Institute of Drug Clinical Trial and State Key Laboratory of Biotherapy, Cancer Center, West China Hospital, Sichuan University, Chengdu, Sichuan, China.
Department of Thoracic Oncology and State Key Laboratory of Biotherapy, Cancer Center, West China Hospital, Sichuan University, Chengdu, Sichuan, China.
Int J Radiat Oncol Biol Phys. 2020 Jul 15;107(4):804-814. doi: 10.1016/j.ijrobp.2020.02.643. Epub 2020 Apr 22.
To determine the role of NLRP3 inflammasome activation in low-dose radiation-induced radiation pneumonitis (RP) and to assess whether inhibition or deletion of the NLRP3 inflammasome is critical for conferring protection against RP.
The human monocytic THP-1 cells were treated with increasing doses of radiation to assess the activation of NLRP3 by Western blot and enzyme-linked immunosorbent assay. Reactive oxygen species (ROS) production was measured by flow cytometry, with or without ROS inhibitor treatment. A mouse thoracic radiation model that received different doses of radiation was used, and the lung tissues of thoracic-irradiated nlrp3 and wild-type C57BL/6 mice were examined by hematoxylin and eosin and immunofluorescence staining. The concentrations of cytokines in the bronchoalveolar lavage fluid were measured by enzyme-linked immunosorbent assay and Luminex multiplex assays. Lipopolysaccharide (LPS) was administered intranasally 28 days after thoracic irradiation, and NLRP3 inhibitor, MCC950 was administered intraperitoneally after irradiation at 2 different doses.
(1) The NLRP3 inflammasome was activated in 2 Gy irradiated THP-1 cells; NLRP3 and cleaved-caspase-1 levels were not associated with dose escalation of irradiation. (2) Activation of the NLRP3 inflammasome was mediated by ROS, and ROS inhibitor treatment decreased the production of IL-1β and IL-18 in vitro. (3) NLRP3 was activated in mouse lungs by irradiation at 2 Gy, 4 Gy, and 16 Gy, and NLRP3 activation was continuous for 8 weeks. (4) NLRP3 deletion protects against LPS-mediated monocyte infiltration in the mouse lung. (5) The administration of MCC950 decreased the inflammation score of the mice irradiated with 2 Gy or 16 Gy in vivo.
Our results indicate that the NLRP3 inflammasome is activated by low-dose irradiation both in vitro and in vivo. Inhibition or deletion of NLRP3 can specifically alleviate the mouse lung inflammation caused by radiation and LPS treatment. This study reveals the mechanism of low-dose radiation therapy-induced RP and offers a possible treatment strategy.
确定 NLRP3 炎性小体激活在低剂量辐射诱导的放射性肺炎（RP）中的作用，并评估抑制或缺失 NLRP3 炎性小体是否对预防 RP 至关重要。
用递增剂量的辐射处理人单核细胞 THP-1 细胞，通过 Western blot 和酶联免疫吸附试验评估 NLRP3 的激活。通过流式细胞术测量活性氧（ROS）的产生，有或没有 ROS 抑制剂处理。使用接受不同剂量辐射的小鼠胸部放射模型，并用苏木精和伊红以及免疫荧光染色检查胸部放射的 nlrp3 和野生型 C57BL/6 小鼠的肺组织。通过酶联免疫吸附试验和 Luminex 多重分析测量支气管肺泡灌洗液中的细胞因子浓度。在胸部照射后 28 天经鼻给予脂多糖（LPS），并在照射后以 2 种不同剂量经腹腔给予 NLRP3 抑制剂 MCC950。
（1）在 2 Gy 照射的 THP-1 细胞中激活了 NLRP3 炎性小体；NLRP3 和切割的 caspase-1 水平与照射剂量的递增无关。（2）NLRP3 炎性小体的激活是由 ROS 介导的，ROS 抑制剂处理减少了体外 IL-1β 和 IL-18 的产生。（3）在 2 Gy、4 Gy 和 16 Gy 照射下，NLRP3 在小鼠肺部被激活，并且 NLRP3 激活持续 8 周。（4）NLRP3 缺失可防止 LPS 介导的小鼠肺部单核细胞浸润。（5）在体内用 MCC950 处理可降低 2 Gy 或 16 Gy 照射的小鼠的炎症评分。
我们的结果表明，NLRP3 炎性小体在体外和体内均由低剂量照射激活。抑制或缺失 NLRP3 可特异性减轻由辐射和 LPS 处理引起的小鼠肺部炎症。本研究揭示了低剂量辐射治疗引起的放射性肺炎的机制，并提供了一种可能的治疗策略。
