Adventitial fibroblasts (AFs) can be activated by angiotensin II (Ang II) and exert pro-fibrotic and pro-inflammatory effects in vascular remodeling. Protease-activated receptor (PAR) 1 and 2 play a significant role in fibrogenic and inflammatory diseases. The present study evaluated the mechanisms underlying PAR1- and PAR2-induced activation of rat aortic adventitial fibroblasts, and whether PAR1 and PAR2 play a role in Ang II-induced AF activation and contribute to adventitial remodeling.Design and Method:
In vitro experiment, AFs were cultured by tissue explant. AF proliferation was detected by CCK8 assay, AF migration by wound scratch assay, protein expression by Western blot, mRNA levels by real-time PCR. In vivo experiment, protein expression in the vascular adventitia was analyzed by immunofluorescence.Results:
We found that direct activation of PAR1 and PAR2 with PAR1-AP and PAR2-AP led to AF activation, including proliferation and differentiation of AFs, extracellular matrix synthesis, as well as production of pro-fibrotic cytokine TGF-β and pro-inflammatory cytokines IL-6 and MCP-1. Furthermore, PAR1 and PAR2 mediated Ang II-induced AF activation, since both PAR1 and PAR2 antagonists inhibited Ang II-induced proliferation, migration, differentiation, extracellular matrix synthesis and production of pro-fibrotic and pro-inflammatory cytokines in AFs. Finally, mechanistic study showed that Ang II, via Ang II type I receptor (AT1R), upregulated both PAR1 and PAR2 expression, and transactivated PAR1 and PAR2, as denoted by internalization of both proteins.Conclusions:
In conclusion, our results suggest that PAR1 and PAR2 play a critical role in Ang II-induced AF activation, and this may contribute to adventitia-related pathological changes.