L-Citrulline Improves Recovery of Enterocytes While Not Affecting Gut Microbiota in an In Vitro Model of Chemotherapy-Induced Gastrointestinal Mucositis

Background/Objectives: Despite significant advancements in cancer treatment outcomes, side effects, such as gastrointestinal mucositis (GIM), continue to impair patients’ quality of life. The recent literature suggests L-citrulline as a novel treatment for GIM. However, no in vitro model to study the potential for L-citrulline as a treatment for GIM is currently available, and the effect of L-citrulline on the gut microbiota remains unclear. This study aims to propose a suitable in vitro model to study the effect of L-citrulline on the gut microbiota and to determine whether it can mitigate GIM. Methods: The CaCo-2 and T84 cell lines were cultured using cell impedance assays and treated with different doses of methotrexate and melphalan to select an appropriate model for L-citrulline research. The selected model was further used to investigate the impact of L-citrulline on gut microbiota cultured using microbial culture assays containing YCFAG. Results: Neither CaCo-2 nor T84 cells treated with methotrexate were suitable models for our study due to varying responses to treatment. T84 cells treated with 100 μg/mL melphalan demonstrated a consistent response, making them a suitable model for in vitro research on treatments for GIM. The use of L-citrulline demonstrated potential protective effects, as melphalan-treated enterocytes showed less cellular damage in its presence and slightly reduced enteroaggregative E. coli growth. Conclusions: L-Citrulline supplementation reduced epithelial cell injury due to melphalan, suggesting therapeutic potential. Further testing is required to determine its efficacy in vivo and clarify the mechanisms underlying this potential benefit.