Lactoferrin promotes MC3T3-E1 osteoblast cells proliferation via MAPK signaling pathways

Lactoferrin has attracted great attention as a potential functional factor to prevent osteoporosis due to its various bioactivities. However, the molecular mechanism underlining the osteogenic activity of lactoferrin is unclear. In this study, effect of lactoferrin on MC3T3-E1 osteoblast cells proliferation was determined using MTT assay, while MAPK signaling pathways related to proliferation of MC3T3-E1 osteoblast cells were investigated based on mRNA and protein expressions. The distribution of cells at different cell cycle stages was evaluated by flow cytometry. Our findings indicated that lactoferrin enhanced MC3T3-E1 osteoblast cells proliferation in a dose-dependent manner; namely, it increased the proportion of cells in S and G2/M phases. Furthermore, we also found that lactoferrin could stimulate ERK, JNK and p38 MAPK. The mRNA expression of MAPK were significantly enhanced after treatment of lactoferrin. Lactoferrin significantly promoted the activation-associated phosphorylation of ERK and p38 MAPK and prevented the activation of JNK. Additionally, lactoferrin could enhance c-Fos and c-Jun expression by 3 times and 26 times, respectively. These results indicated that lactoferrin induced MC3T3-E1 osteoblast cells proliferation through c-Fos and c-Jun by stimulating ERK, JNK and p38, elucidating the molecular basis of the osteogenic activity of lactoferrin on MC3T3-E1 osteoblast cells.