Cerebral amyloid angiopathy: an overview

Cerebral amyloid angiopathy and gene polymorphisms

Cerebral amyloid angiopathy (CAA) is characterized by cerebrovascular amyloid deposition, associated with intracerebral hemorrhage and other cerebrovascular disorders and dementia. Several types of CAA have been identified in association with various amyloid proteins including amyloid beta protein (Abeta), cystatin C, prion protein, ABri/ADan, transthyretin, and gelsolin. Hereditary forms of CAA are associated with mutations in the genes coding these proteins or their precursors. Sporadic CAA of Abeta type is most common in elderly individuals as well as patients with Alzheimer disease (AD). Several gene polymorphisms have been reported to be associated with sporadic CAA or CAA-related hemorrhage, including apolipoprotein E (APOE), presenilin 1 (PS1), and alpha1-antichymotrypsin (ACT). As for the APOE, which has been well studied for CAA as well as AD and Abeta deposition, the epsilon4 allele is found to be associated with CAA, and the epsilon2 with CAA-related hemorrhage. Recently, we investigated whether gene polymorphisms of neprilysin (NEP), an Abeta-degrading enzyme, and the transforming growth factor (TGF)-beta1 (TGF-beta1), a multifunctional cytokine implicated in Abeta deposition, are associated with sporadic CAA. Concerning a GT repeat polymorphism in the enhancer/promoter region of the NEP, the shorter repeat alleles were associated with the CAA severity. The T/C polymorphism at codon 10 in exon 1 of the TGF-beta1 was also associated with the severity of CAA. These data suggest that multiple gene polymorphisms, including molecules related to the Abeta cascade, could be associated with the risk of sporadic CAA.

The decision to anticoagulate: assessing whether benefits outweigh the risks for patients with atrial fibrillation

In a review of relevant articles from the Medline database on stroke risk in atrial fibrillation (AF) and adverse events related to anticoagulation treatment, we found that research to date shows a major potential benefit of warfarin therapy (International Normalized Ratio [INR] 2.0-3.0) for patients with AF (68% risk reduction in primary stroke prevention with warfarin vs. placebo). Despite this highly significant reduction in stroke risk, fewer than 50% of eligible patients are treated, in many cases because of fears of intracranial hemorrhage (ICH). The decision to implement anticoagulant therapy to improve outcome requires balancing the decreased risk for stroke against the increased risk for ICH. Various methods have been developed to define patient-specific stroke risk. In contrast, risk for ICH strongly correlates with the intensity of anticoagulation, which is an unpredictable but controllable variable requiring frequent dose adjustments. Recent studies have also identified subgroups of patients with neurologic pathologies who are at increased risk for ICH. However, when the INR is properly controlled, the benefit from anticoagulation therapy for patients with AF and other risk factors for stroke exceeds the risk for ICH. Careful monitoring of anticoagulation and warfarin dose titration to maintain the INR between 2.0 and 3.0 is critical for reducing the risk for ICH, as is excluding patients with neurologic conditions that increase the likelihood of ICH. Future developments, such as the introduction of oral direct thrombin inhibitors with more predictable pharmacokinetics than warfarin, may further improve the benefit-to-risk ratio of anticoagulation therapy for patients with AF.

Long-Term Outcome after Spontaneous Cerebellar Haemorrhage

We analysed the clinical and radiological findings and the long-term outcome after 49 +/- 34 months in 75 patients (42 men, aged 67 +/- 11 years) with spontaneous cerebellar haemorrhage (SCH). At the follow-up examination, 36 patients had died. Outcome was excellent [Rankin Scale (RS) score 0 + 1] in 22 survivors, 4 patients were moderately (RS score 2 + 3) and 13 patients were severely disabled (RS score 4 + 5). Prognostic factors are haematoma volume, intubation, hydrocephalus and clinical signs of brainstem involvement. Of the 28 surgically treated patients, outcome was favourable (RS score 0 - 2) in 4 patients only, 6 were severely disabled (RS score 3 - 6) and 18 patients had died. We conclude that the long-term outcome after SCH is frequently favourable. Because patients who were surgically treated had less favourable clinical and radiological findings, a good long-term outcome was rarely present in this group.

Domain swapping in N-truncated human cystatin C

Human cystatin C (HCC) inhibits papain-like cysteine proteases by a binding epitope composed of two beta-hairpin loops and the N-terminal segment. HCC is found in all body fluids and is present at a particularly high level in the cerebrospinal fluid. Oligomerization of HCC leads to amyloid deposits in brain arteries at advanced age but this pathological process is greatly accelerated with a naturally occurring Leu68Gln variant, resulting in fatal amyloidosis in early adult life. When proteins are extracted from human cystatin C amyloid deposits, an N-terminally truncated cystatin C (THCC) is found, lacking the first ten amino acid residues of the native sequence. It has been shown that the cerebrospinal fluid may cause this N-terminal truncation, possibly because of disintegration of the leucocytes normally present in this fluid, and the release of leucocyte proteolytic enzymes. HCC is the first disease-causing amyloidogenic protein for which oligomerization via 3D domain swapping has been observed. The aggregates arise in the crystallization buffer and have the form of 2-fold symmetric dimers in which a long alpha-helix of one molecule, flanked by two adjacent beta-strands, has replaced an identical domain of the other molecule, and vice versa. Consistent with a conformational change at one of the beta-hairpin loops of the binding epitope, the dimers (and also any other oligomers, including amyloid aggregates) are inactive as papain inhibitors. Here, we report the structure of N-truncated HCC, the dominant form of cystatin C in amyloid deposits. Although the protein crystallized under conditions that are drastically different from those for the full-length protein, the structure reveals dimerization by the same act of domain swapping. However, the new crystal structure is composed of four independent HCC dimers, none of which has the exact 2-fold symmetry of the full-length dimer. While the four dimers have the same overall topology, the exact relation between the individual domains shows a variability that reflects the flexibility at the dimer-specific open interface, which in the case of 3D domain-swapped HCC consists of beta-interactions between the open hinge loops and results in an unusually long intermolecular beta-sheet. The dimers are engaged in further quaternary interactions resulting in spherical, closed octameric assemblies that are identical to that present in the crystal of the full-length protein. The octamers interact via hydrophobic patches formed on the surface of the domain-swapped dimers as well as by extending the dimer beta-sheet through intermolecular contacts.

Co-accumulation of vascular endothelial growth factor with beta-amyloid in the brain of patients with Alzheimer's disease

Alzheimer's disease (AD) is accompanied by the progressive deposition of beta-amyloid (Abeta) in both senile plaques and cerebral blood vessels, loss of central neurons, and vessel damage. Cerebral hypoperfusion is one of the major clinical features in AD and likely plays a critical role in its pathogenesis. In addition to its major roles in angiogenesis, vascular endothelial growth factor (VEGF) has neurotrophic and neuroprotective effects. VEGF is an ischemia-inducible factor and increased expression of VEGF often occurs in AD. Although the presence of VEGF immunoreactivity in the AD brain has been described previously, the direct interaction of VEGF with Abeta has not been established. Here, we show that VEGF is co-localized with Abeta plaques in the brains of patients with AD. In vitro experiments show that VEGF binds to Abeta with high affinity (K(D) approximate to 50 pM). VEGF is co-aggregated with Abeta without any apparent effect on the rate of aggregation, strongly binds to pre-aggregated Abeta, and is very slowly released from the co-aggregated complex. Continuous deposition of VEGF in the amyloid plaques most likely results in deficiency of available VEGF under hypoperfusion and, thus, may contribute to neurodegeneration and vascular dysfunction in the progression of AD.

The increasing need for anticoagulant therapy to prevent stroke in patients with atrial fibrillation

Ischemic stroke, a major complication of atrial fibrillation (AF), is believed to result from atrial thrombus formation caused by ineffective atrial contraction. Oral anticoagulant therapy effectively reduces the risk of ischemic stroke in patients with AF; this therapy is recommended for patients with any frequency or duration of AF and other risk factors for stroke, such as increased age (>75 years), hypertension, prior stroke, left ventricular dysfunction, diabetes, or heart failure. Recently published data comparing rate-control and rhythm-control strategies in AF emphasized the importance of maintaining an international normalized ratio higher than 2.0 during warfarin therapy and the need for continuing anticoagulant therapy to prevent stroke in high-risk patients, even if the strategy is rhythm control. Hemorrhagic complications can be minimized by stringent control of the international normalized ratio (particularly in elderly patients) and appropriate therapy for comorbidities such as hypertension, gastric ulcer, and early-stage cancers. Undertreatment of patients with AF is a continuing problem, particularly in the elderly population. Patients perceived as likely to be noncompliant, such as the functionally impaired, are less likely to receive warfarin therapy. However, stroke prevention with anticoagulants is cost-effective and improves quality of life, despite the challenges of maintaining appropriate anticoagulation with monitoring and warfarin dose titration. New medications in development with more predictable dosing and fewer drug-drug interactions may reduce the complexities of achieving optimal anticoagulation and increase the practicality of long-term anticoagulant therapy for patients with AF at risk of stroke.

Prevention of Domain Swapping Inhibits Dimerization and Amyloid Fibril Formation of Cystatin C

Amyloidogenic proteins like cystatin C and prion proteins have been shown to form dimers by exchange of subdomains of the monomeric proteins. This process, called "three-dimensional domain swapping," has also been suggested to play a part in the generation of amyloid fibrils. One variant of cystatin C, L68Q cystatin C, is highly amyloidogenic, and persons carrying the corresponding gene suffer from massive cerebral amyloidosis leading to brain hemorrhage and death in early adult life. The present work describes the production of two variants of wild type and L68Q cystatin C with disulfide bridges at positions selected to inhibit domain swapping without affecting the biological function of the four cystatin C variants as cysteine protease inhibitors. The capacity of the four variant proteins to form dimers was tested and compared with that of wild type and L68Q cystatin C. In contrast to the latter two proteins, all four protein variants stabilized by disulfide bridges were resistant toward the formation of dimers. The capacity of the two stabilized variants of wild type cystatin C to form amyloid fibrils was investigated and found to be reduced by 80% compared with that of wild type cystatin C. In an effort to investigate whether exogenous agents could also suppress the formation of dimers of wild type and L68Q cystatin C, a monoclonal antibody or carboxymethylpapain, an inactivated form of a cysteine protease, was added to systems inducing dimerization of wild type and L68Q cystatin C. It was observed that catalytic amounts of both the monoclonal antibody and carboxymethylpapain could suppress dimerization.

Immunohistochemical study of distribution of apolipoproteins E and D in human cerebral beta amyloid deposits

Several molecules are known to be closely associated with amyloid deposits in human brain. Among these, apolipoproteins such as apolipoproteins E (apo E) and J (apo J) have been found in two neuropathological hallmarks of Alzheimer's disease (AD) and cerebral amyloid angiopathy (CAA): senile plaques (SPs) and cerebrovascular amyloid. These apolipoproteins may be implicated in amyloid fibrillogenesis. Apo D is a multiligand-multifunctional glycoprotein present in SPs, as we previously reported. The aim of this work is to study the link between immunolocalization of apo E and apo D in AD and CAA brains. Both apolipoproteins were found in all types of SPs, but apo E was observed more often than apo D in mature plaques. Whereas apo E is always located overlapping the amyloid core, apo D seems to situate preferably around and near the amyloid. Immunohistochemistry revealed that these apolipoproteins behave differently in cerebral vessels. Apo E labeling in vessels appears mainly linked to amyloid deposits, whereas apo D shows a distribution almost opposite to that of apo E. This could be an indication of the different roles that each apolipoprotein plays in the pathogenesis of amyloid deposition.

Cerebral amyloid angiopathy: pathogenesis and effects on the ageing and Alzheimer brain

Cerebral amyloid angiopathy (CAA) is a feature of ageing and Alzheimer's disease (AD); it is also associated with intracerebral hemorrhage and stroke. Here, the pathogenesis of CAA and its effects on the brain are reviewed and the possible effects of CAA on therapies for Alzheimer's disease are evaluated. Tracer experiments in animals and observations on human brains suggest that peptides such as A beta are eliminated along the peri-arterial interstitial fluid drainage pathways that are effectively the lymphatics of the brain. In CAA, A beta becomes entrapped in drainage pathways in the walls of cerebral arteries, reflecting a failure of elimination of A beta from the ageing brain. One consequence of failure in clearance of A beta is accumulation of soluble and insoluble A beta associated with cognitive decline in AD. Replacement of vascular smooth muscle cells by A beta occurs in severe CAA with weakening of artery walls and increased risk of vessel rupture and intracerebral hemorrhage. Risk factors for CAA include mutations of the amyloid precursor protein (APP) gene and possession of the epsilon 4 allele of apolipoprotein E. There is also evidence that cerebrovascular disease may be a factor in the failure of elimination of A beta along perivascular pathways in sporadic AD; this would link ageing in cerebral arteries with the pathogenesis of Alzheimer's disease. If therapeutic agents, including anti-A beta antibodies, are to be used to eliminate A beta in the treatment of Alzheimer's disease, the effects of CAA on the treatment and the effects of the treatment on the CAA need to be considered.

Relationship between lobar intracerebral hemorrhage and leukoencephalopathy associated with cerebral amyloid angiopathy: clinicopathological study of 64 Japanese patients

Cerebral amyloid angiopathy (CAA) has two major clinical manifestations: intracerebral hemorrhages and ischemic lesions. Among these, the lobar type of intracerebral hemorrhage (ICH) is a well-known clinical manifestation, while the CAA-related diffuse deep white matter degeneration known as leukoencephalopathy is thought to be rare. The characteristics of CAA-related leukoencephalopathy are still incompletely understood, and the relationship between lobar ICH and leukoencephalopathy in patients with CAA has not been properly clarified. The main purpose of this study is to elucidate the clinical and histopathological features of CAA-related lobar ICH and leukoencephalopathy in order to determine whether the degree of deep white matter degeneration parallels the severity of CAA-associated vasculopathies that lead to vascular wall rupture. We studied 64 Japanese patients with histopathologically proven amyloid beta protein (A beta) type CAA presenting with lobar ICH (52 biopsy and 12 autopsy). In this study, a total of 106 hematomas were observed. CAA-related cerebral hemorrhages tend to occur recurrently and multifocally. Multiple simultaneous labor hemorrhages occasionally developed (9.4%). CAA-related ICH in the sixth decade was not rare (14.1%). Although most patients suffered relapsing and/or multiple severe ICH, no patient in our series presented with diffuse leukoencephalopathy. In conclusion, A beta type cerebrovascular amyloid deposition causes recurrent, multifocal, and often multiple simultaneous ICH even in relatively younger elderly patients, but rarely produces diffuse leukoencephalopathy. This suggests that CAA-associated vasculopathies that cause vascular wall rupture do not always lead to ischemic deep white matter degeneration, and that there may be another unknown pathogenetic mechanism producing the latter CAA-related white matter lesion.

Secretion and accumulation of Abeta by brain vascular smooth muscle cells from AbetaPP-Swedish transgenic mice

Alzheimer amyloid-beta is deposited in the neuropil and in brain blood vessels in transgenic Tg2576 mice that overexpress human amyloid-beta precursor protein (AbetaPP) containing the Swedish mutation (AbetaPP-Swe). Because the AbetaPP transgene in Tg2576 mice is placed behind the PrP promoter, all amyloid-beta, including vascular amyloid, is considered to be of neuronal origin. We studied the expression of the transgenic AbetaPP in smooth muscle cells cultured from brain blood vessels from Tg2576 mice. We found that brain vascular smooth muscle cells overexpressed human AbetaPP-Swe approximately 4 times the physiological levels of mouse AbetaPP. The cultured cells secreted abundant Abeta1-40 and Abeta1-42 and formed intracellular Abeta-immunoreactive granules. The percentage of cells containing intracellular Abeta and the amount of intracellular Abeta were significantly higher in cultures obtained from 14-month-old than from 4-month-old mice, as tested on first or second passages. During cell senescence in culture, intracellular accumulation of Abeta and C-terminal fragments of AbetaPP increased in cells derived from both 4- and 14-month-old mice. Vascular muscle cells from Tg2576 mice appear to be a valuable model of the intracellular accumulation of Abeta. We suggest that vascular muscle cells may be involved in the production of cerebrovascular amyloid in Tg2576 mice.

Association of neprilysin polymorphism with cerebral amyloid angiopathy

OBJECTIVES

The risk of sporadic cerebral amyloid angiopathy (CAA) may be associated with genetic polymorphisms of molecules related to anabolism or catabolism of amyloid beta protein (Abeta). The authors investigated whether a polymorphism of the gene (NEP) coding for neprilysin, an enzyme catabolising Abeta, is associated with CAA.

METHODS

The study analysed the GT repeat polymorphism in the enhancer/promoter region of NEP and severity of CAA in 164 necropsied elderly Japanese subjects.

RESULTS

The subjects had NEP polymorphisms with 19 to 23 GT repeats and were classified into nine genotypes. CAA severity was significantly higher in the subjects with up to 40 repeats in total than those with more than 40 repeats (p=0.005). There was a significant correlation between the number of the shorter alleles (19 or 20 repeats) and CAA severity (p=0.024). In addition, there was no interaction between the NEP polymorphism and apolipoprotein E genotype.

CONCLUSIONS

These results suggest the association between the NEP polymorphism and the risk of CAA. Further study using more samples from populations with different ethnic backgrounds is necessary.

Amyloid beta-protein stimulates the expression of urokinase-type plasminogen activator (uPA) and its receptor (uPAR) in human cerebrovascular smooth muscle cells

The accumulation of fibrillar amyloid-beta protein (A beta) in cerebral blood vessels, a condition known as cerebral amyloid angiopathy (CAA), is a key pathological feature of Alzheimer's disease and certain related disorders and is intimately associated with cerebrovascular cell death both in vivo and in vitro. Moreover, severe CAA leads to loss of vessel wall integrity and cerebral hemorrhage. Although the basis for these latter pathological consequences in CAA remains unresolved alterations in local proteolytic mechanisms may be involved. Here we show that pathogenic forms of A beta stimulate the expression of plasminogen activator activity in cultured human cerebrovascular smooth muscle (HCSM) cells, an in vitro model of CAA. RNase protection assays and plasminogen zymography showed that urokinase-type plasminogen activator (uPA) was responsible for this activity. There was preferential accumulation of uPA on the HCSM cell surface that was mediated through a concomitant increase in expression of the uPA receptor. In the presence of plasminogen there was robust degradation of A beta that was added to the HCSM cells resulting in restoration of cell viability. This suggests that increased expression of uPA may initially serve as a protective mechanism leading to localized degradation and clearance of the pathogenic stimulus A beta. On the other hand, chronic expression of uPA and plasminogen activation led to a profound loss of HCSM cell attachment. This suggests that a similar prolonged effect in vivo in the cerebral vessel wall may contribute to loss of integrity and cerebral hemorrhage in CAA.

Capillary and arterial cerebral amyloid angiopathy in Alzheimer's disease: defining the perivascular route for the elimination of amyloid beta from the human brain

Accumulation of amyloid beta (Abeta) in the extracellular spaces of the cerebral cortex and in blood vessel walls as cerebral amyloid angiopathy is a characteristic of Alzheimer's disease (AD) and the ageing human brain. Studies in animals suggest that Abeta is eliminated from the brain either directly into the blood or along perivascular interstitial fluid drainage channels. The aim of the present study is to define the perivascular route for the drainage of Abeta from the human brain. Smears and paraffin sections of post-mortem cortical tissue from 17 cases of AD and from two controls were stained with thioflavin and for Abeta by immunohistochemistry. Histology and confocal microscopy showed that deposits of Abeta in the cortical parenchyma were continuous with Abeta in capillary walls but Abeta in artery walls was not in continuity with Abeta in brain parenchyma. Quantitative studies supported these observations. The results of this study suggest that when Abeta is eliminated from the extracellular spaces of the human brain by the perivascular route, it enters pericapillary spaces and from there drains along the walls of cortical arteries to leptomeningeal arteries. Factors such as overproduction of Abeta, entrapment of Abeta in drainage pathways and poor drainage of Abeta due to functional changes in ageing arteries might result in the failure of elimination of Abeta from the ageing brain and play a major role in the pathogenesis of AD. Such factors might affect therapies for AD that entail administration of anti-Abeta antibodies to eliminate Abeta from the human brain.

Serial CT and MRI findings in a patient with isolated angiitis of the central nervous system associated with cerebral amyloid angiopathy

We report serial CT and MRI findings in a biopsy-proven case of cerebral amyloid angiopathy (CAA) with isolated angiitis of the central nervous system (CNS). A 69-year-old man had developed dizziness, dementia, and generalized seizure during the preceding 4 years. An initial examination by brain CT and MRI showed bilateral symmetrical periventricular lesions closely resembling those of Binswanger's disease. Subsequently, the lesions expanded slowly, involving a large area of the right cerebral hemisphere with an obvious mass effect. Since a primary brain tumor was suspected, a brain biopsy was performed, and histopathological examination revealed amyloid beta protein CAA within the meningocortical vessels associated with perivascular monocytic cuffing, indicating the presence of isolated angiitis of the CNS. Multinucleated giant cells containing intracytoplasmic beta protein amyloid around a heavily amyloid-laden cortical vessel were also observed. This is the first case report to show sequential radiographical studies of the leukoencephalopathy associated with CAA and isolated angiitis of the CNS.

Risk factors for cerebral amyloid angiopathy in the elderly

To elucidate risk factors for cerebral amyloid angiopathy (CAA) in the elderly, we have investigated 201 autopsy cases of elderly Japanese (ages: 62-104 years), including 82 patients with Alzheimer's disease (AD). Severity of CAA showed no relationship with the history of hypertension, hyperlipidemia, or diabetes mellitus, nor with severity of atherosclerosis of cerebral and systemic arteries, indicating that common vascular risk factors would not be related to CAA. Incidence and severity of CAA were significantly higher in the AD cases compared with the non-AD cases (p < 0.0001). Severity of CAA correlated with densities of senile plaques and neurofibrillary tangles in total and non-AD cases, although the correlations were not significant within the AD cases. Associations of genetic polymorphisms with CAA have been investigated for genes of apolipoprotein E (APOE), presenilin 1 (PS1), alpha1-antichymotrypsin (ACT), butyrylcholinesterase, alpha2-macroglobulin, and paraoxonase. Severity of CAA in APOE epsilon4 carriers is significantly higher than that in non-epsilon4 carriers in total cases, although no significant difference was found in the CAA severity between the epsilon4 carriers and non-epsilon4 carriers within the AD or non-AD group. An intronic polymorphism of PS1 was significantly associated with the severity of CAA, indicating that the PS1 2/2 genotype may be related to lower risk of CAA. A polymorphism in the signal peptide sequence of ACT was significantly associated with the CAA severity in the AD group. Our results suggest that CAA shares risk factors with AD and that multiple genetic factors would be associated with the risk of CAA in the elderly.

Diagnostic imaging for intracerebral hemorrhage

Magnetic resonance imaging (MRI) is an excellent tool for the diagnosis and evaluation of intracerebral hemorrhage with its unique specificity to hemoglobin degradation products in different stages. Computed tomography (CT) remains the diagnostic test of choice in the setting of acute intracerebral hemorrhage because of its exquisite sensitivity and specificity for small amounts of intracerebral hemorrhage (although there is emerging evidence that MRI may be as sensitive as CT). The effects of the biochemical evolution of intracerebral hemorrhage on the temporal MRI signal changes are described. This article discusses imaging features of the common causes of intracerebral hemorrhage.

Endoplasmic reticulum stress-inducible protein, Herp, enhances presenilin-mediated generation of amyloid beta-protein

Presenilin (PS) is essential for the gamma-cleavage required for the generation of the C terminus of amyloid beta-protein (Abeta). However, the mechanism underlying PS-mediated gamma-cleavage remains unclear. We have identified Herp cDNA by our newly developed screening method for the isolation of cDNAs that increase the degree of gamma-cleavage. Herp was originally identified as a homocysteine-responsive protein, and its expression is up-regulated by endoplasmic reticulum stress. Herp is an endoplasmic reticulum-localized membrane protein that has a ubiquitin-like domain. Here, we report that a high expression of Herp in cells increases the level of Abeta generation, although not in PS-deficient cells. We found that Herp interacts with both PS1 and PS2. Thus, Herp regulates PS-mediated Abeta generation, possibly through its binding to PS. Immunohistochemical analysis of a normal human brain section with an anti-Herp antibody revealed the exclusive staining of neurons and vascular smooth muscle cells. Moreover, the antibody strongly stained activated microglia in senile plaques in the brain of patients with Alzheimer disease. Taken together, Herp could be involved in Abeta accumulation, including the formation of senile plaques and vascular Abeta deposits.

No association of paraoxonase genotype or atherosclerosis with cerebral amyloid angiopathy

BACKGROUND AND PURPOSE

Both cerebral amyloid angiopathy (CAA) and paraoxonase have been reported to be related to lipid metabolism and atherosclerosis. We investigated whether the paraoxonase gene (PON1) polymorphism and atherosclerosis are associated with risk of CAA.

METHODS

Associations of the PON1 polymorphism and atherosclerosis of the aorta and coronary and cerebral arteries with the severity of CAA were investigated in 154 elderly Japanese individuals, including 47 patients with Alzheimer's disease.

RESULTS

The PON1 polymorphism or severity of atherosclerosis of the arteries was not associated with the severity of CAA.

CONCLUSIONS

The PON1 polymorphism and atherosclerosis would not appear to be associated with risk of CAA in the elderly, although further study with larger samples is necessary for confirmation.

Management of acute ischaemic stroke in the elderly: tolerability of thrombolytics

Stroke and its consequences are of global concern. Although stroke can affect individuals of any age, it primarily affects the elderly. It is among the leading causes of severe disability and mortality. In recent years, acute stroke has become a medical emergency requiring urgent evaluation and treatment. Effective management of patients with acute stroke starts with organisation of the entire stroke care chain, from the community and prehospital scene, through the emergency department, to a dedicated stroke unit and then to comprehensive rehabilitation. Intravenous thrombolysis with alteplase (recombinant tissue plasminogen activator; rt-PA) 0.9 mg/kg (maximum dose 90 mg) was shown to significantly improve outcome of acute ischaemic stroke, despite an increased rate of symptomatic intracerebral haemorrhage, if treatment is initiated within 3 hours after the onset of symptoms to patients who meet strict eligibility criteria. Post-marketing studies have demonstrated that intravenous alteplase can be administered appropriately in a wide variety of hospital settings. However, strict adherence to the published protocol is mandatory, as failure to comply may be associated with an increased risk of symptomatic intracerebral haemorrhage. Intra-arterial revascularisation may provide more complete restitution of flow than intravenous thrombolytic therapy and improve the clinical outcome if it can be undertaken in patients with occlusion of the middle cerebral artery, and possibly the basilar artery, within the first hours from stroke onset. However, further data are needed. Although intravenous alteplase is recommended for any age beyond 18 years, elderly patients, in particular patients aged > or = 80 years, were often excluded or under-represented in randomised clinical trials of thrombolysis, so that available data on risk/benefit ratio for the very elderly are limited. Small post-marketing series suggest that despite elderly patients over 80 years having greater pre-stroke disability, the use of intravenous alteplase in this patient group does not significantly differ in effectiveness and complications compared with the same treatment in patients aged under age 80 years. Further studies are necessary and elderly patients with acute stroke should be included in future trials of the merits of thrombolytic therapy.

The diagnostic relevance of cerebral amyloid angiopathy in the setting of forensic pathology - a report of two cases and review of the literature

The neuropathological features seen in two cases with cerebral amyloid angiopathy (CAA) are presented. An 85-year-old woman was found comatose at home and died on the way to the hospital. The cause of death was an intracerebral hemorrhage (ICH) in the right parietal lobe. A 93-year-old woman with a history of traumatic subarachnoid hemorrhage was operated on for a chronic subdural hematoma. Intraoperatively, she developed severe ICH and died. The cause of death was an ICH in the parieto-occipital lobe. The morphology of the vessels was studied on differently stained sections and the neuropathological findings of the surrounding brain tissue were investigated. The affected vessels showed the characteristic alterations seen in CAA and included vascular amyloid deposition, fibrinoid necrosis, double-barrel lumen, splitting of the internal elastic lamina, defects of the vessel wall, and microaneurysms. Visualization of beta-amyloid protein was performed by histological and immunohistochemical methods. The immunohistochemistry for beta-amyloid was more sensitive and yielded better results compared with Congo red. In cases of ICH, CAA has to be considered in the differential diagnosis. Besides the use of Congo red stain, the application of beta-amyloid immunohistochemistry is requested to reliably make the diagnosis of CAA. Additional staining with a modified silver impregnation technique (AgNOR) is useful to detect associated neurodegenerative changes.

Advances in molecular genetics and pathology of cerebrovascular disorders

Progress in molecular genetics has enabled the dissection of several autosomal dominantly inherited forms of cerebrovascular disorders. Mutations in diverse genes might induce pathological changes in intracranial vessels, resulting in cerebral haemorrhages and ischaemic strokes. Such pathologies, however, might also result from systemic vascular disease caused by mutations or polymorphisms in genes that regulate cardiovascular physiology, blood coagulation, lipid metabolism and metabolic functions. Interestingly, several mutations that directly affect CNS vasculature involve genes that control inter- or intracellular signalling functions. Although highly variable phenotypes make it difficult to pinpoint the genotypes, genetic characterization of cerebrovascular disorders is valuable for understanding the pathogenesis and management of sporadic disease.

Spontaneous hemorrhagic stroke in a mouse model of cerebral amyloid angiopathy

A high risk factor for spontaneous and often fatal lobar hemorrhage is cerebral amyloid angiopathy (CAA). We now report that CAA in an amyloid precursor protein transgenic mouse model (APP23 mice) leads to a loss of vascular smooth muscle cells, aneurysmal vasodilatation, and in rare cases, vessel obliteration and severe vasculitis. This weakening of the vessel wall is followed by rupture and bleedings that range from multiple, recurrent microhemorrhages to large hematomas. Our results demonstrate that, in APP transgenic mice, the extracellular deposition of neuron-derived beta-amyloid in the vessel wall is the cause of vessel wall disruption, which eventually leads to parenchymal hemorrhage. This first mouse model of CAA-associated hemorrhagic stroke will now allow development of diagnostic and therapeutic strategies.

Increased frequency of the alpha-1-antichymotrypsin T allele in cerebral amyloid angiopathy

Cerebral amyloid angiopathy (CAA) is a process of unknown etiology characterized by amyloid deposition in the wall of small cerebral and meningeal blood vessels. CAA is also a feature of Alzheimer's disease (AD) and of a subgroup of elderly people. Alpha-1-Antichymotrypsin (ACT) is a serum glycoprotein frequently associated with vascular and senile plaque amyloid. The ACT gene is known to have a bi-allele polymorphism that causes a simple amino acid substitution. In an attempt to clarify the possible role of ACT polymorphism in AD and in cases of CAA, the ACT genotype was investigated in AD, CAA, and intellectually intact controls. Representative brain areas (cerebral cortex, hippocampus, putamen, white matter, and gyrus cinguli) from all cases were studied using classical histologic staining techniques (hematoxylin-eosin (HE), Mallory's thrichromic or alkaline congo red stain), and immunohistochemistry for tau and beta-amyloid proteins. There was a significantly increased T allele and TT genotype frequency in the CAA group, but not in the AD group, suggesting a role for the ACT genotype in the development of vascular lesions. The presence of the apolipoprotein E4 allele (ApoE4) did not correlate with the ACT-A allele, as previously reported, and appeared to be independent of the risk for developing AD.