Proteinase-activated receptor (PAR)-1 and -2 agonists induce mediator release from mast cells by pathways distinct from PAR-1 and PAR-2.
Because thrombin-induced inflammation is partially mast cell-dependent and involves proteinase-activated receptors (PARs), we hypothesized that mast cells express PAR and can be stimulated with PAR-activating peptides (PAR-AP). We demonstrated that rat peritoneal mast cells expressed PAR-1 and PAR-2 mRNA, and that PAR-2AP (tc-LIGRLO-NH(2), 1 microm) induced 64.2 +/- 4.4% specific beta-hexosaminidase release from peritoneal mast cells, whereas another PAR-2AP (SLIGRL-NH(2), 10 microM), trypsin (40 U/ml), and mast cell tryptase (1.5 microg/ml) did not. PAR-1AP (ApfFRChaCitY-NH(2), 10 microM) (Cit) induced 11.7 +/- 3.7% specific beta-hexosaminidase release, whereas another PAR-1AP (TFLLR-NH(2), 40 microM) and human thrombin (10 U/ml) did not. PAR-AP, tc-LIGRLO-NH(2), and Cit increased the free intracellular Ca(2+) concentration, whereas trypsin, tryptase, thrombin, and other PAR-APs did not. Desensitization of Ca(2+) flux with different agonists suggests that although tc-LIGRLO-NH(2), Cit, and compound 48/80 have similar mechanisms of action, tc-LIGRLO-NH(2) also activates mast cells by a mechanism distinct from that of 48/80. Using benzalkonium chloride, which antagonizes the actions of 48/80 by competing for the same G(i) protein, we determined that benzalkonium chloride suppressed tc-LIGRLO-NH(2)-mediated (0.1 microM) beta-hexosaminidase release by 62%. Moreover, removal of sialic acid from peritoneal mast cells, using neuraminidase (2 U/ml), inhibited Cit- (10 microM, 52%) and tc-LIGRLO-NH(2) (0.5 microM, 29%)-mediated beta-hexosaminidase release. Thus, tc-LIGRLO-NH(2) and Cit have at least partially similar mechanisms of action as 48/80. PAR-AP may therefore activate mast cells via multiple mechanisms that are distinct from those of classical PAR-1 and PAR-2. The responsiveness of mast cells to PAR-AP via a non-PAR-1/non-PAR-2 mechanism complicates the interpretation of in vivo studies using these peptides.
Pulmonary Research Group, Department of Medicine, Astra-Zeneca Canada Inc., Glaxo-Heritage Asthma Research Laboratory, University of Alberta, Edmonton, Alberta T6G 2S2, Canada.
Grant R
GR
Stenton
Osamu
O
Nohara
René E
RE
Déry
Harissios
H
Vliagoftis
Mark
M
Gilchrist
Ankur
A
Johri
John L
JL
Wallace
Morley D
MD
Hollenberg
Redwan
R
Moqbel
A Dean
AD
Befus
D000818:Animals; D002118:Calcium / Q000502:physiology; D002460:Cell Line; D005786:Gene Expression Regulation / Q000502:physiology*; D006801:Humans; D007668:Kidney; D008297:Male; D008407:Mast Cells / Q000502:physiology*; D008954:Models, Biological; D051381:Rats; D017207:Rats, Sprague-Dawley; D044463:Receptor, PAR-1; D044464:Receptor, PAR-2; D018179:Receptors, Thrombin / Q000235:genetics*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000502:physiology; D014158:Transcription, Genetic; D001619:beta-N-Acetylhexosaminidases / Q000235:genetics
D044463:Receptor, PAR-1; D044464:Receptor, PAR-2; D018179:Receptors, Thrombin; D001619:beta-N-Acetylhexosaminidases; D002118:Calcium