Antihypertensive medications ameliorate Alzheimer's disease pathology by slowing its propagation.
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ABSTRACT:
SUBMITTER: Affleck AJ
PROVIDER: S-EPMC7424255 | biostudies-literature | 2020
REPOSITORIES: biostudies-literature
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Project description:The involvement of radiofrequency electromagnetic fields (RF-EMF) in the neurodegenerative disease, especially Alzheimer's disease (AD), has received wide consideration, however, outcomes from several researches have not shown consistency. In this study, we determined whether RF-EMF influenced AD pathology in vivo using Tg-5xFAD mice as a model of AD-like amyloid ? (A?) pathology. The transgenic (Tg)-5xFAD and wild type (WT) mice were chronically exposed to RF-EMF for 8 months (1950 MHz, SAR 5W/kg, 2 hrs/day, 5 days/week). Notably, chronic RFEMF exposure significantly reduced not only A? plaques, APP, and APP carboxyl-terminal fragments (CTFs) in whole brain including hippocampus and entorhinal cortex but also the ratio of A?42 and A?40 peptide in the hippocampus of Tg-5xFAD mice. We also found that parenchymal expression of ?-amyloid precursor protein cleaving enzyme 1(BACE1) and neuroinflammation were inhibited by RF-EMF exposure in Tg-5xFAD. In addition, RF-EMF was shown to rescue memory impairment in Tg-5xFAD. Moreover, gene profiling from microarray data using hippocampus of WT and Tg- 5xFAD following RF-EMF exposure revealed that 5 genes (Tshz2, Gm12695, St3gal1, Isx and Tll1), which are involved in A?, are significantly altered inTg-5xFAD mice, exhibiting different responses to RF-EMF in WT or Tg-5xFAD mice; RF-EMF exposure in WT mice showed similar patterns to control Tg-5xFAD mice, however, RF-EMF exposure in Tg- 5xFAD mice showed opposite expression patterns. These findings indicate that chronic RF-EMF exposure directly affects A? pathology in AD but not in normal brain. Therefore, RF-EMF has preventive effects against AD-like pathology in advanced AD mice with a high expression of A?, which suggests that RF-EMF can have a beneficial influence on AD.
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Project description:Neurofibrillary tangles advance from layer II of the entorhinal cortex (EC-II) toward limbic and association cortices as Alzheimer's disease evolves. However, the mechanism involved in this hierarchical pattern of disease progression is unknown. We describe a transgenic mouse model in which overexpression of human tau P301L is restricted to EC-II. Tau pathology progresses from EC transgene-expressing neurons to neurons without detectable transgene expression, first to EC neighboring cells, followed by propagation to neurons downstream in the synaptic circuit such as the dentate gyrus, CA fields of the hippocampus, and cingulate cortex. Human tau protein spreads to these regions and coaggregates with endogenous mouse tau. With age, synaptic degeneration occurs in the entorhinal target zone and EC neurons are lost. These data suggest that a sequence of progressive misfolding of tau proteins, circuit-based transfer to new cell populations, and deafferentation induced degeneration are part of a process of tau-induced neurodegeneration.
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Project description:The gradual deterioration of cognitive functions in Alzheimer's disease is paralleled by a hierarchical progression of amyloid-beta and tau brain pathology. Recent findings indicate that toxic oligomers of amyloid-beta may cause propagation of pathology in a prion-like manner, although the underlying mechanisms are incompletely understood. Here we show that small extracellular vesicles, exosomes, from Alzheimer patients' brains contain increased levels of amyloid-beta oligomers and can act as vehicles for the neuron-to-neuron transfer of such toxic species in recipient neurons in culture. Moreover, blocking the formation, secretion or uptake of exosomes was found to reduce both the spread of oligomers and the related toxicity. Taken together, our results imply that exosomes are centrally involved in Alzheimer's disease and that they could serve as targets for development of new diagnostic and therapeutic principles.
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Project description:The accumulation of extracellular β-amyloid (Aβ) plaques within the brain is unique to Alzheimer's disease (AD) and thought to induce synaptic deficits and neuronal loss. Optimal therapies should tackle the core AD pathophysiology and prevent the decline in memory and cognitive functions. This study aimed to evaluate the therapeutic performance of mesenchymal stem cell-derived exosomes (MSC-exosomes), which are secreted membranous elements encapsulating a variety of MSC factors, on AD. A human neural cell culture model with familial AD (FAD) mutations was established and co-cultured with purified MSC-exosomes. 2-[18F]Fluoro-2-deoxy-d-glucose ([18F]FDG) and novel object recognition (NOR) testing were performed before/after treatment to evaluate the therapeutic effect in vivo. The AD-related pathology and the expression of neuronal memory/synaptic plasticity-related genes were also evaluated. The results showed that MSC-exosomes reduced Aβ expression and restored the expression of neuronal memory/synaptic plasticity-related genes in the cell model. [18F]FDG-PET imaging and cognitive assessment revealed a significant improvement in brain glucose metabolism and cognitive function in AD transgenic mice. The phase of neurons and astrocytes in the brain of AD mice were also found to be regulated after treatment with MSC-exosomes. Our study demonstrates the therapeutic mechanism of MSC-exosomes and provides an alternative therapeutic strategy based on cell-free MSC-exosomes for the treatment of AD.
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Project description:BackgroundObservational studies suggest that the use of antihypertensive medications (AHMs) is associated with a reduced risk of Alzheimer's disease (AD); however, these findings may be biased by confounding and reverse causality. We aimed to explore the effects of blood pressure (BP) and lowering systolic BP (SBP) via the protein targets of different AHMs on AD through a two-sample Mendelian randomization (MR) approach.MethodsGenetic proxies from genome-wide association studies of BP traits and BP-lowering variants in genes encoding AHM targets were extracted. Estimates were calculated by inverse-variance weighted method as the main model. MR Egger regression and leave-one-out analysis were performed to identify potential violations.ResultsThere was limited evidence that genetically predicted SBP/diastolic BP level affected AD risk based on 400/398 single nucleotide polymorphisms (SNPs), respectively (all P > 0.05). Suitable genetic variants for β-blockers (1 SNP), angiotensin receptor blockers (1 SNP), calcium channel blockers (CCBs, 45 SNPs), and thiazide diuretics (5 SNPs) were identified. Genetic proxies for CCB [odds ratio (OR) = 0.959, 95% confidence interval (CI) = 0.941-0.977, P = 3.92 × 10-6] and overall use of AHMs (OR = 0.961, 95% CI = 0.944-0.978, P = 5.74 × 10-6, SNPs = 52) were associated with a lower risk of AD. No notable heterogeneity and directional pleiotropy were identified (all P > 0.05). Additional analyses partly support these results. No single SNP was driving the observed effects.ConclusionsThis MR analysis found evidence that genetically determined lowering BP was associated with a lower risk of AD and CCB was identified as a promising strategy for AD prevention.
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Project description:OBJECTIVE:To examine the association of blood pressure (BP) with incident Alzheimer's disease (AD) dementia. METHODS:This work is based on a longitudinal, cohort study of 18 years, the Chicago Health and Aging Project (CHAP) performed in 2,137 participants (55% black) with systolic BP measured around 8.1 years before incident AD dementia. RESULTS:The association of BP with risk of AD dementia was U-shaped, with the lowest risks of AD dementia near the center of the systolic BP (SBP) and diastolic BP (DBP) distributions, and modestly elevated risk at lower BPs, and greater risk at higher BPs. The degree of U-shape and the range of lowest risk (threshold ranges) varied with antihypertensive medication use and presence of the APOE ?4 allele. The U-shape was most prominent for the subgroup not taking antihypertensive medications and having an APOE ?4 allele. At higher BPs, those having the APOE ?4 allele and not receiving antihypertensive medication were at greater risk of AD dementia than other groups: The risk of incident AD dementia increased by 100% (relative risk [RR]?=?2.00; 95% confidence interval [CI]?=?1.70, 2.31) for every 10?mm Hg increase in SBP above 140?mm Hg. For DBP, the risk of incident of AD dementia increased by 57% (RR?=?1.57; 95% CI?=?1.33, 1.86) for every 5?mm Hg increase in DBP above 76?mm Hg. INTERPRETATION:The BP risk of AD dementia association is U-shaped, with elevated risk at lower and higher BPs. People having the APOE ?4 allele and not receiving antihypertensive medication with higher BPs have notably elevated risk of AD dementia. Ann Neurol 2018;83:935-944.
| S-EPMC6149540 | biostudies-literature
Project description:The goal of this study is to estimate the change in the relationships between use of five classes of antihypertensive medications and stages of Chronic Kidney Disease (CKD) in American adults treated for hypertension.The US National Health and Nutrition Examination Survey (NHANES) data sets 1999-2012 were used with the final analytical sample of 3,045 participants. Population prevalence estimates were calculated using the NHANES survey design weights. Inferential analyses were done with binomial logistic regression models.The odds of advanced (3, 4, and 5 combined) versus early CKD stages (1 and 2 combined) were significantly higher among patients treated with Angiotensin Receptor Blockers (ARB) versus those not treated with ARB in 2009-2012 (adjusted odds ratio (95% confidence interval) = 2.52 (1.32-4.80)). From 1999 to 2012, the increase in this relationship was significant (p = 0.0023) for users of ARB polytherapy and in users of ARB in patients with albuminuria (p = 0.0031).Aggressive pharmacological management of hypertension with ARB as add-on therapy may have accelerated kidney damage in American adults. However, prospective longitudinal studies are needed to establish proper temporal sequence in this relationship.
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Project description:BackgroundDementia is a major health concern for which prevention and treatment strategies remain elusive. Lowering high blood pressure with specific antihypertensive medications (AHMs) could reduce the burden of disease. We investigated whether specific AHM classes reduced the risk for dementia.MethodsWe did a meta-analysis of individual participant data from eligible observational studies published between Jan 1, 1980, and Jan 1, 2019. Cohorts were eligible for inclusion if they prospectively recruited community-dwelling adults; included more than 2000 participants; collected data for dementia events over at least 5 years; had measured blood pressure and verified use of AHMs; included in-person exams, supplemented with additional data, to capture dementia events; and had followed up cases for mortality. We assessed the association of incident dementia and clinical Alzheimer's disease with use of five AHM classes, within strata of baseline high (systolic blood pressure [SBP] ≥140 mm Hg or diastolic blood pressure [DBP] ≥90 mm Hg) and normal (SBP <140 mm Hg and DBP <90 mm Hg) blood pressure. We used a propensity score to control for confounding factors related to the probability of receiving AHM. Study-specific effect estimates were pooled using random-effects meta-analyses.ResultsSix prospective community-based studies (n=31 090 well phenotyped dementia-free adults older than 55 years) with median follow-ups across cohorts of 7-22 years were eligible for analysis. There were 3728 incident cases of dementia and 1741 incident Alzheimer's disease diagnoses. In the high blood pressure stratum (n=15 537), those using any AHM had a reduced risk for developing dementia (hazard ratio [HR] 0·88, 95% CI 0·79-0·98; p=0·019) and Alzheimer's disease (HR 0·84, 0·73-0·97; p=0·021) compared with those not using AHM. We did not find any significant differences between one drug class versus all others on risk of dementia. In the normal blood pressure stratum (n=15 553), there was no association between AHM use and incident dementia or Alzheimer's disease.InterpretationOver a long period of observation, no evidence was found that a specific AHM drug class was more effective than others in lowering risk of dementia. Among people with hypertensive levels of blood pressure, use of any AHM with efficacy to lower blood pressure might reduce the risk for dementia. These findings suggest future clinical guidelines for hypertension management should also consider the beneficial effect of AHM on the risk for dementia.FundingThe Alzheimer's Drug Discovery Foundation and the National Institute on Aging Intramural Research Program.
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