IL-1β stimulates miR-146a and vascular endothelial growth factor along with downregulation of Smad4. Primary rat chondrocytes were treated with IL-1β (10 ng/ml) for the indicated time periods. Expression levels of miR-146a, Smad4, and vascular endothelial growth factor (VEGF) were monitored by quantitative real-time PCR and western blotting. (A) miR-146a expression was significantly increased over a 24-hour time course. (B) mRNA levels of Smad4 were reduced after treatment with IL-1β. (C) VEGF was upregulated by IL-1β. Values are the mean ± standard deviation (SD) of three independent experiments. (D) Protein levels of Smad4 and VEGF were respectively decreased and increased in chondrocytes stimulated with IL-1β. The relative expression levels of protein are shown at the bottom of the bands as normalized by the GAPDH level. (E) Densitometric analysis of immunoblot band intensities for Smad4 normalized by GAPDH. Data are mean ± SD of three independent experiments. (F) Densitometric analysis of immunoblot band intensities for VEGF normalized by GAPDH. Data are mean ± SD of three independent experiments. Control samples (Con) were not treated with IL-1β.