Chlorogenic acid improves the intestinal barrier by relieving endoplasmic reticulum stress and inhibiting ROCK/MLCK signaling pathways

Phenolic acids play an active role in protecting the intestinal barrier, the structural integrity and function of which are crucial for host health. In the present study, we aimed to identify phenolic compounds that protect the intestine and explore the underlying mechanisms. We performed an imaging-based, quantitative, high-content screening (using Caco-2 and LS174T incubated with lipopolysaccharide/palmitic acid, respectively) to identify phenolic acids that could improve the mucosal barrier. We found that chlorogenic acid (CGA), 5-caffeoylquinic acid, protocatechuic acid, and caffeic acid alleviated intestinal barrier disruption. Furthermore, CGA increased transepithelial electrical resistance (TEER) and decreased paracellular permeability. Mechanistically, CGA inhibited the activation of myosin light chain kinase (MLCK) and Rho-associated kinase 1 (ROCK1) signals, thereby downregulating the expression of the downstream molecules phosphorylated myosin phosphatase target subunit 1 (p-MYPT1), MLCK, and phosphorylated myosin light chain (p-MLC), and upregulating the expression of tight junction proteins. In addition, CGA alleviated endoplasmic reticulum (ER) stress by inhibiting the expression levels of ER markers [glucose-regulated protein78 (GRP78) and C/EBP homologous protein (CHOP)] and the nuclear translocation of activating transcription factor 6 (ATF6), thereby promoting the expression of mucin [mucin 2 (Muc2), mucin 5AC (MUC5AC)] and secretory factor trefoil factor family 3 (TFF3) proteins. In summary, we identified four substances that can stabilise intestinal homeostasis. Of these, CGA protects the intestinal barrier by inhibiting ROCK/MLCK signalling pathways and relieving ER stress. These findings highlight the importance of rapidly screening potential active ingredients that benefit the intestinal barrier and provide a theoretical basis for enteral nutrition.