Department of Physiology and Cell Biology, The Ohio State University, Columbus, OH, United States of America.
Department of Internal Medicine, The Ohio State University, Columbus, OH, United States of America.
PLoS One. 2018 Dec 31;13(12):e0209931. doi: 10.1371/journal.pone.0209931. eCollection 2018.
Although the study of pathogen sensing by host defense systems continues to uncover a role for inflammasome components specific to particular pathogens, gaps remain in our knowledge. After internalization, Francisella escapes from the phagosome in mononuclear cells and is thought to be detected by intracellular pathogen-response-receptors pyrin and Aim2 in human and murine models, respectively. However, it remains controversial as to the role of pyrin in detecting Francisella. Our current work aims to study the contribution of inflammasome sensor, Pyrin in regulating microparticulate caspase-1/GSDM-D activation by Francisella. Our findings suggest that NLRP3 is central to the activation/release of active caspase-1/GSDM-D encapsulated in microparticles (MP) by Francisella. We also provide evidence that this regulation is independent of pyrin, implicated in sensing cytosolic Francisella in NLRP3-/- conditions where endogenous Pyrin is present. Absence of NLRP3 completely abrogated Francisella mediated MP caspase-1/GSDM-D activation and release both before and after internalization of the pathogen. However, deletion of pyrin not only enhanced both LPS and Francisella mediated MP active caspase-1/GSDM-D release, but pyrin overexpression resulted in a reduction of inflammasome activation and release; suggesting an inhibitory role of pyrin in LPS and Francisella mediated MP responses. This NLRP3 dependence and inhibitory effect of pyrin correlated with cytokine release as well. These observations also correlated with MPs ability to induce cell death; as LPS and Francisella-induced MPs from pyrin-deficient cells were more potent than wild-type monocytes whereas, NLRP3-/- MPs failed to induce cell death. Taken together, we report that NLPR3 not only mediates Francisella induced cytokine responses, but is also critical for cytokine-independent microparticle-induced inflammasome activation and endothelial cell injury independent of pyrin.
虽然宿主防御系统对病原体感应的研究不断揭示出特定病原体特有的炎症小体成分的作用，但我们的知识仍存在空白。弗朗西斯菌内化后，从单核细胞中的吞噬体中逃逸，据认为分别在人类和鼠模型中被细胞内病原体反应受体 pyrin 和 Aim2 检测到。然而，pyrin 在检测弗朗西斯菌中的作用仍然存在争议。我们目前的工作旨在研究炎症小体传感器 Pyrin 在调节弗朗西斯菌对微颗粒 caspase-1/GSDM-D 的激活中的作用。我们的研究结果表明，NLRP3 是弗朗西斯菌激活/释放封装在微颗粒 (MP) 中的活性 caspase-1/GSDM-D 的核心。我们还提供了证据表明，这种调节独立于 pyrin，在 NLRP3-/-条件下，pyrin 参与了检测细胞质中的弗朗西斯菌，而内源性 Pyrin 存在。NLRP3 的缺失完全阻断了弗朗西斯菌介导的 MP caspase-1/GSDM-D 的激活和释放，无论是在病原体内化之前还是之后。然而，pyrin 的缺失不仅增强了 LPS 和弗朗西斯菌介导的 MP 活性 caspase-1/GSDM-D 的释放，而且 pyrin 的过表达导致了炎症小体的激活和释放减少；表明 pyrin 在 LPS 和弗朗西斯菌介导的 MP 反应中具有抑制作用。这种 NLRP3 依赖性和 pyrin 的抑制作用与细胞因子的释放也有关。这些观察结果也与 MPs 诱导细胞死亡的能力有关；由于来自 pyrin 缺陷细胞的 LPS 和弗朗西斯菌诱导的 MPs 比野生型单核细胞更有效，而 NLRP3-/- MPs 则不能诱导细胞死亡。总之，我们报告 NLRP3 不仅介导了弗朗西斯菌诱导的细胞因子反应，而且对于细胞因子非依赖性的微颗粒诱导的炎症小体激活和内皮细胞损伤也是至关重要的，与 pyrin 无关。
