Telomere Damage Responses and Immune Aging

描述(由申请人提供)：人类免疫系统的逐渐失效极大地阻碍了寿命和晚年生活质量的提高，人体免疫系统保护宿主免受感染和恶性肿瘤的侵袭。保护性免疫力的丧失与慢性阴燃炎症综合征的增加有关。衰老导致免疫恶化的分子机制还不够清楚。自身免疫综合征类风湿性关节炎(RA)患者的免疫老化过程加速了约25年，这些患者患上与年龄相关的疾病(如心血管疾病)的风险更高。类风湿性关节炎患者T细胞中的端粒因年龄而不适当地缩短；但更重要的是，一些染色体有端粒自由端，并经历了端粒融合。这种端粒损伤的表型与ATR-Chk1 DNA修复途径的无效有关。在RA T细胞和75岁以上的T细胞中，端粒携带的ATR负荷增加，但ATR不可或缺的激活剂TopBP1的结合减少。这一提议旨在从机制水平上了解端粒损伤引起的DNA损伤反应，它们如何促进免疫老化过程，以及端粒损伤如何使T细胞从保护性免疫偏向炎症。在具体目标1中，我们将定义年轻和老年T细胞中应激端粒DNA损伤反应的分子成分。我们将在特定的目标2中检查宿主的进展性年龄和炎症状态如何影响端粒损伤修复和由此产生的细胞反应。这些实验将建立在两个研究队列的基础上；由30-90岁的健康人组成的健康老龄化、生活方式和虚弱(一半)队列，以及斯坦福类风湿性关节炎(STAR)队列，这是类风湿性关节炎患者的预期队列。我们将量化端粒TopBP1-ATR模块与年龄增长和RA疾病负担的关系。具体目标3将揭示端粒损伤对T细胞命运、克隆性增殖和功能承诺的影响。通过设置故意的端粒损伤，我们将研究端粒依赖的损伤机制对T细胞凋亡和对Th1、Th2、Th17、Tfh和Treg谱系的影响。此外，我们还将探索端粒损伤是否与老年人接种流感疫苗的有效性有关。在具体目标4中，我们将探索端粒解帽在体内免疫衰老过程中的作用，并建立一个旨在减缓T细胞衰老的治疗干预的临床前测试平台。这些实验依赖于免疫缺陷小鼠与人类T细胞的重建，以测量它们的稳态扩张、它们的凋亡敏感性和它们的NA向记忆的转换。总体而言，这项提议有望提供对发生在老化端粒上的分子事件的新理解，并利用这些知识开发新的治疗策略来对抗免疫衰老。

DESCRIPTION (provided by applicant): Advancements in longevity and later-life quality are hampered greatly by the progressive failure of the human immune system which protects the host from infections and malignancies. Loss of protective immunity is associated with the gain of a chronic, smoldering inflammatory syndrome. Molecular mechanisms underlying aging-induced immune deterioration are insufficiently understood. The process of immune aging is accelerated in patients with the autoimmune syndrome rheumatoid arthritis (RA) by about 25 years and these patients are at higher risk for age-related morbidities, such as cardiovascular disease. Telomeres in T cells from RA patients are age-inappropriately shortened; but, more importantly, some chromosomes have telomere-free ends and undergo telomeric fusions. This phenotype of telomeric damage is related to ineffectiveness of the ATR-Chk1 DNA repair pathway. In RA T cells and in T cells from individuals >75 years, telomeres carry an increased load of ATR, yet binding of TopBP1, an indispensable activator of ATR, is diminished. This proposal is designed to understand on a mechanistic level the DNA damage responses emanating from damaged telomeres, how they contribute to the process of immune aging and how telomeric damage biases T cells away from protective immunity towards inflammation. In Specific Aim 1, we will define the molecular components of the DNA damage response at stressed telomeres in young and old T cells. We will proceed in Specific Aim 2 to examine how progressive age and the inflammatory status of the host affect telomeric damage repair and the resulting cellular response. These experiments will build on two study cohorts; the Healthy Aging, Lifestyle and Frailty (HALF) cohort composed of healthy individuals aged 30-90 years and the Stanford Rheumatoid Arthritis (STAR) cohort, a prospective cohort of patients with rheumatoid arthritis. We will quantify the telomeric TopBP1-ATR module in relation to advancing age and RA disease burden. Specific Aim 3 will reveal the consequences of telomeric damage on T cell fate, clonal expansion and functional commitment. By setting intentional telomere damage we will study the impact of the telomere- dependent damage machinery on T cell apoptosis and commitment to the Th1, Th2, Th17, Tfh and Treg lineage. Also, we will explore whether telomere damage correlates with effectiveness of an influenza vaccine in the elderly. In Specific Aim 4, we will explore the role of telomeric uncapping on the immune aging process in vivo and build a preclinical testing platform for therapeutic interventions aimed at slowing T cell aging. These experiments rely on the reconstitution of immunodeficient mice with human T cells to measure their homeostatic expansion, their apoptotic susceptibility and their na¿ve-to-memory conversion. Overall, this proposal promises to provide new understanding of the molecular events that occur at aging telomeres and to utilize that knowledge to develop novel therapeutic strategies to combat immune aging.