摘要：Background:Acute lung injury (ALI) is one of the most common critical illnesses in clinical practice, with sepsis being the most common cause of ALI. Sivelestat sodium (SV) hydrate is a highly effective inhibitor of neutrophil elastase, specifically targeting ALI related to systemic inflammatory response syndrome. The aim of this study is to examine the mechanisms by which SV can reduce the severity of ALI resulting from sepsis. Methods:Cecum ligation and puncture (CLP) was employed for creating an animal model of ALI caused by sepsis. Primary human pulmonary microvascular endothelial cells (HPMECs) were treated with lipopolysaccharide (LPS) to develop an in vitro model of infection-induced ALI. Lung tissue damage was assessed by employing hematoxylin-eosin (H&E) and Masson staining. Lung edema was determined by calculating the lung wet-to-dry weight ratio. Lung tissue and cell samples were analyzed using Enzyme-linked immunosorbent assay (ELISA) to detect levels of tumor necrosis factor-α (TNF-α), interleukin (IL)-1β, and IL-6. The 5-ethynyl-2'-deoxyuridine (EdU) and wound-healing assay were used to determine the cell proliferation and migration, while flow cytometry was used for detecting cell apoptosis. The association between microRNA (miR)-744 and transforming growth factor (TGF)-β1 was discovered and confirmed through the utilization of bioinformatics analyses and dual-luciferase gene reporter assay. The analysis of TGF-β1, p-Smad3, and Smad3 was carried out through western blotting and immunohistochemistry in both in vitro and in vivo scenarios. Results:In both in vivo and in vitro settings of ALI models of sepsis, there was a significant decrease in the level of miR-744-5p, a significant elevation in the expression of inflammatory factors, and a significant intensification of lung tissue damage. Administration of SV resulted in a significant increase in the level of miR-744-5p, suppressed the inflammatory response, and ultimately improved lung injury. Cell proliferation was significantly enhanced by SV and cell apoptosis was inhibited. The protection of SV was significantly reversed by inhibiting the effect of miR-744-5p. The double-luciferase reporter gene assay revealed substantial interactions occurring between miR-744-5p and TGF-β1. The TGF-β/Smad signaling pathway was significantly inhibited by SV, however, the inhibitory effect can be counteracted by utilizing the miR-744-5p inhibitor. Conclusions:The upregulation of miR-744-5p by SV inhibits the TGF-β/Smad signaling pathway, thereby reducing sepsis-induced ALI.