Ingestion of heat-treated Lactobacillus rhamnosus GG prevents development of atopic dermatitis in NC/Nga mice

Background: Continuous oral administration of live Lactobacillus rhamnosus GG (L. GG) to pregnant subjects with atopic dermatitis and their children, suppressed the frequency of atopic dermatitis. The details of mechanisms and immune systems involved in this suppressive effect, however, remain speculative. Objective: We sought to clarify suppressive mechanisms of L. GG on atopic dermatitis by using NC/Nga mice, a model of human atopic dermatitis. Methods: Maternal mice and infant mice were fed with food containing or not containing heat-treated L. GG during pregnancy and breastfeeding, and after weaning. Results: Control NC/Nga mice raised under an air-uncontrolled condition spontaneously manifested typical skin lesions very similar to those in patients with atopic dermatitis. On the other hand, administration of food containing heat-treated L. GG inhibited the onset and development of atopic skin lesions, accompanied by smaller numbers of mast cells and eosinophils in the affected skin sites. Mice fed with L. GG showed a significant increase in plasma IL-10 levels compared with control mice, while there was no significant difference in the proportion of splenic CD4⁺CD25⁺ regulatory T cells between mice fed with L. GG and control mice. The IL-10 mRNA expression was enhanced in both Peyer's patches and mesenteric lymph nodes in mice fed with L. GG. Conclusion: These findings suggest that some components of heat-treated L. GG may have an ability to delay the onset and suppress the development of atopic dermatitis, probably through a strong induction of IL-10 in intestinal lymphoid organs and systemic levels.