mTORC2 inhibition by JR-AB2-011 improves IL-1β-induced inflammation, catabolic response, and apoptosis in human chondrocytes through IκB-α/NF-κB p65.

Abstract

Osteoarthritis (OA) is a very common chronic joint condition marked by inflammation and cartilage loss. mTOR is a well-known mediator of inflammation, cell survival, and aging; however, its role in OA has not been determined. To explore the role of mTORC2 in OA-and associated pathological changes, we examined the contribution of mTORC2-mediated Akt, rictor and IκB-α/NF-κB p65 pathway in interleukin (IL)-1β-treated human chondrocytes. We focused on the protein expression of proinflammatory cytokines and catabolic and apoptotic factors, including TNF-α, IL-6, iNOS, MMP13, Bax, and caspase3, which may occur through this signalling pathway in IL-1β-treated chondrocytes. Chondrocytes were cultured and treated with either 2 ng/mL IL‑1β alone or in combination with increasing concentrations of JR-AB2-011 (50, 100, or 250 µM), a selective mTORC2 inhibitor. The protein levels of phosphorylated (p)‑Akt, Akt, rictor, p-NF-κB p65, NF-κB p65, IκB-α, p-IκB-α, iNOS, MMP13, Bax, and caspase3 were evaluated by Western blotting. In IL-1β-stimulated chondrocytes, mTORC2 activity was increased with increased phosphorylation of Akt and expression of rictor. IL-1β increased the expression of p-IκBα, p-NF-κB p65, NF-κB p65, IL-6, TNF-α, iNOS, Bax, and caspase3 proteins and decreased the expression of IκB-α. All of these IL-1β-induced alterations were prevented by JR-AB2-011. The main novel finding in the present study is that selective mTORC2 inhibition by JR-AB2-011 prevents the inflammatory, catabolic, and apoptotic responses induced by IL-1β via modulation of IκB-α/NF-κB activity. Therefore, we demonstrated a previously unknown function of mTORC2 inhibition that seems to be a potential therapeutic target for OA.