Fenofibrate Improves Lipopolysaccharide-induced Acute Lung Injury And Its Mechanism

Object:Acute lung injury（ALI）is a highly fatal respiratory disease,yet none of the current treatments have significantly reduced its lethality.Therefore,It is pressed for finding a valid drug with few side reaction to treat ALI.This study aims to explore the effect of fenofibrate（Fen）on ALI and the underlying mechanism.Methods:（1）In vivo experiment.Thirty C57BL/6 male mice were spanided into 6 groups by random numerical table method:normal group,model group（LPS group）,positive drug（dexamethasone）group,Fen low,medium and high doses（20,40,80 mg/kg）group.After 12 hours of group administration,the bronchoalveolar lavage fluid（BALF）was collected,the mice were put to death,the lung tissues were obtained,and the wet-dry mass ratio of the lung tissues were recorded.The contents of TNF-α,IL-1βand IL-6 in lung tissues were detected by enzyme linked immunosorbent assay（ELISA）.The total protein content and immune cell number in the bronchoalveolar larage fluid（BALF）were determined by BCA colorimetry and Wright-Giemsa staining.Hematoxylin-eosin（HE）staining was used to observe lung lesions and pathological scores were made.Western blot was used to detect the expression levels of b-cell lymphoma-2（Bcl-2）,bcl-2-Associated X（Bax）,c-Jun N-terminal kinase（JNK）and phosphorylated c-Jun N-terminal kinase（p-JNK）in lung tissues.（2）In vitro experiment.The experiment consisted of 7groups:control,LPS（10 mg/L）,LPS+Fen（5μmol/L）,LPS+Fen（10μmol/L）,LPS+Fen（20μmol/L）,LPS+Fen（20μmol/L）+H₂O₂（100μmol/L）and LPS+Fen（20μmol/L）+Anisomycin（Ani）（3μmol/L）.A549cells were treated with LPS（10 mg/L）and then added with 5,10,and 20μmol/L of Fen for 12 h,respectively.DCFH-DA,Annexin V-FITC/PI and Western blot were used to detect effects of Fen on ROS levels,apoptosis and expression of apoptosis-related proteins Bcl-2,Bax and p-JNK in A549 cells.After LPS（10 mg/L）+Fen（20μmol/L）treatment,H₂O₂（100μmol/L）was added to observe the changes of ROS,apoptosis rate and expression of apoptosis-related proteins Bcl-2 and Bax.In addition,LPS（10 mg/L）and Fen（20μmol/L）were treated and JNK agonist Ani（3μmol/L）was added to observe the expression changes of Bcl-2 and Bax.Results:（1）Compared with normal group,the wet-dry weight ratio of the lung tissues,lung histopathological scores,the contents of TNF-α,IL-1β,IL-6,the number of total proteins and immune cells in alveolar lavage fluid,p-JNK and Bax expression in model group were significantly increased,and the expression of Bcl-2 was significantly decreased.Compared with model group,the wet-dry weight ratio of the lung tissues,lung histopathological scores,the contents of TNF-α,IL-1β,IL-6,the number of total proteins and immune cells in alveolar lavage fluid,p-JNK and Bax expression in Fen low,medium and high dose groups were significantly decreased,and the expression of Bcl-2 was significantly increased.（2）Fen significantly reduced the increase of ROS level,decreased apoptosis rate,inhibited p-JNK and Bax expression and promoted Bcl-2 expression in LPS-induced A549 cells,which were reversed by H₂O₂treatment.Up-regulation of Bcl-2 and down-regulation of Bax expression induced by Fen in LPS-induced A549 cells were reversed by Ani treatment.Conclusion:Fen can reduce the increase of ROS level in LPS-induced A549 cells,inhibit the JNK signaling pathway,and reduce oxidative stress levels and the rate of apoptosis,thereby improving ALI.