Department of Medicine, University of Calgary, Calgary, AB, Canada; Snyder Institute for Chronic Diseases, University of Calgary, Calgary, AB, Canada.
Department of Biochemistry and Molecular Biology, University of Calgary, Calgary, AB, Canada.
Cell Rep. 2018 Nov 6;25(6):1525-1536.e7. doi: 10.1016/j.celrep.2018.09.071.
The non-canonical caspase-4 and canonical NLRP3 inflammasomes are both activated by intracellular lipopolysaccharide (LPS), but the crosstalk between these two pathways remains unclear. Shiga toxin 2 (Stx2)/LPS complex, from pathogenic enterohemorrhagic Escherichia coli, activates caspase-4, gasdermin D (GSDMD), and the NLRP3 inflammasome in human THP-1 macrophages, but not mouse macrophages that lack the Stx receptor CD77. Stx2/LPS-mediated IL-1β secretion and pyroptosis are dependent on mitochondrial reactive oxygen species (ROS) downstream of the non-canonical caspase-4 inflammasome and cleaved GSDMD, which is enriched at the mitochondria. Blockade of caspase-4 activation and ROS generation as well as GSDMD deficiency significantly reduces Stx2/LPS-induced IL-1β production and pyroptosis. The NLRP3 inflammasome plays a significant role in amplifying Stx2/LPS-induced GSDMD cleavage and pyroptosis, with significant reduction of these responses in NLRP3-deficient THP-1 cells. Together, these data show that Stx2/LPS complex activates the non-canonical inflammasome and mitochondrial ROS upstream of the NLRP3 inflammasome to promote cytokine maturation and pyroptosis.
非经典的半胱天冬酶-4（caspase-4）和经典的 NOD、LRR 和富含半胱氨酸的域蛋白 3（NLRP3）炎性小体均被细胞内脂多糖（LPS）激活，但这两种途径之间的串扰仍不清楚。来自致病性肠出血性大肠杆菌的志贺毒素 2（Stx2）/LPS 复合物可激活人 THP-1 巨噬细胞中的 caspase-4、gasdermin D（GSDMD）和 NLRP3 炎性小体，但缺乏 Stx 受体 CD77 的小鼠巨噬细胞则不会。Stx2/LPS 介导的白细胞介素 1β（IL-1β）分泌和细胞焦亡依赖于非经典 caspase-4 炎性小体和裂解 GSDMD 下游的线粒体活性氧（ROS），GSDMD 在线粒体中富集。阻断 caspase-4 激活和 ROS 生成以及 GSDMD 缺乏可显著减少 Stx2/LPS 诱导的 IL-1β产生和细胞焦亡。NLRP3 炎性小体在放大 Stx2/LPS 诱导的 GSDMD 裂解和细胞焦亡中起重要作用，在 NLRP3 缺陷的 THP-1 细胞中，这些反应显著减少。综上所述，这些数据表明 Stx2/LPS 复合物激活非经典炎性小体和 NLRP3 炎性小体上游的线粒体 ROS，以促进细胞因子成熟和细胞焦亡。
