Platelet-activating factor and protease-activated receptor 2 cooperate
to promote lung inflammation through nuclear factor-kappa B
transactivation
Abstract
Objective This study was conducted to investigate the role of
protease-activated receptor 2 (PAR2) in platelet-activating factor
(PAF)-induced lung inflammation and neutrophil recruitment in lungs of
BALB/c mice. Methods BALB/c mice were pretreated with the PAR2
antagonist ENMD1068, PAF receptor (PAFR) antagonist WEB2086, or
aprotinin, a reversible inhibitor of serine proteases, prior to
intranasal instillation of carbamyl-PAF (C-PAF) or the PAR2 agonist
peptide SLIGRL-NH2 (PAR2-AP). Leukocyte infiltration in bronchoalveolar
lavage fluid (BALF), C-X-C motif ligand 1 (CXCL1) and CXCL2 chemokines,
myeloperoxidase (MPO), and N-acetyl-glycosaminidase (NAG) levels in
BALF, or lung inflammation were evaluated. Intracellular calcium
signaling, PAFR/PAR2 physical interaction, and the expression of PAR2
and nuclear factor-kappa B (NF-КB, p65) transcription factor were
investigated in RAW 264.7 cells stimulated with C-PAF in the presence or
absence of ENMD1068. Results C-PAF- or PAR2-AP-induced neutrophil
recruitment into lungs was inhibited in mice pretreated with ENMD1068
and aprotinin or WEB2086, respectively. PAR2 blockade impaired
C-PAF-induced neutrophil rolling and adhesion, lung inflammation, and
production of MPO, NAG, CXCL1, and CXCL2 production in lungs of mice.
PAFR activation reduced PAR2 expression and physical interaction of PAR2
and PAFR; co-activation is required for PAFR/PAR2 physical interaction.
PAR2 blockade impaired C-PAF-induced calcium signal and NF-κB p65
translocation in RAW 264.7 murine macrophages. Conclusion This study
provides the first evidence for a cooperation between PAFR and PAR2
mediating neutrophil recruitment, lung inflammation, and macrophage
activation.