Innate Inflammation in Osteoarthritis

描述（由申请人提供）： 项目总结/摘要：骨关节炎（OA）与既往软骨生物力学损伤和衰老相关。然而，生物力学损伤和老化并不必然导致OA。这项提案将集中在软骨细胞为中心的先天性炎症机制在OA。我们已经表征了对软骨细胞炎症介导的多功能蛋白质转氨酶2（TG 2）释放的软骨促炎作用。TG 2在OA软骨细胞外基质中丰富，并且TG 2转酰胺催化活性在老化软骨中增加。我们观察到TG 2是OA严重程度的生物标志物，并且我们验证了整体TG 2敲除对小鼠中不稳定诱导的膝关节OA具有保护作用。为了查明生物力学损伤和应力诱导的软骨先天性炎症反应，提供了一个基础上，然后触发或加速骨关节炎，我们将检查TG 2释放和XBP 1（X-box结合蛋白1）激活软骨细胞先天性炎症，我们提出的一个中央开关机制OA的发展和进展的联系。XBP 1的激活是特异性的ER应激的激活，ER应激的成功解决促进细胞从损伤中恢复和存活。然而，XBP 1激活也在先天性炎症的多器官模型中发挥核心作用，包括通过Toll样受体激活。我们观察到，生物力学损伤诱导激活的ER应力在软骨细胞。此外，我们检测到人膝关节OA软骨细胞中活性XBP 1增加。我们还观察到培养的TG 2缺陷软骨细胞具有降低的XBP 1活化，但细胞外TG 2诱导XBP 1活化。此外，我们已经产生了软骨特异性XBP 1敲除小鼠，以探测软骨细胞中的XBP 1功能。在这里，我们将测试一个假设的模型，其中TG 2和XBP 1，通过转导和/或放大对生物力学损伤和氧化应激的反应，开启软骨细胞先天性炎症应激，以促进OA的发展和进展。我们的具体目标是：1.测试以下假设：TG 2增加由HIF-2 α激活和TG 2鸟嘌呤核苷酸结合介导的培养软骨细胞的生物力学损伤诱导的和氧化应激相关的分解代谢和凋亡反应。2.测试TG 2增加损伤和氧化应激诱导的由XBP 1活化和AMPK活性降低介导的培养软骨细胞的分解代谢和凋亡反应的假设。3.在小鼠的补充研究中，验证软骨特异性TG 2和XBP 1缺陷对OA的发展和进展具有保护作用的假设。这些研究的完成将为OA与生物力学损伤和衰老相关的发病机制提供新的线索，并确定潜在的新治疗靶点。

DESCRIPTION (provided by applicant): Project summary/abstract: Osteoarthritis (OA) is associated with past biomechanical injury to cartilage and with aging. However, biomechanical injury and aging do not inevitably lead to OA. This proposal will focus on chondrocyte-centered innate inflammatory mechanisms in OA. We have characterized cartilage catabolism- promoting effects on chondrocytes for inflammation-mediated release of the multifunctional protein transglutaminase 2 (TG2). TG2 is abundant in the OA cartilage extracellular matrix and TG2 transamidation catalytic activity increases in aging cartilage. We observed that TG2 is a biomarker of OA severity, and we validated that global TG2 knockout is protective for instability-induced knee OA in mice. To pinpoint biomechanical injury and stress induced cartilage innate inflammatory responses that provide a foundation upon which OA is then triggered or accelerated, we will examine the linkage of TG2 release and XBP1 (X-box binding protein 1) activation in chondrocyte innate inflammation, proposed by us as a central switching mechanism for OA development and progression. XBP1 activation is specific to activation of ER stress, and successful resolution of ER stress promotes cell recovery and survival from injury. However, XBP1 activation also plays a central role in multiple organ models of innate inflammation, including via Toll-like receptor activation. We observe that biomechanical injury induces activation of ER stress in chondrocytes. Moreover, we detect active XBP1 increased in human knee OA chondrocytes. We also observe that cultured TG2 deficient chondrocytes have decreased XBP1 activation, but that extracellular TG2 induces XBP1 activation. Furthermore, we have generated cartilage-specific XBP1 knockout mice to probe for XBP1 function in chondrocytes. Here, we will test a hypothetical model in which TG2 and XBP1, by transducing and/or amplifying responses to biomechanical injury and oxidative stress, switch on chondrocyte innate inflammatory stress to promote OA development and progression. We specifically aim to: 1. Test the hypothesis that TG2 increases biomechanical injury-induced and oxidative stress-related catabolic and apoptotic responses of cultured chondrocytes mediated by HIF-2alpha activation and TG2 guanine nucleotide binding. 2. Test the hypothesis that TG2 increases injury and oxidative stress-induced catabolic and apoptotic responses of cultured chondrocytes critically mediated by XBP1 activation and decreased AMPK activity. 3. Test the hypothesis, in complementary studies in mice, that both cartilage-specific TG2 and XBP1 deficiency are protective against development and progression of OA. Completion of these studies will shed new light on the pathogenesis of OA related to biomechanical injury and aging, and identify potential new therapeutic targets.