Interaction between the effects of the selective estrogen modulator femarelle and a vitamin D analog in human umbilical artery vascular smooth muscle cells.

To further investigate the interaction between vitamin D system and estrogen-mimetic compounds in the human vasculature we studied the effect of the “less- calcemic” analog of 1,25(OH) 2 D 3 (1,25D); JK 1624F 2 -2 (JKF) in the presence of selective estrogen modulator femarelle (F), the phytoestrogen daidzein (D) and estradiol-17b (E 2 ) on 3 [H] thymidine incorporation (DNA synthesis) and creatine kinase specific activity (CK) in human umbilical artery vascular smooth muscle cells (VSMC). F, D and E 2 , stimulated DNA synthesis at low concentrations, and inhibited it at high concentrations. All estrogen-related compounds increased CK dose- dependently. Daily treatment with JKF (1 nM for 3 days) resulted in decreased DNA synthesis, increased CK and up- regulation of the stimulation of DNA synthesis by low estrogen-related hormones whereas D- and E 2 - mediated inhibition of cell proliferation was abolished by JKF. In contrast, inhibition of cell proliferation by F could not be blocked by JKF. JKF also up-regulated the stimulatory effects on CK by F, E 2 and D. VSMC expressed Estrogen Receptor (ER)a and ERb mRNA at a relative ratio of 2.7:1.0, respectively. JKF pretreatment increased ERa (∼50%) and decreased ERb (∼25%) expression. E 2 did not affect ERs whereas both D and F up-regulated ERb (∼100%) and ERa (∼50%). Additionally, JKF increased the intracellular competitive binding of F (from ∼70 to ∼310%), of D (from ∼60 to ∼250%) and of E 2 from (from ∼ 70 to ∼320%). F reciprocally modulated the vitamin D system by up-regulating VDR- and 25 hydroxyy vitamin D 1-a hydroxylase (1OHase) mRNA expression (∼120%). F also stimulated 1OHase activity as indicated by an increase in the production of 1, 25D (∼250%). A similar increase was elicited by D (∼90%) but not by E 2 . In conclusion, F has unique effects on human VSMC in that it can sustain inhibition of cell growth even in the presence of the vitamin D analog JKF. That JKF increases ER expression and F increased the endogenous production of 1, 25D and VDR expression offer new opportunities to modulate VSMC growth. Whether or not these mutual effects of F and JKF can be exploited to promote vascular health, particularly in estrogen-deficient states (e.g., menopause) is under investigation. [ABSTRACT FROM AUTHOR]