外泌体miR-122-5p在乏氧促进的放射性直肠损伤中的作用及机制研究

Rectal injury is a risk factor to pelvic tumors radiotherapy. Our studies have demonstrated radiation-induced tissue hypoxia contributed the development of rectal injury, its mechanism remains unclear. In further study, we found hypoxia increased exosomal miR-122-5p (microRNA-122-5p), and which can translocate between cells. Its increasing is dependent with aggravated murine rectal injury. MiR-122-5p and its downstream gene AKT3 (v-akt murine thymoma viral oncogene homolog 3, AKT3) were known to be closed with tissue injury. However, the relation between exosomal miR-122-5p and radiation-induced rectal injury is still unclear. These results suggested exosomal miR-122-5p and hypoxia maybe play a role in radiation-induced injury. In these studies, we will study the role of hypoxia in induction and development of injury, and the relation of hypoxic signal and exosomal miR-122-5p in vitro and in vivo by hypoxic culture, mice model of radiation-induced rectal injury and so on. Our study may be good to know the radiation-induced rectal injury well and to improve the quality of life of patients who received pelvic radiotherapy.

辐射后的组织乏氧是促进放射性正常组织损伤的重要因素，但详细机制尚未阐明。我们前期证实，乏氧促进放射性直肠损伤。进一步发现，乏氧促进肠上皮细胞分泌富含miR-122-5p的外泌体，且可进行细胞间传递。MiR-122-5p随直肠损伤程度的加重而增加，miR-122-5p及其下游靶基因AKT3均与组织损伤密切相关，但其影响放射性直肠损伤的机制尚不明确。为此我们提出假设，辐射后的组织乏氧促进的放射性直肠损伤很可能受乏氧细胞分泌的外泌体miR-122-5p介导的细胞间信息传递的影响。为验证这一假设，我们将通过体外细胞实验、放射性直肠损伤小鼠模型等手段，从分子、细胞、组织及动物等多方面探讨及明确外泌体miR-122-5p及乏氧微环境与放射性直肠损伤的相互关系。本研究将从乏氧诱导的外泌体介导的细胞信息传递的影响这个新视点，为揭示放射性直肠损伤发生机制进一步奠定基础，进而为放射性直肠炎的防治提供新思路。

放射性直肠损伤降低盆腔肿瘤的放疗疗效及患者生活质量。我们前期研究证实，照射后的组织乏氧促进放射性直肠损伤的发展，但详细机制尚未阐明。本课题组发现，小鼠放射性直肠损伤模型中，直肠组织中低氧诱导因子-1α（hypoxia inducible factor-1,HIF-1α）表达水平与凋亡程度呈正相关。体外，乏氧处理和乏氧培养的HIEC细胞上清均显著促进常氧人正常肠上皮细胞（human intestinal epithelial crypts，HIEC）细胞凋亡。进一步发现，乏氧培养的HIEC细胞上清来源的外泌体使得常氧HIEC细胞凋亡率增加，DNA双链损伤标志物γH2AX表达升高，pAKT表达下降。对常氧和乏氧HIEC细胞上清外泌体进行miRNA微阵列芯片分析后发现，miR-122-5p在乏氧外泌体中表达升高。进一步在HIEC中抑制miR-122-5p后，乏氧外泌体的促凋亡效应得到缓解。综上，我们发现乏氧外泌体来源的miR-122-5p加重了放射性直肠损伤，pAKT通路可能参与其中。项目研究成果在Toxicology and Applied Pharmacology等国内外期刊发表论文12篇。