title: Cathepsin B is activated as an executive protease in fetal rat alveolar type II cells exposed to hyperoxia.
abstract: Alveolar type II cells are main target of hyperoxia-induced lung injury. The authors investigated whether lysosomal protease, cathepsin B (CB), is activated in fetal alveolar type II cells in the transitional period from the canalicular to saccular stages during 65%-hyperoxia and whether CB is related to fetal alveolar type II cell (FATIIC) death secondary to hyperoxia. FATIICs were isolated from embryonic day 19 rats and exposed to 65%-oxygen for 24 h and 36 h. The cells exposed to room air were used as controls. Cell cytotoxicity was assessed by lactate dehydrogenase-release and flow cytometry, and apoptosis was analyzed by TUNEL assay and flow cytometry. CB activity was assessed by colorimetric assay, qRT-PCR and western blots. 65%-hyperoxia induced FATIIC death via necrosis and apoptosis. Interestingly, caspase-3 activities were not enhanced in FATIICs during 65%-hyperoxia, whereas CB activities were greatly increased during 65%-hyperoxia in a time-dependent manner, and similar findings were observed with qRT-PCR and western blots. In addition, the preincubation of CB inhibitor prior to 65%-hyperoxia reduced FATIIC death significantly. Our studies suggest that CB activation secondary to hyperoxia might have a relevant role in executing the cell death program in FATIICs during the acute stage of 65%-hyperoxia.
authors.affiliation: Department of Pediatrics, Kangwon National University Hospital, Kangwon Naitonal University School of Medicine, Chuncheon, Korea. premee@kangwon.ac.kr
authors.forename: Hyeon-Soo
authors.initials: HS
authors.lastname: Lee
authors.forename: Chun-Ki
authors.initials: CK
authors.lastname: Kim
mesh_terms: D056809:Alveolar Epithelial Cells / Q000166:cytology / Q000378:metabolism*; D000818:Animals; D053148:Caspase 3; D002401:Cathepsin B / Q000378:metabolism*; D016923:Cell Death; D015687:Cell Hypoxia; D004789:Enzyme Activation; D005260:Female; D020287:In Situ Nick-End Labeling; D007770:L-Lactate Dehydrogenase / Q000032:analysis; D008168:Lung / Q000378:metabolism; D009336:Necrosis / Q000378:metabolism; D010100:Oxygen; D016133:Polymerase Chain Reaction; D011247:Pregnancy; D011650:Pulmonary Alveoli / Q000166:cytology / Q000196:embryology / Q000201:enzymology*; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D007770:L-Lactate Dehydrogenase; D053148:Caspase 3; D002401:Cathepsin B; C533916:Ctsb protein, rat; D010100:Oxygen