Stimulation of oestrogen receptor-expressing endothelial cells with oestrogen reduces proliferation of cocultured vascular smooth muscle cells.

1. Oestrogen reduces vascular smooth muscle cell proliferation in mouse vascular injury models. Data on the antiproliferative effect of oestrogen in cultured vascular smooth muscle cells (VSMC) are less conclusive than those obtained in whole animal studies. 2. In the present study, we investigated the hypothesis that oestrogen-induced attenuation of VSMC proliferation is facilitated by the presence of endothelial cells (EC) using a coculture system of EC and VSMC. 3. Treatment with a physiological concentration of oestrogen (17beta-estradiol (E2); 100 nmol/L) had no effect on fetal calf serum (FCS)-stimulated DNA synthesis in either A7r5 VSMC or bEnd.3 EC. However, stimulation of bEnd. 3 cells with E2 in a coculture system of bEnd.3 and A7r5 cells reduced FCS-induced DNA synthesis in A7r5 cells by approximately 45%. The nitric oxide synthase inhibitor N(G)-nitro-L-arginine methyl ester (l-NAME; 100 micromol/L) did not reverse the oestrogen-induced attenuation of DNA synthesis. The antiproliferative effect of E2 may be mediated via either oestrogen receptor (ER) alpha, ERbeta or both because the bEnd.3 cells expressed immunoreactivity for both ER subtypes. 4. These data show that ERalpha- and ERbeta-expressing endothelial cells, which are stimulated with a physiological concentration of oestrogen, release a factor(s) that arrests the proliferation of cocultured VSMC. Oestrogen-induced attenuation of vascular smooth muscle cell proliferation is not prevented by L-NAME, suggesting that a mechanism other than endothelial NO is involved.

Demonstration of mitochondrial oestrogen receptor beta and oestrogen-induced attenuation of cytochrome c oxidase subunit I expression in human periodontal ligament cells.

OBJECTIVE: Periodontal ligament (PDL) cells express oestrogen receptor beta (ERbeta) protein, but cellular functions regulated by ERbeta in these cells have not been identified. In this study we determine if ERbeta is localised to mitochondria and if oestrogen regulates mitochondrial function in human PDL cells obtained from teeth extracted for orthodontic reasons. DESIGN: Subcellular distribution of ERbeta was determined by confocal microscopy of cells co-stained with ERbeta antibody and the mitochondrion-selective probe MitoTracker and by immunogold electron microscopy. Expression of the mitochondrial enzyme cytochrome c oxidase subunit I, involved in oxidative phosphorylation, was determined by Western blotting in cells treated with or without physiological concentrations of the endogenous oestrogen 17beta-oestradiol. RESULTS: ERbeta immunoreactivity was observed both in the nuclei and the cytoplasm. MitoTracker-labelling was observed in the cytoplasm, especially in the perinuclear region, but not in the nuclei. Co-localisation of ERbeta and MitoTracker was observed in cells derived from both male and female subjects. Mitochondrial localisation of ERbeta was confirmed by immunogold electron microscopy. Cells treated with or without 17beta-oestradiol (100 nM) displayed an identical pattern of staining for mitochondria. Treatment with 100 nM 17beta-oestradiol attenuated cytochrome c oxidase subunit I expression by about 30%, while combined treatment with 17beta-oestradiol and the ER blocker ICI 182780 (10 microM) had no effect. CONCLUSION: This study demonstrates mitochondrial localisation of ERbeta and oestrogen-induced decrease in the expression of cytochrome c oxidase subunit I in human PDL cells, suggesting that oestrogen probably via ERbeta influences mitochondrial function and PDL cell energy metabolism.