ERK Signaling in Inflammatory Bone Loss

描述（由申请人提供）：我们的长期目标是开发炎症性骨质流失的预防性治疗方法，如假体松动（感染性或无菌性）和牙周感染。M-SCF和RANKL是刺激巨噬细胞形成破骨细胞的两种必需的促破骨细胞因子和促炎细胞因子。我们的初步数据表明MAP激酶/ ERK1/2是RANKL和MCSF基因表达的重要信号换能器。本A1提案的目的是通过体内和体外机制实验来确定ERK信号在成骨细胞介导的生物材料应答的先天免疫中的作用。我们的中心假设是，ERK信号通过调节促破骨细胞因子表达和炎症性骨溶解，介导骨先天免疫对生物材料的反应。我们将使用临床相关的啮齿动物股骨植入物模型和成骨细胞特异性ERK1/2功能障碍（“ERKdef小鼠”）进行机制研究。使用ERK通路抑制剂在临床上是可行的，因为这些抑制剂目前正在临床试验中用于治疗ERK激活水平升高的癌症。ERK靶向的优势在于ERK是上下游炎症信号交叉的中心信号站。具体目标如下：具体目标确定ERK是否通过调节成骨细胞M-CSF和RANKL基因表达介导炎症性骨丢失。我们将在体外和体内使用成骨特异性ERKdef小鼠，对LPS和UHMWPE刺激后M-CSF和RANKL表达的机制细胞信号通路进行实验。具体目标2。目的探讨阻断ERK信号对临床相关股骨溶骨模型的治疗效果。我们将通过定量显微ct和生物力学拉拔试验来研究ERK信号的药理抑制对UHMWPE或lps诱导的大鼠股骨骨溶解的影响。具体目标3。研究erk1 /2信号阻断如何影响生物材料和植入物污染物（如细菌毒素）下成骨细胞和破骨细胞之间的相互作用。我们将通过ERKdef小鼠细胞和巨噬细胞共培养来检测破骨细胞的发生。我们将测量破骨细胞发生、细胞因子表达和骨吸收在存在和不存在ERK信号阻断的情况下。具体目标确定ERK和NF:B P50共同调控成骨细胞对颗粒生物材料和LPS的M-CSF基因诱导的具体机制。虽然ERK/ATF4/RANKL通路已经建立，但在M-CSF的转录调控方面存在知识空白。我们将研究ERK和NFkb对MCSF基因诱导的协同调控。我们希望验证一种新的成骨细胞先天免疫的概念，并确定ERK信号在生物材料和相关毒素引起的炎症性骨质流失中的作用。公共卫生相关性：本研究的临床基础是，我们可以通过使用特定的局部或全身抑制剂靶向erk介导的炎症途径来预防或治疗临床重要的炎症性骨质流失。

DESCRIPTION (provided by applicant): Our long-term goal is to develop preventative treatments for inflammatory bone loss as manifested in pathologies such as prosthetic loosening (septic or aseptic) and periodontal infection. M-SCF and RANKL are two essential pro-osteoclastogenic and pro-inflammatory cytokines that stimulate macrophages to form osteoclasts. Our preliminary data showed that MAP Kinase/ ERK1/2 is an important signal transducer responsible for RANKL and MCSF gene expression. The objective of this A1 proposal is to define the role of ERK signaling in osteoblast-mediated innate immunity in response to biomaterials by conducting in vivo and in vitro mechanistic experiments. Our central hypothesis that ERK signaling mediates bone innate immunity in response to biomaterials by regulating pro-osteoclastogenic cytokine expression and inflammatory osteolysis. We will conduct mechanistic studies using a clinically relevant rodent femoral implant model and osteoblast-specific ERK1/2 dysfunction ("ERKdef mice"). The use of ERK pathway inhibitors is clinically feasible in that such inhibitors are currently being used in clinical trials for treatment of cancers with heightened levels of ERK activation. The advantage of ERK targeting lies in the fact that ERK is a central signaling station where upstream and downstream inflammatory signals cross. Specific Aims are as follows; Specific Aim 1. To determine whether ERK mediates inflammatory bone loss by regulating M-CSF and RANKL gene expression in osteoblasts. We will conduct experiments on mechanistic cellular signaling pathways responsible for M-CSF and RANKL expression after stimulation with LPS and UHMWPE in vitro and in vivo using osteoblast specific ERKdef mice. Specific Aim 2. To determine the therapeutic effect of ERK signal blockage in a clinically relevant femoral osteolysis model. We will examine the effect of pharmacologic inhibition of ERK signaling on UHMWPE or LPS-induced osteolysis in rat femora by quantitative microCT and biomechanical pullout testing. Specific Aim 3. To examine how ERK 1/2 signaling blockage affects interactions between osteoblasts and osteoclasts in the context of biomaterials and implant contaminants such as bacterial toxin. We will examine osteoclastogenesis by co-culturing ERKdef mice cells and macrophages. We will measure osteoclastogenesis, cytokine expression and bone resorption in the presence and absence of ERK signaling blockage. Specific Aim 4. To determine the specific mechanism by which ERK and NF:B P50 co-regulate M-CSF gene induction in osteoblasts in response to particulate biomaterials and LPS. While the ERK/ATF4/RANKL pathway is well established, there is a knowledge gap in the transcriptional regulation of M-CSF. We will examine the cooperative regulation of MCSF gene induction by ERK and NFkb We expect to verify a novel concept of competent osteoblastic innate immunity and define the role of ERK signaling in inflammatory bone loss in response to biomaterials and related toxins. PUBLIC HEALTH RELEVANCE: The clinical rationale underlying this study is that we can prevent or treat clinically important inflammatory bone loss by targeting an ERK-mediated inflammatory pathway with the use of specific topical or systemic inhibitors.