Extracellular glutathione peroxidase in human lung epithelial lining fluid and in lung cells

The epithelial cells of the lower respiratory tract are exposed to high levels of inhaled oxygen and other oxidants. We hypothesized that lung cells would secrete the antioxidant enzyme, extracellular glutathione peroxidase (eGPx), into epithelial lining fluid (ELF). To investigate this hypothesis,...

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Published inThe American journal of physiology Vol. 270; no. 2 Pt 1; p. L173
Main Authors Avissar, N, Finkelstein, J N, Horowitz, S, Willey, J C, Coy, E, Frampton, M W, Watkins, R H, Khullar, P, Xu, Y L, Cohen, H J
Format Journal Article
LanguageEnglish
Published United States 01.02.1996
Subjects
Adolescent
Adult
Animals
Base Sequence
Bronchoalveolar Lavage Fluid - chemistry
Bronchoalveolar Lavage Fluid - cytology
Cell Separation
Cells, Cultured
Epithelial Cells
Epithelium - enzymology
Extracellular Space - enzymology
Glutathione Peroxidase - genetics
Glutathione Peroxidase - metabolism
Humans
In Situ Hybridization
Lung - cytology
Lung - enzymology
Molecular Probes - genetics
Molecular Sequence Data
Rabbits
RNA, Messenger - metabolism
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Summary:The epithelial cells of the lower respiratory tract are exposed to high levels of inhaled oxygen and other oxidants. We hypothesized that lung cells would secrete the antioxidant enzyme, extracellular glutathione peroxidase (eGPx), into epithelial lining fluid (ELF). To investigate this hypothesis, we used specific immunoprecipitations of GPx enzymes from ELF, specific immunoprecipitations of 75Se metabolically labeled proteins from lung cells in culture, and in situ hybridization, Northern blot, and reverse transcription-polymerase chain reaction (RT-PCR) analyses. Fifty-seven percent of ELF GPx activity was due to eGPx and 40% was due to cellular GPx (cGPx). Primary bronchial epithelial cells (BEC), primary alveolar macrophages (AM), and two human bronchial epithelial cell lines, BEP2D and A549, synthesized both eGPx and cGPx and secreted eGPx into the medium. Freshly isolated human AM and BEC expressed eGPx mRNA, while freshly isolated rabbit type 2 pneumocytes did not. In lung tissue, eGPx mRNA was found mainly in interstitial cells of tissue surrounding airways. It is concluded that more than half of GPx activity in BAL is due to eGPx, and that BEC, AM, and interstitial cells are potential sources of pulmonary eGPx.
ISSN:0002-9513
2163-5773
DOI:10.1152/ajplung.1996.270.2.l173