Divergent effects of 17-β-estradiol on human vascular smooth muscle and endothelial cell function diminishes TNF-α-induced neointima formation

Coronary heart disease (CHD) is a condition characterized by increased levels of proinflammatory cytokines, including tumor necrosis factor-α (TNF-α). TNF-α can induce vascular endothelial cell (EC) and smooth muscle cell (SMC) dysfunction, central events in development of neointimal lesions. The reduced incidence of CHD in young women is believed to be due to the protective effects of estradiol (E2). We therefore investigated the effects of TNF-α on human neointima formation and SMC/EC functions and any modulatory effects of E2. Saphenous vein (SV) segments were cultured in the presence of TNF-α (10ng/ml), E2 (2.5nM) or both in combination. Neointimal thickening was augmented by incubation with TNF-α, an effect that was abolished by co-culture with E2. TNF-α increased SV–SMC proliferation in a concentration-dependent manner that was optimal at 10ng/ml (1.5-fold increase), and abolished by E2 at all concentrations studied (1–50nM). Surprisingly, E2 itself at low concentrations (1 and 5nM) stimulated SV–SMC proliferation to a level comparable to that of TNF-α alone. SV–EC migration was significantly impaired by TNF-α (42% of control), and co-culture with E2 partially restored the ability of SV–EC to migrate and repair the wound. In contrast, TNF-α increased SV–SMC migration by 1.7-fold, an effect that was completely reversed by co-incubation with E2. Finally, TNF-α potently induced ICAM-1 and VCAM-1 expression in both SV–EC and SV–SMC. However there was no modulation by E2 in either cell-type. In conclusion, TNF-α induced SV neointima formation, increased SMC proliferation and migration, impaired SV–EC migration and increased expression of adhesion molecules. E2 exerted distinct cell-type and function-specific modulation, the mechanisms underlying which are worthy of further detailed study.