E-GEOD-48443 - Knockout mice reveal key roles for claudin-18 in alveolar fluid homeostasis.
Released on 6 April 2014, last updated on 3 June 2014
Claudin proteins are major constituents of epithelial and endothelial tight junctions (TJ), where they serve as regulators of paracellular permeability to ions and solutes. Claudin-18, a member of the large claudin family, is highly expressed in lung epithelium. To elucidate the role of claudin-18 in alveolar epithelial barrier function and fluid homeostasis, we generated claudin-18 knockout (C18 KO) mice. Increased alveolar fluid clearance (AFC) observed in C18 KO mice may have accounted for absence of lung edema despite increased alveolar solute permeability compared to wild type (WT) controls. Higher AFC in C18 KO mice was associated with higher Na-K-ATPase activity and increased expression of the Na-K-ATPase β1 subunit compared to WT controls. Consistent with in vivo findings, alveolar epithelial cell (AEC) monolayers derived from C18 KO mice exhibited lower transepithelial electrical resistance (RT) accompanied by increased solute and ion permeability without changes in ion selectivity. Expression of claudin-3 and claudin-4 was markedly increased in whole lung and in freshly isolated AEC from C18 KO mice, while claudin-5 was unchanged. In contrast, occludin, another major component of the TJ complex, was significantly decreased in C18 KO lung. Further analysis revealed rearrangements in the F-actin cytoskeleton in C18 KO MAECM. These findings demonstrate a crucial non-redundant role for claudin-18 in regulation of alveolar epithelial tight junction composition and permeability to ions and solutes. Importantly, increased AFC in C18 KO mice identifies additional roles for claudin-18 in alveolar fluid homeostasis beyond its direct contributions to barrier properties of the alveolar epithelium. Animals with a ubiquitous knockout (C18 KO) were obtained by crossing mice harboring a conditional (floxed) allele of claudin-18 (Cldn18F/F) with CMV-cre deleter mice to delete exons 2 and 3 by Cre/loxP recombination.
transcription profiling by array
Arnold Sipos, Beiyun Zhou, Crystal N Marconett, Danping Gao, Edward D Crandall, Guanglei Li, Hidenori Kage, Ite A Laird-Offringa, Janice M Liebler, Jiao Luo, Kwang-Jin Kim, LaMonta L Beard, Lucas DeMaio, Parviz Minoo, Per Flodby, Yong H Kim, Zea Borok
Knockout mice reveal key roles for claudin 18 in alveolar barrier properties and fluid homeostasis. Li G, Flodby P, Luo J, Kage H, Sipos A, Gao D, Ji Y, Beard LL, Marconett CN, Demaio L, Kim YH, Kim KJ, Laird-Offringa IA, Minoo P, Liebler JM, Zhou B, Crandall ED, Borok Z. , Europe PMC 24588076