Thrombin induces collagen gel contraction partially through PAR1 activation and PKC-epsilon

The ability of fibroblasts to contract three-dimensional Collagen gels has been used as an in vitro model of the tissue contraction which characterises both normal repair and fibrosis. Among its actions, Thrombin can activate the Protease-activated Receptor (PAR)1 and, thereby, stimulate inflammation and repair. The current study evaluated whether Thrombin could stimulate fibroblast-mediated Collagen gel contraction by activating PAR1 and whether its downstream signalling depends on protein kinase C (PKC)-epsilon. Human foetal lung fibroblasts (HFL-1) were cultured in three-dimensional Collagen gels and the area of the gels was measured by image analyser. Both Thrombin and TFLLR, a selective PAR1 Agonist, stimulated Collagen gel contraction mediated by HFL-1. After RNA interference-mediated PAR1 knockdown in HFL-1, both Thrombin and the PAR1 agonist-induced gel contraction were partially inhibited (by 22.4+/-2.2% and 17.6+/-5.6%, respectively). The gel contraction stimulated by Thrombin was also reduced by a nonspecific PKC Inhibitor and a calcium-independent PKC-epsilon inhibitor. Both Thrombin and TFLLR significantly increased PKC-epsilon activity, and this effect was blocked by PAR1 knockdown. Thrombin stimulates Collagen gel contraction at least partially through activation of Protease-activated Receptor 1 and protein kinase C-epsilon, and may contribute to tissue remodelling in inflammatory airway and lung diseases.