Beta-Amyloid-Dependent miRNAs as Circulating Biomarkers in Alzheimer's Disease: a Preliminary Report

The role of exosome-shuttled miRNAs in heavy metal-induced peripheral tissues and neuroinflammation in Alzheimer's disease

Heavy metal-induced neuroinflammation is a significant pathophysiologic mechanism in Alzheimer's disease (AD). Microglia-mediated neuroinflammation plays a crucial role in the pathogenesis of AD. Multiple miRNAs are differentially expressed in peripheral tissues after heavy metal exposure, and increasing evidence suggests that they are involved in AD progression by regulating microglial homeostasis. Exosomes, which are capable of loading miRNAs and crossing the bloodbrain barrier, serve as mediators of communication between peripheral tissues and the brain. In this review, we summarize the current evidence on the link between miRNAs in peripheral tissues and neuroinflammation in AD after heavy metal exposure and propose a role for miRNAs in the microglial neurodegenerative phenotype (MGnD) of AD. This study will help to elucidate the link between peripheral tissue damage and MGnD-mediated neuroinflammation in AD after heavy metal exposure. Additionally, we summarize the regulatory effects of natural compounds on peripheral tissue-derived miRNAs, which could be potential therapeutic targets for natural compounds to regulate peripheral tissue-derived exosomal miRNAs to ameliorate heavy metal-induced MGnD-mediated neuroinflammation in patients with AD after heavy metal exposure.

hsa-mir-(4328, 4422, 548z and -628-5p) in diabetic retinopathy: diagnosis, prediction and linking a new therapeutic target

AIMS

Growing evidence suggests that microRNAs (miRNAs) are crucial in controlling how diabetic retinopathy (DR) develops. We intend to mine miRNAs with diagnostic and predictive value for DR and to investigate new drug therapeutic targets.

METHODS

After performing a differential analysis on the miRNA and mRNA datasets for DR and neovascularization (NEO), miRNA-mRNA networks were created. Combine the results of enrichment analysis, Protein-Protein Interaction Networks (PPI), and Cytoscape to identify key miRNAs. DrugBank was used to find drugs that interacted with transcription factors (TF) predicted by TransmiR. Finally, whole blood and clinical data were collected from 58 patients with type 2 diabetes mellitus (T2DM), and RT-qPCR, logistic analysis, and ROC were used to verify the value of key miRNAs.

RESULTS

Differential analysis indicated the presence of genes and miRNAs that co-regulate DR and NEO. Enrichment analysis showed that key genes are inextricably linked to neovascularization. Combining the results of PPI and Cytoscape identified four key miRNAs, namely hsa-mir-(4328, 4422, 548z and -628-5p). RT-qPCR, logistic, and ROC results showed that decreased expression levels of hsa-mir-(4328, 4422, 548z and -628-5p) signal the risk of evolution to DR in T2DM patients. Finally, we constructed a TF-miRNA network to find the 15 TFs and the 35 drugs that interact with these TFs.

CONCLUSION

hsa-mir-(4328, 4422, 548z and -628-5p) in whole blood are protective factors for DR as novel biomarkers for diagnosis and prediction. In addition, our research provides new drug directions for the treatment of DR, such as Diosmin, Atorvastatin, and so on.

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.

Nucleic acid liquid biopsies in Alzheimer's disease: current state, challenges, and opportunities

Alzheimer's disease (AD) is the most common neurodegenerative disease and affects persons of all races, ethnic groups, and sexes. The disease is characterized by neuronal loss leading to cognitive decline and memory loss. There is no cure and the effectiveness of existing treatments is limited and depends on the time of diagnosis. The long prodromal period, during which patients' ability to live a normal life is not affected despite neuronal loss, often leads to a delayed diagnosis because it can be mistaken for normal aging of the brain. In order to make a substantial impact on AD patient survival, early diagnosis may provide a greater therapeutic window for future therapies to slow AD-associated neurodegeneration. Current gold standards for disease detection include magnetic resonance imaging and positron emission tomography scans, which visualize amyloid β and phosphorylated tau depositions and aggregates. Liquid biopsies, already an active field of research in precision oncology, are hypothesized to provide early disease detection through minimally or non-invasive sample collection techniques. Liquid biopsies in AD have been studied in cerebrospinal fluid, blood, ocular, oral, and olfactory fluids. However, most of the focus has been on blood and cerebrospinal fluid due to biomarker specificity and sensitivity attributed to the effects of the blood-brain barrier and inter-laboratory variation during sample collection. Many studies have identified amyloid β and phosphorylated tau levels as putative biomarkers, however, advances in next-generation sequencing-based liquid biopsy methods have led to significant interest in identifying nucleic acid species associated with AD from liquid tissues. Differences in cell-free RNAs and DNAs have been described as potential biomarkers for AD and hold the potential to affect disease diagnosis, treatment, and future research avenues.

Regulation of microRNAs in Alzheimer´s disease, type 2 diabetes, and aerobic exercise training

Alzheimer's disease (AD) is the most common type of dementia. The evolution and aggregation of amyloid beta (β) oligomers is linked to insulin resistance in AD, which is also the major characteristic of type 2 diabetes (T2D). Being physically inactive can contribute to the development of AD and/or T2D. Aerobic exercise training (AET), a type of physical exercise, can be useful in preventing or treating the negative outcomes of AD and T2D. AD, T2D and AET can regulate the expression of microRNAs (miRNAs). Here, we review some of the changes in miRNAs expression regulated by AET, AD and T2D. MiRNAs play an important role in the gene regulation of key signaling pathways in both pathologies, AD and T2D. MiRNA dysregulation is evident in AD and has been associated with several neuropathological alterations, such as the development of a reactive gliosis. Expression of miRNAs are associated with many pathophysiological mechanisms involved in T2D like insulin synthesis, insulin resistance, glucose intolerance, hyperglycemia, intracellular signaling, and lipid profile. AET regulates miRNAs levels. We identified 5 miRNAs (miR-21, miR-29a/b, miR-103, miR-107, and miR-195) that regulate gene expression and are modulated by AET on AD and T2D. The identified miRNAs are potential targets to treat the symptoms of AD and T2D. Thus, AET is a non-pharmacological tool that can be used to prevent and fight the negative outcomes in AD and T2D.

Circulating MicroRNAs From Plasma Small Extracellular Vesicles as Potential Diagnostic Biomarkers in Pediatric Epilepsy and Drug-Resistant Epilepsy

Pediatric epilepsy is a neurological condition that causes repeated and unprovoked seizures and is more common in 1–5-year-old children. Drug resistance has been indicated as a key challenge in improving the clinical outcomes of patients with pediatric epilepsy. In the present study, we aimed to identify plasma small extracellular vesicles (sEVs) derived microRNAs (miRNAs) from the plasma samples of children for predicting the prognosis in patients with epilepsy and drug-resistant epilepsy. A total of 90 children clinically diagnosed with epilepsy [46 antiepileptic drug (AED)-responsive epilepsy and 44 drug-resistant epilepsy] and 37 healthy controls (HCs) were enrolled in this study. RNA sequencing was performed to identify plasma sEVs derived miRNAs isolated from the children’s plasma samples. Differentially expressed plasma sEVs derived miRNAs were identified using bioinformatics tools and were further validated by reverse transcription-polymerase chain reaction and receiver operator characteristic (ROC) curve analysis. In the present study, 6 miRNAs (hsa-miR-125b-5p, hsa-miR-150-3p, hsa-miR-199a-3p, hsa-miR-584-5p hsa-miR-199a-5p, and hsa-miR-342-5p) were selected for further validation. hsa-miR-584-5p, hsa-miR-342-5p, and hsa-miR-150-5p with area under curve (AUC) values of 0.846, 0.835, and 0.826, respectively, were identified as promising biomarkers of epilepsy. A logistic model combining three miRNAs (hsa-miR-584-5p, hsa-miR-342-5p, and hsa-miR-199a-3p) could achieve an AUC of 0.883 and a six miRNAs model (hsa-miR-342-5p, hsa-miR-584-5p, hsa-miR-150-5p, hsa-miR-125b-5p, hsa-miR-199a-3p, and hsa-miR-199a-5p) could attain an AUC of 0.888. The predicted probability of multiple miRNA panels was evaluated for differentiating between drug-resistant children and drug-responsive children. The AUC of a six-miRNA panel (hsa-miR-342-5p, hsa-miR-584-5p, hsa-miR-150-5p, hsa-miR-125b-5p, hsa-miR-199a-3p, and hsa-miR-199a-5p) reached 0.823. We identified and confirmed plasma sEVs derived miRNA biomarkers that could be considered as potential therapeutic targets for pediatric epilepsy and drug-resistant epilepsy.

Altered Cerebrospinal Fluid Exosomal microRNA Levels in Young-Onset Alzheimer's Disease and Frontotemporal Dementia

Background:

micro-RNAs (miRNAs) are stable, small, non-coding RNAs enriched in exosomes. Their variation in levels according to different disease etiologies have made them a promising diagnostic biomarker for neurodegenerative diseases such as Alzheimer’s disease (AD). Altered expression of miR-320a, miR-328-3p, and miR-204-5p have been reported in AD and frontotemporal dementia (FTD).

Objective:

To determine their reliability, we aimed to examine the expression of three exosomal miRNAs isolated from cerebrospinal fluid (CSF) of patients with young-onset AD and FTD (< 65 years), correlating with core AD biomarkers and cognitive scores.

Methods:

Exosomes were first isolated from CSF samples of 48 subjects (8 controls, 28 AD, and 12 FTD), followed by RNA extraction and quantitative PCR to measure the expression of miR-320a, miR-328-3p, and miR-204-5p.

Results:

Expression of all three markers (miR-320a (p = 0.005), miR-328-3p (p = 0.049), and miR-204-5p (p = 0.036)) were significantly lower in AD versus controls. miR-320a was reduced in FTD versus controls (p = 0.049) and miR-328-3p was lower in AD versus FTD (p = 0.054). Notably, lower miR-328-3p levels could differentiate AD from FTD and controls with an AUC of 0.702, 95% CI: 0.534– 0.870, and showed significant correlation with lower CSF Aβ₄₂ levels (r = 0.359, p = 0.029). Pathway enrichment analysis identified potential targets of miR-328-3p implicated in the AMPK signaling pathway linked to amyloid-β and tau metabolism in AD.

Conclusion:

Overall, we demonstrated miR-320a and miR-204-5p as reliable biomarkers for AD and FTD and report miR-328-3p as a novel AD biomarker.

MicroRNA-4422-5p as a Negative Regulator of Amyloidogenic Secretases: A Potential Biomarker for Alzheimer's Disease

Beta-secretase (BACE1) and gamma-secretase activating protein (GSAP) are pivotal enzymes in the cleavage of amyloid precursor protein (APP). Beta-amyloid (Aß) formation is considered one of the main reasons for Alzheimer's disease (AD) pathology. In our preliminary study, a series of microRNAs (miRs) with possible interaction with BACE1 and/or GSAP was selected using computational analysis. Our results showed that miR-4422-5p had a reduced level in the serum of AD patients. In this study, the effect of miR-4422-5p using miR-4422-5p mimic and inhibitor on BACE1 and GSAP were investigated, and a probable novel early diagnostic marker for AD was introduced. The effect of miR-4422-5p interaction with BACE1 and GSAP was evaluated via in vitro experiments using dual-luciferase assays, western blotting, and Immunocytochemistry. Luciferase assay demonstrated that miR-4422-5p mimic suppresses BACE1 and GSAP expression by directly targeting the 3'UTR of BACE1 and GSAP mRNA in HEK293T cells. Also, western blotting and immunocytochemistry confirmed the regulatory role of miR-4422-5p mimic on BACE1 and GSAP genes. miR-4422-5p mimic significantly decreased BACE1 and GSAP protein expression in SH-SY5Y and A549 cells, respectively. Moreover, miR-4422-5p-inhibitor reversed the expression processes in both cell lines. Our data suggest that miR-4422-5p may be an important regulator of both BACE1 and GSAP genes and can represent a novel potential biomarker or therapeutic target in AD.

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

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