Dual endothelium‐dependent vascular activities of proteinase‐activated receptor‐2‐activating peptides: evidence for receptor heterogeneity

Abstract

1 The vascular actions of the proteinase-activated receptor-2-activating peptides (PAR 2 APs), SLIGRL-NH 2 (SL-NH 2 ) and SLIGKV-NH 2 (KV-NH 2 ) as well as the reverse-sequence peptide, LSIGRL-NH 2 (LS-NH 2 ) and an N-acylated PAR 2 AP derivative, trans-cinnamoyl-LIGRLO-NH 2 (tcLI-NH 2 ), were studied in rat intact and endothelium-denuded artery ring preparations, primarily from the pulmonary artery (RPA). 2 In RPA rings with but not without a functional endothelium, SL-NH 2 (but not LS-NH 2 ) caused either an endothelium-dependent relaxation (at concentrations: 510 mM) or (at higher concentrations: 410 mM), an endothelium-dependent contraction. No contractile response was observed in endotheliumdenuded preparations, that otherwise contracted in response to the PAR 1 AP, TFLLR-NH 2 . 3 The endothelium-dependent contractile response to SL-NH 2 was not blocked by the a-adrenoceptor antagonist prazosin, the endothelin antagonist BQ123, the angiotensin II antagonist DuP753, by tetrodotoxin; nor by the enzyme inhibitors, N o -nitro-L-arginine-methylester (NO-synthase), indomethacin (cyclo-oxygenase), SKF-525A (epoxygenase) and MK886 (leukotriene synthesis inhibitor). 4 In the relaxation assay, KV-NH 2 was 5 fold less potent than SL-NH 2 , whereas in the contractile assay KV-NH 2 was about equipotent with SL-NH 2 . However, the maximal contractile response to KV-NH 2 was lower than that of SL-NH 2 . 5 The PAR 2 AP analogue, tcLI-NH 2 , was as active as SL-NH 2 in the relaxation assay but was inactive as a contractile agonist in the endothelium-intact RPA. 6 The relaxant responses caused by SL-NH 2 and trypsin, as well as the contractile response caused by SL-NH 2 , did not desensitize in the course of repeated exposures of the tissue to agonist; whereas the contractile response to trypsin, only observed at concentrations greater than 30 u ml 71 , was desensitized by previous exposure of the tissue to either thrombin or trypsin. 7 In a contractile assay, where the tissue was desensitized to a concentration of trypsin that would otherwise cause a relaxant response, the preparation still contracted in response to SL-NH 2 . However, the trypsin-desensitized preparations were no longer contracted by thrombin. 8 From the cross-desensitization by thrombin of the contractile response to trypsin (and vice versa), we concluded that the contractile e ect of trypsin was due to activation of the thrombin receptor and not PAR 2 . 9 We concluded that the endothelium-dependent contraction caused by high concentrations of SL-NH 2 is due to an as yet unidenti®ed contracting factor; whereas the endothelium-dependent relaxation response observed at low concentrations of SL-NH 2 (410 mM) is mediated by nitric oxide. 10 The distinct structure activity pro®les for the contractile response (potency of KV-NH 2 4SL-NH 2 ) compared with the relaxant response (potency of KV-NH 2 55SL-NH 2 ); the contractile responsiveness to SL-NH 2 of an endothelium-intact RPA preparation, that did not contract in response to trypsin; and the lack of contractil...

Trypsin activates pancreatic duct epithelial cell ion channels through proteinase-activated receptor-2

“…Activating peptide (AP, SLIGRL-NH 2 ) corresponding to the tethered ligand of mouse PAR-2, and reverse peptide (RP, LRGILS-NH 2 ), were synthesized by solid-phase methods and purified by high-pressure liquid chromatography. Analogues of these peptides, highly selective for PAR-1 (AF[PF]RChaCitY-NH 2 ) or PAR-2 (tc-LIGRLO-NH 2 ), were a gift from M. Hollenberg (University of Calgary, Calgary, Alberta, Canada) (19)(20)(21). The sources of other reagents have been described (15)(16)(17)(18).…”

Role of Protease-activated Receptors in the Vascular System

“…The PAR-2-mediated regulation of vascular tone also varies with species and type of blood vessel, as observed with PAR-1. A PAR-2-mediated endothelium-dependent relaxation has been widely reported (23,73,(102)(103)(104)(105), while an endotheliumdependent contraction (104,106) and a direct contractile effect on smooth muscle (81) were also reported. In the porcine coronary artery, thrombin induces only endothelium-dependent relaxation while having no direct effect on smooth muscle (101).…”

Redundant signaling mechanisms contribute to the vasodilatory response of the afferent arteriole to proteinase-activated receptor-2

“…In a number of vascular preparations, PAR-2-induced vasodilation is eliminated by removal of the endothelium (21,29,30,33,39). Unfortunately, we cannot remove the endothelium in our preparation without affecting vascular reactivity.…”

“…Both trypsin and the selective PAR-2-activating peptide SLIGRL-NH 2 induce endothelium-dependent vasodilation in isolated rat aorta, mouse mesenteric, and renal arteries (21,29,39). In some vessels, but not all, a component of the endothelium-dependent response is resistant to treatment with cyclooxygenase (COX) and nitric oxide synthase (NOS) inhibition, prompting speculation that PAR-2 activation causes the release of an endothelium-derived hyperpolarizing factor (EDHF) (15,21,29,30,41).…”