Knockout Mice Reveal Key Roles for Claudin 18 in Alveolar Barrier Properties and Fluid Homeostasis
Knockout Mice Reveal Key Roles for Claudin 18 in Alveolar Barrier Properties and Fluid Homeostasis
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DOI：
10.1165/rcmb.2013-0353oc
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发表时间：
2014-08-01
影响因子：
6.4
通讯作者：
Borok, Zea
中科院分区：
文献类型：
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作者：
Li, Guanglei;Flodby, Per;Borok, Zea
密蛋白是上皮和内皮紧密连接 (TJ) 的主要成分，可调节细胞旁细胞对离子和溶质的通透性。 Claudin 18 是紧密蛋白大家族的成员，在肺泡上皮细胞中高度表达。为了阐明紧密蛋白 18 在肺泡上皮屏障功能中的作用，我们培育了紧密蛋白 18 敲除 (C18 KO) 小鼠。与野生型对照小鼠相比，C18 KO 小鼠表现出溶质通透性和肺泡液清除率 (AFC) 增加。 C18KO 小鼠中 AFC 的增加与 β-肾上腺素能受体信号传导的增加以及囊性纤维化跨膜电导调节因子的激活、较高的上皮钠通道和 Na-K-ATP 酶（钠泵）活性以及 Na-K-ATP 酶 β 1 亚基表达的增加有关。与体内研究结果一致，C18 KO 肺泡上皮细胞 (AEC) 单层表现出较低的跨上皮电阻以及增加的溶质和离子渗透性，而离子选择性不变。 C18 KO 小鼠中 Claudin 3 和 Claudin 4 表达显着增加，而 Claudin 5 表达没有变化，occludin 显着减少。微阵列分析揭示了 C18 KO 小鼠细胞骨架相关基因表达的变化，与在 AEC 单层中观察到的 F-肌动蛋白细胞骨架重排一致。这些发现证明紧密蛋白 18 在调节肺泡上皮 TJ 组成和通透性特性中发挥着至关重要的非冗余作用。 C18 KO 小鼠中 AFC 的增加表明，密蛋白 18 在肺泡液稳态中的作用超出了其对屏障特性的直接贡献，这可能至少部分补偿了通透性的增加。
Claudin proteins are major constituents of epithelial and endothelial tight junctions (TJs) that regulate paracellular permeability to ions and solutes. Claudin 18, a member of the large claudin family, is highly expressed in lung alveolar epithelium. To elucidate the role of claudin 18 in alveolar epithelial barrier function, we generated claudin 18 knockout (C18 KO) mice. C18 KO mice exhibited increased solute permeability and alveolar fluid clearance (AFC) compared with wild-type control mice. Increased AFC in C18KO mice was associated with increased beta-adrenergic receptor signaling together with activation of cystic fibrosis transmembrane conductance regulator, higher epithelial sodium channel, and Na-K-ATPase (Na pump) activity and increased Na-K-ATPase beta 1 subunit expression. Consistent with in vivo findings, C18 KO alveolar epithelial cell (AEC) monolayers exhibited lower transepithelial electrical resistance and increased solute and ion permeability with unchanged ion selectivity. Claudin 3 and claudin 4 expression was markedly increased in C18 KO mice, whereas claudin 5 expression was unchanged and occludin significantly decreased. Microarray analysis revealed changes in cytoskeleton associated gene expression in C18 KO mice, consistent with observed F-actin cytoskeletal rearrangement in AEC monolayers. These findings demonstrate a crucial nonredundant role for claudin 18 in the regulation of alveolar epithelial TJ composition and permeability properties. Increased AFC in C18 KO mice identifies a role for claudin 18 in alveolar fluid homeostasis beyond its direct contributions to barrier properties that may, at least in part, compensate for increased permeability.