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放疗是临床治疗恶性肿瘤的重要手段之一。在腹腔、盆腔肿瘤患者的放疗中,由于位于腹腔和盆腔内的肠道组织对电离辐射比较敏感,这些患者肠道功能发生改变的概率高达90%。放射性肠损伤是腹部或盆腔肿瘤患者接受局部放疗引起的最常见的并发症,可累及小肠、结肠和直肠[1]。一般在3~6个月内出现以肠黏膜炎症反应为主的急性放射性肠损伤,临床表现为黏膜溃疡、穿孔、瘘以及腹腔脓肿[2]。肠道损伤效应是放疗剂量限制的主要原因,严重影响到患者的生存质量和肿瘤的放疗疗效。如何在保证疗效的同时减少对肠道组织的放射性损伤,是辐射防护领域急需解决的问题。
褪黑素是Lerner等[3]于1959年首次在松果体中分离出来的一种具有多种生物活性的吲哚类物质,由于其进入蛙黑色素细胞后会使蛙全身肤色变浅而得名。褪黑素的化学名称为N-乙酰基-5-甲氧基色胺(N-acetyl-5-methoxytryptamine),具有促进睡眠、调节生物节律、抗衰老、抗氧化、清除自由基、调节免疫、抗肿瘤等多项生理功能[4-6]。近年的研究结果表明,褪黑素能减轻电离辐射对机体造成的损伤,在辐射损伤的防护与治疗的研究中产生了良好的效果[7-8]。
我们在研究褪黑素对辐射诱导的放射性肠损伤的作用时发现,在照射前对C57BL/6J小鼠给予褪黑素,能促进小鼠肠道组织辐射损伤的修复,有效缓解小鼠放射性肠损伤的症状[9]。研究结果表明,肠道菌群参与肠道的稳态维持和机体的生理功能发挥,在放疗引起的组织炎症损伤及其修复中发挥着重要作用[10-11]。那么,肠道菌群是否也参与了褪黑素对放射性肠损伤的防护作用呢?本研究采用16S rDNA扩增子测序技术对小鼠肠道菌群进行分析,探讨肠道菌群在褪黑素对γ射线诱导的小鼠放射性肠损伤的防护中的作用。
褪黑素在γ射线诱导的小鼠放射性肠损伤中对肠道菌群的影响
Melatonin alleviates γ-ray-induced intestinal injury from mice by modulating gut microbiota
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摘要:
目的 探讨褪黑素在γ射线诱导的小鼠放射性肠损伤中对肠道菌群的影响。 方法 采用简单随机分组法将C57BL/6J雄性小鼠分为3组,即对照组(不给予任何处理)、照射组(以13 Gy剂量对小鼠进行腹部照射)和褪黑素+照射组(对小鼠实施褪黑素给药,连续5 d,然后以13 Gy剂量进行腹部照射),每组5只,共15只。照射后3 d收集小鼠粪便,进行16S rDNA扩增子测序,分析小鼠肠道菌群的变化,应用Uparse 软件进行操作分类单元聚类和物种注释,应用Qiime微生物组分析平台进行样品复杂度分析和多样品比较分析。 结果 巴斯德菌属、分节丝状菌属和拟杆菌属是褪黑素+照射组小鼠肠道中丰度最大的菌群。与对照组相比,褪黑素+照射组小鼠肠道菌群的丰度和多样性均下降(均P<0.01),群落结构增加(P<0.001)。由门至种的不同分类级别的变形菌门/纲、肠杆菌目/科、巴斯德菌目/科/属/种和梭状芽孢杆菌纲/目是褪黑素+照射组小鼠肠道菌群组间丰度最大的菌群。在构建小鼠肠道菌群优势菌属共发生网络中,确定了变形菌门、放线菌门、拟杆菌门和厚壁菌门这四大门类下占互作主导地位的菌属以及它们之间互作的关系。 结论 照射前给予褪黑素后小鼠肠道中的优势菌属可能参与了褪黑素缓解γ射线诱导的放射性肠损伤的过程。 Abstract:Objective To explore the effect of melatonin on gut microbiota of a mouse model of γ-ray-induced radiation intestinal injury. Methods C57BL/6J male mice were divided into three groups using a simple random grouping method, namely, the control (without any treatment), irradiation (abdominal irradiation of mice at a dose of 13 Gy), and melatonin+irradiation groups (administration of melatonin to the mice for five consecutive days, followed by abdominal irradiation at a dose of 13 Gy), with five mice in each group. Mouse feces were collected 3 days after radiation, and gut microbiota analysis was conducted via 16S rDNA amplicon sequencing. Operational taxonomic units clustering and species annotation were analyzed using Uparse software. Sample complexity analysis and multisample comparative analysis were completed using the Qiime microbiome analysis platform. Results Pasteurella, Candidatus Arthromitus, and Bacteroides were the most abundant bacteria in the intestines of mice in the melatonin+irradiation group. Compared with the control group, the melatonin+irradiation group showed decreased abundance and diversity of gut microbiota (both P<0.01) and increased community structure (P<0.001). From phylum to species, Proteobacteria phylum/class, Enterobacteriales order/family, Pasteurellales order/family/genus/species and Clostridiales class/order were the most abundant gut microbiota of mice in melatonin+irradiation group. In the construction of a symbiotic network of dominant species in mouse gut microbiota, the dominant interacting species under Proteobacteria, Actinobacteria, Bacteroidetes, and Firmicutes and their interacting relationships were identified. Conclusion The dominant species in the intestines of mice from melatonin+irradiation group might contribute to the relief of γ-ray-induced radiation intestinal injury mediated by melatonin. -
Key words:
- Melatonin /
- Gastrointestinal microbiome /
- Radiation injuries /
- Gamma rays
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