The roles of reactive oxygen species produced by contact allergens and irritants in monocyte-derived dendritic cells

Background: Although reactive oxygen species (ROS) have been produced in both mouse bone marrow-derived dendritic cells (DCs) and XS-106 DCs by contact sensitizers and irritants in previous studies, the generation of ROS in human monocyte-derived DCs (MoDCs) and their role in contact hypersensitivity (CHS) has yet to be elucidated. Objective: The purpose of this study was to determine whether contact allergens and irritants induce ROS in MoDCs and, if so, to evaluate the role of contact al lergen and irritant induced-ROS in MoDCs in CHS. Methods: Production of ROS was measured by 5-(and-6)-chloromethyl-2',7'- dichlorodihydrofluoresceln diacetate (CMH2DCFDA) assay. Surface CD86 and HLA-DR molecules were detected by flow cytometry. Protein carbonylation was detected by Western blotting. Results: ROS were produced by contact allergens such as dinitrochlorobenzene (DNCB) and thimerosal and the irritant benzalkonium chloride (BKC). DNCB-induced, but not BKC-induced, ROS increased surface CD86 and HLA-DR molecules on MoDCs and induced protein carbonylation. These changes were reduced in the presence of antioxidant N-acetyl cysteine. Conclusion: Our results suggest that DNCB-induced ROS may be different from those induced by irritant BKC. The DNCB-induced ROS may be associated with the CHS response, because they activate surface molecules on DCs that are important for generating immune reactions.