Clostridium difficile (C. difficile) infection results in toxin-induced epithelial injury and marked colonic inflammation. Mitogen-activated protein kinase (MAPK) and NF-κB which regulated by MAP kinase phosphatase (MKP, also known as dual specificity phosphatases, DUSP) are fundamental signalling pathways that mediate multiple cellular processes. However, the regulation of DUSP/MAPKs and NF-κB pathway in C. difficile-induced colonic inflammation remains unclear. Here, we report that TcdB significantly inhibits cell viability and induces production of IL-1β and TNF-α and activation of MAPKs and NF-κB. An E3-ubiquitin ligase, TRIM46, ubiquitinates DUSP1, and its knockdown significantly inhibit TcdB-induced activation of MAPKs and NF-κB and production of IL-1β and TNF-α. Moreover, TRIM46 overexpression induced production of IL-1β and TNF-α also reversed by DUSP1 overexpression. We further found that promoter of TRIM46 also demonstrated binding to NF-κBp65, leading to regulate TRIM46 expression. In addition, the increased colonic inflammation induced by C. difficile administration was inhibited by TRIM46 knockdown in vivo. Taken together, the present study shows that TRIM46, as a new regulator of DUSP1/MAPKs and NF-κB signalling pathway, plays an important role in TcdB-induced colonic inflammation.

中文翻译：

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艰难梭菌毒素 B 通过 TRIM46/DUSP1/MAPKs 和 NF-κB 信号通路诱导结肠炎症。

艰难梭菌 (C. difficile) 感染导致毒素诱导的上皮损伤和显着的结肠炎症。丝裂原活化蛋白激酶 (MAPK) 和受 MAP 激酶磷酸酶 (MKP，也称为双特异性磷酸酶，DUSP) 调节的 NF-κB 是介导多种细胞过程的基本信号通路。然而，DUSP/MAPKs 和 NF-κB 通路在艰难梭菌诱导的结肠炎症中的调控仍不清楚。在这里，我们报告 TcdB 显着抑制细胞活力并诱导 IL-1β 和 TNF-α 的产生以及 MAPK 和 NF-κB 的激活。E3-泛素连接酶 TRIM46 泛素化 DUSP1，其敲低显着抑制 TcdB 诱导的 MAPK 和 NF-κB 激活以及 IL-1β 和 TNF-α 的产生。而且，TRIM46 过表达诱导的 IL-1β 和 TNF-α 的产生也被 DUSP1 过表达逆转。我们进一步发现 TRIM46 的启动子也表现出与 NF-κBp65 的结合，从而调节 TRIM46 的表达。此外，体内 TRIM46 敲低抑制了艰难梭菌给药诱导的结肠炎症增加。总之，本研究表明，TRIM46 作为 DUSP1/MAPK 和 NF-κB 信号通路的新调节剂，在 TcdB 诱导的结肠炎症中起重要作用。