Department of Physiology, School of Basic Medicine Science, Central South University, Changsha, 410078, Hunan, China.
Department of Pulmonary and Critical Care Medicine, The Second Xiangya Hospital, Central South University, Changsha, 410011, Hunan, China.
Mol Med. 2022 Jul 30;28(1):85. doi: 10.1186/s10020-022-00514-4.
Uncontrolled inflammation is an important factor in the occurrence and development of acute lung injury (ALI). Fibroblast growth factor-inducible 14 (Fn14), a plasma membrane-anchored receptor, takes part in the pathological process of a variety of acute and chronic inflammatory diseases. However, the role of Fn14 in ALI has not yet been elucidated. This study aimed to investigate whether the activation of Fn14 exacerbated lipopolysaccharide (LPS)-induced ALI in mice.
In vivo, ALI was induced by intratracheal LPS-challenge combined with/without Fn14 receptor blocker aurintricarboxylic acid (ATA) treatment in C57BL/6J mice. Following LPS administration, the survival rate, lung tissue injury, inflammatory cell infiltration, inflammatory factor secretion, oxidative stress, and NLRP3 inflammasome activation were assessed. In vitro, primary murine macrophages were used to evaluate the underlying mechanism by which Fn14 activated the NLRP3 inflammasome. Lentivirus was used to silence Fn14 to observe its effect on the activation of NLRP3 inflammasome in macrophages.
In this study, we found that Fn14 expression was significantly increased in the lungs of LPS-induced ALI mice. The inhibition of Fn14 with ATA downregulated the protein expression of Fn14 in the lungs and improved the survival rate of mice receiving a lethal dose of LPS. ATA also attenuated lung tissue damage by decreasing the infiltration of macrophages and neutrophils, reducing inflammation, and suppressing oxidative stress. Importantly, we found that ATA strongly inhibited the activation of NLRP3 inflammasome in the lungs of ALI mice. Furthermore, in vitro, TWEAK, a natural ligand of Fn14, amplified the activation of NLRP3 inflammasome in the primary murine macrophage. By contrast, inhibition of Fn14 with shRNA decreased the expression of Fn14, NLRP3, Caspase-1 p10, and Caspase-1 p20, and the production of IL-1β and IL-18. Furthermore, the activation of Fn14 promoted the production of reactive oxygen species and inhibited the activation of Nrf2-HO-1 in activated macrophages.
Our study first reports that the activation of Fn14 aggravates ALI by amplifying the activation of NLRP3 inflammasome. Therefore, blocking Fn14 may be a potential way to treat ALI.
失控的炎症是急性肺损伤（ALI）发生和发展的一个重要因素。成纤维细胞生长因子诱导 14（Fn14）是一种位于质膜上的受体，参与多种急、慢性炎症性疾病的病理过程。然而，Fn14 在 ALI 中的作用尚未阐明。本研究旨在探讨 Fn14 激活是否加重脂多糖（LPS）诱导的小鼠 ALI。
体内，通过气管内 LPS 挑战联合/不联合 Fn14 受体阻滞剂金精三羧酸（ATA）处理，在 C57BL/6J 小鼠中诱导 ALI。给予 LPS 后，评估存活率、肺组织损伤、炎症细胞浸润、炎症因子分泌、氧化应激和 NLRP3 炎性体激活。体外，使用原代小鼠巨噬细胞评估 Fn14 激活 NLRP3 炎性体的潜在机制。使用慢病毒沉默 Fn14，观察其对巨噬细胞中 NLRP3 炎性体激活的影响。
在这项研究中，我们发现 LPS 诱导的 ALI 小鼠肺组织中 Fn14 表达明显增加。用 ATA 抑制 Fn14 可下调肺组织中 Fn14 的蛋白表达，并提高接受致死剂量 LPS 小鼠的存活率。ATA 还通过减少巨噬细胞和中性粒细胞浸润、减轻炎症和抑制氧化应激来减轻肺组织损伤。重要的是，我们发现 ATA 可强烈抑制 ALI 小鼠肺组织中 NLRP3 炎性体的激活。此外，体外，Fn14 的天然配体 TWEAK 增强了原代小鼠巨噬细胞中 NLRP3 炎性体的激活。相比之下，用 shRNA 抑制 Fn14 可降低 Fn14、NLRP3、Caspase-1 p10 和 Caspase-1 p20 的表达以及 IL-1β 和 IL-18 的产生。此外，Fn14 的激活促进了活性氧的产生，并抑制了激活的巨噬细胞中 Nrf2-HO-1 的激活。
本研究首次报道 Fn14 的激活通过放大 NLRP3 炎性体的激活加重 ALI。因此，阻断 Fn14 可能是治疗 ALI 的一种潜在方法。
