Amyloid-beta: a chameleon walking in two worlds: a review of the trophic and toxic properties of amyloid-beta

Multifunctional Nanocarriers for Alzheimer's Disease: Befriending the Barriers

Neurodegenerative diseases (NDDs) have been increasing in incidence in recent years and are now widespread worldwide. Neuronal death is defined as the progressive loss of neuronal structure or function which is closely associated with NDDs and represents the intrinsic features of such disorders. Amyotrophic lateral sclerosis, frontotemporal dementia, Alzheimer's, Parkinson's, and Huntington's diseases (AD, PD, and HD, respectively) are considered neurodegenerative diseases that affect a large number of people worldwide. Despite the testing of various drugs, there is currently no available therapy that can remedy or effectively slow the progression of these diseases. Nanomedicine has the potential to revolutionize drug delivery for the management of NDDs. The use of nanoparticles (NPs) has recently been developed to improve drug delivery efficiency and is currently subjected to extensive studies. Nanoengineered particles, known as nanodrugs, can cross the blood-brain barrier while also being less invasive compared to the most treatment strategies in use. Polymeric, magnetic, carbonic, and inorganic NPs are examples of NPs that have been developed to improve drug delivery efficiency. Primary research studies using NPs to cure AD are promising, but thorough research is needed to introduce these approaches to clinical use. In the present review, we discussed the role of metal-based NPs, polymeric nanogels, nanocarrier systems such as liposomes, solid lipid NPs, polymeric NPs, exosomes, quantum dots, dendrimers, polymersomes, carbon nanotubes, and nanofibers and surfactant-based systems for the therapy of neurodegenerative diseases. In addition, we highlighted nanoformulations such as N-butyl cyanoacrylate, poly(butyl cyanoacrylate), D-penicillamine, citrate-coated peptide, magnetic iron oxide, chitosan (CS), lipoprotein, ceria, silica, metallic nanoparticles, cholinesterase inhibitors, an acetylcholinesterase inhibitors, metal chelators, anti-amyloid, protein, and peptide-loaded NPs for the treatment of AD.

Amyloid Targeting Red Emitting AIE Dots for Diagnostic and Therapeutic Application against Alzheimer's Disease

The emergence of neurodegenerative diseases is connected to several pathogenic factors, including metal ions, amyloidogenic proteins, and reactive oxygen species. Recent studies suggest that cytotoxicity is caused by the small, dynamic, and metastable nature of early stage oligomeric species. This work introduces a small molecule-based red-emitting probe with smart features such as increased reactivities against multiple targets, metal-free amyloid-β (Aβ), and metal-bound amyloid-β (Aβ), and most importantly, early stage oligomeric species which are associated with the most common and widespread type of dementia, Alzheimer's disease (AD). Theoretical analyses like molecular dynamics simulation and molecular docking were performed to confirm the reactivity of the molecule toward Aβ and found some excellent interactions between the molecule and the peptide. The in vitro and cellular studies demonstrated that this highly biocompatible molecule effectively reduces the structural damage to mitochondria while shielding cells from apoptosis, scavenges ROS (reactive oxygen species), and attenuates multifaceted amyloid toxicity.

Oxidative Stress Induced Dysfunction of Protein Synthesis in 661W Mice Photoreceptor Cells

Photoreceptor cells are highly susceptible to oxidative-stress-induced damage due to their high metabolic rate. Oxidative stress plays a key role in driving pathological events in several different ocular diseases, which lead to retinal degeneration and ultimately blindness. A growing number of studies have been performed to understand downstream events caused by ROS induced oxidative stress in photoreceptor cells; however, the underlying mechanisms of ROS toxicity are not fully understood. To shed light on ROS induced downstream pathological events, we employed a tandem mass tag (TMT) labelling-based quantitative mass-spectrometric approach to determine proteome changes in 661W photoreceptor cells following oxidative stress induction via the application of different concentrations of H2O2 at different time points. Overall, 5920 proteins were identified and quantified, and 450 differentially expressed proteins (DEPs) were identified, which were altered in a dose and time dependent manner in all treatment groups compared to the control group. These proteins were involved in several biological pathways, including spliceosome and ribosome response, activated glutathione metabolism, decreased ECM-receptor interaction, oxidative phosphorylation, abnormally regulated lysosome, apoptosis, and ribosome biogenesis. Our results highlighted ECM receptor interaction, oxidative phosphorylation and spliceosome pathways as the major targets of oxidative stress that might mediate vascular dysfunction and cellular senescence.

The Neuroprotective Activities of the Novel Multi-Target Iron-Chelators in Models of Alzheimer's Disease, Amyotrophic Lateral Sclerosis and Aging

The concept of chelation therapy as a valuable therapeutic approach in neurological disorders led us to develop multi-target, non-toxic, lipophilic, brain-permeable compounds with iron chelation and anti-apoptotic properties for neurodegenerative diseases, such as Parkinson's disease (PD), Alzheimer's disease (AD), age-related dementia and amyotrophic lateral sclerosis (ALS). Herein, we reviewed our two most effective such compounds, M30 and HLA20, based on a multimodal drug design paradigm. The compounds have been tested for their mechanisms of action using animal and cellular models such as APP/PS1 AD transgenic (Tg) mice, G93A-SOD1 mutant ALS Tg mice, C57BL/6 mice, Neuroblastoma × Spinal Cord-34 (NSC-34) hybrid cells, a battery of behavior tests, and various immunohistochemical and biochemical techniques. These novel iron chelators exhibit neuroprotective activities by attenuating relevant neurodegenerative pathology, promoting positive behavior changes, and up-regulating neuroprotective signaling pathways. Taken together, these results suggest that our multifunctional iron-chelating compounds can upregulate several neuroprotective-adaptive mechanisms and pro-survival signaling pathways in the brain and might function as ideal drugs for neurodegenerative disorders, such as PD, AD, ALS, and aging-related cognitive decline, in which oxidative stress and iron-mediated toxicity and dysregulation of iron homeostasis have been implicated.

Amyloid-beta aggregation implicates multiple pathways in Alzheimer's disease: Understanding the mechanisms

Alzheimer's disease (AD) is a progressive neurodegenerative condition characterized by tau pathology and accumulations of neurofibrillary tangles (NFTs) along with amyloid-beta (Aβ). It has been associated with neuronal damage, synaptic dysfunction, and cognitive deficits. The current review explained the molecular mechanisms behind the implications of Aβ aggregation in AD via multiple events. Beta (β) and gamma (γ) secretases hydrolyzed amyloid precursor protein (APP) to produce Aβ, which then clumps together to form Aβ fibrils. The fibrils increase oxidative stress, inflammatory cascade, and caspase activation to cause hyperphosphorylation of tau protein into neurofibrillary tangles (NFTs), which ultimately lead to neuronal damage. Acetylcholine (Ach) degradation is accelerated by upstream regulation of the acetylcholinesterase (AChE) enzyme, which leads to a deficiency in neurotransmitters and cognitive impairment. There are presently no efficient or disease-modifying medications for AD. It is necessary to advance AD research to suggest novel compounds for treatment and prevention. Prospectively, it might be reasonable to conduct clinical trials with unclean medicines that have a range of effects, including anti-amyloid and anti-tau, neurotransmitter modulation, anti-neuroinflammatory, neuroprotective, and cognitive enhancement.

Role of Alginate Composition on Copper Ion Uptake in the Presence of Histidine or Beta-Amyloid

The anomalous interaction between metal ions and the peptide beta-amyloid is one of the hallmarks of Alzheimer's disease. Metal-binding biopolymers, including polysaccharides, can elucidate the fundamental aspects of metal ions' interactions with biological tissue and their interplay in Alzheimer's disease. This work focuses on the role of the alginate composition on Cu(II) adsorption in the presence of histidine or β-amyloid, the peptide associated with the progression of Alzheimer's disease. Alginate samples with different mannuronic/guluronic (M/G) ratios led to similar Cu(II) adsorption capacities, following the Langmuir isotherm and the pseudo-second-order adsorption kinetic models. Although the presence of histidine produced up to a 20% reduction in the copper adsorption capacity in guluronic-rich alginate samples (M/G~0.61), they presented stable bidentate chelation of the metallic ion. Chemical analyses (FTIR and XPS) demonstrated the role of hydroxyl and carboxyl groups in copper ion chelation, whereas both crystallinity and morphology analyses indicated the prevalence of histidine interaction with guluronic-rich alginate. Similar results were observed for Cu(II) adsorption in alginate beads in the presence of beta-amyloid and histidine, suggesting that the alginate/histidine system is a simple yet representative model to probe the application of biopolymers to metal ion uptake in the presence of biological competitors.

Estropause, Sex Hormones and Metal Homeostasis in the Mouse Brain

Alterations in brain metal ion homeostasis have been reported with aging and are implicated in the pathogenesis of neurodegenerative diseases. To assess whether age-related changes in hypothalamic-pituitary-gonadal (HPG) hormones might be involved in modulating brain metal ion homeostasis, we treated 7.5-month intact, sham-ovariecomized and ovariectomized C57B6SJL mice with vehicle or leuprolide acetate (for 9-months) to differentiate between whether sex steroids or gonadotropins might modulate brain metal ion concentrations. Unlike other aging mammals, there was no increase in plasma luteinizing hormone (LH) and follicle-stimulating hormone (FSH) concentrations following estropause in mice, suggesting there was sufficient residual production by the follicle depleted ovary, of sex steroids like estrogens and protein hormones like the inhibins, in order to suppress pituitary LH/FSH production. Castration on the other hand induced significant increases in circulating LH and FSH. Modulation of plasma sex steroid and gonadotropin levels did not significantly alter the concentrations of brain metals tested (Fe, Zn, Cu, Mn, Co, Ni, Al, Li), although there was a tendency for a decrease in all brain metals following ovariectomy (low estrogens and progesterone, high gonadotropins), a response that was reversed with leuprolide acetate treatment (low sex steroids, low gonadotropins). Brain Cu concentration was the only metal correlated with plasma LH (−0.37, n = 30, p < 0.05) and FSH (−0.42, n = 29, p < 0.01). This study demonstrates that sex hormones do not markedly alter brain metal ion homeostasis, unlike previously reported studies of circulating metal ion homeostasis. The role of gonadotropins in regulating metal ion homeostasis does however warrant further study.

Novel Amylin Analogues Reduce Amyloid-β Cross-Seeding Aggregation and Neurotoxicity

BACKGROUND

Type 2 diabetes related human islet amyloid polypeptide (hIAPP) plays a dual role in Alzheimer's disease (AD). hIAPP has neuroprotective effects in AD mouse models whereas, high hIAPP concentrations can promote co-aggregation with amyloid-β (Aβ) to promote neurodegeneration. In fact, both low and high plasma hIAPP concentration has been associated with AD. Therefore, non-aggregating hIAPP analogues have garnered interest as a treatment for AD. The aromatic amino acids F23 and I26 in hIAPP have been identified as the key residues involved in self-aggregation and Aβ cross-seeding.

OBJECTIVE

Three novel IAPP analogues with single and double alanine mutations (A1 = F23, A2 = I26, and A3 = F23 + I26) were assessed for their ability to aggregate, modulate Aβ oligomer formation, and alter neurotoxicity.

METHODS

A range of biophysical methods including Thioflavin-T, gel electrophoresis, photo-crosslinking, circular dichroism combined with cell viability assays were utilized to assess protein aggregation and toxicity.

RESULTS

All IAPP analogues showed significantly less self-aggregation than hIAPP. Co-aggregated Aβ 42-A2 and A3 also showed reduced aggregation compared to Aβ 42-hIAPP mixtures. Self- and co-oligomerized A1, A2, and A3 exhibited random coil conformations with reduced beta sheet content compared to hIAPP and Aβ 42-hIAPP aggregates. A1 was toxic at high concentrations compared to A2 and A3. However, co-aggregated Aβ 42-A1, A2, or A3 showed reduced neurotoxicity compared to Aβ 42, hIAPP, and Aβ 42-hIAPP aggregates.

CONCLUSION

These findings confirm that hIAPP analogues with non-aromatic residues at positions 23 and 26 have reduced self-aggregation and the ability to neutralize Aβ 42 toxicity. This warrants further characterization of their protective effects in pre-clinical AD models.

Early Cellular, Molecular, Morphological and Behavioral Changes in the Humanized Amyloid-Beta-Knock-In Mouse Model of Late-Onset Alzheimer's Disease

The purpose of our study is to investigate early cellular, molecular, morphological and behavioral changes in humanized amyloid-beta-knock-in (hAbKI) mice. Using seven-month-old homozygous hAbKI mice, we studied behavioral phenotype parameters, including spatial learning and memory (Morris Water Maze), locomotor activity (open field), working memory (Y-maze) and motor coordination (rotarod); mRNA abundance, protein levels, soluble amyloid-beta 40 and 42 levels and regional immunoreactivities of key markers of mitochondrial dynamics, mitochondrial biogenesis, synaptic health, mitophagy and autophagy; mitochondrial function and using transmission electron microscopy & Golgi–Cox staining, we assessed mitochondrial morphology and dendritic spines. Our extensive behavioral analysis revealed that seven-month-old hAbKI mice showed impairments in motor coordination, reduced locomotor and exploration activities, impairments in working memory and spatial learning and memory. Our mRNA and protein analyses revealed the increased expression of mitochondrial-fission genes and reduced expression of mitochondrial-fusion, mitochondrial-biogenesis, synaptic, autophagy and mitophagy genes in seven-month-old hAbKI mice. An immunofluorescence analysis revealed altered immunoreactivities and agreed with the immunoblot results. Transmission-electron-microscopy data revealed increased mitochondrial fragmentation and reduced mitochondrial length in both hippocampal and cortical tissues of seven-month-old hAbKI mice and mitochondrial function defective. A Golgi–Cox-staining analysis revealed reduced dendritic spines in both cerebral cortices and hippocampi of hAbKI mice. Soluble amyloid-beta (1–40 and 1–42) were detected in three-month-old hAbKI mice and progressively increased in seven-month-old mice. These observations suggest that the human amyloid-beta peptide is sufficient to cause behavioral, mitochondrial, synaptic and ultrastructural changes in seven-month-old hAbKI mice. Our study findings also suggest that hAbKI mice might serve as a model for preclinical studies of preventive therapies.

Mechanical Stretching-Induced Traumatic Brain Injury Is Mediated by the Formation of GSK-3β-Tau Complex to Impair Insulin Signaling Transduction

Traumatic brain injury confers a significant and growing public health burden. It is a major environmental risk factor for dementia. Nonetheless, the mechanism by which primary mechanical injury leads to neurodegeneration and an increased risk of dementia-related diseases is unclear. Thus, we aimed to investigate the effect of stretching on SH-SY5Y neuroblastoma cells that proliferate in vitro. These cells retain the dopamine-β-hydroxylase activity, thus being suitable for neuromechanistic studies. SH-SY5Y cells were cultured on stretchable membranes. The culture conditions contained two groups, namely non-stretched (control) and stretched. They were subjected to cyclic stretching (6 and 24 h) and 25% elongation at 1 Hz. Following stretching at 25% and 1 Hz for 6 h, the mechanical injury changed the mitochondrial membrane potential and triggered oxidative DNA damage at 24 h. Stretching decreased the level of brain-derived neurotrophic factors and increased amyloid-β, thus indicating neuronal stress. Moreover, the mechanical injury downregulated the insulin pathway and upregulated glycogen synthase kinase 3β (GSK-3β)^S9/p-Tau protein levels, which caused a neuronal injury. Following 6 and 24 h of stretching, GSK-3β^S9 was directly bound to p-Tau^S396. In contrast, the neuronal injury was improved using GSK-3β inhibitor TWS119, which downregulated amyloid-β/p-Taus396 phosphorylation by enhancing ERK1/2T202/Y204 and AktS473 phosphorylation. Our findings imply that the neurons were under stress and that the inactivation of the GSK3β could alleviate this defect.

Aβ monomers protect lens epithelial cells against oxidative stress by upregulating CDC25B

Our previous studies showed high β-amyloid (Aβ) expression levels in the nuclei of the lens epithelial cells (LECs) of healthy subjects and revealed that Aβ monomers could protect LECs from oxidative damage. Here, we further explored the mechanism by which Aβ monomers act as transcription factors to regulate the oxidative stress of LECs through high-throughput studies. First, we compared the Aβ-binding sites in the lens epithelia (LE) of age-related cataract patients with those in the LE of healthy donors via chromatin immunoprecipitation-sequencing (ChIP-seq), and we identified comparable numbers (1648 and 1445, respectively) of Aβ peaks. Then, the KEGG tool was used for gene function enrichment analysis of these genes, which were more highly enriched in healthy LE. Combining the literature review with these KEGG analysis results, in the current study, we chose four target genes related to oxidative stress, namely, CDC25B, SOS2, CTNNA1 and Cox6a1. Then, ChIP-PCR assays, dual-luciferase reporter assays, real-time PCR and Western blotting were performed to validate the regulatory effects of Aβ on these targets. Our data suggested that Aβ monomers could upregulate the mRNA and protein expression levels of CDC25B in LECs. We also confirmed that Aβ monomers could activate the Akt/Nrf2 pathway in a CDC25B-dependent manner by knockdown experiments in cultured LECs. Furthermore, we performed functional verification of the CDC25B-mediated protective effects of Aβ monomers against oxidative stress. We observed that Aβ monomers significantly improved the antioxidant capacity (the GSH level, SOD activity and total antioxidant capacity) and decreased the oxidative stress (the ROS and MDA levels) of LECs, while CDC25B knockdown decreased the antioxidant effects of Aβ, disrupting redox homeostasis. Therefore, we propose that Aβ monomers activate the Akt/Nrf2 pathway by upregulating CDC25B expression, increase various downstream antioxidant enzyme levels, maintain peroxidation-antioxidant homeostasis in LECs, and prevent the cell damage caused by oxidative stress.

A Primer on the Evolution of Aducanumab: The First Antibody Approved for Treatment of Alzheimer's Disease

Alzheimer's disease (AD) is the most common form of dementia with global burden projected to triple by 2050. It incurs significant biopsychosocial burden worldwide with limited treatment options. Aducanumab is the first monoclonal antibody recently approved by the US-FDA for mild AD through the accelerated approval pathway. It is the first molecule to be approved for AD since 2003 and carries with it a therapeutic promise for the future. As the definition of AD has evolved from a pathological entity to a Clinico-biological construct over the years, the amyloid-β (Aβ) pathway has been increasingly implicated in its pathogenesis. The approval of Aducanumab is based on reduction of the Aβ load in the brain, which forms a surrogate marker for this pathway. The research populace has, however, been globally divided by skepticism and hope regarding this approval. Failure to meet clinical endpoints in the trials, alleged transparency issues, cost-effectiveness, potential adverse effects, need for regular monitoring, and critique of 'amyloid cascade hypothesis' itself are the main caveats concerning the antibody. With this controversy in background, this paper critically looks at antibody research in AD therapeutics, evidence, and evolution of Aducanumab as a drug and the potential clinical implications of its use in future. While the efficacy of this monoclonal antibody in AD stands as a test of time, based on the growing evidence it is vital to rethink and explore alternate pathways of pathogenesis (oxidative stress, neuroinflammation, cholesterol metabolism, vascular factors, etc.) as possible therapeutic targets that may help elucidate the enigma of this complex yet progressive and debilitating neurodegenerative disorder.

Chromone derivatives bearing pyridinium moiety as multi-target-directed ligands against Alzheimer's disease

A new serise of 7-hydroxy-chromone derivatives bearing pyridine moiety were synthesized, and evaluated as multifunctional agents against Alzheimer's disease (AD). Most of the compounds were good AChE inhibitors (IC₅₀ = 9.8-0.71 µM) and showed remarkable BuChE inhibition activity (IC₅₀ = 1.9-0.006 µM) compared with donepezil as the standard drug (IC₅₀ = 0.023 and 3.4 µM). Compounds 14 and 10 showed the best inhibitory activity toward AChE (IC₅₀ = 0.71 µM) and BuChE (IC₅₀ = 0.006 µM), respectively. The ligand-protein docking simulations and kinetic studies revealed that compound 14 and 10 could bind effectively to the peripheral anionic binding site (PAS) of the AChE and BuChE through mixed-type inhibition. In addition, the most potent compounds showed acceptable neuroprotective activity on H₂O₂- and Aβ-induced .neurotoxicity in PC12 cells, more than standard drugs. The compounds could block effectively self- and AChE-induced Aβ aggregation. All the results suggest that compounds 14 and 10 could be considered as promising multi-target-directed ligands against AD.

((E)-N-(4-(((2-Amino-5-phenylpyridin-3-yl)imino)methyl)pyridin-2-yl)cyclopropanecarboxamide) Ameliorated Aβ1-42-Induced Alzheimer's Disease in SD Rats by Inhibiting Oxidative Stress and Apoptosis

Our study investigated the protective effects of ((E)-N-(4-(((2-amino-5-phenylpyridin-3-yl)imino)methyl)pyridin-2-yl)cyclopropanecarboxamide) 9b, a novel glycogen synthase kinase-3β (GSK-3β) inhibitor, on the learning and memory function of rats with amyloid-β_1-42 (Aβ_1-42)-induced Alzheimer's disease (AD) and explored the possible mechanisms. Sixty male Sprague-Dawley (SD) rats were randomly divided into five groups: the control, Aβ, donepezil, and low-dose and high-dose 9b groups. The rats in the Aβ, donepezil, and two 9b intervention groups received a single microinjection of 10 μg of Aβ_1-42 into the hippocampus followed by intragastric administration of 0.5% sodium carboxymethyl cellulose (CMC-Na), 12 (mg/kg)/d donepezil hydrochloride and 6 or 18 (mg/kg)/d compound 9b for 28 days, while the rats in the control group were treated with the vehicles. Learning and memory impairment were attenuated, the activities of superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), acetylcholinesterase (AChE), and adenosine triphosphatase (ATPase) in the brain tissue were significantly increased (p < 0.05), and the concentrations of Aβ_1-42, phospho-tau (p-tau), and malondialdehyde (MDA) in the brain tissue were significantly decreased (p < 0.05) in the compound 9b group compared to the Aβ group. In addition, compound 9b regulated the imbalance in the concentrations of neurotransmitters and alleviated severe damage and apoptosis in the brains of the rats exposed to Aβ_1-42. The novel GSK-3β inhibitor 9b could improve learning and memory dysfunction caused by Aβ_1-42 through its antioxidant and antiapoptotic effects.

The Neuromelanin Paradox and Its Dual Role in Oxidative Stress and Neurodegeneration

Aging is associated with an increasing dysfunction of key brain homeostasis mechanisms and represents the main risk factor across most neurodegenerative disorders. However, the degree of dysregulation and the affectation of specific pathways set apart normal aging from neurodegenerative disorders. In particular, the neuronal metabolism of catecholaminergic neurotransmitters appears to be a specifically sensitive pathway that is affected in different neurodegenerations. In humans, catecholaminergic neurons are characterized by an age-related accumulation of neuromelanin (NM), rendering the soma of the neurons black. This intracellular NM appears to serve as a very efficient quencher for toxic molecules. However, when a neuron degenerates, NM is released together with its load (many undegraded cellular components, transition metals, lipids, xenobiotics) contributing to initiate and worsen an eventual immune response, exacerbating the oxidative stress, ultimately leading to the neurodegenerative process. This review focuses on the analysis of the role of NM in normal aging and neurodegeneration related to its capabilities as an antioxidant and scavenging of harmful molecules, versus its involvement in oxidative stress and aberrant immune response, depending on NM saturation state and its extracellular release.

Beta-amyloid peptides(1-42) and (1-40) in the cerebrospinal fluid during pregnancy: a prospective observational study

To evaluate changes in concentrations of selected biomarkers, neurotrophic factors, and growth factors in the cerebrospinal fluid during pregnancy. A prospective observational study was conducted in 32 pregnant women undergoing gynecological and obstetrical surgery under spinal anesthesia in a university hospital. Beta-amyloid(1-42) and beta-amyloid(1-40) peptides, brain-derived neurotrophic factor, glial cell line-derived neurotrophic factor, and vascular endothelial growth factor were analyzed in cerebrospinal fluid using an enzyme-linked immunosorbent assay. Eight women in second trimester pregnancy who underwent spinal anesthesia for gynecological or obstetrical surgery were compared with 24 matched women in third trimester pregnancies. CSF concentrations of beta-amyloid(1-42) were significantly higher in third trimester pregnancies (p = 0.025). During third trimester, the beta-amyloid ratio correlated with the vascular endothelial growth factor (r_s = 0.657; p = 0.008). Higher concentrations of beta-amyloid(1-42) in cerebrospinal fluid of third trimester pregnancies and correlations between the beta-amyloid ratio and the vascular endothelial growth factor support the hypothesis that beta-amyloid peptides are involved in complex adaptive brain alterations during pregnancy.

Extracellular Amyloid Deposits in Alzheimer's and Creutzfeldt-Jakob Disease: Similar Behavior of Different Proteins?

Neurodegenerative diseases are characterized by the deposition of specific protein aggregates, both intracellularly and/or extracellularly, depending on the type of disease. The extracellular occurrence of tridimensional structures formed by amyloidogenic proteins defines Alzheimer's disease, in which plaques are composed of amyloid β-protein, while in prionoses, the same term "amyloid" refers to the amyloid prion protein. In this review, we focused on providing a detailed didactic description and differentiation of diffuse, neuritic, and burnt-out plaques found in Alzheimer's disease and kuru-like, florid, multicentric, and neuritic plaques in human transmissible spongiform encephalopathies, followed by a systematic classification of the morphological similarities and differences between the extracellular amyloid deposits in these disorders. Both conditions are accompanied by the extracellular deposits that share certain signs, including neuritic degeneration, suggesting a particular role for amyloid protein toxicity.

Activate or Inhibit? Implications of Autophagy Modulation as a Therapeutic Strategy for Alzheimer's Disease

Neurodegenerative diseases result in a range of conditions depending on the type of proteinopathy, genes affected or the location of the degeneration in the brain. Proteinopathies such as senile plaques and neurofibrillary tangles in the brain are prominent features of Alzheimer’s disease (AD). Autophagy is a highly regulated mechanism of eliminating dysfunctional organelles and proteins, and plays an important role in removing these pathogenic intracellular protein aggregates, not only in AD, but also in other neurodegenerative diseases. Activating autophagy is gaining interest as a potential therapeutic strategy for chronic diseases featuring protein aggregation and misfolding, including AD. Although autophagy activation is a promising intervention, over-activation of autophagy in neurodegenerative diseases that display impaired lysosomal clearance may accelerate pathology, suggesting that the success of any autophagy-based intervention is dependent on lysosomal clearance being functional. Additionally, the effects of autophagy activation may vary significantly depending on the physiological state of the cell, especially during proteotoxic stress and ageing. Growing evidence seems to favour a strategy of enhancing the efficacy of autophagy by preventing or reversing the impairments of the specific processes that are disrupted. Therefore, it is essential to understand the underlying causes of the autophagy defect in different neurodegenerative diseases to explore possible therapeutic approaches. This review will focus on the role of autophagy during stress and ageing, consequences that are linked to its activation and caveats in modulating this pathway as a treatment.

Neuroprotective Effects of the Amylin Analog, Pramlintide, on Alzheimer's Disease Are Associated with Oxidative Stress Regulation Mechanisms

Administration of the recombinant analog of the pancreatic amyloid amylin, Pramlintide, has shown therapeutic benefits in aging and Alzheimer's disease (AD) models, both on cognition and amyloid-β (Aβ) pathology. However, the neuroprotective mechanisms underlying the benefits of Pramlintide remain unclear. Given the early and critical role of oxidative stress in AD pathogenesis and the known reactive oxygen species (ROS) modulating function of amyloids, we sought to determine whether Pramlintide's neuroprotective effects involve regulation of oxidative stress mechanisms. To address this, we treated APP/PS1 transgenic mice with Pramlintide for 3 months, starting at 5.5 months prior to widespread AD pathology onset, and measured cognition (Morris Water Maze), AD pathology, and oxidative stress-related markers and enzymes in vivo. In vitro, we determined the ability of Pramlintide to modulate H2O2-induced oxidative stress levels. Our data show that Pramlintide improved cognitive function, altered amyloid-processing enzymes, reduced plaque burden in the hippocampus, and regulated endogenous antioxidant enzymes (MnSOD and GPx1) and the stress marker HO-1 in a location specific manner. In vitro, Pramlintide treatment in neuronal models reduced H2O2-induced endogenous ROS production and lipid peroxidation in a dose-dependent manner. Together, these results indicate that Pramlintide's benefits on cognitive function and pathology may involve antioxidant-like properties of this compound.

Molecular Spectroscopic Markers of Abnormal Protein Aggregation

Abnormal protein aggregation has been intensively studied for over 40 years and broadly discussed in the literature due to its significant role in neurodegenerative diseases etiology. Structural reorganization and conformational changes of the secondary structure upon the aggregation determine aggregation pathways and cytotoxicity of the aggregates, and therefore, numerous analytical techniques are employed for a deep investigation into the secondary structure of abnormal protein aggregates. Molecular spectroscopies, including Raman and infrared ones, are routinely applied in such studies. Recently, the nanoscale spatial resolution of tip-enhanced Raman and infrared nanospectroscopies, as well as the high sensitivity of the surface-enhanced Raman spectroscopy, have brought new insights into our knowledge of abnormal protein aggregation. In this review, we order and summarize all nano- and micro-spectroscopic marker bands related to abnormal aggregation. Each part presents the physical principles of each particular spectroscopic technique listed above and a concise description of all spectral markers detected with these techniques in the spectra of neurodegenerative proteins and their model systems. Finally, a section concerning the application of multivariate data analysis for extraction of the spectral marker bands is included.

Cross-talk between redox signalling and protein aggregation

It is well established that both an increase in reactive oxygen species (ROS: i.e. O2•-, H2O2 and OH•), as well as protein aggregation, accompany ageing and proteinopathies such as Parkinson's and Alzheimer's disease. However, it is far from clear whether there is a causal relation between the two. This review describes how protein aggregation can be affected both by redox signalling (downstream of H2O2), as well as by ROS-induced damage, and aims to give an overview of the current knowledge of how redox signalling affects protein aggregation and vice versa. Redox signalling has been shown to play roles in almost every step of protein aggregation and amyloid formation, from aggregation initiation to the rapid oligomerization of large amyloids, which tend to be less toxic than oligomeric prefibrillar aggregates. We explore the hypothesis that age-associated elevated ROS production could be part of a redox signalling-dependent-stress response in an attempt to curb protein aggregation and minimize toxicity.

Acetylation of Aβ42 at Lysine 16 Disrupts Amyloid Formation

The residue lysine 28 (K28) is known to form an important salt bridge that stabilizes the Aβ amyloid structure, and acetylation of lysine 28 (K28Ac) slows the Aβ42 fibrillization rate but does not affect fibril morphology. On the other hand, acetylation of lysine 16 (K16Ac) residue greatly diminishes the fibrillization property of Aβ42 peptide and also affects its toxicity. This is due to the fact that lysine 16 acetylated amyloid beta peptide forms amorphous aggregates instead of amyloid fibrils. This is likely a result of increased hydrophobicity of the K16-A21 region due to K16 acetylation, as confirmed by molecular dynamic simulation studies. The calculated results show that the hydrophobic patches of aggregates from acetylated peptides were different when compared to wild-type (WT) peptide. K16Ac and double acetylated (KKAc) peptide aggregates show significantly higher cytotoxicity compared to the WT or K28Ac peptide aggregates alone. However, the heterogeneous mixture of WT and acetylated Aβ42 peptide aggregates exhibited higher free radical formation as well as cytotoxicity, suggesting dynamic interactions between different species could be a critical contributor to Aβ pathology.

Simultaneous exposure to noise and carbon monoxide increases the risk of Alzheimer's disease: a literature review

Dementia is a syndrome of cognitive and functional decline, commonly occurring in later life as a result of neurodegenerative and cerebrovascular processes beginning earlier in the life course. An excess of free radicals has an essential role in neurodegenerative diseases and aging. This paper aims to review the effects of noise and carbon monoxide as a risk factor in Alzheimer's disease as well as the role of free radicals in the progress of Alzheimer's disease. Articles included in this review were identified through a search of the databases PubMed, Scopus, and Google Scholar using the search terms Alzheimer's disease, dementia, noise, reactive oxygen species, and Carbon Monoxide. The literature search was restricted to the years 1982 to 2020 and articles published in the English language. The metabolism rate of the body is very high when exposed to noise and carbon monoxide; this leads to overproduction of reactive oxygen species and oxidative stress conditions. Oxidative stress has an essential role in the mechanisms concerned in Alzheimer's disease. In addition to the consequences of noise and a chemical substance on the auditory system, they also have non-auditory effects that affect the brain and induced neurodegenerative disease.

The Microbiota-Gut-Brain Axis-Heart Shunt Part II: Prosaic Foods and the Brain-Heart Connection in Alzheimer Disease

There is a strong cerebrovascular component to brain aging, Alzheimer disease, and vascular dementia. Foods, common drugs, and the polyphenolic compounds contained in wine modulate health both directly and through the gut microbiota. This observation and novel findings centered on nutrition, biochemistry, and metabolism, as well as the newer insights we gain into the microbiota-gut-brain axis, now lead us to propose a shunt to this classic triad, which involves the heart and cerebrovascular systems. The French paradox and prosaic foods, as they relate to the microbiota-gut-brain axis and neurodegenerative diseases, are discussed in this manuscript, which is the second part of a two-part series of concept papers addressing the notion that the microbiota and host liver metabolism all play roles in brain and heart health.

Disruption of Exocytosis in Sympathoadrenal Chromaffin Cells from Mouse Models of Neurodegenerative Diseases

Synaptic disruption and altered neurotransmitter release occurs in the brains of patients and in murine models of neurodegenerative diseases (NDDs). During the last few years, evidence has accumulated suggesting that the sympathoadrenal axis is also affected as disease progresses. Here, we review a few studies done in adrenal medullary chromaffin cells (CCs), that are considered as the amplifying arm of the sympathetic nervous system; the sudden fast exocytotic release of their catecholamines—stored in noradrenergic and adrenergic cells—plays a fundamental role in the stress fight-or-flight response. Bulk exocytosis and the fine kinetics of single-vesicle exocytotic events have been studied in mouse models carrying a mutation linked to NDDs. For instance, in R6/1 mouse models of Huntington’s disease (HD), mutated huntingtin is overexpressed in CCs; this causes decreased quantal secretion, smaller quantal size and faster kinetics of the exocytotic fusion pore, pore expansion, and closure. This was accompanied by decreased sodium current, decreased acetylcholine-evoked action potentials, and attenuated [Ca²⁺]c transients with faster Ca²⁺ clearance. In the SOD1^G93A mouse model of amyotrophic lateral sclerosis (ALS), CCs exhibited secretory single-vesicle spikes with a slower release rate but higher exocytosis. Finally, in the APP/PS1 mouse model of Alzheimer’s disease (AD), the stabilization, expansion, and closure of the fusion pore was faster, but the secretion was attenuated. Additionally, α-synuclein that is associated with Parkinson’s disease (PD) decreases exocytosis and promotes fusion pore dilation in adrenal CCs. Furthermore, Huntington-associated protein 1 (HAP1) interacts with the huntingtin that, when mutated, causes Huntington’s disease (HD); HAP1 reduces full fusion exocytosis by affecting vesicle docking and controlling fusion pore stabilization. The alterations described here are consistent with the hypothesis that central alterations undergone in various NDDs are also manifested at the peripheral sympathoadrenal axis to impair the stress fight-or-flight response in patients suffering from those diseases. Such alterations may occur: (i) primarily by the expression of mutated disease proteins in CCs; (ii) secondarily to stress adaptation imposed by disease progression and the limitations of patient autonomy.

Oxidative stress in alzheimer's disease: A review on emergent natural polyphenolic therapeutics

OBJECTIVES

The aim of this research was to review the literature on Alzheimer's disease (AD) with a focus on polyphenolics as antioxidant therapeutics.

DESIGN

This review included a search of the literature up to and including September 2019 in PubMed and MEDLINE databases using search terms that included: Alzheimer's Disease, Aβ peptide, tau, oxidative stress, redox, oxidation, therapeutic, antioxidant, natural therapy, polyphenol. Any review articles, case studies, research reports and articles in English were identified and subsequently interrogated. Citations within relevant articles were also examined for consideration in this review.

RESULTS

Alzheimer's disease is a neurodegenerative disorder that is clinically characterised by the progressive deterioration of cognitive functions and drastic changes in behaviour and personality. Due to the significant presence of oxidative damage associated with abnormal Aβ accumulation and neurofibrillary tangle deposition in AD patients' brains, antioxidant drug therapy has been investigated as potential AD treatment. In particular, naturally occurring compounds, such as plant polyphenols, have been suggested to have potential neuroprotective effects against AD due to their diverse array of physiological actions, which includes potent antioxidant effects.

CONCLUSIONS

The impact of oxidative stress and various mechanisms of pathogenesis in AD pathophysiology was demonstrated along with the therapeutic potential of emergent antioxidant drugs to address such mechanism of oxidation.

Leveraging the interplay of nanotechnology and neuroscience: Designing new avenues for treating central nervous system disorders

Nanotechnology has the potential to open many novel diagnostic and treatment avenues for disorders of the central nervous system (CNS). In this review, we discuss recent developments in the applications of nanotechnology in CNS therapies, diagnosis and biology. Novel approaches for the diagnosis and treatment of neuroinflammation, brain dysfunction, psychiatric conditions, brain cancer, and nerve injury provide insights into the potential of nanomedicine. We also highlight nanotechnology-enabled neuroscience techniques such as electrophysiology and intracellular sampling to improve our understanding of the brain and its components. With nanotechnology integrally involved in the advancement of basic neuroscience and the development of novel treatments, combined diagnostic and therapeutic applications have begun to emerge. Nanotheranostics for the brain, able to achieve single-cell resolution, will hasten the rate in which we can diagnose, monitor, and treat diseases. Taken together, the recent advances highlighted in this review demonstrate the prospect for significant improvements to clinical diagnosis and treatment of a vast array of neurological diseases. However, it is apparent that a strong dialogue between the nanoscience and neuroscience communities will be critical for the development of successful nanotherapeutics that move to the clinic, benefit patients, and address unmet needs in CNS disorders.

Multiple Antigenic Peptide System Coupled with Amyloid Beta Protein Epitopes As An Immunization Approach to Treat Alzheimer's Disease

Latest studies suggest that Alzheimer's disease (AD) is one of the "four big killers" that threaten the health of the elderly. AD affects about 46 million people across the world, and there is a critical need for research on new therapies for treating AD. The purpose of the present study was to develop and evaluate immunogens to elicit antibodies against the formation of amyloid beta protein (Aβ), a pathological hallmark of AD, as a therapeutic strategy in AD. In this study, serial potential immunogenic epitopes were screened according to the Aβ sequence. The screened linear epitopes on the Aβ C-terminal fragment were coupled with either the carrier protein keyhole limpet hemocyanin (KLH) or the synthesized 4-branch peptide (MAP₄). MAP₄ immunogens could effectively elicit immunogenicity against Aβ_1-42 monomer and fiber in Balb/C mice. Furthermore, MAP₄ sera could also effectively inhibit the formation of the Aβ_1-42 fiber. Interestingly, one of the MAP₄ sera was able to depolymerize the Aβ_1-42 fibers that had aggregated. The monoclonal antibody, 1H7, was shown to inhibit the formation of Aβ_1-42 fiber. MAP₄ carrier may provide benefits over current immunization strategies, as it does not induce inflammation. In conclusion, the MAP₄-Aβ conjugates offer a promising approach for the development of a safe and effective AD vaccine.

Modelling mitochondrial dysfunction in Alzheimer’s disease using human induced pluripotent stem cells

Alzheimer’s disease (AD) is the most common form of dementia. To date, only five pharmacological agents have been approved by the Food and Drug Administration for clinical use in AD, all of which target the symptoms of the disease rather than the cause. Increasing our understanding of the underlying pathophysiology of AD will facilitate the development of new therapeutic strategies. Over the years, the major hypotheses of AD etiology have focused on deposition of amyloid beta and mitochondrial dysfunction. In this review we highlight the potential of experimental model systems based on human induced pluripotent stem cells (iPSCs) to provide novel insights into the cellular pathophysiology underlying neurodegeneration in AD. Whilst Down syndrome and familial AD iPSC models faithfully reproduce features of AD such as accumulation of Aβ and tau, oxidative stress and mitochondrial dysfunction, sporadic AD is much more difficult to model in this way due to its complex etiology. Nevertheless, iPSC-based modelling of AD has provided invaluable insights into the underlying pathophysiology of the disease, and has a huge potential for use as a platform for drug discovery.

Emerging Role of microRNAs in Dementia

MicroRNAs are small non-coding RNAs regulating mRNA translation. They play a crucial role in regulating homeostasis in neurons, especially in regulating local and stimulation dependent protein synthesis. Since activity-mediated protein synthesis in neurons is critical for memory and cognition, microRNAs have become key players in modulating these processes. Dementia is a broad term used for symptoms involving decline of memory and cognition. Several studies have implicated the dysregulation of microRNAs in many brain diseases like neurodegenerative diseases, neurodevelopmental disorders, brain injuries and dementia. In this review, we give an overview of microRNA-mediated regulation of proteins and cellular processes affected in dementia pathology, hence illustrating the importance of microRNAs in normal functioning. We also focus on a relatively less explored area in dementia pathology-the importance of activity-mediated protein synthesis at the synapse and the role of microRNAs in modulating this. Overall, this review will be helpful in looking at the significance of microRNAs in dementia from the perspective of defective regulation of protein synthesis and synaptic dysfunction.

A Unified View of Assessing the Pro-oxidant versus Antioxidant Nature of Amyloid Beta Conformers

Transition-metal-catalyzed oxidative stress is a widespread concern in the pathogenesis of Alzheimer's disease. However, the exact role of amyloid beta oligomers towards oxidative stress is widely debated. Assessing the oxidative nature of the oligomers in vitro is complicated by the different experimental conditions under which they are prepared. We have investigated Cu²⁺ -catalyzed reactive oxygen species (ROS) generation by using oligomers prepared in phosphate-buffered saline (Aβ^O-PBS ) and in cell culture medium (Aβ^O-CCM ), and compared their activities with respect to the monomers and fibrils prepared at neutral and acidic pH. Although both are deca- to dodecamers, the Aβ^O-PBS oligomers have a spherical morphology and are smaller than the Aβ^O-CCM . The Aβ^O-PBS behaved as pro-oxidants; in contrast, Aβ^O-CCM quench OH^. generation attributed to CCM itself. Although the pro-oxidant oligomers showed oxidation, they also partially protect themselves from radical damage and maintain their overall spherical arrangement. The monomers and fibrils manifested antioxidant properties: radical scavenging as opposed to redox silencing. A dual role of Aβ species depending on the stage of the disease is proposed. In the earlier stages, the monomers can act as antioxidants, whereas at the later stages, the oligomers take on a pro-oxidant role. Kaempferol, a natural flavonoid, bound Cu²⁺ in 2:1 ratio and abolished ROS production in all Aβ species. It also distinctly modified the folding landscape of Aβ species into new or altered morphologies.

Recent advancements toward therapeutic vaccines against Alzheimer's disease

INTRODUCTION

Alzheimer's disease (AD) is a devastating neurodegenerative disease characterized by protein aggregates of amyloid β (Aβ) and tau. These proteins have normal physiological functions, but in AD, they undergo a conformational change and aggregate as toxic oligomeric and fibrillar species with a high β-sheet content.

AREAS COVERED

Active and passive immunotherapeutic approaches are among the most attractive methods for targeting misfolded Aβ and tau. Promising preclinical testing of various immunotherapeutic approaches has yet to translate to cognitive benefits in human clinical trials. Knowledge gained from these past failures has led to the development of second-generation Aβ-active immunotherapies, anti-Aβ monoclonal antibodies targeting a wide array of Aβ conformations, and to a number of immunotherapies targeting pathological tau. This review covers the more recent advances in vaccine development for AD from 2016 to present.

EXPERT COMMENTARY

Due to the complex pathophysiology of AD, greatest clinical efficacy will most likely be achieved by concurrently targeting the most toxic forms of both Aβ and tau.

Unraveling the Burden of Iron in Neurodegeneration: Intersections with Amyloid Beta Peptide Pathology

Iron overload is a hallmark of many neurodegenerative processes such as Alzheimer's, Parkinson's, and Huntington's diseases. Unbound iron accumulated as a consequence of brain aging is highly reactive with water and oxygen and produces reactive oxygen species (ROS) or free radicals. ROS are toxic compounds able to damage cell membranes, DNA, and mitochondria. Which are the mechanisms involved in neuronal iron homeostasis and in neuronal response to iron-induced oxidative stress constitutes a cutting-edge topic in metalloneurobiology. Increasing our knowledge about the underlying mechanisms that operate in iron accumulation and their consequences would shed light on the comprehension of the molecular events that participate in the pathophysiology of the abovementioned neurodegenerative diseases. In this review, current evidences about iron accumulation in the brain, the signaling mechanisms triggered by metal overload, as well as the interaction between amyloid β (Aβ) and iron, will be summarized.

Amyloid Beta Peptide VHHQ, KLVFF, and IIGLMVGGVV Domains Involved in Fibrilization: AFM and Electrochemical Characterization

The time-dependent structural modifications and oxidation behavior of specifically chosen five short amyloid beta (Aβ) peptides, Aβ_1-16, Aβ_1-28, Aβ_10-20, Aβ_12-28, and Aβ_17-42, fragments of the complete human Aβ_1-40 peptide, were investigated by atomic force microscopy (AFM) and voltammetry. The objective was to determine the influence of different Aβ domains (VHHQ that contains electroactive histidine H residues, KLVFF that is the peptide hydrophobic aggregation core, and IIGLMVGGVV that is the C-terminus hydrophobic region), and of Aβ peptide hydrophobicity, in the fibrilization mechanism. The short Aβ peptides absence of aggregation or the time-dependent aggregation mechanisms, at room temperature, in free chloride media, within the time window from 0 to 48 h, were established by AFM via changes in their adsorption morphology, and by differential pulse voltammetry, via modifications of the amino acid residues oxidation peak currents. The first oxidation peak was of tyrosine Y residue and the second peak was of histidine H and methionine M residues oxidation. A correlation between the presence of an intact highly hydrophobic KLVFF aggregation core and the time-dependent changes on the Aβ peptides aggregation was found. The hydrophobic C-terminal domain IIGLMVGGVV, present in the Aβ_1-40 peptide, also contributed to accelerate the formation of Aβ_1-40 peptide aggregates and fibrils.

Metabolic Abnormalities of Erythrocytes as a Risk Factor for Alzheimer's Disease

Alzheimer's disease (AD) is a slowly progressive, neurodegenerative disorder of uncertain etiology. According to the amyloid cascade hypothesis, accumulation of non-soluble amyloid β peptides (Aβ) in the Central Nervous System (CNS) is the primary cause initiating a pathogenic cascade leading to the complex multilayered pathology and clinical manifestation of the disease. It is, therefore, not surprising that the search for mechanisms underlying cognitive changes observed in AD has focused exclusively on the brain and Aβ-inducing synaptic and dendritic loss, oxidative stress, and neuronal death. However, since Aβ depositions were found in normal non-demented elderly people and in many other pathological conditions, the amyloid cascade hypothesis was modified to claim that intraneuronal accumulation of soluble Aβ oligomers, rather than monomer or insoluble amyloid fibrils, is the first step of a fatal cascade in AD. Since a characteristic reduction of cerebral perfusion and energy metabolism occurs in patients with AD it is suggested that capillary distortions commonly found in AD brain elicit hemodynamic changes that alter the delivery and transport of essential nutrients, particularly glucose and oxygen to neuronal and glial cells. Another important factor in tissue oxygenation is the ability of erythrocytes (red blood cells, RBC) to transport and deliver oxygen to tissues, which are first of all dependent on the RBC antioxidant and energy metabolism, which finally regulates the oxygen affinity of hemoglobin. In the present review, we consider the possibility that metabolic and antioxidant defense alterations in the circulating erythrocyte population can influence oxygen delivery to the brain, and that these changes might be a primary mechanism triggering the glucose metabolism disturbance resulting in neurobiological changes observed in the AD brain, possibly related to impaired cognitive function. We also discuss the possibility of using erythrocyte biochemical aberrations as potential tools that will help identify a risk factor for AD.

Neural Stem Cell Death Mechanisms Induced by Amyloid Beta

Background and Purpose

Amyloid beta (Aβ) is the main component of amyloid plaques, which are deposited in the brains of patients with Alzheimer's disease (AD). Biochemical and animal studies support the central role of Aβ in AD pathogenesis. Despite several investigations focused on the pathogenic mechanisms of Aβ, it is still unclear how Aβ accumulates in the central nervous system and subsequently initiates the disease at the cellular level. In this study, we investigated the pathogenic mechanisms of Aβ using proteomics and antibody microarrays.

Methods

To evaluate the effect of Aβ on neural stem cells (NSCs), we treated primary cultured cortical NSCs with several doses of Aβ for 48 h. A 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide assay, trypan blue staining, and bromodeoxyuridine cell proliferation assay were performed. We detected several intracellular proteins that may be associated with Aβ by proteomics and Western blotting analysis.

Results

Various viability tests showed that Aβ decreased NSCs viability and cell proliferation in a concentration-dependent manner. Aβ treatment significantly decreased lactate dehydrogenase B, high-mobility group box 1, aldolase C, Ezrin, and survival signals including phosphorylated phosphoinositide 3-kinase, Akt, and glycogen synthase kinase-3β.

Conclusions

These results suggest that several factors determined by proteomics and Western blot hold the clue to Aβ pathogenesis. Further studies are required to investigate the role of these factors.

Targeting therapy for homocysteic acid in the blood represents a potential recovery treatment for cognition in Alzheimer's disease patients

At present, we have no reliable means of recovering cognitive impairment in Alzheimer's disease (AD) patients. We hypothesized that homocysteic acid (HA) in the blood might represent one such pathogen that could be excreted into the urine. Since DHA is known to reduce circulating levels of homocysteine, and since exercise attenuates this effect, it follows that supplementation of the diet with DHA, along with increased levels of physical activity, may help to reduce cognitive impairment in AD patients. Our hypothesis was proven to be correct because memory problems in 3xTg- AD mice (a model for AD in which animals develop amyloid pathology), and in a mouse model of familial AD, were recovered following treatment with an anti-HA antibody and not by amyloid treatment. Interestingly, 3xTg-AD mice with amyloid pathology showed increased levels of HA level. This could perhaps be explained by the fact that amyloid precursor protein and/or presenilin increases calcium influx, which could then increase levels of superoxide and consequently increase levels of HA from homocysteine or methionine. Our hypothesis is also partially supported by an open clinical trial of certain dietary supplements that has shown impressive results. Also there are other treatments hypothesis which would be possible for the effective therapies, such as ribonucleoprotein therapy, a β-secretase inhibitor treatment and the metabolic enhancement treatment.

Diminished stress resistance and defective adaptive homeostasis in age-related diseases

Adaptive homeostasis is defined as the transient expansion or contraction of the homeostatic range following exposure to subtoxic, non-damaging, signaling molecules or events, or the removal or cessation of such molecules or events (Mol. Aspects Med. (2016) 49, 1-7). Adaptive homeostasis allows us to transiently adapt (and then de-adapt) to fluctuating levels of internal and external stressors. The ability to cope with transient changes in internal and external environmental stress, however, diminishes with age. Declining adaptive homeostasis may make older people more susceptible to many diseases. Chronic oxidative stress and defective protein homeostasis (proteostasis) are two major factors associated with the etiology of age-related disorders. In the present paper, we review the contribution of impaired responses to oxidative stress and defective adaptive homeostasis in the development of age-associated diseases.

Expression and Processing of Amyloid Precursor Protein in Vascular Endothelium

Amyloid precursor protein (APP) is evolutionary conserved protein expressed in endothelial cells of cerebral and peripheral arteries. In this review, we discuss mechanisms responsible for expression and proteolytic cleavage of APP in endothelial cells. We focus on physiological and pathological implications of APP expression in vascular endothelium.

Evidence For and Against a Pathogenic Role of Reduced γ-Secretase Activity in Familial Alzheimer's Disease

The majority of mutations causing familial Alzheimer's disease (fAD) have been found in the gene PRESENILIN1 (PSEN1) with additional mutations in the related gene PRESENILIN2 (PSEN2). The best characterized function of PRESENILIN (PSEN) proteins is in γ-secretase enzyme activity. One substrate of γ-secretase is encoded by the gene AMYLOID BETA A4 PRECURSOR PROTEIN (AβPP/APP) that is a fAD mutation locus. AβPP is the source of the amyloid-β (Aβ) peptide enriched in the brains of people with fAD or the more common, late onset, sporadic form of AD, sAD. These observations have resulted in a focus on γ-secretase activity and Aβ as we attempt to understand the molecular basis of AD pathology. In this paper we briefly review some of the history of research on γ-secretase in AD. We then discuss the main ideas regarding the role of γ-secretase and the PSEN genes in this disease. We examine the significance of the "fAD mutation reading frame preservation rule" that applies to PSEN1 and PSEN2 (and AβPP) and look at alternative roles for AβPP and Aβ in fAD. We present a case for an alternative interpretation of published data on the role of γ-secretase activity and fAD-associated mutations in AD pathology. Evidence supports a "PSEN holoprotein multimer hypothesis" where PSEN fAD mutations generate mutant PSEN holoproteins that multimerize with wild type holoprotein and dominantly interfere with an AD-critical function(s) such as autophagy or secretion of Aβ. Holoprotein multimerization may be required for the endoproteolysis that activates PSENs' γ-secretase activity.

Advances in Alzheimer's Diagnosis and Therapy: The Implications of Nanotechnology

Alzheimer's disease (AD) is a type of dementia that causes major issues for patients' memory, thinking, and behavior. Despite efforts to advance AD diagnostic and therapeutic tools, AD remains incurable due to its complex and multifactorial nature and lack of effective diagnostics/therapeutics. Nanoparticles (NPs) have demonstrated the potential to overcome the challenges and limitations associated with traditional diagnostics/therapeutics. Nanotechnology is now offering new tools and insights to advance our understanding of AD and eventually may offer new hope to AD patients. Here, we review the key roles of nanotechnologies in the recent literature, in both diagnostic and therapeutic aspects of AD, and discuss how these achievements may improve patient prognosis and quality of life.

In vivo evaluation of microglia activation by intracranial iron overload in central pain after spinal cord injury

Background

Central pain (CP) is a common clinical problem in patients with spinal cord injury (SCI). Recent studies found the pathogenesis of CP was related to the remodeling of the brain. We investigate the roles of iron overload and subsequent microglia activate in the remodeling of the brain after SCI.

Methods

An SCI-induced CP model was established in Sprague-Dawley rats that were randomly assigned to SCI, sham operation, deferoxamine (DFX), minocycline, and nitric oxide synthase inhibitor treatment groups. At 12 weeks, pain behavior and thermal pain threshold were evaluated in each group, and iron transferrin receptor (TfR)1 and ferritin (Fn) mRNA, as well as iron-regulatory protein (IRP)1, FN, lactoferrin, and nuclear factor (NF)-κB protein levels in the rat brains were measured. Microglia proliferation and differentiation and IRP1 expression were evaluated by immunohistochemistry.

Results

Autophagy was observed in rats after SCI, accompanied by reduced latency of thermal pain, increased iron content and IRP1 and NF-κB levels in the hindlimb sensory area, hippocampus, and thalamus, and decreased Fn levels in the hindlimb sensory area. TfR1 mRNA expression was upregulated in activated microglia. Treatment with an iron-chelating agent, or inhibitors of nitric oxide synthase or microglia suppressed microglia proliferation.

Conclusions

SCI may induce intracranial iron overload, which activates microglia via NF-κB signaling. Microglia secrete inflammatory factors that induce neuronal damage and lead to CP. Treatment with an iron-chelating agent or NF-κB or microglia inhibitors can relieve CP resulting from SCI.