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Using a single integrated analysis, we examined the relationship between brain networks and molecular pathways in a cohort of elderly individuals at risk for Alzheimer's disease. In 205 subjective memory complainers (124 females, mean age: 75.7 ± 3.4), individual functional connectome was computed for a total of 3081 functional connections (set A) and 6 core plasma biomarkers of Alzheimer's disease (set B) were assessed. Partial least squares correlation analysis identified one dimension of population covariation between the 2 sets (p < 0.006), which we named bioneural mode. Five core plasma biomarkers and 190 functional connections presented bootstrap ratios greater than the critical value |1.96|. T-tau protein showed a trend toward significance (bootstrap resampling = 1.64). The salience, the language, the visuospatial, and the default mode networks were the strongest significant networks. We detected a strong association between network dynamics and core pathophysiological blood biomarkers. Innovative composite biomarkers, such as the bioneural mode, are promising to provide outcomes and better inform drug development and clinical practice for neurodegenerative diseases., (Copyright © 2019. Published by Elsevier Inc.)

Frontotemporal lobar degeneration (FTLD) is one of the leading causes of dementia after Alzheimer's disease. A high-ranking candidate to become a diagnostic marker for a major pathological subtype of FTLD is the transactive response DNA binding protein of 43 kDa (TDP-43). The main objective is to elucidate which antibodies are specific for pathological TDP-43, with special interest in its modified isoforms. Indeed, TDP-43 has been shown to be hyperphosphorylated and truncated in disease. A secondary objective is to review existing immunoassays that quantify TDP-43 in biofluids. A systematic review of literature was performed by searching PubMed and Web of Science using predefined keywords. Of considered research papers the methods section was reviewed to select publications that enabled us to answer our learning objective. After quality assessment, antibody characteristics and related outcomes were extracted. We identified a series of well-characterized antibodies based on a scoring system that assessed the ability of each antibody to detect TDP-43 pathology. A selection of 29 unique antibodies was made comprising 10 high-ranking antibodies which were reported multiple times to detect TDP-43 pathology in both immunostaining and immunoblotting experiments and 19 additional antibodies which detected TDP-43 pathology but were only scored once. This systematic review provides an overview of antibodies that are reported to detect pathological TDP-43. These antibodies can be used in future studies of TDP-43 proteinopathies. Additionally, selected antibodies hold the potential to be used in the development of novel immunoassays for the quantification of TDP-43 in biofluids, as a possible biomarker for FTLD-TDP.

A link between Tau phosphorylation and aggregation has been shown in different models for Alzheimer disease, including yeast. We used human Tau purified from yeast models to generate new monoclonal antibodies, of which three were further characterized. The first antibody, ADx201, binds the Tau proline-rich region independently of the phosphorylation status, whereas the second, ADx215, detects an epitope formed by the Tau N terminus when Tau is not phosphorylated at Tyr(18). For the third antibody, ADx210, the binding site could not be determined because its epitope is probably conformational. All three antibodies stained tangle-like structures in different brain sections of THY-Tau22 transgenic mice and Alzheimer patients, and ADx201 and ADx210 also detected neuritic plaques in the cortex of the patient brains. In hippocampal homogenates from THY-Tau22 mice and cortex homogenates obtained from Alzheimer patients, ADx215 consistently stained specific low order Tau oligomers in diseased brain, which in size correspond to Tau dimers. ADx201 and ADx210 additionally reacted to higher order Tau oligomers and presumed prefibrillar structures in the patient samples. Our data further suggest that formation of the low order Tau oligomers marks an early disease stage that is initiated by Tau phosphorylation at N-terminal sites. Formation of higher order oligomers appears to require additional phosphorylation in the C terminus of Tau. When used to assess Tau levels in human cerebrospinal fluid, the antibodies permitted us to discriminate patients with Alzheimer disease or other dementia like vascular dementia, indicative that these antibodies hold promising diagnostic potential., (© 2015 by The American Society for Biochemistry and Molecular Biology, Inc.)

The association of alpha-synuclein (alpha-syn) neuropathology with Parkinson's disease (PD) and several related disorders has led to an intense research effort to develop cerebrospinal fluid (CSF)- or blood-based alpha-syn biomarkers for these types of diseases. Recent studies show that alpha-syn is present in CSF and possible to measure using enzyme-linked immunosorbent assay (ELISA). Here, we describe a novel ELISA that allows for quantification of alpha-syn in CSF down to 50pg/mL. The diagnostic value of the test was assessed using CSF samples from 66 Alzheimer's disease (AD) patients, 15PD patients, 15 patients with dementia with Lewy bodies (DLB) and 55 cognitively normal controls. PD and DLB patients and controls displayed similar CSF alpha-syn levels. AD patients had significantly lower alpha-syn levels than controls (median [inter-quartile range] 296 [234-372] and 395 [298-452], respectively, p<0.001). Moreover, AD patients with mini-mental state examination (MMSE) scores below 20 had significantly lower alpha-syn than AD patients with MMSE scores of 20 or higher (p=0.02). There was also a tendency towards a negative correlation between alpha-syn levels and disease duration in the AD group (r=-0.247, p=0.06). Altogether, our results speak against CSF alpha-syn as a reliable biomarker for PD and DLB. The lower alpha-syn levels in AD, as well as the association of alpha-syn reduction with AD severity, approximated by MMSE, suggests that it may be a general marker of synapse loss, a hypothesis that warrants further investigation.

Axonal damage in multiple sclerosis (MS) is correlated to disease progression. Early axonal damage may be compensated for by regenerative processes. Growth-associated protein 43 (GAP-43) is a marker for axonal growth and synaptogenesis in various neurodegenerative diseases. We investigated the expression of GAP-43 in 48 MS grey and white matter lesions of different stages. Decreased GAP-43 expression was found in 74% of the white matter lesions, independent of the lesion stage. In 19 out of 35 white matter lesions, areas of increased GAP-43 expression were present immediately adjacent to the lesions. Increased or unaltered expression was observed in remyelinated lesions. GAP-43 was expressed in neurofilament-positive structures. GAP-43 expression appeared unchanged in grey matter lesions. Macrophages were present in the areas of changed GAP-43 expression. cerebrospinal fluid GAP-43 levels were negatively correlated with magnetic resonance imaging measures of whole-brain atrophy (r = -0.30). In conclusion, these results indicate that decreased GAP-43 immunopositivity reflects axonal damage in MS lesions, which may again be reflected in decreased cerebrospinal fluid levels. The increased levels of GAP-43 in remyelinated or nondemyelinated white matter close to MS lesions may reflect regenerative attempts by damaged axons.

In Alzheimer's disease, the complex catabolism of amyloid precursor protein (APP) leads to the production of amyloid-beta (Abeta) peptide, the major component of amyloid deposits. APP is cleaved by beta- and alpha-secretases to generate APP carboxy-terminal fragments (CTFs). Abeta peptide and amyloid intracellular domain are resulting from the cleavage of APP-CTFs by the gamma-secretase. In the present study, we hypothesize that post-translational modification of APP-CTFs could modulate their processing by the gamma-secretase. Inhibition of the gamma-secretase was shown to increase the total amount of APP-CTFs. Moreover, we showed that this increase was more marked among the phosphorylated variants and directly related to the activity of the gamma-secretase, as shown by kinetics analyses. Phosphorylated CTFs were shown to associate to presenilin 1, a major protein of the gamma-secretase complex. The phosphorylation of CTFs at the threonine 668 resulting of the c-Jun N-terminal kinase activation was shown to enhance their degradation by the gamma-secretase. Altogether, our results demonstrated that phosphorylated CTFs can be the substrates of the gamma-secretase and that an increase in the phosphorylation of APP-CTFs facilitates their processing by gamma-secretase.

Deposition of beta-amyloid (Abeta) is an early pathogenic event in Alzheimer's disease (AD). We measured Abeta42 and Abeta40 in cerebrospinal fluid (CSF) in a population-based sample of 85-year-olds, 27 demented and 35 non-demented. During the following 3 years, 7 of the 35 non-demented individuals had developed dementia, while 28 remained non-demented. Reduced CSF levels of both Abeta42 (p = 0.001) and Abeta40 (p = 0.0001) were found in patients with manifest AD and vascular dementia at the age of 85. Non-demented individuals who developed dementia during follow-up had lower levels of CSF- Abeta42 (p = 0.003), but not CSF-Abeta40 (p = 0.96), than those who remained non-demented. The odds ratio for development of dementia was 8.2 (p = 0.027) for individuals in the lower 50th percentile of CSF-Abeta42, while none of those in the highest 33rd percentile of CSF-Abeta42 developed dementia during follow-up. There were no significant differences between carriers and non-carriers of the apolipoprotein E epsilon4 allele regarding CSF-Abeta42 or CSF-Abeta40. Our study suggests that low CSF-Abeta42 is found also in an unselected population-based sample of old demented patients and provides the first evidence of a disturbance in the metabolism of Abeta, specifically involving Abeta42, before the onset of clinical symptoms in AD., (Copyright 2003 S. Karger AG, Basel)

CSF-A beta 42 may be a marker of Alzheimer's disease (AD). A decreased level of CSF-A beta 42 is consistently found in AD and has been suggested to be related to the deposition of amyloid plaques in the brain. However, low CSF-A beta 42 levels have also been found in disorders devoid of plaques, for instance Creutzfeldt-Jakob disease. To examine if the level of A beta 42 in CSF is related to inflammatory processes, we studied CSF-A beta 42 levels in eight patients with acute purulent bacterial meningitis, 10 patients with acute viral meningitis and 18 age-matched controls. In acute purulent bacterial meningitis, the CSF-A beta 42 level was markedly reduced (28% of that in controls, P<0.0001), whereas no change was found in viral meningitis. After successful treatment of bacterial meningitis, the CSF-A beta 42 level increased (P<0.05 compared to baseline) and did no longer differ from that in controls (ns). The decrease could not be explained by interference with high protein levels, since addition of increasing volumes of serum did not influence the CSF-A beta 42 levels. Our findings suggest that the reduction in CSF-A beta 42 found in bacterial meningitis is not a direct consequence of the inflammatory process. The cause may be disturbance of the clearance of A beta 42 from the brain.

Tau and beta-amyloid (1-42) (Abeta42) are two independent markers for the early diagnosis of Alzheimer's disease (AD). In the present study, biochemical markers were validated as tools for differential diagnosis between AD and dementia with Lewy bodies (DLB). Tau, Abeta42 and phospho-tau (181P) were measured in cerebrospinal fluid (CSF) from controls (n=40) and from patients with AD (n=80) or DLB (n=43) using the HT7-AT270 assay (prototype version). In comparison with AD, in DLB no differences were found for Abeta42 and lower phospho-tau. ROC analysis was used to compare the discriminatory power of total tau with that of phospho-tau. The area under the curve (AUC) amounted to 0.782 +/- 0.048 (mean +/- SE) for tau and to 0.839 +/- 0.042 for phospho-tau (p = 0.039) for differentiation of AD from DLB. The present results indicate that CSF phospho-tau may be a good marker for differentiation between AD and DLB.

The phosphorylation state of tau-protein is crucial for the regulation of neuronal microtubule organization. Functional conclusions on tau-protein require an accurate assessment of phosphorylated sites. Therefore, the in vivo distribution and postmortem preservation of some phospho-epitopes on tau-protein were examined in the rat brain under different fixation and preparation conditions. Detection of tau-protein with a phosphorylation-independent antiserum revealed both axonal and somatodendritic localizations, which were not influenced by a postmortem interval of 30 min. The phospho-epitopes recognized by 12E8, AT8, and PHF-1 were mainly localized in the somatodendritic compartment. The binding sites of AT8 and PHF-1 were rapidly dephosphorylated postmortem, whereas the Tau-1 epitope was unmasked in the somatodendritic region. The axonally located phospho-epitope of AT270 and the nuclear epitope of AT100 were still detectable after a postmortem interval of 30 min. Postmortem dephosphorylation and inhibition of this process by PP1 and/or PP2A was further demonstrated on Western blot. In conclusion, rapid processing of tau-protein is essential for the correct assessment of investigations on phospho-isoforms.

Alzheimer's disease (AD) is the most common form of dementia, and is characterized by a degeneration of neurones and their synapses, and a higher number of senile plaques (SP) and neurofibrillary tangles (NFT) compared with that found in non-demented individuals of the same age. NFT are composed of a hyperphosphorylated and ubiquitinated form of tau protein. Previous studies have found that in the cerebrospinal fluid (CSF) both tau and ubiquitin are increased in AD. We examined CSF-tau and CSF-ubiquitin in a population based sample of 85-year-olds, 26 demented (11 with probable Alzheimer's disease (AD), 13 with probable vascular dementia (VAD) and 2 with mixed (AD/VAD) type of dementia) and 35 non-demented individuals. CSF-tau was significantly higher both in the probable AD group (254 +/- 113 pg/mL; P < 0.01), and in the probable VAD group (247 +/- 75 pg/mL; P < 0.005), than in the non-demented group (171 +/- 78 pg/mL), but did not significantly differ between the probable AD and probable VAD groups. In contrast, CSF-ubiquitin did not significantly differ between the probable AD (100 +/- 24 ng/mL), probable VAD (102 +/- 16 ng/mL), and non-demented (97 +/- 27 ng/mL) groups. CSF-tau increased with increasing severity of dementia (P < 0.001), though no such relation was found for CSF-ubiquitin. Neither CSF-tau nor CSF-ubiquitin differed between patients with or without the apolipoprotein E E4 isoform. Higher CSF-tau and CSF-ubiquitin levels were also associated with increasing degree of cortical and central brain atrophy as measured by computerized tomography. The relationships between CSF-tau and severity of dementia and to brain atrophy suggest that CSF-tau may be used as a measure of neuronal/axonal degeneration in patients with dementia. We have previously shown a marked increase in both CSF-tau and CSF-ubiquitin in younger patients with AD and VAD. The less pronounced increase in CSF-tau and the lack of difference in CSF-ubiquitin in older patients suggest that the severity of the degenerative process is less in older than in younger demented patients.

The monoclonal antibodies TAU-1 and AT8 are directed at human microtubule-associated protein tau epitopes that contain a dephosphorylated and phosphorylated Ser202, respectively, while AT180 and AT270 are anti-tau monoclonals with epitopes that require phosphorylated Thr181 and Thr231, respectively. We used these antibodies to study the developmental profiles of tau proteins in rat cerebral cortex and chicken optic lobes. In tau extracts from perinatal rat cerebral cortex. AT8 recognized one major protein band of approximately 50 kDa that peaks on postnatal day 6 and declines rapidly to lower levels at day 12. At later stages, the AT8 epitope was expressed by several adult tau isoforms that were, however, stained only very faintly in highly enriched samples. Two additional tau epitopes recognized by AT180 and AT270 were found to be expressed by one or two protein bands up to about postnatal day 19 and then declined. Unlike the AT8 epitope, in the mature brain these epitopes were stained strongly in enriched samples, where they were expressed by a greater number of adult isoforms. Between embryonic day 19 and postnatal day 12, TAU-1 was found to recognize one major protein band of approximately 50 kDa which migrated slightly faster than the AT8-binding band. At postnatal day 19 and all older stages (including adult cortex), at least three additional TAU-1-binding isoforms with higher apparent molecular weights were present. Hence, the transition from one immature to several adult TAU-1-binding tau isoforms between postnatal day 12 and 19 in rat cerebral cortex coincides with the phase of rapid down-regulation of the AT8 epitope. As in the rat cerebrum, in chicken optic lobes there is a developmental decrease of AT8-binding proteins which is paralleled by striking changes in the electrophoretic pattern of tau isoforms recognized by TAU-1. In both rat cerebral cortex and chicken optic lobes, the period of maximal expression of AT8-binding tau is morphologically characterized by intense axonal growth and beginning synaptogenesis, whereas its subsequent rapid down-regulation and the appearance of novel TAU-1-binding isoforms correlates with synaptic maturation, the onset of spontaneous electrical activity and the beginning of myelination.