MicroRNA-455-3p improves synaptic, cognitive functions and extends lifespan: Relevance to Alzheimer's disease

Therapeutic potential of DDQ in enhancing mitochondrial health and cognitive function in Late-Onset Alzheimer's disease

Alzheimer's disease (AD) is a neurodegenerative disorder characterized by cognitive decline, mitochondrial dysfunction, and neuroinflammation. This study evaluates the therapeutic potential of DDQ, a small molecule in the humanized Abeta knockin (hAbKI) mice that represents late-onset AD. Our findings demonstrate that DDQ treatment significantly improves cognitive performance as assessed through behavioral tests, including the rotarod, open field, Y-maze, and Morris water maze, compared to untreated hAbKI mice. At the molecular level, DDQ promoted mitochondrial biogenesis, as evidenced by enhanced expression of key proteins like PGC1α, NRF1, and TFAM. Additionally, DDQ treatment facilitated mitophagy, as indicated by elevated levels of PINK1 and Parkin, and reduced neuroinflammation, reflected by decreased Iba1 and GFAP levels. Transmission electron microscopy analysis revealed a marked improvement in mitochondrial morphology, with increased mitochondrial length and reduced mitochondrial numbers in DDQ-treated mice. Furthermore, DDQ treatment led to an increase in mitophagic vacuoles, suggesting that it effectively removes dysfunctional mitochondria. Taken together, for the first time, our study results support the potential of DDQ as a promising neuroprotective agent for late-onset AD, addressing mitochondrial dysfunction, neuroinflammation, and cognitive decline. Our study focused on developing small molecules that modulate mitophagy, mitochondrial dynamics and neuroinflammatory pathways for aging, AD and other neurodegenerative disorders.

Harnessing the Role of ESR1 in Breast Cancer: Correlation with microRNA, lncRNA, and Methylation

Breast cancer (BC) is a multifactorial condition and it primarily expresses the estrogen receptor α (ERα) that is encoded by the gene estrogen receptor 1 (ESR1), which modulates estrogen signaling. ESR1, by facilitating estrogen overproduction, plays an indispensable role in the progression and survival of the majority of BCs. To obtain molecular insights into these phenomena, we analyzed The Cancer Genome Atlas (TCGA) breast invasive carcinoma (BRCA) RNA-Seq datasets for the expression of ESR1 and its correlation to microRNAs (miRNAs) and long non-coding RNAs (lncRNAs), along with its methylation patterns. Regulation of ESR1 was also assessed with a total of 43 cancerous and non-cancerous breast cell lines. Analyses of both TCGA BRCA and breast cell line RNA-Seq data revealed that specific lncRNAs, i.e., MEG3, BIK, MLL, and FAS are negatively correlated with the ESR1, in which PARP1 demonstrates a positive association. Additionally, both miR-30a and miR-145 showed negative correlations with the ESR1 expression. Of the 54 ESR1 methylation loci analyzed, the majority of them exhibited a negative correlation with the ESR1 expression, highlighting a potentially modifiable regulatory mechanism. These findings underscore the complex regulatory events influencing ESR1 expression and its interaction with diverse signaling pathways, demonstrating novel insights into breast pathogenesis and its potential therapeutics.

The microRNA-455 null mouse shows dysregulated bone turnover

A wide range of specific microRNAs have been shown to have either positive or negative effects on osteoblast differentiation and function, with consequent changes in postnatal bone mass. A number of specific targets have been identified. We previously used CrispR-Cas9 to make a miR-455 null mouse, characterizing a behavioral phenotype with age. The current study identifies a bone phenotype, starting in younger animals. At 3 weeks of age, the miR-455 null mice (both male and female) display increased length of both long bones and vertebrae and, while this difference diminishes across 1 year, it remains significant. Increased bone formation in vivo is mirrored by an increase in osteogenesis from bone marrow-derived stem cells in vitro. This is accompanied by a decrease in osteoclastogenesis and osteoclast function. MicroCT analyses show increased trabecular bone and less porosity/decreased separation in the miR-455 null mouse, suggesting a more dense and stronger bone at 3 weeks of age; these differences normalize by 1 year. Gain-of-function and loss-of-function datasets show that FGF18 expression is regulated by miR-455 and FGF18 was validated as a direct target of miR-455. The regulation of FGF18 by miR-455 is a likely mediator of its effect on bone.

Application of the Trend of miRNA Expression Levels in APP/PS1 Mice Plasma for the Early Diagnosis of Alzheimer's Disease

Alzheimer's disease (AD) is the most common form of dementia and seriously affects people's quality of life. In recent years, many circulating microRNAs (miRNAs) have been reported as potential diagnostic biomarkers for AD. However, there are no reliable miRNAs for early diagnosis of AD because miRNAs are dynamically changing during the disease process. The present study was to seek reliable biomarkers for early diagnosis of AD by detecting changes in miRNAs in plasma from young APPswe/PS1Δ9 double-transgenic mice (APP/PS1 mice) using a quantitative real-time PCR (qRT-PCR) method. Some behavioral experiments and pathological tests were used to characterize the progress of AD in APP/PS1 transgenic mice. The results showed that the expression levels of several plasma miRNAs targeting BACE1 and APP showed consistent trends in the early stages of APP/PS1 mice. The expression levels of miR-34a-5p, miR-29c-3p, miR-107-3p, and miR-101a-3p in the plasma of APP/PS1 female mice decreased with cognitive decline, demonstrating their potential as biomarkers for early diagnosis of female AD patients. The expression levels of these miRNAs fluctuated significantly in APP/PS1 male mice, and the reason for this difference may be related to the biological sex differences in AD. This fluctuation may serve as an indicative risk signal for the early stage of AD in male patients.

MicroRNA-based recent research developments in Alzheimer's disease

Alzheimer's disease (AD) is a chronic neurodegenerative disorder that is characterized by memory and physical impairment in aged individuals. microRNAs (miRNAs) are small, single-stranded noncoding RNAs that induce translational repression by binding to the 3' UTR of a target mRNA. miRNAs play a crucial role in neurological activity by mediating cellular proliferation, synaptic plasticity, apoptosis and more. Ongoing research in patents and clinical trials have called attention to promising miRNAs as biomarkers and therapeutics in AD. Recent research has shown that miRNAs are aberrantly expressed in AD brain, blood, cerebrospinal fluid and serum. Attenuated miRNA expressions have diagnostic potential in AD by interacting with amyloid-β synthesis, phosphorylated tau, and neurofibrillary tangles. In this study, miRNA-29a, miRNA-125b, miRNA-34a, miRNA-146a, and miRNA-155 have shown promise as potential biomarker candidates for AD. Improving cognitive symptoms can be traced to restoring the endogenous miRNA activity by synthesizing miRNA mimics and miRNA antisense oligonucleotides. miRNA-483-5p, miRNA-188-5p, miRNA-219, miRNA135a/5p, miRNA-23/23b-3p, miRNA-124, and miRNA-455-3p are growing therapeutics for AD. However, miRNA-based therapeutics struggle outside of preclinical testing. miRNA-107, miRNA-206, miRNA-30/7, and miRNA-142-3p face bottlenecks in clinical trials due to a lack of experimental design, transparency and volunteer size. Patenting recent miRNA-based developments demonstrates the commitment in identifying a new biomarker and/or therapeutic for AD.

Long noncoding RNA Gm4419 promotes mesangial cell proliferation and extracellular matrix accumulation via the miR-455-3p/histone deacetylase 2 axis

Long noncoding RNAs may function as competitive endogenous RNAs by sponging microRNAs, thereby contributing to the progression of diabetic nephropathy. In this study, a potential diabetic nephropathy-related long noncoding-microRNA-mRNA axis, Gm4419-miR-455-3p-Hdac2, was predicted using bioinformatics methods. To verify the role of the Gm4419-miR-455-3p-Hdac2 axis in diabetic nephropathy, an in vitro high glucose-induced mesangial cell model was established. The expression levels of Gm4419, miR-455-3p and Hdac2 were detected using reverse-transcription quantitative PCR. Protein levels of collagen IV, fibronectin and transforming growth factor-beta 1 were detected using western blotting. Cell counting kit-8 assay and 5-ethynyl-2'-deoxyuridine staining assay were adopted to assess cell proliferation. Cell transfection, fluorescence in situ hybridization, RNA immunoprecipitation, and dual luciferase reporter assay were also performed. Our results revealed significant cell proliferation and extracellular matrix accumulation in high glucose-treated mesangial cells. In addition, Gm4419 and Hdac2 levels were increased and miR-455-3p was decreased in high glucose-treated mesangial cells. The interaction between Gm4419 and miR-455-3p or miR-455-3p and Hdac2 was confirmed by reverse-transcription quantitative PCR and dual luciferase reporter assay. Gene silencing of Gm4419 inhibited mesangial cells proliferation and extracellular matrix accumulation. MiR-455-3p inhibitor counteracted the effects of Gm4419 gene silencing on cell proliferation and extracellular matrix accumulation, which was reversed again by Hdac2 gene silencing. In summary, our research indicates that gene silencing of Gm4419 can effectively inhibit high glucose-induced mesangial cells proliferation and extracellular matrix accumulation. This is achieved through the regulation of the miR-455-3p/Hdac2 axis, highlighting the potential of the Gm4419-miR-455-3p-Hdac2 axis as a promising therapeutic target for the treatment of diabetic nephropathy.

MiRNA-501-3p and MiRNA-502-3p: A Promising Biomarker Panel for Alzheimer's Disease

INTRODUCTION

Alzheimer's disease (AD) lacks a less invasive and early detectable biomarker. Here, we investigated the biomarker potential of miR-501-3p and miR-502-3p using different AD sources.

METHODS

MiR-501-3p and miR-502-3p expressions were evaluated in AD CSF exosomes, serum exosomes, familial and sporadic AD fibroblasts and B-lymphocytes by qRT-PCR analysis. Further, miR-501-3p and miR-502-3p expressions were analyzed in APP, Tau cells and media exosomes.

RESULTS

MiR-501-3p and miR-502-3p expressions were significantly upregulated in AD CSF exosomes relative to controls. MiRNA levels were high in accordance with amyloid plaque and NFT density in multiple brain regions. Similarly, both miRNAs were elevated in AD and MCI serum exosomes compared to controls. MiR-502-3p expression was high in fAD and sAD B-lymphocytes. Finally, miR-501-3p and miR-502-3p expression were elevated intracellularly and secreted extracellularly in response to APP and Tau pathology.

DISCUSSION

These results suggest that miR-501-3p and miR-502-3p could be promising biomarkers for AD.

Non-coding RNAs participate in interactions between senescence and gastrointestinal cancers

Relationships between cellular senescence and gastrointestinal cancers have gained prominence in recent years. The currently accepted theory suggests that cellular senescence and cancer occurrence exhibit "double-edged sword" effects. Cellular senescence is related to cancer via four "meta-hallmarks" i.e., genomic instability, epigenetic alterations, chronic inflammation, and dysbiosis, along with two "antagonistic hallmarks" i.e., telomere attrition and stem cell exhaustion. These relationships are characterized by both agonistic and antagonistic elements, but the existence of an intricate dynamic balance remains unknown. Non-coding RNAs (ncRNAs) have vital roles in post-transcriptional regulation, but how they participate in agonistic and antagonistic relationships between cellular senescence and gastrointestinal cancers remains to be fully investigated. In this article, we systematically review how ncRNAs (including microRNAs (miRNAs), long ncRNAs (lncRNAs), and circularRNAs (circRNAs)) participate in interactions between cellular senescence and gastrointestinal cancers. Our aim is to elucidate a triangular relationship between "ncRNAs-senescence-gastrointestinal cancers" which considered these three elements as an equal important standing. We are keen to identify prognostic or therapeutic targets for gastrointestinal cancers from, i.e., aging-related ncRNAs, or discover novel strategies to treat and manage in the elderly. We seek to clarify complex relationships where ncRNAs participate in "senescence-gastrointestinal cancers" interactions.

Mitochondrial dysfunction as a therapeutic strategy for neurodegenerative diseases: Current insights and future directions

Neurodegenerative diseases, as common diseases in the elderly, tend to become younger due to environmental changes, social development and other factors. They are mainly characterized by progressive loss or dysfunction of neurons in the central or peripheral nervous system, and common diseases include Parkinson's disease, Alzheimer's disease, Huntington's disease and so on. Mitochondria are important organelles for adenosine triphosphate (ATP) production in the brain. In recent years, a large amount of evidence has shown that mitochondrial dysfunction plays a direct role in neurodegenerative diseases, which is expected to provide new ideas for the treatment of related diseases. This review will summarize the main mechanisms of mitochondrial dysfunction in neurodegenerative diseases, as well as collating recent advances in the study of mitochondrial disorders and new therapies.

Blood-based microRNAs as the potential biomarkers for Alzheimer's disease: evidence from a systematic review

Alzheimer's disease (AD) is a neurodegenerative disorder that progresses over time and is identified by the development of neurofibrillary tangles and amyloid deposits in the brain. Mounting evidence has revealed that microRNAs (miRNAs) are significantly involved in AD progression, and may be used as promising biomarkers for diagnosis and prognosis. Nevertheless, the existing body of data regarding dysregulated circulating miRNAs in AD and their therapeutic applications are characterized by a lack of consistency. A comprehensive search was performed across various databases (PubMed, EMBASE, Web of Science, Scopus, Google Scholar, Cochrane, and ProQuest), starting from its inception and ending in January 2023. The criteria for inclusion consisted of original research studies written in English, which utilized Real-Time PCR to analyze miRNA expression in the blood, serum, or plasma of AD patients and healthy controls. The extracted data included the miRNA(s) investigated, dysregulation status, study type, human sample(s), and major findings. The search produced 608 records, which after careful examination, resulted in 48 suitable articles for data extraction. The research revealed a wide range of sample types used, with whole blood (39.59%) and serum (27.09%, including serum-exosome at 4.17%) emerging as the most prominent. The compiled dataset featured 4001 AD patients and 3886 healthy controls, revealing intricate regulatory patterns among 83 up-regulated (35.78%), 66 down-regulated (28.44%), and 83 not significantly altered (35.78%) miRNAs. Our results demonstrated that specific circulating miRNAs are consistently dysregulated in AD and could serve as non-intrusive biomarkers for the identification, prognosis, and prediction of cognitive decline. Further large-scale prospective studies are required to validate their clinical applications.

The Quest for Eternal Youth: Hallmarks of Aging and Rejuvenating Therapeutic Strategies

The impressive achievements made in the last century in extending the lifespan have led to a significant growth rate of elderly individuals in populations across the world and an exponential increase in the incidence of age-related conditions such as cardiovascular diseases, diabetes mellitus type 2, and neurodegenerative diseases. To date, geroscientists have identified 12 hallmarks of aging (genomic instability, telomere attrition, epigenetic alterations, loss of proteostasis, impaired macroautophagy, mitochondrial dysfunction, impaired nutrient sensing, cellular senescence, stem cell exhaustion, defective intercellular communication, chronic inflammation, and gut dysbiosis), intricately linked among each other, which can be targeted with senolytic or senomorphic drugs, as well as with more aggressive approaches such as cell-based therapies. To date, side effects seriously limit the use of these drugs. However, since rejuvenation is a dream of mankind, future research is expected to improve the tolerability of the available drugs and highlight novel strategies. In the meantime, the medical community, healthcare providers, and society should decide when to start these treatments and how to tailor them individually.

Inhibition of miR-4763-3p expression activates the PI3K/mTOR/Bcl2 autophagy signaling pathway to ameliorate cognitive decline

Cognitive decline and memory impairment are subsequently result in neuronal apoptosis and synaptic damage. Aberrant regulation of microRNAs has been implicated in the pathogenesis of Alzheimer's disease (AD) and may play a pivotal role in the early stages of the disease. In this study, we identified the critical role of miR-4763-3p in AD pathogenesis, focusing on early-stage mild cognitive impairment (AD-MCI). Leveraging fluorescence in situ hybridization, we observed miR-4763-3p upregulation in AD hippocampal tissue, colocalizing with Aβ and Tau. Antagomir-mediated inhibition of miR-4763-3p ameliorated cognitive decline in AD-MCI mice. RNA-seq and functional assays revealed that miR-4763-3p targets ATP11A, and antagomir enhancing inward flipping of the "eat me" phosphatidylserine signal on the surface of neuronal cells, autophagy, and clearance of Aβ/lipofuscin, while reducing neuroinflammation and neuronal apoptosis. Mechanistically, miR-4763-3p modulates the PI3K/AKT/mTOR/Bcl2 pathway, thereby promoting neuronal autophagy and reducing apoptotic crosstalk. These findings underscore miR-4763-3p as a therapeutic target for AD-MCI, offering a novel strategy to enhance neuronal autophagy, alleviate inflammation, and improve cognitive function.

The emerging role of exercise in Alzheimer's disease: Focus on mitochondrial function

Alzheimer's disease (AD) is an age-related neurodegenerative disease characterized by memory impairment and cognitive dysfunction, which eventually leads to the disability and mortality of older adults. Although the precise mechanisms by which age promotes the development of AD remains poorly understood, mitochondrial dysfunction plays a central role in the development of AD. Currently, there is no effective treatment for this debilitating disease. It is well accepted that exercise exerts neuroprotective effects by ameliorating mitochondrial dysfunction in the neurons of AD, which involves multiple mechanisms, including mitochondrial dynamics, biogenesis, mitophagy, transport, and signal transduction. In addition, exercise promotes mitochondria communication with other organelles in AD neurons, which should receive more attentions in the future.

Insights into the Role of microRNAs as Clinical Tools for Diagnosis, Prognosis, and as Therapeutic Targets in Alzheimer's Disease

Neurodegenerative diseases (NDDs) are a diverse group of neurological disorders characterized by alterations in the structure and function of the central nervous system. Alzheimer's disease (AD), characterized by impaired memory and cognitive abilities, is the most prevalent type of senile dementia. Loss of synapses, intracellular aggregation of hyperphosphorylated tau protein, and extracellular amyloid-β peptide (Aβ) plaques are the hallmarks of AD. MicroRNAs (miRNAs/miRs) are single-stranded ribonucleic acid (RNA) molecules that bind to the 3' and 5' untranslated regions of target genes to cause post-transcriptional gene silencing. The brain expresses over 70% of all experimentally detected miRNAs, and these miRNAs are crucial for synaptic function and particular signals during memory formation. Increasing evidence suggests that miRNAs play a role in AD pathogenesis and we provide an overview of the role of miRNAs in synapse formation, Aβ synthesis, tau protein accumulation, and brain-derived neurotrophic factor-associated AD pathogenesis. We further summarize and discuss the role of miRNAs as potential therapeutic targets and biomarkers for AD detection and differentiation between early- and late-stage AD, based on recent research. In conclusion, altered expression of miRNAs in the brain and peripheral circulation demonstrates their potential as biomarkers and therapeutic targets in AD.

Use and Reuse of Animal Behavioral, Molecular, and Biochemical Data in Alzheimer's Disease Research: Focus on 3Rs and Saving People's Tax Dollars

Several decades of research on cell and animal models contributed tremendously to understanding human diseases. Particularly, research on rodents and non-human primates revealed that animal research is a major and important component in biomedical research in learning complex pathophysiological processes. Further, animal research helped us to understand human diseases, such as Alzheimer's disease. In addition, animal research has also helped us to test hundreds of drugs and develop treatments for human use. Researchers can gain a better understanding of key biological and physiological processes in humans by comparing them to laboratory animals. Based on their relevance and resemblance to people, or even usual living conditions, scientists rationalize the use of particular animal models in their studies. It is suggested that in the National Institutes of Health and other agencies-funded research, animal models should be carefully selected to study the biology and pathophysiology of human health and diseases such as Alzheimer's disease and other dementias. However, it is critical to use a minimum number of animals for human research. Further, it is also noted that the use and reuse of behavioral,  molecular, and biochemical data from wild-type (WT) control mice with mutant lines of disease models, as long as the genetic background is the same in both WT and disease mice. On the other hand, anonymous readers have challenged the use and reuse of WT mice data for comparison. In the current article, we discuss the minimum utility of animals, covering the 3Rs, Replacement, Reduction, and Refinement, and also discuss the use and reuse of behavioral, molecular, and biochemical data.

Exploring advancements in early detection of Alzheimer's disease with molecular assays and animal models

Alzheimer's Disease (AD) is a challenging neurodegenerative condition, with overwhelming implications for affected individuals and healthcare systems worldwide. Animal models have played a crucial role in studying AD pathogenesis and testing therapeutic interventions. Remarkably, studies on the genetic factors affecting AD risk, such as APOE and TREM2, have provided valuable insights into disease mechanisms. Early diagnosis has emerged as a crucial factor in effective AD management, as demonstrated by clinical studies emphasizing the benefits of initiating treatment at early stages. Novel diagnostic technologies, including RNA sequencing of microglia, offer promising avenues for early detection and monitoring of AD progression. Therapeutic strategies remain to evolve, with a focus on targeting amyloid beta (Aβ) and tau pathology. Advances in animal models, such as APP-KI mice, and the advancement of anti-Aβ drugs signify progress towards more effective treatments. Therapeutically, the focus has shifted towards intricate approaches targeting multiple pathological pathways simultaneously. Strategies aimed at reducing Aβ plaque accumulation, inhibiting tau hyperphosphorylation, and modulating neuroinflammation are actively being explored, both in preclinical models and clinical trials. While challenges continue in developing validated animal models and translating preclinical findings to clinical success, the continuing efforts in understanding AD at molecular, cellular, and clinical levels offer hope for improved management and eventual prevention of this devastating disease.

MicroRNA-455-3P as a peripheral biomarker and therapeutic target for mild cognitive impairment and Alzheimer's disease

MicroRNAs are small non-coding RNAs evolutionary conserved molecules. They regulate cellular processes, including RNA silencing, post-translational gene expression and neurodegeneration. MicroRNAs are involved with human diseases such as cancer, Alzheimer's disease (AD) and others. Interestingly, cerebrospinal fluids (CSF) and the blood of AD patients have altered expressions of many RNAs, which may serve as potential peripheral biomarkers. The intensive investigation from our lab revealed that microRNA-455-3 P (miR-455-3p) is a strong candidate as a potential biomarker and therapeutic target for AD. Several genes implicated in the pathogenesis of AD are directly targeted by miR-455-3p. Several years of our lab research revealed that miR-455-3p regulates important physiological processes associated with AD, such as the processing of the amyloid precursor protein (APP), TGF-β signaling, the regulation of oxidative stress, mitochondrial biogenesis, and synaptic damages. The expression of miR-455-3p in mild cognitive impaired subjects and AD patients pointed out its involvement in AD progression. Recently, our lab generated both transgenic and knockout mice for miR-455-3p. Interestingly miR-455-3p transgenic mice showed superior cognitive learning, improved memory and extended lifespan compared to age matched wild-type mice, whereas miR-455-3-p knockout mice showed cognitive decline and reduced lifespan. Information derived from mouse models further demonstrated the advantageous impact of miR-455-3p on dendritic growth, synaptogenesis, and mitochondrial biogenesis in preventing the onset and progression of AD. The identification of miR-455-3p as a biomarker was suggested by its presence in postmortem AD brains, B-lymphocytes, and fibroblasts. Our hypothesis that miR-455-3p could be a peripheral biomarker and therapeutic target for AD.

Small Differences and Big Changes: The Many Variables of MicroRNA Expression and Function in the Brain

MicroRNAs are emerging as crucial regulators within the complex, dynamic environment of the synapse, and they offer a promising new avenue for the treatment of neurological disease. These small noncoding RNAs modify gene expression in several ways, including posttranscriptional modulation via binding to complementary and semicomplementary sites on target mRNAs. This rapid, finely tuned regulation of gene expression is essential to meet the dynamic demands of the synapse. Here, we provide a detailed review of the multifaceted world of synaptic microRNA regulation. We discuss the many mechanisms by which microRNAs regulate gene expression at the synapse, particularly in the context of neuronal plasticity. We also describe the various factors, such as age, sex, and neurological disease, that can influence microRNA expression and activity in neurons. In summary, microRNAs play a crucial role in the intricate and quickly changing functional requirements of the synapse, and context is essential in the study of microRNAs and their potential therapeutic applications.

MicroRNAs and synapse turnover in Alzheimer's disease

Alzheimer's Disease (AD) is a progressive neurodegenerative disorder characterized by the accumulation of amyloid-beta plaques and neurofibrillary tangles in the brain, leading to synaptic dysfunction and cognitive decline. Healthy synapses are the crucial for normal brain function, memory restoration and other neurophysiological function. Synapse loss and synaptic dysfunction are two primary events that occur during AD initiation. Synapse lifecycle and/or synapse turnover is divided into five key stages and several sub-stages such as synapse formation, synapse assembly, synapse maturation, synapse transmission and synapse termination. In normal state, the synapse turnover is regulated by various biological and molecular factors for a healthy neurotransmission. In AD, the different stages of synapse turnover are affected by AD-related toxic proteins. MicroRNAs (miRNAs) have emerged as critical regulators of gene expression and have been implicated in various neurological diseases, including AD. Deregulation of miRNAs modulate the synaptic proteins and affect the synapse turnover at different stages. In this review, we discussed the key milestones of synapse turnover and how they are affected in AD. Further, we discussed the involvement of miRNAs in synaptic turnover, focusing specifically on their role in AD pathogenesis. We also emphasized the regulatory mechanisms by which miRNAs modulate the synaptic turnover stages in AD. Current studies will help to understand the synaptic life-cycle and role of miRNAs in each stage that is deregulated in AD, further allowing for a better understanding of the pathogenesis of devastating disease.

Betaamyloid protein regulates miR15a and activates Bag5 to influence neuronal apoptosis in Alzheimers disease

OBJECTIVES

The prevalence of Alzheimer's disease (AD) is increasing globally, however its pathogenesis is still unclear. The evidence showed that the progression of AD was closely related to the apoptosis of nerve cells. This study amis to explore the role and specific mechanism of miR-15a and Bag5 in the apoptosis of nerve cells induced by beta-amyloid protein (Aβ) in AD.

METHODS

The AD rat model was constructed by injecting Aβ42 into SD rat brain and the AD cell model was constructed by treating SH-SY5Y cells with Aβ42. The learning and memory ability of rats was detected by Morris Water Maze. Hematoxylin and eosin (HE) staining was used to detect the pathological changes of brain tissues. Nissl staining was used to detect the changes of cell morphology and number in brain tissues. The upstream miRNA that interacted with Bag5 were screened by bioinformatics analysis. Methyl thiazolyl tetrazolium (MTT) assay was used to detect cell proliferation. Flow cytometry was used to detect the apoptosis rate of cells. Real-time reverse transcription PCR (real-time RT-PCR) was used to detect the mRNA levels of miR-15a and Bag5. Western blotting was used to detect the protein expression levels of Bag5, Bax and Caspase-3. MiR-15a knockdown or overexpression vectors or Bag5 knockdown vectors were transfected into AD rat model and AD cell models, respectively. Luciferase reporter assay was used to verify the binding relationship between miR-15a and Bag5.

RESULTS

Morris Water Maze, HE staining and Nissl staining showed that the rat model of AD was established successfully, and Aβ could induce neuronal apoptosis and inhibit the expression of miR-15a in AD rats. Compared with normal cells, Aβ treatment significantly increased apoptosis rate and Bag5 expression, and weakened cell proliferation and miR-15a (all P<0.01). Overexpression of miR-15a further enhanced the effect of Aβ on cell proliferation and apoptosis, while knockdown of miR-15a expression had the opposite effect (all P<0.01). Luciferase reporter assay confirmed that there was a negative targeting relationship between miR-15a and Bag5. Compared with Bag5 knockdown alone, the co-transfection of miR-15a inhibitor and si-Bag5 significantly increased the cell proliferation ability and mRNA and protein levels of Bag5, and significantly reduced the cell apoptosis rate and the expression of Bax and Caspase-3, animal studies have also shown consistent results (all P<0.01).

CONCLUSIONS

Aβ can inhibit the expression of miR-15a, thereby inducing the expression of Bag5 and activating the protective mechanism of Bag5 against Aβ induced apoptosis.

Exploring the Regulatory Landscape of Dementia: Insights from Non-Coding RNAs

Dementia, a multifaceted neurological syndrome characterized by cognitive decline, poses significant challenges to daily functioning. The main causes of dementia, including Alzheimer's disease (AD), frontotemporal dementia (FTD), Lewy body dementia (LBD), and vascular dementia (VD), have different symptoms and etiologies. Genetic regulators, specifically non-coding RNAs (ncRNAs) such as microRNAs (miRNAs), long non-coding RNAs (lncRNAs), and circular RNAs (circRNAs), are known to play important roles in dementia pathogenesis. MiRNAs, small non-coding RNAs, regulate gene expression by binding to the 3' untranslated regions of target messenger RNAs (mRNAs), while lncRNAs and circRNAs act as molecular sponges for miRNAs, thereby regulating gene expression. The emerging concept of competing endogenous RNA (ceRNA) interactions, involving lncRNAs and circRNAs as competitors for miRNA binding, has gained attention as potential biomarkers and therapeutic targets in dementia-related disorders. This review explores the regulatory roles of ncRNAs, particularly miRNAs, and the intricate dynamics of ceRNA interactions, providing insights into dementia pathogenesis and potential therapeutic avenues.

Mitochondria-Associated MicroRNAs and Parkinson's Disease

Parkinson's Disease (PD) occurs as a result of the progressive loss of dopaminergic neurons within the substantia nigra causing motor and non-motor symptoms and has become more prevalent within the last several decades. With mitochondria being essential to cellular survival, mitochondrial dysfunction contributes to the disease progression by increasing neuron loss through (1) insufficient ATP production and (2) reactive oxygen species generation. MicroRNAs (miRNAs) are small molecules located throughout cells that regulate gene expression, particularly mitochondrial function. Through their own dysregulation, miRNAs offset the delicate balance of mitochondrial function by altering or dysregulating the expression of proteins, increasing neuroinflammation, increasing retention of toxic substances, limiting the removal of reactive oxygen species, and preventing mitophagy. Improper mitochondrial function places cells at increased risk of apoptosis, a major concern in individuals with PD due to their reduced number of dopaminergic neurons. This article has identified the 17 most promising mitochondrial associated miRNAs within PD: hsa-miR-4639-5p, miR-376a, miR-205, miR-421, miR-34b/c, miR-150, miR-7, miR-132, miR-17-5p, miR-20a, miR-93, miR-106, miR-181, miR-193b, miR-128, miR-181a, and miR-124-3p. These miRNAs alter mitochondrial function and synaptic energy by impeding normal gene expression when up or downregulated. However, there is limited research regarding mitochondria-localized miRNAs that are typically seen in other diseases. Mitochondria-localized miRNA may have a greater impact on mitochondrial dysfunction due to their proximity. Further research is needed to determine the location of these miRNAs and to better understand their regulatory capabilities on mitochondrial and synaptic function within PD.

Protective effects of SSRI, Citalopram in mutant APP and mutant Tau expressed dorsal raphe neurons in Alzheimer's disease

Depression is among the most common neuropsychiatric comorbidities in Alzheimer's disease (AD) and other Tauopathies. Apart from its anti-depressive and anxiolytic effects, selective serotonin reuptake inhibitor (SSRI) treatment also offers intracellular modifications that may help to improve neurogenesis, reduce amyloid burden & Tau pathologies, and neuroinflammation in AD. Despite its multifaceted impact in the brain, the exact physiological and molecular mechanism by which SSRIs such as Citalopram improve neurogenesis and synaptogenesis in dementia is poorly understood. In the current study, we investigated the protective role of SSRI, Citalopram, in serotonergic, medullary raphe neurons (RN46A-B14). RN46A-B14 cells were transfected with wild-type and mutant APP and Tau cDNAs for 24 h and then treated with 20 μM Cit for 24 h. We then assessed mRNA and protein levels of pTau, total Tau, serotonin related proteins such as TPH2, SERT, and 5HTR1a, synaptic proteins and the cytoskeletal structure. We also assessed cell survival, mitochondrial respiration and mitochondrial morphology. The mutant APP and Tau transfected cells showed increased levels of serotonin related proteins and mRNA, while the mRNA and protein levels of synaptic proteins were downregulated. Citalopram treatment significantly reduced pathologically pTau level along with the serotonin related protein levels. On the other hand, there was a significant increase in the mRNA and protein levels of synaptic genes and cytoskeletal structure in the treated groups. Further, Citalopram also improved cell survival, mitochondrial respiration and mitochondrial morphology in the treated cells that express mAPP and mTau. Taken together these findings suggest Citalopram could not only be a promising therapeutic drug for treating patients with depression, but also for AD patients.

The Information Theory of Aging

Information storage and retrieval is essential for all life. In biology, information is primarily stored in two distinct ways: the genome, comprising nucleic acids, acts as a foundational blueprint and the epigenome, consisting of chemical modifications to DNA and histone proteins, regulates gene expression patterns and endows cells with specific identities and functions. Unlike the stable, digital nature of genetic information, epigenetic information is stored in a digital-analog format, susceptible to alterations induced by diverse environmental signals and cellular damage. The Information Theory of Aging (ITOA) states that the aging process is driven by the progressive loss of youthful epigenetic information, the retrieval of which via epigenetic reprogramming can improve the function of damaged and aged tissues by catalyzing age reversal.

Factors affecting the GABAergic synapse function in Alzheimer's disease: Focus on microRNAs

Alzheimer's disease (AD) is a progressive neurological disease characterized by the loss of cognitive function, confusion, and memory deficit. Accumulation of abnormal proteins, amyloid beta (Aß), and phosphorylated Tau (p-tau) forms plaques and tangles that deteriorate synapse function, resulting in neurodegeneration and cognitive decline in AD. The human brain is composed of different types of neurons and/or synapses that are functionally defective in AD. The GABAergic synapse, the most abundant inhibitory neuron in the human brain was found to be dysfunctional in AD and contributes to disrupting neurological function. This study explored the types of GABA receptors associated with neurological dysfunction and various biological and environmental factors that cause GABAergic neuron dysfunction in AD, such as Aβ, p-tau, aging, sex, astrocytes, microglia, APOE, mental disorder, diet, physical activity, and sleep. Furthermore, we explored the role of microRNAs (miRNAs) in the regulation of GABAergic synapse function in neurological disorders and AD states. We also discuss the molecular mechanisms underlying GABAergic synapse dysfunction with a focus on miR-27b, miR-30a, miR-190a/b, miR-33, miR-51, miR-129-5p, miR-376-3p, miR-376c, miR-30b and miR-502-3p. The purpose of our article is to highlight the recent research on miRNAs affecting the regulation of GABAergic synapse function and factors that contribute to the progression of AD.

A new perspective on Alzheimer's disease: microRNAs and circular RNAs

microRNAs (miRNAs) play a multifaceted role in the pathogenesis of Alzheimer's disease (AD). miRNAs regulate several aspects of the disease, such as Aβ metabolism, tau phosphorylation, neuroinflammation, and synaptic function. The dynamic interaction between miRNAs and their target genes depends upon various factors, including the subcellular localization of miRNAs, the relative abundance of miRNAs and target mRNAs, and the affinity of miRNA-mRNA interactions. The miRNAs are released into extracellular fluids and subsequently conveyed to specific target cells through various modes of transportation, such as exosomes. In comparison, circular RNAs (circRNAs) are non-coding RNA (ncRNA) characterized by their covalently closed continuous loops. In contrast to linear RNA, RNA molecules are circularized by forming covalent bonds between the 3'and 5'ends. CircRNA regulates gene expression through interaction with miRNAs at either the transcriptional or post-transcriptional level, even though their precise functions and mechanisms of gene regulation remain to be elucidated. The current stage of research on miRNA expression profiles for diagnostic purposes in complex disorders such as Alzheimer's disease is still in its early phase, primarily due to the intricate nature of the underlying pathological causes, which encompass a diverse range of pathways and targets. Hence, this review comprehensively addressed the alteration of miRNA expression across diverse sources such as peripheral blood, exosome, cerebrospinal fluid, and brain in AD patients. This review also addresses the nascent involvement of circRNAs in the pathogenesis of AD and their prospective utility as biomarkers and therapeutic targets for these conditions in future research.

Role of MicroRNA-502-3p in Human Diseases

MicroRNAs (miRNAs) are non-coding RNAs that play a major role in gene regulation in several diseases. MicroRNA-502-3p (MiR-502-3p) has been previously characterized in a variety of human diseases such as osteoporosis, diabetes, tuberculosis, cancers, and neurological disorders. Our studies recently explored the new role of miR-502-3p in regulating synapse function in Alzheimer’s disease (AD). AD is the most common cause of dementia in elderly individuals. Synapse is the initial target that is hit during AD progression. The most common causes of synapse dysfunction in AD are amyloid beta, hyperphosphorylated tau, and microglia activation. MiR-502-3p was found to be localized and overexpressed in the AD synapses. Overexpression of miR-502-3p was correlated with AD severity in terms of Braak stages. Studies have shown that miR-502-3p modulates the glutaminergic and GABAergic synapse function in AD. The current study’s emphasis is to discuss the in-depth roles of miR-502-3p in human diseases and AD and the future possibilities concerning miR-502-3p as a therapeutic for AD treatment.

Regulation of retinoid mediated StAR transcription and steroidogenesis in hippocampal neuronal cells: Implications for StAR in protecting Alzheimer's disease

Retinoids (vitamin A and its derivatives) play pivotal roles in diverse processes, ranging from homeostasis to neurodegeneration, which are also influenced by steroid hormones. The rate-limiting step in steroid biosynthesis is mediated by the steroidogenic acute regulatory (StAR) protein. In the present study, we demonstrate that retinoids enhanced StAR expression and pregnenolone biosynthesis, and these parameters were markedly augmented by activation of the PKA pathway in mouse hippocampal neuronal HT22 cells. Deletion and mutational analyses of the 5'-flanking regions of the StAR gene revealed the importance of a retinoic acid receptor (RAR)/retinoid X receptor (RXR)-liver X receptor (LXR) heterodimeric motif at -200/-185 bp region in retinoid responsiveness. The RAR/RXR-LXR sequence motif can bind RARα and RXRα, and retinoid regulated transcription of the StAR gene was found to be influenced by the LXR pathway, representing signaling cross-talk in hippocampal neurosteroid biosynthesis. Steroidogenesis decreases during senescence due to declines in the central nervous system and the endocrine system, and results in hormone deficiencies, inferring the need for hormonal balance for healthy aging. Loss of neuronal cells, involving accumulation of amyloid beta (Aβ) and/or phosphorylated Tau within the brain, is the pathological hallmark of Alzheimer's disease (AD). HT22 cells overexpressing either mutant APP (mAPP) or mutant Tau (mTau), conditions mimetic to AD, enhanced toxicities, and resulted in attenuation of both basal and retinoid-responsive StAR and pregnenolone levels. Co-expression of StAR with either mAPP or mTau diminished cytotoxicity, and concomitantly elevated neurosteroid biosynthesis, pointing to a protective role of StAR in AD. These findings provide insights into the molecular events by which retinoid signaling upregulates StAR and steroid levels in hippocampal neuronal cells, and StAR, by rescuing mAPP and/or mTau-induced toxicities, modulates neurosteroidogenesis and restores hormonal balance, which may have important implications in protecting AD and age-related complications and diseases.

Hallmarks of aging: An expanding universe

Aging is driven by hallmarks fulfilling the following three premises: (1) their age-associated manifestation, (2) the acceleration of aging by experimentally accentuating them, and (3) the opportunity to decelerate, stop, or reverse aging by therapeutic interventions on them. We propose the following twelve hallmarks of aging: genomic instability, telomere attrition, epigenetic alterations, loss of proteostasis, disabled macroautophagy, deregulated nutrient-sensing, mitochondrial dysfunction, cellular senescence, stem cell exhaustion, altered intercellular communication, chronic inflammation, and dysbiosis. These hallmarks are interconnected among each other, as well as to the recently proposed hallmarks of health, which include organizational features of spatial compartmentalization, maintenance of homeostasis, and adequate responses to stress.

Meta-hallmarks of aging and cancer

Both aging and cancer are characterized by a series of partially overlapping "hallmarks" that we subject here to a meta-analysis. Several hallmarks of aging (i.e., genomic instability, epigenetic alterations, chronic inflammation, and dysbiosis) are very similar to specific cancer hallmarks and hence constitute common "meta-hallmarks," while other features of aging (i.e., telomere attrition and stem cell exhaustion) act likely to suppress oncogenesis and hence can be viewed as preponderantly "antagonistic hallmarks." Disabled macroautophagy and cellular senescence are two hallmarks of aging that exert context-dependent oncosuppressive and pro-tumorigenic effects. Similarly, the equivalence or antagonism between aging-associated deregulated nutrient-sensing and cancer-relevant alterations of cellular metabolism is complex. The agonistic and antagonistic relationship between the processes that drive aging and cancer has bearings for the age-related increase and oldest age-related decrease of cancer morbidity and mortality, as well as for the therapeutic management of malignant disease in the elderly.

Modulators of ASIC1a and its potential as a therapeutic target for age-related diseases

Age-related diseases have become more common with the advancing age of the worldwide population. Such diseases involve multiple organs, with tissue degeneration and cellular apoptosis. To date, there is a general lack of effective drugs for treatment of most age-related diseases and there is therefore an urgent need to identify novel drug targets for improved treatment. Acid-sensing ion channel 1a (ASIC1a) is a degenerin/epithelial sodium channel family member, which is activated in an acidic environment to regulate pathophysiological processes such as acidosis, inflammation, hypoxia, and ischemia. A large body of evidence suggests that ASIC1a plays an important role in the development of age-related diseases (e.g., stroke, rheumatoid arthritis, Huntington's disease, and Parkinson's disease.). Herein we present: 1) a review of ASIC1a channel properties, distribution, and physiological function; 2) a summary of the pharmacological properties of ASIC1a; 3) and a consideration of ASIC1a as a potential therapeutic target for treatment of age-related disease.

Targeting Novel microRNAs in Developing Novel Alzheimer's Disease Treatments

Alzheimer's disease (AD) is considered a multifactorial disease and a significant cause of dementia during aging. This neurodegenerative disease process is classically divided into two different pathologies cerebral accumulation of amyloid-β and hyperphosphorylated neurofibrillary tau tangles. In recent years, massive efforts have been made to treat AD by decreasing amyloid-β and tau in the brains of patients with AD, with no success. The dysfunction of a wide range of microRNAs promotes the generation and insufficient clearance of amyloid-β (Aβ) and increases tau plaques which are the pathophysiological markers of AD. Disturbance of these microRNAs is associated with mitochondrial dysfunction, oxidative damage, inflammation, apolipoprotein E4 (APOE4) pathogenic process, synaptic loss, and cognitive deficits induced by AD. Targeting a specific microRNA to restore AD-induced impairments at multiple stages might provide a promising approach for developing new drugs and therapeutic strategies for patients with AD. This review focuses on different mechanisms of microRNAs in AD pathophysiology.

Methods to Study Mitochondria: Techniques Used to Study the Effects of Age-Related Diseases Including Alzheimer's

Various laboratories across the world have developed methods to study mitochondrial proteins/markers through extraction of mitochondrial RNA and protein to assess mitophagy/autophagy in Alzheimer's disease and other age-related diseases. Techniques outlined in this article include qRT-PCR, immunoblotting, immunofluorescence, transmission electron microscopy, Seahorse bioanalysis, staining for mitochondrial membrane potential, detection of mitophagy, and mitochondrial functional assays. Most of these techniques have been performed in vitro (in human and mouse neuronal cell lines transfected with mutant amyloid precursor protein or tau protein cDNAs) and in vivo (in brain tissues from different mouse models of Alzheimer's and other neurological diseases). Mitochondrial abnormalities in Alzheimer's disease have taken various forms, including excessive reactive oxygen species production, mitochondrial calcium dyshomeostasis, loss of ATP, defects in mitochondrial dynamics and transport, and mitophagy. Mitochondrial dysfunction is largely involved in aging; age-related diseases such as cancer, diabetes, and obesity; and neurodegenerative disorders including Alzheimer's disease, Parkinson's disease, Huntington's disease, amyotrophic lateral sclerosis, multiple sclerosis, and others. The goal of this article is to make protocols/methods available to students, scholars, and researchers of mitochondria in order to facilitate future mitochondrial studies. © 2023 Wiley Periodicals LLC. Basic Protocol 1: Analyzing mitochondrial gene expression in mouse brain tissue and HT22 cells by qRT-PCR Basic Protocol 2: Analyzing protein expression in mouse brain tissue and HT22 cells by immunoblotting Basic Protocol 3: Immunofluorescence staining of cells and tissue sections Basic Protocol 4: Staining for mitochondrial membrane potential Basic Protocol 5: Assessing mitochondrial structure by transmission electron microscopy Basic Protocol 6: Methods for detecting mitophagy Basic Protocol 7: Bioenergetics assay via Seahorse Basic Protocol 8: Assays for mitochondrial function.

Regulation of LncRNAs and microRNAs in neuronal development and disease

Non-coding RNAs (ncRNAs) are RNAs that do not encode proteins but play important roles in regulating cellular processes. Multiple studies over the past decade have demonstrated the role of microRNAs (miRNAs) in cancer, in which some miRNAs can act as biomarkers or provide therapy target. Accumulating evidence also points to the importance of long non-coding RNAs (lncRNAs) in regulating miRNA-mRNA networks. An increasing number of ncRNAs have been shown to be involved in the regulation of cellular processes, and dysregulation of ncRNAs often heralds disease. As the population ages, the incidence of neurodegenerative diseases is increasing, placing enormous pressure on global health systems. Given the excellent performance of ncRNAs in early cancer screening and treatment, here we attempted to aggregate and analyze the regulatory functions of ncRNAs in neuronal development and disease. In this review, we summarize current knowledge on ncRNA taxonomy, biogenesis, and function, and discuss current research progress on ncRNAs in relation to neuronal development, differentiation, and neurodegenerative diseases.

A Combination Therapy of Urolithin A+EGCG Has Stronger Protective Effects Than Single Drug Urolithin A in a Humanized Amyloid Beta Knockin Mice for Late-Onset Alzheimer’s Disease

In the current study, for the first time, we study mitophagy enhancer urolithin A and a combination of urolithin A+green tea extract EGCG against human Aβ peptide-induced mitochondrial and synaptic, dendritic, inflammatory toxicities and behavioral changes in humanized homozygous amyloid beta knockin (hAbKI) mice of late-onset Alzheimer’s disease (AD). Our findings reveal significantly increased positive effects of urolithin A and a combination treatment of urolithin A+EGCG in hAbKI mice for phenotypic behavioral changes including motor coordination, locomotion/exploratory activity, spatial learning and working memory. mRNA and protein levels of mitochondrial fusion, synaptic, mitophagy and autophagy genes were upregulated, and mitochondrial fission genes are downregulated in urolithin A and combine treatment in hAbKI mice; however, the effect is stronger in combined treatment. Immunofluorescence analysis of hippocampal brain sections shows similar findings of mRNA and protein levels. Mitochondrial dysfunction is significantly reduced in both treatment groups, but a stronger reduction is observed in combined treatment. Dendritic spines and lengths are significantly increased in both treatment groups, but the effect is stronger in combined treatment. The fragmented number of mitochondria is reduced, and mitochondrial length is increased, and mitophagosomal formations are increased in both the groups, but the effect is stronger in the combined treatment. The levels of amyloid beta (Aβ) 40 and Aβ42 are reduced in both treatments, however, the reduction is higher for combined treatment. These observations suggest that urolithin A is protective against human Aβ peptide-induced toxicities; however, combined treatment of urolithin A+EGCG is effective and stronger, indicating that combined therapy is promising to treat late-onset AD patients.

miR-455-3p Is Negatively Regulated by Myostatin in Skeletal Muscle and Promotes Myoblast Differentiation

Myostatin (MSTN) is a growth and differentiation factor that regulates proliferation and differentiation of myoblasts, which in turn controls skeletal muscle growth. It may regulate myoblast differentiation by influencing miRNA expression, and the present study aimed to clarify its precise mechanism of action. Here, we found that MSTN^-/- pigs showed an overgrowth of skeletal muscle and upregulated miR-455-3p level. Intervention of MSTN expression using siMSTN in C2C12 myoblasts also showed that siMSTN significantly increased the expression of miR-455-3p. It was found that miR-455-3p directly targeted the 3'-untranslated region of Smad2 by dual-luciferase assay. qRT-PCR, Western blotting, and immunofluorescence analyses indicated that miR-455-3p overexpression or Smad2 silencing in C2C12 myoblasts significantly promoted myoblast differentiation. Furthermore, siMSTN significantly increased the expression of GATA3. The levels of miR-455-3p were considerably reduced in C2C12 myoblasts following GATA3 knockdown. Consistently, GATA3 knockdown also reduced the enhanced miR-455-3p expression caused by siMSTN. Finally, we illustrated that GATA3 has a role in myoblast differentiation regulation. Taken together, we identified the expression profiles of miRNAs in MSTN^-/- pigs and found that miR-455-3p positively regulates myoblast differentiation. In addition, we revealed that MSTN acts through the GATA3/miR-455-3p/Smad2 cascade to regulate muscle development.

Synaptosome microRNAs regulate synapse functions in Alzheimer's disease

MicroRNAs (miRNAs) are found in nerve terminals, synaptic vesicles, and synaptosomes, but it is unclear whether synaptic and cytosolic miRNA populations differ in Alzheimer's disease (AD) or if synaptosomal miRNAs affect AD synapse activity. To address these questions, we generated synaptosomes and cytosolic fractions from postmortem brains of AD and unaffected control (UC) samples and analyzed them using a global Affymetrix miRNAs microarray platform. A group of miRNAs significantly differed (P < 0.0001) with high fold changes variance (+/- >200-fold) in their expressions in different comparisons: (1) UC synaptosome vs UC cytosol, (2) AD synaptosomes vs AD cytosol, (3) AD cytosol vs UC cytosol, and (4) AD synaptosomes vs UC synaptosomes. MiRNAs data analysis revealed that some potential miRNAs were consistently different across sample groups. These differentially expressed miRNAs were further validated using AD postmortem brains, brains of APP transgenic (Tg2576), Tau transgenic (P301L), and wild-type mice. The miR-501-3p, miR-502-3p, and miR-877-5p were identified as potential synaptosomal miRNAs upregulated with disease progression based on AD Braak stages. Gene Ontology Enrichment and Ingenuity Pathway Analysis of synaptosomal miRNAs showed the involvement of miRNAs in nervous system development, cell junction organization, synapse assembly formation, and function of GABAergic synapse. This is the first description of synaptic versus cytosolic miRNAs in AD and their significance in synapse function.

Early Cellular, Molecular, Morphological and Behavioral Changes in the Humanized Amyloid-Beta-Knock-In Mouse Model of Late-Onset Alzheimer's Disease

The purpose of our study is to investigate early cellular, molecular, morphological and behavioral changes in humanized amyloid-beta-knock-in (hAbKI) mice. Using seven-month-old homozygous hAbKI mice, we studied behavioral phenotype parameters, including spatial learning and memory (Morris Water Maze), locomotor activity (open field), working memory (Y-maze) and motor coordination (rotarod); mRNA abundance, protein levels, soluble amyloid-beta 40 and 42 levels and regional immunoreactivities of key markers of mitochondrial dynamics, mitochondrial biogenesis, synaptic health, mitophagy and autophagy; mitochondrial function and using transmission electron microscopy & Golgi–Cox staining, we assessed mitochondrial morphology and dendritic spines. Our extensive behavioral analysis revealed that seven-month-old hAbKI mice showed impairments in motor coordination, reduced locomotor and exploration activities, impairments in working memory and spatial learning and memory. Our mRNA and protein analyses revealed the increased expression of mitochondrial-fission genes and reduced expression of mitochondrial-fusion, mitochondrial-biogenesis, synaptic, autophagy and mitophagy genes in seven-month-old hAbKI mice. An immunofluorescence analysis revealed altered immunoreactivities and agreed with the immunoblot results. Transmission-electron-microscopy data revealed increased mitochondrial fragmentation and reduced mitochondrial length in both hippocampal and cortical tissues of seven-month-old hAbKI mice and mitochondrial function defective. A Golgi–Cox-staining analysis revealed reduced dendritic spines in both cerebral cortices and hippocampi of hAbKI mice. Soluble amyloid-beta (1–40 and 1–42) were detected in three-month-old hAbKI mice and progressively increased in seven-month-old mice. These observations suggest that the human amyloid-beta peptide is sufficient to cause behavioral, mitochondrial, synaptic and ultrastructural changes in seven-month-old hAbKI mice. Our study findings also suggest that hAbKI mice might serve as a model for preclinical studies of preventive therapies.

Exosomes Mediate APP Dysregulation via APP-miR-185-5p Axis

APP misexpression plays a crucial role in triggering a complex pathological cascade, leading to Alzheimer’s disease (AD). But how the expression of APP is regulated in pathological conditions remains poorly understood. In this study, we found that the exosomes isolated from AD mouse brain promoted APP expression in neuronal N2a cells. Moreover, exosomes derived from N2a cells with ectopic expression of APP (APP-EXO) also induced APP dysregulation in normal N2a cells. Surprisingly, the effects of APP-EXO on APP expression in recipient cells were not mediated by the direct transferring of APP gene products. Instead, the effects of APP-EXO were highly likely mediated by the reduction of the expression levels of exosomal miR-185-5p. We found that the 3′UTR of APP transcripts binds to miR-185-5p, therefore inhibiting the sorting of miR-185-5p to exosomes. N2a cell-derived exosomes with less amount of miR-185-5p exert similar roles in APP expression to APP-EXO. Lastly, we demonstrated a significant decline of serum exosomal miR-185-5p in AD patients and AD mice, versus the corresponding controls. Together, our results demonstrate a novel mechanism in the exosome-dependent regulation of APP, implying exosomes and exosomal miRNAs as potential therapeutic targets and biomarkers for AD treatment and diagnosis, respectively.