Abstract:

Objective To investigate the effect of lactadherin on secretion of interleukin (IL)-12 and IL-10 by immature dendritic cells (iDCs) through ERK and p38 MAPK signaling pathway. Methods Cord blood monocytes were isolated from human umbilical cord blood and cultured in vitro in the presence of recombinant human granulocyte-macrophage colony-stimulating factor (50 ng/mL) and recombinant human interleukin-4 (10 ng/mL) to obtain the iDCs. According to different interventions with lactadherin (10 μg/mL) and signaling pathway inhibitors, iDCs were divided into 8 groups: ①control group; ②lactadherin group; ③ERK signaling pathway inhibitor group; ④ERK signaling pathway inhibitor+lactadherin group; ⑤p38 MAPK signaling pathway inhibitor group; ⑥p38 MAPK signaling pathway inhibitor+lactadherin group; ⑦JNK signaling pathway inhibitor group; ⑧JNK signaling pathway inhibitor+lactadherin group. The phosphorylation of ERK, JNK and p38MAPK protein was detected by Western blotting, and the levels of IL-12 and IL-10 in the culture media were determined by ELISA. Results Compared with control group, the phosphorylation of ERK protein was increased (P<0.05), the phosphorylation of p38 MAPK protein was decreased (P<0.05), the levels of IL-12 and IL-10 were significantly decreased (P<0.05), and the ratio of IL-12/IL-10 was significantly increased in lactadherin group (P<0.05). There was almost no phosphorylation of ERK protein in ERK signaling pathway inhibitor group and ERK signaling pathway inhibitor+lactadherin group, the levels of IL-12 and IL-10 in ERK signaling pathway inhibitor+lactadherin group were significantly higher than those in lactadherin group (P<0.05), and the ratio of IL-12/IL-10 in ERK signaling pathway inhibitor+lactadherin group was significantly lower than that in lactadherin group (P<0.05). There was almost no phosphorylation of p38 MAPK protein in p38 MAPK signaling pathway inhibitor group and p38 MAPK signaling pathway inhibitor+lactadherin group, the levels of IL-12 and IL-10 in p38 MAPK signaling pathway inhibitor+lactadherin group were significantly lower than those in lactadherin group (P<0.05), and the ratio of IL-12/IL-10 in p38 MAPK signaling pathway inhibitor+lactadherin group was significantly higher than that in lactadherin group (P<0.05). Conclusion Lactadherin regulates the secretion of IL-12 and IL-10 by iDCs through activation of ERK signaling pathway and inactivation of p38 MAPK signaling pathway.

Key words: lactadherin, ERK, p38 MAPK, immature dendritic cells, cytokines, IL-12, IL-10