Atmospheric fine particulate matter (PM) induces pulmonary fibrosis by regulating different cell fates via autophagy.

The presence of respiratory diseases demonstrates a positive correlation with atmospheric fine particulate matter (PM) exposure. The respiratory system is the main target organ affected by PM, and exposure to PM elevates the likelihood of developing pulmonary fibrosis (PF). In this study, lung epithelial cell (BEAS-2B) and fibroblast (NIH-3T3) were used as in vitro exposure models to explore the mechanisms of PF. PM exposure caused mitochondrial damage in BEAS-2B cells and increased a fibrotic phenotype in NIH-3T3 cells. Epithelial cells and fibroblasts have different fates after PM exposure due to their different sensitivities to trigger autophagy. Exposure to PM inhibits mitophagy in BEAS-2B cells, which hinders the removal of damaged mitochondria and triggers cell death. In this process, the nuclear retention of the mitophagy-related protein Parkin prevents it from being recruited to mitochondria, resulting in mitophagy inhibition. In contrast, fibroblasts exhibit increased levels of autophagy, which may isolate PM and cause abnormal fibroblast proliferation and migration. Fibrotic phenotypes such as collagen deposition and increased α-actin also appear in fibroblasts. Our results identify PM as a trigger of PF and delineate the molecular mechanism of autophagy in PM induced PF, which provides new insights into the pulmonary injury.