Background: Acute lung injury (ALI) is a severe and life-threatening lung inflammation with high morbidity and mortality, underscoring the importance to develop effective drugs. Qingjin Huatan decoction (QJHTD), as a classic ancient prescription, has been widely used for treating respiratory diseases. However, the role and mechanism of QJHTD against ALI remain unclear. Objective: This study aimed to explore the therapeutic effect of QJHTD on lipopolysaccharide (LPS)-induced ALI in mice and uncover its mechanism. Methods: The therapeutic effect of QJHTD on LPS-induced ALI in mice was evaluated by the histopathological changes in the lung tissue, the lung wet/dry weight ratio, and the levels of inflammatory cytokines and thrombin-antithrombin complexes. Transcriptomics was used to predict the mechanism of QJHTD in treating ALI. The expression levels of citrullinated histone 3 in the lung tissue, the content of cell-free DNA in the bronchoalveolar lavage fluid (BALF), and the platelet-associated formation of neutrophil extracellular traps (NETs) in vitro were determined. Results: Qingjin Huatan decoction exerted protective effect against LPS-induced ALI by suppressing interstitial edema, maintaining the alveolar-capillary barrier, inhibiting the infiltration of neutrophils and platelets in the lung tissue, and lowering the levels of tumor necrosis factor α, interleukin 1β, interleukin 6, and thrombin-antithrombin complexes in BALF. Kyoto Encyclopedia of Genes and Genomes pathway enrichment analysis indicated that the formation of NETs was the main regulatory pathway for QJHTD against ALI. Qingjin Huatan decoction could treat ALI by inhibiting the release of NETs via reducing the content of citrullinated histone 3 in lung tissue and cell-free DNA in BALF in vivo, and suppressing the NETs formation induced by LPS-stimulated platelets under flow and static conditions in vitro. The formation of NETs was considered to bridge the interactions between neutrophils and platelets. Conclusions: This research demonstrated the effects of QJHTD in treating ALI and provided new insights for clarifying the complex regulation of neutrophils, platelets, and NETs in ALI.

ObjectiveBased on the inhibitory activity of phosphodiesterase （PDE）， a method for determining the anti-inflammatory activity of Qingjin Huatantang was established to supplement and improve the quality control system of this famous classical formula. MethodHigh performance liquid chromatography （HPLC） was used to determine the activity of PDE， and the dose-effect relationship of inhibiting PDE activity of Qingjin Huatantang was investigated. The mobile phase consisted of methanol-0.5% acetic acid aqueous solution （5∶95）， and the detection wavelength was 254 nm. By measuring the PDE inhibition rate of multiple batches of Qingjin Huatantang water extract lyophilized powder， biological activity was marked with the activity of the neutralizing enzyme in the international unit U. ResultWhen the concentration of reaction substrate （cyclic adenosine monophosphate） was 50 μmol·L^-1 and the reaction time was 60 min， the enzymatic reaction was stable with 4 U·mL^-1 of PDE. In this reaction system， when the concentration of Qingjin Huatantang water extract lyophilized powder was 0.11-3.0 g·L^-1， the inhibitory effect of PDE showed a concentration-dependent relationship. It was determined that the concentration of Qingjin Huatantang water extract lyophilized powder to be tested was 1 g·L^-1， which showed a significant and stable inhibitory effect on PDE， and the inhibitory rate was >45%， that is， 1 mg of Qingjin Huatantang water extract lyophilized powder could neutralize the activity of 1.8 U PDE at least. ConclusionThis study establishes a biological activity evaluation method of Qingjin Huatantang based on the inhibitory activity of PDE， and the anti-inflammatory activity of Qingjin Huatantang is characterized by international unit U of PDE activity， which can provide a new method for the determination of biological activity of traditional Chinese medicine compounds.