| AIM:To investigate the effect of 1,25-（OH）2-VitD3 on osteoclast differentiation via extracellular-regulated kinase 5（ERK5）pathway.METHODS:Bone marrow macrophages（BMMs）were incubated with 1,25-（OH）2-VitD3 at different concentrations(0,10-9,10-8,10-77 mol/L).The appropriate concentration of1,25-（OH）2-VitD3 to activate ERK5 pathway was selected.BMM cells were divided into 4different groups:normal cells group,XMD8-92 group,1,25-（OH）2-VitD3 group and1,25-（OH）2-VitD3+XMD8-92 group,the cells were treated with different reagents for 6 d.The osteoclast differentiation was measured by the TRAP staining.The protein levels of p-ERK5,ERK5 were measured by Western blot.Toluidine blue staining was applied on bone slices and bone resorption area was analyzed.The relative mRNA expression of NFATc1 and CAMKⅡwere detected by RT-PCR.RESULT:1,25-（OH）2-VitD3 at 10-88 mol/L significantly activated the phosphorylation of ERK5 in the osteoclast（P<0.05）and enhanced the differentiation of osteoclasts（P<0.01）.However,this effect was restrained by ERK5 selective inhibitor XMD8-92（P<0.05）.ERK5markedly increased the mRNA expression of CAMKⅡand NFATc1（P<0.01）.XMD8-92significantly inhibited the mRNA expression of CAMKⅡ,but did not affect the mRNA expression of NFATc1（P>0.05）.Low concentration of 1,25-（OH）2-VitD3 can enhance the differentiation and bone resorption of osteoclasts by activating ERK5 molecular signal,and CAMK II is a downstream signal of ERK5 to participate in this regulation process. |
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