The Role of MAPK-Activated Protein Kinase 2 in Periodontal Disease

描述(申请人提供)：大约50%的美国人，年龄在30岁及以上，患有牙周病。随着牙周病的发展，炎症最终会导致不可逆转的骨质和牙齿丢失。丝裂原活化蛋白激酶(MAPKs)在牙周病过程中调节固有的宿主炎症反应。丝裂原活化蛋白激酶活化蛋白激酶2(MK2)是p38MAPK下游靶点，在侵袭性牙周病动物模型中调节巨噬细胞的炎症反应。巨噬细胞和破骨细胞都来自单核细胞系，表达表面趋化因子受体，对从循环到周围感染部位的趋化作用至关重要。我们项目实验室以前的结果表明，一种侵袭性牙周病病原体伴生放线杆菌和伴生放线杆菌脂多糖(LPS)激活了MK2。在放线菌伴内毒素驱动的大鼠模型中，MK2正向调节炎症浸润和骨丢失。初步数据支持MK2作为CD11bhi表达细胞上CXCR4细胞表面表达的调节因子，提示在MK2抑制下，趋化因子受体表达的调节可能是减少巨噬细胞浸润的重要机制。MK2信号在病理性破骨细胞形成中起关键作用，与MK2+/+相比，MK2-/-CD11blo破骨细胞前体细胞(OCPs)中由内毒素诱导的破骨细胞形成减少。在体内，在小鼠颅骨模型中，MK2信号在伴放线放线菌诱导的骨丢失中也是至关重要的。这些数据支持我们的假设，即在宿主-病原体相互作用过程中，MK2信号是单核细胞趋化和随后分化为巨噬细胞和破骨细胞所必需的。为了解决这一假说，我们将使用骨髓移植来创建MK2嵌合动物，然后使用“气囊模型”来评估造血MK2信号在放线菌挑战下单核细胞趋化中的作用(目标#1)。在体外，我们将利用OCPs研究伴随放线菌诱导破骨细胞形成的MK2信号与破骨细胞生成的主要转录因子NFATc1有关的机制。小鼠颅骨丢失模型将被用来证实MK2对放线菌在体内驱动的破骨细胞形成至关重要(目标2)。这项拟议的研究将有助于阐明MK2信号对单核细胞迁移到局部牙周病感染部位以及进一步分化为巨噬细胞和破骨细胞的影响。

DESCRIPTION (provided by applicant): Approximately 50% of Americans, age 30 and over, have periodontal disease. As periodontal disease progresses, inflammation can ultimately lead to irreversible bone and tooth loss. Mitogen-activated protein kinases (MAPKs) modulate the innate host inflammatory response during periodontal disease. Mitogen- activated protein kinase-activated protein kinase 2 (MK2), a downstream target of p38 MAPK, regulates inflammation in macrophages in aggressive periodontal disease animal models. Both macrophages and osteoclasts are derived from a monocyte lineage that expresses surface chemokine receptors critical for chemotaxis from circulation to peripheral sites of infection. Previous results from our project laboratory show that A. actinomycetemcomitans, an aggressive periodontal disease pathogen, and A. actinomycetemcomitans lipopolysaccharide (LPS) activate MK2. In an A. actinomycetemcomitans LPS-driven rat model, MK2 positively regulates inflammatory infiltration and bone loss. Preliminary data support a role for MK2 as a regulator of CXCR4 cell surface expression on CD11bhi-expressing cells, suggesting modulation of chemokine receptor expression may be an important mechanism of decreasing macrophage infiltrates under MK2 inhibition. MK2 signaling is critical for pathologic osteoclastogenesis, as supported by a decrease in LPS-driven osteoclast formation in Mk2-/- CD11blo osteoclast progenitor cells (OCPs) compared to Mk2+/+ (WT). In vivo, MK2 signaling was also critical for A. actinomycetemcomitans-induced bone loss in a murine calvarial model. These data support our hypothesis that MK2 signaling is required for monocyte chemotaxis and subsequent differentiation into macrophages and osteoclasts during host-pathogen interactions. To address the hypothesis, we will use bone marrow transplant to create MK2 chimeric animals followed by an "air pouch model" to assess the role of hematopoietic MK2 signaling in monocyte chemotaxis under A. actinomycetemcomitans challenge (Aim #1). The mechanism of MK2 signaling in A. actinomycetemcomitans- induced osteoclastogenesis with regards to NFATc1, the master transcription factor of osteoclastogenesis, will be studied in vitro using OCPs. The murine calvarial bone loss model will be used to confirm that MK2 is critical for A. actinomycetemcomitans driven osteoclastogenesis in vivo (Aim #2). This proposed research will support delineation of the impact of MK2 signaling on monocyte migration to the site of local periodontal disease infection and further differentiation into macrophages and osteoclasts.