Oxidative stress caused by pyocyanin impairs CFTR Cl super(-) transport in human bronchial epithelial cells

• Published in: Free radical biology & medicine 2008-12, Vol.45 (12), p.1653-1662
• Main Authors: Schwarzer, Christian, Fischer, Horst, Kim, Eun-Jin, Barber, Katharine J, Mills, Aaron D, Kurth, Mark J, Gruenert, Dieter C, Suh, Jung H, Machen, Terry E, Illek, Beate
• Format: Article
• Language: English
• Subjects: Pseudomonas aeruginosa
• ISSN: 0891-5849
• DOI: 10.1016/j.freeradbiomed.2008.09.011

Pyocyanin (N-methyl-1-hydroxyphenazine), a redox-active virulence factor produced by the human pathogen Pseudomonas aeruginosa, is known to compromise mucociliary clearance. Exposure of human bronchial epithelial cells to pyocyanin increased the rate of cellular release of H sub(2)O sub(2) threefold above the endogenous H sub(2)O sub(2) production. Real-time measurements of the redox potential of the cytosolic compartment using the redox sensor roGFP1 showed that pyocyanin (100 mu M) oxidized the cytosol from a resting value of - 318 +/- 5 mV by 48.0 +/- 4.6 mV within 2 h; a comparable oxidation was induced by 100 mu M H sub(2)O sub(2). Whereas resting Cl super(-) secretion was slightly activated by pyocyanin (to 10% of maximal currents), forskolin-stimulated Cl super(-) secretion was inhibited by 86%. The decline was linearly related to the cytosolic redox potential (1.8% inhibition/mV oxidation). Cystic fibrosis bronchial epithelial cells homozygous for Delta F508 CFTR failed to secrete Cl super(-) in response to pyocyanin or H sub(2)O sub(2), indicating that these oxidants specifically target the CFTR and not other Cl super(-) conductances. Treatment with pyocyanin also decreased total cellular glutathione levels to 62% and cellular ATP levels to 46% after 24 h. We conclude that pyocyanin is a key factor that redox cycles in the cytosol, generates H sub(2)O sub(2), depletes glutathione and ATP, and impairs CFTR function in Pseudomonas-infected lungs.