Beta-amyloid pathology in human brain microvessel extracts from the parietal cortex: relation with cerebral amyloid angiopathy and Alzheimer’s disease
Several pieces of evidence suggest that blood–brain barrier (BBB) dysfunction is implicated in the pathophysiology of Alzheimer’s disease (AD), exemplified by the frequent occurrence of cerebral amyloid angiopathy (CAA) and the defective clearance of Aβ peptides. However, the specific role of brain microvascular cells in these anomalies remains elusive. In this study, we validated by Western, ELISA and immunofluorescence analyses a procedure to generate microvasculature-enriched fractions from frozen samples of human cerebral cortex. We then investigated Aβ and proteins involved in its clearance or production in microvessel extracts generated from the parietal cortex of 60 volunteers in the Religious Orders Study. Volunteers were categorized as AD (n = 38) or controls (n = 22) based on the ABC scoring method presented in the revised guidelines for the neuropathological diagnosis of AD. Higher ELISA-determined concentrations of vascular Aβ40 and Aβ42 were found in persons with a neuropathological diagnosis of AD, in apoE4 carriers and in participants with advanced parenchymal CAA, compared to respective age-matched controls. Vascular levels of two proteins involved in Aβ clearance, ABCB1 and neprilysin, were lower in persons with AD and positively correlated with cognitive function, while being inversely correlated to vascular Aβ40. In contrast, BACE1, a protein necessary for Aβ production, was increased in individuals with AD and in apoE4 carriers, negatively correlated to cognitive function and positively correlated to Aβ40 in microvessel extracts. The present report indicates that concentrating microvessels from frozen human brain samples facilitates the quantitative biochemical analysis of cerebrovascular dysfunction in CNS disorders. Data generated overall show that microvessels extracted from individuals with parenchymal CAA–AD contained more Aβ and BACE1 and less ABCB1 and neprilysin, evidencing a pattern of dysfunction in brain microvascular cells contributing to CAA and AD pathology and symptoms.
KeywordsBlood–brain barrier Brain microvascular cells Alzheimer’s disease Cerebral amyloid angiopathy Beta-amyloid
Funding was provided by the Canadian Institutes of Health Research (CIHR) to F.C (MOP 125930). The study was supported in part by P30AG10161 and R01AG15819 (D.A.B). F.C is a Fonds de recherche du Québec-Santé (FRQ-S) senior research scholar. P.B held scholarships from the Réseau québécois de recherche sur le médicament (RQRM), Fondation du CHU de Québec and a joined scholarship from the FRQ-S and the Alzheimer Society of Canada (ASC) and now holds a scholarship from the CIHR. The authors are thankful to Gregory Klein, from the Rush Alzheimer’s Disease Research Center, for his assistance with data related to our cohort. The authors are indebted to the nuns, priests and brothers from the Catholic clergy participating in the Religious Orders Study. The authors are thankful to Dr. Vincent Émond for his proofreading of the manuscript.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki Declaration and its later amendments or comparable ethical standards.
Informed consent was obtained from all individual participants included in the study.
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