Stigmasterol Depresses the Proliferation and Facilitates the Apoptosis of Fibroblast-Like Synoviocytes via the PI3K/AKT Signaling Pathway in Collagen-Induced Arthritis Rats.

Rheumatoid arthritis (RA) is a chronic disease characterized by persistent synovitis and angiogenesis. Its clinical manifestations are synovial hyperplasia and progressive destruction of bone and cartilage, eventually leading to joint deformation and even disability. The healing effect of monomer stigmasterol, the main active ingredient of the Jinwujiangu recipe the Chinese Herbal Compound, on RA has been confirmed in several studies. Fibroblast-like synoviocytes (FLS) are related to the occurrence and development of RA. This study aims to investigate the effects of stigmasterol on FLS cell proliferation and apoptosis, as well as its impact on FLS cell cycle proteins and key genes in the Phosphatidylinositol 3 kinase/protein kinase B (PI3K/AKT) pathway, providing insights into the development of stigmasterol as an alternative therapeutic drug for RA. We administered 20 g/kg stigmasterol to rats continuously for 5 d to obtain stigmasterol-containing serum, and established rat models of osteoarthritis induced by ossein to obtain FLS. To explore the effects of stigmasterol on the viability, migration, proliferation and apoptosis of collagen-induced arthritis (CIA)-FLS cells, we selected 0% (control), 5% (low concentration), 10% (medium concentration) and 20% (high concentration) drug-containing serum to intervene cells and conducted Cell Counting Kit-8 (CCK-8), Transwell, 5-ethynyl-2' -deoxyuridine (EdU) staining and Terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) experiments, respectively. The results showed that compared with the control group, low, medium, and high serum significantly inhibited the activity, migration, and proliferation of FLS cells, and promoted their apoptosis, and high serum had the best effect. In addition, we investigated the mechanism of stigmasterol inhibiting FLS proliferation and promoting its apoptosis by qPCR, Western blot, and immunofluorescence assays. The results showed that stigmasterol significantly inhibited the expression of Cyclin D1, cyclin-dependent kinase 4 (CDK4), and Retinoblastoma (Rb), and decreased the expression of key genes kinase insert domain-containing receptor (KDR), PI3K, AKT, phosphorylated PI3K (p-PI3K) and phosphorylated AKT (p-AKT) in the KDR-mediated PI3K/AKT signaling pathway, thus inhibiting the proliferation of FLS and promoting the apoptosis of FLS. It was suggested that stigmasterol may be a potential alternative drug for RA treatment.