Astrocytic A beta 1-42 uptake is determined by A beta-aggregation state and the presence of amyloid-associated proteins.
Intracerebral accumulation of amyloid-beta (A beta) leading to A beta plaque formation, is the main hallmark of Alzheimer's disease and might be caused by defective A beta-clearance. We previously found primary human astrocytes and microglia able to bind and ingest A beta 1-42 in vitro, which appeared to be limited by A beta 1-42 fibril formation. We now confirm that astrocytic A beta-uptake depends on size and/or composition of A beta-aggregates as astrocytes preferably take up oligomeric A beta over fibrillar A beta. Upon exposure to either fluorescence-labelled A beta 1-42 oligomers (A beta(oligo)) or fibrils (A beta(fib)), a larger (3.7 times more) proportion of astrocytes ingested oligomers compared to fibrils, as determined by flow cytometry. A beta-internalization was verified using confocal microscopy and live-cell imaging. Neither uptake of A beta(oligo) nor A beta(fib), triggered proinflammatory activation of the astrocytes, as judged by quantification of interleukin-6 and monocyte-chemoattractant protein-1 release. Amyloid-associated proteins, including alpha1-antichymotrypsin (ACT), serum amyloid P component (SAP), C1q and apolipoproteins E (ApoE) and J (ApoJ) were earlier found to influence A beta-aggregation. Here, astrocytic uptake of A beta(fib) increased when added to the cells in combination with SAP and C1q (SAP/C1q), but was unchanged in the presence of ApoE, ApoJ and ACT. Interestingly, ApoJ and ApoE dramatically reduced the number of A beta(oligo)-positive astrocytes, whereas SAP/C1q slightly reduced A beta(oligo) uptake. Thus, amyloid-associated proteins, especially ApoJ and ApoE, can alter A beta-uptake in vitro and hence may influence A beta clearance and plaque formation in vivo.
Nielsen
Henrietta M
HM
Department of Clinical Chemistry, VU University Medical Center Amsterdam, De Boelelaan 1117, 1081 HV Amsterdam, The Netherlands. henrietta.nielsen@med.lu.se
Mulder
Sandra D
SD
Beliën
Jeroen A M
JA
Musters
René J P
RJ
Eikelenboom
Piet
P
Veerhuis
Robert
R
D000682:Amyloid / Q000378:metabolism*; D016229:Amyloid beta-Peptides / Q000378:metabolism*; D001057:Apolipoproteins E / Q000378:metabolism; D001253:Astrocytes / Q000276:immunology / Q000378:metabolism* / Q000648:ultrastructure; D015153:Blotting, Western; D016923:Cell Death / Q000502:physiology; D002478:Cells, Cultured; D018932:Chemokine CCL2 / Q000378:metabolism; D051152:Clusterin / Q000378:metabolism; D004797:Enzyme-Linked Immunosorbent Assay; D005434:Flow Cytometry; D006801:Humans; D015850:Interleukin-6 / Q000378:metabolism; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D018613:Microscopy, Confocal; D008854:Microscopy, Electron; D010446:Peptide Fragments / Q000378:metabolism*; D055503:Protein Multimerization
D000682:Amyloid; D016229:Amyloid beta-Peptides; D001057:Apolipoproteins E; C111835:CCL2 protein, human; C495242:CLU protein, human; D018932:Chemokine CCL2; D051152:Clusterin; C508600:IL6 protein, human; D015850:Interleukin-6; D010446:Peptide Fragments; C075222:amyloid beta-protein (1-42); D007770:L-Lactate Dehydrogenase