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Modulation of Bronchial Epithelial Cell Barrier Function by in vitro Ozone Exposure
Xiao-Ying Yu, Nobuyoshi Takahashi, Thomas L. Croxton, and Ernst W. Spannhake
Department of Environmental Health Sciences, The Johns Hopkins School of Hygiene and Public Health, Baltimore, MD 21205 USA
Abstract
The epithelial cells lining the small, peripheral airways function as important targets for the action of inspired ozone. Loss of epithelial barrier integrity in these regions is a common element in ozone-induced airway inflammation. To investigate the direct effect of ozone on epithelial barrier function, canine bronchial epithelial (CBE) cells grown with an air interface were exposed for 3 hr to 0.2, 0.5, or 0.8 ppm ozone or to air. Mannitol flux, used as an index of paracellular permeability, increased above air controls by 461%, 774%, and 1172% at the three ozone concentrations, respectively. Transcellular electrical resistance exhibited a dose-related decrease. The immediate effect of 0.8 ppm ozone on permeability was significantly inhibited by preincubation for 48 hr in the presence of 1 ng/ml vitamin E (33%) or 1 µM vitamin A (34%). Responses to 0.5 ppm or 0.8 ppm were inhibited by pretreatment of the cells with 0.1 µM of the actin polymerizing agent phalloidin (34% and 25% inhibition, respectively). The increases in permeability induced by 0.2 and 0.5 ppm ozone were attenuated by 54% and 22%, respectively, at 18 hr after exposure, whereas that to 0.8 ppm was further enhanced by 42% at this time. The effects of ozone are modulated by the availability of antioxidants to the cells and appear to be associated with cytoskeletal dysfunction in CBE cells. The data are consistent with a loss of barrier function linked to a direct oxidative effect of ozone on individual CBE cells and indicate that the reversible or progressive nature of this effect is dose dependent. Key words: mannitol, paracellular flux, permeability, primary culture, transepithelial electrical resistance. Environ Health Perspect 102: 1068-1072 (1994).
Please address correspondence to E. W. Spannhake, Division of Physiology, Department of Environmental Health Sciences, Johns Hopkins School of Hygiene and Public Health, 615 N. Wolfe Street, Baltimore, MD 21205 USA.
This paper is dedicated to the memory of our friend and colleague, Nobuyoshi Takahashi, who was a visiting scientist from the Division of Pulmonary Medicine in the Department of Internal Medicine at Tsukuba University, Japan. We thank Jacqueline Luyimbazi for her excellent technical assistance. This work was supported by grants ES 03505 and ES 03819 from the National Institute of Environmental Health Sciences.
