Department of Respiratory and Critical Care Medicine, Zhongshan Hospital, Fudan University, 180 Fenglin Road, Shanghai, 200032, P.R. China.
Breast Surgery, Obstetrics and Gynecology Hospital of Fudan University, Shanghai, 200011, China.
Respir Res. 2024 Nov 27;25(1):417. doi: 10.1186/s12931-024-03044-1.
Acute lung injury or acute respiratory distress syndrome (ALI/ARDS) is a devastating clinical syndrome with high incidence and mortality rates. IRE1α-XBP1 pathway is one of the three major signaling axes of endoplasmic reticulum stress that is involved in inflammation, metabolism, and immunity. The role and potential mechanisms of IRE1α-XBP1 axis in ALI/ARDS has not well understood.
The ALI murine model was established by intratracheal administration of lipopolysaccharide (LPS). Hematoxylin and eosin (H&E) staining and analysis of bronchoalveolar lavage fluid (BALF) were used to evaluate degree of lung injury. Inflammatory responses were assessed by ELISA and RT-PCR. Apoptosis was evaluated using TUNEL staining and western blot. Moreover, western blot, immunohistochemistry, and immunofluorescence were applied to test expression of IRE1α, XBP1, NLRP3, TXNIP, IL-1β, ERK1/2 and NF-κB p65.
The expression of IRE1α significantly increased after 24 h of LPS treatment. Inhibition of the IRE1α-XBP1 axis with 4µ8C notably improved LPS-induced lung injury and inflammatory infiltration, reduced the levels of IL-6, IL-1β, and TNF-α, and decreased cell apoptosis as well as the activation of the NLRP3 inflammasome. Besides, in LPS-stimulated Beas-2B cells, both 4µ8C and knockdown of XBP1 diminished the mRNA levels of IL-6 and IL-1B, inhibited cell apoptosis and reduced the protein levels of TXNIP, NLRP3 and secreted IL-1β. Mechanically, the phosphorylation and nuclear translocation of ERK1/2 and p65 were significantly suppressed by 4µ8C and XBP1 knockdown.
In summary, our findings suggest that IRE1α-XBP1 axis is crucial in the pathogenesis of ALI/ARDS, whose suppression could mitigate the pulmonary inflammatory response and cell apoptosis in ALI through the TXNIP/NLRP3 inflammasome and ERK/p65 signaling pathway. Our study may provide new evidence that IRE1α-XBP1 may be a promising therapeutic target for ALI/ARDS.
急性肺损伤或急性呼吸窘迫综合征（ALI/ARDS）是一种具有高发病率和死亡率的破坏性临床综合征。IRE1α-XBP1 途径是内质网应激的三个主要信号轴之一，参与炎症、代谢和免疫。IRE1α-XBP1 轴在 ALI/ARDS 中的作用和潜在机制尚未得到很好的理解。
通过气管内给予脂多糖（LPS）建立 ALI 小鼠模型。苏木精和伊红（H&E）染色和支气管肺泡灌洗液（BALF）分析用于评估肺损伤程度。ELISA 和 RT-PCR 用于评估炎症反应。TUNEL 染色和 Western blot 用于评估细胞凋亡。此外，Western blot、免疫组织化学和免疫荧光用于检测 IRE1α、XBP1、NLRP3、TXNIP、IL-1β、ERK1/2 和 NF-κB p65 的表达。
LPS 处理 24 小时后，IRE1α 的表达明显增加。用 4µ8C 抑制 IRE1α-XBP1 轴显著改善了 LPS 诱导的肺损伤和炎症浸润，降低了 IL-6、IL-1β 和 TNF-α 的水平，并减少了细胞凋亡和 NLRP3 炎性体的激活。此外，在 LPS 刺激的 Beas-2B 细胞中，4µ8C 和 XBP1 敲低均降低了 IL-6 和 IL-1B 的 mRNA 水平，抑制了细胞凋亡，并降低了 TXNIP、NLRP3 和分泌的 IL-1β 的蛋白水平。机制上，4µ8C 和 XBP1 敲低显著抑制了 ERK1/2 和 p65 的磷酸化和核转位。
综上所述，我们的研究结果表明，IRE1α-XBP1 轴在 ALI/ARDS 的发病机制中至关重要，抑制 IRE1α-XBP1 轴可以通过 TXNIP/NLRP3 炎性体和 ERK/p65 信号通路减轻 ALI 中的肺炎症反应和细胞凋亡。我们的研究可能为 IRE1α-XBP1 可能成为 ALI/ARDS 的有前途的治疗靶点提供新的证据。
