Synergistic effect of toll-like receptor 4 and thymic stromal lymphopoietin on the maturation of murine dendritic cells

Objectives: To investigate whether there was a synergistic effect of toll-like receptor (TLR) 4 and thymic stromal lymphopoietin (TSLP) on dendritic cells (DCs) activation. Methods: The maturation of bone marrow dendritic cells (BMDCs) cultured in the presence of lipopolysaccharide (LPS), LPS plus TLR4-myeloid differentiation protein (MD)-2, LPS plus TSLP receptor (TSLPR)-immunoglobulin (Ig) G, or LPS plus TLR4-MD2 combined with TSLPR-Ig G, was detected. CD80 and CD86 expression was analyzed by flow cytometry (FCM). Quantitative real-time polymerase chain reaction (qRT-PCR) was performed to assess the expression of TSLP and TLR4. Besides, TSLP concentrations of culture supernatants were determined using enzyme-linked immunosorbent assay (ELISA). Protein levels of mitogen-activated protein kinase (MAPK), phosphorylation extracellular regulated protein kinases (pERK) 1/2, and signal transducers and activators of transcription (STAT) 3 were measured by Western blotting. Results: CD80+ and CD86+ cell percentages were significantly decreased by TLR4-MD2, TSLPR-Ig G, and TLR4-MD2 plus TSLPR-Ig G. The mRNA levels of TLR4 could be effectively reduced by TSLPR-Ig G (P < 0.05), but TSLP level was not affected by TLR4-MD2. However, the TSLP concentrations were effectively decreased by TLR4-MD2 compared with LPS group. Moreover, the protein levels of MAPK and pERK1 were significantly reduced by TSLPR-Ig G, and the protein levels of MAPK and STAT3 were significantly reduced by TLR4-MD2. Conclusion: These data indicate that TLR4 combined with TSLP could exert synergistic action on BMDCs maturation. The synergistic effect may be regulated by MAPK signaling pathway.