Estrogen receptor-alpha antisense decreases brain estrogen receptor levels and affects ventilation in male and female rats

Menstrual phase does not influence ventilatory responses to group III/IV afferent signaling in eumenorrheic young females

Estrogen can reduce sympathetic activity, but its effects on minute ventilation (V_E) with group III/IV afferent activation remain unclear. This study examined the influence of estrogen on V_E during lower-extremity exercise with group III/IV activation. Females completed two identical visits in follicular and ovulatory menstrual phases. Nine participants (age 25 ± 4 years) performed three minutes of baseline steady-state cycle ergometry and then group III/IV afferents were further activated with proximal thigh cuffs inflated to 20, 60, and 100 mmHg (randomized) for two minutes and five minutes of cycling between each occlusion. Metaboreflex was isolated by post-exercise circulatory occlusion. Ventilation was measured continuously and rating of perceived exertion (RPE) was recorded for each stage. During rest and exercise, V_E (p < 0.001) and tidal volume (V_T) (p = 0.033) were higher in the follicular than ovulatory phase. Minute ventilation, V_T, and respiratory rate (R_R) with ergoreflex and metaboreflex activation were similar across phases. With cuff occlusion of 100 mmHg, V_E increased from baseline by 26.3 ± 7.0 L/min in the follicular phase (p < 0.001) and by 25.3±7.7 L/min in the ovulatory phase (p < 0.001), with no difference between phases (p> 0.05); R_R and V_T increased similarly with occlusion, also with no phase differences. In eumenorrheic females, menstrual phase influences ventilation but not ventilatory responses to group III/IV isolation.

Protective role of estrogen against excessive erythrocytosis in Monge's disease

Monge's disease (chronic mountain sickness (CMS)) is a maladaptive condition caused by chronic (years) exposure to high-altitude hypoxia. One of the defining features of CMS is excessive erythrocytosis with extremely high hematocrit levels. In the Andean population, CMS prevalence is vastly different between males and females, being rare in females. Furthermore, there is a sharp increase in CMS incidence in females after menopause. In this study, we assessed the role of sex hormones (testosterone, progesterone, and estrogen) in CMS and non-CMS cells using a well-characterized in vitro erythroid platform. While we found that there was a mild (nonsignificant) increase in RBC production with testosterone, we observed that estrogen, in physiologic concentrations, reduced sharply CD235a+ cells (glycophorin A; a marker of RBC), from 56% in the untreated CMS cells to 10% in the treated CMS cells, in a stage-specific and dose-responsive manner. At the molecular level, we determined that estrogen has a direct effect on GATA1, remarkably decreasing the messenger RNA (mRNA) and protein levels of GATA1 (p < 0.01) and its target genes (Alas2, BclxL, and Epor, p < 0.001). These changes result in a significant increase in apoptosis of erythroid cells. We also demonstrate that estrogen regulates erythropoiesis in CMS patients through estrogen beta signaling and that its inhibition can diminish the effects of estrogen by significantly increasing HIF1, VEGF, and GATA1 mRNA levels. Taken altogether, our results indicate that estrogen has a major impact on the regulation of erythropoiesis, particularly under chronic hypoxic conditions, and has the potential to treat blood diseases, such as high altitude severe erythrocytosis.

Sexual dimorphism of cardiopulmonary regulation in the arcuate nucleus of the hypothalamus

The arcuate nucleus of the hypothalamus (ANH) interacts with other hypothalamic nuclei, forebrain regions, and downstream brain sites to affect autonomic nervous system outflow, energy balance, temperature regulation, sleep, arousal, neuroendocrine function, reproduction, and cardiopulmonary regulation. Compared to studies of other ANH functions, how the ANH regulates cardiopulmonary function is less understood. Importantly, the ANH exhibits structural and functional sexually dimorphic characteristics and contains numerous neuroactive substances and receptors including leptin, neuropeptide Y, glutamate, acetylcholine, endorphins, orexin, kisspeptin, insulin, Agouti-related protein, cocaine and amphetamine-regulated transcript, dopamine, somatostatin, components of renin-angiotensin system and gamma amino butyric acid that modulate physiological functions. Moreover, several clinically relevant disorders are associated with ANH ventilatory control dysfunction. This review highlights how ANH neurotransmitter systems and receptors modulate breathing differently in male and female rodents. Results highlight the significance of the ANH in cardiopulmonary regulation. The paucity of studies in this area that will hopefully spark investigations of sexually dimorphic ANH-modulation of breathing.

Muscimol microinjected in the arcuate nucleus affects metabolism, body temperature & ventilation

Effects of microinjection of 2 doses of γ-aminobutyric acid (GABA)A receptor agonist, muscimol (M), into the hypothalamic arcuate nucleus on oxygen consumption and control of ventilation over time and body temperature (BT) at the end of the experiment were compared in adult male and female rats. Relative to cerebrospinal fluid (CSF, 0 nmol), BT was decreased only in male rats with both doses of M, while in female rats, the 5 nmol dose depressed oxygen consumption. Ventilation was depressed by 5 nmol M in male and 10 nmol M in female rats by decreasing tidal volume. M did not affect the ventilatory response of male or female rats to hypoxia, whereas in females 5 and 10 nmol M and in males 10 nmol M depressed the ventilatory response to hypercapnia. Thus, in rats GABAA receptors in the arcuate nucleus modulate BT, oxygen consumption, and ventilation in air and in response to hypercapnia in a sexually dimorphic manner.

Hormonal influences on lung function and response to environmental agents: lessons from animal models of respiratory disease

Numerous studies in humans and experimental animals have identified considerable sex differences in respiratory physiology and in the response of the lung to environmental agents. These differences appear to be mediated, at least in part, by sex hormones and their nuclear receptors. Moreover, animal models are increasingly used to study pathogenic mechanisms and test potential therapies for a variety of human lung diseases, many of which appear to be influenced by sex and sex hormones. In this article, data are summarized from studies of lung function and disease in which sex differences have been observed. Specific attention is paid to animal models of acute lung injury, nonallergic and allergic lung inflammation, and lung fibrosis. It is anticipated that continued investigation of the role of sex and sex hormones in animal models will provide valuable insight into the pathogenesis and potential treatments for a variety of acute and chronic human lung diseases.

The impact of sex and sex hormones on lung physiology and disease: lessons from animal studies

Numerous animal studies have revealed significant effects of sex and sex hormones on normal lung development, lung physiology, and various lung diseases. The primary goal of this review is to summarize knowledge to date on the effects of sex and sex hormones on lung development, physiology, and disease in animals. Specific emphasis will be placed on fibrosis, allergic airway disease, acute lung injury models, respiratory infection, and lung toxicology studies.

Organ growth functions in maturing male Sprague-Dawley rats based on a collective database

Ten different organ weights (liver, spleen, kidneys, heart, lungs, brain, adrenals, testes, epididymes, and seminal vesicles) of male Sprague-Dawley (S-D) rats of different ages (1-280 d) were extracted based on a thorough literature survey database. A generalized Michaelis-Menten (GMM) model, used to fit organ weights versus age in a previous study (Schoeffner et al., 1999) based on a limited data, was used to find the best fit model for the present expanded data compilation. The GMM model has the functional form: Wt = (Wt(o).K(gamma) + Wt(max).Age(gamma))/(K(gamma) + Age(gamma)) where Wt is organ/tissue weight at a specified age, Wt(o) and Wt(max) are weight at birth and maximal growth, respectively, and K and gamma are constants. Organ weights were significantly correlated with their respective ages for all organs and tissues. GMM-derived organ growth and percent body weight (%BW) fractions of different tissues were plotted against animal age and compared with experimental values as well as previously published models. The GMM-based organ growth and %BW fraction profiles were in general agreement with our empirical data as well as with previous studies. The present model was compared with the GMM model developed previously for six organs--liver, spleen, kidneys, heart, lungs, and brain--based on a limited data, and no significant difference was noticed between the two sets of predictions. It was concluded that the GMM models presented herein for different male S-D rats organs (liver, spleen, kidneys, heart, lungs, brain, adrenals, testes, epididymes, and seminal vesicles) are capable of predicting organ weights and %BW ratios accurately at different ages.

Function of estrogen receptor isoforms alpha and beta in endometrial carcinoma cells

The aim of this study was to explore how to modulate the expression of estrogen receptors (ER) alpha and beta and to verify the role of ERalpha and beta in relationship to estrogen and tamoxifen (TAM). A series of oligodeoxyribonucleotides (ODN) corresponding to regions of the ERalpha or beta was tested in human endometrial cancer cell lines (HEC-1B). The change in HEC-1B proliferation in response to 17beta-estradiol (E(2)) and TAM under the impact of antisense ODN was studied. The results of the study are as follows: 1) transfection with antisense ODN significantly inhibited ERalpha and ERbeta protein production, 2) the cells lost the ability to proliferate in response to E(2) after transfection with ERalpha antisense ODN especially at 24, 48, and 72 h. There was no obvious change in response to E(2) in HEC-1B cell lines that were transfected with ERbeta antisense ODN, and 3) after transfection with ERalpha antisense ODN, HEC-1B cells lost the ability to proliferate in response to TAM at 48 h. This inhibition was also observed after transfection with ERbeta antisense ODN at 24 h. ERalpha may be the primary receptor in the proliferation of HEC-1B cells in response to E(2). Both ERalpha and ERbeta are involved in the agonist impact of TAM on endometrial cancer cells.

Sex-specific densities of estrogen receptors alpha and beta in the subnuclei of the nucleus tractus solitarius, hypoglossal nucleus and dorsal vagal motor nucleus weanling rats

In rats ventilatory responses to N-methyl-d-aspartate (NMDA) receptor modulation are sexually dimorphic and may be altered by manipulating brain levels of estrogen receptors. Here we used image analysis and immunohistochemistry in weanling male and female rats to quantitate areas and densities of ER alpha and ER beta-positive neurons within medullary regions associated with cardiopulmonary regulation including the hypoglossal nucleus, subnuclei of the nucleus of the solitary tract (NTS), and the dorsal motor nucleus of the vagus. Weanling rats were selected because ventilation, metabolic rate, and body and brain weights are comparable at this age and there are no large fluctuations in plasma hormone levels. Females, relative to males, had smaller areas in the A2 region and parts of the NTS. Counts and densities for ER alpha were greater in females than males in almost all regions studied. In contrast sex differences in ER beta were found in fewer nuclei, but in those higher counts and densities were noted in females. In general, ER beta-positive neurons in the brainstem regions examined were less prevalent than ER alpha neurons. Thus, in weanling rats sex affected ER alpha and ER beta neuronal densities in brainstem regions associated with cardiopulmonary regulation that may be responsible for sex differences in control of breathing.

Specific contribution of estrogen receptors on mitogen-activated protein kinase pathways and vascular cell activation

Randomized clinical trials have not provided conclusive data that hormone replacement therapy confers cardioprotection against coronary artery disease in postmenopausal women. However, other studies have shown that estrogens can induce beneficial effects on the vasculature. Nevertheless, the specific contribution of estrogen receptors (ERs) alpha and beta on vascular cells is not well characterized. Therefore, we used an antisense gene therapy approach to investigate the contribution of ERalpha and ERbeta on p38 and p42/44 mitogen-activated protein kinase (MAPK) activation and on vascular cell responsiveness. Treatment of porcine smooth muscle cells (PSMCs) with platelet-derived growth factor-BB induced p38 and p42/44 MAPK activation and their migration and proliferation. These effects were prevented by pretreatment with 17beta-estradiol (17betaE). The inhibitory effects of 17betaE on PSMCs were abrogated by the downregulation of ERbeta protein expression with selective ERbeta mRNA antisense oligomers, whereas the downregulation of ERalpha had no effect. However, treatment of porcine aortic endothelial cells with 17betaE promoted p38 and p42/44 MAPK phosphorylation and their migration and proliferation. These effects were ERalpha dependent, as defined by antisense gene therapy. These results suggest that in PSMCs, 17betaE reduces p42/44 and p38 MAPK activity through ERbeta stimulation, whereas in contrast, in porcine aortic endothelial cells, 17betaE induces p42/44 and p38 MAPK through ERalpha activation. 17betaE may contribute to the vascular healing process and to the prevention of restenosis by improving reendothelialization through ERalpha activation and by decreasing smooth muscle cell migration and proliferation through ERbeta stimulation.

Neonatal sex steroids affect ventilatory responses to aspartic acid and NMDA receptor subunit 1 in rats

We hypothesized that administration of estradiol benzoate to males and testosterone propionate to female neonatal rat pups alters sex-specific ventilatory responses to aspartic acid with correspondent changes in N-methyl-D-aspartate receptor subunit 1 (NR1) expression determined by Western blot in specific brain regions. One-day-old rat pups received estradiol benzoate, testosterone propionate, or vehicle and were studied at weanling and adulthood. Different groups had distinct patterns of changes in tidal volume and frequency of breathing after aspartic acid administration. NR1 expression in hypothalamus was altered by age, sex, and treatment. Medullary and pontine NR1 expression correlated with baseline ventilation and magnitude of the ventilatory response to aspartic acid in some groups. Thus 1) tidal volume and breathing frequency patterns in response to aspartic acid are gender, age, and treatment dependent; 2) sex, age, and exogenous steroid hormones affect NR1 expression primarily in the hypothalamus; and 3) there is correlation between NR1 expression in pons and medulla with ventilatory parameters.