Stark Ryan, Choi Hyehun, Koch Stephen, Lamb Fred, Sherwood Edward
Department of Pediatric Critical Care, Vanderbilt University School of Medicine, Nashville, TN, USA
Department of Pediatric Critical Care, Vanderbilt University School of Medicine, Nashville, TN, USA.
Innate Immun. 2015 Aug;21(6):565-74. doi: 10.1177/1753425914564172. Epub 2014 Dec 24.
Monophosphoryl lipid A (MPLA) is a TLR4 agonist that is used as an immunomodulator in human vaccines; additionally, it has been shown to be protective in models of sepsis. As endothelial cells regulate inflammation, we hypothesized that MPLA would decrease activation of human umbilical vein endothelial cells (HUVECs) to LPS. We studied HUVECs challenged with LPS (100 ng/ml), MPLA (0.001-100 µg/ml) or a combination. Secretion of IL-6, RANTES (CCL5) and IP-10 (CXCL10) were assessed by ELISA. Activation of MAPK phosphorylation and cytokine transcription were assessed by Western blot analysis and PCR, respectively. MPLA alone was a weak stimulator of myeloid differentiation primary response protein 88-dependent IL-6 and did not induce TIR-domain-containing adapter-inducing IFN-β (TRIF)-dependent chemokine responses. MPLA significantly reduced LPS-mediated IL-6 production. This inhibitory effect was also conferred for the TRIF-dependent chemokines RANTES and IP-10. Inhibition of LPS-mediated activation by MPLA was associated with reduced p38 phosphorylation and mRNAs encoding inflammatory cytokines. MPLA inhibition of LPS signaling appeared to be at the level of the TLR4 receptor, acting as a receptor antagonist with weak agonistic properties. This study provides evidence of a novel mechanism for the inhibitory effect of MPLA on LPS-induced endothelial activation.
单磷酰脂质A（MPLA）是一种Toll样受体4（TLR4）激动剂，在人类疫苗中用作免疫调节剂；此外，它在脓毒症模型中已显示出具有保护作用。由于内皮细胞调节炎症，我们推测MPLA会降低人脐静脉内皮细胞（HUVECs）对脂多糖（LPS）的激活。我们研究了用LPS（100 ng/ml）、MPLA（0.001 - 100 μg/ml）或二者组合刺激的HUVECs。通过酶联免疫吸附测定（ELISA）评估白细胞介素-6（IL-6）、调节激活正常T细胞表达和分泌因子（RANTES，即CCL5）及干扰素诱导蛋白10（IP-10，即CXCL10）的分泌。分别通过蛋白质免疫印迹分析和聚合酶链反应（PCR）评估丝裂原活化蛋白激酶（MAPK）磷酸化的激活及细胞因子转录情况。单独的MPLA是髓样分化初级反应蛋白88依赖性IL-6的弱刺激剂，且不诱导含TIR结构域的接头分子诱导干扰素-β（TRIF）依赖性趋化因子反应。MPLA显著降低LPS介导的IL-6产生。这种抑制作用也作用于TRIF依赖性趋化因子RANTES和IP-10。MPLA对LPS介导激活的抑制作用与p38磷酸化及编码炎性细胞因子的信使核糖核酸（mRNAs）减少有关。MPLA对LPS信号传导的抑制作用似乎在TLR4受体水平，作为具有弱激动特性的受体拮抗剂发挥作用。本研究为MPLA对LPS诱导的内皮细胞激活的抑制作用提供了一种新机制的证据。
