Department of Hematology and Key Laboratory of Non-resolving Inflammation and Cancer of Hunan Province, Third Xiangya Hospital, Central South University, Changsha, Hunan 410000, China; Postdoctoral Research Station of Clinical Medicine, Third Xiangya Hospital, Central South University, Changsha, Hunan 410000, China.
Department of Hematology and Key Laboratory of Non-resolving Inflammation and Cancer of Hunan Province, Third Xiangya Hospital, Central South University, Changsha, Hunan 410000, China.
J Biol Chem. 2019 May 24;294(21):8384-8394. doi: 10.1074/jbc.RA118.006508. Epub 2019 Apr 10.
The NLR family pyrin domain-containing 3 (NLRP3) inflammasome is a multimeric protein complex that mediates maturation of the cytokines IL-1β and IL-18 as well as release of the proinflammatory protein high-mobility group box 1 (HMGB1) and contributes to several inflammatory diseases, including sepsis, gout, and type 2 diabetes. In this context, the well-studied active complement fragment C5a and its receptor C5aR1 or C5aR2 orchestrate the inflammatory responses in many diseases. Although a C5a-C5aR interaction in NLRP3-associated diseases has been suggested, little is known about the details of C5a-C5aR cross-talk with the NLRP3 inflammasome in macrophages. In this study, using mice and murine macrophages and cytokines, immunoblotting, siRNA, and quantitative real-time PCR assays, we demonstrate that C5aR2 deficiency restricts activation of the NLRP3 inflammasome and release of HMGB1 both and Mechanistically, we found that C5aR2 promotes NLRP3 activation by amplifying dsRNA-dependent PKR expression, which is an important NLRP3-activating factor. We also observed that elevation of PKR expression because of the C5a-C5aR2 interaction depends on the mitogen-activated protein kinase/extracellular signal-regulated kinase kinase pathway and type I IFN signaling. In conclusion, these findings reveal that C5aR2 contributes to NLRP3 inflammasome activation and HMGB1 release from macrophages.
NLR 家族包含 pyrin 结构域蛋白 3（NLRP3）炎性小体是一种多聚体蛋白复合物，可介导细胞因子 IL-1β 和 IL-18 的成熟，以及促炎蛋白高迁移率族蛋白 B1（HMGB1）的释放，并有助于多种炎症性疾病，包括败血症、痛风和 2 型糖尿病。在这种情况下，研究充分的活性补体片段 C5a 及其受体 C5aR1 或 C5aR2 协调许多疾病中的炎症反应。尽管已经提出了 NLRP3 相关疾病中的 C5a-C5aR 相互作用，但对于 C5a-C5aR 与巨噬细胞中 NLRP3 炎性小体的交叉对话的细节知之甚少。在这项研究中，我们使用小鼠和鼠巨噬细胞和细胞因子，通过免疫印迹、siRNA 和实时定量 PCR 检测，证明 C5aR2 缺乏限制了 NLRP3 炎性小体的激活和 HMGB1 的释放。从机制上讲，我们发现 C5aR2 通过放大 dsRNA 依赖性 PKR 表达来促进 NLRP3 的激活，PKR 是一种重要的 NLRP3 激活因子。我们还观察到，由于 C5a-C5aR2 相互作用，PKR 表达的升高取决于丝裂原活化蛋白激酶/细胞外信号调节激酶激酶途径和 I 型 IFN 信号。总之，这些发现揭示了 C5aR2 有助于巨噬细胞中 NLRP3 炎性小体的激活和 HMGB1 的释放。
