β-Amyloid targeting nanodrug for neuron-specific delivery of nucleic acids in Alzheimer's disease mouse models

Delivery of therapeutic substances into the brain poses a significant challenge in the treatment of neurological disorders. This is primarily due to the blood-brain barrier (BBB), which restricts access, alongside the limited stability and distribution of these agents within the brain tissue. Here we demonstrate an efficient delivery of microRNA (miRNA) and antisense RNA preferentially to neurons compared to astroglia in the brain of healthy and Alzheimer's disease mice, via disulfide-linked conjugation with poly(ß-L-malic acid-trileucine)-copolymer a biodegradable, amphiphilic, and multivalent platform. By conjugating a D-configured (D3)-peptide (vector) for specific targeting, highly efficient delivery across the BBB is achieved through the Low-Density Lipoprotein Receptor-Related Protein-1 (LRP-1) transcytosis pathway, amyloid beta (Aβ) peptides. Nanodrug distribution was determined by fluorescent labeling and analyzed by microscopy in neurons, astroglia, and in extracellular amyloid plaques typical for Alzheimer's disease. Whereas D-configured BBB-vectors can efficiently target neurons, L-configured (e.g., AP2-peptide) guided vector can only cross BBB but not seem to bind neurons. An analysis of post-injection fluorescence distribution, and RNA-seq followed by real-time PCR validation, confirmed a successful in vivo delivery of morpholino-miRNA-186 nanoconjugates into mouse brain. The size and fluorescence intensity of the intracellular nanodrug particulates were analyzed and verified by a competition with non-fluorescent conjugates. Differentially expressed genes (DEGs) from RNA-seq were identified in the nanodrug injected mice, and the changes of selected DEGs related to Alzheimer's disease were further validated by western blot and real-time PCR. Collectively, these results demonstrated that D3-peptide-conjugated nanopolymer drug is able to achieve neuron-selective delivery of miRNA and can serve as an efficient brain delivery vehicle in Alzheimer's disease (AD) mouse models.

circRNA from APP Gene Changes in Alzheimer's Disease Human Brain

Alzheimer's disease (AD) is the most common cause of age-related dementia. Amyloid precursor protein (APP) is the precursor of Aβ peptides, and its role in AD has been widely investigated. Recently, it has been reported that a circular RNA (circRNA) originated from APP gene can serve as a template for Aβ synthesis, postulating it as an alternative pathway for the Aβ biogenesis. Moreover, circRNAs play important roles in brain development and in neurological diseases. Therefore, our aim was to study the expression of a circAPP (hsa_circ_0007556) and its linear cognate in AD human entorhinal cortex, a brain region most vulnerable to AD pathology. First, we confirmed the presence of circAPP (hsa_circ_0007556) in human entorhinal cortex samples using RT-PCR and Sanger sequencing of PCR products. Next, a 0.49-fold decrease in circAPP (hsa_circ_0007556) levels was observed in entorhinal cortex of AD cases compared to controls (p-value < 0.05) by qPCR. In contrast, APP mRNA expression did not show changes in the entorhinal cortex between AD cases and controls (Fold-change = 1.06; p-value = 0.81). A negative correlation was found between Aβ deposits and circAPP (hsa_circ_0007556) and APP expression levels (Rho Spearman = -0.56, p-value < 0.001 and Rho Spearman = -0.44, p-values < 0.001, respectively). Finally, by using bioinformatics tools, 17 miRNAs were predicted to bind circAPP (hsa_circ_0007556), and the functional analysis predicted that they were involved in some pathways, such as the Wnt-signaling pathway (p = 3.32 × 10^-6). Long-term potentiation (p = 2.86 × 10^-5), among others, is known to be altered in AD. To sum up, we show that circAPP (hsa_circ_0007556) is deregulated in the entorhinal cortex of AD patients. These results add to the notion that circAPP (hsa_circ_0007556) could be playing a role in the pathogenesis of AD disease.

Extracellular Vesicles, Stem Cells and the Role of miRNAs in Neurodegeneration

There are different modalities of intercellular communication governed by cellular homeostasis. In this review, we will explore one of these forms of communication called extracellular vesicles (EVs). These vesicles are released by all cells in the body and are heterogeneous in nature. The primary function of EVs is to share information through their cargo consisting of proteins, lipids and nucleic acids (mRNA, miRNA, dsDNA etc.) with other cells, which have a direct consequence on their microenvironment. We will focus on the role of EVs of mesenchymal stem cells (MSCs) in the nervous system and how these participate in intercellular communication to maintain physiological function and provide neuroprotection. However, deregulation of this same communication system could play a role in several neurodegenerative diseases, such as Alzheimer's disease, Parkinson's disease, Amyotrophic lateral sclerosis, multiple sclerosis, prion disease and Huntington's disease. The release of EVs from a cell provides crucial information to what is happening inside the cell and thus could be used in diagnostics and therapy. We will discuss and explore new avenues for the clinical applications of using engineered MSC-EVs and their potential therapeutic benefit in treating neurodegenerative diseases.

MicroRNAs as Potential Orchestrators of Alzheimer's Disease-Related Pathologies: Insights on Current Status and Future Possibilities

Alzheimer's disease (AD) is a progressive and deleterious neurodegenerative disease, strongly affecting the cognitive functions and memory of seniors worldwide. Around 58% of the affected patients live in low and middle-income countries, with estimates of increasing deaths caused by AD in the coming decade. AD is a multifactor pathology. Mitochondrial function declines in AD brain and is currently emerging as a hallmark of this disease. It has been considered as one of the intracellular processes severely compromised in AD. Many mitochondrial parameters decline already during aging; mitochondrial efficiency for energy production, reactive oxygen species (ROS) metabolism and the de novo synthesis of pyrimidines, to reach an extensive functional failure, concomitant with the onset of neurodegenerative conditions. Besides its impact on cognitive functions, AD is characterized by loss of synapses, extracellular amyloid plaques composed of the amyloid-β peptide (Aβ), and intracellular aggregates of hyperphosphorylated Tau protein, accompanied by drastic sleep disorders, sensory function alterations and pain sensitization. Unfortunately, till date, effective management of AD-related disorders and early, non-invasive AD diagnostic markers are yet to be found. MicroRNAs (miRNAs) are small non-coding nucleic acids that regulate key signaling pathway(s) in various disease conditions. About 70% of experimentally detectable miRNAs are expressed in the brain where they regulate neurite outgrowth, dendritic spine morphology, and synaptic plasticity. Increasing studies suggest that miRNAs are intimately involved in synaptic function and specific signals during memory formation. This has been the pivotal key for considering miRNAs crucial molecules to be studied in AD. MicroRNAs dysfunctions are increasingly acknowledged as a pivotal contributor in AD via deregulating genes involved in AD pathogenesis. Moreover, miRNAs have been proved to control pain sensitization processes and regulate circadian clock system that affects the sleep process. Interestingly, the differential expression of miRNA panels implies their emerging potential as diagnostic AD biomarkers. In this review, we will present an updated analysis of miRNAs role in regulating signaling processes that are involved in AD-related pathologies. We will discuss the current challenges against wider use of miRNAs and the future promising capabilities of miRNAs as diagnostic and therapeutic means for better management of AD.

Reduced serum miR-202 may promote the progression of Alzheimer's disease patients via targeting amyloid precursor protein

The current study investigated whether the expression of miR-202 was abnormal in the serum of patients with Alzheimer's disease (AD) and evaluated the potential clinical significance, thereby shedding light on the diagnosis of AD. Here, our data showed that the level of miR-202 decreased significantly in the serum of AD patients (n = 121) compared with that of healthy controls (n = 86). Further analysis showed that the level of serum miR-202 was gradually decreased in the mild AD group (n = 31), moderate AD group (n = 52) and severe AD group (n = 38) compared with the healthy control group. Receiver operating characteristic (ROC) curve analysis demonstrated that serum miR-202 could differentiate AD patients from healthy controls, with an AUC of 0.892. Spearman correlation analysis showed that serum miR-202 was positively correlated with the Mini-Mental State Examination (MMSE). Based on TargetScan, a conserved binding site was identified in the 3'UTR of amyloid precursor protein (APP). The dual luciferase assay showed that miR-202 suppressed the relative luciferase activity of pmirGLO-APP-3'UTR. Western blot assays indicated that overexpression of miR-202 suppressed the expression of APP, while the expression of APP was enhanced after inhibition of miR-202 in PC12 cells, indicating that APP was a possible target gene of miR-202. Moreover, the cell apoptosis induced by transfection of miR-202 inhibitor was abolished by silencing APP. In summary, we showed novel data that downregulation of serum miR-202 may be used as a potential biomarker for AD and may promote the development of AD by targeting APP.

MicroRNA-298 reduces levels of human amyloid-β precursor protein (APP), β-site APP-converting enzyme 1 (BACE1) and specific tau protein moieties

Alzheimer's disease (AD) is the most common age-related form of dementia, associated with deposition of intracellular neuronal tangles consisting primarily of hyperphosphorylated microtubule-associated protein tau (p-tau) and extracellular plaques primarily comprising amyloid- β (Aβ) peptide. The p-tau tangle unit is a posttranslational modification of normal tau protein. Aβ is a neurotoxic peptide excised from the amyloid-β precursor protein (APP) by β-site APP-cleaving enzyme 1 (BACE1) and the γ-secretase complex. MicroRNAs (miRNAs) are short, single-stranded RNAs that modulate protein expression as part of the RNA-induced silencing complex (RISC). We identified miR-298 as a repressor of APP, BACE1, and the two primary forms of Aβ (Aβ40 and Aβ42) in a primary human cell culture model. Further, we discovered a novel effect of miR-298 on posttranslational levels of two specific tau moieties. Notably, miR-298 significantly reduced levels of ~55 and 50 kDa forms of the tau protein without significant alterations of total tau or other forms. In vivo overexpression of human miR-298 resulted in nonsignificant reduction of APP, BACE1, and tau in mice. Moreover, we identified two miR-298 SNPs associated with higher cerebrospinal fluid (CSF) p-tau and lower CSF Aβ42 levels in a cohort of human AD patients. Finally, levels of miR-298 varied in postmortem human temporal lobe between AD patients and age-matched non-AD controls. Our results suggest that miR-298 may be a suitable target for AD therapy.

Extracellular Vesicle as a Source of Alzheimer's Biomarkers: Opportunities and Challenges

Alzheimer’s disease (AD) is a chronic progressive neurodegenerative disease characterized by memory decline and cognitive dysfunction. Although the primary causes of AD are not clear, it is widely accepted that the accumulation of amyloid beta (Aβ) and consecutive hyper-phosphorylation of tau, synaptic loss, oxidative stress and neuronal death might play a vital role in AD pathogenesis. Recently, it has been widely suggested that extracellular vesicles (EVs), which are released from virtually all cell types, are a mediator in regulating AD pathogenesis. Clinical evidence for the diagnostic performance of EV-associated biomarkers, particularly exosome biomarkers in the blood, is also emerging. In this review, we briefly introduce the biological function of EVs in the central nervous system and discuss the roles of EVs in AD pathogenesis. In particular, the roles of EVs associated with autophagy and lysosomal degradation systems in AD proteinopathy and in disease propagation are discussed. Next, we summarize candidates for biochemical AD biomarkers in EVs, including proteins and miRNAs. The accumulating data brings hope that the application of EVs will be helpful for early diagnostics and the identification of new therapeutic targets for AD. However, at the same time, there are several challenges in developing valid EV biomarkers. We highlight considerations for the development of AD biomarkers from circulating EVs, which includes the standardization of pre-analytical sources of variability, yield and purity of isolated EVs and quantification of EV biomarkers. The development of valid EV AD biomarkers may be facilitated by collaboration between investigators and the industry.

MiR-186 Inhibited Migration of NSCLC via Targeting cdc42 and Effecting EMT Process

In this study, qRT-PCR was employed to identify that miR-186 expression level in NSCLC tissues are highly associated with lymph node metastasis. In addition, through the application of western blotting, luciferase assay and qRT-PCR, it was found that miR-186 targeted 3'UTR of cdc42 mRNA and down-regulated cdc42 protein level in a post-transcriptional manner. Transwell assay indicated that cdc42 partially reversed the effect of miR-186 mimics. Besides, miR-186 was proved to regulate EMT by influencing biomarkers of this process and cell adhesion ability. Thus, miR-186 is a potential target for NSCLC therapy. miR-186 is proposed to be one of tumor-suppressors and may serve as a therapeutic target in NSCLC treatment.

miR-98-5p Acts as a Target for Alzheimer's Disease by Regulating Aβ Production Through Modulating SNX6 Expression

Accumulation of amyloid β-peptide (Aβ) in the brain of Alzheimer disease (AD) patients is believed to be the main pathological feature of the disease. Meanwhile, miR-98-5p dysregulation was found in AD. However, whether miR-98-5p is involved in the accumulation of Aβ in AD, the underlying molecule mechanism remains unclear. In the present study, we confirmed that miR-98-5p negatively regulated sorting nexin 6 (SNX6) expression by targeting the 3'-UTR of SNX6 mRNA. Downregulation of miR-98-5p alleviated Aβ-induced viability inhibition and decreased apoptosis in SK-N-SH and SH-SY5Y cells by upregulating SNX6 expression. Furthermore, downregulation of miR-98-5p decreased SNX6-dependent levels of Aβ40, Aβ42, β-site APP-cleaving enzyme 1 (BACE1), soluble amyloid precursor protein β (sAPPβ), and membrane-associated APP β-carboxyl terminal fragment (βCTF) in SK-N-SH and HEK293 cells. Our findings demonstrate that miR-98-5p modulates SNX6 expression and thus plays a critical role in accumulation of Aβ. Therefore, miR-98-5p may be a novel therapeutic target for AD.