Elsevier

Neurobiology of Aging

Volume 28, Issue 7, July 2007, Pages 977-986
Neurobiology of Aging

Microvascular injury and blood–brain barrier leakage in Alzheimer's disease

https://doi.org/10.1016/j.neurobiolaging.2006.05.016Get rights and content

Abstract

Thinning and discontinuities within the vascular basement membrane (VBM) are associated with leakage of the plasma protein prothrombin across the blood–brain barrier (BBB) in Alzheimer's disease (AD). Prothrombin immunohistochemistry and ELISA assays were performed on prefrontal cortex. In severe AD, prothrombin was localized within the wall and neuropil surrounding microvessels. Factor VIII staining in severe AD patients indicated that prothrombin leakage was associated with shrinkage of endothelial cells. ELISA revealed elevated prothrombin levels in prefrontal cortex AD cases that increased with the Braak stage (Control = 1.39, I–II = 1.76, III–IV = 2.28, and V–VI = 3.11 ng prothrombin/mg total protein). Comparing these four groups, there was a significant difference between control and Braak V–VI (p = 0.0095) and also between Braak stages I–II and V–VI (p = 0.0048). There was no significant difference in mean prothrombin levels when cases with versus without cerebral amyloid angiopathy (CAA) were compared (p-value = 0.3627). When comparing AD patients by APOE genotype (ApoE3,3 = 2.00, ApoE3,4 = 2.49, and ApoE4,4 = 2.96 ng prothrombin/mg total protein) an analysis of variance indicated a difference between genotypes at the 10% significance level (p = 0.0705). Tukey's test indicated a difference between the 3,3 and 4,4 groups (p = 0.0607). These studies provide evidence that in advanced AD (Braak stage V–VI), plasma proteins like prothrombin can be found within the microvessel wall and surrounding neuropil, and that leakage of the blood–brain barrier may be more common in patients with at least one APOE4 allele.

Introduction

Impaired cognitive function and short-term memory clinically characterize Alzheimer's disease (AD) [52]. Underlying pathologic features of AD include neuronal and synaptic loss in the cerebral cortex as well as β-amyloid-containing diffuse and neuritic plaques (senile plaques), intraneuronal neurofibrillary tangles (NFTs), and cerebral amyloid angiopathy [14], [25], [39], [52].

While pathologic vascular aberrations are commonly observed in both healthy elderly and AD patients [33], their contribution to the pathogenesis of AD remains largely unstudied. Both vascular risk factors and vascular disease closely correlate with the incidence of AD [10]. Homozygosity of the APOE4 allele on chromosome 19 has been associated with an increased risk of sporadic Alzheimer's disease through mechanisms that remain to be defined [13]. The strong association among vascular pathology, ApoE genotype, and AD dementia suggests that microvascular damage may be a factor in the pathogenesis of AD.

Most human studies of age-related cerebral vascular pathology have focused on atherosclerotic occlusion of the major arteries and arteriolar sclerosis (lipohyalinosis) of the arterioles. Our observation that the solubility properties of agrin are altered in AD, resulting in basement membrane thinning and discontinuity, as well as a redistribution of agrin within neuritic plaques, has led us to hypothesize that blood–brain barrier leakage may be a primary event in the pathogenesis of AD [7], [19], [53].

The exact relationship between cerebral capillaries and senile plaques remains a mystery. In carefully performed ultrastructural analyses, capillaries were consistently observed within senile plaques, suggesting that the latter may result from leaky capillaries [41], [42]. Others, however, have argued that this is largely a chance association and observed no evidence that capillary damage is a prerequisite for senile plaque formation [34].

SPECT and PET scans have documented a preferential decrease in cerebral blood flow to brain areas affected by AD [15], [20], [22], [44], [45]. CT and MRI have shown an increase in small vessel pathology in AD patients [18], [55], [56]. Ironically, despite the widespread recognition of in vivo microvascular dysfunction and significant pathologic alteration in AD patients, the utility of these techniques for demonstrating a defect in BBB integrity has been elusive. It should be noted, however, that most modern imaging techniques have a maximum resolution of approximately 1–10 mm, which may be insufficient to resolve subtle defects in the BBB [28].

The presence of plasma-derived proteins within the perivascular neuropil has been previously shown to be a reliable indicator of early blood–brain barrier compromise in diseases affecting the central nervous system [48], [50], [51]. Prothrombin, a 72 kDa pre-propeptide synthesized in the liver, is best known for its essential role in the coagulation cascade [16], [17]. Circulating prothrombin is largely excluded from the CNS by the blood–brain barrier [38].

In a previous study of the cerebral microvasculature in AD, we reported that prothrombin immunoreactivity in control prefrontal cortex was limited to faint staining within the lumen of vessels and focal staining of cortical neurons [7]. In severe Alzheimer's disease, there was a notable shift in the distribution of prothrombin reaction product. A penumbra of staining became evident within the perivascular neuropil [7]. In the present study we examine the changes in the distribution of prothrombin immunoreactivity that occur at the various Braak stages of Alzheimer's disease severity and correlate these changes with biochemical analyses of prothrombin concentration and APOE genotype.

Section snippets

Human tissues

All brains were obtained postmortem within 1–18 h of death (Table 1). The diagnosis of Alzheimer's disease was made in accordance with accepted National Institute of Aging criteria [61]. AD staging was determined using the criteria of Braak and Braak [9]. APOE genotype in all AD cases was determined by PCR [54]. Control brains were obtained from patients who displayed no pathological evidence of AD or clinical history of neurological disease. All AD patients died as a result of pneumonia,

Results

Patients were divided into three different groups according to their Braak stage of pathologic severity as well as a control group (Table 1).

Discussion

These studies provide evidence that in advanced AD (Braak stage V–VI), plasma proteins like prothrombin can be found within the microvessel wall and surrounding neuropil, and that leakage of the blood–brain barrier may be more common in patients with at least one APOE4 allele. Prothrombin leakage appears to be independent of amyloid angiopathy and may even precede its development. In addition, our data suggest that endothelial cell injury may contribute to plasma protein leakage, although the

Acknowledgments

This work was supported by AG05128, AG09301, NS27601, AG17975, and Glaxo Smith Kline. The authors thank John Ervin and Victoria Kuo-LeBlanc for their technical assistance, and Robin Kiernan for her help in preparing this manuscript.

References (64)

  • R.N. Kalaria et al.

    Serum amyloid P immunoreactivity in hippocampal tangles, plaques and vessels: implications for leakage across the blood–brain barrier in Alzheimer's disease

    Brain Res

    (1990)
  • R.N. Kalaria et al.

    Amyloid P component and other acute-phase proteins associated with cerebellar A beta-deposits in Alzheimer's disease

    Brain Res

    (1993)
  • A.D. Kay et al.

    CSF and serum concentrations of albumin and IgG in Alzheimer's disease

    Neurobiol Aging 2000

    (1987)
  • A. Leonardi et al.

    The integrity of the blood–brain barrier in Alzheimer's type and multi-infarct dementia evaluated by the study of albumin and IgG in serum and cerebrospinal fluid

    J Neurol Sci

    (1985)
  • M. Mulder et al.

    Apolipoprotein E protects against neuropathology induced by a high-fat diet and maintains the integrity of the blood–brain barrier during aging

    Lab Invest

    (2001)
  • E. Pompili et al.

    Trimethyltin-induced differential expression of PAR subtypes in reactive astrocytes of the rat hippocampus

    Brain Res Mol Brain Res

    (2004)
  • A.D. Roses

    The Alzheimer diseases

    Curr Opin Neurobiol

    (1996)
  • S. Salloway et al.

    Effect of APOE genotype on microvascular basement membrane in Alzheimer's disease

    J Neurol Sci.

    (2002)
  • I. Skoog et al.

    15-year longitudinal study of blood pressure and dementia

    Lancet

    (1996)
  • J.Q. Trojanowski et al.

    Strategies for improving the postmortem neuropathological diagnosis of Alzheimer's disease

    Neurobiol Aging

    (1997)
  • G. Aliev et al.

    Mitochondrial and vascular lesions as a central target for the development of Alzheimer's disease and Alzheimer disease-like pathology in transgenic mice

    Neurol Res

    (2003)
  • T. Arai et al.

    Thrombin and prothrombin are expressed by neurons and glial cells and accumulate in neurofibrillary tangles in Alzheimer disease brain

    J Neuropathol Exp Neurol

    (2006)
  • M.K. Aronson et al.

    Women, myocardial infarction, and dementia in the very old

    Neurology

    (1990)
  • J. Attems et al.

    Only cerebral capillary amyloid angiopathy correlates with Alzheimer pathology—a pilot study

    Acta Neuropathol (Berl.)

    (2004)
  • K. Blennow et al.

    Blood–brain barrier disturbance in patients with Alzheimer's disease is related to vascular factors

    Acta Neurol Scand

    (1990)
  • H. Braak et al.

    Neuropathological staging of Alzheimer-related changes

    Acta Neuropathol (Berl.)

    (1991)
  • M.M. Breteler

    Vascular involvement in cognitive decline and dementia Epidemiologic evidence from the Rotterdam Study and the Rotterdam Scan Study

    Ann N Y Acad Sci

    (2000)
  • L. Buee et al.

    Brain microvascular changes in Alzheimer's disease and other dementias

    Ann N Y Acad Sci

    (1997)
  • F. Cacciatore et al.

    The role of blood pressure in cognitive impairment in an elderly population Osservatorio Geriatrico Campano Group

    J Hypertens

    (1997)
  • E. Corder et al.

    Gene dose of apolipoprotein E type 4 allele and the risk of Alzheimer's disease in late onset families

    Science

    (1993)
  • S.T. DeKosky et al.

    Assessing utility of single photon emission computed tomography (SPECT) scan in Alzheimer disease: correlation with cognitive severity

    Alzheimer Dis Assoc Disord

    (1990)
  • R.S. Doddy et al.

    Cognitive consequences of subcortical magnetic resonance imaging changes in Alzheimer's disease: comparison to small vessel ischemic vascular dementia

    Neuropsychiatry Neuropsychol Behav Neurol

    (1998)
  • Cited by (379)

    View all citing articles on Scopus
    View full text