Ramanathan Gajalakshmi, Chen Jane H, Mehrotra Nitya, Trieu Tiffany, Huang Aaron, Mas Eduard, Monterrosa Mena Jessica E, Bliss Bishop, Herman David A, Kleinman Michael T, Fleischman Angela G
Department of Medicine, Division of Hematology/Oncology, University of California, Irvine, Irvine, CA, United States.
Department of Medicine, Division of Occupational and Environmental Medicine, University of California, Irvine, Irvine, CA, United States.
Front Oncol. 2023 Jul 21;13:1210528. doi: 10.3389/fonc.2023.1210528. eCollection 2023.
Somatic mutations in myeloid growth factor pathway genes, such as JAK2, and genes involved in epigenetic regulation, such as TET2, in hematopoietic stem cells (HSCs) leads to clonal hematopoiesis of indeterminate potential (CHIP) which presents a risk factor for hematologic malignancy and cardiovascular disease. Smoking behavior has been repeatedly associated with the occurrence of CHIP but whether smoking is an environmental inflammatory stressor in promoting clonal expansion has not been investigated.
We performed in vivo smoke exposures in both wildtype (WT) mice and transplanted mice carrying Jak2 mutant and Tet2 knockout (Tet-/-) cells to determine the impact of cigarette smoke (CS) in the HSC compartment as well as favoring mutant cell expansion.
WT mice exposed to smoke displayed increased oxidative stress in long-term HSCs and suppression of the hematopoietic stem and progenitor compartment but smoke exposure did not translate to impaired hematopoietic reconstitution in primary bone marrow transplants. Gene expression analysis of hematopoietic cells in the bone marrow identified an imbalance between Th17 and Treg immune cells suggesting a local inflammatory environment. We also observed enhanced survival of Jak2V617F cells exposed to CS in vivo and cigarette smoke extract (CSE) in vitro. WT bone marrow hematopoietic cells from WT/Jak2V617F chimeric mice exposed to CS demonstrated an increase in neutrophil abundance and distinct overexpression of bone marrow stromal antigen 2 (Bst2) and retinoic acid early transcript 1 (Raet1) targets. Bst2 and Raet1 are indicative of increased interferon signaling and cellular stress including oxidative stress and DNA damage, respectively. In chimeric mice containing both WT and Tet2-/- cells, we observed an increased percentage of circulating mutant cells in peripheral blood post-cigarette smoke exposure when compared to pre-exposure levels while this difference was absent in air-exposed controls.
Altogether, these findings demonstrate that CS results in an inflamed bone marrow environment that provides a selection pressure for existing CHIP mutations such as Jak2V617F and Tet2 loss-of-function.
造血干细胞（HSC）中髓系生长因子通路基因（如JAK2）和参与表观遗传调控的基因（如TET2）的体细胞突变会导致意义未明的克隆性造血（CHIP），这是血液系统恶性肿瘤和心血管疾病的一个危险因素。吸烟行为多次与CHIP的发生相关，但吸烟是否作为一种环境炎症应激源促进克隆性扩增尚未得到研究。
我们对野生型（WT）小鼠以及携带Jak2突变体和Tet2基因敲除（Tet-/-）细胞的移植小鼠进行了体内烟雾暴露，以确定香烟烟雾（CS）对HSC区室的影响以及对突变细胞扩增的促进作用。
暴露于烟雾的WT小鼠在长期造血干细胞中表现出氧化应激增加以及造血干祖细胞区室受到抑制，但烟雾暴露并未导致原发性骨髓移植中造血重建受损。对骨髓中造血细胞的基因表达分析确定了辅助性T细胞17（Th17）和调节性T细胞（Treg）免疫细胞之间的失衡，提示存在局部炎症环境。我们还观察到，体内暴露于CS和体外暴露于香烟烟雾提取物（CSE）的Jak2V617F细胞存活率提高。暴露于CS的WT/Jak2V617F嵌合小鼠的WT骨髓造血细胞显示中性粒细胞丰度增加，骨髓基质抗原2（Bst2）和维甲酸早期转录本1（Raet1）靶点明显过表达。Bst2和Raet1分别指示干扰素信号增强以及包括氧化应激和DNA损伤在内的细胞应激增加。在同时含有WT和Tet2-/-细胞的嵌合小鼠中，我们观察到，与暴露前水平相比，香烟烟雾暴露后外周血中循环突变细胞的百分比增加，而在暴露于空气的对照组中则没有这种差异。
总之，这些发现表明，CS会导致骨髓环境炎症化，为现有的CHIP突变（如Jak2V617F和Tet2功能丧失）提供选择压力。
