Activation of autophagy by Citri Reticulatae Semen extract ameliorates amyloid-beta-induced cell death and cognition deficits in Alzheimer’s disease

Amyloid-beta-induced neuronal cell death contributes to cognitive decline in Alzheimer’s disease.Citri Reticulatae Semen has diverse beneficial effects on neurodegenerative diseases,including Parkinson’s and Huntington’s diseases,however,the effect of Citri Reticulatae Semen on Alzheimer’s disease remains unelucidated.In the current study,the anti-apoptotic and autophagic roles of Citri Reticulatae Semen extract on amyloid-beta-induced apoptosis in PC12 cells were first investigated.Citri Reticulatae Semen extract protected PC12 cells from amyloid-beta-induced apoptosis by attenuating the Bax/Bcl-2 ratio via activation of autophagy.In addition,Citri Reticulatae Semen extract was confirmed to bind amyloid-beta as revealed by biolayer interferometry in vitro,and suppress amyloid-beta-induced pathology such as paralysis,in a transgenic Caenorhabditis elegans in vivo model.Moreover,genetically defective Caenorhabditis elegans further confirmed that the neuroprotective effect of Citri Reticulatae Semen extract was autophagy-dependent.Most importantly,Citri Reticulatae Semen extract was confirmed to improve cognitive impairment,neuronal injury and amyloid-beta burden in 3×Tg Alzheimer’s disease mice.As revealed by both in vitro and in vivo models,these results suggest that Citri Reticulatae Semen extract is a potential natural therapeutic agent for Alzheimer’s disease via its neuroprotective autophagic effects.

Liver as a new target organ in Alzheimer's disease:insight from cholesterol metabolism and its role in amyloid-beta clearance

Alzheimer's disease,the primary cause of dementia,is characterized by neuropathologies,such as amyloid plaques,synaptic and neuronal degeneration,and neurofibrillary tangles.Although amyloid plaques are the primary characteristic of Alzheimer's disease in the central nervous system and peripheral organs,targeting amyloid-beta clearance in the central nervous system has shown limited clinical efficacy in Alzheimer's disease treatment.Metabolic abnormalities are commonly observed in patients with Alzheimer's disease.The liver is the primary peripheral organ involved in amyloid-beta metabolism,playing a crucial role in the pathophysiology of Alzheimer's disease.Notably,impaired cholesterol metabolism in the liver may exacerbate the development of Alzheimer's disease.In this review,we explore the underlying causes of Alzheimer's disease and elucidate the role of the liver in amyloid-beta clearance and cholesterol metabolism.Furthermore,we propose that restoring normal cholesterol metabolism in the liver could represent a promising therapeutic strategy for addressing Alzheimer's disease.

Divalent cation tolerance protein binds to β-secretase and inhibits the processing of amyloid precursor protein

The deposition of amyloid-beta is a pathological hallmark of Alzheimer＇s disease, Amyloid-beta is derived from amyloid precursor protein through sequential proteolytic cleavages by β-secretase （beta-site amyloid precursor protein-cleaving enzyme 1） and r-secretase. To further elucidate the roles of beta-site amyloid precursor protein-cleaving enzyme 1 in the development of AIzheimer＇s disease, a yeast two-hybrid system was used to screen a human embryonic brain cDNA library for proteins directly interacting with the intracellular domain of beta-site amyloid precursor protein-cleaving enzyme 1. A potential beta-site amyloid precursor protein-cleaving enzyme 1- interacting protein identified from the positive clones was divalent cation tolerance protein. Immunoprecipitation studies in the neuroblastoma cell line N2a showed that exogenous divalent cation tolerance protein interacts with endogenous beta-site amyloid precursor protein-cleaving enzyme 1. The overexpression of divalent cation tolerance protein did not affect beta-site amyloid precursor protein-cleaving enzyme 1 protein levels, but led to increased amyloid precursor protein levels in N2a/APP695 cells, with a concomitant reduction in the processing product amyloid precursor protein C-terminal fragment, indicating that divalent cation tolerance protein inhibits the processing of amyloid precursor protein. Our experimental findings suggest that divalent cation tolerance protein negatively regulates the function of beta-site amyloid precursor protein-cleaving enzyme 1. Thus, divalent cation tolerance protein could play a protective role in Alzheimer＇s disease.

Influence of Ginkgo Biloba extract on beta-secretase in rat hippocampal neuronal cultures following chronic hypoxic and hypoglycemic conditions

BACKGROUND： Preparation of Ginkgo leaf has been widely used to improve cognitive deficits and dementia, in particular in Alzheirner＇s disease patients. However, the precise mechanism of action of Ginkgo leaf remains unclear. OBJECTIVE： To explore the effect of Ginkgo Biloba extract （Egb761）, Ginaton, on β -secretase expression in rat hippocampal neuronal cultures following chronic hypoxic and hypoglycemic conditions. DESIGN, TIME AND SETTNG： Completely by randomized, grouping study. The experiment was performed at the Laboratory of Molecular Imaging, Southeast University between August 2006 and August 2007. MATERIALS： A total of 128 Wistar rats aged 24 hours were selected, and hippocampal neurons were harvested for primary cultures. METHODS： On day 7, primary hippocampal neuronal cultures were treated with Egb761 （0, 25, 50, 100, 150, and 200μg/mL） under hypoxic/hypoglycemic or hypoglycemic culture conditions for 12, 24, and 36 hours, respectively. Hippocampal neurons cultured in primary culture medium served as control. MAIN OUTCOME MEASURES： Cell viability was assayed using 3-（4,5-Dimethylthiazol-2-yl）- 2,5-diphenyltetrazolium bromide （MTT）; fluorescence detection of β -secretase activity was performed; Western Blot was used to measure β -secretase expression. RESULTS： Cell viability under hypoxic/hypoglycemic or hypoglycemic culture conditions was significantly less than control cells （P 〈 0.05）. Under hypoxic/hypoglycemic or hypoglycemic culture conditions, treatment with 25 μg/mL Egb761 did not alter cell viability. However, 〉 25 μg/mL Egb761 induced greater cell viability （P 〈 0.05）. No differences were observed between hypoxic/hypoglycemic or hypoglycemic cells （P 〉 0.05）. α -secretase activity was increased after 12 hours in hypoxic/hypoglycemic culture （P 〈 0.01）. There were no significant differences between the 12-, 24-, or 36-hour Egb761 groups and the hypoxic/hypoglycemic groups （P 〉 0.05）. β -secretase activity was greater after 12, 24, and 36 hours in hypoxic/hypoglycemic culture conditions, compared with control conditions （P 〈 0.05）. β-secretase activity was significantly decreased in neurons treated with Egb761 for 12, 24, or 36 hours, compared with the hypoxichaypoglycemic group （P 〈 0.05）. β -secretase protein expression was significantly up-regulated in neurons cultured in hypoxic/hypoglycemic conditions for 12, 24, or 36 hours, compared to control cells （P 〈 0.05）, and was decreased compared to neurons treated with Egb761 （P 〈 0.05）. CONCLUSION： β -secretase expression and activity in rat neonatal hippocampal neurons were influenced by hypoxic and hypoglycemic culture. Egb761 played a protective role in hippocampal neurons damaged by chronic hypoxic and hypoglycemic culture conditions, possibly through its effect on β -secretase expression and activity.

Improving cognitive impairment by Tongxinluo via inhibiting expression of beta-secretase 1/beta-amyloid peptide in experimental vascular dementia

BACKGROUND： Tongxinluo has been clinically proven to be effective in improving memory and cognitive function in patients with post-stroke vascular dementia. Is the mechanism related to the deposition of beta-amyloid peptide （A β ） in hippocampus？ OBJECTIVE： To observe the effect of Tongxinluo on cognitive impairment in a mouse model with vascular dementia and the changes of A β deposition and β -secretase 1 （BACE1） expression. DESIGN： Randomized controlled study. SETTING： State Key Laboratory of Pharmaceutical Biotechnology of Nanjing University and Affiliated Drum Tower Hospital of Nanjing University Medical School. MATERIALS： The experiment was carried out in the State Key Laboratory of Pharmaceutical Biotechnology of Nanjing University and Affiliated Drum Tower Hospital of Nanjing University Medical School from March 2006 to January 2007. A total of 36 healthy Kunming mice, 18 of each gender, were chosen. The study was conducted in accordance with the National Regulations of Experimental Animal Administration, and all animal experiments were approved by the Committee of Experimental Animal Administration of Nanjing University. Tongxinluo was provided by Shijiazhuang Yiling Pharmaceutical Co., Ltd. METHODS： All mice were randomly divided into 6 groups, including naive control （n=6）, sham-operated control （n=6） and experimental groups treated with different doses of Tongxinluo （0.2, 0.4, and 0.6 g/kg/d; n=6 for each group） or vehicle （n=6）. Five groups were subjected to bilateral common carotid arteries （2-VO） occlusion to produce a vascular dementia model （no occlusion was performed in sham-operated group）. The mice in the Tongxinluo treatment groups were intragastricly administered daily with a Tongxinluo suspension （40 g/L in distilled water） at doses of 0.2, 0.4 or 0.6 g/kg/d from day 1 to day 30 post-surgery. The animals in vehicle, sham-operated and naive groups were administered an equal volume of distilled water. MAIN OUTCOME MEASURES： ①Escape latency time determined in all groups of mice before and after 2-VO occlusion by Morris water maze. ②Changes in BACEI mRNA expression in the hippocampi of mice among the six groups by RT-PCR assay, and BACEI and A β protein expression in the hippocampi of mice by Western blot. RESULTS： All 36 mice were involved in the final analysis.① No difference was detected in escape latency time to a hidden platform among all groups in water maze test before surgery （P 〉 0.05） At 30 days after 2-VO occlusion, the vehicle animals exhibited a significantly longer latency in finding the hidden platform compared to that of sham-operated and naive animals （P 〈 0.01）. The prolonged escape latency was significantly reduced by oral administration of 0.4 g or 0.6 kg/day （P 〈 0.01, P 〈 0.05）. BACEI mRNA and protein expression in vehicle animals were much higher than in sham-operated and naive animals （P 〈 0.01）. The ischemia-induced increases in BACE1 mRNA and protein level were attenuated by all three doses of Tongxinluo treatment （P 〈 0.01）, and the 0.4 g/kg/d treatment was the most effective. A β protein expression in vehicle animals after 2-VO occlusion were much higher than in sham-operated and naive animals （P 〈 0.01）. 2-VO occlusion-induced A β generation was significantly attenuated by all doses of Tongxinluo treatment, with the most effective dose being 0.4 g/kg/d （P 〈 0.01）. CONCLUSION： BACE1 mRNA levels and protein levels of BACEI and A β are reduced in the hippocampi of vascular dementia model mice by all three doses of Tongxinluo treatment, with the most effective dose being 0.4 g/kg/d. The results suggest that inhibition of post-ischemia BACEI expression and A β generation in brain might underlie Tongxinluo＇s effects in improving cognitive impairment.

Emerging roles of astrocytes in blood-brain barrier disruption upon amyloid-beta insults in Alzheimer's disease

Blood-brain barrier disruption occurs in the early stages of Alzheimer’s disease.Recent studies indicate a link between blood-brain barrier dysfunction and cognitive decline and might accelerate Alzheimer’s disease progression.Astrocytes are the most abundant glial cells in the central nervous system with important roles in the structural and functional maintenance of the blood-brain barrier.For example,astrocytic cove rage around endothelial cells with perivascular endfeet and secretion of homeostatic soluble factors are two major underlying mechanisms of astrocytic physiological functions.Astrocyte activation is often observed in Alzheimer’s disease patients,with astrocytes expressing a high level of glial fibrillary acid protein detected around amyloid-beta plaque with the elevated phagocytic ability for amyloid-beta.Structural alte rations in Alzheimer’s disease astrocytes including swollen endfeet,somata shrinkage and possess loss contribute to disruption in vascular integrity at capillary and arte rioles levels.In addition,Alzheimer’s disease astrocytes are skewed into proinflammatory and oxidative profiles with increased secretions of vasoactive mediators inducing endothelial junction disruption and immune cell infiltration.In this review,we summarize the findings of existing literature on the relevance of astrocyte alte ration in response to amyloid pathology in the context of blood-brain barrier dysfunction.First,we briefly describe the physiological roles of astrocytes in blood-brain barrier maintenance.Then,we review the clinical evidence of astrocyte pathology in Alzheimer’s disease patients and the preclinical evidence in animal and cellular models.We further discuss the structural changes of blood-brain barrier that correlates with Alzheimer’s disease astrocyte.Finally,we evaluate the roles of soluble factors secreted by Alzheimer’s disease astrocytes,providing potential molecular mechanisms underlying blood-brain barrier modulation.We conclude with a perspective on investigating the therapeutic potential of targeting astrocytes for blood-brain barrier protection in Alzheimer’s disease.

Effects of chronic cerebral hypoperfusion of beta- and gamma-secretase on learning and memory in rats

BACKGROUND： Chronic cerebral hypoxia and ischemia have been shown to be related to occurrence of sporadic Alzheimer＇s disease, and β- and y-secretase play an important role in the generation of β-amyloid protein. Early clinical symptoms in Alzheimer＇s disease patients include learning and memory deficits. OBJECTIVE： To measure learning and memory, as well as β- and β-secretase activities in the hippocampus of a cerebral ischemia/hypoxia rat model with chronic cerebral hypoperfusion. DESIGN, TIME AND SETTING： A randomized, controlled, animal experiment was performed at the Department of Pathology, Capital Medical University from March to December, 2008. MATERIALS： β- and y-secretase activity kits were purchased from R ＆ D Systems, USA. METHODS： Male Sprague Dawiey rats, aged 23 weeks, were randomly assigned to model （n = 56） and sham-surgery （n = 46） groups. Cerebral hypoperfusion rat models were established by bilateral common carotid occlusion. MAIN OUTCOME MEASURES： Morris water maze was used to test changes in escape latency and path length, and β- and y-secretase activities were measured on days 10, 30, 90, and 180 following surgery. RESULTS： Progressive cognitive impairment resulted from 30 days of chronic cerebral hypoperfusion, which lasted for 180 days after cerebral hypoperfusion. β-secretase activity was increased at 10 days after hypoperfusion, which continued until 180 days, with a 14.25% increase compared to the sham-surgery group; y-secretase activity was increased by 10.5%. CONCLUSION： Chronic cerebral hypoperfusion results in impaired spatial memory and upregulated β- and y-secretase activities, which could play an important role in β-amyloid production.

Neuroprotective effects of exogenous brain-derived neurotrophic factor on amyloid-beta 1-40-induced retinal degeneration

Amyloid-beta(Aβ)-related alterations,similar to those found in the brains of patients with Alzheimer's disease,have been observed in the retina of patients with glaucoma.Decreased levels of brain-derived neurotrophic factor(BDNF)are believed to be associated with the neurotoxic effects of Aβpeptide.To investigate the mechanism underlying the neuroprotective effects of BDNF on Aβ_(1-40)-induced retinal injury in Sprague-Dawley rats,we treated rats by intravitreal administration of phosphate-buffered saline(control),Aβ_(1-40)(5 nM),or Aβ_(1-40)(5 nM)combined with BDNF(1μg/mL).We found that intravitreal administration of Aβ_(1-40)induced retinal ganglion cell apoptosis.Fluoro-Gold staining showed a significantly lower number of retinal ganglion cells in the Aβ_(1-40)group than in the control and BDNF groups.In the Aβ_(1-40)group,low number of RGCs was associated with increased caspase-3 expression and reduced TrkB and ERK1/2 expression.BDNF abolished Aβ_(1-40)-induced increase in the expression of caspase-3 at the gene and protein levels in the retina and upregulated TrkB and ERK1/2 expression.These findings suggest that treatment with BDNF prevents RGC apoptosis induced by Aβ_(1-40)by activating the BDNF-TrkB signaling pathway in rats.

Precise location of proton of beta-secretase for catalytic aspartates(Asp 32 and Asp 228)in Alzheimer’s patients

BACKGROUND：β-secretase （β-site APP cleavage rate-limiting enzyme, BACE） has been proposed as a promising therapeutic target for Alzheimer＇s disease （AD）. BACE inhibition reduces production of β-amyloid peptide （Aβ） and promotes neural regeneration. Two catalytic aspartates （Asp 32 and Asp 228） exist in a monoprotonated state in the active BACE site, but the precise proton location remains unclear.OBJECTIVE：To explore the entire process of BACE enzymatic hydrolysis using quantum chemistry calculations, and to identify the precise proton location for Asp 32 and Asp 228 during the enzymatic process.DESIGN, TIME AND SETTING：According to protonation state of BACE, four tautomers were designed and quantum chemistry calculations were performed at the Department of Human Anatomy, Zhongshan School of Medicine, Sun Yat-sen University, China between October 2008 and March 2009.MATERIALS：Hardware：linux workstation （Department of Equipment, Sun Yat-sen University, China）; software：QSITE, Glide, Maestro （Schrodinger LLC, USA）, MOPAC 2007 （CAChe Research LLC, USA）, Triton 4.0 （National Centre for Biomolecular Research, Czech Republic） were used.METHODS：Using crystal structures of BACE to build a catalytic model （enzyme, catalytic water, and substrate peptide EVNLAAEF） on the computer and superimposition, four BACE tautomers （32i, 320, 228i, and 2280） in the monoprotonated state were developed with Schrodinger package. Hybrid quantum mechanical/molecular mechanic （QM/MM） calculations were performed at the B3LYP density functional theory level to identify the precise proton location for the dyad aspartic residues （Asp 32 and Asp 228）. Using the most possible tautomer as the reactant, the entire enzymatic hydrolysis of substrate EVNL/AAEF was simulated at the semiempirical level.MAIN OUTCOME MEASURES：The precise proton location of was measured by analyzing co-planarities of 4 BACE tautorners （32i, 32o, 228i, and 2280） in the monoprotonated state, because the dihedral formed by the carboxyl oxygen atoms of the dyad aspartic residues. The transition state and the production state, as well as activation energies and reaction enthalpies, were measured by calculating geometric and energy changes during catalytic reaction of the system.RESULTS：In the 2280 BACE tautomer, the dihedral angle of the four oxygen atoms in the catalytic aspartates was 8.7°, which was the lowest of four tautomers. The lowest activation energy and highest reaction enthalpy （Ea = 216.30 kJ/mol, AH = 30.98 kJ/mol） were also found in 2280, among the four tautomers during the catalytic reaction. In addition, when the reaction proceeded to the transition state, followed by product generation, the proton location was reversed to the inner oxygen of Asp 32 （32i） from the outer oxygen of Asp 228 （228o）.CONCLUSION：Results demonstrated the mechanism of Aβ generation. At beginning of BACE catalytic reaction, the precise proton location was preferred on the outer oxygen of Asp 228 （228o）. In this protonation state, catalytic reaction can proceed smoothly, with reduced active energy and heat release. When the reaction proceeded to the transition state and product generation, the proton location was reversed to the inner oxygen of Asp 32 （32i）. These results provide theoretical guidance for designing new drugs to protect neural cells and promote neural regeneration in Alzheimer＇s patients.

Pharmacological Assessment of <i>γ</i>-Secretase Activity from Rodent and Human Brain

γ-Secretase is involved in the final processing of the amyloid precursor protein into a heterogeneous pool of β-amyloid (Aβ) peptides. Current Alzheimer’s disease drug discovery efforts include targeting γ-secretase activity in brain to attenuate production of the neurotoxic Aβ species. The resulting pharmacology may be affected by species-specific differences in the γ-secretase core complex or its associated proteins. Therefore, we utilized partially purified γ-secretase membranes derived from the brains of different species, including human cortex, to quantitatively assess the de novo production of both Aβ42 and Aβ40 following treatment with known γ-secretase inhibitors and modulators. We determined that the inhibitory activity of a Notch-1 sparing γ-secretase inhibitor and the modulatory activity of two classes of γ-secretase modulators were equipotent at affecting the production of Aβ across rodent and human brain membrane preparations. Additionally, the observed modulator-specific Aβ profile in isolated brain membranes across species was similar to that observed in HeLa cell membranes, and the brain and CSF of guinea pigs following oral administration. By utilizing rapidly purified γ-secretase, we were able to probe and compare the complex pharmacology of γ-secretase in the brain across common rodent species and human cortex.

Purification of Full-Length <i>β</i>-Secretase Involved in Alzheimer’s Disease, and Proteomic Identification of Binding Partners

β-Secretase (BACE1 or β-site APP cleaving enzyme) is an acid protease that releases the neurotoxic 40 - 42 residue peptides (β-amyloid or A-β) from its glycoprotein precursor, (APP or amyloid precursor protein) which when released in brain is thought to give rise to cognitive decline in patients with Alzheimer’s Disease. Most structural studies on β-secretase have previously been performed with recombinant forms of the protease, in which the transmembrane coding region has been deleted. However, interactions with proteins of the same species are best studied using the full-length β-secretase as interactions are likely to be influenced by the hydrophobic nature and localization of its transmembrane regions. Here we develop a multi-step purification procedure that isolates a complex containing BACE1 from recombinant human cells using mild detergents in a procedure that retains other proteins within the complex and remains active in its β-site APP cleaving activity. Some of these proteins, eg reticulon 4, are identified by proteomics, and are known by previous studies performed by others to regulate the activity of BACE1 against APP. These interactions may aid the development of small proteins and peptides that could inhibit the release of aggregated forms of β-amyloid, and thus be useful therapeutically.

Design, Synthesize and Bio-Evaluate 1,2-Dihydroisoquinolin-3(4H)-One Derivates as Acetylcholinesterase and β-Secretase Dual Inhibitors in Treatment with Alzheimer’s Disease

With the recent research advances in molecular biology and technology, many credible hypothe-ses about the progress of Alzheimer’s disease (AD) have been proposed, among which the amyloid and cholinergic hypotheses are commonly used to develop reliable therapeutic agents. The multitarget-directed ligand (MTDL) approach was taken in this work to develop multi-functional agents, which can mainly serve as dual BACE 1 and AChE inhibitors. Depending on the scaffolds of (+)-(S)- dihydro-ar-tumerone and (-)-gallocatechin gallate, 3 series of new compounds have been designed, synthesized and evaluated, from which we have identified 2-(2-(3-methylbenzoyl)-3-oxo-1,2,3,4- tetrahydroisoquinolin-6-yl) isoindoline-1,3-dione (3d) as a new cholinesterase and β-secretase dual inhibitor without toxicity. Furthermore, 3d also exhibits hydrogen peroxide scavenging activity which could help to reduce the reactive oxygen species (ROS) in the brain of AD patients.

Impaired autophagy in amyloid-beta pathology:A traditional review of recent Alzheimer's research

Alzheimer’s disease(AD) is the most prevalent neurodegenerative disorder. The major pathological changes in AD progression are the generation and accumulation of amyloid-beta(Aβ) peptides as well as the presence of abnormally hyperphosphorylated tau proteins in the brain. Autophagy is a conserved degradation pathway that eliminates abnormal protein aggregates and damaged organelles. Previous studies have suggested that autophagy plays a key role in the production and clearance of Aβ peptides to maintain a steady-state of Aβ peptides levels.However, a growing body of evidence suggests that autophagy is significantly impaired in the pathogenesis of AD, especially in Aβ metabolism. Therefore, this article reviews the latest studies concerning the mechanisms of autophagy, the metabolism of Aβ peptides, and the defective autophagy in the production and clearance of Aβpeptides. Here, we also summarize the established and new strategies for targeting autophagy in vivo and through clinical AD trials to identify gaps in our knowledge and to generate further questions.

A systematic review of salivary biomarkers in Parkinson's disease

The search fo r reliable and easily accessible biomarkers in Parkinson's disease is receiving a growing emphasis,to detect neurodegeneration from the prodromal phase and to enforce disease-modifying therapies.Despite the need for non-invasively accessible biomarke rs,the majo rity of the studies have pointed to cerebrospinal fluid or peripheral biopsies biomarkers,which require invasive collection procedures.Saliva represents an easily accessible biofluid and an incredibly wide source of molecular biomarkers.In the present study,after presenting the morphological and biological bases for looking at saliva in the search of biomarkers for Parkinson's disease,we systematically reviewed the results achieved so far in the saliva of different cohorts of Parkinson's disease patients.A comprehensive literature search on PubMed and SCOPUS led to the discovery of 289articles.After screening and exclusion,34 relevant articles were derived fo r systematic review.Alpha-synuclein,the histopathological hallmark of Parkinson's disease,has been the most investigated Parkinson's disease biomarker in saliva,with oligomeric alphasynuclein consistently found increased in Parkinson's disease patients in comparison to healthy controls,while conflicting results have been reported regarding the levels of total alpha-synuclein and phosphorylated alpha-synuclein,and few studies described an increased oligomeric alpha-synuclein/total alpha-synuclein ratio in Parkinson's disease.Beyond alpha-synuclein,other biomarkers to rgeting diffe rent molecular pathways have been explored in the saliva of Parkinson's disease patients:total tau,phosphorylated tau,amyloid-β1-42(pathological protein aggregation biomarkers);DJ-1,heme-oxygenase-l,metabolites(alte red energy homeostasis biomarkers);MAPLC-3beta(aberrant proteostasis biomarker);cortisol,tumor necrosis factor-alpha(inflammation biomarkers);DNA methylation,miRNA(DNA/RNA defects biomarkers);acetylcholinesterase activity(synaptic and neuronal network dysfunction biomarkers);Raman spectra,proteome,and caffeine.Despite a few studies investigating biomarkers to rgeting molecular pathways different from alpha-synuclein in Parkinson's disease,these results should be replicated and observed in studies on larger cohorts,considering the potential role of these biomarkers in determining the molecular variance among Parkinson's disease subtypes.Although the need fo r standardization in sample collection and processing,salivary-based biomarkers studies have reported encouraging results,calling for large-scale longitudinal studies and multicentric assessments,given the great molecular potentials and the non-invasive accessibility of saliva.

Impact of apolipoprotein E isoforms on sporadic Alzheimer's disease:beyond the role of amyloid beta

The impact of apolipoprotein E(ApoE)isoforms on sporadic Alzheimer's disease has long been studied;however,the influences of apolipoprotein E gene(APOE)on healthy and pathological human brains are not fully understood.ApoE exists as three common isoforms(ApoE2,ApoE3,and ApoE4),which differ in two amino acid residues.Traditionally,ApoE binds cholesterol and phospholipids and ApoE isoforms display diffe rent affinities for their receptors,lipids transport and distribution in the brain and periphery.The role of ApoE in the human depends on ApoE isoforms,brain regions,aging,and neural injury.APOE E4 is the strongest genetic risk factor for sporadic Alzheimer's disease,considering its role in influencing amyloid-beta metabolism.The exact mechanisms by which APOE gene variants may increase or decrease Alzheimer's disease risk are not fully understood,but APOE was also known to affect directly and indirectly tau-mediated neurodegeneration,lipids metabolism,neurovascular unit,and microglial function.Consistent with the biological function of ApoE,ApoE4 isoform significantly alte red signaling pathways associated with cholesterol homeostasis,transport,and myelination.Also,the rare protective APOE variants confirm that ApoE plays an important role in Alzheimer's disease pathogenesis.The objectives of the present mini-review were to describe classical and new roles of various ApoE isoforms in Alzheimer's disease pathophysiology beyond the deposition of amyloid-beta and to establish a functional link between APOE,brain function,and memory,from a molecular to a clinical level.APOE genotype also exerted a heterogeneous effect on clinical Alzheimer's disease phenotype and its outcomes.Not only in learning and memory but also in neuro psychiatric symptoms that occur in a premorbid condition.Cla rifying the relationships between Alzheimer's disease-related pathology with neuropsychiatric symptoms,particularly suicidal ideation in Alzheimer's disease patients,may be useful for elucidating also the underlying pathophysiological process and its prognosis.Also,the effects of anti-amyloid-beta drugs,recently approved for the treatment of Alzheimer's disease,could be influenced by the APOE genotype.

Amyloid-beta peptide and tau protein crosstalk in Alzheimer’s disease

Alzheimer’s disease is a neurodegenerative disease that accounts for most of the 50-million dementia cases worldwide in 2018.A large amount of evidence supports the amyloid cascade hypothesis,which states that amyloid-beta accumulation triggers tau hyperphosphorylation and aggregation in form of neurofibrillary tangles,and these aggregates lead to inflammation,synaptic impairment,neuronal loss,and thus to cognitive decline and behavioral abnormalities.The poor correlation found between cognitive decline and amyloid plaques,have led the scientific community to question whether amyloid-beta accumulation is actually triggering neurodegeneration in Alzheimer’s disease.The occurrence of tau neurofibrillary tangles better correlates to neuronal loss and clinical symptoms and,although amyloid-beta may initiate the cascade of events,tau impairment is likely the effector molecule of neurodegeneration.Recently,it has been shown that amyloid-beta and tau cooperatively work to impair transcription of genes involved in synaptic function and,more importantly,that downregulation of tau partially reverses transcriptional perturbations.Despite mounting evidence points to an interplay between amyloid-beta and tau,some factors could independently affect both pathologies.Thus,the dual pathway hypothesis,which states that there are common upstream triggers causing both amyloid-beta and tau abnormalities has been proposed.Among others,the immune system seems to be strongly involved in amyloid-beta and tau pathologies.Other factors,as the apolipoprotein Eε4 isoform has been suggested to act as a link between amyloid-beta and tau hyperphosphorylation.Interestingly,amyloid-beta-immunotherapy reduces not only amyloid-beta but also tau levels in animal models and in clinical trials.Likewise,it has been shown that tau-immunotherapy also reduces amyloid-beta levels.Thus,even though amyloid-beta immunotherapy is more advanced than tau-immunotherapy,combined amyloid-beta and tau-directed therapies at early stages of the disease have recently been proposed as a strategy to stop the progression of Alzheimer’s disease.

Intranasal neprilysin rapidly eliminates amyloid-beta plaques, but causes plaque compensations: the explanation why the amyloid-beta cascade may fail?

Neurodegenerative brain disorders are a major burden in our society,such as Alzheimer´s disease.In order to repair or prevent such diseases,drugs are designed which enter the brain,but the blood-brain barrier limits their entry and the search for alternative pathways is important.Recently,we reported that intranasal delivery of the amyloid-beta degrading enzyme neprilysin eliminated amyloid-beta plaques in transgenic Alzheimer´s disease mice.This review describes the anatomical structure of the intranasal pathway,explains the intranasal delivery of pure neprilysin,cell-loaded neprilysin(platelets)and collagen-embedded neprilysin to destruct amyloid-beta plaques in Alzheimer´s disease in transgenic APP_SweDI mice and hypothesizes why this may cause compensation and why the amyloid-beta cascade hypothesis may fail.

Toxicities of amyloid-beta and tau protein are reciprocally enhanced in the Drosophila model

Extracellular aggregation of amyloid-beta(Aβ)and intracellular tau tangles are two major pathogenic hallmarks and critical factors of Alzheimer’s disease.A linear interaction between Aβand tau protein has been characterized in several models.Aβinduces tau hyperphosphorylation through a complex mechanism;however,the master regulators involved in this linear process are still unclear.In our study with Drosophila melanogaster,we found that Aβregulated tau hyperphosphorylation and toxicity by activating c-Jun N-terminal kinase.Importantly,Aβtoxicity was dependent on tau hyperphosphorylation,and flies with hypophosphorylated tau were insulated against Aβ-induced toxicity.Strikingly,tau accumulation reciprocally interfered with Aβdegradation and correlated with the reduction in mRNA expression of genes encoding Aβ-degrading enzymes,including dNep1,dNep3,dMmp2,dNep4,and dIDE.Our results indicate that Aβand tau protein work synergistically to further accelerate Alzheimer’s disease progression and may be considered as a combined target for future development of Alzheimer’s disease therapeutics.

Amyloid-beta-dependent phosphorylation of collapsin response mediator protein-2 dissociates kinesin in Alzheimer＇s disease

Alzheimer’s disease（AD）is a neurodegenerative disorder characterized by accumulation of amyloid plaques and neurofibrillary tangles.Prior to the development of these characteristic pathological hallmarks of AD,anterograde axonal transport is impaired.However,the key proteins that initiate these intracellular impairments remain elusive.The collapsin response mediator protein-2（CRMP-2）plays an integral role in kinesin-1-dependent axonal transport and there is evidence that phosphorylation of CRMP-2releases kinesin-1.Here,we tested the hypothesis that amyloid-beta（Aβ）-dependent phosphorylation of CRMP-2 disrupts its association with the kinesin-1（an anterograde axonal motor transport protein）in AD.We found that brain sections and lysates from AD patients demonstrated elevated phosphorylation of CRMP-2 at the T555 site.Additionally,in the transgenic Tg2576 mouse model of familial AD（FAD）that exhibits Aβaccumulation in the brain with age,we found substantial co-localization of p T555CRMP-2and dystrophic neurites.In SH-SY5Y differentiated neuronal cultures,Aβ-dependent phosphorylation of CRMP-2 at the T555 site was also elevated and this reduced the CRMP-2 association with kinesin-1.The overexpression of an unphosphorylatable form of CRMP-2 in neurons promoted the re-establishment of CRMP-2-kinesin association and axon elongation.These data suggest that Aβ-dependent phosphorylation of CRMP-2 at the T555 site may directly impair anterograde axonal transport protein function,leading to neuronal defects.

Glycogen and amyloid-beta: key players in the shift from neuronal hyperactivity to hypoactivity observed in Alzheimer's disease?

Introduction：Alzheimer’s disease（AD）begins to develop decades prior to its clinical manifestation（Sperling et al.,2011）,and while it is the most common form of dementia,as of yet there is no cure.Two of the most researched pathological features contributing to disease development are the extracellular amyloid plaques composed of amyloid-beta proteins（Aβ）and neurofibrillary tangles of tau proteins.Another feature of AD is the progression of early neuronal excitability/hyperactivity to silencing/hypoactivity（Palop and Mucke,2010）,