ABSTRACT
In this study, we examined the relationship between various ß-amyloid (Aß) oligomer assemblies in autopsy brain with the levels of fibrillar Aß and cholinergic synaptic function. Brain tissues obtained from the frontal cortex of 14 Alzheimer's disease (AD) patients grouped into early-onset AD (EOAD) and late-onset AD (LOAD) and 12 age-matched control subjects were used to extract and quantify Aß oligomers in soluble (TBS), detergent soluble (TBST), and insoluble (GuHCl) fractions. The predominant oligomeric Aß assemblies detected were dodecamers, decamers, and pentamers, and different patterns of expression were observed between EOAD and LOAD patients. There was no association between any of the detected Aß oligomer assemblies and fibrillar Aß levels measured by N-methyl[(3)H] 2-(40-methylaminophenyl)-6-hydroxy-benzothiazole ([(3)H]PIB) binding. Levels of pentamers in the soluble fraction significantly correlated with a reduction in choline acetyltransferase activity in AD patients. The number of nicotinic acetylcholine receptors negatively correlated with the total amount of Aß oligomers in the insoluble fraction in EOAD patients, and with decamers in the soluble fraction in LOAD patients. These novel findings suggest that distinct Aß oligomers induce impairment of cholinergic neurotransmission in AD pathogenesis.
Subject(s)
Age of Onset , Alzheimer Disease/pathology , Amyloid beta-Peptides/metabolism , Brain/metabolism , Cholinergic Agents/metabolism , Peptide Fragments/metabolism , Age Factors , Aged , Aged, 80 and over , Alzheimer Disease/genetics , Aniline Compounds , Apolipoproteins E/genetics , Benzothiazoles/pharmacokinetics , Brain/drug effects , Enzyme-Linked Immunosorbent Assay/methods , Female , Genotype , Humans , Immunoprecipitation , Male , Middle Aged , Nicotine/pharmacokinetics , Nicotinic Agonists/pharmacokinetics , Postmortem Changes , Protein Binding/drug effects , Statistics as Topic , Thiazoles , Tritium/pharmacokineticsABSTRACT
Cognitive impairment in Alzheimer's disease (AD) patients is associated with a decline in the levels of growth factors, impairment of axonal transport and marked degeneration of basal forebrain cholinergic neurons (BFCNs). Neurogenesis persists in the adult human brain, and the stimulation of regenerative processes in the CNS is an attractive prospect for neuroreplacement therapy in neurodegenerative diseases such as AD. Currently, it is still not clear how the pathophysiological environment in the AD brain affects stem cell biology. Previous studies investigating the effects of the ß-amyloid (Aß) peptide on neurogenesis have been inconclusive, since both neurogenic and neurotoxic effects on progenitor cell populations have been reported. In this study, we treated pluripotent human embryonic stem (hES) cells with nerve growth factor (NGF) as well as with fibrillar and oligomeric Aß1-40 and Aß1-42 (nM-µM concentrations) and thereafter studied the differentiation in vitro during 28-35 days. The process applied real time quantitative PCR, immunocytochemistry as well as functional studies of intracellular calcium signaling. Treatment with NGF promoted the differentiation into functionally mature BFCNs. In comparison to untreated cells, oligomeric Aß1-40 increased the number of functional neurons, whereas oligomeric Aß1-42 suppressed the number of functional neurons. Interestingly, oligomeric Aß exposure did not influence the number of hES cell-derived neurons compared with untreated cells, while in contrast fibrillar Aß1-40 and Aß1-42 induced gliogenesis. These findings indicate that Aß1-42 oligomers may impair the function of stem cell-derived neurons. We propose that it may be possible for future AD therapies to promote the maturation of functional stem cell-derived neurons by altering the brain microenvironment with trophic support and by targeting different aggregation forms of Aß.
