Amyloid Against Amyloid: Dimeric Amyloid Fragment Ameliorates Cognitive Impairments by Direct Clearance of Oligomers and Plaques.

Amyloid-ß (Aß) in the form of neurotoxic aggregates is regarded as the main pathological initiator and key therapeutic target of Alzheimer's disease. However, anti-Aß drug development has been impeded by the lack of a target needed for structure-based drug design and low permeability of the blood-brain barrier (BBB). An attractive therapeutic strategy is the development of amyloid-based anti-Aß peptidomimetics that exploit the self-assembling nature of Aß and penetrate the BBB. Herein, we designed a dimeric peptide drug candidate based on the N-terminal fragment of Aß, DAB, found to cross the BBB and solubilize Aß oligomers and fibrils. Administration of DAB reduced amyloid burden in 5XFAD mice, and downregulated neuroinflammation and prevented memory impairment in the Y-maze test. Peptide mapping assays and molecular docking studies were utilized to elucidate DAB-Aß interaction. To further understand the active regions of DAB, we assessed the dissociative activity of DAB with sequence modifications.

Discovery of Chemicals to Either Clear or Indicate Amyloid Aggregates by Targeting Memory-Impairing Anti-Parallel Aß Dimers.

Amyloid-ß (Aß) oligomers are implicated in Alzheimer disease (AD). However, their unstable nature and heterogeneous state disrupts elucidation of their explicit role in AD progression, impeding the development of tools targeting soluble Aß oligomers. Herein parallel and anti-parallel variants of Aß(1-40) dimers were designed and synthesized, and their pathogenic properties in AD models characterized. Anti-parallel dimers induced cognitive impairments with increased amyloidogenesis and cytotoxicity, and this dimer was then used in a screening platform. Through screening, two FDA-approved drugs, Oxytetracycline and Sunitinib, were identified to dissociate Aß oligomers and plaques to monomers in 5XFAD transgenic mice. In addition, fluorescent Astrophloxine was shown to detect aggregated Aß in brain tissue and cerebrospinal fluid samples of AD mice. This screening platform provides a stable and homogeneous environment for observing Aß interactions with dimer-specific molecules.

Taurine Directly Binds to Oligomeric Amyloid-ß and Recovers Cognitive Deficits in Alzheimer Model Mice.

Alzheimer's disease (AD) is the most common cause of dementia leading to severe cognitive decline. During the progression of AD, amyloid-ß (Aß) monomers aggregate into neurotoxic soluble oligomeric Aß that causes cognitive impairments. Our previous study indicates that oral supplementation of taurine at 1000 mg/kg/day significantly ameliorates hippocampal-dependent cognitive deficits in APP/PS1 transgenic AD mouse model. However, Aß plaques and oligomeric Aß levels are not affected after administration of taurine and the oral dosage of taurine was relatively high. Thus, in this study, we focused on direct correlation between taurine and oligomeric Aß, causing memory deficits in a lower oral dosage of taurine, 250 mg/kg/day. We induced AD-like cognitive impairments to adult normal mice and orally administered taurine via drinking water for 10 days. We confirmed that taurine administration improved cognitive deficits in oligomeric Aß-infusion mice in Y-maze and passive avoidance tests without activity alteration of mice. In addition, we found that taurine directly bound to oligomeric Aß in surface plasmon resonance analyses. Our results propose that taurine can ameliorate cognitive impairment by directly binding to oligomeric Aß in oral administration of 250 mg/kg/day for 10 days.

Taurine-Carbohydrate Derivative Stimulates Fibrillogenesis of Amyloid-ß and Reduce Alzheimer-Like Behaviors.

Amyloid-ß (Aß) aggregates are a hallmark of Alzheimer's disease (AD). Through the misfolding process of Aß in the brain, oligomeric forms of Aß accumulate and significantly damage the brain cells inducing neuronal loss and cognitive dysfunctions that lead to AD. We hypothesized that decrease in Aß oligomers during the aggregation process might be able to reduce Aß-dependent brain damage. As taurine-like chemicals are often reported to have direct binding abilities to Aß, we prepared a chemical library that consisted of taurine-carbohydrate derivatives to search for molecules that target Aß and accelerate its fibrillogenesis. Here, we report that 1-deoxy-1-(2-sulfoethylamino)-D-fructose stimulates the formation of relatively less toxic Aß fibrils leading to prevention of cognitive deficits in AD acute model mice.

PyrPeg, a Blood-Brain-Barrier-Penetrating Two-Photon Imaging Probe, Selectively Detects Neuritic Plaques, Not Tau Aggregates.

Amyloid-ß (Aß) tracers have made a significant contribution to the treatment of Alzheimer's disease (AD) by allowing a definitive diagnosis in living patients. Unfortunately, they also detect tau and other protein aggregates that compromise test accuracy. In AD research, there has been a growing need for in vivo Aß imaging by two-photon microscopy, which enables deep-brain-fluorescence imaging. There is no suitable neuritic Aß probe for two-photon microscopy. Here we report PyrPeg, a novel two-photon fluorescent probe that can selectively target insoluble Aß rather than tau and α-synuclein aggregates in the AD model brain and postmortem brain. When injected intravenously, PyrPeg detects the neuritic plaques in the brain and olfactory bulb of the AD model. PyrPeg may serve as a useful blood-brain-barrier-penetrating diagnostic tool for optical and functional monitoring of insoluble forms of Aß aggregates in the living AD brain.

Fluorescent 1,4-Naphthoquinones To Visualize Diffuse and Dense-Core Amyloid Plaques in APP/PS1 Transgenic Mouse Brains.

Recent clinical approvals of brain imaging radiotracers targeting amyloid-ß provided clinicians the tools to detect and confirm Alzheimer's disease pathology without autopsy or biopsy. While current imaging agents are effective in postsymptomatic Alzheimer's patients, there is much room for improvement in earlier diagnosis, hence prompting a need for new and improved amyloid imaging agents. Here we synthesized 41 novel 1,4-naphthoquinone derivatives and initially discovered 14 antiamyloidogenic compounds via in vitro amyloid-ß aggregation assay; however, qualitative analyses of these compounds produced conflicting results and required further investigation. Follow-up docking and biophysical studies revealed that four of these compounds penetrate the blood-brain barrier, directly bind to amyloid-ß aggregates, and enhance fluorescence properties upon interaction. These compounds specifically stain both diffuse and dense-core amyloid-ß plaques in brain sections of APP/PS1 double transgenic Alzheimer's mouse models. Our findings suggest 1,4-naphthoquinones as a new scaffold for amyloid-ß imaging agents for early stage Alzheimer's.

A small molecule Nec-1 directly induces amyloid clearance in the brains of aged APP/PS1 mice.

Alzheimer's disease (AD) is a progressive neurodegenerative disorder characterized by the formation of toxic amyloid-ß (Aß) oligomers and plaques. Considering that Aß misfolding and aggregation precedes the progressive development of cognitive impairment in AD, investigating a therapeutic means by clearance of pre-existing Aß aggregates shows promise as a viable disease-modifying treatment. Here, we report that a small molecule, necrostatin-1 (Nec-1), reduces Aß aggregates back to non-toxic monomers in vitro and in vivo. Intravenous administration of Nec-1 reduced the levels of Aß plaques in the brains of aged APP/PS1 double transgenic mice. In addition, Nec-1 exhibited therapeutic effects against Aß aggregates by inhibiting Aß-induced brain cell death in neuronal and microglial cell lines. Nec-1 also showed anti-apoptotic and anti-necroptotic effects in the cortex of aged APP/PS1 mice by reducing levels of phosphorylated-RIPK3 and Bax and increasing the levels of Bcl-2. According to our data in vitro and in silico, the methyl group of the amine in the 2-thioxo-4-imidazolidinone is the key moiety of Nec-1 that directs its activity against aggregated Aß. Given that the accumulation of Aß aggregates is an important hallmark of AD, our studies provide strong evidence that Nec-1 may serve a key role in the development of AD treatment.

Comparative analyses of plasma amyloid-ß levels in heterogeneous and monomerized states by interdigitated microelectrode sensor system.

Detection of amyloid-ß (Aß) aggregates contributes to the diagnosis of Alzheimer disease (AD). Plasma Aß is deemed a less invasive and more accessible hallmark of AD, as Aß can penetrate blood-brain barriers. However, correlations between biofluidic Aß concentrations and AD progression has been tenuous. Here, we introduce a diagnostic technique that compares the heterogeneous and the monomerized states of Aß in plasma. We used a small molecule, EPPS [4-(2-hydroxyethyl)-1-piperazinepropanesulfonic acid], to dissociate aggregated Aß into monomers to enhance quantification accuracy. Subsequently, Aß levels of EPPS-treated plasma were compared to those of untreated samples to minimize inter- and intraindividual variations. The interdigitated microelectrode sensor system was used to measure plasma Aß levels on a scale of 0.1 pg/ml. The implementation of this self-standard blood test resulted in substantial distinctions between patients with AD and individuals with normal cognition (NC), with selectivity and sensitivity over 90%.

Nec-1 alleviates cognitive impairment with reduction of Aß and tau abnormalities in APP/PS1 mice.

Alzheimer's disease (AD) is a neurodegenerative disorder characterized by cognitive symptoms of learning and memory deficits. Such cognitive impairments are attributed to brain atrophy resulting from progressive neuronal and synaptic loss; therefore, alleviation of neural cell death is as an important target of treatment as other classical hallmarks of AD, such as aggregation of amyloid-ß (Aß) and hyperphosphorylation of tau. Here, we found that an anti-necroptotic molecule necrostatin-1 (Nec-1) directly targets Aß and tau proteins, alleviates brain cell death and ameliorates cognitive impairment in AD models. In the cortex and hippocampus of APP/PS1 double-transgenic mice, Nec-1 treatment reduced the levels of Aß oligomers, plaques and hyperphosphorylated tau without affecting production of Aß, while it altered the levels of apoptotic marker proteins. Our results showing multiple beneficial modes of action of Nec-1 against AD provide evidence that Nec-1 may serve an important role in the development of preventive approach for AD.

Age-dependent inverse correlations in CSF and plasma amyloid-ß(1-42) concentrations prior to amyloid plaque deposition in the brain of 3xTg-AD mice.

Amyloid-ß (Aß) plays a critical role as a biomarker in Alzheimer's disease (AD) diagnosis. In addition to its diagnostic potential in the brain, recent studies have suggested that changes of Aß level in the plasma can possibly indicate AD onset. In this study, we found that plasma Aß(1-42) concentration increases with age, while the concentration of Aß(1-42) in the cerebrospinal fluid (CSF) decreases in APPswe, PS1M146V and TauP301L transgenic (3xTg-AD) mice, if measurements were made before formation of ThS-positive plaques in the brain. Our data suggests that there is an inverse correlations between the plasma and CSF Aß(1-42) levels until plaques form in transgenic mice's brains and that the plasma Aß concentration possesses the diagnostic potential as a biomarker for diagnosis of early AD stages.