Effect Of FABP4 On Macrophage Polarization And Lipid Deposition In Silicotic Fibrosis Through PI3K/AKT/mTOR Signaling Pathway

Objectives To explore the effects of fatty acid binding protein 4（FABP4）on the polarization and lipid deposition of macrophages stimulated by SiO₂,and the regulatory role of phosphatidylinositol 3 kinase（PI3K）/protein kinase B（AKT）/mammalian target of rapamycin（mTOR）signaling pathway,so as to clarify the possible mechanism of silicosis.Methods C57BL/6J male mice were randomly divided into control group and 7,14 and28 day model group according to body weight.The silicosis model of mice was established by non tracheal exposure.The pathological changes and collagen deposition in the lung were observed by hematoxylin eosin staining and Sirius red staining.The period with the most severe infiltration of inflammatory cells was selected as the model group.The expression of FABP4 in the lung was observed by Western blot and immunohistochemical staining,The expression of inducible nitric oxide synthase（iNOS）and Arginase-1（ARG-1）,markers of macrophage polarization,reflects the polarization of macrophages.RAW264.7 was selected in vitro macrophage system:the cells were stimulated with different concentrations of SiO₂suspension for different times.According to the polarization degree of macrophages,the optimal stimulation concentration and time of SiO₂ were selected.The cells were treated with FABP4 inhibitor BMS309403.The expressions of iNOS and ARG-1 were detected by cellular immunofluorescence and Western blot.The contents of total cholesterol（TC）,free cholesterol（FC）and triglyceride（TG）in macrophages were measured by enzyme kit,To explore the effect of FABP4 on macrophage polarization and lipid deposition,Western blot was used to detect the expression of p-PI3K,p-AKT and p-mTOR proteins in each group,to observe the effect of FABP4 on the activation of PI3K/AKT/mTOR pathway,to treat cells with PI3K inhibitor LY294002,to detect the expression of iNOS and ARG-1 and the content of TC,FC and TG in cells,and to study the effect of PI3K/AKT/mTOR signal pathway on macrophage polarization and lipid deposition.Results In vivo experiments showed that there were a large number of inflammatory cell infiltration in the lung tissue of the 7 day model group compared with the control group;Immunofluorescence,immunohistochemistry and Western blot showed that macrophages were activated to M1 and M2 in lung tissue;Western blot showed that the protein expression of FABP4 increased in lung tissue.In vitro studies showed that compared with the control group,SiO₂ stimulated RAW264 7 cells,the expression of iNOS protein increased（P<0.05）,and the number of iNOS positive cells increased,indicating that the cells transformed into M1 type,not M2 type.SiO₂ stimulation increased the expression of FABP4 protein,lipid droplet deposition and the contents of TC,FC and TG in macrophages（P<0.05）,The inhibitor BMS309403 of FABP4 can inhibit RAW264 7 cells transformed into M1 type and reduced the contents of TC,FC and TG in cells.In addition,the increase of FABP4 after SiO₂ stimulation can activate PI3K/AKT/mTOR pathway in macrophages,that is,the expression of p-PI3K,p-AKT and p-mTOR proteins increased compared with the control group,The difference was statistically significant（P<0.05）.BMS30940,an inhibitor of FABP4,inhibited the activation of PI3K/AKT/mTOR pathway,cell M1 polarization and intracellular lipid deposition,and returned to the level of the control group.LY294002,an inhibitor of PI3K,inhibited the M1 polarization of macrophages induced by SiO₂,the content of TC,FC and TG in cells and intracellular lipid deposition,and prevented the polarization and intracellular lipid deposition induced by SiO₂ stimulated macrophages.Conclusions FABP4 affects the polarization of macrophages stimulated by SiO₂ to M1and the lipid deposition of macrophages through PI3K/AKT/mTOR pathway,so as to participate in the progress of silicotic fibrosis.Figure19;Table15;Reference 152...