Elevated concentrations of amyloid-ß oligomers and their proapoptotic effects on age-related cataract.

Recently, amyloid-ß oligomers (AßOs) have been studied as the primary pathogenic substances in Alzheimer's disease (AD). Our previous study revealed that the Aß expression level is closely related to ARC progression. Here, we demonstrated that the accumulation of AßOs in the lens epithelium of age-related cataract (ARC) patients increased during ARC progression and that this alteration was consistent with the changes in mitochondrial function, oxidative stress, and cellular apoptosis. In vitro, human lens epithelial cells (HLECs) treated with AßOs exhibited Ca2+ dyshomeostasis, impaired mitochondrial function, elevated oxidative stress levels, and increased apoptosis. Moreover, the proapoptotic effect of AßOs was alleviated after the uptake of mitochondrial Ca2+ was inhibited. These results establish that AßOs may promote HLEC apoptosis by inducing mitochondrial Ca2+ overload, thus preliminarily revealing the possible association between the accumulation of AßOs and other pathological processes in ARC.

Amyloid-ß oligomer-induced neurotoxicity by exosomal interactions between neuron and microglia.

A hallmark of Alzheimer's disease (AD) is amyloid-ß (Aß) plaque deposition in the brain, causing deficits in cognitive function. Amyloid-beta oligomers (AßOs), the soluble precursor peptides producing Aß plaques, also produce neurotoxicity and microgliosis together with glycolytic reprogramming. Recently, monocarboxylate transporter 1 (MCT1), a key glycolysis regulator, and its ancillary protein, CD147, are found to play an important role in the secretion of exosomes, 30-200 nm vesicles in size, which are considered as toxic molecule carriers in AD. However, the effect of low-concentration AßOs (1 nM) on microglia MCT1 and CD147 expression as well as 1 nM AßOs-treated microglia-derived exosomes on neuronal toxicity remain largely elusive. In this study, 1 nM AßOs induce significant axonopathy and microgliosis. Furthermore, 1 nM AßOs-treated neurons- or microglia-derived exosomes produce axonopathy through their autologous or heterologous uptake by neurons, supporting the role of exosomes as neurotoxicity mediators in AD. Interestingly, MCT1 and CD147 are enhanced in microglia by treatment with 1 nM AßOs or exosomes from 1 nM AßOs-treated- microglia or neurons, suggesting the implication of AßOs-induced enhanced MCT1 and CD147 in microglia with AD neuropathogenesis, which is consistent with the in-silico analysis of the single cell RNA sequencing data from microglia in mouse models of AD and AD patients.

Hybrid resolution molecular dynamics simulations of amyloid proteins interacting with membranes.

A broad range of human diseases, including Alzheimer's and Parkinson's diseases, arise from or have as key players intrinsically disordered proteins. The aggregation of these amyloid proteins into fibrillar aggregates are the key events of such diseases. Characterizing the conformation dynamics of the proteins involved is crucial for understanding the molecular mechanisms of aggregation, which in turn is important for drug development efforts against these diseases. Computational approaches have provided extensive detail about some steps of the aggregation process, however the biologically relevant elements responsible for the aggregation and or aggregation propagation have not been fully characterized. Here we describe a hybrid resolution molecular dynamics simulation method that can be employed to investigate the interaction of amyloid proteins with lipid membranes, shown to dramatically accelerate the aggregation propensity of amyloid proteins. The hybrid resolution method enables routine and accurate simulation of multi-protein and complex membrane systems, mimicking biologically relevant lipid membranes, on microsecond time scales. The hybrid resolution method was applied to computer modeling of the interactions of α -synuclein protein with a mixed lipid bilayer.

Plantainoside B in Bacopa monniera Binds to Aß Aggregates Attenuating Neuronal Damage and Memory Deficits Induced by Aß.

Alzheimer's disease (AD) is a progressive neurodegenerative disease characterized by dementia. The most characteristic pathological changes in AD brain include extracellular amyloid-ß (Aß) accumulation and neuronal loss. Particularly, cholinergic neurons in the nucleus basalis of Meynert are some of the first neuronal groups to degenerate; accumulating evidence suggests that Aß oligomers are the primary form of neurotoxicity. Bacopa monniera is a traditional Indian memory enhancer whose extract has shown neuroprotective and Aß-reducing effects. In this study, we explored the low molecular weight compounds from B. monniera extracts with an affinity to Aß aggregates, including its oligomers, using Aß oligomer-conjugated beads and identified plantainoside B. Plantainoside B exhibited evident neuroprotective effects by preventing Aß attachment on the cell surface of human induced pluripotent stem cell (hiPSC)-derived cholinergic neurons. Moreover, it attenuated memory impairment in mice that received intrahippocampal Aß injections. Furthermore, radioisotope experiments revealed that plantainoside B has affinity to Aß aggregates including its oligomers and brain tissue from a mouse model of Aß pathology. In addition, plantainoside B could delay the Aß aggregation rate. Accordingly, plantainoside B may exert neuroprotective effects by binding to Aß oligomers, thus interrupting the binding of Aß oligomers to the cell surface. This suggests its potential application as a theranostics in AD, simultaneously diagnostic and therapeutic drugs.

Neuroprotective and Therapeutic Effects of Tocovid and Twendee-X on Aß Oligomer-Induced Damage in the SH-SY5Y Cell Line.

BACKGROUND: Alzheimer's disease (AD) is the most frequent cause of dementia among the elderly. The accumulation of amyloid beta (Aß) and its downstream pathological events such as oxidative stress play central roles in AD. Recent studies revealed that Aß oligomer (AßO)-induced strong neurotoxicity in SH-SY5Y cells via the induction of oxidative stress. OBJECTIVE: In the present study, we investigated the effect of two antioxidants, Tocovid and Twendee-X, on AßO-induced SH-SY5Y cell damage. METHODS: AßOs (2.5 µM) were applied to induce cellular damage in the SH-SY5Y cell line. Cell viability following AßO toxicity, Tau protein phosphorylation, cell morphology, and intracellular reactive oxygen species were assayed with or without different concentrations of Tocovid or Twendee-X. RESULTS: Tocovid (60 µg/mL) and Twendee-X (150 µg/mL) significantly recovered cell viability from AßO toxicity (**p < 0.01, vs. control), attenuated Tau protein phosphorylation (**p < 0.01, vs. AßOs), improved cell morphology (**p < 0.01, vs. AßOs), and suppressed intracellular ROS (**p < 0.01, vs. AßOs) in SH-SY5Y cells. CONCLUSION: These findings suggest the neuroprotective and therapeutic potential of Tocovid and Twendee-X for AD treatment.

Determination of ß-amyloid oligomer using electrochemiluminescent aptasensor with signal enhancement by AuNP/MOF nanocomposite.

In order to effectively and conveniently detect the ß-amyloid oligomer (AßO) for earlier diagnosis of Alzheimer's disease (AD), a disposable aptamer biosensor has been developed with high performance, facile operation, and low cost. Using a nanocomposite by in situ reduction of chloroauric acid to decorate Au nanoparticles (AuNPs) on Fe-MIL-88NH2 material via Au-N bond to effectively enhance the electrochemiluminescence (ECL) of luminol, the functioned basal electrode provides adequate background for sensing response. When the aptamer is linked via Au-S bond on the surface, the sensor gets the ability of specific recognition and coalescence toward the target (AßO). After incubating the sample on the aptasensor, its ECL signal is inhibited owing to the steric hindrance of the AßO macromolecules. The relative inhibition ratio linearly depends to the logarithm of AßO concentration in the range 0.1 pM to 10 pM, with an LOD of 71 fM. The aptasensor has high selectivity to AßO among its analogs. The recoveries in human serum were 98.9-105.4%. This research provides a new approach for sensitive detection of AßO in clinic laboratories for investigation and diagnosis of AD.

An electrochemical aptasensor for amyloid-ß oligomer based on double-stranded DNA as "conductive spring".

In order to overcome the antibody-based sensor's shortcomings, an electrochemical aptamer (Apt)-based sensor was developed for amyloid-ß40 oligomer (Aß40-O). The aptasensor was constructed by locating Apt and ferrocence (Fc) on streptavidin-modified gold (SA-gold) nanoparticles. The obtained AptFc@SA-gold nanoparticles were linked onto the Au electrode via the connection of double-stranded DNA (dsDNA) as a "conductive spring." The determination of Aß40-O was performed with square-wave voltammetry (SWV). Upon bio-recognition between Apt and Aß40-O, the conformation of Apt changed and the formed Apt/Aß40-O complex separated from the SA-gold surface. As a result, the surface charge of SA-gold positively shifted, weakening the electrostatic attraction between the SA-gold and the positively charged Au electrode surface (at potential range of 0.1~0.5 V, corresponding to the Fc redox transformation), and stretching the dsDNA chain. Based on the exponential decay of dsDNA's electron transfer efficiency on its chain stretching, the oxidation current density from Fc decreased and displayed linear correlation to the concentration of Aß40-O. A wide linear range of 0.100 nM to 1.00 µM with a low detection limit of 93.0 pM was obtained. The aptasensor displayed excellent selectivity toward Aß40-O in contrast to other possible interfering analogs (Aß40 monomer, Aß42 monomer, and oligomer) at × 100 higher concentrations. The recoveries for Aß40-O-spiked artificial cerebrospinal fluid and healthy human serum were 94.0~104% and 92.8~95.4%, respectively. The electrochemical aptasensor meets the demands of clinic determination of Aß40-O, which is significant for the early diagnosis of AD. Graphical abstract Schematic representation of the electrochemical aptasensor for amyloid-ß oligomer based on the surface charge change induced by target binding.

Porins and Amyloids are Coded by Similar Sequence Motifs.

The relationship between amino acid sequences of the ß-hairpin structures and amyloidogenic ß-arcade-forming motifs are of special interest because, similar to amyloid fibrils, most of the ß-hairpin repeat (BHR) structures have the so-called cross-ß arrangement. Moreover, ß-hairpin is considered as a probable intermediate structure in amyloidogenesis. In this work, a bioinformatics sequence analysis of the known BHR structures is performed in search of amylodogenic motifs able to form ß-arcade fibrils. The analysis shows that the occurrence of the predicted ß-arcade motifs in the BHR regions is very different depending on the BHR structural fold, cellular localization, and phylogeny. One of the most striking observations is the high level of sequence similarity between the BHRs of membranous porins and ß-arcade motifs. This sequence similarity provides additional evidence that the structure of the membranous porins and annular amyloid oligomers may bear a resemblance. Moreover, these results explain how some amyloidogenic sequence can fold in either the ring-like shape oligomers or elongated amyloid fibrils. It has been also found that potentially lethal amyloidogenic ß-arcade motifs are absent in the elongated BHR structures of intracellular eukaryotic proteins. It allows to hypothesize that, in this case, the selective evolutionary pressure acts against aggregation.

Amyloid ß oligomers (AßOs) in Alzheimer's disease.

The causative role of amyloid ß 1-42 (Aß42) aggregation in the pathogenesis of Alzheimer's disease (AD) has been under debate for over 25 years. Primarily, scientific efforts have focused on the dyshomeostasis between production and clearance of Aß42. This imbalance may result from mutations either in genes for the substrate, i.e., amyloid precursor protein or in genes encoding presenilin, the enzyme of the reaction that generates Aß42. Currently, it is supposed that soluble oligomers of amyloid beta (AßOs) and not fibrillar Aß42 within neuritic plaques may be the toxic factors acting on a very early stage of AD, perhaps even initiating pathological cascade. For example, soluble AßOs isolated from AD patients' brains reduced number of synapses, inhibited long-term potentiation, and enhanced long-term synaptic depression in brain regions responsible for memory in animal models of AD. Concentrations of AßOs in the cerebrospinal fluid (CSF) of AD patients are often reported higher than in non-demented controls, and show a negative correlation with mini-mental state examination scores. Furthermore, increased Aß42/oligomer ratio in the CSF of AD/MCI patients indicated that the presence of soluble AßOs in CSF may be linked to lowering of natively measured monomeric Aß42 by epitopes masking, and hence, concentrations of AßOs in the CSF are postulated to as useful AD biomarkers.

Cellular Receptors of Amyloid ß Oligomers (AßOs) in Alzheimer's Disease.

It is estimated that Alzheimer's disease (AD) affects tens of millions of people, comprising not only suffering patients, but also their relatives and caregivers. AD is one of age-related neurodegenerative diseases (NDs) characterized by progressive synaptic damage and neuronal loss, which result in gradual cognitive impairment leading to dementia. The cause of AD remains still unresolved, despite being studied for more than a century. The hallmark pathological features of this disease are senile plaques within patients' brain composed of amyloid beta (Aß) and neurofibrillary tangles (NFTs) of Tau protein. However, the roles of Aß and Tau in AD pathology are being questioned and other causes of AD are postulated. One of the most interesting theories proposed is the causative role of amyloid β oligomers (AßOs) aggregation in the pathogenesis of AD. Moreover, binding of AßOs to cell membranes is probably mediated by certain proteins on the neuronal cell surface acting as AßO receptors. The aim of our paper is to describe alternative hypotheses of AD etiology, including genetic alterations and the role of misfolded proteins, especially Aß oligomers, in Alzheimer’s disease. Furthermore, in this review we present various putative cellular AßO receptors related to toxic activity of oligomers.

Phosphorylation of the amyloid ß-peptide at Ser26 stabilizes oligomeric assembly and increases neurotoxicity.

Aggregation and toxicity of the amyloid ß-peptide (Aß) are considered as critical events in the initiation and progression of Alzheimer's disease (AD). Recent evidence indicated that soluble oligomeric Aß assemblies exert pronounced toxicity, rather than larger fibrillar aggregates that deposit in the forms of extracellular plaques. While some rare mutations in the Aß sequence that cause early-onset AD promote the oligomerization, molecular mechanisms that induce the formation or stabilization of oligomers of the wild-type Aß remain unclear. Here, we identified an Aß variant phosphorylated at Ser26 residue (pSer26Aß) in transgenic mouse models of AD and in human brain that shows contrasting spatio-temporal distribution as compared to non-phosphorylated Aß (npAß) or other modified Aß species. pSer26Aß is particularly abundant in intraneuronal deposits at very early stages of AD, but much less in extracellular plaques. pSer26Aß assembles into a specific oligomeric form that does not proceed further into larger fibrillar aggregates, and accumulates in characteristic intracellular compartments of granulovacuolar degeneration together with TDP-43 and phosphorylated tau. Importantly, pSer26Aß oligomers exert increased toxicity in human neurons as compared to other known Aß species. Thus, pSer26Aß could represent a critical species in the neurodegeneration during AD pathogenesis.

Neuronal amyloid-ß accumulation within cholinergic basal forebrain in ageing and Alzheimer's disease.

The mechanisms that contribute to selective vulnerability of the magnocellular basal forebrain cholinergic neurons in neurodegenerative diseases, such as Alzheimer's disease, are not fully understood. Because age is the primary risk factor for Alzheimer's disease, mechanisms of interest must include age-related alterations in protein expression, cell type-specific markers and pathology. The present study explored the extent and characteristics of intraneuronal amyloid-ß accumulation, particularly of the fibrillogenic 42-amino acid isoform, within basal forebrain cholinergic neurons in normal young, normal aged and Alzheimer's disease brains as a potential contributor to the selective vulnerability of these neurons using immunohistochemistry and western blot analysis. Amyloid-ß1-42 immunoreactivity was observed in the entire cholinergic neuronal population regardless of age or Alzheimer's disease diagnosis. The magnitude of this accumulation as revealed by optical density measures was significantly greater than that in cortical pyramidal neurons, and magnocellular neurons in the globus pallidus did not demonstrate a similar extent of amyloid immunoreactivity. Immunoblot analysis with a panel of amyloid-ß antibodies confirmed accumulation of high concentration of amyloid-ß in basal forebrain early in adult life. There was no age- or Alzheimer-related alteration in total amyloid-ß content within this region. In contrast, an increase in the large molecular weight soluble oligomer species was observed with a highly oligomer-specific antibody in aged and Alzheimer brains when compared with the young. Similarly, intermediate molecular weight oligomeric species displayed an increase in aged and Alzheimer brains when compared with the young using two amyloid-ß42 antibodies. Compared to cortical homogenates, small molecular weight oligomeric species were lower and intermediate species were enriched in basal forebrain in ageing and Alzheimer's disease. Regional and age-related differences in accumulation were not the result of alterations in expression of the amyloid precursor protein, as confirmed by both immunostaining and western blot. Our results demonstrate that intraneuronal amyloid-ß accumulation is a relatively selective trait of basal forebrain cholinergic neurons early in adult life, and increases in the prevalence of intermediate and large oligomeric assembly states are associated with both ageing and Alzheimer's disease. Selective intraneuronal amyloid-ß accumulation in adult life and oligomerization during the ageing process are potential contributors to the degeneration of basal forebrain cholinergic neurons in Alzheimer's disease.

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-ß (Aß), and metal-bound amyloid-ß (Aß), 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 Aß 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.

CT1812, a Small Molecule Sigma-2 Receptor Antagonist for Alzheimer's Disease Treatment: A Systematic Review of Available Clinical Data.

Background: Alzheimer's disease (AD) is of growing concern worldwide as the demographic changes to a more aged population. Amyloid-ß (Aß deposition is thought to be a key target for treating AD. However, Aß antibodies have had mixed results, and there is concern over their safety. Studies have shown that the sigma-2 receptor (σ-2R)/TMEM97 is a binding site for Aß oligomers. Therefore, targeting the receptor may be beneficial in displacing Aß oligomers from the brain. CT1812 is a σ-2R/TMEM97 antagonist that is effective in preclinical studies of AD and has been entered into clinical trials. Objective: The objective of this study was to systematically review the safety and efficacy of CT1812 for the treatment of AD. Methods: Between June and August 2023, we searched the primary literature (PubMed, Scopus, Google Scholar, etc.) and clinical trials databases (http://www.clinicaltrails.gov). The extracted data is evaluated within this manuscript. Results: CT1812 is relatively safe, with only mild adverse events reported at doses up to 840 mg. CT1812 can displace Aß in the clinical studies, in line with the preclinical data. Studies have investigated brain connectivity and function in response to CT1812. However, the cognitive data is still lacking, with only one study including cognitive data as a secondary outcome. Conclusions: CT1812 safely works to displace Aß however, whether this is enough to prevent/slow the cognitive decline seen in AD remains to be seen. Longer clinical trials are needed to assess the efficacy of CT1812; several trials of this nature are currently ongoing.

Sleep deprivation aggravated amyloid ß oligomers-induced damage to the cerebellum of rats: Evidence from magnetic resonance imaging.

For quite a long time, researches on Alzheimer's disease (AD) primarily focused on the cortex and hippocampus, while the cerebellum has been ignored because of its abnormalities considered to appear in the late stage of AD. In recent years, increasing evidence suggest that the cerebellar pathological changes possibly occur in the preclinical phase of AD, which is also associated with sleep disorder. Sleep disturbance is a high risk factor of AD. However, the changes and roles of cerebellum has rarely been reported under conditions of AD accompanied with sleep disorders. In this study, using an amyloid-ß oligomers (AßO)-induced rat model of AD subjected to sleep deprivation, combining with a 7.0 T animals structural magnetic resonance imaging (MRI), we assessed structural changes of cerebellum in MRI. Our results showed that sleep deprivation combined with AßO led to an increased FA value in the anterior lobe of cerebellum, decreased ADC value in the cerebellar lobes and cerebellar nuclei, and increased cerebellum volume. Besides that, sleep deprivation exacerbated the damage of AßO to the cerebellar structural network. This study demonstrated that sleep deprivation could aggravate the damage to cerebellum induced by AßO. The present findings provide supporting evidence for the involvement of cerebellum in the early pathology of AD and sleep loss. Our data would contribute to advancing the understanding of the mysterious role of cerebellum in AD and sleep disorders, as well as would be helpful for developing non-invasive MRI biomarkers for screening early AD patients with self-reported sleep disturbances.

MicroRNA-140-5p inhibitor attenuates memory impairment induced by amyloid-ß oligomer in vivo possibly through Pin1 regulation.

AIMS: The peptidyl-prolyl cis/trans isomerase, Pin1, has a protective role in age-related neurodegeneration by targeting different phosphorylation sites of tau and the key proteins required to produce Amyloid-ß, which are the well-known molecular signatures of Alzheimer's disease (AD) neuropathology. The direct interaction of miR-140-5p with Pin1 mRNA and its inhibitory role in protein translation has been identified. The main purpose of this study was to investigate the role of miRNA-140-5p inhibition in promoting Pin1 expression and the therapeutic potential of the AntimiR-140-5p in the Aß oligomer (AßO)-induced AD rat model. METHODS: Spatial learning and memory were assessed in the Morris water maze. RT-PCR, western blot, and histological assays were performed on hippocampal samples at various time points after treatments. miRNA-140-5p inhibition enhanced Pin1 and ADAM10 mRNA expressions but has little effect on Pin1 protein level. RESULTS: The miRNA-140-5p inhibitor markedly ameliorated spatial learning and memory deficits induced by AßO, and concomitantly suppressed the mRNA expression of inflammatory mediators TNFα and IL-1ß, and phosphorylation of tau at three key sites (thr231, ser396, and ser404) as well as increased phosphorylated Ser473-Akt. CONCLUSION: According to our results, Antimir-140-mediated improvement of AßO-induced neuronal injury and memory impairment in rats may provide an appropriate rationale for evaluating miR-140-5p inhibitors as a promising agent for the treatment of AD.

Protective and anti-oxidative effects of curcumin and resveratrol on Aß-oligomer-induced damage in the SH-SY5Y cell line.

Alzheimer's disease (AD) is a degenerative disorder characterized by the loss of synapses and neurons in the brain, and results in the accumulation of amyloid-based neurotic plaques. Amyloid-ß oligomers (AßO) are widely accepted as the main neurotoxin that induces oxidative stress and neuronal loss in AD. In this study, an oxidative stress model of the neuroblastoma SH-SY5Y cell line exposed to AßO was established to simulate an AD cell model. Exposure to AßO significantly reduced the viability of cultured SH-SY5Y cells (p < 0.05) and significantly increased intracellular reactive oxygen species (ROS) (p < 0.01). AßO exposure also induced oxidative stress in SH-SY5Y cells. Furthermore, AßO significantly increased the level of hyperphosphorylation of tau at sites T181 and T205 in SH-SY5Y cells (p < 0.01). Using edaravone, a free radical scavenger with neuroprotective properties, as the control, the possible protective and anti-oxidative effects of curcumin (40 µM) and resveratrol (20 µM) were evaluated. The results suggest that curcumin and resveratrol decreased ROS generation, attenuated oxidative stress, inhibited tau hyperphosphorylation, and protected SH-SY5Y cells from AßO damage. Both curcumin and resveratrol are promising supplements or medicine as therapeutic agents for the treatment of AD.

An electrochemical aptasensor based on AuPt alloy nanoparticles for ultrasensitive detection of amyloid-ß oligomers.

Amyloid-ß oligomer is an important biomarker and a potential therapeutic target of Alzheimer's disease in its early stage. Here, we combined superhydrophobic carbon fiber paper (CFP) with AuPt alloy nanoparticles to prepare a CFP/AuPt nanocomposite with larger specific surface area and hydrophobic surface. On this basis, we constructed an electrochemical aptasensor based on CFP/AuPt for the ultrasensitive detection of amyloid-ß oligomers. The surface-coated AuPt nanoparticles greatly enhanced the electroactive area, and the hydrophobic surface increased the resisting nonspecific adsorption performance of sensor. A combination of these two features significantly improved the sensitivity and specificity of the sensor. This electrochemical aptasensor based on CFP/AuPt displayed a low detection limit of 0.16 pg/mL. This work shows a promising future in clinical diagnosis of Alzheimer's disease and provides a possible solution to electrochemical biosensors that are susceptible to interference in biological fluids.

Amyloid-ß oligomer targeted theranostic probes for in vivo NIR imaging and inhibition of self-aggregation and amyloid-ß induced ROS generation.

To enable the early detection and intervention of Alzheimer's disease (AD), it is highly desirable to develop novel theranostic agents for simultaneous detection of toxic and pathogenic amyloid-ß (Aß) oligomers in vivo and attenuation of Aß-induced toxicity. Herein, we report a new series of oligomeric Aß targeted near infrared (NIR) emissive dibutylnaphthylamine-based cyanine probes for in vivo and ex vivo imaging of Aß in AD mouse model. These new fluorophores exhibited strong solvatochromism and a large bathochromic shift of the emission spectrum upon binding with Aß species, giving rise to advantageous NIR emission. Besides, they showed an intriguingly stronger fluorescence enhancement upon interacting with Aß oligomers and monomers, and binding affinity toward Aß oligomers and monomers than Aß fibrils, suggesting they were selective to Aß oligomers and monomers. In addition to low toxicity, one of the fluorophores, DBAN-SLM, showed remarkably effective inhibitory effect on Aß aggregation, significant neuroprotection effect against the Aß-induced toxicities, and suppression on Aß-induced reactive oxygen species (ROS) generation. Because of excellent blood-brain barrier (BBB) permeability, good biocompatibility and stability, high specificity towards Aß oligomers as well as strong turn-on fluorescence upon Aß binding, DBAN-SLM was successfully applied for in vivo and ex vivo imaging of Aß in AD mouse model, signifying its great promise as a useful theranostic agent for the early diagnosis and therapy of AD. Our results also demonstrated for the first time that the dibutyl-2-naphthylamine moiety is a useful and effective structural building block to promote the targeting capability of oligomeric Aß.

Out-of-Register Parallel ß-Sheets and Antiparallel ß-Sheets Coexist in 150-kDa Oligomers Formed by Amyloid-ß(1-42).

We present solid-state NMR measurements of ß-strand secondary structure and inter-strand organization within a 150-kDa oligomeric aggregate of the 42-residue variant of the Alzheimer's amyloid-ß peptide (Aß(1-42)). We build upon our previous report of a ß-strand spanned by residues 30-42, which arranges into an antiparallel ß-sheet. New results presented here indicate that there is a second ß-strand formed by residues 11-24. Contrary to expectations, NMR data indicate that this second ß-strand is organized into a parallel ß-sheet despite the co-existence of an antiparallel ß-sheet in the same structure. In addition, the in-register parallel ß-sheet commonly observed for amyloid fibril structure does not apply to residues 11-24 in the 150-kDa oligomer. Rather, we present evidence for an inter-strand registry shift of three residues that likely alternate in direction between adjacent molecules along the ß-sheet. We corroborated this unexpected scheme for ß-strand organization using multiple two-dimensional NMR and 13C-13C dipolar recoupling experiments. Our findings indicate a previously unknown assembly pathway and inspire a suggestion as to why this aggregate does not grow to larger sizes.