Low molecular weight chondroitin sulfate ameliorates pathological changes in 5XFAD mice by improving various functions in the brain.

Our previous study found that low molecular weight chondroitin sulfate (LMWCS) had neuroprotective effects against the toxicity of amyloid-ß (Aß) peptides both in vitro and in vivo, and we speculated that the effects might be related with its anti-oxidative activities. In this study, the anti-Alzheimer's disease (AD) activity of LMWCS was further studied in 5XFAD transgenic mice. After 4-month gavage, the levels of Aß1-42 level, amyloid precursor protein (APP) and presenilin 1 (PS1) were significantly decreased in the brains of 5XFAD mice, indicating the alteration of APP metabolism by LMWCS. Besides, LMWCS inhibited the secretions of pro-inflammatory cytokines, including interleukin-1ß (IL-1ß), tumor necrosis factor-α (TNF-α) and IL-6. Furthermore, the suppression of neuroinflammation by LMWCS was supported by the decreased expressions of glial fibrillary acidic protein (GFAP) and toll-like receptor 2 (TLR2) in the brains. LMWCS also reduced the production of reactive oxygen species (ROS) and the level of phospho-tau (Ser404) in the brains. Nevertheless, the changes in the behavior tests were moderate. In conclusion, LMWCS administration ameliorated APP metabolism, neuroinflammation, ROS production and tau protein abnormality in the brains of 5XFAD mice, displaying the potential to improve the pathological changes of AD mouse brain. LMWCS could be considered as a promising anti-AD drug candidate, nonetheless, the therapy regimen need to be optimized to improve its pharmacotherapy efficacy.

Green Tea Epigallocatechin-3-gallate (EGCG) Targeting Protein Misfolding in Drug Discovery for Neurodegenerative Diseases.

The potential to treat neurodegenerative diseases (NDs) of the major bioactive compound of green tea, epigallocatechin-3-gallate (EGCG), is well documented. Numerous findings now suggest that EGCG targets protein misfolding and aggregation, a common cause and pathological mechanism in many NDs. Several studies have shown that EGCG interacts with misfolded proteins such as amyloid beta-peptide (Aß), linked to Alzheimer's disease (AD), and α-synuclein, linked to Parkinson's disease (PD). To date, NDs constitute a serious public health problem, causing a financial burden for health care systems worldwide. Although current treatments provide symptomatic relief, they do not stop or even slow the progression of these devastating disorders. Therefore, there is an urgent need to develop effective drugs for these incurable ailments. It is expected that targeting protein misfolding can serve as a therapeutic strategy for many NDs since protein misfolding is a common cause of neurodegeneration. In this context, EGCG may offer great potential opportunities in drug discovery for NDs. Therefore, this review critically discusses the role of EGCG in NDs drug discovery and provides updated information on the scientific evidence that EGCG can potentially be used to treat many of these fatal brain disorders.

Aminoguanidine ameliorates ovariectomy-induced neuronal deficits in rats by inhibiting AGE-mediated Aß production.

Advanced glycation end products (AGEs) have been reported to cause neurodegeneration, senile plaque formation and spatial learning and memory deficits. There is much evidence describing the beneficial effects of aminoguanidine (AG) on the central nervous system; AG is able to inhibit the receptor for AGEs and beta-amyloid (Aß) deposition in the brain, thus preventing cognitive decline and neurodegeneration. In this study, we investigated whether AG protects against ovariectomy-induced neuronal deficits and Aß deposition in rats. Animals in the ovariectomy group (OVX) group, and those in the OVX+AG group were treated with AG (100 mg/kg/day) for 8 weeks. Learning and memory were evaluated using the electric Y maze. AGE and Aß1-40 biochemical assessments were performed using enzyme-linked immunosorbent assay (ELISA) kits. Furthermore, evaluations of brain amyloid precursor protein 695 (APP695) mRNA expression by RT-PCR and AGE expression by immunohistochemistry were carried out. Ovariectomized rats exhibited memory impairment and Aß production disorder with upregulated APP695 mRNA and AGE expression levels. AG pretreatment relieved the ovariectomy-induced learning and memory disorder and significantly ameliorated the Aß production disturbance and AGE generation. Additionally, pathological changes in morphology were also significantly recovered. Our data reveal that AG plays a potentially neuroprotective role against ovariectomy-induced learning and cognitive impairment and Aß production disorder.Advanced glycation end products (AGEs) have been reported to cause neurodegeneration, senile plaque formation and spatial learning and memory deficits. There is much evidence describing the beneficial effects of aminoguanidine (AG) on the central nervous system; AG is able to inhibit the receptor for AGEs and beta-amyloid (Aß) deposition in the brain, thus preventing cognitive decline and neurodegeneration. In this study, we investigated whether AG protects against ovariectomy-induced neuronal deficits and Aß deposition in rats. Animals in the ovariectomy group (OVX) group, and those in the OVX+AG group were treated with AG (100 mg/kg/day) for 8 weeks. Learning and memory were evaluated using the electric Y maze. AGE and Aß1-40 biochemical assessments were performed using enzyme-linked immunosorbent assay (ELISA) kits. Furthermore, evaluations of brain amyloid precursor protein 695 (APP695) mRNA expression by RT-PCR and AGE expression by immunohistochemistry were carried out. Ovariectomized rats exhibited memory impairment and Aß production disorder with upregulated APP695 mRNA and AGE expression levels. AG pretreatment relieved the ovariectomy-induced learning and memory disorder and significantly ameliorated the Aß production disturbance and AGE generation. Additionally, pathological changes in morphology were also significantly recovered. Our data reveal that AG plays a potentially neuroprotective role against ovariectomy-induced learning and cognitive impairment and Aß production disorder.

Protective effects of a small molecule inhibitor, DDQ against amyloid beta in Alzheimer's disease.

The purpose of our study is to determine the protective effects of the newly discovered molecule DDQ (diethyl (3,4-dihydroxyphenethylamino)(quinolin-4-yl) methylphosphonate) against mutant APP and amyloid-beta (Aß) in Alzheimer's disease (AD). To achieve our objective, we used a well characterized amyloid-beta precursor protein (APP) transgenic mouse model (Tg2576 strain). We administered DDQ, a 20 mg/kg body weight (previously determined in our laboratory) intra-peritoneally 3-times per week for 2 months, starting at the beginning of the 12th month, until the end of the 14th month. Further, using biochemical and molecular methods, we measured the levels of DDQ in the blood, skeletal muscle, and brain. Using Morris Water Maze, Y-maze, open field, and rotarod tests, we assessed cognitive behavior after DDQ treatment. Using q-RT-PCR, immunoblotting, transmission electron microscopy, and Golgi-cox staining methods, we studied mRNA and protein levels of longevity genes SIRTUINS, mitochondrial number & length, and dendritic spine number and length in DDQ-treated APP mice. Our extensive pharmacodynamics analysis revealed high peak levels of DDQ in the skeletal muscle, followed by serum and brain. Our behavioral analysis of rotarod, open field, Y-maze, and Morris Water Maze tests revealed that DDQ ameliorated cognitive decline (Morris Water Maze), improved working memory (Y-Maze), exploratory behavior (open field), and motor coordination (rotarod) in DDQ-treated APP mice. Interestingly, longevity genes SIRTUINS, mitochondrial biogenesis, fusion, mitophagy, autophagy and synaptic genes were upregulated in DDQ-treated APP mice relative to untreated APP mice. Dendritic spines and the quality mitochondria were significantly increased in DDQ treated APP mice. Current study findings, together with our previous study observations, strongly suggest that DDQ has anti-aging, and anti-amyloid-beta effects and a promising molecule to reduce age-and amyloid-beta-induced toxicities in AD.

Cholesterol-lowering drugs reduce APP processing to Aß by inducing APP dimerization.

Amyloid beta (Aß) is a major component of amyloid plaques, which are a key pathological hallmark found in the brains of Alzheimer's disease (AD) patients. We show that statins are effective at reducing Aß in human neurons from nondemented control subjects, as well as subjects with familial AD and sporadic AD. Aß is derived from amyloid precursor protein (APP) through sequential proteolytic cleavage by BACE1 and γ-secretase. While previous studies have shown that cholesterol metabolism regulates APP processing to Aß, the mechanism is not well understood. We used iPSC-derived neurons and bimolecular fluorescence complementation assays in transfected cells to elucidate how altering cholesterol metabolism influences APP processing. Altering cholesterol metabolism using statins decreased the generation of sAPPß and increased levels of full-length APP (flAPP), indicative of reduced processing of APP by BACE1. We further show that statins decrease flAPP interaction with BACE1 and enhance APP dimerization. Additionally, statin-induced changes in APP dimerization and APP-BACE1 are dependent on cholesterol binding to APP. Our data indicate that statins reduce Aß production by decreasing BACE1 interaction with flAPP and suggest that this process may be regulated through competition between APP dimerization and APP cholesterol binding.

Isoorientin, a GSK-3ß inhibitor, rescues synaptic dysfunction, spatial memory deficits and attenuates pathological progression in APP/PS1 model mice.

ß-Amyloid (Aß) elevation, tau hyperphosphorylation, and neuroinflammation are major hallmarks of Alzheimer's disease (AD). Glycogen synthase kinase-3ß (GSK-3ß) is a key protein kinase implicated in the pathogenesis of AD. Blockade of GSK-3ß is an attractive therapeutic strategy for AD. Isoorientin, a 6-C-glycosylflavone, was previously shown to be a highly selective inhibitor of GSK-3ß, while exerting neuroprotective effects in neuronal models of AD. In the present study, we evaluated the in vivo effects of isoorientin on GSK-3ß, tau phosphorylation, Aß deposition, neuroinflammatory response, long-term potentiation, and spatial memory in amyloid precursor protein/presenilin 1 (APP/PS1) transgenic mice using biochemical, electrophysiological, and behavioral tests. Chronic oral administration of isoorientin to APP/PS1 mice at 8 months of age attenuated multiple AD pathogenic hallmarks in the brains, including GSK-3ß overactivation, tau hyperphosphorylation, Aß deposition, and neuroinflammation. For neuroinflammation, isoorientin treatment reduced the number of activated microglia associated with Aß-positive plaques, and in parallel reduced the levels of pro-inflammatory factors in the brains of APP/PS1 mice. Strikingly, isoorientin reversed deficits in synaptic long-term potentiation and spatial memory relevant to cognitive functions. Together, the findings suggest that isoorientin is a brain neuroprotector and may be a promising drug lead for treatment of AD and related neurodegenerative disorders.

9R, the cholinesterase and amyloid beta aggregation dual inhibitor, as a multifunctional agent to improve cognitive deficit and neuropathology in the triple-transgenic Alzheimer's disease mouse model.

Alzheimer's disease (AD) is the most common kind of dementia in the aging population leading to great social and financial burdens in many countries around the world. For decades, disease-modifying drug developed using the "one target, one drug" strategy failed to conquer this disease. Recently, we have designed and synthesized 9R, which exhibited dual inhibition of cholinesterase and amyloid beta (Aß) aggregation in vitro. Herein, we evaluated the in vivo efficacy of 9R in a triple transgenic AD (3xTg-AD) mouse model. 3xTg-AD mice (10-month-old) were dosed intraperitoneally with 9R (daily 3, 10 or 30 mg/kg) for a month. Known cholinesterase inhibitor donepezil (0.3 mg/kg) and Aß aggregation inhibitor tramiprosate (30 mg/kg) were used as positive controls. Cognitive performance of the mice was then evaluated by using Morris Water Maze (MWM), Y-maze tasks and Open Field test. The acetylcholine level, degree of Aß deposition, amyloid precursor protein (APP) processing, neuroinflammation, tau deposition and tau hyperphosphorylation in the brains of the 3xTg-AD mice were examined. We have observed that one-month treatment with 9R significantly improved cognitive deficits in 3xTg-AD mice. Moreover, 9R treatment enhanced the brain acetylcholine level and mitigated the amyloid burden, tau hyperphosphorylation and neuroinflammation in the mouse brains. The effects of 9R on APP processing, neuroinflammation, tau hyperphosphorylation and Cdk-p25 action demonstrated its multifunctional role in 3xTg-AD mouse model. Our results suggested that the use of multi-target compound could be a potential approach to treat AD.

Alterations of fatty acid composition and metabolism in APP/PS1 transgenic mice.

Accumulating evidence suggests that abnormal fatty acid composition is related to the development of Alzheimer's disease (AD). However, there is no consistency in the fatty acid profile and metabolism associated with AD pathogenesis. This study aims to define the characteristics of fatty acid composition and metabolism in AD. Using 6-month-old APP/PS1 transgenic mice with wild-type mice as a control, we examined the serum lipids, brain fatty acid composition, and the expression levels of various genes involved in liver fatty acid ß-oxidation. The results of our study demonstrate that APP/PS1 mice present decreased serum free fatty acids, altered brain fatty acid profiles, and minimal change in liver fatty acid ß-oxidation. Our results suggest that abnormal fatty acid compositions and contents may play potential roles in AD progression. This study provides further evidence for the metabolic basis of AD pathogenesis.

The aroylhydrazone INHHQ prevents memory impairment induced by Alzheimer's-linked amyloid-ß oligomers in mice.

Converging evidence indicates that neurotoxicity and memory impairment in Alzheimer's disease is induced by brain accumulation of soluble amyloid-ß oligomers (AßOs). Physiological metals are poorly distributed and concentrated in the senile plaques typical of Alzheimer's disease, where they may be coordinated to the amyloid-ß peptide (Aß). Indeed, zinc and copper increase Aß oligomerization and toxicity. Metal-protein attenuating compounds represent a class of agents proposed for Alzheimer's disease treatment, as they reduce abnormal interactions of metal ions with Aß, inhibit Aß oligomerization and prevent deleterious redox reactions in the brain. The present work investigates the protective action of an isoniazid-derived aroylhydrazone, INHHQ, on AßO-induced memory impairment. Systemic administration of a single dose of INHHQ (1 mg/kg) prevented both short-term and long-term memory impairment caused by AßOs in mice. In-vitro studies showed that INHHQ prevents Cu(Aß)-catalyzed production of reactive oxygen species. Although the mechanism of protection by INHHQ is not yet fully understood at a molecular level, the results reported herein certainly point to the value of aroylhydrazones as promising neuroprotective agents in Alzheimer's disease and related disorders.

Impact of Cannabis-Based Medicine on Alzheimer's Disease by Focusing on the Amyloid ß-Modifications: A Systematic Study.

Deposition of Amyloid-beta (Aß) peptide in the brain is the leading source of the onset and progression of Alzheimer's Disease (AD). Recent studies have suggested that anti-amyloidogenic agents may be a suitable therapeutic strategy for AD. The current review was proposed to address the beneficial effects of cannabis-based drugs for the treatment of AD, focusing primarily on Aß modifications. Keywords related to AD, Aß, and cannabis-based on MeSH were identified and were searched in PubMed, Google Scholar, Scopus, Ovid-Medline, and Web of Science from inception until 15 March 2020. The full text of identified papers was obtained and assessed based on exclusion and inclusion criteria. The review is based on articles that have focused on AD and the amyloidogenic pathway. A total of 17 studies were identified based on the inclusion criteria; however, nine studies qualified for this systematic review. The maximum and minimum cannabis dosages, mostly CBD and THC in animal studies, were 0.75 and 50 mg/kg, respectively. Cannabis (CBD and THC) was injected for 10 to 21 days. The findings of the 9 articles indicated that cannabis-based drugs might modulate Aß modifications in several AD models. Our findings establish that cannabis-based drugs inhibited the progression of AD by modulating Aß modifications.

Comparative Effects of Alpha- and Gamma-Tocopherol on Mitochondrial Functions in Alzheimer's Disease In Vitro Model.

Vitamin E acts as an antioxidant and reduces the level of reactive oxygen species (ROS) in Alzheimer's disease (AD). Alpha-tocopherol (ATF) is the most widely studied form of vitamin E besides gamma-tocopherol (GTF) which also shows beneficial effects in AD. The levels of amyloid-beta (Aß) and amyloid precursor protein (APP) increased in the brains of AD patients, and mutations in the APP gene are known to enhance the production of Aß. Mitochondrial function was shown to be affected by the increased level of Aß and may induce cell death. Here, we aimed to compare the effects of ATF and GTF on their ability to reduce Aß level, modulate mitochondrial function and reduce the apoptosis marker in SH-SY5Y cells stably transfected with the wild-type or mutant form of the APP gene. The Aß level was measured by ELISA, the mitochondrial ROS and ATP level were quantified by fluorescence and luciferase assay respectively whereas the complex V enzyme activity was measured by spectrophotometry. The expressions of genes involved in the regulation of mitochondrial membrane permeability such as voltage dependent anion channel (VDAC1), adenine nucleotide translocase (ANT), and cyclophilin D (CYPD) were determined by quantitative real-time polymerase chain reaction (qRT-PCR), while the expressions of cyclophilin D (CypD), cytochrome c, Bcl2 associated X (BAX), B cell lymphoma-2 (Bcl-2), and pro-caspase-3 were determined by western blot. Our results showed that mitochondrial ROS level was elevated accompanied by decreased ATP level and complex V enzyme activity in SH-SY5Y cells expressing the mutant APP gene (p < 0.05). Treatment with both ATF and GTF reduced the mitochondrial ROS level with maximum reduction was observed in the cells treated with high concentrations of ATF and GTF (p < 0.05). However, only GTF at 80 µM significantly increase the ATP level and complex V enzyme activity (p < 0.05). VDAC1 and CYPD were downregulated and CypD protein was significantly overexpressed in cells transfected with the wild-type (WT) and mutant APP gene (p < 0.05). Cytochrome c release, the ratio of BAX/Bcl-2, and pro-caspase-3 expression increased in cells expressing mutated APP gene (p < 0.05). The expression of CypD and pro-caspase 3 protein, and the ratio of BAX/Bcl-2 were increased in the following order; SH-SY5Y-APP-WT < SH-SY5Y-APP Swe

New BACE1 Chimeric Peptide Inhibitors Selectively Prevent AßPP-ß Cleavage Decreasing Amyloid-ß Production and Accumulation in Alzheimer's Disease Models.

BACKGROUND: A disease-modifying therapy for Alzheimer's disease (AD) is still an unmet clinical need. The formation of amyloid-ß (Aß) requires the initial cleavage of the amyloid-ß protein precursor (AßPP) by BACE1 (beta-site AßPP cleaving enzyme 1), which is a prime therapeutic target for AD. OBJECTIVE: We aimed to design and develop a selective BACE1 inhibitor suitable to AD treatment. METHODS: The new BACE1 inhibitors consist on a chimeric peptide including a sequence related to the human Swedish mutant form of AßPP (AßPPswe) conjugated with the TAT carrier that facilitates cell membrane permeation and the crossing of the blood-brain barrier. Additionally to the chimeric peptide in the L-form, we developed a D-retroinverso chimeric peptide. The latter strategy, never used with BACE1 inhibitors, is considered to favor a significantly higher half-life and lower immunogenicity. RESULTS: We found that both chimeric peptides inhibit recombinant BACE1 activity and decrease Aß40/42 production in Neuro-2a (N2A) cells expressing AßPPswe without inducing cytotoxicity. The intraperitoneal administration of these peptides to 3xTg-AD mice decreased plasma and brain Aß40/42 levels, as well as brain soluble AßPPß production. Also, a reduction of insoluble Aß was observed in the brain after chronic treatment. Noteworthy, the chimeric peptides selectively inhibited the AßPP-ß cleavage relatively to the proteolysis of other BACE1 substrates such as close homologue of L1 (CHL1) and seizure-related gene 6 (SEZ6). CONCLUSIONS: Overall these new BACE1 chimeric peptideshold promising potential as a selective disease-modifying therapy for AD.

Anti-HIV drugs promote ß-amyloid deposition and impair learning and memory in BALB/c mice.

OBJECTIVES: Growing evidence suggested that antiretroviral (ARV) drugs may promote amyloid beta (Aß) accumulation in HIV-1-infected brain and the persistence of HIV-associated neurocognitive disorders (HANDs). It has also been shown that lipid peroxidation upregulates ß-site amyloid precursor protein (APP) cleaving enzyme 1 (BACE1) expression and subsequently promotes Aß peptide production. In the present study, we examined whether chronic exposure to the anti-HIV drugs tenofovir disoproxil fumarate (TDF) and nevirapine induces lipid peroxidation thereby promoting BACE1 and Aß generation and consequently impair cognitive function in mice. METHODS: TDF or nevirapine was orally administered to female BALB/c mice once a day for 8 weeks. On the 7th week of treatment, spatial learning and memory were assessed using the Morris water maze test. The levels of lipid peroxidation, BACE1, amyloid ß 1-42 (Aß1-42) and Aß deposits were measured in the hippocampal tissue upon completion of treatment. RESULTS: Chronic administration of nevirapine induced spatial learning and memory impairment in the Morris water maze test, whereas TDF did not have an effect. TDF and nevirapine administration increased hippocampal lipid peroxidation and Aß1-42 concentration. Nevirapine further upregulated BACE1 expression and Aß deposits. CONCLUSION: Our results suggest that chronic exposure to TDF and nevirapine contributes to hippocampal lipid peroxidation and Aß accumulation, respectively, as well as spatial learning and memory deficits in mice even in the absence of HIV infection. These findings further support a possible link between ARV drug toxicity, Aß accumulation and the persistence of HANDs.

Neuroprotective Effect of ß-secretase Inhibitory Peptide from Pacific Hake (Merluccius productus) Fish Protein Hydrolysate.

BACKGROUND: Various methodologies have been employed for the therapeutic interpolation of the progressive brain disorder Alzheimer's disease. Thus, ß-secretase inhibition is significant to prevent disease progression in the early stages. OBJECTIVE: This study seeks to purify and characterize a novel ß-secretase inhibitory peptide from Pacific hake enzymatic hydrolysate. METHODS: A potent ß-secretase inhibitory peptide was isolated by sequential purifications using Sephadex G-25 column chromatography and octadecylsilane (ODS) C18 reversed-phase HPLC. A total of seven peptides were synthesized using the isolated peptide sequences. SH-SY5Y cells stably transfected with the human ''Swedish'' amyloid precursor protein (APP) mutation APP695 (SH-SY5YAPP695swe) were used as an in-vitro model system to investigate the effect of Leu-Asn peptide on APP processing. RESULTS: The ß-secretase inhibitory activity (IC50) of the purified peptide (Ser-Leu-Ala-Phe-Val-Asp- Asp-Val-Leu-Asn) from fish protein hydrolysate was 18.65 µM and dipeptide Leu-Asn was the most potent ß-secretase inhibitor (IC50 value = 8.82 µM). When comparing all the seven peptides, the inhibition pattern of Leu-Asn dipeptide was found to be competitive by Lineweaver-Burk plot and Dixon plot (Ki value = 4.24 µM). The 24 h treatment with Leu-Asn peptide in SH-SY5Y cells resulted in reducing the ß-amyloid (Aß) production in a dose-dependent manner. CONCLUSION: Therefore, the results of this study suggest that ß-secretase inhibitory peptides derived from marine organisms could be potential candidates to develop nutraceuticals or pharmaceuticals as antidementia agents.

Ozone Inhibits APP/Aß Production and Improves Cognition in an APP/PS1 Transgenic Mouse Model.

Alzheimer's disease (AD) is a progressive neurodegenerative disorder without effective treatment. Accumulating evidence demonstrates the production and deposition of amyloid-ß peptides (Aß) in the pathological mechanism of this disease. In our study, we investigated the effect of an ozone intraperitoneal injection on AD pathology in APP/PS1 transgenic mouse model. The male mice (5-months-old) received either ozone intraperitoneal injection (at 30 µg/ml or 50 µg/ml) or abdominocentesis administration daily for 25 days, and they were evaluated in the Morris water maze and the open field test for improvements in spatial learning-memory and working memory and anxious. Prefrontal cortex and hippocampus amyloid-ß precursor protein (APP), along with other relevant biomarkers for AD, were measured through ELISA, western blot and immunohistochemistry. Results showed that ozone ameliorated the behavioral and pathological deterioration of APP/PS1 transgenic mice, and reduced the level of APP, which supports the therapeutic potential of administration of ozone in APP/PS1 mice.

JBPOS0101 attenuates amyloid-ß accumulation and memory loss in a mouse model of Alzheimer's disease.

Alzheimer's disease (AD) is a major neurodegenerative disorder characterized by the accumulation of amyloid-ß (Aß) in the brain. Defects in Aß clearance or the interference of Aß homeostasis could result in Aß aggregation. JBPOS0101 has been studied for its antiepileptic activity. It showed a neuroprotective effect and prevented memory deficits in lithium-pilocarpine-induced status epilepticus rats. In this study, we tested the effect of JBPOS0101 in an AD model. We showed that JBPOS0101 attenuated the accumulation of Aß in 5XFAD mouse brains. Moreover, the treatment of JBPOS0101 rescued the deficits in learning and memory in 5XFAD mice. These data suggest that JBPOS0101 could be a potential therapeutic drug candidate for AD.

The cyanobacterial neurotoxin ß-N-methylamino-l-alanine prevents addition of heparan sulfate to glypican-1 and increases processing of amyloid precursor protein in dividing neuronal cells.

The neurotoxin ß-N-methylamino-l-alanine replaces l-serine in proteins and produces Alzheimer-like pathology. In proteoglycans, e.g. glypican-1, this should preclude substitution with heparan sulfate chains. Reduced release of heparan sulfate should increase ß-secretase activity and processing of amyloid precursor protein. Cultured cells were treated with ß-N-methylamino-l-alanine during the growth-phase and the effect on heparan sulfate substitution and amyloid precursor protein processing was evaluated using antibodies specific for heparan sulfate, the N- and C-termini of the C-terminal fragment of ß-cleaved amyloid precursor protein, and amyloid beta followed by immunofluorescence microscopy, flow cytometry or SDS-PAGE. Mouse fibroblasts, N2a neuroblastoma cells and human neural stem cells released less heparan sulfate when grown in the presence of ß-N-methylamino-l-alanine. Cells expressing a recombinant, anchor-less glypican-1 secreted heparan sulfate-deficient glypican-1. There was increased processing of amyloid precursor protein in N2a cells when grown in the presence of the neurotoxin. The degradation products accumulated in cytoplasmic clusters. Secretion of amyloid beta increased approx. 3-fold. Human neural stem cells also developed cytoplasmic clusters containing degradation products of amyloid precursor protein. When non-dividing mouse N2a cells or cortical neurons were exposed to ß-N-methylamino-l-alanine there was no effect on heparan sulfate substitution in glypican-1 or on amyloid precursor protein processing.

Structure-Based Design of Selective ß-Site Amyloid Precursor Protein Cleaving Enzyme 1 (BACE1) Inhibitors: Targeting the Flap to Gain Selectivity over BACE2.

BACE1 inhibitors hold potential as agents in disease-modifying treatment for Alzheimer's disease. BACE2 cleaves the melanocyte protein PMEL in pigment cells of the skin and eye, generating melanin pigments. This role of BACE2 implies that nonselective and chronic inhibition of BACE1 may cause side effects derived from BACE2. Herein, we describe the discovery of potent and selective BACE1 inhibitors using structure-based drug design. We targeted the flap region, where the shape and flexibility differ between these enzymes. Analysis of the cocrystal structures of an initial lead 8 prompted us to incorporate spirocycles followed by its fine-tuning, culminating in highly selective compounds 21 and 22. The structures of 22 bound to BACE1 and BACE2 revealed that a relatively high energetic penalty in the flap of the 22-bound BACE2 structure may cause a loss in BACE2 potency, thereby leading to its high selectivity. These findings and insights should contribute to responding to the challenges in exploring selective BACE1 inhibitors.

Small Molecule Amyloid-ß Protein Precursor Processing Modulators Lower Amyloid-ß Peptide Levels via cKit Signaling.

Alzheimer's disease (AD) is characterized by the accumulation of neurotoxic amyloid-ß (Aß) peptides consisting of 39-43 amino acids, proteolytically derived fragments of the amyloid-ß protein precursor (AßPP), and the accumulation of the hyperphosphorylated microtubule-associated protein tau. Inhibiting Aß production may reduce neurodegeneration and cognitive dysfunction associated with AD. We have previously used an AßPP-firefly luciferase enzyme complementation assay to conduct a high throughput screen of a compound library for inhibitors of AßPP dimerization, and identified a compound that reduces Aß levels. In the present study, we have identified an analog, compound Y10, which also reduced Aß. Initial kinase profiling assays identified the receptor tyrosine kinase cKit as a putative Y10 target. To elucidate the precise mechanism involved, AßPP phosphorylation was examined by IP-western blotting. We found that Y10 inhibits cKit phosphorylation and increases AßPP phosphorylation mainly on tyrosine residue Y743, according to AßPP751 numbering. A known cKit inhibitor and siRNA specific to cKit were also found to increase AßPP phosphorylation and lower Aß levels. We also investigated a cKit downstream signaling molecule, the Shp2 phosphatase, and found that known Shp2 inhibitors and siRNA specific to Shp2 also increase AßPP phosphorylation, suggesting that the cKit signaling pathway is also involved in AßPP phosphorylation and Aß production. We further found that inhibitors of both cKit and Shp2 enhance AßPP surface localization. Thus, regulation of AßPP phosphorylation by small molecules should be considered as a novel therapeutic intervention for AD.

Norepinephrine Inhibits Alzheimer's Amyloid-ß Peptide Aggregation and Destabilizes Amyloid-ß Protofibrils: A Molecular Dynamics Simulation Study.

The abnormal self-assembly of amyloid-ß (Aß) peptides into toxic fibrillar aggregates is associated with the pathogenesis of Alzheimer's disease (AD). The inhibition of ß-sheet-rich oligomer formation is considered as the primary therapeutic strategy for AD. Previous experimental studies reported that norepinephrine (NE), one of the neurotransmitters, is able to inhibit Aß aggregation and disaggregate the preformed fibrils. Moreover, exercise can markedly increase the level of NE. However, the underlying inhibitory and disruptive mechanisms remain elusive. In this work, we performed extensive replica-exchange molecular dynamic (REMD) simulations to investigate the conformational ensemble of Aß1-42 dimer with and without NE molecules. Our results show that without NE molecules, Aß1-42 dimer transiently adopts a ß-hairpin-containing structure, and the ß-strand regions of this ß-hairpin (residues 15QKLVFFA21 and 33GLMVGGVV40) strongly resemble those of the Aß fibril structure (residues 15QKLVFFA21 and 30AIIGLMVG37) reported in an electron paramagnetic resonance spectroscopy study. NE molecules greatly reduce the interpeptide ß-sheet content and suppress the formation of the above-mentioned ß-hairpin, leading to a more disordered coil-rich Aß dimer. Five dominant binding sites are identified, and the central hydrophobic core 16KLVFFA21 site and C-terminal 31IIGLMV36 hydrophobic site are the two most favorable ones. Our data reveal that hydrophobic, aromatic stacking, hydrogen-bonding and cation-π interactions synergistically contribute to the binding of NE molecules to Aß peptides. MD simulations of Aß1-42 protofibril show that NE molecules destabilize Aß protofibril by forming H-bonds with residues D1, A2, D23, and A42. This work reveals the molecular mechanism by which NE molecules inhibit Aß1-42 aggregation and disaggregate Aß protofibrils, providing valuable information for developing new drug candidates and exercise therapy against AD.