AGING AND LEYDIG CELL FUNCTION

描述（由申请人提供）：褐挪威大鼠间质细胞产生睾酮的最大能力随着年龄的增长而显著下降。我们的主要目标是阐明分子机制。这一应用的一个中心假设是，间质细胞自身产生的活性氧（ROS）在间质细胞睾酮产生的与年龄相关的减少中起重要作用。提出了三个具体目标。第一个是确定是否通过将黄体生成素直接注射到老年大鼠的睾丸中，或将老年细胞包封并植入年轻大鼠体内，可以逆转与年龄相关的间质细胞睾酮分泌减少。这些研究将验证一种假设，即年老的间质细胞产生睾丸激素的能力下降可能是由于间质细胞外的因素造成的。在第二个特定目标中，我们将确定随着这些细胞老化而发生的间质细胞活性氧产生的增加是来自线粒体运输链，甾体生成的P450反应，还是两者兼而有之；以及间质细胞中活性氧的主要酶清除剂——SOD、谷胱甘肽过氧化物酶和过氧化氢酶的mRNA、蛋白质和/或活性水平是否存在与年龄相关的变化。第三个目的是研究在衰老过程中操纵活性氧负荷对间质细胞类固醇生成的影响，基于活性氧，无论是来自电子传递链，类固醇生成，还是两者兼有，在老化的间质细胞产生的睾丸激素减少中起重要作用的假设。我们将通过研究体内氧化应激负荷对间质细胞功能的影响来验证这一假设，包括：维生素E补充和剥夺的影响；年龄对间质细胞对其主要非酶抗氧化剂谷胱甘肽耗竭的急性反应的影响；以及热量限制的影响。总之，这些研究将为间质细胞如何应对在衰老过程中存在或增加的应激源提供新的见解，并将阐明在衰老过程中发生的间质细胞功能变化的潜在分子基础。

DESCRIPTION (provided by applicant): The maximal capacity of Brown Norway rat Leydig cells to produce testosterone decreases significantly with age. Our major objective is to elucidate the molecular mechanisms that are responsible. A central hypothesis of this application is that reactive oxygen species (ROS), produced by the Leydig cells themselves, play an important role in age-related reductions in Leydig cell testosterone production. Three specific aims are proposed. The first is to determine whether age-related reductions in Leydig cell testosterone production are reversed by administering LH directly to the testes of old rats, or by encapsulating old cells and implanting them into young rats. These studies will test the hypothesis that factors outside the Leydig cells might be responsible for the reduced ability of old Leydig cells to produce testosterone. In the second specific aim, we will determine whether the increases in Leydig cell reactive oxygen production that occur as these cells age are from the mitochondrial transport chain, the P450 reactions of steroidogenesis, or both; and whether there are age-related changes in mRNA, protein, and/or activity levels of the major enzymatic scavengers of reactive oxygen species in Leydig cells - SOD, glutathione peroxidase and catalase. The third aim is to examine the effects of manipulating reactive oxygen load on Leydig cell steroidogenesis during aging, based on the hypothesis that reactive oxygen, whether derived from the electron transport chain, steroidogenesis, or both, plays an important role in the reduced testosterone produced by aging Leydig cells. We will test this hypothesis by examining the consequences of manipulating oxidative stress load in vivo on Leydig cell function, including: the effects of vitamin E supplementation and deprivation; the effects of age on the acute response of Leydig cells to depletion of its major non-enzymatic antioxidant, glutathione; and the effects of caloric restriction. Together, these studies will provide new insights into how Leydig cells cope with stressors that are present or increase during aging, and will shed light on the underlying molecular basis for functional changes in Leydig cells that occur during aging.