Claudin 4 knockout mice: normal physiological phenotype with increased susceptibility to lung injury

H Kage, P Flodby, D Gao, YH Kim… - … of Physiology-Lung …, 2014 - journals.physiology.org
H Kage, P Flodby, D Gao, YH Kim, CN Marconett, L DeMaio, KJ Kim, ED Crandall, Z Borok
American Journal of Physiology-Lung Cellular and Molecular …, 2014journals.physiology.org
Claudins are tight junction proteins that regulate paracellular ion permeability of epithelium
and endothelium. Claudin 4 has been reported to function as a paracellular sodium barrier
and is one of three major claudins expressed in lung alveolar epithelial cells (AEC). To
directly assess the role of claudin 4 in regulation of alveolar epithelial barrier function and
fluid homeostasis in vivo, we generated claudin 4 knockout (Cldn4 KO) mice. Unexpectedly,
Cldn4 KO mice exhibited normal physiological phenotype although increased permeability …
Claudins are tight junction proteins that regulate paracellular ion permeability of epithelium and endothelium. Claudin 4 has been reported to function as a paracellular sodium barrier and is one of three major claudins expressed in lung alveolar epithelial cells (AEC). To directly assess the role of claudin 4 in regulation of alveolar epithelial barrier function and fluid homeostasis in vivo, we generated claudin 4 knockout (Cldn4 KO) mice. Unexpectedly, Cldn4 KO mice exhibited normal physiological phenotype although increased permeability to 5-carboxyfluorescein and decreased alveolar fluid clearance were noted. Cldn4 KO AEC monolayers exhibited unchanged ion permeability, higher solute permeability, and lower short-circuit current compared with monolayers from wild-type mice. Claudin 3 and 18 expression was similar between wild-type and Cldn4 KO alveolar epithelial type II cells. In response to either ventilator-induced lung injury or hyperoxia, claudin 4 expression was markedly upregulated in wild-type mice, whereas Cldn4 KO mice showed greater degrees of lung injury. RNA sequencing, in conjunction with differential expression and upstream analysis after ventilator-induced lung injury, suggested Egr1, Tnf, and Il1b as potential mediators of increased lung injury in Cldn4 KO mice. These results demonstrate that claudin 4 has little effect on normal lung physiology but may function to protect against acute lung injury.
American Physiological Society