in CD341 cells via mitogen-activated protein kinase- dependent and NF-jB-independent pathways

To elucidate the role of Toll-like receptor 9 (TLR9) activation along with the intracellular signaling pathways triggered by CpG DNA in CD341 cells, we investigated whether synthetic oligodeoxy-nucleotides (ODNs), containing unmethylated CpG motifs, could induce IL-8 expression in CD341 cells through mitogen-activated protein kinase (MAPK) or nuclear factor-jB (NF-jB) pathway. We demonstrated evidence for the first time that CD341 cells constitutively expressed TLR9. Exposure of the cells to CpG ODN resulted in a time- and dose-dependent increase of IL-8 expression, and activation of phosphorylated ERK1/2 and phosphorylated p38. In addition, CpG ODN stimulated AP-1, but not NF-jB, signals. Moreover, inhibitors of MAPK (U0126 and SB203580) significantly reduced the IL-8 production, while the inhibition of NF-jB (pyrrolidinedithiocarbamate and retrovirus containing dominant-negative IjBa plasmid) did not affect the IL-8 expression increased by CpG ODN. Moreover, co-stimulation with LPS and CpG synergistically up-regulates IL-8 in CD341 cells. These results suggest that CpG DNA, acting on TLR9, activates CD341 cells to express IL-8 through MAPK-dependent and NF-jB-independent pathways