Cause Of AD Research Articles

Study on hypothesis of amyloid beta protein being the causative factor of Alzheimers disease

Abstract. At present, people have many hypotheses about the cause of Alzheimers disease, AD is used in the following text, among which the amyloid beta protein hypothesis is one of the most famous hypotheses about the cause of AD. Therefore, to study the method of completely curing AD, amyloid beta protein, A is used in the following text, is the most important research object, and the study of drugs targeting A has become the hope of peoples treatment of AD. The research topic of this review is whether A is the cause of AD, that is, whether the amyloid beta hypothesis is valid. By reading literature and analyzing several drugs that have been developed and have effects on A, this paper proves whether A is related to AD. The results showed that the number of A had an important relationship with the severity of AD that is, the amyloid beta hypothesis was established.

Chloride intracellular channel 4 blockade improves cognition in mice with Alzheimer's disease: CLIC4 protein expression and tau protein hyperphosphorylation

Numerous academic literature suggests that amyloid-β (Aβ) deposition, tau protein phosphorylation, and irreversible neuronal death are the three major causes of AD. The chloride intracellular channel (CLIC) protein family not only regulates the polarisation of neurons, but also has important implications for neuronal survival. Chloride intracellular channel 4 (CLIC4) can be pathologically activated by cyclin-dependent kinase 5 (Cdk5), which causes a significant increase in the expression of CLIC4 and mediates neuronal apoptosis. CLIC4 knockdown inhibits H2O2-induced neuronal apoptosis; however, the relationship between CLIC4 and AD remains unknown. In the present study, we showed that CLIC4 expression was elevated in the hippocampus of AD mice; knockdown of hippocampal CLIC4 alleviated Aβ25–35-induced cognitive impairment in mice; overexpression of hippocampal CLIC4 accelerated Aβ deposition and tau protein hyperphosphorylation in young AD mice (APP/PS1 mice at three months of age). CLIC4 overexpressing mice had a longer escape latency compared to controls in behavioural testing (Morris water maze and T-maze tests). By Co-immunoprecipitation/mass spectrometry (Co-IP/MS) of HT22 cells to identify proteins that specifically bind to CLIC4, we found interactions with CCAAT enhancer binding protein (C/EBPβ); a critical pathway involved in the development of various neurodegenerative diseases. In addition, the knockdown of hippocampal CLIC4 alleviated AD-like pathology by inhibiting the C/EBPβ/AEP signaling pathway. These data suggest an essential role for high CLIC4 expression in the pathophysiology of AD and reveal that inhibition of CLIC4 expression may provide an opportunity for treatment.

The memory ameliorating effects of novel N-benzyl pyridine-2-one derivatives on scopolamine-induced cognitive deficits in mice

BackgroundAlzheimer's disease (AD), the most common form of progressive dementia in the elderly, is a chronic neurological disorder that decreases cognitive ability. Although the underlying cause of AD is yet unknown, oxidative stress and brain acetylcholine shortage are the key pathogenic causes.ResultsThe current study shows that these derivatives have the potential to improve memory in mice by inhibiting scopolamine-induced acetylcholinesterase activity, oxidative and nitrosative stress, and improving locomotor activity and muscle grip strength in the rota rod test. When compared to the illness control, the memory-enhancing potential of novel N-benzyl pyridine-2-one derivatives was highly significant (P < 0.0001).ConclusionsThe observed memory ameliorating effect of novel N-benzyl pyridine-2-one makes them as a a good choice for treatment of individuals with cognitive impairment.Graphical abstract

The HSP40 family chaperone isoform DNAJB6b prevents neuronal cells from tau aggregation

BackgroundAlzheimer’s disease (AD) is the most common neurodegenerative disorder with clinical presentations of progressive cognitive and memory deterioration. The pathologic hallmarks of AD include tau neurofibrillary tangles and amyloid plaque depositions in the hippocampus and associated neocortex. The neuronal aggregated tau observed in AD cells suggests that the protein folding problem is a major cause of AD. J-domain-containing proteins (JDPs) are the largest family of cochaperones, which play a vital role in specifying and directing HSP70 chaperone functions. JDPs bind substrates and deliver them to HSP70. The association of JDP and HSP70 opens the substrate-binding domain of HSP70 to help the loading of the clients. However, in the initial HSP70 cycle, which JDP delivers tau to the HSP70 system in neuronal cells remains unclear.ResultsWe screened the requirement of a diverse panel of JDPs for preventing tau aggregation in the human neuroblastoma cell line SH-SY5Y by a filter retardation method. Interestingly, knockdown of DNAJB6, one of the JDPs, displayed tau aggregation and overexpression of DNAJB6b, one of the isoforms generated from the DNAJB6 gene by alternative splicing, reduced tau aggregation. Further, the tau bimolecular fluorescence complementation assay confirmed the DNAJB6b-dependent tau clearance. The co-immunoprecipitation and the proximity ligation assay demonstrated the protein–protein interaction between tau and the chaperone–cochaperone complex. The J-domain of DNAJB6b was critical for preventing tau aggregation. Moreover, reduced DNAJB6 expression and increased tau aggregation were detected in an age-dependent manner in immunohistochemical analysis of the hippocampus tissues of a mouse model of tau pathology.ConclusionsIn summary, downregulation of DNAJB6b increases the insoluble form of tau, while overexpression of DNAJB6b reduces tau aggregation. Moreover, DNAJB6b associates with tau. Therefore, this study reveals that DNAJB6b is a direct sensor for its client tau in the HSP70 folding system in neuronal cells, thus helping to prevent AD.

Analyzing fuzzy boundary value problems: a study on the influence of mitochondria and ER fluxes on calcium ions in neuron cells.

Cytosolic-free calcium ions play an important role in various physical and physiological processes. A vital component of neural signaling is the free calcium ion concentration often known as the second messenger. There are many parameters that effect the cytosolic free calcium concentration like buffer, voltage-gated ion channels, Endoplasmic reticulum, Mitochondria, etc. Mitochondria are small organelles located within thenervous system that are involved in processes within cells such as calcium homeostasis management, energy generation, response to stress, and cell demise pathways. In this work, a mathematical model with fuzzy boundary values has been developed to study the effect of Mitochondria and ER fluxes on free Calcium ions. The intended findings are displayed utilizingthe physiological understanding that amyloid beta plaques and tangles of neurofibrillary fibers have been identified as the two main causes of AD. The key conclusion of the work is the investigation of [Formula: see text] for healthy cells and cells affected by Alzheimer's disease, which may aid in the study of such processes for computational scientists and medical practitioners. Also, it has been shown that when a unique solution is found for a specific precise problem, it also successfully deals with any underlying ambiguity within the problem by utilizinga technique based on the principles of linear transformation. Furthermore, the comparison between the analytical approach and the generalized hukuhara derivative approach is shown here, which illustrates the benefits of the analytical approach. The simulation is carried out in MATLAB.

Scaffold morphing and in silico studies of potential BACE1 (β‐secretase) inhibitors: A hope for newer dawn in anti‐Alzheimer therapeutics

AbstractBackgroundAD (Alzheimer’s disease) is the prime causes for 65‐85% cases of senile dementia occurs due to the plaques aggregation and tangles formation in various parts of brains neurons (cortical and hippocampal) leading to brain cell death. The major cause of AD is the extracellular plaques accretion made of β‐amyloid protein. The β‐secretase enzyme also known as BACE‐1 is the key player behind this phenomenon catalyzing the rate determining step of the reactions generating β‐amyloid. Therefore, efforts are being applied for research and development of novel entities that can inhibit the BACE‐1 enzyme and thus halting the plaque build‐up.MethodIn our study, we analyzed some of the analogues of Elenbecestat, which is a β‐secretase inhibitor currently in clinical trials designed by using scaffold morphing and structure‐based designing approach with a superior therapeutic profile, followed by in silico screening i.e. pharmacokinetics and docking methodologies.ResultThe designed molecules showed good interactions with the active pockets (Asp32 and Asp228, catalytic dyad residues) of β‐secretase protein and having drug likeliness properties.ConclusionHenceforward, molecular dynamic studies are required to fully establish their possible utility as the promising BACE1 inhibitors.

Effect of tricyclic 1,2-thiazine derivatives in neuroinflammation induced by preincubation with lipopolysaccharide or coculturing with microglia-like cells

BackgroundAlzheimer’s disease (AD) is considered the most common cause of dementia among the elderly. One of the modifiable causes of AD is neuroinflammation. The current study aimed to investigate the influence of new tricyclic 1,2-thiazine derivatives on in vitro model of neuroinflammation and their ability to cross the blood–brain barrier (BBB).MethodsThe potential anti-inflammatory effect of new tricyclic 1,2-thiazine derivatives (TP1, TP4, TP5, TP6, TP7, TP8, TP9, TP10) was assessed in SH-SY5Y cells differentiated to the neuron-like phenotype incubated with bacterial lipopolysaccharide (5 or 50 μg/ml) or THP-1 microglial cell culture supernatant using MTT, DCF-DA, Griess, and fast halo (FHA) assays. Additionally, for cultures preincubated with 50 µg/ml lipopolysaccharide (LPS), a cyclooxygenase (COX) activity assay was performed. Finally, the potential ability of tested compounds to cross the BBB was evaluated by computational studies. Molecular docking was performed with the TLR4/MD-2 complex to assess the possibility of binding the tested compounds in the LPS binding pocket. Prediction of ADMET parameters (absorption, distribution, metabolism, excretion and toxicity) was also conducted.ResultsThe unfavorable effect of LPS and co-culture with THP-1 cells on neuronal cell viability was counteracted with TP1 and TP4 in all tested concentrations. Tested compounds reduced the oxidative and nitrosative stress induced by both LPS and microglia activation and also reduced DNA damage. Furthermore, new derivatives inhibited total COX activity. Additionally, new compounds would cross the BBB with high probability and reach concentrations in the brain not lower than in the serum. The binding affinity at the TLR4/MD-2 complex binding site of TP4 and TP8 compounds is similar to that of the drug donepezil used in Alzheimer's disease. The ADMET analysis showed that the tested compounds should not be toxic and should show high intestinal absorption.ConclusionsNew tricyclic 1,2-thiazine derivatives exert a neuroregenerative effect in the neuroinflammation model, presumably via their inhibitory influence on COX activity and reduction of oxidative and nitrosative stress.

Combination of Acupoints for Alzheimer's Disease: An Association Rule Analysis.

BackgroundAlzheimer’s disease (AD) is an ongoing neurological degeneration characterized by amnesia and a decline in cognitive abilities. Hippocampal neurogenesis is the leading cause of AD. Mild cognitive impairment (MCI), a prodromal state of AD, is mainly due to the degradation of neuropsychiatric manifestations. Previous systematic reviews demonstrated that treatment with acupuncture with Chinese herbs is tolerable and effective in improving cognitive function in patients with AD. Our investigation aimed to discover the main acupoint combination for AD management based on a preceding systematic review and meta-analysis of randomized control trials (RCTs).Materials and MethodsOur investigation was executed using association rule analysis, which is a common data mining technique accessible within R. Our study elucidated acupoint locations as binary data from 15 of the included studies using the Apriori algorithm.ResultsThirty-two acupoints were selected from 15 RCTs. The 10 most frequent acupoints were selected. We inspected 503 association rules using the interpreted acupuncture data. The obtained results showed that {SP6, BI10} ≥ {HT7} and {HT7, BI10} ≥ {SP6} were the most associated rules in 15 RCTs.ConclusionThe combination of acupoints ({SP6, BI10} ≥ {HT7} and {HT7, BI10} ≥ {SP6}) can be acknowledged as a core combination for future acupuncture regimens of AD.

An Overview on the Aetiology and Treatment of Alzheimer's Disease

Alzheimer’s disease is a disease that mainly leads to the degeneration of cells in the brain and it causes dementia. This reduces thinking capacity and doesn't allow the person to be independently do their own work. Two main causes of AD are cholinergic and amyloid hypothesis. Other risk factors include age, genetics, infections in the brain etc. currently only two types of drugs can treat AD, cholinesterase enzyme inhibitors and NMDA antagonists, but these are only able to treat the symptoms not the whole disease. At this moment the researchers are trying to target several mechanisms such as abnormal tau protein metabolism, inflammation and damage in the cholinergic system.

A Cell That Acts Like a Pill: Using iPSC-Derived Cholinergic Neurons to Treat Alzheimer’s Disease

Alzheimer&amp;rsquo;s disease (AD), the most common subtype of dementia, affects approximately 44 million people worldwide. One of the most major and direct causes of AD, as proposed by the cholinergic hypothesis, is a severe deficiency of cholinergic neurons located in the basal forebrain. This paper proposes a novel approach of using replacement therapy to treat Alzheimer&amp;rsquo;s disease with stem cell technology. The overarching idea is to inject new cholinergic neurons, which are developed from induced pluripotent stem cells (iPSC), into the brains of AD patients to reverse the cholinergic deficit outlined in the cholinergic hypothesis. The proposed idea is founded on a similar study carried out recently by a team lead by Jeffrey S. Schweitzer that used iPSCs to create dopaminergic neurons which were injected into the brain of a Parkinson&amp;rsquo;s disease patient and has been proven successful. The proposed treatment development plan would consist of three stages: development of induced pluripotent stem cells and differentiation into basal forebrain acetylcholinergic progenitor cells (APCs); animal studies where researchers inject APCs into the basal forebrain of AD mice models and track progress and improvement in cognitive behavior; and clinical trials involving volunteer AD patients when the procedure of APC development and injection will be repeated, and results will be analyzed. The resulting effects of this treatment can be expected to yield medical, economic, and social benefits.

Anti-inflammatory effects of Eclipta prostrata Linné on house dust mite-induced atopic dermatitis in vivo and in vitro

Ethnopharmacological relevanceAtopic dermatitis (AD) is a kind of inflammation on the skin following with swollen, itchy, dryness and cracked skin. Though the exact cause of AD is unknown, there are evidence that people with AD have a compromised skin barrier along with inflammation. Eclipta prostrata Linné is a traditional herbal medicinal plant, has been used for the diabetes, obesity, jaundice, and inflammation. We supposed E. prostrata L. has an anti-inflammatory effect on the skin. Aim of the studyWe aimed to assess the effect of E. prostrata L. EtOH extract (EP) and elucidate the associated molecular mechanisms. Materials and methodsThe effect of EP and the molecular mechanisms were eluciated in house dust mite (HDM)-induced AD mice model and TNF-α/IFN-γ-stimulated HaCaT keratinocytes by histological analysis, enzyme-linked immunosorbent assay, quantitative real time polymerase chain reaction, and Western blot. ResultsThe results revealed that EP improved the progression of AD symptoms, decreasing epidermis/dermis thickness, infiltrated immune cells, and restored the skin barrier dysfunction and imbalanced immune response. EP suppressed the expressions of T helper (Th)1, Th2, Th17 cytokines, phosphorylation of extracellular signal-regulated kinase/signal transducer and activator of transcription 1 in skin of HDM-induced AD mice as well as inhibition the translocation of nuclear factor-κB in HaCaT keratinocytes. ConclusionsCollectively, EP improved the allergic inflammation of the skin through recovery the skin barrier, and regulation the immune balance. These results suggest EP may have therapeutic potential as an anti-atopic agent.

Redefining the Use of Digital Communities: AD Knowledge in an Online Educated Cohort of Midlife and Older Blacks

The normalization of memory loss continues to contribute to diagnostic delays among older adult African Americans with dementia. We utilized an innovative recruitment method to establish a solely online study to examine perceptions and knowledge levels of Alzheimer’s Disease in a highly educated geographically diverse cohort of 223 African Americans aged 50-84. Participants were recruited through largely electronic communications. Sample participants were primarily female (n=196), with 51.1% having completed a master’s degree, and 58.2% of participants with household incomes of $90,000 or higher. Study findings revealed that although highly educated, 42% of sample participants believed significant memory loss was a normal part of aging and 59.6% felt that God’s Will was a possible cause of AD. A sizable majority of participants, 86.5%, felt most family physicians were not trained to diagnose AD. Findings underscore the need for physician and community education within diverse populations, regardless of education and SES status.

Emergence of distinct and heterogeneous strains of amyloid beta with advanced Alzheimer\u2019s disease pathology in Down syndrome

Amyloid beta (Aβ) is thought to play a critical role in the pathogenesis of Alzheimer’s disease (AD). Prion-like Aβ polymorphs, or “strains”, can have varying pathogenicity and may underlie the phenotypic heterogeneity of the disease. In order to develop effective AD therapies, it is critical to identify the strains of Aβ that might arise prior to the onset of clinical symptoms and understand how they may change with progressing disease. Down syndrome (DS), as the most common genetic cause of AD, presents promising opportunities to compare such features between early and advanced AD. In this work, we evaluate the neuropathology and Aβ strain profile in the post-mortem brain tissues of 210 DS, AD, and control individuals. We assayed the levels of various Aβ and tau species and used conformation-sensitive fluorescent probes to detect differences in Aβ strains among individuals and populations. We found that these cohorts have some common but also some distinct strains from one another, with the most heterogeneous populations of Aβ emerging in subjects with high levels of AD pathology. The emergence of distinct strains in DS at these later stages of disease suggests that the confluence of aging, pathology, and other DS-linked factors may favor conditions that generate strains that are unique from sporadic AD.

The Unifying Hypothesis of Alzheimer's Disease: Heparan Sulfate Proteoglycans/Glycosaminoglycans Are Key as First Hypothesized Over 30 Years Ago.

The updated “Unifying Hypothesis of Alzheimer’s disease” (AD) is described that links all the observed neuropathology in AD brain (i.e., plaques, tangles, and cerebrovascular amyloid deposits), as well as inflammation, genetic factors (involving ApoE), “AD-in-a-Dish” studies, beta-amyloid protein (Aβ) as a microbial peptide; and theories that bacteria, gut microflora, gingivitis and viruses all play a role in the cause of AD. The common link is the early accumulation of heparan sulfate proteoglycans (HSPGs) and heparan sulfate glycosaminoglycans (GAGs). HS GAG accumulation and/or decreased HS GAG degradation is postulated to be the key initiating event. HS GAGs and highly sulfated macromolecules induce Aβ 1–40 (but not 1–42) to form spherical congophilic maltese-cross star-like amyloid core deposits identical to those in the AD brain. Heparin/HS also induces tau protein to form paired helical filaments (PHFs). Increased sulfation and/or decreased degradation of HSPGs and HS GAGs that occur due to brain aging leads to the formation of plaques and tangles in AD brain. Knockout of HS genes markedly reduce the accumulation of Aβ fibrils in the brain demonstrating that HS GAGs are key. Bacteria and viruses all use cell surface HS GAGs for entry into cells, including SARS-CoV-2. Bacteria and viruses cause HS GAGs to rapidly increase to cause near-immediate aggregation of Aβ fibrils. “AD-in-a-dish” studies use “Matrigel” as the underlying scaffold that spontaneously causes plaque, and then tangle formation in a dish. Matrigel mostly contains large amounts of perlecan, the same specific HSPG implicated in AD and amyloid disorders. Mucopolysaccharidoses caused by lack of specific HS GAG enzymes lead to massive accumulation of HS in lysosomal compartments in neurons and contribute to cognitive impairment in children. Neurons full of HS demonstrate marked accumulation and fibrillization of Aβ, tau, α-synuclein, and prion protein (PrP) in mucopolysaccharidosis animal models demonstrating that HS GAG accumulation is a precursor to Aβ accumulation in neurons. Brain aging leads to changes in HSPGs, including newly identified splice variants leading to increased HS GAG sulfation in the AD brain. All of these events lead to the new “Unifying Hypothesis of Alzheimer’s disease” that further implicates HSPGs /HS GAGs as key (as first hypothesized by Snow and Wight in 1989).

Some Candidate Drugs for Pharmacotherapy of Alzheimer's Disease.

Alzheimer’s disease (AD; progressive neurodegenerative disorder) is associated with cognitive and functional impairment with accompanying neuropsychiatric symptoms. The available pharmacological treatment is of a symptomatic nature and, as such, it does not modify the cause of AD. The currently used drugs to enhance cognition include an N-methyl-d-aspartate receptor antagonist (memantine) and cholinesterase inhibitors. The PUBMED, Medical Subject Heading and Clinical Trials databases were used for searching relevant data. Novel treatments are focused on already approved drugs for other conditions and also searching for innovative drugs encompassing investigational compounds. Among the approved drugs, we investigated, are intranasal insulin (and other antidiabetic drugs: liraglitude, pioglitazone and metformin), bexarotene (an anti-cancer drug and a retinoid X receptor agonist) or antidepressant drugs (citalopram, escitalopram, sertraline, mirtazapine). The latter, especially when combined with antipsychotics (for instance quetiapine or risperidone), were shown to reduce neuropsychiatric symptoms in AD patients. The former enhanced cognition. Procognitive effects may be also expected with dietary antioxidative and anti-inflammatory supplements—curcumin, myricetin, and resveratrol. Considering a close relationship between brain ischemia and AD, they may also reduce post-brain ischemia neurodegeneration. An investigational compound, CN-105 (a lipoprotein E agonist), has a very good profile in AD preclinical studies, and its clinical trial for postoperative dementia is starting soon.

In Silico Study of Centella asiatica Active Compound as BACE1 Inhibitor in Alzheimer’s Disease

Alzheimer (AD) is a chronical neurodegenerative disease which is the 6 th leading cause of death worldwide. About 36 million cases in the world and may increase to 115 million in 2050. The pathological cause of AD is the presence of residual Aβ peptides . Aβ peptides is produced in the cleavage process of the amyloid precursor protein (APP) sequentially by Beta amyloid precursor protein cleavage enzyme 1 (BACE1) and γ-secretase. Flavonol, germacrene B, and sitosterol are compounds found in Centella asiatica which is has potential as BACE1 inhibitor. The aim of this study was to analyze the interaction between BACE1 with flavonol, germacrene B and sitosterol by molecular docking to predict the BACE1 inhibitor potent of those compound. We obtained BACE1 from RSCB database, flavonol, germacrene B and sitosterol from PubChem database. Molecular dockcing was done using Hex 8.0.0. The docking result were vizualized with Discovery Studio 3.5. Interaction of BACE1 resulted binding energy for sitosterol was -239,7 kcal/mol , flavonol was -188,1 kcal/mol, and germacrene B was -185,6 kcal/mol. Flavonol and sitosterol bound to the active site of BACE1 involving Thr232 and Ile110 on flavonol, while Tyr71 on sitosterol. All of the active compounds didn’t have the interaction at S1’ subsite, which is the center of BACE1 active site which has become the key of APP activation from BACE1 . This study has shown that flavonol and sitosterol had potential to reduce BACE1 activity but not directly inhibit BACE1 activity .

A Positive Feedback Loop of Hippo- and c-Jun-Amino-Terminal Kinase Signaling Pathways Regulates Amyloid-Beta-Mediated Neurodegeneration.

Alzheimer's disease (AD, OMIM: 104300) is an age-related disorder that affects millions of people. One of the underlying causes of AD is generation of hydrophobic amyloid-beta 42 (Aβ42) peptides that accumulate to form amyloid plaques. These plaques induce oxidative stress and aberrant signaling, which result in the death of neurons and other pathologies linked to neurodegeneration. We have developed a Drosophila eye model of AD by targeted misexpression of human Aβ42 in the differentiating retinal neurons, where an accumulation of Aβ42 triggers a characteristic neurodegenerative phenotype. In a forward deficiency screen to look for genetic modifiers, we identified a molecularly defined deficiency, which suppresses Aβ42-mediated neurodegeneration. This deficiency uncovers hippo (hpo) gene, a member of evolutionarily conserved Hippo signaling pathway that regulates growth. Activation of Hippo signaling causes cell death, whereas downregulation of Hippo signaling triggers cell proliferation. We found that Hippo signaling is activated in Aβ42-mediated neurodegeneration. Downregulation of Hippo signaling rescues the Aβ42-mediated neurodegeneration, whereas upregulation of Hippo signaling enhances the Aβ42-mediated neurodegeneration phenotypes. It is known that c-Jun-amino-terminal kinase (JNK) signaling pathway is upregulated in AD. We found that activation of JNK signaling enhances the Aβ42-mediated neurodegeneration, whereas downregulation of JNK signaling rescues the Aβ42-mediated neurodegeneration. We tested the nature of interactions between Hippo signaling and JNK signaling in Aβ42-mediated neurodegeneration using genetic epistasis approach. Our data suggest that Hippo signaling and JNK signaling, two independent signaling pathways, act synergistically upon accumulation of Aβ42 plaques to trigger cell death. Our studies demonstrate a novel role of Hippo signaling pathway in Aβ42-mediated neurodegeneration.

Small-Molecule Amyloid Beta-Aggregation Inhibitors in Alzheimer's Disease Drug Development

AbstractAlzheimer's disease (AD) is still an incurable neurodegenerative disease that causes dementia. AD changes the brain function that, over time, impairs memory and diminishes judgment and reasoning ability. Pathophysiology of AD is complex. Till now the cause of AD remains unknown, but risk factors include family history and genetic predisposition. The drugs previously approved for AD treatment do not modify the disease process and only provide symptomatic improvement. Over the past few decades, research has led to significant progress in the understanding of the disease, leading to several novel strategies that may modify the disease process. One of the major developments in this direction is the amyloid β (Aβ) aggregation. Small molecules could block the initial stages of Aβ aggregation, which could be the starting point for the design and development of new AD drugs in the near future. In this review we summarize the most promising small-molecule Aβ-aggregation inhibitors including natural compounds, novel small molecules, and also those are in clinical trials. Moreover, we briefly summarized some reported docking studies of small-molecule Aβ aggregation inhibitors. These will give us an idea about the chemical features required to design novel small molecules with anti-Aβ aggregation properties.

Metabolomic Analysis Identifies Alterations of Amino Acid Metabolome Signatures in the Postmortem Brain of Alzheimer's Disease.

Despite significant advances in neuroscience research over the past several decades, the exact cause of AD has not yet fully understood. The metabolic hypothesis as well as the amyloid and tau hypotheses have been proposed to be associated with AD pathogenesis. In order to identify metabolome signatures from the postmortem brains of sporadic AD patients and control subjects, we performed ultra performance liquid chromatography coupled with linear ion trap-Orbitrap mass spectrometer (UPLC-LTQ–Orbitrap-MS). Not only our study identified new metabolome signatures but also verified previously known metabolome profiles in the brain. Statistical modeling of the analytical data and validation of the structural assignments discovered metabolic biomarkers associated with the AD pathogenesis. Interestingly, hypotaurin, myo-inositol and oxo-proline levels were markedly elevated in AD while lutamate and N-acetyl-aspartate were decreased in the postmortem brain tissue of AD patients. In addition, neurosteroid level such as cortisol was significantly increased in AD. Together, our data indicate that impaired amino acid metabolism is associated with AD pathogenesis and the altered amino acid signatures can be useful diagnostic biomarkers of AD. Thus, modulation of amino acid metabolism may be a possible therapeutic approach to treat AD.

Understanding the Amyloid Hypothesis in Alzheimer's Disease.

The amyloid hypothesis (AH) is still the most accepted model to explain the pathogenesis of inherited Alzheimer's disease (IAD). However, despite the neuropathological overlapping with the non-inherited form (NIAD), AH waver in explaining NIAD. Thus, 30 years after its first statement several questions are still open, mainly regarding the role of amyloid plaques (AP) and apolipoprotein E (APOE). Accordingly, a pathogenetic model including the role of AP and APOE unifying IAD and NIAD pathogenesis is still missing. In the present understanding of the AH, we suggested that amyloid-β (Aβ) peptides production and AP formation is a physiological aging process resulting from a systemic age-related decrease in the efficiency of the proteins catabolism/clearance machinery. In this pathogenetic model Aβ peptides act as neurotoxic molecules, but only above a critical concentration [Aβ]c. A threshold mechanism triggers IAD/NIAD onset only when [Aβ]≥[Aβ]c. In this process, APOE modifies [Aβ]c threshold in an isoform-specific way. Consequently, all factors influencing Aβ anabolism, such as amyloid beta precursor protein (APP), presenilin 1 (PSEN1), and presenilin 2 (PSEN2) gene mutations, and/or Aβ catabolism/clearance could contribute to exceed the threshold [Aβ]c, being characteristic of each individual. In this model, AP formation does not depend on [Aβ]c. The present interpretation of the AH, unifying the pathogenetic theories for IAD and NIAD, will explain why AP and APOE4 may be observed in healthy aging and why they are not the cause of AD. It is clear that further studies are needed to confirm our pathogenetic model. Nevertheless, our suggestion may be useful to better understand the pathogenesis of AD.