title: Transport pathways for clearance of human Alzheimer's amyloid beta-peptide and apolipoproteins E and J in the mouse central nervous system.
abstract: Amyloid beta-peptide (Abeta) clearance from the central nervous system (CNS) maintains its low levels in brain. In Alzheimer's disease, Abeta accumulates in brain possibly because of its faulty CNS clearance and a deficient efflux across the blood-brain barrier (BBB). By using human-specific enzyme-linked immunosorbent assays, we measured a rapid 30 mins efflux at the BBB and transport via the interstitial fluid (ISF) bulk flow of human-unlabeled Abeta and of Abeta transport proteins, apolipoprotein E (apoE) and apoJ in mice. We show (i) Abeta40 is cleared rapidly across the BBB via low-density lipoprotein receptor-related protein (LRP)1 at a rate of 0.21 pmol/min g ISF or 6-fold faster than via the ISF flow; (ii) Abeta42 is removed across the BBB at a rate 1.9-fold slower compared with Abeta40; (iii) apoE, lipid-poor isoform 3, is cleared slowly via the ISF flow and across the BBB (0.03-0.04 pmol/min g ISF), and after lipidation its transport at the BBB becomes barely detectable within 30 mins; (iv) apoJ is eliminated rapidly across the BBB (0.16 pmol/min g ISF) via LRP2. Clearance rates of unlabeled and corresponding 125I-labeled Abeta and apolipoproteins were almost identical, but could not be measured at low physiologic levels by mass spectrometry. Amyloid beta-peptide 40 binding to apoE3 reduced its efflux rate at the BBB by 5.7-fold, whereas Abeta42 binding to apoJ enhanced Abeta42 BBB clearance rate by 83%. Thus, Abeta, apoE, and apoJ are cleared from brain by different transport pathways, and apoE and apoJ may critically modify Abeta clearance at the BBB.
authors.affiliation: Frank P Smith Laboratory for Neuroscience and Neurosurgical Research, Department of Neurosurgery, University of Rochester Medical Center, Rochester, New York 14642, USA.
authors.forename: Robert D
authors.initials: RD
authors.lastname: Bell
authors.forename: Abhay P
authors.initials: AP
authors.lastname: Sagare
authors.forename: Alan E
authors.initials: AE
authors.lastname: Friedman
authors.forename: Gurrinder S
authors.initials: GS
authors.lastname: Bedi
authors.forename: David M
authors.initials: DM
authors.lastname: Holtzman
authors.forename: Rashid
authors.initials: R
authors.lastname: Deane
authors.forename: Berislav V
authors.initials: BV
authors.lastname: Zlokovic
mesh_terms: D000544:Alzheimer Disease / Q000378:metabolism*; D016229:Amyloid beta-Peptides / Q000378:metabolism*; D000818:Animals; D001057:Apolipoproteins E / Q000378:metabolism*; D001693:Biological Transport, Active / Q000502:physiology; D001812:Blood-Brain Barrier; D051152:Clusterin / Q000378:metabolism*; D004591:Electrophoresis, Polyacrylamide Gel; D004797:Enzyme-Linked Immunosorbent Assay; D006801:Humans; D007457:Iodine Radioisotopes; D008024:Ligands; D051379:Mice; D008810:Mice, Inbred C57BL; D015233:Models, Statistical; D021241:Spectrometry, Mass, Electrospray Ionization; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
chemical_list: D016229:Amyloid beta-Peptides; D001057:Apolipoproteins E; D051152:Clusterin; D007457:Iodine Radioisotopes; D008024:Ligands