The study shows that the natural antimicrobial peptide LL‑37 helps gut cells release mucus and protective proteins, which improves the gut’s ability to clear harmful bacteria. Mice lacking LL‑37 had weaker mucus release, more bacteria, and lower reactive oxygen species (ROS) in the gut. In human gut‑like cells, adding LL‑37 boosted secretion of key mucus‑associated proteins through a ROS‑dependent pathway.

Colonic goblet cells play a crucial role in mucosal defense by secreting Muc2 mucin and other proteins that entrap and expel enteropathogens. However, the role of innate effectors in the gut like cathelicidin peptides in regulating the mucus barrier during infections remains unclear. In this study, we used cathelicidin-deficient (<i>Camp</i>^<i>-/-</i>) littermates, colonoids, and human LS174T goblet-like cells to investigate how cathelicidin modulates goblet cell function and mucosal defense against attaching/effacing enteropathogen <i>Citrobacter rodentium</i>. We showed that increased fecal shedding and epithelial colonization by <i>C. rodentium</i> in <i>Camp</i>^<i>-/-</i> littermates was accompanied by impaired mucus secretion and higher retention of mucin granules and trefoil factor 3 (Tff3) in bloated colonic goblet cells. Reduction in mucus secretion by goblet cells was accompanied by reduced reactive oxygen species (ROS) production during <i>C. rodentium</i> infection in <i>Camp</i>^<i>-/-</i> as compared to <i>Camp</i>^<i>+/+</i> littermate controls. In LS174T goblet-like cells, human cathelicidin LL-37 stimulated the secretion of TFF3 and resistin-like molecule &#x3b2; (RELM&#x3b2;) in a ROS-dependent manner. These findings reveal that cathelicidin regulates goblet cell mucus and mucus-associated protein secretion through a ROS-mediated mechanism critical for bacterial clearance and maintenance of gut homeostasis.