Systems proteomic analysis reveals that clusterin and tissue inhibitor of metalloproteinases 3 increase in leptomeningeal arteries affected by cerebral amyloid angiopathy

Aims

Amyloid beta (Aβ) accumulation in the walls of leptomeningeal arteries as cerebral amyloid angiopathy (CAA) is a major feature of Alzheimer's disease. In this study, we used global quantitative proteomic analysis to examine the hypothesis that the leptomeningeal arteries derived from patients with CAA have a distinct endophenotypic profile compared to those from young and elderly controls.

Methods

Freshly dissected leptomeningeal arteries from the Newcastle Brain Tissue Resource and Edinburgh Sudden Death Brain Bank from seven elderly (82.9 ± 7.5 years) females with severe capillary and arterial CAA, as well as seven elderly (88.3 ± 8.6 years) and five young (45.4 ± 3.9 years) females without CAA were used in this study. Arteries from four patients with CAA, two young and two elderly controls were individually analysed using quantitative proteomics. Key proteomic findings were then validated using immunohistochemistry.

Results

Bioinformatics interpretation of the results showed a significant enrichment of the immune response/classical complement and extracellular matrix remodelling pathways (P < 0.05) in arteries affected by CAA vs. those from young and elderly controls. Clusterin (apolipoprotein J) and tissue inhibitor of metalloproteinases‐3 (TIMP3), validated using immunohistochemistry, were shown to co‐localize with Aβ and to be up‐regulated in leptomeningeal arteries from CAA patients compared to young and elderly controls.

Conclusions

Global proteomic profiling of brain leptomeningeal arteries revealed that clusterin and TIMP3 increase in leptomeningeal arteries affected by CAA. We propose that clusterin and TIMP3 could facilitate perivascular clearance and may serve as novel candidate therapeutic targets for CAA.

Attenuation of Abeta deposition in the entorhinal cortex of normal elderly individuals associated with tobacco smoking

Investigating correlates of tobacco smoking provides the only currently available opportunity of examining effects of long-term exposure of nicotinic receptors on a specific nicotinic agonist in human. Alzheimer-type pathology (Abeta and abnormally phosphorylated tau assessed on the basis of AT8 immunoreactivity) together with vascular markers has been compared in age-matched groups of normal elderly smokers and non-smokers in the entorhinal cortex, an area of noted age-related pathology. The density of total Abeta and diffuse Abeta immunoreactivity, together with formic acid-extractable Abeta42 but not Abeta40, was reduced in smokers (n = 10-18) compared with non-smokers (n = 10-20) (P < 0.05). There was also a reduced percentage of cortical and leptomeningeal vessels with associated Abeta immunoreactivity in smokers (n = 13) compared with non-smokers (n = 14) (P < 0.005 and 0.05, respectively). There was a significant inverse correlation between formic acid-extractable Abeta42 and pack years (n = 34, r = -0.389, P = 0.025), with a similar trend for total Abeta immunoreactivity which did not reach statistical significance (n = 30, r = -0.323, P = 0.082). In contrast, there were no significant group differences for vascular markers (collagen IV, alpha-actin or glucose transporter 1), AT8 immunoreactivity or phosphate-buffered saline-soluble Abeta peptides, and no significant associations with gender for any of the measured parameters. These findings are consistent with previously reported reductions in histologically assessed amyloid plaques in aged human brain associated with tobacco use and dramatic lessening of Abeta deposits in APPsw mice after nicotine treatment. Development of nicotinic drugs to protect against beta-amyloidosis as one of the principal pathological hallmarks of brain ageing and Alzheimer's disease is indicated.

Carotid sinus syndrome is common in dementia with Lewy bodies and correlates with deep white matter lesions

BACKGROUND

Carotid sinus syndrome (CSS) is a common cause of syncope in older persons. There appears to be a high prevalence of carotid sinus hypersensitivity (CSH) in patients with dementia with Lewy bodies (DLB) but not in Alzheimer's disease.

OBJECTIVE

To compare the prevalence of CSH in DLB and Alzheimer's disease, and to determine whether there is an association between CSH induced hypotension and brain white matter hyperintensities on magnetic resonance imaging (MRI).

METHODS

Prevalence of CSH was compared in 38 patients with DLB (mean (SD) age, 76 (7) years), 52 with Alzheimer's disease (80 (6) years), and 31 case controls (73 (5) years) during right sided supine carotid sinus massage (CSM). CSH was defined as cardioinhibitory (CICSH; >3 s asystole) or vasodepressor (VDCSH; >30 mm Hg fall in systolic blood pressure (SBP)). T2 weighted brain MRI was done in 45 patients (23 DLB, 22 Alzheimer). Hyperintensities were rated by the Scheltens scale.

RESULTS

Overall heart rate response to CSM was slower (RR interval = 3370 ms (640 to 9400)) and the proportion of patients with CICSH greater (32%) in DLB than in Alzheimer's disease (1570 (720 to 7800); 11.1%) or controls (1600 (720 to 3300); 3.2%) (p<0.01)). The strongest predictor of heart rate slowing and CSH was a diagnosis of DLB (Wald 8.0, p<0.005). The fall in SBP during carotid sinus massage was greater with DLB (40 (22) mm Hg) than with Alzheimer's disease (30 (19) mm Hg) or controls (24 (19) mm Hg) (both p<0.02). Deep white matter hyperintensities were present in 29 patients (64%). In DLB, there was a correlation between magnitude of fall in SBP during CSM and severity of deep white matter changes (R = 0.58, p = 0.005).

CONCLUSIONS

Heart rate responses to CSM are prolonged in patients with DLB, causing hypotension. Deep white matter changes from microvascular disease correlated with the fall in SBP. Microvascular pathology is a key substrate of cognitive impairment and could be reversible in DLB where there are exaggerated heart rate responses to carotid sinus stimulation.

Nicotinic receptors in dementia of Alzheimer, Lewy body and vascular types

OBJECTIVES

Comparisons were made of nicotinic receptors in 3 major forms of dementia in old age. Although it is well established the involvement of nicotinic receptors in Alzheimer's disease (AD), their status in the other two main causes of dementia in old age-dementia with Lewy bodies (DLB) and vascular dementia (VaD) is not widely reported.

METHODS

Temporal cortex was examined for epibatidine and alpha-bungarotoxin binding, and immunoreactivity of alpha4 and alpha7 nAChR subunits.

RESULTS

There were selective abnormalities in nicotinic receptor subtypes in the disorders examined. In AD there is a loss of high affinity receptor binding, reflecting a selective loss of alpha4 subunit, but no change in alpha7 subunits. Similar abnormalities in ligand binding are also apparent in DLB. In the VaD series, there was no overall loss of epibatidine binding or immunoreactivity for alpha4 or alpha7 subunits.

CONCLUSIONS

Loss of cortical receptor alpha4 subunit appears to be a characteristic feature of neurodegenerative dementia but not dementia of vascular origin. Since nicotinic receptors control cerebral vasodilation, the relative integrity of the receptors in VaD may auger well for nicotinic therapy in this disorder in which there is a cholinergic abnormality, to judge by the loss of the presynaptic enzyme.

Detection of complement factor B in the cerebrospinal fluid of patients with cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy disease using two-dimensional gel electrophoresis and mass spectrometry

Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is a hereditary condition with onset in mid-adulthood and is associated with mutations in the Notch-3 gene. (Joutel, A., Corepechot, C., Ducros, A., Vahedi, K., Chabriat, H., Mouton, P., Alamowitch, S., Domenda, V., Cecilion, M., Marechal, J., Vayssiere, C., Cruaud, C., Cabanis, E.A., Ruchoux, M.M. , Weissenvach, J., Bach, J.F., Bousser, M.G. and Tournier-Lasserve, E., Notch3 mutations in CADASIL, a hereditary adult-onset condition causing stroke and dementia. Nature, 383 (1996) 707-710) Ultrastructural examination of the pathology of the cerebral infarcts reveals deposits in the vascular smooth muscle cells of the small arteries of the brain, but there is no obvious indication how the Notch-3 mutations give rise the observed pathology, nor is there any information on the exact nature of the deposits. We have investigated cerebrospinal fluid (CSF) from three CADASIL cases with known mutations in Notch-3 using two-dimensional gel electrophoresis. CSF from these patients was compared to that of six controls. We detected a single spot in the protein maps of patients which was absent from all the controls. In-gel tryptic digestion of this protein followed by mass spectrometric analysis of the tryptic fragments and a database search identified the spot as human complement factor B. These preliminary findings suggest that the alternative complement pathway may play a role in the pathogenesis of CADASIL.

Neuropathological substrates of dementia and depression in vascular dementia, with a particular focus on cases with small infarct volumes

The neuropathological substrates of dementia and depression were evaluated in 30 patients with cerebrovascular disease and significant cognitive impairment (VaD), with a particular focus on patients with small infarct volumes (<15 ml). VaD patients with small infarct volumes had a similar degree of cognitive impairment to those with larger infarct volumes (>15 ml) but were significantly more likely to be depressed and to have areas of microinfarction. A review of individual cases with small infarct volumes suggested that the combination of microinfarction, diffuse white matter disease and perivascular changes, or the overlap of neurodegenerative pathologies and microvascular changes were particularly important. Microinfarction was also significantly associated with major depression.

Neuroimaging of vessel amyloid in Alzheimer's disease

Despite extensive recent advances in understanding Alzheimer's disease (AD) we are unable to noninvasively establish a definite diagnosis during life and cannot monitor the cerebral deposition of amyloid beta protein (A beta) in living patients. We evaluated the use of 10H3, a monoclonal antibody Fab targeting A beta protein 1-28 labeled with Tc-99m. Six subjects with probable AD were studied using single-photon emission computed tomography (SPECT) at times from 0-24 hours following injection. Curves of radioactivity in blood demonstrate a half-life of the injected Fab of 2-3 hours. Images show uptake around the head in the scalp or bone marrow in all subjects. There is no evidence of cerebral uptake of the antibody. Scalp biopsies in all six patients demonstrate diffuse staining with 10H3 of the scalp, a pattern indistinguishable from that found in controls. Evidence of amyloid deposition in the scalp in AD is not seen with other anti-A beta antibodies, suggesting that 10H3 is cross-reacting with another protein. Further studies with anti-A beta antibodies will require longer-lived radionuclides to detect cerebral uptake at later times after injection to allow for complete clearance from the blood. Alternately, imaging using labeled A beta itself may provide a means for noninvasive targeting of cerebral amyloid.

Evidence for oxidative stress in Pick disease and corticobasal degeneration

Oxidative stress is increasingly implicated in a number of neurodegenerative disorders characterized by abnormal filament accumulation in affected neurons, including Alzheimer disease, Parkinson disease, and amyotrophic lateral sclerosis. To further evaluate the role of oxidative stress in the neurodegenerative process and the accumulation of abnormal filaments, we examined the pathologic lesions in Pick disease and of corticobasal degeneration with immunocytochemistry by using antisera to heme oxygenase-1 (HO-1) - a putative marker of oxidative injury. Immunoreactivity to HO-1 was demonstrated in ballooned neurons, Pick bodies, neuropil threads, and glial inclusions (the latter two in a case of corticobasal degeneration). By immunoelectron microscopy, HO-1 immunolabelling of Pick bodies was closely associated with the abnormal filaments comprising the inclusion. Apparently unaffected neurons in all cases showed only background levels of HO-1 immunoreactivity. These data suggest that oxidative stress is important in the formation of the lesions characteristic of Pick disease and corticobasal degeneration. Moreover, taken together with our previous demonstration that HO-1 immunoreactivity is associated with the neurofibrillary pathology of Alzheimer disease, progressive supranuclear palsy, and subacute sclerosing panencephalitis, it appears that oxidative stress specifically targets the cytoskeleton in a variety of neurodegenerative disorders characterized by abnormal filament accumulation.