cycle. However, the precise contribution of the circadian clock gene BMAL1 to PM2.5-induced cell cycle change remains unclear. This study aims to explore the impact of PM2.5 exposure on BMAL1 expression and the cell cycle in human umbilical vein endothelial cells (HUVECs).

Methods

HUVECs was exposed to PM2.5 for 24 hours at different concentrations ((0, 12.5, 25, 75 and 100 μg.mL-1) to elucidate the potential toxic mechanism. Following exposure to PM2.5, cell viability, ROS, cell cycle, and the expression of key genes and proteins were detected.

Results

A remarkable decrease in cell viability is observed in the PM2.5-exposed HUVECs, as well as a significant increase in ROS production. In addition, PM2.5-exposed HUVECs have cycle arrest in G0/G1 phase, and the gene expression of p27 is also markedly increased. The protein expression of BMAL1 and the gene expression of BMAL1 are increased significantly. Moreover, the protein expressions of p-p38 MAPK and p-ERK1/2 exhibit a marked increase in the PM2.5-exposed HUVECs. Furthermore, following the transfection of HUVECs with siBMAL1 to suppress BMAL1 expression, we observed a reduction in both the protein and gene expression of the MAPK/ERK pathway in HUVECs exposed to PM2.5.

Conclusions

Overall, our results indicate that PM2.5 exposure significantly upregulates the circadian clock gene expression of BMAL1 and regulates G0/G1 cell cycle arrest in HUVECs through the MAPK/ERK pathway, which may provide new insights into the potential molecular mechanism regarding BMAL1 on PM2.5-induced cardiovascular diseases.

Navigating the dementia landscape: Biomarkers and emerging therapies

The field of dementia research has witnessed significant developments in our understanding of neurodegenerative disorders, with a particular focus on Alzheimer's disease (AD) and Frontotemporal Dementia (FTD). Dementia, a collection of symptoms arising from the degeneration of brain cells, presents a significant healthcare challenge, especially as its prevalence escalates with age. This abstract delves into the complexities of these disorders, the role of biomarkers in their diagnosis and monitoring, as well as emerging neurophysiological insights. In the context of AD, anti-amyloid therapy has gained prominence, aiming to reduce the accumulation of amyloid-beta (Aβ) plaques in the brain, a hallmark of the disease. Notably, Leqembi recently received full FDA approval, marking a significant breakthrough in AD treatment. Additionally, ongoing phase 3 clinical trials are investigating novel therapies, including Masitinib and NE3107, focusing on cognitive and functional improvements in AD patients. In the realm of FTD, research has unveiled distinct neuropathological features, including the involvement of proteins like TDP-43 and progranulin, providing valuable insights into the diagnosis and management of this heterogeneous condition. Biomarkers, including neurofilaments and various tau fragments, have shown promise in enhancing diagnostic accuracy. Neurophysiological techniques, such as transcranial magnetic stimulation (TMS), have contributed to our understanding of AD and FTD. TMS has uncovered unique neurophysiological signatures, highlighting impaired plasticity, hyperexcitability, and altered connectivity in AD, while FTD displays differences in neurotransmitter systems, particularly GABAergic and glutamatergic circuits. Lastly, ongoing clinical trials in anti-amyloid therapy for AD, such as Simufilam, Solanezumab, Gantenerumab, and Remternetug, offer hope for individuals affected by this devastating disease, with the potential to alter the course of cognitive decline. These advancements collectively illuminate the evolving landscape of dementia research and the pursuit of effective treatments for these challenging conditions.

The CDK Pho85 inhibits Whi7 Start repressor to promote cell cycle entry in budding yeast

Pho85 is a multifunctional CDK that signals to the cell when environmental conditions are favorable. It has been connected to cell cycle control, mainly in Start where it promotes the G1/S transition. Here we describe that the Start repressor Whi7 is a key target of Pho85 in the regulation of cell cycle entry. The phosphorylation of Whi7 by Pho85 inhibits the repressor and explains most of the contribution of the CDK in the activation of Start. Mechanistically, Pho85 downregulates Whi7 protein levels through the control of Whi7 protein stability and WHI7 gene transcription. Whi7 phosphorylation by Pho85 also restrains the intrinsic ability of Whi7 to associate with promoters. Furthermore, although Whi5 is the main Start repressor in normal cycling cells, in the absence of Pho85, Whi7 becomes the major repressor leading to G1 arrest. Overall, our results reveal a novel mechanism by which Pho85 promotes Start through the regulation of the Whi7 repressor at multiple levels, which may confer to Whi7 a functional specialization to connect the response to adverse conditions with the cell cycle control.

Targeting protein kinases for the treatment of Alzheimer's disease: Recent progress and future perspectives

Alzheimer's disease (AD) is a serious neurodegenerative disease characterized by memory impairment, mental retardation, impaired motor balance, loss of self-care and even death. Among the complex and diverse pathological changes in AD, protein kinases are deeply involved in abnormal phosphorylation of Tau proteins to form intracellular neuronal fiber tangles, neuronal loss, extracellular β-amyloid (Aβ) deposits to form amyloid plaques, and synaptic disturbances. As a disease of the elderly, the growing geriatric population is directly driving the market demand for AD therapeutics, and protein kinases are potential targets for the future fight against AD. This perspective provides an in-depth look at the role of the major protein kinases (GSK-3β, CDK5, p38 MAPK, ERK1/2, and JNK3) in the pathogenesis of AD. At the same time, the development of different protein kinase inhibitors and the current state of clinical advancement are also outlined.

Dual-specificity protein phosphatase 6 (DUSP6) overexpression reduces amyloid load and improves memory deficits in male 5xFAD mice

Background

Dual specificity protein phosphatase 6 (DUSP6) was recently identified as a key hub gene in a causal network that regulates late-onset Alzheimer's disease. Importantly, decreased DUSP6 levels are correlated with an increased clinical dementia rating in human subjects, and DUSP6 levels are additionally decreased in the 5xFAD amyloidopathy mouse model.

Methods

AAV5-DUSP6 or AAV5-GFP (control) were stereotactically injected into the dorsal hippocampus (dHc) of female and male 5xFAD or wild type mice to overexpress DUSP6 or GFP. Spatial learning memory of these mice was assessed in the Barnes maze, after which hippocampal tissues were isolated for downstream analysis.

Results

Barnes maze testing indicated that DUSP6 overexpression in the dHc of 5xFAD mice improved memory deficits and was associated with reduced amyloid plaque load, Aß 1-40 and Aß 1-42 levels, and amyloid precursor protein processing enzyme BACE1, in male but not in female mice. Microglial activation and microgliosis, which are increased in 5xFAD mice, were significantly reduced by dHc DUSP6 overexpression in both males and females. Transcriptomic profiling of female 5xFAD hippocampus revealed upregulated expression of genes involved in inflammatory and extracellular signal-regulated kinase (ERK) pathways, while dHc DUSP6 overexpression in female 5xFAD mice downregulated a subset of genes in these pathways. A limited number of differentially expressed genes (DEGs) (FDR<0.05) were identified in male mice; gene ontology analysis of DEGs (p<0.05) identified a greater number of synaptic pathways that were regulated by DUSP6 overexpression in male compared to female 5xFAD. Notably, the msh homeobox 3 gene, Msx3 , previously shown to regulate microglial M1/M2 polarization and reduce neuroinflammation, was one of the most robustly upregulated genes in female and male wild type and 5xFAD mice overexpressing DUSP6.

Conclusions

In summary, our data indicate that DUSP6 overexpression in dHc reduced amyloid deposition and memory deficits in male but not female 5xFAD mice, whereas reduced neuroinflammation and microglial activation were observed in both males and females. The sex-dependent regulation of synaptic pathways by DUSP6 overexpression, however, correlated with the improvement of spatial memory deficits in male but not female 5xFAD.

The role of epigenetic modifications in sensory hair cell development, survival, and regulation

The cochlea is the sensory organ in the periphery, and hair cells are its main sensory cells. The development and survival of hair cells are highly controlled processes. When cells face intracellular and environmental stimuli, epigenetic regulation controls the structure and function of the genome in response to different cell fates. During sensory hair cell development, different histone modifications can induce normal numbers of functional hair cells to generate. When individuals are exposed to environmental-related hair cell damage, epigenetic modification also plays a significant role in the regulation of hair cell fate. Since mammalian hair cells cannot regenerate, their loss can cause permanent sensorineural hearing loss. Many breakthroughs have been achieved in recent years in understanding the signaling pathways that determine hair cell regeneration, and it is fascinating to note that epigenetic regulation plays a significant role in hair cell regeneration. In this review, we discuss the role of epigenetics in inner ear cell development, survival and regeneration and the significant impact on hearing protection.