Investigation and evaluation of gastrointestinal toxicity biomarkers in rats with different sites of gastrointestinal injury

There are few reliable biomarkers for gastrointestinal toxicity, and the further identification of such markers can improve the accuracy and speed of toxicological evaluations. This study aimed to evaluate the effectiveness of several recently proposed biomarkers-plasma citrulline, fecal calprotectin, fecal bile acid, and plasma miRNAs (miR-194 and -215)-in detecting intestinal toxicity. To this end, cysteamine hydrocholoride (cysteamine, 600 or 900 mg/kg, PO), indomethacin (10 mg/kg, PO), or 2,4-Dinitrobenzenesulfonic acid hydrate (DNBS, 20 mg/kg, IR) were administered to male Wistar rats to establish models of gastric/duodenal, jejunum/ileum, or colonic damage, respectively. Both novel biomarkers and traditional toxicological parameters were evaluated in these rat models. Standard in-life observations, such as fecal properties or body weight, were inadequate for monitoring intestinal toxicity, as there were few observable changes indicative of intestinal injury, especially in the cysteamine and indomethacin models. Plasma citrulline drastically decreased in cysteamine or indomethacin-treated rats, with a milder decrease in DNBS-treated animals. Fecal total bile acids and calprotectin levels increased only in rats treated with indomethacin or DNBS, but not with cysteamine. While plasma miR-194 remained unchanged across all models, miR-215 levels decreased after cysteamine treatment. Together, these results suggest that plasma citrulline and fecal calprotectin may be effective biomarkers for monitoring intestinal injury. Fecal TBA and plasma miR-215 also show potential as useful biomarkers, but further research is needed to confirm their efficacy. Specifically, plasma citrulline is indicative of damage from the stomach to the ileum, fecal total bile acids and calprotectin are indicative of damage from the jejunum to the rectum, and plasma miR-215 is indicative of damage from the stomach and the duodenum. Integrating these novel biomarkers with standard toxicological parameters will help in predicting actual intestinal sites of damage. This integration has the potential to improve the quality of toxicological evaluations. Our findings support the use of these biomarkers in clinical settings.