Both NAC and catalase inhibit CaM activation leading to subsequent up-regulation of IL-12 p40 induction in activated RAW 264.7 macrophages. The RAW 264.7 macrophages were stimulated with either LPS plus IFN-γ (A,C,E) or LPS (B,D,F) in the absence or presence of 100 μM NAC. The intracellular H₂O₂ contents (A-B) were measured using H₂O₂ colorimetric assay kit and the CaM levels (C-D) were estimated by EIA. The IL-12 p40 levels secreted in the culture supernatants (E-F) were measured by EIA. Results shown are representative of 4 independent experiments. In another experiment, RAW 264.7 macrophages were stimulated with LPS plus IFN-γ in the absence or presence of 100 U/mL catalase and inductions of CaM (G) and IL-12 p40 (H) were measured by EIA. Results shown are representative of 3 independent experiments.