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Metabolic characterization and RNA profiling reveal glycolytic dependence of pro-fibrotic phenotype of alveolar macrophages in lung fibrosis

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AJP Lung Cellular and Molecular Physiology

Published online on

Abstract

Metabolic reprogramming has been intrinsically linked to macrophage activation. Alveolar macrophages are known to play an important role in the pathogenesis of pulmonary fibrosis. However, systematic characterization of expression profile in these cells is still lacking. Furthermore, main metabolic programs and their regulation of cellular phenotype are completely unknown. In this study, we comprehensively analyzed the expression profile and main metabolic programs in alveolar macrophages from mice with or without experimental pulmonary fibrosis. We found that alveolar macrophages from both bleomycin and active TGF-β1 induced fibrotic mouse lungs demonstrated a primarily pro-fibrotic M2-like profile that was distinct from the well-defined M1 or any of the M2 subtypes. More importantly, we found that fibrotic lung alveolar macrophages assumed augmented glycolysis, which was likely attributed to enhanced expression of multiple key glycolytic mediators. We also found that fatty acid oxidation was upregulated in these cells. However, the pro-fibrotic M2-like profile of fibrotic lung alveolar macrophages was not dependent on fatty acid oxidation and synthesis or lipolysis, but instead on glycolysis, in contrast to the typical IL-4 induced macrophages M(IL-4). Additionally, glutaminolysis, a key metabolic program that has been implicated in numerous pathologies, was not required for the pro-fibrotic M2-like phenotype of these macrophages. In summary, our study identifies a unique expression and metabolic profile in alveolar macrophages from fibrotic lungs and suggests glycolytic inhibition as an effective anti-fibrotic strategy in treating lung fibrosis.