title: Toll-like receptors 2 and 4 mediate Abeta(1-42) activation of the innate immune response in a human monocytic cell line.
abstract: The primary molecules for mediating the innate immune response are the Toll-like family of receptors (TLRs). Recent work has established that amyloid-beta (Abeta) fibrils, the primary components of senile plaques in Alzheimer's disease (AD), can interact with the TLR2/4 accessory protein CD14. Using antibody neutralization assays and tumor necrosis factor alpha release in the human monocytic THP-1 cell line, we determined that both TLR2 and TLR4 mediated an inflammatory response to aggregated Abeta(1-42). This was in contrast to exclusive TLR ligands lipopolysaccharide (LPS) (TLR4) and tripalmitoyl cysteinyl seryl tetralysine (Pam(3)CSK(4)) (TLR2). Atomic force microscopy imaging showed a fibrillar morphology for the proinflammatory Abeta(1-42) species. Pre-treatment of the cells with 10 microg/mL of a TLR2-specific antibody blocked approximately 50% of the cell response to fibrillar Abeta(1-42), completely blocked the Pam(3)CSK(4) response, and had no effect on the LPS-induced response. A TLR4-specific antibody (10 microg/mL) blocked approximately 35% of the cell response to fibrillar Abeta(1-42), completely blocked the LPS response, and had no effect on the Pam(3)CSK(4) response. Polymyxin B abolished the LPS response with no effect on Abeta(1-42) ruling out bacterial contamination of the Abeta samples. Combination antibody pre-treatments indicated that neutralization of TLR2, TLR4, and CD14 together was much more effective at blocking the Abeta(1-42) response than the antibodies used alone. These data demonstrate that fibrillar Abeta(1-42) can trigger the innate immune response and that both TLR2 and TLR4 mediate Abeta-induced tumor necrosis factor alpha production in a human monocytic cell line.
authors.affiliation: Department of Chemistry and Biochemistry, University of Missouri, St Louis, Missouri 63121, USA.
authors.forename: Maria L D
authors.initials: ML
authors.lastname: Udan
authors.forename: Deepa
authors.initials: D
authors.lastname: Ajit
authors.forename: Nikkilina R
authors.initials: NR
authors.lastname: Crouse
authors.forename: Michael R
authors.initials: MR
authors.lastname: Nichols
mesh_terms: D016229:Amyloid beta-Peptides / Q000378:metabolism / Q000494:pharmacology*; D000906:Antibodies / Q000494:pharmacology; D002448:Cell Adhesion / Q000187:drug effects; D002460:Cell Line; D003545:Cysteine / Q000031:analogs & derivatives / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004347:Drug Interactions; D006801:Humans; D018625:Microscopy, Atomic Force / Q000379:methods; D009000:Monocytes / Q000187:drug effects / Q000276:immunology / Q000378:metabolism; D010446:Peptide Fragments / Q000378:metabolism / Q000494:pharmacology*; D011112:Polymyxin B / Q000494:pharmacology; D011134:Polysaccharides / Q000494:pharmacology; D013997:Time Factors; D051195:Toll-Like Receptor 2 / Q000502:physiology*; D051197:Toll-Like Receptor 4 / Q000502:physiology*; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism
chemical_list: D016229:Amyloid beta-Peptides; D000906:Antibodies; D010446:Peptide Fragments; D011134:Polysaccharides; C495342:TLR2 protein, human; D051195:Toll-Like Receptor 2; D051197:Toll-Like Receptor 4; D014409:Tumor Necrosis Factor-alpha; C075222:amyloid beta-protein (1-42); C038837:tripalmitoyl cysteine; D011112:Polymyxin B; D003545:Cysteine