Effects of inflammaging on intestinal epithelial cells and aspirin chemoprevention.

项目摘要 先前的随机对照试验（RCT）表明，低剂量阿司匹林（LDA，81- 100 mg/天）可降低 结直肠癌（CRC）的风险。美国预防服务工作组（USPSTF）建议LDA 预防50-59岁成人的CRC。然而，最近一项针对19,114名老年人（65岁以上）的随机对照试验报告称， 在生命晚期开始LDA对CRC发病率没有益处，并且对死亡率有潜在的不利影响。因为 CRC的发病率随着年龄的增长而上升，了解衰老对CRC的关系和功能影响， LDA的化学预防作用是高度优先的。我们的工作模型是LDA对结肠的影响 由于年龄相关的肠干细胞（ISC）数量和功能的变化， 导致基础炎症反应加剧，也就是“发炎”。通常，CRC似乎主要是 由Lgr 5 + ISC中的致癌突变驱动，阿司匹林样NSAID似乎优先消除 癌前Lgr 5 + ISCs。然而，我们的初步数据表明，老年小鼠（20-22个月[月]）， 与年轻小鼠（2-3个月）相比，具有更少的再生性小肠Lgr 5 + ISCs，其也 在Apc肿瘤抑制模型中致瘤性较低。尽管如此，和人类一样， 发展更多的肿瘤，表明非Lgr 5+细胞也是肠癌的起源。 这些细胞对LDA不太敏感。LDA调节前列腺素（PG）水平，包括 前列腺素E2。我们还发现PGE 2通过其受体Ptger 4影响ISC的功能，这种信号传导可以驱动ISC 进入由Hippo/雅普信号传导介导的胎儿样状态（Hopx+）。因此，在炎症的情况下， 升高的PGE 2可能不可逆地损害结肠（cISC）池，导致结肠内的代偿功能。 选择促进肿瘤发生的cISC。通过我们的双盲、安慰剂对照RCT，我们证明了 PG张力的调节和PG合成的抑制是阿司匹林作用模式的中心。我们的中央 假设是衰老和年龄相关过程促进cISC池（Lgr 5 + cISC）的减少， 通常对阿司匹林化学预防敏感。我们建议在生命的早期开始LDA可以防止 这种年龄相关的、炎症相关的和/或PGE 2介导的对cISC池的损伤。相比之下， 随着年龄的增长，可能会出现一个“不归路点”，在这个点上，LDA的启动不再能防止年龄的增长- cISC池中的相关变化。在这项建议中，我们将扩大现有的随机对照试验，以研究 单细胞分辨率下结肠上皮、患者源性类器官和老年人尿PG的LDA。 我们将使用新的体内临床前模型来剖析炎症对PG信号传导和LDA在炎症中的作用。 cISC。然后，我们将研究这些途径对结肠肿瘤发病率和进展的因果关系。这些 研究可以为LDA在老年人中的差异效应的意外发现提供生物学解释， 这可能会影响临床指南或生物标志物的发展，以优化LDA的风险-效益概况。

PROJECT ABSTRACT Previous randomized controlled trials (RCT)s demonstrate that low-dose aspirin (LDA, 81-100mg/day) reduces the risk of colorectal cancer (CRC). The U.S. Preventive Services Task Force (USPSTF) recommends LDA to prevent CRC in adults aged 50-59. However, a recent RCT among 19,114 older (65+) individuals reported that initiating LDA late in life had no benefit on CRC incidence and was potentially detrimental for mortality. Because CRC incidence rises with age, understanding the relationship and functional impact of aging on the chemopreventive effects of LDA is a high priority. Our working model is that the effect of LDA on the colon differs in older individuals due to age-related changes in intestinal stem cell (ISC) number and function secondary to a process of higher basal inflammatory tone, a.k.a. “inflammaging”. Normally, CRC appears to be primarily driven by oncogenic mutations in Lgr5+ ISCs and aspirin-like NSAIDs appear to preferentially eliminate premalignant Lgr5+ ISCs. However, our preliminary data demonstrates that old mice (20-22 months [mos]), as compared to young mice (2-3 mos), have fewer, less regenerative small intestinal Lgr5+ ISCs, which are also less tumorigenic in an Apc tumor suppressor model. Nonetheless, like humans, aged mice spontaneously develop a greater number of tumors, indicating that non-Lgr5+ cells are also the origin of intestinal cancers in aged mice and that these cells are less sensitive to LDA. LDA modulates prostaglandin (PG) levels, including PGE2. We also find that PGE2 impacts ISC function through its receptor Ptger4 and this signaling can drive ISCs into a fetal-like state (Hopx+) that is mediated by Hippo/Yap signaling. Thus, in the setting of inflammaging, elevated PGE2 may irreversibly compromise the colon (cISC) pool leading to compensatory functions within select cISCs that promote tumorigenesis. Through our double-blind, placebo-controlled RCT, we demonstrated that modulation of PG tone and inhibition of PG synthesis is central to aspirin’s mode of action. Our central hypothesis is that aging and age-related processes promote a decrease in the cISC pool (Lgr5+ cISCs) that is normally sensitive to aspirin chemoprevention. We propose that initiation of LDA earlier in life protects against this age-related, inflammation-associated, and/or PGE2-mediated damage to the cISC pool. In contrast, with advancing age there may be a “point-of-no-return” in which initiation of LDA is no longer protective against age- related changes in the cISC pool. In this proposal, we will expand our existing RCT to examine the impact of LDA on colonic epithelium at single cell resolution, patient-derived organoids, and urinary PGs in older adults. We will use novel in vivo preclinical models to dissect the role of inflammaging on PG signaling and LDA on cISCs. We will then examine the causality of these pathways on colon tumor incidence and progression. These studies may offer a biological explanation for the unexpected finding of a differential effect of LDA in older adults, which may influence clinical guidelines or the development of biomarkers to optimize LDA’s risk-benefit profile.