Yanagawa Yoshiki, Onoé Kazunori
Division of Immunobiology, Institute for Genetic Medicine, Hokkaido University, Sapporo, Japan.
J Immunol. 2007 May 15;178(10):6173-80. doi: 10.4049/jimmunol.178.10.6173.
LPS tolerance has been investigated extensively in monocytes/macrophages. However, the LPS restimulation studies are not well documented in dendritic cells (DCs). In the present study, we investigated influences of TLR restimulation using murine bone marrow-derived DCs. Purified bone marrow-derived DCs (>98% CD11c+ B220-) were stimulated with TLR4 and TLR2 ligands for 24 h and then cultured with medium alone for 48 h as a resting interval (TLR4,2-primed DCs). The TLR4-MD2 expression was markedly reduced immediately after the TLR stimulation, but was restored following the resting interval. The TLR4,2-primed DCs exhibited significantly enhanced IL-10 production, but markedly diminished IL-12p40 production upon TLR4 restimulation compared with naive (unprimed) DCs. TLR4-mediated activation of p38 MAPK was markedly suppressed, whereas that of ERK1/2 was enhanced in the TLR4,2-primed DCs compared with naive DCs. Blocking the activation of ERK1/2 with U0126 reduced the enhanced IL-10 production by the TLR4,2-primed DCs upon the TLR4 restimulation. The U0126 showed no significant effects on the IL-12p40 production. Thus, the enhanced ERK1/2 activation appears to be, at least in part, responsible for the enhanced IL-10 production in the TLR4,2-primed DCs. In addition, TNFR-associated factor 3 expression was significantly up-regulated in the TLR4,2-primed DCs compared with that in naive DCs. We demonstrated in this study that DCs primed with TLR4 and TLR2 ligands and rested for 48 h showed enhanced IL-10 production upon TLR4 restimulation. The enhanced IL-10 production by the TLR4,2-primed DCs may be attributed to the altered balance of intracellular signaling pathways via p38 MAPK, ERK1/2, and TNFR-associated factor 3 upon TLR restimulation.
脂多糖（LPS）耐受性已在单核细胞/巨噬细胞中得到广泛研究。然而，LPS再刺激研究在树突状细胞（DCs）中尚无充分记录。在本研究中，我们使用小鼠骨髓来源的DCs研究了Toll样受体（TLR）再刺激的影响。纯化的骨髓来源的DCs（>98% CD11c+ B220-）用TLR4和TLR2配体刺激24小时，然后单独用培养基培养48小时作为静息间隔（TLR4,2预刺激的DCs）。TLR刺激后，TLR4-MD2表达立即显著降低，但在静息间隔后恢复。与未刺激（未预刺激）的DCs相比，TLR4,2预刺激的DCs在TLR4再刺激时表现出IL-10产生显著增强，但IL-12p40产生明显减少。与未刺激的DCs相比，TLR4介导的p38丝裂原活化蛋白激酶（MAPK）激活在TLR4,2预刺激的DCs中受到显著抑制，而细胞外信号调节激酶1/2（ERK1/2）的激活则增强。用U0126阻断ERK1/2的激活可降低TLR4,2预刺激的DCs在TLR4再刺激时增强的IL-10产生。U0126对IL-12p40产生无显著影响。因此，ERK1/2激活增强似乎至少部分负责TLR4,2预刺激的DCs中IL-10产生增强。此外，与未刺激的DCs相比，TLR4,2预刺激的DCs中肿瘤坏死因子受体相关因子3（TNFR-associated factor 3）表达显著上调。我们在本研究中证明，用TLR4和TLR2配体预刺激并静息48小时的DCs在TLR4再刺激时表现出IL-10产生增强。TLR4,2预刺激的DCs中IL-10产生增强可能归因于TLR再刺激时通过p38 MAPK、ERK1/2和TNFR相关因子3改变的细胞内信号通路平衡。
