Effect of ERK1/2 signal pathway on the expression of OPG/RANKL in cementoblasts under stress stimulation / 解放军医学杂志

ABSTRACT

Objective To explore the effect of extracellular signal regulated kinase (ERK1/2) on the expression of osteoprotegerin/receptor activator of nuclear factor kB ligand (OPG/RANKL) in cementoblasts under mechanical tensile stress stimulation. Methods Using Flexcell FX4000T tension loading system and the ERK1/2-specific inhibitor PD98059, cementoblasts OCCM30 were randomly divided into four groups: group A (without loading and inhibitor), group B (without loading but inhibitor), group C (loading but without inhibitor), and group D (with both loading and inhibitor). The phosphorylation level of ERK1/2 was measured by Western blotting after 5, 15, 30 and 60min loading. OPG and RANKL mRNA were analyzed with fluorescent quantitative RT-PCR after 12h loading. Results Mechanical tensile stress activated ERK1/2 signal pathway of group C rapidly, and the P-ERK1/2 levels were significantly higher in group C than in group A at 5, 15 and 30min (P<0.05), then the P-ERK1/2 level of group C resumed to similar level of group A at 60min. The P-ERK levels of group B and D were significantly reduced by inhibitor PD98059. Tension stress up-regulated the expression of RANKL mRNA, and down-regulated the expression of OPG mRNA in OCCM30, the RANKL/OPG ratio increased after tension loading. With PD98059, the expression of RANKL mRNA decreased, that of OPG mRNA increased, and the RANKL/OPG ratio decreased (P<0.05). Conclusion ERK1/2 may be a signal transduction pathway for the regulation of OPG and RANKL expression after tension stress loading, but it is not the only one of activation pathways, and there maybe other common signal pathways involved in the regulation of OPG and RANKL expression.