Laboratory of Radiopathology and Experimental Therapies, Institute for Radiological Protection and Nuclear Safety, Fontenay-aux-Roses, France.
J Pharmacol Exp Ther. 2013 Jul;346(1):75-85. doi: 10.1124/jpet.113.204040. Epub 2013 Apr 17.
Radiation-induced acute intestinal toxicity remains a major limitation to the delivery of tumoricidal doses of colorectal irradiation. Recent reports indicate that Toll-like receptor (TLR) agonists TLR4 and TLR5 protect against toxicity due to intestinal irradiation. The phenotype (M1 or M2) of macrophages expressing TLRs may play a role in tissue repair. The aim was to investigate whether administration of TLR4 agonist lipopolysaccharide (LPS) or TLR5 agonist flagellin after irradiation modified the recruitment and phenotype of colonic macrophages and improved tissue damage. Rats were exposed to single 20- or 27-Gy doses of colorectal irradiation. TLR4 agonist LPS or TLR5 agonist flagellin (at 50 or 200 µg/rat) was administered i.p. 3 days after irradiation. Flow cytometric analysis, immunostaining, and real-time polymerase chain reaction analysis were used to assess the M1/M2 phenotype and crypt cell proliferation 7 days after irradiation. Irradiation (20 and 27 Gy) increased TLR4⁺ and TLR5⁺ macrophage frequency in the mucosa. LPS or flagellin administration maintained this elevated frequency after the 27-Gy irradiation. LPS and flagellin drove macrophages toward the anti-inflammatory M2 phenotype by increasing Arg1 and CD163 expression and microenvironmental effector molecules (C-C motif chemokine 22, transforming growth factor-β1, and interleukin-10). Proliferating cell nuclear antigen immunostaining, Ki67 expression, and antimicrobial factor Reg3γ showed that the M2 shift correlated with epithelial regeneration. In conclusion, administration of either LPS or flagellin after colorectal irradiation may provide effective protection against epithelial remodeling. This tissue repair was associated with an M2 macrophage shift. Using TLR agonists to moderately activate innate immunity should be considered as a strategy for protecting healthy tissue from irradiation.
辐射诱导的急性肠道毒性仍然是结直肠照射给予肿瘤杀伤剂量的主要限制。最近的报告表明，Toll 样受体 (TLR) 激动剂 TLR4 和 TLR5 可防止因肠道照射引起的毒性。表达 TLR 的巨噬细胞的表型（M1 或 M2）可能在组织修复中发挥作用。目的是研究照射后给予 TLR4 激动剂脂多糖 (LPS) 或 TLR5 激动剂鞭毛蛋白是否改变结肠巨噬细胞的募集和表型，并改善组织损伤。大鼠接受单次 20 或 27 Gy 结直肠照射。照射后 3 天，腹腔内给予 TLR4 激动剂 LPS 或 TLR5 激动剂鞭毛蛋白（50 或 200 µg/大鼠）。流式细胞术分析、免疫染色和实时聚合酶链反应分析用于评估照射后 7 天的 M1/M2 表型和隐窝细胞增殖。照射（20 和 27 Gy）增加了黏膜中 TLR4⁺和 TLR5⁺巨噬细胞的频率。LPS 或鞭毛蛋白给药在 27 Gy 照射后维持了这种升高的频率。LPS 和鞭毛蛋白通过增加 Arg1 和 CD163 表达以及微环境效应分子（C-C 基序趋化因子 22、转化生长因子-β1 和白细胞介素-10）使巨噬细胞向抗炎 M2 表型转变。增殖细胞核抗原免疫染色、Ki67 表达和抗菌因子 Reg3γ 表明，M2 转变与上皮再生相关。总之，结直肠照射后给予 LPS 或鞭毛蛋白可能提供对上皮重塑的有效保护。这种组织修复与 M2 巨噬细胞转变相关。适度激活固有免疫的 TLR 激动剂应被视为保护健康组织免受辐射的一种策略。
