敲除NAD+水解酶CD38保护放射性肺损伤的机制研究

Radiation-induced lung injury (RILI) remains a major obstacle and main dose-limiting factor in the radiotherapy of thoracic cancer. The prevention and treatment of RILI have long been a clinical challenge. Cell senescence post radiation presents a critical role in the pathological process of RILI. CD38 is a multifunctional protein. In our previous study, we revealed that compared with wildtype (WT) mice, CD38 gene konckout mice (CD38-/-) developed an attenuated RILI and a prolonged survival; CD38 deficiency produced high levels of NAD+ and the expressions of NAD+-dependent deacetylases, SIRT1 and SIRT6; overexpression of SIRT1 or SIRT6 efficiently alleviated RILI in WT mice. Furhtermore, CD38 siRNA significantly mitigated the radiation-induced cell senescence in vitro. Current research and our previous works indicated that CD38 deficiency ameliorated the senescence and RILI via upregulating the levels of NAD+, the expressions and activities of SIRT1 and SIRT6. In the further study, we will complete the preliminary studies and determine the exact molecular mechanism of CD38(-/-)-NAD(+)-SIRT1/6 signaling in the regulation of senescence and RILI through DNA repair, ROS, and NF-κB pathway. The gene knockout mice and overexpression and/or RNA interference experiments will be used in the mechanism study. The study will provide a potential preventative and therapeutic avenue for RILI.

放射性肺损伤（RILI）是胸部肿瘤放疗主要的剂量限制性因素，目前尚缺乏有效防治手段。细胞衰老在RILI病理进程中具有重要作用。CD38是一种多功能蛋白，我们前期工作发现：相较于野生型（WT）小鼠，CD38基因敲除小鼠（CD38-/-）全肺照射后，肺损伤明显减轻，生存率提高，肺组织NAD+及NAD+依赖的去乙酰化酶SIRT1、SIRT6表达增高；过表达SIRT1或SIRT6均可减轻WT小鼠的RILI；CD38 siRNA可抑制放射线引起的细胞衰老。提示：CD38-/-通过上调NAD+，增加SIRT1/6的表达及活性，抑制细胞衰老，保护RILI。本研究拟使用CD38-/-等基因敲除小鼠，结合过表达/干扰实验，从DNA损伤修复、ROS及NF-κB通路三个方面，明确CD38(-/-)-NAD(+)-SIRT1/6信号通路抑制衰老，保护RILI的分子机制，以期为RILI的防治提供新的思路及方法。

放射性肺损伤（RILI）是肺癌放疗常见及严重并发症，限制肿瘤靶区的放疗剂量，影响患者生活质量，目前尚缺乏有效治疗手段。CD38是一种跨膜糖蛋白，功能广泛，我们工作证实，CD38基因敲除小鼠（CD38-/-）全肺照射后肺损伤较野生型小鼠明显减轻，生存率明显提高；CD38-/-小鼠肺组织NAD水平以及NAD依赖的去乙酰化酶SIRT1/SIRT6表达明显高于野生型小鼠。同时，研究发现过表达SIRT1，SIRT6可以显著减轻肺损伤，SIRT1/SIRT6通过促进DNA损伤修复和抑制细胞内ROS产生等抑制细胞衰老。同时，我们发现CD38表达下调通过促进NAD的产生，参与调节了细胞外泌体的产生，具有调节细胞间信号交流的作用。CD38表达下调或NAD处理内皮细胞分泌的外泌体，通过旁分泌作用于临近细胞，具有抑制细胞内ROS产生，保护放射线引起的细胞衰老的作用。因此，CD38对细胞间的“communication”及旁分泌作用的调控，及外泌体内具体效应分子是该课题下一步探讨的重点内容。本课题从细胞NAD能量代谢和细胞间“communication”两方面，为照射后延缓细胞衰老开辟了新的研究方向。本课题研究为RILI的防治提供新的思路及方法。

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