Abstract

Lung ischemia–reperfusion injury (IRI), a significant factor contributing to early mortality following lung transplantation (LTx), is driven by molecular mechanisms that are not yet fully understood. In this study, we elucidate a crucial signaling pathway initiated by extracellular histones (ex-His), which connects mitochondrial damage to inflammatory cell death. Through the use of a murine model of lung IRI and in vitro experiments with alveolar macrophages, we demonstrate that ex-His facilitate Drp1-dependent mitochondrial fission, resulting in the release of oxidized mitochondrial DNA (ox-mtDNA) into the cytosol. Our mechanistic analysis reveals that cytosolic ox-mtDNA is detected by the transcription factor IRF1, which subsequently upregulates NLRC5 at the transcriptional level. Additionally, we identify NLRC5 as a non-canonical scaffold that is essential for the assembly of the PANoptosome, a multi-protein complex that mediates PANoptosis, an inflammatory cell death pathway that aggravates tissue damage. The clinical relevance of this pathway was then examined in lung transplant recipients. An analysis of their peripheral blood mononuclear cells (PBMCs) revealed that patients who developed primary graft dysfunction (PGD) exhibited markedly elevated levels of circulating histones and cytosolic ox-mtDNA. This was associated with hyperactivation of the core signaling axis, characterized by increased Drp1 phosphorylation and elevated expression of IRF1 and NLRC5. Collectively, our study elucidates a comprehensive pathogenic cascade from an extracellular danger signal to a specific cell death program, identifying the ex-His-mitochondria-IRF1-NLRC5 axis as a critical driver of macrophage PANoptosis and a promising therapeutic target for alleviating lung IRI.