PAR1 is involved in NF-κB and c-Jun activation in heat stressed HUVECs. (A) After 48 h transfection with NC siRNA or PAR1 siRNA, or an 1 h pretreatment with DMSO or 150 nM SCH, HUVECs were incubated at 37°C (control) or 43°C (heat stress) for 90 min, followed by a 6-h recovery period at 37°C. NF-κB binding to DNA was quantified. (B) HUVECs underwent an incubation period at 37°C (control) or 43°C (heat stress) for 90 min, followed by a recovery period at 37°C for 0, 2, 6 or 12 h. Protein expression levels of p-c-Jun and c-Jun were detected in HUVECs by western blotting. **P<0.01 and ***P<0.001 vs. control. (C) After 48 h transfection with NC siRNA or PAR1 siRNA, or (D) an 1 h pretreatment with DMSO or 150 nM SCH, HUVECs were incubated at 37°C (control) or 43°C (heat stress) for 90 min, followed by a 6-h recovery period at 37°C. Expression of p-c-Jun and c-Jun were detected by western blotting. Data are expressed as the mean ± standard deviation of three independent experiments. *P<0.05; **P<0.01; ***P<0.001. PAR1, protease-activated receptor 1; NF-κB, nuclear factor-κB; HUVECs, human umbilical vein endothelial cells; NC, negative control; siRNA, small interfering RNA; SCH, SCH79797; DMSO, dimethyl sulfoxide; HS, heat stress; Cont, control; R, recovery time; p, phosphorylated.