DLL4+ neutrophils promote Notch1-mediated endothelial PANoptosis to exacerbate acute lung injury in sepsis.

Neutrophils play a critical role in sepsis-induced acute lung injury (ALI). Extracellular cold-inducible RNA-binding protein (eCIRP), a damage-associated molecular pattern, promotes neutrophil heterogeneity. While delta-like ligand 4 (DLL4) expression has been studied in various cell populations, its expression in neutrophils and impact on inflammation remain unknown. Here, we discovered that eCIRP induces DLL4+ neutrophils. These neutrophils trigger PANoptosis, a novel proinflammatory form of cell death initiated by Z-DNA-binding protein-1 (ZBP1) in pulmonary vascular endothelial cells (PVECs). In sepsis, DLL4+ neutrophils increase in the blood and lungs, upregulating ZBP1, cleaved gasdermin D, cleaved caspase-3, and phosphorylated MLKL, all of which are markers of PANoptosis, exacerbating ALI. DLL4 binds to Notch1 on PVECs and activates Notch1 intracellular domain to increase ZBP1-mediated endothelial PANoptosis. We discovered what we believe to be a novel Notch1-DLL4 inhibitor (NDI), derived from Notch1 to specifically block this interaction. Our findings reveal that NDI reduced endothelial PANoptosis in vitro and in vivo, attenuated pulmonary injury induced by DLL4+ neutrophils, and decreased lung water content and permeability, indicating improved barrier function. NDI also reduced serum injury and inflammatory markers and improved survival rate in sepsis. These findings underscore the Notch1-DLL4 pathway's critical role in DLL4+ neutrophil-mediated ALI. Targeting the Notch1-DLL4 interaction with an NDI represents a promising therapeutic strategy for sepsis-induced ALI.