Responsiveness to phytoestrogens in primary human osteoblasts is modulated differentially by a “less-calcemic” analog of 1,25 dihydroxyvitamin D3: JK 1624F2-2 (JKF)

We have reported previously, that female-derived bone cells responded to 17β-estradiol (E2) and raloxifene (Ral), and male-derived cells responded only to dihydrotestosterone (DHT) when the stimulation of creatine kinase specific activity (CK), which is a marker for hormone responsiveness, was measured. We also found that pre-treatment with the less-calcemic analog of Vitamin D, JK 1624 F2-2 (JKF), upregulated the response of CK to E2 and Ral. In this study, we analyzed the response of human bone cells from pre- and post-menopausal females and males, to phytoestrogens. Bone cells derived from pre-menopausal women showed greater stimulation of CK than cells from post-menopausal women, after treatment with E2 (30 nM), daidzein (D, 3000 nM), genistein (G, 3000 nM) and Ral (3000 nM); whereas the responses to biochainin A (BA 3000 nM), quecertin (Qu 3000 nM) or the carboxy derivative of G (cG 300 nM) were not age-dependent. Male-derived cells did not respond to phytoestrogens. When cells derived from female bones at both age groups were pre-treated with JKF, by daily addition of 1 nM, for 3 days, there was an upregulation of the response to E2, Ral, G and D but not to BA or Qu. Nuclear binding of 3[H] E2 was characteristic of the different phytoestrogens, with increase of the specific binding after pre-treatment with JKF. In contrast, the membranal binding of E2-Ov-Eu, which was specific for the estrogenic compounds except Ral, was inhibited by pre-treatment with JKF except for ICI 161480 (ICI). Male bone cells did not bind E2-Ov-Eu but bound T-BSA-Eu; this binding was abolished by pre-treatment with JKF. Pre-treatment with JKF increased mRNA for ERα and decreased mRNA for ERβ in bone cells from both age groups of females and from males, all of which expressed both ERs, with a ratio of ERα to ERβ of 121:1 in pre- and 78:1 in post-menopausal and 105:1 in male bone cells. This study raises the possibility of combined Vitamin D analog and phytoestrogen for hormonal replacement therapy to prevent post-menopausal osteoporosis, which is a subject of ongoing research in animal models.