Institute of Clinical Medicine, College of Medicine, National Cheng Kung University, Tainan, 70101, Taiwan, ROC; Department of Surgery, Puzi Hospital, Ministry of Health and Welfare, Chiayi, Taiwan, ROC.
Department of Pharmacology, College of Medicine, National Cheng Kung University, Tainan, 70101, Taiwan, ROC.
Biochem Biophys Res Commun. 2020 Sep 24;530(3):487-493. doi: 10.1016/j.bbrc.2020.05.084. Epub 2020 Jun 25.
Gout is an inflammatory arthritis caused by the phagocytosis of monosodium urate (MSU) crystal deposition in joints. NOD-, LRR-, and pyrin domain-containing 3 (NLRP3) inflammasome-dependent caspase-1 activation is implicated in the processing of interleukin-1β (IL-1β), which is the major effector cytokine in the acute inflammatory response of gout. Mechanisms underlying caspase-1 activation remain unclear. Epidermal growth factor receptor pathway substrate no. 8 (Eps8) is a signal transducer and actin filament organizer that plays a key role in lipopolysaccharide-stimulated phagocytosis in macrophages. Here, RAW264.7 macrophages that have no intact NLRP3 inflammasomes were used to investigate the role of Eps8 in MSU crystal-mediated caspase-1 activation. A kinetic study revealed that the induction of Eps8 expression by MSU crystals occurred before NLRP3, p46/p33 caspase-1, and mature IL-1β in RAW 264.7 cells. In addition, actin cytoskeleton dynamics was required for Eps8 induction and caspase-1 activation in MSU crystal stimulation. Silencing Eps8 had no effect on the basal expression of p46/p33 caspase-1 and NLRP3, but nearly abolished MSU crystal-induced NLRP3 expression and caspase-1 activation. Furthermore, MSU crystals induced Eps8-pro-caspase-1 complex formation and Eps8 formed a stable complex with p33 caspase-1, but not with NLRP3. In summary, our results demonstrated for the first time the importance of Eps8 in MSU crystal-mediated caspase-1 activation without the involvement of NLRP3 inflammasomes.
痛风是一种炎症性关节炎，由单钠尿酸盐（MSU）晶体在关节中的吞噬作用引起。NOD、LRR 和富含 pyrin 域的 3（NLRP3）炎性小体依赖性半胱天冬酶-1 的激活与白细胞介素-1β（IL-1β）的加工有关，IL-1β是痛风急性炎症反应的主要效应细胞因子。半胱天冬酶-1 激活的机制尚不清楚。表皮生长因子受体途径底物 8（Eps8）是一种信号转导蛋白和肌动蛋白丝组织者，在巨噬细胞中脂多糖刺激的吞噬作用中发挥关键作用。在这里，使用没有完整 NLRP3 炎性小体的 RAW264.7 巨噬细胞来研究 Eps8 在 MSU 晶体介导的半胱天冬酶-1 激活中的作用。动力学研究表明，MSU 晶体诱导 Eps8 表达发生在 RAW 264.7 细胞中的 NLRP3、p46/p33 半胱天冬酶-1 和成熟的 IL-1β之前。此外，肌动蛋白细胞骨架动力学是 Eps8 诱导和 MSU 晶体刺激中半胱天冬酶-1 激活所必需的。沉默 Eps8 对半胱天冬酶-1 和 NLRP3 的基础表达没有影响，但几乎消除了 MSU 晶体诱导的 NLRP3 表达和半胱天冬酶-1 激活。此外，MSU 晶体诱导 Eps8-pro-caspase-1 复合物形成，Eps8 与 p33 半胱天冬酶-1形成稳定的复合物，而不是与 NLRP3。总之，我们的结果首次证明了 Eps8 在 MSU 晶体介导的半胱天冬酶-1 激活中的重要性，而不涉及 NLRP3 炎性小体。
