Serrano-Pozo Alberto, Sánchez-García Manuel A, Heras-Garvín Antonio, March-Díaz Rosana, Navarro Victoria, Vizuete Marisa, López-Barneo José, Vitorica Javier, Pascual Alberto
Department of Neurology, University of Iowa Hospitals & Clinics, Iowa city, Iowa, United States of America.
Instituto de Biomedicina de Sevilla (IBiS), Hospital Universitario Virgen del Rocío/CSIC/Universidad de Sevilla, Seville, Spain.
PLoS One. 2017 Jan 18;12(1):e0170345. doi: 10.1371/journal.pone.0170345. eCollection 2017.
Recent epidemiological evidence has linked hypoxia with the development of Alzheimer disease (AD). A number of in vitro and in vivo studies have reported that hypoxia can induce amyloid-β peptide accumulation through various molecular mechanisms including the up-regulation of the amyloid-β precursor protein, the β-secretase Bace1, or the γγ-secretase complex components, as well as the down-regulation of Aβ-degrading enzymes.
To investigate the effects of acute and chronic sustained hypoxia in Aβ generation in vivo.
2-3 month-old C57/Bl6J wild-type mice were exposed to either normoxia (21% O2) or hypoxia (9% O2) for either 4 to 72 h (acute) or 21-30 days (chronic sustained) in a hermetic chamber. Brain mRNA levels of Aβ-related genes were measured by quantitative real-time PCR, whereas levels of Bace1 protein, full length AβPP, and its C-terminal fragments (C99/C88 ratio) were measured by Western blot. In addition, 8 and 14-month-old APP/PS1 transgenic mice were subjected to 9% O2 for 21 days and levels of Aβ40, Aβ42, full length AβPP, and soluble AβPPα (sAβPPα) were measured by ELISA or WB.
Hypoxia (either acute or chronic sustained) did not impact the transcription of any of the Aβ-related genes in young wild-type mice. A significant reduction of Bace1 protein level was noted with acute hypoxia for 16 h but did not correlate with an increased level of full length AβPP or a decreased C99/C83 ratio. Chronic sustained hypoxia did not significantly alter the levels of Bace1, full length AβPP or the C99/C83 ratio. Last, chronic sustained hypoxia did not significantly change the levels of Aβ40, Aβ42, full length AβPP, or sAβPPα in either young or aged APP/PS1 mice.
Our results argue against a hypoxia-induced shift of AβPP proteolysis from the non-amyloidogenic to the amyloidogenic pathways. We discuss the possible methodological caveats of previous in vivo studies.
最近的流行病学证据表明缺氧与阿尔茨海默病（AD）的发生有关。多项体外和体内研究报告称，缺氧可通过多种分子机制诱导淀粉样β肽积累，包括淀粉样β前体蛋白、β-分泌酶Bace1或γ-分泌酶复合物成分的上调，以及Aβ降解酶的下调。
研究急性和慢性持续性缺氧对体内Aβ生成的影响。
将2-3月龄的C57/Bl6J野生型小鼠置于密闭舱中，分别暴露于常氧（21% O2）或缺氧（9% O2）环境4至72小时（急性）或21至30天（慢性持续性）。通过定量实时PCR检测Aβ相关基因的脑mRNA水平，而通过蛋白质印迹法检测Bace1蛋白、全长AβPP及其C末端片段（C99/C88比值）的水平。此外，将8月龄和14月龄的APP/PS1转基因小鼠置于9% O2环境中21天，通过酶联免疫吸附测定（ELISA）或蛋白质印迹法检测Aβ40、Aβ42、全长AβPP和可溶性AβPPα（sAβPPα）的水平。
缺氧（急性或慢性持续性）对年轻野生型小鼠中任何Aβ相关基因的转录均无影响。急性缺氧16小时时，Bace1蛋白水平显著降低，但与全长AβPP水平升高或C99/C83比值降低无关。慢性持续性缺氧并未显著改变Bace1、全长AβPP或C99/C83比值。最后，慢性持续性缺氧在年轻或老年APP/PS1小鼠中均未显著改变Aβ40、Aβ42、全长AβPP或sAβPPα的水平。
我们的结果反对缺氧诱导AβPP蛋白水解从非淀粉样生成途径向淀粉样生成途径转变的观点。我们讨论了先前体内研究可能存在的方法学缺陷。
