Antioxidant Defense System and Leydig Cell Aging

描述(由申请人提供)：随着人类和啮齿动物年龄的增长，血清中的睾酮水平会降低。以前对大鼠的研究已经提供了相关的证据，表明与年龄相关的氧化应激增加和/或抗氧化防御系统的缺陷可能与衰老的间质细胞产生睾酮的能力降低有关。转基因和基因敲除动物是将候选基因及其蛋白质产物与生理结果联系起来，从而检验因果关系的强大工具。本文提出的研究的主要目的是利用这一方法获得所需的信息，以开始测试自由基产生与衰老Leydig细胞的类固醇生成功能之间的因果关系。该方案的第一个目的是通过检验以下假设来描述小鼠睾丸间质细胞衰老的参数：随着年龄的增长，C57BL/6小鼠睾丸间质细胞产生的睾酮减少，线粒体超氧化物歧化产物增加，衰老细胞的ROS清除系统(超氧化物歧化酶、谷胱甘肽过氧化物酶、过氧化氢酶)存在缺陷。第二个目标将集中在过表达Gpx4的转基因小鼠和Gpx4基因敲除/敲除小鼠上，以检验这样的假设：保护性蛋白的过度表达导致抑制或延缓与年龄相关的类固醇合成下降，这是衰老的Leydig细胞的特征，以及抗氧化防御系统的缺陷会导致这种下降的加速或加剧。这项研究的成功完成将使衰老的自由基理论开始在老化的间质细胞中进行测试，这是一个非常明确的系统。如果成功，结果将开始推动对“衰老的自由基理论”的分析，从令人信服的相关分析转向归因于因果关系。男性与年龄相关的睾酮水平下降与重要的生活质量问题有关，如老年男性人口中骨质疏松增加、认知能力下降和性欲下降。研究睾酮是如何减少的，以及可以采取什么措施来防止这种情况的发生，将为间质细胞如何应对随着年龄增长而存在(或增加)的应激源提供新的见解，揭示间质细胞与年龄相关的功能变化的潜在分子基础，并为如何预防或逆转这些变化提供线索。

DESCRIPTION (provided by applicant): Serum levels of testosterone are reduced as humans and rodents age. Previous studies of the rat have provided correlative evidence suggesting that age-related increases in oxidative stress and/or deficiencies in the antioxidant defense system may be involved in the reduced ability of aged Leydig cells to produce testosterone. Transgenic and knockout animals represent powerful tools by which to relate candidate genes and their protein products to physiologic outcomes, and thus to examine cause-effect relationships. The major goal of the studies that are proposed herein is to utilize this approach to gain the information needed to begin to test cause-effect relationships between free radical production and the steroidogenic function of aging Leydig cells. The first aim of the proposal is to describe parameters of Leydig cell aging in the mouse by testing the hypotheses that, with aging, testosterone production by Leydig cells of C57BL/6 mice is reduced, mitochondrial superoxide production increases, and there are deficits in the ROS scavenging system (SOD, glutathione peroxidase, catalase) of aged cells. The second aim will focus on transgenic mice that overexpress Gpx4 and on Gpx4 knockdown/knockout mice to test the hypothesis that the overexpression of protective proteins results in suppression or delay in age-related steroidogenic decline that is characteristic of aging Leydig cells, and that deficiencies in the antioxidant defense system result in acceleration or exacerbation of the decline. The successful completion of this research will allow the free radical theory of aging to begin to be tested in aging Leydig cells, an exceptionally well defined system. If successful, the results will begin to move analyses of the "free radical theory of aging" from compelling, though correlative, analyses to ascribing cause and effect. Age-related decline in testosterone in men has relevance to important quality of life issues such as increased osteoporosis, reduced cognition and reduced libido in the aging male population. Studying how testosterone decreases, and what might be done to prevent this from occurring, will provide new insights into how Leydig cells cope with stressors that are present (or increase) with aging, shed light on the underlying molecular basis for age-related functional changes in the Leydig cells, and provide clues as to how to prevent or reverse these changes.