| J Steroid Biochem Molecular Biol 89-90: 397-399, 2004 |
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| A non-calcemic Vitamin D analog modulates both nuclear and putative
membranal estrogen receptors in cultured human vascular smooth muscle
cells |
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| Dalia Somjen, , Fortune Kohen, Batya Gayerb, Esther Knoll, Rona Limor,
Merav Baz, Orly Sharon, Gary H. Posner and Naftali Stern |
|
| Institute of Endocrinology, Metabolism and Hypertension, Tel Aviv
Sourasky Medical Center, 6 Weizman Street, Tel Aviv 64239, Israel |
|
In cultured human vascular smooth muscle cells (VSMC), estradiol-17
(E2) induced a biphasic effect on DNA synthesis, i.e., stimulation
at low concentrations and inhibition at high concentrations. Additionally,
E2 increased the specific activity of creatine kinase (CK) in these
cells. Observations that novel protein-bound membrane impermeant estrogenic
complexes could elicit inhibition of DNA synthesis, suggested interaction
via membranal binding sites. Nevertheless other effects, such as increasing
CK activity were only seen with native E2 but not with E2–BSA, thus
indicating that the classical nuclear receptor pathway was involved.
In the present report, we confirm that human VSMC express both ER alpha
and ER. beta Further, pretreatment of cultured VSMC with the Vitamin
D non-calcemic analog JK 1624 F2-2 (JKF) increased ER alpha mRNA (100–200%)
but decreased ER beta mRNA (30–40%) expression as measured by real
time PCR. ER alpha protein expression assessed by Western blot analysis
increased (25–50%) in parallel, whereas ER beta protein expression
declines (25–55%). Using ovalbumin bound to E2 (Ov–E2) linked to Eu
(Eu–Ov–E2), to assess specific membrane binding sites, we observed
that membranal binding was down regulated by JKF by 70–80%. In contrast,
total cell binding of 3[H] E2, that nearly entirely represents intracellular
E2 binding, was increased by 60–100% by the same Vitamin D analog.
The results provide evidence that the effects of JKF on ER alpha /
ER beta as well as on membranal versus nuclear binding of estrogen
are divergent and show differential modulation.
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