Correcting miR92a-vGAT-Mediated GABAergic Dysfunctions Rescues Human Tau-Induced Anxiety in Mice

Mitochondrial calcium uniporter knockdown in hippocampal neurons alleviates anxious and depressive behavior in the 3XTG Alzheimer's disease mouse model

Alzheimer's disease (AD) is a progressive and degenerative disorder accompanied by emotional disturbance, especially anxiety and depression. More and more evidence shows that the imbalance of mitochondrial Ca2+ (mCa2+) homeostasis has a close connection with the pathogenesis of anxiety and depression. The Mitochondrial Calcium Uniporter (MCU), a key channel of mCa2+ uptake, induces the imbalance of mCa2+ homeostasis and may be a therapeutic target for anxiety and depression of AD. In the present study, we revealed for the first time that MCU knockdown in hippocampal neurons alleviated anxious and depressive behaviors of APP/PS1/tau mice through elevated plus-maze (EPM), elevated zero maze (EZM), sucrose preference test (SPT) and tail suspension test (TST). Western blot analysis results demonstrated that MCU knockdown in hippocampal neurons increased levels of glutamate decarboxylase 67 (GAD67), vesicular GABA transporter (vGAT) and GABAA receptor α1 (GABRA1) and activated the PKA-CREB-BDNF signaling pathway. This study indicates that MCU inhibition has the potential to be developed as a novel therapy for anxiety and depression in AD.

Vitamin B6 prevents heart failure with preserved ejection fraction through downstream of kinase 3 in a mouse model

BACKGROUND

There is an urgent need to develop an efficient therapeutic strategy for heart failure with preserved ejection fraction (HFpEF), which is mediated by phenotypic changes in cardiac macrophages. We previously reported that vitamin B6 (VB6) inhibits macrophage-mediated inflammasome activation OBJECTIVE: We sought to examine whether the prophylactic use of VB6 prevents HFpEF METHODS: HFpEF model was elicited by a combination of high fat diet and Nω-nitro-l-arginine methyl ester in mice. Cardiac function was assessed using conventional echocardiography and Doppler imaging. Immunohistochemistry and immunoblotting were used to detect changes in the macrophage phenotype and myocardial remodeling-related molecules RESULTS: Co-administration of VB6 with HFpEF mice mitigated HFpEF phenotypes, including diastolic dysfunction, cardiac macrophage phenotypic shifts, fibrosis, and hypertrophy. Echocardiographic improvements were observed, with the E/E' ratio decreasing from 42.0 to 21.6 and the E/A ratio improving from 2.13 to 1.17. The exercise capacity also increased from 295.3 m to 657.7 m. However, these beneficial effects were negated in downstream of kinase 3 (DOK3)-deficient mice. Mechanistically, VB6 increased DOK3 protein levels and inhibited macrophage phenotypic changes, which were abrogated by an AMP-activated protein kinase inhibitor CONCLUSION: VB6 increases DOK3 signaling to lower the risk of HFpEF by inhibiting phenotypic changes in cardiac macrophages.

MicroRNA biomarkers as next-generation diagnostic tools for neurodegenerative diseases: a comprehensive review

Neurodegenerative diseases (NDs) are characterized by abnormalities within neurons of the brain or spinal cord that gradually lose function, eventually leading to cell death. Upon examination of affected tissue, pathological changes reveal a loss of synapses, misfolded proteins, and activation of immune cells-all indicative of disease progression-before severe clinical symptoms become apparent. Early detection of NDs is crucial for potentially administering targeted medications that may delay disease advancement. Given their complex pathophysiological features and diverse clinical symptoms, there is a pressing need for sensitive and effective diagnostic methods for NDs. Biomarkers such as microRNAs (miRNAs) have been identified as potential tools for detecting these diseases. We explore the pivotal role of miRNAs in the context of NDs, focusing on Alzheimer's disease, Parkinson's disease, Multiple sclerosis, Huntington's disease, and Amyotrophic Lateral Sclerosis. The review delves into the intricate relationship between aging and NDs, highlighting structural and functional alterations in the aging brain and their implications for disease development. It elucidates how miRNAs and RNA-binding proteins are implicated in the pathogenesis of NDs and underscores the importance of investigating their expression and function in aging. Significantly, miRNAs exert substantial influence on post-translational modifications (PTMs), impacting not just the nervous system but a wide array of tissues and cell types as well. Specific miRNAs have been found to target proteins involved in ubiquitination or de-ubiquitination processes, which play a significant role in regulating protein function and stability. We discuss the link between miRNA, PTM, and NDs. Additionally, the review discusses the significance of miRNAs as biomarkers for early disease detection, offering insights into diagnostic strategies.

Profiling Small RNA From Brain Extracellular Vesicles in Individuals With Depression

BACKGROUND

Major depressive disorder (MDD) is a leading cause of disability with significant mortality risk. Despite progress in our understanding of the etiology of MDD, the underlying molecular changes in the brain remain poorly understood. Extracellular vesicles (EVs) are lipid-bound particles that can reflect the molecular signatures of the tissue of origin. We aimed to optimize a streamlined EV isolation protocol from postmortem brain tissue and determine whether EV RNA cargo, particularly microRNAs (miRNAs), have an MDD-specific profile.

METHODS

EVs were isolated from postmortem human brain tissue. Quality was assessed using western blots, transmission electron microscopy, and microfluidic resistive pulse sensing. EV RNA was extracted and sequenced on Illumina platforms. Functional follow-up was performed in silico.

RESULTS

Quality assessment showed an enrichment of EV markers, as well as a size distribution of 30 to 200 nm in diameter, and no contamination with cellular debris. Small RNA profiling indicated the presence of several RNA biotypes, with miRNAs and transfer RNAs being the most prominent. Exploring miRNA levels between groups revealed decreased expression of miR-92a-3p and miR-129-5p, which was validated by qPCR and was specific to EVs and not seen in bulk tissue. Finally, in silico functional analyses indicate potential roles for these 2 miRNAs in neurotransmission and synaptic plasticity.

CONCLUSION

We provide a streamlined isolation protocol that yields EVs of high quality that are suitable for molecular follow-up. Our findings warrant future investigations into brain EV miRNA dysregulation in MDD.

Longitudinal faster anxiety progression of GBA variant carriers in the early Parkinson's disease cohort

Objective

Anxiety symptoms are prevalent neuropsychiatric manifestations in Parkinson's disease (PD) and impact the development of motor complications. Our aim was to evaluate the association of GBA variants with the anxiety development in early PD cohort.

Methods

This cohort study used data from the Parkinson Progression Marker Initiative. The primary outcome anxiety was assessed by State-Trait Anxiety Inventory (STAI). The association between GBA and longitudinal change in the STAI total score was examined using linear mixed-effects model, and the association between GBA and anxiety progression was examined using Cox survival analysis.

Results

A total of 385 patients with PD were included in this study, 39 of them were GBA variant carriers and 346 were idiopathic PD without GBA variants. Patients with GBA variants had faster annual increase in anxiety score (β = 0.44; 95% CI, 0.18 to 0.71; p < 0.001) and were at higher risk of anxiety progression (HR 1.87; 95% CI, 1.03 to 3.41; p = 0.03,). Higher baseline scores for Scales for Outcomes in Parkinson's Disease-Autonomic (SCOPA-AUT), which indicated the autonomic dysfunction, also independently predicted faster increase in anxiety score (β = 0.48; 95%CI, 0.19 to 0.69; p < 0.001) and higher incidence of anxiety development (HR = 1.05; 95% CI, 1.01 to 1.08; p = 0.008).

Interpretation

These findings suggest that longitudinal anxiety symptoms worsening was faster in PD patients who were GBA variant carriers and have dysautonomia, and this association was enhanced if they have both.

The GABAergic system in Alzheimer's disease: a systematic review with meta-analysis

The γ-aminobutyric acid (GABA)ergic system is the primary inhibitory neurotransmission system in the mammalian brain. Its dysregulation has been shown in multiple brain conditions, but in Alzheimer's disease (AD) studies have provided contradictory results. Here, we conducted a systematic review with meta-analysis to investigate whether the GABAergic system is altered in AD patients compared to healthy controls (HC), following the PRISMA 2020 Statement. We searched PubMed and Web of Science from database inception to March 18th, 2023 for studies reporting GABA, glutamate decarboxylase (GAD) 65/67, GABAA, GABAB, and GABAC receptors, GABA transporters (GAT) 1-3 and vesicular GAT in the brain, and GABA levels in the cerebrospinal fluid (CSF) and blood. Heterogeneity was estimated using the I2 index, and the risk of bias was assessed with an adapted questionnaire from the Joanna Briggs Institute Critical Appraisal Tools. The search identified 3631 articles, and 48 met the final inclusion criteria (518 HC, mean age 72.2, and 603 AD patients, mean age 75.6). Random-effects meta-analysis [standardized mean difference (SMD)] revealed that AD patients presented lower GABA levels in the brain (SMD = -0.48 [95% CI = -0.7, -0.27], adjusted p value (adj. p) < 0.001) and in the CSF (-0.41 [-0.72, -0.09], adj. p = 0.042), but not in the blood (-0.63 [-1.35, 0.1], adj. p = 0.176). In addition, GAD65/67 (-0.67 [-1.15, -0.2], adj. p = 0.006), GABAA receptor (-0.51 [-0.7, -0.33], adj. p < 0.001), and GABA transporters (-0.51 [-0.92, -0.09], adj. p = 0.016) were lower in the AD brain. Here, we showed a global reduction of GABAergic system components in the brain and lower GABA levels in the CSF of AD patients. Our findings suggest the GABAergic system is vulnerable to AD pathology and should be considered a potential target for developing pharmacological strategies and novel AD biomarkers.

The role of epigenetics in anxiety disorders

Anxiety disorders (ADs) are extremely common psychiatric conditions that frequently co-occur with other physical and mental disorders. The pathophysiology of ADs is multifaceted and involves intricate connections among biological elements, environmental stimuli, and psychological mechanisms. Recent discoveries have highlighted the significance of epigenetics in bridging the gap between multiple risk factors that contribute to ADs and expanding our understanding of the pathomechanisms underlying ADs. Epigenetics is the study of how changes in the environment and behavior can have an impact on gene function. Indeed, researchers have found that epigenetic mechanisms can affect how genes are activated or inactivated, as well as whether they are expressed. Such mechanisms may also affect how ADs form and are protected. That is, the bulk of pharmacological trials evaluating epigenetic treatments for the treatment of ADs have used histone deacetylase inhibitors (HDACi), yielding promising outcomes in both preclinical and clinical studies. This review will provide an outline of how epigenetic pathways can be used to treat ADs or lessen their risk. It will also present the findings from preclinical and clinical trials that are currently available on the use of epigenetic drugs to treat ADs.

Understanding the Roles and Regulation of Mitochondrial microRNAs (MitomiRs) in Neurodegenerative Diseases: Current Status and Advances

MicroRNAs (miRNA) are a class of small non-coding RNA, roughly 21 - 22 nucleotides in length, which are master gene regulators. These miRNAs bind to the mRNA's 3' - untranslated region and regulate post-transcriptional gene regulation, thereby influencing various physiological and cellular processes. Another class of miRNAs known as mitochondrial miRNA (MitomiRs) has been found to either originate from the mitochondrial genome or be translocated directly into the mitochondria. Although the role of nuclear DNA encoded miRNA in the progression of various neurological diseases such as Parkinson's disease, Alzheimer's disease, Huntington's disease, etc. is well known, accumulating evidence suggests the possible role of deregulated mitomiRs in the progression of various neurodegenerative diseases with unknown mechanism. We have attempted to outline the current state of mitomiRs role in controlling mitochondrial gene expression and function through this review, paying particular attention to their contribution to neurological processes, their etiology, and their potential therapeutic use.

Identification of miRNAs regulating MAPT expression and their analysis in plasma of patients with dementia

Background

Dementia is one of the most common diseases in elderly people and hundreds of thousand new cases per year of Alzheimer's disease (AD) are estimated. While the recent decade has seen significant advances in the development of novel biomarkers to identify dementias at their early stage, a great effort has been recently made to identify biomarkers able to improve differential diagnosis. However, only few potential candidates, mainly detectable in cerebrospinal fluid (CSF), have been described so far.

Methods

We searched for miRNAs regulating MAPT translation. We employed a capture technology able to find the miRNAs directly bound to the MAPT transcript in cell lines. Afterwards, we evaluated the levels of these miRNAs in plasma samples from FTD (n = 42) and AD patients (n = 33) and relative healthy controls (HCs) (n = 42) by using qRT-PCR.

Results

Firstly, we found all miRNAs that interact with the MAPT transcript. Ten miRNAs have been selected to verify their effect on Tau levels increasing or reducing miRNA levels by using cell transfections with plasmids expressing the miRNAs genes or LNA antagomiRs. Following the results obtained, miR-92a-3p, miR-320a and miR-320b were selected to analyse their levels in plasma samples of patients with FTD and AD respect to HCs. The analysis showed that the miR-92a-1-3p was under-expressed in both AD and FTD compared to HCs. Moreover, miR-320a was upregulated in FTD vs. AD patients, particularly in men when we stratified by sex. Respect to HC, the only difference is showed in men with AD who have reduced levels of this miRNA. Instead, miR-320b is up-regulated in both dementias, but only patients with FTD maintain this trend in both genders.

Conclusions

Our results seem to identify miR-92a-3p and miR-320a as possible good biomarkers to discriminate AD from HC, while miR-320b to discriminate FTD from HC, particularly in males. Combining three miRNAs improves the accuracy only in females, particularly for differential diagnosis (FTD vs. AD) and to distinguish FTD from HC.

MAPK Is a Mutual Pathway Targeted by Anxiety-Related miRNAs, and E2F5 Is a Putative Target for Anxiolytic miRNAs

Anxiety-related disorders (ARDs) are chronic neuropsychological diseases and the sixth leading cause of disability in the world. As dysregulation of microRNAs (miRs) are observed in the pathological course of neuropsychiatric disorders, the present study aimed to introduce miRs that underlie anxiety processing in the brain. First, we collected the experimentally confirmed anxiety-related miRNAs (ARmiRs), predicted their target transcripts, and introduced critical cellular pathways with key commune hub genes. As a result, we have found nine anxiolytic and ten anxiogenic ARmiRs. The anxiolytic miRs frequently target the mRNA of Acyl-CoA synthetase long-chain family member 4 (Acsl4), AFF4-AF4/FMR2 family member 4 (Aff4), and Krüppel like transcription factor 4 (Klf4) genes, where miR-34b-5p and miR-34c-5p interact with all of them. Moreover, the anxiogenic miRs frequently target the mRNA of nine genes; among them, only two miR (miR-142-5p and miR-218-5p) have no interaction with the mRNA of trinucleotide repeat-containing adaptor 6B (Tnrc6b), and miR-124-3p interacts with all of them where MAPK is the main signaling pathway affected by both anxiolytic and anxiogenic miR. In addition, the anxiolytic miR commonly target E2F transcription factor 5 (E2F5) in the TGF-β signaling pathway, and the anxiogenic miR commonly target Ataxin 1 (Atxn1), WASP-like actin nucleation promoting factor (Wasl), and Solute Carrier Family 17 Member 6 (Slc17a6) genes in the notch signaling, adherence junction, and synaptic vesicle cycle pathways, respectively. Taken together, we conclude that the most important anxiolytic (miR-34c, Let-7d, and miR-17) and anxiogenic (miR-19b, miR-92a, and 218) miR, as hub epigenetic modulators, potentially influence the pathophysiology of anxiety, primarily via interaction with the MAPK signaling pathway. Moreover, the role of E2F5 as a novel putative target for anxiolytic miRNAs in ARDs disorders deserves further exploration.

Transition from Animal-Based to Human Induced Pluripotent Stem Cells (iPSCs)-Based Models of Neurodevelopmental Disorders: Opportunities and Challenges

Neurodevelopmental disorders (NDDs) arise from the disruption of highly coordinated mechanisms underlying brain development, which results in impaired sensory, motor and/or cognitive functions. Although rodent models have offered very relevant insights to the field, the translation of findings to clinics, particularly regarding therapeutic approaches for these diseases, remains challenging. Part of the explanation for this failure may be the genetic differences-some targets not being conserved between species-and, most importantly, the differences in regulation of gene expression. This prompts the use of human-derived models to study NDDS. The generation of human induced pluripotent stem cells (hIPSCs) added a new suitable alternative to overcome species limitations, allowing for the study of human neuronal development while maintaining the genetic background of the donor patient. Several hIPSC models of NDDs already proved their worth by mimicking several pathological phenotypes found in humans. In this review, we highlight the utility of hIPSCs to pave new paths for NDD research and development of new therapeutic tools, summarize the challenges and advances of hIPSC-culture and neuronal differentiation protocols and discuss the best way to take advantage of these models, illustrating this with examples of success for some NDDs.

Exosomal miR92a Promotes Cytarabine Resistance in Myelodysplastic Syndromes by Activating Wnt/β-catenin Signal Pathway

Cytarabine (Ara-C) has been one of the frontline therapies for clonal hematopoietic stem cell disorders, such as myelodysplastic syndrome (MDS) and acute myeloid leukemia (AML), but Ara-C resistance often occurs and leads to treatment failure. Exosomal microRNAs (miRNAs, miRs) as small noncoding RNA that play important roles in post-transcriptional gene regulation, can be delivered into recipient cells by exosomes and regulate target genes' expression. miR92a has been reported to be dysregulated in many cancers, including MDS and AML. However, the effects of exosomal miR92a in hematologic malignancies have not been fully investigated. In this study, qualitative analysis showed the significantly enhanced expression of exosomal miR92a in MDS/AML plasma. Subsequent functional assays indicated that exosomal miR92a can be transported and downregulate PTEN in recipient cells and, furthermore, activate the Wnt/β-catenin signaling pathway and interfere with the Ara-C resistance of receipt MDS/AML cells in vitro and in vivo. Altogether, our findings offer novel insights into plasma exosomal miR92a participating in Ara-C resistance in MDS/AML and we propose miR92a as a potential therapeutic target for MDS/AML.

Plasma microRNAs as potential biomarkers in early Alzheimer disease expression

The microRNAs (miRNAs) are potential biomarkers for complex pathologies due to their involvement in the regulation of several pathways. Alzheimer Disease (AD) requires new biomarkers in minimally invasive samples that allow an early diagnosis. The aim of this work is to study miRNAS as potential AD biomarkers and their role in the pathology development. In this study, participants (n = 46) were classified into mild cognitive impairment due to AD (MCI-AD, n = 19), preclinical AD (n = 8) and healthy elderly controls (n = 19), according to CSF biomarkers levels (amyloid β42, total tau, phosphorylated tau) and neuropsychological assessment. Then, plasma miRNAomic expression profiles were analysed by Next Generation Sequencing. Finally, the selected miRNAs were validated by quantitative PCR (q-PCR). A panel of 11 miRNAs was selected from omics expression analysis, and 8 of them were validated by q-PCR. Individually, they did not show statistically significant differences among participant groups. However, a multivariate model including these 8 miRNAs revealed a potential association with AD for three of them. Specifically, relatively lower expression levels of miR-92a-3p and miR-486-5p are observed in AD patients, and relatively higher levels of miR-29a-3p are observed in AD patients. These biomarkers could be involved in the regulation of pathways such as synaptic transmission, structural functions, cell signalling and metabolism or transcription regulation. Some plasma miRNAs (miRNA-92a-3p, miRNA-486-5p, miRNA-29a-3p) are slightly dysregulated in AD, being potential biomarkers of the pathology. However, more studies with a large sample size should be carried out to verify these results, as well as to further investigate the mechanisms of action of these miRNAs.

Neuropathological and behavioral features of an APP/PS1/MAPT (6xTg) transgenic model of Alzheimer’s disease

Alzheimer's disease is associated with various brain dysfunctions, including memory impairment, neuronal loss, astrocyte activation, amyloid-β plaques, and neurofibrillary tangles. Transgenic animal models of Alzheimer's disease have proven to be invaluable for the basic research of Alzheimer's disease. However, Alzheimer's disease mouse models developed so far do not fully recapitulate the pathological and behavioral features reminiscent of Alzheimer's disease in humans. Here, we investigated the neurobehavioral sequelae in the novel 6xTg mouse model of Alzheimer's disease, which was developed by incorporating human tau containing P301L mutation in the widely used 5xFAD mouse model of Alzheimer's disease. At 11-months-old, 6xTg mice displayed the core pathological processes found in Alzheimer's disease, including accumulation of amyloid-β plaque, extensive neuronal loss, elevated level of astrocyte activation, and abnormal tau phosphorylation in the brain. At 9 to 11-months-old, 6xTg mice exhibited both cognitive and non-cognitive behavioral impairments relevant to Alzheimer’s disease, including memory loss, hyperlocomotion, anxiety-like behavior, depression-like behavior, and reduced sensorimotor gating. Our data suggest that the aged 6xTg mouse model of Alzheimer's disease presents pathological and cognitive-behavioral features reminiscent of Alzheimer's disease in humans. Thus, the 6xTg mouse model of Alzheimer's disease may be a valuable model for studying Alzheimer’s disease-relevant non-cognitive behaviors.

miR-92a-2-5p Regulates the Proliferation and Differentiation of ASD-Derived Neural Progenitor Cells

Autism spectrum disorder (ASD) is a group of complex neurodevelopmental disorders with abnormal behavior. However, the pathogenesis of ASD remains to be clarified. It has been demonstrated that miRNAs are essential regulators of ASD. However, it is still unclear how miR-92a-2-5p acts on the developing brain and the cell types directly. In this study, we used neural progenitor cells (NPCs) derived from ASD-hiPSCs as well as from neurotypical controls to examine the effects of miR-92a-2-5p on ASD-NPCs proliferation and neuronal differentiation, and whether miR-92a-2-5p could interact with genetic risk factor, DLG3 for ASD. We observed that miR-92a-2-5p upregulated in ASD-NPCs results in decreased proliferation and neuronal differentiation. Inhibition of miR-92a-2-5p could promote proliferation and neuronal differentiation of ASD-NPCs. DLG3 was negatively regulated by miR-92a-2-5p in NPCs. Our results suggest that miR-92a-2-5p is a strong risk factor for ASD and potentially contributes to neuropsychiatric disorders.

Human tau accumulation promotes glycogen synthase kinase-3β acetylation and thus upregulates the kinase: A vicious cycle in Alzheimer neurodegeneration

BACKGROUND

Glycogen synthase kinase-3β (GSK-3β) is one of the most effective kinases in promoting tau hyperphosphorylation and accumulation in Alzheimer's disease (AD). However, it is not clear how GSK-3β activity is regulated during AD progression.

METHODS

We firstly used mass spectrometry to identify the acetylation site of GSK-3β, and then established the cell and animal models of GSK-3β acetylation. Next, we conducted molecular, cell biological and behavioral tests. Finally, we designed a peptide to test whether blocking tau-mediated GSK-3β acetylation could be beneficial to AD.

FINDINGS

We found that GSK-3β protein levels increased in the brains of AD patients and the transgenic mice. Overexpressing tau increased GSK-3β protein level with increased acetylation and decreased ubiquitination-related proteolysis. Tau could directly acetylate GSK-3β at K15 both in vitro and in vivo. K15-acetylation inhibited ubiquitination-associated proteolysis of GSK-3β and changed its activity-dependent phosphorylation, leading to over-activation of the kinase. GSK-3β activation by K15-acetylation in turn exacerbated the AD-like pathologies. Importantly, competitively inhibiting GSK-3β K15-acetylation by a novel-designed peptide remarkably improved cognitive impairment and the AD-like pathologies in 3xTg-AD mice.

INTERPRETATION

Tau can directly acetylate GSK-3β at K15 which reveals a vicious cycle between tau hyperphosphorylation and GSK-3β activation.

FUNDING

This study was supported in parts by grants from Science and Technology Committee of China (2016YFC1305800), Hubei Province (2018ACA142), Natural Science Foundation of China (91949205, 82001134, 31730035, 81721005), Guangdong Provincial Key S&T Program (018B030336001).

Expression of Calbindin, a Marker of Gamma-Aminobutyric Acid Neurons, Is Reduced in the Amygdala of Oestrogen Receptor β-Deficient Female Mice

Oestrogen receptor β (ERβ) knock-out female mice display increased anxiety and decreased threshold for synaptic plasticity induction in the basolateral amygdala. This may suggest that the γ-aminobutyric acid (GABA) inhibitory system is altered. Therefore, the immunoreactivity of main GABAergic markers-i.e., calbindin, parvalbumin, calretinin, somatostatin, α1 subunit-containing GABA_A receptor and vesicular GABA transporter-were compared in the six subregions (LA, BL, BM, ME, CE and CO) of the amygdala of adult female wild-type and ERβ knock-out mice using immunohistochemistry and quantitative methods. The influence of ERβ knock-out on neuronal loss and glia was also elucidated using pan-neuronal and astrocyte markers. The results show severe neuronal deficits in all main amygdala regions in ERβ knock-out mice accompanied by astroglia overexpression only in the medial, basomedial and cortical nuclei and a decrease in calbindin-expressing neurons (CB+) in the amygdala in ERβ knock-out mice compared with controls, while other markers of the GABAergic system remain unchanged. Concluding, the lack of ERβ led to failure in the structural integrity of the CB+ subpopulation, reducing interneuron firing and resulting in a disinhibitory effect over pyramidal function. This fear-promoting excitatory/inhibitory alteration may lead to the increased anxiety observed in these mice. The impact of neuronal deficits and astroglia overexpression on the amygdala functions remains unknown.

Key Genes and Biochemical Networks in Various Brain Regions Affected in Alzheimer's Disease

Alzheimer’s disease (AD) is one of the most complicated progressive neurodegenerative brain disorders, affecting millions of people around the world. Ageing remains one of the strongest risk factors associated with the disease and the increasing trend of the ageing population globally has significantly increased the pressure on healthcare systems worldwide. The pathogenesis of AD is being extensively investigated, yet several unknown key components remain. Therefore, we aimed to extract new knowledge from existing data. Ten gene expression datasets from different brain regions including the hippocampus, cerebellum, entorhinal, frontal and temporal cortices of 820 AD cases and 626 healthy controls were analyzed using the robust rank aggregation (RRA) method. Our results returned 1713 robust differentially expressed genes (DEGs) between five brain regions of AD cases and healthy controls. Subsequent analysis revealed pathways that were altered in each brain region, of which the GABAergic synapse pathway and the retrograde endocannabinoid signaling pathway were shared between all AD affected brain regions except the cerebellum, which is relatively less sensitive to the effects of AD. Furthermore, we obtained common robust DEGs between these two pathways and predicted three miRNAs as potential candidates targeting these genes; hsa-mir-17-5p, hsa-mir-106a-5p and hsa-mir-373-3p. Three transcription factors (TFs) were also identified as the potential upstream regulators of the robust DEGs; ELK-1, GATA1 and GATA2. Our results provide the foundation for further research investigating the role of these pathways in AD pathogenesis, and potential application of these miRNAs and TFs as therapeutic and diagnostic targets.

The Role of the GABAergic System in Diseases of the Central Nervous System

It is well known that the central nervous system (CNS) is a complex neuronal network and its function depends on the balance between excitatory and inhibitory neurons. Disruption of the excitatory/inhibitory (E/I) balance is the main cause for the majority of the CNS diseases. In this review, we will discuss roles of the inhibitory system in the CNS diseases. The GABAergic system as the main inhibitory system, is essential for the appropriate functioning of the CNS, especially as it is engaged in the formation of learning and memory. Many researchers have reported that the GABAergic system is involved in regulating synaptic plasticity, cognition and long-term potentiation. Some clinical manifestations (such as cognitive dysfunctions, attention deficits, etc.) have also been shown to emerge after abnormalities in the GABAergic system accompanied with concomitant diseases, that include Alzheimer's disease (AD), Parkinson's disease (PD), Autism spectrum disorder (ASD), Schizophrenia, etc. The GABAergic system consists of GABA, GABA transporters, GABAergic receptors and GABAergic neurons. Changes in any of these components may contribute to the dysfunctions of the CNS. In this review, we will synthesize studies which demonstrate how the GABAergic system participates in the pathogenesis of the CNS disorders, which may provide a new idea that might be used to treat the CNS diseases.

Aging-Related Neural Disruption Might Predispose to Postoperative Cognitive Impairment Following Surgical Trauma

BACKGROUND

Accumulating evidence has demonstrated that aging is associated with an exaggerated response to surgical trauma together with cognitive impairments. This has significant implications for the development of clinical phenotype such as perioperative neurocognitive disorders (PND), which is a common complication following surgery, especially for the elderly. However, the mechanism by which aging brain is vulnerable to surgical trauma remains to be elucidated.

OBJECTIVE

To test whether age-related alterations in hippocampal network activities contribute to increased risk of PND following surgery.

METHODS

Thirty-two adult and seventy-two aged male C57BL/6 mice undergone sevoflurane anesthesia and exploratory laparotomy were used to mimic human abdominal surgery. For the interventional study, mice were treated with minocycline. Behavioral tests were performed post-surgery with open field, novel object recognition and fear conditioning tests, respectively. The brain tissues were then harvested and subjected to biochemistry studies. Local field potential (LFP) recording was performed in another separate experiment.

RESULTS

Aged mice displayed signs of neuroinflammation, as reflected by significantly increased proinflammatory mediators in the hippocampus. Also, aged mice displayed persistently decreased oscillation activities under different conditions, both before and after surgery. Further correlation analysis suggested that theta power was positively associated with time with novel object, while γ oscillation activity was positively associated with freezing time to context. Of note, downregulation of neuroinflammation by microglia inhibitor minocycline reversed some of these abnormities.

CONCLUSION

Our study highlights that age-related hippocampal oscillation dysregulation increases the risk of PND incidence, which might provide diagnostic/prognostic biomarkers for PND and possible other neurodegenerative diseases.

The role of exosomal non-coding RNAs in aging-related diseases

Aging is a biological process caused by the accumulation of senescent cells with a permanent proliferative arrest. To the influence of aging on human life expectancy, there is essential for new biomarkers which possibly will assistance in recognizing age-associated pathologies. Exosomes, which are cell-secreted nanovesicles, make available a new biomarker detection and therapeutic approach for the transfer of different molecules with high capacity. Recently, non-coding RNAs (ncRNA) which are contained in exosomes have developed as important molecules regulating the complexity of aging and relevant human diseases. The discovery of ncRNA provided perceptions into an innovative regulatory platform that could interfere with cellular senescence. The non-coding transcriptome includes a different of RNA species, spanning from short ncRNAs (<200 nucleotides) to long ncRNAs, that are >200 bp long. Upgraded evidence displays that targeting ncRNAs possibly will influence senescence pathways. In this article, we will address ncRNAs that participated in age-related and cellular senescence diseases. Growing conception of ncRNAs in the aging process possibly will be responsible for new understandings into the improvement of age-related diseases and elongated life span.

Mitochondrial Dysfunction and Mitophagy Closely Cooperate in Neurological Deficits Associated with Alzheimer's Disease and Type 2 Diabetes

Alzheimer's disease (AD) and type 2 diabetes (T2D) are known to be correlated in terms of their epidemiology, histopathology, and molecular and biochemical characteristics. The prevalence of T2D leading to AD is approximately 50-70%. Moreover, AD is often considered type III diabetes because of the common risk factors. Uncontrolled T2D may affect the brain, leading to memory and learning deficits in patients. In addition, metabolic disorders and impaired oxidative phosphorylation in AD and T2D patients suggest that mitochondrial dysfunction is involved in both diseases. The dysregulation of pathways involved in maintaining mitochondrial dynamics, biogenesis and mitophagy are responsible for exacerbating the impact of hyperglycemia on the brain and neurodegeneration under T2D conditions. The first section of this review describes the recent views on mitochondrial dysfunction that connect these two disease conditions, as the pathways are observed to overlap. The second section of the review highlights the importance of different mitochondrial miRNAs (mitomiRs) involved in the regulation of mitochondrial dynamics and their association with the pathogenesis of T2D and AD. Therefore, targeting mitochondrial biogenesis and mitophagy pathways, along with the use of mitomiRs, could be a potent therapeutic strategy for T2D-related AD. The last section of the review highlights the known drugs targeting mitochondrial function for the treatment of both disease conditions.

GABA and glutamate deficits from frontotemporal lobar degeneration are associated with disinhibition

Behavioural disinhibition is a common feature of the syndromes associated with frontotemporal lobar degeneration (FTLD). It is associated with high morbidity and lacks proven symptomatic treatments. A potential therapeutic strategy is to correct the neurotransmitter deficits associated with FTLD, thereby improving behaviour. Reductions in the neurotransmitters glutamate and GABA correlate with impulsive behaviour in several neuropsychiatric diseases and there is post-mortem evidence of their deficit in FTLD. Here, we tested the hypothesis that prefrontal glutamate and GABA levels are reduced by FTLD in vivo, and that their deficit is associated with impaired response inhibition. Thirty-three participants with a syndrome associated with FTLD (15 patients with behavioural variant frontotemporal dementia and 18 with progressive supranuclear palsy, including both Richardson's syndrome and progressive supranuclear palsy-frontal subtypes) and 20 healthy control subjects were included. Participants undertook ultra-high field (7 T) magnetic resonance spectroscopy and a stop-signal task of response inhibition. We measured glutamate and GABA levels using semi-LASER magnetic resonance spectroscopy in the right inferior frontal gyrus, because of its strong association with response inhibition, and in the primary visual cortex, as a control region. The stop-signal reaction time was calculated using an ex-Gaussian Bayesian model. Participants with frontotemporal dementia and progressive supranuclear palsy had impaired response inhibition, with longer stop-signal reaction times compared with controls. GABA concentration was reduced in patients versus controls in the right inferior frontal gyrus, but not the occipital lobe. There was no group-wise difference in partial volume corrected glutamate concentration between patients and controls. Both GABA and glutamate concentrations in the inferior frontal gyrus correlated inversely with stop-signal reaction time, indicating greater impulsivity in proportion to the loss of each neurotransmitter. We conclude that the glutamatergic and GABAergic deficits in the frontal lobe are potential targets for symptomatic drug treatment of frontotemporal dementia and progressive supranuclear palsy.

MicroRNAs in Alzheimer's Disease: Function and Potential Applications as Diagnostic Biomarkers

Alzheimer’s disease (AD) is the most common form of dementia. Although the incidence of AD is high, the rates of diagnosis and treatment are relatively low. Moreover, effective means for the diagnosis and treatment of AD are still lacking. MicroRNAs (miRNAs, miRs) are non-coding RNAs that play regulatory roles by targeting mRNAs. The expression of miRNAs is conserved, temporal, and tissue-specific. Impairment of microRNA function is closely related to AD pathogenesis, including the beta-amyloid and tau hallmarks of AD, and there is evidence that the expression of some microRNAs differs significantly between healthy people and AD patients. These properties of miRNAs endow them with potential diagnostic and therapeutic value in the treatment of this debilitating disease. This review provides comprehensive information about the regulatory function of miRNAs in AD, as well as potential applications as diagnostic biomarkers.

Too Much Tau in Interneurons Impairs Adult Hippocampal Neurogenesis in Alzheimer's Disease

Understanding why adult hippocampal neurogenesis (AHN) is impaired in Alzheimer's disease (AD) is essential for unravelling its role in pathogenesis. In this issue of Cell Stem Cell, Zheng et al. (2020) report that human tau accumulation in dentate gyrus GABAergic interneurons disrupts AHN and strengthening GABAergic signaling restores AHN and improves cognition in an AD mouse model.

Mitochondrial MicroRNAs in Aging and Neurodegenerative Diseases

MicroRNAs (miRNAs) are important regulators of several biological processes, such as cell growth, cell proliferation, embryonic development, tissue differentiation, and apoptosis. Currently, over 2000 mammalian miRNAs have been reported to regulate these biological processes. A subset of microRNAs was found to be localized to human mitochondria (mitomiRs). Through years of research, over 400 mitomiRs have been shown to modulate the translational activity of the mitochondrial genome. While miRNAs have been studied for years, the function of mitomiRs and their role in neurodegenerative pathologies is not known. The purpose of our article is to highlight recent findings that relate mitomiRs to neurodegenerative diseases, including Alzheimer’s, Parkinson’s, and Huntington’s. We also discuss the involvement of mitomiRs in regulating the mitochondrial genome in age-related neurodegenerative diseases.

Paradoxical network excitation by glutamate release from VGluT3+ GABAergic interneurons

In violation of Dale's principle several neuronal subtypes utilize more than one classical neurotransmitter. Molecular identification of vesicular glutamate transporter three and cholecystokinin expressing cortical interneurons (CCK+VGluT3+INTs) has prompted speculation of GABA/glutamate corelease from these cells for almost two decades despite a lack of direct evidence. We unequivocally demonstrate CCK+VGluT3+INT-mediated GABA/glutamate cotransmission onto principal cells in adult mice using paired recording and optogenetic approaches. Although under normal conditions, GABAergic inhibition dominates CCK+VGluT3+INT signaling, glutamatergic signaling becomes predominant when glutamate decarboxylase (GAD) function is compromised. CCK+VGluT3+INTs exhibit surprising anatomical diversity comprising subsets of all known dendrite targeting CCK+ interneurons in addition to the expected basket cells, and their extensive circuit innervation profoundly dampens circuit excitability under normal conditions. However, in contexts where the glutamatergic phenotype of CCK+VGluT3+INTs is amplified, they promote paradoxical network hyperexcitability which may be relevant to disorders involving GAD dysfunction such as schizophrenia or vitamin B6 deficiency.

Interneuron Accumulation of Phosphorylated tau Impairs Adult Hippocampal Neurogenesis by Suppressing GABAergic Transmission

Phospho-tau accumulation and adult hippocampal neurogenesis (AHN) impairment both contribute importantly to the cognitive decline in Alzheimer's disease (AD), but whether and how tau dysregulates AHN in AD remain poorly understood. Here, we found a prominent accumulation of phosphorylated tau in GABAergic interneurons in the dentate gyrus (DG) of AD patients and mice. Specific overexpression of human tau (hTau) in mice DG interneurons induced AHN deficits but increased neural stem cell-derived astrogliosis, associating with a downregulation of GABA and hyperactivation of neighboring excitatory neurons. Chemogenetic inhibition of excitatory neurons or pharmacologically strengthening GABAergic tempos rescued the tau-induced AHN deficits and improved contextual cognition. These findings evidenced that intracellular accumulation of tau in GABAergic interneurons impairs AHN by suppressing GABAergic transmission and disinhibiting neural circuits within the neurogenic niche, suggesting a potential of GABAergic potentiators for pro-neurogenic or cell therapies of AD.

Exosome-encapsulated microRNAs as promising biomarkers for Alzheimer’s disease

Alzheimer’s disease (AD) is a chronic neurodegenerative disease that locks into long clinical latency and low curative ratio. Therefore, early diagnosis before the clinical phase is quite essential and may be effective for therapeutic prevention. Peripheral blood or cerebrospinal fluid biomarkers symbolizing functional neuronal impairment are gradually applied to diagnose AD in research studies. Exosomes have generated immense interest in the diagnosis field of neurodegenerative disorders after confirmation of their roles as mediators, delivering important proteins and microRNAs (miRNAs) in intercellular communication. Compelling research results reveal that miRNAs released from exosomes modulate expression and function of amyloid precursor proteins and tau proteins. These findings open up possibility that dysfunctional exosomal miRNAs may influence AD progression. In this review, we summarized the existing knowledge of exosomal miRNAs and their involvement in AD, emphasizing their potential to serve as diagnostic biomarkers during the preclinical phase of AD.

Nature of Tau-Associated Neurodegeneration and the Molecular Mechanisms

Neurodegeneration is defined as the progressive loss of structure or function of the neurons. As the nature of degenerative cell loss is currently not clear, there is no specific molecular marker to measure neurodegeneration. Therefore, researchers have been using apoptotic markers to measure neurodegeneration. However, neurodegeneration is completely different from apoptosis by morphology and time course. Lacking specific molecular marker has been the major hindrance in research of neurodegenerative disorders. Alzheimer's disease (AD) is the most common neurodegenerative disorder, and tau accumulation forming neurofibrillary tangles is a hallmark pathology in the AD brains, suggesting that tau must play a critical role in AD neurodegeneration. Here we review part of our published papers on tau-related studies, and share our thoughts on the nature of tau-associated neurodegeneration in AD.

Novel Insights on Systemic and Brain Aging, Stroke, Amyotrophic Lateral Sclerosis, and Alzheimer's Disease

The mechanisms that underlie the pathophysiology of aging, amyotrophic lateral sclerosis (ALS), Alzheimer's disease (AD) and stroke are not fully understood and have been the focus of intense and constant investigation worldwide. Studies that provide insights on aging and age-related disease mechanisms are critical for advancing novel therapies that promote successful aging and prevent or cure multiple age-related diseases. The April 2019 issue of the journal, "Aging & Disease" published a series of articles that confer fresh insights on numerous age-related conditions and diseases. The age-related topics include the detrimental effect of overweight on energy metabolism and muscle integrity, senoinflammation as the cause of neuroinflammation, the link between systemic C-reactive protein and brain white matter loss, the role of miR-34a in promoting healthy heart and brain, the potential of sirtuin 3 for reducing cardiac and pulmonary fibrosis, and the promise of statin therapy for ameliorating asymptomatic intracranial atherosclerotic stenosis. Additional aging-related articles highlighted the involvement of miR-181b-5p and high mobility group box-1 in hypertension, Yes-associated protein in cataract formation, multiple miRs and long noncoding RNAs in coronary artery disease development, the role of higher meat consumption on sleep problems, and the link between glycated hemoglobin and depression. The topics related to ALS suggested that individuals with higher education and living in a rural environment have a higher risk for developing ALS, and collagen XIX alpha 1 is a prognostic biomarker of ALS. The topics discussed on AD implied that extracellular amyloid β42 is likely the cause of intraneuronal neurofibrillary tangle accumulation in familial AD and traditional oriental concoctions may be useful for slowing down the progression of AD. The article on stroke suggested that inhibition of the complement system is likely helpful in promoting brain repair after ischemic stroke. The significance of the above findings for understanding the pathogenesis in aging, ALS, AD, and stroke, slowing down the progression of aging, ALS and AD, and promoting brain repair after stroke are discussed.

MicroRNAs and the Genetic Nexus of Brain Aging, Neuroinflammation, Neurodegeneration, and Brain Trauma

Aging is a complex and integrated gradual deterioration of cellular activities in specific organs of the body, which is associated with increased mortality. This deterioration is the primary risk factor for major human pathologies, including cancer, diabetes, cardiovascular disorders, neurovascular disorders, and neurodegenerative diseases. There are nine tentative hallmarks of aging. In addition, several of these hallmarks are increasingly being associated with acute brain injury conditions. In this review, we consider the genes and their functional pathways involved in brain aging as a means of developing new strategies for therapies targeted to the neuropathological processes themselves, but also as targets for many age-related brain diseases. A single microRNA (miR), which is a short, non-coding RNA species, has the potential for targeting many genes simultaneously and, like practically all other cellular processes, genes associated with many features of brain aging and injury are regulated by miRs. We highlight how certain miRs can mediate deregulation of genes involved in neuroinflammation, acute neuronal injury and chronic neurodegenerative diseases. Finally, we review the recent progress in the development of effective strategies to block specific miR functions and discuss future approaches with the prediction that anti-miR drugs may soon be used in the clinic.

MicroRNA-mediated downregulation of potassium-chloride-cotransporter and vesicular γ-aminobutyric acid transporter expression in spinal cord contributes to neonatal cystitis-induced visceral pain in rats

Loss of GABAergic inhibition in pain pathways has been considered to be a key component in the development of chronic pain. In the present study, we intended to examine whether miR-92b-mediated posttranscriptional dysregulation of spinal potassium chloride cotransporter (KCC2) and vesicular γ-aminobutyric acid transporter (VGAT) plays a major role in the development and maintenance of long-term visceral hyperalgesia in neonatal zymosan-treated rats. Neonatal cystitis was induced by transurethral zymosan administration from postnatal (P) days 14 to 16 (protocol 1). Two other zymosan protocols were also used: adult rechallenge on P57 to 59 following neonatal P14 to 16 exposures (protocol 2), and adult zymosan exposures on P57 to 59 (protocol 3). Both neonatal and adult bladder inflammation protocols demonstrated an increase in spinal miR-92b-3p expression and subsequent decrease in KCC2 and VGAT expression in spinal dorsal horn neurons. In situ hybridization demonstrated a significant upregulation of miR-92b-3p in the spinal dorsal horn neurons of neonatal cystitis rats compared with saline-treated controls. In dual in situ hybridization and immunohistochemistry studies, we further demonstrated coexpression of miR-92b-3p with targets KCC2 and VGAT in spinal dorsal horn neurons, emphasizing a possible regulatory role both at pre- and post-synaptic levels. Intrathecal administration of lentiviral pLSyn-miR-92b-3p sponge (miR-92b-3p inhibitor) upregulated KCC2 and VGAT expression in spinal dorsal horn neurons. In behavioral studies, intrathecal administration of lentiviral miR-92b-3p sponge attenuated an increase in visceromotor responses and referred viscerosomatic hypersensitivity following the induction of cystitis. These findings indicate that miR-92b-3p-mediated posttranscriptional regulation of spinal GABAergic system plays an important role in sensory pathophysiology of zymosan-induced cystitis.