https://parkerlab.bio.uci.edu/publication%20attachments/2005_demuro_mina_kayed_milton_parker_glabe_133.pdf

Calcium dysregulation and membrane disruption as a ubiquitous neurotoxic mechanism of soluble amyloid oligomers.

An amyloid protein that precipitates in the cerebral vessel walls of Dutch patients with hereditary cerebral hemorrhage with amyloidosis is similar to the amyloid protein in vessel walls and senile plaques in brains of patients with Alzheimer's disease, Down syndrome, and sporadic cerebral amyloid angiopathy. Cloning and sequencing of the two exons that encode the amyloid protein from two patients with this amyloidosis revealed a cytosine-to-guanine transversion, a mutation that caused a single amino acid substitution (glutamine instead of glutamic acid) at position 22 of the amyloid protein. The mutation may account for the deposition of this amyloid protein in the cerebral vessel walls of these patients, leading to cerebral hemorrhages and premature death.

Mutation of the Alzheimer’s disease amyloid gene in hereditary cerebral hemorrhage, Dutch type. The role of amyloid in dementia and stroke

Characterization of soluble oligomeric amyloid beta (Abeta) species in the brains of Alzheimer's disease (AD) patients and transgenic models has raised the possibility that different conformations of Abeta may contribute to AD pathology via different mechanisms. To characterize the toxic effect of different Abeta conformations, we tested side by side the effect of well characterized Abeta oligomers (AbetaOs), Abeta-derived diffusible ligands (ADDLs), and fibrillar Abeta (Abetaf) preparations in human cortical neurons (HCNs). Both AbetaOs and ADDLs bind rapidly and with high affinity to synaptic contacts and cellular membranes. AbetaOs (5 microm) induced rapid and massive neuronal death. Calcium influx accelerated, but was not required for, AbetaO toxicity. AbetaOs elicited a stereotyped succession of cellular changes consistent with the activation of a mitochondrial death apoptotic pathway. At low concentrations AbetaOs caused chronic and subtler mitochondrial alterations but minimal cell death. ADDLs induced similar toxic changes as AbetaOs but on a fivefold longer time scale. Higher concentrations of Abetaf and longer incubation times were required to produce widespread neuritic dystrophy but modest HCN cell death. Thus various Abeta species may play relevant roles in AD, causing neurotoxicity by distinct non-overlapping mechanisms affecting neuronal function and viability over multiple time courses.

https://www.jneurosci.org/content/jneuro/26/22/6011.full.pdf

Different conformations of amyloid beta induce neurotoxicity by distinct mechanisms in human cortical neurons.

Neuronal loss is prominent in Alzheimer's disease (AD), and its mechanisms remain unresolved. Apoptotic cell death has been implicated on the basis of studies demonstrating DNA fragmentation and an up-regulation of proapoptotic proteins in the AD brain. However, DNA fragmentation in neurons is too frequent to account for the continuous neuronal loss in a degenerative disease extending over many years. Furthermore, the typical apoptotic morphology has not been convincingly documented in AD neurons with fragmented DNA. We report the detection of the activated form of caspase-3, the central effector enzyme of the apoptotic cascade, in AD and Down's syndrome (DS) brain using an affinity-purified antiserum. In AD and DS, single neurons with apoptotic morphology showed cytoplasmic immunoreactivity for activated caspase-3, whereas no neurons were labeled in age-matched controls. Apoptotic neurons were identified at an approximate frequency of 1 in 1100 to 5000 neurons in the cases examined. Furthermore, caspase-3 immunoreactivity was detected in granules of granulovacuolar degeneration. Our results provide direct evidence for apoptotic neuronal death in AD with a frequency compatible with the progression of neuronal degeneration in this chronic disease and identify autophagic vacuoles of granulovacuolar degeneration as possible means for the protective segregation of early apoptotic alterations in the neuronal cytoplasm.

/pdf/activation-of-caspase-3-in-single-neurons-and-autophagic-438v084wwn.pdf

Activation of Caspase-3 in Single Neurons and Autophagic Granules of Granulovacuolar Degeneration in Alzheimer’s Disease : Evidence for Apoptotic Cell Death

The invention provides compositions and methods for treatment of amyloidogenic diseases. Such methods entail administering an agent that induces a beneficial immune response against an amyloid deposit in the patient. The methods are particularly useful for prophylactic and therapeutic treatment of Alzheimer's disease. In such methods, a suitable agent is Aβ peptide or an antibody thereto.

Prevention and treatment of amyloidogenic disease

β-Amyloid induces apoptosis in human-derived neurotypic SH-SY5Y cells

The beta-amyloid deposits in Alzheimer's diseased (AD) brain are made up mainly of beta A4 peptides which show both N- and C-terminal heterogeneity. The predominant C-terminal species, identified by peptide sequencing of purified beta-amyloid, end either at position 40 or 42 of the beta A4 peptide. The distribution of these two beta A4 species in postmortem tissue as well as their generation in vitro could not be addressed previously due to the lack of specific antibodies that could differentiate them. This report describes the generation of a highly specific monoclonal antibody, MAb 369.2B which was raised against a synthetic peptide consisting of the C-terminus of the 1-42 beta A4 species. MAb 369.2B does not recognize the shorter beta A4 species 1-40 in solution or in solid phase. Furthermore, both beta A4 1-40 and 1-43 were unable to absorb out the antibody when used immunocytochemically. The regional distribution of MAb 369.2B immunoreactivity in AD and non-AD brain samples were compared to MAb 286.8A, an antibody raised against the N-terminal region of beta A4. Overall, the staining patterns were very similar. In AD cases with extreme vascular involvement, the N-terminal (MAb 286.8A) antibody was more likely to label the vascular basement membrane of affected vessels, and to label them more uniformly. In addition, preliminary quantitative analyses revealed that the C-terminal antibody labeled fewer, larger plaques than the N-terminal antibody. Qualitative analyses revealed that these smaller plaques were typically subregions of the larger plaques. The data corroborate the biochemical findings of N-terminal raggedness in beta A4 plaques. Further studies are required to explain this differential pattern of deposition.

Anne F. Bushnell

Papers

β-Amyloid induces apoptosis in human-derived neurotypic SH-SY5Y cells

Development and Characterization of a Monoclonal Antibody 369.2B Specific for the Carboxyl‐Terminus of the βA4 Peptide

DNA nick end labeling: a reliable marker for apoptosis?