N. Avissar et al., EXTRACELLULAR GLUTATHIONE-PEROXIDASE IN HUMAN LUNG EPITHELIAL LINING FLUID AND IN LUNG-CELLS, American journal of physiology. Lung cellular and molecular physiology, 14(2), 1996, pp. 173-182
The epithelial cells of the lower respiratory tract are exposed to hig
h levels of inhaled oxygen and other oxidants. We hypothesized that lu
ng cells would secrete the antioxidant enzyme, extracellular glutathio
ne peroxidase (eGPx), into epithelial lining fluid (ELF). To investiga
te this hypothesis, we used specific immunoprecipitations of GPx enzym
es from ELF, specific immunoprecipitations of Se-75 metabolically labe
led proteins from lung cells in culture, and in situ hybridization, No
rthern blot, and reverse transcription-polymerase chain reaction (RT-P
CR) analyses. Fifty-seven percent of ELF GPx activity was due to eGPx
and 40% was due to cellular GPx (cGPx). Primary bronchial epithelial c
ells (BEG), 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 ce
lls of tissue surrounding airways. It is concluded that more than half
of GPx activity in BAL is due to eGPx, and that BEG, AM, and intersti
tial cells are potential sources of pulmonary eGPx.