| Summary: | Coagulation factor (F) Xa induces proinflammatory responses through activation of protease-activated receptors (PARs). However, the effect of FXa on cardiac fibroblasts (CFs) and the contribution of PARs in FXa-induced cellular signalling in CF has not been fully characterised. To answer these questions, human and rat CFs were incubated with FXa (or TRAP-14, PAR-1 agonist). Gene expression of pro-fibrotic and proinflammatory markers was determined by qRT-PCR after 4 and 24 h. Gene silencing of <i>F2R</i> (PAR-1) and <i>F2RL1</i> (PAR-2) was achieved using siRNA. MCP-1 protein levels were measured by ELISA of FXa-conditioned media at 24 h. Cell proliferation was assessed after 24 h of incubation with FXa ± SCH79797 (PAR-1 antagonist). In rat CFs, FXa induced upregulation of <i>Ccl2</i> (MCP-1; >30-fold at 4 h in atrial and ventricular CF) and <i>Il6</i> (IL-6; ±7-fold at 4 h in ventricular CF). Increased MCP-1 protein levels were detected in FXa-conditioned media at 24 h. In human CF, FXa upregulated the gene expression of <i>CCL2</i> (>3-fold) and <i>IL6</i> (>4-fold) at 4 h. Silencing of <i>F2R</i> (PAR-1 gene), but not <i>F2RL1</i> (PAR-2 gene), downregulated this effect. Selective activation of PAR-1 by TRAP-14 increased <i>CCL2</i> and <i>IL6</i> gene expression; this was prevented by <i>F2R</i> (PAR-1 gene) knockdown. Moreover, SCH79797 decreased FXa-induced proliferation after 24 h. In conclusion, our study shows that FXa induces overexpression of proinflammatory genes in human CFs via PAR-1, which was found to be the most abundant PARs isoform in this cell type.
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