SGK1 and the control of periodontal inflammation

摘要 宿主对口腔微生物群的炎性免疫应答受到多种促炎和炎症因子的严格调节。 抗炎机制。这两种活动的平衡确保了免疫稳态的状态 这对于防止微生物侵入和避免随后的附带组织损伤是至关重要的。 为了限制炎症的猛烈程度，存在许多既定的途径来抑制先天免疫系统。 反应我们最近的研究表明，血清和糖皮质激素诱导的 激酶1（SGK 1），一种与PI 3 K途径相关的丝氨酸/苏氨酸激酶，在抑制 E.人单核细胞中卷曲LPS介导的促炎细胞因子产生。这方面的初步数据 应用首次表明，SGK 1在人单核细胞中响应于 挑战多种口腔细菌。此外，使用牙龈卟啉单胞菌，一种成熟的口腔生物模型， 对于牙周组织中宿主-病原体相互作用的研究，我们发现SGK 1的抑制 增强促炎细胞因子（TNF、IL-12、IL-6、IL-1β、IL-8）的产生并降低IL-10水平， 通过使用Cre-loxP介导的SGK 1敲除小鼠也证实了该结果。此外，抗炎 我们的初步体内证据证实了SGK 1的作用，表明全身给予 SGK 1抑制剂，EMD 638683，增加中性粒细胞和巨噬细胞向牙龈组织的浸润， 加重口腔感染牙龈卟啉单胞菌小鼠牙槽骨吸收的严重程度。因此，我们有 确定了SGK 1作为炎症负调节剂新作用，并提出刺激这种作用， 宿主中的内源性抗炎途径将有助于限制或防止牙龈卟啉单胞菌诱导的组织炎症 杀伤性在本申请中待检验的具体假设是，在牙龈卟啉单胞菌的情况下， 激发后，SGK 1抑制促炎细胞因子的产生;下调募集 炎症细胞的牙周组织;并反过来防止牙槽骨流失，通过 炎症信号分子包括Nedd 4 -2、MKP-1和TAK 1的下游修饰， 最终聚集在NF-κB上。我们将以三个具体目标挑战这一假设： 将SGK 1表征为体外炎症反应的先天性免疫抑制剂;（ii）为了阐明 SGK 1通过其控制宿主炎症反应的信号传导机制;和（iii）建立体内 使用小鼠皮下腔和牙槽骨研究SGK 1在宿主炎症控制中的相关性 损失模型这些研究的成功完成将首次描述抗炎药的特征， SGK 1在宿主对牙龈卟啉单胞菌的炎症反应中的功能，并阐明新的抗炎 SGK 1-MKP 1模块介导的信号网络在炎症进展的控制中起重要作用。在 从长远来看，这项工作可以为开发针对SGK 1的新型抗炎药物铺平道路 或MKP-1不仅改善或预防牙龈卟啉单胞菌诱导的组织破坏， 紊乱这种方法与牙周病和慢性炎症都有相关性。 一般的条件。

Abstract Host inflammatory immune responses to oral microbiota are tightly regulated by multiple pro-inflammatory and anti-inflammatory mechanisms. The balance of there two activities ensures a state of immune homeostasis which is critical for protecting against microbial invasion and avoiding subsequent collateral tissue damages. To limit the ferocity of inflammation, a number of established pathways exist that dampen the innate immune response. Our recent publication has demonstrated a novel role for serum- and glucocorticoid- inducible kinase 1 (SGK1), a serine/threonine kinase associated with the PI3K pathway, in restraining the production of E. coil LPS-mediated pro-inflammatory cytokine production in human monocytes. Preliminary data for this application show for the first time that SGK1 is phospho-activated in human monocytes in response to challenge with multiple oral bacteria. In addition, using P. gingivalis, a well-established model oral organism for the investigation of host-pathogen interactions in the periodontium, we show that inhibition of SGK1 robustly enhances the production of pro-inflammatory cytokines (TNF, IL-12, IL-6, IL-1β, IL-8) and reduces IL-10 levels, a result also confirmed by using Cre-loxP-mediated SGK1 knockout mice. Moreover, the anti-inflammatory role for SGK1 was validated by our preliminary in vivo evidence showing that systemic administration of the SGK1 inhibitor, EMD638683, elevated infiltration of neutrophils and macrophages into the gingival tissues and aggravated the severity of alveolar bone resorption in mice orally infected with P. gingivalis. Thus, we have identified a novel role for SGK1 as a negative regulator of inflammation, and propose that stimulation of this endogenous anti-inflammatory pathway in the host will help limit or prevent P. gingivalis-induced tissue destruction. The specific hypothesis to be tested in this application is that in the context of P. gingivalis challenge, SGK1 constrains the production of pro-inflammatory cytokines; down-regulates recruitment of inflammatory cells to the periodontium; and in turn protects against alveolar bone loss through downstream modification of inflammatory signaling molecules including Nedd4-2, MKP-1, and TAK1, which ultimately converge on NF-κB. We will challenge this hypothesis with three specific Aims: (i) To characterize SGK1 as an innate immune suppressor of inflammatory responses in vitro; (ii) To elucidate the signaling mechanisms by which SGK1 controls host inflammatory responses; and (iii) To establish the in vivo relevance of SGK1 in the control of host inflammation using mouse subcutaneous chamber and alveolar bone loss models. Successful completion of these studies will characterize, for the first time, the anti-inflammatory function of SGK1 in host inflammatory responses to P. gingivalis, and elucidate the novel anti-inflammatory signaling network mediated by the SGK1-MKP1 module in the control of the inflammation progression. In the long term, this work could pave the way for the development of novel anti-inflammatory agents targeting SGK1 or MKP-1 to ameliorate or prevent not only P. gingivalis-induced tissue destruction, but other inflammatory disorders. Such an approach has relevance both for periodontal disease and for chronic inflammatory conditions in general.