Lipoxin A4 mitigates ferroptosis via FPR2 signaling during lung ischemia-reperfusion injury

Abstract Ischemia-reperfusion injury (IRI) after lung transplantation entails dysregulation of inflammation-resolution pathways leading to primary graft dysfunction. We investigated the role of ω-3-derived specialized pro-resolving lipid mediators, i.e. Lipoxin A4 (LxA4), and formyl peptide receptor (FPR2) signaling in the resolution of lung IRI. We used an established murine model of lung hilar ligation for IRI using C57BL/6 wild-type (WT) and FPR2−/− mice that underwent sham surgery or IRI (1hr left lung ischemia followed by 6- or 24hrs reperfusion). Lung function was measured using an isolated, buffer-perfused apparatus. Cytokine levels were measured in bronchoalveolar lavage (BAL) fluid, and neutrophil infiltration was assessed by immunohistochemistry. Post-lung transplant BAL from human patients was analyzed by liquid chromatography-mass spectrometry that demonstrated a significant increase in LxA4 on day 7 compared to days 0 and 1. In the murine model, we observed a significant increase in hallmarks of ferroptosis i.e. induction of lipid peroxidation (malonyldialdehyde), inhibition of glutathione peroxidase 4 (GPX4) as well as nuclear factor erythroid 2 (Nrf2) after IRI. Treatment of WT mice with recombinant LxA4 significantly attenuated lung dysfunction (decreased airway resistance and pulmonary artery pressure, and increased pulmonary compliance), inflammation (IL-17, TNF-a, CXCL1, HMGB1), injury (neutrophil infiltration) and ferroptosis (decreased MDA as well as increased Nrf2 and GPX4 expressions) compared to IRI alone, that was abolished in LxA4 treated-FPR2−/− mice. Collectively, our results indicate that lung IRI is regulated by ferroptosis which can be prevented by LxA4/FPR2-mediated signaling.