Knockdown of JNK1/2 by siRNA inhibits PGN-induced iNOS expression and NO production. Mouse peritoneal macrophages were transfected with JNK1 and JNK2 siRNA (JNK) or scrambled siRNA (Scr). (A) After 36 h of transfection, Macrophages were stimulated with PGN (10 μg/ml) for 30 min, and cell lysates were immunoblotted with antibodies against phospho-JNK (p-p46 and p-p54) and JNK2. The lower panel shows the densitometry analysis of phospho-JNK bands. (B) Macrophages were stimulated with PGN for 30 min, and cell lysates were immunoblotted with anti-phospho c-Jun and c-Jun antibody. (C) After 36 h of transfection, macrophages were stimulated with PGN (10 μg/ml) for 18 h, and the NO in culture supernatants was evaluated by using a Griess reagent assay. Each bar represents the standard error of three independent experiments. *, P < 0.05 compared to scramble siRNA. (D) Macrophages were similarly stimulated with PGN for 18 h, followed by immunoblotting of cell lysates with anti-iNOS polyclonal antibody. The same blot was reprobed with anti-actin antibody to demonstrate equal protein loading.