Pereboeva Larisa, Hubbard Meredith, Goldman Frederick D, Westin Erik R
Department of Medicine, Division of Hematology Oncology, University of Alabama at Birmingham, Birmingham, Alabama, United States of America.
Department of Pediatrics, Division of Hematology Oncology, University of Alabama, Birmingham, Alabama, United States of America.
PLoS One. 2016 Feb 9;11(2):e0148793. doi: 10.1371/journal.pone.0148793. eCollection 2016.
Dyskeratosis Congenita (DC) is an inherited multisystem premature aging disorder with characteristic skin and mucosal findings as well as a predisposition to cancer and bone marrow failure. DC arises due to gene mutations associated with the telomerase complex or telomere maintenance, resulting in critically shortened telomeres. The pathogenesis of DC, as well as several congenital bone marrow failure (BMF) syndromes, converges on the DNA damage response (DDR) pathway and subsequent elevation of reactive oxygen species (ROS). Historically, DC patients have had poor outcomes following bone marrow transplantation (BMT), perhaps as a consequence of an underlying DNA hypersensitivity to cytotoxic agents. Previously, we demonstrated an activated DDR and increased ROS, augmented by chemotherapy and radiation, in somatic cells isolated from DC patients with a mutation in the RNA component of telomerase, TERC. The current study was undertaken to determine whether previous findings related to ROS and DDR in TERC patients' cells could be extended to other DC mutations. Of particular interest was whether an antioxidant approach could counter increased ROS and decrease DC pathologies. To test this, we examined lymphocytes from DC patients from different DC mutations (TERT, TINF2, and TERC) for the presence of an active DDR and increased ROS. All DC mutations led to increased steady-state p53 (2-fold to 10-fold) and ROS (1.5-fold to 2-fold). Upon exposure to ionizing radiation (XRT), DC cells increased in both DDR and ROS to a significant degree. Exposing DC cells to hydrogen peroxide also revealed that DC cells maintain a significant oxidant burden compared to controls (1.5-fold to 3-fold). DC cell culture supplemented with N-acetylcysteine, or alternatively grown in low oxygen, afforded significant proliferative benefits (proliferation: maximum 2-fold increase; NAC: 5-fold p53 decrease; low oxygen: maximum 3.5-fold p53 decrease). Together, our data supports a mechanism whereby telomerase deficiency and subsequent shortened telomeres initiate a DDR and create a pro-oxidant environment, especially in cells carrying the TINF2 mutations. Finally, the ameliorative effects of antioxidants in vitro suggest this could translate to therapeutic benefits in DC patients.
先天性角化不良（DC）是一种遗传性多系统早衰疾病，具有特征性的皮肤和黏膜表现，以及易患癌症和骨髓衰竭的倾向。DC是由于与端粒酶复合物或端粒维持相关的基因突变引起的，导致端粒严重缩短。DC以及几种先天性骨髓衰竭（BMF）综合征的发病机制都集中在DNA损伤反应（DDR）途径和随后活性氧（ROS）的升高上。从历史上看，DC患者在骨髓移植（BMT）后预后较差，这可能是由于对细胞毒性药物存在潜在的DNA超敏反应。此前，我们在从患有端粒酶RNA成分TERC突变的DC患者中分离出的体细胞中证明了DDR的激活和ROS的增加，化疗和放疗会使其增强。当前的研究旨在确定先前在TERC患者细胞中与ROS和DDR相关的发现是否可以扩展到其他DC突变。特别令人感兴趣的是抗氧化方法是否可以对抗ROS增加并减少DC病理。为了验证这一点，我们检查了来自不同DC突变（TERT、TINF2和TERC）的DC患者的淋巴细胞中是否存在活跃的DDR和增加的ROS。所有DC突变都导致稳态p53增加（2倍至10倍）和ROS增加（1.5倍至2倍）。暴露于电离辐射（XRT）后，DC细胞的DDR和ROS均显著增加。将DC细胞暴露于过氧化氢也表明，与对照组相比，DC细胞维持着显著的氧化应激负担（1.5倍至3倍）。用N-乙酰半胱氨酸补充DC细胞培养物，或者在低氧条件下培养，都能带来显著的增殖益处（增殖：最大增加2倍；NAC：p53降低5倍；低氧：p53最大降低3.5倍）。总之，我们的数据支持一种机制，即端粒酶缺乏和随后的端粒缩短会引发DDR并创造一个促氧化环境，尤其是在携带TINF2突变的细胞中。最后，抗氧化剂在体外的改善作用表明这可能转化为对DC患者的治疗益处。
