Fig. 2

β-ARs were downregulated in response to IL-1β. (A)~(C) The mRNA levels of β₁-, β₂-, and β₃-AR in IL-1β-treated chondrocytes. Chondrocytes were stimulated with IL-1β (1 ng/ml) for 6, 24, 48, and 72 h. mRNA levels of β-ARs were quantified using Quanti Fast SYBR Green-based real-time PCR (RT-PCR). The expression ratios of β-adrenergic receptors relative to glyceraldehyde 3-phosphate dehydrogenase (GAPDH), the internal control, are shown. Data represent the mean ± standard deviation (SD) for duplicate data from five different donors. ****P < 0.0001 vs. untreated chondrocytes by Mann-Whitney test. (D) Reduction of β₁-, β₂-, and β₃-AR proteins in IL-1β-treated chondrocytes. Human chondrocytes were treated with IL-1β (1 ng/ml) for 6, 24, 48, and 72 h. Protein levels of β-ARs were measured using western blot analysis. β-actin was used as a loading control