title: Restricted ability of human mast cell tryptase to activate proteinase-activated receptor-2 in rat aorta.
abstract: We investigated the potential of human mast cell tryptase to induce relaxation of rat aorta. Trypsin and the selective PAR2-activating peptide (PAR2-AP) SLIGRL-NH2 stimulated robust relaxation of phenylephrine-precontracted rat aortic rings. However, human lung tryptase (1-100 nM) either in the presence or absence of heparin failed to induce any significant relaxation. Notwithstanding, incubation of the aorta with tryptase (100 nM), following the addition of a peptide corresponding to the cleavage/activation sequence of rat PAR2 (rPAR2), resulted in relaxation of precontracted tissue due to the proteolytic release of the PAR2-AP SLIGRL/ from the parent peptide. Thus, tryptase was enzymatically active in the bioassay system. Preincubation of aorta with neuraminidase to remove cell-surface sialic acid unmasked the ability of tryptase to induce relaxation of the aorta, but had no effect on relaxation induced by trypsin, SLIGRL-NH2, or acetylcholine (Ach). Like trypsin and SLIGRL-NH2, the tryptase-induced relaxation was inhibited by either removal of the endothelium or pretreatment of the tissue with NG-nitro-L-arginine methyl ester (L-NAME), suggesting an endothelium-derived nitric oxide mechanism. Interestingly, tryptase in the presence of heparin failed to induce relaxation of precontracted neuraminidase-treated rat aorta. We conclude that tryptase-induced relaxation of rat aorta, most likely via PAR2, is tightly regulated by heparin and cell-surface sialic acid.
authors.affiliation: Department of Pharmacology & Therapeutics, University of Calgary, Calgary, AB T2N 4N1, Canada. S.J.Compton@Hull.ac.uk
authors.forename: Steven J
authors.initials: SJ
authors.lastname: Compton
authors.forename: John J
authors.initials: JJ
authors.lastname: McGuire
authors.forename: Mahmoud
authors.initials: M
authors.lastname: Saifeddine
authors.forename: Morley D
authors.initials: MD
authors.lastname: Hollenberg
mesh_terms: D000818:Animals; D001013:Aorta, Thoracic / Q000187:drug effects / Q000502:physiology; D006801:Humans; D066298:In Vitro Techniques; D008297:Male; D008407:Mast Cells / Q000201:enzymology*; D009119:Muscle Contraction / Q000187:drug effects; D009126:Muscle Relaxation / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000502:physiology; D009439:Neuraminidase / Q000494:pharmacology; D009842:Oligopeptides / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D044464:Receptor, PAR-2; D018179:Receptors, Thrombin / Q000819:agonists* / Q000378:metabolism; D012697:Serine Endopeptidases / Q000494:pharmacology*; D014357:Trypsin / Q000494:pharmacology; D053802:Tryptases; D014664:Vasodilation / Q000187:drug effects / Q000502:physiology; D014665:Vasodilator Agents / Q000494:pharmacology
chemical_list: D009842:Oligopeptides; D044464:Receptor, PAR-2; D018179:Receptors, Thrombin; D014665:Vasodilator Agents; C112356:seryl-leucyl-isoleucyl-glycyl--arginyl-leucinamide; D009439:Neuraminidase; D012697:Serine Endopeptidases; D014357:Trypsin; C509223:Tpsab1 protein, rat; C509221:Tpsb2 protein, rat; D053802:Tryptases