IGF-1, oxidative stress and telomere dynamics in cultured human somatic cells

描述(申请人提供)：这个项目的主要目标是研究胰岛素样生长因子1(IGF-1)影响人体体细胞氧化应激、端粒动力学和衰老的机制。胰岛素样生长因子-1(IGF-1)介导的细胞增殖刺激对机体组织的维持和修复至关重要。然而，这种效应通常与FOXO转录因子穿梭在细胞核外以及抗氧化酶下调有关。IGF-1还刺激一氧化氮合酶(NOS)，增加一氧化氮(NO)的产生，一氧化氮是一种抗氧化剂和抗增殖剂。因此，IGF-1的整体作用将取决于FOXO和NOS通路之间的平衡。这一建议的中心假设是，在大多数人类组织中，IGF-1介导的作用倾向于FOXO途径，即增殖和氧化应激增加。然而，在人血管内皮细胞中，IGF-1的作用向内皮型一氧化氮合酶(ENOS)倾斜。这样，IGF-1的综合作用将服务于胞体的维持和修复需要，同时减弱氧化应激对血管系统的影响。由于端粒缩短记录了氧化应激的增殖史和累积负担，IGF-1的不同作用在很大程度上表达在不同类型细胞的端粒动力学中。这一假说将通过两个目的得到验证：一是通过检测胰岛素样生长因子-1对皮肤成纤维细胞增殖/衰老、端粒磨损、FOXO转录因子、抗氧化能力、eNOS表达和一氧化氮产生的影响来评价胰岛素样生长因子-1影响皮肤成纤维细胞端粒动力学的机制；二是根据目标1评估胰岛素样生长因子-1对培养的人脐静脉内皮细胞的S效应。这些相互关联的机制可以解释关于IGF-1在低等生物(蠕虫、苍蝇)、短暂哺乳动物(老鼠)和人类的衰老和长寿中所起作用的经常相互矛盾的结论。这个项目将提供关于一个关键的生长因子如何作用于人类细胞的机械性见解，这对于理解它在人类衰老生物学和衰老相关疾病中的作用是必不可少的。这些信息将有助于设计预防和治疗方式，以对抗与衰老有关的疾病。

DESCRIPTION (provided by applicant): The primary objective of this project is to study mechanisms by which the insulin-like growth factor 1 (IGF-1) affects oxidative stress, telomere dynamics and senescence in human somatic cells. IGF-1 mediated stimulation of cell proliferation is crucial for maintenance and repair of somatic tissues. However, this effect is often associated with the shuttling of FOXO transcription factors out of the nucleus and the downregulation of antioxidative enzymes. IGF-1 also stimulates the nitric oxide synthase (NOS), increasing production of nitric oxide (NO), an antioxidant and antiproliferative agent. The overall effect of IGF-1 would thus depend on a balance between the FOXO and NOS pathways. The central hypothesis of this proposal is that in most human tissues the IGF-1 mediated effect is tilted towards the FOXO pathway, i.e., proliferation and increased oxidative stress. However, in the human vascular endothelium, the effect of IGF-1 is tilted towards endothelial NOS (eNOS). In this way, the integrative effect of IGF-1 would serve the maintenance and repair needs of the soma, while attenuating the effect of oxidative stress on the vasculature. As telomere shortening registers the proliferative history and accruing burden of oxidative stress, the diverse effects of IGF-1 would be largely expressed in telomere dynamics of different cell types. This hypothesis will be tested through two aims: one, to evaluate mechanisms by which IGF-1 influences telomere dynamics in cultured skin fibroblasts by examining the effects of IGF-1 on proliferation/senescence, telomeric attrition, FOXO transcription factors, antioxidative capacity, eNOS expression and NO production; and two, to evaluate IGF-1's effect in cultured human umbilical vein endothelial cells, as per aim 1. Findings will provide a comprehensive account of the mechanisms by which IGF-1 impacts proliferation, oxidative stress, telomere dynamics and senescence in human somatic cells. These interrelated mechanisms could account for the often conflicting conclusions about the role of IGF-1 in aging and longevity of lower organisms (the worm, fly), short-lived mammals (mouse) and humans. This project will provide mechanistic insight as to how a key growth factor acts on human cells, which is essential for understanding its role in the biology of human aging and in aging related disorders. Such information will be instrumental in designing preventive and therapeutic modalities to fight aging related diseases.