IL-33 as a component of neutrophil extracellular traps mediates contrast-induced acute kidney injury by promoting ferroptosis in tubular epithelial cells.
INTRODUCTION Contrast-induced acute kidney injury (CIAKI) is a leading cause of hospital-acquired kidney dysfunction, yet its immune-mediated pathogenic mechanisms remain poorly defined. Neutrophil extracellular traps (NETs) have been implicated in acute kidney injury. However, whether contrast agents directly induce NETs formation and whether NETs drive tubular ferroptosis through IL-33 has not been investigated. METHODS A prospective cohort of 330 patients undergoing coronary angiography was enrolled, with serial measurement of circulating NETs markers (myeloperoxidase, neutrophil elastase) and IL-33 at pre-contrast, two- and 12-hour time points. A murine CIAKI model was established in wild-type, peptidyl arginine deaminase 4 (PAD4) -knockout, and IL-33-knockout mice, and single-cell transcriptomic profiling of CIAKI kidneys was performed. In vitro, the serine/threonine kinase IKKα- and β-catenin-overexpressing and knockdown HK-2 cells were stimulated with iodixanol-induced NETs to evaluate how NETs regulate ferroptosis through IL-33-mediated modulation of IKKα and β-catenin. RESULTS CIAKI occurred in 12.1% (40/330) of patients. Circulating NETs markers and IL-33 were significantly elevated at two and 12 hours post-contrast in CIAKI compared with non-CIAKI patients. Single-cell transcriptomics identified neutrophils as the predominant source of IL-33 in CIAKI kidneys and revealed enrichment of NET formation and ferroptosis pathways. In vivo, PAD4 and IL-33 deficiency each significantly attenuated NETs and ferroptosis in CIAKI mice. Mechanistically, IL-33-enriched NETs suppressed IKKα expression, disrupted IKKα-β-catenin interaction, and impaired β-catenin nuclear translocation, thereby de-repressing long chain acyl CoA synthetase 4 transcription and amplifying ferroptotic injury. Restoration of IKKα stabilized β-catenin and attenuated NET-induced ferroptosis. CONCLUSION Our study demonstrates that IL-33-enriched NETs promote renal tubular ferroptosis in CIAKI by suppressing IKKα and impairing β-catenin nuclear translocation. These findings identify the NETs-IL-33-IKKα-β-catenin pathway as a novel and therapeutically actionable mechanism underlying CIAKI, providing potential targets for its diagnosis and treatment.