Although from our experiments the increase in the catalytic activity of IDO1 following treatment with NAS is evident, we cannot exclude that IDO1-independ effects may contribute to its protective effect against colitis.11,42 NAS is an immediate precursor of melatonin which has been shown to have the ability to suppress inflammatory responses.50 NAS has also been shown to have the ability to activate the brain-derived neurotrophic factor (BDNF) receptor,51 implicated in inflammatory bowel pathophysiology.52,53. The gene discussed is BDNF; the disease is colitis.