Thrombin and Its Protease-Activated Receptor-1 (PAR1) Participate in the Endothelial–Mesenchymal Transdifferentiation Process

Abstract

The serine protease thrombin, independently of its participation in hemostasis and thrombosis, has been involved in tissue repair and remodeling, embryogenesis, angiogenesis, and development and progression of atherosclerosis. Many of these functions appear to be mediated by specific thrombin receptors, particularly the protease-activated receptor-1 (PAR1). In this study, we investigated whether both thrombin and PAR1 were present in the aortic wall of chicken embryos at days 11 and 12 of development. We found that PAR1 was limited to some cells of the intimal thickening and the inner media, whereas thrombin appeared distributed across the aortic wall. We also investigated whether PAR1 was present during endothelial-mesenchymal transdifferentiation (EMT) in vitro. A moderate immunoreactivity was detected in the monolayer of endothelial cells. In contrast, a strong cytoplasmic immunoreactivity was observed in the detaching and migrating cells and those that had acquired mesenchymal characteristics. This PAR1 expression was confirmed by flow cytometry. In this study, the addition of thrombin to arrested endothelial cell cultures was assessed. We found that thrombin stimulated endothelial cell spreading and migration, as no migrating cells were observed in serum-free medium (SFM) condition. Immunolocalization of PAR1 in the thrombin-treated cultures showed strong cytoplasmic immunoreactivity in the monolayers and in spreading and migrating cells, whereas in the SFM condition undetectable PAR1 immunoreactivity was observed. Flow cytometry of these cultures revealed an elevated expression of PAR1 in the presence of thrombin, in contrast to that detected in SFM and complete medium. These data indicate that both thrombin and PAR1 are involved in the remodeling of the aortic wall and intimal thickening formation, and in the endothelial-mesenchymal transdifferentiation process.

Senescent Fibroblasts Enhance Early Skin Carcinogenic Events via a Paracrine MMP-PAR-1 Axis

“…This last suggestion is strengthened by the fact that TWIST-1-positive cells were found scattered though the papillary dermis only in aged skins where PAR-1-positive cells were also scattered through this compartment. It has previously been shown that PAR-1 can govern cell shape and motility [41] and EMT-related migration [72], [73] and that transformed cells undergoing EMT can arise from hyperplasias and disseminate [74], [75], [76]. Here we show that EMT might take place even earlier, almost concomitantly with generation of the first neoplastic cells through senescence evasion.…”

RNA-Seq Analysis of Abdominal Fat in Genetically Fat and Lean Chickens Highlights a Divergence in Expression of Genes Controlling Adiposity, Hemostasis, and Lipid Metabolism

“…[ 95 ] found that the interaction of F2 and PAR1 in 3T3-L1 adipocytes stimulates FABP4 which regulates the expression of interleukin 6 (IL–6) and vascular endothelial growth factor (VEGF). Although there have been no studies describing F2-PAR1 interactions in adipose tissue of chickens, an earlier report indicates that interaction between thrombin and PAR1 is required for “endothelial mesenchymal transdifferentation” in the aorta of chick embryos [ 96 ]. Our present study shows that genes involved in thrombin signaling are differentially expressed in visceral fat of FL and LL chickens.…”

Therapeutic Promise of Dabigatran Etexilate, an Oral Direct Thrombin Inhibitor in a Preclinical Model of Colon Carcinogenesis

“…Reiterating the Trousseau syndrome of link between cancer and coagulation, thrombin via PAR-1 is believed to play a critical role in embryonic and adult vascular development and also in EMT by virtue of which tumor cells convert themselves from low to high grade for distant metastasis [78,79]. Also thrombin-induced HIF-1α protein occurs through PAR-1 activation and it is regulated by MAPK and PI3K/Akt/mTOR pathway is a previously reported observation.…”