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Effects of gonadal steroids and their antagonists on DNA synthesis in human vascular cells
1Institute of Endocrinology, Tel Aviv Sourasky Medical Center, The Sackler Faculty of Medicine, Tel Aviv University, Israel.
Abstract:
The cardiovascular effect of estrogen is currently under intense investigation, but the role of androgens in vascular biology has attracted little attention. Because endothelial repair and vascular smooth muscle cell (VSMC) proliferation affect atherogenesis, we analyzed the effects of 17beta-estradiol (E2), dihydrotestosterone (DHT), and sex hormone antagonists on DNA synthesis in human umbilical VSMCs and in E304 cells (a human umbilical endothelial cell line). In VSMCs, both E2 and DHT had a biphasic effect on [3H]thymidine incorporation into DNA: low concentrations (0.3 nmol/L for E2, 3 nmol/L for DHT) stimulated [3H]thymidine incorporation (+35% and +41%, respectively), whereas high concentrations (30 nmol/L for E2, 300 nmol/L for DHT) inhibited [3H]thymidine incorporation (-40%). In contrast, E2 (0.3 to 300 nmol/L) and DHT (3 to 3000 nmol/L) dose-dependently enhanced [3H]thymidine incorporation in E304 cells (peak, +85% for both). In VSMCs, high concentrations of E2 and DHT inhibited platelet-derived growth factor (PDGF)-or insulin-like growth factor (IGF-1)-induced DNA synthesis (-50% to 80%), whereas PDGF- or IGF-1-dependent DNA synthesis in E304 cells was further increased by E2. The antiestrogens tamoxifen and raloxifene mimicked the effects of E2 on DNA synthesis in both VSMCs and E304 cells. However, when coincubated with a stimulatory concentration of E2 (0.3 nmol/L), tamoxifen and raloxifene blocked E2-induced [3H]thymidine incorporation in E304 cells but not in VSMCs. Finally, the androgen antagonist flutamide inhibited the biphasic effects of DHT on VSMCs and blocked the increase in DNA elicited by DHT in E304 cells. The results suggest complex, dose-dependent, and cell-specific interactions of estrogens, androgens, and their respective antagonists in the control of cellular proliferation in the vascular wall. Gonadal steroid-dependent inhibition of VSMC proliferation and stimulation of endothelial replication may contribute to vascular protection and remodeling responses to vascular injury.
Insights
Estrogen and androgens have complex, dose-dependent effects on vascular cell proliferation. Low hormone doses stimulate, while high doses inhibit vascular smooth muscle cell growth, but stimulate endothelial cells, potentially protecting against vascular injury.
Area of Science:
- Cardiovascular Biology
- Endocrinology
- Vascular Cell Biology
Background:
- Estrogen's cardiovascular effects are well-studied, but androgens' roles in vascular biology are less understood.
- Endothelial repair and vascular smooth muscle cell (VSMC) proliferation are critical in atherogenesis.
Purpose of the Study:
- To investigate the effects of 17beta-estradiol (E2) and dihydrotestosterone (DHT) on DNA synthesis in human VSMCs and endothelial cells (E304).
- To analyze the impact of sex hormone antagonists on these cellular processes.
Main Methods:
- Assessed [3H]thymidine incorporation to measure DNA synthesis in VSMCs and E304 cells.
- Exposed cells to varying concentrations of E2, DHT, and their antagonists (tamoxifen, raloxifene, flutamide).
- Investigated the effects on basal and growth factor (PDGF, IGF-1)-stimulated DNA synthesis.
Main Results:
- E2 and DHT exhibited biphasic effects on VSMC DNA synthesis (stimulation at low doses, inhibition at high doses).
- E2 and DHT dose-dependently enhanced DNA synthesis in E304 endothelial cells.
- Hormone antagonists modulated these effects in cell-specific manners, with flutamide inhibiting DHT effects and antiestrogens blocking E2 effects in E304 cells.
Conclusions:
- Estrogen and androgen actions on vascular cells are complex, dose-dependent, and cell-specific.
- Inhibition of VSMC proliferation and stimulation of endothelial cell replication by gonadal steroids may contribute to vascular protection and repair.