title: Altered expression of tight junction molecules in alveolar septa in lung injury and fibrosis.
abstract: The dysfunction of alveolar barriers is a critical factor in the development of lung injury and subsequent fibrosis, but the underlying molecular mechanisms remain poorly understood. To clarify the pathogenic roles of tight junctions in lung injury and fibrosis, we examined the altered expression of claudins, the major components of tight junctions, in the lungs of disease models with pulmonary fibrosis. Among the 24 known claudins, claudin-1, claudin-3, claudin-4, claudin-7, and claudin-10 were identified as components of airway tight junctions. Claudin-5 and claudin-18 were identified as components of alveolar tight junctions and were expressed in endothelial and alveolar epithelial cells, respectively. In experimental bleomycin-induced lung injury, the levels of mRNA encoding tight junction proteins were reduced, particularly those of claudin-18. The integrity of the epithelial tight junctions was disturbed in the fibrotic lesions 14 days after the intraperitoneal instillation of bleomycin. These results suggest that bleomycin mainly injured alveolar epithelial cells and impaired alveolar barrier function. In addition, we analyzed the influence of transforming growth factor-β (TGF-β), a critical mediator of pulmonary fibrosis that is upregulated after bleomycin-induced lung injury, on tight junctions in vitro. The addition of TGF-β decreased the expression of claudin-5 in human umbilical vein endothelial cells and disrupted the tight junctions of epithelial cells (A549). These results suggest that bleomycin-induced lung injury causes pathogenic alterations in tight junctions and that such alterations seem to be induced by TGF-β.
authors: Dept. of Respiratory Medicine, Tohoku University Graduate School of Medicine, Sendai 980-8574, Japan. hiroota4793@gmail.com
authors: Hiromitsu
authors: H
authors: Ohta
authors: Shigeki
authors: S
authors: Chiba
authors: Masahito
authors: M
authors: Ebina
authors: Mikio
authors: M
authors: Furuse
authors: Toshihiro
authors: T
authors: Nukiwa
mesh_terms: D000818:Animals; D001761:Bleomycin; D015824:Blood-Air Barrier / Q000187:drug effects / Q000473:pathology; D002460:Cell Line; D057167:Claudins / Q000378:metabolism*; D004847:Epithelial Cells / Q000187:drug effects / Q000648:ultrastructure; D005260:Female; D061307:Human Umbilical Vein Endothelial Cells; D006801:Humans; D008168:Lung / Q000378:metabolism / Q000473:pathology; D055370:Lung Injury / Q000139:chemically induced / Q000378:metabolism / Q000473:pathology*; D051379:Mice; D008810:Mice, Inbred C57BL; D011650:Pulmonary Alveoli / Q000378:metabolism / Q000473:pathology*; D011658:Pulmonary Fibrosis / Q000139:chemically induced / Q000378:metabolism / Q000473:pathology*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D020545:Respiratory Mucosa / Q000378:metabolism; D019108:Tight Junctions / Q000378:metabolism* / Q000648:ultrastructure*; D016212:Transforming Growth Factor beta / Q000378:metabolism / Q000494:pharmacology
chemical_list: D057167:Claudins; D012333:RNA, Messenger; D016212:Transforming Growth Factor beta; D001761:Bleomycin