17beta-Estradiol and smooth muscle cell proliferation in aortic cells of male and female rats.

The low incidence of cardiovascular disease in women before menopause or during hormone replacement therapy suggests a protective effect of estrogens. The mechanism(s) are uncertain but may involve effects on lipids, coagulation and the endothelium. Vascular smooth muscle cell (VSMC) proliferation also contributes to atherosclerosis. Hence, we investigated whether 17 beta-estradiol (E2) inhibits VSMC proliferation. VSMC of 6 female and 6 male Wistar Kyoto rats (WKY; age 10-12 weeks) were incubated for 24 h with E2 and/or fetal calf serum (FCS). E2 (10(-9)-10(-5) M) alone reduced [3H]thymidine uptake at 10(-5) (n=8, p<0.05 vs control) in female cells only. In female and male VSMC, FCS (1%) increased [3H]thymidine uptake (4.5-fold, p<0.05 vs. control). When given simultaneously, E2 did not prevent this effect of FCS (1%). However, when cells were preincubated for 24 h with E2 and then stimulated with FCS, [3H]thymidine uptake was reduced by E2 at 10(-5) M in female VSMC (n=7, p<0.05 vs FCS alone), while in male VSMC this effect was minimal (n.s.): Both female and male VSMC expressed estrogen receptors as demonstrated by RT-PCR. Pretreatment of female VSMC cells with the E2 receptor antagonist tamoxifen prevented the antiproliferative effects exerted by E2. In aortic VSMC of female rats, E2 moderately inhibited proliferation on its own and during stimulation with FCS, while this effect was small in VSM of male rats. The expression of the E2 receptor in female and male VSMC and the effects of tamoxifen suggest that this effect is mediated by E2 receptor

Bimodal effects of angiotensin II on migration of human and rat smooth muscle cells

Angiotensin II may be an important mediator of neointima formation in vascular disease. This study was designed to examine the mechanisms involved in angiotensin II-stimulated migration of human and rat aortic vascular smooth muscle cells (VSMCs). VSMCs were seeded in one corner of Nunc four-well culture chambers; angiotensin II within filter paper was glued onto the wall of the opposite side. After 48 hours of incubation in serum-free medium containing growth-arresting factor, migrated cells were counted using a light microscope. Angiotensin II (2 x 10(-11) to 2 x 10(-8) mol/L) increased migration of VSMCs in a concentration-dependent manner. Interestingly, at higher concentrations of angiotensin II (up to 2 x 10(-6) mol/L), migration was reduced to levels comparable with control levels. Losartan, an AT1 receptor antagonist, prevented migration, while PD123319, an AT2 receptor antagonist, had no significant inhibitory effect. Transforming growth factor-beta 1 (TGF-beta 1; 0.01 to 10.0 pg/mL) inhibited migration induced by angiotensin II (2 x 10(-8) mol/L) in a concentration-dependent manner. A neutralizing TGF-beta antibody unmasked migratory effects of high concentrations of angiotensin II. Furthermore, angiotensin II (10(-6) mol/L) upregulated TGF-beta 1 mRNA levels fivefold in rat and fourfold in human VSMCs; this effect was prevented by losartan but not by PD123319. Thus, the effects of angiotensin II on migration of VSMCs are bimodal, ie, both migratory and antimigratory pathways are activated. Autocrine release of TGF-beta 1 induced by angiotensin II exerts an antimigratory effect in rat and human VSMCs. The AT1 receptor is involved in regulation of both pathway