Background Lipoxins （LXs）, endogenous anti-inflammatory and pro-resolving eicosanoids generated during various inflammatory conditions, have novel immunomodulatory properties. Because dendritic cells （DCs） play crucial roles in the initiation and maintenance of immune response, we determined whether LXs could modulate the maturation process of DCs and investigated the effects of lipoxin A4 （LXA4） on lipopolysaccharide （LPS）-induced differentiation of RAW264.7 cells into dendritic-like cells. Methods RAW264.7 cells were cultured in vitro with 1 pg/ml LPS in the absence or presence of LXA4 for 24 hours, and cellular surface markers （MHC-II, CD80 （B7-1）, CD86（B7-2）） were measured by flow cytometry （FCM）. Mixed lymphocyte reaction was performed to evaluate the allostimulatory activity. Cytoplastic IKB degradation and nuclear factor kappa B （NF-KB） translocation were detected by Western blotting. Luciferase reporter plasmid was transiently transfected into RAW264.7 cells, and luciferase activity was determined to measure the transcriptional activity of NF-KB. Results LXA4 reduced the ratio of LPS-treated RAW264.7 cells to DCs with morphological characteristics and inhibited the expression of MHC I1. LPS-induced up-regulation of CD86 was moderately suppressed by LXA4 but no obvious change of CD80 was observed. Moreover, LXA4 weakened the aUostimulatory activity of LPS-treated RAW264.7 cells. These alterations of LPS＋LXA4-treated cells were associated with a marked inhibition of IKB degradation, NF-KB translocation and then the transcriptional activity of NF-KB. Conclusions LXA4 negatively regulates LPS-induced differentiation of RAW264.7 cells into dendritic-like cells.This activity reveals an undescribed mechanism of LXA4 to prevent excessive and sustained immune reaction by regulating maturation of DCs.
