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Neprilysin Inhibitors in Heart Failure: The Science, Mechanism of Action, Clinical Studies, and Unanswered Questions. JACC. BASIC TO TRANSLATIONAL SCIENCE 2022; 8:88-105. [PMID: 36777165 PMCID: PMC9911324 DOI: 10.1016/j.jacbts.2022.05.010] [Citation(s) in RCA: 23] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/23/2022] [Revised: 05/18/2022] [Accepted: 05/18/2022] [Indexed: 11/16/2022]
Abstract
This article provides a contemporary review and a new perspective on the role of neprilysin inhibition in heart failure (HF) in the context of recent clinical trials and addresses potential mechanisms and unanswered questions in certain HF patient populations. Neprilysin is an endopeptidase that cleaves a variety of peptides such as natriuretic peptides, bradykinin, adrenomedullin, substance P, angiotensin I and II, and endothelin. It has a broad role in cardiovascular, renal, pulmonary, gastrointestinal, endocrine, and neurologic functions. The combined angiotensin receptor and neprilysin inhibitor (ARNi) has been developed with an intent to increase vasodilatory natriuretic peptides and prevent counterregulatory activation of the angiotensin system. ARNi therapy is very effective in reducing the risks of death and hospitalization for HF in patients with HF and New York Heart Association functional class II to III symptoms, but studies failed to show any benefits with ARNi when compared with angiotensin-converting enzyme inhibitors or angiotensin receptor blocker in patients with advanced HF with reduced ejection fraction or in patients following myocardial infarction with left ventricular dysfunction but without HF. These raise the questions about whether the enzymatic breakdown of natriuretic peptides may not be a very effective solution in advanced HF patients when there is downstream blunting of the response to natriuretic peptides or among post-myocardial infarction patients in the absence of HF when there may not be a need for increased natriuretic peptide availability. Furthermore, there is a need for additional studies to determine the long-term effects of ARNi on albuminuria, obesity, glycemic control and lipid profile, blood pressure, and cognitive function in patients with HF.
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Key Words
- ACE, angiotensin-converting enzyme
- ANP, atrial natriuretic peptide
- ARB, angiotensin receptor blocker
- ARN, angiotensin receptor–neprilysin
- ARNi
- Aβ, amyloid beta
- BNP, brain natriuretic peptide
- BP, blood pressure
- CSF, cerebrospinal fluid
- EF, ejection fraction
- FDA, U.S. Food and Drug Administration
- GFR, glomerular filtration rate
- HF, heart failure
- HFpEF, heart failure with preserved ejection fraction
- HFrEF, heart failure with reduced ejection fraction
- LV, left ventricular
- LVEF, left ventricular ejection fraction
- MI, myocardial infarction
- NEP inhibitor
- NT-proBNP, N-terminal pro–brain natriuretic peptide
- NYHA, New York Heart Association
- PDE, phosphodiesterase
- RAAS, renin-angiotensin-aldosterone system
- UACR, urinary albumin/creatine ratio
- angiotensin receptor–neprilysin inhibitor
- cGMP, cyclic guanosine monophosphate
- eGFR, estimated glomerular filtration rate
- heart failure
- neprilysin
- neprilysin inhibitor
- sacubitril
- sacubitril/valsartan
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Mitochondrial complex I as a therapeutic target for Alzheimer's disease. Acta Pharm Sin B 2022; 12:483-495. [PMID: 35256930 PMCID: PMC8897152 DOI: 10.1016/j.apsb.2021.11.003] [Citation(s) in RCA: 37] [Impact Index Per Article: 18.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2021] [Revised: 10/01/2021] [Accepted: 10/25/2021] [Indexed: 02/08/2023] Open
Abstract
Alzheimer's disease (AD), the most prominent form of dementia in the elderly, has no cure. Strategies focused on the reduction of amyloid beta or hyperphosphorylated Tau protein have largely failed in clinical trials. Novel therapeutic targets and strategies are urgently needed. Emerging data suggest that in response to environmental stress, mitochondria initiate an integrated stress response (ISR) shown to be beneficial for healthy aging and neuroprotection. Here, we review data that implicate mitochondrial electron transport complexes involved in oxidative phosphorylation as a hub for small molecule-targeted therapeutics that could induce beneficial mitochondrial ISR. Specifically, partial inhibition of mitochondrial complex I has been exploited as a novel strategy for multiple human conditions, including AD, with several small molecules being tested in clinical trials. We discuss current understanding of the molecular mechanisms involved in this counterintuitive approach. Since this strategy has also been shown to enhance health and life span, the development of safe and efficacious complex I inhibitors could promote healthy aging, delaying the onset of age-related neurodegenerative diseases.
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Key Words
- AD, Alzheimer's disease
- ADP, adenosine diphosphate
- AIDS, acquired immunodeficiency syndrome
- AMP, adenosine monophosphate
- AMPK, AMP-activated protein kinase
- APP/PS1, amyloid precursor protein/presenilin 1
- ATP, adenosine triphosphate
- Alzheimer's disease
- Aβ, amyloid beta
- BBB, blood‒brain barrier
- BDNF, brain-derived neurotrophic factor
- CP2, tricyclic pyrone compound two
- Complex I inhibitors
- ER, endoplasmic reticulum
- ETC, electron transport chain
- FADH2, flavin adenine dinucleotide
- FDG-PET, fluorodeoxyglucose-positron emission tomography
- GWAS, genome-wide association study
- HD, Huntington's disease
- HIF-1α, hypoxia induced factor 1 α
- Healthy aging
- ISR, integrated stress response
- Integrated stress response
- LTP, long term potentiation
- MCI, mild cognitive impairment
- MPTP, 1-methyl 4-phenyl-1,2,3,6-tetrahydropyridine
- Mitochondria
- Mitochondria signaling
- Mitochondria targeted therapeutics
- NAD+ and NADH, nicotinamide adenine dinucleotide
- NF-κB, nuclear factor kappa-light-chain-enhancer of activated B cells
- NRF2, nuclear factor E2-related factor 2
- Neuroprotection
- OXPHOS, oxidative phosphorylation
- PD, Parkinson's disease
- PGC1α, peroxisome proliferator-activated receptor gamma coactivator 1 alpha
- PMF, proton-motive force
- RNAi, RNA interference
- ROS, reactive oxygen species
- T2DM, type II diabetes mellitus
- TCA, the tricarboxylic acid cycle
- mtDNA, mitochondrial DNA
- mtUPR, mitochondrial unfolded protein response
- pTau, hyper-phosphorylated Tau protein
- ΔpH, proton gradient
- Δψm, mitochondrial membrane potential
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Oxyphylla A ameliorates cognitive deficits and alleviates neuropathology via the Akt-GSK3β and Nrf2-Keap1-HO-1 pathways in vitro and in vivo murine models of Alzheimer's disease. J Adv Res 2022; 34:1-12. [PMID: 35024177 PMCID: PMC8655137 DOI: 10.1016/j.jare.2021.09.002] [Citation(s) in RCA: 29] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2021] [Revised: 08/09/2021] [Accepted: 09/05/2021] [Indexed: 12/16/2022] Open
Abstract
Introduction Alzheimer’s disease (AD) is a progressive brain disorder, and one of the most common causes of dementia and amnesia. Due to the complex pathogenesis of AD, the underlying mechanisms remain unclear. Although scientists have made increasing efforts to develop drugs for AD, no effective therapeutic agents have been found. Objectives Natural products and their constituents have shown promise for treating neurodegenerative diseases, including AD. Thus, in-depth study of medical plants, and the main active ingredients thereof against AD, is necessary to devise therapeutic agents. Methods In this study, N2a/APP cells and SAMP8 mice were employed as in vitro and in vivo models of AD. Multiple molecular biological methods were used to investigate the potential therapeutic actions of oxyphylla A, and the underlying mechanisms. Results Results showed that oxyphylla A, a novel compound extracted from Alpinia oxyphylla, could reduce the expression levels of amyloid precursor protein (APP) and amyloid beta (Aβ) proteins, and attenuate cognitive decline in SAMP8 mice. Further investigation of the underlying mechanisms showed that oxyphylla A exerted an antioxidative effect through the Akt-GSK3β and Nrf2-Keap1-HO-1 pathways. Conclusions. Taken together, our results suggest a new horizon for the discovery of therapeutic agents for AD.
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Key Words
- AD, Alzheimer’s disease
- AOE, ethanolic extract of Alpinia oxyphylla
- APP, amyloid precursor protein
- ARE, antioxidant response element
- ARE, antioxidant responsive element
- Alzheimer’s disease
- Amyloid beta proteins
- Aβ, amyloid beta
- GSK3, glycogen synthase kinase 3
- HO-1, heme oxygenase-1
- Keap1, Keleh-like ECH-associated protein
- MWM, Morris Water Maze
- NFTs, neurofibrillary tangles
- NQO1, NAD(P)H:quinone oxidoreductase1
- Nrf2, erythroid-derived 2-related factor 2
- Oxidative stress
- PD, Parkinson’s disease
- PHF, paired helical filaments
- RLU, relative luciferase units
- ROS, reactive oxygen species
- SAMP8
- SAMP8 mice, senescence-accelerated mouse prone 8
- oxyphylla A
- pRL-TK, Renilla luciferase reporter plasmid
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Evolution of blood-brain barrier in brain diseases and related systemic nanoscale brain-targeting drug delivery strategies. Acta Pharm Sin B 2021; 11:2306-2325. [PMID: 34522589 PMCID: PMC8424230 DOI: 10.1016/j.apsb.2020.11.023] [Citation(s) in RCA: 112] [Impact Index Per Article: 37.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2020] [Revised: 09/30/2020] [Accepted: 10/09/2020] [Indexed: 02/07/2023] Open
Abstract
Blood–brain barrier (BBB) strictly controls matter exchange between blood and brain, and severely limits brain penetration of systemically administered drugs, resulting in ineffective drug therapy of brain diseases. However, during the onset and progression of brain diseases, BBB alterations evolve inevitably. In this review, we focus on nanoscale brain-targeting drug delivery strategies designed based on BBB evolutions and related applications in various brain diseases including Alzheimer's disease, Parkinson's disease, epilepsy, stroke, traumatic brain injury and brain tumor. The advances on optimization of small molecules for BBB crossing and non-systemic administration routes (e.g., intranasal treatment) for BBB bypassing are not included in this review.
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Key Words
- AD, Alzheimer's disease
- AMT, alpha-methyl-l-tryptophan
- Aβ, amyloid beta
- BACE1, β-secretase 1
- BBB, blood–brain barrier
- BDNF, brain derived neurotrophic factor
- BTB, blood–brain tumor barrier
- Blood–brain barrier
- Brain diseases
- Brain-targeting
- CMT, carrier-mediated transportation
- DTPA-Gd, Gd-diethyltriaminepentaacetic acid
- Drug delivery systems
- EPR, enhanced permeability and retention
- GLUT1, glucose transporter-1
- Gd, gadolinium
- ICAM-1, intercellular adhesion molecule-1
- KATP, ATP-sensitive potassium channels
- KCa, calcium-dependent potassium channels
- LAT1, L-type amino acid transporter 1
- LDL, low density lipoprotein
- LDLR, LDL receptor
- LFA-1, lymphocyte function associated antigen-1
- LRP1, LDLR-related protein 1
- MFSD2A, major facilitator superfamily domain-containing protein 2a
- MMP9, metalloproteinase-9
- MRI, magnetic resonance imaging
- NPs, nanoparticles
- Nanoparticles
- P-gp, P-glycoprotein
- PD, Parkinson's disease
- PEG, polyethyleneglycol
- PEG-PLGA, polyethyleneglycol-poly(lactic-co-glycolic acid)
- PLGA, poly(lactic-co-glycolic acid)
- PSMA, prostate-specific membrane antigen
- RAGE, receptor for advanced glycosylation end products
- RBC, red blood cell
- RMT, receptor-mediated transcytosis
- ROS, reactive oxygen species
- TBI, traumatic brain injury
- TJ, tight junction
- TfR, transferrin receptor
- VEGF, vascular endothelial growth factor
- ZO1, zona occludens 1
- siRNA, short interfering RNA
- tPA, tissue plasminogen activator
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Adipose-derived mesenchymal stem cells rescue rat hippocampal cells from aluminum oxide nanoparticle-induced apoptosis via regulation of P53, Aβ, SOX2, OCT4, and CYP2E1. Toxicol Rep 2021; 8:1156-1168. [PMID: 34150525 PMCID: PMC8190131 DOI: 10.1016/j.toxrep.2021.06.003] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2021] [Revised: 05/01/2021] [Accepted: 06/02/2021] [Indexed: 12/20/2022] Open
Abstract
Mesenchymal stem cells (MSCs) possess a preventive capacity against free radical toxicity in various tissues. The present study aimed to demonstrate the reformative and treatment roles of adipose-derived MSCs (AD-MSCs) against severe toxicity in the hippocampal cells of the brain caused by aluminum oxide nanoparticles (Al2O3-NPs). Rats were divided into five experimental groups: an untreated control group, a control group receiving NaCl, a group receiving Al2O3-NPs (6 mg/kg) for 20 days, a group that was allowed to recover (R) for 20 days following treatment with Al2O3-NPs, and a Al2O3-NPs + AD-MSCs group, where each rat was injected with 0.8 × 106 AD-MSCs via the caudal vein. Oral administration of Al2O3-NPs increased the protein levels of P53, cleaved caspase-3, CYP2E1, and beta-amyloid (Aβ); contrarily, AD-MSCs transplantation downregulated the levels of these proteins. In addition, the AD-MSCs-treated hippocampal cells were protected from Al2O3-NPs-induced toxicity, as detected by the expression levels of Sox2 and Oct4 that are essential for the maintenance of self-renewal. It was also found that AD-MSCs injection significantly altered the levels of brain total peroxide and monoamine oxidase (MAO)-A and MAO-B activities. Histologically, our results indicated that AD-MSCs alleviated the severe damage in the hippocampal cells induced by Al2O3-NPs. Moreover, the role of AD-MSCs in reducing hippocampal cell death was reinforced by the regulation of P53, cleaved caspase-3, Aβ, and CYP2E1 proteins, as well as by the regulation of SOX2 and OCT4 levels and MAO-A and MAO-B activities.
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Key Words
- AD-MSCs, adipose-derived mesenchymal stem cells
- Adipose-Derived mesenchymal stem cells
- Al2O3-NPs, Aluminum oxide nanoparticles
- Aluminum oxide nanoparticles
- Apoptosis
- Aβ, amyloid beta
- EGTA, ethylene glycol tetraacetic acid
- Hippocampal cells
- MAO-A and B, monoamine oxidase A, B
- Oct4, octamer-binding transcription factor 4
- ROS, reactive oxygen species
- Sox2, sex-determining region Y-box 2
- TEM, transmission electron microscopy
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Escape from abluminal LRP1-mediated clearance for boosted nanoparticle brain delivery and brain metastasis treatment. Acta Pharm Sin B 2021; 11:1341-1354. [PMID: 34094838 PMCID: PMC8148067 DOI: 10.1016/j.apsb.2020.10.015] [Citation(s) in RCA: 31] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2020] [Revised: 09/14/2020] [Accepted: 09/23/2020] [Indexed: 02/06/2023] Open
Abstract
Breast cancer brain metastases (BCBMs) are one of the most difficult malignancies to treat due to the intracranial location and multifocal growth. Chemotherapy and molecular targeted therapy are extremely ineffective for BCBMs due to the inept brain accumulation because of the formidable blood‒brain barrier (BBB). Accumulation studies prove that low density lipoprotein receptor-related protein 1 (LRP1) is promising target for BBB transcytosis. However, as the primary clearance receptor for amyloid beta and tissue plasminogen activator, LRP1 at abluminal side of BBB can clear LRP1-targeting therapeutics. Matrix metalloproteinase-1 (MMP1) is highly enriched in metastatic niche to promote growth of BCBMs. Herein, it is reported that nanoparticles (NPs-K-s-A) tethered with MMP1-sensitive fusion peptide containing HER2-targeting K and LRP1-targeting angiopep-2 (A), can surmount the BBB and escape LRP1-mediated clearance in metastatic niche. NPs-K-s-A revealed infinitely superior brain accumulation to angiopep-2-decorated NPs-A in BCBMs bearing mice, while comparable brain accumulation in normal mice. The delivered doxorubicin and lapatinib synergistically inhibit BCBMs growth and prolongs survival of mice bearing BCBMs. Due to the efficient BBB penetration, special and remarkable clearance escape, and facilitated therapeutic outcome, the fusion peptide-based drug delivery strategy may serve as a potential approach for clinical management of BCBMs.
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Key Words
- 231Br, MDA-MB-231Br-HER2
- A, angiopep-2
- AUC0‒t, area under the curve from zero to time t
- Abluminal LRP1
- Amyloid beta
- Aβ, amyloid beta
- BBB, blood‒brain barrier
- BCBMs, breast cancer brain metastases
- BMECs, brain microvascular endothelial cells
- Blood‒brain barrier
- Brain clearance
- Breast cancer brain metastases
- CI, combination index
- CL, clearance
- DMEM, Dulbecco's modified eagle medium
- DMSO, dimethyl sulfoxide
- DOX, doxorubicin
- FBS, fetal bovine serum
- Fa, the fraction of tumor cells affected
- Fusion peptide
- K, KAAYSL
- LAP, lapatinib
- LRP1, low density lipoprotein receptor-related protein 1
- MAL-PEG-SCM, maleimide polyethylene glycol succinimidyl carboxymethyl ester
- MCM, MDA-MB-231Br-HER2 conditioned medium
- MMP
- MMP1, matrix metalloproteinase-1
- MRT0‒t, mean residence time from zero to time t
- NPs, nanoparticles
- Nanoparticles
- PLGA, poly(lactic-co-glycolic acid)
- PLGA-PLL, poly(lactic-co-glycolic acid)-poly(ε-carbobenzoxy-l-lysine)
- PLL, poly(ε-carbobenzoxy-l-lysine)
- PVA, polyvinyl alcohol
- SDS, sodium dodecyl sulfate
- i, insensitive GDQGIAGF
- s, sensitive VPMS-MRGG
- t1/2, half time
- tPA, tissue plasminogen activator
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A simplified and sensitive immunoprecipitation mass spectrometry protocol for the analysis of amyloid-beta peptides in brain tissue. CLINICAL MASS SPECTROMETRY 2019; 14 Pt B:83-88. [PMID: 34917764 DOI: 10.1016/j.clinms.2019.07.001] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/26/2019] [Revised: 07/09/2019] [Accepted: 07/09/2019] [Indexed: 10/26/2022]
Abstract
In the field of Alzheimer's disease, there is an urgent need for novel analytical tools to identify disease-specific biomarkers and to evaluate therapeutics. Preclinical trials commonly employ amyloid beta (Aβ) peptide signatures as a read-out. In this paper, we report a simplified and detailed protocol for robust immunoprecipitation of Aβ in brain tissue prior to mass spectrometric detection exemplified by a study using transgenic mice. The established method employed murine monoclonal and rabbit polyclonal antibodies and was capable of yielding well-reproducible peaks of high intensity with low background signal intensities corresponding to various Aβ forms.
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Key Words
- AD, Alzheimer’s disease
- APP, amyloid precursor protein
- Amyloid beta peptides
- Aβ, amyloid beta
- BSA, bovine serum albumine
- Brain
- FA, formic acid
- IP, Immunoprecipitation
- Immunoprecipitation
- MALDI-TOF MS
- MALDI-TOF MS, matrix-assisted-laser-desorption time-of-flight mass spectrometry
- MS, mass spectrometry
- PBS, phosphate buffered saline
- S/N, signal-to-noice ratio
- SA, sinapinic acid
- VD, volume of Dynabeads suspension
- Wt, wild type
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Identifying natural compounds as multi-target-directed ligands against Alzheimer's disease: an in silico approach. J Biomol Struct Dyn 2018; 37:1282-1306. [PMID: 29578387 DOI: 10.1080/07391102.2018.1456975] [Citation(s) in RCA: 34] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
Alzheimer's disease (AD) is a multi-factorial disease, which can be simply outlined as an irreversible and progressive neurodegenerative disorder with an unclear root cause. It is a major cause of dementia in old aged people. In the present study, utilizing the structural and biological activity information of ligands for five important and mostly studied vital targets (i.e. cyclin-dependant kinase 5, β-secretase, monoamine oxidase B, glycogen synthase kinase 3β, acetylcholinesterase) that are believed to be effective against AD, we have developed five classification models using linear discriminant analysis (LDA) technique. Considering the importance of data curation, we have given more attention towards the chemical and biological data curation, which is a difficult task especially in case of big data-sets. Thus, to ease the curation process we have designed Konstanz Information Miner (KNIME) workflows, which are made available at http://teqip.jdvu.ac.in/QSAR_Tools/ . The developed models were appropriately validated based on the predictions for experiment derived data from test sets, as well as true external set compounds including known multi-target compounds. The domain of applicability for each classification model was checked based on a confidence estimation approach. Further, these validated models were employed for screening of natural compounds collected from the InterBioScreen natural database ( https://www.ibscreen.com/natural-compounds ). Further, the natural compounds that were categorized as 'actives' in at least two classification models out of five developed models were considered as multi-target leads, and these compounds were further screened using the drug-like filter, molecular docking technique and then thoroughly analyzed using molecular dynamics studies. Finally, the most potential multi-target natural compounds against AD are suggested.
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Key Words
- 3D, three-dimensional
- ACh, acetylcholine
- AChE, acetylcholinesterase
- AD, Alzheimer’s disease
- ADME, absorption, distribution, metabolism, and elimination
- APP, amyloid precursor protein
- AUROC, area under the ROC curve
- Alzheimer’s disease
- Aβ, amyloid beta
- BACE1, beta-APP-cleaving enzyme 1
- CDK5, cyclin-dependant kinase 5
- FDA, food and drug administration
- FN, false negative
- FP, false positive
- GSK-3β, glycogen synthase kinase 3β
- HTVS, high-throughput virtual screening
- InChI, International Chemical Identifier
- KNIME, Konstanz Information Miner
- LBDD, ligand-based drug design
- LDA, linear discriminant analysis
- MAO-B, monoamine oxidase B
- MMGBSA, molecular mechanics/generalized born surface area
- MMPBSA, molecular mechanics/Poisson–Boltzmann surface area
- MMPs, matched molecular pairs
- MSA, molecular spectrum analysis
- MTDLs, multi-target-directed ligands
- NMDA, N-methyl-D-aspartate
- PDB, protein data bank
- PP, posterior probability
- QSAR, quantitative structure–activity relationship
- RMSD, root-mean-square deviation
- ROC, receiver operating curve
- ROS, reactive oxygen species
- SBDD, structure-based drug design
- SDF, structure data format
- SMILES, simplified molecular-input line-entry system
- TN, true negative
- TP, true positive
- big data
- data curation
- linear discriminant analysis
- molecular docking
- molecular dynamics
- multi-target drug design
- natural compounds
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Neuroimaging and other modalities to assess Alzheimer's disease in Down syndrome. NEUROIMAGE-CLINICAL 2017; 17:263-271. [PMID: 29159043 PMCID: PMC5683343 DOI: 10.1016/j.nicl.2017.10.022] [Citation(s) in RCA: 50] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Received: 08/18/2017] [Revised: 10/18/2017] [Accepted: 10/23/2017] [Indexed: 12/29/2022]
Abstract
People with Down syndrome (DS) develop Alzheimer's disease (AD) at higher rates and a younger age of onset compared to the general population. As the average lifespan of people with DS is increasing, AD is becoming an important health concern in this group. Neuroimaging is becoming an increasingly useful tool in understanding the pathogenesis of dementia development in relation to clinical symptoms. Furthermore, neuroimaging has the potential to play a role in AD diagnosis and monitoring of therapeutics. This review describes major recent findings from in vivo neuroimaging studies analysing DS and AD via ligand-based positron emission tomography (PET), [18F] fluorodeoxyglucose (FDG)-PET, structural magnetic resonance imaging (sMRI), and diffusion tensor imaging (DTI). Electroencephalography (EEG) and retinal imaging are also discussed as emerging modalities. The review is organized by neuroimaging method and assesses the relationship between cognitive decline and neuroimaging changes. We find that amyloid accumulation seen on PET occurs prior to dementia onset, possibly as a precursor to the atrophy and white matter changes seen in MRI studies. Future PET studies relating tau distribution to clinical symptoms will provide further insight into the role this protein plays in dementia development. Brain activity changes demonstrated by EEG and metabolic changes seen via FDG-PET may also follow predictable patterns that can help track dementia progression. Finally, newer approaches such as retinal imaging will hopefully overcome some of the limitations of neuroimaging and allow for detection of dementia at an earlier stage. We review recent neuroimaging findings in the field of Down syndrome and Alzheimer's disease. Review is organized by neuroimaging methodology. Correlation between cognitive decline and imaging findings is considered. Neuroimaging is a useful tool for studying and monitoring Alzheimer's disease in the Down syndrome population.
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Key Words
- AD, Alzheimer's disease
- APP, amyloid precursor protein
- Aβ, amyloid beta
- Biomarkers
- DS, Down syndrome
- DTI, diffusion tensor imaging
- Dementia
- Diffusion tensor imaging (DTI)
- EEG, electroencephalography
- Electroencephalography (EEG)
- FDG, fluordexoyglucose
- Magnetic resonance imaging (MRI)
- NFT, neurofibrillary tangles
- PET, positron emission tomography
- Positron emission tomography (PET)
- sMRI, structural magnetic resonance imaging
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Use of T1-weighted/T2-weighted magnetic resonance ratio to elucidate changes due to amyloid β accumulation in cognitively normal subjects. NEUROIMAGE-CLINICAL 2016; 13:209-214. [PMID: 28003959 PMCID: PMC5157788 DOI: 10.1016/j.nicl.2016.11.029] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/29/2016] [Revised: 11/25/2016] [Accepted: 11/26/2016] [Indexed: 01/14/2023]
Abstract
The ratio of signal intensity in T1-weighted (T1w) and T2-weighted (T2w) magnetic resonance imaging (MRI) was recently proposed to enhance the sensitivity of detecting changes in disease-related signal intensity. The objective of this study was to test the effectiveness of T1w/T2w image ratios as an easily accessible biomarker for amyloid beta (Aβ) accumulation. We performed the T1w/T2w analysis in cognitively normal elderly individuals. We applied [11C] Pittsburgh Compound B (PiB)-PET to the same individuals, and Aβ deposition was quantified by its binding potential (PiB-BPND). The subjects were divided into low and high PiB-BPND groups, and group differences in regional T1w/T2w values were evaluated. In the regions where we found a significant group difference, we conducted a correlation analysis between regional T1w/T2w values and PiB-BPND. Subjects with high global cortical PiB-BPND showed a significantly higher regional T1w/T2w ratio in the frontal cortex and anterior cingulate cortex. We found a significant positive relationship between the regional T1w/T2w ratio and Aβ accumulation. Moreover, with a T1w/T2w ratio of 0.55 in the medial frontal regions, we correctly discriminated subjects with high PiB-BPND from the entire subject population with a sensitivity of 84.6% and specificity of 80.0%. Our results indicate that early Aβ-induced pathological changes can be detected using the T1w/T2w ratio on MRI. We believe that the T1w/T2w ratio is a prospective stable biological marker of early Aβ accumulation in cognitively normal individuals. The availability of such an accessible marker would improve the efficiency of clinical trials focusing on the initial disease stages by reducing the number of subjects who require screening by Aβ-PET scan or lumbar puncture. We examined the T1w/T2w ratio of MR images in cognitively normal elderly subjects. Aβ deposition was quantified by [11C] PiB-PET binding potential (PiB-BPND). The T1w/T2w ratios were positively correlated with PiB-BPND values. We correctly discriminated subjects with high PIB-BPND using the T1w/T2w ratio. The T1w/T2w ratio from MRI is a potential biological marker of early Aβ deposition.
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Key Words
- 11C–labeled Pittsburgh Compound B ([11C]PiB)
- AD, Alzheimer's disease
- Alzheimer's disease (AD)
- Amyloid-β (Aβ)
- Aβ, amyloid beta
- BP, binding potential
- CSF, cerebrospinal fluid
- FWHM, full-width at half maximum
- MRI, magnetic resonance imaging
- PET, positron emission tomography
- PiB, Pittsburgh Compound B
- PiB-BPND, PiB-BP estimates relative to non-displaceable (ND) binding
- Positron emission tomography (PET)
- ROC, receiver operating characteristic
- T1-weighted/T2-weighted magnetic resonance ratio images
- T1w, T1-weighted
- T2w, T2-weighted
- VOI, volumes of interest
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Abstract
Termination of transcription of short non-coding RNAs is carried out in yeast by the Nab3-Nrd1-Sen1 complex. Nab3 and Nrd1 are hnRNP-like proteins that dimerize and bind RNA with sequence specificity. We show here that an essential region of Nab3 that is predicted to be prion-like based upon its sequence bias, formed amyloid-like filaments. A similar region from Nrd1 also assembled into filaments in vitro. The purified Nab3 domain formed a macroscopic gel whose lattice organization was observed by X-ray fiber diffraction. Filaments were resistant to dissociation in anionic detergent, bound the fluorescent dye thioflavin T, and showed a β-sheet rich structure by circular dichroism spectroscopy, similar to human amyloid β which served as a reference amyloid. A version of the Nab3 domain with a mutation that impairs its termination function, also formed fibers as observed by electron microscopy. Using a protein fragment interaction assay, the purified Nab3 domain was seen to interact with itself in living yeast. A similar observation was made for full length Nab3. These results suggest that the Nab3 and Nrd1 RNA-binding proteins can attain a complex polymeric form and raise the possibility that this property is important for organizing their functional state during termination. These findings are congruent with recent work showing that RNA binding proteins with low complexity domains form a dynamic subcellular matrix in which RNA metabolism takes place but can also aberrantly yield pathological aggregated particles.
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Key Words
- Aβ, amyloid beta
- BSA, bovine serum albumin
- CPEB, cytoplasmic polyadenylation element binding protein
- CTD, carboxy terminal domain
- DHFR, dihydrofolate reductase
- DMSO, dimethyl sulfoxide
- EDTA, ethylenediaminetetraacetic acid
- GFP, green fluorescent protein
- HFIP, hexafluoroisopropanol
- IPTG, isopropyl β-D-1-thiogalactopyranoside
- PCR, polymerase chain reaction
- RNA binding protein
- RRM, RNA recognition motif
- SDD-AGE, semi-denaturing detergent agarose gel electrophoresis
- SDS, sodium dodecyl sulfate
- TEV, tobacco etch virus
- amyloid
- fibril
- hnRNP
- hnRNP, heterogeneous nuclear ribonucleoprotein
- transcription termination
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