The up-regulation of BACE1 mediated by hypoxia and ischemic injury: role of oxidative stress and HIF1alpha.
While it is well established that stroke and cerebral hypoperfusion are both significant risk factors for Alzheimer's disease, the molecular link between ischemia and amyloid precursor protein processing has only been recently established. Specifically, hypoxia significantly increases beta-site APP cleaving enzyme (BACE1) gene transcription through the over-expression of hypoxia inducible factor 1alpha, resulting in increased BACE1 secretase activity and amyloid-beta production. In this study, we significantly extend these findings both in vitro, in differentiated SK-N-BE neuroblastoma cells, and in vivo, in rats subjected to cerebral ischemia, showing that hypoxia up-regulates BACE1 expression through a biphasic mechanism. The early post-hypoxic up-regulation of BACE1 depends on the production of reactive oxygen species mediated by the sudden interruption of the mitochondrial electron transport chain, while the later expression of BACE1 is caused by hypoxia inducible factor 1alpha activation. The involvement of reactive oxygen species released by mitochondria in the BACE1 up-regulation was confirmed by the complete protection exerted by complex I inhibitors such as rotenone and diphenyl-phenylen iodonium. Moreover, the oxidative stress-mediated up-regulation of BACE1 is mediated by c-jun N terminal kinase pathway as demonstrated by the protection exerted by the silencing of c-jun N-terminal kinase isoforms 1 and 2. Our study strengthens the hypothesis that oxidative stress is a basic common mechanism of amyloid-beta accumulation.
Guglielmotto
Michela
M
Department of Experimental Medicine and Oncology, University of Turin, Italy.
Aragno
Manuela
M
Autelli
Riccardo
R
Giliberto
Luca
L
Novo
Erica
E
Colombatto
Sebastiano
S
Danni
Oliviero
O
Parola
Maurizio
M
Smith
Mark A
MA
Perry
George
G
Tamagno
Elena
E
Tabaton
Massimo
M
D000544:Alzheimer Disease / Q000209:etiology / Q000378:metabolism / Q000503:physiopathology; D053829:Amyloid Precursor Protein Secretases / Q000378:metabolism*; D016229:Amyloid beta-Peptides / Q000378:metabolism*; D000818:Animals; D016282:Aspartic Acid Endopeptidases / Q000378:metabolism*; D001921:Brain / Q000378:metabolism / Q000503:physiopathology; D045744:Cell Line, Tumor; D004195:Disease Models, Animal; D042967:Electron Transport Complex I / Q000037:antagonists & inhibitors / Q000378:metabolism; D006801:Humans; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000378:metabolism*; D020925:Hypoxia-Ischemia, Brain / Q000150:complications / Q000378:metabolism* / Q000503:physiopathology; D007527:Isoenzymes / Q000378:metabolism; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism; D008297:Male; D018384:Oxidative Stress / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar; D017382:Reactive Oxygen Species / Q000378:metabolism; D014475:Uncoupling Agents / Q000494:pharmacology; D015854:Up-Regulation / Q000502:physiology
D016229:Amyloid beta-Peptides; C497444:Hif1a protein, rat; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D007527:Isoenzymes; D017382:Reactive Oxygen Species; D014475:Uncoupling Agents; D048031:JNK Mitogen-Activated Protein Kinases; D053829:Amyloid Precursor Protein Secretases; D016282:Aspartic Acid Endopeptidases; C509281:Bace1 protein, rat; D042967:Electron Transport Complex I