Effects of Exercise on EEG Activity and Standard Tools Used to Assess Concussion.

A variety of cognitive assessment tools are used to determine the functional status of the brain before and after injury in athletes. Questionnaires, neuropsychological tests, and electroencephalographic (EEG) measures have been recently used to directly assess brain function on and near the playing field. However, exercise can affect cognitive performance and EEG measures of cortical activity.

Methyl-substitution of an iminohydantoin spiropiperidine β-secretase (BACE-1) inhibitor has a profound effect on its potency.

The IC50 of a beta-secretase (BACE-1) lead compound was improved ∼200-fold from 11 μM to 55 nM through the addition of a single methyl group. Computational chemistry, small molecule NMR, and protein crystallography capabilities were used to compare the solution conformation of the ligand under varying pH conditions to its conformation when bound in the active site. Chemical modification then explored available binding pockets adjacent to the ligand.

Exploration of EEG features of Alzheimer's disease using continuous wavelet transform.

We have developed a novel approach to elucidate several discriminating EEG features of Alzheimer's disease. The approach is based on the use of a variety of continuous wavelet transforms, pairwise statistical tests with multiple comparison correction, and several decision tree algorithms, in order to choose the most prominent EEG features from a single sensor. A pilot study was conducted to record EEG signals from Alzheimer's disease (AD) patients and healthy age-matched control (CTL) subjects using a single dry electrode device during several eyes-closed (EC) and eyes-open (EO) resting conditions.

Identification of resting and active state EEG features of Alzheimer's disease using discrete wavelet transform.

Alzheimer's disease (AD) is associated with deficits in a number of cognitive processes and executive functions. Moreover, abnormalities in the electroencephalogram (EEG) power spectrum develop with the progression of AD. These features have been traditionally characterized with montage recordings and conventional spectral analysis during resting eyes-closed and resting eyes-open (EO) conditions.

Evaluation of plasma proteomic data for Alzheimer disease state classification and for the prediction of progression from mild cognitive impairment to Alzheimer disease.

Previous studies that have examined the potential for plasma markers to serve as biomarkers for Alzheimer disease (AD) have studied single analytes and focused on the amyloid-β and τ isoforms and have failed to yield conclusive results. In this study, we performed a multivariate analysis of 146 plasma analytes (the Human DiscoveryMAP v 1.0 from Rules-Based Medicine) in 527 subjects with AD, mild cognitive impairment (MCI), or cognitively normal elderly subjects from the Alzheimer's Disease Neuroimaging Initiative database.

Characterization of plasma β-secretase (BACE1) activity and soluble amyloid precursor proteins as potential biomarkers for Alzheimer's disease.

Reduction in cerebrospinal fluid (CSF) amyloid β42 (Aβ42) and elevation in total tau and phospho-thr181 tau consistently differentiate between Alzheimer's disease (AD) and age-matched control subjects. In contrast, CSF β-site APP-cleaving enzyme activity (BACE1) and soluble amyloid precursor proteins α and β (sAPPα and sAPPβ) are without consistent patterns in AD subjects. Plasma sampling is much easier, with fewer side effects, and is readily applied in primary care centers, so we have developed and validated novel plasma BACE activity, sAPPβ, and sAPPα assays and investigated their ability to distinguish AD from age-matched controls.

Reference measurement procedures for Alzheimer's disease cerebrospinal fluid biomarkers: definitions and approaches with focus on amyloid β42.

Cerebrospinal fluid (CSF) biomarkers for Alzheimer's disease (AD) are increasingly used in clinical settings, research and drug trials. However, their broad-scale use on different technology platforms is hampered by the lack of standardization at the level of sample handling, determination of concentrations of analytes and the absence of well-defined performance criteria for in vitro diagnostic or companion diagnostic assays, which influences the apparent concentration of the analytes measured and the subsequent interpretation of the data. There is a need for harmonization of CSF AD biomarker assays that can reliably, across centers, quantitate CSF biomarkers with high analytical precision, selectivity and stability over long time periods.

Plasma biomarkers associated with the apolipoprotein E genotype and Alzheimer disease.

Background: A blood-based test that could be used as a screen for Alzheimer disease (AD) may enable early intervention and better access to treatment.

Objective: To apply a multiplex immunoassay panel to identify plasma biomarkers of AD using plasma samples from the Alzheimer's Disease Neuroimaging Initiative cohort.

Design: Cohort study.

Cisterna magna cannulated repeated CSF sampling rat model--effects of a gamma-secretase inhibitor on Aβ levels.

Cerebrospinal fluid (CSF) provides a window into central nervous system (CNS) physiology and pathophysiology in human neurodegenerative conditions such as Alzheimer's disease. Changes in CSF bioanalytes also provide a direct readout of target engagement in the CNS following pharmacological interventions in clinical trials. Given the importance of tracking CNS bioanalytes in drug discovery, we have developed a novel cisterna magna cannulated rat model for repeated CSF sampling and used it to assess an amyloid beta (Aβ) lowering agent.

Pharmacological applications of a novel neoepitope antibody to a modified amyloid precursor protein-derived beta-secretase product.

We have previously described a novel artificial NFEV β-secretase (BACE1) cleavage site, which when introduced into the amyloid-β precursor protein (APP), significantly enhances APP cleavage by BACE1 in in vitro and cellular assays. In this study, we describe the identification and characterization of a single chain fragment of variable region (scFv), specific to the EV neo-epitope derived from BACE1 cleavage of the NFEV-containing peptide, and its conversion to IgG1. Both the scFv displayed on phage and EV-IgG1 show exquisite specificity for binding to the EV neoepitope without cross-reactivity to other NFEV containing peptides or WT-APP KMDA cleavage products.

Decrease in brain soluble amyloid precursor protein β (sAPPβ) in Alzheimer's disease cortex.

Amyloid-β peptide (Aβ) is generated by sequential cleavage of the amyloid precursor protein (APP) by β-site amyloid precursor protein cleaving enzyme 1 (β-secretase, or BACE1) and γ-secretase. Several reports demonstrate increased BACE1 enzymatic activity in brain and cerebrospinal fluid (CSF) from Alzheimer's disease (AD) subjects, suggesting that an increase in BACE1-mediated cleavage of APP drives amyloid pathophysiology in AD. BACE1 cleavage of APP leads to the generation of a secreted N-terminal fragment of APP (sAPPβ).

Qualification of the analytical and clinical performance of CSF biomarker analyses in ADNI.

The close correlation between abnormally low pre-mortem cerebrospinal fluid (CSF) concentrations of amyloid-β1-42 (Aβ(1-42)) and plaque burden measured by amyloid imaging as well as between pathologically increased levels of CSF tau and the extent of neurodegeneration measured by MRI has led to growing interest in using these biomarkers to predict the presence of AD plaque and tangle pathology. A challenge for the widespread use of these CSF biomarkers is the high variability in the assays used to measure these analytes which has been ascribed to multiple pre-analytical and analytical test performance factors. To address this challenge, we conducted a seven-center inter-laboratory standardization study for CSF total tau (t-tau), phospho-tau (p-tau(181)) and Aβ(1-42) as part of the Alzheimer's Disease Neuroimaging Initiative (ADNI).

Days to criterion as an indicator of toxicity associated with human Alzheimer amyloid-beta oligomers.

Objective: Recent evidence suggests that high molecular weight soluble oligomeric Abeta (oAbeta) assemblies (also known as Abeta-derived diffusible ligands, or ADDLs) may represent a primary neurotoxic basis for cognitive failure in Alzheimer disease (AD). To date, most in vivo studies of oAbeta/ADDLs have involved injection of assemblies purified from the cerebrospinal fluid of human subjects with AD or from the conditioned media of Abeta-secreting cells into experimental animals. We sought to study the bioactivities of endogenously formed oAbeta/ADDLs generated in situ from the physiological processing of human amyloid precursor protein (APP) and presenitin1 (PS1) transgenes.

Acute gamma-secretase inhibition of nonhuman primate CNS shifts amyloid precursor protein (APP) metabolism from amyloid-beta production to alternative APP fragments without amyloid-beta rebound.

The accumulation of amyloid beta (Abeta) in Alzheimer's disease is caused by an imbalance of production and clearance, which leads to increased soluble Abeta species and extracellular plaque formation in the brain. Multiple Abeta-lowering therapies are currently in development: an important goal is to characterize the molecular mechanisms of action and effects on physiological processing of Abeta, as well as other amyloid precursor protein (APP) metabolites, in models which approximate human Abeta physiology. To this end, we report the translation of the human in vivo stable-isotope-labeling kinetics (SILK) method to a rhesus monkey cisterna magna ported (CMP) nonhuman primate model, and use the model to test the mechanisms of action of a gamma-secretase inhibitor (GSI).

Modeling effect of a γ-secretase inhibitor on amyloid-β dynamics reveals significant role of an amyloid clearance mechanism.

Aggregation of the small peptide amyloid beta (Aβ) into oligomers and fibrils in the brain is believed to be a precursor to Alzheimer's disease. Aβ is produced via multiple proteolytic cleavages of amyloid precursor protein (APP), mediated by the enzymes β- and γ-secretase. In this study, we examine the temporal dynamics of soluble (unaggregated) Aβ in the plasma and cerebral-spinal fluid (CSF) of rhesus monkeys treated with different oral doses of a γ-secretase inhibitor.

SAR of tertiary carbinamine derived BACE1 inhibitors: role of aspartate ligand amine pKa in enzyme inhibition.

The optimization of tertiary carbinamine derived inhibitors of BACE1 from its discovery as an unstable lead to low nanomolar cell active compounds is described. Five-membered heterocycles are reported as stable and potency enhancing linkers. In the course of this work, we have discovered a clear trend where the activity of inhibitors at a given assay pH is dependent on pK(a) of the amino group that interacts directly with the catalytic aspartates.

Application of an end-to-end biomarker discovery platform to identify target engagement markers in cerebrospinal fluid by high resolution differential mass spectrometry.

The rapid identification of protein biomarkers in biofluids is important to drug discovery and development. Here, we describe a general proteomic approach for the discovery and identification of proteins that exhibit a statistically significant difference in abundance in cerebrospinal fluid (CSF) before and after pharmacological intervention. This approach, differential mass spectrometry (dMS), is based on the analysis of full scan mass spectrometry data.

A novel pathway for amyloid precursor protein processing.

Amyloid precursor protein (APP) can be proteolytically processed along two pathways, the amyloidogenic that leads to the formation of the 40-42 amino acid long Alzheimer-associated amyloid β (Aβ) peptide and the non-amyloidogenic in which APP is cut in the middle of the Aβ domain thus precluding Aβ formation. Using immunoprecipitation and mass spectrometry we have shown that Aβ is present in cerebrospinal fluid (CSF) as several shorter isoforms in addition to Aβ1-40 and Aβ1-42. To address the question by which processing pathways these shorter isoforms arise, we have developed a cell model that accurately reflects the Aβ isoform pattern in CSF.

First demonstration of cerebrospinal fluid and plasma A beta lowering with oral administration of a beta-site amyloid precursor protein-cleaving enzyme 1 inhibitor in nonhuman primates.

beta-Site amyloid precursor protein (APP)-cleaving enzyme (BACE) 1 cleavage of amyloid precursor protein is an essential step in the generation of the potentially neurotoxic and amyloidogenic A beta 42 peptides in Alzheimer's disease. Although previous mouse studies have shown brain A beta lowering after BACE1 inhibition, extension of such studies to nonhuman primates or man was precluded by poor potency, brain penetration, and pharmacokinetics of available inhibitors. In this study, a novel tertiary carbinamine BACE1 inhibitor, tertiary carbinamine (TC)-1, was assessed in a unique cisterna magna ported rhesus monkey model, where the temporal dynamics of A beta in cerebrospinal fluid (CSF) and plasma could be evaluated.

Discovery and X-ray crystallographic analysis of a spiropiperidine iminohydantoin inhibitor of beta-secretase.

A high-throughput screen at 100 microM inhibitor concentration for the BACE-1 enzyme revealed a novel spiropiperidine iminohydantoin aspartyl protease inhibitor template. An X-ray cocrystal structure with BACE-1 revealed a novel mode of binding whereby the inhibitor interacts with the catalytic aspartates via bridging water molecules. Using the crystal structure as a guide, potent compounds with good brain penetration were designed.

Elevated cerebrospinal fluid BACE1 activity in incipient Alzheimer disease.

Background: We used a sensitive and specific beta-site amyloid precursor protein (APP)-cleaving enzyme 1 (BACE1) assay to determine the relationship between BACE1 activity in cerebrospinal fluid (CSF) and markers of APP metabolism and axonal degeneration in early and late stages of Alzheimer disease (AD).

Objective: To assess CSF BACE1 activity in AD.

Design: Case-control and longitudinal follow-up study.

Decrease in age-adjusted cerebrospinal fluid beta-secretase activity in Alzheimer's subjects.

Objectives: To develop a novel cerebrospinal fluid (CSF) beta-secretase-1 activity assay and evaluate beta-secretase-1 (BACE-1) activity as a potential biomarker in human Alzheimer's disease.

Methods: The assay consisted of an enzymatic reaction of CSF samples with an optimized beta-secretase peptide substrate and the cleavage products were detected using a neo-epitope specific antibody.

Results: The CSF BACE-1 activity assay described exhibits time, temperature, dose, and pH dependence, with sensitivity down to <1 pM of recombinant BACE-1 enzyme, and is completely blocked by BACE-1 inhibitors.

Enhanced in vivo transgene expression and immunogenicity from plasmid vectors following electrostimulation in rodents and primates.

Safe and efficient methods for in vivo delivery of transgenes of interest must be developed so that the promise of these therapies can be practically used in the clinic. In this work, we describe the use of electrostimulation to enhance the in vivo efficiency of plasmid DNA delivery. The method was optimized to work over a range of moderate frequencies, utilizing low field strengths and simple symmetrical waveforms.

In vivo beta-secretase 1 inhibition leads to brain Abeta lowering and increased alpha-secretase processing of amyloid precursor protein without effect on neuregulin-1.

beta-Secretase (BACE) cleavage of amyloid precursor protein (APP) is one of the first steps in the production of amyloid beta peptide Abeta42, the putative neurotoxic species in Alzheimer's disease. Recent studies have shown that BACE1 knockdown leads to hypomyelination, putatively caused by a decline in neuregulin (NRG)-1 processing. In this study, we have tested a potent cell-permeable BACE1 inhibitor (IC(50) approximately 30 nM) by administering it directly into the lateral ventricles of mice, expressing human wild-type (WT)-APP, to determine the consequences of BACE1 inhibition on brain APP and NRG-1 processing.