Impact of acid ceramidase activity on MIF-mediated migration of circulating osteoclast precursors to periodontal bone lesions in relation to aging

摘要 在老龄化社会中，迫切需要新的策略来预防和/或治疗牙周骨丢失 然而，美国与年龄相关的发病率升高和致病的潜在机制 牙周炎的表现，特别是骨吸收，仍然难以捉摸。这项研究将调查 新的宿主-细菌相互作用，其发病机制只出现在牙周炎的年龄。我们的 早期的研究表明，一种新的毒性脂质，磷酸甘油二氢神经酰胺(PGDHC)， 牙龈卟啉单胞菌可上调RANKL诱导的破骨细胞生成 以及炎症骨局部产生巨噬细胞移动抑制因子(MIF) 骨吸收损伤通过结合诱导血液循环中的破骨细胞前体向骨吸收部位趋化 与其同源受体CXCR4结合。我们的初步体外实验结果表明，PGDHC诱导的MIF- 在牙周病变中，成纤维细胞是MIF的主要细胞来源，其表达显著上调 与年轻小鼠相比，从老年小鼠分离出的细菌内毒素没有表现出任何年龄依赖性的变化 从成纤维细胞中产生MIF。其他初步结果表明，宿主酸性神经酰胺酶(ACDase) 下调PGDHC诱导的破骨细胞生成，并显著降低aCDase的表达 在老年小鼠与年轻小鼠的健康牙龈组织中进行比较。关于这些结果，我们最近 文献报道牙龈假单胞菌下调宿主上皮细胞aCDase的表达 在试管中。总的来说，宿主衍生的CDase对有毒的脂质具有保护作用是非常可信的。 PGDHC和aCDase活性随年龄增长而降低可能导致活性pGDHC向牙周组织破坏 组织。因此，我们假设牙周病变中随年龄变化的aCDase活性可能是 负责保护宿主免受牙龈假单胞菌产生的PGDHC类脂的影响。目标1的设计目的是测试 年龄依赖性改变的aCDase活性对PGDHC介导的致病作用的保护作用 特别是MIF的本地化生产。在目标2中，随着年龄的增加，活性物质的组织渗透率增加 体外研究PGDHC对血液循环中破骨细胞前体向骨吸收部位的趋化作用 以及在年轻和老年小鼠诱导的牙周炎中也是如此。这些研究的完成预计会导致 年龄相关性牙周炎宿主-口腔细菌相互作用研究中的范例-狗屎和帮助 年龄相关性牙周炎的新诊断工具和治疗方案的开发。

ABSTRACT There is a critical need for new strategies to prevent and/or treat periodontal bone loss in the aging society of the U.S. However, the underlying mechanisms for age-dependently elevated incidence and pathogenic manifestations of periodontitis, especially bone resorption, remain elusive. This study will investigate the novel host-bacterial interaction of which pathogenesis only emerges with aging in periodontitis. Our earlier studies demonstrated that that a novel virulent lipid, phosphoglycerol dihydroceramide (PGDHC), produced by the keystone pathogen Porphyromonas gingivalis upregulates RANKL-induced osteoclastogenesis in vitro and in vivo, and that locally produced macrophage migration inhibitory factor (MIF) in inflammatory bone resorption lesion induces chemotaxis of blood circulating osteoclast precursors to bone resorption site via binding to its cognate receptor CXCR4. Our preliminary in vitro results showed that, PGDHC-induced MIF-production from fibroblasts, a primary cellular source of MIF in periodontal lesions, is significantly upregulated by those isolated from old mice, compared to young mice, while bacterial LPS did not show any age-dependent change in production of MIF from fibroblasts. Other preliminary results demonstrated that host acid ceramidase (aCDase) downregulates PGDHC-elicited osteoclastogenesis and that aCDase expression is significantly diminished in healthy gingival tissue of aged mice compared to young mice. In relation to those results, our recent publication reported that P. gingivalis downregulates expression of aCDase expression from host epithelial cells in vitro. Collectively, it is highly plausible that host derived aCDase has a protective role against the virulent lipid PGDHC, and age-dependently diminished aCDase activity may leads to breach of active PGDHC to periodontal tissue. Thus, we hypothesized that age-dependently altered aCDase activity in periodontal lesions may be responsible for protecting host from PGDHC lipid produced by P. gingivalis. The Aim 1 is designed to test protective the role of age-dependently altered aCDase activity against PGDHC-mediated pathogenesis, especially the local production of MIF. In Aim 2, effects of age-dependently increased tissue penetration of active PGDHC on chemotaxis of blood circulating osteoclast precursors to bone resorption site will be examined in vitro as well as in periodontatis induced in young and aged mice. Completion of these studies is anticipated to cause the paradigm-shit in the study of host-oral bacterial interaction in age-associated periodontitis and help development of novel diagnostic tools and therapeutic regimes for age-associated periodontitis.