低浓度外源性一氧化碳对辐射旁效应体内传递的调控作用及机理研究

It is considered that the original “radiation-induced secondary cancer”, threating the health of radiotherapy survivals, beyond the irradiated area after radiotherapy has tight relationship with radiation-induced bystander effect (RIBE). RIBE is defined as the irradiated cells would release damage signal(s) to cause genetoxicity, such as cell proliferation, DNA or chromosome damage, gene mutation or even tumor formation, in the neighboring or even abscopal non-irradiated cells or tissues. It is necessary that modulating or inhibiting RIBE effectively to decrease the health risk of non-irradiated tissue in radiotherapy. Low concentration of carbon monoxide (CO), an important molecule modulating many signal pathways in organisms, has plenty of potential clinic application. We have approved exogenous low concentration of CO could protect bystander cells via modulating RIBE transduction in 2- and 3-dimentional cell models. Herein, we go on this study in the in vivo mouse models, which showed more complicated RIBE mechanisms than those in cell models. We will detect the level of DNA double strand breaks, DNA methylation and apoptosis to evaluate RIBE modulation by CO in the bystander tissues beyond the locally irradiated area in the models of BALB/C mice and mice with tumor via simulating radiotherapy. The mechanisms studies will focus on how CO modulating the expression and function of critical proteins of various RIBE signal pathways. We hope our study will help to understand well low concentration of CO as potential protective agent to decrease the genetic risk of bystander tissues after radiotherapy.

放疗后辐射区域外的原发“二次”癌症与辐射旁效应紧密关联。旁效应导致受辐射细胞/组织释放出损伤信号，对附近或远端细胞/组织造成遗传毒性，导致细胞增殖、遗传物质损伤和基因突变甚至肿瘤形成。寻找有效调控方法，降低旁效应造成的健康风险，十分重要。低浓度一氧化碳（CO）是机体内重要信号调控分子，临床应用价值很大。申请人在二维和三维细胞模型中，证实低浓度CO可有效调控旁效应传递，保护旁细胞。申请人拟开展深入研究：在旁效应传递更为复杂的体内模型（BALB/C小鼠及其荷瘤模型）中，模拟放疗进行局部照射，通过评估不同旁区组织中的DNA双链断裂、DNA甲基化水平和凋亡水平，研究低浓度CO气体调控旁效应的作用规律；通过研究CO对旁效应信号通路中关键蛋白表达和功能的影响，探索调控机理。在动物模型中开展的研究，更接近临床状况。研究结果将有利于推进低浓度CO作为辐射防护剂，降低放疗中辐射区域外的遗传风险。

放射治疗中，辐射区域外的二次癌症发生，被认为与辐射引发的旁效应有着紧密的联系。本项目在体内研究模型（小鼠）中，探索低浓度外源性一氧化碳（CO）对辐射旁效应的调控作用和可能的机理。研究结果表明，辐射旁区（睾丸和脑）中的DNA双链断裂水平在辐射后6小时达到最高；小鼠吸入低浓度外源性CO（200 ppm）可以有效保护辐射旁区（睾丸和脑）中的细胞，有效降低细胞中的DNA双链断裂水平，表明低浓度外源性CO对辐射旁效应具有显著调节作用。机理研究方面，现已排除iNOS/TGF-β和NF-κB/COX-2信号通路的参与，但CO调控的具体旁效应传递信号通路尚未确定，后续研究将继续探索，并将研究结果上报基金委。