[Acteoside ameliorates lung injury in septic mice by suppressing neutrophil extracellular trap formation through ROS/MAPK/PAD4 signaling pathway].

This study investigated the effects of acteoside on neutrophil extracellular traps(NETs) formation in the lung tissue of septic mice via the reactive oxygen species(ROS)/mitogen-activated protein kinase(MAPK)/peptidylarginine deiminase 4(PAD4) signaling pathway. A sepsis model was established by intraperitoneal injection of lipopolysaccharide(LPS). Mice were administered high-, medium-, or low-dose acteoside by gavage, and N-acetyl-L-cysteine(NAC) was used as a positive control. The 96 h survival rate of mice was observed. Pathological changes in lung tissue were evaluated by HE staining. Total cell count and total protein content in bronchoalveolar lavage fluid(BALF) were determined. Levels of tumor necrosis factor-α(TNF-α), interleukin(IL)-1β, and IL-6 in BALF were measured by ELISA. Intracellular ROS levels in BALF cells were detected by flow cytometry. Cell-free DNA(cf-DNA) content in BALF was quantified using a commercial assay kit. Immunofluorescence staining was performed to detect the expression of myeloperoxidase(MPO) and citrullinated histone H3(CitH3) in lung tissue. Protein expression levels of phosphorylated extracellular signal-regulated kinase(p-ERK)/ERK, phosphorylated p38 MAPK(p-p38)/p38, phosphorylated c-Jun N-terminal kinase(p-JNK)/JNK, PAD4, MPO, and CitH3/H3 in lung tissue were evaluated by Western blot. The results showed that acteoside at doses of 100 and 200 mg·kg~(-1) markedly increased the survival rate of septic mice, reduced the leukocyte count and total protein concentration, decreased the levels of inflammatory cytokines including TNF-α, IL-6, and IL-1β in BALF, and alleviated lung inflammation in septic mice. Acteoside dose-dependently decreased intracellular ROS levels in BALF cells and downregulated the protein expression of pERK/ERK, p-p38/p38, and p-JNK/JNK in the lung tissue of septic mice. In addition, acteoside treatment reduced cf-DNA content in BALF, decreased the co-localized fluorescence intensity of MPO and CitH3 in lung tissue, and downregulated the protein expression of PAD4, MPO, and CitH3, suggesting that acteoside inhibited sepsis-induced NETs formation in lung tissue. These findings indicate that acteoside mitigates sepsis-induced acute lung injury by suppressing NETs formation through regulation of the ROS/MAPK/PAD4 signaling pathway.