Institute of Immunology, Department of General Pediatrics, University Children’s Hospital Münster, Münster, Germany.
J Leukoc Biol. 2012 Nov;92(5):1069-81. doi: 10.1189/jlb.0112014. Epub 2012 Aug 14.
The Staphylococcus aureus pore-forming toxin PVL is most likely causative for life-threatening necrotizing infections, which are characterized by massive tissue inflammation and necrosis. Whereas the cytotoxic action of PVL on human neutrophils is already well established, the PVL effects on other sensitive cell types, such as monocytes and macrophages, are less clear. In this study, we used different types of human leukocytes (neutrophils, monocytes, macrophages, lymphocytes) to investigate cell-specific binding of PVL subunits and subsequent proinflammatory and cytotoxic effects. In all PVL-sensitive cells, we identified the binding of the subunit LukS-PV as the critical factor for PVL-induced cytotoxicity, which was followed by binding of LukF-PV. LukS-PV binds to monocytes, macrophages, and neutrophils but not to lymphocytes. Additionally, we showed that PVL binding to monocytes and macrophages leads to release of caspase-1-dependent proinflammatory cytokines IL-1β and IL-18. PVL activates the NLRP3 inflammasome, a signaling complex of myeloid cells that is involved in caspase-1-dependent IL-1β processing in response to pathogens and endogenous danger signals. Specific inhibition of this pathway at several steps significantly reduced inflammasome activation and subsequent pyronecrosis. Furthermore, we found that PAMPs and DAMPs derived from dying neutrophils can dramatically enhance this response by up-regulating pro-IL-1β in monocytes/macrophages. This study analyzes a specific host signaling pathway that mediates PVL-induced inflammation and cytotoxicity, which has high relevance for CA-MRSA-associated and PVL-mediated pathogenic processes, such as necrotizing infections.
金黄色葡萄球菌成孔毒素 PVL 很可能是导致危及生命的坏死性感染的原因，这种感染的特征是大量组织炎症和坏死。虽然 PVL 对人中性粒细胞的细胞毒性作用已经得到很好的证实，但 PVL 对其他敏感细胞类型（如单核细胞和巨噬细胞）的作用尚不清楚。在这项研究中，我们使用了不同类型的人白细胞（中性粒细胞、单核细胞、巨噬细胞、淋巴细胞）来研究 PVL 亚基的细胞特异性结合及其随后的促炎和细胞毒性作用。在所有 PVL 敏感的细胞中，我们确定了 LukS-PV 亚基的结合是 PVL 诱导细胞毒性的关键因素，随后是 LukF-PV 的结合。LukS-PV 结合单核细胞、巨噬细胞和中性粒细胞，但不结合淋巴细胞。此外，我们还表明，PVL 与单核细胞和巨噬细胞的结合导致 caspase-1 依赖性促炎细胞因子 IL-1β 和 IL-18 的释放。PVL 激活 NLRP3 炎性体，这是一种髓样细胞的信号复合物，参与 caspase-1 依赖性 IL-1β 加工，以响应病原体和内源性危险信号。该途径的几个步骤的特异性抑制显著降低了炎性体的激活和随后的细胞焦亡。此外，我们发现，来自死亡中性粒细胞的 PAMPs 和 DAMPs 可以通过在上皮细胞和巨噬细胞中上调前体 IL-1β 来显著增强这种反应。这项研究分析了一种特定的宿主信号通路，该通路介导了 PVL 诱导的炎症和细胞毒性，这对于 CA-MRSA 相关和由 PVL 介导的致病过程（如坏死性感染）具有重要意义。
