1.Protease-activated receptor-1 (PAR1) and PAR2 but not PAR4 mediate relaxations in lower esophageal sphincter.
Huang SC Regul Pept. 2007 Jul 5;142(1-2):37-43. Epub 2007 Jan 31.
Protease-activated receptor-1 (PAR1), PAR2 and PAR4 activation can alter the gastrointestinal motility. To investigate effects mediated by PARs in the lower esophageal sphincter, we measured contraction or relaxation of transverse strips from the guinea-pig lower esophageal sphincter caused by PAR1 (TFLLR-NH2 and SFLLRN-NH2), PAR2 (SLIGKV-NH2 and SLIGRL-NH2) and PAR4 peptide agonists (GYPGKF-NH2, GYPGQV-NH2 and AYPGKF-NH2) as well as PAR protease activators (thrombin and trypsin). In resting lower esophageal sphincter strips, TFLLR-NH2 and SFLLRN-NH2 caused moderate concentration-dependent relaxation whereas thrombin did not cause any relaxation or contraction. Furthermore, in carbachol-contracted strips, TFLLR-NH2 and SFLLRN-NH2 caused marked whereas thrombin caused mild concentration-dependent relaxation. These indicate the existence of PAR1 mediating relaxation. Similarly, in resting lower esophageal sphincter strips, trypsin caused moderate concentration-dependent relaxation whereas SLIGRL-NH2 and SLIGKV-NH2 did not cause any relaxation or contraction. In addition, in carbachol-contracted strips, trypsin caused marked whereas SLIGRL-NH2 and SLIGKV-NH2 caused mild concentration-dependent relaxation.
2.Activation of human colon mast cells through proteinase activated receptor-2.
He SH;He YS;Xie H World J Gastroenterol. 2004 Feb 1;10(3):327-31.
AIM: ;To investigate the ability of agonists of PAR-2 to stimulate release of tryptase and histamine from human colon mast cells and the potential mechanisms.;METHODS: ;Enzymatically dispersed cells from human colons were challenged with tc-LIGRLO, tc-OLRGIL, SLIGKV, VKGILS, trypsin, anti-IgE or calcium ionophore A23187, and the cell supernatants after challenge were collected. Tryptase release was determined with a sandwich ELISA procedure and histamine release was measured using a glass fibre-based fluorometric assay.;RESULTS: ;Both PAR-2 agonists tc-LIGRLO-NH2 and SLIGKV-NH2 were able to induce dose dependent release of tryptase and histamine from colon mast cells. More than 2.5 fold increase in both tryptase and histamine release was provoked by 100 micromol/mL tc-LIGRLO-NH2, in comparison with only 2.0 fold increase being stimulated by SLIGKV-NH2. The reverse peptides tc-OLRGIL-NH2 and VKGILS -NH2 at the concentrations tested had no effect on the release of these two mediators. The maximum tryptase release elicited by tc-LIGRLO-NH2 was similar to that induced by anti-IgE (10 microg/mL) or calcium ionophore (1 microg/mL), though the latter was a more potent stimulus for histamine release.
3.Agonists of proteinase-activated receptor 2 induce TNF-alpha secretion from astrocytoma cells.
Kim MS;Jo H;Um JY;Yi JM;Kim DK;Choi SC;Kim TH;Nah YH;Kim HM;Lee YM Cell Biochem Funct. 2002 Dec;20(4):339-45.
Proteinase-activated receptor 2 (PAR2) is cleaved and activated by trypsin or mast cell tryptase, and may play an important role in inflammation. We have investigated the potential of PAR2 agonists to modulate TNF-alpha secretion from human astrocytoma cell line CCF-STTG1. We found that CCF-STTG1 expresses PAR2 by RT-PCR and Western blot analysis. Agonists such as trypsin, the peptide SLIGKV-NH(2) (corresponding to the PAR2 tethered ligand), or mast cell tryptase directly signal to CCF-STTG1 to stimulate secretion of TNF-alpha but do not stimulate in the presence of soybean trypsin inhibitor (SBTI) or VKGILS-NH(2) (reverse peptide). The secretion of TNF-alpha by trypsin was significantly blocked by pretreatment with either 50 microM PD98059 or 1 microM SB203580. Furthermore, trypsin stimulated the activation of extracellular signal-regulated kinase (ERK) and p38 MAP kinase homologue in CCF-STTG1 without any detectable activation of c-Jun N-terminal kinase (JNK). These results show that trypsin may induce TNF-alpha secretion following activation of ERK and p38 via PAR2 in CCF-STTG1.
