Wedelolactone ameliorates synovial inflammation and cardiac complications in a murine model of collagen-induced arthritis by inhibiting NF-κB/NLRP3 inflammasome activation.

INTRODUCTION: Rheumatoid arthritis (RA) is an autoimmune disorder associated with joint damage and attendant cardiovascular complications. Wedelolactone (Wed), derived from Eclipta alba, possesses anti-inflammatory activity. Whether Wed regulates RA inflammation and related heart damage remains unknown.

MATERIAL AND METHODS: A murine model of collagen-induced arthritis (CIA) was well-established by two subcutaneous injections of type II collagen (days 0 and 21). Wed was then administered via intraperitoneal injection every other day from day 28 to day 48. Joint swelling was monitored and paw thickness was calculated. Histopathological changes in synovial tissues or ankle cartilage were evaluated by hematoxylin and eosin (H&E) and Safranin O-Fast Green staining. The concentrations of inflammatory factors in serum and synovial tissues were detected by ELISA. The qRT-PCR, Western blotting, immunohistochemistry (IHC), and immunofluorescence (IF) were performed to assess receptor activator of nuclear factor kappa ligand (RANKL), matrix metalloprotease (MMP)-3, NLRP3, caspase-1 (pro- and cleaved forms), p-p65, IκBα, p-IκBα, p65, αsmooth-actin 2 (ACTA2), collagen type I and E-cadherin expression. H&E and Masson staining were used to assess the pathological alterations in the heart.

RESULTS: Treatment with Wed ameliorated ankle joint swelling and cartilage degradation. Wed decreased the infiltration of inflammatory cells, the release of pro-inflammatory cytokines (IL-1β, IL-6, TNF-α, and IL-18), and the expression of RANKL and MMP-3 in serum and synovial tissues of CIA mice. Moreover, Wed increased the expression of NLRP3 and cleaved-caspase-1 in the synovium, leading to IL-1β and IL-18 secretion. Nuclear factor-kappaB (NF-κB) activation in synovial tissues was suppressed by Wed, as manifested by reduced phosphorylation of p65 and IκBα and nuclear translocation of p65. Furthermore, Wed reduced in CIA mice heart weight/body weight ratio and dampened cardiac inflammation and fibrosis that was accompanied at the mRNA level by down-regulation of ACTA2 and collagen I and up-regulation of E-cadherin.

CONCLUSIONS: These findings suggested that Wed attenuated synovial inflammation and joint damage in a mouse model of RA via inhibiting NF-κB/NLRP3 inflammasome activation, and ameliorated RA-induced cardiac complications.