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Subversion of a lysosomal pathway regulating neutrophil apoptosis by a major bacterial toxin, pyocyanin

Prince, L. R., Bianchi, S. M., Vaughan, K. M., Bewley, M. A., Marriott, H. M., Walmsley, S. R., Taylor, G. W., Buttle, D. J., Sabroe, I., Dockrell, D. H. and Whyte, M. K. B. (2008) Subversion of a lysosomal pathway regulating neutrophil apoptosis by a major bacterial toxin, pyocyanin. The Journal of Immunology, 180 (5). pp. 3502-11. ISSN 0022-1767

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Neutrophils undergo rapid constitutive apoptosis that is accelerated following bacterial ingestion as part of effective immunity, but is also accelerated by bacterial exotoxins as a mechanism of immune evasion. The paradigm of pathogen-driven neutrophil apoptosis is exemplified by the Pseudomonas aeruginosa toxic metabolite, pyocyanin. We previously showed pyocyanin dramatically accelerates neutrophil apoptosis both in vitro and in vivo, impairs host defenses, and favors bacterial persistence. In this study, we investigated the mechanisms of pyocyanin-induced neutrophil apoptosis. Pyocyanin induced early lysosomal dysfunction, shown by altered lysosomal pH, within 15 min of exposure. Lysosomal disruption was followed by mitochondrial membrane permeabilization, caspase activation, and destabilization of Mcl-1. Pharmacological inhibitors of a lysosomal protease, cathepsin D (CTSD), abrogated pyocyanin-induced apoptosis, and translocation of CTSD to the cytosol followed pyocyanin treatment and lysosomal disruption. A stable analog of cAMP (dibutyryl cAMP) impeded the translocation of CTSD and prevented the destabilization of Mcl-1 by pyocyanin. Thus, pyocyanin activated a coordinated series of events dependent upon lysosomal dysfunction and protease release, the first description of a bacterial toxin using a lysosomal cell death pathway. This may be a pathological pathway of cell death to which neutrophils are particularly susceptible, and could be therapeutically targeted to limit neutrophil death and preserve host responses.

Item Type: Article
Institution: The University of Sheffield
Academic Units: The University of Sheffield > Faculty of Medicine, Dentistry and Health (Sheffield) > School of Medicine (Sheffield)
Depositing User: Miss Anthea Tucker
Date Deposited: 29 Mar 2012 09:53
Last Modified: 29 Mar 2012 09:53
Published Version: http://www.jimmunol.org/content/180/5/3502.long
Status: Published
Publisher: American Association of Immunologists
Related URLs:
URI: http://eprints.whiterose.ac.uk/id/eprint/43799

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