Abeta peptides can enter the brain through a defective blood-brain barrier and bind selectively to neurons.
We have investigated the possibility that soluble, blood-borne amyloid beta (Abeta) peptides can cross a defective blood-brain barrier (BBB) and interact with neurons in the brain. Immunohistochemical analyses revealed extravasated plasma components, including Abeta42 in 19 of 21 AD brains, but in only 3 of 13 age-matched control brains, suggesting that a defective BBB is common in AD. To more directly test whether blood-borne Abeta peptides can cross a defective BBB, we tracked the fate of fluorescein isothiocyanate (FITC)-labeled Abeta42 and Abeta40 introduced via tail vein injection into mice with a BBB rendered permeable by treatment with pertussis toxin. Both Abeta40 and Abeta42 readily crossed the permeabilized BBB and bound selectively to certain neuronal subtypes, but not glial cells. By 48 h post-injection, Abeta42-positive neurons were widespread in the brain. In the cerebral cortex, small fluorescent, Abeta42-positive granules were found in the perinuclear cytoplasm of pyramidal neurons, suggesting that these cells can internalize exogenous Abeta42. An intact BBB (saline-injected controls) blocked entry of blood-borne Abeta peptides into the brain. The neuronal subtype selectivity of Abeta42 and Abeta40 was most evident in mouse brains subjected to direct intracranial stereotaxic injection into the hippocampal region, thereby bypassing the BBB. Abeta40 was found to preferentially bind to a distinct subset of neurons positioned at the inner face of the dentate gyrus, whereas Abeta42 bound selectively to the population of large neurons in the hilus region of the dentate gyrus. Our results suggest that the blood may serve as a major, chronic source of soluble, exogenous Abeta peptides that can bind selectively to certain subtypes of neurons and accumulate within these cells.
Clifford
Peter M
PM
New Jersey Institute for Successful Aging, University of Medicine and Dentistry of New Jersey/SOM, 2 Medical Center Drive, Stratford, NJ 08084, USA.
Zarrabi
Shabnam
S
Siu
Gilbert
G
Kinsler
Kristin J
KJ
Kosciuk
Mary C
MC
Venkataraman
Venkateswar
V
D'Andrea
Michael R
MR
Dinsmore
Steven
S
Nagele
Robert G
RG
D000368:Aged; D000369:Aged, 80 and over; D000544:Alzheimer Disease / Q000378:metabolism / Q000473:pathology / Q000503:physiopathology; D016229:Amyloid beta-Peptides / Q000378:metabolism*; D000818:Animals; D001812:Blood-Brain Barrier / Q000187:drug effects / Q000503:physiopathology*; D001921:Brain / Q000473:pathology*; D002199:Capillary Permeability / Q000187:drug effects / Q000502:physiology*; D016022:Case-Control Studies; D024141:Collagen Type IV / Q000378:metabolism; D005455:Fluorescent Antibody Technique / Q000379:methods; D006801:Humans; D007211:Indoles; D051379:Mice; D009474:Neurons / Q000378:metabolism*; D037342:Pertussis Toxin / Q000494:pharmacology; D011180:Postmortem Changes; D021381:Protein Transport / Q000502:physiology; D013997:Time Factors
D016229:Amyloid beta-Peptides; D024141:Collagen Type IV; D007211:Indoles; C007293:DAPI; D037342:Pertussis Toxin