title: Photosensitized oxidation and inactivation of pyocyanin, a virulence factor of Pseudomonas aeruginosa.
abstract: Pyocyanin (PyO-) (1-hydroxy-5-methylphenazine) is a cytotoxic compound secreted by Pseudomonas aeruginosa, an omnipresent bacterium and a human pathogen. We report that visible light illumination in the presence of rose bengal, or riboflavin, in aerated solutions (pH 7.0-7.2) induces irreversible loss of the pigment's characteristic absorption band at 690 nm, indicating its oxidation. This photobleaching was paralleled by generation of a multiline Electron Paramagnetic Resonance (EPR) spectrum attributed to a PyO(-)-derived radical. The reaction was dependent on the presence of air, sensitizers and light, was inhibited by sodium azide and was unaffected by ethanol. This suggests that PyO- was oxidized largely via singlet oxygen and that hydroxyl radicals were not involved. The photochemically modified pigment was less efficient in oxidizing NAD(P)H and generated less superoxide (by approximately 50%) than the intact PyO-, indicating its partial inactivation. 1-Methoxy-5-methylphenazine, a PyO- analog in which the -O- moiety was replaced by the methoxy group (-OMe), was resistant to oxidation, suggesting that oxidation of PyO- involves its phenolate moiety. These results also suggest that photosensitization could be a potentially useful method for inactivation of PyO- and, possibly, detoxification of superficial wounds (skin, eye) infected with P. aeruginosa.
authors.affiliation: Research Service, VA Medical Center, Iowa City, Iowa, USA. reszkakj@ucmail.uc.edu
authors.forename: Krzysztof J
authors.initials: KJ
authors.lastname: Reszka
authors.forename: Gerene M
authors.initials: GM
authors.lastname: Denning
authors.forename: Bradley E
authors.initials: BE
authors.lastname: Britigan
mesh_terms: D002478:Cells, Cultured; D004578:Electron Spin Resonance Spectroscopy; D006801:Humans; D017665:Hydroxyl Radical / Q000378:metabolism; D009243:NAD / Q000378:metabolism; D010084:Oxidation-Reduction; D010636:Phenols / Q000737:chemistry / Q000378:metabolism; D038761:Photobleaching; D017319:Photosensitizing Agents / Q000494:pharmacology*; D011550:Pseudomonas aeruginosa / Q000472:pathogenicity / Q000528:radiation effects*; D011710:Pyocyanine / Q000737:chemistry / Q000378:metabolism / Q000528:radiation effects*; D017382:Reactive Oxygen Species / Q000378:metabolism; D019810:Sodium Azide / Q000494:pharmacology; D037521:Virulence Factors / Q000528:radiation effects*
chemical_list: D010636:Phenols; D017319:Photosensitizing Agents; D017382:Reactive Oxygen Species; D037521:Virulence Factors; D009243:NAD; D017665:Hydroxyl Radical; D019810:Sodium Azide; D011710:Pyocyanine