Molecularly imprinted sensor based on poly-o-phenylenediamine-hydroquinone polymer for ß-amyloid-42 detection.

A sensitive and selective molecularly imprinted polymer (MIP) sensor was developed for the determination of amyloid-ß (1-42) (Aß42). The glassy carbon electrode (GCE) was successively modified with electrochemical reduction graphene oxide (ERG) and poly(thionine-methylene blue) (PTH-MB). The MIPs were synthesized by electropolymerization with Aß42 as a template and o-phenylenediamine (o-PD) and hydroquinone (HQ) as functional monomers. Cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), chronoamperometry (CC), and differential pulse voltammetry (DPV) were used to study the preparation process of the MIP sensor. The preparation conditions of the sensor were investigated in detail. In optimal experimental conditions, the response current of the sensor was linear in the range of 0.12-10 µg mL-1 with a detection limit of 0.018 ng mL-1. The MIP-based sensor successfully detected Aß42 in commercial fetal bovine serum (cFBS) and artificial cerebrospinal fluid (aCSF).

Remarked suppression of Aß42 protomer-protomer dissociation reaction elucidated by molecular dynamics simulation.

Multimeric protein complexes are molecular apparatuses to regulate biological systems and often determine their fate. Among proteins forming such molecular assemblies, amyloid proteins have drawn attention over a half-century since amyloid fibril formation of these proteins is supposed to be a common pathogenic cause for neurodegenerative diseases. This process is triggered by the accumulation of fibril-like aggregates, while the microscopic mechanisms are mostly elusive due to technical limitation of experimental methodologies in individually observing each of diverse aggregate species in the aqueous solution. We then addressed this problem by employing atomistic molecular dynamics simulations for the paradigmatic amyloid protein, amyloid-ß (Aß42 ). Seven different dimeric forms of oligomeric Aß42 fibril-like aggregate in aqueous solution, ranging from tetramer to decamer, were considered. We found additive effects of the size of these fibril-like aggregates on their thermodynamic stability and have clarified kinetic suppression of protomer-protomer dissociation reactions at and beyond the point of pentamer dimer formation. This observation was obtained from the specific combination of the Aß42 protomer structure and the physicochemical condition that we here examined, while it is worthwhile to recall that several amyloid fibrils take dimeric forms of their protomers. We could thus conclude that the stable formation of fibril-like protomer dimer should be involved in a turning point where rapid growth of amyloid fibrils is triggered.

Role of amber extract in protecting SHSY5Y cells against amyloid ß1-42-induced neurotoxicity.

Alzheimer disease (AD) is an irreversible, progressive brain disease. Amyloid ß plays a critical role in AD development. Some Chinese traditional medicines, such as the fossilized plant resin, amber, have been applied as mental stabilizers. However, the effects of amber on AD pathogenesis remain unknown. Therefore, we aimed to determine the potential of amber extract for treating AD by evaluating its effects on amyloid-ß (1-42) (Aß (1-42))-induced neuronal cell death. We measured levels of ROS, Bcl-2, and Bax mRNA, and found that amber extract decreased Aß (1-42)-induced cell apoptosis via the reactive oxygen species (ROS)-mediated mitochondrial pathway. Amber extract also decreased ß-site amyloid precursor protein cleaving enzyme 1 (BACE1) and increased microtubule-associated proteins 1A/1B light chain 3B (LC3II) and Beclin 1. These findings suggested that amber extract protects neuronal cells against Aß (1-42)-induced cell apoptosis by upregulating autophagy and downregulating BACE1.

Protective Effect of Dalbergia sissoo Extract Against Amyloid-ß (1-42)-induced Memory Impairment, Oxidative Stress, and Neuroinflammation in Rats.

OBJECTIVES: The ayurvedic literature reports that Dalbergia sissoo, a common medicinal plant for gastric and skin problems, has brain-revitalizing effects. However, the neuroprotective effect of this herb on an amyloid-ß (Aß) 1-42 model of Alzheimer's disease (AD) is yet unknown. The current study describes the protective effect of ethanolic extracts of D. sissoo leaves (EEDS) against Aß (1-42)-induced cognitive deficit, oxidative stress, and neuroinflammation in rats. MATERIALS AND METHODS: EEDS (300 and 500 mg/kg) was orally administered to rats for 2 weeks prior to intracerebroventricular Aß (1-42) treatment. The neuroprotective effect of EEDS was assessed by evaluating behavioral, biochemical, and neuroinflammatory parameters in the rat hippocampus. Memory function was assessed via the Morris water maze (MWM) task 2 weeks after Aß (1-42) administration. After 3 weeks, surgery was performed, all biochemical parameters were evaluated, and histopathological examination of the tissues was carried out. RESULTS: EEDS improved the cognitive ability of Aß (1-42)-administered rats in the MWM task. It reduced oxidative stress by significantly decreasing nitrite and malondialdehyde levels and increasing catalase activity and glutathione levels in the rat brain. Moreover, EEDS mitigated neuroinflammation in rats by decreasing the concentration of neuroinflammatory markers in a dose-dependent manner. CONCLUSION: D. sissoo leaf extract has a beneficial role in alleviating cognitive deficits in AD by modulating cholinergic function, oxidative stress, and neuroinflammation.

A Sensitive and Cost-Effective Chemiluminescence ELISA for Measurement of Amyloid-ß 1-42 Peptide in Human Plasma.

BACKGROUND: Amyloid-ß42 (Aß42) is associated with plaque formation in the brain of patients with Alzheimer's disease (AD). Studies have suggested the potential utility of plasma Aß42 levels in the diagnosis, and in longitudinal study of AD pathology. Conventional ELISAs are used to measure Aß42 levels in plasma but are not sensitive enough to quantitate low levels. Although ultrasensitive assays like single molecule array or immunoprecipitation-mass spectrometry have been developed to quantitate plasma Aß42 levels, the high cost of instruments and reagents limit their use. OBJECTIVE: We hypothesized that a sensitive and cost-effective chemiluminescence (CL) immunoassay could be developed to detect low Aß42 levels in human plasma. METHODS: We developed a sandwich ELISA using high affinity rabbit monoclonal antibody specific to Aß42. The sensitivity of the assay was increased using CL substrate to quantitate low levels of Aß42 in plasma. We examined the levels in plasma from 13 AD, 25 Down syndrome (DS), and 50 elderly controls. RESULTS: The measurement range of the assay was 0.25 to 500 pg/ml. The limit of detection was 1 pg/ml. All AD, DS, and 45 of 50 control plasma showed measurable Aß42 levels. CONCLUSION: This assay detects low levels of Aß42 in plasma and does not need any expensive equipment or reagents. It offers a preferred alternative to ultrasensitive assays. Since the antibodies, peptide, and substrate are commercially available, the assay is well suited for academic or diagnostic laboratories, and has a potential for the diagnosis of AD or in clinical trials.

A Probeless Capacitive Biosensor for Direct Detection of Amyloid Beta 1-42 in Human Serum Based on an Interdigitated Chain-Shaped Electrode.

Amyloid beta (aß) 1-42, a peptide that is 1-42 amino acids long, is a major component of senile plaques in the brains of patients with Alzheimer's disease. Aß detection has become an essential antecedence to predict the declining mental abilities of patients. In this paper, a probeless capacitive biosensor for the non-Faradaic detection of aß 1-42 peptide was developed by immobilizing a specific anti-aß antibody onto a self-assembled monolayer functionalized interdigitated chain-shaped electrode (anti-aß/SAM/ICE). The novelty and difference of this article from previous studies is the direct detection of aß peptide with no redox probe ((Fe(CN)6)3-/4-), which can avoid the denaturation of the protein caused by the metallization (binding of aß to metal ion Fe which is presented in the redox couple). The direct detection of aß with no redox probe is performed by non-Faradaic capacitive measurement, which is greatly different from the Faradaic measurement of the charge transfer resistance of the redox probe. The detection of various aß 1-42 peptide concentrations in human serum (HS) was performed by measuring the relative change in electrode interfacial capacitance due to the specific antibody-aß binding. Capacitance change in the anti-aß/SAM/ICE biosensor showed a linear detection range between 10 pg mL-1 and 104 pg mL-1, and a detection limit of 7.5 pg mL-1 in HS, which was much lower than the limit of detection for CSF aß 1-42 (~500 pg mL-1) and other biosensors. The small dissociation constant Kd of the antibody-antigen interaction was also found to be 0.016 nM in HS, indicating the high binding affinity of the anti-aß/SAM/ICE biosensor in the recognizing of aß 1-42. Thus, the developed sensor can be used for label-free and direct measurement of aß 1-42 peptide and for point-of-care diagnosis of Alzheimer's disease without redox probe.

Effects of Astaxanthin from Shrimp Shell on Oxidative Stress and Behavior in Animal Model of Alzheimer's Disease.

This study aimed to investigate the effect of astaxanthin (ASX) extracted and ASX powder from shrimp (Litopenaeus vannamei) shells on Wistar rats with Alzheimer's disease, induced by amyloid-ß (1-42) peptides. In this task, the rats were divided into eight groups: (1) Control, (2) sham operate, (3) negative control (vehicle) + Aß1-42, (4) ASX extract+Aß1-42, (5) commercial ASX + Aß1-42, (6) ASX powder + Aß1-42, (7) blank powder + Aß1-42, and (8) vitamin E + Aß1-42. All treatments were orally administrated for 30 days. At 14- and 29-days post injection, animals were observed in behavioral tests. On the 31st day, animals were sacrificed; the hippocampus and cortex were collected. Those two brain areas were then homogenized and stored for biochemical and histological analysis. The results showed that the Aß1-42 infused group significantly reduced cognitive ability and increased memory loss, as assessed by the Morris water maze test, novel object recognition test, and novel object location test. Moreover, the Aß1-42 infused group exhibited a deterioration of oxidative markers, including glutathione peroxidase enzymes (GPx), lipid peroxidation (MDA), products of protein oxidation, and superoxide anion in the cortex and the hippocampus. Meanwhile, ASX powder (10 mg/kg body weight) showed a significant reduction in cognitive and memory impairments and oxidative stress which is greater than ASX extract in the same dose of compound or vitamin E (100 mg/kg body weight). Our study indicates the beneficial properties of ASX in alleviation of cognitive functions and reducing neurodegeneration in Wistar rats induced by amyloid-ß (1-42) peptides.

Sensitive electrochemical detection of amyloid beta peptide in human serum using an interdigitated chain-shaped electrode.

In this study, we developed a small size, low cost, highly sensitive electrochemical biosensor with a low limit of detection by immobilizing specific anti-amyloid-ß (aß) antibody onto a self-assembled monolayer functionalized interdigitated chain-shaped electrode (anti-aß/EDC-NHS/SAM/ICE). The anti-aß/EDC-NHS/SAM/ICE specifically detects aß 1-42 peptide (a peptide 1-42 amino acids long), which is one of main biomarkers of Alzheimer's disease in human serum (HS). Electrochemical impedance spectroscopy (EIS) was used to characterize the impedance change of the anti-aß/EDC-NHS/SAM/ICE biosensor for aß 1-42 detection, which provided a wide linear range of detection from 10-3-103 ng mL-1, and a low limit of detection of aß in HS (100 pg mL-1) much lower than the limit of detection of CSF aß 1-42 (∼500 pg mL-1), and other biosensors. Therefore, the developed biosensor is sensitive enough to be used for the diagnosis of early stage Alzheimer's disease.

Change of Amyloid-ß 1-42 Toxic Conformer Ratio After Cerebrospinal Fluid Diversion Predicts Long-Term Cognitive Outcome in Patients with Idiopathic Normal Pressure Hydrocephalus.

BACKGROUND: Alzheimer's disease (AD) pathology in idiopathic normal pressure hydrocephalus (iNPH) contributes to poor shunt responses. Amyloid-ß 1- 42 (Aß42) toxic conformer was recently identified with features of rapid oligomerization, strong neurotoxicity and synaptotoxicity. OBJECTIVE: This observational study points to Aß42 toxic conformer as a biomarker for AD pathology and for poor postoperative prognosis in patients with iNPH. METHODS: The first cohort consisted of patients with AD (n = 17) and iNPH (n = 17), and cognitively normal individuals (CN, n = 12). The second cohort, consisted of 51 patients with iNPH, was divided into two groups according to phosphorylated Tau (pTau) level (low- and high-pTau groups); the low-pTau group was further subdivided according to one-year postoperative change in Aß42 toxic conformer ratio (%) [Aß42 toxic conformer/Aß42×100] (decreased- and increased-conformer subgroups). Enzyme-linked immunosorbent assay was used to measure pTau, Aß42, and Aß42 toxic conformer in cerebrospinal fluid. Outcomes were evaluated using neuropsychological tests one- and two-years postoperatively. RESULTS: In the first cohort, Aß42 toxic conformer ratio in the iNPH group (10.8%) was significantly higher than that in the CN group (6.3%) and significantly lower than that in the AD group (17.2%). In the second cohort, the high-pTau group showed cognitive decline two-years postoperatively compared to baseline. However, the low-pTau group showed favorable outcomes one-year postoperatively; furthermore, the increased-conformer subgroup showed cognitive decline two-years postoperatively while the decreased-conformer subgroup maintained the improvement. CONCLUSIONS: Change in Aß42 toxic conformer ratio predicts long-term cognitive outcome in iNPH, even in the low-pTau group.

CSF biomarkers of Alzheimer's disease concord with amyloid-ß PET and predict clinical progression: A study of fully automated immunoassays in BioFINDER and ADNI cohorts.

INTRODUCTION: We studied whether fully automated Elecsys cerebrospinal fluid (CSF) immunoassay results were concordant with positron emission tomography (PET) and predicted clinical progression, even with cutoffs established in an independent cohort. METHODS: Cutoffs for Elecsys amyloid-ß1-42 (Aß), total tau/Aß(1-42), and phosphorylated tau/Aß(1-42) were defined against [18F]flutemetamol PET in Swedish BioFINDER (n = 277) and validated against [18F]florbetapir PET in Alzheimer's Disease Neuroimaging Initiative (n = 646). Clinical progression in patients with mild cognitive impairment (n = 619) was studied. RESULTS: CSF total tau/Aß(1-42) and phosphorylated tau/Aß(1-42) ratios were highly concordant with PET classification in BioFINDER (overall percent agreement: 90%; area under the curve: 94%). The CSF biomarker statuses established by predefined cutoffs were highly concordant with PET classification in Alzheimer's Disease Neuroimaging Initiative (overall percent agreement: 89%-90%; area under the curves: 96%) and predicted greater 2-year clinical decline in patients with mild cognitive impairment. Strikingly, tau/Aß ratios were as accurate as semiquantitative PET image assessment in predicting visual read-based outcomes. DISCUSSION: Elecsys CSF biomarker assays may provide reliable alternatives to PET in Alzheimer's disease diagnosis.

Relation of Odor Identification with Alzheimer's Disease Markers in Cerebrospinal Fluid and Cognition.

BACKGROUND: Impaired olfactory function is an early characteristic of Alzheimer's disease (AD), but it remains unclear if odor identification also relates to early markers of AD in cerebrospinal fluid (CSF). OBJECTIVE: To investigate the association between odor identification and amyloid-ß 1-42 (Aß42) and total tau (t-tau) concentrations in CSF. In addition, to examine the relation between odor identification and cognitive function at baseline and at follow-up, and whether these associations are moderated by CSF Aß42 and t-tau and apolipoprotein E (APOE) genotype. METHODS: We included 160 individuals (40 with normal cognition, 45 with mild cognitive impairment (MCI), 42 with AD-type dementia, and 26 individuals with non-AD dementia) from the EDAR study. Individuals were recruited from six memory clinics across Europe. Odor identification was tested with the brief University of Pennsylvania Smell Identification Test. CSF Aß42 and t-tau were assessed with INNO-BIA AlzBio3 Luminex assay. Neuropsychological assessment included tests for verbal memory, verbal fluency, attention, executive function, and visuoconstruction. Follow-up was performed within 3 years after baseline. RESULTS: Lower odor identification scores correlated with increased CSF t-tau concentrations and with lower scores on all cognitive measures at baseline independent of diagnostic group. Lower odor identification scores predicted decline on the MMSE in the total group, and decline on wordlist learning and delayed recall in APOE ɛ4 carriers and in individuals with abnormal Aß42. CONCLUSION: Odor identification impairment may be an indicator of neuronal injury rather than amyloid pathology.

Association Between Later Life Lifestyle Factors and Alzheimer's Disease Biomarkers in Non-Demented Individuals: A Longitudinal Descriptive Cohort Study.

BACKGROUND: Lifestyle factors have been associated with the risk of dementia, but the association with Alzheimer's disease (AD) remains unclear. OBJECTIVE: To examine the association between later life lifestyle factors and AD biomarkers (i.e., amyloid-ß 1-42 (Aß42) and tau in cerebrospinal fluid (CSF), and hippocampal volume) in individuals with subjective cognitive decline (SCD) and mild cognitive impairment (MCI). In addition, to examine the effect of later life lifestyle factors on developing AD-type dementia in individuals with MCI. METHODS: We selected individuals with SCD (n = 111) and MCI (n = 353) from the DESCRIPA and Kuopio Longitudinal MCI studies. CSF Aß42 and tau concentrations were assessed with ELISA assay and hippocampal volume with multi-atlas segmentation. Lifestyle was assessed by clinical interview at baseline for: social activity, physical activity, cognitive activity, smoking, alcohol consumption, and sleep. We performed logistic and Cox regression analyses adjusted for study site, age, gender, education, and diagnosis. Prediction for AD-type dementia was performed in individuals with MCI only. RESULTS: Later life lifestyle factors were not associated with AD biomarkers or with conversion to AD-type dementia. AD biomarkers were strongly associated with conversion to AD-type dementia, but these relations were not modulated by lifestyle factors. Apolipoprotein E (APOE) genotype did not influence the results. CONCLUSIONS: Later life lifestyle factors had no impact on key AD biomarkers in individuals with SCD and MCI or on conversion to AD-type dementia in MCI.

Repetitive pupil light reflex: potential marker in Alzheimer's disease?

It was investigated whether alterations of the pupil's light reflex might reflect Alzheimer's disease (AD) pathology. Changes in the pupil's system might be expected due to AD pathology present in the oculomotor system of the Edinger-Westphal nucleus, and a cholinergic deficit caused by degeneration of the nucleus basalis Meynert. A rather new method of repetitive light stimulation was applied assessing variations in pupil size, latency, and amplitude over time. We analyzed 44 healthy controls, 42 subjects with mild cognitive impairment (MCI), and 66 AD patients. AD and MCI showed a less pronounced pupil size decrease and amplitude increase over time than controls. A higher MMSE was associated with a higher increase of relative amplitude and greater decrease of latency in AD and MCI, and absolute amplitude increase in AD alone. Pupil size increase correlated with cerebrospinal fluid markers in AD. Summarized pupil light reflex is not stable under repetitive stimulation, but changes systematically and less pronounced in AD and MCI. Thus repetitive stimulation of the pupil's response potentially indicates AD pathology.