The Role Of Leptin/obR Regulating M1 Macrophage Polarization In Obesity-related Neutrophilic Airway Inflammation

Objective: Obesity plays an important role in chronic inflammatory response by secreting fat-related factors such as leptin.However,the roles of leptin and the long-form leptin receptor(obR-b)in the pathogenesis of neutrophil airway inflammation in obesity-associated asthma remain unclear.Therefore,our study aimed to explore the effects and mechanisms.Methods:1.Leptin/obR regulating M1 macrophage polarization in an obesity-associated neutrophil airway inflammation mouse model1)Our study used an enzyme linked immunosorbent assay(ELISA)assay to detect serum leptin level in mice.Lipopolysaccharides(LPS)/ovalbumin(OVA)were used to construct neutrophil airway inflammation mouse model.2)Our study used flow cytometry,western blot(WB),real-time fluorescent quantitative PCR(RT-PCR),immunofluorescence methods,macrophage clearance and adoptive transfer experiments to evaluate the regulatory effect of leptin on airway inflammation and M1 macrophages.2.The corresponding mechanisms of leptin/obR on M1 macrophage polarization1)Bone marrow-derived macrophage(BMDMs)and neutrophils were isolated from mouse bone marrow which were intervened with different conditions.2)Flow cytometry,RT-PCR,and WB methods were used to detect the activation of M1 macrophages and obR-b-JNK/STAT3/AKT phosphorylation.3)The expression of CXCL2 were detected using RT-PCR and an ELISA assay.4)The chemotaxis of neutrophils were detected using a transwell assay.3.The relationship between serum leptin levels and the numbers of M1 macrophages in induced sputum in patients with asthma1)An assay ELISA was used to detect serum leptin levels.2)Flow cytometry were used to detect he numbers of M1 macrophages and neutrophils in induced sputum.3)WB was used to detect the activation level of obR-b in human macrophages.Results:1.Leptin/obR regulating M1 macrophage polarization in an obesity-associated neutrophil airway inflammation mouse model1)Compared with lean mice,high-fat diet-induced obese mice had higher serum leptin levels.2)Compared with LPS/OVA+OVA-induced lean mice,LPS/OVA+OVA-induced obese mice had higher percentages of neutrophils and M1 macrophage acctivation levels in bronchoalveolar lavage fluid,higher inflammatory infiltration levels,and the phosphorylation levels of ob-Rb.The inhibition and deletion of obR-b could significantly reduce those effects.5)The difference in neutrophil airway inflammation of obese and lean model mice was directly related to M1 macrophages.2.The corresponding mechanisms of leptin/obR on M1 macrophage polarization1)LPS/IFN-γ successfully induced the polarization of M1 macrophages,the phosphorylation levels of the obR-b/JNK/STAT3/AKT signaling pathway,the expression of CXCL2,and the chemotactic effects on neutrophils.2)Those effects could be reversed by obR-b/JNK/STAT3/AKT corresponding inhibitors.3.The relationship between serum leptin levels and the numbers of M1 macrophages in induced sputum in patients with asthma1)Obesity-related asthma had higher serum leptin levels,higher numbers of neutrophils and M1 macrophages in induced sputum.2)The numbers of M1 macrophages in induced sputum were significantly positively correlated with serum leptin levels in patients with asthma.4)Leptin synergizes with LPS/IFN-γ to enhance the activation level of obR-b in human M1 macrophages.Conclusion:1)Leptin participates in the mechanism of neutrophil airway inflammation and M1 macrophage polarization in obese mice.2)Leptin synergizes with LPS/IFN-γ to promote M1 macrophage polarization and neutrophil chemotaxis via upregulating the phosphorylation levels of obR-b/JNK/STAT3/AKT pathways.3)The correlation between leptin and M1 macrophages may be involved in the pathogenesis of obesity-associated neutrophil airway inflammation.25 pictures,15 tables,445 references...