MicroRNAs 99b-5p/100-5p Regulated by Endoplasmic Reticulum Stress are Involved in Abeta-Induced Pathologies

MiR-100-5p-rich small extracellular vesicles from activated neuron to aggravate microglial activation and neuronal activity after stroke

Ischemic stroke is a common cause of mortality and severe disability in human and currently lacks effective treatment. Neuronal activation and neuroinflammation are the major two causes of neuronal damage. However, little is known about the connection of these two phenomena. This study uses middle cerebral artery occlusion mouse model and chemogenetic techniques to study the underlying mechanisms of neuronal excitotoxicity and severe neuroinflammation after ischemic stroke. Chemogenetic inhibition of neuronal activity in ipsilesional M1 alleviates infarct area and neuroinflammation, and improves motor recovery in ischemia mice. This study identifies that ischemic challenge triggers neuron to produce unique small extracellular vesicles (EVs) to aberrantly activate adjacent neurons which enlarge the neuron damage range. Importantly, these EVs also drive microglia activation to exacerbate neuroinflammation. Mechanistically, EVs from ischemia-evoked neuronal activity induce neuronal apoptosis and innate immune responses by transferring higher miR-100-5p to adjacent neuron and microglia. MiR-100-5p can bind to and activate TLR7 through U18U19G20-motif, thereby activating NF-κB pathway. Furthermore, knock-down of miR-100-5p expression improves poststroke outcomes in mice. Taken together, this study suggests that the combination of inhibiting aberrant neuronal activity and the secretion of specific EVs-miRNAs may serve as novel methods for stroke treatment.

Non-Coding RNAs and Neurodegenerative Diseases: Information of their Roles in Apoptosis

Apoptosis can be known as a key factor in the pathogenesis of neurodegenerative disorders. In disease conditions, the rate of apoptosis expands and tissue damage may become apparent. Recently, the scientific studies of the non-coding RNAs (ncRNAs) has provided new information of the molecular mechanisms that contribute to neurodegenerative disorders. Numerous reports have documented that ncRNAs have important contributions to several biological processes associated with the increase of neurodegenerative disorders. In addition, microRNAs (miRNAs), circular RNAs (circRNAs), as well as, long ncRNAs (lncRNAs) represent ncRNAs subtypes with the usual dysregulation in neurodegenerative disorders. Dysregulating ncRNAs has been associated with inhibiting or stimulating apoptosis in neurodegenerative disorders. Therefore, this review highlighted several ncRNAs linked to apoptosis in neurodegenerative disorders. CircRNAs, lncRNAs, and miRNAs were also illustrated completely regarding the respective signaling pathways of apoptosis.

Macrophage-derived mir-100-5p orchestrates synovial proliferation and inflammation in rheumatoid arthritis through mTOR signaling

BACKGROUND

Rheumatoid arthritis (RA) is a chronic autoimmune disorder characterized by synovial inflammation, causing substantial disability and reducing life quality. While macrophages are widely appreciated as a master regulator in the inflammatory response of RA, the precise mechanisms underlying the regulation of proliferation and inflammation in RA-derived fibroblast-like synoviocytes (RA-FLS) remain elusive. Here, we provide extensive evidence to demonstrate that macrophage contributes to RA microenvironment remodeling by extracellular vesicles (sEVs) and downstream miR-100-5p/ mammalian target of rapamycin (mTOR) axis.

RESULTS

We showed that bone marrow derived macrophage (BMDM) derived-sEVs (BMDM-sEVs) from collagen-induced arthritis (CIA) mice (cBMDM-sEVs) exhibited a notable increase in abundance compared with BMDM-sEVs from normal mice (nBMDM-sEVs). cBMDM-sEVs induced significant RA-FLS proliferation and potent inflammatory responses. Mechanistically, decreased levels of miR-100-5p were detected in cBMDM-sEVs compared with nBMDM-sEVs. miR-100-5p overexpression ameliorated RA-FLS proliferation and inflammation by targeting the mTOR pathway. Partial attenuation of the inflammatory effects induced by cBMDM-sEVs on RA-FLS was achieved through the introduction of an overexpression of miR-100-5p.

CONCLUSIONS

Our work reveals the critical role of macrophages in exacerbating RA by facilitating the transfer of miR-100-5p-deficient sEVs to RA-FLS, and sheds light on novel disease mechanisms and provides potential therapeutic targets for RA interventions.

Mesenchymal Stem Cells from Familial Alzheimer's Patients Express MicroRNA Differently

Alzheimer's disease (AD) is a progressive neurodegenerative disorder and the predominant form of dementia globally. No reliable diagnostic, predictive techniques, or curative interventions are available. MicroRNAs (miRNAs) are vital to controlling gene expression, making them valuable biomarkers for diagnosis and prognosis. This study examines the transcriptome of olfactory ecto-mesenchymal stem cells (MSCs) derived from individuals with the PSEN1(A431E) mutation (Jalisco mutation). The aim is to determine whether this mutation affects the transcriptome and expression profile of miRNAs and their target genes at different stages of asymptomatic, presymptomatic, and symptomatic conditions. Expression microarrays compare the MSCs from mutation carriers with those from healthy donors. The results indicate a distinct variation in the expression of miRNAs and mRNAs among different symptomatologic groups and between individuals with the mutation. Using bioinformatics tools allows us to identify target genes for miRNAs, which in turn affect various biological processes and pathways. These include the cell cycle, senescence, transcription, and pathways involved in regulating the pluripotency of stem cells. These processes are closely linked to inter- and intracellular communication, vital for cellular functioning. These findings can enhance our comprehension and monitoring of the disease's physiological processes, identify new disorder indicators, and develop innovative treatments and diagnostic tools for preventing or treating AD.

Abnormal expression profile of plasma exosomal microRNAs in exclusive electronic cigarette adult users

Background

Exposure to electronic cigarette (e-cigarette) aerosol has been linked to several health concerns, including DNA damage, elevated oxidative stress, the release of inflammatory cytokine, and dysfunctions in epithelial barriers. However, little is known about the effect of exclusive e-cigarette use on expression profiles of exosomal miRNAs, which play critical regulatory roles in many inflammatory responses and disease processes including cancer. We aim to compare the exosomal microRNA expression profile between exclusive e-cigarette users and normal controls without any tobacco product use (non-users).

Methods

Using plasma samples from 15 exclusive e-cigarette users and 15 non-users in the Population Assessment of Tobacco and Health (PATH) Wave 1 study (2013-2014), we examined exosomal microRNAs expression levels through Illumina NextSeq 500/550 sequencing. The differential analyses between exclusive e-cigarette users and non-users were examined using the generalized linear model approach in the DESeq2 package in R/Bioconductor after adjusting the significant confounding effect from race. Gene enrichment analyses were conducted on target genes regulated by significant microRNAs in the differential analyses. Further, molecular-based techniques using the micro RNA mimics and inhibitors were applied for the validation of the expressions of the micro RNAs in vitro.

Results

We identified four microRNAs that have significantly higher expression levels in exclusive e-cigarette users than non-users including hsa-miR-100-5p, hsa-miR-125a-5p, hsa-miR-125b-5p, and hsa-miR-99a-5p. GO enrichment analysis on the target genes regulated by the four microRNAs showed that dysregulation of the four microRNAs in exclusive e-cigarette users involved in multiple cell processes such as protein kinase binding and miRNA metabolic process. KEGG pathway enrichment analysis found the four upregulated miRNAs in exclusive e-cigarette users involved in many cancer pathways such as the non-small cell lung cancer, small cell lung cancer, pancreatic cancer, p53 signaling pathway, Hippo signaling pathway, HIF-1 signaling pathway, and MAPK signaling pathway. Overexpression of miRNA hsa-miR-125b-5p was shown to promote DNA damage in bronchial epithelia cells.

Conclusions

Four plasma exosomal microRNAs involved in cancer development had higher expression levels in exclusive e-cigarette users than non-users, which might indicate a potentially elevated risk of cancer among exclusive e-cigarette users.

miR-129-5p as a biomarker for pathology and cognitive decline in Alzheimer's disease

BACKGROUND

Alzheimer's dementia (AD) pathogenesis involves complex mechanisms, including microRNA (miRNA) dysregulation. Integrative network and machine learning analysis of miRNA can provide insights into AD pathology and prognostic/diagnostic biomarkers.

METHODS

We performed co-expression network analysis to identify network modules associated with AD, its neuropathology markers, and cognition using brain tissue miRNA profiles from the Religious Orders Study and Rush Memory and Aging Project (ROS/MAP) (N = 702) as a discovery dataset. We performed association analysis of hub miRNAs with AD, its neuropathology markers, and cognition. After selecting target genes of the hub miRNAs, we performed association analysis of the hub miRNAs with their target genes and then performed pathway-based enrichment analysis. For replication, we performed a consensus miRNA co-expression network analysis using the ROS/MAP dataset and an independent dataset (N = 16) from the Gene Expression Omnibus (GEO). Furthermore, we performed a machine learning approach to assess the performance of hub miRNAs for AD classification.

RESULTS

Network analysis identified a glucose metabolism pathway-enriched module (M3) as significantly associated with AD and cognition. Five hub miRNAs (miR-129-5p, miR-433, miR-1260, miR-200a, and miR-221) of M3 had significant associations with AD clinical and/or pathologic traits, with miR129-5p by far the strongest across all phenotypes. Gene-set enrichment analysis of target genes associated with their corresponding hub miRNAs identified significantly enriched biological pathways including ErbB, AMPK, MAPK, and mTOR signaling pathways. Consensus network analysis identified two AD-associated consensus network modules and two hub miRNAs (miR-129-5p and miR-221). Machine learning analysis showed that the AD classification performance (area under the curve (AUC) = 0.807) of age, sex, and APOE ε4 carrier status was significantly improved by 6.3% with inclusion of five AD-associated hub miRNAs.

CONCLUSIONS

Integrative network and machine learning analysis identified miRNA signatures, especially miR-129-5p, as associated with AD, its neuropathology markers, and cognition, enhancing our understanding of AD pathogenesis and leading to better performance of AD classification as potential diagnostic/prognostic biomarkers.

Cerebrospinal fluid microRNAs as potential biomarkers in Alzheimer's disease

Alzheimer's disease (AD) is the leading form of dementia worldwide, but its early detection and diagnosis remain a challenge. MicroRNAs (miRNAs) are a group of small endogenous RNA molecules that regulate mRNA expression. Recent evidence suggests miRNAs play an important role in the five major hallmarks of AD pathophysiology: amyloidogenesis, tauopathy, neuroinflammation, synaptic dysfunction, and neuronal death. Compared to traditional biomarkers of AD, miRNAs display a greater degree of stability in cerebrospinal fluid. Moreover, aberrant changes in miRNA expression can be measured over time to monitor and guide patient treatment. Specific miRNA profiles and combinations may also be used to distinguish AD subjects from normal controls and other causes of dementia. Because of these properties, miRNAs are now being considered as promising and potential biomarkers of AD. This review comprehensively summarizes the diagnostic potential and regulatory roles miRNAs play in AD.

Modulation of AKT Pathway-Targeting miRNAs for Cancer Cell Treatment with Natural Products

Many miRNAs are known to target the AKT serine-threonine kinase (AKT) pathway, which is critical for the regulation of several cell functions in cancer cell development. Many natural products exhibiting anticancer effects have been reported, but their connections to the AKT pathway (AKT and its effectors) and miRNAs have rarely been investigated. This review aimed to demarcate the relationship between miRNAs and the AKT pathway during the regulation of cancer cell functions by natural products. Identifying the connections between miRNAs and the AKT pathway and between miRNAs and natural products made it possible to establish an miRNA/AKT/natural product axis to facilitate a better understanding of their anticancer mechanisms. Moreover, the miRNA database (miRDB) was used to retrieve more AKT pathway-related target candidates for miRNAs. By evaluating the reported facts, the cell functions of these database-generated candidates were connected to natural products. Therefore, this review provides a comprehensive overview of the natural product/miRNA/AKT pathway in the modulation of cancer cell development.

Roles of exosomes and exosome-derived miRNAs in pulmonary fibrosis

Pulmonary fibrosis is a chronic, progressive fibrosing interstitial lung disease of unknown etiology that leads rapidly to death. It is characterized by the replacement of healthy tissue through an altered extracellular matrix and damage to the alveolar structure. New pharmacological treatments and biomarkers are needed for pulmonary fibrosis to ensure better outcomes and earlier diagnosis of patients. Exosomes are nanoscale vesicles released by nearly all cell types that play a central role as mediators of cell-to-cell communication. Moreover, exosomes are emerging as a crucial factor in antigen presentation, immune response, immunomodulation, inflammation, and cellular phenotypic transformation and have also shown promising therapeutic potential in pulmonary fibrosis. This review summarizes current knowledge of exosomes that may promote pulmonary fibrosis and be utilized for diagnostics and prognostics. In addition, the utilization of exosomes and their cargo miRNAs as novel therapeutics and their potential mechanisms are also discussed. This review aims to elucidate the role of exosomes in the pathogenesis of pulmonary fibrosis and paves the way for developing novel therapeutics for pulmonary fibrosis. Further in-depth research and clinical trials on this topic are encouraged in the future.

MicroRNA Alterations in Chronic Traumatic Encephalopathy and Amyotrophic Lateral Sclerosis

Repetitive head impacts (RHI) and traumatic brain injuries are risk factors for the neurodegenerative diseases chronic traumatic encephalopathy (CTE) and amyotrophic lateral sclerosis (ALS). ALS and CTE are distinct disorders, yet in some instances, share pathology, affect similar brain regions, and occur together. The pathways involved and biomarkers for diagnosis of both diseases are largely unknown. MicroRNAs (miRNAs) involved in gene regulation may be altered in neurodegeneration and be useful as stable biomarkers. Thus, we set out to determine associations between miRNA levels and disease state within the prefrontal cortex in a group of brain donors with CTE, ALS, CTE + ALS and controls. Of 47 miRNAs previously implicated in neurological disease and tested here, 28 (60%) were significantly different between pathology groups. Of these, 21 (75%) were upregulated in both ALS and CTE, including miRNAs involved in inflammatory, apoptotic, and cell growth/differentiation pathways. The most significant change occurred in miR-10b, which was significantly increased in ALS, but not CTE or CTE + ALS. Overall, we found patterns of miRNA expression that are common and unique to CTE and ALS and that suggest shared and distinct mechanisms of pathogenesis.

A novel approach to type 3 diabetes mechanism: The interplay between noncoding RNAs and insulin signaling pathway in Alzheimer's disease

Today, growing evidence indicates that patients with type 2 diabetes (T2D) are at a higher risk of developing Alzheimer's disease (AD). Indeed, AD as one of the main causes of dementia in people aged more than 65 years can be aggravated by insulin resistance (IR) and other metabolic risk factors related to T2D which are also linked to the function of the brain. Remarkably, a new term called "type 3 diabetes" has been suggested for those people who are diagnosed with AD while also showing the symptoms of IR and T2D. In this regard, the role of genetic and epigenetic changes associated with AD has been confirmed by many studies. On the other hand, it should be noted that the insulin signaling pathway is highly regulated by various mechanisms, including epigenetic factors. Among these, the role of noncoding RNAs (ncRNAs), including microRNAs and long noncoding RNAs has been comprehensively studied with respect to the pathology of AD and the most well-known underlying mechanisms. Nevertheless, the number of studies exploring the association between ncRNAs and the downstream targets of the insulin signaling pathway in the development of AD has notably increased in recent years. With this in view, the present study aimed to review the interplay between different ncRNAs and the insulin signaling pathway targets in the pathogenesis of AD to find a new approach in the field of combining biomarkers or therapeutic targets for this disease.

Deciphering the Link Between ERUPR Signaling and MicroRNA in Pathogenesis of Alzheimer’s Disease

Alzheimer’s disease (AD) is a neurodegenerative proteinopathic disease. The deposits of misfolded Amyloid β and Tau proteins in the brain of patients with AD suggest an imbalance in endoplasmic reticulum (ER) proteostasis. ER stress is due to accumulation of aberrant proteins in the ER lumen, which then leads to activation of three sensor protein pathways that ultimately evokes the adaptive mechanism of the unfolded protein response (UPR). The UPR mechanism operates via adaptive UPR and the apoptotic UPR. Adaptive UPR tries to restore imbalance in ER hemostasis by decreasing protein production, enhanced chaperone involvement to restore protein folding, misfolded protein decay by proteasome, and suppression of ribosomal translation ultimately relieving the excessive protein load in the ER. Subsequently, apoptotic UPR activated under severe ER stress conditions triggers cell death. MicroRNAs (miRNAs) are small non-coding protein causing dysregulated translational of mRNAs in a sequential manner. They are considered to be critical elements in the maintenance of numerous cellular activities, hemostasis, and developmental processes. Therefore, upregulation or downregulation of miRNA expression is implicated in several pathogenic processes. Evidence from scientific studies suggest a strong correlation between ER^UPR signaling and miRNA dysregulation but the research done is still dormant. In this review, we summarized the cross-talk between ER stress, and the UPR signaling processes and their role in AD pathology by scrutinizing and collecting information from original research and review articles.

Small RNA Sequencing in the Tg4–42 Mouse Model Suggests the Involvement of snoRNAs in the Etiology of Alzheimer’s Disease

Background: The Tg4-42 mouse model for sporadic Alzheimer’s disease (AD) has unique features, as the neuronal expression of wild type N-truncated Aβ4–42 induces an AD-typical neurological phenotype in the absence of plaques. It is one of the few models developing neuron death in the CA1 region of the hippocampus. As such, it could serve as a powerful tool for preclinical drug testing and identification of the underlying molecular pathways that drive the pathology of AD. Objective: The aim of this study was to use a differential co-expression analysis approach for analyzing a small RNA sequencing dataset from a well-established murine model in order to identify potentially new players in the etiology of AD. Methods: To investigate small nucleolar RNAs in the hippocampus of Tg4-42 mice, we used RNA-Seq data from this particular tissue and, instead of analyzing the data at single gene level, employed differential co-expression analysis, which takes the comparison to gene pair level and thus affords a new angle to the interpretation of these data. Results: We identified two clusters of differentially correlated small RNAs, including Snord55, Snord57, Snord49a, Snord12, Snord38a, Snord99, Snord87, Mir1981, Mir106b, Mir30d, Mir598, and Mir99b. Interestingly, some of them have been reported to be functionally relevant in AD pathogenesis, as AD biomarkers, regulating tau phosphorylation, TGF-β receptor function or Aβ metabolism. Conclusion: The majority of snoRNAs for which our results suggest a potential role in the etiology of AD were so far not conspicuously implicated in the context of AD pathogenesis and could thus point towards interesting new avenues of research in this field.

Blood-Based miRNA Biomarkers as Correlates of Brain-Based miRNA Expression

The use of easily accessible peripheral samples, such as blood or saliva, to investigate neurological and neuropsychiatric disorders is well-established in genetic and epigenetic research, but the pathological implications of such biomarkers are not easily discerned. To better understand the relationship between peripheral blood- and brain-based epigenetic activity, we conducted a pilot study on captive baboons (Papio hamadryas) to investigate correlations between miRNA expression in peripheral blood mononuclear cells (PBMCs) and 14 different cortical and subcortical brain regions, represented by two study groups comprised of 4 and 6 animals. Using next-generation sequencing, we identified 362 miRNAs expressed at ≥ 10 read counts in 80% or more of the brain samples analyzed. Nominally significant pairwise correlations (one-sided P < 0.05) between peripheral blood and mean brain expression levels of individual miRNAs were observed for 39 and 44 miRNAs in each group. When miRNA expression levels were averaged for tissue type across animals within the groups, Spearman's rank correlations between PBMCs and the brain regions are all highly significant (r _s = 0.47-0.57; P < 2.2 × 10^-16), although pairwise correlations among the brain regions are markedly stronger (r _s = 0.86-0.99). Principal component analysis revealed differentiation in miRNA expression between peripheral blood and the brain regions for the first component (accounting for ∼75% of variance). Linear mixed effects modeling attributed most of the variance in expression to differences between miRNAs (>70%), with non-significant 7.5% and 13.1% assigned to differences between blood and brain-based samples in the two study groups. Hierarchical UPGMA clustering revealed a major co-expression branch in both study groups, comprised of miRNAs globally upregulated in blood relative to the brain samples, exhibiting an enrichment of miRNAs expressed in immune cells (CD14+, CD15+, CD19+, CD3+, and CD56 + leukocytes) among the top blood-brain correlates, with the gene MYC, encoding a master transcription factor that regulates angiogenesis and neural stem cell activation, representing the most prevalent miRNA target. Although some differentiation was observed between tissue types, these preliminary findings reveal wider correlated patterns between blood- and brain-expressed miRNAs, suggesting the potential utility of blood-based miRNA profiling for investigating by proxy certain miRNA activity in the brain, with implications for neuroinflammatory and c-Myc-mediated processes.

The Research Progress of Exosomes in Osteoarthritis, With Particular Emphasis on the Therapeutic Effect

Exosomes participate in many physiological and pathological processes by regulating cell-to-cell communication. This affects the etiology and development of diseases, such as osteoarthritis (OA). Although exosomes in the OA tissue microenvironment are involved in the progression of OA, exosomes derived from therapeutic cells represent a new therapeutic strategy for OA treatment. Recent studies have shown that exosomes participate in OA treatment by regulating the proliferation, apoptosis, inflammation, and extracellular matrix synthesis of chondrocytes. However, studies in this field are scant. This review summarizes the therapeutic properties of exosomes on chondrocytes in OA and their underlying molecular mechanisms. We also discuss the challenges and prospects of exosome-based OA treatment.

Endoplasmic Reticulum Stress and miRNA Impairment in Aging and Age-Related Diseases

Aging is a physiological process defined by decreased cellular and tissue functions. Reduced capacity of protein degradation is one of the important hallmarks of aging that may lead to misfolded protein accumulation and progressive loss of function in organ systems. Recognition of unfolded/misfolded protein aggregates via endoplasmic reticulum (ER) stress sensors activates an adaptive mechanism, the unfolded protein response (UPR). The initial step of UPR is defined by chaperone enhancement, ribosomal translation suppression, and misfolded protein degradation, while prolonged ER stress triggers apoptosis. MicroRNAs (miRNAs) are non-coding RNAs affecting various signaling pathways through degradation or translational inhibition of targeted mRNAs. Therefore, UPR and miRNA impairment in aging and age-related diseases is implicated in various studies. This review will highlight the recent insights in ER stress–miRNAs alterations during aging and age-related diseases, including metabolic, cardiovascular, and neurodegenerative diseases and several cancers.

Machine Learning Identifies Cellular and Exosomal MicroRNA Signatures of Lyssavirus Infection in Human Stem Cell-Derived Neurons

Despite being vaccine preventable, rabies (lyssavirus) still has a significant impact on global mortality, disproportionally affecting children under 15 years of age. This neurotropic virus is deft at avoiding the immune system while travelling through neurons to the brain. Until recently, research efforts into the role of non-coding RNAs in rabies pathogenicity and detection have been hampered by a lack of human in vitro neuronal models. Here, we utilized our previously described human stem cell-derived neural model to investigate the effect of lyssavirus infection on microRNA (miRNA) expression in human neural cells and their secreted exosomes. Conventional differential expression analysis identified 25 cellular and 16 exosomal miRNAs that were significantly altered (FDR adjusted P-value <0.05) in response to different lyssavirus strains. Supervised machine learning algorithms determined 6 cellular miRNAs (miR-99b-5p, miR-346, miR-5701, miR-138-2-3p, miR-651-5p, and miR-7977) were indicative of lyssavirus infection (100% accuracy), with the first four miRNAs having previously established roles in neuronal function, or panic and impulsivity-related behaviors. Another 4-miRNA signatures in exosomes (miR-25-3p, miR-26b-5p, miR-218-5p, miR-598-3p) can independently predict lyssavirus infected cells with >99% accuracy. Identification of these robust lyssavirus miRNA signatures offers further insight into neural lineage responses to infection and provides a foundation for utilizing exosome miRNAs in the development of next-generation molecular diagnostics for rabies.

MicroRNA-100-5p and microRNA-298-5p released from apoptotic cortical neurons are endogenous Toll-like receptor 7/8 ligands that contribute to neurodegeneration

Background

MicroRNA (miRNA) expression in the brain is altered in neurodegenerative diseases. Recent studies demonstrated that selected miRNAs conventionally regulating gene expression at the post-transcriptional level can act extracellularly as signaling molecules. The identity of miRNA species serving as membrane receptor ligands involved in neuronal apoptosis in the central nervous system (CNS), as well as the miRNAs’ sequence and structure required for this mode of action remained largely unresolved.

Methods

Using a microarray-based screening approach we analyzed apoptotic cortical neurons of C56BL/6 mice and their supernatant with respect to alterations in miRNA expression/presence. HEK-Blue Toll-like receptor (TLR) 7/8 reporter cells, primary microglia and macrophages derived from human and mouse were employed to test the potential of the identified miRNAs released from apoptotic neurons to serve as signaling molecules for the RNA-sensing receptors. Biophysical and bioinformatical approaches, as well as immunoassays and sequential microscopy were used to analyze the interaction between candidate miRNA and TLR. Immunocytochemical and -histochemical analyses of murine CNS cultures and adult mice intrathecally injected with miRNAs, respectively, were performed to evaluate the impact of miRNA-induced TLR activation on neuronal survival and microglial activation.

Results

We identified a specific pattern of miRNAs released from apoptotic cortical neurons that activate TLR7 and/or TLR8, depending on sequence and species. Exposure of microglia and macrophages to certain miRNA classes released from apoptotic neurons resulted in the sequence-specific production of distinct cytokines/chemokines and increased phagocytic activity. Out of those miRNAs miR-100-5p and miR-298-5p, which have consistently been linked to neurodegenerative diseases, entered microglia, located to their endosomes, and directly bound to human TLR8. The miRNA-TLR interaction required novel sequence features, but no specific structure formation of mature miRNA. As a consequence of miR-100-5p- and miR-298-5p-induced TLR activation, cortical neurons underwent cell-autonomous apoptosis. Presence of miR-100-5p and miR-298-5p in cerebrospinal fluid led to neurodegeneration and microglial accumulation in the murine cerebral cortex through TLR7 signaling.

Conclusion

Our data demonstrate that specific miRNAs are released from apoptotic cortical neurons, serve as endogenous TLR7/8 ligands, and thereby trigger further neuronal apoptosis in the CNS. Our findings underline the recently discovered role of miRNAs as extracellular signaling molecules, particularly in the context of neurodegeneration.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13024-021-00498-5.

miR-301a-3p induced by endoplasmic reticulum stress mediates the occurrence and transmission of trastuzumab resistance in HER2-positive gastric cancer

Trastuzumab resistance negatively influences the clinical efficacy of the therapy for human epidermal growth factor receptor 2 (HER2) positive gastric cancer (GC), and the underlying mechanisms remain elusive. Exploring the mechanisms and finding effective approaches to address trastuzumab resistance are of great necessity. Here, we confirmed that endoplasmic reticulum (ER) stress-induced trastuzumab resistance by up-regulating miR-301a-3p in HER2-positive GC cells. Moreover, we elucidated that miR-301a-3p mediated trastuzumab resistance by down-regulating the expression of leucine-rich repeats and immunoglobulin-like domains containing protein 1 (LRIG1) and subsequently activating the expression of insulin-like growth factor 1 receptor (IGF-1R) and fibroblast growth factor receptor 1 (FGFR1) under ER stress. We also found that intercellular transfer of miR-301a-3p by exosomes disseminated trastuzumab resistance. The present study demonstrated that exosomal miR-301a-3p could serve as a non-invasive biomarker for trastuzumab resistance, which was maybe a novel potential therapeutic target to overcome trastuzumab resistance and improve the curative effect of trastuzumab in HER2-positive GC patients.

Circulating microRNA profile in humans and mice with congenital GH deficiency

Reduced inflammation, increased insulin sensitivity, and protection against cancer are shared between humans and mice with GH/IGF1 deficiency. Beyond hormone levels, miRNAs are important regulators of metabolic changes associated with healthy aging. We hypothesized that GH deficiency in humans alters the abundance of circulating miRNAs and that a subset of those miRNAs may overlap with those found in GH-deficient mice. In this study, subjects with untreated congenital isolated GH deficiency (IGHD; n = 23) and control subjects matched by age and sex (n = 23) were recruited and serum was collected for miRNA sequencing. Serum miRNAs from young (6 month) and old (22 month) Ames dwarf (df/df) mice with GH deficiency and their WT littermates (n = 5/age/genotype group) were used for comparison. We observed 14 miRNAs regulated with a genotype by age effect and 19 miRNAs regulated with a genotype effect independent of age in serum of IGHD subjects. These regulated miRNAs are known for targeting pathways associated with longevity such as mTOR, insulin signaling, and FoxO. The aging function was overrepresented in IGHD individuals, mediated by hsa-miR-31, hsa-miR-146b, hsa-miR-30e, hsa-miR-100, hsa-miR-181b-2, hsa-miR-195, and hsa-miR-181b-1, which target the FoxO and mTOR pathways. Intriguingly, miR-181b-5p, miR-361-3p, miR-144-3p, and miR-155-5p were commonly regulated in the serum of humans and GH-deficient mice. In vitro assays confirmed target genes for the main up-regulated miRNAs, suggesting miRNAs regulated in IGHD individuals can regulate the expression of age-related genes. These findings indicate that systemic miRNAs regulated in IGHD individuals target pathways involved in aging in both humans and mice.

Exosomes from human umbilical cord mesenchymal stem cells inhibit ROS production and cell apoptosis in human articular chondrocytes via the miR-100-5p/NOX4 axis

Cyclic strain-induced chondrocyte damage is actively involved in the pathogenesis of osteoarthritis and arthritis. MicroRNAs (miRNAs) carried by exosomes have been implicated in various diseases. However, the role of miR-100-5p in cyclic strain-induced chondrocyte damage remains to be elucidated. miR-100-5p and NADPH oxidase 4 (NOX4) were silenced or overexpressed in human primary articular chondrocytes. PKH-67 Dye was used to trace exosome endocytosis. Reactive oxygen species (ROS) production was monitored using DCFH-DA. Cell apoptosis was measured using a flow cytometer. Quantitative RT-PCR and Western blots were used to evaluate gene expression. Cyclic strain promoted ROS production and apoptosis in primary articular chondrocytes in a time-dependent manner. HucMSCs-derived exosomal miR-100-5p inhibited cyclic strain-induced ROS production and apoptosis in primary articular chondrocytes. miR-100-5p directly targeted NOX4. Overexpressing NOX4 attenuated hucMSCs-derived exosomes-mediated protective effects in primary articular chondrocytes. Cyclic strain promotes ROS production and apoptosis in primary articular chondrocytes, which was abolished by hucMSCs-derived exosomal miR-100-5p through its target NOX4. The findings highlight the importance of miR-100-5p/NOX4 axis in primary articular chondrocytes injury and provide new insights into therapeutic strategies for articular chondrocytes injury and osteoarthritis.

Deep Sequencing Identified Dysregulated Circulating MicroRNAs in Late Onset Preeclampsia

BACKGROUND/AIM

To characterize global microRNA (miRNA) expression profile in the first trimester maternal plasma of women who subsequently develop late-onset preeclampsia (LOPE) compared to uncomplicated pregnancies.

MATERIALS AND METHODS

Five first trimester plasma samples from women who developed LOPE and 5 controls were analyzed using next generation sequencing technology (NGS) followed by target prediction, Gene Ontology analysis and pathway identification. Quantitative real-time polymerase chain reaction (qRT-PCR) was performed for confirmation in an independent cohort of 12 LOPE cases and 12 controls.

RESULTS

miR-23b-5p and miR-99b-5p were down-regulated by >1.5 fold in LOPE complicated pregnancies (p value <0.05) compared to controls. Target prediction showed that the major targets of these miRNAs are associated with glycometabolism and immune response.

CONCLUSION

miR-23b-5p and miR-99b-5p are possibly implicated in the pathogenic mechanisms leading to the induction of LOPE and may serve as candidate non-invasive biomarkers for early prediction and prevention.

Rapamycin Added to Diet in Late Mid-Life Delays Age-Related Hearing Loss in UMHET4 Mice

Our previous study demonstrated rapamycin added to diet at 4 months of age had significantly less age-related outer hair cell loss in the basal half of the cochlea at 22 months of age compared to mice without rapamycin. The present study tested adding rapamycin to diet later in life, at 14 months of age, and added a longitudinal assessment of auditory brain stem response (ABR). The present study used UMHET4 mice, a 4 way cross in which all grandparental strains lack the Cdh23^753A allele that predisposes to early onset, progressive hearing loss. UMHET4 mice typically have normal hearing until 16-17 months, then exhibit threshold shifts at low frequencies/apical cochlea and later in more basal high frequency regions. ABR thresholds at 4, 12, 24, and 48 kHz were assessed at 12, 18, and 24 months of age and compared to baseline ABR thresholds acquired at 5 months of age to determine threshold shifts (TS). There was no TS at 12 months of age at any frequency tested. At 18 months of age mice with rapamycin added to diet at 14 months had a significantly lower mean TS at 4 and 12 kHz compared to mice on control diet with no significant difference at 24 and 48 kHz. At 24 months of age, the mean 4 kHz TS in rapamycin diet group was no longer significantly lower than the control diet group, while the 12 kHz mean remained significantly lower. Mean TS at 24 and 48 kHz in the rapamycin diet group became significantly lower than in the control diet group at 24 months. Hair cell counts at 24 months showed large loss in the apical half of most rapamycin and control diet mice cochleae with no significant difference between groups. There was only mild outer hair cell loss in the basal half of rapamycin and control diet mice cochleae with no significant difference between groups. The results show that a later life addition of rapamycin can decrease age-related hearing loss in the mouse model, however, it also suggests that this decrease is a delay/deceleration rather than a complete prevention.

MiR-99b-5p Attenuates Adipogenesis by Targeting SCD1 and Lpin1 in 3T3-L1 Cells

The number and distribution of adipocytes directly affect the quality of livestock meat products. The analysis of the adipogenesis mechanism is the basis for improving meat quality. The formation of adipocytes is regulated by many factors, including a class of endogenous small RNAs, named microRNA (miRNA). Previous studies have shown that miRNAs could affect adipogenesis by post-transcriptional regulation of target genes. In our study, a decreased miR-99b-5p expression level was found in the adipose tissue of obese mice. Overexpression of miR-99b-5p could increase cell proliferation by promoting the cell cycle while inhibiting cell differentiation. In addition, interference with miR-99b-5p obtained the opposite result. Furthermore, the proteomics sequencing analysis screened 1154 differentially expressed proteins, which are closely related to adipocyte differentiation and fatty acid metabolism. In addition, the results of the dual-luciferase test showed that miR-99b-5p can directly target the proteins SCD1 and Lpin1 with significantly different expression levels in proteomic sequencing. Then, this result was verified at the level of mRNA and protein in a further study. Collectively, these results suggested that miR-99b-5p may be a target for improving meat quality.

microRNAs Mediated Regulation of the Ribosomal Proteins and its Consequences on the Global Translation of Proteins

Ribosomal proteins (RPs) are mostly derived from the energy-consuming enzyme families such as ATP-dependent RNA helicases, AAA-ATPases, GTPases and kinases, and are important structural components of the ribosome, which is a supramolecular ribonucleoprotein complex, composed of Ribosomal RNA (rRNA) and RPs, coordinates the translation and synthesis of proteins with the help of transfer RNA (tRNA) and other factors. Not all RPs are indispensable; in other words, the ribosome could be functional and could continue the translation of proteins instead of lacking in some of the RPs. However, the lack of many RPs could result in severe defects in the biogenesis of ribosomes, which could directly influence the overall translation processes and global expression of the proteins leading to the emergence of different diseases including cancer. While microRNAs (miRNAs) are small non-coding RNAs and one of the potent regulators of the post-transcriptional gene expression, miRNAs regulate gene expression by targeting the 3' untranslated region and/or coding region of the messenger RNAs (mRNAs), and by interacting with the 5' untranslated region, and eventually finetune the expression of approximately one-third of all mammalian genes. Herein, we highlighted the significance of miRNAs mediated regulation of RPs coding mRNAs in the global protein translation.

MiRNA Profiling in Plasma Neural-Derived Small Extracellular Vesicles from Patients with Alzheimer's Disease

Small extracellular vesicles (EVs) are able to pass from the central nervous system (CNS) into peripheral blood and contain molecule markers of their parental origin. The aim of our study was to isolate and characterize total and neural-derived small EVs (NDEVs) and their micro RNA (miRNA) cargo in Alzheimer's disease (AD) patients. Small NDEVs were isolated from plasma in a population consisting of 40 AD patients and 40 healthy subjects (CTRLs) using high throughput Advanced TaqMan miRNA OpenArrays^®, which enables the simultaneous determination of 754 miRNAs. MiR-23a-3p, miR-223-3p, miR-100-3p and miR-190-5p showed a significant dysregulation in small NDEVs from AD patients as compared with controls (1.16 ± 0.49 versus 7.54 ± 2.5, p = 0.026; 9.32 ± 2.27 versus 0.66 ± 0.18, p <0.0001; 0.069 ± 0.01 versus 0.5 ± 0.1, p < 0.0001 and 2.9 ± 1.2 versus 1.93 ± 0.9, p < 0.05, respectively). A further validation analysis confirmed that miR-23a-3p, miR-223-3p and miR-190a-5p levels in small NDEVs from AD patients were significantly upregulated as compared with controls (p = 0.008; p = 0.016; p = 0.003, respectively) whereas miR-100-3p levels were significantly downregulated (p = 0.008). This is the first study that carries out the comparison between total plasma small EV population and NDEVs, demonstrating the presence of a specific AD NDEV miRNA signature.

Inhibition of Endoplasmic Reticulum Stress Attenuated Ethanol-Induced Exosomal miR-122 and Acute Liver Injury in Mice

AIMS

In acute alcoholic liver injury, alcohol can directly or indirectly induce endoplasmic reticulum stress (ERS) to participate in liver injury, and it is found that the expression of serum exosomal miR-122 is significantly affected. Therefore, the present study investigated the effects of endoplasmic reticulum stress inhibition on the expression of serum exosomal miR-122 and acute liver injury.

METHODS

The acute alcoholic liver injury models were established by the intragastric administration of ethanol (5 g/kg) in ICR mice. Intervention group received 4-phenylbutyric acid (PBA, endoplasmic reticulum stress inhibitor; 75 mg/kg and 150 mg/kg, intraperitoneal) 12 and 24 hours before intragastric administration. Mice treated with saline were used as controls.

RESULTS

The ethanol treated mice exhibited significantly elevated hepatosomatic index (liver weight/body weight) and alanine aminotransferase (ALT), compared with those in the control group (P < 0.05). The ERS inhibitor 4-phenylbutyric acid protected against ethanol induced acute liver injury and hepatocyte necrosis, and PBA 150 mg/kg significantly attenuated ethanol induced hepatic ER stress-related proteins (GRP78, pIRE1α and pIF2α) (P < 0.05). Moreover, PBA 150 mg/kg markedly alleviated ethanol induced elevation of hepatic and serum exosomal miR-122 and pri-miR-122 (P < 0.05).

CONCLUSIONS

These findings suggest that ER stress inhibitor PBA attenuated ethanol induced acute liver injury and serum exosomal miR-122, and provides a potential therapy strategy for acute alcoholic liver injury.

Identification of circulating microRNA signatures as potential biomarkers in the serum of elk infected with chronic wasting disease

Chronic wasting disease (CWD) is an emerging infectious prion disorder that is spreading rapidly in wild populations of cervids in North America. The risk of zoonotic transmission of CWD is as yet unclear but a high priority must be to minimize further spread of the disease. No simple diagnostic tests are available to detect CWD quickly or in live animals; therefore, easily accessible biomarkers may be useful in identifying infected animals. MicroRNAs (miRNAs) are a class of small, non-coding RNA molecules that circulate in blood and are promising biomarkers for several infectious diseases. In this study we used next-generation sequencing to characterize the serum miRNA profiles of 35 naturally infected elk that tested positive for CWD in addition to 35 elk that tested negative for CWD. A total of 21 miRNAs that are highly conserved amongst mammals were altered in abundance in sera, irrespective of hemolysis in the samples. A number of these miRNAs have previously been associated with prion diseases. Receiver operating characteristic (ROC) curve analysis was performed to evaluate the discriminative potential of these miRNAs as biomarkers for the diagnosis of CWD. We also determined that a subgroup of 6 of these miRNAs were consistently altered in abundance in serum from hamsters experimentally infected with scrapie. This suggests that common miRNA candidate biomarkers could be selected for prion diseases in multiple species. Furthermore, Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses pointed to a strong correlation for 3 of these miRNAs, miR-148a-3p, miR-186-5p, miR-30e-3p, with prion disease.

MiR-409-5p as a Regulator of Neurite Growth Is Down Regulated in APP/PS1 Murine Model of Alzheimer's Disease

Alzheimer’s disease (AD) is a heterogeneous neurodegenerative disease. Recent studies suggest that miRNA expression changes are associated with the development of AD. Our previous study showed that the expression level of miR-409-5p was stably downregulated in the early stage of APP/PS1 double transgenic mice model of AD. We now report that miR-409-5p impairs neurite outgrowth, decreases neuronal viability, and accelerates the progression of Aβ_1–42-induced pathologies. In this study, we found that Aβ_1–42 peptide significantly decreased the expression of miR-409-5p, which was consistent with the expression profile of miR-409-5p in the APP/PS1 mice cortexes. Plek was confirmed to be a potential regulatory target of miR-409-5p by luciferase assay and Western blotting. Overexpression of miR-409-5p has an obvious neurotoxicity in neuronal cell viability and differentiation, whereas Plek overexpression could partially rescue neurite outgrowth from this toxicity. Some cytoskeleton regulatory proteins have been found to be related to AD pathogenesis. Our data show some clues that cytoskeletal reorganization may play roles in AD pathology. The early downregulation of miR-409-5p in AD progression might be a self-protective reaction to alleviate the synaptic damage induced by Aβ, which may be used as a potential early biomarker of AD.

Concise Review: Therapeutic Potential of the Mesenchymal Stem Cell Derived Secretome and Extracellular Vesicles for Radiation-Induced Lung Injury: Progress and Hypotheses

Radiation-induced lung injury (RILI) is a common complication in radiotherapy of thoracic tumors and limits the therapeutic dose of radiation that can be given to effectively control tumors. RILI develops through a complex pathological process, resulting in induction and activation of various cytokines, infiltration by inflammatory cells, cytokine-induced activation of fibroblasts, and subsequent tissue remodeling by activated fibroblasts, ultimately leading to impaired lung function and respiratory failure. Increasing evidence shows that mesenchymal stem cells (MSCs) may play a main role in modulating inflammation and immune responses, promoting survival and repair of damaged resident cells and enhancing regeneration of damaged tissue through soluble paracrine factors and therapeutic extracellular vesicles. Therefore, the use of the MSC-derived secretome and exosomes holds promising potential for RILI therapy. Here, we review recent progress on the potential mechanisms of MSC therapy for RILI, with an emphasis on soluble paracrine factors of MSCs. Hypotheses on how MSC derived exosomes or MSC-released exosomal miRNAs could attenuate RILI are also proposed. Problems and translational challenges of the therapies based on the MSC-derived secretome and exosomes are further summarized and underline the need for caution on rapid clinical translation. Stem Cells Translational Medicine 2019;8:344-354.

Physical Activity Alleviates Cognitive Dysfunction of Alzheimer's Disease through Regulating the mTOR Signaling Pathway

Alzheimer's disease (AD) is one of the most common aging-related progressive neurodegenerative disorders, and can result in great suffering for a large portion of the aged population. Although the pathogenesis of AD is being elucidated, the exact mechanisms are still unclear, thereby impeding the development of effective drugs, supplements, and other interventional strategies for AD. In recent years, impaired autophagy associated with microRNA (miRNA) dysfunction has been reported to be involved in aging and aging-related neurodegenerative diseases. Therefore, miRNA-mediated regulation for the functional status of autophagy may become one of the potent interventional strategies for AD. Mounting evidence from in vivo AD models has demonstrated that physical activity can exert a neuroprotective role in AD. In addition, autophagy is strictly regulated by the mTOR signaling pathway. In this article, the regulation of the functional status of autophagy through the mTOR signaling pathway during physical activity is systematically discussed for the prevention and treatment of AD. This concept will be beneficial to developing novel and effective targets that can create a direct link between pharmacological intervention and AD in the future.

miR-100-5p-abundant exosomes derived from infrapatellar fat pad MSCs protect articular cartilage and ameliorate gait abnormalities via inhibition of mTOR in osteoarthritis

Osteoarthritis (OA) is the most common disabling joint disease throughout the world and its therapeutic effect is still not satisfactory in clinic nowadays. Recent studies showed that the exosomes derived from several types of mesenchymal stem cells (MSCs) could maintain chondrocyte homeostasis and ameliorate the pathological severity of OA in animal models, indicating that MSCs-derived exosomes could be a novel promising strategy for treating OA. In this study, we investigated the role and underlying mechanisms of infrapatellar fat pad (IPFP) MSCs-derived exosomes (MSC^IPFP-Exos) on OA in vitro and in vivo. Our data revealed that MSC^IPFP could produce amounts of MSC^IPFP-Exos, which exhibited the typical morphological features of exosomes. The MSC^IPFP-Exos ameliorated the OA severity in vivo and inhibited cell apoptosis, enhanced matrix synthesis and reduced the expression of catabolic factor in vitro. Moreover, MSC^IPFP-Exos could significantly enhance autophagy level in chondrocytes partially via mTOR inhibition. Exosomal RNA-seq showed that the level of miR-100-5p that could bind to the 3'-untranslated region (3'UTR) of mTOR was the highest among microRNAs. MSC^IPFP-Exos decreased the luciferase activity of mTOR 3'UTR, while inhibition of miR-100-5p could reverse the MSC^IPFP-Exos-decreased mTOR signaling pathway. Intra-articular injection of antagomir-miR-100-5p dramatically attenuated MSC^IPFP-Exos-mediated protective effect on articular cartilage in vivo. In brief, MSC^IPFP-derived exosomes protect articular cartilage from damage and ameliorate gait abnormality in OA mice by maintaining cartilage homeostasis, the mechanism of which may be related to miR100-5p-regulated inhibition of mTOR-autophagy pathway. As it is relatively feasible to obtain human IPFP from OA patients by arthroscopic operation in clinic, MSC^IPFP-derived exosomes may be a potential therapy for OA in the future.

Association of the peripheral blood levels of circulating microRNAs with both recurrent miscarriage and the outcomes of embryo transfer in an in vitro fertilization process

BACKGROUND

Implantation failure is not only a major cause of early pregnancy loss, but it is also an obstacle to assisted reproductive technologies. The identification of potential circulating biomarkers for recurrent miscarriage (RM) and/or recurrent implantation failure would contribute to the development of novel diagnosis and prediction techniques.

METHODS

MiR (miR-23a-3p, 27a-3p, 29a-3p, 100-5p, 127-3p and 486-5p) expression in the villi, decidual tissues and peripheral blood plasma and serum were validated by qPCR, and the localization of miRs in the villi and decidual tissues of RM and normal pregnancy (NP) women were detected by in situ hybridization. The invasiveness of HTR8/SVneo cells was determined using a Transwell assay. The predictive values of miRs for RM and the outcome of IVF-ET were respectively calculated by the receiver operating characteristic analysis.

RESULTS

The signals of six miRs were observed in the villi and decidual tissues of RM and NP women. The villus miR-27a-3p, miR-29a-3p and miR-100-5p were significantly up-regulated, whereas miR-127-3p and miR-486-5p appeared to be down-regulated in RM women compared to NP women. The invasiveness of HTR8/SVneo cells transfected with miR-23a-3p mimics was evidently weakened, whereas that of cells transfected with miR-127-3p mimics was obviously enhanced. The peripheral blood plasma levels of miR-27a-3p, miR-29a-3p, miR-100-5p and miR-127-3p were significantly increased, whereas that of miR-486-5p was remarkably decreased in RM compared to NP women. By contrast, serum miR-23a-3p and miR-127-3p were significantly decreased, whereas that of miR-486-5p was remarkably increased. The combination of six plasma miRs levels discriminated RM with a sensitivity of 100% and a specificity of 83.3%, whereas that of six serum miRs levels showed a sensitivity of 78.3% and a specificity of 93.1%. In the IVF-ET cohort, the significantly decreased peripheral blood plasma levels of miR-23a-3p, miR-27a-3p, miR-100-5p and miR-127-3p, and the serum levels of miR-100-5p and miR-486-5p, in addition to the significantly increased serum level of miR-27a-3p, were found to be associated with the failure of ET. Moreover, the combination of plasma miR-23a-3p, miR-27a-3p, miR-29a-3p, miR-100-5p, miR-127-3p and miR-486-5p levels discriminated the outcome of IVF-ET with a sensitivity of 68.1% and a specificity of 54.1%, whereas the combination of plasma miR-127-3p and miR-486-5p levels showed a sensitivity of 50.0% and a specificity of 75.3%.

CONCLUSIONS

Circulating miR-23a-3p, miR-27a-3p, miR-29a-3p, miR-100-5p, miR-127-3p and miR-486-5 might be involved in RM pathogenesis and present potential diagnostic biomarkers for RM. Meanwhile, these miRs, in particular miR-127-3p and miR-486-5p, provide promising prediction indexes for the outcomes of IVF-ET.

The role of the miR-99b-5p/mTOR signaling pathway in neuroregeneration in mice following spinal cord injury

The present study aimed to investigate the role of microRNA (miR)-99b-5p in spinal cord injury (SCI). Reverse transcription-quantitative polymerase chain reaction demonstrated that, compared with control mice, the expression levels of miR-99b-5p were upregulated in the mouse spinal cord following SCI. Mechanistic target of rapamycin (mTOR) was predicted to be the possible target of miR-99b-5p according to TargetScan and microrna databases. Dual-luciferase reporter assay verified that miR-99b-5p was able to target mTOR. Furthermore, the results of an apoptosis analysis demonstrated that there were few apoptotic neurons in the control group, whereas SCI induced a significant increase in the number of apoptotic cells. Conversely, apoptosis was inhibited following transfection with a miR-99b-5p inhibitor. The effects of miR-99b-5p on neurite growth were also evaluated. The results of an immunofluorescence analysis indicated that neurite growth was normal in the control group, whereas SCI induced a reduction in neurite growth, which was rescued following transfection with a miR-99b-5p inhibitor. The protein expression levels of mTOR were detected in the three groups by western blotting. The results demonstrated that, compared with the control group, the protein expression levels of mTOR were significantly reduced in SCI neurons, whereas transfection with a miR-99b-5p inhibitor suppressed the SCI-induced reduction of mTOR. In conclusion, treatment with a miR-99b-5p inhibitor may attenuate SCI-induced harmful alterations in spinal cord neurons via the regulation of mTOR expression.

Growth of malignant extracranial tumors alters microRNAome in the prefrontal cortex of TumorGraft mice

A wide array of central nervous system complications, neurological deficits, and cognitive impairments occur and persist as a result of systemic cancer and cancer treatments. This condition is known as chemo brain and it affects over half of cancer survivors. Recent studies reported that cognitive impairments manifest before chemotherapy and are much broader than chemo brain alone, thereby adding in tumor brain as a component. The molecular mechanisms of chemo brain are under-investigated, and the mechanisms of tumor brain have not been analyzed at all. The frequency and timing, as well as the long-term persistence, of chemo brain and tumor brain suggest they may be epigenetic in nature. MicroRNAs, small, single-stranded non-coding RNAs, constitute an important part of the cellular epigenome and are potent regulators of gene expression. miRNAs are crucial for brain development and function, and are affected by a variety of different stresses, diseases and conditions. However, nothing is known about the effects of extracranial tumor growth or chemotherapy agents on the brain microRNAome. We used the well-established TumorGraft ™ mouse models of triple negative (TNBC) and progesterone receptor positive (PR+BC) breast cancer, and profiled global microRNAome changes in tumor-bearing mice upon chemotherapy, as compared to untreated tumor-bearing mice and intact mice. Our analysis focused on the prefrontal cortex (PFC), based on its roles in memory, learning, and executive functions, and on published data showing the PFC is a target in chemo brain. This is the first study showing that tumor presence alone significantly impacted the small RNAome of PFC tissues. Both tumor growth and chemotherapy treatment affected the small RNAome and altered levels of miRNAs, piRNAs, tRNAs, tRNA fragments and other molecules involved in post-transcriptional regulation of gene expression. Amongst those, miRNA changes were the most pronounced, involving several miRNA families, such as the miR-200 family and miR-183/96/182 cluster; both were deregulated in tumor-bearing and chemotherapy-treated animals. We saw that miRNA deregulation was associated with altered levels of brain-derived neurotrophic factor (BDNF), which plays an important role in cognition and memory and is one of the known miRNA targets. BDNF downregulation has been associated with an array of neurological conditions and could be one of the mechanisms underlying tumor brain and chemo brain. In the future our study could serve as a roadmap for further analysis of cancer and chemotherapy's neural side effects, and differentially expressed miRNAs should be explored as potential tumor brain and chemo brain biomarkers.

MicroRNA analysis in mouse neuro-2a cells after pseudorabies virus infection

Pseudorabies virus (PRV), an alpha herpesvirus can enter the mammalian nervous system, causing Aujezsky's disease. Previous studies have reported an alteration of microRNA (miRNA) expression levels during PRV infections. However, knowledge regarding miRNA response in nervous cells to PRV infection is still unknown. To address this issue, small RNA libraries from infected and uninfected mouse neuroblastoma cells were assessed after Illumina deep sequencing. A total of eight viral miRNA were identified, and ten host miRNAs showed significantly different expression upon PRV infection. Among these, five were analyzed by stem-loop RT-qPCR, which confirmed the above data. Interestingly, these viral miRNAs were mainly found in the large latency transcript region of PRV, and predicted to target a variety of genes, forming a complicated regulatory network. Moreover, ten cellular miRNAs were expressed differently upon PRV infection, including nine upregulated and one downregulated miRNAs. Host targets of these miRNAs obtained by bioinformatics analysis belonged to large signaling networks, mainly encompassing calcium signaling pathway, cAMP signaling pathway, MAPK signaling pathway, and other nervous-associated pathways. These findings further highlighted miRNA features in nervous cells after PRV infection and contributed to unveil the underlying mechanisms of neurotropism as well as the neuropathogenesis of PRV.

The Protective Role of microRNA-200c in Alzheimer's Disease Pathologies Is Induced by Beta Amyloid-Triggered Endoplasmic Reticulum Stress

MicroRNAs are small non-coding RNAs that repress the expression of their target proteins. The roles of microRNAs in the development of Alzheimer's disease (AD) are not clear. In this study we show that miR-200c represses the expression of PTEN protein. PTEN downregulation by miR-200c supports the survival and differentiation of cultured neurons. AD is a progressive neurodegenerative disease signified by beta amyloid (Aβ) peptide aggregation and deposition. In a mouse model of AD that is induced by APPswe and PS1ΔE9 double transgenes, we found Aβ deposition results in neuronal ER stress that induces miR200c. Pharmacological blockade of ER stress inhibited Aβ-induced miR-200c overexpression in AD brains. MiR-200c was detected in the serum of both AD mice and human AD patients. These findings suggest that miR-200c functions as part of the neuronal cell-intrinsic adaptive machinery, and supports neuronal survival and differentiation in response to Aβ induced ER-stress by downregulating PTEN.

Role of miR-211 in Neuronal Differentiation and Viability: Implications to Pathogenesis of Alzheimer's Disease

Alzheimer's disease (AD) is an age-related irreversible neurodegenerative disorder characterized by extracellular β Amyloid(Aβ) deposition, intracellular neurofibrillary tangles and neuronal loss. The dysfunction of neurogenesis and increased degeneration of neurons contribute to the pathogenesis of AD. We now report that miR-211-5p, a small non-coding RNA, can impair neurite differentiation by directly targeting NUAK1, decrease neuronal viability and accelerate the progression of Aβ-induced pathologies. In this study, we observed that during embryonic development, the expression levels of miR-211-5p were down-regulated in the normal cerebral cortexes of mice. However, in APPswe/PS1ΔE9 double transgenic adult mice, it was up-regulated from 9 months of age compared to that of the age-matched wild type mice. Studies in primary cortical neuron cultures demonstrated that miR-211-5p can inhibit neurite growth and branching via NUAK1 repression and decrease mature neuron viability. The impairments were more obvious under the action of Aβ. Our data showed that miR-211-5p could inhibit cortical neuron differentiation and survival, which may contribute to the synaptic failure, neuronal loss and cognitive dysfunction in AD.