Inflammation is a common pathophysiological process as well as a clinical threat that occurs in various diseases worldwide. It is well-documented that nuclear factor-κB (NF-κB) and mitogen-activated protein kinase pathways are involved in inflammatory reactions to microbial infections in lipopolysaccharide (LPS)-activated macrophages. The deubiquitinase ubiquitin carboxyl-terminal hydrolase-L1 (UCHL1) has been reported as an oncoprotein to promote the growth and progression of cancer cells. However, the regulatory mechanism of UCHL1 in inflammation is currently unclear. Here, we aimed to assess the effects of UCHL1 on LPS-associated inflammatory response in vitro and in vivo by enzyme-linked immunosorbent assay, quantitative reverse-transcription polymerase chain reaction, and western blot analysis. This study identified that inhibition or knockdown of UCHL1 decreased the amounts of the key pro-inflammatory cytokines, including interleukin-6 and tumor necrosis factor-α in macrophages. Additionally, inhibition of UCHL1 suppressed LPS-induced extracellular signal‑regulated protein kinase 1/2 phosphorylation and NF-κB translocation by regulating the inhibitor of NF-κB. Mechanically, UCHL1 interacts with IκBα protein in THP-1. Meanwhile, inhibition of UCHL1 blocked the LPS-induced degradation of IκBα through the ubiquitin-proteasome system. Moreover, in vivo assay showed that suppression of UCHL1 notably reduced the LPS-induced animal death and release of pro-inflammatory cytokines. Overall, the current findings uncover that UCHL1 functions as a crucial regulator for inflammatory response via reversing the degradation of IκBα, representing a potential target for the treatment of inflammatory diseases.

中文翻译：

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UCHL1 通过 LPS 激活的巨噬细胞中的 MAPK 和 NF-κB 通路调节炎症

炎症是一种常见的病理生理过程，也是世界范围内各种疾病发生的临床威胁。有充分证据表明，核因子-κB (NF-κB) 和丝裂原活化蛋白激酶通路参与脂多糖 (LPS) 激活的巨噬细胞对微生物感染的炎症反应。据报道，去泛素化酶泛素羧基末端水解酶-L1 (UCHL1) 是一种促进癌细胞生长和进展的癌蛋白。然而，UCHL1在炎症中的调控机制目前尚不清楚。在这里，我们旨在通过酶联免疫吸附测定、定量逆转录聚合酶链反应和蛋白质印迹分析来评估 UCHL1 在体外和体内对 LPS 相关炎症反应的影响。该研究发现，UCHL1 的抑制或敲低降低了巨噬细胞中关键促炎细胞因子的数量，包括白细胞介素 6 和肿瘤坏死因子 α。此外，UCHL1 的抑制通过调节 NF-κB 的抑制剂来抑制 LPS 诱导的细胞外信号调节蛋白激酶 1/2 磷酸化和 NF-κB 易位。在机械上，UCHL1 与 THP-1 中的 IκBα 蛋白相互作用。同时，抑制 UCHL1 通过泛素-蛋白酶体系统阻断 LPS 诱导的 IκBα 降解。此外，体内试验表明，UCHL1 的抑制显着降低了 LPS 诱导的动物死亡和促炎细胞因子的释放。总体而言，目前的研究结果揭示了 UCHL1 通过逆转 IκBα 的降解作为炎症反应的关键调节因子，