CP-25 monotherapy and combined administration ameliorate progression of animal arthritis model by inhibition on GRK2 translocation

OBJECTIVE Increased efficacy without increased toxicity is expected when treating rheumatoid arthritis(RA).However,there are many difficulties associated with currently available RA treatments.Reportedly,CP-25,a new compound developed by our group,significantly inhibits the progression of arthritis in animal models through reducing membrane expression of GRK2.This study observed CP-25 monotherapy and combined administration with MTX/LEF in treating animal arthritis model and investigated possible mechanisms.METHODS We set up AA rat and collageninduced arthritis(CIA)mice model.Experimental groups were divided into normal group,vehicle group,monotherapy groups and CP-25-combined MTX/LEF groups.We focused on the role of GRK2 on macrophage polarization and fibro⁃blast-like synoviocytes(FLS)proliferation.We measured cytokine levels,phosphorylation and protein expression,and interactions between proteins.Targeted disruption of GRK2 in FLS and macrophages through GRK2 siRNA and CRIS⁃PR/Cas9.RESULTS Equivalent therapeutic effects were observed between CP-25-combination groups and high-dose MTX/LEF groups.In the vehicle group,GRK2 membrane expression increased leading to the decreased GRK2-p-ERK interactions in FLS(leading to the phosphorylation of ERK related with FLS over-proliferation),and increased GRK2-EP4 interaction in macrophage(leading to the abnormal PGE2-EP4-cAMP-CREB signal related with imbalance of macro⁃phage polarization).CONCLUSION CP-25 monotherapy and combined administration with MTX/LEF ameliorate the progression of animal arthritis model.CP-25 inhibited p-ERK by reducing the membrane expression of GRK2 in FLS from AA rats.CP-25 restored normal PGE2-EP4-cAMP-CREB signal through inhibiting GRK2 transferring to membrane.These results highlighted CP-25 a kind of potential for treating patients with RA.