| Am J Hypertens. 2004 May;17(5):462-9 |
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| Role of putative membrane receptors in the effects of estradiol on
human vascular cell growth |
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| Somjen D, Kohen F, Gayer B, Sharon O, Baz M, Limor R, Kulik T, Knoll
E, Stern N. |
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| Institute of Endocrinology, Metabolism, and Hypertension (DS, OS,
RL, EK, NS), Tel Aviv Sourasky Medical Center and Sackler Faculty of
Medicine, Tel Aviv University, Tel Aviv, Israel. |
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| The present study was designed to determine whether some of the effects
of estrogen on human vascular cell growth are exerted through membrane-binding
sites, using native as well as novel protein-bound, membrane non-permeant
estrogenic complexes. We measured changes in DNA synthesis and creatine
kinase-specific activity (CK), after treatment with estradiol-17beta
(E(2)), estradiol-17beta-6-(O)-carboxymethyl oxime conjugated to bovine
serum albumin (BSA) (E(2)-BSA), 6-carboxymethyl genistein (CG) or 6-
carboxymethyl genistein bound to the high molecular protein keyhole
limpet hemocyanin (CG-KLH), and 7-(O)-carboxymethyl daidzein (CD) or
7-(O)-carboxymethyl daidzein linked to keyhole limpet hemocyanin (CD-KLH).
High concentrations of either E(2) or E(2)-BSA inhibited DNA synthesis
in vascular smooth muscle cells (VSMC) (-39% +/- 28% v -32% +/- 15%).
Estradiol as well as CG and CD increased DNA synthesis dose dependently
in endothelial ECV-304 cells. The CG and CD, as well as CG-KLH and
CD-KLH, stimulated DNA synthesis dose dependently in VSMC (66% +/-
2%, 100% +/- 12%, 66% +/- 6%, and 41% +/- 8% at 300 nmol/L, respectively).
In contrast all forms of protein-bound hormones were unable to affect
DNA synthesis in ECV-304 cells or CK in either cell type. In VSMC,
both free and bound hormones increased mitogen-activated protein-kinase
(MAPK)-kinase activity, which was blocked by UO126, an inhibitor of
MAPK-kinase. Furthermore, the effects of E(2), E(2)-BSA, or CG-KLH
on DNA synthesis were inhibited by UO126. Using the E(2)-BSA linked
to the fluorescent dye Cy3.5, we directly demonstrated the presence
of membrane-binding sites for E(2) in VSMC and ECV 304 cells. Hence,
the effects of E(2) on DNA synthesis in human VSMC, but not in endothelial
cells, are apparently exerted by membrane-binding sites for E(2) and
do not require intracellular entry of E(2) through the classic nuclear
receptor route. |
