Department of Gastroenterology, Kunshan Hospital of Traditional Chinese Medicine, Kunshan Affiliated Hospital of Nanjing University of Chinese Medicine, Kunshan, China.
Department of Respiratory and Critical Care, The Fifth Affiliated Hospital Sun Yat-Sen University, Zhuhai, China.
Front Immunol. 2021 May 19;12:644862. doi: 10.3389/fimmu.2021.644862. eCollection 2021.
NLRP3 inflammasome has emerged as a crucial regulator of inflammatory bowel disease (IBD) characterized by a chronic inflammatory disease of the gastrointestinal tract. The expression of MCT4 is significantly increased in intestinal mucosal tissue of IBD, which has been identified to regulate intestinal barrier function. However, the function of MCT4 in cell pyroptosis remained unknown. In this study, we have established a stable cell line with MCT4 overexpression in HT-29 and CaCO2 cells, respectively. Functional analysis revealed that ectopic expression of MCT4 in CaCO2 cells contributed to cell pyroptosis as evidenced by LDH assay, which is largely attributed to Caspase-1-mediated canonical pyroptosis, but not Caspase-4 and Caspase-5, leading to cleave pro-IL-1β and IL-18 into mature form and release mediated by cleaved GSDMD. Mechanically, MCT4 overexpression in HT-29 and CaCO2 cell triggered the phosphorylation of ERK1/2 and NF-B p65, while inhibition of MCT4 by MCT inhibitor -Cyano-4-hydroxycinnamic acid (-CHCA) in HT-29 and CaCO2 cells led to a significant downregulation of ERK1/2 and NF-B activity. What's more, blockade of ERK1/2-NF-B pathway could reverse the promotion effect of MCT4 on IL-1β expression. Importantly, both MCT4 and Caspase-1, GSDMD were significantly increased in patients with IBD, and a positive clinical correlation between MCT4 and Caspase-1 expression was observed (p < 0.001). Taken together, these findings suggested that MCT4 promoted Caspase-1-mediated canonical cell pyroptosis to aggravate intestinal inflammation in intestinal epithelial cells (IECs) through the ERK1/2-NF-B pathway.
NLRP3 炎性小体已成为炎症性肠病 (IBD) 的关键调节因子，IBD 是一种胃肠道慢性炎症性疾病。MCT4 的表达在 IBD 的肠黏膜组织中显著增加，已被确定可调节肠道屏障功能。然而，MCT4 在细胞焦亡中的功能仍然未知。在这项研究中，我们分别在 HT-29 和 CaCO2 细胞中建立了 MCT4 过表达的稳定细胞系。功能分析表明，CaCO2 细胞中 MCT4 的异位表达导致细胞焦亡，这主要归因于 Caspase-1 介导的经典焦亡，而不是 Caspase-4 和 Caspase-5，导致 pro-IL-1β 和 IL-18 被切割成成熟形式，并通过切割的 GSDMD 介导释放。在机制上，HT-29 和 CaCO2 细胞中 MCT4 的过表达触发了 ERK1/2 和 NF-B p65 的磷酸化，而 HT-29 和 CaCO2 细胞中 MCT 抑制剂 -Cyano-4-hydroxycinnamic acid (-CHCA) 抑制 MCT4 导致 ERK1/2 和 NF-B 活性的显著下调。更重要的是，ERK1/2-NF-B 通路的阻断可以逆转 MCT4 对 IL-1β 表达的促进作用。重要的是，MCT4 和 Caspase-1、GSDMD 在 IBD 患者中均显著增加，并且观察到 MCT4 与 Caspase-1 表达之间存在正的临床相关性 (p < 0.001)。总之，这些发现表明，MCT4 通过 ERK1/2-NF-B 通路促进 Caspase-1 介导的经典细胞焦亡，从而加重肠道上皮细胞 (IECs) 中的肠道炎症。
