title: Altered processing of amyloid precursor protein in the human neuroblastoma SH-SY5Y by chronic hypoxia.
abstract: Alzheimer's disease (AD) is more prevalent following an ischemic or hypoxic episode, such as stroke. Indeed, brain levels of amyloid precursor protein (APP) and the cytotoxic amyloid beta peptide (Abeta) fragment are enhanced in these patients and in animal models following experimental ischaemia. We have investigated the effect of chronic hypoxia (CH; 2.5% O2, 24 h) on processing of APP in the human neuroblastoma, SH-SY5Y. We demonstrate that constitutive and muscarinic-receptor-enhanced secretion of the alpha-secretase cleaved fragment of APP, sAPPalpha, was reduced by approximately 60% in CH cells. The caspase inhibitor BOC-D(Ome)FMK did not reverse this effect of CH, and CH cells were as viable as controls, based on MTT assays. Thus, loss of sAPPalpha is not related to cell death or caspase processing of APP. Pre-incubation with antioxidants did not reverse the effect of CH, and the effect could not be mimicked by H2O2, discounting the involvement of reactive oxygen species in hypoxic loss of sAPPalpha. CH did not affect muscarinic activation of extracellular-signal regulated kinase. However, expression of ADAM 10 (widely believed to be alpha-secretase) was decreased approximately 50% following CH. Thus, CH selectively decreases processing of APP by the alpha-secretase pathway, most likely by decreasing levels of ADAM 10.
authors.affiliation: Institute for Cardiovascular Research, University of Leeds, Leeds, UK.
authors.forename: Nicola J
authors.initials: NJ
authors.lastname: Webster
authors.forename: Kim N
authors.initials: KN
authors.lastname: Green
authors.forename: Chris
authors.initials: C
authors.lastname: Peers
authors.forename: Peter F T
authors.initials: PF
authors.lastname: Vaughan
mesh_terms: D053829:Amyloid Precursor Protein Secretases; D016564:Amyloid beta-Protein Precursor / Q000378:metabolism*; D000818:Animals; D000975:Antioxidants / Q000494:pharmacology; D016282:Aspartic Acid Endopeptidases; D015153:Blotting, Western; D061945:Caspase Inhibitors; D015687:Cell Hypoxia / Q000502:physiology; D002470:Cell Survival / Q000187:drug effects; D010450:Endopeptidases / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006801:Humans; D009116:Muscarine / Q000494:pharmacology; D018721:Muscarinic Agonists / Q000494:pharmacology; D009447:Neuroblastoma / Q000188:drug therapy / Q000378:metabolism*; D016877:Oxidants / Q000494:pharmacology; D016716:PC12 Cells; D010446:Peptide Fragments / Q000378:metabolism; D011499:Protein Processing, Post-Translational / Q000502:physiology; D051381:Rats; D014407:Tumor Cells, Cultured
chemical_list: D016564:Amyloid beta-Protein Precursor; D000975:Antioxidants; D061945:Caspase Inhibitors; D004791:Enzyme Inhibitors; D018721:Muscarinic Agonists; D016877:Oxidants; D010446:Peptide Fragments; D009116:Muscarine; D053829:Amyloid Precursor Protein Secretases; D010450:Endopeptidases; D016282:Aspartic Acid Endopeptidases; C509280:BACE1 protein, human