Fibrinogen and Altered Hemostasis in Alzheimer's Disease

Laboratory of Neurobiology and Genetics, The Rockefeller University, New York, NY, USA.
Journal of Alzheimer's disease: JAD (Impact Factor: 4.15). 08/2012; 32(3). DOI: 10.3233/JAD-2012-120820
Source: PubMed

ABSTRACT Alzheimer's disease (AD) is characterized by amyloid-β (Aβ) plaques, tau tangles, brain atrophy, and vascular pathology. Vascular defects include cerebrovascular dysfunction, decreased cerebral blood flow, and blood brain barrier (BBB) disruption, among others. Here, we review the evidence that links Aβ with the vascular pathology present in AD, with a specific focus on the hemostatic system and the clotting protein fibrinogen. Fibrinogen is normally found circulating in blood, but in AD it deposits with Aβ in the brain parenchyma and cerebral blood vessels. We found that Aβ and fibrin(ogen) interact, and their binding leads to increased fibrinogen aggregation, Aβ fibrillization, and the formation of degradation-resistant fibrin clots. Decreasing fibrinogen levels not only lessens cerebral amyloid angiopathy and BBB permeability, but it also reduces microglial activation and improves cognitive performance in AD mouse models. Moreover, a prothrombotic state in AD is evidenced by increased clot formation, decreased fibrinolysis, and elevated levels of coagulation factors and activated platelets. Abnormal deposition and persistence of fibrin(ogen) in AD may result from Aβ-fibrin(ogen) binding and altered hemostasis and could thus contribute to Aβ deposition, decreased cerebral blood flow, exacerbated neuroinflammation, and eventual neurodegeneration. Blocking the interaction between fibrin(ogen) and Aβ may be a promising therapeutic target for AD.

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Available from: Marta Cortes-Canteli, Jun 11, 2014
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    • "Under normal circumstances, fibrinogen is excluded from the brain by the BBB, but due to BBB dysfunction it can be found co-localized with A␤ deposit in AD brain [75]. A␤ can bind fibrin(ogen) directly, promoting the deposition of A␤ in AD brain parenchyma and vessels, leading to formation of abnormal fibrin clots and cerebrovascular dysfunction [75]. Here levels of fibrinogen ␤-chain were lower in MCI but higher in AD. "
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