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Oxidant-Injured Airway Epithelial Cells Upregulate Thioredoxin but Do Not Produce Interleukin-8

Center for Comparative Respiratory Biology and Medicine, and Department of Anatomy, Physiology, and Cell Biology, School of Veterinary Medicine, University of California Davis, Davis, California

Address correspondence to: Dallas M. Hyde, Ph.D., The Center for Comparative Respiratory Biology and Medicine, School of Veterinary Medicine, One Shields Ave., Davis, CA 95616. E-mail: dmhyde{at}ucdavis.edu

We tested the hypothesis that oxidant-injured cells upregulate thioredoxin, whereas oxidant-stressed, but not injured, cells upregulate interleukin (IL)-8 after injury. We exposed primary human tracheobronchial epithelial cells and transformed human bronchial epithelial cells (BEAS-2B S.6) to 0, 200, 400, or 600 µM H₂O₂ for 1 h followed by an additional 7 h of incubation. Subsequently, the cells were double-labeled with markers of injury (either Ethidium Homodimer-1 for cellular injury or MitoTracker dye for functional mitochondria) or oxidant stress (5-[and 6]-chloromethyl-2',7'-dicholorodihydrofluorescein diacetate) and antibodies specific for the chemoattractants IL-8 or thioredoxin. We found significant inverse relationships between numbers and stained chemoattractant volumes of IL-8 and thioredoxin-positive cells with increasing H₂O₂ dose. Cells with mitochondrial injury produced thioredoxin but not IL-8, and oxidant-stressed cells were more likely to produce thioredoxin than IL-8. Isolated human neutrophils were more likely to colocalize with thioredoxin-positive BEAS-2B S.6 cells than thioredoxin-negative cells. The H₂O₂ injury did not induce significant apoptosis in the BEAS-2B S.6 cells as measured by caspase 3 activation. We conclude that oxidant-injured and stressed airway epithelial cells upregulate thioredoxin, but produce little IL-8, which may be important in airway epithelial cell–mediated multistep navigation of neutrophils to sites of oxidant injury.

Abbreviations: activator protein-1, AP-1 • bronchial epithelial growth medium, BEGM • bovine serum albumin, BSA • fluorescein isothiocyanate, FITC • Hanks' balanced salt solution, HBSS • interleukin, IL • nuclear factor IL-6, NF–IL-6 • nuclear factor-B, NF-B • phosphate-buffered saline, PBS • phycoerythrin, PE • room temperature, RT • tumor necrosis factor-, TNF- • tracheobronchial epithelial cells, TBE cells