Establishment of periodontitis treatment method by inhibition of RANK-Toll like receptor signal

MDP是负责肽聚糖免疫佐剂活性的最小基本结构单位，广泛分布于革兰氏阴性和阳性细菌的细胞壁中。研究表明，MDP对免疫活性细胞具有多种生物学效应。结果表明，亚甲基二磷酸果糖注射小鼠可引起内毒素超敏反应：肿瘤坏死因子-α的产生增加，攻击注射内毒素后可致致死性休克。我们还发现，MDP协同增强了内毒素诱导的人单核细胞中促炎细胞因子的产生。最近，有人提出核苷酸结合寡聚化结构域(NOD)2是Apaf1/NOD蛋白家族的成员，是MDP的胞内感受器。NOD2由一个N端的caspase招募结构域、一个位于中心的核苷酸结合域和C端的富含亮氨酸的重复序列组成，是一个信号转导接头。促炎细胞因子和内毒素可促进NOD2的表达。1α、25(OH)2D3、前列腺素E_2、内毒素和…在小鼠成骨细胞和造血细胞共培养中，更多的IL-1α刺激破骨细胞的形成。MDP单独作用不能诱导破骨细胞的形成，但能促进脂多糖、IL-1α或肿瘤坏死因子-α诱导的破骨细胞形成，但不能促进1α、25(OH)2D3或PGE_2诱导的破骨细胞形成。MDP不能促进RANKL或肿瘤坏死因子-α诱导的破骨细胞前体细胞的形成。亚甲基二磷酸对脂多糖或肿瘤坏死因子-α诱导的成骨细胞RANKL表达上调，但对1-α，25(OH)2D3无明显影响。成骨细胞在内毒素、IL-1α或肿瘤坏死因子-α刺激下表达NOD2mRNA，但不表达1-α、25(OH)2D3。TLR4和MYD88对成骨细胞NOD2mRNA表达的诱导依赖于TLR4和MYD88，而TLR4和MYD88对成骨细胞NOD2mRNA的诱导作用不明显。小干扰RNA耗尽细胞内NOD2可阻断MDP诱导的成骨细胞RANKL基因表达上调。脂多糖和RANKL可刺激破骨细胞存活，MDP不能增强这一作用。这些结果提示，亚甲基二磷酸通过RANKL的表达协同促进脂多糖、IL-1α和肿瘤坏死因子-α诱导的破骨细胞的形成，NOD2介导的信号参与了亚甲基二磷酸诱导的成骨细胞RANKL的表达。较少

MDP, the minimal essential structural unit responsible for the immunoadjuvant activity of peptidoglycans, is distributed ubiquitously in cell walls of both Gram-negative and-positive bacteria. MDP has been shown to exert diverse biological effects on immunocompetent cells. We have shown that injection of MDP into mice resulted in endotoxin hypersensitivity : enhanced production of TNF-α and lethal shock upon challenge injection of LPS. We also showed that MDP synergistically enhanced LPS-induced proinflammatory cytokine production in human monocytic cells. Recently, it was proposed that nucleotide-binding oligomerization domain (Nod) 2, a member of the Apaf1/Nod protein family, is an intracellular sensor of MDP. Nod2 consists of an N-terminal caspase-recruitment domain, a centrally located nucleotide-binding domain and C-terminal leucine-rich repeats, and acts as a signal-transducing adaptor. Nod2 expression is enhanced by proinflammatory cytokines and LPS. 1 α,25(OH)2D3, PGE2, LPS and … More IL-1 a stimulate osteoclast formation in mouse cocultures of osteoblasts and hemopoietic cells. MDP alone could not induce osteoclast formation in the coculture, but enhanced osteoclast formation induced by LPS, IL-1α or TNF-α but not 1 α,25(OH)2D3 or PGE2. MDP failed to enhance osteoclast formation from osteoclast progenitors induced by RANKL or TNF-α. MDP up-regulated RANKL expression in osteoblasts treated with LPS or TNF-α but not 1 α,25(OH)2D3. Osteoblasts expressed mRNA of Nod2 in response to LPS, IL-1α or TNF-α but not 1 α,25(OH)2D3. Induction of Nod2 mRNA expression by LPS but not by TNF-α in osteoblasts was dependent on TLR4 and MyD88. The depletion of intracellular Nod2 by small interfering RNA blocked MDP-induced up-regulation of RANKL mRNA in osteoblasts. LPS and RANKL stimulated the survival of osteoclasts, and this effect was not enhanced by MDP. These results suggest that MDP synergistically enhances osteoclast formation induced by LPS, IL-1α and TNF-a through RANKL expression in osteoblasts, and that Nod2-mediated signals are involved in the MDP-induced RANKL expression in osteoblasts. Less