Activated protein C (APC) is a physiological anticoagulant with anti-inflammatory, anti-apoptotic, pro-angiogenic and barrier-stabilizing properties. This study determined the role of APC in the regulation of rheumatoid synoviocytes (RASF) and endothelial cells and to assess the efficacy of APC in the prevention of murine inflammatory arthritis.
METHODS:
RASF or osteoarthritis (OA) synoviocytes (OASF) were isolated from synovial tissues of OA and RA patients. Human umbilical vein endothelial cells (HUVEC) were isolated from the umbilical cord. Cytokines and cell signaling molecules by these cells in response to APC treatment were measured by enzyme-linked immunosorbent assay and western blot. Cell viability and proliferation were measured by MTT and BrdU proliferation assays, respectively. Endothelial permeability was assessed using the Evans blue-albumin method. The in vivo inhibitory effect of APC was evaluated in a mouse collagen-induced arthritis (CIA) model.
RESULTS:
In vitro, RASF produced more inflammatory cytokines than OASF. APC treatment reduced interleukin (IL)-1β, IL-17 and TNF-α production by RASF. Although APC had no effect on the growth of RASF, it significantly reduced IL-17 stimulated cell proliferation. The invasion of RASF was also reduced in response to APC. In HUVEC, APC treatment resulted in decreases in angiopoietin (Ang)-2, the main mediator of abnormal angiogenesis in RA and in endothelial permeability stimulated by tumor necrosis factor-α or vascular endothelial growth factor. In vivo, APC treatment of mice decreased the incidence and the severity of CIA by more than 50%. Histological examination showed that APC inhibited pannus formation, and cartilage and bone destruction within the joint.
CONCLUSION:
APC suppresses inflammation and invasion of RASF and inhibits pathological angiogenesis, stimulating resolution of inflammation in arthritis.