Therapeutic Strategy For Alzheimer's Disease Treatment Research Articles

Osmundacetone ameliorates Alzheimer's-like pathologies by inhibiting β-amyloid fibrillation, oxidative damage and neuroinflammation in APP/PS1 transgenic mice

Backgroundβ-Amyloid (Aβ) fibrillation is critical for Aβ deposition and cytotoxicity during the progression of Alzheimer's disease (AD). Consequently, anti-Aβ monoclonal antibody drugs targeting Aβ oligomers and aggregation are considered potential therapeutic strategies for AD treatment. Similar to the working mechanisms of anti-Aβ monoclonal antibody drugs, our study identified osmundacetone (OAC), a small-molecule compound isolated from the traditional Chinese medicine Rhizoma Osmundae, as exerting anti-AD effects by targeting Aβ. PurposeThis study sought to determine whether OAC influences the Aβ burden in APP/PS1 mice and to identify potential regulatory mechanisms. MethodsFive-month-old APP/PS1 mice were injected intraperitoneally with OAC at a dose of 1 mg/kg for 12 weeks. The cognitive functions of the mice were assessed via the Morris water maze test and the open field test. Osmundacetone was analyzed via molecular docking, an isothermal dose‒response fingerprint-cellular context thermal shift assay, a thioflavine T fluorescence assay, and an atomic force microscopy assay to analyze the effects of OAC on Aβ fibrillation. Immunofluorescence, immunoblotting, and immunohistochemistry were used to assess Aβ clearance, AD pathology, oxidative stress, and inflammatory responses. ResultsThe innovative biochemical and physical data illustrated that the ability of OAC to inhibit Aβ fibrillation was accomplished by binding directly to Aβ, which differed from the majority of previously reported natural polyphenols that modulate the Aβ content and structure in an indirect manner. The inhibition of Aβ fibrosis by OAC subsequently promoted Aβ lysosomal degradation, resulting in a decreased Aβ burden in APP/PS1 mice. Furthermore, OAC treatment inhibited oxidative damage by upregulating glutathione peroxidase expression and attenuated the production of inflammatory factors by downregulating nuclear factor-kB phosphorylation in APP/PS1 mice. ConclusionThese findings demonstrate, for the first time, that OAC could reduce the brain Aβ burden in APP/PS1 mice by inhibiting Aβ fibrillation through direct binding to Aβ and improve cognitive dysfunction by attenuating oxidative damage and neuroinflammation. These findings indicate that OAC may be a promising candidate for the treatment of AD.

ArhGAP11A mediates amyloid-β generation and neuropathology in an Alzheimer’s disease-like mouse model

Amyloid-β (Aβ) plays an important role in the neuropathology of Alzheimer's disease (AD), but some factors promoting Aβ generation and Aβ oligomer (Aβo) neurotoxicity remain unclear. We here find that the levels of ArhGAP11A, a Ras homology GTPase-activating protein, significantly increase in patients with AD and amyloid precursor protein (APP)/presenilin-1 (PS1) mice. Reducing the ArhGAP11A level in neurons not only inhibits Aβ generation by decreasing the expression of APP, PS1, and β-secretase (BACE1) through the RhoA/ROCK/Erk signaling pathway but also reduces Aβo neurotoxicity by decreasing the expressions of apoptosis-related p53 target genes. In APP/PS1 mice, specific reduction of the ArhGAP11A level in neurons significantly reduces Aβ production and plaque deposition and ameliorates neuronal damage, neuroinflammation, and cognitive deficits. Moreover, Aβos enhance ArhGAP11A expression in neurons by activating E2F1, which thus forms a deleterious cycle. Our results demonstrate that ArhGAP11A may be involved in AD pathogenesis and that decreasing ArhGAP11A expression may be a promising therapeutic strategy for AD treatment.

Multifunctional Supramolecular Vesicles as Zn2+ -Triggered Microglial Modulator Alleviates Alzheimer's Disease.

Zn2+ -induced β-amyloid protein (Aβ) aggregation and microglia activation are the predominant contributors in Alzheimer's disease (AD). Regulating intracephalic excessive Zn2+ is a promising therapeutic strategy for AD treatment. However, only inhibition of Zn2+ is hardly to repair continuous damages caused by activated microglia. Herein, an intelligent resveratrol-loaded supramolecular vesicles (RES-loaded vesicles) with zinc ion chelation function and responsive release capability are constructed to alleviate Aβ fibrillation, oxidative stress, and microglial dysfunction. The resveratrol encapsulation efficiency and drug loading efficiency are calculated to be 49.67% and 7.87%, respectively. In vitro studies demonstrate that the RES-loaded vesicles can modulate Zn2+ -dependent Aβ aggregation. More importantly, the cargoes will be released in zinc environment and further reprograms microglia from proinflammatory M1 phenotype toward anti-inflammatory M2 phenotype, which prevents spontaneous neuroinflammation and alleviates cytotoxicity of cultured cells from 29% to 12%. With the stereotactic or intranasal administration, RES-loaded vesicles can overcome the blood brain barrier, alleviate neuronal apoptosis, neuroinflammation, and ultimately ameliorate cognitive impairment in two AD mouse models. This work provides a new sight for taking advantage of Zn2+ to treat CNS disorders.

RETRACTED ARTICLE: Polyphenols from Conyza dioscoridis (L.) ameliorate Alzheimer’s disease- like alterations through multi-targeting activities in two animal models

BackgroundRecent investigations suggested that anticancer agents may inhibit the progression of Alzheimer's disease (AD) pathology. Conyza dioscoridis (L.) was demonstrated to have anticancer, antioxidant, anti-inflammatory and antidiabetic effects. This study was carried out to investigate the efficacy of polyphenols from Conyza dioscoridis (L.) extract (PCDE) on AD.MethodsImpacts of 3 doses of PCDE and donepezil, a reference drug, on the features of Alzheimer's disease in two animal models were investigated.ResultsPCDE ameliorated the memory and learning impairment shown in rats following a single dose of scopolamine (scopolamine model) or 17 weeks of high-fat/high-fructose(HF/Hfr) diet coupled with a single dose of streptozotocin, (25 mg/kg) (T2D model). They reduced significantly the high hippocampal cholinesterase activity in the two models of rats. Administration of PCDE for 8 weeks in the T2D model showed a significant reduction in hippocampal GSK-3β, caspase-3 activity and increase in the inhibited glutamate receptor expression (AMPA GluR1 subunit and NMDA receptor subunits NR1, NR2A, NR2B). A significant reduction of HOMA-insulin resistance and serum hypercholesterolemia was observed. The Tau hyperphosphorylation and Aβ 1–42 generation in the hippocampal of T2D rats were significantly decreased by PCDE. Modulation of the oxidative stress markers, (rise in GH and SOD; decrease in MDA levels) and a significant reduction of TNF-α and IL-1β in the hippocampus of T2D rats treated by PCDE extract were important findings in this study. The highest dose tested was 4% of the highest safe dose.ConclusionOur study suggests that PCDE is multi-targeting agent with multiple beneficial activities in combating features of AD. This study may provide a novel therapeutic strategy for AD treatment that warrants clinical studies.

Hypoxia Inducible Factor-1α binds and activates γ-secretase for Aβ production under hypoxia and cerebral hypoperfusion.

Hypoxic-ischemic injury has been linked with increased risk for developing Alzheimer's disease (AD). The underlying mechanism of this association is poorly understood. Here, we report distinct roles for hypoxia-inducible factor-1α (Hif-1α) in the regulation of BACE1 and γ-secretase activity, two proteases involved in the production of amyloid-beta (Aβ). We have demonstrated that Hif-1α upregulates both BACE1 and γ-secretase activity for Aβ production in brain hypoxia-induced either by cerebral hypoperfusion or breathing 10% O2. Hif-1α binds to γ-secretase, which elevates the amount of active γ-secretase complex without affecting the level of individual subunits in hypoxic-ischemic mouse brains. Additionally, the expression of full length Hif-1α increases BACE1 and γ-secretase activity in primary neuronal culture, whereas a transcriptionally incompetent Hif-1α variant only activates γ-secretase. These findings indicate that Hif-1α transcriptionally upregulates BACE1 and nontranscriptionally activates γ-secretase for Aβ production in hypoxic-ischemic conditions. Consequently, Hif-1α-mediated Aβ production may be an adaptive response to hypoxic-ischemic injury, subsequently leading to increased risk for AD. Preventing the interaction of Hif-1α with γ-secretase may therefore be a promising therapeutic strategy for AD treatment.

Sleep-Wake Disorders in Alzheimer's Disease: A Review.

Alzheimer's disease (AD) is a multifactorial disease, and it has become a serious health problem in the world. Senile plaques (SPs) and neurofibrillary tangles (NFTs) are two main pathological characters of AD. SP mainly consists of aggregated β-amyloid (Aβ), and NFT is formed by hyperphosphorylated tau protein. Sleep-wake disorders are prevalent in AD patients; however, the links and mechanisms of sleep-wake disorders on the AD pathogenesis remain to be investigated. Here, we referred to the sleep-wake disorders and reviewed some evidence to demonstrate the relationship between sleep-wake disorders and the pathogenesis of AD. On one hand, the sleep-wake disorders may lead to the increase of Aβ production and the decrease of Aβ clearance, the spreading of tau pathology, as well as oxidative stress and inflammation. On the other hand, the ApoE4 allele, a risk gene for AD, was reported to participate in sleep-wake disorders. Furthermore, some neurotransmitters, such as acetylcholine, glutamate, serotonin, melatonin, and orexins, and their receptors were suggested to be involved in AD development and sleep-wake disorders. We discussed and suggested some possible therapeutic strategies for AD treatment based on the view of sleep regulation. In general, this review explored different views to find novel targets of diagnosis and therapy for AD.

Emerging role of HDL in brain cholesterol metabolism and neurodegenerative disorders

High-density lipoproteins (HDL) play a key role in cholesterol homeostasis maintenance in the central nervous system (CNS), by carrying newly synthesized cholesterol from astrocytes to neurons, to support their lipid-related physiological functions. As occurs for plasma HDL, brain lipoproteins are assembled through the activity of membrane cholesterol transporters, undergo remodeling mediated by specific enzymes and transport proteins, and finally deliver cholesterol to neurons by a receptor-mediated internalization process. A growing number of evidences indicates a strong association between alterations of CNS cholesterol homeostasis and neurodegenerative disorders, in particular Alzheimer's disease (AD), and a possible role in this relationship may be played by defects in brain HDL metabolism. In the present review, we summarize and critically examine the current state of knowledge on major modifications of HDL and HDL-mediated brain cholesterol transport in AD, by taking into consideration the individual steps of this process. We also describe potential and encouraging HDL-based therapies that could represent new therapeutic strategies for AD treatment. Finally, we revise the main plasma and brain HDL modifications in other neurodegenerative disorders including Parkinson's disease (PD), Huntington's disease (HD), and frontotemporal dementia (FTD).

Lysosomal TPCN (two pore segment channel) inhibition ameliorates beta-amyloid pathology and mitigates memory impairment in Alzheimer disease

ABSTRACT Impairment of the macroautophagy/autophagy-lysosomal pathway (ALP) can lead to amyloid plaque accumulation in Alzheimer disease (AD); however, the underlying mechanism remains unresolved. This study revealed a mechanism of ALP impairment mediated by gain-of-function of lysosomal TPCN2/TPC2 (two pore segment channel 2) and suggests a molecular target for AD intervention. Using mutant PSEN1/PS1 (presenilin 1)-expressing human neuroblastoma SH-SY5Y and familial AD fibroblasts collected from human patients, we showed lysosomal pH was increased in AD cells due to exaggerated TPCN2-mediated calcium (Ca2+) release which increases lysosomal pH and compromises ALP degradation. Genetic knockdown or pharmacological inhibition of the TPCN2 channel restored lysosomal Ca2+ homeostasis, acidity of the lysosome and ALP function. Furthermore, AD mice (5xFAD) that had received treatment with the TPCN2 inhibitor tetrandrine for 6 months or injection of AAV-shTpcn2 to knock down Tpcn2 showed reduction in amyloid plaques in cortical and hippocampal regions. These treatments also improved spine morphology and density and corrected cognitive deficits in 5xFAD mice assayed by immunohistochemistry, behavioral tests, and electrophysiological measurements, respectively. Taken together, these findings reveal a previously under-appreciated role of lysosomal TPCN2 in ALP impairment of AD. They also suggest targeting the lysosomal TPCN2 can serve as a therapeutic strategy for AD treatment in future drug development. Abbreviations Aβ: β-amyloid; AD: Alzheimer disease; AIF1/IBA1: allograft inflammatory factor 1; ALP: autophagy-lysosomal pathway; APP: amyloid beta precursor protein; ATP6V1B1/V-ATPase V1b1: ATPase H+ transporting V1 subunit B1; AVs: autophagy vacuoles; BAF: bafilomycin A1; CFC: contextual/cued fear conditioning assay; CHX: Ca2+/H+ exchanger; CTF-β: carboxy-terminal fragment derived from β-secretase; CTSD: cathepsin D; fAD: familial Alzheimer disease; GFAP: glial fibrillary acidic protein; LAMP1: lysosomal associated membrane protein 1; LTP: long‐term potentiation; MCOLN1/TRPML1: mucolipin 1; MAP1LC3B/LC3B: microtubule associated protein 1 light chain 3 beta; MAPT: microtubule associated protein tau; MWM: Morris water maze; NFT: neurofibrillary tangles; PFC: prefrontal cortex; PSEN1: presenilin 1; SQSTM1/p62: sequestosome 1; TBS: theta burst stimulation; TEM: transmission electronic microscopy; TPCN2/TPC2: two pore segment channel 2; WT: wild-type; V-ATPase: vacuolar type H+-ATPase

MiR-204-3p/Nox4 Mediates Memory Deficits in a Mouse Model of Alzheimer’s Disease

Alzheimer's disease (AD) is the most common neurodegenerative disorder leading to dementia in the elderly, and the mechanisms of AD are not fully defined. MicroRNAs (miRNAs) have been shown to contribute to memory deficits in AD. In this study, we identified that miR-204-3p was downregulated in the hippocampus and plasma of 6-month-old APPswe/PS1dE9 (APP/PS1) mice. miR-204-3p overexpression attenuated memory and synaptic deficits in APP/PS1 mice. The amyloid levels and oxidative stress were decreased in the hippocampus of APP/PS1 mice after miR-204-3p overexpression. Nicotinamide adenine dinucleotide phosphate (NADPH) oxidase 4 (Nox4) was a target of miR-204-3p, and Nox4 inhibition by GLX351322 protected neuronal cells against Aβ1-42-induced neurotoxicity. Furthermore, GLX351322 treatment rescued synaptic and memory deficits, and decreased oxidative stress and amyloid levels in the hippocampus of APP/PS1 mice. These results revealed that miR-204-3p attenuated memory deficits and oxidative stress in APP/PS1 mice by targeting Nox4, and miR-204-3p overexpression and/or Nox4 inhibition might be a potential therapeutic strategy for AD treatment.

Polyampholyte-Based Synthetic Chaperone Modulate Amyloid Aggregation and Lithium Delivery.

Protein misfolding and aggregation is the pathological hallmark of Alzheimer's disease (AD). The etiopathogenesis of AD involves the accumulation of amyloid-β (Aβ) plaques in the brain, which disrupt the neuronal network and communication, causing neuronal death and severe cognitive impairment. Modulation of Aβ aggregation by exogenous therapeutic agents is considered an effective strategy to treat AD. Frequent failure of drug candidates in various phases of clinical trials reiterates the need for alternative therapeutic strategies for AD treatment. Polyampholytes with cationic and anionic segments are considered as artificial protein mimics capable of modulating the protein misfolding and aggregation. We report a diblock copolymer of tryptophan-functionalized methacrylic acid (PTMA) polyampholyte synthesized through reversible addition-fragmentation chain transfer (RAFT) polymerization. Investigation revealed that PTMA acts as a synthetic chaperone to protect the native structure of the lysozyme under heat-induced aggregation conditions. PTMA effectively modulates Aβ aggregation and rescues neuronal cells. Lithium has been shown to exhibit therapeutic efficacy in chronic neurological diseases including AD. PTMA sequesters and releases lithium ions in response to neuropathological pH stimuli, making it a promising candidate for lithium transport and delivery. The detailed studies demonstrate PTMA as aggregation modulator and lithium carrier with implications for combinational therapy to treat AD.

Direct Activation of Protein Phosphatase 2A (PP2A) by Tricyclic Sulfonamides Ameliorates Alzheimer's Disease Pathogenesis in Cell and Animal Models.

Alzheimer's disease (AD) is a multifactorial neurodegenerative disease for which there are limited therapeutic strategies. Protein phosphatase 2A (PP2A) activity is decreased in AD brains, which promotes the hyperphosphorylation of Tau and APP, thus participate in the formation of neurofibrillary tangles (NFTs) and β-amyloid (Aβ) overproduction. In this study, the effect of synthetic tricyclic sulfonamide PP2A activators (aka SMAPs) on reducing AD-like pathogenesis was evaluated in AD cell models and AD-like hyperhomocysteinemia (HHcy) rat models. SMAPs effectively increased PP2A activity, and decreased tau phosphorylation and Aβ40/42 levels in AD cell models. In HHcy-AD rat models, cognitive impairments induced by HHcy were rescued by SMAP administration. HHcy-induced tau hyperphosphorylation and Aβ overproduction were ameliorated through increasing PP2A activity on compound treatment. Importantly, SMAP therapy also prevented neuronal cell spine loss and neuronal synapse impairment in the hippocampus of HHcy-AD rats. In summary, our data reveal that pharmacological PP2A reactivation may be a novel therapeutic strategy for AD treatment, and that the tricyclic sulfonamides constitute a novel candidate class of AD therapeutic.

Cerebrovascular miRNAs correlate with the clearance of Aβ through perivascular route in younger 3xTg-AD mice.

The "two-hit vascular hypothesis for Alzheimer's disease (AD)" and amyloid-β (Aβ) oligomer hypothesis suggest that impaired soluble Aβ oligomers clearance through the cerebral vasculature may be an initial step of the AD process. Soluble Aβ oligomers are driven into perivascular spaces from the brain parenchyma and toward peripheral blood flow. The underlying vascular-based mechanism, however, has not been defined. Given that microRNAs (miRNAs), emerging as novel modulators, are involved in numerous physiological and pathological processes, we hypothesized that cerebrovascular miRNAs may regulate the activities of brain blood vessels, which further affects the concentration of Aβ in the AD brain. In this study, perivascular Aβ deposits, higher vascular activation, increased pericyte coverage and up-regulated capillaries miRNAs at 6 months old (6 mo) were found to correlate with the lower Aβ levels of middle AD stage (9 mo) in 3xTg-AD (3xTg) mice. It is implicated that at the early stage of AD when intracellular Aβ appeared, higher expression of vessel-specific miRNAs, elevated pericyte coverage, and activated endothelium facilitate Aβ oligomer clearance through the perivascular route, resulting in a transient reduction of Aβ oligomers at 9 mo. Additionally, ghrelin-induced upregulation of capillary miRNAs and increased pericyte coverage attenuated Aβ burden at 9 mo, in further support of the relationship between vascular miRNAs and Aβ clearance. This work suggests a cerebral microvessel miRNA may boost endothelial highly activated phenotypes to promote elimination of Aβ oligomers through the perivascular drainage pathway and contribute to AD progression. The targeting of brain vessel-specific miRNAs may provide a new rationale for the development of innovative therapeutic strategies for AD treatment.

Fruitless Wolfberry-Sprout Extract Rescued Cognitive Deficits and Attenuated Neuropathology in Alzheimer's Disease Transgenic Mice.

Alzheimer's disease (AD) is a neurodegenerative disease featured by memory loss, neuroinflammation and oxidative stress. Overproduction or insufficient clearance of Aβ leads to its pathological aggregation and deposition, which is considered the predominant neuropathological hallmark of AD. Therefore, reducing Aβ levels and inhibiting Aβ-induced neurotoxicity are feasible therapeutic strategies for AD treatment. Wolfberry has been traditionally used as a natural antioxidant and anti-aging product. However, whether wolfberry species has therapeutic potential on AD remains unknown. The effects of fruitless wolfberry-sprout extract (FWE) on Aβ fibrillation and fibril disaggregation was measured by thioflavin T fluorescence and transmission electron microscope imaging; Aβ oligomer level was determined by dot-blot; Cell viability and apoptosis was assessed by MTT and TUNEL assay. The levels of Aβ40/42, oxidative stress biomarkers and inflammatory cytokines were detected by corresponding kits. 8-month-old male APP/PS1 mice and their age-matched WT littermates were treated with FWE or vehicle by oral administration (gavage) once a day for 4 weeks. Then the cognitive performance was determined using object recognition test and Y-maze test. The Aβ burden and gliosis was evaluated by immunostaining and immunoblotting, respectively. FWE significantly inhibited Aβ fibrillation and disaggregated the formed Aβ fibrils, lowered Aβ oligomer level and Aβ-induced neuro-cytotoxicity, and attenuated oxidative stress in vitro. Oral administration of FWE remarkably improved cognitive function, reduced Aβ burden, decreased gliosis and inflammatory cytokines release, and ameliorated oxidative stress in the brains of APP/PS1 mice. These findings indicate that FWE is a promising natural agent for AD treatment.

Amyloid β-Derived Diffusible Ligands (ADDLs) Induce Abnormal Autophagy Associated with Aβ Aggregation Degree.

Autophagy is disturbed in Alzheimer's disease (AD) and maintaining normal autophagy homeostasis is a new therapeutic strategy for AD treatment. Amyloid β-derived diffusible ligands (ADDLs), the most toxic species of which are oligomeric forms of amyloid β peptide (Aβ) that originate from amyloid β precursor protein (APP) via autophagy; however, whether ADDLs are involved in autophagy-related AD pathogenesis remains unclear. In this study, we primarily defined the specific subsets of ADDLs, A-0, A-12, A-24, and A-48, which were generated from ADDL aggregation mixtures at different time courses of assembly. The secondary structures of ADDL subsets were detected by circular dichroism (CD). Neuronal or non-neuronal cells were exposed to the subsets of ADDLs in vitro, and then, autophagic markers were detected. Our results first showed that exogenous or endogenous LC3 puncta (autophagosomes) were induced in the cytoplasm of cells exposed to ADDLs and that the LC3 puncta were the strongest with A-24 exposure. Then, the CD spectroscopy data also indicated that the proportion of α-helices decreased, whereas the proportion of β-strands and β-turns increased during ADDL assembly from 0 to 24h. In addition, the quantitative Western blot data demonstrated that the ratio of LC3B-II/I was significantly increased, and SQSTM1/p62 decreased over time. Finally, our results indicated that the level of phosphorylated p70 S6 kinase (p-p70 S6 kinase), which is a substrate protein in the MTOR pathway, and the ratio of p-p70 S6 kinase/p70 S6 kinase significantly decreased following A-24 exposure. Taken together, our data suggest that ADDL-induced abnormal autophagy is correlated with Aβ aggregation degree and the MTOR pathway, which might contribute to ADDL-induced AD pathogenesis.

The Intersection of NGF/TrkA Signaling and Amyloid Precursor Protein Processing in Alzheimer's Disease Neuropathology.

Dysfunction of nerve growth factor (NGF) and its high-affinity Tropomyosin receptor kinase A (TrkA) receptor has been suggested to contribute to the selective degeneration of basal forebrain cholinergic neurons (BFCN) associated with the progressive cognitive decline in Alzheimer's disease (AD). The aim of this review is to describe our progress in elucidating the molecular mechanisms underlying the dynamic interplay between NGF/TrkA signaling and amyloid precursor protein (APP) metabolism within the context of AD neuropathology. This is mainly based on the finding that TrkA receptor binding to APP depends on a minimal stretch of ~20 amino acids located in the juxtamembrane/extracellular domain of APP that carries the α- and β-secretase cleavage sites. Here, we provide evidence that: (i) NGF could be one of the “routing” proteins responsible for modulating the metabolism of APP from amyloidogenic towards non-amyloidogenic processing via binding to the TrkA receptor; (ii) the loss of NGF/TrkA signaling could be linked to sporadic AD contributing to the classical hallmarks of the neuropathology, such as synaptic loss, β-amyloid peptide (Aβ) deposition and tau abnormalities. These findings will hopefully help to design therapeutic strategies for AD treatment aimed at preserving cholinergic function and anti-amyloidogenic activity of the physiological NGF/TrkA pathway in the septo-hippocampal system.

A computational study of self-assembled hexapeptide inhibitors against amyloid-β (Aβ) aggregation.

The fibrillation and deposition of amyloid-β (Aβ) peptides in human brains are pathologically linked to Alzheimer's disease (AD). Development of different inhibitors (peptides, organic molecules, and nanoparticles) to prevent Aβ aggregation becomes a promising therapeutic strategy for AD treatment. We recently propose a "like-interacts-like" design principle to computationally design/screen and experimentally validate a new set of hexapeptide inhibitors with completely different sequences from the Aβ sequence. These hexapeptide inhibitors inhibit Aβ aggregation and reduce Aβ-induced cytotoxicity. However, inhibitory mechanisms of these hexapeptides and the underlying interactions between hexapeptides and Aβ remain unclear. Herein we apply multi-scale computational methods (quantum-chemical calculations, molecular docking and explicit-solvent molecular dynamic simulation) to explore the structure, dynamics, and interaction between 3 identified hexapeptides (CTLWWG, GTVWWG, and CTIYWG) and different Aβ-derived fragments and an Aβ17-42 pentamer. When interacting with 6 Aβ-derived fragments, 3 hexapeptide inhibitors show stronger interactions with two lysine-included fragments (16KLVFFA21 and 27NKGAII33) than other fragments, indicating different sequence-specific interactions with Aβ. When interacting with the Aβ17-42 pentamer, the 3 peptides show similar binding modes and interaction mechanisms by preferentially binding to the edge of the Aβ17-42 pentamer to potentially block the Aβ elongation pathway. This work provides structural-based binding information on further modification and optimization of these peptide inhibitors to experimentally enhance their inhibitory abilities against Aβ aggregation.

KCa3.1 constitutes a pharmacological target for astrogliosis associated with Alzheimer's disease.

Alzheimer's disease (AD) is the most common type of dementia and is characterized by a progression from decline of episodic memory to a global impairment of cognitive function. Astrogliosis is a hallmark feature of AD, and reactive gliosis has been considered as an important target for intervention in various neurological disorders. We previously found in astrocyte cultures that the expression of the intermediate conductance calcium-activated potassium channel KCa3.1 was increased in reactive astrocytes induced by TGF-β, while pharmacological blockade or genetic deletion of KCa3.1 attenuated astrogliosis. In this study, we sought to suppress reactive gliosis in the context of AD by inhibiting KCa3.1 and evaluate its effects on the cognitive impairment using murine animal models such as the senescence-accelerated mouse prone 8 (SAMP8) model that exhibits some AD-like symptoms. We found KCa3.1 expression was increased in reactive astrocytes as well as neurons in the brains of both SAMP8 mice and Alzheimer's disease patients. Blockade of KCa3.1 with the selective inhibitor TRAM-34 in SAMP8 mice resulted in a decrease in astrogliosis as well as microglia activation, and moreover an attenuation of memory deficits. Using KCa3.1 knockout mice, we further confirmed that deletion of KCa3.1 reduced the activation of astrocytes and microglia, and rescued the memory loss induced by intrahippocampal Aβ1-42 peptide injection. We also found in astrocyte cultures that blockade of KCa3.1 or deletion of KCa3.1 suppressed Aβ oligomer-induced astrogliosis. Our data suggest that KCa3.1 inhibition might represent a promising therapeutic strategy for AD treatment.

Mitochondrial Dysfunction in Neocortex and Hippocampus of Olfactory Bulbectomized Mice, a Model of Alzheimer's Disease.

Structural and functional impairments of mitochondria in brain tissues in the pathogenesis of Alzheimer's disease (AD) cause energy deficiency, increased generation of reactive oxygen species (ROS), and premature neuronal death. However, the causal relations between accumulation of beta-amyloid (Aβ) peptide in mitochondria and mitochondrial dysfunction, as well as molecular mechanisms underlying deleterious effects of both these factors in sporadic AD, the most common form in humans, remain unknown. Here we used olfactory bulbectomized (OBX) mice of NMRI strain as a model for sporadic AD. Five weeks after surgery, the OBX mice developed major behavioral and biochemical features of AD neurodegeneration, including spatial memory loss, increased brain levels of Aβ, and energy deficiency. Mitochondria isolated from the neocortex and hippocampus of OBX mice displayed severe functional impairments, such as low NADH oxidation rate, reduced transmembrane potential, and decreased cytochrome c oxidase (complex IV) activity that correlated with high levels of soluble Aβ1-40. Mitochondria from OBX mice showed increased contents of lipid peroxidation products, indicative of the development of oxidative stress. We found that neurodegeneration caused by olfactory bulbectomy is accompanied by energy metabolism disturbances and oxidative stress in brain mitochondria similar to those occurring in transgenic animals - familial AD models and patients with sporadic AD. Therefore, OBX mice can serve as a valid AD model for investigating the mechanisms of AD neurodegeneration, drug testing, and development of therapeutic strategies for AD treatment.

Specific Knockdown of Endogenous Tau Protein by Peptide-Directed Ubiquitin-Proteasome Degradation

Tau, an important pathological protein of Alzheimer's disease (AD), can mediate the toxicity of amyloid β (Aβ). Thus, reduction of Tau with chemical molecules may offer a novel strategy for treating AD. Here, we designed and synthesized a series of multifunctionalmolecules that contained Tau-recognition moieties and E3 ligase-binding moieties to enhance Tau degradation. Among these molecules, TH006 had thehighest activity of inducing Tau degradation by increasing its poly-ubiquitination. The decrement in Tau induced by TH006 could decrease the cytotoxicity caused by Aβ. Furthermore, TH006 could regulate the Tau level in the brain of an AD mouse model. Therefore, partial reduction of Tau with such multifunctional peptides may open up a novel therapeutic strategy for AD treatment.

The Voltage-dependent Anion Channel 1 Mediates Amyloid β Toxicity and Represents a Potential Target for Alzheimer Disease Therapy

The voltage-dependent anion channel 1 (VDAC1), found in the mitochondrial outer membrane, forms the main interface between mitochondrial and cellular metabolisms, mediates the passage of a variety of molecules across the mitochondrial outer membrane, and is central to mitochondria-mediated apoptosis. VDAC1 is overexpressed in post-mortem brains of Alzheimer disease (AD) patients. The development and progress of AD are associated with mitochondrial dysfunction resulting from the cytotoxic effects of accumulated amyloid β (Aβ). In this study we demonstrate the involvement of VDAC1 and a VDAC1 N-terminal peptide (VDAC1-N-Ter) in Aβ cell penetration and cell death induction. Aβ directly interacted with VDAC1 and VDAC1-N-Ter, as monitored by VDAC1 channel conductance, surface plasmon resonance, and microscale thermophoresis. Preincubated Aβ interacted with bilayer-reconstituted VDAC1 and increased its conductance ∼ 2-fold. Incubation of cells with Aβ resulted in mitochondria-mediated apoptotic cell death. However, the presence of non-cell-penetrating VDAC1-N-Ter peptide prevented Aβ cellular entry and Aβ-induced mitochondria-mediated apoptosis. Likewise, silencing VDAC1 expression by specific siRNA prevented Aβ entry into the cytosol as well as Aβ-induced toxicity. Finally, the mode of Aβ-mediated action involves detachment of mitochondria-bound hexokinase, induction of VDAC1 oligomerization, and cytochrome c release, a sequence of events leading to apoptosis. As such, we suggest that Aβ-mediated toxicity involves mitochondrial and plasma membrane VDAC1, leading to mitochondrial dysfunction and apoptosis induction. The VDAC1-N-Ter peptide targeting Aβ cytotoxicity is thus a potential new therapeutic strategy for AD treatment.