Fig. 2. IL-18 induces TRAF3IP2 expression via Nox4 and H₂O₂.

A, IL-18 induces TRAF3IP2 expression. The quiescent CF treated with IL-18 (10 ng/ml) were analyzed for TRAF3IP2 expression by immunoblotting (n=3). B, IL-18 induces TRAF3IP2 expression via Nox4. CF were transduced with Ad.siNox4 (moi 100 for 48 h), made quiescent, and then treated with IL-18 (10 ng/ml for 2 h). Studies were also performed after DPI pre-treatment (10 µg/ml for 30 min). Knockdown of Nox4 was confirmed by immunoblotting (right side). Akt served as an off-target. TRAF3IP2 expression was analyzed by immunoblotting as in A (n=3). C, IL-18 stimulates Nox4-dependent H₂O₂ generation. CF infected with Ad.siNox4 (moi 100 for 48 h) or treated with DPI (10 µg/ml for 30 min) prior to IL-18 addition (10 ng/ml) were analyzed for H₂O₂ production using the Amplex Red assay. *P< 0.01 vs. untreated; †P< at least 0.05 vs. IL-18 (n=6). D, The H₂O₂ scavenger sodium pyruvate inhibits IL-18-induced H₂O₂ production and TRAF3IP2 induction. CF treated as in C, but with sodium pyruvate (10 mM for 1 h) prior to IL-18 addition (10 ng/ml) were analyzed for H₂O₂ production by Amplex Red assay (C; n=6) and TRAF3IP2 expression by immunoblotting (D; n=3).