Beta-protein deposition: a pathogenetic link between Alzheimer's disease and cerebral amyloid angiopathies

Proteomic Analysis of Amyloid Corneal Aggregates from TGFBI-H626R Lattice Corneal Dystrophy Patient Implicates Serine-Protease HTRA1 in Mutation-Specific Pathogenesis of TGFBIp

TGFBI-associated corneal dystrophies are inherited disorders caused by TGFBI gene variants that promote deposition of mutant protein (TGFBIp) as insoluble aggregates in the cornea. Depending on the type and position of amino acid substitution, the aggregates may be amyloid fibrillar, amorphous globular or both, but the molecular mechanisms that drive these different patterns of aggregation are not fully understood. In the current study, we report the protein composition of amyloid corneal aggregates from lattice corneal dystrophy patients of Asian origin with H626R and R124C mutation and compared it with healthy corneal tissues via LC-MS/MS. We identified several amyloidogenic, nonfibrillar amyloid associated proteins and TGFBIp as the major components of the deposits. Our data indicates that apolipoprotein A-IV, apolipoprotein E, and serine protease HTRA1 were significantly enriched in patient deposits compared to healthy controls. HTRA1 was also found to be 7-fold enriched in the amyloid deposits of patients compared to the controls. Peptides sequences (G511DNRFSMLVAAIQSAGLTETLNR533 and Y571HIGDEILVSGGIGALVR588) derived from the fourth FAS-1 domain of TGFBIp were enriched in the corneal aggregates in a mutation-specific manner. Biophysical studies of these two enriched sequences revealed high propensity to form amyloid fibrils under physiological conditions. Our data suggests a possible proteolytic processing mechanism of mutant TGFBIp by HTRA1 and peptides generated by mutant protein may form the β-amyloid core of corneal aggregates in dystrophic patients.

An Ancillary Tool for the Diagnosis of Amyloid A Amyloidosis in a Variety of Domestic and Wild Animals

Immunohistochemistry, the standard method for diagnosing amyloid A (AA) amyloidosis, is limited in animals because it requires a large array of animal-specific anti-AA antibodies, not commercially available. The Shtrasburg method (SH method) is a highly specific and sensitive technique, helping in the diagnosis and determination of AA amyloidosis in humans. The aim of this study is to determine whether the SH method is applicable in the diagnosis of AA amyloidosis in a variety of animals. Tissue samples were obtained from animals suffering from spontaneous or experimentally induced AA amyloidosis (mice, hamsters, guinea pigs, cheetahs, cats, cows, ducks, a dog, a goose, a chicken, and a turaco). Detection of the amyloid and quantitative evaluation were performed using Congo red staining, and specific AA typing was performed by the potassium permanganate technique. The studied tissues were subjected to the SH method, which confirmed the AA nature of the amyloid deposit, by displaying in polyacrylamide gel electrophoresis protein bands consistent with the molecular weight of the species-specific AA, in all the animals examined, except mice, hamsters, and guinea pigs. N-terminal analysis of these bands corroborated their AA origin. We conclude that the SH method may be used as an ancillary simple tool for the diagnosis of AA amyloidosis in a large number of domestic and wild animals. Moreover, our findings further increase the feasibility of applying this method in humans.

Effect of aldehydes derived from oxidative deamination and oxidative stress on β-amyloid aggregation; pathological implications to Alzheimer’s disease

Formaldehyde and methylglyoxal are generated via deamination from methylamine and aminoacetone respectively catalyzed by semicarbazide-sensitive amine oxidase (SSAO). Malondialdehyde (MDA) and 4-hydroxynonenal (HNE) are end products of lipid peroxidation due to oxidative stress. These aldehydes are capable of inducing protein cross-linkage. Elevated levels of aldehydes were found in Alzheimer's disease (AD). These reactive metabolites may potentially play important roles in beta-amyloid (Abeta) aggregation related to the pathology of AD. In the present study thioflavin-T (ThT) fluorometry, an immuno-dot-blot assay and atomic force microscopy (AFM) were employed to reveal the effect of aldehydes on Abeta aggregation in vitro. The target on Abeta for interaction with formaldehyde was identified. The results support the involvement of endogenous aldehydes in amyloid deposition related to AD.

Potential implications of endogenous aldehydes in ?-amyloid misfolding, oligomerization and fibrillogenesis

Aldehydes are capable of inducing protein cross-linkage. An increase in aldehydes has been found in Alzheimer's disease. Formaldehyde and methylglyoxal are produced via deamination of, respectively, methylamine and aminoacetone catalyzed by semicarbazide-sensitive amine oxidase (SSAO, EC 1.4.3.6. The enzyme is located on the outer surface of the vasculature, where amyloidosis is often initiated. A high SSAO level has been identified as a risk factor for vascular disorders. Serum SSAO activity has been found to be increased in Alzheimer's patients. Malondialdehyde and 4-hydroxynonenal are derived from lipid peroxidation under oxidative stress, which is also associated with Alzheimer's disease. Aldehydes may potentially play roles in beta-amyloid aggregation related to the pathology of Alzheimer's disease. In the present study, thioflavin-T fluorometry, dynamic light scattering, circular dichroism spectroscopy and atomic force microscopy were employed to reveal the effect of endogenous aldehydes on beta-amyloid at different stages, i.e. beta-sheet formation, oligomerization and fibrillogenesis. Formaldehyde, methylglyoxal and malondialdehyde and, to a lesser extent, 4-hydroxynonenal are not only capable of enhancing the rate of formation of beta-amyloid beta-sheets, oligomers and protofibrils but also of increasing the size of the aggregates. The possible relevance to Alzheimer's disease of the effects of these aldehydes on beta-amyloid deposition is discussed.

Relationships in Alzheimer's disease between the extent of Abeta deposition in cerebral blood vessel walls, as cerebral amyloid angiopathy, and the amount of cerebrovascular smooth muscle cells and collagen

The relationship between degree of cerebral amyloid angiopathy (CAA) and the amount of smooth muscle cells (SMCs) and deposition of collagen IV fibres (COL IV) was investigated in the frontal and occipital cortex of 70 patients with autopsy confirmed Alzheimer's disease (AD). The extent of CAA was significantly greater in occipital than in frontal cortex, although SMC loss was greater in frontal than in occipital cortex. COL IV staining was significantly higher in occipital than in frontal cortex. The degree of SMC loss correlated with CAA, as Abeta40 but not as Abeta42 or total Abeta, in frontal cortex, but not in occipital cortex. Leptomeningeal arteries within occipital cortex showed significantly greater external diameter, greater wall thickness and greater luminal area than those in frontal cortex. The degree of CAA correlated with thickness of blood vessel wall and external diameter in frontal cortex, whereas extent of SMC loss correlated with thickness of blood vessel wall in occipital cortex. There were significant negative correlations between duration of disease and thickness of vessel wall, external diameter and luminal area. In patients with disease durations exceeding 10 years, external vessel diameter and thickness of the vessel wall were both halved compared with patients with durations less than 5 years; luminal area was reduced by about 75%. Blood vessels in AD undergo degenerative changes involving deposition of Abeta and COL IV with loss of SMC. SMC loss may relate to increasing Abeta deposition in early stages of disease, but this relationship may be lost with disease progression.

Pathogenesis of mental deficiency in trisomy 21

In trisomy 21, pathogenesis of mental retardation is still poorly understood although the knowledge of the genic content of chromosome 21 is steadily increasing. Short of discovering how to silence selectively one of the 3 chromosomes 21, no rational medication can be envisaged before pathogenesis has been unraveled, at least partially. A biochemical scheme of impairment of mental efficiency is presented. Secondarily, the possible deleterious effects of a given gene overdose are discussed. Cu/Zn SOD, cystathionine beta synthase, S 100 beta protein, phosphofructokinase, purine synthesis and adenosine pharmacology, thyroid disturbance, and elevated TSH with low rT3 as well as biopterine metabolism interferences are reviewed. It is observed that the metabolic paths controlled by these genes, although unrelated at first glance, are in fact tightly related by their effects, just as if synteny was in some way related to biochemical cooperation or mutually controlled regulation. Experiments in vitro have demonstrated a peculiar sensitivity of trisomic 21 lymphocytes to methotrexate. From this starting point, systematic research of special sensitivities has begun. Clinical observations and relevant statistical methods allow study of the speed of mental development under various medications. The interest of regulating thyroid metabolism, when needed, is exemplified. Reequilibration of monocarbon metabolism is discussed and the seemingly favourable effect of folinic acid medication in pseudo-Alzheimer complication is presented.

Chemical characterization of a lambda I amyloid protein isolated from formalin-fixed and paraffin-embedded tissue sections

Amyloid protein was isolated from formalin-fixed paraffin-embedded heart tissue sections from a patient with primary (AL) amyloidosis by extraction with 6 M guanidine HCl. SDS-PAGE analysis of extracted material showed a major band at 16 kDa and a minor band at 18 kDa. Edman degradation analysis before and after pyroglutamate aminopeptidase treatment showed that the amyloid protein contained N-terminal pyroglutamic acid and was derived from an immunoglobulin lambda light chain. Analysis of tryptic peptides from the extract identified the amyloid protein as a lambda I. Of particular interest is that almost the entire amyloid protein amino acid sequence could be obtained from the cardiac sections. These results demonstrate that formalin-fixed paraffin-embedded tissue sections can be used for extensive biochemical characterization of amyloid proteins and will become a valuable source for isolation and extensive biochemical characterization of amyloid proteins as they are now a valuable source for isolation of DNA for genetic analysis.

Micropurification techniques in the analysis of amyloid proteins

This review describes the different microtechniques developed for the extraction and purification of amyloid proteins from small specimens of fresh and formalin fixed tissues. These procedures differ with respect to solvent type, extraction conditions, and protein purification strategy. The advantages and disadvantages of the different microtechniques are discussed by taking into consideration tissue type (fresh of fixed) and size, amyloid type, and its content in the tissue. The review demonstrates the applicability of these techniques for the immunochemical and chemical characterisation of amyloid in different clinical forms of amyloidosis and in experimental small animal models. The clinical value of the applied microtechniques and their importance in the study of the pathogenesis of amyloid related diseases are outlined.

Microextraction and purification techniques applicable to chemical characterization of amyloid proteins in minute amounts of tissue

This article described micromethods useful for the extraction, purification, and amino acid sequencing of amyloid proteins contained in minute specimens obtained from patients with systemic forms of amyloidosis. We posit that these procedures can also be applied to the biochemical characterization of cerebral amyloid deposits. The selection of the techniques is dependent on the type of sample to be extracted (fresh or formalin fixed) as well as the amount of congophilic material present. Although amyloid proteins are isolated and purified more easily from fresh tissue, it must be noted that formalin-fixed specimens are available more readily for analysis due to the common diagnostic use of fine needle tissue biopsies and are therefore, important for both current and retrospective studies. Remarkably, despite the expected difficulties associated with formalin treatment we were able to extract and sequence amyloid proteins from fixed tissues presumably due to the resistance of amyloid to formalin cross-linking. Through the continued development of techniques for small-scale protein separation and application of highly sensitive microsequencing and mass spectral methods, exact identification of the protein contained in fibrillar amyloid deposits can be determined. Such information has therapeutic and prognostic relevance and can increase our understanding of the pathogenesis of amyloidosis.

Cerebrovascular transport of Alzheimer's amyloid beta and apolipoproteins J and E: possible anti-amyloidogenic role of the blood-brain barrier

It is uncertain whether soluble circulating amyloid beta (sA beta) is the precursor of amyloid beta (A beta) found in cerebrovascular and parenchymal amyloid lesions in Alzheimer's Disease, and if so, how the transition to the filamentous form is brought about. Several lines of evidence suggest that apolipoprotein E (apoE) and apolipoprotein J (apoJ) may be involved in the regulation of amyloidogenesis. They both bind sA beta/A beta in vivo and in vitro. It has been suggested that apoE may modulate beta-pleated conformation of A beta and therefore act as a proamyloidogenic factor. On the other hand, apoJ as a major carrier protein of sA beta in body fluids may keep the peptide in a soluble form, thus having an anti-amyloidogenic effect. Using a well established guinea-pig brain perfusion model we have studied the blood-brain barrier (BBB) processes involved in the regulation of cerebral capillary sequestration, transport and metabolism of i) sA beta 1-40 and sA beta 1-42, synthetic peptides identical to the 40 and 42 residue forms of A beta, found primarily in vascular deposits and senile plaques, respectively; and ii) apoJ, apoE3 and apoE4 alone, and in a complex with sA beta. Specific saturable BBB luminal binding of both peptides was followed by transport into brain parenchyma and metabolism at the abluminal side of the BBB and/or in brain. The capillary sequestration of sA beta 1-40 was significant, while retention by the microvasculature of sA beta 1-42 was negligible. Binding to microvessels and blood-to-brain transport of both intact apoJ and sA beta 1-40 apoJ complexes were among the highest ever recorded for peptides and proteins at the BBB in vivo. These processes appear to be mediated by glycoprotein 330 (gp330/megalin), a receptor for multiple ligands, including apoJ. In contrast, capillary retention and transport of apoE3, apoE4 and sA beta 1-40-apoE3 complex were low to negligible, while blood-brain transport of sA beta 1-40-apoE4 was moderate. It is suggested that normal BBB may have predominantly anti-amyloidogenic functions by i) degrading sA beta during blood-to-brain transport; ii) favoring sequestration and transport of apoJ alone and in complex with sA beta via gp330 receptor-mediated mechanism and iii) excluding apoE3 and apoE4 isoforms from brain.

Hereditary cerebral haemorrhage with amyloidosis, Dutch type (HCHWA-D): clinicopathological studies

Clinical and neuropathological findings are reported in 63 patients with hereditary cerebral haemorrhage with amyloid angiopathy. Patients had mostly recurrent strokes, and at least 80% of these were haemorrhages. Almost a third of the patients died within a year of their first and only recorded haemorrhage, half of them within two weeks. This angiopathy was restricted to the cerebral and cerebellar cortex and its covering leptomeninges. As the most important consequence, haemorrhagic infarcts and haemorrhages occurred in the subcortical white matter--that is, the region most vulnerable to impaired cortical circulation. Further development of these subcortical lesions gives rise to the fatal haemorrhages seen at necropsy. In so far as dementia occurs this is likely to result from multiple microinfarcts or haemorrhages. In most cases preamyloid lesions or diffuse plaques and early plaques were seen. No other type of plaque or neurofibrillary degeneration was found. The plaques occur in conjunction with the angiopathy, but may not occur even when the angiopathy is severe. In one patient plaques were totally absent. Angiopathy and plaques may be the result of the same mutation, the expression of which is governed by tissue factors or phenotypic differences between individual subjects.

Alzheimer's disease, beta-amyloidosis, and aging

Alzheimer's disease (AD) is rapidly moving from the obscure category of degenerative diseases to the more precise one of metabolic disorders. Recent discoveries have substantiated the hypothesis that AD results from the deposition of beta-amyloid, which is formed by polymers of a proteolytic fragment of the amyloid protein precursor (APP), and may induce intraneuronal aggregation of the microtubule-associated protein tau into paired helical filaments and neuronal death. There is also evidence that AD is a heterogeneous age-related disorder of multifactorial origin, which may arise as a consequence of point mutations of genes encoding APP or other proteins involved in its metabolism (familial AD), or a combination of genetic and non-genetic factors (sporadic AD). Familial AD displays genetic and phenotypic heterogeneity, meaning that mutations of different genes may cause the AD phenotype, and that different mutations of the same gene may cause phenotypically distinct disorders, including Alzheimer-type dementia and cerebral amyloid angiopathy with cerebral hemorrhages and stroke. On the other hand, aging, gender, head trauma, and variants of the apolipoprotein E gene have been shown to increase the risk of developing the more prevalent sporadic form of AD. The mechanisms by which these factors influence amyloidogenesis are beginning to be understood, and this will provide a rational basis for future therapy. Knowledge of the molecular basis of AD would eventually allow accurate risk prediction before the disease becomes clinically apparent, and better chances for early treatment and prevention.

Microvascular pathology and vascular basement membrane components in Alzheimer's disease

Several factors have highlighted the vasculature in Alzheimer's disease (AD): Cerebral amyloid angiopathy (CAA) is common, amyloid fibrils emanate from the vascular basement membrane (VBM), and similar forms of beta-amyloid are found in vascular and parenchymal amyloid accumulations. The present article discusses the presence of microvascular pathology in AD. Microangiopathy, in addition to neurofibrillary tangles, senile plaques, and CAA, is a common pathologic hallmark of AD. VBM components are associated with amyloid plaques, and nonamyloidotic alterations of the VBM occur in brain regions susceptible to AD lesions. Also, intra-VBM perivascular cells (traditionally called pericytes), a subset of which share the immunophenotype of microglia and other mononuclear phagocytic system (MPS) cells, have been implicated in vascular alterations and cerebrovascular amyloid deposition. Perivascular and parenchymal MPS cells have access to several sources of the beta-amyloid protein precursor, including platelets, circulating white cells, and neurons. MPS cells would thus be ideally situated to uptake and process the precursor, and deposit beta-amyloid in a fashion analogous to that seen in other forms of systemic and cerebral amyloidoses.

Unifying features of systemic and cerebral amyloidosis

Amyloidosis is a generic term for a group of clinically and biochemically diverse diseases that are characterized by the deposition of an insoluble fibrillar protein in the extracellular space. Over 16 biochemically distinct amyloids are known. Despite this diversity, all amyloids have a particular ultrastructural and tinctorial appearance, a beta-pleated sheet structure, and are codeposited with a group of amyloid-associated proteins. The most common amyloidosis is Alzheimer's disease (AD), where A beta is the main component of the amyloid. Recently it has been found that A beta exists as a normal soluble protein (sA beta) in biological fluids. This links AD more closely to some of the systemic amyloidoses, where the amyloid precursor is found in the circulation normally. Numerous mutations have been found in the A beta precursor (beta PP) gene, associated with familial AD. Many mutations are also found in some of the hereditary systemic amyloidoses. For example, over 40 mutations in the transthyretin (TTR) gene are associated with amyloid. However, both A beta and TTR related amyloid deposition can occur with no mutation. The pathogenesis of amyloid is complex, and appears to be associated with genetic and environmental risk factors that can be similar in the systemic and cerebral amyloidoses.

Spontaneous cerebral haemorrhage from cerebral amyloid angiopathy

Three cases of spontaneous intracerebral haemorrhage treated by acute evacuation of haematoma are described. All cases proved to have cerebral amyloid angiopathy as the primary cause of the haemorrhage. Only one patient survived. Previous reports are discussed.

The cellular pathology associated with Alzheimer beta-amyloid deposits in non-demented aged individuals

In this study, we have compared the cellular pathology associated with beta-amyloid (beta A) deposits which characterize Alzheimer's disease (AD) in demented patients with pathologically confirmed AD, with that in non-demented aged individuals. Brain sections from two severely demented AD cases, six non-demented individuals with beta A deposits, and six age-matched controls devoid of beta A deposits were double-immunostained with antibodies against beta A, and antibody markers for neurofibrillary tangles (NFT), astrocytes and microglial cells. We found that the severely demented patients displayed numerous plaques of variable morphology, most of which were associated with NFT, hypertrophied astrocytes and reactive microglial cells. In contrast, non-demented patients showed fewer plaques, few or not NFT and less astroglial and microglial reaction. The number of plaques with associated abnormal cellular elements were much lower in non-demented than in demented cases. Furthermore, classical plaques were more likely to be associated with abnormal cellular elements than diffuse plaques, which were most often devoid of any associated cellular change. These findings suggest that: (i) beta A plaques in non-demented individuals may represent an early stage of AD; (ii) beta A deposition is the first recognizable pathological abnormality of AD; and (iii) NFT, and astro- and microglial proliferation are later features, possibly secondary to the known dystrophic effects of the beta A peptide and other fragments of its precursor protein.

Epitope map of two polyclonal antibodies that recognize amyloid lesions in patients with Alzheimer's disease

Two synthetic peptides with sequences identical with those of fragments of the extracellular domain of the Alzheimer's-disease amyloid precursor protein (APP) were used to raise antibodies. SP28 comprises positions 597-624 of the APP695 isoform, whereas SP41 extends towards the N-terminus (amino acids 584-624) and contains the entire SP28 peptide. Using e.l.i.s.a. and inhibition experiments we identified the two beta-turn-containing segments 602-607 and 617-624 as the epitopes recognized by anti-SP41 and anti-SP28 respectively. Both antibodies immunolabelled amyloid lesions in brains from Alzheimer's-disease patients and patients with related disorders, whereas they were unreactive in control brains. However, when probed on immunoblots, anti-SP28 failed to detect full-length APP from baculovirus-infected Sf9 cells, and anti-SP41 reacted weakly compared with other anti-APP antisera. The data suggest that these antibodies are directed to conformational epitopes not existent in the native molecules but present after alternative APP processing.

Distribution of Alzheimer's disease amyloid protein precursor in normal human and rat nervous system

Alzheimer's disease and cerebral amyloid angiopathies (CAA) are clinically heterogeneous diseases, but pathogenically related by the deposition of beta A4-amyloid in the brain in the form of neuritic plaques and/or vascular infiltrates. Antibodies directed against the N-terminal region of the predicted sequence of the beta A4 amyloid protein precursor (APP) were used to investigate the cellular distribution of this protein in the brain of normal humans and rats. We found a widespread presence of APP throughout the nervous tissue, including neurons, blood vessels, meningeal membranes, choroid plexus and ependymal cells. The highest APP immunoreactivity in both species was found in neuronal cell bodies and their processes, and around blood vessels. These findings may account for the clinical, pathological and aetiological differences found among the beta A4-amyloidosis.

Re-examination of ex-boxers' brains using immunohistochemistry with antibodies to amyloid beta-protein and tau protein

A histopathological study was carried out on the brains of eight ex-boxers (ages 56 to 83) using conventional histological staining methods and immunocytochemistry with antibodies to amyloid beta-protein and the PHF-related tau protein. All cases showed a large number of tau-immunoreactive neurofibrillary tangles and also beta-protein immunoreactive senile plaques in the cortex. In the areas with many neurofibrillary tangles, neuropil threads with tau-immunoreactivity were also observed, and some of the senile plaque lesions were surrounded by abnormal neurites with tau-immunoreactivity. Moreover, three cases revealed beta-protein-type cerebrovascular amyloid deposits on both leptomeningeal and cortical blood vessels. The present observations indicate that the cerebral pathology of dementia pugilistica is very similar to that of Alzheimer's disease and suggest that these two disorders share some common etiological and pathogenic mechanisms.

Early senile plaques in Alzheimer's disease demonstrated by histochemistry, immunocytochemistry, and electron microscopy

To clarify early pathologic changes in Alzheimer's disease, the brains from two cases from a single family with this disease were examined. A mother who died at age 75 with severe dementia showed an abundance of typical senile plaques, neurofibrillary tangles, and cerebrovascular amyloidosis. The senile plaque and cerebrovascular amyloid were strongly immunoreactive to anti-beta protein antibody. Her son manifested erratic and bizarre behavior, and was suspected of having committed suicide at age 52. His brain weight and macroscopic observations were normal; however, Bielschowsky's silver impregnation and methenamine silver stains showed numerous argyrophilic plaque-like lesions in the neocortex. They were weakly immunolabeled by anti-beta protein antibody, but lacked any abnormal neurites of Congophilic amyloid deposits. These lesions resembled the "type 3" immunoreactive lesions (previously reported by us in Alzheimer's disease and Down's syndrome) which seem to be an early stage of senile plaque formation. These putative early plaque lesions were also examined by methenamine silver electron microscopy, and were seen to consist of loose aggregations of irregular spindle-shaped structures with a heavy deposition of silver grains, with genuine amyloid fibrils not being apparent. It is believed that the accumulation of beta-protein immunoreactive material without amyloid fibril formation might be an initial step in the development of the senile plaque, and that the son, having extensive cortical involvement with type 3 plaque lesions, demonstrated clinical manifestations of less completely developed Alzheimer's disease.

Immunohistochemical study of cerebral amyloid angiopathy. III. Widespread Alzheimer A4 peptide in cerebral microvessel walls colocalizes with gamma trace in patients with leukoencephalopathy

Brain tissue from 11 patients with cerebral amyloid angiopathy, changes of Alzheimer's disease, and variable degrees of subcortical leukoencephalopathy was examined by immunohistochemical methods, using primary antibodies to peptide segments representing portions of the Alzheimer A4 (beta-) peptide or gamma-trace peptide (seen most commonly in Icelandic patients with cerebral hemorrhage (hereditary cerebral hemorrhage with amyloidosis [HCHWA-I]). Variable A4 immunostaining was seen within cortical (and rarely white matter) parenchyma in the form of senile plaques (with or without central cores), and within capillary and arteriolar walls. Within individual patients, A4 deposits were often primarily parenchymal or vascular, and when they were vascular they tended to be more prominent in arteriolar than in capillary wall segments. Perivascular A4 deposits were often detected around strongly immunoreactive microvessels. Gamma-trace immunoreactivity was noted in many A4-positive microvessel walls, but staining was always less intense than with the anti-A4 antibody. We conclude that patients with severe cerebral amyloid angiopathy may show wide variation in the severity and topography of A4 deposits within brain parenchyma. A4 may colocalize with gamma-trace peptide, suggesting that A4 and gamma-trace forms of cerebral amyloid angiopathy may not be as biochemically distinctive as has been suggested. Other proteases or protease inhibitors may contribute to the pathogenesis of cerebral amyloid angiopathy or cerebral amyloid angiopathy-related stroke syndromes.

Amyloid beta protein precursor gene and hereditary cerebral hemorrhage with amyloidosis (Dutch)

Human hereditary cerebral hemorrhage with amyloidosis of the Dutch type (HCHWA-D), an autosomal dominant form of cerebral amyloid angiopathy (CAA), is characterized by extensive amyloid deposition in the small leptomeningeal arteries and cortical arterioles, which lead to an early death of those afflicted in their fifth or sixth decade. Immunohistochemical and biochemical studies have indicated that the amyloid subunit in HCHWA-D is antigenically related to and homologous in sequence with the amyloid beta protein isolated from brains of patients with Alzheimer's disease and Down syndrome. The amyloid beta protein is encoded by the amyloid beta protein precursor (APP) gene located on chromosome 21. Restriction fragment length polymorphisms detected by the APP gene were used to examine whether this gene is a candidate for the genetic defect in HCHWA-D. The data indicate that the APP gene is tightly linked to HCHWA-D and therefore, in contrast to familial Alzheimer's disease, cannot be excluded as the site of mutation in HCHWA-D.

Immunohistochemical characterization of cerebrovascular amyloid in 46 autopsied cases using antibodies to beta protein and cystatin C

Using immunohistochemical staining methods with antibodies to amyloid beta protein and human cystatin C, we examined cerebrovascular amyloid protein in the brains from 46 cases with cerebral amyloid angiopathy (seven with Alzheimer's disease, one with Down's syndrome, 18 with intracranial hemorrhage, 10 with cerebral infarction, and 10 elderly patients without any neurologic disorder). All cerebrovascular amyloid deposits in these 46 cases were consistently immunoreactive to anti-beta protein antibody. However, in nine cases some vascular walls with strong beta protein immunoreactivity also reacted less intensely with the anti-cystatin C antiserum. Of these nine cases, seven showed relatively heavy cerebrovascular amyloid deposition, and all seven had suffered a fatal subcortical hemorrhage presumably caused by cerebral amyloid angiopathy. Previous limited studies have suggested that the amyloid protein seen in elderly individuals with cerebral amyloid angiopathy is composed of beta protein. However, subcortical hemorrhage rarely occurs in such individuals. Our study shows that aged patients with different brain disorders commonly suffer from beta protein-type cerebral amyloid angiopathy, and we also suggest that the severity of beta protein-type cerebrovascular amyloid deposition is a fundamental factor in cerebral amyloid angiopathy-induced brain hemorrhage in the elderly. The nature of the cystatin C-immunoreactive substance in some of these vascular lesions is uncertain, but it might conceivably play an additional important role in the pathogenesis of brain hemorrhage in these cases.

Cerebral amyloid angiopathy as a cause of subarachnoid hemorrhage

Cerebral amyloid angiopathy is a pathologic condition characterized by the deposition of amyloid in the walls of small vessels in the cerebral cortex and meninges. Intracerebral hemorrhage is common in persons with this condition, but pure subarachnoid or subdural hemorrhage is rarely seen. Recently, the existence of two types of amyloid proteins related to cerebral amyloid angiopathy, beta protein and cystatin C, has been reported, and immunohistochemical methods using antisera to these proteins have become available. We describe a patient with fatal subarachnoid hemorrhage presumably caused by beta protein-type cerebral amyloid angiopathy, which was demonstrated immunohistochemically by using a monoclonal antibody to a synthetic peptide corresponding to residues 8-17 of beta protein. We suggest that beta protein-type cerebral amyloid angiopathy is a possible etiologic factor in subarachnoid hemorrhage of unknown cause.

Primary systemic amyloidosis--a diagnostic primer

Primary systemic amyloidosis (immunoglobulin light chain-derived) (AL) is an uncommon dysproteinemia with highly varied initial clinical manifestations. Among 153 patients with this disorder, the median survival was 20.4 months (5-year survival, 19.6%). The worst outcome was associated with overt congestive heart failure (median survival, 7.7 months; 5-year survival, 2.4%). The patients with the best outcome were those who had amyloid neuropathy without associated cardiac or renal involvement (median survival, 39.7 months; 5-year survival, 31.6%). Serum protein electrophoresis and immunoelectrophoresis are the most important tests because a monoclonal protein can be detected in almost two-thirds of the patients. When screening of both serum and urine is performed, a monoclonal protein is found in 86% of patients. Such screening is helpful if primary systemic amyloidosis is to be detected and treated early.

Binswanger's disease (Part II): Pathogenesis of subcortical arteriosclerotic encephalopathy and its relation to other dementing processes

Subcortical arteriosclerotic encephalopathy (SAE) is a common though infrequently recognized dementia of the elderly. The unique vascular anatomy of the subcortical white matter and central brain stem probably predisposes those regions to chronic ischemia and incomplete infarction in the presence of various cardiovascular and hemodynamic insults. Recent studies have begun to define the risk factors for SAE, and others have shown it to be a condition frequently comorbid with the dementias of Alzheimer's disease, the multi-infarct state, and normal pressure hydrocephalus. Recent research into the etiologies of these disorders suggest certain pathogenetic links between them, strongly implying that they are not neatly distinct disease entities, as is commonly believed, and accounting for some of the overlap between these dementing illnesses seen clinically.