Fig. 2.

IL-1β-induced cytokine synthesis in muscle progenitors is inhibited only by high concentrations of IL-10 (≥25 ng/ml). A: C₂C₁₂ myoblasts were treated with IL-1β (1 ng/ml) for 24, 16, 8, 4, and 2 h or with medium alone for 24 h (zero time point). The amount of IL-6 protein was measured with an ELISA specific for murine IL-6. IL-1β significantly increased IL-6 expression in a time-dependent manner with a statistically significant increase as early as 2 h (n = 3). B: C₂C₁₂ myoblasts were pretreated with 0, 10, 25, or 50 ng/ml IL-10 before incubation with IL-1β (1 ng/ml) for an additional 24 h or with medium alone or IL-10 alone for 24 h. Results obtained with an IL-6-specific ELISA demonstrated that IL-10 significantly inhibited IL-6 expression only at concentrations ≥25 ng/ml but not at the lower concentration (10 ng/ml) (n = 4). IL-6 expression was not detected in supernatants from untreated cells or cells treated with IL-10 alone (lower limit of sensitivity of 7 pg/ml). C: IL-10 (10 ng/ml), IGF-I (50 ng/ml), IL-1β (1 ng/ml), or the combination of IL-10 and IGF-I did not induce detectible levels of TNFα expression (lower limit of sensitivity of 9 pg/ml). Recombinant murine TNFα was used as a positive control (2,450, 350, and 50 ng/ml) (n = 3). *P < 0.05; **P < 0.01.