Lipoxin A4/FPR2 Signaling Mitigates Ferroptosis of Alveolar Epithelial Cells via NRF2-Dependent Pathway During Lung Ischemia-Reperfusion Injury

Abstract

Post-lung transplant (LTx) injury can involve sterile inflammation due to ischemia-reperfusion injury (IRI) that contributes to allograft dysfunction. In this study, we investigated the cell-specific role of ferroptosis (excessive iron-mediated cell death) in mediating lung IRI and investigated if specialized pro-resolving mediators such as Lipoxin A4 (LxA₄) can protect against ferroptosis in lung IRI. Single-cell RNA sequencing analysis of lung tissue from post-LTx patients was performed, and lung IRI was evaluated in C57BL/6 (WT), formyl peptide receptor 2 knockout (Fpr2^-/-) and nuclear factor erythroid 2-related factor 2 knockout (Nrf2^-/-) mice using a hilar-ligation model with or without LxA₄ administration. Furthermore, the protective efficacy of LxA₄ was evaluated employing a murine orthotopic LTx model and in vitro studies using alveolar type II epithelial (ATII) cells. The results show differential expression of ferroptosis-related genes in post-LTx patient samples compared to healthy controls. A significant increase in the levels of oxidized lipids and a reduction in the levels of intact lipids were observed in mice subjected to IRI compared to shams. Importantly, LxA₄ treatment attenuated pulmonary dysfunction, ferroptosis, and inflammation in WT mice subjected to lung IRI, but not in Fpr2^-/- or Nrf2^-/- mice after IRI. In the murine LTx model, LxA₄ treatment increased PaO₂ levels and attenuated lung IRI. Mechanistically, LxA₄-mediated protection involves an increase in NRF2 activation and glutathione concentration as well as a decrease in MDA levels in ATII cells. In summary, our results collectively show that LxA₄/FPR2 signaling on ATII cells mitigates ferroptosis via NRF2 activation and protects against lung IRI.

Keywords: ferroptosis; ischemia–reperfusion injury; lipoxin A4; liproxstatin‐1; lung transplant.