To explore the role of forsythoside A (FA) in regulating neutrophil extracellular traps (NETs) and alleviating sepsis-related ARDS, as well as its possible mechanism.

A total of 80 mice were randomly divided into sham, model (CLP), FA, and FA+PPAR-γ groups. A sepsis-induced lung injury mice model was established using the classic cecal ligation and puncture (CLP) procedure. The sham group underwent only laparotomy. siPPAR-γ (10 nmol/20g) was administered via tail vein injection (twice a week for 2 weeks), while FA was administered via intraperitoneal injection (80 mg/kg, once daily for 3 days). After successful model establishment, Kaplan-Meier survival curves were used to analyze the cumulative 7-day survival rate of 10 mice per group. For the remaining mice, six per group were randomly selected to collect lung tissue. Inflammatory factors (TNF-α, IL-6, IL-1β) and NET markers (NE-DNA, MPO-NDA) were detected using ELISA kits. SOD, MDA, and ROS levels were measured by spectrophotometry. The lung wet/dry weight (W/D) ratio was calculated. Pathological changes were observed under light microscope after H&E staining, and lung injury histopathological scoring was conducted. Immunofluorescence was used to detect H3-cit protein expression in lung tissue. Western blotting was performed to measure the relative expression levels of PPAR-γ, H3-cit, MPO, and NE proteins.

Kaplan-Meier survival curve analysis revealed that the 7-day cumulative survival rate in the FA group was significantly higher than in the CLP and FA+PPAR-γ groups (P<0.05). The CLP group showed partial alveolar destruction, thickened alveolar septa, extensive inflammatory cell infiltration, alveolar and partial alveolar hyaline membrane formation, and alveolar collapse. In the FA group, H&E staining showed significant reduction in inflammatory cell infiltration, thinner alveolar septa, and less alveolar collapse. Compared to the sham group, the CLP group exhibited higher lung injury histopathological scores and W/D ratios (P<0.05), increased levels of inflammation factors (TNF-α, IL-6, IL-1β, P<0.05), elevated NE-DNA and MPO-NDA expressions (P<0.05), increased MDA and ROS levels (P<0.05), and decreased SOD levels (P<0.05). PPAR-γ protein expression was reduced (P<0.05), while H3-cit, MPO, and NE protein expressions were elevated (P<0.05). Compared to the CLP group, the FA group showed lower lung injury histopathological scores and W/D ratios (P<0.05), decreased levels of inflammatory factors (TNF-α, IL-6, IL-1β, P<0.05), reduced NE-DNA and MPO-NDA expression (P<0.05), lower MDA and ROS levels (P<0.05), higher SOD levels (P<0.05), and increased PPAR-γ protein expression (P<0.05). H3-cit, MPO, and NE proteins were reduced (P<0.05).

Forsythoside A alleviates sepsis-related ARDS by activating PPAR-γ to inhibit the formation of neutrophil extracellular traps.