Widespread Cerebral Amyloid Angiopathy Research Articles

Amyloid and Tau in Neurodegeneration

Background and Hypothesis:Familial British dementia (FBD) and familial Danish dementia (FDD) are two autosomal dominant neurodegenerative diseases caused by mutations in the BRI2 gene. FBD and FDD are characterized by widespread cerebral amyloid angiopathy (CAA), parenchymal amyloid deposition, and neurofibrillary tangles.Previous studies have shown that accumulation of Danish amyloid peptide (ADan) induces hyperphosphorylation of tau and cell cytotoxicity; however, progress in our understanding of the interaction between ADan and tau has been hindered by the lack of antibodies against ADan. In addition, whether the British amyloid peptide (ABri) has a similar effect on tau phosphorylation remains unknown. The main goals of our project are to generate monoclonal antibodies against ADan and to test whether the ABri peptide induces hyperphosphorylation of tau and cell cytotoxicity.
 Experimental Design or Project Methods:A peptide homologous to the C-terminus of the ADan peptide was used to immunize 5 mice. Serum samples were tested from mice with high ELISA titers and the best 2 animals were used for cell fusion. Cell culture supernatants were screened by ELISA, western blot and immunohistochemistry. ABri peptides were used as negative controls.HEK cells expressing human tau were used to assess the interaction between ABri and tau. We performed immunocytochemistry and Western blot analysis to investigate tau phosphorylation.
 Results:A total of 11 clones tested positive by western blot. 3 clones tested positive for ABri and were discarded. 5 clones were tested by immunohistochemistry. 3 of the positive clones will be used for subcloning to complete clonality. Work in progress on the interaction between ABri and tau will determine whether ABri induces tau hyperphosphorylation in cell culture.
 Conclusion and Potential Impact:Our work will provide novel tools to study the interaction between amyloid and tau in neurodegenerative diseases and may uncover possible new targets for pharmaceutical intervention in tauopathies.

Cerebrovascular pathology in Down syndrome and Alzheimer disease

People with Down syndrome (DS) are at high risk for developing Alzheimer disease (AD) with age. Typically, by age 40 years, most people with DS have sufficient neuropathology for an AD diagnosis. Interestingly, atherosclerosis and hypertension are atypical in DS with age, suggesting the lack of these vascular risk factors may be associated with reduced cerebrovascular pathology. However, because the extra copy of APP leads to increased beta-amyloid peptide (Aβ) accumulation in DS, we hypothesized that there would be more extensive and widespread cerebral amyloid angiopathy (CAA) with age in DS relative to sporadic AD. To test this hypothesis CAA, atherosclerosis and arteriolosclerosis were used as measures of cerebrovascular pathology and compared in post mortem tissue from individuals with DS (n = 32), sporadic AD (n = 80) and controls (n = 37). CAA was observed with significantly higher frequencies in brains of individuals with DS compared to sporadic AD and controls. Atherosclerosis and arteriolosclerosis were rare in the cases with DS. CAA in DS may be a target for future interventional clinical trials.

Oxidative stress and mitochondria-mediated cell death mechanisms triggered by the familial Danish dementia ADan amyloid

Familial Danish Dementia (FDD), an early-onset non-amyloid-β (Aβ) cerebral amyloidosis, is neuropathologically characterized by widespread cerebral amyloid angiopathy, parenchymal amyloid and preamyloid deposits, as well as neurofibrillary degeneration indistinguishable to that seen in Alzheimer's disease (AD). The main amyloid subunit composing FDD lesions, a 34-amino acid de-novo generated peptide ADan, is the direct result of a genetic defect at the 3′-end of the BRI2 gene and the physiologic action of furin-like proteolytic processing at the C-terminal region of the ADan precursor protein. We aimed to study the impact of the FDD mutation, the additional formation of the pyroglutamate (pE) posttranslational modification as well as the relevance of C-terminal truncations —all major components of the heterogeneous FDD deposits— on the structural and neurotoxic properties of the molecule. Our data indicates that whereas the mutation generated a β-sheet-rich hydrophobic ADan subunit of high oligomerization/fibrillization propensity and the pE modification further enhanced these properties, C-terminal truncations had the opposite effect mostly abolishing these features. The potentiation of pro-amyloidogenic properties correlated with the initiation of neuronal cell death mechanisms involving oxidative stress, perturbation of mitochondrial membrane potential, release of mitochondrial cytochrome c, and downstream activation of caspase-mediated apoptotic pathways. The amyloid-induced toxicity was inhibited by targeting specific components of these detrimental cellular pathways, using reactive oxygen scavengers and monoclonal antibodies recognizing the pathological amyloid subunit. Taken together, the data indicate that the FDD mutation and the pE posttranslational modification are both primary elements driving intact ADan into an amyloidogenic/neurotoxic pathway while truncations at the C-terminus eliminate the pro-amyloidogenic characteristics of the molecule, likely reflecting effect of physiologic clearance mechanisms.

脳アミロイドアンギオパチーによる多発性皮質微小梗塞が認知症の進行に影響したと考えられる１剖検例

A Japanese male showed gradually progressing dementia with psychiatric symptoms including abnormal behavior, night and day reversal, nocturnal delirium, loud shouting, agitation, resistance to care, and loud soliloquy. The patient had a history of right cerebral embolism due to atrial fibrillation 1 month before the onset of dementia. Head CT revealed widespread cerebral infarction in the right cerebral hemisphere with bilateral lateral ventricular dilatation. The patient died at the age of 83, 10 months after the onset of cerebral embolism. The clinical diagnosis was mixed-type dementia. On autopsy the brain weighed 1,160 g. Widespread cerebral amyloid angiopathy (CAA) was observed, with distribution most severe in the cerebral cortical vessels and slightly milder in the leptomeningial and subarachnoid vessels. The artery, arteriole, and capillary walls were thickened by the deposition of amorphous, eosinophilic and beta-protein immunopositive amyloid. Abeta-deposition was more severe in capillaries and CAA tended to be more severe in the occipital regions. Multiple cortical microinfarcts were found, particularly in the crests of the cerebral gyri of watershed zones. Cerebral white matter, basal ganglia, thalamus, brainstem and spinal cord were relatively preserved from CAA. Infarction was not apparent, except for an embolic lesion in the right cerebral hemisphere and the cortical microinfarcts. We did not observe fibrinoid necrosis, granulomatous angiitis or giant cell reaction associated with CAA-vasculopathies. Rare instances were observed of neurofibrillary tangles and senile plaques corresponding to Braak stages II and A, respectively. We thought the multiple cortical microinfarcts occurred due to chronic hypoperfusion associated with CAA-associated vasculopathies of capillaries in the cerebral cortex. We suspected that the dementia was influenced by the CAA with multiple cortical microinfarcts. Pathologic findings of the patient suggest that CAA without AD-related Abeta-deposition might exist and that capillary Abeta-deposition might be an important factor of hemodynamic perturbation.

Modeling familial British and Danish dementia.

Familial British dementia (FBD) and familial Danish dementia (FDD) are two autosomal dominant neurodegenerative diseases caused by mutations in the BRI ( 2 ) gene. FBD and FDD are characterized by widespread cerebral amyloid angiopathy (CAA), parenchymal amyloid deposition, and neurofibrillary tangles. Transgenic mice expressing wild-type and mutant forms of the BRI(2) protein, Bri ( 2 ) knock-in mutant mice, and Bri ( 2 ) gene knock-out mice have been developed. Transgenic mice expressing a human FDD-mutated form of the BRI ( 2 ) gene have partially reproduced the neuropathological lesions observed in FDD. These mice develop extensive CAA, parenchymal amyloid deposition, and neuroinflammation in the central nervous system. These animal models allow the study of the molecular mechanism(s) underlying the neuronal dysfunction in these diseases and allow the development of potential therapeutic approaches for these and related neurodegenerative conditions. In this review, a comprehensive account of the advances in the development of animal models for FBD and FDD and of their relevance to the study of Alzheimer disease is presented.

Cerebral Amyloid Angiopathy and Parenchymal Amyloid Deposition in Transgenic Mice Expressing the Danish Mutant Form of Human BRI2

Familial Danish dementia (FDD) is an autosomal dominant neurodegenerative disease clinically characterized by the presence of cataracts, hearing impairment, cerebellar ataxia and dementia. Neuropathologically, FDD is characterized by the presence of widespread cerebral amyloid angiopathy (CAA), parenchymal amyloid deposition and neurofibrillary tangles. FDD is caused by a 10‐nucleotide duplication‐insertion in the BRI2 gene that generates a larger‐than‐normal precursor protein, of which the Danish amyloid subunit (ADan) comprises the last 34 amino acids. Here, we describe a transgenic mouse model for FDD (Tg‐FDD) in which the mouse Prnp (prion protein) promoter drives the expression of the Danish mutant form of human BRI2 . The main neuropathological findings in Tg‐FDD mice are the presence of widespread CAA and parenchymal deposition of ADan. In addition, we observe the presence of amyloid‐associated gliosis, an inflammatory response and deposition of oligomeric ADan. As the animals aged, they showed abnormal grooming behavior, an arched back, and walked with a wide‐based gait and shorter steps. This mouse model may give insights on the pathogenesis of FDD and will prove useful for the development of therapeutics. Moreover, the study of Tg‐FDD mice may offer new insights into the role of amyloid in neurodegeneration in other disorders, including Alzheimer disease.

Oligomerization and neurotoxicity of the amyloid ADan peptide implicated in familial Danish dementia.

Familial Danish dementia (FDD) is a rare neurodegenerative disorder, which is pathologically characterized by widespread cerebral amyloid angiopathy, parenchymal protein deposits and neurofibrillary degeneration. FDD is associated with mutation in the BRI gene. In FDD a decamer duplication between codons 265 and 266 in the 3' region of the BRI gene originates an amyloid peptide named ADan, 11 residues longer than the wild-type peptide produced from the normal BRI gene. ADan deposits have been found widely distributed in the CNS of FDD cases. The deposits of ADan are predominantly non-fibrillar aggregates. We show here that synthetic ADan forms oligomers in vitro, seen by Tricine-PAGE and gel filtration, and higher aggregates, which are seen by atomic force spectroscopy and electron microscopy as carrot-shaped objects that bunch together. Here we report that oligomeric ADan is toxic to neuronal cell lines. We find that the soluble non-fibrillar oligomeric species of both the reduced and oxidized forms of ADan are toxic. These results support the idea that the non-fibrillar soluble aggregates are the pathogenic species, which may play a central role in the pathogenesis of FDD, and imply that similar mechanism may also be involved in other neurodegenerative diseases associated with amyloid deposits.

A decamer duplication in the 3' region of the BRI gene originates an amyloid peptide that is associated with dementia in a Danish kindred.

Familial Danish dementia (FDD), also known as heredopathia ophthalmo-oto-encephalica, is an autosomal dominant disorder characterized by cataracts, deafness, progressive ataxia, and dementia. Neuropathological findings include severe widespread cerebral amyloid angiopathy, hippocampal plaques, and neurofibrillary tangles, similar to Alzheimer's disease. N-terminal sequence analysis of isolated leptomeningeal amyloid fibrils revealed homology to ABri, the peptide originated by a point mutation at the stop codon of gene BRI in familial British dementia. Molecular genetic analysis of the BRI gene in the Danish kindred showed a different defect, namely the presence of a 10-nt duplication (795-796insTTTAATTTGT) between codons 265 and 266, one codon before the normal stop codon 267. The decamer duplication mutation produces a frame-shift in the BRI sequence generating a larger-than-normal precursor protein, of which the amyloid subunit (designated ADan) comprises the last 34 C-terminal amino acids. This de novo-created amyloidogenic peptide, associated with a genetic defect in the Danish kindred, stresses the importance of amyloid formation as a causative factor in neurodegeneration and dementia.

Characterization of amyloid β protein species in cerebral amyloid angiopathy of a squirrel monkey by immunocytochemistry and enzyme-linked immunosorbent assay

We analyzed the composition of amyloid β protein (A β) species in cerebral amyloid angiopathy (CAA) of an aged squirrel monkey. Immunocytochemistry demonstrated that the cerebral cortex contained no lesions other than widespread CAA with A β40 as its apparent major component. However, enzyme-linked immunosorbent assay revealed that A β42(43) predominated over A β40 in a formic acid-extracted cortical fraction. These findings suggest possible underestimation of A β42(43) levels in some previous immunocytochemical investigations.