Abstract
Background: Asthma is a complex respiratory disease characterized by airway inflammation and remodeling. MicroRNAs (miRNAs) mediate various cellular processes including macrophage polarization and play an important role in the pathogenesis of asthma. In present study, we aimed to screen miRNA profiling involved in macrophage polarization and investigate its possible functions and mechanisms.Methods: An OVA-sensitized mouse model was established and 2-chloroadenosine (2-CA) was used to interfere with macrophages. The airway inflammation and remodeling were assessed. The identification and function of M2 alveolar macrophages were assessed by flow cytometry, RT-qPCR, arginase activity and co-culture experiment. Microarray screening was used to select miRNAs which were related to macrophage polarization and RNA interference (RNAi) technique was performed to confirm the function of the selected miRNA and its target gene.Results: Alveolar macrophages of asthmatic mice showed significant M2 polarization. 2-CA alleviated airway inflammation and remodeling as well as M2 polarization. In vitro, IL-4-induced M2 macrophages promoted the proliferation of α-SMA-positive cells. And miRNA profiling showed a remarkable increased expression of miR-378a-3p in IL-4 induced M2 macrophages. Dual luciferase reporter assay confirmed growth factor receptor binding protein 2 (GRB2) was a target gene of miR-378a-3p. A miR-378a-3p inhibitor and knockdown of GRB2 repolarized alveolar macrophages from M1 to M2 phenotype.Conclusion: Our findings suggest that miR-378a-3p/GRB2 pathway regulates the polarization of alveolar macrophages which acts as a potential therapeutic target for airway inflammation and remodeling in asthma.
Highlights
Asthma is a chronic inflammatory airway disorder in which eosinophils, neutrophils, macrophages and CD4+ T cells migrate into the airways and release powerful mediators which lead to airway inflammation and remodeling (Anderson 2008; Holgate 2012; Fehrenbach et al, 2017)
HE staining revealed inflammatory cell infiltration; a large number of Periodic acidSchiff (PAS)+ goblet cells were detected by PAS staining; immunohistochemical staining of ECP-1 showed a significant increase of eosinophilic infiltration; the total amount of collagen was significantly increased as defined by Masson staining; and marked airway smooth muscle cell hyperplasia and hypertrophy have been identified by α-SMA immunohistochemical staining of the lungs (Figure 1B)
With OVA challenges, a significant downregulation of CD80+ classically activated macrophages (M1) macrophages and upregulation of CD206+ alternatively activated macrophages (M2) macrophages were detected in the Bronchoalveolar lavage fluid (BALF) of asthmatic mice (Figure 1F)
Summary
Asthma is a chronic inflammatory airway disorder in which eosinophils, neutrophils, macrophages and CD4+ T cells migrate into the airways and release powerful mediators which lead to airway inflammation and remodeling (Anderson 2008; Holgate 2012; Fehrenbach et al, 2017). It has been reported that the depletion of AMs in mice with asthma attenuated airway inflammation and remodeling (Lee et al, 2015). Hadjigol et al found that the depletion of pulmonary macrophages by administration of 2-CA into the lungs suppressed airway hyperresponsiveness and reduced the expression of IL-13, TNF-α and IFN-γ (Hadjigol et al, 2020). M2 macrophages have been known to facilitate the Th2 immune response and the secretion of chemokines and cytokines which regulate airway inflammation, tissue repair and airway remodeling in the lung (Murray and Wynn 2011; Yang et al, 2012; Byrne et al, 2015). MicroRNAs (miRNAs) mediate various cellular processes including macrophage polarization and play an important role in the pathogenesis of asthma. We aimed to screen miRNA profiling involved in macrophage polarization and investigate its possible functions and mechanisms
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