ERK1/2 MAPKs are involved in increases of mRNA and soluble protein TNF-alpha by arecoline in THP1 cells. (A) (B) Arecoline increased mRNA (A) and soluble protein (B) of TNF-alpha. THP1 (2 × 106 in 1.5 mL) cells were treated with indicated doses of arecoline for 6 hours. (C) (D) PD98059 inhibited TNF-alpha mRNA (C) and soluble protein (D) inductioin via arecoline. Cells were pretreated with 10 μM PD98059 for 1 h and further treated with 400 μM arecoline for 6 hours. Those mRNA and soluble protein of TNF-alpha levels were measured by RT-qPCR and ELISA. These results represent mean ± SD of three independent experiments; asterisk shows significant difference (p < 0.05) compared with controls (0 μM).