Fine particulate matter inhibits phagocytosis of macrophages by disturbing autophagy

Mounting evidence from epidemiological and clinical studies has revealed marked correlations between the air pollutant fine particulate matter (FPM) and respiratory diseases. FPM reaches distal airways and deposits in alveolar regions where it can act directly on alveolar macrophages. However, the detailed effect of FPM on the physiological function of alveolar macrophages and the underlying mechanisms remain unclear. In this study, we showed that exposing THP-1-derived macrophages to FPM led to autophagy dysfunction. FPM activated the extracellular signal-regulated kinase 1/2 (ERK1/2) signaling pathway, which promoted the expression of autophagy-related 2A (ATG2A) and reactive oxygen species generation. The overexpression of ATG2A enhanced the synthesis of autophagic membranes, and the excessive production of reactive oxygen species caused autophagy flux inhibition through disrupting the lysosomal activity. More importantly, FPM impaired the phagocytic ability of macrophages on Escherichia coli and apoptotic neutrophils. Finally, we showed that restoring autophagy rescued the impairment of phagocytic ability induced by FPM. In summary, these results reveal the molecular mechanism of autophagy dysfunction caused by FPM and provide a novel approach to resolve the impaired function of macrophages in respiratory diseases induced by FPM.