Oxidative Stress and the Development of Osteoarthritis

描述(申请人提供)：该项目的长期目标是通过重点研究活性氧(ROS)改变关节软骨和半月板细胞信号的机制，确定氧化应激在骨关节炎(OA)发病机制中的作用。当ROS水平超过细胞的抗氧化能力时，就会产生氧化应激。到目前为止的研究表明，氧化应激可以促进骨关节炎的基本过程，包括相对于合成代谢活动的过度分解代谢和细胞死亡，但相关机制尚未确定。线粒体是细胞内ROS的重要来源，我们的初步研究表明，在转基因小鼠中，针对线粒体的抗氧化酶过氧化氢酶的过度表达可以减轻年龄相关性骨性关节炎的严重程度。我们认为，在骨性关节炎中，病理水平的ROS是由线粒体产生的，当线粒体与缺乏抗氧化能力结合时，导致蛋白质过度氧化，从而使细胞信号转变为有利于分解代谢。 合成代谢信号和促进细胞死亡。我们的研究将集中在过高的ROS水平扰乱IRS-1-PI-3激酶-Akt信号通路的机制。AKT在整合合成代谢和分解代谢信号以及促进细胞存活方面发挥着核心作用。我们发现，在骨关节炎软骨细胞和被诱导呈现氧化应激的正常细胞中，Akt的激活被抑制，这与基质合成减少和细胞死亡易感性增加有关。我们将追求以下具体目标：1)确定氧化应激过程中软骨细胞中IRS-1-PI-3激酶-Akt信号的抑制机制，并验证过高水平的ROS氧化激活MAP激酶途径的特定蛋白的假说，该通路通过抑制IRS-1-PI-3激酶信号而抑制Akt1的激活；2)确定针对线粒体的过氧化氢酶过表达在小鼠骨关节炎发生发展中的作用，并检验过表达过氧化氢酶将减轻骨关节炎严重程度的假说。对被发现对抑制Akt具有重要作用的信号蛋白的影响将被研究。这项工作的发现将被用来开发新的治疗方法，用更有针对性的方法来取代无靶向的一般抗氧化剂方法，以针对受氧化应激影响并导致骨性关节炎的特定途径。 公共卫生相关性：骨关节炎是老年人慢性残疾的最常见原因，但缺乏减缓疾病进展的治疗。该项目的结果将提供有关骨关节炎关节组织破坏的基本机制的新信息。为了发现减缓或阻止疾病发展的新靶点，需要这些信息。

DESCRIPTION (provided by applicant): The long-term objective of this project is to determine the mechanisms by which oxidative stress contributes to the pathogenesis of osteoarthritis (OA) by focusing on mechanisms by which reactive oxygen species (ROS) alter cell signaling in the articular cartilage and meniscus. Oxidative stress results when levels of ROS exceed the anti-oxidant capacity of cells. Studies to date suggest that oxidative stress can contribute to fundamental processes found in OA, including excessive catabolic relative to anabolic activity and cell death, but the mechanisms responsible have not been defined. Mitochondria are an important source of intracellular ROS and our preliminary studies demonstrate that overexpression of the anti-oxidant enzyme catalase, targeted to the mitochondria in transgenic mice, reduces the severity of age-associated OA. We propose that in OA, pathological levels of ROS are generated by the mitochondria which, when combined with a deficient anti-oxidant capacity, results in excessive protein oxidation that shifts cell signaling to favor catabolic over anabolic signaling and to promote cell death. Our studies will focus on mechanisms by which excessive levels of ROS disrupt the IRS-1-PI-3 kinase-Akt signaling pathway. Akt plays a central role in integrating anabolic and catabolic signaling as well as in promoting cell survival. We have found that in OA chondrocytes and in normal cells induced to exhibit oxidative stress, Akt activation is inhibited and this is associated with reduced matrix synthesis and increased susceptibility to cell death. We will pursue the following specific aims: 1) Determine the mechanism for inhibition of IRS-1-PI-3kinase-Akt signaling in chondrocytes during oxidative stress and test the hypothesis that excessive levels of ROS oxidize specific proteins that activate the MAP kinase pathway which inhibits Akt1 activation through inhibition of IRS-1-PI-3 kinase signaling and 2) Determine the effects of overexpression of catalase targeted to the mitochondria on the development of osteoarthritis in mice and test the hypothesis that overexpression of catalase will reduce OA severity. Effects on the signaling proteins discovered to be important in inhibiting Akt will be studied. The discoveries made by this work will be used to develop new therapies that would replace the untargeted general anti-oxidant approach with more a more targeted approach aimed at the specific pathways affected by oxidative stress and contributing to OA. PUBLIC HEALTH RELEVANCE: Osteoarthritis is the most common cause of chronic disability in older adults but treatments to slow the progression of the disease are lacking. The results from this project will provide new information about basic mechanisms relevant to joint tissue breakdown in osteoarthritis. This information is needed in order to discover new targets for slowing or stopping the progression of the disease.