Effect of oral administration of <i>Bifidobacterium breve strain Yakult</i> on atopic dermatitis via improvement of the intestinal environment in a mouse model

<p>Atopic dermatitis (AD) is characterized by pruritus and eczema and is caused by biased differentiation of type 2 helper T cells (Th2). Regulatory T cells (Treg) regulate the immune response and prevent the development of AD. Because AD is closely associated with the gut microbiota, we focused on the probiotic Bifidobacterium breve strain Yakult (BY) . In this study, we investigated the effect of oral administration of BY on AD in Nc/Nga mice. Picryl chloride solution was applied onto the backs of the mice to induce AD. We then orally administered tap water (0.2 mL/day) to mice in the AD group and BY solution (5×10⁹ CFU/0.2 mL/day) to mice in the BY group. The control group comprised mice in which AD was not induced; these mice were orally administered tap water (0.2 mL/day). After the experimental period, the skin on the back and small intestinal specimens were collected from the mice and examined. The lesions on the back showed greater improvement in the BY group than in the AD group. The expression level of cyclooxygenase-2 was significantly decreased in the lesion site. Th1 and Th2 expression levels were lower and Treg expression levels were higher in the BY group than in the AD group. In the small intestine, the Th1 and Treg expression levels were higher and the Th2 expression levels were lower in the BY group than in the AD group. In the lesion site, BY treatment improved AD by suppressing Th2 expression levels with an increase in Treg expression levels. In the small intestine, the increase in Treg expression levels also improved the immune balance. These results suggest that administration of BY improves AD through improvement of intestinal immunity.</p>