A Novel Mediator Extracellular Caspase-1 Worsens Acute Lung Injury in Sepsis 2257697

Introduction Sepsis is a severe systemic inflammatory condition. Over half of the septic patients develop acute lung injury (ALI), worsening mortality. Inflammasome activation triggers procaspase-1 cleavage to active Caspase-1 (p10/p20 tetramer), which then cleaves GSDMD, forming membrane pores for the release of DAMPs. We hypothesize that Caspase-1 is released via GSDMD pores, and extracellular Caspase-1 (eCasp-1) exacerbates ALI in sepsis. Methods Plasma from surgical intensive care unit patients and healthy controls was analyzed for eCasp-1 by ELISA. Sepsis was induced in mice by cecal ligation and puncture, and their plasma was assessed for eCasp-1. Murine peritoneal macrophages were treated with LPS+Nigerecin ± GSDMD inhibitor disulfiram, and eCasp-1 levels were assessed. The eCasp-1/TLR4 interaction was assessed by BIAcore, and the TLR4-mediated effects of eCasp-1 were evaluated using TLR4-/- mice. A small peptide, C16, was developed to interrupt eCasp-1/TLR4 interaction, and its therapeutic effects on ALI were evaluated in septic mice. Results We discovered that the p20 subunit of Caspase-1 (termed eCasp-1) significantly increased in the blood of patients and septic mice but is undetectable in healthy controls or sham mice. We determined that eCasp-1 is released via GSDMD pores. We identified a strong affinity between eCasp-1 and TLR4, demonstrating that eCasp-1-induced inflammation occurs via TLR4. eCasp-1 administration (i.p.) significantly increased systemic inflammatory and organ injury markers in WT mice. These effects were significantly reduced in TLR4-/- mice. In septic mice, C16 treatment significantly decreased blood injury and inflammatory markers, reduced lung chemokine/cytokine expression, and decreased histologic lung injury. C16 treatment significantly improved the survival rate in sepsis from 40% to 80%. Conclusion eCasp-1 is a novel DAMP that exacerbates ALI in sepsis. Targeting eCasp-1 with C16 attenuates ALI and improves survival, suggesting a novel therapeutic approach for sepsis. Funding Source National Institutes of Health (NIH) grants R35GM118337, and R01HL076179 Topic Categories Innate Immune Responses and Host Defense: Molecular Mechanisms (INM)