Interferon γ stimulates accumulation of gas phase nitric oxide in differentiated cultures of normal and cystic fibrosis airway epithelial cells.
BACKGROUND
Exhaled nitric oxide (NO) levels have been reported to be lower in patients with cystic fibrosis (CF) than in controls; however the mechanism(s) responsible and the effect on pathogenesis are unclear. The objective of these studies was to determine if the low levels of gas phase NO (gNO) could be reproduced in well-differentiated air-liquid interface (ALI) cultures of normal and CF cells.


METHODS
Human bronchial epithelial (HBE) cells from CF and control tissues were cultured under ALI conditions that promote differentiation into a mostly ciliated, pseudostratified epithelium similar to that of the in vivo airway. Cultures were incubated in gas tight chambers and the concentration of gNO was measured using a Sievers nitric oxide analyzer.


RESULTS
In CF and control cultures the level of accumulated gNO under baseline conditions was low (<20 ppb). Treatment with interferon gamma (IFNγ) induced iNOS expression and increased gNO significantly in differentiated cultures, while having no significant effect on undifferentiated cultures. Submersion of the apical surface with fluid drastically reduced the level of gNO. Importantly, the average level of gNO measured after IFNγ treatment of control cells (576 ppb) was threefold greater than that from CF cells (192 ppb).


CONCLUSIONS
The results demonstrate that the lower level of exhaled NO observed in CF patients is reproduced in well-differentiated primary cultures of HBE cells treated with IFNγ, supporting the hypothesis that the regulation of NO production is altered in CF. The results also demonstrate that IFNγ treatment of differentiated cells results in higher levels of gNO than treatment of undifferentiated cells, and that a layer of fluid on the apical surface drastically reduces the amount of gNO, possibly by limiting the availability of oxygen.
Department of Cell and Developmental Biology, Cystic Fibrosis/Pulmonary Research and Treatment Center, School of Medicine, The University of North Carolina, CB# 7248, 6123A Thurston-Bowles Bldg., Chapel Hill, NC 27599-7248, USA. ostro@med.unc.edu
Lawrence E
LE
Ostrowski
Daniel
D
Stewart
Milan
M
Hazucha
D001980:Bronchi / Q000187:drug effects* / Q000378:metabolism; D002454:Cell Differentiation; D002478:Cells, Cultured; D003550:Cystic Fibrosis / Q000188:drug therapy* / Q000378:metabolism; D004847:Epithelial Cells / Q000187:drug effects / Q000378:metabolism; D006801:Humans; D007371:Interferon-gamma / Q000494:pharmacology*; D009569:Nitric Oxide / Q000032:analysis / Q000096:biosynthesis*; D052247:Nitric Oxide Synthase Type II / Q000096:biosynthesis
D009569:Nitric Oxide; D007371:Interferon-gamma; C496319:NOS2 protein, human; D052247:Nitric Oxide Synthase Type II