Inosine ameliorated bone destruction and inflammation in rheumatoid arthritis via inhibiting osteclastogenesis and synovial fibroblasts activation.

Abstract

This study aim to investigate the effects of inosine on rheumatoid arthritis (RA) disease and explore the potential mechanism. Collagen-Induced Arthritis (CIA) rats were used to investigate the effects of inosine on bone destruction and inflammation. Micro-CT scan was used to detect the bone injury. H&E and Safranin O staining were used to evaluate the synovial inflammation and cartilage damage. RANKL-induced osteoclasts differentiation assay was used to investigate the effects of inosine on osteclastogenesis. CCK-8 and transwell experiments were performed to investigate the RA synovioblast (RASFs) proliferation and invasion. We observed that inosine intraperitoneal injection led to significant reduction in arthritis score of CIA rats. Micro-CT scan showed the decreased degree of bone destruction and increased bone mass in inosine treated CIA-rats. H&E and Safranin O staining showed that inosine significantly inhibited the inflammation and cartilage erosion in CIA-rats. The IL-6 and IL-8 levels in synovial tissues were lower in inosine treated CIA-rats than that in vehicle group. Furthermore, TRAP staining showed that the osteoclasts numbers were decreased in inosine treated CIA-rats. In vitro, inosine led to the decrease of osteoclasts numbers, F-actin ring and the expression of osteoclasts-specific markers. Furthermore, we found that inosine inhibited osteoclastogenesis via down-regulating OPN. OPN supplementation could counteract the inhibiting effect of inosine on osteoclastogenesis. Additionally, we observed that inosine significantly inhibited proliferation, invasion and inflammatory cytokines secretion of RASFs. In conclusion, inosine alleviated bone destruction and inflammation in CIA-rats by inhibiting osteoclastogenesis and RASFs activation. Hence, inosine supplementation may be a potential strategy for RA therapy.