Tormentic acid inhibits IL-1β-induced chondrocyte apoptosis by activating the PI3K/Akt signaling pathway

Interleukin-1 (IL-1) accelerates degradation of the cartilage matrix and induces apoptosis of chondrocytes. Tormentic acid (TA) is a triterpene isolated from the stem bark of the Vochysia divergens plant, which has been demonstrated to exert in vitro inhibitory activity against hepatocyte apoptosis. However, the effects of TA on IL-1-induced apoptosis of human chondrocytes remain unclear. Therefore, the present study investigated the in vitro effects of TA on human osteoarthritic chondrocyte apoptosis cultivated in the presence of IL-1. Human chondrocytes were pretreated with or without various concentrations of TA and then co-incubated in the absence or presence of IL-1 for 24 h. Cell viability was determined using the MTT assay, and cell apoptosis was detected using a Nucleosome ELISA kit. Caspase-3 activity was detected using a caspase-3 colorimetric assay kit. The levels of B-cell lymphoma 2 (Bcl-2)-associated X protein (Bax), Bcl-2, phosphorylated (p)-phosphoinositide 3-kinase (PI3K), PI3K, p-protein kinase B (Akt) and Akt were measured by western blotting. The results revealed that pretreatment with TA inhibited IL-1-induced cytotoxicity and apoptosis in chondrocytes. In addition, TA pretreatment increased B-cell lymphoma (Bcl)-2 expression, and decreased caspase-3 activity and Bax expressionin human chondrocytes. In addition, pretreatment with TA markedly increased the expression of p-PI3K and p-Akt in IL-1-induced chondrocytes. Collectively, these results indicate that TA inhibits IL-1-induced chondrocyte apoptosis by activating the PI3K/Akt signaling pathway. Therefore, TA may be considered a potential therapeutic target for the treatment of osteoarthritis.