The anti-mitogenic activity of 17β -estradiol in coronary smooth muscle cells correlates with protein binding to its responsive element

The cellular and molecular mechanisms responsible for the protection afforded by 17β -estradiol against coronary atherosclerosis in premenopausal women remain undefined. The present studies were conducted to assess the impact of 17β -estradiol (1-100 nM) on coronary smooth muscle cell (c-SMC) proliferation and the integrity of estrogen signaling in these cells. c-SMCs were isolated from 9-month old Sinclair pigs and established in culture by standard procedures. Basal DNA synthetic rates were increased 3-fold by 24 hr in cultures challenged with 1% serum. 17β -estradiol did not modulate basal proliferation rates, but markedly reduced the mitogenic response elicited by serum in a concentration-dependent manner. The anti-mitogenic effects of 17β -estradiol in c-SMCs was compromised when cells were maximally stimulated with serum. Electrophoretic mobility shift analysis of nuclear extracts of c-SMCs using a double-stranded oligonucleotide derived from the estrogen responsive element of the vitellogenin A2 gene confirmed the occurrence of ligand-induced specific protein/DNA complexes. These data implicate anti-mitogenic effects in the protection against coronary atherosclerosis by 17β -estradiol and suggest that the response involves orotein/DNA interactions influenced bv the degree of mitoeenic stimulation of c-SMCs.