H3K18la- driven neutrophil secretory autophagy promotes pulmonary endothelial dysfunction in sepsis-induced lung injury

Endothelial dysfunction is a critical determinant of sepsis-associated organ injury, often driven by its interaction with overactivated immune cells. Neutrophils, the dominant early responders in sepsis, contribute to endothelial barrier disruption, yet the underlying metabolic and epigenetic mechanisms remain poorly understood. Here, we observed elevated intracellular lactate levels in neutrophils from septic patients which correlated with organ dysfunction and systemic inflammatory markers. Mechanistically, lactate-induced histone H3K18 lactylation (H3K18la) enhanced ATG7/GSA7 (autophagy related 7) transcription, initiating a non-degradative, secretory autophagy program. This facilitated the extracellular release of IL1B/IL-1B (interleukin 1 beta), a key driver of endothelial dysfunction. Interference of lactate production, ATG7 expression or IL1B signaling alleviated endothelial dysfunction in vitro. In vivo, myeloid-specific deletion of the lactylation writer EP300/p300 (EP300 lysine acetyltransferase) mitigated pulmonary endothelial dysfunction and lung injury. Additionally, the stress-responsive transcription factor ATF4/CREB-2 (activating transcription factor 4) was found to directly interact with both EP300 and H3K18la, amplifying H3K18la-driven ATG7 transcription. Our findings uncover a metabolically driven, epigenetically regulated secretory autophagy pathway in neutrophils that mediates endothelial dysfunction. Our study provides mechanistic insights into neutrophil-endothelial crosstalk in sepsis and identifies EP300, ATG7, and IL1B as potential therapeutic targets for sepsis. Abbreviations: ALI: acute lung injury; ANOVA: analysis of variance; ATF4/CREB-2: activating transcription factor 4; ATG7/GSA7: autophagy related 7; ATP: adenosine triphosphate; BafA1: bafilomycin A₁; BMDN: bone marrow-derived neutrophil; C-CASP1: cleaved-caspase 1; CDH5/CD144: cadherin 5; CRP/PTX1: C-reactive protein; CST3: cystatin C; CXCL8/IL-8: C-X-C motif chemokine ligand 8; DAPI: 4’,6-diamidino-2-phenylindole; DEG: differentially expressed gene; dHL-60: dimethyl sulfoxide-differentiated HL-60 cell; DMSO: dimethyl sulfoxide; ELISA: enzyme-linked immunosorbent assay; EP300/p300: EP300 lysine acetyltransferase; GOT1/AST: glutamic-oxaloacetic transaminase 1; GPT/ALT: glutamic – pyruvic transaminase; GSDMD-N: gasdermin D N-terminal; H&E: hematoxylin and eosin; H3K18la: histone H3K18 lactylation; HRP: horseradish peroxidase; ICU: intensive care unit; IHC: immunohistochemistry; IL1B/IL-1B: interleukin 1 beta; IL1R1/CD121A: interleukin 1 receptor type 1; IL6/IL-6: interleukin 6; KEGG: Kyoto Encyclopedia of Genes and Genomes; LAMP1/CD107a: lysosome associated membrane protein 1; LDHA: lactate dehydrogenase A; LPS: lipopolysaccharide; 3-MA: 3-methyladenine; NLRP3/NALP3: NLR family pyrin domain containing 3; PBS: phosphate-buffered saline; PCT: procalcitonin; PMN: peripheral neutrophils; Rapa: rapamycin; RNA-seq: RNA-sequencing; SERPINE1/PAI1: serpin family E member 1; SDS-PAGE: sodium dodecyl sulfate polyacrylamide gel electrophoresis; SOFA: Sequential Organ Failure Assessment; SQSTM1/p62: sequestosome 1; TEM: transmission electron microscopy; TNF/TNF-alpha: tumor necrosis factor; panKla: pan-histone lactylation; VCAM1/CD106: vascular cell adhesion molecule 1.