Amyloid pathology influences aß1-42 cerebrospinal fluid levels in dementia with lewy bodies.

A significant proportion of patients with dementia with Lewy bodies (DLB) show Alzheimer's disease (AD) pathology like senile plaques and neurofibrillary tangles. Biomarkers in cerebrospinal fluid (CSF), such as amyloid-ß1-42 (Aß1-42), total tau (T-tau), and hyperphosphorylated tau (P-tau181P), are linked to the different pathological hallmarks of AD. We set up a study to investigate the influence of AD co-pathology on CSF biomarker concentrations and profiles in autopsy-confirmed DLB. DLB patients with senile plaques showed significantly lower CSF Aß1-42 concentrations than DLB patients without senile plaques, but not compared to the AD patients. There were no significant differences in CSF T-tau or P-tau181P concentrations between DLB patients with and without neurofibrillary tangles. A correlation was found between the number of APOE ε4 alleles and Aß1-42 CSF levels in DLB patients with senile plaques. Although the CSF biomarkers Aß1-42, T-tau, and P-tau181P have an added diagnostic value for the differential dementia diagnosis, concomitant amyloid pathology in DLB limits the use of CSF Aß1-42 for the differential diagnosis of AD versus DLB.

No association of CSF biomarkers with APOEepsilon4, plaque and tangle burden in definite Alzheimer's disease.

The CSF biomarkers beta-amyloid peptide (Abeta(1-42)), total tau protein (T-tau) and tau phosphorylated at threonine 181 (P-tau(181P)) were determined in autopsy-confirmed Alzheimer's disease patients in order to study possible associations with the epsilon4 allele of APOE and density and spread of plaques (SP) and tangles (NFT). CSF levels of Abeta(1-42), T-tau and P-tau(181P) were determined in 50 Alzheimer's disease patients using commercially available single parameter ELISA kits (INNOTEST(R)). Genomic DNA was extracted from whole blood and the APOE genotype was determined using standard methods. Tangle burden was assessed by means of Braak's NFT stages (I-VI), whereas the plaque burden was assessed by means of Braak's SP stages (A-C). CSF biomarker levels were not different when comparing epsilon4 carriers (n = 21) and non-carriers (n = 29) (P > 0.05 for all comparisons). No significant correlations between the number of epsilon4 alleles (0, 1 or 2) and CSF levels of Abeta(1-42) (Spearman Rank Order: r = -0.057, P = 0.695), T-tau (r = 0.104, P = 0.472) and P-tau(181P) (r = 0.062, P = 0.668) were found. Braak's SP (Abeta(1-42): r = -0.155, P = 0.280; T-tau: r = -0.044, P = 0.763; P-tau(181P): r = -0.010, P = 0.947) and NFT (Abeta(1-42): r = -0.145, P = 0.315; T-tau: r = 0.117, P = 0.415; P-tau(181P): r = 0.150, P = 0.296) stages were not significantly correlated with CSF biomarker levels. In conclusion, CSF levels of Abeta(1-42), T-tau and P-tau(181P) were not associated with epsilon4, tangle or plaque burden in 50 autopsy-confirmed Alzheimer's disease patients. In the light of future biomarker applications like monitoring of disease progression and as allocortical neuropathological changes significantly contribute to clinical symptoms, the concept of in vivo surrogate biomarkers should be further explored.

Genetic risk and transcriptional variability of amyloid precursor protein in Alzheimer's disease.

It is well established that Alzheimer's disease causing mutations in APP, PSEN1 and PSEN2 lead to a relative increased production of Abeta42, thereby fostering its deposition in plaques. Recently others and we showed that amyloid precursor protein (APP) overproduction, either as a result of genomic locus duplication or altered regulatory sequences in the APP promoter region, leads to early-onset disease. Here, we have expanded our study of genetic variability in the APP promoter to a large group of well-documented Belgian patients (n = 750, mean onset age = 75.0 +/- 8.6, range = 37-96). We identified three different APP promoter mutations (-369C-->G, -534G-->A and -479C-->T) in seven patients. In patients with onset < or =70 years (n = 204), we identified one patient carrying the London APP V717I mutation while no patients carried an APP locus duplication, indicating that APP promoter mutations (n = 2) were more frequently associated with increased risk for early-onset Alzheimer's disease. The two mutations (-369C-->G and -534G-->A) increasing APP promoter activity by nearly 2-fold and mimicking an APP duplication, appeared in probands of families with multiple patients with dementia. The -479C-->T mutation that increased APP expression only mildly (1.2-fold), was observed in four patients with onset ages ranging from 62 to 79 years (mean 71.5 years), suggesting that its contribution to disease risk is more pronounced at later age due to modulating factors. In conclusion, we provided evidence that mutations in APP regulatory sequences are more frequent than APP coding mutations, and that increased APP transcriptional activity constitutes a risk factor for Alzheimer's disease with onset ages inversely correlated with levels of APP expression.

Extracellular protein deposition correlates with glial activation and oxidative stress in Creutzfeldt-Jakob and Alzheimer's disease.

The relation of protein deposition with glial cells and oxidative stress was studied in Creutzfeldt-Jakob disease (CJD), Alzheimer's disease (AD) and neurologically healthy control patients. Three neocortical areas, the hippocampus, and the cerebellum of 20 CJD, 10 AD and 10 control patients were immunohistochemically examined for the presence of astroglia, microglia, and protein depositions. To investigate the level of oxidative stress the percentage of neurons with cytoplasmic hydroxylated DNA was determined. Astroglia, microglia and oxidative stress were located around amyloid-beta depositions and a clear quantitative relation was identified. These markers were only increased in the hippocampus of AD compared to controls. Quantitative analysis in these groups showed a correlation between the oxidative stress level and the number of microglia in the grey matter. All markers were increased in the grey matter and the cerebellum of CJD when compared to AD and controls. The highest numbers of lesions were observed in a CJD population with a rapid disease progression. Quantitative analysis showed a correlation between the oxidative stress level and all glial cells. Further analysis showed that the number of microglia was related to the intensity of the prion depositions. Glial cells in the brain are thought to be the main producers of oxidative stress, resulting in neuronal death. Our results confirm that this close relationship exists in both AD and CJD. We also show that an increased number of glial cells and therefore possibly oxidative stress is associated with the disease progression.

Molecular diagnostic tools in Creutzfeldt-Jakob disease and other prion disorders.

Clinical criteria and cerebrospinal fluid biomarkers for the diagnosis of human prion diseases (sporadic, iatrogenic or variant Creutzfeldt-Jakob disease and genetic inherited transmissible spongiform encephalopathies) are now widely available and show a sensitivity and specificity of approximately 98%. Final diagnosis of prion diseases is obtained by post-mortem examination upon identification of the pathological conformer of the prion protein (PrPSc) in the brain. Several diagnostic kits are now available that facilitate the immunochemical measurement of PrPSc. Several new molecular diagnostic techniques, aimed at increasing the sensitivity and specificity of PrPSc detection and at identifying markers of disease other than PrPSc, are the subject of ongoing studies. The aim of these studies is to develop preclinical screening tests for the identification of infected but still healthy individuals. These tests are also essential to investigate the safety of blood or blood-derived products and to ensure meat safety in European countries.