Submitted on May 12, 2004
Accepted on November 15, 2004
Activation of Proteinase Activated Receptor-2 in Mesothelial Cells Induces Pleural Inflammation
Y C Gary Lee1*, Darryl A. Knight2, Kirk B. Lane3, Dong Shing Cheng3, M Audrey Koay3, Lisete R. Teixeira4, Jon C. Nesbitt5, Rachel C. Chambers6, Philip J. Thompson2, and Richard W. Light7
1 University College London, Centre for Respiratory Research, London, United Kingdom; Pulmonary and Critical Care Medicine, Vanderbilt University, Nashville, Tennessee, USA; St. Thomas Hospital, Nashville, Tennessee, USA
2 University of Western Australia, Asthma and Allergy Research Institute & Ctr for Asthma, Allergy and Respiratory Research, Perth, WA, Australia
3 Pulmonary and Critical Care Medicine, Vanderbilt University, Nashville, Tennessee, USA
4 Respiratory Division, INCOR, University of Sao Paulo, Sao Paulo, Brazil
5 St. Thomas Hospital, Nashville, Tennessee, USA
6 University College London, Centre for Respiratory Research, London, United Kingdom
7 Pulmonary and Critical Care Medicine, Vanderbilt University, Nashville, Tennessee, USA; St. Thomas Hospital, Nashville, Tennessee, USA
* To whom correspondence should be addressed. E-mail: ycgarylee{at}hotmail.com.
Pleural inflammation underlies many pleural diseases, but its pathogenesis remains unclear. Proteinase activated receptor-2 (PAR2) is a novel seven-transmembrane receptor with immuno-regulatory roles. We hypothesized that PAR2 is present on mesothelial cells and can induce pleural inflammation. PAR2 was detected by immunohistochemistry in all (19 parietal and 11 visceral) human pleural biopsies examined. In cultured murine mesothelial cells, a
specific PAR2 activating peptide (SLIGRL-NH2) at 10, 100, 1000µM stimulated a 3-, 42- and 1330-fold increase of MIP-2 release relative to media control respectively (p<0.05 all) and a 2-,
32- and 75-fold rise over the control peptide (LSIGRL-NH2) (p<0.05 all). A similar pattern was
seen for TNF
release. Known physiological activators of PAR2 - tryptase, trypsin and
coagulation factor Xa - also stimulated dose-dependent MIP-2 release from mesothelial cells in vitro. Dexamethasone inhibited the PAR2-mediated MIP-2 release in a dose-dependent manner. In vivo, pleural fluid MIP-2 levels in C57BL/6 mice injected intrapleurally with
SLIGRL-NH2 (10mg/kg) were significantly higher than in mice injected with LSIGRL-NH2 or PBS (2710±165 vs 880±357 vs 88±46pg/mL respectively), p<0.001. Pleural fluid neutrophil counts were higher in SLIGRL-NH2 group than in the LSIGRL-NH2 and PBS groups (by 40- and 26-fold respectively), p<0.05. This study establishes that activation of mesothelial cell PAR2 potently induces the release of inflammatory cytokines in vitro and neutrophil recruitment into the pleural cavity in vivo.
