Interaction of the Pseudomonas aeruginosa secretory products pyocyanin and pyochelin generates hydroxyl radical and causes synergistic damage to endothelial cells. Implications for Pseudomonas-associated tissue injury.

Abstract

IntroductionPyocyanin, a secretory product of Pseudomonas aeruginosa, has the capacity to undergo redox cycling under aerobic conditions with resulting generation of superoxide and hydrogen peroxide. By using spin trapping techniques in conjunction with electron paramagnetic resonance spectrometry (EPR), superoxide was detected during the aerobic reduction of pyocyanin by NADH or porcine endothelial cells. No evidence of hydroxyl radical formation was detected. Chromium oxalate eliminated the EPR spectrum of the superoxide-derived spin adduct resulting from endothelial cell exposure to pyocyanin, suggesting superoxide formation close to the endothelial cell plasma membrane. We have previously reported that iron bound to the P. aeruginosa siderophore pyochelin (ferripyochelin) catalyzes the formation of hydroxyl free radical from superoxide and hydrogen peroxide via the Haber-Weiss reaction. In the present study, spin trap evidence of hydroxyl radical formation was detected when NADH and pyocyanin were allowed to react in the presence of ferripyochelin. Similarly, endothelial cell exposure to pyocyanin and ferripyochelin also resulted in hydroxyl radical production which appeared to occur in close proximity to the cell surface. As assessed by 51Cr release, endothelial cells which were treated with pyocyanin or ferripyochelin alone demonstrated minimal injury. However, endothelial cell exposure to the combination of pyochelin and pyocyanin resulted in 55% specific 51Cr release. Injury was not observed with the substitution of iron-free pyochelin and was diminished by the presence of catalase or dimethyl thiourea. These data suggest the possibility that the P. aeruginosa secretory products pyocyanin and pyochelin may act synergistically via the generation of hydroxyl radical to damage local tissues at sites of pseudomonas infection. (J. Clin. Invest. 1992. 90:2187-2196

The Multiple Signaling Systems Regulating Virulence in Pseudomonas aeruginosa

“…7), a specificity that has been useful in the rapid diagnosis of this opportunistic pathogen (63,76,100). This blue phenazine is one of the major virulence factors in this pathogen, contributing to both acute and chronic infections (123,207), as it suppresses lymphocyte proliferation (146), damages epithelial cells as a consequence of hydroxyl radical formation (20,207), inactivates protease inhibitors (consequently causing tissue damage by endogenous proteases) (19), and targets multiple cellular functions (44,101,139,166,185,196).…”

Biological effects of menadione photochemistry: effects of menadione on biological systems may not involve classical oxidant production

“…Since we routinely detect DMPO\dOH formation as a consequence of pyocyanine-induced O # d − generation in A549 cells [25,29,30], we hypothesized that the formation of DMPO\dOH in A549 cells exposed to menadione resulted from O # d − formation by similar cell-associated pathways. However, in contrast to our previous experience with pyocyanine or paraquat [14,25,[29][30][31], we observed that exogenous addition of superoxide dismutase (SOD) was apparently ineffective at inhibiting DMPO\dOH generation resulting from the addition of menadione to samples containing A549 cells (results not shown). These results suggested that a mechanism other than O # d − formation could be responsible for the DMPO\dOH detected in response to menadione.…”

Discovery of a biofilm electrocline using real-time 3D metabolite analysis

“…PYO was chosen for study because it is a multifunctional molecule, serving both as a QS signal (26), a potent antimicrobial in vitro and in situ (3,27), and as a virulence factor important for P. aeruginosa pathogenesis (28,29). Our data reveal that P. aeruginosa biofilms produce high levels of PYO that is actively maintained in the reduced state proximal to the biofilm.…”