ThePseudomonassecretory product pyocyanin inhibits catalase activity in human lung epithelial cells

Abstract

Pyocyanin, produced by Pseudomonas aeruginosa, has many deleterious effects on human cells that relate to its ability to generate reactive oxygen species (ROS), such as superoxide and hydrogen peroxide. Human cells possess several mechanisms to protect themselves from ROS, including manganese superoxide dismutase (MnSOD), copper zinc superoxide dismutase (CuZnSOD), and catalase. Given the link between pyocyanin-mediated epithelial cell injury and oxidative stress, we assessed pyocyanin's effect on MnSOD, CuZnSOD, and catalase levels in the A549 human alveolar epithelial cell line and in normal human bronchial epithelial cells. In both cell types, CuZnSOD and MnSOD were unaltered, but over 24 h pyocyanin significantly decreased cellular catalase activity and protein content. Pyocyanin also decreased catalase mRNA. Overexpression of MnSOD in A549 cells prevented pyocyanin-mediated loss of catalase protein, but catalase activity still declined. Furthermore, pyocyanin decreased catalase activity, but not protein, in A549 cells overexpressing human catalase. These data suggest a direct effect of pyocyanin on catalase activity. Addition of pyocyanin to catalase in a cell-free system also decreased catalase activity. Mammalian catalase binds four NADPH molecules, helping maintain enzyme activity. Spin-trapping data suggest that pyocyanin directly oxidizes this NADPH, producing superoxide. We conclude that pyocyanin may decrease cellular catalase activity via both transcriptional regulation and direct inactivation of the enzyme. Decreased cellular catalase activity and failure to augment MnSOD could contribute to pyocyanin-dependent cytotoxicity.

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

“…PYO-deficient P. aeruginosa elicits less mortality in P. aeruginosa-mediated burn-sepsis model in mice, and PYO appears to be important for persistence of P. aeruginosa in lungs of CF patients (3,4,11). PYO has a multitude of effects on the physiology of epithelial cells, including inhibition or alteration of antioxidant enzymes (12,13), ciliary function (14), cellular metabolism, and organelle H ϩ v-ATPase (2,15). A key aspect of PYO pathology may result from its ability to trigger inflammation leading to the influx of neutrophils to the P. aeruginosa-infected region; PYO stimulates ICAM-1 and IL8 production on its own and also synergizes with IL1␤ and TNF␣ in stimulating IL8 production (16 -18).…”

Caspase-3-dependent Cell Death in B lymphocyte Caused by Pseudomonas aeruginosa Pyocyanin

“…The cytotoxicity of pyocyanin were also confirmed by previous studies on bronchial epithelium, pulmonary epithelium, and neutrophil. [6][7][8] Pyocyanin induced production of inflammatory mediators and caused cellular change on bronchial epithelium. Those mechanisms involved disturbance of intracellular antioxidant function that result in the inhibition of catalase activity.…”

“…Those mechanisms involved disturbance of intracellular antioxidant function that result in the inhibition of catalase activity. 6 Implication of death mechanism on B cell induced by pyocyanin indicates disturbance in the immune responses played by this cell. B lymphocyte plays an important role in humoral immune system.…”

“…This cytotoxin is responsible for the bacterial invasion, induction of inflammatory reaction, and cellular damage on respiratory epithelium cells, apoptotic cell death on neutrophil, and persistent infection caused by P. aeruginosa. [6][7][8] In adition, pyocyanin also cause apoptotic cell death on neutrophil. This ability facilitate the bacterium to excuse from the host protection mechanism and lead to persistent infection.…”

Bacterial Mechanosensitive Channels: Models for Studying Mechanosensory Transduction

“…For example, a Pseudomonas bacterium produces redox-active phenazines in order to kill off competing fungi (147) through generation of reactive oxygen species (ROS). Production of zwitterionic pyocyanins by Pseudomonas aeruginosa also induces acute nosocomial pneumonia in humans through ROS generation (84,112). Besides their redox activity, the zwitterionic nature of many of the phenazines and pyocyanins means that they could readily insert into the cell membrane and, therefore, may also act as amphipaths, possibly influencing MS channel gating.…”