ABSTRACT
ß-Amyloid (Aß) plaques in Alzheimer (AD) brains are surrounded by severe dendritic and axonal changes, including local spine loss, axonal swellings and distorted neurite trajectories. Whether and how plaques induce these neuropil abnormalities remains unknown. We tested the hypothesis that oligomeric assemblies of Aß, seen in the periphery of plaques, mediate the neurodegenerative phenotype of AD by triggering activation of the enzyme GSK-3ß, which in turn appears to inhibit a transcriptional program mediated by CREB. We detect increased activity of GSK-3ß after exposure to oligomeric Aß in neurons in culture, in the brain of double transgenic APP/tau mice and in AD brains. Activation of GSK-3ß, even in the absence of Aß, is sufficient to produce a phenocopy of Aß-induced dendritic spine loss in neurons in culture, while pharmacological inhibition of GSK-3ß prevents spine loss and increases expression of CREB-target genes like BDNF. Of note, in transgenic mice GSK-3ß inhibition ameliorated plaque-related neuritic changes and increased CREB-mediated gene expression. Moreover, GSK-3ß inhibition robustly decreased the oligomeric Aß load in the mouse brain. All these findings support the idea that GSK3ß is aberrantly activated by the presence of Aß, and contributes, at least in part, to the neuronal anatomical derangement associated with Aß plaques in AD brains and to Aß pathology itself.
Subject(s)
Alzheimer Disease/metabolism , Amyloid beta-Peptides/metabolism , Brain/metabolism , Glycogen Synthase Kinase 3/metabolism , Neurites/metabolism , Alzheimer Disease/genetics , Alzheimer Disease/pathology , Amyloid beta-Peptides/genetics , Animals , Brain/pathology , Cells, Cultured , Dendritic Spines/metabolism , Dendritic Spines/pathology , Glycogen Synthase Kinase 3 beta , Mice , Mice, Transgenic , Neurites/pathology , Neurons/metabolism , Neurons/pathology , tau Proteins/genetics , tau Proteins/metabolismABSTRACT
Cerebrospinal fluid (CSF) biomarkers are useful in the diagnosis and the prediction of progression of several neurodegenerative diseases. Among them, CSF neurofilament light (NfL) protein has particular interest, as its levels reflect neuroaxonal degeneration, a common feature in various neurodegenerative diseases. In the present study, we analyzed NfL levels in the CSF of 535 participants of the SPIN (Sant Pau Initiative on Neurodegeneration) cohort including cognitively normal participants, patients with Alzheimer disease (AD), Down syndrome (DS), frontotemporal dementia (FTD), amyotrophic lateral sclerosis (ALS), dementia with Lewy bodies (DLB), progressive supranuclear palsy (PSP) and corticobasal syndrome (CBS). We evaluated the differences in CSF NfL accross groups and its association with other CSF biomarkers and with cognitive scales. All neurogenerative diseases showed increased levels of CSF NfL, with the highest levels in patients with ALS, FTD, CBS and PSP. Furthermore, we found an association of CSF NfL levels with cognitive impairment in patients within the AD and FTD spectrum and with AD pathology in DLB and DS patients. These results have implications for the use of NfL as a marker in neurodegenerative diseases.