scholarly journals Alzheimer’s Disease—Rationales for Potential Treatment with the Thrombin Inhibitor Dabigatran

2021 ◽  
Vol 22 (9) ◽  
pp. 4805
Author(s):  
Klaus Grossmann
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Vascular Dysfunction ◽  
Amyloid Β ◽  
Brain Parenchyma ◽  
Thrombin Inhibitor ◽  
Amyloid Angiopathy ◽  
Barrier Dysfunction ◽  
Neuron Death ◽  
The Brain

Alzheimer’s disease (AD) is caused by neurodegenerative, but also vascular and hemostatic changes in the brain. The oral thrombin inhibitor dabigatran, which has been used for over a decade in preventing thromboembolism and has a well-known pharmacokinetic, safety and antidote profile, can be an option to treat vascular dysfunction in early AD, a condition known as cerebral amyloid angiopathy (CAA). Recent results have revealed that amyloid-β proteins (Aβ), thrombin and fibrin play a crucial role in triggering vascular and parenchymal brain abnormalities in CAA. Dabigatran blocks soluble thrombin, thrombin-mediated formation of fibrin and Aβ-containing fibrin clots. These clots are deposited in brain parenchyma and blood vessels in areas of CAA. Fibrin-Aβ deposition causes microvascular constriction, occlusion and hemorrhage, leading to vascular and blood–brain barrier dysfunction. As a result, blood flow, perfusion and oxygen and nutrient supply are chronically reduced, mainly in hippocampal and neocortical brain areas. Dabigatran has the potential to preserve perfusion and oxygen delivery to the brain, and to prevent parenchymal Aβ-, thrombin- and fibrin-triggered inflammatory and neurodegenerative processes, leading to synapse and neuron death, and cognitive decline. Beneficial effects of dabigatran on CAA and AD have recently been shown in preclinical studies and in retrospective observer studies on patients. Therefore, clinical studies are warranted, in order to possibly expand dabigatran approval for repositioning for AD treatment.

scholarly journals The Neurovascular Unit Dysfunction in Alzheimer’s Disease

2021 ◽  
Vol 22 (4) ◽  
pp. 2022 ◽  
Author(s):  
Luis O. Soto-Rojas ◽  
Mar Pacheco-Herrero ◽  
Paola A. Martínez-Gómez ◽  
B. Berenice Campa-Córdoba ◽  
Ricardo Apátiga-Pérez ◽  
...  
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Neurovascular Unit ◽  
Amyloid Β ◽  
Brain Parenchyma ◽  
Amyloid Angiopathy ◽  
Amyloid Β Peptide ◽  
Vascular Risk ◽  
Therapeutic Approaches ◽  
The Brain

Alzheimer’s disease (AD) is the most common neurodegenerative disease worldwide. Histopathologically, AD presents with two hallmarks: neurofibrillary tangles (NFTs), and aggregates of amyloid β peptide (Aβ) both in the brain parenchyma as neuritic plaques, and around blood vessels as cerebral amyloid angiopathy (CAA). According to the vascular hypothesis of AD, vascular risk factors can result in dysregulation of the neurovascular unit (NVU) and hypoxia. Hypoxia may reduce Aβ clearance from the brain and increase its production, leading to both parenchymal and vascular accumulation of Aβ. An increase in Aβ amplifies neuronal dysfunction, NFT formation, and accelerates neurodegeneration, resulting in dementia. In recent decades, therapeutic approaches have attempted to decrease the levels of abnormal Aβ or tau levels in the AD brain. However, several of these approaches have either been associated with an inappropriate immune response triggering inflammation, or have failed to improve cognition. Here, we review the pathogenesis and potential therapeutic targets associated with dysfunction of the NVU in AD.

scholarly journals Heparanase overexpression impedes perivascular clearance of amyloid-β from murine brain: relevance to Alzheimer’s disease

2021 ◽  
Vol 9 (1) ◽  
Author(s):  
Xiao Zhang ◽  
Paul O’Callaghan ◽  
Honglian Li ◽  
Yingxia Tan ◽  
Ganlin Zhang ◽  
...  
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Amyloid Β ◽  
Multiple Roles ◽  
Amyloid Angiopathy ◽  
Elevated Expression ◽  
Aβ Clearance ◽  
The Brain ◽  
Perivascular Drainage ◽  
Astrocyte Endfeet

AbstractDefective amyloid-β (Aβ) clearance from the brain is a major contributing factor to the pathophysiology of Alzheimer’s disease (AD). Aβ clearance is mediated by macrophages, enzymatic degradation, perivascular drainage along the vascular basement membrane (VBM) and transcytosis across the blood–brain barrier (BBB). AD pathology is typically associated with cerebral amyloid angiopathy due to perivascular accumulation of Aβ. Heparan sulfate (HS) is an important component of the VBM, thought to fulfill multiple roles in AD pathology. We previously showed that macrophage-mediated clearance of intracortically injected Aβ was impaired in the brains of transgenic mice overexpressing heparanase (Hpa-tg). This study revealed that perivascular drainage was impeded in the Hpa-tg brain, evidenced by perivascular accumulation of the injected Aβ in the thalamus of Hpa-tg mice. Furthermore, endogenous Aβ accumulated at the perivasculature of Hpa-tg thalamus, but not in control thalamus. This perivascular clearance defect was confirmed following intracortical injection of dextran that was largely retained in the perivasculature of Hpa-tg brains, compared to control brains. Hpa-tg brains presented with thicker VBMs and swollen perivascular astrocyte endfeet, as well as elevated expression of the BBB-associated water-pump protein aquaporin 4 (AQP4). Elevated levels of both heparanase and AQP4 were also detected in human AD brain. These findings indicate that elevated heparanase levels alter the organization and composition of the BBB, likely through increased fragmentation of BBB-associated HS, resulting in defective perivascular drainage. This defect contributes to perivascular accumulation of Aβ in the Hpa-tg brain, highlighting a potential role for heparanase in the pathogenesis of AD.

scholarly journals Insoluble Vascular Amyloid Deposits Trigger Disruption of the Neurovascular Unit in Alzheimer’s Disease Brains

2021 ◽  
Vol 22 (7) ◽  
pp. 3654
Author(s):  
Luis O. Soto-Rojas ◽  
B. Berenice Campa-Córdoba ◽  
Charles R. Harrington ◽  
Andrés Salas-Casas ◽  
Mario Hernandes-Alejandro ◽  
...  
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Neurovascular Unit ◽  
Amyloid Β ◽  
Brain Parenchyma ◽  
Amyloid Β Peptide ◽  
Cerebral Blood Vessels ◽  
Amyloid Deposits ◽  
Cellular Components ◽  
The Brain

Alzheimer’s disease (AD) is a neurodegenerative disease, characterized histopathologically by intra-neuronal tau-related lesions and by the accumulation of amyloid β-peptide (Aβ) in the brain parenchyma and around cerebral blood vessels. According to the vascular hypothesis of AD, an alteration in the neurovascular unit (NVU) could lead to Aβ vascular accumulation and promote neuronal dysfunction, accelerating neurodegeneration and dementia. To date, the effects of insoluble vascular Aβ deposits on the NVU and the blood–brain barrier (BBB) are unknown. In this study, we analyze different Aβ species and their association with the cells that make up the NVU. We evaluated post-mortem AD brain tissue. Multiple immunofluorescence assays were performed against different species of Aβ and the main elements that constitute the NVU. Our results showed that there are insoluble vascular deposits of both full-length and truncated Aβ species. Besides, insoluble aggregates are associated with a decrease in the phenotype of the cellular components that constitute the NVU and with BBB disruption. This approach could help identify new therapeutic targets against key molecules and receptors in the NVU that can prevent the accumulation of vascular fibrillar Aβ in AD.

scholarly journals Interactions between Amyloid-Β Proteins and Human Brain Pericytes: Implications for the Pathobiology of Alzheimer’s Disease

2020 ◽  
Vol 9 (5) ◽  
pp. 1490 ◽  
Author(s):  
Donald J. Alcendor
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Neurovascular Unit ◽  
Amyloid Β ◽  
Brain Parenchyma ◽  
Blood Retinal Barrier ◽  
Endothelin 1 ◽  
Brain Pericytes ◽  
Aging Populations ◽  
The Brain

Alzheimer’s disease (AD) is a progressive neurodegenerative disease that is the most common cause of dementia, especially among aging populations. Despite advances in AD research, the underlying cause and the discovery of disease-modifying treatments have remained elusive. Two key features of AD pathology are the aberrant deposition of amyloid beta (amyloid-β or Aβ) proteins in the brain parenchyma and Aβ toxicity in brain pericytes of the neurovascular unit/blood–brain barrier (NVU/BBB). This toxicity induces oxidative stress in pericytes and leads to capillary constriction. The interaction between pericytes and Aβ proteins results in the release of endothelin-1 in the pericytes. Endothelin-1 interacts with ETA receptors to cause pericyte contraction. This pericyte-mediated constriction of brain capillaries can cause chronic hypoperfusion of the brain microvasculature, subsequently leading to the neurodegeneration and cognitive decline observed in AD patients. The interaction between Aβ proteins and brain pericytes is largely unknown and requires further investigation. This review provides an updated overview of the interaction between Aβ proteins with pericytes, one the most significant and often forgotten cellular components of the BBB and the inner blood–retinal barrier (IBRB). The IBRB has been shown to be a window into the central nervous system (CNS) that could allow the early diagnosis of AD pathology in the brain and the BBB using modern photonic imaging systems such as optical coherence tomography (OCT) and two-photon microscopy. In this review, I explore the regulation of Aβ proteins in the brain parenchyma, their role in AD pathobiology, and their association with pericyte function. This review discusses Aβ proteins and pericytes in the ocular compartment of AD patients as well as strategies to rescue or protect pericytes from the effects of Aβ proteins, or to replace them with healthy cells.

scholarly journals Syndapin-2 Mediates Amyloid-β Transcytosis at the Brain Endothelium: Implications in Alzheimer’s Disease

2020 ◽  
Author(s):  
Diana M. Leite ◽  
Mohsen Seifi ◽  
Jerome D. Swinny ◽  
Giuseppe Battaglia
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Low Density Lipoprotein ◽  
Amyloid Β ◽  
Density Lipoprotein ◽  
Amyloid Angiopathy ◽  
Brain Endothelium ◽  
Endosomal Sorting ◽  
Density Lipoprotein Receptor ◽  
The Brain

A faulty transport of amyloid-β (Aβ) across the blood-brain barrier (BBB), and its diminished clearance from the brain, contributes to neurodegenerative and vascular pathologies, including Alzheimer’s disease (AD) and cerebral amyloid angiopathy, respectively. At the BBB, Aβ efflux transport is associated with the low-density lipoprotein receptor-related protein 1 (LRP1). However, the precise mechanisms governing the Aβ transport across the BBB, in health and disease, remain to be fully understood. New evidences suggest that LRP1 transcytosis occur through a tubular mechanism mediated by an F-BAR protein, syndapin-2. We show here that syndapin-2 is associated with Aβ clearance across the BBB. We further demonstrate whether risk factors for AD, Aβ expression and ageing, impact on native syndapin-2 expression in the brain endothelium, with syndapin-2 mediating Aβ transcytosis. Both increased Aβ expression and ageing significantly decreased expression of syndapin-2. These are mirrored by an alteration of the endosome-associated protein Rab5, with an increase of expression with Aβ accumulation and ageing. Collectively, our data reveal that the syndapin-2-mediated pathway and its balance with endosomal sorting at endothelial level are critical for the clearance of neuronally-derived Aβ, and thus proposing a new measure to assess AD and ageing, as well as, a potential target for counteracting the build-up of brain Aβ.

scholarly journals Anticoagulants for Treatment of Alzheimer’s Disease

2020 ◽  
Vol 77 (4) ◽  
pp. 1373-1382 ◽  
Author(s):  
Klaus Grossmann
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Blood Vessels ◽  
Oral Anticoagulants ◽  
Amyloid Β ◽  
Brain Parenchyma ◽  
Amyloid Angiopathy ◽  
Amyloid Β Protein ◽  
Cerebral Blood Vessels ◽  
Cognitive Changes

Alzheimer’s disease (AD) is a multifactorial syndrome with a plethora of progressive, degenerative changes in the brain parenchyma, but also in the cerebrovascular and hemostatic system. A therapeutic approach for AD is reviewed, which is focused on the role of amyloid–β protein (Aβ) and fibrin in triggering intra-brain vascular dysfunction and connected, cognitive decline. It is proposed that direct oral anticoagulants (DOACs) counteract Aβ-induced pathological alterations in cerebral blood vessels early in AD, a condition, known as cerebral amyloid angiopathy (CAA). By inhibiting thrombin for fibrin formation, anticoagulants can prevent accumulations of proinflammatory thrombin and fibrin, and deposition of degradation-resistant, Aβ-containing fibrin clots. These fibrin–Aβ clots are found in brain parenchyma between neuron cells, and in and around cerebral blood vessels in areas of CAA, leading to decreased cerebral blood flow. Consequently, anticoagulant treatment could reduce hypoperfusion and restricted supply of brain tissue with oxygen and nutrients. Concomitantly, hypoperfusion-enhanced neurodegenerative processes, such as progressive Aβ accumulation via synthesis and reduced perivascular clearance, neuroinflammation, and synapse and neuron cell loss, could be mitigated. Given full cerebral perfusion and reduced Aβ- and fibrin-accumulating and inflammatory milieu, anticoagulants could be able to decrease vascular-driven progression in neurodegenerative and cognitive changes, present in AD, when treated early, therapeutically, or prophylactically.

scholarly journals Dissecting the Crosstalk between Endothelial Mitochondrial Damage, Vascular Inflammation, and Neurodegeneration in Cerebral Amyloid Angiopathy and Alzheimer’s Disease

Cells ◽  
2021 ◽  
Vol 10 (11) ◽  
pp. 2903
Author(s):  
Rebecca M. Parodi-Rullán ◽  
Sabzali Javadov ◽  
Silvia Fossati
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Cerebral Amyloid Angiopathy ◽  
Vascular Inflammation ◽  
Neurovascular Unit ◽  
Brain Parenchyma ◽  
Amyloid Angiopathy ◽  
Wide Range ◽  
Cerebral Amyloid ◽  
The Brain

Alzheimer’s disease (AD) is the most prevalent cause of dementia and is pathologically characterized by the presence of parenchymal senile plaques composed of amyloid β (Aβ) and intraneuronal neurofibrillary tangles of hyperphosphorylated tau protein. The accumulation of Aβ also occurs within the cerebral vasculature in over 80% of AD patients and in non-demented individuals, a condition called cerebral amyloid angiopathy (CAA). The development of CAA is associated with neurovascular dysfunction, blood–brain barrier (BBB) leakage, and persistent vascular- and neuro-inflammation, eventually leading to neurodegeneration. Although pathologically AD and CAA are well characterized diseases, the chronology of molecular changes that lead to their development is still unclear. Substantial evidence demonstrates defects in mitochondrial function in various cells of the neurovascular unit as well as in the brain parenchyma during the early stages of AD and CAA. Dysfunctional mitochondria release danger-associated molecular patterns (DAMPs) that activate a wide range of inflammatory pathways. In this review, we gather evidence to postulate a crucial role of the mitochondria, specifically of cerebral endothelial cells, as sensors and initiators of Aβ-induced vascular inflammation. The activated vasculature recruits circulating immune cells into the brain parenchyma, leading to the development of neuroinflammation and neurodegeneration in AD and CAA.

Protective Effect of Rivaroxaban Against Amyloid Pathology and Neuroinflammation Through Inhibiting PAR-1 and PAR-2 in Alzheimer’s Disease Mice

2022 ◽  
pp. 1-13
Author(s):  
Zhihong Bian ◽  
Xia Liu ◽  
Tian Feng ◽  
Haibo Yu ◽  
Xiao Hu ◽  
...  
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Oral Anticoagulant ◽  
Amyloid Β ◽  
Underlying Mechanism ◽  
Amyloid Angiopathy ◽  
Mice Model ◽  
Barrier Dysfunction ◽  
Term Administration ◽  
Anticoagulant Drug

Background: Recent studies have revealed that atrial fibrillation (AF) patients have a high risk of developing cognitive impairment, vascular dementia, and Alzheimer’s disease (AD). Some reports suggest that the application of oral anticoagulant with an appropriate dose may have a preventive effect on AD. However, which oral anticoagulant drug is more appropriate for preventing AD and the underlying mechanism(s) is still unknown. Objective: The aim of the present study was to assess the treatment effect of rivaroxaban administration as well as investigate the roles of PAR-1 and PAR-2 in the AD + CAA mice model. Methods: In the present study, we compared a traditional oral anticoagulant, warfarin, and a direct oral anticoagulant (DOAC), rivaroxaban, via long-term administration to an AD with cerebral amyloid angiopathy (CAA) mice model. Results: Rivaroxaban treatment attenuated neuroinflammation, blood-brain barrier dysfunction, memory deficits, and amyloid-β deposition through PAR-1/PAR-2 inhibition in the AD + CAA mice model compared with warfarin and no-treatment groups. Conclusion: The present study demonstrates that rivaroxaban can attenuate AD progress and can be a potential choice to prevent AD.

scholarly journals Oral Amylin Treatment Reduces the Pathological Cascade of Alzheimer’s Disease in a Mouse Model

2021 ◽  
Vol 36 ◽  
pp. 153331752110128
Author(s):  
Hana Na ◽  
Hua Tian ◽  
Zhengrong Zhang ◽  
Qiang Li ◽  
Jack B. Yang ◽  
...  
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Calcium Binding ◽  
Oral Delivery ◽  
Amyloid Β ◽  
Enteric Neurons ◽  
Cyclin Dependent Kinase ◽  
Receptor Activity Modifying Proteins ◽  
The Brain ◽  
Cyclin Dependent Kinase 5

Intraperitoneal injection of amylin or its analog reduces Alzheimer’s disease (AD) pathology in the brains. However, self-injecting amylin analogs is difficult for patients due to cognitive deficits. This work aims to study the effects of amylin on the brain could be achieved by oral delivery as some study reported that amylin receptor may be present in the gastrointestinal tract. A 6-week course of oral amylin treatment reduced components of AD pathology, including the levels of amyloid-β, phosphorylated tau, and ionized calcium binding adaptor molecule 1. The treatment reduced active forms of cyclin-dependent kinase 5. Oral amylin treatment led to improvements in social deficit in AD mouse. Using immunofluorescence, we observed the amylin receptor complexed with the calcitonin receptor and receptor activity-modifying proteins in the enteric neurons. The study suggests the potential of the oral delivery of amylin analogs for the treatment of AD and other neurodegenerative diseases through enteric neurons.

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