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

摘要 迫切需要新的策略来预防和/或治疗老龄化社会中的牙周骨丢失， 然而，年龄依赖性发病率和致病性升高的潜在机制 牙周炎，特别是骨吸收的表现仍然难以捉摸。本研究将探讨 新的宿主-细菌相互作用，其发病机制仅随着牙周炎的老化而出现。我们 早期的研究表明，一种新的有毒脂质，磷酸甘油二氢神经酰胺（PGDHC）， 由关键病原体牙龈卟啉单胞菌产生上调RANKL诱导的破骨细胞生成 以及炎症骨中局部产生巨噬细胞移动抑制因子（MIF 骨吸收损伤诱导血循环破骨细胞前体通过结合向骨吸收部位趋化 与其同源受体CXCR 4结合。我们的初步体外实验结果表明，PGDHC诱导的MIF产生 成纤维细胞是牙周病变中MIF的主要细胞来源， 与年轻小鼠相比，从老年小鼠分离的细菌LPS没有显示出任何年龄依赖性变化 从成纤维细胞产生MIF。其他初步结果表明，宿主酸性神经酰胺酶（aCD酶） 下调PGDHC诱导的破骨细胞生成，aCD酶表达显著减少， 健康牙龈组织中的比例。根据这些结果，我们最近 出版物报道牙龈卟啉单胞菌下调宿主上皮细胞的aCD酶表达 体外总的来说，宿主来源的aCD酶对有毒脂质具有保护作用是非常合理的。 PGDHC和年龄依赖性降低的aCD酶活性可能导致活性PGDHC破坏到牙周 组织.因此，我们假设牙周损伤中aCD酶活性的年龄依赖性改变可能是 负责保护宿主免受牙龈卟啉单胞菌产生的PGDHC脂质的侵害。Aim 1旨在测试 保护年龄依赖性改变的aCD酶活性对PGDHC介导的发病机制的作用， 特别是当地生产的MIF。在目标2中，年龄依赖性地增加活性药物的组织渗透的作用。 PGDHC对血液循环破骨细胞前体向骨吸收部位的趋化性将在体外进行检查 以及在青年和老年小鼠中诱导的牙周炎中。预计这些研究的完成将导致 年龄相关性牙周炎中宿主-口腔细菌相互作用的研究范式 开发新的诊断工具和年龄相关性牙周炎的治疗方案。

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.