Development of prevention method of periodontal diseases by understanding the mechanisms of intracellular invasion by periodontopathic bacteria

放线菌是一种革兰氏阴性嗜红球芽孢杆菌，被认为是青少年和成人严重牙周炎的病因。以往的研究表明放线菌可侵入晚期牙周炎的牙周组织，并在宿主细胞内存活。我们之前的研究表明放线菌感染可诱导海洋巨噬细胞样细胞系的凋亡细胞死亡。在细胞凋亡过程中，观察到几种半胱天冬酶的活化。在普通医学中，一些重要的致病菌可以感染并在宿主细胞内繁殖，并引起严重的危及生命的感染。详细分析了一些致病菌的细胞内侵袭机制，并报道了几种半胱天冬酶在侵袭过程中被激活。我们假设导致军团病的嗜肺军团菌和牙周病细菌放线菌可能以类似的方式侵入宿主细胞，因为它们都以巨噬细胞为目标侵入并激活宿主细胞中类似的半胱天冬酶。我们首先将为放线菌球菌设计的侵袭试验适用于嗜肺乳杆菌。小鼠巨噬细胞系J744.1和小鼠单核细胞细胞系RAW264.7均可通过感染这些细菌诱导细胞死亡。而嗜肺乳杆菌的细胞死亡表现为坏死，因为在细胞爆炸之前，细胞内充满了大量的细菌细胞。即使激活了一组相似的半胱天冬酶，不同细菌引起的细胞死亡的差异可能取决于感染激活的信号通路不同。组成性表达抗凋亡细胞Bcl-2或Bcl-x_L的RAW264.7细胞在放线菌感染后不能挽救细胞死亡。综上所述，放线菌的侵袭和感染机制是独特的，我们需要进一步分析这些机制来预防牙周病。少

Actinobacillus actinomycetemcomitans is a Gram-negative, capnophilic coccobacillus which has been considered to be an etiologic agent especially in the severe form of juvenile and adult periodontitis. Previous studies suggested that A.actinomycetemcomitans can invade into periodontal tissues of advanced periodontitis and then survive inside the host cells. We previously showed that apoptotic cell death of the marine macrophage-like cell line was induced by A. actinomycetemcomitans infection. During the course of this apoptosis, activation of several caspases was observed. In general medicine, the facts that severl important pathogenic bacteria can infect and multiple inside the host cells and cause the severe life-threaten infection has been reported. Intracellular invasion mechanisms of some pathogenic bacteria were analyzed in detail, and several caspases has been reported to activate during the course of invasion. We hypothesized that Legionella pneumophila, which causes legion dise … More ase, and periodontopathic bacteria, A.actinomycetemcomitans, might invade inside the host cells in similar manner, because both target macrophaees to invade and activate similar set of caspases in host cells. We first adapted the invasion assay designed for A. actinomycetemcomitans to that for L. pneumphila. Mouse macrophage cell line J744.1 and mouse monocyte cell line RAW264.7 are both showed to induce cell death by infection of these bacteria. However, the cell death cased by L. pneumophila was necrosis because the content of cell is filled with multipled bacterial cells just before cell explosion. The difference of the cell death caused by each bacterium might depended on the different signal pathway which are activated by infection even if the similar set of caspases was activated. The RAW264.7 cells which constitutively expressed anti-apopotic Bcl-2 or Bcl-x_L did not rescue cell death by the infection of A. actinomycetemcomitans. Considering all, the mechanisms of invasion and infection of A. actinomycetemcomitans is unique and we need further analysis of these mechanisms for preventing periodontal diseases. Less