These results suggest that PEG may have an ability to induce eosinophil infiltration in the skin through RANTES production by LCs, and would explain the role of S. aureus colonization in AD patients.

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Background: Atopic dermatitis (AD) is a chronic inflammatory skin disease with immunopathologic features that vary depending on the duration of the lesion. Skin lesions of AD patients show an increased number of Th2 cells in the dermis and superficial Staphylococcus aureus colonization. The purpose of this study was to predict the effects of peptido- glycan (PEG) from S. aureus on the induction of interleukin (IL)-4 production in AD patients. Methods: PEG was applied to barrier-disrupted abdominal mouse skin every 5 days. Twenty days later, IL-4 production in the spleen was investigated by reverse transcription-polymerase chain reaction (RT-PCR). Spleen cells from normal mice were also treated in vitro with PEG and processed for IL-4 production by RT-PCR and enzyme-linked immunosorbent assay. Results: IL-4 production was significantly increased in the spleen of PEG-treated mice compared with that of PBS-applied mice. In addition, in vitro experiments demonstrated that PEG was able to induce IL-4 production in murine spleen cells. Furthermore, IL-4 production was associated with IL-18 production, but not with IL-2 production from PEG-stimulated spleen cells, and IL-4 mRNA was expressed in CD4+ lymphocytes in the spleen cells. In in vivo experiments, percutaneous treatment with PEG induced mRNA expression not only for IL-4 but also for IL-18 in the spleen. Conclusion: These results suggest that PEG may influence the induction of a Th2-dominant cytokine response in AD patients through IL-4 production from CD4+ T cells stimulated with PEG-induced IL-18.

Background: Our previous study showed that percutaneous application of peptidoglycan from Staphylococcus aureus induced eosinophil infiltration in murine skin through production of CCL5/RANTES (regulated upon activation in normal T cells expressed and secreted) from epidermal Langerhans cells. Although it is well known that peptidoglycan is an agonist of Toll-like receptor (TLR)-2, it is unclear whether other TLR agonists are able to induce RANTES production from Langerhans cells. Methods: Langerhans cells were purified from murine epidermal cells by the panning method using anti-IA^d monoclonal antibody. RANTES production by Langerhans cells was investigated by RT-PCR and ELISA. Analysis of the signaling pathways responsible for RANTES production by Langerhans cells was performed by ELISA using N-acetyl-L-cysteine, SP600125, SB203580 and PD98059, which are specific inhibitors of NF-κB activation, JNK, p38 MAPK and ERK, respectively, and was finally confirmed by Western blot analysis. Results: Peptidoglycan, poly(I:C), lipopolysaccharide and CpG DNA, which signal through TLR-2, TLR-3, TLR-4 and TLR-9, respectively, were found to strongly induce RANTES production. Treatment with N-acetyl-L-cysteine inhibited all TLR agonist-induced RANTES production. However, treatment with SP600125 did not inhibit CpG DNA-induced RANTES production. Furthermore, treatment with SB203580 inhibited only peptidoglycan- and lipopolysaccharide-induced RANTES production and the inhibition was correlated with that of p38 MAPK phosphorylation. Conclusion: These results suggest that the signaling pathway of RANTES production from murine Langerhans cells induced by different TLR stimuli is not necessarily the same, and that inhibition of p38 MAPK may be a more specific therapeutic target for eosinophilic inflammation in patients with atopic dermatitis associated with S. aureus colonization.