Staphylococcus aureus α-Toxin Induces Inflammatory Cytokines via Lysosomal Acid Sphingomyelinase and Ceramides
Staphylococcus aureus α-Toxin Induces Inflammatory Cytokines via Lysosomal Acid Sphingomyelinase and Ceramides
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DOI：
10.1159/000484296
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发表时间：
2017-01-01
影响因子：
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通讯作者：
Becker, Katrin Anne
中科院分区：
文献类型：
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作者：
Ma, Jie;Gulbins, Erich;Becker, Katrin Anne
背景/目的：金黄色葡萄球菌（S.金黄色葡萄球菌）感染是主要的临床问题，其范围从轻度皮肤和软组织感染到严重甚至致命的感染，例如肺炎、心内膜炎、败血症、骨髓炎和中毒性休克综合征。从S.金黄色葡萄球菌介导许多这些作用。在这里，我们的目的是确定分子机制如何α毒素，一个主要的S。金黄色葡萄球菌毒素，引起炎症。方法：从野生型和酸性鞘磷脂酶缺陷小鼠骨髓中分离巨噬细胞，用S。对金黄色葡萄球菌α-毒素和酸性鞘磷脂酶的活化进行定量。通过共聚焦显微镜测定神经酰胺的亚细胞形成。通过蛋白质印迹、共聚焦显微镜和ELISA分析组织蛋白酶从溶酶体的释放、炎性体蛋白的活化以及白细胞介素-1 β（IL-1 β）和肿瘤坏死因子-α（TNF-α）的形成。结果：我们证明了S。金黄色葡萄球菌α-毒素激活离体巨噬细胞中的酸性鞘磷脂酶并引发神经酰胺的释放。诱导产生的神经酰胺类物质。金黄色葡萄球菌α-毒素定位于溶酶体并介导组织蛋白酶B和D从溶酶体释放到细胞质中。胞质组织蛋白酶B与Nlrc 4形成复合物。用α-毒素处理巨噬细胞诱导IL-1 β和TNF-α的形成。在缺乏酸性鞘磷脂酶的细胞中，以及在用酸性鞘磷脂酶的功能性抑制剂阿米替林处理巨噬细胞后，这些事件分别减少或消除。组织蛋白酶B的药理学抑制阻止了炎性小体的活化，以IL-1 β的释放测量，而TNF-α的形成不依赖于组织蛋白酶B。结论：我们证明了细菌毒素激活炎性体并介导细胞因子形成和释放的新机制：S。金黄色葡萄球菌α-毒素触发酸性鞘磷脂酶的活化和神经酰胺的释放，导致溶酶体组织蛋白酶B的释放和促炎细胞因子的形成。(C)2017作者（s）由S. Karger AG，巴塞尔
Background/Aims: Staphylococcus aureus (S. aureus) infections are a major clinical problem and range from mild skin and soft-tissue infections to severe and even lethal infections such as pneumonia, endocarditis, sepsis, osteomyelitis, and toxic shock syndrome. Toxins that are released from S. aureus mediate many of these effects. Here, we aimed to identify molecular mechanisms how alpha-toxin, a major S. aureus toxin, induces inflammation. Methods: Macrophages were isolated from the bone marrow of wildtype and acid sphingomyelinase-deficient mice, stimulated with S. aureus alpha-toxin and activation of the acid sphingomyelinase was quantified. The subcellular formation of ceramides was determined by confocal microscopy. Release of cathepsins from lysosomes, activation of inflammasome proteins and formation of Interleukin-1 beta (IL-1 beta) and Tumor Necrosis Factor-alpha (TNF-alpha) were analyzed by western blotting, confocal microscopy and ELISA. Results: We demonstrate that S. aureus alpha-toxin activates the acid sphingomyelinase in ex vivo macrophages and triggers a release of ceramides. Ceramides induced by S. aureus alpha-toxin localize to lysosomes and mediate a release of cathepsin B and D from lysosomes into the cytoplasm. Cytosolic cathepsin B forms a complex with Nlrc4. Treatment of macrophages with alpha-toxin induces the formation of IL-1 beta and TNF-alpha. These events are reduced or abrogated, respectively, in cells lacking the acid sphingomyelinase and upon treatment of macrophages with amitriptyline, a functional inhibitor of acid sphingomyelinase. Pharmacological inhibition of cathepsin B prevented activation of the inflammasome measured as release of IL-1 beta, while the formation of TNF-alpha was independent of cathepsin B. Conclusion: We demonstrate a novel mechanism how bacterial toxins activate the inflammasome and mediate the formation and release of cytokines: S. aureus alpha-toxin triggers an activation of the acid sphingomyelinase and a release of ceramides resulting in the release of lysosomal cathepsin B and formation of pro-inflammatory cytokines. (C) 2017 The Author(s) Published by S. Karger AG, Basel