Inhibition of CREB-mediated ZO-1 and activation of NF-κB-induced IL-6 by colonic epithelial MCT4 destroys intestinal barrier function

Abstract

Objective: Inflammatory bowel disease (IBD) is a disorder intestinal inflammation and impaired barrier function, associated with increased epithelial expression of monocarboxylate transporter 4 (MCT4). However, the specific non-metabolic function and clinical relevance of MCT4 in IBD remain to be fully elucidated. Methods: Lentivirus-mediated overexpression of MCT4 was used to assess the role of MCT4 in transcriptionally regulating ZO-1 and IL-6 expression by luciferase assays, WB and ChIP. IP was used to analyse the effect of MCT4 on the interaction NF-κB-CBP or CREB-CBP, and these MCT4-mediated effects were confirmed in vivo assay. Results: We showed that ectopic expression of MCT4 inhibited ZO-1 expression, while increased pro-inflammatory factors expression, leading to destroy intestinal epithelial barrier function in vitro and in vivo. Mechanistically, MCT4 contributed NF-κB p65 nuclear translocation and increased the binding of NF-κB p65 to the promoter of IL-6, which is attributed to MCT4 enhanced NF-κB-CBP interaction and dissolved CREB-CBP complex, resulting in reduction of CREB activity and CREB-mediated ZO-1 expression. In addition, treatment of experimental colitis with MCT4 inhibitor α-cyano-4-hydroxycinnamate (CHC) ameliorated mucosal intestinal barrier function, which was due to attenuation of pro-inflammation factors expression and enhancement of ZO-1 expression. Conclusion: These findings suggested a novel role of MCT4 in controlling development of IBD and provided evidence for potential targets of IBD.