ABSTRACT
Objective To investigate the function of cAMP response element binding protein (CREB) and extracellular signal-regulated kinase (ERK1/2) in osteoclast differentiation mediated by Ca2+/calmodulin-dependent kinase Ⅱ (CaMK Ⅱ)δ,and elucidate the molecular mechanism thereof.Methods CaMK Ⅱδ RNA interference lentivirus vector was constructed and mouse RAW264.7 cells were transfected with the virus to determine the interference efficiency.After virus transfection,RAW264.7 cells were treated with 50ng/ml receptor activator of nuclear factor κB ligand (RANKL) and the phosphorylation levels of CREB and ERK1/2 were detected at different time points.The cells were also treated with PD98059,an ERK1/2 inhibitor,to determine the effect of ERK1/2 signal blocking on the expression of nuclear factor activated T-cells cytoplasmic 1 (NFATc1) and osteoclast differentiation.Results Interference efficiency of recombinant CaMK Ⅱδ virus vector was 77.2％ at mRNA level and 70.2％ at protein level.CaMK Ⅱδ RNA interference significantly suppressed phosphorylation of CREB and ERK1/2,and the levels ofp-CREB and p-ERK1/2 were down-regulated by 21％-55％ and 55％-64％,respectively.ERK1/2 inhibitor significantly down-regulated the protein expression of NFATc1,and the number of osteoclast,the number and size of bone resorption lacunae decreased by 39.3％,50.0％ and 52.3％,respectively.Conclusion CaMK Ⅱδ RNA interference may significantly suppress the phosphorylation of CREB and ERK1/2,and CREB and ERK1/2 have mediated the CaMK Ⅱδ-induced osteoclast differentiation.
ABSTRACT
Objective To study the effect of zoledronate (ZOL) on Ca2+/calmodulin-dependent kinase Ⅱ δ (CaMK Ⅱ δ) and down-stream gene expressions during osteoclast differentiation.Methods Mouse osteoclast precursors RAW264.7 cells were divided into the control group and ZOL group.The cells in both groups were induced with 50μg/L receptor activator of nuclear factor kappa B ligand (RANKL) and were harvested on 5 d,while the cells in ZOL group were also simultaneously treated with 1 × 10-6 mol/L ZOL for 2 d.Five days later,the cells were harvested and examined osteoclastogenesis,as well as gene expressions of CaMK Ⅱ δ,nuclear factor of activated T-cells cytoplasmic 1 (NFATc1),tartrate-resistant acid phosphatase (TRAP) and cell-sarcoma receptor coactivator (c-Src).Results The number of TRAP positive multinuclear osteoclasts,number and size of dentin absorption lacunae and area in the ZOL group were (20.0±3.2),(18.0±4.2) and (6 335.3± 1 043.2)μm2 respectively,which were significantly lower than (36.0 ± 8.4),(37.2 ± 5.0) and (11 636.2 ± 3 661.1) μm2 in the control group and decreased by 44.4 ％,51.6 ％ and 45.6 ％ respectively (P＜0.01).ZOL also significantly inhibited the gene expressions of CaMK Ⅱ δ,NFATc1,TRAP and c-Src,and the mRNA levels of these genes were decreased by 44.1％,49.0％,53.8％ and 49.6％ respectively,the protein level were decreased by 43.5 ％,32.2 ％,45.5 ％ and 48.0 ％ respectively.The immunofluorescent cytochemistry detection results showed the fluorescence intensity of CaMK Ⅱ δ,NFATc1,TRAP and c-Srcin in the ZOL group was significantly weakened when compared with the control group.Conclusion ZOL could significantly inhibit the osteoclast formation and bone absorption function,and down-regulates gene expressions of CaMK Ⅱ δ,NFATc1,TRAP and c-Src in osteoclast differentiation.