Efficacy of Traditional Herbal Medicine, Bojungikki-Tang (Hochuekkito, Bu-ZhongYi-Qi-Tang), in Irritable Bowel Syndrome: Mechanisms Involving TRP and NaV Channels

Background: Irritable bowel syndrome (IBS) is a common functional disorder of the gastrointestinal (GI) tract, typically presenting with abdominal discomfort, distension, and irregular bowel movements. In IBS, the underlying mechanisms are thought to include visceral hypersensitivity and altered regulation of ion channels, where both transient receptor potential (TRP) channels and voltage-gated sodium (NaV) channels are considered key contributors. Objectives: While Bojungikki-Tang (BJIKT), a traditional herbal medicine, has been used for GI disorders, its efficacy and mechanisms in IBS remain unclear. Materials and Methods: A zymosan-induced IBS animal model was used to evaluate the effects of BJIKT on colon length, weight, mucosa thickness, body weight, and inflammatory markers. BJIKT-induced changes in TRP and NaV channel activity were examined through electrophysiological methods. Results: BJIKT depolarized pacemaker potentials in interstitial cells of Cajal (ICC) in vitro. BJIKT restored shortened colon length, normalized increased colon weight, and reduced mucosal thickness and tumor necrosis factor-alpha (TNF-α) levels in the IBS animal model. BJIKT also prevented body weight loss. Electrophysiological studies revealed that BJIKT enhanced TRPV1 and TRPV4 currents, suppressed TRPA1 currents, and suppressed NaV1.5 and NaV1.7 channel currents in a dosedependent fashion. Conclusion: BJIKT alleviates IBS symptoms by regulating TRP and NaV ion channels, reducing inflammation, and restoring GI function. These findings provide a scientific basis for the therapeutic potential of BJIKT in IBS management.