Mutual Modulation of Femarelle and Vitamin D Analog Activities in Human Derived Female Cultured Osteoblasts

Femarelle (F) activates human derived cultured female bone cells (hObs) and human bone cell line (SaOS2), which express receptors for estradiol-17β (E2; ERα and ERβ) and vitamin D (VDR). Vitamin D metabolites and analogs regulate cell proliferation (DNA) and the specific activity of creatine kinase (CK). Pretreatment with vitamin D less-calcemic analog: JKF 1624F2-2 (JKF) up-regulated responsiveness to estrogens via modulation of ERs mRNA expression. The estrogens in turn induce VDR and 25- hydroxy vitamin D3 1-α hydroxylase (1OHase) expression and 1,25(OH)2D3 (1,25D) synthesis. We compared the effects of F to those of its precourser daidzein (D) and E2 on DNA and CK, and effect of JKF pretreatment. We found: 1. F, D and E2 stimulated DNA and CK. 2. JKF increased ERα and decreased ERβ mRNA expression, up-regulated DNA and CK response to E2 and D but not to F. 3. JKF increased only E2 intracellular competitive binding. 4. F, D and E2 increased VDR and 1OHase mRNA expression and its activity measured by 1,25D production. In conclusion, F, D and E2 increases DNA and CK, as well as 1,25D production and VDR and 1OHase mRNA expression. Pre- treatment with JKF modulates the effect of E2 and D but not of F while all estrogens modulate VDR expression and both mRNA expression and activity of 1OHase in the cells. These finding that F effects are not affected by the vitamin D levels in female-derived osteoblasts may contribute to its beneficial role in treatment of post-menopausal bone loss.