Mitonuclear signaling pathways in senescence-associated inflammation

项目摘要 细胞衰老是衰老过程的标志，并导致慢性疾病的脆弱性。 虽然衰老作为一种肿瘤抑制机制急性，慢性它也有助于 通过衰老相关分泌表型（SASP）的衰老组织炎症。因此， 体内衰老细胞的减少改善了健康和寿命，并挽救了与过多 表型和衰老的疾病。然而，药理学“衰老清除”方法往往具有毒性， 副作用，可能限制了senolytics作为促进健康衰老的工具的效用。作为概念验证， 另一种方法是，体内抑制SASP可减少慢性肝脏炎症并延迟 肝细胞癌 最近，我们发现SASP依赖于细胞质染色质片段（CCF）的排出， 细胞核进入衰老细胞的细胞质。衰老细胞中含有功能失调的线粒体， 反映为膜电位降低、ROS产生升高、线粒体吞噬周转降低，以及 改变中间代谢。我们最近发现衰老细胞中功能失调的线粒体与 CCF生产，因此SASP，通过逆行线粒体信号通路。该途径 涉及线粒体ROS介导的激酶JNK 1/2的活化，这是CCF形成所需的， 以及抑制CCF形成的DNA修复蛋白53 BP 1。然而，链接机制 JNK 1/2至53 BP 1未知。 扩展这些发现，在非脊椎动物生物体中的研究也表明， 逆行信号通路可以改变衰老和寿命，这表明识别和 靶向这些途径在治疗与年龄相关的疾病中具有治疗潜力。然而，在这方面， 这些途径在哺乳动物系统中知之甚少。 我假设衰老细胞中的线粒体信号调节衰老细胞表型， 衰老相关的人类疾病。在K99辅导阶段，本建议书有两个目标，即：1） 确定JNK 1/2调节53 BP 1诱导CCF形成的机制; 2）研究 JNK 1/2衰老细胞的53 BP 1非依赖性作用;以及独立R 00中的额外Aim 3）研究ATF 4的抑制作用以及ATF 4与ATF 4之间的串扰， 衰老细胞中的其他应激反应。阐明这些线粒体信号通路， 哺乳动物细胞对所有生物学家都具有广泛的普遍兴趣，但也可以确定治疗靶点， 降低SASP。这种方法可以发现衰老药物的替代品，用于治疗与年龄相关的 疾病，促进健康老龄化。

PROJECT SUMMARY Cellular senescence is a hallmark of the aging process and contributes to chronic disease vulnerability. Although senescence acts acutely as a tumor suppressor mechanism, chronically it also contributes to inflammation in aged tissue through the senescence-associated secretory phenotype (SASP). Hence, removal of senescent cells in vivo improves healthspan and lifespan, and rescues pathology associated with a plethora of phenotypes and diseases of aging. However, pharmacological “senolytic” approaches tend to have toxic side effects, likely limiting the utility of senolytics as tools to promote healthy aging. As proof-of-concept for an alternative approach, suppression of SASP in vivo reduces chronic liver inflammation and delays onset of hepatocellular carcinoma. Recently, we have shown that SASP is dependent on expulsion of cytosolic chromatin fragments (CCF) from the nucleus into the cytoplasm of senescent cells. Senescent cells harbor dysfunctional mitochondria, as reflected by decreased membrane potential, elevated ROS production, decreased mitophagic turnover, and altered intermediary metabolism. We have recently linked dysfunctional mitochondria in senescent cells to CCF production, and hence SASP, through a retrograde mitonuclear signaling pathway. This pathway involves mitochondrial ROS-mediated activation of the kinase JNK1/2, which is required for CCF formation, and the DNA repair protein 53BP1, which suppresses CCF formation. However, the mechanism linking JNK1/2 to 53BP1 is unknown. Extending these findings, studies in non-vertebrate organisms also suggest that mitochondria-nucleus retrograde signaling pathways can modify aging and longevity, altogether suggesting that identification and targeting of these pathways has therapeutic potential in the treatment of age-associated diseases. However, these pathways are poorly understood in mammalian systems. I hypothesize that mitonuclear signaling in senescent cells modulates the senescent cell phenotype and hence senescence-associated human disease. This proposal has two Aims in the mentored K99 phase, to: 1) Determine the mechanism by which JNK1/2 regulates 53BP1 to induce CCF formation; 2) Investigate the 53BP1-independent role of JNK1/2 senescent cells; and an additional Aim in the independent R00 phase, to 3) Investigate the role of mitochondria-mediated suppression of ATF4 and crosstalk between other stress responses in senescent cells. Elucidation of these mitonuclear signaling pathways in mammalian cells is of broad general interest to all biologists but can also identify therapeutic targets for reduction of SASP. This approach can uncover alternatives to senolytic drugs for treatment of age-associated disease and promote healthy aging.