MicroRNA-26b is upregulated in a double transgenic mouse model of Alzheimer's disease and promotes the expression of amyloid-β by targeting insulin-like growth factor 1

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

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

Insulin-Like Growth Factor Signaling in Alzheimer's Disease: Pathophysiology and Therapeutic Strategies

Alzheimer's disease (AD) is the leading cause of dementia among the elderly population, posing a significant public health challenge due to limited therapeutic options that merely delay cognitive decline. AD is associated with impaired energy metabolism and reduced neurotrophic signaling. The insulin-like growth factor (IGF) signaling pathway, crucial for central nervous system (CNS) development, metabolism, repair, cognition, and emotion regulation, includes IGF-1, IGF-2, IGF-1R, IGF-2R, insulin receptor (IR), and six insulin-like growth factor binding proteins (IGFBPs). Research has identified abnormalities in IGF signaling in individuals with AD and AD models. Dysregulated expression of IGFs, receptors, IGFBPs, and disruptions in downstream phosphoinositide 3-kinase-protein kinase B (PI3K/AKT) and mitogen-activated protein kinase (MAPK) pathways collectively increase AD susceptibility. Studies suggest modulating the IGF pathway may ameliorate AD pathology and cognitive decline. This review explores the CNS pathophysiology of IGF signaling in AD progression and assesses the potential of targeting the IGF system as a novel therapeutic strategy. Further research is essential to elucidate how aberrant IGF signaling contributes to AD development, understand underlying molecular mechanisms, and evaluate the safety and efficacy of IGF-based treatments.

Gut microbiota defined epigenomes of Alzheimer's and Parkinson's diseases reveal novel targets for therapy

The origins of Alzheimer's disease (AD) and Parkinson's disease (PD) involve genetic mutations, epigenetic changes, neurotoxin exposure and gut microbiota dysregulation. The gut microbiota's dynamic composition and its metabolites influence intestinal and blood-brain barrier integrity, contributing to AD and PD development. This review explores protein misfolding, aggregation and epigenetic links in AD and PD pathogenesis. It also highlights the role of a leaky gut and the microbiota-gut-brain axis in promoting these diseases through inflammation-induced epigenetic alterations. In addition, we investigate the potential of diet, probiotics and microbiota transplantation for preventing and treating AD and PD via epigenetic modifications, along with a discussion related to current challenges and future considerations. These approaches offer promise for translating research findings into practical clinical applications.

Epigenetic Aspects of a New Probiotic Concept-A Pilot Study

Several studies report the important role of an altered gut microbiota in the development of obesity, highlighting the potential use of probiotics in the treatment of obesity. The aim of this study is to investigate the effect of a novel probiotic approach on the expression of specific miRNAs and mRNAs associated with obesity in combination with the hypocholesterolemic octacosanol. Twenty overweight/obese women participated in a randomized, placebo-controlled, double-blind study and were randomly divided into two groups: the intervention group (daily one capsule containing Lactobacillus plantarum 299v (DSM9843), Saccharomyces cerevisiae var. boulardii, and 40 mg octacosanol; N = 12) and the placebo group (N = 8). Changes in lipid parameters and expression of miRNAs and mRNAs were assessed before (T0) and after the 12-week intervention (T1). After the intervention, the expression of miR-155-5p (9.38 ± 0.85 vs. 8.38 ± 1.06, p = 0.05) and miR-24-3p (3.42 ± 0.38 vs. 2.71 ± 0.97, p = 0.031) showed significant decreases in the intervention group when compared to the control group. At T1, the expression of miR-155-5p (8.69 ± 1.31 vs. 9.3 ± 0.85, p = 0.04), miR-125b-5p (5.41 ± 1.18 vs. 5.99 ± 1.36, p = 0.049), and TNF-α (10.24 ± 1.66 vs. 11.36 ± 1.12, p = 0.009) were significantly decreased in the intervention group. No changes in lipids and anthropometric parameters were observed. The novel probiotic approach had a positive effect on regulating the expression of certain miRNAs and mRNAs important for regulating inflammation and adipogenesis, which are essential for obesity onset and control.

Roles of Non-Coding RNA in Alzheimer's Disease Pathophysiology

Alzheimer's disease (AD) is a chronic neurodegenerative disorder that is accompanied by deficits in memory and cognitive functions. The disease is pathologically characterised by the accumulation and aggregation of an extracellular peptide referred to as amyloid-β (Aβ) in the form of amyloid plaques and the intracellular aggregation of a hyperphosphorelated protein tau in the form of neurofibrillary tangles (NFTs) that cause neuroinflammation, synaptic dysfunction, and oxidative stress. The search for pathomechanisms leading to disease onset and progression has identified many key players that include genetic, epigenetic, behavioural, and environmental factors, which lend support to the fact that this is a multi-faceted disease where failure in various systems contributes to disease onset and progression. Although the vast majority of individuals present with the sporadic (non-genetic) form of the disease, dysfunctions in numerous protein-coding and non-coding genes have been implicated in mechanisms contributing to the disease. Recent studies have provided strong evidence for the association of non-coding RNAs (ncRNAs) with AD. In this review, we highlight the current findings on changes observed in circular RNA (circRNA), microRNA (miRNA), short interfering RNA (siRNA), piwi-interacting RNA (piRNA), and long non-coding RNA (lncRNA) in AD. Variations in these ncRNAs could potentially serve as biomarkers or therapeutic targets for the diagnosis and treatment of Alzheimer's disease. We also discuss the results of studies that have targeted these ncRNAs in cellular and animal models of AD with a view for translating these findings into therapies for Alzheimer's disease.

Non-coding RNAs as key players in the neurodegenerative diseases: Multi-platform strategies and approaches for exploring the Genome's dark matter

A growing amount of evidence in the last few years has begun to unravel that non-coding RNAs have a myriad of functions in gene regulation. Intensive investigation on non-coding RNAs (ncRNAs) has led to exploring their broad role in neurodegenerative diseases (NDs) owing to their regulatory role in gene expression. RNA sequencing technologies and transcriptome analysis has unveiled significant dysregulation of ncRNAs attributed to their biogenesis, upregulation, downregulation, aberrant epigenetic regulation, and abnormal transcription. Despite these advances, the understanding of their potential as therapeutic targets and biomarkers underpinning detailed mechanisms is still unknown. Advancements in bioinformatics and molecular technologies have improved our knowledge of the dark matter of the genome in terms of recognition and functional validation. This review aims to shed light on ncRNAs biogenesis, function, and potential role in NDs. Further deepening of their role is provided through a focus on the most recent platforms, experimental approaches, and computational analysis to investigate ncRNAs. Furthermore, this review summarizes and evaluates well-studied miRNAs, lncRNAs and circRNAs concerning their potential role in pathogenesis and use as biomarkers in NDs. Finally, a perspective on the main challenges and novel methods for the future and broad therapeutic use of ncRNAs is offered.

Inhibiting microRNA-142-5p improves learning and memory in Alzheimer's disease rats via targeted regulation of the PTPN1-mediated Akt pathway

OBJECTIVE

MicroRNAs (miRNAs) have been recognized as possible biomarkers for Alzheimer's disease (AD). MiR-142-5p has been reported to be abnormally expressed in brain tissues. However, the role of miR-142-5p in AD pathogenesis keeps unclear. This study aimed to investigate the effect of miR-142-5p on the learning and memory of AD rats via regulation of protein tyrosine phosphatase nonreceptor type 1 (PTPN1)-mediated protein kinase B (Akt) pathway.

METHODS

The AD model was established by injection of Aβ_1-42 oligomer once into the lateral ventricle of rats, and the spatial learning and memory ability of rats was measured. AD rats were injected with miR-142-5p or PTPN1 vectors to explore their functions in inflammation, Aβ, p-tau protein, apoptosis in brain tissues, and the effects on Akt pathway. The targeting relationship between miR-142-5p and PTPN1 was detected.

RESULTS

Overexpressed miR-142-5p, down-regulated PTPN1 and inactivated Akt pathway were exhibited in AD. MiR-142-5p targeted PTPN1 to mediate Akt pathway. Reduced miR-142-5p and elevated PTPN1 improved the behavior of AD rats. MiR-142-5p targeted PTPN1 to effectively inhibit Aβ formation and abnormal phosphorylation of p-tau protein, suppress the inflammation in the brain tissues of AD rat, and improve the survival rate of brain tissue cells. MiR-142-5p regulated PTPN1 to activate the Akt pathway, further inhibiting the apoptosis of brain neurons in AD rats.

CONCLUSION

Down-regulating miR-142-5p targets PTPN1 to activate Akt pathway, thus improving the learning and memory of AD rats and playing an anti-AD role.

The Neuroepigenetic Landscape of Vertebrate and Invertebrate Models of Neurodegenerative Diseases

Vertebrate and invertebrate models of neurodegenerative diseases, such as Alzheimer's disease, Parkinson's disease, and amyotrophic lateral sclerosis, have been paramount to our understanding of the pathophysiology of these conditions; however, the brain epigenetic landscape is less well established in these disease models. DNA methylation, histone modifications, and microRNAs are among commonly studied mechanisms of epigenetic regulation. Genome-wide studies and candidate studies of specific methylation marks, histone marks, and microRNAs have demonstrated the dysregulation of these mechanisms in models of neurodegenerative diseases; however, the studies to date are scarce and inconclusive and the implications of many of these changes are still not fully understood. In this review, we summarize epigenetic changes reported to date in the brain of vertebrate and invertebrate models used to study neurodegenerative diseases, specifically diseases affecting the aging population. We also discuss caveats of epigenetic research so far and the use of disease models to understand neurodegenerative diseases, with the aim of improving the use of model organisms in this context in future studies.

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.

Posttranscriptional Regulation of Insulin Resistance: Implications for Metabolic Diseases

Insulin resistance defines an impairment in the biologic response to insulin action in target tissues, primarily the liver, muscle, adipose tissue, and brain. Insulin resistance affects physiology in many ways, causing hyperglycemia, hypertension, dyslipidemia, visceral adiposity, hyperinsulinemia, elevated inflammatory markers, and endothelial dysfunction, and its persistence leads to the development metabolic disease, including diabetes, obesity, cardiovascular disease, or nonalcoholic fatty liver disease (NAFLD), as well as neurological disorders such as Alzheimer’s disease. In addition to classical transcriptional factors, posttranscriptional control of gene expression exerted by microRNAs and RNA-binding proteins constitutes a new level of regulation with important implications in metabolic homeostasis. In this review, we describe miRNAs and RBPs that control key genes involved in the insulin signaling pathway and related regulatory networks, and their impact on human metabolic diseases at the molecular level, as well as their potential use for diagnosis and future therapeutics.

MicroRNA-Target Interaction Regulatory Network in Alzheimer's Disease

Alzheimer’s Disease (AD) is a progressive neurodegenerative disorder and the most common cause of dementia; however, early diagnosis of the disease is challenging. Research suggests that biomarkers found in blood, such as microRNAs (miRNA), may be promising for AD diagnostics. Experimental data on miRNA–target interactions (MTI) associated with AD are scattered across databases and publications, thus making the identification of promising miRNA biomarkers for AD difficult. In response to this, a list of experimentally validated AD-associated MTIs was obtained from miRTarBase. Cytoscape was used to create a visual MTI network. STRING software was used for protein–protein interaction analysis and mirPath was used for pathway enrichment analysis. Several targets regulated by multiple miRNAs were identified, including: BACE1, APP, NCSTN, SP1, SIRT1, and PTEN. The miRNA with the highest numbers of interactions in the network were: miR-9, miR-16, miR-34a, miR-106a, miR-107, miR-125b, miR-146, and miR-181c. The analysis revealed seven subnetworks, representing disease modules which have a potential for further biomarker development. The obtained MTI network is not yet complete, and additional studies are needed for the comprehensive understanding of the AD-associated miRNA targetome.

miRNAs as Therapeutic Tools in Alzheimer's Disease

Alzheimer's disease (AD), an age-dependent, progressive neurodegenerative disorder, is the most common type of dementia, accounting for 50-70% of all dementia cases. Due to the increasing incidence and corresponding socioeconomic burden of dementia, it has rapidly emerged as a challenge to public health worldwide. The characteristics of AD include the development of extracellular amyloid-beta plaques and intracellular neurofibrillary tangles, vascular changes, neuronal inflammation, and progressive brain atrophy. However, the complexity of the biology of AD has hindered progress in elucidating the underlying pathophysiological mechanisms of AD, and the development of effective treatments. MicroRNAs (miRNAs, which are endogenous, noncoding RNAs of approximately 22 nucleotides that function as posttranscriptional regulators of various genes) are attracting attention as powerful tools for studying the mechanisms of diseases, as they are involved in several biological processes and diseases, including AD. AD is a multifactorial disease, and several reports have suggested that miRNAs play an important role in the pathological processes of AD. In this review, the basic biology of miRNAs is described, and the function and physiology of miRNAs in the pathological processes of AD are highlighted. In addition, the limitations of current pharmaceutical therapies for the treatment of AD and the development of miRNA-based next-generation therapies are discussed.

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

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

Differential expression of microRNAs associated with neurodegenerative diseases and diabetic nephropathy in protein l-isoaspartyl methyltransferase-deficient mice

Protein l-isoaspartyl methyltransferase (PIMT/PCMT1), an enzyme repairing isoaspartate residues in peptides and proteins that result from the spontaneous decomposition of normal l-aspartyl and l-asparaginyl residues during aging, has been revealed to be involved in neurodegenerative diseases (NDDs) and diabetes. However, the molecular mechanisms for a putative association of PIMT dysfunction with these diseases have not been clarified. Our study aimed to identify differentially expressed microRNAs (miRNAs) in the brain and kidneys of PIMT-deficient mice and uncover the epigenetic mechanism of PIMT-involved NDDs and diabetic nephropathy (DN). Differentially expressed miRNAs by sequencing underwent target prediction and enrichment analysis in the brain and kidney of PIMT knockout (KO) mice and age-matched wild-type (WT) littermates. Sequence analysis revealed 40 differentially expressed miRNAs in the PIMT KO mouse brain including 25 upregulated miRNAs and 15 downregulated miRNAs. In the PIMT KO mouse kidney, there were 80 differentially expressed miRNAs including 40 upregulated miRNAs and 40 downregulated miRNAs. Enrichment analysis and a systematic literature review of differentially expressed miRNAs indicated the involvement of PIMT deficiency in the pathogenesis in NDDs and DN. Some overlapped differentially expressed miRNAs between the brain and kidney were quantitatively assessed in the brain, kidney, and serum-derived exosomes, respectively. Despite being preliminary, these results may aid in investigating the pathological hallmarks and identify the potential therapeutic targets and biomarkers for PIMT dysfunction-related NDDs and DN.

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

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

Transcriptome signature of miRNA-26b KO mouse model suggests novel targets

Background

MicroRNAs (miRNAs) are short (20–24 nt) non-coding RNAs that are involved in post-transcriptional regulation of gene expression in multicellular organisms by affecting both the stability and translation of mRNAs. One of the miRNAs that has been shown to play a role in various pathologies like cancer, neurological disorders and cardiovascular diseases is miRNA-26b. However, these studies only demonstrated rather ambiguous associations without revealing a causal relationship. Therefore, the aim of this study is to establish and validate a mouse model which enables the elucidation of the exact role of miRNA-26b in various pathologies.

Results

A miRNA-26b-deficient mouse model was established using homologous recombination and validated using PCR. miRNA-26b-deficient mice did not show any physiological abnormalities and no effects on systemic lipid levels, blood parameters or tissue leukocytes. Using next generation sequencing, the gene expression patterns in miRNA-26b-deficient mice were analyzed and compared to wild type controls. This supported the already suggested role of miRNA-26b in cancer and neurological processes, but also revealed novel associations of miRNA-26b with thermogenesis and allergic reactions. In addition, detailed analysis identified several genes that seem to be highly regulated by miRNA-26b, which are linked to the same pathological conditions, further confirming the role of miRNA-26b in these pathologies and providing a strong validation of our mouse model.

Conclusions

miRNA-26b plays an important role in various pathologies, although causal relationships still have to be established. The described mouse model of miRNA-26b deficiency is a crucial first step towards the identification of the exact role of miRNA-26b in various diseases that could identify miRNA-26b as a promising novel diagnostic or even therapeutic target in a broad range of pathologies.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12863-021-00976-1.

TimiRGeN: R/Bioconductor package for time series microRNA-mRNA integration and analysis

Motivation

The analysis of longitudinal datasets and construction of gene regulatory networks (GRNs) provide a valuable means to disentangle the complexity of microRNA (miRNA)–mRNA interactions. However, there are no computational tools that can integrate, conduct functional analysis and generate detailed networks from longitudinal miRNA–mRNA datasets.

Results

We present TimiRGeN, an R package that uses time point-based differential expression results to identify miRNA–mRNA interactions influencing signaling pathways of interest. miRNA–mRNA interactions can be visualized in R or exported to PathVisio or Cytoscape. The output can be used for hypothesis generation and directing in vitro or further in silico work such as GRN construction.

Availability and implementation

TimiRGeN is available for download on Bioconductor (https://bioconductor.org/packages/TimiRGeN) and requires R v4.0.2 or newer and BiocManager v3.12 or newer.

Supplementary information

Supplementary data are available at Bioinformatics online.

The Eminent Role of microRNAs in the Pathogenesis of Alzheimer's Disease

Alzheimer's disease (AD) is an irrevocable neurodegenerative condition characterized by the presence of senile plaques comprising amassed β-amyloid peptides (Aβ) and neurofibrillary tangles mainly comprising extremely phosphorylated Tau proteins. Recent studies have emphasized the role of microRNAs (miRNAs) in the development of AD. A number of miRNAs, namely, miR-200a-3p, miR-195, miR-338-5p, miR-34a-5p, miR-125b-5p, miR-132, miR-384, miR-339-5p, miR-135b, miR-425-5p, and miR-339-5p, have been shown to participate in the development of AD through interacting with BACE1. Other miRNAs might affect the inflammatory responses in the course of AD. Aberrant expression of several miRNAs in the plasma samples of AD subjects has been shown to have the aptitude for differentiation of AD subjects from healthy subjects. Finally, a number of AD-modifying agents affect miRNA profile in cell cultures or animal models. We have performed a comprehensive search and summarized the obtained data about the function of miRNAs in AD in the current review article.

microRNAs as Early Biomarkers of Alzheimer's Disease: A Synaptic Perspective

Pathogenic processes underlying Alzheimer's disease (AD) affect synaptic function from initial asymptomatic stages, long time before the onset of cognitive decline and neurodegeneration. Therefore, reliable biomarkers enabling early AD diagnosis and prognosis are needed to maximize the time window for therapeutic interventions. MicroRNAs (miRNAs) have recently emerged as promising cost-effective and non-invasive biomarkers for AD, since they can be readily detected in different biofluids, including cerebrospinal fluid (CSF) and blood. Moreover, a growing body of evidence indicates that miRNAs regulate synaptic homeostasis and plasticity processes, suggesting that they may be involved in early synaptic dysfunction during AD. Here, we review the current literature supporting a role of miRNAs during early synaptic deficits in AD, including recent studies evaluating their potential as AD biomarkers. Besides targeting genes related to Aβ and tau metabolism, several miRNAs also regulate synaptic-related proteins and transcription factors implicated in early synaptic deficits during AD. Furthermore, individual miRNAs and molecular signatures have been found to distinguish between prodromal AD and healthy controls. Overall, these studies highlight the relevance of considering synaptic-related miRNAs as potential biomarkers of early AD stages. However, further validation studies in large cohorts, including longitudinal studies, as well as implementation of standardized protocols, are needed to establish miRNA-based biomarkers as reliable diagnostic and prognostic tools.

Thymoquinone administration ameliorates Alzheimer's disease-like phenotype by promoting cell survival in the hippocampus of amyloid beta1-42 infused rat model

BACKGROUND

Thymoquinone (TQ), a biologically active ingredient of Nigella sativa, has anti-inflammatory, anti-oxidative and neuroprotective properties. Therefore, it could be a good candidate in the recovery of Alzheimer`s disease (AD) pathology rather than current symptomatic reliefs.

PURPOSE

In the present study, we examined the molecular healing effects of TQ in amyloid beta 1-42 (Aβ_1-42) peptide-infused AD rat hippocampus.

STUDY DESIGN

A micro-osmotic pump containing aggregated Aβ_1-42 was cannulated into the hippocampus of adult female rats. After two weeks infusion, the dose of TQ (10 mg/kg or 20 mg/kg) was determined according to the HPLC results of cerebrospinal fluid and TQ was given to rats intragastrically for 15 days.

METHODS

The memory performance of rats was determined by Morris water maze test. Afterwards, the acetylcholinesterase (AChE) level were measured by ELISA. Histopathological examinations of hippocampal tissue were performed for cell survival by Nissl staining, for detection of amyloid plaque deposits by Congo red staining and for determination of degenerating neurons by Fluoro Jade C staining. MicroRNA/mRNA levels and protein expressions of AD-related genes and proteins were analyzed by Real-Time Polymerase Chain Reaction and Western Blotting, respectively.

RESULTS

Administration of TQ enhanced the memory performance of Aβ_1-42 infused rats and it also ameliorated the neuronal loss in the cornu ammonis (CA1), but not in the dentate gyrus (DG). In addition, TQ treatment decreased the fibril deposition whose accumulation was significantly higher in the Aβ_1-42-infused animals compared to that of the control group. The expression profiles of mir29c and Bax which significantly upregulated in the Aβ_1-42-infused animals were attenuated by TQ. Furthermore, administration of TQ decreased the expressions of Aβ, phosphorylated-tau, and BACE-1 proteins. There was no significant therapeutic effect of TQ on the AKT/GSK3β or MAPK signaling pathways which were affected due to Aβ_1-42 infusion.

CONCLUSION

TQ has the capacity to recover the neuropathology by removing Aβ plaques and by restoring neuron viability. All might have established the molecular basement of the consolidation in the memory observed by means of TQ treatment.

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

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

MicroRNAs alteration as early biomarkers for cancer and neurodegenerative diseases: New challenges in pesticides exposure

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Current knowledge linking pesticide exposure, cancer and neuro-degenerative diseases to dysregulation of microRNA network was summarized.

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Literature indicates differential miRNA expression targeting biomolecules and pathways involved in cancer and neurodegenerative diseases.

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Evaluation of miRNA expression may be used to develop new non-invasive strategies for the prediction and prognosis of diseases including cancer.

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The application of miRNAs as diagnostic and therapeutic biomarkers in the clinical field is extremely challenging.

This review summarizes the current knowledge linking cancer and neuro-degenerative diseases to dysregulation of microRNA network following pesticide exposure. Most findings revealed differential miRNA expression targeting biomolecules and pathways involved in various neoplastic localizations and neurodegenerative diseases.

A growing body of evidence in recent literature indicates that alteration of specific miRNAs can represent an early biomarker of disease following exposure to chemical agents, including pesticides. Different miRNAs seem to regulate cell proliferation, apoptosis, migration, invasion, and metastasis via many biological pathways through modulation of the expression of target mRNAs.

The evaluation of miRNA expression levels may be used to develop new non-invasive strategies for the prediction and prognosis of many diseases, including cancer. However, the application of miRNAs as diagnostic and therapeutic biomarkers in the clinical field is extremely challenging.

The Cross-Talk Between Sphingolipids and Insulin-Like Growth Factor Signaling: Significance for Aging and Neurodegeneration

Bioactive sphingolipids: sphingosine, sphingosine-1-phosphate (S1P), ceramide, and ceramide-1-phosphate (C1P) are increasingly implicated in cell survival, proliferation, differentiation, and in multiple aspects of stress response in the nervous system. The opposite roles of closely related sphingolipid species in cell survival/death signaling is reflected in the concept of tightly controlled sphingolipid rheostat. Aging has a complex influence on sphingolipid metabolism, disturbing signaling pathways and the properties of lipid membranes. A metabolic signature of stress resistance-associated sphingolipids correlates with longevity in humans. Moreover, accumulating evidence suggests extensive links between sphingolipid signaling and the insulin-like growth factor I (IGF-I)-Akt-mTOR pathway (IIS), which is involved in the modulation of aging process and longevity. IIS integrates a wide array of metabolic signals, cross-talks with p53, nuclear factor κB (NF-κB), or reactive oxygen species (ROS) and influences gene expression to shape the cellular metabolic profile and stress resistance. The multiple connections between sphingolipids and IIS signaling suggest possible engagement of these compounds in the aging process itself, which creates a vulnerable background for the majority of neurodegenerative disorders.

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

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

Thymoquinone activates MAPK pathway in hippocampus of streptozotocin-treated rat model

Streptozotocin (STZ), a glucosamine-nitrosourea compound, produces deficiencies in learning, memory, and cognitive functions when it was administered intracerebroventricularly (i.c.v). In molecular level, increase in neuroinflammation and oxidative stress in brain, and decrease in the number of surviving neurons are the outcomes of STZ administration. Herein, we aimed to investigate the effect of thymoquinone (TQ), an anti-inflammatory, immunomodulatory and neuroprotective agent, on STZ-induced neurodegeneration in rats. For this purpose, bilateral i.c.v. injection of STZ (3 mg/kg) was given to adult female rats on days 1 and 3. TQ (20 mg/kg/day in cornoil) was administered intragastrically to rats for 15 days starting from the 15th day of STZ injection. The Morris water maze test and passive avoidance test were applied to measure the learning and memory performance of animals. Following the behavioral tests, all of the rats were sacrificed for evaluation of molecular alterations. Rats in the STZ-TQ group showed higher performance in passive avoidance test than rats in the STZ group whose memory performance declined compared to control group. The worse memory performance in STZ group was correlated with low number of surviving neurons and high number of degenerating neurons. In addition, an increase in APOE expression and a decrease in NGF expression were observed with STZ injection. Administration of TQ reversed these STZ-triggered cognitive and molecular alterations. In the present study, we observed the neuroregenerative effects of TQ by activation of JNK protein, upregulation of mir-124, and downregulation of ERK1/2 and NOS enzymes. The same ameliorative effect of TQ was also observed in the pTau protein expression. To sum up, we can say that the healing effect of TQ on STZ induced neurodegeneration opens a new door for the development of Alzheimer's disease treatment using natural products as an adjuvant when their action mechanism was explained in detail.

[Chloroquine induces apoptosis of human hepatocellular carcinoma cells in vitro by miR-26b-mediated regulation of Mcl-1]

OBJECTIVE

To investigate the effect of chloroquine in inducing apoptosis of human hepatocellular carcinoma cells and explore the possible mechanism.

METHODS

MTT assay and flow cytometry were used to evaluate chloroquine-induced growth inhibition and apoptosis in human hepatocellular carcinoma HepG2 cells, respectively. The ATP levels in chloroquine-treated cells were detected using an ATP assay kit. PCR and Western blotting were used to detect the expression levels of miR-26b and Mcl-1 in the cells, respectively.

RESULTS

Chloroquine inhibited the proliferation of HepG2 cells in a time- and concentration-dependent manner. Treatments with 80 µmol/L chloroquine for 24, 48, and 72 h induced survival rates of (71.59∓0.2)%, (45.40∓0.5)%, and (26.34∓1.4)% in the cells. Treatments with chloroquine at 40, 80, and 160 µmol/L for 5 h resulted in obviously lowered intracellular ATP levels in the cells to 87.80%, 71.29%, and 38.02% of the control level, respectively. At 80 µmol/L, chloroquine significantly increased the expression of miR-26b and down-regulated the expression of Mcl-1 in HepG2 cells, and the application of the miR-26b inhibitor increased the cellular expression of Mcl-1.

CONCLUSION

s Chloroquine can inhibit the cell proliferation, reduce ATP level and induce apoptosis in HepG2 cells possibly through miR-26b-mediated regulation of Mcl-1.