Classically Activated Macrophages Protect against Lipopolysaccharide-induced Acute Lung Injury by Expressing Amphiregulin in Mice

Abstract

Background Alveolar macrophages (AMs) activated into M1 phenotype are involved in the development of lipopolysaccharide-induced acute lung injury (ALI). However, whether AMs express amphiregulin and what roles amphiregulin plays in lipopolysaccharide-induced ALI remain poorly understood. Methods Acute lung injury was induced by intratracheal instillation of lipopolysaccharide in male C57BL/6 mice. Lung injury scores, level of protein, and level of neutrophils in bronchial alveolar lavage fluid of lipopolysaccharide-induced ALI mice were compared with those in mice challenged with recombinant exogenous amphiregulin and antiamphiregulin antibody. Amphiregulin expression in macrophages and neutrophils in bronchial alveolar lavage fluid of lipopolysaccharide-induced ALI mice was determined by using immunofluorescence technique and further detected in M0, M1, and M2 phenotypes of both peritoneal macrophages and AMs. The effect of amphiregulin on apoptosis of MLE12 cells and activation of epithelial growth factor receptor-AKT pathway were, respectively, examined by using flow cytometry and western blotting. Results Alveolar macrophages were found to highly express amphiregulin in ALI mice. Amphiregulin neutralization aggravated, whereas recombinant exogenous amphiregulin attenuated lipopolysaccharide-induced ALI in mice (n = 6). In cultured AMs and peritoneal macrophages, amphiregulin was mainly generated by M1, rather than M0 or M2 phenotype (n = 5). Apoptosis ratio of lipopolysaccharide-challenged MLE12 cells was significantly reduced by recombinant exogenous amphiregulin from 16.60 ± 1.82 to 9.47 ± 1.67% (n = 5) but significantly increased from 17.45 ± 1.13 to 21.67 ± 1.10% (n = 5) after stimulation with supernatant of M1-polarized AM media conditioned with amphiregulin-neutrolizing antibody. Western blotting revealed that amphiregulin activated epithelial growth factor receptor and AKT in the lung tissues and MLE12 cells (n = 5). Conclusions Different from the common notion that classically activated AMs have just a detrimental effect on the lung tissues, the results of this study showed that classically activated AMs also exerted a protective effect on the lung tissues by producing high-level amphiregulin in lipopolysaccharide-induced ALI.

Combined Collagen-Induced Arthritis and Organic Dust-Induced Airway Inflammation to Model Inflammatory Lung Disease in Rheumatoid Arthritis

“…The data support a potential balance shift with the coexposure modeling towards interstitial disease because collagen deposition and tissue levels of extracellular matrix proteins (ie, hyaluronan and fibronectin) remained elevated or augmented in the setting of CIA + ODE despite decreased levels of the classic inflammatory mediators. AREG has been characterized as both protective and injurious in the progression of various lung diseases as it can promote proresolution effector cell function and epithelial repair processes, but overexpression can lead to fibrotic remodeling . Amphiregulin remained elevated with coexposure in the lung tissues, which is interpreted to be supportive of evidence towards interstitial disease.…”

Airway macrophages as the guardians of tissue repair in the lung

“…A direct function of amphiregulin in restoring lung function was initially demonstrated in influenza virus‐infected mice and patients with COPD and asthma have increased amphiregulin expression in their sputum and lungs . An increasing number of reports suggest that myeloid cells in the lung may also produce amphiregulin, and recently, it was demonstrated that proinflammatory AM produce high levels of amphiregulin during lipopolysaccharide‐induced lung injury to dampen inflammation . Similarly, in a bleomycin mouse lung injury model, amphiregulin generated from adoptively transferred AM promoted activation of fibroblast proliferation, motility, and indirectly, myofibroblast differentiation .…”

Inhibition of glutamine metabolism accelerates resolution of acute lung injury

“…; Xu et al. ). Prior studies have found that AREG promotes epithelial repair in LPS‐induced ALI and influenza infection, and in vitro studies have shown that it enhances regulatory T cell activity (Monticelli et al.…”

“…In fact, administration of an antibody to neutralize AREG worsens LPS‐induced ALI, whereas administration of exogenous AREG ameliorates lung injury (Xu et al. ; Ogata‐Suetsugu et al. ).…”