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Estrogen increases smooth muscle expression of _2C-adrenoceptors and cold-induced constriction of cutaneous arteries

¹Davis Heart and Lung Research Institute, The Ohio State University, Columbus, Ohio; ²Department of Anesthesiology and Critical Care Medicine, Johns Hopkins University, Baltimore, Maryland; and ³Faculty of Veterinary Science, University of Melbourne, Parkville, Victoria, Australia

Submitted 12 March 2007 ; accepted in final form 17 July 2007

Raynaud's phenomenon, which is characterized by intense cold-induced constriction of cutaneous arteries, is more common in women compared with men. Cold-induced constriction is mediated in part by enhanced activity of _2C-adrenoceptors (_2C-ARs) located on vascular smooth muscle cells (VSMs). Experiments were therefore performed to determine whether 17-estradiol regulates _2C-AR expression and function in cutaneous VSMs. 17-Estradiol (0.01–10 nmol/l) increased expression of the _2C-AR protein and the activity of the _2C-AR gene promoter in human cultured dermal VSMs, which was assessed following transient transfection of the cells with a promoter-reporter construct. The effect of 17-estradiol was associated with increased accumulation of cAMP and activation of the cAMP-responsive Rap2 GTP-binding protein. Transient transfection of VSMs with a dominant-negative mutant of Rap2 inhibited the 17-estradiol-induced activation of the _2C-AR gene promoter, whereas a constitutively active mutant of Rap2 increased _2C-AR promoter activity. The effects of 17-estradiol were inhibited by the estrogen receptor (ER) antagonist, ICI-182780 (1 µmol/l), and were mimicked by a cell-impermeable form of the hormone (estrogen:BSA) or by the selective ER- receptor agonist 4,4',4'''-(4-propyl-[¹H]-pyrazole-1,3,5-triyl)tris-phenol (PPT; 10 nmol/l) or the selective ER- receptor agonist 2,3-bis(4-hydroxyphenyl)-propionitrile (DPN; 10 nmol/l). Therefore, 17-estradiol increased expression of _2C-ARs by interacting with cell surface receptors to cause a cAMP/Rap2-dependent increase in _2C-AR transcription. In mouse tail arteries, 17-estradiol (10 nmol/l) increased _2C-AR expression and selectively increased the cold-induced amplification of ₂-AR constriction, which is mediated by _2C-ARs. An estrogen-dependent increase in expression of cold-sensitive _2C-ARs may contribute to the increased activity of cold-induced vasoconstriction under estrogen-replete conditions.

Raynaud's phenomenon; Rap1; Rap2; adenosine 3',5'-cyclic monophosphate; estrogen receptors

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