HIF-1α Promotes Macrophage Extracellular Trap Formation and Exacerbates Acute Lung Injury in Neonatal Sepsis.

Background: Acute lung injury (ALI) is a major contributor to mortality in neonatal sepsis, yet the mechanisms underlying early lung damage remain incompletely understood. Although extracellular traps (ETs) have been implicated in inflammatory injury, the cellular origin and regulatory pathways of ET formation in neonatal sepsis remain unclear. This study aimed to determine the source of ETs and to investigate the role of hypoxia-inducible factor-1α (HIF-1α) in regulating macrophage extracellular traps (METs) formation and lung injury. Methods: Neonatal sepsis was induced in mice by intraperitoneal injection of cecal slurry. METs formation was assessed by immunofluorescence staining, Western blotting, and extracellular DNA quantification. Selective depletion of macrophages or neutrophils was performed to determine the cellular source of ETs. In vitro experiments were conducted using macrophages stimulated with lipopolysaccharide or phorbol 12-myristate 13-acetate. RNA sequencing analysis and pharmacological inhibition were used to examine the roles of HIF-1α, glycolysis, and enolase 2 (ENO2) in METs formation, lung injury, and survival outcomes. Results: We identify macrophages as a predominant source of ETs in the lung and demonstrate that METs contribute to lung injury in neonatal sepsis. Depletion of macrophages or pharmacological inhibition of METs formation markedly attenuated lung injury and improved survival in neonatal sepsis mice. Mechanistically, we suggest that HIF-1α promotes METs formation by driving glycolysis in macrophages. Furthermore, this process appears to involve the upregulation of key glycolytic enzymes, including ENO2, potentially facilitating METs release. In turn, METs are implicated in enhancing macrophage inflammatory activation, which could exacerbate lung injury. Importantly, pharmacological targeting of HIF-1α pathways reduces METs formation, attenuates lung inflammation, and improves survival outcomes. Conclusions: These findings suggest a role for HIF-1α in regulating METs formation and support that targeting this pathway could represent a potential therapeutic strategy for neonatal sepsis-associated acute lung injury.