Kim Hyun Young, Baik Jung Eun, Ahn Ki Bum, Seo Ho Seong, Yun Cheol-Heui, Han Seung Hyun
Department of Oral Microbiology and Immunology, DRI and BK21 Plus Program, School of Dentistry, Seoul National University, Seoul 08826, Republic of Korea.
Radiation Biotechnology Research Division, Advanced Radiation Technology Institute, Korea Atomic Energy Research Institute, Jeongeup 34057, Republic of Korea.
Mol Immunol. 2017 Feb;82:75-83. doi: 10.1016/j.molimm.2016.12.016. Epub 2016 Dec 27.
Streptococcus gordonii, a Gram-positive commensal in the oral cavity, is an opportunistic pathogen that can cause endodontic and systemic infections resulting in infective endocarditis. Lipoteichoic acid (LTA) and lipoprotein are major virulence factors of Gram-positive bacteria that are preferentially recognized by Toll-like receptor 2 (TLR2) on immune cells. In the present study, we investigated the effect of S. gordonii LTA and lipoprotein on the production of the representative inflammatory mediator nitric oxide (NO) by the mouse macrophages. Heat-killed S. gordonii wild-type and an LTA-deficient mutant (ΔltaS) but not a lipoprotein-deficient mutant (Δlgt) induced NO production in mouse primary macrophages and the cell line, RAW 264.7. S. gordonii wild-type and ΔltaS also induced the expression of inducible NO synthase (iNOS) at the mRNA and protein levels. In contrast, the Δlgt mutant showed little effect under the same condition. Furthermore, S. gordonii wild-type and ΔltaS induced NF-κB activation, STAT1 phosphorylation, and IFN-β expression, which are important for the induction of iNOS gene expression, with little activation by Δlgt. S. gordonii wild-type and ΔltaS showed an increased adherence and internalization to RAW 264.7 cells compared to Δlgt. In addition, S. gordonii wild-type and ΔltaS, but not Δlgt, substantially increased TLR2 activation while none of these induced NO production in TLR2-deficient macrophages. Triton X-114-extracted lipoproteins from S. gordonii were sufficient to induce NO production. Collectively, we suggest that lipoprotein is an essential cell wall component of S. gordonii to induce NO production in macrophages through TLR2 triggering NF-κB and STAT1 activation.
戈登氏链球菌是口腔中的一种革兰氏阳性共生菌，是一种机会致病菌，可引起牙髓感染和全身感染，导致感染性心内膜炎。脂磷壁酸（LTA）和脂蛋白是革兰氏阳性菌的主要毒力因子，可被免疫细胞上的Toll样受体2（TLR2）优先识别。在本研究中，我们研究了戈登氏链球菌LTA和脂蛋白对小鼠巨噬细胞产生代表性炎症介质一氧化氮（NO）的影响。热灭活的戈登氏链球菌野生型和LTA缺陷突变体（ΔltaS），而非脂蛋白缺陷突变体（Δlgt），可诱导小鼠原代巨噬细胞和细胞系RAW 264.7产生NO。戈登氏链球菌野生型和ΔltaS还在mRNA和蛋白质水平上诱导诱导型NO合酶（iNOS）的表达。相比之下，Δlgt突变体在相同条件下几乎没有影响。此外，戈登氏链球菌野生型和ΔltaS诱导NF-κB激活、STAT1磷酸化和IFN-β表达，这些对iNOS基因表达的诱导很重要，而Δlgt几乎没有激活作用。与Δlgt相比，戈登氏链球菌野生型和ΔltaS对RAW 264.7细胞的黏附和内化增加。此外，戈登氏链球菌野生型和ΔltaS，但不是Δlgt，显著增加TLR2激活，而这些在TLR2缺陷的巨噬细胞中均未诱导NO产生。从戈登氏链球菌中用Triton X-114提取的脂蛋白足以诱导NO产生。总的来说，我们认为脂蛋白是戈登氏链球菌细胞壁的重要组成部分，可通过TLR2触发NF-κB和STAT1激活来诱导巨噬细胞产生NO。
