Icariside II alleviates lipopolysaccharide-induced acute lung injury by inhibiting lung epithelial inflammatory and immune responses mediated by neutrophil extracellular traps

Acute lung injury (ALI) is a life-threatening lung disease characterized by inflammatory cell infiltration and lung epithelial injury. Icariside II (ICS II), one of the main active ingredients of Herba Epimedii, exhibits anti-inflammatory and immunomodulatory effects. However, the effect and mechanism of ICS II in ALI remain unclear. The purpose of the current study was to investigate the pharmacological effect and underlying mechanism of ICS II in ALI. Models of neutrophil-like cells, human peripheral blood neutrophils, and lipopolysaccharide (LPS)-induced ALI mouse model were utilized. RT-qPCR and Western blotting determined the gene and protein expression levels. Protein distribution and quantification were analyzed by immunofluorescence. ICS II significantly reduced lung histopathological damage, edema, and inflammatory cell infiltration, and it reduced pro-inflammatory cytokines in ALI. There is an excessive activation of neutrophils leading to a significant production of NETs in ALI mice, a process mitigated by the administration of ICS II. In vivo and in vitro studies found that ICS II could decrease NET formation by targeting neutrophil C-X-C chemokine receptor type 4 (CXCR4). Further data showed that ICS II reduces the overproduction of dsDNA, a NETs-related component, thereby suppressing cGAS/STING/NF-κB signalling pathway activation and inflammatory mediators release in lung epithelial cells. This study suggested that ICS II may alleviate LPS-induced ALI by modulating the inflammatory response, indicating its potential as a therapeutic agent for ALI treatment. The mechanism by which ICSII relieved acute lung injury was illustrated. The ICS II administration was carried out through gavage, while the ALI model was induced by LPS. Mechanistically, ICS II bound to the CXCR4 protein, resulting in the inhibition of neutrophils' release of NETs (Neutrophil Extracellular Traps). This, in turn, hampered a cascade of inflammatory immune responses orchestrated by NETs. dsDNA (double-stranded DNA) present in NETs entered endothelial cells. Within these cells, it activated the cGAS/STING/NF-κB pathway, triggering the transcription of inflammatory cytokines including IL-1β, IL-6, and TNF-α. These inflammatory factors, in turn, had the potential to worsen lung epithelial damage and amplify the inflammation in the surrounding tissue. [Display omitted] •Icariside II alleviates lipopolysaccharide-induced acute lung injury in mice.•Icariside II inhibits neutrophil