Submitted on January 23, 2007
Accepted on December 7, 2007
Role of PAR2 in Murine Pulmonary Pseudomonal Infection
Theo Joasinho Moraes1, Raiza Martin2, Jonathan D Plumb2, Eric Vachon2, Cheryl M Cameron3, Ali Danesh3, David J Kelvin3, Wolfram Ruf4, and Gregory P. Downey5*
1 Toronto General Hospital Research Institute, The University Health Network, Toronto, Canada; Respiratory Medicine, The Hospital for Sick Children, 555 University Ave, Toronto, M5G 1X8, Canada
2 Toronto General Hospital Research Institute, The University Health Network, Toronto, Canada
3 Immunology, University of Toronto, Toronto, Canada
4 Immunology, Scripps Res Inst, La Jolla, California, United States
5 Department of Medicine, Clinical Science Division, University of Toronto, Toronto, Canada; Toronto General Hospital Research Institute, The University Health Network, Toronto, Canada
* To whom correspondence should be addressed. E-mail: downeyg{at}njc.org.
Proteinases can influence lung inflammation by various mechanisms including via cleavage and activation of protease activated receptors (PAR) such as PAR2. In addition, proteinases such as neutrophil and/or Pseudomonas derived elastase can disarm PAR2 resulting in loss of PAR2 signalling. Currently, the role of PAR2 in host defence against bacterial infection is not known. Using a murine model of acute Pseudomonas aeruginosa pneumonia, we examined differences in the pulmonary inflammatory response between wild-type and PAR2-/- mice. As compared to wild-type mice, PAR2-/- mice displayed more severe lung inflammation and injury in response to P. aeruginosa infection as indicated by higher bronchoalveolar lavage fluid neutrophil numbers, protein concentration, and TNF-
levels. By contrast, IFN-
levels were markedly reduced in PAR2-/- compared to wild type mice. Importantly, clearance of P. aeruginosa was diminished in PAR2-/- mice. In vitro testing revealed that PAR2-/- neutrophils killed significantly less bacteria than wild-type murine neutrophils. Further, both neutrophils and macrophages from PAR2-/- mice displayed significantly reduced phagocytic efficiency as compared to wild-type phagocytes. Stimulation of PAR2 on macrophages using a PAR2 activating peptide resulted in enhanced phagocytosis directly implicating PAR2 signalling in the phagocytic process. We conclude that genetic deletion of PAR2 is associated with decreased clearance of P. aeruginosa. Our data suggest that a deficiency in IFN- production and impaired bacterial phagocytosis are two potential mechanisms responsible for this defect.
