Objective IL-17A and TNF act in synergy to induce proinflammatory mediators in synovial fibroblasts thus contributing to diseases associated with chronic arthritis. Many of these factors are regulated by transcription factor E74-like factor 3 (ELF3). Therefore, we sought to investigate ELF3 as a downstream target of IL-17A and TNF signalling and to characterize its role in the molecular mechanism of synergy between IL-17A and TNF. Methods Regulation of ELF3 expression by IL-17A and TNF was studied in synovial fibroblasts of RA and OA patients and RA synovial explants. Signalling leading to ELF3 mRNA induction and the impact of ELF3 on the response to IL-17A and TNF were studied using siRNA, transient overexpression and signalling inhibitors in synovial fibroblasts and HEK293 cells. Results ELF3 was marginally affected by IL-17A or TNF alone, but their combination resulted in high and sustained expression. ELF3 expression was regulated by NF-κB pathway and C/EBPβ but its induction required synthesis of NF-κB co-factor IκBζ. siRNA-mediated depletion of ELF3 attenuated the induction of cytokines and matrix metalloproteinases by the combination of IL-17A and TNF. Overexpression of ELF3 or Ikβζ showed synergistic effect with TNF in upregulating expression of CCL8, and depletion of ELF3 abrogated CCL8 mRNA induction by the combination of IκBζ overexpression and TNF. Conclusion Altogether, our results establish ELF3 as an important mediator of the synergistic effect of IL-17A and TNF in synovial fibroblasts. The findings provide novel information of the pathogenic mechanisms of IL-17A in chronic arthritis and implicate ELF3 as potential therapeutic target.

中文翻译：

---

IL-17A 和 TNF 通过 IκBζ 依赖性诱导 ELF3 协同驱动滑膜成纤维细胞中促炎介质的表达

目的 IL-17A 和 TNF 协同作用，在滑膜成纤维细胞中诱导促炎介质，从而导致与慢性关节炎相关的疾病。其中许多因子受转录因子 E74 样因子 3 (ELF3) 调节。因此，我们试图研究 ELF3 作为 IL-17A 和 TNF 信号传导的下游靶标，并表征其在 IL-17A 和 TNF 协同作用的分子机制中的作用。方法 在 RA 和 OA 患者的滑膜成纤维细胞和 RA 滑膜外植体中研究了 IL-17A 和 TNF 对 ELF3 表达的调节。在滑膜成纤维细胞和 HEK293 细胞中使用 siRNA、瞬时过表达和信号抑制剂研究了导致 ELF3 mRNA 诱导的信号以及 ELF3 对 IL-17A 和 TNF 反应的影响。结果 ELF3 仅受 IL-17A 或 TNF 的轻微影响，但它们的结合导致了高而持续的表达。ELF3 表达受 NF-κB 通路和 C/EBPβ 调节，但其诱导需要 NF-κB 辅因子 IκBζ 的合成。siRNA 介导的 ELF3 耗竭通过 IL-17A 和 TNF 的组合减弱了细胞因子和基质金属蛋白酶的诱导。ELF3 或 Ikβζ 的过表达在上调 CCL8 表达方面显示出与 TNF 的协同作用，并且 ELF3 的消耗消除了 IκBζ 过表达和 TNF 联合诱导的 CCL8 mRNA。结论 总之，我们的结果证实 ELF3 是滑膜成纤维细胞中 IL-17A 和 TNF 协同作用的重要介质。这些发现提供了 IL-17A 在慢性关节炎中的致病机制的新信息，并暗示 ELF3 是潜在的治疗靶点。