Objective: Cinnamaldehyde (CA) is an active ingredient of Wenyang Tongluo capsule. This study was performed to investigate the function of CA on human chondrocytes.

Design: Different doses of CA were used to treat C28/I2 cells, which were stimulated by interleukin-1β (IL-1β), and then the viability and apoptosis of the cells were examined by cell counting kit-8 and flow cytometry. Interleukin-6 (IL-6), interleukin-20 (IL-20), and tumor necrosis factor-α (TNF-α) were measured by enzyme-linked immunosorbent assay. Quantitative real-time reverse transcriptase polymerase chain reaction was performed to measure miR-1285-5p, miR-140-5p, IL-20, and high-mobility group box 1 (HMGB1) messenger RNA (mRNA) expression. Western blot assay was performed to detect IL-20, HMGB1, IKBα, phospho-IKBα, IKKα/β, and phospho-IKKα/β expression. Moreover, the relationships between miR-1285-5p and IL-20, as well as miR-140-5p and HMGB1, were validated by dual-luciferase reporter assay.

Results: CA promoted the viability and inhibited the apoptosis of C28/I2 cells stimulated by IL-1β and repressed IL-6, IL-20, and TNF-α levels. CA increased miR-1285-5p and miR-140-5p expression levels. MiR-1285-5p and miR-140-5p promoted the viability and inhibited the apoptosis and inflammation of C28/I2 cells. IL-20 was a target gene of miR-1285-5p, and HMGB1 was a target gene of miR-140-5p. Overexpression of IL-20 or HMGB1 could reverse the effect of CA on C28/I2 cells treated with IL-1β. In addition, HMGB1 increased phospho-IKBα and phospho-IKKα/β expression in IL-1β- and CA-treated C28/I2 cells.

Conclusions: CA protects chondrocytes via regulating miR-1285-5p/IL-20 axis and miR-140-5p/HMGB1/nuclear factor kappa B pathway.