Activates Dynorphin Quorum Sensing Quinolone Signaling in Pseudomonas aeruginosa
Olga Zaborina1, Francois Lepine2, Gaoping Xiao3, Vesta Valuckaite4, Yimei Chen5, Terry Li6, Mae Ciancio4, Alex Zaborin1, Elaine Petroff4, Jerrold R. Turner7, Laurence G. Rahme3, Eugene Chang4, John C. Alverdy1*
1 Department of Surgery, Pritzker School of Medicine, University of Chicago, Chicago, Illinois, United States of America, 2 Institut National de la Recherche Scientifique (INRS)Institut Armand-Frappier, Laval, Quebec, Canada, 3 Department of Surgery, Harvard Medical School, Massachusetts General Hospital, Boston, Massachusetts, United States of America, 4 Department of Medicine, Pritzker School of Medicine, University of Chicago, Chicago, Illinois, United States of America, 5 Department of Biochemistry and Molecular Biology, Pritzker School of Medicine, University of Chicago, Chicago, Illinois, United States of America, 6 Department of Immunohistochemistry, Pritzker School of Medicine, University of Chicago, Chicago, Illinois, United States of America, 7 Department of Pathology, Pritzker School of Medicine, University of Chicago, Chicago, Illinois, United States of America
There is now substantial evidence that compounds released during host stress directly activate the virulence of certain opportunistic pathogens. Here, we considered that endogenous opioids might function as such compounds, given that they are among the first signals to be released at multiple tissue sites during host stress. We tested the ability of various opioid compounds to enhance the virulence of Pseudomonas aeruginosa using pyocyanin production as a biological readout, and demonstrated enhanced virulence when P. aeruginosa was exposed to synthetic (U-50,488) and endogenous (dynorphin) j-agonists. Using various mutants and reporter strains of P. aeruginosa, we identified involvement of key elements of the quorum sensing circuitry such as the global transcriptional regulator MvfR and the quorum sensing-related quinolone signaling molecules PQS, HHQ, and HQNO that respond to j-opioids. The in vivo significance of j-opioid signaling of P. aeruginosa was demonstrated in mice by showing that dynorphin is released from the intestinal mucosa following ischemia/reperfusion injury, activates quinolone signaling in P. aeruginosa, and enhances the virulence of P. aeruginosa against Lactobacillus spp. and Caenorhabditis elegans. Taken together, these data demonstrate that P. aeruginosa can intercept opioid compounds released during host stress and integrate them into core elements of quorum sensing circuitry leading to enhanced virulence.
Citation: Zaborina O, Lepine F, Xiao G , Valuckaite V, Chen Y, et al. (2007) Dynorphin activates quorum sensing quinolone signaling in Pseudomonas aeruginosa. PLoS Pathog 3(3): e35. doi:10.1371/journal.ppat.0030035
Introduction
It has been suggested for microbial pathogens that colonize the mucosal surface of a healthy host that symbiosis can be viewed as a form of molecular detente, a settled negotiation that is sustained by an ongoing chemical dialogue between the host and its flora [1]. Even for an opportunistic pathogen, virulence expression against its host presents a fundamental tradeoff in that it will provoke immune retaliation and deplete the host of critical resources, and, as such, bacteria are constantly assessing the costs versus benefits of expressing virulence. Although bacteria use complex systems of communication like the quorum sensing signaling (QS) system to collect, process, and share information about the chemical composition of their environment [2], whether such events are influenced by specific host-derived signals that indicate a major change in host health status is less well defined. Our laboratory has been interested in host-derived bacterial signaling compounds that are proximate causes of microbial virulence activation during physiologic stress. To date, several host-derived bacterial signaling compounds have been identified that include adaptive elements of the immune system such as interferon c [3], tumor necrosis factor a [4], and interleukin-1 [5], as well as innate elements including adenosine [6], epinephrine [710], and antimicrobial peptides [1113]. While in vitro exposure to various host compounds can activate the virulence of bacteria, much remains to be learned about how these compounds are collected, processed,
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and transduced within the various virulence regulatory systems of bacteria. One of the best studied systems of virulence regulation in bacteria is the QS system. The QS system functions via autoinducer molecules that are released and taken up by bacteria to provide a cellcell communication network whereby complex assemblage behavior can be carried out by large populations of bacteria responding to local concentrations of QS molecules [2]. In some cases, host-derived bacterial signaling molecules such as epinephrine have been shown to act as a surrogate QS autoinducer molecule [8], activating various virulence genes in intestinal bacteria such as Escherichia coli. In other cases, the QS system is activated by the binding of host-derived bacterial signaling molecules to specific membrane receptors on the bacteria, such as when
Editor: Partho Ghosh, University of California San Diego, United States of America Received September 15, 2006; Accepted January 24, 2007; Published March 16, 2007 Copyright: 2007 Zaborina et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Abbreviations: HHQ, 4-hydroxy-2-heptylquinoline; HQNO, 2-heptyl-4-hydroxyquinoline N-oxide; I/R, ischemia/reperfusion; MvfR, multiple virulence factor regulator; PA-IL, PA-I lectin; PBS, phosphate buffered saline; PCN, pyocyanin; PQS, 3,4dihydroxy-2-heptylquinoline; QS, quorum sensing signaling * To whom correspondence should be addressed. E-mail: [e-mail]. uchicago.edu
March 2007 | Volume 3 | Issue 3 | e35
Dynorphin Induces P. aeruginosa Virulence
Author Summary
Precisely how bacterial pathogens such as Pseudomonas aeruginosa cause fatal infections in critically ill humans is unknown. Evidence suggests that a major source of infection may be the patient's own intestinal microflora, which is subjected to unusual environmental conditions during critical illness. Here, we show that intestinal P. aeruginosa can be alerted to the presence of a physiological disturbance in its host by dynorphin, a human morphine-like chemical released during severe stress. Exposure of P. aeruginosa to dynorphin activates its virulence machinery to produce harmful toxins and to suppress the growth of probiotic bacteria, which are known to promote intestinal health. The molecular mechanisms of these events involve the activation of highly regulated virulence machinery in Pseudomonas, called quorum sensing, that allows bacteria to sense host stress and respond with enhanced harmfulness. These observations suggest that opportunistic pathogens like P. aeruginosa are equipped with sophisticated surveillance systems that take advantage of a weakened host by intercepting and responding to naturally occurrin...
Zaborinaetal2007