Exp Mol Med.  2011 Apr;43(4):223-229. 10.3858/emm.2011.43.4.027.

Cathepsin B is activated as an executive protease in fetal rat alveolar type II cells exposed to hyperoxia

• Lee HS
• Kim CK

• KMID: 1104392
• DOI: http://doi.org/10.3858/emm.2011.43.4.027

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.

Keyword

caspase-3; cathepsin B; cell death; fetal alveolar type II cell; hyperoxia

MeSH Terms

Animals
Caspase 3
Cathepsin B/*metabolism
Cell Death
Cell Hypoxia
Enzyme Activation
Female
In Situ Nick-End Labeling
L-Lactate Dehydrogenase/analysis
Lung/metabolism
Necrosis/metabolism
Oxygen
Pneumocytes/cytology/*metabolism
Polymerase Chain Reaction
Pregnancy
Pulmonary Alveoli/cytology/embryology/*enzymology
Rats
Rats, Sprague-Dawley