Caspase-11-mediated HMGB1 release from the liver drives immune cell pyroptosis in sepsis.

Abstract

Abstract High mobility group box 1 (HMGB1) was identified as a damage associated molecular pattern in sepsis. Neutralization of the HMGB1 even 24 hrs after the onset of sepsis is protective in experimental models. However, the sources of extracellular HMGB1 in sepsis and its function are not known. To address these questions, we generated myeloid (Lyz-creX HMGB1loxp/loxp) and hepatocyte (HC)-specific (Alb-creX HMGB1loxp/loxp) mouse strains and subjected these mice to cecal ligation and puncture (CLP) sepsis. Whereas CLP led to significant and sustained increases in HMGB1 levels in wild type and myeloid-specific HMGB1−/− mice, the levels were 75% lower in HC-specific HMGB1−/− mice at 18 hrs. This indicates that the liver is dominant source of HMGB1 during sepsis. The HC-specific knockout mice also showed significantly higher survival rates, as well as decreased immune cell pyroptosis in the peritoneum, spleen, and gut. Interestingly, HMGB1 level increased in HC culture media after LPS stimulation, which was not associated with cell death. Furthermore, using Liquid chromatography–mass spectrometry, we found that the HMGB1 released from HC are mainly acetyl form, suggesting that HC actively releases HMGB1 after LPS stimulation. We also found that the release of HMGB1 from cultured LPS-treated HC was TLR4 and caspase-11-dependent. Co-culture of wild type but not HMGB1−/− HC with bone marrow-derived macrophages led to increased pyroptosis of the cultured macrophages in response to LPS in a caspase-11-dependent manner. Our findings indicate that HC release HMGB1 during sepsis in a process that caspase-11-dependent and that liver-derived HMGB1 drives immune cell pyroptosis in severe sepsis.