Dexamethasone impairs the differentiation and maturation of murine dendritic cells by Toll-like receptor 4-nuclear factor-kappaB pathway.
BACKGROUND
Recent studies have demonstrated that dexamethasone (DEX) interferes with immune responses by targeting key functions of dendritic cells (DCs) at the earliest stage. However, the cellular and molecular mechanisms are still incompletely understood. This study aimed to explore the possible mechanisms by investigating the roles of DEX on differentiation, maturation & function of murine DCs and the effects of DEX on DCs via Toll-like receptor 4 (TLR4)-nuclear factor (NF)-kappaB mediated signal pathway.


METHODS
Immature DCs (imDCs) were cultured from murine bone marrow (BM) cells. We added DEX into culture medium at different time. The expression of CD11c, CD86 and I-A(b) (mouse MHC class II molecule) was determined by flow cytometry. We determined the expression of NF-kappaB and its inhibitory protein I-kappaBalpha by electrophoretic mobility shift assay (EMSA) and Western blotting, respectively. The productions of interleukin (IL)-12p70 and IL-10 in cell culture supernatants were determined by enzyme-linked immunosorbent assay (ELISA).


RESULTS
DEX impaired differentiation of DCs from murine bone marrow progenitors, and inhibited lipopolysaccharide (LPS) induced maturation of DCs. DEX significantly inhibited NF-kappaB expression of normal DCs, the higher the DEX concentration or the longer the DEX treatment time, the more obvious the effect. However, DEX had little effect on LPS-induced NF-kappaB activation, and partially impaired LPS-induced I-kappaBalpha degradation. DEX significantly decreased LPS induced IL-12p70 production by DCs. Interestingly, our results showed a synergistic effect between DEX and LPS on the production of IL-10 by DCs.


CONCLUSIONS
DEX inhibits the differentiation and maturation of murine DCs involved in TLR4-I-kappaB-NF-kappaB pathway, and also indirectly impairs Th1 development and interferes with the Th1-Th2 balance through IL-12 and/or IL-10 secretion by DCs.
He
Xiao-kui
XK
Department of Immunology, School of Basic Medical Science, Capital Medical University, Beijing 100069, China.
Wu
Xiang-ling
XL
He
Xiu-juan
XJ
Li
Bo
B
Hu
Yong-xiu
YX
D000818:Animals; D015153:Blotting, Western; D001854:Bone Marrow Cells / Q000166:cytology; D002454:Cell Differentiation / Q000187:drug effects*; D002478:Cells, Cultured; D003713:Dendritic Cells / Q000166:cytology* / Q000378:metabolism*; D003907:Dexamethasone / Q000494:pharmacology*; D024202:Electrophoretic Mobility Shift Assay; D004797:Enzyme-Linked Immunosorbent Assay; D005434:Flow Cytometry; D008297:Male; D051379:Mice; D016328:NF-kappa B / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects*; D051197:Toll-Like Receptor 4 / Q000378:metabolism*
D016328:NF-kappa B; D051197:Toll-Like Receptor 4; D003907:Dexamethasone