Drp1-mediated mitochondrial fission promotes pulmonary fibrosis progression through the regulation of lipid metabolic reprogramming by ROS/HIF-1α.

Objective: To confirm the mechanism of dynamic-related protein 1 (Drp1)-mediated mitochondrial fission through ROS/HIF-1α-mediated regulation of lipid metabolic reprogramming in the progression of pulmonary fibrosis (PF).

Methods: A mouse model of PF was established by intratracheal instillation of bleomycin (BLM) (2.5 mg/kg). A PF cell model was constructed by stimulating MRC-5 cells with TGF-β (10 ng/mL). Pathological changes in the lung tissue and related protein levels were observed via tissue staining. The indicators related to lipid oxidation were detected by a kit, and lipid production was confirmed through oil red O staining. Inflammatory factors were detected by enzyme-linked immunosorbent assay (ELISA). RT-qPCR, Western blotting and immunofluorescence staining were used to detect the expression of genes and proteins related to the disease. We used CCK-8 and EdU staining to confirm cell proliferation, flow cytometry was used to confirm apoptosis and ROS levels, α-SMA expression was detected by immunofluorescence staining, and mitochondria were observed by MitoTracker staining.

Results: The BLM induced lung tissue structure and alveolar wall thickening in mice. Mitochondrial fission was observed in MRC-5 cells induced by TGF-β, which led to increased cell proliferation; decreased apoptosis; increased expression of collagen, α-SMA and Drp1; and increased lipid oxidation and inflammation. Treatment with the Drp1 inhibitor mdivi-1 or transfection with si-Drp1 attenuated the induction of BLM and TGF-β. For lipid metabolism, lipid droplets were formed in BLM-induced lung tissue and in TGF-β-induced cells, fatty acid oxidation genes and lipogenesis-related genes were upregulated, ROS levels in cells were increased, and the expression of HIF-1α was upregulated. Mdivi-1 treatment reversed TGF-β induction, while HO treatment or OE-HIF-1α transfection reversed the effect of mdivi-1.

Conclusion: In PF, inhibition of Drp1 can prevent mitochondrial fission in fibroblasts and regulate lipid metabolism reprogramming through ROS/HIF-1α; thus, fibroblast activation was inhibited, alleviating the progression of PF.