ObjectiveTo investigate the mechanism of action of FF in the treatment of ALI by studying the effects of Forsythiae Fructus-Lonicerae Japonicae Flos （FF） on serum metabolomics of rats with acute lung injury （ALI）.MethodsThirty male SD rats were acclimatized for 1 week， and 6 rats were randomly selected as the blank group. The other 24 rats were injected with lipopolysaccharide （LPS） solution by tracheal drip to establish an ALI model. After the ALI model was successfully constructed， the rats were randomly divided into the model group， the FF low-dose group （3.0 g kg^-1）， the FF high-dose group （6.0 g kg^-1）， and the dexamethasone group （5 mg kg-¹）， with six rats in each group. The FF low and high dose groups and the dexamethasone group were gavaged once a day with the corresponding dose of drug， and the blank group and the model group were gavaged with an equal amount of saline for 3 d. The pathological conditions of the rat lung tissue were evaluated by hematoxylin-eosin （HE） staining， the wet/dry mass ratio of the lung tissue （W/D）， and the concentration of proteins in the alveolar lavage fluid （BALF） of the rats. Metabolomics analysis of rat serum was performed by ultra performance liquid chromatography-quadrupole-time of flight tandem mass spectrometry （UPLC-Q-TOF-MS）， combined with multivariate statistical analysis， and screened by variable importance projection （VIP） value >1， P<0.05 from t-test， and Log₂FC>l or log₂FC<-1 potential biomarkers for FF treatment of ALI. The Kyoto Encyclopedia of Genes and Genomes （KEGG） database combined with MetaboAnalyst （http：//www.MetaboAnalyst.ca/） was used for pathway analysis of the screened differential metabolites. The protein expression levels of sphingosine 1-phosphate （S1P）， phosphatidylinositol 3-kinase （PI3K）， protein kinase B （Akt1）， and phosphorylated protein kinase B （p-Akt1） were examined by Western bolt assay. The expression levels of interleukin-6 （IL-6）， IL-1β， and tumor necrosis factor-α （TNF-α） in BALF were detected by enzyme-linked immunosorbent assay （ELISA）.ResultsCompared with the blank group， rats in the model group showed ALI pathological features such as alveolar lumen dilatation， interstitial hemorrhage and massive inflammatory cell infiltration， and the protein concentration in BALF and W/D value of lung tissues were significantly elevated （P<0.01）， and the pulmonary bronchial hemorrhage of the rats in the low and high dose groups of FF and the group of dexamethasone was reduced， and the protein concentration in BALF and the W/D value of BALF were significantly reduced compared with those in the model group （P< 0.05）， and lung injury was significantly alleviated. The serum metabolomics of rats was analyzed and 38 biomarkers were recalled by FF. Metabolic pathway enrichment analysis showed that FF exerted its therapeutic effects mainly by affecting 7 key metabolic pathways， including arginine biosynthesis， sphingomyelin metabolism， alanine， aspartate and glutamate metabolism， taurine and hypotaurine metabolism， α-linolenic acid metabolism， niacin and nicotinamide metabolism， and retinol metabolism.The results of Western bolt and ELISA showed that， comparing with the blank group， model group The expression levels of S1P， PI3K， Akt1 and p-Akt1 and the expression levels of IL-6， IL-1β and TNF-α in BALF were significantly higher （P<0.01）. Compared with the model group， the expression of FF was significantly lower in the low and high dose groups and the dexamethasone group （P<0.05）.ConclusionFF may play a role in ALI by regulating amino acid metabolism and lipid metabolism， and its mechanism of action may be related to the inhibition of the S1P/PI3K/Akt1 signaling pathway to attenuate the inflammatory response caused by ALI.

Forsythiae Fructus;Lonicerae Japonicae Flos;acute lung injury;metabolomics;amino acid metabolism;sphingolipid metabolism;sphingosine-1-phosphate（S1P）/phosphoinositide 3-kinase（PI3K）/protein kinase B1（Akt1） signaling pathway