The hypothesis that cross-talk between membrane-active beta-adrenergic agonists and estrogens includes beta-adrenergic modulation of estrogen receptor (ER)-regulated gene expression was investigated. Vascular smooth muscle-derived A7r5 cells were transfected with an ERalpha expression plasmid (pCR3.1-hERalpha), the estrogen response element (ERE)-linked reporter pERE-E1b-luciferase (ERE-Luc), and pCMV-beta-galactosidase using a lysine-conjugated adenovirus transfection method. Hormone or agonist treatment and harvest followed 6 hours and 24 hours later, respectively. Treatment with 17beta-estradiol (E(2), 1 nmol/L) significantly stimulated ERE-Luc activity. Isoproterenol (10-9 to 10-6 mol/L) treatment alone did not stimulate ERE-Luc activity. Cotreatment with both E(2) and isoproterenol resulted in complete inhibition of E(2)-stimulated ERE-Luc activity. This isoproterenol effect was prevented by the beta-adrenergic antagonist propanolol (10-6 mol/L). Adrenomedullin treatment in these cells (1-50 nmol/L) did not inhibit ER/ERE-Luc activity, whether in the presence or absence of E(2). Moreover, isoproterenol did not affect vitamin D-stimulated VDRE-Luc expression, indicating that the inhibitory effect of isoproterenol on E(2)-directed ERE-Luc expression is specific among nuclear transcription factor receptors. Moreover, in MCF-7 breast cancer cells, there was no effect of isoproterenol on ER/ERE-directed transcription in the absence or presence of E(2), demonstrating tissue specificity of this isoproterenol effect. These studies demonstrate cross-talk between the beta-adrenergic agonist isoproterenol and ER-directed reporter gene expression in A7r5 cells. Furthermore, this cross-talk is specific with respect to agonist, nuclear receptor species, and cell type. These observations may have important implications both for the use of beta-adrenergic agents to treat hypertension and for possible gender-related differences in cardiovascular regulation.
