miR-342-5p Decreases Ankyrin G Levels in Alzheimer’s Disease Transgenic Mouse Models

Changes in circulating extracellular vesicle cargo are associated with cognitive decline after major surgery: an observational case-control study

BACKGROUND

Postoperative neurocognitive decline is a frequent complication triggered by unclear signalling mechanisms. This observational case-control study investigated the effects of hip or knee replacement surgery on the composition of circulating extracellular vesicles (EVs), potential periphery-to-brain messengers, and their association with neurocognitive outcomes.

METHODS

We mapped the microRNAome and proteome of plasma-derived EVs from 12 patients (six with good and six with poor neurocognitive outcomes at 3 months after surgery) at preoperative and postoperative timepoints (4, 8, 24, and 48 h). Complement C3-EV association was confirmed by flow cytometry in plasma- and cerebrospinal fluid (CSF)-derived EVs, with total plasma and CSF C3 and C3a concentrations determined using enzyme-linked immunosorbent assay.

RESULTS

Differential expression analysis found eight dysregulated EV microRNAs (miRNAs) exclusively in the poor neurocognitive outcomes group. Pathway analysis suggested potential downregulation of proliferative pathways and activation of extracellular matrix and inflammatory response pathways in EV target tissues. Proteome analysis revealed a time-dependent increase in immune-related EV proteins, including complement system proteins, notably EV surface-associated C3. Such upward kinetics was detected earlier in the poor neurocognitive outcomes group. Interestingly, CSF-derived EVs from the same group showed a drastic drop of C3 at 48 h with unchanged concentrations in the good neurocognitive outcomes group. Functionally, the complement system was activated in both patient groups in plasma, but only in the poor neurocognitive outcomes group in CSF.

CONCLUSIONS

Our findings highlight the impact of surgery on plasma- and CSF-derived EVs, particularly in patients with poor neurocognitive outcomes, indicating a potential role for EVs. The small sample size necessitates verification with a larger patient cohort.

Exercise-induced modulation of miRNAs and gut microbiome: a holistic approach to neuroprotection in Alzheimer's disease

Alzheimer's disease (AD), a progressive neurodegenerative disorder, is marked by cognitive decline, neuroinflammation, and neuronal loss. MicroRNAs (miRNAs) have emerged as critical regulators of gene expression, influencing key pathways involved in neuroinflammation and neurodegeneration in AD. This review delves into the multifaceted role of exercise in modulating miRNA expression and its interplay with the gut microbiome, proposing a comprehensive framework for neuroprotection in AD. By synthesizing current research, we elucidate how exercise-induced changes in miRNA profiles can mitigate inflammatory responses, promote neurogenesis, and reduce amyloid-beta and tau pathologies. Additionally, we explore the gut-brain axis, highlighting how exercise-driven alterations in gut microbiota composition can further influence miRNA expression, thereby enhancing cognitive function and reducing neuroinflammatory markers. This holistic approach underscores the potential of targeting exercise-regulated miRNAs and gut microbiome interactions as a novel, noninvasive therapeutic strategy to decelerate AD progression and improve quality of life for patients. This approach aims to decelerate disease progression and improve patient outcomes, offering a promising avenue for enhancing the effectiveness of AD management.

Axon initial segment structure and function in health and disease

At the simplest level, neurons are structured to integrate synaptic input and perform computational transforms on that input, converting it into an action potential (AP) code. This process, converting synaptic input into AP output, typically occurs in a specialized region of the axon termed the axon initial segment (AIS). The AIS, as its name implies, is often contained to the first section of axon abutted to the soma and is home to a dizzying array of ion channels, attendant scaffolding proteins, intracellular organelles, extracellular proteins, and, in some cases, synapses. The AIS serves multiple roles as the final arbiter for determining if inputs are sufficient to evoke APs, as a gatekeeper that physically separates the somatodendritic domain from the axon proper, and as a regulator of overall neuronal excitability, dynamically tuning its size to best suit the needs of parent neurons. These complex roles have received considerable attention from experimentalists and theoreticians alike. Here, we review recent advances in our understanding of the AIS and its role in neuronal integration and polarity in health and disease.

Transcriptomic alterations in APP/PS1 mice astrocytes lead to early postnatal axon initial segment structural changes

Alzheimer´s disease (AD) is characterized by neuronal function loss and degeneration. The integrity of the axon initial segment (AIS) is essential to maintain neuronal function and output. AIS alterations are detected in human post-mortem AD brains and mice models, as well as, neurodevelopmental and mental disorders. However, the mechanisms leading to AIS deregulation in AD and the extrinsic glial origin are elusive. We studied early postnatal differences in AIS cellular/molecular mechanisms in wild-type or APP/PS1 mice and combined neuron-astrocyte co-cultures. We observed AIS integrity alterations, reduced ankyrinG expression and shortening, in APP/PS1 mice from P21 and loss of AIS integrity at 21 DIV in wild-type and APP/PS1 neurons in the presence of APP/PS1 astrocytes. AnkyrinG decrease is due to mRNAs and protein reduction of retinoic acid synthesis enzymes Rdh1 and Aldh1b1, as well as ADNP (Activity-dependent neuroprotective protein) in APP/PS1 astrocytes. This effect was mimicked by wild-type astrocytes expressing ADNP shRNA. In the presence of APP/PS1 astrocytes, wild-type neurons AIS is recovered by inhibition of retinoic acid degradation, and Adnp-derived NAP peptide (NAPVSIPQ) addition or P2X7 receptor inhibition, both regulated by retinoic acid levels. Moreover, P2X7 inhibitor treatment for 2 months impaired AIS disruption in APP/PS1 mice. Our findings extend current knowledge on AIS regulation, providing data to support the role of astrocytes in early postnatal AIS modulation. In conclusion, AD onset may be related to very early glial cell alterations that induce AIS and neuronal function changes, opening new therapeutic approaches to detect and avoid neuronal function loss.

Circ_0008146 Exacerbates Ferroptosis via Regulating the miR-342-5p/ACSL4 Axis After Cerebral Ischemic/Reperfusion

Purpose

Acute ischemic stroke (AIS) has seriously threatened people's health worldwide and there is an urge need for early diagnosis and effective treatment of AIS. This research intended to clarify the regulatory role of circ_0008146/miR-342-5p/ACSL4 axis in AIS.

Methods

High-throughput small RNA sequencing analysis was adapted to identify differentially expressed miRNAs between the AIS and control group. The circ_0008146, miR-342-5p, and ACSL4 levels were detected by qRT-PCR. Middle cerebral artery occlusion/reperfusion (MCAO/R) models were constructed in C57BL/6J mice. Assay kits were used to determine Fe2+ levels and a battery of oxidative stress and lipid peroxidation indicators, including ROS, MDA, LPO, SOD and GSH/GSSG ratio. The protein levels of ACSL4 were measured by Western blot. The behavioral function was assessed using neurobehavioral tests. TTC staining was employed to visualize infarction size. Nissl staining was adapted to detect histopathological changes. Receiver operating characteristic curve and correlation analysis were applied to investigate the clinical value and association of miR-342-5p and ACSL4.

Results

A total of 44 AIS patients and 49 healthy controls were enrolled in our study. The small RNA sequencing unveiled a significant decrease in miR-342-5p levels in AIS patients. MiR-342-5p inhibited oxidative stress and RSL3-induced ferroptosis after cerebral ischemic/reperfusion injury in vivo by targeting ferroptosis-related gene ACSL4. Circ_0008146 acted as a sponge of miR-342-5p, and overexpression of circ_0008146 increased neurological deficits and brain injury in mice. Circ_0008146 contributed to ferroptosis in cerebral infarction via sponging miR-342-5p to regulate ACSL4. Plasma miR-342-5p and ACSL4 demonstrated significant correlation and good diagnostic value for AIS patients.

Conclusion

This study provides the first in vivo evidence to show that circ_0008146 exacerbates neuronal ferroptosis after AIS via the miR-342-5p/ACSL4 axis. Furthermore, miR-342-5p/ACSL4 axis holds promise as a viable therapeutic target and practical biomarkers for AIS patients.

Beyond CSF and Neuroimaging Assessment: Evaluating Plasma miR-145-5p as a Potential Biomarker for Mild Cognitive Impairment and Alzheimer's Disease

Alzheimer's disease (AD) is the most common cause of dementia. New strategies for the early detection of MCI and sporadic AD are crucial for developing effective treatment options. Current techniques used for diagnosis of AD are invasive and/or expensive, so they are not suitable for population screening. Cerebrospinal fluid (CSF) biomarkers such as amyloid β1-42 (Aβ1-42), total tau (T-tau), and phosphorylated tau181 (P-tau181) levels are core biomarkers for early diagnosis of AD. Several studies have proposed the use of blood-circulating microRNAs (miRNAs) as potential novel early biomarkers for AD. We therefore applied a novel approach to identify blood-circulating miRNAs associated with CSF biomarkers and explored the potential of these miRNAs as biomarkers of AD. In total, 112 subjects consisting of 28 dementia due to AD cases, 63 MCI due to AD cases, and 21 cognitively healthy controls were included. We identified seven Aβ1-42-associated plasma miRNAs, six P-tau181-associated plasma miRNAs, and nine Aβ1-42-associated serum miRNAs. These miRNAs were involved in AD-relevant biological processes, such as PI3K/AKT signaling. Based on this signaling pathway, we constructed an miRNA-gene target network, wherein miR-145-5p has been identified as a hub. Furthermore, we showed that miR-145-5p performs best in the prediction of both AD and MCI. Moreover, miR-145-5p also improved the prediction performance of the mini-mental state examination (MMSE) score. The performance of this miRNA was validated using different datasets including an RT-qPCR dataset from plasma samples of 23 MCI cases and 30 age-matched controls. These findings indicate that blood-circulating miRNAs that are associated with CSF biomarkers levels and specifically plasma miR-145-5p alone or combined with the MMSE score can potentially be used as noninvasive biomarkers for AD or MCI screening in the general population, although studies in other AD cohorts are necessary for further validation.

Unveiling the Role of Novel miRNA PC-5P-12969 in Alleviating Alzheimer's Disease

Background

The intricate and complex molecular mechanisms that underlie the progression of Alzheimer's disease (AD) have prompted a concerted and vigorous research endeavor aimed at uncovering potential avenues for therapeutic intervention.

Objective

This study aims to elucidate the role of miRNA PC-5P-12969 in the pathogenesis of AD.

Methods

We assessed the differential expression of miRNA PC-5P-12969 in postmortem AD brains, AD animal and cell models using real-time reverse-transcriptase RT-PCR, we also checked the gene and protein expression of GSK3α and APP.

Results

Our investigation revealed a notable upregulation of miRNA PC-5P-12969 in postmortem brains of AD patients, in transgenic mouse models of AD, and in mutant APP overexpressing-HT22 cells. Additionally, our findings indicate that overexpression of miRNA PC-5P-12969 exerts a protective effect on cell survival, while concurrently mitigating apoptotic cell death. Further-more, we established a robust and specific interaction between miRNA PC-5P-12969 and GSK3α. Our luciferase reporter assays provided confirmation of the binding between miRNA PC-5P-12969 and the 3'-UTR of the GSK3α gene. Manipulation of miRNA PC-5P-12969 levels in cellular models of AD yielded noteworthy alterations in the gene and protein expression levels of both GSK3α and APP. Remarkably, the manipulation of miRNA PC-5P-12969 levels yielded significant enhancements in mitochondrial respiration and ATP production, concurrently with a reduction in mitochondrial fragmentation, thus unveiling a potential regulatory role of miRNA PC-5P-12969 in these vital cellular processes.

Conclusions

In summary, this study sheds light on the crucial role of miRNA PC-5P-12969 and its direct interaction with GSK3α in the context of AD.

Shared Molecular Pathways in Glaucoma and Other Neurodegenerative Diseases: Insights from RNA-Seq Analysis and miRNA Regulation for Promising Therapeutic Avenues

Advances in RNA-sequencing technologies have led to the identification of molecular biomarkers for several diseases, including neurodegenerative diseases, such as Alzheimer's, Parkinson's, Huntington's diseases and Amyotrophic Lateral Sclerosis. Despite the nature of glaucoma as a neurodegenerative disorder with several similarities with the other above-mentioned diseases, transcriptional data about this disease are still scarce. microRNAs are small molecules (~17-25 nucleotides) that have been found to be specifically expressed in the CNS as major components of the system regulating the development signatures of neurodegenerative diseases and the homeostasis of the brain. In this review, we sought to identify similarities between the functional mechanisms and the activated pathways of the most common neurodegenerative diseases, as well as to discuss how those mechanisms are regulated by miRNAs, using RNA-Seq as an approach to compare them. We also discuss therapeutically suitable applications for these disease hallmarks in clinical future studies.

Extracellular Tau Oligomers Damage the Axon Initial Segment

BACKGROUND

In Alzheimer's disease (AD) brain, neuronal polarity and synaptic connectivity are compromised. A key structure for regulating polarity and functions of neurons is the axon initial segment (AIS), which segregates somatodendritic from axonal proteins and initiates action potentials. Toxic tau species, including extracellular oligomers (xcTauOs), spread tau pathology from neuron to neuron by a prion-like process, but few other cell biological effects of xcTauOs have been described.

OBJECTIVE

Test the hypothesis that AIS structure is sensitive to xcTauOs.

METHODS

Cultured wild type (WT) and tau knockout (KO) mouse cortical neurons were exposed to xcTauOs, and quantitative western blotting and immunofluorescence microscopy with anti-TRIM46 monitored effects on the AIS. The same methods were used to compare TRIM46 and two other resident AIS proteins in human hippocampal tissue obtained from AD and age-matched non-AD donors.

RESULTS

Without affecting total TRIM46 levels, xcTauOs reduce the concentration of TRIM46 within the AIS and cause AIS shortening in cultured WT, but not TKO neurons. Lentiviral-driven tau expression in tau KO neurons rescues AIS length sensitivity to xcTauOs. In human AD hippocampus, the overall protein levels of multiple resident AIS proteins are unchanged compared to non-AD brain, but TRIM46 concentration within the AIS and AIS length are reduced in neurons containing neurofibrillary tangles.

CONCLUSION

xcTauOs cause partial AIS damage in cultured neurons by a mechanism dependent on intracellular tau, thereby raising the possibility that the observed AIS reduction in AD neurons in vivo is caused by xcTauOs working in concert with endogenous neuronal tau.

miR-9a-5p expression is decreased in the hippocampus of rats resistant to lamotrigine: A behavioural, molecular and bioinformatics assessment

The major obstacle in developing new treatment strategies for refractory epilepsy is the complexity and poor understanding of its mechanisms. Utilizing the model of lamotrigine-resistant seizures, we evaluated whether changes in the expression of sodium channel subunits are responsible for the diminished responsiveness to lamotrigine (LTG) and if miRNAs, may also be associated. Male rats were administered LTG (5 mg/kg) before each stimulation during kindling acquisition. Challenge stimulation following LTG exposure (30 mg/kg) was performed to confirm resistance in fully kindled rats. RT-PCR was used to measure the mRNA levels of sodium channel subunits (SCN1A, SCN2A, and SCN3A) and miRNAs (miR-155-5p, miR-30b-5p, miR-137-3p, miR-342-5p, miR-301a-3p, miR-212-3p, miR-9a-5p, and miR-133a-3p). Western blot analysis was utilized to measure Nav1.2 protein, and bioinformatics tools were used to perform target prediction and enrichment analysis for miR-9a-5p, the only affected miRNA according to the responsiveness to LTG. Amygdala kindling seizures downregulated Nav1.2, miR-137-3p, miR-342-5p, miR-155-5p, and miR-9a-5p as well as upregulated miR-212-3p. miR-9a-5p was the only molecule decreased in rats resistant to LTG. The bioinformatic assessment and disease enrichment analysis revealed that miR-9a-5p targets expressed with high confidence in the hippocampus are the most significantly associated with epilepsy. Due to the miR-9a-5p dysregulation, major pathways affected are neurotrophic processes, neurotransmission, inflammatory response, cell proliferation and apoptosis. Interaction network analysis identified LTG target SCN2A as interacting with highest number of genes regulated by miR-9-5p. Further studies are needed to propose specific genes and miRNAs responsible for diminished responsiveness to LTG. miR-9a-5p targets, like KCNA4, KCNA2, CACNB2, SCN4B, KCNC1, should receive special attention in them.

Retinal ganglion cells adapt to ionic stress in experimental glaucoma

Introduction

Identification of early adaptive and maladaptive neuronal stress responses is an important step in developing targeted neuroprotective therapies for degenerative disease. In glaucoma, retinal ganglion cells (RGCs) and their axons undergo progressive degeneration resulting from stress driven by sensitivity to intraocular pressure (IOP). Despite therapies that can effectively manage IOP many patients progress to vision loss, necessitating development of neuronal-based therapies. Evidence from experimental models of glaucoma indicates that early in the disease RGCs experience altered excitability and are challenged with dysregulated potassium (K+) homeostasis. Previously we demonstrated that certain RGC types have distinct excitability profiles and thresholds for depolarization block, which are associated with sensitivity to extracellular K+.

Methods

Here, we used our inducible mouse model of glaucoma to investigate how RGC sensitivity to K+ changes with exposure to elevated IOP.

Results

In controls, conditions of increased K+ enhanced membrane depolarization, reduced action potential generation, and widened action potentials. Consistent with our previous work, 4 weeks of IOP elevation diminished RGC light-and current-evoked responses. Compared to controls, we found that IOP elevation reduced the effects of increased K+ on depolarization block threshold, with IOP-exposed cells maintaining greater excitability. Finally, IOP elevation did not alter axon initial segment dimensions, suggesting that structural plasticity alone cannot explain decreased K+ sensitivity.

Discussion

Thus, in response to prolonged IOP elevation RGCs undergo an adaptive process that reduces sensitivity to changes in K+ while diminishing excitability. These experiments give insight into the RGC response to IOP stress and lay the groundwork for mechanistic investigation into targets for neuroprotective therapy.

MiR-342-5p protects neurons from cerebral ischemia induced-apoptosis through regulation of Akt/NF-κB pathways by targeting CCAR2

OBJECTIVES

Ischemic stroke causes high morbidity, mortality and health burden in the world. MiR-342-5p was associated with Alzheimer's disease and cardio-protection. Herein, we aimed to reveal effects of miR-342-5p on cerebral ischemia injury as well as novel targets for stroke.

MATERIALS AND METHODS

AgomiR-342-5p was intracerebroventricularly injected into the middle cerebral artery occlusion (MCAO) mouse models to evaluate functions of miR-342-5p on cerebral ischemia. RT-qPCR and western blot assays were used to evaluate genes expression. Oxygen-glucose deprivation (OGD) was used as an in vitro model for ischemia. Viability and apoptosis ratio of neurons was evaluated by CCK-8, LDH release detection, and flow cytometry. The potential targets of miR-342-5p were predicted by Targetscan, and their interaction was confirmed by luciferase assay.

RESULTS

The intervention of miR-342-5p effectively attenuated ischemic injury in MCAO mice. MiR-342-5p overexpression could protect neurons against OGD-induced injury, as revealed by increased cell viability and BCL2 expression, and decreased LDH release, apoptosis ratio, and BAX expression in OGD-induced neurons. Mechanically, miR-342-5p could directly bound with CCAR2 to inhibit its expression. Overexpressing CARR2 aggravated the OGD-induced injury of neurons, which was partly restrained by overexpressing miR-342-5p reversed. Furthermore, miR-342-5p/CARR2 axis regulates Akt/NF-κB signaling pathway in vitro as well as in vivo cerebral ischemia models.

CONCLUSIONS

MiR-342-5p inhibited neuron apoptosis by regulating Akt/NF-kB signaling pathway via CCAR2 suppression. Our findings revealed the neuroprotection of miR-342-5p in cerebral ischemia.

Circulating Small Extracellular Vesicle-Derived miR-342-5p Ameliorates Beta-Amyloid Formation via Targeting Beta-site APP Cleaving Enzyme 1 in Alzheimer's Disease

Alzheimer's disease (AD) is a common neurodegenerative disorder with progressive cognitive impairment in the elderly. Beta-amyloid (Aβ) formation and its accumulation in the brain constitute one of the pathological hallmarks of AD. Until now, how to modulate Aβ formation in hippocampal neurons remains a big challenge. Herein, we investigated whether the exosomal transfer of microRNA (miR) relates to amyloid pathology in the recipient neuron cells. We isolated circulating small extracellular vesicles (sEVs) from AD patients and healthy controls, determined the miR-342-5p level in the sEVs by RT-PCR, and evaluated its diagnostic performance in AD. Then, we took advantage of biomolecular assays to estimate the role of miR-342-5p in modulating the amyloid pathway, including amyloid precursor protein (APP), beta-site APP cleaving enzyme 1 (BACE1), and Aβ42. Furthermore, we subjected HT22 cells to the sEVs from the hippocampal tissues of transgenic APP mice (Exo-APP) or C57BL/6 littermates (Exo-CTL), and the Exo-APP enriched with miR-342-5p mimics or the control to assess the effect of the sEVs' delivery of miR-342-5p on Aβ formation. We observed a lower level of miR-342-5p in the circulating sEVs from AD patients compared with healthy controls. MiR-342-5p participated in Aβ formation by modulating BACE1 expression, specifically binding its 3'-untranslated region (UTR) sequence. Exo-APP distinctly promoted Aβ42 formation in the recipient cells compared to Exo-CTL. Intriguingly, miR-342-5p enrichment in Exo-APP ameliorated amyloid pathology in the recipient cells. Our study indicated that miR-342-5p was dysregulated in human circulating sEVs from AD patients; sEV transfer of miR-342-5p ameliorates Aβ formation by modulating BACE1 expression. These findings highlight the promising potential of exosomal miRNAs in AD clinical therapy.

The largest isoform of Ankyrin-G is required for lattice structure of the axon initial segment

Alzheimer's disease (AD) is the most frequent neurodegenerative disease and a common dementia in elderly individuals. Previous studies found a strong correlation between axon initial segment (AIS) defects and AD, but it remains unclear whether AD itself changes the arrangement of AIS components, and the mechanisms by which adaptor proteins and ion channels in the AIS are disturbed in AD are not well understood. With super-resolution structured illumination microscopy (SIM) revealing axonal structures, here we imaged the lattice structure of completely assembled AIS in APP/PS1 neurons. By analyzing the images with Gaussian fitting and 1D mean autocorrelation, we found dual spacings (∼200 nm and ∼370 nm) of Ankyrin-G (AnkG), Na_v1.2 and βIV-spectrin in AD model APP/PS1 mice due to the low-expressed 480-kDa AnkG. To identify the roles of each AnkG isoform, two isoforms were separately expressed in neurons from AnkG conditional knockout mice. Mice rescued with 270-kDa AnkG displayed dual spacings of AnkG components in cultured neurons and impaired in spatial memory, while transgenic mice expressing 480-kDa AnkG showed a normal molecular distribution in the AIS and normal cognitive performance. Our findings provide new insight into the mechanisms underlying impaired cognition associated with neurodegenerative diseases such as AD.

The neurobiology of non-coding RNAs and Alzheimer's disease pathogenesis: Pathways, mechanisms and translational opportunities

In the past two decades, advances in sequencing technology and analysis of the human and mouse genome have led to the discovery of many non-protein-coding RNAs (ncRNAs) including: microRNA, small-interfering RNAs, piwi-associated small RNAs, transfer RNA-derived small RNAs, long-non-coding RNAs and circular RNAs. Compared with healthy controls, levels of some ncRNAs are significantly altered in the central nervous system and blood of patients affected by neurodegenerative disorders like Alzheimer's disease (AD). Although the mechanisms are still not fully elucidated, studies have revealed that these highly conserved ncRNAs are important modulators of gene expression, amyloid-β production, tau phosphorylation, inflammation, synaptic plasticity and neuronal survival, all features considered central to AD pathogenesis. Despite considerable difficulties due to their large heterogeneity, and the complexity of their regulatory pathways, research in this rapidly growing field suggests that ncRNAs hold great potential as biomarkers and therapeutic targets against AD. Herein, we summarize the current knowledge regarding the neurobiology of ncRNA in the context of AD pathophysiology.

Reduced Levels of miR-342-5p in Plasma Are Associated With Worse Cognitive Evolution in Patients With Mild Alzheimer's Disease

Background

Progressive cognitive decline is the most relevant clinical symptom of Alzheimer’s disease (AD). However, the rate of cognitive decline is highly variable between patients. Synaptic deficits are the neuropathological event most correlated with cognitive impairment in AD. Considering the important role of microRNAs (miRNAs) in regulating synaptic plasticity, our objective was to identify the plasma miRNAs associated with the rate of cognitive decline in patients with mild AD.

Methods

We analyzed 754 plasma miRNAs from 19 women diagnosed with mild AD using TaqMan low-density array cards. The patients were grouped based on the rate of decline in the MMSE score after 2 years [<4 points (N = 11) and ≥4 points (N = 8)]. The differentially expressed miRNAs between the two groups were validated in an independent cohort of men and women (N = 53) with mild AD using RT-qPCR.

Results

In the discovery cohort, 17 miRNAs were differentially expressed according to the fold change between patients with faster declines in cognition and those with slower declines. miR-342-5p demonstrated differential expression between the groups and a good correlation with the rate of cognitive decline in the validation cohort (r = −0.28; p = 0.026). This miRNA had a lower expression level in patients who suffered from more severe decline than in those who were cognitively more stable after 2 years (p = 0.049).

Conclusion

Lower levels of miR-342-5p in plasma were associated with faster cognitive decline in patients with mild AD after 2 years of follow-up.

The Role of Non-coding RNAs in Alzheimer's Disease: From Regulated Mechanism to Therapeutic Targets and Diagnostic Biomarkers

Alzheimer’s disease (AD) is a progressive neurodegenerative disorder. AD is characterized by the production and aggregation of beta-amyloid (Aβ) peptides, hyperphosphorylated tau proteins that form neurofibrillary tangles (NFTs), and subsequent neuroinflammation, synaptic dysfunction, autophagy and oxidative stress. Non-coding RNAs (ncRNAs) can be used as potential therapeutic targets and biomarkers due to their vital regulatory roles in multiple biological processes involved in disease development. The involvement of ncRNAs in the pathogenesis of AD has been increasingly recognized. Here, we review the ncRNAs implicated in AD and elaborate on their main regulatory pathways, which might have contributions for discovering novel therapeutic targets and drugs for AD.

lncRNA-Associated Competitive Endogenous RNA Regulatory Network in an Aβ25-35-Induced AD Mouse Model Treated with Tripterygium Glycoside

BACKGROUND

Tripterygium glycoside (TG) has been suggested to have protective effects on the diseases of the central nervous system including Alzheimer's disease (AD). The mechanisms involving lncRNA-associated competing endogenous RNAs (ceRNAs) were shown to play important roles in the development of AD. However, the ceRNA mechanism of TG in treating AD is still unknown. Thus, we aimed to explore the ceRNA mechanism in the treatment of AD with TG.

METHODS

A total of 32 C57BL/6J mice were administered 3 µL of Aβ25-35 (dual side, 1 mg/mL) by a single stereotactic injection in the brain to conduct AD mouse model. AD mouse models were randomly selected and divided into the AD+normal saline (NS) group (n=16) and the AD+TG group (n=16). The expression data of lncRNAs, mRNAs, and miRNAs in the hippocampus of mice from AD+NS group (n=3) and the AD+TG group (n=3) were obtained by microarray analysis. The MuTaME method was used to predict the ceRNA regulatory network. Gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses were performed using the DAVID database. A protein-protein interaction (PPI) network was constructed by using STRING software.

RESULTS

TG can significantly improve spatial memory and inhibit the production of p-tau in an Aβ25-35-induced AD mouse model. A total of 661 differentially expressed lncRNAs, 503 mRNAs, and 13 miRNAs were identified. A ceRNA network involving the top 200 mRNA-miRNA-lncRNA pairs with 16 lncRNAs, 11 miRNAs, and 52 mRNAs was visualized. And a PPI network complex filtered 26 gene nodes in DEGs was predicted.

CONCLUSION

We have identified 503 DEGs, 661 DElncRNAs, and 13 DEmiRNAs during treatment with TG in Aβ25-35-induced AD mouse model. A ceRNA network based on the DElncRNAs, DEmRNAs, and DEmiRNAs was conducted, which provided new insight into the lncRNA-mediated ceRNA regulatory mechanisms underlying the effects of TG in the treatment of AD.

Circulating miR-342-5p serves as a diagnostic biomarker in patients with carotid artery stenosis and predicts the occurrence of the cerebral ischemic event

BACKGROUND

Carotid artery stenosis (CAS) is an important risk factor for cerebral ischemia events (CIE). Previous studies have shown that microRNAs (miRNAs) are involved in the occurrence and development of CAS.

AIMS

The purpose of this study was to reveal the clinical diagnostic value of miR-342-5p for asymptomatic CAS (ACAS) and to evaluate its predictive value for the occurrence of CIE in patients.

METHODS

A total of 92 ACAS patients and 86 healthy controls were enrolled as subjects. The expression level of serum miR-342-5p was detected by qRT-PCR. The receiver operating characteristic (ROC) curve was used to detect the diagnostic value of miR-342-5p in ACAS. Kaplan-Meier survival and Cox regression analysis assessed the predictive value of miR-342-5p for the occurrence of CIE in ACAS patients.

RESULTS

The level of serum miR-342-5p in ACAS patients was significantly higher than that in healthy controls (P < 0.05). ROC curve showed the high diagnostic value of serum miR-342-5p, which could distinguish ACAS patients from healthy controls. Multivariate Cox regression analysis confirmed that miR-342-5p was an independent predictor (HR = 5.512, 95%CI = 1.370-22.176, P = 0.016). What is more, Kaplan-Meier analysis confirmed that patients with high miR-342-5p expression develop more CIE (log-rank, P = 0.020).

CONCLUSIONS

miR-342-5p was significantly overexpressed in ACAS. And the upregulation of serum miR-342-5p is a valuable diagnostic biomarker and can predict the occurrence of CIE.

Modeling protein-protein interactions in axon initial segment to understand their potential impact on action potential initiation

The axon initial segment (AIS) region is crucial for action potential initiation due to the presence of high-density AIS protein voltage-gated sodium channels (Na_v). Na_v channels comprise several serine residues responsible for the recruitment of Na_v channels into the structure of AIS through interactions with ankyrin-G (AnkG). In this study, a series of computational experiments are performed to understand the role of AIS proteins casein kinase 2 and AnkG on Na_v channel recruitment into the AIS. The computational simulation results using Virtual cell software indicate that Na_v channels with all serine sites available for phosphorylation bind to AnkG with strong affinity. At the low initial concentration of AnkG and casein kinase 2, the concentration of Na_v channels reduces significantly, suggesting the importance of casein kinase 2 and AnkG in the recruitment of Na_v channels.

Lamin A involvement in ageing processes

Lamin A, a main constituent of the nuclear lamina, is the major splicing product of the LMNA gene, which also encodes lamin C, lamin A delta 10 and lamin C2. Involvement of lamin A in the ageing process became clear after the discovery that a group of progeroid syndromes, currently referred to as progeroid laminopathies, are caused by mutations in LMNA gene. Progeroid laminopathies include Hutchinson-Gilford Progeria, Mandibuloacral Dysplasia, Atypical Progeria and atypical-Werner syndrome, disabling and life-threatening diseases with accelerated ageing, bone resorption, lipodystrophy, skin abnormalities and cardiovascular disorders. Defects in lamin A post-translational maturation occur in progeroid syndromes and accumulated prelamin A affects ageing-related processes, such as mTOR signaling, epigenetic modifications, stress response, inflammation, microRNA activation and mechanosignaling. In this review, we briefly describe the role of these pathways in physiological ageing and go in deep into lamin A-dependent mechanisms that accelerate the ageing process. Finally, we propose that lamin A acts as a sensor of cell intrinsic and environmental stress through transient prelamin A accumulation, which triggers stress response mechanisms. Exacerbation of lamin A sensor activity due to stably elevated prelamin A levels contributes to the onset of a permanent stress response condition, which triggers accelerated ageing.

Modulation of MicroRNAs as a Potential Molecular Mechanism Involved in the Beneficial Actions of Physical Exercise in Alzheimer Disease

Alzheimer disease (AD) is one of the most common neurodegenerative diseases, affecting middle-aged and elderly individuals worldwide. AD pathophysiology involves the accumulation of beta-amyloid plaques and neurofibrillary tangles in the brain, along with chronic neuroinflammation and neurodegeneration. Physical exercise (PE) is a beneficial non-pharmacological strategy and has been described as an ally to combat cognitive decline in individuals with AD. However, the molecular mechanisms that govern the beneficial adaptations induced by PE in AD are not fully elucidated. MicroRNAs are small non-coding RNAs involved in the post-transcriptional regulation of gene expression, inhibiting or degrading their target mRNAs. MicroRNAs are involved in physiological processes that govern normal brain function and deregulated microRNA profiles are associated with the development and progression of AD. It is also known that PE changes microRNA expression profile in the circulation and in target tissues and organs. Thus, this review aimed to identify the role of deregulated microRNAs in the pathophysiology of AD and explore the possible role of the modulation of microRNAs as a molecular mechanism involved in the beneficial actions of PE in AD.

Central and Peripheral Metabolic Defects Contribute to the Pathogenesis of Alzheimer's Disease: Targeting Mitochondria for Diagnosis and Prevention

Significance: Epidemiological studies indicate that metabolic disorders are associated with an increased risk for Alzheimer's disease (AD). Metabolic remodeling occurs in the central nervous system (CNS) and periphery, even in the early stages of AD. Mitochondrial dysfunction has been widely accepted as a molecular mechanism underlying metabolic disorders. Therefore, focusing on early metabolic changes, especially from the perspective of mitochondria, could be of interest for early AD diagnosis and intervention. Recent Advances: We and others have identified that the levels of several metabolites are fluctuated in the periphery before their accumulation in the CNS, which plays an important role in the pathogenesis of AD. Mitochondrial remodeling is likely one of the earliest signs of AD, linking nutritional imbalance to cognitive deficits. Notably, by improving mitochondrial function, mitochondrial nutrients efficiently rescue cellular metabolic dysfunction in the CNS and periphery in individuals with AD. Critical Issues: Peripheral metabolic disorders should be intensively explored and evaluated for the early diagnosis of AD. The circulating metabolites derived from mitochondrial remodeling represent novel potential diagnostic biomarkers for AD that are more readily detected than CNS-oriented biomarkers. Moreover, mitochondrial nutrients provide a promising approach to preventing and delaying AD progression. Future Directions: Abnormal mitochondrial metabolism in the CNS and periphery is involved in AD pathogenesis. More clinical studies provide evidence for the suitability and reliability of circulating metabolites and cytokines for the early diagnosis of AD. Targeting mitochondria to rewire cellular metabolism is a promising approach to preventing AD and ameliorating AD-related metabolic disorders.

Changes in microRNAs Expression Profile of Mimetic Aging Mice Treated with Melanin from Sepiella japonica Ink

A natural melanin extracted from Sepiella japonica ink (MSJI) is a polymer with antioxidant properties. In this study, the effects of MSJI treatment on microRNAs differentially expressed during aging in mimetic mice were investigated. The results revealed that 8 miRNAs: mmu-miR-1971, mmu-miR-3070b-3p, mmu-miR-320-3p, mmu-miR-342-3p, mmu-miR-350-3p, mmu-miR-5132-5p, mmu-miR-697, and mmu-miR-712-5p showed significantly different expression between mice treated with MSJI gavage and aging mice. GO analysis and signaling pathway analysis revealed that the predicted target genes were involved in diverse biological processes such as steroid and cholesterol metabolism, xenobiotic, demethylation, and circadian regulation of gene expression, suggesting a potential role in antiaging. The dual-luciferase reporter gene assay confirmed the downregulation of mmu-miR-697 in HS samples and targeting of the Gpt2 which plays an important role in aging. This study supports the hypothesis that MSJI prolongs the cell cycle by acting as an antioxidant to delay decrepitude.

Interplay between MicroRNAs and Oxidative Stress in Neurodegenerative Diseases

MicroRNAs are post-transcriptional regulators of gene expression, crucial for neuronal differentiation, survival, and activity. Age-related dysregulation of microRNA biogenesis increases neuronal vulnerability to cellular stress and may contribute to the development and progression of neurodegenerative diseases. All major neurodegenerative disorders are also associated with oxidative stress, which is widely recognized as a potential target for protective therapies. Albeit often considered separately, microRNA networks and oxidative stress are inextricably entwined in neurodegenerative processes. Oxidative stress affects expression levels of multiple microRNAs and, conversely, microRNAs regulate many genes involved in an oxidative stress response. Both oxidative stress and microRNA regulatory networks also influence other processes linked to neurodegeneration, such as mitochondrial dysfunction, deregulation of proteostasis, and increased neuroinflammation, which ultimately lead to neuronal death. Modulating the levels of a relatively small number of microRNAs may therefore alleviate pathological oxidative damage and have neuroprotective activity. Here, we review the role of individual microRNAs in oxidative stress and related pathways in four neurodegenerative conditions: Alzheimer’s (AD), Parkinson’s (PD), Huntington’s (HD) disease, and amyotrophic lateral sclerosis (ALS). We also discuss the problems associated with the use of oversimplified cellular models and highlight perspectives of studying microRNA regulation and oxidative stress in human stem cell-derived neurons.

Identification of MicroRNA Targeting Mlph and Affecting Melanosome Transport

Melanosomes undergo a complex maturation process and migrate into keratinocytes. Melanophilin (Mlph), a protein complex involving myosin Va (MyoVa) and Rab27a, enables the movement of melanosomes in melanocytes. In this study, we found six miRNAs targeting Mlph in mouse using two programs (http://targetscan.org and DianaTools). When melan-a melanocytes were treated with six synthesized microRNAs, miR-342-5p, miR-1839-5p, and miR-3082-5p inhibited melanosome transport and induced melanosome aggregation around the nucleus. The other microRNAs, miR-5110, miR-3090-3p, and miR-186-5p, did not inhibit melanosome transport. Further, miR-342-5p, miR-1839-5p, and miR-3082-5p decreased Mlph expression. The effect of miR-342-5p was the strongest among the six synthesized miRNAs. It inhibited melanosome transport in melan-a melanocytes and reduced Mlph expression in mRNA and protein levels in a dose-dependent manner; however, it did not affect Rab27a and MyoVa expressions, which are associated with melanosome transport. To examine miR-342-5p specificity, we performed luciferase assays in a mouse melanocyte-transfected reporter vector including Mlph at the 3′-UTR (untranslated region). When treated with miR-342-5p, luciferase activity that had been reduced by approximately 50% was restored after inhibitor treatment. Therefore, we identified a novel miRNA affecting Mlph and melanosome transport, and these results can be used for understanding Mlph expression and skin pigmentation regulation.

MicroRNA in Alzheimer's disease revisited: implications for major neuropathological mechanisms

Pathology of Alzheimer's disease (AD) goes far beyond neurotoxicity resulting from extracellular deposition of amyloid β (Aβ) plaques. Aberrant cleavage of amyloid precursor protein and accumulation of Aβ in the form of the plaque or neurofibrillary tangles are the known primary culprits of AD pathogenesis and target for various regulatory mechanisms. Hyper-phosphorylation of tau, a major component of neurofibrillary tangles, precipitates its aggregation and prevents its clearance. Lipid particles, apolipoproteins and lipoprotein receptors can act in favor or against Aβ and tau accumulation by altering neural membrane characteristics or dynamics of transport across the blood-brain barrier. Lipids also alter the oxidative/anti-oxidative milieu of the central nervous system (CNS). Irregular cell cycle regulation, mitochondrial stress and apoptosis, which follow both, are also implicated in AD-related neuronal loss. Dysfunction in synaptic transmission and loss of neural plasticity contribute to AD. Neuroinflammation is a final trail for many of the pathologic mechanisms while playing an active role in initiation of AD pathology. Alterations in the expression of microRNAs (miRNAs) in AD and their relevance to AD pathology have long been a focus of interest. Herein we focused on the precise pathomechanisms of AD in which miRNAs were implicated. We performed literature search through PubMed and Scopus using the search term: ('Alzheimer Disease') OR ('Alzheimer's Disease') AND ('microRNAs' OR 'miRNA' OR 'MiR') to reach for relevant articles. We show how a limited number of common dysregulated pathways and abnormal mechanisms are affected by various types of miRNAs in AD brain.

Cell cycle reentry triggers hyperploidization and synaptic dysfunction followed by delayed cell death in differentiated cortical neurons

Cell cycle reentry followed by neuronal hyperploidy and synaptic failure are two early hallmarks of Alzheimer's disease (AD), however their functional connection remains unexplored. To address this question, we induced cell cycle reentry in cultured cortical neurons by expressing SV40 large T antigen. Cell cycle reentry was followed by hyperploidy in ~70% of cortical neurons, and led to progressive axon initial segment loss and reduced density of dendritic PSD-95 puncta, which correlated with diminished spike generation and reduced spontaneous synaptic activity. This manipulation also resulted in delayed cell death, as previously observed in AD-affected hyperploid neurons. Membrane depolarization by high extracellular potassium maintained PSD-95 puncta density and partially rescued both spontaneous synaptic activity and cell death, while spike generation remained blocked. This suggests that AD-associated hyperploid neurons can be sustained in vivo if integrated in active neuronal circuits whilst promoting synaptic dysfunction. Thus, cell cycle reentry might contribute to cognitive impairment in early stages of AD and neuronal death susceptibility at late stages.

miR‑342‑5p promotes Zmpste24‑deficient mouse embryonic fibroblasts proliferation by suppressing GAS2

Cellular senescence is an irreversible growth arrest of cells that maintain their metabolic activities. Premature senescence can be induced by different stress factors and occurs in mouse embryonic fibroblasts (MEFs) derived from Zmpste24 metalloproteinase-deficient mice, a progeria mouse model of Hutchinson-Gilford Progeria Syndrome. Previous studies have shown that miR-342-5p, an intronic microRNA (miRNA/miR) reportedly involved in ageing associated diseases, is downregulated in Zmpste24^−/− MEFs. However, whether miR-342-5p is associated with the premature senescence phenotype of Zmpste24^−/− MEFs remains unclear. Thus, the present study investigated the effects of miR-342-5p on cellular senescence and cell proliferation in Zmpste24^−/− MEFs. The results showed that miR-342-5p overexpression ameliorated the cellular senescence phenotype to a certain extent, promoted cell proliferation and increased the G2+M cell cycle phase in Zmpste24^−/− MEFs. Nonetheless, it was difficult to observe the opposite cell phenotypes in wild-type (WT) MEFs transfected with the miR-342-5p inhibitor. Growth-arrest-specific 2 (GAS2) was identified as a target gene of miR-342-5p in Zmpste24^−/− MEFs. In addition, miR-342-5p was identified to be downregulated in WT MEFs during replicative senescence, while Gas2 was upregulated. Taken together, these findings suggest that downregulated miR-342-5p is involved in regulating cell proliferation and cell cycles in Zmpste24^−/− MEFs by suppressing GAS2 in vitro.

AnkG hemizygous mice present cognitive impairment and elevated anxiety/depressive-like traits associated with decreased expression of GABA receptors and postsynaptic density protein

Recent genome-wide association studies (GWAS) of patient populations and genetic linkage assessments have demonstrated that the ankyrin-G (AnkG) gene is involved in neuropsychiatric disorders, including bipolar disorder, schizophrenia, and Alzheimer's disease, but it remains unclear how the genetic variants of AnkG contribute to neuropsychiatric disorders. Here, we generated AnkG hemizygous mice using the gene trapping approach. Homozygous AnkG was embryonically lethal. Western blotting and real-time polymerase chain reaction (qPCR) assessments of wild type (WT) and AnkG ^+/- mutant mice demonstrated a 50% reduction of ANKG levels, at the gene and protein levels, in AnkG hemizygous mice. In behavioral tests, AnkG hemizygous mice exhibited elevated anxiety- and depression-like traits, as well as cognitive impairment. Moreover, the expression levels of cognitive-related proteins (including metabotropic glutamate receptor subtype-1, brain-derived neurotrophic factor, postsynaptic density-95, GABA-B receptor, and GABA-A receptor alpha-1) were significantly decreased (P < 0.05), suggesting a possible role for AnkG in cognition. It is possible that the loss of AnkG in the brain disrupts the excitation/inhibition balance of neurotransmitters, hindering the synaptic plasticity of neurons, and consequently leading to abnormal behavioral symptoms. Therefore, AnkG possibly contributes to neuroprotection and normal brain function, and may constitute a new target for treating neuropsychiatric diseases, especially cognitive dysfunction.

Linking deregulation of non-coding RNA to the core pathophysiology of Alzheimer's disease: An integrative review

The human genome encodes a vast repertoire of protein non-coding RNAs (ncRNA), some specific to the brain. MicroRNAs, which interfere with the translation of target mRNAs, are of particular interest since their deregulation has been implicated in neurodegenerative disorders like Alzheimer's disease (AD). However, it remains challenging to link the complex body of observations on miRNAs and AD into a coherent framework. Using extensive graphical support, this article discusses how a diverse panoply of miRNAs convergently and divergently impact (and are impacted by) core pathophysiological processes underlying AD: neuroinflammation and oxidative stress; aberrant generation of β-amyloid-42 (Aβ42); anomalies in the production, cleavage and post-translational marking of Tau; impaired clearance of Aβ42 and Tau; perturbation of axonal organisation; disruption of synaptic plasticity; endoplasmic reticulum stress and the unfolded protein response; mitochondrial dysfunction; aberrant induction of cell cycle re-entry; and apoptotic loss of neurons. Intriguingly, some classes of miRNA provoke these cellular anomalies, whereas others act in a counter-regulatory, protective mode. Moreover, changes in levels of certain species of miRNA are a consequence of the above-mentioned anomalies. In addition to miRNAs, circular RNAs, piRNAs, long non-coding RNAs and other types of ncRNA are being increasingly implicated in AD. Overall, a complex mesh of deregulated and multi-tasking ncRNAs reciprocally interacts with core pathophysiological mechanisms underlying AD. Alterations in ncRNAs can be detected in CSF and the circulation as well as the brain and are showing promise as biomarkers, with the ultimate goal clinical exploitation as targets for novel modes of symptomatic and course-altering therapy.

Effects of ankyrin 3 gene risk variants on brain structures in patients with bipolar disorder and healthy subjects

AIM

The intronic single-nucleotide polymorphism rs10994336 of the ankyrin 3 gene (ANK3 ) is one of the genome-wide supported risk variants for bipolar disorder (BD), and the T-allele of rs10761482 is also reported to have relevance to BD. We investigated the effect of ANK3 rs10761482 genetic variation on brain structure.

METHODS

Subjects were 43 BD patients and 229 healthy volunteers. We evaluated the effects of ANK3 rs10761482 genetic variation on diagnosis, and of the genotype-by-diagnosis interaction on the brain structure and the degree of age-related brain atrophy on magnetic resonance imaging data evaluated by voxel-based morphometry.

RESULTS

BD patients showed significantly lower fractional anisotropy value in the bilateral parietal regions, left fronto-occipital fasciculus, and corpus callosum, compared to healthy subjects. Further, we found considerable decreases of fractional anisotropy in the forceps minor in non-T-allele BD patients compared with the T-carrier patient group. We also found significant lessening of age-related brain atrophy in the T-allele carrier groups compared with the non-T-allele carrier groups in the area around the cerebrospinal space, cingulate cortices, and cerebellum.

CONCLUSION

Our results suggest the influence of the ANK3 on age-related brain atrophy. The ankyrin 3 genotype may be associated with pathogenesis of age-related neurodegeneration, and, in part, of BD.

Axon Initial Segment Cytoskeleton: Architecture, Development, and Role in Neuron Polarity

The axon initial segment (AIS) is a specialized structure in neurons that resides in between axonal and somatodendritic domains. The localization of the AIS in neurons is ideal for its two major functions: it serves as the site of action potential firing and helps to maintain neuron polarity. It has become increasingly clear that the AIS cytoskeleton is fundamental to AIS functions. In this review, we discuss current understanding of the AIS cytoskeleton with particular interest in its unique architecture and role in maintenance of neuron polarity. The AIS cytoskeleton is divided into two parts, submembrane and cytoplasmic, based on localization, function, and molecular composition. Recent studies using electron and subdiffraction fluorescence microscopy indicate that submembrane cytoskeletal components (ankyrin G, βIV-spectrin, and actin filaments) form a sophisticated network in the AIS that is conceptually similar to the polygonal/triangular network of erythrocytes, with some important differences. Components of the AIS cytoplasmic cytoskeleton (microtubules, actin filaments, and neurofilaments) reside deeper within the AIS shaft and display structural features distinct from other neuronal domains. We discuss how the AIS submembrane and cytoplasmic cytoskeletons contribute to different aspects of AIS polarity function and highlight recent advances in understanding their AIS cytoskeletal assembly and stability.

MicroRNA-146a represses LRP2 translation and leads to cell apoptosis in Alzheimer's disease

MicroRNA regulation of transcript expression has been reported in patients with Alzheimer's disease (AD). Here, we investigate the role of microRNA-146a (miRNA-146a), a brain-enriched miRNA, which is upregulated in AD patients. Through analysis of predicted targets of miRNA-146a, low-density lipoprotein receptor-related protein-2 (Lrp2), a member of the LDLR family that is known to play a protective role in AD, was identified. Overexpression of miRNA-146a in SH-SY5Y cells significantly decreased Lrp2 expression, resulting in a reduction of Akt activation and induction of proapoptotic caspase-3, thereby increasing cell apoptosis. Thus, specific miRNA-146a regulation may contribute to AD by downregulating the Lrp2/Akt pathway.

MicroRNA-574 is involved in cognitive impairment in 5-month-old APP/PS1 mice through regulation of neuritin

Alzheimer's disease (AD) is the most common form of dementia in the elderly. The recent evidence in AD research suggests that alterations in the microRNA (miRNA) could contribute to risk for the disease. However, little is understood about the roles of miRNAs in cognitive impairment of early Alzheimer's disease (AD). Here, we used 5-month-old APP/PS1 mice, which mimic many of the salient features of the early stage of AD pathological process, to further investigate the roles of miRNAs in synaptic loss involved in learning and memory. We used miRNA expression microarrays on RNA extracted from the hippocampus of 5-month-old APP/PS1 mice and wild type mice. Real-time reverse transcription PCR was conducted to verify the candidate miRNAs discovered by microarray analysis. The data showed that miR-574 was increased significantly in the hippocampus of 5-month-old APP/PS1 mice, which were concomitant with that APP/PS1 mice at the same age displayed a significant synaptic loss and cognitive deficits. Bioinformatic analysis predicted that neuritin (Nrn1) mRNA is targeted by miR-574. Overexpression of miR-574 lowers the levels of neuritin and synaptic proteins expression in primary hippocampal neurons damage induced by Aβ25-35. And the expression of miR-574 was also up-regulated in the hippocampal neurons from APP/PS1 mice compared with WT littermates. In contrast, suppression of miR-574 by miR-574 inhibitor significantly results in higher levels of neuritin and synaptic proteins expression. Taken together, miR-574 is involved in cognitive impairment in 5-month-old APP/PS1 mice through regulation of neuritin.

Alzheimer's Disease: Genomics and Beyond

Alzheimer's disease (AD) is a major form of senile dementia. Despite the critical roles of Aβ and tau in AD pathology, drugs targeting Aβ or tau have so far reached limited success. The advent of genomic technologies has made it possible to gain a more complete picture regarding the molecular network underlying the disease progression which may lead to discoveries of novel treatment targets. In this review, we will discuss recent progresses in AD research focusing on genome, transcriptome, epigenome, and related subjects. Advancements have been made in the finding of novel genetic risk factors, new hypothesis for disease mechanism, candidate biomarkers for early diagnosis, and potential drug targets. As an integration effort, we have curated relevant data in a database named AlzBase.

Molecular mechanism of regulation of villus cell Na-K-ATPase in the chronically inflamed mammalian small intestine

Na-K-ATPase located on the basolateral membrane (BLM) of intestinal epithelial cells provides a favorable intracellular Na+ gradient to promote all Na dependent co-transport processes across the brush border membrane (BBM). Down-regulation of Na-K-ATPase activity has been postulated to alter the absorption via Na-solute co-transporters in human inflammatory bowel disease (IBD). Further, the altered activity of a variety of Na-solute co-transporters in intact villus cells has been reported in animal models of chronic enteritis. But the molecular mechanism of down-regulation of Na-K-ATPase is not known. In the present study, using a rabbit model of chronic intestinal inflammation, which resembles human IBD, Na-K-ATPase in villus cells was shown to decrease. The relative mRNA abundance of α-1 and β-1 subunits was not altered in villus cells during chronic intestinal inflammation. Similarly, the protein levels of these subunits were also not altered in villus cells during chronic enteritis. However, the BLM concentration of α-1 and β-1 subunits was diminished in the chronically inflamed intestinal villus cells. An ankyrin-spectrin skeleton is necessary for the proper trafficking of Na-K-ATPase to the BLM of the cell. In the present study, ankyrin expression was markedly diminished in villus cells from the chronically inflamed intestine resulting in depolarization of ankyrin-G protein. The decrease of Na-K-ATPase activity was comparable to that seen in ankyrin knockdown IEC-18 cells. Therefore, altered localization of Na-K-ATPase as a result of transcriptional down-regulation of ankyrin-G mediates the down-regulation of Na-K-ATPase activity during chronic intestinal inflammation.

Selective filtering defect at the axon initial segment in Alzheimer's disease mouse models

Axon pathology has been widely reported in Alzheimer's disease (AD) patients and AD mouse models. Herein we report that increased miR-342-5p down-regulates the expression of ankyrin G (AnkG), a protein known to play a critical role in establishing selective filtering machinery at the axon initial segment (AIS). Diminished AnkG expression leads to defective AIS filtering in cultured hippocampal neurons from AD mouse models, as monitored by selective exclusion of large macromolecules from the axons. Furthermore, AnkG-deficiency impairs AIS localization of Nav 1.6 channels and confines NR2B to the somatodendritic compartments. The expression of exogenous AnkG improved the cognitive performance of 12-mo-old APP/PS1 mice; thus, our data suggest that AnkG and impairment of AIS filtering may play important roles in AD pathology.

MicroRNA and diseases: therapeutic potential as new generation of drugs

MicroRNA (miRNA) is a small non-coding regulatory RNA of 21-25 nucleotides (nts) in length. miRNA works as a post-transcriptional regulator of a specific mRNA by inducing degradation or translation repression resulting in gene silencing. A large number of miRNA have been reported and many more are yet to be discovered. Aberrant expression of miRNA has been linked to numerous diseases. Attempts have been made to attenuate miRNA misregulation under pathophysiological conditions. Additionally, the potential use of miRNA in the diagnosis and treatment of diseases has been studied. Several preclinical and clinical results have been obtained, and miRNA-based therapeutics are still under investigations. In this review, the role of miRNA in a variety of pathological conditions has been summarized. Recent findings from preclinical and clinical investigations examining the role of miRNA as diagnostic markers, and their potential as drug candidates, are also highlighted. The current results summarized in this review may elucidate new dimensions of miRNA therapeutic and diagnostic techniques for biomedical academic and industry research.