Madeira M F M, Queiroz-Junior C M, Cisalpino D, Werneck S M C, Kikuchi H, Fujise O, Ryffel B, Silva T A, Teixeira M M, Souza D G
Departamento de Microbiologia, ICB, Universidade Federal de Minas Gerais (UFMG), Belo Horizonte, MG, Brazil; Departamento de Bioquímica e Imunologia, ICB, UFMG, Belo Horizonte, MG, Brazil.
Mol Oral Microbiol. 2013 Dec;28(6):415-24. doi: 10.1111/omi.12034. Epub 2013 Jul 30.
Aggregatibacter actinomycetemcomitans is a Gram-negative bacteria highly associated with localized aggressive periodontitis. The recognition of microbial factors, such as lipopolysaccharide from A. actinomycetemcomitans ((Aa)LPS), in the oral environment is made mainly by surface receptors known as Toll-like receptors (TLR). TLR4 is the major LPS receptor. This interaction leads to the production of inflammatory cytokines by myeloid differentiation primary-response protein 88 (MyD88) -dependent and -independent pathways, which may involve the adaptor Toll/interleukin-1 receptor-domain-containing adaptor inducing interferon-β (TRIF). The aim of this study was to assess the involvement of MyD88 in alveolar bone loss induced by (Aa)LPS in mice. C57BL6/J wild-type (WT) mice, MyD88, TRIF or TRIF/MyD88 knockout mice received 10 injections of Aa LPS strain FDC Y4 (5 μg in 3 μl), in the palatal gingival tissue of the right first molar, every 48 h. Phosphate-buffered saline was injected in the opposite side and used as control. Animals were sacrificed 24 h after the 10th injection and the maxillae were removed for macroscopic and biochemical analyses. The injections of Aa LPS induced significant alveolar bone loss in WT mice. In the absence of MyD88 or TRIF/MyD88 no bone loss induced by (Aa)LPS was observed. In contrast, responses in TRIF(-/-) mice were similar to those in WT mice. Diminished bone loss in the absence of MyD88 was associated with fewer TRAP-positive cells and increased expression of osteoblast markers, RUNX2 and osteopontin. There was also reduced tumor necrosis factor-α production in MyD88(-/-) mice. There was less osteoclast differentiation of hematopoietic bone marrow cells from MyD88(-/-) mice after (Aa)LPS stimulation. Hence, the signaling through MyD88 is pivotal for (Aa)LPS-induced osteoclast formation and alveolar bone loss.
伴放线聚集杆菌是一种与局限性侵袭性牙周炎高度相关的革兰氏阴性菌。在口腔环境中，对微生物因子的识别，如来自伴放线聚集杆菌的脂多糖（（Aa）LPS），主要由称为Toll样受体（TLR）的表面受体完成。TLR4是主要的LPS受体。这种相互作用通过髓样分化初级反应蛋白88（MyD88）依赖性和非依赖性途径导致炎性细胞因子的产生，这可能涉及衔接蛋白Toll/白细胞介素-1受体结构域含诱导干扰素-β的衔接蛋白（TRIF）。本研究的目的是评估MyD88在（Aa）LPS诱导的小鼠牙槽骨吸收中的作用。C57BL6/J野生型（WT）小鼠、MyD88、TRIF或TRIF/MyD88基因敲除小鼠每48小时在右侧第一磨牙的腭侧牙龈组织中接受10次Aa LPS菌株FDC Y4（5μg溶于3μl）注射。在对侧注射磷酸盐缓冲盐水并用作对照。在第10次注射后24小时处死动物，取出上颌骨进行宏观和生化分析。注射Aa LPS在WT小鼠中诱导了显著的牙槽骨吸收。在没有MyD88或TRIF/MyD88的情况下，未观察到（Aa）LPS诱导的骨吸收。相反，TRIF（-/-）小鼠的反应与WT小鼠相似。在没有MyD88的情况下骨吸收减少与抗酒石酸酸性磷酸酶（TRAP）阳性细胞减少和成骨细胞标志物RUNX2和骨桥蛋白的表达增加有关。在MyD88（-/-）小鼠中肿瘤坏死因子-α的产生也减少。（Aa）LPS刺激后，MyD88（-/-）小鼠造血骨髓细胞的破骨细胞分化较少。因此，通过MyD88的信号传导对于（Aa）LPS诱导的破骨细胞形成和牙槽骨吸收至关重要。
