Laboratory of Mucosal Immunology and Immunoregulation, VIB Center for Inflammation Research, Ghent, Belgium; Department of Internal Medicine and Pediatrics, Ghent University, Ghent, Belgium.
Institute of Clinical Chemistry, University and University Hospital Zurich, Zurich, Switzerland.
J Allergy Clin Immunol. 2019 Dec;144(6):1648-1659.e9. doi: 10.1016/j.jaci.2019.06.041. Epub 2019 Jul 20.
Genome-wide association studies in asthma have repeatedly identified single nucleotide polymorphisms in the ORM (yeast)-like protein isoform 3 (ORMDL3) gene across different populations. Although the ORM homologues in yeast are well-known inhibitors of sphingolipid synthesis, it is still unclear whether and how mammalian ORMDL3 regulates sphingolipid metabolism and whether altered sphingolipid synthesis would be causally related to asthma risk.
We sought to examine the in vivo role of ORMDL3 in sphingolipid metabolism and allergic asthma.
Ormdl3-LacZ reporter mice, gene-deficient Ormdl3 mice, and overexpressing Ormdl3 mice were exposed to physiologically relevant aeroallergens, such as house dust mite (HDM) or Alternaria alternata, to induce experimental asthma. Mass spectrometry-based sphingolipidomics were performed, and airway eosinophilia, T2 cytokine production, immunoglobulin synthesis, airway remodeling, and bronchial hyperreactivity were measured.
HDM challenge significantly increased levels of total sphingolipids in the lungs of HDM-sensitized mice compared with those in control mice. In Ormdl3 mice the allergen-induced increase in lung ceramide levels was significantly reduced, whereas total sphingolipid levels were not affected. Conversely, in liver and serum, levels of total sphingolipids, including ceramides, were increased in Ormdl3 mice, whereas they were decreased in Ormdl3 mice. This difference was independent of allergen exposure. Despite these changes, all features of asthma were identical between wild-type, Ormdl3, and Ormdl3 mice across several models of experimental asthma.
ORMDL3 regulates systemic ceramide levels, but genetically interfering with Ormdl3 expression does not result in altered experimental asthma.
哮喘的全基因组关联研究在不同人群中反复发现了酵母样蛋白异构体 3（ORMDL3）基因中的单核苷酸多态性。尽管酵母中的 ORM 同源物是众所周知的鞘脂合成抑制剂，但哺乳动物 ORMDL3 是否以及如何调节鞘脂代谢，以及鞘脂合成的改变是否与哮喘风险有因果关系，目前尚不清楚。
我们旨在研究 ORMDL3 在鞘脂代谢和过敏性哮喘中的体内作用。
使用 ORMDL3-LacZ 报告基因小鼠、基因缺失 Ormdl3 小鼠和过表达 Ormdl3 小鼠暴露于生理相关的气传过敏原，如屋尘螨（HDM）或Alternaria alternata，以诱导实验性哮喘。进行基于质谱的鞘脂组学分析，并测量气道嗜酸性粒细胞浸润、T2 细胞因子产生、免疫球蛋白合成、气道重塑和气道高反应性。
与对照组相比，HDM 致敏小鼠的肺部总鞘脂水平在 HDM 挑战后显著增加。在 Ormdl3 小鼠中，过敏原诱导的肺神经酰胺水平增加显著减少，而总鞘脂水平不受影响。相反，在肝脏和血清中，总鞘脂水平，包括神经酰胺，在 Ormdl3 小鼠中增加，而在 Ormdl3 小鼠中减少。这种差异与过敏原暴露无关。尽管存在这些变化，但在几种实验性哮喘模型中，野生型、Ormdl3 和 Ormdl3 小鼠的哮喘所有特征均相同。
ORMDL3 调节系统性神经酰胺水平，但遗传干扰 Ormdl3 表达不会导致实验性哮喘改变。
