Caffeine suppresses MAPK pathway activation in THP-1 macrophages stimulated by LPS. (A) The protein levels of JNK, ERK, p38, and their phosphorylated forms (P-JNK, P-ERK, and P-p38) were evaluated by western blotting in THP-1 macrophages pretreated with caffeine for 1 h and then incubated with LPS (1 μg/ml) for 3 h. (B) Densitometric analysis was used to quantify the phosphorylation of JNK at Thr183/Tyr185. (C) Densitometric analysis was used to quantify the phosphorylation of ERK1/2 at Thr202/Tyr1204. (D) Densitometric analysis was used to quantify the phosphorylation of p38 at Thr180/Tyr182. The results represent the mean ± SD for three experiments. *** p< 0.001 vs. the control group. # p<0.05, ## p<0.01, and ### p< 0.001 vs. the LPS group.