1.DRI, and BK21 Program, School of Dentistry, Seoul National University, 28 Yongon-Dong, Chongno-Gu, Seoul 110-749, Republic of Korea.
J Leukoc Biol. 2013 Dec;94(6):1275-84. doi: 10.1189/jlb.1012522. Epub 2013 Aug 20.
Enterococcus faecalis is one of the most common opportunistic pathogens responsible for nosocomial infections, and its LTA is known as an important virulence factor causing inflammatory responses. As chemokines play a key role in inflammatory diseases by triggering leukocyte infiltration into the infection site, we purified EfLTA and investigated its effect on the expression of chemokines, IP-10, MIP-1α, and MCP-1, in murine macrophages. EfLTA induced the expression of these chemokines at the mRNA and protein levels. TLR2, CD14, and MyD88 were involved in the EfLTA-induced chemokine expression, as the expression was reduced remarkably in macrophages derived from TLR2-, CD14-, or MyD88-deficient mice. EfLTA induced phosphorylation of MAPKs and enhanced the DNA-binding activity of NF-κB, AP-1, and NF-IL6 transcription factors. The induction of IP-10 required ERK, JNK, p38 MAPK, PKC, PTK, PI3K, and ROS. We noticed that all of these signaling molecules, except p38 MAPK and ROS, were indispensable for the induction of MCP-1 and MIP-1α. Interestingly, the EfLTA-induced chemokine expression was mediated through PAFR/JAK/STAT1 signaling pathways without IFN-β involvement, which is different from LPS-induced chemokine expression requiring IFN-β/JAK/STAT1 signaling pathways. Furthermore, the culture supernatant of EfLTA-treated RAW 264.7 cells promoted the platelet aggregation, and exogenous PAF induced the chemokine expression in macrophages derived from WT and TLR2-deficient mice. These results suggest that EfLTA induces the expression of chemokines via signaling pathways requiring TLR2 and PAFR, which is distinct from that of LPS-induced chemokine expression.
粪肠球菌是引起医院感染的最常见机会性病原体之一，其脂磷壁酸（LTA）被认为是引起炎症反应的重要毒力因子。趋化因子通过触发白细胞浸润感染部位在炎症性疾病中发挥关键作用，因此我们纯化了 EfLTA 并研究了其对小鼠巨噬细胞中趋化因子 IP-10、MIP-1α 和 MCP-1 表达的影响。EfLTA 在 mRNA 和蛋白质水平上诱导这些趋化因子的表达。TLR2、CD14 和 MyD88 参与了 EfLTA 诱导的趋化因子表达，因为 TLR2-、CD14-或 MyD88 缺陷型巨噬细胞中的表达显著降低。EfLTA 诱导 MAPK 的磷酸化，并增强 NF-κB、AP-1 和 NF-IL6 转录因子的 DNA 结合活性。IP-10 的诱导需要 ERK、JNK、p38 MAPK、PKC、PTK、PI3K 和 ROS。我们注意到，除了 p38 MAPK 和 ROS 之外，所有这些信号分子对于 MCP-1 和 MIP-1α 的诱导都是必不可少的。有趣的是，EfLTA 诱导的趋化因子表达是通过 PAFR/JAK/STAT1 信号通路介导的，而不涉及 IFN-β，这与 LPS 诱导的需要 IFN-β/JAK/STAT1 信号通路的趋化因子表达不同。此外，EfLTA 处理的 RAW 264.7 细胞的培养上清液促进血小板聚集，外源性 PAF 诱导 WT 和 TLR2 缺陷型小鼠来源的巨噬细胞中趋化因子的表达。这些结果表明，EfLTA 通过需要 TLR2 和 PAFR 的信号通路诱导趋化因子的表达，这与 LPS 诱导的趋化因子表达不同。
