Chronic exposure of Allura Red AC (AR) at a dose found in commonly consumed dietary products exacerbates experimental colitis in mice. Chronic exposure to AR induces mild colitis, associated with elevated colonic serotonin (5-HT) levels and impairment of the epithelial barrier function via myosin light chain kinase (MLCK). This effect is dependent on tryptophan hydroxylase 1 (TPH1), the rate-limiting enzyme for 5-HT biosynthesis. Cecal transfer of the microbiota perturbed by AR exposure worsens colitis in recipient germ-free (GF) mice, and AR elevates colonic 5-HT in naïve GF mice. The study suggests chronic, but not intermittent, AR exposure promotes experimental colitis via colonic 5-HT through microbiota-dependent and -independent pathways in mice.

Yun Han Kwon, Suhrid Banskota, Huaqing Wang, Laura Rossi, Jensine A. Grondin, Saad A. Syed, Yeganeh Yousefi, Jonathan D. Schertzer, Katherine M. Morrison, Michael G. Wade, Alison C. Holloway, Michael G. Surette, Gregory R. Steinberg, Waliul I. Khan