Figure 3. TNFα-induced IL-6 expression is not inhibited by low concentrations of IL-10.

A, C₂C₁₂ myoblasts were treated with TNFα for 0, 2, 4, 8, 16 and 24 h (gray bars) or pre-treated with IL-10 (10 ng/ml) for 1 h prior to treatment with TNFα (black bars). Expression of IL-6 protein in culture supernatants was determined by an ELISA. TNFα induced a time-dependent increase in IL-6 expression that peaks at 24 h (N = 4; gray bars). IL-10 (10 ng/ml) did not inhibit the expression of IL-6 (N = 3; black bars). B, To test the ability of IL-10 at higher concentrations to inhibit IL-6 expression, C₂C₁₂ myoblasts were pre-treated with three doses of IL-10 (10, 25 and 50 ng/ml) for 1 h prior to treatment with TNFα (1 ng/ml) for an additional 24 h (N = 4). Consistent with results in A, IL-10 at the lower concentration (10 ng/ml) did not inhibit the ability of TNFα to induce IL-6 expression. However, a higher concentration of IL-10 (50 ng/ml) inhibited TNFα-induced expression of IL-6 by 33% (50 ng/ml). IL-10 at 25 ng/ml reduced IL-6 expression by 22%, but this decrease was not significant (P < 0.06). In the absence of TNFα, IL-10 (50 ng/ml) did not alter IL-6 expression. * P < 0.05; ** P < 0.01