Cited by 3,076Barrier Structure and Function StudiesDrug Transport and Resistance MechanismsCerebrospinal fluid and hydrocephalus

Blood–brain barrier breakdown in Alzheimer disease and other neurodegenerative disorders

Open access
Sweeney, Melanie D., Sagare, Abhay P., Zlokovic, Berislav V.·2018·Nature Reviews Neurology

Abstract

The blood–brain barrier (BBB) is a continuous endothelial membrane within brain microvessels that has sealed cell-to-cell contacts and is sheathed by mural vascular cells and perivascular astrocyte end-feet. The BBB protects neurons from factors present in the systemic circulation and maintains the highly regulated CNS internal milieu, which is required for proper synaptic and neuronal functioning. BBB disruption allows influx into the brain of neurotoxic blood-derived debris, cells and microbial pathogens and is associated with inflammatory and immune responses, which can initiate multiple pathways of neurodegeneration. This Review discusses neuroimaging studies in the living human brain and post-mortem tissue as well as biomarker studies demonstrating BBB breakdown in Alzheimer disease, Parkinson disease, Huntington disease, amyotrophic lateral sclerosis, multiple sclerosis, HIV-1-associated dementia and chronic traumatic encephalopathy. The pathogenic mechanisms by which BBB breakdown leads to neuronal injury, synaptic dysfunction, loss of neuronal connectivity and neurodegeneration are described. The importance of a healthy BBB for therapeutic drug delivery and the adverse effects of disease-initiated, pathological BBB breakdown in relation to brain delivery of neuropharmaceuticals are briefly discussed. Finally, future directions, gaps in the field and opportunities to control the course of neurological diseases by targeting the BBB are presented.

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Registry

Crossref · 10.1038/nrneurol.2017.188

Cites

257 of 257 references verified0 citation errors · 0 not checkable

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  • In advanced Alzheimer's disease, widespread leakage and deposition of blood-derived proteins such as fibrinogen, thrombin, and albumin are observed.

    “Simultaneously, widespread leakage and deposition of blood-derived proteins such as fibrinogen, thrombin, and albumin are observed [49, 55].”

    From Targeted Nanoparticles for Drug Delivery Across the Blood–Brain Barrier in Early and Late Stages of Alzheimer's Disease: A Review (2026) · cites this paper as [55]

    The 'Postmortem evidence of BBB disruption > Capillary leakages' section reports leakage and accumulation of fibrinogen, thrombin, and albumin in several brain regions of patients with Alzheimer’s disease. It does not specify advanced-stage disease or characterize the leakage as widespread, so those qualifiers are not established by this source. (LLM, conf=0.85)

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  • In late-stage Alzheimer's disease, the blood-brain barrier becomes significantly disrupted due to vascular degeneration, chronic inflammation, and endothelial damage, leading to increased but non-specific permeability.

    “As AD progresses to its late stages, the effectiveness of nanoparticle-based therapies often diminishes due to the increased disruption of the BBB [148].”

    From Targeted Nanoparticles for Drug Delivery Across the Blood–Brain Barrier in Early and Late Stages of Alzheimer's Disease: A Review (2026) · cites this paper as [162]

    The “How BBB breakdown affects drug delivery” section says vascular changes in neurodegeneration persist as disease progresses and hinder delivery of therapeutic agents; it also mentions nanoparticles as a delivery approach (page not available). It does not specifically show that nanoparticle-based therapies become less effective in late-stage Alzheimer’s disease. (LLM, conf=0.86)

    Experimental — accuracy not yet measured
  • Stimulating intracellular degradation without restoring BBB efflux may be insufficient to reduce vascular and parenchymal Aβ accumulation.

    “Conversely, stimulating intracellular degradation without restoring BBB efflux may be insufficient to reduce vascular and parenchymal A β accumulation [ 58 ].”

    From Restores Aβ Clearance by Overcoming PCSK9–LRP1 Dysregulation and TRIB3‐Mediated Autophagy Blockade in Alzheimer's Disease (2026) · cites this paper as [58]

    The Postmortem evidence of BBB disruption > Molecular changes section says reduced BBB clearance promotes Aβ accumulation in the brain and that some Aβ-clearance therapies require brain-to-blood transport. It does not assess whether stimulating intracellular degradation without restoring efflux would be insufficient, or establish that conclusion for both vascular and parenchymal Aβ accumulation. Page numbers were not available in our copy. (LLM, conf=0.82)

    Experimental — accuracy not yet measured
  • TJ proteins are affected under multiple pathological conditions or by approaches causing transient disruption, compromising BBB integrity and increasing influx of substances via the paracellular pathway.

    “However, the TJ proteins are reported to be affected under multiple pathological conditions or by approaches causing transient disruption, compromising the integrity of BBB and increasing influx of substances via the paracellular pathway [121, 122].”

    From Designing and optimizing AAV-mediated gene therapy for neurodegenerative diseases: from bench to bedside (2024) · cites this paper as [122]

    The Introduction links tightly sealed endothelial contacts to low paracellular permeability and says BBB breakdown permits blood-derived substances to enter the brain. “BBB breakdown and neurodegeneration” reports loss of tight-junction proteins in neurodegenerative disorders. “How BBB breakdown affects drug delivery” mentions opening the BBB with focused ultrasound, but does not establish that such approaches transiently affect tight-junction proteins or increase influx specifically through the paracellular pathway. Page numbers were not provided in our copy. (LLM, conf=0.84)

    Experimental — accuracy not yet measured
  • Astrocytic processes surround most of the vascular surface and regulate blood-brain barrier permeability by modulating tight junction proteins such as claudin-5 and endothelial proteins such as vimentin.

    “Astrocytic processes surround most of the vascular surface, regulating the blood–brain barrier (BBB) permeability [6, 7, 8, 9]—by modulating tight junction proteins such as claudin‐5 [10], or endothelial proteins such vimentin, which is associated with the stability of cerebral vasculature [11]—and integrate neuronal activity with blood flow [1, 2, 3, 4, 5, 12, 13, 14, 15, 16, 17, 18, 19, 20].”

    From Gliovascular alterations in sporadic and familial Alzheimer's disease: <scp><i>APOE3</i></scp> Christchurch homozygote glioprotection (2023) · cites this paper as [9]

    The Introduction (page unavailable) says astrocyte end-feet sheath the endothelial BBB, supporting the claim that astrocytic processes surround the vasculature. It does not establish that they regulate BBB permeability; it describes tight endothelial contacts and limited transcytosis as restricting permeability. The claudin-5 and vimentin mechanisms have separate citations in the citing sentence and are not attributed to this source. (LLM, conf=0.78)

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Authors
Sweeney, M. D., Sagare, A. P., & Zlokovic, B. V.
Affiliations
University of Southern California (US)
Venue
Nature Reviews Neurology
Published
2018-01-29
Volume
14
Issue
3
Pages
133-150
ISSN
  • 1759-4758 (ISSN-L)
  • 1759-4766
OpenAlex
W2786608785
Cited by
3,076
References
257
Citations by year
2026: 419 · 2025: 455 · 2024: 467 · 2023: 402 · 2022: 378 · 2021: 377 · 2020: 313 · 2019: 183 · 2018: 78
FWCI
22.61
Type
journal article
Language
en
Open access
Locations
  • Nature Reviews Neurology (publishedVersion)
  • PubMed (publishedVersion)
  • Europe PMC (PubMed Central) (acceptedVersion)
  • PubMed Central (acceptedVersion)
Funders
  • National Institute on Aging (R01AG023084, R01AG039452, F31AG044997, P50AG005142, RF1AG039452, P01AG052350)
  • National Institute of Neurological Disorders and Stroke (R01NS100459, R01NS090904, R01NS034467)
Topics
  • Life Sciences › Neuroscience › Neurology › Barrier Structure and Function Studies
  • Health Sciences › Medicine › Oncology › Drug Transport and Resistance Mechanisms
  • Life Sciences › Neuroscience › Cellular and Molecular Neuroscience › Cerebrospinal fluid and hydrocephalus
Keywords
blood-brain barrier disruption, neurodegeneration, Alzheimer's disease, Parkinson's disease, Huntington's disease, amyotrophic lateral sclerosis, multiple sclerosis, HIV-associated dementia, chronic traumatic encephalopathy, neuroinflammation, synaptic dysfunction, postmortem brain
MeSH terms
Blood-Brain Barrier, Humans, Neurodegenerative Diseases

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