An electrochemical aptasensor for amyloid-ß oligomer based on double-stranded DNA as "conductive spring".

In order to overcome the antibody-based sensor's shortcomings, an electrochemical aptamer (Apt)-based sensor was developed for amyloid-ß40 oligomer (Aß40-O). The aptasensor was constructed by locating Apt and ferrocence (Fc) on streptavidin-modified gold (SA-gold) nanoparticles. The obtained AptFc@SA-gold nanoparticles were linked onto the Au electrode via the connection of double-stranded DNA (dsDNA) as a "conductive spring." The determination of Aß40-O was performed with square-wave voltammetry (SWV). Upon bio-recognition between Apt and Aß40-O, the conformation of Apt changed and the formed Apt/Aß40-O complex separated from the SA-gold surface. As a result, the surface charge of SA-gold positively shifted, weakening the electrostatic attraction between the SA-gold and the positively charged Au electrode surface (at potential range of 0.1~0.5 V, corresponding to the Fc redox transformation), and stretching the dsDNA chain. Based on the exponential decay of dsDNA's electron transfer efficiency on its chain stretching, the oxidation current density from Fc decreased and displayed linear correlation to the concentration of Aß40-O. A wide linear range of 0.100 nM to 1.00 µM with a low detection limit of 93.0 pM was obtained. The aptasensor displayed excellent selectivity toward Aß40-O in contrast to other possible interfering analogs (Aß40 monomer, Aß42 monomer, and oligomer) at × 100 higher concentrations. The recoveries for Aß40-O-spiked artificial cerebrospinal fluid and healthy human serum were 94.0~104% and 92.8~95.4%, respectively. The electrochemical aptasensor meets the demands of clinic determination of Aß40-O, which is significant for the early diagnosis of AD. Graphical abstract Schematic representation of the electrochemical aptasensor for amyloid-ß oligomer based on the surface charge change induced by target binding.

Plasma Amyloid-ß in Relation to Cardiac Function and Risk of Heart Failure in General Population.

BACKGROUND: Amyloid-ß (Aß) may be related to cardiac function. However, there are limited data on the association of plasma Aß with cardiac function and risk of heart failure (HF) in the general population. OBJECTIVES: This study sought to determine the associations of plasma amyloid-ß40 (Aß40) and amyloid-ß42 (Aß42) with echocardiographic measurements of cardiac dysfunction and with incident HF in the general population. METHODS: The study included 4,156 participants of the population-based Rotterdam Study (mean age: 71.4 years; 57.1% women), who had plasma Aß samples collected between 2002 and 2005 and had no established dementia and HF at baseline. Multivariable linear regression models were used to explore the cross-sectional association of plasma Aß with echocardiographic measures. Participants were followed up until December 2016. Cox proportional hazards models were used to assess the association of Aß levels with incident HF. Models were adjusted for cardiovascular risk factors. RESULTS: A per 1-SD increase in log-transformed plasma Aß40 was associated with a 0.39% (95% CI: -0.68 to -0.10) lower left ventricular ejection fraction and a 0.70 g/m2 (95% CI: 0.06-1.34) larger left ventricular mass indexed by body surface area. Aß42 was not significantly associated with echocardiographic measures cross-sectionally. During follow-up (median: 10.2 years), 472 incident HF cases were identified. A per 1-SD increase in log-transformed Aß40 was associated with a 32% greater risk of HF (HR: 1.32; 95% CI: 1.15-1.51), and the association was significant in men, but not in women. Higher plasma Aß42 levels were associated with an increased risk of HF (HR: 1.12; 95% CI: 1.02-1.24), although the association was attenuated after further adjustment for concomitant Aß40 (HR: 1.03; 95% CI: 0.92-1.16). CONCLUSIONS: Higher levels of Aß40 were associated with worse cardiac function and higher risk of new onset HF in the general population, in particular among men.

Herpud1 deficiency could reduce amyloid-ß40 expression and thereby suppress homocysteine-induced atherosclerosis by blocking the JNK/AP1 pathway.

Homocysteine (Hcy) is considered an independent risk factor for various cardiovascular diseases including atherosclerosis which is associated with lipid metabolism, inflammation, and oxidative stress. Results from our previous study suggested that Hcy-induced atherosclerosis could be reversed by Herpud1 knockout which inhibits vascular smooth muscle cell (VSMC) phenotype switching. Here, we aim to investigate more precise mechanisms behind the improvement in Hcy-induced atherosclerosis. Amyloid-ß40 (Aß40), a vital protein in Alzheimer disease (AD), has been regarded as an important component in the atherosclerosis program in recent years due to the biological similarity between AD and atherosclerosis. Thus, we determined to assess the value of Aß40 in a Herpud1 knockout Hcy-induced atherosclerosis mouse model by measuring Aß40 expression in tissue and biomarkers of lipid metabolism, inflammation, and oxidative stress in serum. Additionally, since endothelial dysfunction plays a prominent role in atherosclerosis, we tested human umbilical vein endothelial cell (HUVEC) function following Herpud1 silencing in vitro and evaluated JNK/AP1 signaling activation in our models because of its close relationship with Aß40. As a result, our animal models showed that Herpud1 knockout reduced Aß40 expression, inflammation, and oxidative stress levels other than lipid metabolism and alleviated atherosclerosis via JNK/AP1 signaling inhibition. Similarly, our cell experiments implied that Hcy-induced Aß40 elevation and HUVEC dysfunction involving cell proliferation and apoptosis could be restored by Herpud1 silence through restraining JNK/AP1 pathway. Collectively, our study demonstrates that Herpud1 deficiency could reduce Aß40 expression, thereby suppressing Hcy-induced atherosclerosis by blocking the JNK/AP1 pathway. This may provide novel potential targets for atherosclerosis prevention or treatment.

Erythrocyte Amyloid Beta Peptide Isoform Distributions in Alzheimer and Mild Cognitive Impairment.

INTRODUCTION: We recently showed that Amyloid Beta (Aß)40 accumulates in erythrocytes and possibly causes cell damage as evidenced by an increased number of assumed injured low-density (kg/L) erythrocytes. Furthermore, we have suggested a separation technique to isolate and concentrate such damaged red blood cells for subsequent analysis. OBJECTIVES: We isolated high- and low-density erythrocytes and investigated the accumulation patterns of the Aß peptides (Aß40, Aß42, and Aß43) in Alzheimer (AD), mild cognitive impairment (MCI), and Subjective Cognitive Impairment (SCI). METHODS: Whole blood was fractionated through a density gradient, resulting in two concentrated highand presumed injured low-density erythrocyte fractions. After cell lysis, intracellular Aß40, Aß42, and Aß43 were quantified by ELISA. RESULTS: In both high- and low-density erythrocytes, Aß40 displayed the lowest concentration in MCI, while it was equal and higher in AD and SCI. Aß40 was detected at a 10-fold higher level than Aß42, and in injured low-density erythrocytes, the lowest quantity of Aß42 was found in AD and MCI. Aß40 exhibited a 100-fold greater amount than Aß43, and lighter erythrocytes of MCI subjects displayed less intracellular Aß43 than SCI. CONCLUSION: Red blood cell accumulation patterns of Aß40, Aß42, and Aß43 differ significantly between AD, MCI, and SCI. The data must be verified through larger clinical trials. It is, however, tenable that Aß peptide distributions in erythrocyte subpopulations have the potential to be used for diagnostic purposes.

A Synthetic Pro-Drug Peptide Reverses Amyloid-ß-Induced Toxicity in the Rat Model of Alzheimer's Disease.

BACKGROUND: Alzheimer's disease (AD), the most prevalent neurodegenerative disorder, involves the formation of the extracellular amyloid-ß (Aß) plaques and intracellular neurofibrillary tangles. The current therapies against AD are symptomatic with limited benefits but associated with major side effects. Inhibition of self-aggregation of Aß peptides into higher order cross-ß structure is one of the potential therapeutic approach which may counter oligomerization of Aß peptide. OBJECTIVE: The present study aimed to evaluate the neuroprotective and anti-inflammatory potential of a synthetic Pro-Drug type peptide (PDp) against Aß-induced toxicity in rat model of AD. METHODS: Intra-hippocampal microinjection of toxic Aß40 (IHAß40) by stereotaxic surgery was performed in the male Sprague-Dawley rats to generate an Aß-induced AD model. Sub-chronic toxicity of synthetic PDp using hematological, biochemical, and histopathological parameters was investigated. Evaluation of PDp on Aß-induced neurodegeneration and neuroinflammation was performed. RESULTS: PDp inhibits plaque formation with increase in Nissl granule staining in the rat hippocampus. Aß-induced toxicity associated imbalance in reactive oxygen species and antioxidant enzymes activity such as superoxide dismutase and catalase in the rat brain was overcome by PDp treatment. Tau protein hyperphosphorylation was normalized with PDp treatment. Also, the neuroinflammatory response was suppressed with PDp treatment. CONCLUSION: The present study depicts the potential neuroprotective role of PDp against Aß-induced toxicity in rat. PDp inhibits plaque formation thereby normalizing oxidative stress, inhibiting tau protein hyperphosphorylation, and suppressing neuroinflammatory responses. Future studies done in this direction will pave way for new therapeutic strategies.