title: Premature cellular senescence induced by pyocyanin, a redox-active Pseudomonas aeruginosa toxin.
abstract: Pseudomonas aeruginosa is an important nosocomial pathogen that can cause acute and chronic infection, particularly of the respiratory system. Pyocyanin is a major P. aeruginosa virulence factor that displays redox activity and induces oxidative stress in cellular systems. The effect of pyocyanin on replicating human pulmonary epithelial (A549) cells was investigated. Cells were exposed to pyocyanin for 24 h and their subsequent growth and development were followed for 7 days. Pyocyanin (5-10 microM) arrested cell growth and resulted in the development of a morphological phenotype consistent with cellular senescence, that is, an enlarged and flattened appearance. The senescent nature of these cells was supported by positive staining for increased lysosomal content and senescence-associated beta-galactosidase activity. All cells treated with pyocyanin (10 microM) converted to the senescent phenotype, which remained stable for up to 7 days. Exposure to pyocyanin at 25 microM or greater resulted in cell death due to apoptosis. A549 cells exposed to pyocyanin generated hydrogen peroxide in a dose-dependent manner and the senescence-inducing effect of pyocyanin was inhibited by the antioxidant, glutathione, suggesting the involvement of reactive oxygen species. The induction of premature cellular senescence by redox-active bacterial toxins may be a hitherto unrecognized aspect of infection pathology and a limiting factor in the tissue repair response to infection.
authors.affiliation: Centre for Education and Research on Ageing, ANZAC Research Institute, University of Sydney, Concord RG Hospital, Sydney NSW 2139, Australia. mmuller@anzac.edu.au
authors.forename: Michael
authors.initials: M
authors.lastname: Muller
mesh_terms: D000975:Antioxidants / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects*; D049109:Cell Proliferation; D002478:Cells, Cultured; D016922:Cellular Senescence / Q000187:drug effects*; D004848:Epithelium / Q000187:drug effects / Q000378:metabolism; D005978:Glutathione / Q000494:pharmacology; D006801:Humans; D006861:Hydrogen Peroxide / Q000378:metabolism; D008168:Lung / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D008247:Lysosomes / Q000378:metabolism; D010084:Oxidation-Reduction; D010641:Phenotype; D011550:Pseudomonas aeruginosa / Q000737:chemistry; D011710:Pyocyanine / Q000494:pharmacology*; D017382:Reactive Oxygen Species / Q000378:metabolism; D001616:beta-Galactosidase / Q000378:metabolism
chemical_list: D000975:Antioxidants; D017382:Reactive Oxygen Species; D011710:Pyocyanine; D006861:Hydrogen Peroxide; D001616:beta-Galactosidase; D005978:Glutathione