Orientin inhibits the progression of fibroblast-like synovial cells in rheumatoid arthritis by regulating MAPK-signaling pathway

Abstract

Background: Natural compounds are found to play an essential role in diverse inflammatory diseases, including rheumatoid arthritis (RA). Orientin, a flavonoid compound, is closely related to diverse pathological processes. Nevertheless, the role of orientin in RA is still unknown. Methods: The cell viability was tested through cell counting kit 8 (CCK-8) assay, and the number of cell colonies was calculated via colony formation assay. In addition, flow cytom-etry assay was employed to detect apoptosis rate in human RA fibroblast-like synoviocytes (RA-FLS). Besides, Transwell assay was introduced to determine cell migratory and invasive abilities. Moreover, the level of cytokines (IL-8, IL-1β, and IL-6) was estimated with quantitative real-time polymerase chain reaction and enzyme-linked immunosorbent serologic assay. Furthermore, western blotting analysis was used to test the protein levels of cleavedcaspase-3, Bax, BCL-2, matrix metalloproteinase (MMP)-2, MMP-9, phosphorylated c-Jun N-terminal kinase, p-P38, and phospho-extracellular signal-related kinase. Results: Orientin inhibited cell viability, migration as well as invasion in a concentration-dependent manner in human RA-FLS. Additionally, treatment of orientin facilitated apoptosis and decreased the secretion of cytokines induced by tumor necrosis factor alpha (TNF-α) in human RA-FLS. Moreover, orientin inactivated mitogen-activated protein kinase (MAPK)-related signaling pathway, notably in human RA-FLS. Conclusion: These findings confirmed that orientin inhibited human RA-FLS development and decreased TNF-α-induced inflammatory factors, at least partly, by modulating MAPK-signaling pathway, which implied that orientin might be an effective agent for treating RA.