Neutral Sphingomyelinase-2 Deficiency Ameliorates Alzheimer's Disease Pathology and Improves Cognition in the 5XFAD Mouse
Neutral Sphingomyelinase-2 Deficiency Ameliorates Alzheimer's Disease Pathology and Improves Cognition in the 5XFAD Mouse
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DOI：
10.1523/jneurosci.1429-16.2016
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发表时间：
2016-08-17
影响因子：
5.3
通讯作者：
Bieberich, Erhard
中科院分区：
文献类型：
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作者：
Dinkins, Michael B.;Enasko, John;Bieberich, Erhard
近期证据表明，外泌体与阿尔茨海默病中β - 淀粉样蛋白（Aβ）的聚集以及tau蛋白的扩散有关。在神经细胞中，通过抑制或沉默中性鞘磷脂酶 - 2（nSMase2）可以阻断外泌体的形成。我们培育了基因上nSMase2缺陷的5XFAD小鼠（fro；5XFAD），以在神经酰胺生成持续减少的小鼠模型中评估与阿尔茨海默病相关的病理学特征。我们进行了体外实验，以评估在有和没有通过超速离心分离的外泌体的情况下，Aβ（42）的聚集以及神经胶质的清除情况，并通过颗粒计数确定外泌体诱导的淀粉样蛋白聚集。我们利用场景恐惧条件反射和线索恐惧条件反射，分析了5XFAD小鼠与fro；5XFAD小鼠的脑外泌体含量、淀粉样斑块形成、神经元变性、鞘脂、Aβ（42）和磷酸化tau蛋白水平以及与记忆相关的行为。在体外，星形胶质细胞衍生的外泌体加速了Aβ（42）的聚集，并阻碍了神经胶质对Aβ（42）的清除。通过将一种双功能神经酰胺类似物预装入外泌体进行体外实验，以及使用抗神经酰胺IgG进行体内实验，发现Aβ（42）聚集体与细胞外神经酰胺共定位，这表明富含神经酰胺的外泌体与斑块形成有关。与5XFAD小鼠相比，fro；5XFAD小鼠的脑外泌体、神经酰胺水平、血清抗神经酰胺IgG、神经胶质激活、总Aβ（42）和斑块负荷、tau蛋白磷酸化均降低，并且在恐惧条件学习任务中的认知能力得到改善。富含神经酰胺的外泌体似乎通过促进Aβ的聚集而加剧了与阿尔茨海默病相关的脑部病理。nSMase2功能缺失导致的外泌体分泌减少改善了5XFAD小鼠模型中的病理状况和认知能力。
Recent evidence implicates exosomes in the aggregation of A beta and spreading of tau in Alzheimer's disease. In neural cells, exosome formation can be blocked by inhibition or silencing of neutral sphingomyelinase-2 (nSMase2). We generated genetically nSMase2-deficient 5XFAD mice (fro; 5XFAD) to assess AD-related pathology in a mouse model with consistently reduced ceramide generation. We conducted in vitro assays to assess A beta(42) aggregation and glial clearance with and without exosomes isolated by ultracentrifugation and determined exosome-induced amyloid aggregation by particle counting. We analyzed brain exosome content, amyloid plaque formation, neuronal degeneration, sphingolipid, A beta(42) and phospho-tau levels, and memory-related behaviors in 5XFAD versus fro; 5XFAD mice using contextual and cued fear conditioning. Astrocyte-derived exosomes accelerated aggregation of A beta(42) and blocked glial clearance of A beta(42) in vitro. A beta(42) aggregates were colocalized with extracellular ceramide in vitro using a bifunctional ceramide analog preloaded into exosomes and in vivo using anticeramide IgG, implicating ceramide-enriched exosomes in plaque formation. Compared with 5XFAD mice, the fro; 5XFAD mice had reduced brain exosomes, ceramide levels, serum anticeramide IgG, glial activation, total A beta(42) and plaque burden, tau phosphorylation, and improved cognition in a fear-conditioned learning task. Ceramide-enriched exosomes appear to exacerbate AD-related brain pathology by promoting the aggregation of A beta. Reduction of exosome secretion by nSMase2 loss of function improves pathology and cognition in the 5XFAD mouse model.