GPX4 Inhibitor Down-regulates BMPR2 Protein Expression in Lung Fibroblast

Idiopathic pulmonary fibrosis (IPF) is chronic progressive and irreversible lung disease that is characterized by aberrant myofibroblast differentiation and extracellular matrix (ECM) accumulation. Bone morphogenetic protein receptor 2 (BMPR2) was discovered to significantly decreased in human lung from IPF patients and lung fibrosis in mice. However, the molecular mechanisms of regulation of BMPR2 have not been well-studied. It has been reported that the products of lipid peroxidation increase in IPF lungs and bleomycin-induced murine lung fibrosis. It suggests lipid peroxidation is likely to play an important role in the pathogenesis of pulmonary fibrosis, but the effect of lipid peroxidation on BMPR2 in lung fibrosis has been unclear. GPX4 is an antioxidant enzyme to reduce phospholipid hydroperoxide which is involved into suppressing lipid peroxidation, and it has been identified to downregulated in IPF lungs and GPX4-deficient mice shows enhancement of bleomycin-induced lung fibrosis. In this study, we use GPX4 inhibitor, RSL3, to induce the lipid peroxidation in lung fibroblast cells to investigate its effects. Since that BMPR2 protein levels are significantly reduced in lung fibrosis. We treated RSL3 in normal human lung fibroblast (IMR90) cells in different doses and time points, and found that RSL3 (0.5μM) 3-hour treatment for significantly reduced BMPR2 protein levels. Next, BMP4-induced Phosphated-Smad1/5 expression could be reduced by RSL3 treatment. Further, proteasome inhibitor MG132 and lysosome inhibitor leupeptin was pre-treated for 1 hour and following stimulated RSL3 (0.5μM) another 3 hours. The result indicated MG132 rescued the reduction of BMPR2 by RSL3. It suggests that RSL3 downregulates BMPR2 protein through proteasome. Further, we performed ubiquitin assay in lung fibroblasts and identified RLS3 reducing BMPR2 protein through K48-linked polyubiquitination. In conclusion, this study demonstrates that RSL3-induced lipid peroxidation downregulates BMPR2 protein levels and BMP-Smad pathway via K48- linked polyubiquitination. It partially reveals the molecular regulation of BMPR2 in lung fibroblasts, and provides the potential research direction of BMPR2 modulation in lung fibrosis. This research was funded by grant 24PRE1198621 from American Heart Association. This abstract was presented at the American Physiology Summit 2025 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.