title: Caffeine, Through Adenosine A3 Receptor-Mediated Actions, Suppresses Amyloid-β Protein Precursor Internalization and Amyloid-β Generation.
abstract: Intraneuronal accumulation and extracellular deposition of amyloid-β (Aβ) protein continues to be implicated in the pathogenesis of Alzheimer's disease (AD), be it familial in origin or sporadic in nature. Aβ is generated intracellularly following endocytosis of amyloid-β protein precursor (AβPP), and, consequently, factors that suppress AβPP internalization may decrease amyloidogenic processing of AβPP. Here we tested the hypothesis that caffeine decreases Aβ generation by suppressing AβPP internalization in primary cultured neurons. Caffeine concentration-dependently blocked low-density lipoprotein (LDL) cholesterol internalization and a specific adenosine A3 receptor (A3R) antagonist as well as siRNA knockdown of A3Rs mimicked the effects of caffeine on neuronal internalization of LDL cholesterol. Further implicating A3Rs were findings that a specific A3R agonist increased neuronal internalization of LDL cholesterol. In addition, caffeine as well as siRNA knockdown of A3Rs blocked the ability of LDL cholesterol to increase Aβ levels. Furthermore, caffeine blocked LDL cholesterol-induced decreases in AβPP protein levels in neuronal plasma membranes, increased surface expression of AβPP on neurons, and the A3R antagonist as well as siRNA knockdown of A3Rs mimicked the effects of caffeine on AβPP surface expression. Moreover, the A3R agonist decreased neuronal surface expression of AβPP. Our findings suggest that caffeine exerts protective effects against amyloidogenic processing of AβPP at least in part by suppressing A3R-mediated internalization of AβPP.
authors.forename: Shanshan
authors.initials: S
authors.lastname: Li
authors.forename: Nicholas H
authors.initials: NH
authors.lastname: Geiger
authors.forename: Mahmoud L
authors.initials: ML
authors.lastname: Soliman
authors.forename: Liang
authors.initials: L
authors.lastname: Hui
authors.forename: Jonathan D
authors.initials: JD
authors.lastname: Geiger
authors.forename: Xuesong
authors.initials: X
authors.lastname: Chen
mesh_terms: D016229:Amyloid beta-Peptides / Q000378:metabolism*; D016564:Amyloid beta-Protein Precursor / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D002110:Caffeine / Q000494:pharmacology*; D002478:Cells, Cultured; D002540:Cerebral Cortex / Q000166:cytology; D008078:Cholesterol, LDL / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004622:Embryo, Mammalian; D004705:Endocytosis / Q000187:drug effects*; D006801:Humans; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D009447:Neuroblastoma / Q000473:pathology; D009474:Neurons / Q000187:drug effects; D010446:Peptide Fragments / Q000378:metabolism*; D010726:Phosphodiesterase Inhibitors / Q000494:pharmacology*; D034741:RNA, Small Interfering / Q000494:pharmacology; D051381:Rats; D043684:Receptor, Adenosine A3 / Q000235:genetics / Q000378:metabolism*
chemical_list: D016229:Amyloid beta-Peptides; D016564:Amyloid beta-Protein Precursor; D008078:Cholesterol, LDL; D010446:Peptide Fragments; D010726:Phosphodiesterase Inhibitors; D034741:RNA, Small Interfering; D043684:Receptor, Adenosine A3; C078592:amyloid beta-protein (1-40); D002110:Caffeine; D007770:L-Lactate Dehydrogenase
keywords: Adenosine A3 receptor; Alzheimer’s disease; LDL cholesterol; amyloid-β; amyloid-β protein precursor; caffeine; endocytosis