A novel role for oxidized lipid mediators as effectors of muscle atrophy and weakness in aging

抽象的。骨质疏松症是指随着年龄的增长，肌肉质量和功能的丧失，是一个普遍存在的问题。 老年人口。要设计有效的干预措施，需要更好地理解(S)负责的机制 用于肌肉衰老过程中肌肉萎缩和虚弱的启动和进展。我们实验室和其他实验室的研究已经 研究表明，随着年龄的增长，失去神经是肌肉萎缩的关键驱动因素。这项提案的目标是测试 一种新的假设，即生物活性脂质介体(氧化脂和氧化磷脂(OxPL)) 肌肉萎缩和虚弱的主要效应者。我们的假设得到了我们的数据的有力支持 表明去神经支配可诱导磷脂酶A2(CPLA2)激活，从而释放花生四烯酸(AA)。 非酶或通过12/15促进氧化脂质生成的肌膜 脂氧合酶(ALOX15)依赖的生成。我们还表明，失神经导致的肌肉损失是 当AA释放和氧化脂质通过抑制cPLA2或Alox15或通过清除而被阻止时，减少 使用Liproxstatin-1或Gpx4Tg小鼠的LOOH，从而支持oxPL/oxlipins作为关键的机械环节 在失去神经和肌肉萎缩之间。然而，oxPL/oxlipins导致肌肉的机制 萎缩还没有定义。根据先前确定的这些脂质介体的靶点，我们特地 验证去神经诱导的oxPL/oxlipins会对膜造成损害的假设， 促进线粒体改变，激活蛋白降解和细胞死亡途径，诱导年龄相关 肌肉萎缩。在目标1中，我们将通过抑制氧化脂质对萎缩相关靶点的影响来确定其作用。 用cPLA2KO和ALOX15KO小鼠产生oxPL/oxlipins并改变其降脂作用 过氧化氢(使用Gpx4/Tg和肌肉特异性Gpx4KO小鼠和Liproxstatin-1治疗) 膜氧化损伤、线粒体功能、肌肉降解和细胞死亡途径与肌肉 失神经后肿块。这些实验将确定失神经肌肉中产生的初级氧脂。 并确定导致肌肉萎缩和虚弱的氧化脂的关键靶点。在目标2中，我们将测量 体外培养的C2C12肌细胞AIM 1关键氧脂对线粒体氧化损伤的影响 功能、蛋白质降解途径和肌纤维直径。这些实验将提供新的 关于特定氧脂对肌肉新陈代谢和线粒体功能影响的信息。最后，在AIM中 3，我们将测试是否抑制肌肉特异性ALOX15KO小鼠体内氧脂的生成或降低水平 在Gpx4表达水平升高的小鼠中应用过氧化脂质(LOOH)可以保护小鼠免受年龄相关的伤害 衰老小鼠体内肌肉萎缩。我们预测，oxPL/oxlipins的生成减少和增强 脂质过氧化氢(LOOH)的解毒作用将改变目标1中概述的萎缩目标，减少肌肉 衰老小鼠的萎缩和虚弱。总体而言，这些实验将是第一次研究氧化脂质的作用 肌萎缩症及其作为干预肌肉丧失和虚弱的目标的潜力。

Abstract. Sarcopenia, the loss of muscle mass and function with age, is a universal problem in the growing elderly population. To design effective interventions we need to better understand the mechanism(s) responsible for initiation and progression of muscle atrophy and weakness in aging. Studies from our lab and others have shown that loss of innervation is a key driver of muscle atrophy with age. The goal of this proposal is to test a novel hypothesis that bioactive lipid mediators (oxylipins and oxidized phospholipids (oxPL)), are primary effectors for muscle atrophy and weakness. Our hypothesis is strongly supported by our data showing that denervation induces activation of phospholipase A2 (cPLA2), releasing arachidonic acid (AA) from muscle membranes that can promote generation of oxidized lipids, either non-enzymatically or via 12/15 lipoxygenase (Alox15) dependent generation. We have also shown that denervation-induced muscle loss is decreased when AA release and oxidized lipids are blocked by inhibition of cPLA2 or Alox15, or by scavenging of LOOH using liproxstatin-1 or Gpx4Tg mice, thus supporting oxPL/oxylipins as a critical mechanistic link between denervation and muscle wasting. However, the mechanisms by which oxPL/oxylipins cause muscle atrophy have not been defined. Based on previously identified targets of these lipid mediators, we are specifically testing the hypothesis that oxPL/oxylipins induced by denervation cause damage to membranes, promote mitochondrial changes and activate proteolytic and cell death pathways to induce age-related muscle atrophy. In Aim 1, we will define the effect of modulating oxylipins on atrophy related targets by inhibiting generation of oxPL/oxylipins (using cPLA2KO and Alox15KO mice) and by altering reduction of lipid hydroperoxides (using Gpx4/Tg and muscle specific Gpx4KO mice and treatment with liproxstatin-1) on membrane oxidative damage, mitochondrial function, muscle degradative and cell death pathways and muscle mass after denervation. These experiments will identify the primary oxylipins produced in denervated muscle and identify the critical targets of oxylipins that lead to muscle atrophy and weakness. In Aim 2, we will measure the effect of key oxylipins identified in Aim 1 in vitro in C2C12 muscle cells on oxidative damage, mitochondrial function, protein degradation pathways and muscle fiber diameter. These experiments will provide new information on the effect of specific oxylipins on muscle metabolism and mitochondrial function. Finally, in Aim 3, we will test whether inhibiting oxylipin generation in vivo in muscle specific Alox15KO mice or reducing levels of lipid hydroperoxides (LOOH) in mice with elevated levels of Gpx4 expression can protect against age-related muscle atrophy in vivo in aging mice. We predict that reduced generation of oxPL/oxylipins and enhanced detoxification of lipid hydroperoxides (LOOH) will modify the atrophy targets outlined in Aim 1, reducing muscle atrophy and weakness in aging mice. Overall, these experiments will be the first to investigate the role of oxylipins in sarcopenia and their potential as a target for intervention in muscle loss and weakness.