Alpha-linolenic acid pretreatment alleviates NETs-induced alveolar macrophage pyroptosis by inhibiting pyrin inflammasome activation in a mouse model of sepsis-induced ALI/ARDS

Abstract

BackgroundNeutrophil extracellular traps (NETs) can cause acute lung injury (ALI)/acute respiratory distress syndrome (ARDS) by inducing macrophage pyroptosis. The purpose of this study was to find out whether pretreatment of alpha-linolenic acid (ALA) could inhibit NETs-induced macrophage pyroptosis in sepsis-induced ALI/ARDS, as well as to identify which inflammasome is involved in this process.MethodsLPS was instilled into the trachea to establish sepsis-induced ALI/ARDS in a mouse model. ​Lung injury was assessed by microscopic examination of lung tissue after hematoxylin and eosin staining, pathology score, and bronchoalveolar lavage fluid (BALF) total protein concentration. The level of NETs in lung tissue was detected by MPO-DNA ELISA. Purified NETs, extracted from peritoneal neutrophils, induced macrophage pyroptosis in vitro. Expression of pyroptosis-related proteins (Cl-caspase-1, Cl-GSDMD, ASC) and IL-1β in the lung tissue and bone marrow-derived macrophages (BMDMs) were determined by western blotting or ELISA. Specks of Pyrin/ASC were examined by confocal immunofluorescence microscopy. Mefv (Pyrin)-/- mice were used to study the role of Pyrin in the process of sepsis-induced ALI/ARDS.ResultsALA alleviated LPS-induced lung injury. ALA reduced the level of NETs, pyroptosis-related proteins (Cl-caspase-1, Cl-GSDMD, ASC), and IL-1β in the lung tissue of sepsis mice. In vitro, NETs increased the expression of pyroptosis-related proteins (Cl-caspase-1, Cl-GSDMD, ASC) and IL-1β significantly in BMDMs. Pyrin protein was found to be higher and form the inflammasome with ASC in NETs challenged-BMDMs. Knockout of Mefv (Pyrin) gene fully restored the increased expression of pyroptosis-related proteins (Cl-caspase-1, Cl-GSDMD, ASC) and IL-1β in vitro and in vivo. Lung injury was alleviated significantly in Mefv (Pyrin)-/- mice as well.​ ALA suppresses all the NETs-induced changes as mentioned above.ConclusionOur study is the first to demonstrate Pyrin inflammasome driving NETs-induced macrophage pyroptosis, and ALA may reduce ALI/ARDS by inhibiting the activation of the Pyrin inflammasome-driven macrophage pyroptosis.

The role of fatty acid metabolism in acute lung injury: a special focus on immunometabolism

“…Besides, ALA is a plant-derived ω-3 fatty acid that possesses anti-inflammatory properties. Recent studies have demonstrated that pretreatment with ALA can ameliorate LPS-induced ALI by not only reducing the release of IL-1β cytokines from apoptosis cells but also inhibiting the activation of Pyrin inflammasome-driven macrophage sepsis [ 132 , 133 ], offering a potential therapeutic option for managing ALI/ARDS through enteral nutrition.…”

Acute Lung Injury and the NLRP3 Inflammasome

“…The development of ALI is highly intricate, involving multiple mechanisms such as inflammation activation, 6 cell apoptosis, 21 oxidative stress injury, 22 and coagulation dysfunction. 23 It is widely believed that at the core of its pathogenesis is an uncontrolled inflammatory response.…”

Acute lung injury caused by sepsis: how does it happen?

“…The current treatment strategies for this mechanism are also a hot spot. It is found that inflammatory cytokines such as IL-1β and TNF-α can alleviate inflammatory reactions and tissue damage (42,65). Anti-cytokine drugs such as tocilizumab, adalimumab and celastrol have been used clinically to treat ALI (66)(67)(68).…”

“…They play an essential role in enhancing alveolar fluid clearance and reducing pulmonary inflammatory response (40). Due to the protective effect of alveolar epithelial cells on the lung tissue barrier, the onset of ALI can manifest as apoptosis of alveolar epithelial cells and damage to the alveolar wall capillary barrier (41,42). The mechanisms by which sepsis leads to the development of ALI are shown in Figure 1.…”