Mixture of probiotics alleviates the symptoms of atopic dermatitis through recovering immune balance in mice

Abstract

Atopic dermatitis (AD) is a chronic inflammatory skin disease, seen mostly in children causing eczema often together with intense itching. AD can be caused by genetic factors, immune system dysfunction and/or environmental factors in conjunction with the uncontrolled permeability of the skin. AD is caused by excessive T helper (Th) 2 responses, which induce immunoglobulin (Ig)E. Hypersensitivity of Th2 cells to AD is also associated with increased risk of other allergy diseases such as asthma. There are variety of therapies available to relieve AD, including emollients, anti-inflammatory agents and inhibitors. However, excessive use of these therapies causes side effects such as skin thinning, purpura, telangiectasias, drowsiness and edema. Therefore, for a fundamental atopic treatment, a particular strategy to maintain the continuous immune balance seems to be necessary. The use of probiotics could be such strategy for overcoming AD. However, selection of probiotics and their combination are important task when consider AD treatment. Therefore, to overcome AD, it is necessary to understand the exact immune mechanism induced by each probiotic. In the first study, the immunomodulatory capacity of Duolac ATP, a mixed formulation of probiotics, was examined. Results showed that the expression of programmed death-ligand (PD-L)1 was significantly upregulated on dendritic cells (DCs) treated with Duolac ATP. Furthermore, the anti-inflammatory cytokines, interleukin (IL)-10 and transforming growth factor (TGF)-β were both upregulated when BMDCs were treated with Duolac ATP. The percentage of proliferated regulatory T cells (Tregs) was enhanced when CD4+ T cells were co-cultured with Duolac ATP-treated DCs on plates coated with anti-CD3/CD28 antibodies. Intriguingly, IL-10 secretion from CD4+ T cells was also observed. The AD symptoms, histologic scores, and serum IgE levels in spontaneous mutation AD mice (Nc/Nga) were significantly decreased after oral treatment with Duolac ATP. Moreover, the Th1-mediated response in AD-induced mice treated with oral Duolac ATP showed upregulation of IL-2 and IFN- as well as of downstream signaling molecules T-bet, STAT1, and STAT4. Conversely, Duolac ATP suppressed Th2 and Th17 responses in AD-like mice, as evidenced by the downregulation of GATA3, C-maf, IL-4, IL-5, and IL-17. Additionally, Duolac ATP increased the number of Tregs found at Peyer's patches (PP) in AD mice. These results suggest that Duolac ATP modulates DCs to initiate both Th1 and Treg responses in AD mice. In the second study, the mechanism of alleviation of AD by YK4, a probiotic mixture consisting four strains of Lactobacillus and Bifidobacterium, was unveiled through intestinal galectin-9 production and immune cells analysis. The results showed that administration of YK4 in AD mouse alleviates symptoms of AD by regulating Th2-mediated response. YK4 inhibited the expression of skin thymic stromal lymphopoietin and serum IgE to near normal concentration. YK4 administration also resulted in decrease in IL-4 producing CD4+ T cells whereas increased Tregs population in PP and mesenteric lymph node (mLN). Moreover, YK4 induced an increase in interferon-gamma (IFN-producing CD4+ T cells in spleen. Furthermore, the proportion of CD103+ DCs in mLN and spleen was significantly increased in repetitive treatment of skin irritants AD mice administered with YK4 when compared to AD mice. Expression of galectin-9 in the intestine was significantly increased in AD mice administered with YK4. The expression of CD44, a receptor of galectin-9, together with PD-L1 was significantly up regulated on BMDCs when treated with YK4. Furthermore, the anti-inflammatory cytokine, IL-10 was upregulated when BMDCs were treated with YK4. The percentage of proliferated Tregs was enhanced when CD4+ T cells were co-cultured with YK4-treated BMDCs. Galectin-9 appeared to be partially contributed to the proliferation of Tregs. In summary, in the spontaneous mutation mouse model, Duolac ATP regulated IL-10 and TGF-β expression and allowed DCs to become functionally tolerant and potentially induce Treg differentiation. Furthermore, Duolac ATP regulated transcription factors and cytokines to drive naïve T cell differentiation toward Th1 lineages. In the skin irritation mouse model, YK4 induced expression of IL-10 and IL-12 in DCs, which inhibited Th2 responses by inducing Tregs differentiation. Furthermore, YK4 regulated intestinal galectin-9 and CD103+ DCs to drive naïve T cell differentiation toward Th1 and Tregs. Taken together, these results suggest that the probiotic mixture, Duolac ATP and YK4 have therapeutic potential to prevent AD symptoms and may act as an immunomodulator for AD patients.