New RNA-Based Breakthroughs in Alzheimer's Disease Diagnosis and Therapeutics

RNA-Based Therapies for Neurodegenerative Diseases Targeting Pathogenic Proteins

Neurodegeneration is featured by the gradual stagnation of neuronal function and structure, leading to significant motor and cognitive impairments. The primary histopathological features underlying these conditions include the cumulation of pathological protein aggregates, chronic inflammation, and neuronal cell death. Alzheimer's disease (AD) and Parkinson's disease (PD) are prominent examples of neurodegenerative diseases (NDDs). As of 2023, over 65 million people worldwide are affected by AD and PD, with the prevalence of these conditions steadily increasing over time. Interestingly, there are no effective therapies available to halt or slow NDD progression. Most approved treatments are focused on symptom management and are often associated with substantial side effects. Given these limitations, the development of novel therapeutic approaches targeting the molecular mechanisms underlying these disorders is essential. Notably, RNA-based therapeutics have recently emerged as a potential therapeutic approach for managing various neurological diseases, offering the potential for innovative molecular interventions in NDD. In this review, we have discussed the pathogenic role of various protein aggregates in NDD and highlighted emerging RNA-based strategies aimed at targeting these pathological proteins.

Rg1 improves Alzheimer's disease by regulating mitochondrial dynamics mediated by the AMPK/Drp1 signaling pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Alzheimer's disease (AD) is the most prevalent form of dementia, characterized by a complex pathogenesis that includes Aβ deposition, abnormal phosphorylation of tau protein, chronic neuroinflammation, and mitochondrial dysfunction. In traditional medicine, ginseng is revered as the 'king of herbs'. Ginseng has the effects of greatly tonifying vital energy, strengthening the spleen and benefiting the lungs, generating fluids and nourishing the blood, and calming the mind while enhancing intelligence. Ginsenoside Rg1 (Rg1) is a well-defined major active component found in ginseng, known for its relatively high content. It has been demonstrated to exhibit neuroprotective effects in both in vivo and in vitro models, capable of ameliorating Aβ and tau pathology, regulating synaptic function, and reducing inflammation, oxidative stress, and apoptosis. However, the potential of Rg1 to improve AD pathology through the regulation of mitochondrial dynamics is still uncertain.

AIM OF THE STUDY

Despite the active research efforts on drugs for AD, the currently available anti-AD medications can only slow disease progression and manage symptoms, yet unable to provide a cure for AD. Furthermore, some anti-AD drugs failed phase III and IV clinical trials due to significant side effects. Therefore, there is an urgent need to further investigate the pathogenesis of AD, to identify new therapeutic targets, and to explore more effective therapies. The aim of this study is to evaluate the potential therapeutic effects of Rg1 on APP/PS1 double transgenic mice and Aβ42-induced HT22 cell models, and to investigate the potential mechanisms through which it provides neuroprotective effects.

MATERIALS AND METHODS

This study investigates the effects of Rg1 in treating AD on APP/PS1 double transgenic mice and Aβ42-induced HT22 cells. In the in vivo experiments, APP/PS1 mice were divided into a model group, Rg1-L group, Rg1-H group, and donepezil group, with C57BL/6 mice serving as the control group (n = 12 per group). The Rg1-L and Rg1-H groups were administered Rg1 at doses of 5 mg/kg/d and 10 mg/kg/d, respectively, while the donepezil group received donepezil at a dose of 1.3 mg/kg/d. Both the control and model groups received an equal volume of physiological saline daily for 28 days. Learning and spatial memory were assessed by the Morris water maze (MWM) and novel object recognition (NOR) tests, and neuronal damage by Nissl staining. Aβ deposition was analyzed through immunohistochemistry and Western blot, while the expression levels of synaptic proteins PSD95 and SYN were evaluated via immunofluorescence staining and Western blot. The dendritic spines of neurons was observed by Golgi staining.The ultrastructure of neuronal mitochondria and synapses was examined by transmission electron microscopy (TEM). Mitochondrial function was assessed through measurements of Reactive oxygen species (ROS), Superoxide Dismutase (SOD), and Adenosine Triphosphate (ATP), and Western blot analysis was performed to detect the expression levels of AMPK, p-AMPK, Drp1, p-Drp1, OPA1, Mfn1, and Mfn2, thereby investigating the protective effects of Rg1 on mitochondrial dysfunction and cognitive impairment in APP/PS1 double transgenic mice. In vitro experiments, HT22 cells were treated with Aβ42 of 10 μM for 24 h to verify the therapeutic effects of Rg1. Flow cytometry was used to detect ROS and JC-1, biochemical methods were employed to measure SOD and ATP, immunofluorescence staining was used to detect the expression levels of PSD95 and SYN, and Western blot analysis was conducted to elucidate its potential mechanisms of action.

RESULTS

The findings suggest that after 28 days of Rg1 treatment, cognitive dysfunction in APP/PS1 mice was improved. Pathological and immunohistochemical analyses demonstrated that Rg1 treatment significantly reduced Aβ deposition and neuronal loss. Rg1 can improve synaptic dysfunction and mitochondrial function in APP/PS1 mice. Rg1 activated AMPK, enhanced p-AMPK expression, inhibited Drp1, and reduced p-Drp1 levels, which led to increased expression of OPA1, Mfn1, and Mfn2, thereby inhibiting mitochondrial fission and facilitating mitochondrial fusion. Additionally, Rg1 effectively reversed the decrease in mitochondrial membrane potential (MMP) and the increase in ROS production induced by Aβ42 in HT22 cells, restoring SOD and ATP levels. Furthermore, Rg1 regulated mitochondrial fission mediated by the AMPK/Drp1 signaling pathway, promoting mitochondrial fusion and improving synaptic dysfunction.

CONCLUSION

Our research provides evidence for the neuroprotective mechanisms of Rg1 in AD models. Rg1 modulates mitochondrial dynamics through the AMPK/Drp1 signaling pathway, thereby reducing synaptic and mitochondrial dysfunction in APP/PS1 mice and AD cell models.

Biophysical characterization of microRNA mixtures based on Molecular Beacons

Diverse studies have shown a relationship between dysregulated microRNAs (miRNAs), including miRNA-29b and miRNA-9, and several diseases. So, it is hypothesized that miRNAs can be studied as potential agents to be exploited in biomedical applications, due to their ability to take part in gene expression regulation at a post-transcriptional level. Considering the possibility of using miRNAs, it is important to characterize and validate this bioproduct, structurally and functionally. The goal of this work is to optimize an assay that can detect and biophysically characterize a miRNA sample without interference from the respective precursor form, by using molecular beacons (MB). MBs are hairpin-shaped probes composed of nucleic acid labeled with a quencher at the 3' end and a fluorophore (reporter) at the 5' end. Here, MB loops were designed so MB-9-1 and MB-29-1 would be complementary to the miRNA-9-1-5p and the miRNA-29b-1-3p, respectively. The MBs designed in this work specifically identified each target miRNA, even in artificial mixtures or complex samples, and the obtained fluorescence was directly proportional to miRNA concentration. Even if the precursor forms (pre-miRNAs) were present in the samples, no significant signal was shown, allowing the distinction between both forms. The outcomes of this work confirm the MBs potential to assess and characterize miRNA samples to be exploited in biochemical, biophysical, or biomedical fields.

Exosomal mRNA Signatures as Predictive Biomarkers for Risk and Age of Onset in Alzheimer's Disease

Alzheimer's disease (AD) is a neurodegenerative disorder characterized by progressive cognitive decline and memory loss. While the precise causes of AD remain unclear, emerging evidence suggests that messenger RNA (mRNA) dysregulation contributes to AD pathology and risk. This study examined exosomal mRNA expression profiles of 15 individuals diagnosed with AD and 15 healthy controls from Barranquilla, Colombia. Utilizing advanced bioinformatics and machine learning (ML) techniques, we identified differentially expressed mRNAs and assessed their predictive power for AD diagnosis and AD age of onset (ADAOO). Our results showed that ENST00000331581 (CADM1) and ENST00000382258 (TNFRSF19) were significantly upregulated in AD patients. Key predictors for AD diagnosis included ENST00000311550 (GABRB3), ENST00000278765 (GGTLC1), ENST00000331581 (CADM1), ENST00000372572 (FOXJ3), and ENST00000636358 (ACY1), achieving > 90% accuracy in both training and testing datasets. For ADAOO, ENST00000340552 (LIMK2) expression correlated with a delay of ~12.6 years, while ENST00000304677 (RNASE6), ENST00000640218 (HNRNPU), ENST00000602017 (PPP5D1), ENST00000224950 (STN1), and ENST00000322088 (PPP2R1A) emerged as the most important predictors. ENST00000304677 (RNASE6) and ENST00000602017 (PPP5D1) showed promising predictive accuracy in unseen data. These findings suggest that mRNA expression profiles may serve as effective biomarkers for AD diagnosis and ADAOO, providing a cost-efficient and minimally invasive tool for early detection and monitoring. Further research is needed to validate these results in larger, diverse cohorts and explore the biological roles of the identified mRNAs in AD pathogenesis.

An insight into structure-activity relationship of naturally derived biological macromolecules for the treatment of Alzheimer's disease: a review

Alzheimer's disease (AD) is a neurological disorder that affects millions of people worldwide. There are currently no cures for AD, although various drugs are used to manage the symptoms and reduce the disease's progression. AChE inhibitors such as rivastigmine, donepezil, galantamine, and the NMDA glutamate receptor antagonist memantine are currently FDA-approved drugs used in the treatment of AD. Recently, naturally derived biological macromolecules have shown promising results in the treatment of AD. Several biological macromolecules derived from natural sources are in various stages of preclinical and clinical trials. During the literature search, it was observed that there is a lack of a comprehensive review that particularly focuses on the role of naturally derived biological macromolecules (protein, carbohydrates, lipids, and nucleic acids) in the treatment of AD and the structure-activity relationship (SAR) approach for understanding the medicinal chemistry perspective. This review focuses on the SAR and probable mechanisms of action of biological macromolecules derived from natural sources for the treatment of AD, including peptides, proteins, enzymes, and polysaccharides. The paper further addresses the therapeutic possibilities of monoclonal antibodies, enzymes, and vaccines for the treatment of AD. Overall, the review provides insight into the SAR of naturally derived biological macromolecules in the treatment of AD. The ongoing research in this field holds great promise for the future development of AD treatment and provides hope for individuals affected by this devastating disease.Communicated by Ramaswamy H. Sarma.

Pongamol Alleviates Neuroinflammation and Promotes Autophagy in Alzheimer's Disease by Regulating the Akt/mTOR Signaling Pathway

Alzheimer's disease (AD), one of the neurodegenerative disorders, is highly correlated with the abnormal hyperphosphorylation of Tau and aggregation of β-amyloid (Aβ). Oxidative stress, neuroinflammation, and abnormal autophagy are key drivers of AD and how they contribute to neuropathology remains largely unknown. The flavonoid compound pongamol is reported to possess a variety of pharmacological activities, such as antioxidant, antibacterial, and anti-inflammatory. This study investigated the neuroprotective effect and its mechanisms of pongamol in lipopolysaccharide (LPS)-induced BV2 cells, d-galactose/sodium nitrite/aluminum chloride (d-gal/NaNO2/AlCl3)-induced AD mice, and Caenorhabditis elegans models. Our research revealed that pongamol reduced the release of inflammatory factors IL-1β, TNF-α, COX-2, and iNOS in LPS-induced BV2 cells. Pongamol also protected neurons and significantly restored memory function, inhibited Tau phosphorylation, downregulated Aβ aggregation, and increased oxidoreductase activity in the hippocampus of AD mice. In addition, pongamol reversed the nuclear transfer of NF-κB and increased the levels of Beclin 1 and LC3 II/LC3 I. Most importantly, the anti-inflammatory and promoter autophagy effects of pongamol may be related to the regulation of the Akt/mTOR signaling pathway. In summary, these results showed that pongamol has a potential neuroprotective effect, which greatly enriched the research on the pharmacological activity of pongamol for improving AD.

Autophagy-associated non-coding RNAs: Unraveling their impact on Parkinson's disease pathogenesis

BACKGROUND

Parkinson's disease (PD) is a degenerative neurological condition marked by the gradual loss of dopaminergic neurons in the substantia nigra pars compacta. The precise etiology of PD remains unclear, but emerging evidence suggests a significant role for disrupted autophagy-a crucial cellular process for maintaining protein and organelle integrity.

METHODS

This review focuses on the role of non-coding RNAs (ncRNAs) in modulating autophagy in PD. We conducted a comprehensive review of recent studies to explore how ncRNAs influence autophagy and contribute to PD pathophysiology. Special attention was given to the examination of ncRNAs' regulatory impacts in various PD models and patient samples.

RESULTS

Findings reveal that ncRNAs are pivotal in regulating key processes associated with PD progression, including autophagy, α-synuclein aggregation, mitochondrial dysfunction, and neuroinflammation. Dysregulation of specific ncRNAs appears to be closely linked to these pathogenic processes.

CONCLUSION

ncRNAs hold significant therapeutic potential for addressing autophagy-related mechanisms in PD. The review highlights innovative therapeutic strategies targeting autophagy-related ncRNAs and discusses the challenges and prospective directions for developing ncRNA-based therapies in clinical practice. The insights from this study underline the importance of ncRNAs in the molecular landscape of PD and their potential in novel treatment approaches.

Therapeutic approaches in proteinopathies

A family of maladies known as amyloid disorders, proteinopathy, or amyloidosis, are characterized by the accumulation of abnormal protein aggregates containing cross-β-sheet amyloid fibrils in many organs and tissues. Often, proteins that have been improperly formed or folded make up these fibrils. Nowadays, most treatments for amyloid illness focus on managing symptoms rather than curing or preventing the underlying disease process. However, recent advances in our understanding of the biology of amyloid diseases have led to the development of innovative therapies that target the emergence and accumulation of amyloid fibrils. Examples of these treatments include the use of small compounds, monoclonal antibodies, gene therapy, and others. In the end, even if the majority of therapies for amyloid diseases are symptomatic, greater research into the biology behind these disorders is identifying new targets for potential therapy and paving the way for the development of more effective treatments in the future.

Noncoding RNAs in Alzheimer's Disease: Overview of Functional and Therapeutic Significance

Alzheimer's disease (AD) is a multifactorial disorder resulting from the complex interaction between genetic, epigenetic, and environmental factors. It represents an impending epidemic and lacks effective pharmacological interventions. The emergence of high throughput sequencing techniques and comprehensive genome evaluation has uncovered a diverse spectrum of noncoding RNA (ncRNA) families. ncRNAs are the critical modulators of an eclectic array of biological processes and are now transpiring as imperative players in diagnosing and treating various diseases, including neurodegenerative disorders. Several ncRNAs are explicitly augmented in the brain, wherein they potentially regulate cognitive abilities and other functions of the central nervous system. Growing evidence suggests the substantial role of ncRNAs as modulators of tau phosphorylation, Aβ production, neuroinflammation, and neuronal survival. It indicates their therapeutic relevance as a biomarker and druggable targets against AD. The current review summarizes the existing literature on the functional significance of ncRNAs in AD pathogenesis and its imminent implications in clinics.

Neuronanomedicine for Alzheimer's and Parkinson's disease: Current progress and a guide to improve clinical translation

Neuronanomedicine is an emerging multidisciplinary field that aims to create innovative nanotechnologies to treat major neurodegenerative disorders, such as Alzheimer's (AD) and Parkinson's disease (PD). A key component of neuronanomedicine are nanoparticles, which can improve drug properties and demonstrate enhanced safety and delivery across the blood-brain barrier, a major improvement on existing therapeutic approaches. In this review, we critically analyze the latest nanoparticle-based strategies to modify underlying disease pathology to slow or halt AD/PD progression. We find that a major roadblock for neuronanomedicine translation to date is a poor understanding of how nanoparticles interact with biological systems (i.e., bio-nano interactions), which is partly due to inconsistent reporting in published works. Accordingly, this review makes a set of specific recommendations to help guide researchers to harness the unique properties of nanoparticles and thus realise breakthrough treatments for AD/PD.

Targeting epigenetics: A novel promise for Alzheimer's disease treatment

So far, the search for a cure for Alzheimer Disease (AD) has been unsuccessful. The only approved drugs attenuate some symptoms, but do not halt the progress of this disease, which affects 50 million people worldwide and will increase its incidence in the coming decades. Such scenario demands new therapeutic approaches to fight against this devastating dementia. In recent years, multi-omics research and the analysis of differential epigenetic marks in AD subjects have contributed to our understanding of AD; however, the impact of epigenetic research is yet to be seen. This review integrates the most recent data on pathological processes and epigenetic changes relevant for aging and AD, as well as current therapies targeting epigenetic machinery in clinical trials. Evidence shows that epigenetic modifications play a key role in gene expression, which could provide multi-target preventative and therapeutic approaches in AD. Both novel and repurposed drugs are employed in AD clinical trials due to their epigenetic effects, as well as increasing number of natural compounds. Given the reversible nature of epigenetic modifications and the complexity of gene-environment interactions, the combination of epigenetic-based therapies with environmental strategies and drugs with multiple targets might be needed to properly help AD patients.

A New Perspective for the Treatment of Alzheimer's Disease: Exosome-like Liposomes to Deliver Natural Compounds and RNA Therapies

With the increment of the aging population in recent years, neurodegenerative diseases exert a major global disease burden, essentially as a result of the lack of treatments that stop the disease progression. Alzheimer's Disease (AD) is an example of a neurodegenerative disease that affects millions of people globally, with no effective treatment. Natural compounds have emerged as a viable therapy to fill a huge gap in AD management, and in recent years, mostly fueled by the COVID-19 pandemic, RNA-based therapeutics have become a hot topic in the treatment of several diseases. Treatments of AD face significant limitations due to the complex and interconnected pathways that lead to their hallmarks and also due to the necessity to cross the blood-brain barrier. Nanotechnology has contributed to surpassing this bottleneck in the treatment of AD by promoting safe and enhanced drug delivery to the brain. In particular, exosome-like nanoparticles, a hybrid delivery system combining exosomes and liposomes' advantageous features, are demonstrating great potential in the treatment of central nervous system diseases.

Noncoding RNA therapeutics for substance use disorder

Although noncoding RNAs (ncRNAs) have been shown to regulate maladaptive neuroadaptations that drive compulsive drug use, ncRNA-targeting therapeutics for substance use disorder (SUD) have yet to be clinically tested. Recent advances in RNA-based drugs have improved many therapeutic issues related to immune response, specificity, and delivery, leading to multiple successful clinical trials for other diseases. As the need for safe and effective treatments for SUD continues to grow, novel nucleic acid-based therapeutics represent an appealing approach to target ncRNA mechanisms in SUD. Here, we review ncRNA processes implicated in SUD, discuss recent therapeutic approaches for targeting ncRNAs, and highlight potential opportunities and challenges of ncRNA-targeting therapeutics for SUD.

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.

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

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