25 hydroxy-vitamin D3-1α hydroxylase expression and activity in cultured human osteoblasts and their modulation by parathyroid hormone, estrogenic compounds and dihydrotestosterone
- 作者：Dalia Somjen ; Sara Katzburg ; Naftali Stern ; Fortune Kohen ; Orly Sharon ; Rona Limor ; Niva Jaccard ; David Hendel ; Yosef Weisman
- 关键词：Osteoblasts ; Vitamin D ; Hydroxylase ; Estrogens ; Phytoestrogens
- 刊名：The Journal of Steroid Biochemistry and Molecular Biology
- 出版年：2007
- 期刊代码：172_09600760
- 类别：med
- 出版时间：November-December 2007
- 卷：107
- 期：3-5
- 页码：238-244
- 文件大小：531 K
摘要
Human osteoblasts (hOB) produce and respond to 1,25(OH)2D3 (1,25D), suggesting an autocrine/paracrine system. We therefore examined hormonal modulation of the expression and activity of 25 hydroxy-vitamin D3-1α hydroxylase (1-Ohase) in hOB. Cells from pre- and post-menopausal women or men, were treated with estrogenic compounds and 1-OHase expression and activity were measured. 1-OHase mRNA expression was highest in pre-menopausal women hOB and was increased by all hormones tested. In post-menopausal hOB all hormones except biochainin A (BA) and genistein (G) increased 1-OHase mRNA expressions to less extent. In male-derived hOB only dihydrotestosterone (DHT) and carboxy BA (cBA) increased 1-OHase mRNA expression. 1,25D production from 25(OH)D3 had a Km of 
769–400 ng/ml (1.92–1.07 μM) and Vmax of 31.3–17.4 ng/ml (0.078–0.044 μM/60 min/5 × 106 cells) respectively, and was increased by all hormones except raloxifene (Ral) with higher stimulation in pre- than in post-menopausal cells. Only BA was almost five times more potent in pre- rather than post-menopausal hOBs. In male hOB only DHT and cBA increased 1,25D production whereas estradiol-17β (E2) had no effect and BA decreased it. These results provide evidence for the expression of 1-OHase mRNA and production of 1,25D in hOBs, which are age and sex dependent and are hormonally modulated. The role of this local autocrine/paracrine 1,25D system in bone physiology deserves further investigation.
769–400 ng/ml (1.92–1.07 μM) and Vmax of 31.3–17.4 ng/ml (0.078–0.044 μM/60 min/5 × 106 cells) respectively, and was increased by all hormones except raloxifene (Ral) with higher stimulation in pre- than in post-menopausal cells. Only BA was almost five times more potent in pre- rather than post-menopausal hOBs. In male hOB only DHT and cBA increased 1,25D production whereas estradiol-17β (E2) had no effect and BA decreased it. These results provide evidence for the expression of 1-OHase mRNA and production of 1,25D in hOBs, which are age and sex dependent and are hormonally modulated. The role of this local autocrine/paracrine 1,25D system in bone physiology deserves further investigation.