吲哚胺2, 3-双加氧酶1对急性放射性肠道损伤的保护作用

目的：探讨吲哚胺2, 3-双加氧酶1（IDO1）对急性放射性肠道损伤的作用。方法：使用TCGA和GTEX数据集中结肠癌、直肠癌组织和正常对照组织的测序结果，分析IDO1基因在肠癌组织及正常肠道组织中的表达情况。使用CRISPR/Cas9技术敲除鼠正常肠上皮IEC-6细胞中IDO1基因的部分第2、3外显子序列，建立鼠IEC-6的IDO1 KO（IDO1-/-）细胞系，并给予两个细胞系（野生型和IDO1-/-）放射处理。C57BL/6野生型小鼠和IDO1基因敲除（IDO1-/-）小鼠也给予腹部X射线照射以建立细胞和动物急性放射性肠道损伤模型。使用蛋白质印记法（Western blot）检测野生型和IDO1-/-的IEC-6细胞及小鼠肠道组织中上皮紧密连接蛋白在放射前、后的蛋白表达水平。结果：Western blot证实IDO1在鼠IEC-6细胞、肠道组织中均有表达。对TCGA和GTEX数据集分析后也同样看到IDO1基因在结肠癌、直肠癌、正常肠道组织中均有表达，但癌组织中IDO1水平较正常肠道组织高（P ＜0.05）。体内外的放射照射后，IDO1、Claudin 1、Occludin、ZO-1等出现明显变化：与放射前比，放射后的细胞和小鼠组织中的IDO1的表达水平升高（P ＜0.05），而紧密连接蛋白Claudin 1、Occludin、ZO-1则下降（P ＜0.05）；与野生型IEC-6细胞和小鼠相比，在IDO1-/- IEC-6细胞和小鼠肠组织中，Claudin 1、Occludin、ZO-1 下降更显著（P ＜0.05）。结论：IDO1在急性放射性肠道损伤中起保护作用，其保护作用可能是通过保护肠上皮细胞间紧密连接功能而实现的。

The protective effect of indoleamine 2, 3-dioxygenase 1 on the acute intestinal radiation injury

Objective: To investigate the protective mechanism of indoleamine 2, 3-dioxygenase 1 (IDO1) against radiation-induced acute intestinal injury. Methods: The expression level of IDO1 gene in colorectal cancer tissues and normal intestinal tissues were analyzed based on the TCGA and GTEX database. CRISPR/Cas9 technology was employed to delete the promoter and first exon sequences of IDO1 gene in IEC-6 cell for generating the IDO1 knockout (IDO1-/-, IDO1-KO) cell line, then wild type (WT) and knockout (IDO1-KO) IEC-6 cells were given radiation treatment. What’s more, C57BL/6 wild-type mice and IDO1 knockout (IDO1-/-) mice were given abdominal X-ray irradiation to establish radiation-induced intestinal damage model. Western blot was used to determine the IDO1 and epithelial tight junction proteins Claudin 1, Occludin, ZO-1 levels in cells and mouse intestinal tissues before and after radiation. Results: IDO1 gene was expressed in colon cancer, rectal cancer, and normal intestinal tissues. Compared with normal tissues, the expression level of IDO1 gene in cancer cells was higher, based on the TCGA and GTEX database analysis (P<0.05). Western blot indicated that IDO1expressed in IEC-6 cells and mouse intestinal tissues in vitro and in vivo. The protein levels of IDO1, Claudin 1, Occludin and ZO-1 showed significant changes after irradiation. The expression level of IDO1 increased significantly while tight junction protein Claudin 1, Occludin and ZO-1 decreased after radiation in IEC-6 cells and mouse intestinal tissues (P<0.05). Interestingly, the tight junction proteins decreased even more in IDO1-KO IEC-6 cells and mouse intestinal tissues (P<0.05). Conclusion: IDO1 has protective effect on intestinal radiation injury, which may be achieved by promoting the tight junctions of intestinal epithelial cells.