Phototherapy with artificial light suppresses dextran sulfate sodium-induced colitis in a mouse model

Background and Aim: Medical treatment for inflammatory bowel disease (IBD) requires chronic administration and causes side effects. Recently, anti-inflammatory effects of phototherapy were reported in animal models. The present study evaluated whether phototherapy improves dextran sulfate sodium (DSS)-induced colitis in a mouse model of IBD. Methods: Mice were divided into four equal groups: Control, DSS, DSS+light low (LL), and DSS+light high (LH) groups. Normal fluorescent light intensity in the Control and DSS groups was 200 lux. Artificial light intensities were as follows: DSS+LL group, 1000 lux; DSS+LH group, 2500 lux. After administering phototherapy for 7 days, we evaluated disease activity index (DAI), histological score, colon length/weight, serum 1,25-dihydroxyvitamin D(3) level, and serum and colonic cytokines in the mice. Results: DAI and histological scores were significantly lower in the DSS+LL group than in the DSS group (both, P<0.05). Colon length and weight were significantly higher in the DSS+LL group than in the DSS group (both, P<0.05). Serum interleukin (IL)-6, TNF-α, and IL-17 in the DSS+LL group were significantly lower, and serum and colonic IL-10 were significantly higher in the DSS+LL group than in the DSS group (all, P<0.05). Serum 1,25-dihydroxyvitamin D(3) levels in the DSS+LH group were significantly increased compared with those in the DSS+LL and DSS groups. Conclusion: Artificial light phototherapy suppressed DSS-induced colitis in mice by suppression of pro-inflammatory cytokines and promotion of anti-inflammatory cytokines.