Quenching of Singlet Oxygen by Pyocyanin and Related Phenazines

Authors

  • Krzysztof J. Reszka,

    Corresponding author
    1. Research Service and Medical Service, VA Medical Center, Cincinnati, OH, USA
    2. Department of Internal Medicine, University of Cincinnati, Cincinnati, OH, USA
      Corresponding author email: reszkakj@ucmail.uc.edu (Krzysztof J. Reszka)
    Search for more papers by this author
  • Piotr J. Bilski,

    1. Laboratory of Pharmacology, National Institute of Environmental Health Sciences, NIH, Research Triangle Park, NC, USA
    Search for more papers by this author
    • Contract to SRA International.

  • Bradley E. Britigan

    1. Research Service and Medical Service, VA Medical Center, Cincinnati, OH, USA
    2. Department of Internal Medicine, University of Cincinnati, Cincinnati, OH, USA
    Search for more papers by this author

  • This invited paper is part of the Symposium-in-Print: “Phototoxicity of the Skin and Eye,” in honor of Dr. Colin Chignell.

Corresponding author email: reszkakj@ucmail.uc.edu (Krzysztof J. Reszka)

Abstract

Pseudomonas aeruginosa is a human pathogen, which causes infections of various organs, including lung, skin and eye, particularly in individuals who are immunocompromised. Pyocyanin (1-hydroxy-5-methylphenazine), a cytotoxic pigment secreted by the bacterium, is among the factors that contribute to virulence of this pathogen. We have previously shown that rose bengal and riboflavin photosensitize oxidation of pyocyanin to a product(s) with diminished reactivity and toxicity. Singlet oxygen was suggested as the major oxidant, based on the inhibitory effect of sodium azide. In the present study, we used the time resolved technique to investigate direct interaction of pyocyanin and related phenazines (1-hydroxyphenazine [1-OH-Phen], 1-methoxy-5-methylphenazine [1-MeO-PCN] and phenazine methosulfate [PMS]) with 1O2. The rate constants for the 1O2 quenching (physical + chemical) by pyocyanin and 1-OH-Phen in D2O buffer (pD ∼7.2) have been determined to be 4.8 × 108 and 6.8 × 108 M−1 s−1, respectively. 1-MeO-PCN and PMS were markedly less efficient 1O2 quenchers. Among the phenazines studied only phenazine methosulfate photogenerated 1O2 (Φ(1O2) = 0.56 in acetonitrile). Interaction of 1O2 with pyocyanin and other related phenazines produced by the bacteria may be important in determining the potential utility of photochemical/pharmacological approaches to eradicate P. aeruginosa from infected tissues.

Ancillary