High-mobility group box-1 (HMGB1), a ubiquitous nuclear protein, acts as a late mediator of lethality when released extracellularly during sepsis. The major source of circulating HMGB1 in sepsis is hepatocytes. However, the mechanism of HMGB1 release of hepatocytes during sepsis is not very clear. We have previously shown that bacterial endotoxin [lipopolysaccharide (LPS)] sensing pathways, including Toll-like receptor (TLR)4 and caspase-11, regulate hepatocyte HMGB1 release in response to LPS. Here, we report the novel function of caspase-11 and gasdermin D (GsdmD) in LPS-induced active HMGB1 released from hepatocytes. HMGB1 release during endotoxemia was caspase-11/GsdmD dependent via an active way in vivo and in vitro. Caspase-11/GsdmD was responsible for HMGB1 translocation from nucleus to the cytoplasm via calcium changing-induced phosphorylation of calcium-calmodulin kinase kinase (camkk)β during endotoxemia. Cleaved GsdmD accumulated on the endoplasmic reticulum, suggesting this may lead to calcium leak and intracellular calcium increase. Furthermore, we investigated that exosome was an important pathway for HMGB1 release from hepatocytes; this process was dependent on TLR4, independent of caspase-11 and GsdmD in vivo and in vitro. These findings provide a novel mechanism that TLR4 signaling results in an increase in caspase-11 expression, as well as increased exosome release, while caspase-11/GsdmD activation/cleavage leads to accumulation of HMGB1 in the cytoplasm through a process associated with the release of calcium from the endoplasmic reticulum and camkkβ activation.

中文翻译：

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LPS 通过 TLR4 和 Caspase-11/GSDMD 信号传导的协调活动，诱导活性 HMGB1 从肝细胞释放到外泌体中。


高迁移率族盒-1 (HMGB1) 是一种普遍存在的核蛋白，在脓毒症期间释放到细胞外时可充当致死性的晚期介质。脓毒症中循环 HMGB1 的主要来源是肝细胞。然而，脓毒症期间肝细胞释放HMGB1的机制尚不十分清楚。我们之前已经证明细菌内毒素[脂多糖（LPS）]传感途径，包括Toll样受体（TLR）4和caspase-11，调节肝细胞响应LPS释放HMGB1。在此，我们报道了 caspase-11 和gasdermin D (GsdmD) 在 LPS 诱导的肝细胞释放活性 HMGB1 中的新功能。内毒素血症期间 HMGB1 的释放通过体内和体外的主动方式依赖于 caspase-11/GsdmD。 Caspase-11/GsdmD 在内毒素血症期间通过钙变化诱导的钙钙调蛋白激酶激酶 (camkk)β 磷酸化负责 HMGB1 从细胞核易位到细胞质。裂解的 GsdmD 在内质网上积累，表明这可能导致钙泄漏和细胞内钙增加。此外，我们研究了外泌体是肝细胞释放 HMGB1 的重要途径。在体内和体外，该过程依赖于TLR4，独立于caspase-11和GsdmD。这些发现提供了一种新机制，即 TLR4 信号传导导致 caspase-11 表达增加以及外泌体释放增加，而 caspase-11/GsdmD 激活/裂解通过与释放相关的过程导致 HMGB1 在细胞质中积累来自内质网的钙和 camkkβ 激活。