Luppen Cynthia A, Chandler Ronald L, Noh Tommy, Mortlock Douglas P, Frenkel Baruch
Department of Biochemistry and Molecular Biology, Keck School of Medicine, University of Southern California, Institute for Genetic Medicine, Los Angeles, CA 90033, USA.
Growth Factors. 2008 Aug;26(4):226-37. doi: 10.1080/08977190802277880.
Pharmacological glucocorticoids (GCs) inhibit bone formation, leading to osteoporosis. GCs inhibit bone morphogenetic protein-2 (Bmp2) expression, and rhBMP-2 restores mineralization in GC-arrested osteoblast cultures. To better understand how GCs regulate BMPs, we investigated Bmp transcription, as well as rhBMP-induced Smad and alkaline phosphatase (ALP) activity. Bmp2 cis-regulatory regions were analyzed by reporter plasmids and LacZ-containing bacterial artificial chromosomes. We found that GCs inhibited Bmp2 via a domain > 50 kb downstream of the coding sequence. Bmp expression was evaluated by RT-PCR; whereas GCs strongly inhibited Bmp2, Bmp4 was abundantly expressed and resistant to GCs. Both rhBMP-2 and rhBMP-4 restored mineralization in GC-arrested cultures; rhBMP-2 was 5-fold more effective when dosing was based on ALP activation, however, the rhBMPs were equipotent when dosing was based on Smad transactivation. In conclusion, GCs regulate Bmp2 via a far-downstream domain, and activation of Smad, not ALP, best predicts the pro-mineralization potential of rhBMPs.
药理糖皮质激素（GCs）抑制骨形成，导致骨质疏松症。GCs抑制骨形态发生蛋白2（Bmp2）的表达，而重组人骨形态发生蛋白-2（rhBMP-2）可恢复GCs阻滞的成骨细胞培养中的矿化作用。为了更好地理解GCs如何调节骨形态发生蛋白（BMPs），我们研究了Bmp转录以及rhBMP诱导的Smad和碱性磷酸酶（ALP）活性。通过报告质粒和含LacZ的细菌人工染色体分析Bmp2顺式调控区。我们发现GCs通过编码序列下游>50 kb的一个结构域抑制Bmp2。通过逆转录聚合酶链反应（RT-PCR）评估Bmp表达；虽然GCs强烈抑制Bmp2，但Bmp4大量表达且对GCs有抗性。rhBMP-2和rhBMP-4均可恢复GCs阻滞培养中的矿化作用；然而，当基于ALP激活给药时，rhBMP-2的效果要强5倍，而当基于Smad反式激活给药时，rhBMPs的效力相当。总之，GCs通过一个远下游结构域调节Bmp2，并且Smad的激活而非ALP的激活最能预测rhBMPs的促矿化潜力。
