Development Of Alzheimer's Disease Research Articles

The impact of sex on memory during aging and Alzheimer's disease progression: Epigenetic mechanisms.

Alzheimer's disease (AD) is a leading cause of dementia, disability, and death in the elderly. While the etiology of AD is unknown, there are several established risk factors for the disease including, aging, female sex, and genetics. However, specific genetic mutations only account for a small percentage (1-5%) of AD cases and the much more common sporadic form of the disease has no causative genetic basis, although certain risk factor genes have been identified. While the genetic code remains static throughout the lifetime, the activation and expression levels of genes change dynamically over time via epigenetics. Recent evidence has emerged linking changes in epigenetics to the pathogenesis of AD, and epigenetic alterations also modulate cognitive changes during physiological aging. Aging is the greatest risk factor for the development of AD and two-thirds of all AD patients are women, who experience an increased rate of symptom progression compared to men of the same age. In humans and other mammalian species, males and females experience aging differently, raising the important question of whether sex differences in epigenetic regulation during aging could provide an explanation for sex differences in neurodegenerative diseases such as AD. This review explores distinct epigenetic changes that impact memory function during aging and AD, with a specific focus on sexually divergent epigenetic alterations (in particular, histone modifications) as a potential mechanistic explanation for sex differences in AD.

Amyloid beta-activated alpha-1-syntrophin has ramifications on Rac1 activation, ROS production and neuronal cell death.

Alzheimer's disease (AD) is a progressive neurodegenerative disorder characterized by the presence of β-amyloid (Aβ)-containing extracellular neuritic plaques and phosphorylated tau-containing intracellular neurofibrillary tangles. It remains the primary neuropathological criteria for the diagnosis of AD. Additionally, several other processes are currently being recognized as significant risk factors for AD development, including the brain's susceptibility to reactive oxygen species (ROS). The ROS production is among the early signs in the progression of AD. However, the underlying mechanisms behind increased ROS production in AD remain poorly understood. We have observed SNTA1 plays critical role in regulating ROS levels in different pathological conditions. Here, we wanted to gain further insight into the role of SNTA1 in the development of AD by using IMR32 cell line. Our results show that the accumulation of Aβ plaques in Alzheimer's model neuroblastoma cells significantly increases the expression and activation of SNTA1 and MKK6 kinase. The activation of MKK6 results in the phosphorylation of SNTA1, creating a binding site for Rac1, leading to its activation and subsequent production of ROS. Excessive ROS production leads to cell cycle arrest in the G2/M phase, a hallmark of AD. Our study provides new insight into the mechanism of Aβ-mediated cell death in AD and suggests that MKK6-mediated activation of alpha-1-syntrophin promotes ROS production in neuronal cells, resulting in cell death. This study presents a mechanistic insight into Aβ-mediated cell death and could serve as a paradigm for reducing neuronal cell death in AD.

The mediating role of plasma glial fibrillary acidic protein in amyloid and tau pathology in Down's syndrome.

Development of Alzheimer's disease (AD) pathology in Down's syndrome (DS) occurs within a compressed timeline compared to sporadic or other genetic forms of AD. Plasma glial fibrillary acidic protein (GFAP) and plasma pTau-217 levels were compared by AD pathophysiology (amyloid (A+) and tau (T+) positron emission tomography [PET]) in persons with DS (N=348) and sibling controls (N=42). Plasma GFAP, plasma pTau-217, amyloid-PET, and tau-PET levels were compared with regard to estimated years to onset of clinical symptoms (52.5 years old). We evaluated if plasma GFAP mediated the relationship between amyloid PET and plasma pTau-217 or tau PET. Plasma GFAP, a measure of astrogliosis, was elevated in A+/T- and A+/T+ individuals with DS. Plasma pTau-217 was elevated in A+/T+ individuals with DS. GFAP partially mediated the relationship between amyloid-PET and tau-PET (15.3%) and amyloid-PET and plasma pTau-217 (42.1%). Astrogliosis is a key component in the advancement of preclinical AD pathophysiology in DS. Amyloid may be a necessary precursor for stimulating astrocytes. Astrogliosis may play a key role in modifications to tau phosphorylation. Targeting neuroinflammation may only aid amyloid positive individuals. Alzheimer's disease timecourse is compressed in individuals with Down's syndrome.

OATP1A2 mediates Aβ1-42 transport and may be a novel target for the treatment of Alzheimer’s disease

Alzheimer’s disease (AD) is a neurodegenerative disease with an unknown cause. Many studies have suggested that the imbalance between the clearance and accumulation of β-amyloid protein (Aβ) in the brain of AD patients is the main cause of AD development of AD. Meanwhile, drug transporters play a key role in the transport of drugs and endogenous substances in vivo as well as in the development of many diseases. Could they be related to the imbalance between Aβ clearance and accumulation? OATP1A2 is the most abundant subfamily of organic anion transporting polypeptides (OATPs) that transport amphipathic substrates. Its high bilateral expression in brain endothelial cells suggests it plays a crucial role in delivering drugs and neuroactive peptides to brain tissue. Could it also be involved in mediating the production and accumulation of Aβ in the central system? This could lead to an imbalance between Aβ clearance and accumulation, ultimately resulting in AD development. This hypothesis would be bold and novel in the field of science. In this study, we successfully established the OATP1A2-HEK293T transgenic cell model, and found that the uptake of Aβ1-42 by OATP1A2-HEK293T cells was significantly higher than that of NC-HEK293T control cells and human astrocytes by adding different concentrations of Aβ1-42 to the cells of each group, suggesting that OATP1A2 expressed in the human brain is involved in Aβ amyloid protein transport.

Helicobacter pylori outer membrane vesicles directly promote Aβ aggregation and enhance Aβ toxicity in APP/PS1 mice

Helicobacter pylori (H. pylori) infection has been found associated with Alzheimer’s disease (AD) with unclear mechanisms. Outer Membrane Vesicles (OMVs) are spherical particles secreted by Gram-negative bacteria. Here we explore the effect of H. pylori OMVs on Aβ aggregation and toxicity. We show intraperitoneally-injected H. pylori OMVs enter the brain and co-localize with Aβ plaques in APP/PS1 mice, accompanied by aggravated Aβ pathology, exacerbated cognitive deficits and synaptic impairment, indicating that H. pylori OMVs promote β-amyloidosis and AD development. The in vitro results further identify that H. pylori OMVs significantly accelerate Aβ aggregation and increase Aβ-induced neurotoxicity. Through lipidomic analysis, we reveal that lipid components, particularly LPC 18:0 in H. pylori OMVs accelerate Aβ aggregation and enhance Aβ neurotoxicity. Moreover, H. pylori OMVs-enhanced Aβ neurotoxicity is mediated by Ca2+. These findings reveal a mechanism of H. pylori OMVs in accelerating AD development in which the bacterial OMVs-originated lipid components play a key role in promoting Aβ aggregation and neurotoxicity.

Different Markers of Semantic–Lexical Impairment Allow One to Obtain Different Information on the Conversion from MCI to AD: A Narrative Review of an Ongoing Research Program

Background: In this narrative review, we have surveyed results obtained from a research program dealing with the role of semantic memory disorders as a predictor of progression from mild cognitive impairment (MCI) to Alzheimer’s disease (AD). Objectives: In this research program, we have taken into account many different putative markers, provided of a different complexity in the study of the semantic network. These markers ranged from the number of words produced on a semantic fluency task to the following: (a) the discrepancy between scores obtained on semantic vs. phonemic word fluency tests; (b) the presence, at the single-word level, of features (such as a loss of low typical words on a category verbal fluency task) typical of a degraded semantic system; or (c) the presence of more complex phenomena (such as the semantic distance between consecutively produced word pairs) concerning the organization of the semantic network. In the present review, all these studies have been presented, providing separate subsections for (a) methods, (b) results, and (c) a short discussion. Some tentative general conclusions have been drawn at the end of the review. We found that at baseline all these markers are impaired in MCI patients who will later convert to AD, but also that they do not necessarily show a linear worsening during the progression to AD and allow one to make different predictions about the time of development of AD. Our conclusions were that, rather than searching for the best marker of conversion, we should use a range of different markers allowing us to obtain the information most appropriate to the goal of our investigation.

Inhibition of Aβ Aggregation and Tau Phosphorylation with Functionalized Biomimetic Nanoparticles for Synergic Alzheimer's Disease Therapy.

The main pathological mechanisms of Alzheimer's Disease (AD) are extracellular senile plaques caused by β-amyloid (Aβ) deposition and intracellular neurofibrillary tangles derived from hyperphosphorylated Tau protein (p-Tau). However, it is difficult to obtain a good curative effect because of the poor brain bioavailability of drugs, which is attributed to the blood-brain barrier (BBB) restriction and complicated brain conditions. Herein, HM-DK was proposed for synergistic therapy of AD by using hollow mesoporous manganese dioxide (HM) as a carrier to deliver an Aβ-inhibiting peptide and a Dp-peptide inhibitor of Tau-related fibril formation synergistically. Inspired by 4T1 cancer cells promoting BBB penetration during brain metastasis, a prospective biomimetic nanocarrier (HM-DK@CM) encapsulated by 4T1 cell membranes was designed. After crossing the BBB, HM-DK@CM inhibited Aβ aggregation and prevented Tau phosphorylation simultaneously. Moreover, by taking advantage of the catalase-like activity of HM, HM-DK@CM relieved oxidative stress and altered the microenvironment associated with the development of AD. Compared with the single therapeutic drug, HM-DK@CM restored nerve damage and improved AD mice's learning and memory abilities by decreasing Aβ oligomer, p-Tau protein, and inflammation through various pathways for synergistic therapy, which has broad prospects for the effective treatment of AD.

Epistatic effects of IGHG and FCGRIIB genes on the development of Alzheimer’s disease in African Americans

Genome-wide association studies (GWAS) of Alzheimer’s disease (AD) have identified a large number of susceptibility genes, but most of AD heritability remains unexplained, implying the existence of additional genes. Furthermore, the majority of the GWAS have been conducted in people of European descent, and the genes important for AD susceptibility in people of African descent have been underexplored. In this hypothesis-generating prospective cohort study, we genotyped 191 African Americans (AAs) from three longitudinal cohorts on aging for the IgG3 allotype GM6, which is expressed exclusively in people of African descent, and assessed its interaction with IGHG, FCGRIIB, and HLA-DRB1 genes. Cox proportional hazards modeling showed that GM6 by itself was not significantly associated with AD development. However, there was evidence of epistatic interaction: The risk of developing AD associated with GM6 positivity was significantly different (p = 0.0098) in non-GM17/GM17 participants compared with GM 17/GM17 participants. Specifically, in non-GM17/GM17 participants, the risk of AD was over fourfold higher in GM6-positive participants compared with GM 6-negative participants (HR = 4.63). Similarly, risk of developing AD associated with GM6 positivity was marginally different in non-FCGRIIB TT participants compared with FCGRIIB TT participants. In non-FCGRIIB TT participants, the risk of developing AD was over twofold higher in GM6-positive participants compared with GM6-negative participants (HR = 2.44). This is the first report suggesting that immunoglobulin GM allotypes might play a role in AD etiology among AAs; however, since this was largely a hypothesis-generating study, replication in larger cohorts would be required to confirm this finding.

Fluorescence Detection and Inhibition Mechanisms of DNTPH on Aβ42 Oligomers Characterized as Products in the Four Stages of Aggregation.

Aβ42 aggregation was implicated in the pathogenesis of Alzheimer's disease (AD) without effective treatment available currently. Future efforts in clinical trials should instead focus on applying those antiamyloid treatment strategies to the preclinical stage and "the earlier, the better". How to identify and inhibit Aβ42 oligomers in the different stages of aggregation is therefore becoming the key to controlling primary aggregation and consequent AD development. Aggregation-induced emission probe DNTPH was demonstrated recently, enabling detection of amyloid at wavelengths up to 710 nm and exhibiting strong inhibitory effects on Aβ fibrosis at low dose. However, the detection and inhibition mechanisms of Aβ oligomers at various early stages of aggregation remain unknown. To this end, we built four different morphologies of Aβ42 pentamers characterized by products in monomeric aggregate (PM), primary nucleation (PP), secondary nucleation (PS), and fibril stages (PF) to explore the distinguishable ability and inhibition mechanisms of DNTPH with different concentrations upon binding. The results showcased that DNTPH does detect the four different Aβ42 oligomers with conspicuous fluorescence (λPM = 657 nm, λPP = 639 nm, λPS = 630 nm, and λPF = 648 nm) but fails to distinguish them, indicating that additional improvements are required further for the probe to achieve it. The inhibition mechanisms of DNTPH on the four Aβ42 aggregation are however of amazing differences. For PM and PP, aggregation was inhibited by altering the secondary structural composition, i.e., by decreasing the β-sheet and toxic turn (residues 22-23) probabilities, respectively. For PS, inhibition was achieved by segregating and keeping the two disordered monomeric species (PSM) away from the ordered secondary seed species (PSF) and consequently blocking further growth of the PSF seed. The inhibition mechanism for PS is first probed and proposed so far, as far as we know, and the corresponding aggregation stage of PS is the most important one among the four stages. The inhibition of PF was triggered by distorting the fibril chains, disrupting the ordered fibril surface for the contact of monomers. In addition, the optimal inhibitory concentrations of DNTPH for PM, PP, and PF were determined to be 1:3, while for PS, it was 1:5. This outcome offers a novel perspective for designing drugs targeting Aβ42 oligomers at different aggregation stages.

Non-canonical Pathways Associated to Amyloid Beta and Tau Protein Dyshomeostasis in Alzheimer's disease: a narrative review.

Alzheimer's Disease (AD) is the most common form of dementia among elderly people. This disease imposes a significant burden on the healthcare system, society, and economy due to the increasing global aging population. Current trials with drugs or bioactive compounds aimed at reducing cerebral Amyloid beta (Aβ) plaques and tau protein neurofibrillary tangles, which are the two main hallmarks of this devastating neurodegenerative disease, have not provided significant results in terms of their neuropathological outcomes nor met the expected clinical end-points. Ageing, genetic and environmental risk factors, along with different clinical symptoms suggest that AD is a complex and heterogeneous disorder with multiple interconnected pathological pathways rather than a single disease entity. In the present review, we highlight and discuss various non-canonical, Aβ-independent mechanisms, like gliosis, unhealthy dietary intake, lipid and sugar signaling, and cerebrovascular damage that contribute to the onset and development of AD. We emphasize that challenging the traditional "amyloid cascade hypothesis" may improve our understanding of this age-related complex syndrome and help fight the progressive cognitive decline in AD.

The Role of Neuropeptide Y in the Pathogenesis of Alzheimer’s Disease: Diagnostic Significance and Neuroprotective Functions

Background. Alzheimer’s disease (AD) is one of the most common neurodegenerative diseases. It has been suggested that the factors that cause pathologic changes and lead to the development of AD may also include changes in certain neuropeptides. The implication of the neuropeptide (NPY) in the pathogenesis of AD and its potential therapeutic role is possible due to the following properties: involvement in adult neurogenesis, regulatory effects on the immune system, the inhibition of potential-dependent Ca2+ channels, and the reduction in glutamate excitotoxicity. The aim of our review was to summarize recent data on the role of NPY in AD development and to explore its potential as a biomarker and a possible therapeutic target. Materials and methods. We performed a systematic review of studies, for which we search using the keywords “Alzheimer’s disease and neuropeptide Y”, “Alzheimer’s disease and NPY”, “AD and NPY”, “Neuropeptide Y and Neurodegenerative disease”. Nineteen articles were included in the review. Results. The NPY levels in cerebrospinal fluid and plasma have been found to be reduced or unchanged in AD patients; however, these findings need to be confirmed in more recent studies. Data obtained in transgenic animal models support the role of NPY in AD pathogenesis. The neuroprotective effects of NPY have been demonstrated in vitro and in vivo in AD models. Conclusion. The findings may open new possibilities for using NPY as a diagnostic marker to detect AD at earlier stages of the disease or as a potential therapeutic target due to its neuroprotective properties.

Epigenetic Mechanisms of Aluminum-Induced Neurotoxicity and Alzheimer's Disease: A Focus on Non-Coding RNAs.

Aluminum (Al) is known to induce neurotoxic effects, potentially contributing to Alzheimer's disease (AD) pathogenesis. Recent studies suggest that epigenetic modification may contribute to Al neurotoxicity, although the mechanisms are still debatable. Therefore, the objective of the present study was to summarize existing data on the involvement of epigenetic mechanisms in Al-induced neurotoxicity, especially AD-type pathology. Existing data demonstrate that Al exposure induces disruption in DNA methylation, histone modifications, and non-coding RNA expression in brains. Alterations in DNA methylation following Al exposure were shown to be mediated by changes in expression and activity of DNA methyltransferases (DNMTs) and ten-eleven translocation proteins (TETs). Al exposure was shown to reduce histone acetylation by up-regulating expression of histone deacetylases (HDACs) and impair histone methylation, ultimately contributing to down-regulation of brain-derived neurotrophic factor (BDNF) expression and activation of nuclear factor κB (NF-κB) signaling. Neurotoxic effects of Al exposure were also associated with aberrant expression of non-coding RNAs, especially microRNAs (miR). Al-induced patterns of miR expression were involved in development of AD-type pathology by increasing amyloid β (Aβ) production through up-regulation of Aβ precursor protein (APP) and β secretase (BACE1) expression (down-regulation of miR-29a/b, miR-101, miR-124, and Let-7c expression), increasing in neuroinflammation through NF-κB signaling (up-regulation of miR-9, miR-125b, miR-128, and 146a), as well as modulating other signaling pathways. Furthermore, reduced global DNA methylation, altered histone modification, and aberrant miRNA expression were associated with cognitive decline in Al-exposed subjects. However, further studies are required to evaluate the contribution of epigenetic mechanisms to Al-induced neurotoxicity and/or AD development.

Involvement of inflammasomes in the pathogenesis of Alzheimer's disease.

Alzheimer's disease (AD) is a neurodegenerative disease with a long preclinical and prodromal stage near 20 years. The neuropathological hallmarks of AD include amyloid plaques, neurofibrillary tangles, and neuroinflammation, those lead to neuronal and synaptic loss. Important fact, oxidative stress participates in the AD development by promoting amyloid-β deposition, tau hyperphosphorylation. However, the inflammatory response and pyroptotic death are mediated by the aberrant expression of NLRP inflammasome activated caspase-1, which leads to cleavage pro-inflammatory cytokines such as pro-interleukin-1β and pro-IL-18. IL-1β, TNF-α, and IL-6 which amplify the neuroinflammation loop, are produce by activated microglia and astrocytes, that can serve as early diagnostic markers or therapeutic targets in AD. In this review, we summarize our current understanding of the role of inflammasome in the pathogenesis of AD, highlighting key issues that need to be addressed to improve the development of new therapies.

Prevention and Treatment of Alzheimer's Disease Via the Regulation of the Gut Microbiota With Traditional Chinese Medicine.

Alzheimer's disease (AD) is caused by a variety of factors, and one of the most important factors is gut microbiota dysbiosis. An imbalance in the gut mincrobiota have been shown to change the concentrations of lipopolysaccharide and short-chain fatty acids. These microorganisms synthesize substances that can influence the levels of a variety of metabolites and cause multiple diseases through the immune response, fatty acid metabolism, and amino acid metabolism pathways. Furthermore, these metabolic changes promote the formation of β-amyloid plaques and neurofibrillary tangles. Thus, the microbiota-gut-brain axis plays an important role in AD development. In addition to traditional therapeutic drugs such as donepezil and memantine, traditional Chinese medicines (TCMs) have also showed to significantly decrease the severity of AD symptoms and suppress the underlying related mechanisms. We searched for studies on the effects of different herbal monomers, single herbs, and polyherbal formulas on the gut microbiota of AD patients and identified the relevant pathways through which the gut microbiota affected AD. We conclude that improvements in the gut microbiota not only decrease the occurrence of inflammatory reactions but also reduce the deposition of central pathological products. Herbal monomers have a stronger effect on improving of central pathology. Polyherbal formulas have the most extensive effect on the gut microbiota in patients with AD. Among the effects of formulas, the anti-inflammatory effect is the most essential and is also the main concern regarding the use of TCMs in treating AD from the viewpoint of the gut microbiota. We hope that this review will be helpful for providing new ideas for the clinical application of TCMs in the treatment of AD.

Endothelial Dysfunctions in Blood-Brain Barrier Breakdown in Alzheimer's Disease: From Mechanisms to Potential Therapies.

Recent research has shown the presence of blood-brain barrier (BBB) breakdown in Alzheimer's disease (AD). BBB is a dynamic interface consisting of a continuous monolayer of brain endothelial cells (BECs) enveloped by pericytes and astrocytes. The restricted permeability of BBB strictly controls the exchange of substances between blood and brain parenchyma, which is crucial for brain homeostasis by excluding blood-derived detrimental factors and pumping out brain-derived toxic molecules. BBB breakdown in AD is featured as a series of BEC pathologies such as increased paracellular permeability, abnormal levels and functions of transporters, and inflammatory or oxidative profile, which may disturb the substance transportation across BBB, thereafter induce CNS disorders such as hypometabolism, Aβ accumulation, and neuroinflammation, eventually aggravate cognitive decline. Therefore, it seems important to protect BEC properties for BBB maintenance and neuroprotection. In this review, we thoroughly summarized the pathological alterations of BEC properties reported in AD patients and numerous AD models, including paracellular permeability, influx and efflux transporters, and inflammatory and oxidative profiles, and probably associated underlying mechanisms. Then we reviewed current therapeutic agents that are effective in ameliorating a series of BEC pathologies, and ultimately protecting BBB integrity and cognitive functions. Regarding the current drug development for AD proceeds extremely hard, this review aims to discuss the therapeutic potentials of targeting BEC pathologies and BBB maintenance for AD treatment, therefore expecting to shed a light on the future AD drug development by targeting BEC pathologies and BBB protection.

Mitochondrial Quality Control in Alzheimer’s Disease: Insights from Caenorhabditis elegans Models

Alzheimer’s disease (AD) is a complex neurodegenerative disorder that is classically defined by the extracellular deposition of senile plaques rich in amyloid-beta (Aβ) protein and the intracellular accumulation of neurofibrillary tangles (NFTs) that are rich in aberrantly modified tau protein. In addition to aggregative and proteostatic abnormalities, neurons affected by AD also frequently possess dysfunctional mitochondria and disrupted mitochondrial maintenance, such as the inability to eliminate damaged mitochondria via mitophagy. Decades have been spent interrogating the etiopathogenesis of AD, and contributions from model organism research have aided in developing a more fundamental understanding of molecular dysfunction caused by Aβ and toxic tau aggregates. The soil nematode C. elegans is a genetic model organism that has been widely used for interrogating neurodegenerative mechanisms including AD. In this review, we discuss the advantages and limitations of the many C. elegans AD models, with a special focus and discussion on how mitochondrial quality control pathways (namely mitophagy) may contribute to AD development. We also summarize evidence on how targeting mitophagy has been therapeutically beneficial in AD. Lastly, we delineate possible mechanisms that can work alone or in concert to ultimately lead to mitophagy impairment in neurons and may contribute to AD etiopathology.

Relationship of Retroelements with Antiviral Proteins and Epigenetic Factors in Alzheimer's Disease

Genetic factors such as allelic variants of the PSEN1, PSEN2, APP, and APOE genes play an important role in Alzheimer's disease development. Still, they cannot explain all cases of the disease and cannot form the basis for effective treatment methods for the pathology. Alzheimer's disease is the most common neurodegenerative disease, so identifying new mechanisms of pathogenesis may reveal new ways of treating it. Since Alzheimer's disease is associated with aging, the hypothesis is proposed that an important trigger mechanism for it is the pathological activation of retroelements during aging, leading to epigenetic changes. This is due to the role of retroelements in gene expression regulation and the origin of long noncoding RNAs and microRNAs from transposons, changes in the expression of which are observed both during aging and Alzheimer's disease. Normally, activation of retroelements is observed in hippocampal neuronal stem cells, which is necessary for epigenetic programming during neuronal differentiation. Direct changes in the expression of retroelements in Alzheimer's disease have also been described. It has been suggested that aging is a trigger for the development of Alzheimer's disease due to the pathological activation of retroelements. To confirm this hypothesis, an analysis of specific microRNAs associated with Alzheimer's disease and aging in the MDTE DB (microRNAs derived from Transposable elements) database was conducted. As a result, identified expression changes in Alzheimer's disease of 37 individual microRNAs derived from retroelements (25 from LINE, 7 from SINE, 5 from HERV), of which 12 changes expression during physiological aging, which confirms my hypothesis that the activation of retroelements during physiological aging is a driver for Alzheimer's disease. This is evidenced by the defeat of diseases mainly by the elderly and older adults. Since 3 of the 12 miRNAs associated with aging and Alzheimer's disease originated from SINE/MIRs that evolved from tRNAs, the role of tRNAs and the tRFs and tRNA halves derived from them in the development of Alzheimer's disease, which are evolutionarily closely related to retroelements was described. These results are promising for targeted disease therapy in the mechanisms of RNA-directed DNA methylation with possible complex use of retroelement enzyme inhibitors. Additional evidence for the role of retroelements in the development of Alzheimer's disease is that overexpression of tau, which has antiviral properties, with its interaction with beta-amyloid leads to dysregulation of retroelements, and in tauopathies, activation of ERV is determined. At the same time, the effect of retroelements as inducers of proteinopathy and tau aggregation has been described. In addition, HIV and herpes viruses, which affect beta-amyloid and tau protein, are also activators of retroelements. Also, polymorphisms associated with Alzheimer's disease are located mainly in intronic and intergenic regions where retroelements are located, affecting changes in their activity.

Effect of bioactive extracts from Eucalyptus globulus leaves in experimental models of Alzheimer's disease.

Current therapies for Alzheimer's disease (AD) do not delay its progression, therefore, novel disease-modifying strategies are urgently needed. Recently, an increasing number of compounds from natural origin with protective properties against AD have been identified. Mixtures or extracts obtained from natural products containing several bioactive compounds have multifunctional properties and have drawn the attention because multiple AD pathways can be simultaneously modulated. This study evaluated the in vitro and in vivo effect of the essential oil (EO) obtained from the hydrodistillation of Eucalyptus globulus leaves, and an extract obtained from the hydrodistillation residual water (HRW). It was observed that EO and HRW have anti-inflammatory effect in brain immune cells modeling AD, namely lipopolysaccharide (LPS)- and amyloid-beta (Aβ)-stimulated microglia. In cell models that mimic AD-related neuronal dysfunction, HRW attenuated Aβ secretion and Aβ-induced mitochondrial dysfunction. Since the HRW's major components did not cross the blood-brain barrier, both EO and HRW were administered to the APP/PS1 transgenic AD mouse model by an intranasal route, which reduced cortical and hippocampal Aβ levels, and to rescue memory deficits and anxiety-like behaviors. Finally, HRW and EO were found to regulate cholesterol levels in aged mice after intranasal administration, suggesting that these extracts can reduce hypercholesterolemia and avoid risk for AD development. Overall, findings support a protective role of E. globulus extracts against AD‑like pathology and cognitive impairment highlighting the underlying mechanisms. These extracts obtained from underused forest biomass could be useful to develop nutraceutical supplements helpful to avoid AD risk and to prevent its progression.

Longitudinal and Multi-Kingdom Gut Microbiome Alterations in a Mouse Model of Alzheimer's Disease.

Gut microbial dysbiosis, especially bacteriome, has been implicated in Alzheimer's disease (AD). However, nonbacterial members of the gut microbiome in AD, such as the mycobiome, archaeome, and virome, are unexplored. Here, we perform higher-resolution shotgun metagenomic sequencing on fecal samples collected longitudinally from a mouse model of AD to investigate longitudinal and multi-kingdom gut microbiome profiling. Shotgun metagenomic sequencing of fecal samples from AD mice and healthy mice returns 41,222 bacterial, 414 fungal, 1836 archaeal, and 1916 viral species across all time points. The ecological network pattern of the gut microbiome in AD mice is characterized by more complex bacterial-bacterial interactions and fungal-fungal interactions, as well as simpler archaeal-archaeal interactions and viral-viral interactions. The development of AD is accompanied by multi-kingdom shifts in the gut microbiome composition, as evidenced by the identification of 1177 differential bacterial, 84 differential fungal, 59 differential archaeal, and 10 differential viral species between healthy and AD mice across all time points. In addition, the functional potential of the gut microbiome is partially altered in the development of AD. Collectively, our findings uncover longitudinal and multi-kingdom gut microbiome alterations in AD and provide a motivation for considering microbiome-based therapeutics during the prevention and treatment of AD.

The Role of circRNAs in the Pathological Mechanisms of Alzheimer's Disease and May Serve as Potential Biomarkers.

Alzheimer's disease (AD) is the most common neurodegenerative disease leading to dementia in the elderly, and the mechanisms of AD have not been fully defined. Circular RNAs (circRNAs), covalently closed RNAs produced by reverse splicing, have critical effects in the pathogenesis of AD. CircRNAs participate in production and clearance of Aβ and tau, regulate neuroinflammation, synaptic plasticity and the process of apoptosis and autophagy, indicating that circRNAs may be alternative biomarkers and therapeutic targets. Our review summarizes the functions of circRNAs in the progression and development of AD, which provide insights into the prospect of circRNAs in the diagnosis and treatment of AD.