TFLLR-NH2 (TFA) is a selective PAR1 agonist with an EC50 of 1.9 μM. EC50: 1.9 μM (PAR1)[1]
PAR1 agonists stimulate concentration-dependent increases in [Ca2+]i and in the proportions of neurones. The maximal increase in [Ca2+]i above basal is detected in response to 10 μm TF-NH2 (peak 196.5±20.4 nM, n=25) when 50-80% of identified neurones responded[1]. SW620 cells cultured in the supernatant of TFLLR-NH2-activated platelets upregulate E-cadherin expression and downregulate the vimentin expression. In the in vitro platelet culture system, a TFLLR-NH2 dose-dependent increase of secreted TGF-β1 is detected in the supernatant[2].
Injection of TF-NH2 into the rat paw stimulates a marked and sustained oedema. An NK1R antagonist and ablation of sensory nerves with capsaicin inhibit oedema by 44% at 1 h and completely by 5 h. In wild-type but not PAR1-/- mice, TF-NH2 stimulates Evans blue extravasation in the bladder, oesophagus, stomach, intestine and pancreas by 2-8 fold. Extravasation in the bladder, oesophagus and stomach is abolished by an NK1R antagonist[1]. TFp-NH2 produces notable contraction at 3-50 μM and relaxation at 0.3-50 μM, in the absence of apamin. The concentration-response curve for TFp-NH2-induced contraction is remarkably shifted left, when the TFp-NH2-induced relaxation is blocked by apamin at 0.1 μM[3].
[1]. de Garavilla L, et al. Agonists of proteinase-activated receptor 1 induce plasma extravasation by a neurogenic mechanism. Br J Pharmacol. 2001 Aug;133(7):975-87. [2]. Kawabata A, et al. Characterization of the protease-activated receptor-1-mediated contraction and relaxation in the rat duodenal smooth muscle. [3]. Jia Y, et al. Activation of platelet protease-activated receptor-1 induces epithelial-mesenchymal transition and chemotaxis of colon cancer cell line SW620. Oncol Rep. 2015 Jun;33(6):2681-8.