Deposition Of Amyloid Beta-protein Research Articles

Amyloid beta-protein, APOE genotype and head injury.

Deposition of amyloid beta-protein (A beta) in the brain plays a key role in the pathogenesis of Alzheimer's disease. Head injury is an epidemiological risk factor for Alzheimer's disease, and deposition of A beta occurs in approximately one third of individuals dying shortly after a severe head injury. Of the three common apolipoprotein E alleles (APOE-epsilon 2, epsilon 3, and epsilon 4) APOE-epsilon 4 allele is a strong risk factor for both sporadic and some familial cases of Alzheimer's disease and there is in vitro evidence that apolipoprotein E is directly involved in A beta deposition. We have examined the frequency of APOE-epsilon 4 in those individuals with A beta deposition following head injury and found that the APOE-epsilon 4 frequency (0.52) is higher than in most studies of sporadic Alzheimer's disease. In those head-injured individuals without amyloid deposition the APOE-epsilon 4 frequency (0.16) is similar to that in non-Alzheimer's disease controls (p < 0.00001). Our data indicate an interaction between known environmental and genetic risk factors for Alzheimer's disease and underlines the importance of convergence of data around the common mechanism of A beta deposition. Furthermore, it indicates a genetic susceptibility to the effects of a head injury which may be of significance both to those who have recently sustained such an injury and to those whose activities put them at risk of trauma.

Systemic overexpression of a C-terminal fragment of human amyloid beta-protein precursor causes accumulation of Alzheimer beta-amyloid fibrils in pancreas of transgenic mice.

The deposition of amyloid beta-protein (A beta), derived from amyloid beta-protein precursor (beta APP), is a specific and early event in development of Alzheimer's disease. Transgenic mice carrying the carboxyl-terminus of beta APP gene linked to the cytomegalovirus enhancer/chicken beta-actin promoter sequence were studied. Deposition of amyloid fibrils, composing A beta, was observed in the transgenic pancreas, accompanied with cell degeneration. This result will provide a model to investigate the beta APP processing mechanism in vivo and a clue to generate possible A beta amyloidosis in animal brains.

Apolipoprotein E, dementia, and cortical deposition of beta-amyloid protein.

The epsilon 4 allele of apolipoprotein E has been associated with an increased risk of late-onset Alzheimer's disease. In a cohort of elderly subjects we prospectively investigated the relation between the apolipoprotein E genotype, dementia, and the accumulation of beta-amyloid protein in the cerebral cortex. Autopsy involving neuropathological analysis and DNA analysis of frozen blood samples were performed in 92 of 271 persons who were at least 85 years of age, who had been living in Vantaa, Finland, on April 1, 1991, and who had died between that time and the end of 1993. All subjects had been tested for dementia. Apolipoprotein E genotyping was done with a solid-phase minisequencing technique. The percentage of the cortex occupied by methenamine silver-stained plaques was used as an estimate of the extent of beta-amyloid protein deposition. The frequency of the epsilon 4 allele was significantly higher in the subjects with Alzheimer's disease than in the subjects without dementia (30 percent vs. 8 percent, P < 0.001). There was a greater accumulation of beta-amyloid protein in the brain and more neurofibrillary tangles in the subjects with the epsilon 4 allele than in those without it (P < 0.001). The deposition of beta-amyloid protein varied according to the genotype in both the subjects with dementia and those without dementia: it was lowest in those with the epsilon 2/epsilon 3 genotype, intermediate in those with the epsilon 3/epsilon 3 genotype, and highest in those with the epsilon 3/epsilon 4 genotype. A single subject had the epsilon 4/epsilon 4 genotype and had dementia. The epsilon 4 allele of apolipoprotein E is significantly associated with Alzheimer's disease. Even in elderly subjects without dementia, the apolipoprotein E genotype is related to the degree of deposition of beta-amyloid protein in the cerebral cortex.

GM1 ganglioside-bound amyloid beta-protein (A beta): a possible form of preamyloid in Alzheimer's disease.

The earliest event so far known that occurs in the brain affected with Alzheimer's disease (AD) is the deposition and fibril formation of amyloid beta-protein (A beta). A beta is cleaved from a glycosylated membrane protein, called beta-amyloid protein precursor, and normally secreted into the extracellular space. Here we report on the presence of membrane-bound A beta that tightly binds GM1 ganglioside. This suggests that this novel A beta species, rather than secreted A beta, may act as a 'seed' for amyloid and further that intracellular abnormalities in the membrane recycling already exist at the stage of amyloidogenesis.

Amyloid beta-protein induces its own production in cultured degenerating cerebrovascular smooth muscle cells.

The progression of Alzheimer's disease and related disorders involves amyloid beta-protein (A beta) deposition and pathologic changes in the parenchyma as well as cerebral blood vessels. The cerebrovascular A beta deposits in these disorders are associated with degenerating smooth muscle cells in the vessel wall, which have been shown to express the A beta precursor (A beta PP) and A beta. Here, we show that A beta 1-42, an abundant cerebrovascular form of A beta, causes cellular degeneration in cultured human cerebrovascular smooth muscle cells. This stress response is accompanied by a striking increase in the levels of cellular A beta PP and soluble A beta peptide produced in these degenerating cells. These data provide the first experimental evidence that A beta can potentially contribute to the onset and progression of the cerebrovascular pathology. The present findings suggest that this mechanism may involve a molecular cascade with a novel product-precursor relationship that results in the adverse production and subsequent accumulation of A beta.

White matter amyloid in Alzheimer's disease brain.

Amyloid beta-protein (A beta) deposits in the white matter were investigated by the double immunohistochemical staining for A beta and neuritic, glial or vascular components. Reactive astroglia and neurite abnormality were absent around A beta deposits in the white matter (w-A beta) even those with a core. The association of w-A beta with blood vessels was not consistent. Aggregates of activated microglia were found to be the sole but a consistent accompaniment of A beta deposits even in the absence of other components such as neuron, synapse, neurite abnormality and reactive astroglia, as observed in the white matter. This suggests that the aggregates of activated microglia most likely represent one of the factors promoting the process of A beta deposition.

Serum amyloid P component prevents proteolysis of the amyloid fibrils of Alzheimer disease and systemic amyloidosis.

Extracellular deposition of amyloid fibrils is responsible for the pathology in the systemic amyloidoses and probably also in Alzheimer disease [Haass, C. & Selkoe, D. J. (1993) Cell 75, 1039-1042] and type II diabetes mellitus [Lorenzo, A., Razzaboni, B., Weir, G. C. & Yankner, B. A. (1994) Nature (London) 368, 756-760]. The fibrils themselves are relatively resistant to proteolysis in vitro but amyloid deposits do regress in vivo, usually with clinical benefit, if new amyloid fibril formation can be halted. Serum amyloid P component (SAP) binds to all types of amyloid fibrils and is a universal constituent of amyloid deposits, including the plaques, amorphous amyloid beta protein deposits and neurofibrillary tangles of Alzheimer disease [Coria, F., Castano, E., Prelli, F., Larrondo-Lillo, M., van Duinen, S., Shelanski, M. L. & Frangione, B. (1988) Lab. Invest. 58, 454-458; Duong, T., Pommier, E. C. & Scheibel, A. B. (1989) Acta Neuropathol. 78, 429-437]. Here we show that SAP prevents proteolysis of the amyloid fibrils of Alzheimer disease, of systemic amyloid A amyloidosis and of systemic monoclonal light chain amyloidosis and may thereby contribute to their persistence in vivo. SAP is not an enzyme inhibitor and is protective only when bound to the fibrils. Interference with binding of SAP to amyloid fibrils in vivo is thus an attractive therapeutic objective, achievement of which should promote regression of the deposits.

Are advanced glycation end-products associated with amyloidosis in Alzheimer's disease?

Recent studies have suggested that advanced glycation end-products (AGE) of the Maillard reaction are associated with amyloidosis in Alzheimer's disease. To evaluate this possibility, the present immunohistochemical study was undertaken to locate AGE in cerebral cortices of Alzheimer's disease, using a monoclonal antibody specific for AGE-proteins. Deposits of beta-amyloid protein within cores of classic senile plaques and vascular walls in amyloid angiopathy showed no AGE-positive reaction, while primitive plaques, coronas of classic plaques and some glial cells were positive for AGE. These findings are inconsistent with the suggestion that AGE may be involved primarily in amyloidosis in Alzheimer's disease.

Distribution of beta-amyloid protein in the brain following severe head injury.

Deposits of beta-amyloid protein (beta AP) can be found in the brains of 30% of fatally head-injured patients; they have been found in children and after survival times of only 4 h. The principal aims of this study were to map the distribution of beta AP in 14 patients aged 65 years or less in whom it was known that the protein had been deposited, and to correlate its distribution with the pathologies of traumatic brain injury. The results show that beta AP is widely distributed, and that there is no correlation between its presence and cerebral contusions, intracranial haematoma, axonal injury, ischaemic brain damage, brain swelling or the pathology of raised intracranial pressure. These findings suggest that the deposition of beta AP is a consequence of the acute phase response of nerve cells to stress in susceptible individuals. Further studies will be required to establish the possible relationship between the deposition of beta AP following head injury and the molecular neuropathology of Alzheimer's disease.

Apolipoprotein E epsilon 4 allele is associated with deposition of amyloid beta-protein following head injury.

Deposition of amyloid beta-protein (A beta) in the brain plays a key role in the pathogenesis of Alzheimer's disease. Apolipoprotein E epsilon 4 allele (apo E-epsilon 4) is a strong risk factor for Alzheimer's disease, and there is in vitro evidence that apo E is directly involved in A beta deposition. Head injury is an epidemiological risk factor for Alzheimer's disease and deposition of A beta occurs in approximately one-third of individuals dying after a severe head injury. We report here that the frequency of apo E-epsilon 4 in those individuals with A beta deposition following head injury (0.52) is higher than in most studies of Alzheimer's disease, while in those head-injured individuals without A beta deposition the apo E-epsilon 4 frequency (0.16) is similar to controls without Alzheimer's disease (P < 0.00001). This finding provides further evidence linking apo E-epsilon 4 with A beta deposition in vivo and suggests that known environmental and genetic risk factors for Alzheimer's disease may act additively. In addition our finding indicates a genetic susceptibility to the effects of a head injury.

Nerve growth factor strategy and preparation of animal model for Alzheimer-type senile dementia

Nerve growth factor (NGF) plays an important role in the survival and maintenance of cholinergic neurons in the central nervous system. In senile dementia of the Alzheimer type (SDAT), learning and memory are impaired by the loss of neurons in the magnocellular cholinergic neuronal system. It is, therefore, of interest to investigate the role of NGF in this degenerative disorder. Since NGF does not cross the blood-brain barrier and is easily metabolized by peptidases when administered peripherally, it can be used for medical treatment only when directly injected into the brain. We tried to develop drugs which could be taken orally and stimulate the NGF synthesis in the brain. In addition, we attempted to develop a SDAT animal model using osmotic minipump to infuse beta-amyloid protein into cerebral ventricle, since there are no SDAT model animals accompanied with various pathophysiological changes. We demonstrate here that the oral administration of propentofylline, idebenone and trimethylquinone derivative, potent in vitro NGF synthesis stimulators, induced the increase in NGF protein and mRNA, and in choline acetyltransferase activity, in basal forebrain-lesioned and aged rats, but not in intact young rats. These drugs also ameliorated the behavioral deficits in habituation, water maze, and passive avoidance tasks in these animals. These results suggest that these drugs stimulated NGF synthesis in vivo and ameliorated the behavioral deficits which were accompanied with the reduced choline acetyltransferase activity in the basal forebrain-lesioned and aged rats. In terms of the SDAT animal model, the performance of the water maze and passive avoidance tasks was impaired and choline acetyltransferase activity significantly decreased in beta-amyloid protein-treated rats. Histochemical results showed the deposition of beta-amyloid protein in the cortex and hippocampus and atrophy and loss of hippocampal neurons. These results suggest that the deposition of beta-amyloid protein in the brain is related to the impairment of learning and cholinergic neuronal degeneration, and that beta-amyloid protein-treated rats could be an animal model for SDAT and used for the screening of drugs for SDAT.

Single-laser three-color immunolabeling of a histological section by laser scanning microscopy: application to senile plaque-related structures in post-mortem human brain tissue.

We describe a method for observing three-color immunofluorescence simultaneously in a histological section under a confocal laser scanning microscope. In this study we investigated the spatial relationship of blood vessels, reactive microglia, and amyloid beta-protein (A beta) deposits in post-mortem brain tissue of patients with Alzheimer's disease. HLA-DR was employed as a marker for activated microglia and von Willebrand factor (vWF) as a marker for vascular endothelial cells. HLA-DR was labeled with R-phycoerythrin (R-PE) and vWF with fluorescein isothiocyanate. A beta-protein was immunostained with the tandem conjugate of R-PE and cyanin 5. Three images were obtained serially by scanning a tissue section with a 488-nm laser beam in combination with an appropriate emission filter for each fluorochrome. Overlaying of these three images permitted simultaneous observation of three distinct structures: activated microglia, blood vessels, and A beta deposits. This technique provides an improved way to study the localization of three different antigens in a single tissue section.

Immune mechanism in senile plaque formation

Alzheimer disease (AD) is characterized by the appearance of two very different lesions, senile plaques and neurofibrillary tangles (NFTs). The pathological process which causes the disease must be responsible for both, but how they are linked is still a mystery. Neurofibrillary tangles develop intracellularly and involve the appearance of abnormally phosphorylated forms of tau. Senile plaques develop extracellularly with the deposition of beta-amyloid protein (BAP), a component of the larger amyloid precursor protein (APP). Neurofibrillary tangles are not unique to AD. They appear in a number of degenerative neurological diseases in which senile plaques are absent. This is an argument against NFTs causing the appearance of senile plaques. Conversely, extracellular deposits of BAP occur in areas where NFTs do not develop, indicating that BAP deposits, by themselves, do not cause NFTs. However, when senile plaques “mature”, dystrophic neuntes which contain abnormally phosphorylated tau are always present. Thus, it is possible that NFTs evolve from developing senile plaques.

Mutations associated with a locus for familial Alzheimer's disease result in alternative processing of amyloid beta-protein precursor

Alzheimer's disease (AD) is a progressive neurodegenerative disorder characterized by the extracellular deposition of amyloid beta-protein (A beta), a molecule produced by post-translational processing of the beta-amyloid precursor protein (beta APP). Mutations within the gene encoding beta APP have been linked to early onset forms of AD, but the pathogenetic mechanism(s) producing the phenotype are unknown. We analyzed the effects on beta APP processing in vitro of a naturally occurring Ala-->Gly mutation at position 692 of beta APP770 (A692G) (Hendriks, L., Duijin, C., Cras, P., Cruts, M., van Hul, W., van Harskamp, F., Warren, A., McInnis, M., Antonarakis, S., Martin, J.-J., Hofman, A., and van Broeckhoven, C. (1992) Nature Genet. 1, 218-221), as well as the effects of five genetically engineered mutations at or near this site. Substitution of glycine or proline for Ala692, or for Phe690, produced relative increases in secretion of A beta and relative decreases in secretion of the p3 peptide(s) arising after alpha-secretase generation of soluble APP (APPs). The Phe690-->Pro substitution also resulted in the synthesis of truncated APPs molecules. The structurally conservative substitutions Ala692-->Val and Phe690-->Tyr did not exhibit these effects. Certain of the substitutions also resulted in the production of a minor peptides, previously undescribed in vitro, beginning at Ala2, Lys16, and Phe19 of A beta. These data show that beta APP mutations carboxyl-terminal to alpha-secretase and beta-secretase cleavage sites can exert strong control over beta APP processing. Increased secretion of A beta may accelerate amyloidogenesis by providing more precursors for aggregation. It is also possible that truncated A beta peptides resulting from several of these mutations may accelerate amyloidogenesis through self-aggregation and/or seeding the fibrillogenesis of longer, more abundant A beta species.

Beta amyloid protein deposition in the brain after severe head injury: implications for the pathogenesis of Alzheimer's disease.

In a recent preliminary study it was reported that a severe head injury resulted in the deposition of beta amyloid protein (beta AP) in the cortical ribbon of 30% of patients who survived for less than two weeks. Multiple cortical areas have now been examined from 152 patients (age range 8 weeks-81 years) after a severe head injury with a survival time of between four hours and 2.5 years. This series was compared with a group of 44 neurologically normal controls (age range 51 to 80 years). Immunostaining with an antibody to beta AP confirmed the original findings that 30% of cases of head injury have beta AP deposits in one or more cortical areas. Increasing age seemed to accentuate the extent of beta AP deposition and potential correlations with other pathological changes associated with head injury were also investigated. In addition, beta amyloid precursor protein (beta APP) immunoreactivity was increased in the perikarya of neurons in the vicinity of beta AP deposits. The data from this study support proposals that increased expression of beta APP is part of an acute phase response to neuronal injury in the human brain, that extensive overexpression of beta APP can lead to deposition of beta AP and the initiation of an Alzheimer disease-type process within days, and that head injury may be an important aetiological factor in Alzheimer's disease.

Identification of amyloid beta protein in the brain of the small, short-lived Lemurian primate Microcebus murinus

The deposition of amyloid beta (Aβ) protein in the brain has been demonstrated immunocytochemically in the small Lemurian primate Microcebus murinus. Both meningocerebral vascular deposits and cortical parenchymal deposits occur. All eight aged (> 8 years old) Microcebus examined showed vascular amyloid deposits, whereas only four exhibited parenchymal plaques. The vascular amyloid infiltrated the tunica media of the leptomeningeal and cortical arteries and arterioles and was also found in capillaries. Aβ was observed to be deposited in three general forms in the cortical neuropil: round or elliptical plaques that were thioflavin-negative but sometimes showed a central concentration of Aβ immunoreactivity, round plaques with a densely immunoreactive core that was thioflavin-positive; extensive ribbon-like infiltrations enclosing multiple cortical blood vessels. These observations, taken together with previous descriptions of age-related neurodegenerative changes in Microcebus, indicate that this species undergoes a (β-amyloid-associated neuropathology highly similar to that seen in Alzheimer's disease. We conclude that this lemurian primate of small size and relatively short life expectancy, provides a compelling animal model of some principal features of Alzheimer's disease.

Aggregation of amyloid beta-protein and its neurotoxicity: enhancement by aluminum and other metals.

The aggregation of amyloid beta-protein has been suggested to enhance its neurotoxicity in cultured hippocampal neurons. We found that aluminum, an epidemiologic risk factor for Alzheimer's disease, promoted the aggregation of synthetic amyloid beta-protein (beta 1-40) using immunoblotting and centrifugation. There were no significant changes by Ca or Mg. Other metals including Zn, Fe caused the small degree of aggregation compared to Al. Furthermore, beta 1-40 which was aggregated by aluminum was applied on cultured rat hippocampal neurons, and the characteristic deposition of amyloid fibrils was observed on cultured neurons. These results suggested that the degeneration of neurons and the deposition of amyloid beta-protein were enhanced by aluminum.

Acidic FGF expression in the surroundings of senile plaques.

Immunohistochemical examination of postmortem brain tissue of Alzheimer's disease revealed that acidic fibroblast growth factor (aFGF) was specifically expressed in a subpopulation of reactive astrocytes which were congregated at the margin of the senile plaque. Double immunostaining indicated that such upregulation of aFGF expression might be related to the presence of reactive microglia rather than beta-amyloid protein deposits. Although, on the other hand, immunohistochemical staining for fibroblast growth factor receptor-1 occurred in some cortical neurons of Alzheimer's disease, the staining pattern did not differ from that in age-matched controls. Possible significance of aFGF-positive astrocytes in the surroundings of the senile plaque will be discussed in relation to receptor mediated or non-mediated mechanisms.

Presence of apolipoprotein E on extracellular neurofibrillary tangles and on meningeal blood vessels precedes the Alzheimer ?-amyloid deposition

The localization of apolipoprotein E (ApoE) has been examined immunohistochemically in the autopsied brains of middle-aged and old-aged control subjects, with and without amyloid beta protein (A beta) deposits, and of Alzheimer's disease patients. Senile plaques were consistently labeled with ApoE antiserum even in the very early stage of senile plaque formation seen in the fifth decade. In the cerebellar molecular layer, small dots of ApoE immunoreactivity, which were prominent in the Alzheimer's disease subjects, were observed in addition to immunoreactivity in diffuse plaques. ApoE antisera labeled all of the extracellular neurofibrillary tangles (NFT), whereas only a small minority of extracellular NFT were positive for A beta. A punctate pattern of ApoE immunoreactivity was seen at the media of the meningeal vessels lacking amyloid, when senile plaques were present in the nearby cortex. In the early stage of amyloid angiopathy, the distribution of ApoE immunoreactivity was much more extensive than that of A beta positivity. These findings suggest that ApoE accumulates in the early stage of senile plaque formation and, furthermore, that ApoE accumulation precedes A beta deposition in extracellular NFT and amyloid angiopathy.

Pathological proteins in senile plaques.

The beta-amyloid protein deposits of Alzheimer disease, whether in diffuse or consoliated form, are an agglomeration of many extracellular proteins. At least 35 have been reported as components of senile plaques, most of which also occur in diffuse deposits. More than half of these proteins are directly associated with the immune system. Since diffuse deposits are believed to be the precursors of senile plaques, it is important to define the precise molecular events that lead to the transition. Diffuse deposits share with senile plaques the presence of opsonizing components of complement, the complement activators beta-amyloid protein, amyloid P, thrombin, and apolipoprotein E. However, senile plaques contain, in addition, dystrophic neurites, agglomerates of activated microglia, components of the membrane attack complex, and the inhibitors of the membrane attack complex, clusterin, protectin and vitronectin. Microglial cells are professional phagocytes which possess the respiratory burst apparatus when activated. It produces extracellular superoxide molecules which can then form additional toxic products such as hydrogen peroxide and hydroxyl free radicals. It has long been known that opsonized zymosan is a powerful activator of the respiratory burst system. We found this activation could be inhibited by antibodies to complement receptors in the nanomolar range. Dapsone and indomethacin, two antiinflammatory agents that may have therapeutic potential in Alzheimer disease, were weakly inhibitory (10(-4) M range).(ABSTRACT TRUNCATED AT 250 WORDS)