Pyocyanin and Its Precursor Phenazine-1-Carboxylic Acid Increase IL-8 and Intercellular Adhesion Molecule-1 Expression in Human Airway Epithelial Cells by Oxidant-Dependent Mechanisms

Abstract

Pseudomonas aeruginosa secretes numerous factors that alter host cell function and may contribute to disease pathogenesis. Among recognized virulence factors is the redox-active phenazine pyocyanin. We have recently demonstrated that the precursor for pyocyanin, phenazine-1-carboxylic acid (PCA), increases oxidant formation and alters gene expression in human airway epithelial cells. We report in this work that PCA and pyocyanin increase expression of ICAM-1 both in vivo and in vitro. Moreover, phenazines enhanced cytokine-dependent increases in IL-8 and ICAM-1. Antioxidant intervention studies indicated both similarities and differences between PCA and pyocyanin. The thiol antioxidant N-acetyl cysteine, extracellular catalase, and inducible NO synthase inhibitors inhibited ICAM-1 and IL-8 increases in response to both phenazines. However, pyocyanin was significantly more sensitive to N-acetylcysteine inhibition. Interestingly, hydroxyl radical scavengers inhibited the response to pyocyanin, but not to PCA. These studies suggest that P. aeruginosa phenazines coordinately up-regulate chemokines (IL-8) and adhesion molecules (ICAM-1) by mechanisms that are, at least in part, oxidant dependent. However, results indicate that the mechanisms by which PCA and pyocyanin exert their effects are not identical, and not all antioxidant interventions are equally effective in inhibiting phenazine-mediated proinflammatory effects.

Redox-independent Activation of NF-κB by Pseudomonas aeruginosa Pyocyanin in a Cystic Fibrosis Airway Epithelial Cell Line

“…Unpublished experiments have shown similar synergism between PYO and TNF␣ in activating NF-B-luciferase (data not shown). 3 Previous experiments showed that 24 h of exposure to PYO elicited similar activation of NF-B in the presence of TNF␣ or IL1␤ (18). Thus, PYO elicited synergistic activation of NF-B in the presence of agonists that activated NF-B.…”

“…However, even in this condition PYO may be an important modulator of 3 C. Schwarzer and T. E. Machen, unpublished observations. innate immune responses of airway epithelial cells because both neutrophils and macrophages release IL1␤ and TNF␣ and other proinflammatory cytokines that activate NF-B into the ASL, and PYO may then synergize with these to augment responses of the airway epithelia (17,18).…”

“…and, through the action of superoxide dismutase, H 2 O 2 might contribute to proinflammatory signaling by PYO (16). In addition, the antioxidant N-acetylcysteine and the HO ⅐ scavenger DMSO reduced the proinflammatory effects of PYO, consistent with PYO triggering inflammatory processes through its pro-oxidant effects (18). However, none of these experiments made direct, quantitative measurements on the proposed effect of PYO to produce ROS and oxidize the cytosol.…”

6-Hydroxymethyl-1-phenazine-carboxamide and 1,6-phenazinedimethanol from a marine bacterium, Brevibacterium sp. KMD 003, associated with marine purple vase sponge

“…24 PCA also increases oxidant formation and alters the expression of IL-8 (interleukin-8) and ICAM-1 (intercellular adhesion molecule-1) in human airway epithelial cells by oxidant-dependent mechanisms. 27 Compounds 1 and 2 showed antimicrobial activity toward three human pathogenic microorganisms (MIC 50 ¼20 mM against B. subtilis, 5 mM against E. hirae and 5 mM against M. luteus). In previously reported literature, 23 the structural neighbors of compound 1, PCA and PCN, efficiently inhibited the growth of Bacillus cereus (MIC o2 mM), whereas showed only modest antimicrobial activity against M. luteus (MIC 20 mM).…”

Virulence profiles of clinical and environmental Pseudomonas aeruginosa isolates from Central Morocco

“…Pyocyanin, a representative pigment produced by P. aeruginosa, targets multiple cellular functions and contributes to acute as well as chronic infections, as it has several effects such as stimulating IL-8 release (Look et al, 2005), depressing host-response and inducing apoptosis in neutrophils (Allen et al, 2005). Pyoverdin is also a virulence marker in this pathogen, it was found that pyoverdin regulates its own secretion and the secretion of other P. aeruginosa virulence factors, such as exotoxin A (Lamont et al, 2002).…”