Hyaluronic acid-ethylenediamine-cinnamic acid attenuates IBS-D via regulating 5-hydroxytryptamine signaling pathway, intestinal barrier and gut microbiota

Current clinical management of diarrhea-predominant irritable bowel syndrome (IBS-D) faces substantial challenges due to the limited efficacy of existing therapeutic strategies. This study aimed to synthesize and characterize the hyaluronic acid-ethylenediamine-cinnamic acid conjugate (HA-EDA-CA), investigate its oral bioavailability and colonic tissue distribution, and validate its therapeutic potential along with underlying mechanisms of action in IBS-D models. Following oral administration of free CA or HA-EDA-CA, the colon concentration of CA released from the derivative was significantly higher than that of free CA alone. Both free and conjugated forms of CA likely contributed to the therapeutic effects against IBS-D. The IBS-D model was established by a combination of senna decoction administration and physical restraint stress. After HA-EDA-CA intervention, IBS-D model mice showed marked improvements in stool consistency, fecal water content, stool output, body weight, visceral hypersensitivity, and colon length. ELISA results indicated significant reduction in enteric neurotransmitter levels, including 5-hydroxytryptamine, substance P, and vasoactive intestinal peptide, after oral gavage administration of HA-EDA-CA. Additionally, intestinal permeability assessment and immunofluorescence analyse revealed that HA-EDA-CA improved intestinal barrier function. Western blot analysis indicated HA-EDA-CA inhibited 5-hydroxytryptamine signaling pathway. Furthermore, HA-EDA-CA modulated gut microbiota composition. These findings suggested the potential of HA-EDA-CA as a promising therapeutic candidate for IBS-D treatment. Key novelties: (i) First colon-targeted CA-HA conjugate: We developed and characterized the first hyaluronic acid-based conjugate specifically designed for colon-targeted delivery of cinnamic acid. (ii) Multi-mechanism rescue: The conjugate simultaneously restores gut homeostasis by modulating the 5-hydroxytryptamine signaling pathway, enhancing intestinal barrier function, and rebalancing gut microbiota. (iii) Enhanced therapeutic efficacy: HA-EDA-CA demonstrates superior colonic drug accumulation and integrated therapeutic outcomes compared to free cinnamic acid or simple drug mixtures. (iv) Open-source data availability: All relevant data and analysis scripts supporting the findings are publicly accessible to ensure reproducibility and further research.