Emerging antimicrobial peptides in gastrointestinal disorders: Dual role in immunity and therapy.

Antimicrobial peptides (AMPs) are small, cationic effectors of innate immunity that are central to gastrointestinal homeostasis and increasingly attractive as therapeutics for infection, inflammation, and malignancy. Produced by intestinal epithelial and immune cells, AMPs such as defensins and cathelicidins act as frontline regulators, responding to microbial cues through pattern-recognition receptors, shaping microbiota composition, reinforcing the mucosal barrier, and tuning the balance between pro-inflammatory and anti-inflammatory signalling. This review frames AMP biology around a central duality: The same peptides that defend the gut can, when dysregulated in concentration, location, or context, contribute to pathology, from the α-defensin deficiency that initiates ileal Crohn's disease to the concentration-dependent switch by which LL-37 turns from a wound-healing mediator into a tumour-promoting one. This duality dictates therapeutic strategy, favouring restoration where disease arises from deficiency and restraint where it arises from aberrant signalling. We examine the mechanistic basis of AMP action (membrane disruption, intracellular targeting, and receptor-mediated immunomodulation) and evaluate preclinical and clinical evidence across inflammatory bowel disease, enteric infection, and gastrointestinal cancers, drawing the recurring lesson that microbiological success rarely guarantees clinical benefit. Persistent barriers of proteolytic instability, narrow therapeutic windows, and manufacturing cost are increasingly addressed through convergent advances in artificial intelligence-guided peptide design, sequence stabilisation, gut-targeted and stimulus-responsive delivery, and engineered live biotherapeutics that produce peptides