Protease-Activated Receptor 2 Controls Vascular Smooth Muscle Cell Proliferation in Cyclic AMP-Dependent Protein Kinase/Mitogen-Activated Protein Kinase Kinase 1/2-Dependent Manner

Introduction: Cardiovascular disorders are characterized by vascular smooth muscle (VSM) transition from a contractile to proliferative state. Protease-activated receptor 2 (PAR2) involvement in this phenotypic conversion remains unclear. We hypothesized that PAR2 controls VSM cell proliferation in phenotype-dependent manner and through specific protein kinases. Methods: Rat clonal low (P-Lo; P3-P6) and high passage (P-Hi; P10-P15) VSM cells were established as respective models of quiescent and proliferative cells, based on reduced PKG-1 and VASP. Western blotting determined expression of cytoskeletal/contractile proteins, PAR2, and select protein kinases. DNA synthesis and cell proliferation were measured 24-72 h following PAR2 agonism (SLIGRL; 100 nM-10 mu<sc>m</sc>) with/without PKA (PKI; 10 mu<sc>m</sc>), MEK1/2 (PD98059; 10 mu<sc>m</sc>), and PI3K (LY294002; 1 mu<sc>m</sc>) blockade. Results: PKG-1, VASP, SM22 alpha, calponin, cofilin, and PAR2 were reduced in P-Hi versus P-Lo cells. Following PAR2 agonism, DNA synthesis and cell proliferation increased in P-Lo cells but decreased in P-Hi cells. Western analyses showed reduced PKA, MEK1/2, and PI3K in P-Hi versus P-Lo cells, and kinase blockade revealed PAR2 controls VSM cell proliferation through PKA/MEK1/2. Discussion: Findings highlight PAR2 and PAR2-driven PKA/MEK1/2 in control of VSM cell growth and provide evidence for continued investigation of PAR2 in VSM pathology.