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blood-brain barrier; blood-CSF barrier; plasma-CSF barrier (BBB)

Structure: - continuous layer of endothelial cells connected by tight junctions - similar capillaries are found in the retina, iris, inner ear & endoneurium of peripheral nerves - in circumventricular organs, the blood brain barrier (BBB) is absent; the endothelium is fenestrated - the BBB (plasma-CSF barrier) is provided by tight junctions between ependymal cells Function: - the choroid plexus regulates nutrient, lipid & protein transport across the BBB - opposes passage of most ions & large molecular weight compounds from the blood into the cerebrospinal fluid & brain tissue - glucose, amino acids, vitamins, & trace elements are selectively delivered across the BBB by specific carrier-mediated transport systems [8] - peptides & protein hormones, including insulin, cross the BBB primarily through receptor-mediated transcytosis [6,8] - insulin can penetrate the hippocampus [4] - cytokines (except IL-2) cross the BBB via saturable transport system [7,8] - lipoproteins cross the BBB through receptor-mediated transport mechanisms * insulin can be delivered through the nose to the brain, via a simple nasal spray [4] Pathology: - breakdown of the BBB sxpands the range of biomolecules that can - occurs in many neurodegenerative disorders [3,6] - Alzheimer disease - Parkinson disease - Huntington disease - amyotrophic lateral sclerosis - multiple sclerosis - HIV-1-associated dementia - chronic traumatic encephalopathy Comparative biology: - p16INK4a expressing (dubbed senescent) endothelial cells associated with compromised blood brain barrier in mice [2] Notes: - alternative entry routes of biomolecules into CSF (not through BBB) include: - circumventricular organs (which lack a BBB) - local synthesis in the choroid plexus - activation of afferent vagal nerves.

Related

circumventricular organ

General

vascular endothelium

References

  1. Stedman's Medical Dictionary 27th ed, Williams & Wilkins, Baltimore, 1999
  2. Yamazaki Y, Baker DJ, Tachibana M et al Vascular Cell Senescence Contributes to Blood-Brain Barrier Breakdown. Stroke. 2016 Feb 16. PMID: 26883501
  3. Sweeney MD, Sagare AP, Zlokovic BV Blood-brain barrier breakdown in Alzheimer disease and other neurodegenerative disorders. Nature Reviews Neurology. Jan 29, 2018 PMID: 29377008 https://www.nature.com/articles/nrneurol.2017.188 - Sweeney MD, Zhao Z, Montagne A et al Blood-Brain Barrier: From Physiology to Disease and Back. Physiol Rev. 2019 Jan 1;99(1):21-78. doi: 10.1152/physrev.00050.2017. PMID: 30280653 PMCID: PMC6335099 Free PMC article. Review. https://pmc.ncbi.nlm.nih.gov/articles/PMC6335099/
  4. Szalinski C A New Way to 'Smuggle' Drugs Through the Blood-Brain Barrier. Medscape. Oct 10, 2024 https://www.medscape.com/viewarticle/new-way-smuggle-drugs-through-blood-brain-barrier-2024a1000ijs
  5. Liu J, Wang T, Dong J, Lu Y. The blood-brain barriers: novel nanocarriers for central nervous system diseases. J Nanobiotechnology. 2025 Feb 26;23(1):146. PMID: 40011926 PMCID: PMC11866817 Free PMC article. Review.
  6. Goncalves RA, De Felice FG. The crosstalk between brain and periphery: Implications for brain health and disease. Neuropharmacology. 2021 Oct 1;197:108728. PMID: 34331960 Review.
  7. Banks WA, Kastin AJ, Broadwell RD. Passage of cytokines across the blood-brain barrier. Neuroimmunomodulation. 1995 Jul-Aug;2(4):241-8. PMID: 8963753 Review.
  8. Campos-Bedolla P, Walter FR, Veszelka S, Deli MA. Role of the blood-brain barrier in the nutrition of the central nervous system. Arch Med Res. 2014 Nov;45(8):610-38. PMID: 25481827 Review.

Component-of

brain