Abstract
Our previous study demonstrated that supplemental naringenin reduced the development of colitis induced by dextran sodium sulfate (DSS) in mice, however, the effect of naringenin on the recovery from colonic damage was totally unknown. The primary purpose was to investigate if naringenin promoted recovery from colonic damage in DSS-administered mice and colonic tissues. When mice were fed diets lacking or containing naringenin (0.3%, w/w) for 11 days after colitis induction through DSS administration, the supplemental naringenin was found to promote a reversal of body weight loss and suppress tumor necrosis factor (TNF)-α mRNA expression in the DSS-administered mice. Moreover, protein expression of two tight junction proteins, claudin-3 and junctional adhesion molecule-A, was higher in DSS-administered mice that were fed naringenin than in the mice that did not receive naringenin. To examine the early mechanisms underlying the naringenin-mediated reduction of colonic damage, the inflamed colonic tissues of DSS-administered mice were incubated with or without naringenin for 24 hours; in tissues incubated with naringenin, TNF-α production was lower and interleukin (IL)-10 and CD206 mRNA expression was higher than in tissues incubated without naringenin, but naringenin did not affect the expression of the tight junction proteins. Flow cytometry results further demonstrated that naringenin reduced TNF-α-positive epithelial cells, but not macrophages, and promoted the polarization of M2-type macrophages in the colonic tissues. Thus, supplemental naringenin promoted recovery from colonic damage in mice with colitis, and suppression of epithelial TNF-α production and induction of M2-type macrophages might represent the early mechanisms underlying this naringenin effect.