Circ_0001715 Mediated Progression and Inflammation in Fibroblast-Like Synoviocytes of Rheumatoid Arthritis by Targeting miR-326/TLR-4-NF-κB Pathway.

Rheumatoid arthritis (RA) is a systemic autoimmune disease. Circular RNA_0001715 (circ_0001715) has been demonstrated to be involved in the progression of cancers. This study aimed to discuss the function of circ_0001715 on the development of RA. Tumor necrosis factor-α (TNF-α) was used to active human RA fibroblast-like synoviocytes (FLS) (HFLS-RA) cells. The role of circ_0001715 in the progression of RA was determined by cell counting kit-8, flow cytometry, enzyme-linked immunosorbent assay. The target of circ_0001715 was predicted using the circinteractome database and validated by the luciferase reporter assay. The relative protein expression of toll-like receptor (TLR)-4/nuclear factor-kappa B (NF-κB) axis was detected by western blot. Moreover, a collagen-induced arthritis (CIA) mouse model was constructed through the secondary immunization. The role of circ_0001715 in vivo was determined by hematoxylin and eosin (H&E), Safranin O, TRAP, ELISA and western blot. Increased levels of circ_0001715 were discovered in tissues from RA patients, TNF-α-induced HFLS-RA cells, and synovial tissues of CIA-induced mice. Knockdown of circ_0001715 decreased proliferation and inflammation, but promoted apoptosis of RA both in vitro and in vivo. Additionally, miR-326 was predicted as the target of circ_0001715, which was confirmed by the luciferase reporter assay. Knockdown of miR-326 reversed the results of proliferation, apoptosis and inflammation resulted from the circ_0001715 knockdown. Mechanically, knockdown of circ_0001715 reduced the expression of TLR-4/NF-κB axis, which were rescued by the downregulation of miR-326. Circ_0001715 sequestered miR-326 to regulate the growth, apoptosis and inflammation of HFLS-RA cells via TLR-4/NF-κB axis.