Development of In Vitro Method for Prediction of Drug-Induced Gastrointestinal Toxicity Using Colon-Derived Organoids -Based on Mechanistic Analysis of Serotonin-Induced Fluid Secretion

Abstract

Predicting GI toxicity such as diarrhea and constipation is important to develop oral drugs having higher safety and effectiveness. However, drug-induced GI toxicity is not easy to predict because its mechanism is complicated by multiple physiological factors (e.g., fluid/electrolyte balance, GI hormone), and no effective in vitro prediction system has yet been developed. In the present study, we propose an in vitro system for prediction of drug-induced GI toxicity with organoid technology that can reflect physiological functions by mechanistically analyzing the effect of drug exposure on serotonin (5-HT) disposition and fluid regulation in the GI tract, using metformin as a model drug which clinically causes diarrhea. Studies using Caco-2 cells and Xenopus oocytes indicated that metformin inhibits SERT-mediated 5-HT uptake. Administration of metformin into the rat intestinal lumen significantly increased the GI fluid volume and simultaneously elevated 5-HT and Cl^- levels in the GI tract. Taken together, these results suggested that metformin increases the luminal 5-HT levels by inhibiting SERT-mediated intestinal uptake, promoting fluid secretion due to increased luminal Cl^- levels. Consistent with these observations, in vitro swelling assay using rat colon-derived organoids showed that exposure to 5-HT and forskolin, a Cl^- channel activator, significantly increased water secretion. In conclusion, our proposed method for predicting drug-induced GI toxicity using colon-derived organoids can be a useful system that can reflect the mechanism of GI toxicity in vivo.