Centre of Molecular Inflammation Research, Norwegian University of Science and Technology, Trondheim, Norway.
Department of Clinical and Molecular Medicine, Norwegian University of Science and Technology, Trondheim, Norway.
J Leukoc Biol. 2020 Apr;107(4):673-683. doi: 10.1002/JLB.3A0120-114R. Epub 2020 Feb 21.
We recently showed that TLR8 is critical for the detection of Gram-positive bacteria by human monocytes. Here, we hypothesized that TLR8 and complement together regulate antibacterial responses in human blood. Anticoagulated blood was treated with selective inhibitors of TLR8 and/or complement C5, and then challenged with live Streptococcus agalactiae (Group B streptococcus, GBS), Staphylococcus aureus, or Escherichia coli. Cytokine production, plasma membrane permeability, bacterial survival, phagocytosis, and activation of coagulation was examined. GBS and S. aureus, but not E. coli, triggered TLR8-dependent production of IL-12p70, IL-1β, TNF, and IL-6 in fresh human whole blood. In purified polymorphonuclear neutrophils (PMN), GBS and S. aureus induced IL-8 release in part via TLR8, whereas PMN plasma membrane leakage and extracellular DNA levels increased independently of TLR8. TLR8 was more important than C5 for bacteria-induced production of IL-12p70, IL-1β, and TNF in blood, whereas IL-8 release was more C5 dependent. Both TLR8 and C5 induced IL-6 release and activation of prothrombin cleavage, and here their combined effects were additive. Blocking of C5 or C5aR1 attenuated phagocytosis and increased the extracellular growth of GBS in blood, whereas TLR8 inhibition neither reduced phagocytosis nor intracellular killing of GBS and S. aureus. In conclusion, TLR8 is more important than C5 for production of IL-12p70, IL-1β, and TNF upon GBS and S. aureus infection in blood, whereas C5 is central for IL-8 release and phagocytosis. Both TLR8 and C5 mediate IL-6 release and activation of coagulation during challenge with Gram-positive bacteria in blood.
我们最近表明，TLR8 对于人类单核细胞识别革兰氏阳性菌至关重要。在这里，我们假设 TLR8 和补体共同调节人类血液中的抗菌反应。用 TLR8 和/或补体 C5 的选择性抑制剂处理抗凝血液，然后用活的酿脓链球菌（B 型链球菌，GBS）、金黄色葡萄球菌或大肠杆菌进行挑战。检测细胞因子产生、质膜通透性、细菌存活、吞噬作用和凝血激活。GBS 和金黄色葡萄球菌，但不是大肠杆菌，在新鲜的人全血中触发 TLR8 依赖性的 IL-12p70、IL-1β、TNF 和 IL-6 的产生。在纯化的多形核粒细胞（PMN）中，GBS 和金黄色葡萄球菌诱导部分通过 TLR8 释放 IL-8，而 PMN 质膜渗漏和细胞外 DNA 水平的增加与 TLR8 无关。在血液中，TLR8 比 C5 更重要，可诱导细菌诱导的 IL-12p70、IL-1β 和 TNF 的产生，而 IL-8 释放则更依赖 C5。TLR8 和 C5 均诱导 IL-6 释放和促凝血酶原裂解的激活，在此，它们的联合作用是相加的。阻断 C5 或 C5aR1 减弱了 GBS 在血液中的吞噬作用并增加了其细胞外生长，而 TLR8 抑制既不减少 GBS 和金黄色葡萄球菌的吞噬作用，也不减少其细胞内杀伤作用。总之，在血液中 GBS 和金黄色葡萄球菌感染时，TLR8 比 C5 更重要，可诱导产生 IL-12p70、IL-1β 和 TNF，而 C5 对于 IL-8 释放和吞噬作用至关重要。TLR8 和 C5 在血液中革兰氏阳性菌挑战时均介导 IL-6 释放和凝血激活。
