miR-124 downregulates BACE 1 and alters autophagy in APP/PS1 transgenic mice

Critical role of microRNAs in cellular quality control during brain aging and neurological disorders: Interplay between autophagy and proteostasis

A decline in cellular quality control mechanisms is one of the processes of brain aging. Autophagy and proteostasis are two regulatory mechanisms that maintain cellular component turnover to preserve cellular homeostasis, optimal function, and neuronal health by eliminating damaged and aggregated proteins and preventing neurodegenerative disorders (NDDs). Impaired autophagy and proteostasis are significant hallmarks of aging and many age-related NDDs. MicroRNAs are noncoding RNA molecules that have recently been shown to be essential for regulating several biological processes, such as autophagy, proteostasis, cellular differentiation, and development by targeting mRNA's 3'untranslated region (3'UTR). During brain aging, miRNAs have been shown to dysregulate proteostasis and autophagy, resulting in abnormal cellular activity and protein aggregation, a characteristic of age-related NDDs. This review highlights the complex interactions of miRNAs in the orchestration of proteostasis and autophagy. This dysregulation impairs autophagic flux and proteostasis and accelerates age-related disorders, neuroinflammation, and neurodegeneration. Understanding the complex interactions among miRNAs, autophagy, and proteostasis in the aging brain is essential for novel therapeutics development for age-related NDDs.

Unlocking the therapeutic promise of miRNAs in promoting amyloid-β clearance for Alzheimer's disease

Alzheimer's disease (AD) is a neurological disorder that affects cognition and behavior, accounting for 60-70 % of dementia cases. Its mechanisms involve amyloid aggregates, hyperphosphorylated tau tangles, and loss of neural connections. Current treatments have limited efficacy due to a lack of specific targets. Recently, microRNAs (miRNAs) have emerged as key modulators in AD, regulating gene expression through interactions with mRNA. Dysregulation of specific miRNAs contributes to disease progression by disrupting clearance pathways. Antisense oligonucleotide (ASO)-based therapies show promise for AD treatment, particularly when combined with miRNA mimics or antagonists, targeting complex regulatory networks. However, miRNAs can interact with each other, complicating cellular processes and potentially leading to side effects. Our review emphasizes the role of miRNAs in regulating amyloid-beta (Aβ) clearance and highlights their potential as therapeutic targets and early biomarkers for AD, underscoring the need for further research to enhance their efficacy and safety.

Circular RNAs, miRNAs, and Exosomes: Their Roles and Importance in Amyloid-Beta and Tau Pathologies in Alzheimer's Disease

Alzheimer's disease (AD) is a devastating neurodegenerative disorder. The pathology of this disease is based on two basic mechanisms: amyloid-beta (Aβ) and tau fibrillation. Many genes and mechanisms have been identified as the primary causes of AD in clinical settings, and there have been exciting developments in drug treatments. Several molecules and biological structures regulate the genome outside of the standard DNA function. As in many diseases, circular RNAs (circRNAs), microRNAs (miRNAs), and exosomes (EXOs), investigated from different aspects of AD, are useful for treatment and diagnosis. This review examines two biological elements regarding their roles in the Aβ-tau pathology of AD and their potential as treatment targets. Importantly, the activities of miRNAs that play a role in these processes were evaluated. Trial Registration: ClinicalTrials.gov identifiers: NCT04120493, NCT04969172, NCT04388982.

Modulation of β secretase and neuroinflammation by biomimetic nanodelivery system for Alzheimer's disease therapy

Alzheimer's disease (AD) is an irreversible and progressive neurodegenerative disorder. The vicious circle between amyloid-β peptide (Aβ) overgeneration and microglial dysfunction is an important pathological event that promotes AD progression. However, therapeutic strategies toward only Aβ or microglial modulation still have many problems. Herein, inspired by the Aβ transportation, an Aβ-derived peptide (CKLVFFAED) engineered biomimetic nanodelivery system (MK@PC-R NPs) is reported for realizing BBB penetration and reprogram neuron and microglia in AD lesion sites. This hollow mesoporous Prussian blue-based MK@PC-R NPs carrying curcumin and miRNA-124 can down-regulate β secretase expression, thereby inhibiting Aβ production and reducing Aβ-induced neurotoxicity. Meanwhile, MK@PC-R NPs with excellent antioxidant and anti-inflammatory properties could normalize the microglial phenotype and promote Aβ degradation, providing neuroprotection. As expected, after treatment with MK@PC-R NPs, the Aβ burdens, neuron damages, neuroinflammation, and memory deficits of transgenic AD mice (APP/PS1 mice) are significantly attenuated. Overall, this biomimetic nanodelivery system with anti-Aβ and anti-inflammatory properties provides a promising strategy for the multi-target therapy of early AD.

miRNA-124 loaded extracellular vesicles encapsulated within hydrogel matrices for combating chemotherapy-induced neurodegeneration

Chemotherapy-induced neurodegeneration represents a significant challenge in cancer survivorship, manifesting in cognitive impairments that severely affect patients' quality of life. Emerging neuroregenerative therapies offer promise in mitigating these adverse effects, with miRNA-124 playing a pivotal role due to its critical functions in neural differentiation, neurogenesis, and neuroprotection. This review article delves into the innovative approach of using miRNA-124-loaded extracellular vesicles (EVs) encapsulated within hydrogel matrices as a targeted strategy for combating chemotherapy-induced neurodegeneration. We explore the biological underpinnings of miR-124 in neuroregeneration, detailing its mechanisms of action and therapeutic potential. The article further examines the roles and advantages of EVs as natural delivery systems for miRNAs and the application of hydrogel matrices in creating a sustained release environment conducive to neural tissue regeneration. By integrating these advanced materials and biological agents, we highlight a synergistic therapeutic strategy that leverages the bioactive properties of miR-124, the targeting capabilities of EVs, and the supportive framework of hydrogels. Preclinical studies and potential pathways to clinical translation are discussed, alongside the challenges, ethical considerations, and future directions in the field. This comprehensive review underscores the transformative potential of miR-124-loaded EVs in hydrogel matrices, offering insights into their development as a novel and integrative approach for addressing the complexities of chemotherapy-induced neurodegeneration.

The role of autophagy in brain health and disease: Insights into exosome and autophagy interactions

Effective management of cellular components is essential for maintaining brain health, and studies have identified several crucial biological processes in the brain. Among these, autophagy and the role of exosomes in cellular communication are critical for brain health and disease. The interaction between autophagy and exosomes in the nervous system, as well as their contributions to brain damage, have garnered significant attention. This review summarizes that exosomes and their cargoes have been implicated in the autophagy process in the pathophysiology of nervous system diseases. Furthermore, the onset and progression of neurological disorders may be affected by autophagy regulation of the secretion and release of exosomes. These findings may provide new insights into the potential mechanism by which autophagy mediates different exosome secretion and release, as well as the valuable biomedical applications of exosomes in the prevention and treatment of various brain diseases by targeting autophagy.

Spermidine as an epigenetic regulator of autophagy in neurodegenerative disorders

Autophagy is an abnormal protein degradation and recycling process that is impaired in various neurological diseases like Alzheimer's disease (AD), Parkinson's disease (PD), and Huntington's disease. Spermidine is a natural polyamine found in various plant- and meat-based diets that can induce autophagy, and is decreased in various neurodegenerative diseases. It acts on epigenetic enzymes like E1A-binding protein p300, HAT enzymes like Iki3p and Sas3p, and α-tubulin acetyltransferase 1 that modulate autophagy. Histone modifications like acetylation, phosphorylation, and methylation could influence autophagy. Autophagy is epigenetically regulated in various neurodegenerative disorders with many epigenetic enzymes and miRNAs. Polyamine regulation plays an essential role in the disease pathogenesis of AD and PD. Therefore, in this review, we discuss various enzymes and miRNAs involved in the epigenetic regulation of autophagy in neurodegenerative disorders and the role of spermidine as an autophagy enhancer. The alterations in spermidine-mediated regulation of Beclin-1, LC3-II, and p62 genes in AD and other PD-associated enzymes could impact the process of autophagy in these neurodegenerative diseases. With the ever-growing data and such promising effects of spermidine in autophagy, we feel it could be a promising target in this area and worth further detailed studies.

Daphnetin protects neurons in an Alzheimer disease mouse model and normal rat neurons by inhibiting BACE1 activity and activating the Nrf2/HO-1 pathway

The common neurodegenerative disorder Alzheimer disease (AD) is characterized by memory dysfunction and cognitive decline in the elderly. Neuropathological features include aggregated β-amyloid (Aβ) accumulation, neuroinflammation, and oxidative stress in the brain. Daphnetin (DAPH), a natural coumarin derivative, has the potential for inhibiting inflammatory and oxidative responses. We explored neuroprotective roles of DAPH treatment in the APP/PS1 transgenic mouse AD model. DAPH ameliorated spatial learning disabilities in Morris water maze tests and reduced Aβ deposition, assessed by immunohistochemistry. It also reduced the Aβ content in supernatants of neurons from fetal APP/PS1 mice, assessed by cell-based soluble ELISA. Molecular docking and fluorescence resonance energy transfer-based assay results suggested that DAPH could directly inhibit BACE1 activity. Furthermore, in vitro experiments utilizing isolated rat neurons assessing RNA expression profiling, immunofluorescence, TUNEL assay, and Western-blot analysis, suggested the potential of DAPH for regulating BDNF and GM-CSF expression and mitigating Aβ1-42-induced cortical injury, synaptic loss, and apoptosis. HO-1 and Nrf2 mRNA and protein expression were also increased in a dose-dependent manner. These results underscore the potential of DAPH as a neuroprotective agent in reversing memory deficits associated with AD and bolster its candidacy as a multitarget natural small-molecule drug for AD patients.

Reducing Nogo-B Improves Hepatic Fibrosis by Inhibiting BACe1-Mediated Autophagy

BACKGROUND

Hepatic fibrosis (HF) is a histopathological change in the process of long-term liver injury caused by cytokine secretion and internal environment disturbance, resulting in excessive liver repair and fiber scar. Nogo-B protein is widely distributed in peripheral tissues and organs and can regulate the migration of endothelial cells by activating TGF-β1 in vascular remodeling after injury. Nogo-B has been shown to promote organ fibrosis. This study was to determine the role of Nogo-B in HF.

METHODS

An HF model was built by intraperitoneal injections with 20% carbon tetrachloride. Localization of Nogo-B was detected by FISH. The interaction between Nogo-B and BACE1 was confirmed by Co-IP. Autophagy flux was analyzed using tandem mRFP-GFP-LC3 fluorescence microscopy, electron microscopy, and western blotting. Detection of serum AST and ALT and H&E staining were utilized to detect the degree of liver injury. The HF was evaluated by Masson trichromatic staining. RT-qPCR, western blotting, and immunofluorescence were employed to detect relevant indicators.

RESULTS

Reducing Nogo-B suppressed AST and ALT levels, the accumulation of collagen I and α-SMA, and expressions of pro-fibrotic genes in mouse liver. BACE1 was a potential downstream target of Nogo-B. Nogo-B was upregulated in TGF-β1-activated hepatic stellate cells (HSCs). Knocking down Nogo-B caused the downregulation of pro-fibrotic genes and inhibited viability of HSCs. Nogo-B knockdown prevented CCL4-induced fibrosis, accompanied by downregulation of extracellular matrix. Nogo-B inhibited HSC autophagy and increased lipid accumulation. BACE1 knockdown inhibited HSC autophagy and activation in LX-2 cells.

CONCLUSION

Nogo-B knockdown prevents HF by directly inhibiting BACe1-mediated autophagy.

The Potential of Targeting Autophagy-Related Non-coding RNAs in the Treatment of Alzheimer's and Parkinson's Diseases

Clearance of accumulated protein aggregates is one of the functions of autophagy. Recently, a clearer understanding of non-coding RNAs (ncRNAs) functions documented that ncRNAs have important roles in several biological processes associated with the development and progression of neurodegenerative disorders. Subtypes of ncRNA, including microRNA (miRNA), long noncoding RNA (lncRNA), and circular RNA (circRNA), are commonly dysregulated in neurodegenerative disorders such as Alzheimer and Parkinson diseases. Dysregulation of these non-coding RNAs has been associated with inhibition or stimulation of autophagy. Decreased miR-124 led to decreased/increased autophagy in experimental model of Alzheimer and Parkinson diseases. Increased BACE1-AS showed enhanced autophagy in Alzheimer disease by targeting miR-214-3p, Beclin-1, LC3-I/LC3-II, p62, and ATG5. A significant increase in NEAT1led to stimulated autophagy in experimental model of PD by targeting PINK1, LC3-I, LC3-II, p62 and miR-374c-5p. In addition, increased BDNF-AS and SNHG1 decreased autophagy in MPTP-induced PD by targeting miR-125b-5p and miR-221/222, respectively. The upregulation of circNF1-419 and circSAMD4A resulted in an increased autophagy by regulating Dynamin-1 and miR-29c 3p, respectively. A detailed discussion of miRNAs, circRNAs, and lncRNAs in relation to their autophagy-related signaling pathways is presented in this study.

Potential Implications of miRNAs in the Pathogenesis, Diagnosis, and Therapeutics of Alzheimer's Disease

Alzheimer's disease (AD) is a complex multifactorial disorder that poses a substantial burden on patients, caregivers, and society. Considering the increased aging population and life expectancy, the incidence of AD will continue to rise in the following decades. However, the molecular pathogenesis of AD remains controversial, superior blood-based biomarker candidates for early diagnosis are still lacking, and effective therapeutics to halt or slow disease progression are urgently needed. As powerful genetic regulators, microRNAs (miRNAs) are receiving increasing attention due to their implications in the initiation, development, and theranostics of various diseases, including AD. In this review, we summarize miRNAs that directly target microtubule-associated protein tau (MAPT), amyloid precursor protein (APP), and β-site APP-cleaving enzyme 1 (BACE1) transcripts and regulate the alternative splicing of tau and APP. We also discuss related kinases, such as glycogen synthase kinase (GSK)-3β, cyclin-dependent kinase 5 (CDK5), and death-associated protein kinase 1 (DAPK1), as well as apolipoprotein E, that are directly targeted by miRNAs to control tau phosphorylation and amyloidogenic APP processing leading to Aβ pathologies. Moreover, there is evidence of miRNA-mediated modulation of inflammation. Furthermore, circulating miRNAs in the serum or plasma of AD patients as noninvasive biomarkers with diagnostic potential are reviewed. In addition, miRNA-based therapeutics optimized with nanocarriers or exosomes as potential options for AD treatment are discussed.

Biometals in Alzheimer disease: emerging therapeutic and diagnostic potential of molybdenum and iodine

The current ageing trend of the world population has, in part, accounted for Alzheimer disease (AD) being a public health issue in recent times. Although some progress has been made in clarifying AD-related pathophysiological mechanisms, effective intervention is still elusive. Biometals are indispensable to normal physiological functions of the human body-for example, neurogenesis and metabolism. However, their association with AD remains highly controversial. Copper (Cu) and zinc (Zn) are biometals that have been investigated at great length in relation to neurodegeneration, whereas less attention has been afforded to other trace biometals, such as molybdenum (Mo), and iodine. Given the above context, we reviewed the limited number of studies that have evidenced various effects following the usage of these two biometals in different investigative models of AD. Revisiting these biometals via thorough investigations, along with their biological mechanisms may present a solid foundation for not only the development of effective interventions, but also as diagnostic agents for AD.

The Epigenetic Role of miR-124 in HIV-1 Tat- and Cocaine-Mediated Microglial Activation

HIV-1 and drug abuse have been indissolubly allied as entwined epidemics. It is well-known that drug abuse can hasten the progression of HIV-1 and its consequences, especially in the brain, causing neuroinflammation. This study reports the combined effects of HIV-1 Transactivator of Transcription (Tat) protein and cocaine on miR-124 promoter DNA methylation and its role in microglial activation and neuroinflammation. The exposure of mouse primary microglial cells to HIV-1 Tat (25 ng/mL) and/or cocaine (10 μM) resulted in the significantly decreased expression of primary (pri)-miR-124-1, pri-miR-124-2, and mature miR-124 with a concomitant upregulation in DNMT1 expression as well as global DNA methylation. Our bisulfite-converted genomic DNA sequencing also revealed significant promoter DNA methylation in the pri-miR-124-1 and pri-miR-124-2 in HIV-1 Tat- and cocaine-exposed mouse primary microglial cells. We also found the increased expression of proinflammatory cytokines such as IL1β, IL6 and TNF in the mouse primary microglia exposed to HIV-1 Tat and cocaine correlated with microglial activation. Overall, our findings demonstrate that the exposure of mouse primary microglia to both HIV-1 Tat and cocaine could result in intensified microglial activation via the promoter DNA hypermethylation of miR-124, leading to the exacerbated release of proinflammatory cytokines, ultimately culminating in neuroinflammation.

miR-124: A Promising Therapeutic Target for Central Nervous System Injuries and Diseases

Central nervous system injuries and diseases, such as ischemic stroke, spinal cord injury, neurodegenerative diseases, glioblastoma, multiple sclerosis, and the resulting neuroinflammation often lead to death or long-term disability. MicroRNAs are small, non-coding, single-stranded RNAs that regulate posttranscriptional gene expression in both physiological and pathological cellular processes, including central nervous system injuries and disorders. Studies on miR-124, one of the most abundant microRNAs in the central nervous system, have shown that its dysregulation is related to the occurrence and development of pathology within the central nervous system. Herein, we review the molecular regulatory functions, underlying mechanisms, and effective delivery methods of miR-124 in the central nervous system, where it is involved in pathological conditions. The review also provides novel insights into the therapeutic target potential of miR-124 in the treatment of human central nervous system injuries or diseases.

The Potential Role of miRNA-Regulated Autophagy in Alzheimer’s Disease

As a neurodegenerative disease, Alzheimer’s disease (AD) shows a higher incidence during the aging process, mainly revealing the characteristics of a significant decrease in cognition, uncontrolled emotion, and reduced learning and memory capacity, even leading to death. In the prevention and treatment of AD, some pharmacological therapy has been applied in clinical practice. Unfortunately, there are still limited effective treatments for AD due to the absence of clear and defined targets. Currently, it is recognized that the leading causes of AD include amyloid-β peptide (Aβ) deposition, hyperphosphorylation of tau protein, neurofibrillary tangles, mitochondrial dysfunction, and inflammation. With in-depth mechanistic exploration, it has been found that these causes are highly correlated with the dysfunctional status of autophagy. Numerous experimental results have also confirmed that the development and progression of AD is accompanied by an abnormal functional status of autophagy; therefore, regulating the functional status of autophagy has become one of the important strategies for alleviating or arresting the progression of AD. With the increasing attention given to microRNAs (miRNAs), more and more studies have found that a series of miRNAs are involved in the development and progression of AD through the indirect regulation of autophagy. Therefore, regulating autophagy through targeting these miRNAs may be an essential breakthrough for the prevention and treatment of AD. This article summarizes the regulation of miRNAs in autophagy, with the aim of providing a new theoretical reference point for the prevention and treatment of AD through the indirect regulation of miRNA-mediated autophagy.

Neuronal microRNAs safeguard ER Ca2+ homeostasis and attenuate the unfolded protein response upon stress

Ca2+ is a critical mediator of neurotransmitter release, synaptic plasticity, and gene expression, but also excitotoxicity. Ca2+ signaling and homeostasis are coordinated by an intricate network of channels, pumps, and calcium-binding proteins, which must be rapidly regulated at all expression levels. Τhe role of neuronal miRNAs in regulating ryanodine receptors (RyRs) and inositol 1,4,5-triphosphate receptors (IP3Rs) was investigated to understand the underlying mechanisms that modulate ER Ca2+ release. RyRs and IP3Rs are critical in mounting and propagating cytosolic Ca2+ signals by functionally linking the ER Ca2+ content, while excessive ER Ca2+ release via these receptors is central to the pathophysiology of a wide range of neurological diseases. Herein, two brain-restricted microRNAs, miR-124-3p and miR-153-3p, were found to bind to RyR1-3 and IP3R3 3'UTRs, and suppress their expression at both the mRNA and protein level. Ca2+ imaging studies revealed that overexpression of these miRNAs reduced ER Ca2+ release upon RyR/IP3R activation, but had no effect on [Ca2+]i under resting conditions. Interestingly, treatments that cause excessive ER Ca2+ release decreased expression of these miRNAs and increased expression of their target ER Ca2+ channels, indicating interdependence of miRNAs, RyRs, and IP3Rs in Ca2+ homeostasis. Furthermore, by maintaining the ER Ca2+ content, miR-124 and miR-153 reduced cytosolic Ca2+ overload and preserved protein-folding capacity by attenuating PERK signaling. Overall, this study shows that miR-124-3p and miR-153-3p fine-tune ER Ca2+ homeostasis and alleviate ER stress responses.

Dysregulated miRNAs as Biomarkers and Therapeutical Targets in Neurodegenerative Diseases

Alzheimer’s disease (AD), Parkinson’s disease (PD), and Amyotrophic Lateral Sclerosis (ALS) are representative neurodegenerative diseases (NDs) characterized by degeneration of selective neurons, as well as the lack of effective biomarkers and therapeutic treatments. In the last decade, microRNAs (miRNAs) have gained considerable interest in diagnostics and therapy of NDs, owing to their aberrant expression and their ability to target multiple molecules and pathways. Here, we provide an overview of dysregulated miRNAs in fluids (blood or cerebrospinal fluid) and nervous tissue of AD, PD, and ALS patients. By emphasizing those that are commonly dysregulated in these NDs, we highlight their potential role as biomarkers or therapeutical targets and describe the use of antisense oligonucleotides as miRNA therapies.

Exosomes Derived From M2 Microglia Cells Attenuates Neuronal Impairment and Mitochondrial Dysfunction in Alzheimer’s Disease Through the PINK1/Parkin Pathway

The accumulation of abnormal aggregation of amyloid-β plaques is one of the most distinguishing pathologies of Alzheimer’s disease (AD) and is highly toxic to neurons. Exosomes have demonstrated great potential for AD therapy. However, the impact and underlying mechanism of M2 microglia-derived exosomes (M2-EXOs) in AD progression and outcome are seldom explored. Therefore, we employed an Aβ1-42 oligomer (Aβ)-induced AD model in neuronal HT-22 cells and 7-month-old APP/PS1 mice to investigate the effects of M2-EXOs on AD. We revealed that the AD cell model established by Aβ was accompanied by the upregulation of Aβ1-42, neuronal death, alternation of mitochondrial function and autophagy. M2-EXOs can be internalized by HT-22 cells and MAP2-positive neuronal cells in APP/PS1 mice, and exert neuroprotective functions. Specifically, the administration of M2-EXOs in the AD cell model partially increased cell viability, restored the destruction of mitochondrial membrane potential, and reduced the accumulation of reactive oxygen species inside the mitochondria and cells in a dose-dependent manner. Moreover, we demonstrated that PINK1/Parkin mediated mitophagy was enhanced, while incubation with M2-EXOs decreased beclin1, LC3II, PINK1, and Parkin expression levels. Finally, we observed that compared with APP/PS1 mice treated with PBS, the application of M2-EXOs could decrease Aβ plaque deposition and minus Aβ oligomer expression along with improved PINK1/Parkin pathway-mediated autophagy. Overall, our results imply that M2-EXOs play a protective role in the pathogenesis of AD by ameliorating PINK1/Parkin-mediated mitophagy, indicating that it may provide a novel therapeutic strategy to treat AD.

Brain-Penetration and Neuron-Targeting DNA Nanoflowers Co-Delivering miR-124 and Rutin for Synergistic Therapy of Alzheimer's Disease

Alzheimer disease (AD) is the leading cause of dementia that affects millions of old people. Despite significant advances in the understanding of AD pathobiology, no disease modifying treatment is available. MicroRNA-124 (miR-124) is the most abundant miRNA in the normal brain with great potency to ameliorate AD-like pathology, while it is deficient in AD brain. Herein, the authors develop a DNA nanoflowers (DFs)-based delivery system to realize exogenous supplementation of miR-124 for AD therapy. The DFs with well-controlled size and morphology are prepared, and a miR-124 chimera is attached via hybridization. The DFs are further modified with RVG29 peptide to simultaneously realize brain-blood barrier (BBB) penetration and neuron targeting. Meanwhile, Rutin, a small molecular ancillary drug, is co-loaded into the DFs structure via its intercalation into the double stranded DNA region. Interestingly, Rutin could synergize miR-124 to suppress the expression of both BACE1 and APP, thus achieving a robust inhibition of amyloid β generation. The nanosystem could pro-long miR-124 circulation in vivo, promote its BBB penetration and neuron targeting, resulting in a significant increase of miR-124 in the hippocampus of APP/PS1 mice and robust therapeutic efficacy in vivo. Such a bio-derived therapeutic system shows promise as a biocompatible nanomedicine for AD therapy.

Effects of microRNA-298 on APP and BACE1 translation differ according to cell type and 3'-UTR variation

Alzheimer's disease (AD) is marked by neurofibrillary tangles and senile plaques composed of amyloid β (Aβ) peptides. However, specific contributions of different cell types to Aβ deposition remain unknown. Non-coding microRNAs (miRNA) play important roles in AD by regulating translation of major associated proteins, such as Aβ precursor protein (APP) and β-site APP-cleaving enzyme (BACE1), two key proteins associated with Aβ biogenesis. MiRNAs typically silence protein expression via binding specific sites in mRNAs' 3'-untranslated regions (3'-UTR). MiRNAs regulate protein levels in a cell-type specific manner; however, mechanisms of the variation of miRNA activity remain unknown. We report that miR-298 treatment reduced native APP and BACE1 protein levels in an astrocytic but not in a neuron-like cell line. From miR-298's effects on APP-3'-UTR activity and native protein levels, we infer that differences in APP 3'-UTR length could explain differential miR-298 activity. Such varied or truncated, but natural, 3'-UTR specific to a given cell type provides an opportunity to regulate native protein levels by particular miRNA. Thus, miRNA's effect tailoring to a specific cell type, bypassing another undesired cell type with a truncated 3'-UTR would potentially advance clinically-relevant translational research.

MicroRNAs in the pathophysiology of Alzheimer's disease and Parkinson's disease: an overview

Neurodegenerative diseases are characterized by a progressive loss of neurons of the central nervous system (CNS) and serve as a major cause of morbidity, mortality and functional dependence especially among the elderly. Despite extensive research and development efforts, the success rate of clinical pipelines has been very limited. However, microRNAs (miRs) have been proved to be of crucial importance in regulating intracellular pathways for various pathologic conditions including those of a neurodegenerative nature. There is ample evidence of altered levels of various miRs in clinical samples of Alzheimer's disease and Parkinson's disease patients with potentially major clinical implications. In the current review, we aim to summarize the relevant literature on the role of miRs in the pathophysiology of Alzheimer's disease (AD) and Parkinson's disease (PD) as the two globally predominant neurodegenerative conditions.

Neuronal Dynamics and miRNA Signaling Differ between SH-SY5Y APPSwe and PSEN1 Mutant iPSC-Derived AD Models upon Modulation with miR-124 Mimic and Inhibitor

Neuronal miRNA dysregulation may have a role in the pathophysiology of Alzheimer's disease (AD). miRNA(miR)-124 is largely abundant and a critical player in many neuronal functions. However, the lack of models reliably recapitulating AD pathophysiology hampers our understanding of miR-124's role in the disease. Using the classical human SH-SY5Y-APP695 Swedish neuroblastoma cells (SH-SWE) and the PSEN1 mutant iPSC-derived neurons (iNEU-PSEN), we observed a sustained upregulation of miR-124/miR-125b/miR-21, but only miR-124 was consistently shuttled into their exosomes. The miR-124 mimic reduced APP gene expression in both AD models. While miR-124 mimic in SH-SWE neurons led to neurite outgrowth, mitochondria activation and small Aβ oligomer reduction, in iNEU-PSEN cells it diminished Tau phosphorylation, whereas miR-124 inhibitor decreased dendritic spine density. In exosomes, cellular transfection with the mimic predominantly downregulated miR-125b/miR-21/miR-146a/miR-155. The miR-124 inhibitor upregulated miR-146a in the two experimental cell models, while it led to distinct miRNA signatures in cells and exosomes. In sum, though miR-124 function may be dependent on the neuronal AD model, data indicate that keeping miR-124 level strictly controlled is crucial for proper neuronal function. Moreover, the iNEU-PSEN cellular model stands out as a useful tool for AD mechanistic studies and perhaps for the development of personalized therapeutic strategies.

Multifaceted Regulation of MicroRNA Biogenesis: Essential Roles and Functional Integration in Neuronal and Glial Development

MicroRNAs (miRNAs) are small, non-coding RNAs that function as endogenous gene silencers. Soon after the discovery of miRNAs, a subset of brain-enriched and brain-specific miRNAs were identified and significant advancements were made in delineating miRNA function in brain development. However, understanding the molecular mechanisms that regulate miRNA biogenesis in normal and diseased brains has become a prevailing challenge. Besides transcriptional regulation of miRNA host genes, miRNA processing intermediates are subjected to multifaceted regulation by canonical miRNA processing enzymes, RNA binding proteins (RBPs) and epitranscriptomic modifications. Further still, miRNA activity can be regulated by the sponging activity of other non-coding RNA classes, namely circular RNAs (circRNAs) and long non-coding RNAs (lncRNAs). Differential abundance of these factors in neuronal and glial lineages partly underlies the spatiotemporal expression and function of lineage-specific miRNAs. Here, we review the continuously evolving understanding of the regulation of neuronal and glial miRNA biogenesis at the transcriptional and posttranscriptional levels and the cooperativity of miRNA species in targeting key mRNAs to drive lineage-specific development. In addition, we review dysregulation of neuronal and glial miRNAs and the detrimental impacts which contribute to developmental brain disorders.

MicroRNA-3473b regulates the expression of TREM2/ULK1 and inhibits autophagy in inflammatory pathogenesis of Parkinson disease

Parkinson disease (PD) is a neurodegenerative disease characterized by selective loss of dopaminergic (DA) neurons in the midbrain. The regulatory role of a variety of microRNAs in PD has been confirmed, and our study is the first to demonstrate that miR-3473b is involved in the regulation of PD. In vitro, an miR-3473b inhibitor can inhibit the secretion of inflammatory factors (TNF-α and IL-1β) in moues microglia cell line (BV2) cells induced by lipopolysaccharide (LPS) and promote autophagy in BV2 cells. In vivo, miR-3473b antagomir can inhibit the activation of substantia nigra pars compacta (SNpc) microglia of C57BL/6 mice induced by 1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) and promote autophagy. Deletion of TREM2, one of the most highly expressed receptors in microglia, leads to the occurrence and development of PD. ULK1 is a component of the Atg1 complex. Deletion of ULK1 aggravates the pathological reaction of PD. TREM2 and ULK1 are predicted potential targets of miR-3473b by Targetscan. Then, the results of our experiments indicate that transfection with a miR-3473b mimic can inhibit the expression of TREM2 and ULK1. Data from a double luciferase experiment indicate that the 3'-UTR of TREM2, but not ULK1, is the direct target of miR-3473b. Then we aim to investigate the regulation of TREM2 and ULK1 in PD. We found that the expression of p-ULK1 was significantly increased via up-regulation of TREM2. The increased expression of p-ULK1 can promote autophagy and inhibit the expression of inflammatory factors. The regulation of ULK1 by miR-3473b may be accomplished indirectly through TREM2. Thus, miR-3473b may regulate the secretion of proinflammatory mediators by targeting TREM2/ULK1 expression to regulate the role of autophagy in the pathogenesis of inflammation in Parkinson's disease, suggesting that mir-3473b may be a potential therapeutic target to regulate the inflammatory response in PD.

An update on the role of miR-124 in the pathogenesis of human disorders

MicroRNA-124 (miR-124) is a copious miRNA in the brain, but it is expressed in a wide range of human/animal tissues participating in the pathogenesis of several disorders. Based on its important function in the development of the nervous system, abnormal expression of miR-124 has been detected in nervous system diseases including Alzheimer's disease, Parkinson's disease, Hypoxic-Ischemic Encephalopathy, Huntington's disease, and ischemic stroke. In addition to these conditions, miR-124 contributes to the pathogenesis of cardiovascular disorders, hypertension, and atherosclerosis. Besides, it has been shown to be down-regulated in a wide range of human cancers such as colorectal cancer, breast cancer, gastric cancer, glioma, pancreatic cancer, and other types of cancer. Yet, few studies have reported upregulation of miR-124 in some cancer types. In the current study, we describe the role of miR-124 in these malignant and non-malignant conditions.

MicroRNAs Regulating Autophagy in Neurodegeneration

Social and economic impacts of neurodegenerative diseases (NDs) become more prominent in our constantly aging population. Currently, due to the lack of knowledge about the aetiology of most NDs, only symptomatic treatment is available for patients. Hence, researchers and clinicians are in need of solid studies on pathological mechanisms of NDs. Autophagy promotes degradation of pathogenic proteins in NDs, while microRNAs post-transcriptionally regulate multiple signalling networks including autophagy. This chapter will critically discuss current research advancements in the area of microRNAs regulating autophagy in NDs. Moreover, we will introduce basic strategies and techniques used in microRNA research. Delineation of the mechanisms contributing to NDs will result in development of better approaches for their early diagnosis and effective treatment.

Tetramethylpyrazine Attenuated Sevoflurane-Induced Neurotoxicity by Enhancing Autophagy through GPR50/CREB Pathway in SH-SY5Y Cells

Tetramethylpyrazine has shown neuroprotective and axonal outgrowth-promoting effects and can improve cognitive deficit in a rat model of chronic hypoperfusion. However, the role of tetramethylpyrazine in sevoflurane-induced neurotoxicity is still vague. Therefore, this study was designed to investigate the effects and mechanisms of tetramethylpyrazine on sevoflurane-induced autophagy, apoptosis, and the expression of BACE1 and A[Formula: see text] in SH-SY5Y cells. We measured the expression levels of the apoptosis protein markers Bax and Bcl-2, autophagy protein markers Atg5 and LC3-II, BACE1, and A[Formula: see text] in SH-SY5Y cells after sevoflurane treatment and determined the effects of tetramethylpyrazine on sevoflurane-induced expression of these proteins after silencing GPR50 or Atg5 with siRNA in vitro. We found that exposure to 3.4% sevoflurane for 6 h decreased the expression of autophagy protein markers and increased the expression of the apoptosis protein markers, BACE1, and A[Formula: see text] in SH-SY5Y cells. The number of red puncta (autolysosomes) and yellow puncta (autophagosomes) in each SH-SY5Y cell decreased after transient transfection with the mRFP-GFP-LC3 expression plasmid. Silencing of GPR50 decreased the expression of pCREB, Atg5, and LC3-II, while silencing of Atg5 increased the expression of BACE1 and A[Formula: see text] in SH-SY5Y cells. Our results demonstrate that tetramethylpyrazine attenuated sevoflurane-induced neurotoxicity by enhancing autophagy through the GPR50/CREB pathway in SH-SY5Y cells.

The Regulation of microRNAs in Alzheimer's Disease

MicroRNAs are small non-coding nucleic acids that are responsible for regulating the gene expression by binding to the coding region and 3' and 5' un-translated region of target messenger RNA. Approximately 70% of known microRNAs are expressed in the brain and increasing evidences demonstrate the possible involvement of microRNAs in Alzheimer's disease (AD) according to the statistics. The characteristic symptoms of AD are the progressive loss of memory and cognitive functions due to the deposition of amyloid β (Aβ) peptide, intracellular aggregation of hyperphosphorylated Tau protein, the loss of synapses, and neuroinflammation, as well as dysfunctional autophagy. Therefore, microRNA-mediated regulation for above-mentioned changes may be the potential therapeutic strategies for AD. In this review, the role of specific microRNAs involved in AD and corresponding applications are systematically discussed, including positive effects associated with the reduction of Aβ or Tau protein, the protection of synapses, the inhibition of neuroinflammation, the mitigation of aging, and the induction of autophagy in AD. It will be beneficial to develop effective targets for establishing a cross link between pharmacological intervention and AD in the near future.

Functional roles and networks of non-coding RNAs in the pathogenesis of neurodegenerative diseases

Recent transcriptome analyses have revealed that noncoding RNAs (ncRNAs) are broadly expressed in mammalian cells and abundant in the CNS, with tissue and cell type-specific expression patterns. Moreover, ncRNAs have been found to intricately and dynamically regulate various signaling pathways in neurodegeneration. As such, some antisense transcripts and microRNAs are known to directly affect neurodegeneration in disease contexts. The functions of ncRNAs in pathogenesis are unique for each disorder, as are the pertinent networks of ncRNA/miRNA/mRNA that mediate these functions. Thus, further understanding of ncRNA biogenesis and effects might aid the discovery of diagnostic biomarkers or development of effective therapeutics for neurodegenerative disorders. Here, we review the ncRNAs that have so far been identified in major neurodegenerative disease etiology and the mechanisms that link ncRNAs with disease-specific phenotypes, such as HTT aggregation in HD, α-synuclein in PD, and Aβ plaques and hyperphosphorylated Tau in AD. We also summarize the known lncRNA/miRNA/mRNA networks that participate in neurodegenerative diseases, and we discuss ncRNA-related treatments shown to delay disease onset and prolong lifespan in rodent models.

Synergic Effects of Berberine and Curcumin on Improving Cognitive Function in an Alzheimer's Disease Mouse Model

Alzheimer's disease (AD) is one of the most common neurodegenerative diseases, and no effective therapies have been found to prevent or cure AD to date. Berberine and curcumin are extracts from traditional Chinese herbs that have a long history of clinical benefits for AD. Here, using a transgenic AD mouse model, we found that the combined berberine and curcumin treatment had a much better effect on improving the cognitive function of mice than the single-drug treatment, suggesting synergic effects of the combined berberine and curcumin treatment. In addition, we found that the combined berberine and curcumin treatment had significant synergic effects on reducing soluble amyloid-β-peptide_(1-42) production. Furthermore, the combination treatment also had remarkable synergic effects on decreasing inflammatory responses and oxidative stress in both the cortex and hippocampus of AD mice. We also found that the combination treatment performed much better than the single drugs in reducing the APP and BACE1 levels and increasing AMPKα phosphorylation and cell autophagy, which might be the underlying mechanism of the synergic effects. Taken together, the result of this study reveal the synergic effects and potential underlying mechanisms of the combined berberine and curcumin treatment in improving the symptoms of AD in mice. This study sheds light on a new strategy for exploring new phytotherapies for AD and also emphasizes that more research should focus on the synergic effects of herbal drugs in the future.

Epigenetic mechanisms of neurodegenerative diseases and acute brain injury

Epigenetic modifications are emerging as major players in the pathogenesis of neurodegenerative disorders and susceptibility to acute brain injury. DNA and histone modifications act together with non-coding RNAs to form a complex gene expression machinery that adapts the brain to environmental stressors and injury response. These modifications influence cell-level operations like neurogenesis and DNA repair to large, intricate processes such as brain patterning, memory formation, motor function and cognition. Thus, epigenetic imbalance has been shown to influence the progression of many neurological disorders independent of aberrations in the genetic code. This review aims to highlight ways in which epigenetics applies to several commonly researched neurodegenerative diseases and forms of acute brain injury as well as shed light on the benefits of epigenetics-based treatments.

Exploring the bi-directional relationship between autophagy and Alzheimer's disease

Alzheimer's disease (AD) is characterized by β-amyloid (Aβ) deposition and Tau phosphorylation, in which its pathogenesis has not been cleared so far. The metabolism of Aβ and Tau is critically affected by the autophagy. Abnormal autophagy is thought to be involved in the pathogenesis of AD, regulating autophagy may become a new strategy for AD treatment. In the early stage of AD, the presence of Aβ and Tau can induce autophagy to promote their clearance by means of mTOR-dependent and independent manners. As AD progress, the autophagy goes aberrant. As a result, Aβ and Tau generate continually, which aggravates both autophagy dysfunction and AD. Besides, several related genes and proteins of AD can also adapt autophagy to make an effect on the AD development. There seems to be a bi-directional relationship between AD pathology and autophagy. At present, this article reviews this relationship from these aspects: (a) the signaling pathways of regulating autophagy; (b) the relationships between the autophagy and the processing of Aβ; (c) Aβ and Tau cause autophagy dysfunction; (d) normal autophagy promotes the clearance of Aβ and Tau; (e) the relationships between the autophagy and both genes and proteins related to AD: TFEB, miRNAs, Beclin-1, Presenilin, and Nrf2; and (f) the small molecules regulating autophagy on AD therapy. All of the above may help to further elucidate the pathogenesis of AD and provide a theoretical basis for clinical treatment of AD.

Emerging molecular functions of microRNA-124: Cancer pathology and therapeutic implications

MicroRNAs are characterized as small, single-stranded, non-coding RNA molecules that bind to their target mRNA to prevent protein synthesis. MicroRNAs regulate various normal processes; however, they are aberrantly regulated in many cancers. They control the expression of various genes, including cancer-related genes. This causes microRNAs to be considered as a good target for further investigations for designing novel therapeutic strategies. Since miR124 is known for some time already, it has a tumor-suppressing role in various cancers. Numerous studies indicate its definite roles in malignant processes such as epithelial-to-mesenchymal transition, cell cycle arrest, metastasis, cancer stem cell formation and induction of apoptosis. However, some studies have indicated a dual role for miR-124 in oncogenic processes like autophagy and multi-drug resistance. In this article, we will review recent researches on the biological functions and clinical implications of miR-124. Subsequently, we will discuss future perspectives in terms of the roles of this miRNA in cancers.

Silencing of long noncoding RNA XIST attenuated Alzheimer's disease-related BACE1 alteration through miR-124

Alzheimer's disease (AD) is a chronic progressive neurodegenerative disorder. However, its pathogenetic mechanism is still poorly understood. An increasing number of studies have evidenced the important role of long noncoding RNAs (lncRNAs) in AD. The aim of the current study was to investigate the effect and molecular mechanism of the lncRNA X-inactive specific transcript (XIST) in AD. Bilateral common carotid artery occlusion (2VO) was used to induce an AD model in mice. Hydrogen peroxide (H₂ O₂ ) was used to induce an AD model in N2a cells. The lncRNA XIST, miR-124, and BACE1 messenger RNA expression levels were detected by a real-time polymerase chain reaction. The BACE1 protein expression level was detected by western blot and immunofluorescence assay. The Aβ_1-42 expression level was detected using an enzyme-linked immunosorbent assay kit. The expression level of lncRNA XIST was significantly upregulated in AD models, both in vivo and in vitro. Silencing of lncRNA XIST negatively regulated miR-124 and positively regulated BACE1 expression in N2a cells, which is attenuated by cotransfection of anti-miR-124 oligodeoxyribonucleotide (AMO-124). Silencing of lncRNA XIST reversed the effect of H₂ O₂ on miR-124, BACE1, and Aβ_1-42 expression in N2a cells, which was reversed by cotransfection of AMO-124. Silencing of lncRNA XIST attenuated AD-related BACE1 alteration through miR-124. LncRNA XIST may be a new potential target for the treatment of AD.

Cerebral Amyloid Angiopathy, Alzheimer's Disease and MicroRNA: miRNA as Diagnostic Biomarkers and Potential Therapeutic Targets

The protein molecules must fold into unique conformations to acquire functional activity. Misfolding, aggregation, and deposition of proteins in diverse organs, the so-called "protein misfolding disorders (PMDs)", represent the conformational diseases with highly ordered assemblies, including oligomers and fibrils that are linked to neurodegeneration in brain illnesses such as cerebral amyloid angiopathy (CAA) and Alzheimer's disease (AD). Recent studies have revealed several aspects of brain pathology in CAA and AD, but both the classification and underlying mechanisms need to be further refined. MicroRNAs (miRNAs) are critical regulators of gene expression at the post-transcriptional level. Increasing evidence with the advent of RNA sequencing technology suggests possible links between miRNAs and these neurodegenerative disorders. To provide insights on the small RNA-mediated regulatory circuitry and the translational significance of miRNAs in PMDs, this review will discuss the characteristics and mechanisms of the diseases and summarize circulating or tissue-resident miRNAs associated with AD and CAA.

A novel kit for early diagnosis of Alzheimer's disease using a fluorescent nanoparticle imaging

Alzheimer's disease (AD) is a progressive neurodegenerative disease and chronic illness with long preclinical phases and a long clinical duration. Until recently, a lack of potential therapeutic agents against AD was the primary focus of research, which resulted in less effort directed towards developing useful diagnostic approaches. In this study, we developed a WO2002/088706 kit that is composed of fluorescent nanoparticles for the early detection of AD. We provided a fluorescent nanoparticle for detecting markers and a kit for the early diagnosis of AD. The kit consists of a probe molecule comprising an oligonucleotide capable of detecting one or more AD-specific microRNAs (miRNAs) and biomarkers related to AD. Through screening, we selected miR-106b, miR-146b, miR-181a, miR-200a, miR-34a, miR-124b, miR-153, miR-155, Aβ_1-42 monomer (mAβ), Aβ_1-42 oligomer (oAβ), UCHL1, NLRP3, Tau, STAT3, SORL1, Clusterin, APOE3, APOE4, Nogo-A, IL-13, and Visfatin to serve as AD- and inflammation-related markers. For detection of kit-binding properties, we checked the expression levels of amyloid beta (Aβ), tau protein, and inflammatory mediators in APP/PS/ApoE knockdown (KD) mice and a control group using co-localisation analysis conducted with a confocal microscope. Using a similar approach, we checked the expression levels of miRNAs in HT22 cells. Finally, we used the plasma from AD patients to confirm that our fluorescent nanoparticles and the WO2002/088706 kit will provide a possible early diagnosis to serve as an AD detector that can be further improved for future studies on targeting AD.

microRNA dysregulation in neurodegenerative diseases: A systematic review

While the root causes for individual neurodegenerative diseases are distinct, many shared pathological features and mechanisms contribute to neurodegeneration across diseases. Altered levels of microRNAs, small non-coding RNAs involved in post transcriptional regulation of gene expression, are reported for numerous neurodegenerative diseases. Yet, comparison between diseases to uncover commonly dysregulated microRNAs during neurodegeneration in general is lagging. We performed a systematic review of peer-reviewed publications describing differential microRNA expression in neurodegenerative diseases and related animal models. We compiled the results from studies covering the prevalent neurodegenerative diseases in the literature: Alzheimer's disease, amyotrophic lateral sclerosis, age-related macular degeneration, ataxia, dementia, myotonic dystrophy, epilepsy, glaucoma, Huntington's disease, multiple sclerosis, Parkinson's disease, and prion disorders. MicroRNAs which were dysregulated most often in these diseases and their models included miR-9-5p, miR-21-5p, the miR-29 family, miR-132-3p, miR-124-3p, miR-146a-5p, miR-155-5p, and miR-223-3p. Common pathways targeted by these predominant miRNAs were identified and revealed great functional overlap across diseases. We also identified a strong role for each microRNA in both the neural and immune components of diseases. microRNAs regulate broad networks of genes and identifying microRNAs commonly dysregulated across neurodegenerative diseases could cultivate novel hypotheses related to common molecular mechanisms underlying neurodegeneration.

MicroRNA-200a-3p Mediates Neuroprotection in Alzheimer-Related Deficits and Attenuates Amyloid-Beta Overproduction and Tau Hyperphosphorylation via Coregulating BACE1 and PRKACB

Alzheimer’s disease (AD) is characterized by two landmark pathologies, the overproduction of amyloid-beta peptides (Aβ), predominated by the β-amyloid protein precursor cleaving enzyme 1 (BACE1), and hyperphosphorylation of the microtubule protein, tau, because of an imbalance in a kinase/phosphatase system that involves the activation of the protein kinase A (PKA). Current evidence indicates that brain microRNAs participate in multiple aspects of AD pathology. Here, the role and underlying molecular mechanisms of microRNA-200a-3p (miR-200a-3p) in mediating neuroprotection against AD-related deficits were investigated. The expression of miR-200a-3p was measured in the hippocampus of APP/PS1 and SAMP8 mice and in an AD cell model in vitro, as well as in blood plasma extracted from AD patients. The targets of miR-200a-3p were determined using bioinformatics and dual-luciferase assay analyses. In addition, cell apoptosis was detected using flow cytometry, and related protein levels were measured using Western blot and enzyme-linked immunosorbent assay (ELISA) techniques. miR-200a-3p was confirmed to be depressed in microarray miRNA profile analysis in vitro and in vivo, suggesting that miR-200a-3p is a potential biomarker of AD. Subsequently, miR-200a-3p was demonstrated to inhibit cell apoptosis accompanied by the inactivation of the Bax/caspase-3 axis and downregulation of Aβ_1-42 and tau phosphorylation levels in vitro. Further mechanistic studies revealed that miR-200a-3p reduced the production of Aβ_1-42 and decreased hyperphosphorylation of tau by regulating the protein translocation of BACE1 and the protein kinase cAMP-activated catalytic subunit beta (PRKACB) associated with the three prime untranslated regions, respectively. Importantly, the function of miR-200a-3p was reversed by overexpression of BACE1 or PRKACB in cultured cells. This resulted in an elevation in cell apoptosis and increases in Aβ_1-42 and tau hyperphosphorylation levels, involving the epitopes threonine 205 and serine 202, 214, 396, and 356, the favorable phosphorylated sites of PKA. In conclusion, our study suggests that miR-200a-3p is implicated in the pathology of AD, exerting neuroprotective effects against Aβ-induced toxicity by two possible mechanisms: one involving the inhibition of Aβ overproduction via suppression of the expression of BACE1 and synergistically decreasing the hyperphosphorylation of tau via attenuation of the expression of PKA.

The long-non-coding RNA NEAT1 is a novel target for Alzheimer's disease progression via miR-124/BACE1 axis

OBJECTIVES

Long-non-coding RNAs (lncRNAs) have been involved in central nervous system recently. A number of studies have reported that lncRNA NEAT1 exerts critical roles in neurodegenerative disorder. Beta-site amyloid precursor protein cleaving enzyme 1 (BACE1) has been reported to exert function in the accumulation of amyloid-β (Aβ). Moreover, BACE1 acts as a target of miR-124 in the progression of AD. So far, the biological role and underlying mechanisms of NEAT1 and miR-124 in AD remains elusive.

METHODS

The relative NEAT1 and miR-124 expression was examined by qRT-PCR in the tissues and cells line of AD. Cell apoptosis was examined by FACS. Luciferase reporter assay was performed to verify that miR-124 is a direct target of NEAT1, and BACE1 is a downstream target of miR-124. qRT-PCR and western blot analysis were also performed to determinate the BACE1 and the phosphorylation of tau protein.

RESULTS

NEAT1 was notably up-regulated and miR-124 was remarkably down-regulated in AD mouse model. Knockdown of NEAT1 or overexpression of miR-124 showed the protective effects on cellular AD model induced by Aβ. Moreover, miR-124 expression could be up- and down-regulated by suppression or overexpression of NEAT1, respectively. In addition, the expression of BACE1 was the potential functional target of miR-124. These findings suggested that NEAT1 might play a vital role in the development of AD by regulating miR-124/BACE1 axis.

DISCUSSION

The present study showed that NEAT1 worked as a regulating factor to promote the development of AD via modulating miR-124/BACE1 axis, which might be considered as a novel target in AD treatment.

MiR-16 attenuates β-amyloid-induced neurotoxicity through targeting β-site amyloid precursor protein-cleaving enzyme 1 in an Alzheimer's disease cell model

The aberrant deposition of β-amyloid (Aβ) is closely linked to the pathogenesis and development of Alzheimer's disease (AD). MiR-16 was abnormally downregulated and may be related to the development of AD. However, the functional role and molecular mechanism of miR-16 in AD pathogenesis are still not well elucidated. The expressions of miR-16 and β-site amyloid precursor protein-cleaving enzyme 1 (BACE1) mRNA and protein levels in AD brain tissues and Aβ-treated PC12 cellular AD model were examined by qRT-PCR and western blot analyses. Luciferase reporter assay was used to verify the potential target of miR-16. The cell viability, apoptosis, and caspase-3 activity in PC12 cells were determined by the MTT assay, flow cytometry analysis, and caspase-3 activity assay, respectively. Downregulation of miR-16 and upregulation of BACE1 existed in AD tissues and the cellular AD model of PC12. In addition, miR-16 directly suppressed BACE1 expression. Moreover, miR-16 overexpression and BACE1 knockdown facilitated Aβ-induced cell toxicity, apoptosis, and caspase-3 activity in N2a cells, which was partially eliminated by overexpression of BACE1. In contrast, BACE1 knockdown reversed the miR-16 inhibition-mediated inhibitory effect on Aβ-induced cell toxicity, apoptosis, and caspase-3 activity in PC12 cells. Collectively, miR-16 attenuated Aβ-induced neurotoxicity through targeting BACE1 in an Aβ insult cellular AD model, providing a potential therapeutic target for AD treatment.

Osthole attenuates APP-induced Alzheimer's disease through up-regulating miRNA-101a-3p

AIM

Alzheimer's disease (AD) is a slowly progressing neurodegenerative disorder that attributed to the increase of amyloid precursor protein (APP). Recently, evidence indicates that microRNA alterations are involved in the development of AD. In this paper, we demonstrated whether osthole could delay the occurrence of AD by regulating miRNA.

METHODS

Microarray was used to discover differential miRNAs in AD. The target genes regulated by miRNA were predicted by databases; The protective effects of osthole on APP/PS1 mice were determined by Morris Water Maze, H&E and Nissl staining; The APP-SH-SY5Y cells were transfected with miRNA-101a-3p inhibitor, the expression of miRNA-101a-3p and APP mRNA in APP/PS1 mice and APP-SH-SY5Y cells were detected by RT-PCR; And western blot and ICC staining were used to detect the APP and Aβ proteins expression.

KEY FINDINGS

MiRNA-101a-3p was the osthole-mediated miRNA in AD and APP is the target gene. Osthole could increase the learning and memory ability in APP/PS1 mice and inhibit APP mRNA/protein expression by up-regulating miRNA-101a-3p. For exploring the underlying mechanism, miR-101a-3p inhibitor was transfected into the APP-SH-SY5Y cells. We can know that osthole had a protective effect on APP-SH-SY5Y cells, and it could raise miRNA-101a-3p expression and inhibit APP mRNA/protein expression, the formation of Aβ protein was inhibited too.

SIGNIFICANCE

These results emphasized that osthole had a protective effect on APP/PS1 mice and APP-SH-SY5Y cells. The main cause was due to osthole could inhibit APP expression by up-regulating miRNA-101a-3p so as to help delay the occurrence of AD.

DA-JC1 improves learning and memory by antagonizing Aβ31-35-induced circadian rhythm disorder

Studies have shown that a normal circadian rhythm is crucial to learning and memory. Circadian rhythm disturbances that occur at early stages of Alzheimer’s disease (AD) aggravate the progression of the disease and further reduce learning and memory in AD patients. The novel, dual GLP-1R/GIPR agonist DA-JC1 has been found to exert a stronger hypoglycemic effect than a GLP-1R agonist alone and has been shown to exert neuroprotective effects. However, it is not clear whether DA-JC1 improves the Aβ31–35-induced decline in learning and memory ability by restoring disrupted circadian rhythms. In the present study, we carried out a mouse wheel-running experiment and Morris water maze test (MWM) and found that DA-JC1 could effectively improve the decline of learning and memory and circadian rhythm disorders induced by Aβ31–35. After downregulating Per2 expression via lentivirus-shPer2 in the hippocampus and the hippocampal HT22 cells, we found that circadian rhythm disorders occurred, and that DA-JC1 could not improve the impaired learning and memory. These results suggest that DA-JC1 improves damage to learning and memory by antagonizing circadian rhythm disorders induced by Aβ31–35. The outcome of this ongoing study may provide a novel therapeutic intervention for AD in the future.

Reduced hsa-miR-124-3p levels are associated with the poor survival of patients with hepatocellular carcinoma

Hsa-MicroRNA-124a-3p (hsa-miR-124-3p) is involved in tumor progression in certain malignant tumors. However, its function and clinical implication in hepatocellular carcinoma (HCC) have not yet been illustrated. In this study, we explored the expression and prognostic value of hsa-miR-124-3p in patients with HCC. Hsa-miR-124-3p expression in HCC was analyzed in silico, which was subsequently confirmed by quantitative PCR in 155 HCC biopsy samples. Overall survival (OS) and disease-free survival in HCC patients was evaluated by Kaplan-Meier survival analysis, and univariate and multivariate Cox proportional hazard models were used. The in silico results demonstrated that hsa-miR-124-3p was reduced in cell lines and tissues of HCC, and hsa-miR-124-3p expression was lower in HCC tumor samples than in normal liver tissues. Moreover, a decrease in hsa-miR-124-3p expression was closely correlated with tumor diameter (≥ 5 cm) and number of lesions (multiple). Lower hsa-miR-124-3p expression was shown to be correlated with a shorter OS and poor prognosis in HCC. Our findings demonstrate that hsa-miR-124-3p might be a potential target for the diagnosis and prognosis of HCC.

Inhibition of Autophagy in Microglia Alters Depressive-Like Behavior via BDNF Pathway in Postpartum Depression

Postpartum depression (PPD) is associated with mood disorders and elevated inflammation. Studies have evidenced the activation/inhibition of autophagy and excessive activation of microglia to have a close relationship with depression. C57 and microglia-specific autophagy-deficient mice (Cx3Cr1Cre/+ATG5loxp/loxp) were employed to establish the chronic unpredicted mild stress depression mice model from embryonic day 7 (E7) to embryonic day 16 (E16). Fluoxetine was administered for 3 weeks (commencing from 1 week after birth). Behavioral tests (open field, forced swimming, and sucrose preference tests) were implemented. Western blot and immunofluorescence staining were employed to assess the brain-derived neurotrophic factor (BDNF) expression level, autophagy-associated proteins, and inflammatory factors. Depressive behavior was reversed following fluoxetine treatment; this was evidenced via open field, sucrose preference, and forced swimming tests. Both BDNF and autophagy-associated proteins (ATG5, Beclin-1, and LC3II) were upregulated following fluoxetine treatment. Inflammatory factors including nuclear factor kappa B and inducible nitric oxide synthase were reduced while anti-inflammatory factor interleukin-10 (IL-10) was increased after fluoxetine treatment. Microglia-specific autophagy-deficient mice (Cx3Cr1Cre/+ATG5loxp/loxp) showed a curtailed autophagy level, higher inflammatory level, and reduced BDNF expression when compared with C57 mice. Autophagy inhibition in microglia contributes to inflammation, which further instigates PPD. Fluoxetine might mediate its antidepressant effect in PPD through the autophagic pathway while upregulating BDNF expression. In view of this, regulating BDNF in microglia is a potential novel therapy target for PPD.

Non-coding RNA influences in dementia

Dementia is a complex clinical syndrome characterised by progressive decline in cognitive function. It usually presents itself as impairment in memory, loss of judgement, abstract thinking and other disturbances that are severe enough to interfere with activities of daily living. It has long been considered as one of the major challenges at present posing an ever-increasing demand on global health and social care systems. Of all the different forms of dementia, Alzheimer's disease (AD) is the most common. The term non-coding RNA (ncRNA) refers to RNA sequences which do not have the ability to be translated into proteins and therefore mainly fall within the realm of the recently acknowledged ‘dark matter’ of the genome. This genomic dark matter encompasses a whole spectrum of differing ncRNA families such as microRNAs (miRNAs), long non-coding RNAs (lncRNAs), PIWI-interacting RNAs (piRNAs), transfer RNAs (tRNAs), small nuclear RNAs (snoRNAs) and circular RNAs (circRNAs), to name but a few. Consequently, due to the widespread influences of miRNAs and lncRNAs across all disease pathways, it is of critical importance for researchers in the field of dementia to focus their attention on possible ncRNA-induced pathogeneses, with the ultimate goal of identifying novel diagnostic procedures and drug targets, together with the development of novel therapies to control such a devastating mental condition in the patient population.

miR‑92b promotes autophagy and suppresses viability and invasion in breast cancer by targeting EZH2

MicroRNAs (miRs) are a small non-coding RNA family with a length of 18–22 nucleotides. They are able to regulate gene expression by either triggering target messenger RNA degradation or by inhibiting mRNA translation. Enhancer of zeste homolog 2 (EZH2) is the core enzymatic subunit of polycomb repressor complex 2 and is responsible for the trimethylation of histone 3 on lysine 27 (H3K27me3); it is also able to silence a bundle of tumor suppressor genes through promoter binding. However, little is known regarding the effect of miR-92b on cell autophagy, viability and invasion as well as how it interacts with EZH2. The present study investigated the major role of miR-92b in the autophagy, viability and invasion of breast cancer. It was revealed that in MCF-7 and MDA-MB-453 cells, the expression of miR-92b promoted autophagy induced by starvation and rapamycin treatment. The results of in vitro experiments results demonstrated that miR-92b inhibited breast cancer cell viability, invasion and migration. To further elucidate the regulatory mechanisms of miR-92b in autophagy, a dual luciferase reporter assay was performed to determine whether miR-92b targeted the EZH2 gene. The expression of miR-92b was negatively correlated to EZH2 mRNA expression in breast cancer. Depletion of EZH2 induced phenocopied effects on miR-92b overexpression, thereby demonstrating its importance in autophagy. These results indicated that miR-92b may serve an important role in breast cancer in controlling autophagy, viability and invasion. The present study indicated that miR-92b and EZH2 may serve as potential biomarkers for cancer detection and highlighted their possible therapeutic implications.

Using Drosophila Models of Amyloid Toxicity to Study Autophagy in the Pathogenesis of Alzheimer's Disease

Autophagy is a conserved catabolic pathway that involves the engulfment of cytoplasmic components such as large protein aggregates and organelles that are delivered to the lysosome for degradation. This process is important in maintaining neuronal function and raises the possibility of a role for autophagy in neurodegenerative diseases. Alzheimer's disease (AD) is the most prevalent form of these diseases and is characterized by the accumulation of amyloid plaques in the brain which arise due to the misfolding and aggregation of toxic peptides, including amyloid beta (Aβ). There is substantial evidence from both AD patients and animal models that autophagy is dysregulated in this disease. However, it remains to be determined whether this is protective or pathogenic as there is evidence that autophagy can act to promote the degradation as well as function in the generation of toxic Aβ peptides. Understanding the molecular details of the extensive crosstalk that occurs between the autophagic and endolysosomal cellular pathways is essential for identifying the molecular details of amyloid toxicity. Drosophila models that express the toxic proteins that aggregate in AD have been generated and have been shown to recapitulate hallmarks of the disease. Here we focus on what is known about the role of autophagy in amyloid toxicity in AD from mammalian models and how Drosophila models can be used to further investigate AD pathogenesis.