Oxidative Stress By Pyocyanin Impairs CFTR Cl- Transport In Human Bronchial Epithelial Cells

• Published in: Free radical biology & medicine 2008-09, 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
• 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 2 O 2 3-fold above the endogenous H 2 O 2 production. Real-time measurements of the redox-potential of the cytosolic compartment using the redox sensor roGFP1 showed that pyocyanin (100 μM) oxidized the cytosol from a resting value of -318 ± 5 mV by 48.0 ± 4.6 mV within 2 hours; a comparable oxidation was induced by 100 μM H 2 O 2 . While resting Cl - secretion was slightly activated by pyocyanin (to 10% of maximal currents), forskolin-stimulated Cl - secretion was inhibited by 86%. The decline was linearly related to the cytosolic redox potential (1.8% inhibition/mV oxidation). CF bronchial epithelial cells homozygous for ΔF508 CFTR failed to secrete Cl - in response to pyocyanin or H 2 O 2 indicating that these oxidants specifically target CFTR and not other Cl - conductances. Treatment with pyocyanin also decreased total cellular glutathione levels to 62% and cellular ATP levels to 46% after 24 hours. We conclude that pyocyanin is a key factor that redox cycles in the cytosol, generates H 2 O 2 , depletes glutathione and ATP, and impairs CFTR function in Pseudomonas infected lungs.