Fig. 5

The effect of NE and β-AR blockers on IL-1β-induced expression of MMPs and extracellular matrix proteins. The effect of NE and β-AR blockers on IL-1β-induced expression of (A) MMP-1, -3, (B) MMP-13 and (C) extracellular matrix proteins (ACAN and Col II). Chondrocytes were pre-incubated with NE (1 ng/ml) or β-AR blockers (propranolol (P), atenolol (A), nebivolol (B), and nadolol (N); 1 ng/ml) for 2 h followed by treatment with IL-1β (1 ng/ml) for 48 h. Protein levels in the samples were measured using western blot analysis. β-actin was used as a loading control. (D), (E) NE suppresses IL-1β-induced release of glycosaminoglycan (GAG) into the medium in cartilage explant culture. (D) GAG release in cartilage explant culture treated with IL-1β and NE or β-AR blockers. Cartilage tissue (40 mg) was preincubated with NE (1.0 ng/ml) or β-AR blockers (P, A, B, and N; 1.0 ng/ml) 2 h before treatment with IL-1β (1 ng/ml) for 1, 4, and 7 days. NE or β-AR blockers were contained throughout the experiment. Culture medium was changed every two days for culture period. Concentration of GAG in culture medium was measured using Sulfated Glycosaminoglycan Assay kit. (D) Data represent the mean ± SD of duplicate data from three different donors. *P < 0.05, **P < 0.01, and ****P < 0.0001vs. IL-1β-treated cartilage tissue by Kruskal-Wallis test followed with post hoc Dunn’s multiple comparison test. (E) Safranin O staining of explant culture of human joint cartilage in the presence of IL-1β and NE. Scale bars = 50 μm