Insight into Ulcerative Colitis and Associated Diarrhea: Exploring the Interplay of Cellular and Molecular Axis with Advancement in Treatments.

Ulcerative Colitis (UC)-associated diarrhea is a debilitating symptom of persistent intestinal inflammation that significantly reduces a patient's quality of life. Epithelial ion transport failure, tight junction remodeling, dysregulated mucus secretion, immunological overactivation, gut microbiota dysbiosis, and mitochondrial oxidative stress all interact intimately to cause its pathogenesis. While cytokine-mediated suppression of ENaC, NHE3 (Na+/H+ exchanger 3), DRA (SLC26A3), and PAT1 (SLC26A6) significantly reduces fluid and electrolyte absorption, chronic inflammation promotes "claudin switching" and tight junction breakdown, increasing paracellular permeability. Mucosal barrier failure is sustained and inflammatory cascades are intensified by concurrent deregulation of the NF-κB, JAK/STAT, and PXR signaling pathways. Recent findings highlight the critical role of immune-microbiota crosstalk and reactive oxygen species formed from mitochondria in sustaining this pathogenic cycle. Recent developments in biologics, targeted small molecules, colon-specific hydrogels, and nanomedicine offer potential approaches for site-specific drug delivery, immunologic control, and epithelial barrier restoration, in addition to traditional pharmacotherapies. This review highlights future options for tailored, multi-targeted therapies. It provides a framework for mechanism-guided management of UC-associated diarrhea by synthesizing existing mechanistic insights and translational therapeutic advancements.