The Endotoxin Delivery Protein HMGB1 Mediates Caspase-11-Dependent Lethality in Sepsis. Immunity Caspase-11, a cytosolic endotoxin (lipopolysaccharide: LPS) receptor, mediates pyroptosis, a lytic form of cell death. Caspase-11-dependent pyroptosis mediates lethality in endotoxemia, but it is unclear how LPS is delivered into the cytosol for the activation of caspase-11. Here we discovered that hepatocyte-released high mobility group box 1 (HMGB1) was required for caspase-11-dependent pyroptosis and lethality in endotoxemia and bacterial sepsis. Mechanistically, hepatocyte-released HMGB1 bound LPS and targeted its internalization into the lysosomes of macrophages and endothelial cells via the receptor for advanced glycation end-products (RAGE). Subsequently, HMGB1 permeabilized the phospholipid bilayer in the acidic environment of lysosomes. This resulted in LPS leakage into the cytosol and caspase-11 activation. Depletion of hepatocyte HMGB1, inhibition of hepatocyte HMGB1 release, neutralizing extracellular HMGB1, or RAGE deficiency prevented caspase-11-dependent pyroptosis and death in endotoxemia and bacterial sepsis. These findings indicate that HMGB1 interacts with LPS to mediate caspase-11-dependent pyroptosis in lethal sepsis. 10.1016/j.immuni.2018.08.016

The role of type 1 interferons in coagulation induced by gram-negative bacteria. Yang Xinyu,Cheng Xiaoye,Tang Yiting,Qiu Xianhui,Wang Zhongtai,Fu Guang,Wu Jianfeng,Kang Haixia,Wang Jing,Wang Haichao,Chen Fangping,Xiao Xianzhong,Billiar Timothy R,Lu Ben Blood Bacterial infection not only stimulates innate immune responses but also activates coagulation cascades. Overactivation of the coagulation system in bacterial sepsis leads to disseminated intravascular coagulation (DIC), a life-threatening condition. However, the mechanisms by which bacterial infection activates the coagulation cascade are not fully understood. Here we show that type 1 interferons (IFNs), a widely expressed family of cytokines that orchestrate innate antiviral and antibacterial immunity, mediate bacterial infection-induced DIC by amplifying the release of high-mobility group box 1 (HMGB1) into the bloodstream. Inhibition of the expression of type 1 IFNs and disruption of their receptor IFN-α/βR or downstream effector (eg, HMGB1) uniformly decreased gram-negative bacteria-induced DIC. Mechanistically, extracellular HMGB1 markedly increased the procoagulant activity of tissue factor by promoting the externalization of phosphatidylserine to the outer cell surface, where phosphatidylserine assembles a complex of cofactor-proteases of the coagulation cascades. These findings not only provide novel insights into the link between innate immune responses and coagulation, but they also open a new avenue for developing novel therapeutic strategies to prevent DIC in sepsis. 10.1182/blood.2019002282

Bacterial Endotoxin Activates the Coagulation Cascade through Gasdermin D-Dependent Phosphatidylserine Exposure. Yang Xinyu,Cheng Xiaoye,Tang Yiting,Qiu Xianhui,Wang Yupeng,Kang Haixia,Wu Jianfeng,Wang Zhongtai,Liu Yukun,Chen Fangping,Xiao Xianzhong,Mackman Nigel,Billiar Timothy R,Han Jiahuai,Lu Ben Immunity Excessive activation of the coagulation system leads to life-threatening disseminated intravascular coagulation (DIC). Here, we examined the mechanisms underlying the activation of coagulation by lipopolysaccharide (LPS), the major cell-wall component of Gram-negative bacteria. We found that caspase-11, a cytosolic LPS receptor, activated the coagulation cascade. Caspase-11 enhanced the activation of tissue factor (TF), an initiator of coagulation, through triggering the formation of gasdermin D (GSDMD) pores and subsequent phosphatidylserine exposure, in a manner independent of cell death. GSDMD pores mediated calcium influx, which induced phosphatidylserine exposure through transmembrane protein 16F, a calcium-dependent phospholipid scramblase. Deletion of Casp11, ablation of Gsdmd, or neutralization of phosphatidylserine or TF prevented LPS-induced DIC. In septic patients, plasma concentrations of interleukin (IL)-1α and IL-1β, biomarkers of GSDMD activation, correlated with phosphatidylserine exposure in peripheral leukocytes and DIC scores. Our findings mechanistically link immune recognition of LPS to coagulation, with implications for the treatment of DIC. 10.1016/j.immuni.2019.11.005

Heparin prevents caspase-11-dependent septic lethality independent of anticoagulant properties. Tang Yiting,Wang Xiangyu,Li Zhaozheng,He Zhihui,Yang Xinyu,Cheng Xiaoye,Peng Yue,Xue Qianqian,Bai Yang,Zhang Rui,Zhao Kai,Liang Fang,Xiao Xianzhong,Andersson Ulf,Wang Haichao,Billiar Timothy R,Lu Ben Immunity Heparin, a mammalian polysaccharide, is a widely used anticoagulant medicine to treat thrombotic disorders. It is also known to improve outcomes in sepsis, a leading cause of mortality resulted from infection-induced immune dysfunction. Whereas it is relatively clear how heparin exerts its anticoagulant effect, the immunomodulatory mechanisms enabled by heparin remain enigmatic. Here, we show that heparin prevented caspase-11-dependent immune responses and lethality in sepsis independent of its anticoagulant properties. Heparin or a chemically modified form of heparin without anticoagulant function inhibited the alarmin HMGB1-lipopolysaccharide (LPS) interaction and prevented the macrophage glycocalyx degradation by heparanase. These events blocked the cytosolic delivery of LPS in macrophages and the activation of caspase-11, a cytosolic LPS receptor that mediates lethality in sepsis. Survival was higher in septic patients treated with heparin than those without heparin treatment. The identification of this previously unrecognized heparin function establishes a link between innate immune responses and coagulation. 10.1016/j.immuni.2021.01.007

Z-DNA binding protein 1 promotes heatstroke-induced cell death. Science (New York, N.Y.) Heatstroke is a heat stress-induced, life-threatening condition associated with circulatory failure and multiple organ dysfunctions. If global warming continues, heatstroke might become a more prominent cause of mortality worldwide, but its pathogenic mechanism is not well understood. We found that Z-DNA binding protein 1 (ZBP1), a Z-nucleic acid receptor, mediated heatstroke by triggering receptor-interacting protein kinase 3 (RIPK3)-dependent cell death. Heat stress increased the expression of ZBP1 through heat shock transcription factor 1 (HSF1) and activated ZBP1 through a mechanism independent of the nucleic acid sensing action. Deletion of ZBP1, RIPK3, or both mixed lineage kinase domain-like (MLKL) and caspase-8 decreased heat stress-induced circulatory failure, organ injury, and lethality. Thus, ZBP1 appears to have a second function that orchestrates host responses to heat stress. 10.1126/science.abg5251