Characterization of tau positron emission tomography tracer [18F]AV-1451 binding to postmortem tissue in Alzheimer's disease, primary tauopathies, and other dementias.

INTRODUCTION: Aggregation of tau is a hallmark of many neurodegenerative diseases, and tau imaging with positron emission tomography (PET) may allow early diagnosis and treatment monitoring. We assessed binding of the PET tracer [18F]AV-1451 in a range of dementias. METHODS: Phosphorimaging was used to quantify binding to postmortem brain tissue from 33 patients with different, histopathologically characterized, neurodegenerative dementias. RESULTS: [18F]AV-1451 showed high specific binding in cases with Alzheimer's disease (AD), moderate binding in Pick's disease and frontotemporal dementia with parkinsonism-17, and low but displaceable binding in corticobasal degeneration, progressive supranuclear palsy, non-tau proteinopathies, and in controls without pathology. Tracer binding did not correlate with tau load within disease groups. DISCUSSION: [18F]AV-1451 binds to tau in AD, and some other tauopathies. However, evidence for a non-tau binding site and lack of correlation between tracer binding and antibody staining suggest that reliable quantification of tau load with this tracer is problematic.

Alterations in global DNA methylation and hydroxymethylation are not detected in Alzheimer's disease.

AIMS: Genetic factors do not seem to account fully for Alzheimer disease (AD) pathogenesis. There is evidence for the contribution of environmental factors, whose effect may be mediated by epigenetic mechanisms. Epigenetics involves the regulation of gene expression independently of DNA sequence and these epigenetic changes are influenced by age and environmental factors, with DNA methylation being one of the best characterized epigenetic mechanisms. The human genome is predominantly methylated on CpG motifs, which results in gene silencing; however methylation within the body of the gene may mark active transcription. There is evidence suggesting an involvement of environmental factors in the pathogenesis of Alzheimer's disease (AD), which prompted our study examining DNA methylation in this disorder. METHODS: Using immunohistochemistry with 5-methylcytosine/5-hydroxymethylcytosine antibodies we studied, in comparison with age matched controls, DNA methylation in sporadic and familial AD cases in the entorhinal cortex that exhibits substantial pathology and the cerebellum, which is relatively spared. RESULTS: Neuronal nuclear labelling with 5-methylcytosine (5mC) and 5-hydroxymethylcytosine (5hmC) was evident in all cases studied. We did not detect any significant change in the levels of nuclear staining in the AD samples compared to neurologically normal controls. In the entorhinal cortex we also examined global DNA methylation and hydroxymethylation using an enzyme-linked immunosorbent assay (ELISA). CONCLUSION: No significant differences were found between AD and control cases in global levels of 5mC and 5hmC in the entorhinal cortex using immunohistochemistry and enzyme-linked immunosorbent assays.

Genetic determinants of white matter hyperintensities and amyloid angiopathy in familial Alzheimer's disease.

Familial Alzheimer's disease (FAD) treatment trials raise interest in the variable occurrence of cerebral amyloid angiopathy (CAA); an emerging important factor in amyloid-modifying therapy. Previous pathological studies reported particularly severe CAA with postcodon 200 PSEN1 mutations and amyloid beta coding domain APP mutations. As CAA may manifest as white matter hyperintensities (WMH) on magnetic resonance imaging, particularly posteriorly, we investigated WMH in 52 symptomatic FAD patients for associations with mutation position. WMH were visually rated in 39 PSEN1 (18 precodon 200); 13 APP mutation carriers and 25 healthy controls. Ten PSEN1 mutation carriers (5 precodon 200) had postmortem examination. Increased WMH were observed in the PSEN1 postcodon 200 group and in the single APP patient with an amyloid beta coding domain (p.Ala692Gly, Flemish) mutation. WMH burden on MRI correlated with severity of CAA and cotton wool plaques in several areas. The precodon 200 group had younger ages at onset, decreased axonal density and/or integrity, and a greater T-lymphocytic response in occipital deep white matter. Mutation site contributes to the phenotypic and pathological heterogeneity witnessed in FAD.

The utility of patient specific induced pluripotent stem cells for the modelling of Autistic Spectrum Disorders.

Until now, models of psychiatric diseases have typically been animal models. Whether they were to be used to further understand the pathophysiology of the disorder, or as drug discovery tools, animal models have been the choice of preference in mimicking psychiatric disorders in an experimental setting. While there have been cellular models, they have generally been lacking in validity. This situation is changing with the advent of patient-specific induced pluripotent stem cells (iPSCs). In this article, we give a methodological evaluation of the current state of the iPS technology with reference to our own work in generating patient-specific iPSCs for the study of autistic spectrum disorder (ASD). In addition, we will give a broader perspective on the validity of this technology and to what extent it can be expected to complement animal models of ASD in the coming years.

Ca 2+ -dependent autophagy is enhanced by the pharmacological agent PK11195.

The 1-(2-Chlorophenyl-N-methylpropyl)-3-isoquinolinecarboxamide, PK11195, is a proven enhancer of apoptotic cell death in a variety of cellular models. Recently, we have shown that by targeting the oncogene Bcl-2, PK11195 increases the [Ca ( 2+) ] in the Endoplasmic Reticulum ([Ca ( 2+) ]er) as well as IP3 induced mitochondrial ([Ca ( 2+) ]m) and cytosolic ([Ca ( 2+) ]c) Ca ( 2+) transients in HeLa cervix carcinoma cells. Here, in the same cells, we have investigated PK11195 contribution to models of pharmacologically induced macroautophagy. To do so, we have monitored the pattern of LC3 (the mammalian orthologue of yeast Atg8) distribution and post transcriptional modifications after challenging with Ca ( 2+) -dependent (ATP, Vitamin D3) and independent (Rapamycin and H 2O 2) stimuli for autophagy execution. We found that PK11195 plays a pro-autophagy role if associated with ATP and Vitamin D3 to be ineffective if co-incubated with Rapamycin and H 2O 2. Notably, Bcl-2 deletion abolished PK11195 effects thus suggesting a selective way of action against the oncogene. By these means, PK11195 is proposed as facilitator of Ca ( 2+) mediated autophagy and tool to ascertain the Bcl-2 contribution to the onset and unfolding of this essential catabolic process for cellular homeostasis.