Pro-fibrotic macrophages escape redox associated cell death by upregulation of anti-ferroptotic metabolic pathways

Increasing evidence suggests macrophages play a crucial role in fibrosis pathogenesis, including lung fibrosis. Understanding mechanisms that underly pro-fibrotic macrophage can help identify new drug targets for anti-fibrotic therapies. Lung fibrosis has been associated with oxidative stress. Here, we hypothesize that pro-fibrotic macrophages have distinct metabolic adaptations aiding their survival under conditions of oxidative stress. In vitro exposure of human primary macrophages to pro-fibrotic (IL4/IL13+TNFα) and pro-reparative (IL4/IL13) cytokine cocktails induced transcriptional phenotypes resembling those found in respective macrophage populations in lungs of patients with idiopathic pulmonary fibrosis (IPF). Multi-omics analysis revealed distinct expression patterns of redox balance-associated regulators involved in ferroptosis, in homeostatic and fibrotic primary human macrophages. Importantly, these metabolic pathways were also observed in fibrotic and reparative macrophages in fibrotic lungs. Inhibitors were used to test the relevance of these metabolic adaptations to cellular survival and ferroptosis sensitivity in pro-fibrotic and pro-reparative macrophages. Pro-fibrotic macrophages exhibited a priori protection from ferroptosis, in contrast to pro-reparative macrophages. Mechanistically, this protection could be linked to the expression of GPX4 and GCH1 pathways, known regulators of ferroptosis protection in cancer cells. We found that pro-fibrotic macrophages adapt metabolically to resist redox stress-related cell death. This reveals new metabolic regulators in pro-fibrotic macrophages offering potential drug targets for managing fibrosis.