Effect of 17beta-estradiol exposure on vasorelaxation induced by K(+) channel openers and Ca(2+) channel blockers

Calcium signaling in endothelial and vascular smooth muscle cells: sex differences and the influence of estrogens and androgens

Calcium signaling in vascular endothelial cells (ECs) and smooth muscle cells (VSMCs) is essential for the regulation of vascular tone. However, the changes to intracellular Ca2+ concentrations are often influenced by sex differences. Furthermore, a large body of evidence shows that sex hormone imbalance leads to dysregulation of Ca2+ signaling and this is a key factor in the pathogenesis of cardiovascular diseases. In this review, the effects of estrogens and androgens on vascular calcium-handling proteins are discussed, with emphasis on the associated genomic or nongenomic molecular mechanisms. The experimental models from which data were collected were also considered. The review highlights 1) in female ECs, transient receptor potential vanilloid 4 (TRPV4) and mitochondrial Ca2+ uniporter (MCU) enhance Ca2+-dependent nitric oxide (NO) generation. In males, only transient receptor potential canonical 3 (TRPC3) plays a fundamental role in this effect. 2) Female VSMCs have lower cytosolic Ca2+ levels than males due to differences in the activity and expression of stromal interaction molecule 1 (STIM1), calcium release-activated calcium modulator 1 (Orai1), calcium voltage-gated channel subunit-α1C (CaV1.2), Na+-K+-2Cl- symporter (NKCC1), and the Na+/K+-ATPase. 3) When compared with androgens, the influence of estrogens on Ca2+ homeostasis, vascular tone, and incidence of vascular disease is better documented. 4) Many studies use supraphysiological concentrations of sex hormones, which may limit the physiological relevance of outcomes. 5) Sex-dependent differences in Ca2+ signaling mean both sexes ought to be included in experimental design.

Rapid estrogen actions on ion channels: A survey in search for mechanisms

A survey of nearly two hundred reports shows that rapid estrogenic actions can be detected across a range of kinds of estrogens, a range of doses, on a wide range of tissue, cell and ion channel types. Striking is the fact that preparations of estrogenic agents that do not permeate the cell membrane almost always mimic the actions of the estrogenic agents that do permeate the membrane. All kinds of estrogens, ranging from natural ones, through receptor modulators, endocrine disruptors, phytoestrogens, agonists, and antagonists to novel G-1 and STX, have been reported to be effective. For actions on specific types of ion channels, the possibility of opposing actions, in different cases, is the rule, not the exception. With this variety there is no single, specific action mechanism for estrogens per se, although in some cases estrogens can act directly or via some signaling pathways to affect ion channels. We infer that estrogens can bind a large number of substrates/receptors at the membrane surface. As against the variety of subsequent routes of action, this initial step of the estrogen's binding action is the key.

Influence of sex steroid hormones on cerebrovascular function

The cerebral vasculature is a target tissue for sex steroid hormones. Estrogens, androgens, and progestins all influence the function and pathophysiology of the cerebral circulation. Estrogen decreases cerebral vascular tone and increases cerebral blood flow by enhancing endothelial-derived nitric oxide and prostacyclin pathways. Testosterone has opposite effects, increasing cerebral artery tone. Cerebrovascular inflammation is suppressed by estrogen but increased by testosterone and progesterone. Evidence suggests that sex steroids also modulate blood-brain barrier permeability. Estrogen has important protective effects on cerebral endothelial cells by increasing mitochondrial efficiency, decreasing free radical production, promoting cell survival, and stimulating angiogenesis. Although much has been learned regarding hormonal effects on brain blood vessels, most studies involve young, healthy animals. It is becoming apparent that hormonal effects may be modified by aging or disease states such as diabetes. Furthermore, effects of testosterone are complicated because this steroid is also converted to estrogen, systemically and possibly within the vessels themselves. Elucidating the impact of sex steroids on the cerebral vasculature is important for understanding male-female differences in stroke and conditions such as menstrual migraine and preeclampsia-related cerebral edema in pregnancy. Cerebrovascular effects of sex steroids also need to be considered in untangling current controversies regarding consequences of hormone replacement therapies and steroid abuse.

Differential regulation of K+ and Ca2+ channel gene expression by chronic treatment with estrogen and tamoxifen in rat aorta

The beneficial effect of estrogen on the vascular system is partly associated with its ability to reduce vascular contractility. Estrogen acutely activates large-conductance Ca(2+)-activated K(+) channel (BK(Ca)) and inhibits L-type voltage-gated Ca(2+) channel (VGCC) in vascular smooth muscle cells. However, a long-term influence of estrogen, estrogen deficiency, or selective estrogen receptor modulators on gene expression of these ion channels is unclear. This study was therefore aimed to determine the relative mRNA expression levels of alpha- and beta-subunits of BK(Ca), K(V)1.5 subtype of delayed rectifier K(+) channel (K(V)), and alpha(1C) subunit of L-type VGCC in endothelium-denuded aortas from female rats by a semiquantitative reverse transcription-polymerase chain reaction (RT-PCR) analysis. Rats were divided into four experimental groups: (i) sham-operated control, (ii) ovariectomized, (iii) ovariectomized with 17 beta-estradiol treatment and (iv) ovariectomized with tamoxifen treatment. The results showed that ovariectomy decreased the mRNA expression of K(V)1.5 while it increased the mRNA expression of alpha(1C) subunit of L-type VGCC. Ovariectomy-induced modulation of gene expression of these ion channels was completely prevented in ovariectomized rats receiving chronic treatment with estrogen or tamoxifen. In contrast, the expression levels of genes encoding both alpha- and beta-subunits of BK(Ca) remained the same in the four animal groups. The present study has provided the first line of evidence suggesting the long-term beneficial effects of estrogen and tamoxifen therapy on vascular ion channel expressions, which may be an important mechanism by which the favorable modulation of vessel tone by estrogen or selective estrogen receptor modulators is mediated.