title: Ischemic conditions and ß-secretase activation: The impact of membrane cholesterol enrichment as triggering factor in rat brain endothelial cells.
abstract: Among harmful conditions damaging the blood–brain barrier, cerebral stroke and reperfusion injuries were proposed as contributing factors to Alzheimer's disease etiology. Indeed it was reported that ischemic conditions promote β-amyloid peptide production in brain endothelial cells, although implicated mechanisms are yet not fully understood.Oxidative injury related to ischemia affects membrane-lipids profile by altering their biochemical properties and structural dynamics, which are also believed to play significant role in the amyloid precursor protein processing, suggesting a link between alterations in lipid membrane composition and β-amyloid peptide production enhancement.Using brain microvascular endothelial cells, here we demonstrate how oxygen and glucose deprivation followed by normal conditions restoration, mimicking ischemic environment, increases cell cholesterol amount (+20%), reduces membrane fluidity and results in strong activation (+40%) of β-secretase 1 enzymatic activity. Moreover, we observed an increase of amyloid precursor protein and β-secretase 1 protein levels with altered localization in non-discrete (Triton X-100 soluble) membrane domains, leading to an enhanced production of amyloid precursor protein β-carboxyl-terminal fragment. Therefore, lipid alterations induced by oxygen and glucose deprivation enhance β-secretase 1 activity, favor its proximity to amyloid precursor protein and may concur to increased amyloidogenic cleavage. The latter, represents a detrimental event that may contribute to β-amyloid homeostasis impairment in the brain and to Alzheimer's disease-related BBB dysfunctions.
authors.forename: Anna
authors.initials: A
authors.lastname: Brambillaa
authors.forename: Elena
authors.initials: E
authors.lastname: Lonati
authors.forename: Chiara
authors.initials: C
authors.lastname: Milani
authors.forename: Angela Maria
authors.initials: AM
authors.lastname: Rizzo
authors.forename: Francesca
authors.initials: F
authors.lastname: Farina
authors.forename: Laura
authors.initials: L
authors.lastname: Botto
authors.forename: Massimo
authors.initials: M
authors.lastname: Masserini
authors.forename: Paola
authors.initials: P
authors.lastname: Palestini
authors.forename: Alessandra
authors.initials: A
authors.lastname: Bulbarelli
mesh_terms: D053829:Amyloid Precursor Protein Secretases / Q000378:metabolism*; D000818:Animals; D016282:Aspartic Acid Endopeptidases / Q000378:metabolism*; D002545:Brain Ischemia / Q000201:enzymology; D015687:Cell Hypoxia; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism*; D002784:Cholesterol / Q000502:physiology*; D042783:Endothelial Cells / Q000201:enzymology*; D004789:Enzyme Activation; D008560:Membrane Fluidity; D051381:Rats
chemical_list: D002784:Cholesterol; D053829:Amyloid Precursor Protein Secretases; D016282:Aspartic Acid Endopeptidases; C509281:Bace1 protein, rat