Sex and salt hormones: rapid effects in epithelia

Neuroprotective Role of Hypothermia in Hypoxic-ischemic Brain Injury: Combined Therapies using Estrogen

Hypoxic-ischemic brain injury is a complex network of factors, which is mainly characterized by a decrease in levels of oxygen concentration and blood flow, which lead to an inefficient supply of nutrients to the brain. Hypoxic-ischemic brain injury can be found in perinatal asphyxia and ischemic-stroke, which represent one of the main causes of mortality and morbidity in children and adults worldwide. Therefore, knowledge of underlying mechanisms triggering these insults may help establish neuroprotective treatments. Selective Estrogen Receptor Modulators and Selective Tissue Estrogenic Activity Regulators exert several neuroprotective effects, including a decrease of reactive oxygen species, maintenance of cell viability, mitochondrial survival, among others. However, these strategies represent a traditional approach of targeting a single factor of pathology without satisfactory results. Hence, combined therapies, such as the administration of therapeutic hypothermia with a complementary neuroprotective agent, constitute a promising alternative. In this sense, the present review summarizes the underlying mechanisms of hypoxic-ischemic brain injury and compiles several neuroprotective strategies, including Selective Estrogen Receptor Modulators and Selective Tissue Estrogenic Activity Regulators, which represent putative agents for combined therapies with therapeutic hypothermia.

Estrogen and estrogen receptors in the modulation of gastrointestinal epithelial secretion

Gastrointestinal (GI) epithelial ion transport is physiologically important in many aspects of humans, such as in maintaining fluid balance of whole body, and also plays a role in the development and progression of common GI disease. Estrogen and estrogen receptors have been shown to modulate the activity of epithelial ion secretion in GI tract. This review aims to address the current state of knowledge about the role of estrogen and estrogen receptors in modulation of GI epithelial secretion and to elucidate the underlying mechanisms. We highlight the recent findings regarding the importance of estrogen and estrogen receptors in GI epithelia protection and body fluid balance by modulation of gastrointestinal epithelial HCO₃^- and Cl^- secretion, especially current information about the regulatory mechanisms of duodenal HCO₃^- secretion based on our study in this field. Since there are no reviews on this topic but only few papers to address the main issues, we hope to timely provide new perspectives for the association between estrogen and GI disease.

Evidence for non genomic action of 17β estradiol on transepithelial resistance of human fetal membranes

BACKGROUND

The role of hormones in the transport mechanisms of human fetal membranes in pregnancy is unclear. Estrogens are essential hormones in pregnancy and they play an important role in the ion transport via membranes.

AIM

The aim of this study was to investigate the effect of 17β-estradiol on transepithelial electrical resistance in the human amniochorion.

MATERIAL AND METHODS

Specimens of human fetal membranes were obtained. 17β-estradiol, tamoxifen and their combination were added in an Ussing chamber. Transepithelial resistance was measured before and after the addition of each solution.

RESULTS

An increase in transepithelial resistance was seen after the addition of estradiol to both sides of the membranes. The effect was rapid with a peak at the 1st min of application and dose-depended. Tamoxifen, caused a similar effect but smaller in magnitude and shorter in duration. Tamoxifen in combination with estradiol inhibited only in part the action of estradiol.

CONCLUSIONS

These results suggest that estradiol induces a rapid increase of transepithelial resistance in human fetal membranes in vitro via a non-genomic pathway. It is possible those changes in transepithelial resistance play a role in the control of permeability of human amniochorion.

Genomic priming of the antisecretory response to estrogen in rat distal colon throughout the estrous cycle

The secretion of Cl(-) across distal colonic crypt cells provides the driving force for the movement of fluid into the luminal space. 17beta-Estradiol (E2) produces a rapid and sustained reduction in secretion in females, which is dependent on the novel protein kinase C delta (PKC delta) isozyme and PKA isoform I targeting of KCNQ1 channels. This sexual dimorphism in the E2 response is associated with a higher expression level of PKC delta in female compared with the male tissue. The present study revealed the antisecretory response is regulated throughout the female reproductive (estrous) cycle and is primed by genomic regulation of the kinases. E2 (1-10 nm) decreased cAMP-dependent secretion in colonic epithelia during the estrus, metestrus, and diestrus stages. A weak inhibition of secretion was demonstrated in the proestrus stage. The expression levels of PKC delta and PKA fluctuated throughout the estrous cycle and correlated with the potency of the antisecretory effect of E2. The expression of PKC delta and PKA were up-regulated by estrogen at a transcriptional level via a PKC delta-MAPK-cAMP response element-binding protein-regulated pathway indicating a genomic priming of the antisecretory response. PK Cdelta was activated by the membrane-impermeant E2-BSA, and this response was inhibited by the estrogen receptor antagonist ICI 182,780. The 66-kDa estrogen receptor-alpha isoform was present at the plasma membrane of female colonic crypt cells with a lower abundance found in male colonic crypts. The study demonstrates estrogen regulation of intestinal secretion both at a rapid and transcriptional level, demonstrating an interdependent relationship between both nongenomic and genomic hormone responses.

Novel female sex-dependent actions of oestrogen in the intestine

The intestine is an oestrogen responsive organ and circulatory oestrogens suppress Cl(-) secretion across the epithelium of the colon to promote fluid retention at the luteal stage of the menstrual cycle. Ion transporters in the colon which are involved in Cl(-) secretion show differential expression between males and females as do the signalling protein kinase intermediates involved in acutely regulating these transporters. Work from our laboratory has identified the KCNQ1/KCNE3 channel as one of the principal targets for oestrogen-induced signalling cascades in the distal colon. Through inhibition of the KCNQ1 channel, basolateral K(+) recycling is decreased so reducing the favourable electrochemical gradient for Cl(-) extrusion at the apical membrane. The actions of oestrogen on non-reproductive tissues such as the colon, kidney, lung and sweat gland will affect whole body electrolyte and fluid homeostasis and also have consequences for reproductive potential.

Sex-specific impact of aldosterone receptor antagonism on ventricular remodeling and gene expression after myocardial infarction

Aldosterone receptor antagonism reduces mortality and improves post-myocardial infarction (MI) remodeling. Because aldosterone and estrogen signaling pathways interact, we hypothesized that aldosterone blockade is sex-specific. Therefore, we investigated the impact of eplerenone on left ventricular (LV) remodeling and gene expression of male infarcted rats versus female infarcted rats. MI and Sham animals were randomized to receive eplerenone (100 mg/kg/day) or placebo 3 days post-surgery for 4 weeks and assessed by echocardiography. In the MI placebo group, left ventricular end-diastolic dimension (LVEDD) increased from 7.3 +/- 0.4 mm to 10.2 +/- 1.0 mm (p < 0.05) and ejection fraction (EF) decreased from 82.3 +/- 4% to 45.5 +/- 11% (p < 0.05) in both sexes (p = NS between groups). Eplerenone attenuated LVEDD enlargement more effectively in females (8.8 +/- 0.2 mm, p < 0.05 vs. placebo) than in males (9.7 +/- 0.2 mm, p = NS vs. placebo) and improved EF in females (56.7 +/- 3%, p < 0.05 vs. placebo) but not in males (50.6 +/- 3%, p = NS vs. placebo). Transcriptomic analysis using Rat_230-2.0 microarrays (Affymetrix) revealed that in females 19% of downregulated genes and 44% of upregulated genes post-MI were restored to normal by eplerenone. In contrast, eplerenone only restored 4% of overexpressed genes in males. Together, these data suggest that aldosterone blockade reduces MI-induced cardiac remodeling and phenotypic alterations of gene expression preferentially in females than in males. The use of transcriptomic signatures to detect greater benefit of eplerenone in females has potential implications for personalized medicine.

Gender-specific protection of estrogen against gastric acid-induced duodenal injury: stimulation of duodenal mucosal bicarbonate secretion

Because human duodenal mucosal bicarbonate secretion (DMBS) protects duodenum against acid-peptic injury, we hypothesize that estrogen stimulates DMBS, thereby attributing to the clinically observed lower incidence of duodenal ulcer in premenopausal women than the age-matched men. We found that basal and acid-stimulated DMBS responses were 1.5 and 2.4-fold higher in female than male mice in vivo, respectively. Acid-stimulated DMBS in both genders was abolished by ICI 182,780 and tamoxifen. Estradiol-17beta (E2) and the selective estrogen receptor (ER) agonists of ERalpha [1,3,5-Tris(4-hydroxyphenyl)-4-propyl-1H-pyrazole] and ERbeta [2,3-bis(4-hydroxyphenyl) propionitrile], but not progesterone, rapidly stimulated ER-dependent murine DMBS in vivo. E2 dose dependently stimulated murine DMBS, which was attenuated by a Cl(-)/HCO3(-) anion exchanger inhibitor 4,4'-didsothio- cyanostilbene-2, 2'-disulfonic acid, removal of extracellular Cl(-), and in cystic fibrosis transmembrane conductance regulator knockout female mice. E2 stimulated murine DMBS in vitro in both genders with significantly greater response in female than male mice (female to male ratio = 4.3). ERalpha and ERbeta mRNAs and proteins were detected in murine duodenal epithelium of both genders; however, neither ERalpha nor ERbeta mRNA and protein expression levels differed according to gender. E2 rapidly mobilized intracellular calcium in a duodenal epithelial SCBN cell line that expresses ERalpha and ERbeta, whereas BAPTA-AM abolished E2-stimulated murine DMBS. Thus, our data show that E2 stimulates DMBS via ER dependent mechanisms linked to intracellular calcium, cystic fibrosis transmembrane conductance regulator, and Cl(-)/HCO3(-) anion exchanger. Gender-associated differences in basal, acid- and E2-stimulated DMBS may have offered a reasonable explanation for the clinically observed lower incidence of duodenal ulcer in premenopausal women than age-matched men.

Progressive diastolic dysfunction in the female mRen(2). Lewis rat: influence of salt and ovarian hormones

This study determined the contribution of chronic salt loading and early loss of ovarian hormones on diastolic function in the hypertensive female mRen(2). Lewis rat, a monogenetic strain that expresses the mouse renin-2 gene in various tissues. Estrogen-intact mRen2 rats fed a high salt (HS) (8% sodium chloride) diet exhibited early diastolic dysfunction when compared to normal salt-fed (NS) (1% sodium chloride) rats. In contrast, ovariectomized (OVX) rats on either NS or HS diets showed impaired relaxation with evidence of elevated left ventricular filling pressures (E/e') or pseudonormalization. This more advanced stage of diastolic dysfunction was associated with increases in interstitial cardiac fibrosis and high circulating levels of aldosterone, two factors leading to reduced ventricular compliance. These findings may explain the preponderance of diastolic dysfunction and diastolic heart failure in postmenopausal women and provide a potential animal model for evaluating prevention and treatment interventions for this disorder.