A proposed key event in the pathogenesis of Alzheimer’s disease (AD) is the formation of neurotoxic amyloid β (Aβ) oligomers and amyloid plaques in specific brain regions that are affected by the disease. The main plaque component is the 42 amino acid isoform of Aβ (Aβ1-42), which is thought to initiate plaque formation and AD pathogenesis. Numerous isoforms of Aβ, e.g., Aβ1-42, Aβ1-40 and the 3-pyroglutamate derivate of Aβ3-42 (pGluAβ3-42), have been detected in the brains of sporadic AD (SAD) and familial AD (FAD) subjects. However, the relative importance of these isoforms in the pathogenesis of AD is not fully understood. Here, we report a detailed study using immunoprecipitation in combination with mass spectrometric analysis to determine the Aβ isoform pattern in the cerebellum, cortex and hippocampus in AD, including subjects with a mutation in the presenilin (M146V) or amyloid precursor protein (KM670/671NL) genes, SAD subjects and non-demented controls. We show that the dominating Aβ isoforms in the three different brain regions analyzed from control, SAD, and FAD are Aβ1-42, pGluAβ3-42, Aβ4-42 and Aβ1-40 of which Aβ1-42 and Aβ4-42 are the dominant isoforms in the hippocampus and the cortex in all groups analyzed, controls included. No prominent differences in Aβ isoform patterns between FAD and SAD patients were seen, underscoring the similarity in the amyloid pathology of these two disease entities.

Background: Pyroglutamate A␤ is an abundant, toxic peptide in Alzheimer disease brain. Results: Pyroglutamate A␤ aggravates the pre-existing behavioral phenotype of 5XFAD mice. Conclusion: These results support a major pathological function of pyroglutamate A␤ in Alzheimer disease. Significance: The data further indicate that pyroglutamate A␤ is an important therapeutic target.

BackgroundAlzheimer's disease (AD) is associated with deposition of amyloid β (Aβ) in the brain, which is reflected by low concentration of the Aβ1-42 peptide in the cerebrospinal fluid (CSF). There are at least 15 additional Aβ peptides in human CSF and their relative abundance pattern is thought to reflect the production and degradation of Aβ. Here, we test the hypothesis that AD is characterized by a specific CSF Aβ isoform pattern that is distinct when comparing sporadic AD (SAD) and familial AD (FAD) due to different mechanisms underlying brain amyloid pathology in the two disease groups.ResultsWe measured Aβ isoform concentrations in CSF from 18 patients with SAD, 7 carriers of the FAD-associated presenilin 1 (PSEN1) A431E mutation, 17 healthy controls and 6 patients with depression using immunoprecipitation-mass spectrometry. Low CSF levels of Aβ1-42 and high levels of Aβ1-16 distinguished SAD patients and FAD mutation carriers from healthy controls and depressed patients. SAD and FAD were characterized by similar changes in Aβ1-42 and Aβ1-16, but FAD mutation carriers exhibited very low levels of Aβ1-37, Aβ1-38 and Aβ1-39.ConclusionSAD patients and PSEN1 A431E mutation carriers are characterized by aberrant CSF Aβ isoform patterns that hold clinically relevant diagnostic information. PSEN1 A431E mutation carriers exhibit low levels of Aβ1-37, Aβ1-38 and Aβ1-39; fragments that are normally produced by γ-secretase, suggesting that the PSEN1 A431E mutation modulates γ-secretase cleavage site preference in a disease-promoting manner.

BACE1 is a key enzyme for amyloid-β (Aβ) production, and an attractive therapeutic target in Alzheimer's disease (AD). Here we report that BACE1 inhibitors have distinct effects on neuronal Aβ metabolism, inducing a unique pattern of secreted Aβ peptides, analyzed in cell media from amyloid precursor protein (APP) transfected cells and in cerebrospinal fluid (CSF) from dogs by immunoprecipitation-mass spectrometry, using several different BACE1 inhibitors. Besides the expected reductions in Aβ1-40 and Aβ1-42, treatment also changed the relative levels of several other Aβ isoforms. In particular Aβ1-34 decreased, while Aβ5-40 increased, and these changes were more sensitive to BACE1 inhibition than the changes in Aβ1-40 and Aβ1-42. The effects on Aβ5-40 indicate the presence of a BACE1 independent pathway of APP degradation. The described CSF Aβ pattern may be used as a pharmacodynamic fingerprint to detect biochemical effects of BACE1-therapies in clinical trials, which might accelerate development of novel therapies.

Amyloid precursor protein (APP) is the precursor protein to amyloid β (Aβ), the main constituent of senile plaques in Alzheimer's disease (AD). Endogenous Aβ peptides reflect the APP processing, and greater knowledge of different APP degradation pathways is important to understand the mechanism underlying AD pathology. When one analyzes longer Aβ peptides by low-energy collision-induced dissociation tandem mass spectrometry (MS/MS), mainly long b-fragments are observed, limiting the possibility to determine variations such as amino acid variants or post-translational modifications (PTMs) within the N-terminal half of the peptide. However, by using electron capture dissociation (ECD), we obtained a more comprehensive sequence coverage for several APP/Aβ peptide species, thus enabling a deeper characterization of possible variants and PTMs. Abnormal APP/Aβ processing has also been described in the lysosomal storage disease Niemann-Pick type C and the major large animal used for studying this disease is cat. By ECD MS/MS, a substitution of Asp7 → Glu in cat Aβ was identified. Further, sialylated core 1 like O-glycans at Tyr10, recently discovered in human Aβ (a previously unknown glycosylation type), were identified also in cat cerebrospinal fluid (CSF). It is therefore likely that this unusual type of glycosylation is common for (at least) species belonging to the magnorder Boreoeutheria. We here describe a detailed characterization of endogenous APP/Aβ peptide species in CSF by using an online top-down MS-based method.

People with stroke had a strong drive to integrate ICT in order to manage and bring meaning to their everyday lives, although sometimes they needed support and adaptations. It is not only possible but also necessary to start using ICT in rehabilitation in order to support people's recovery and promote participation in everyday life after stroke. Implications for rehabilitation People with stroke have a strong drive for using information and communication technology in their everyday lives, although support and adaptations are needed. The recovery process of people with stroke could benefit from the use of ICT in the rehabilitation and ICT could possibly contribute to independence and promote participation in everyday life. Knowledge from this study can be used in the development of an ICT-based stroke rehabilitation model.

Transformation of chloride (Cl(-)) to organic chlorine (Cl(org)) occurs naturally in soil but it is poorly understood how and why transformation rates vary among environments. There are still few measurements of chlorination rates in soils, even though formation of Cl(org) has been known for two decades. In the present study, we compare organic matter (OM) chlorination rates, measured by (36)Cl tracer experiments, in soils from eleven different locations (coniferous forest soils, pasture soils and agricultural soils) and discuss how various environmental factors effect chlorination. Chlorination rates were highest in the forest soils and strong correlations were seen with environmental variables such as soil OM content and Cl(-) concentration. Data presented support the hypothesis that OM levels give the framework for the soil chlorine cycling and that chlorination in more organic soils over time leads to a larger Cl(org) pool and in turn to a high internal supply of Cl(-) upon dechlorination. This provides unexpected indications that pore water Cl(-) levels may be controlled by supply from dechlorination processes and can explain why soil Cl(-) locally can be more closely related to soil OM content and the amount organically bound chlorine than to Cl(-) deposition.

IntroductionLY450139 (semagacestat) inhibits γ-secretase, a key enzyme for generation of amyloid β (Aβ), the peptide deposited in plaques in Alzheimer disease (AD). Previous data have shown that LY450139 lowers plasma Aβ, but has no clear effect on Aβ1-40 or Aβ1-42 levels in cerebrospinal fluid (CSF). By using targeted proteomics techniques, we recently identified several shorter Aβ isoforms, such as Aβ1-16, that in experimental settings increase during γ-secretase inhibitor treatment, and thus may serve as sensitive biochemical indices of the treatment effect. Here, we test the hypothesis that these shorter Aβ isoforms may be biomarkers of γ-secretase inhibitor treatment in clinical trials.MethodsIn a phase II clinical trial, 35 individuals with mild to moderate AD were randomized to placebo (n = 10) or LY450139 (100 mg (n = 15) or 140 mg (n = 10)) and underwent lumbar puncture at baseline and after 14 weeks of treatment. The CSF Aβ isoform pattern was analyzed with immunoprecipitation combined with MALDI-TOF mass spectrometry.ResultsThe CSF levels of Aβ1-14, Aβ1-15, and Aβ1-16 showed a dose-dependent increase by 57% and 74%, 21% and 35%, and 30% and 67%, respectively in the 100-mg and 140-mg treatment groups. Aβ1-40 and Aβ1-42 were unaffected by treatment.ConclusionsCSF Aβ1-14, Aβ1-15, and Aβ1-16 increase during γ-secretase inhibitor treatment in AD, even at doses that do not affect Aβ1-42 or Aβ1-40, probably because of increased substrate availability of the C99 APP stub (APP β-CTF) induced by γ-secretase inhibition. These Aβ isoforms may be novel sensitive biomarkers to monitor the biochemical effect in clinical trials.Trial registrationClinical Trials.gov NCT00244322