Figure 3.

Inhibition of STAT3 tyrosine phosphorylation halts cytokine production. (A) THP1 cells were pretreated with stattic, and TNF levels were quantified by ELISA at 3 h after LPS stimulation. *p<0.01 versus LPS (n = 3; One-way ANOVA with Bonferroni's modifications). (B) STAT3 phosphorylation was determined in peritoneal macrophages by Western blot. The upper panel shows a representative Western blot, whereas the lower panel represents the densitometric data of three different experiments (mean±SD, normalized as percent of the LPS treatment). (C) Control peritoneal macrophages or cells transfected with the dominant-negative form of STAT3F were pretreated with choline or stattic and LPS, and the TNF levels were quantified by ELISA and represented in mean±SD. *p<0.01 versus LPS (n = 3; One-way ANOVA with Bonferroni's corrections). (D) STAT3 depletion increased TNF production. THP1 cells were pretreated with control RNA or the STAT3 siRNA at the indicated concentrations for 24 h prior to LPS stimulation. STAT3 expression in control and treated cells were analyzed by Western blot using β-actin as a loading control (upper panel). Graph shows the data of three different experiments in mean±SD. (E) THP1 cells pretreated with control RNA or STAT3 siRNA were treated with choline (50 mM) 30 min prior to LPS stimulation. Graph shows data of three experiments in mean±SD. *p<0.01 versus LPS (n = 3; One-way ANOVA with Bonferroni's corrections).