Mechanisms Of Fatty Acid Binding Protein 4 On The Dysfunction Of Airway Epithelial Cells In Asthma

Background and objective:Bronchial asthma(asthma)is a disease characterized by chronic inflammation of the airway,airway hyperresponsiveness and airway remodeling.Epithelial cells of the airways consist of the body's first barrier against the external environment.The barrier function in patients with asthma is significantly impaired,and airway damage is one of the causes of chronic inflammation and airway hyperresponsiveness.Fatty Acid Binding Protein 4(FABP4)is one of the major members of the FABP family,could regulate both the metabolism of intracellular fatty acids and inflammatory response.However,the role and mechanism of FABP4 in causing impairment of the barrier function is unclear.Methods:In vivo experiments,Mouse models of asthma induced by house dust mites(HDM)were established.BMS(an inhibitor of FABP4)was administered.The models were observed for airway response,inflammation and expression of E-cadherin(connecting epithelial cells together).In vitro experiment,16-HBE cells(a type of epithelial cells of the airways)in the experimental groups were treated with HDM,hrFABP4,siFABP4,BMS,RCM-1(an inhibitor of Foxm1)and NAC(an inhibitor of reactive oxygen species/ROS),respectively.The levels of IL-4,IL-5 and IL-13(Th2 cytokines)in the culture supernatant were measured using ELISA.Transmembrane electrical resistance(TER)was measured with a resistance meter.Dextran-FITC was used to measure cell permeability.E-cadherin expression and distribution was detected with immunofluorescence.DCF-DA staining was used to measure the level of ROS.Results:1.Inhibition of FABP4 significantly attenuated airway inflammation and destruction of E-cadherin in asthmatic mice.Compared with the HDM-induced asthma group,airway hyperresponsiveness,Th2 inflammatory factors(IL-4,IL-5 and IL-13),IgE,macrophage count,neutrophil count and eosinophil count in alveolar lavage fluid after oral administration of FABP4 inhibitor BMS were significantly decreased(P<0.05);HE staining of lung tissue showed that the inflammatory response surrounding the airways was also significantly reduced(P<0.05);Immunohistochemistry results showed decreased damage to expression and distribution of E-cadherin.2.HDM induced epithelial inflammatory response and caused damage to the barrier by stimulating expression of FABP4.In the 16-HBE cell model,FABP4 expression increased with the increase of HDM stimulation concentration(P<0.05),knockdown of FABP4 expression,can significantly reduce HDM-induced release of Th2 inflammatory factors'(IL-4,IL-5 and IL-13),decreased TER,increased cell permeability,and decreased damage to distribution of E-cadherin(P<0.05).3.HDM and FABP4 induced airway epithelial inflammatory response and caused damage to the barrier function via Foxml.Expression of Foxml in epithelial cells and lung tissues of the asthma group of asthmatic mice was significantly higher than that of the control group and that of the BMS group(P<0.05;P<0.05).That in the cells which were treated with HDM or hrFABP4 was significantly higher than that of the control group(P<0.05).HBM-induced Foxm1 expression was significantly inhibited in 16-HBE cells with BMS pretreatment or FABP4 low expression(P<0.05).At the same time,16-HBE cells pretreated with Foxm1 inhibitor RCM-1,HDM or hrFABP4-induced Foxm1 expression,Th2 inflammatory factors(IL-4,IL-5 and IL-13)release,TER reduction,cell permeability Both the increase and the distribution damage of E-cadherin were significantly inhibited(P<0.05).4.HDM induced expression of Foxml in airway epithelial cells via FABP4/ROS.Expression of Foxm1 in the H202 group was significantly higher than that of the control group(P<0.05).The level of ROS increased significantly in the 16-HBE cells treated with HDM or hrFABP4(P<0.05),whereas expression of ROS induced by HDM or hrFABP4 was significantly inhibited in 16-HBE cells which were pretreated with BMS or NAC or had low expression level of FABP4(P<0.05).After inhibition of ROS by NAC,HDM or hrFABP4 induces high expression of Foxml in 16-HBE cells,release of Th2 inflammatory factors(IL-4,IL-5 and IL-13),decreased TER,increased cell permeability and distribution damage of E-cadherin were significantly inhibited(P<0.05).ConclusionsFABP4 could induce chronic airway inflammation and impair the barrier function in mice with asthma;and its mechanism may be related to the activation of ROS/Foxm1 pathway.