Effect of Ovariectomy on Renal Estrogen Receptor-α and Estrogen Receptor-β in Young Salt-Sensitive and -Resistant Rats

A randomized vagus nerve stimulation study demonstrates that serum aldosterone levels decrease with age in women, but not in men

In this randomized, sham-controlled study, we explored the effects of acute transcutaneous vagus nerve stimulation (tVNS) on serum aldosterone in 20 younger (21-26 years) and 19 older (40-70 years) healthy participants. Blood samples were collected on two different days before and after a 20-min application of active tVNS at the inner tragus or sham stimulation of the earlobe. Irrespective of the stimulation mode, aldosterone levels decreased from pre- to post-stimulation in both the young (active: β = - 1.610 (- 2.855, - 0.365), p = 0.022; sham: β = - 0.857 (- 2.102, 0.388), p = 0.257) and the old cohort (active: β = - 1.969 (- 3.234, - 0.703), p = 0.005; sham: β = - 1.334 (- 2.600, - 0.069), p = 0.063). Although this decline was significant during active tVNS, the difference in estimated β-coefficients between active and sham stimulation was not statistically significant in either cohort. Nevertheless, aldosterone concentrations showed a significant interaction effect between sex and age (p = 0.001). Among all study participants, younger women (23.3 ± 1.6 years) had the highest mineralocorticoid levels (pre active: 172.1 ± 102.0 pg/ml, pre sham: 214.3 ± 82.3 pg/ml), whereas the lowest were observed in older females (59.4 ± 9.4 years) (pre active: 104.9 ± 85.8 pg/ml, pre sham: 81.1 ± 53.8 pg/ml). This post hoc analysis did not suggest that active auricular tVNS reduces serum aldosterone levels compared to sham stimulation in healthy subjects. However, serum aldosterone levels differed among subjects depending on their age and sex, irrespective of tVNS.

Sex differences in the renin-angiotensin-aldosterone system and its roles in hypertension, cardiovascular, and kidney diseases

Cardiovascular disease is a pathology that exhibits well-researched biological sex differences, making it possible for physicians to tailor preventative and therapeutic approaches for various diseases. Hypertension, which is defined as blood pressure greater than 130/80 mmHg, is the primary risk factor for developing coronary artery disease, stroke, and renal failure. Approximately 48% of American men and 43% of American women suffer from hypertension. Epidemiological data suggests that during reproductive years, women have much lower rates of hypertension than men. However, this protective effect disappears after the onset of menopause. Treatment-resistant hypertension affects approximately 10.3 million US adults and is unable to be controlled even after implementing ≥3 antihypertensives with complementary mechanisms. This indicates that other mechanisms responsible for modulating blood pressure are still unclear. Understanding the differences in genetic and hormonal mechanisms that lead to hypertension would allow for sex-specific treatment and an opportunity to improve patient outcomes. Therefore, this invited review will review and discuss recent advances in studying the sex-specific physiological mechanisms that affect the renin-angiotensin system and contribute to blood pressure control. It will also discuss research on sex differences in hypertension management, treatment, and outcomes.

Regulation of ABC transporters by sex steroids may explain differences in drug resistance between sexes

Drug efficacy is dependent on the pharmacokinetics and pharmacodynamics of therapeutic agents. Tight junctions, detoxification enzymes, and drug transporters, due to their localization on epithelial barriers, modulate the absorption, distribution, and the elimination of a drug. The epithelial barriers which control the pharmacokinetic processes are sex steroid hormone targets, and in this way, sex hormones may also control the drug transport across these barriers. Thus, sex steroids contribute to sex differences in drug resistance and have a relevant impact on the sex-related efficacy of many therapeutic drugs. As a consequence, for the further development and optimization of therapeutic strategies, the sex of the individuals must be taken into consideration. Here, we gather and discuss the evidence about the regulation of ATP-binding cassette transporters by sex steroids, and we also describe the signaling pathways by which sex steroids modulate ATP-binding cassette transporters expression, with a focus in the most important ATP-binding cassette transporters involved in multidrug resistance.

GPER limits adverse changes to Ca2+ signalling and arrhythmogenic activity in ovariectomised guinea pig cardiomyocytes

Background: The increased risk of post-menopausal women developing abnormalities of heart function emphasises the requirement to understand the effect of declining oestrogen levels on cardiac electrophysiology and structure, and investigate possible therapeutic targets, namely the G protein-coupled oestrogen receptor 1 (GPER). Methods: Female guinea pigs underwent sham or ovariectomy (OVx) surgeries. Cardiomyocytes were isolated 150-days post-operatively. Membrane structure was assessed using di-8-ANEPPs staining and scanning ion conductance microscopy. Imunnohistochemistry (IHC) determined the localisation of oestrogen receptors. The effect of GPER activation on excitation-contraction coupling mechanisms were assessed using electrophysiological and fluorescence techniques. Downstream signalling proteins were investigated by western blot. Results: IHC staining confirmed the presence of nuclear oestrogen receptors and GPER, the latter prominently localised to the peri-nuclear region and having a clear striated pattern elsewhere in the cells. Following OVx, GPER expression increased and its activation reduced Ca²⁺ transient amplitude (by 40%) and sarcomere shortening (by 32%). In these cells, GPER activation reduced abnormal spontaneous Ca²⁺ activity, shortened action potential duration and limited drug-induced early after-depolarisation formation. Conclusion: In an animal species with comparable steroidogenesis and cardiac physiology to humans, we show the expression and localisation of all three oestrogen receptors in cardiac myocytes. We found that following oestrogen withdrawal, GPER expression increased and its activation limited arrhythmogenic behaviours in this low oestrogen state, indicating a potential cardioprotective role of this receptor in post-menopausal women.

Paeoniflorin Alleviates Skeletal Muscle Atrophy in Ovariectomized Mice through the ERα/NRF1 Mitochondrial Biogenesis Pathway

Muscle atrophy in postmenopausal women is caused by estrogen deficiency and a variety of inflammatory factors, including tumor necrosis factor alpha (TNFα). Paeoniflorin (PNF), a natural compound with anti-inflammatory properties, improves estradiol synthesis. Here, we demonstrate that PNF inhibits the progression of TNFα-induced skeletal muscle atrophy after menopause by restoring mitochondrial biosynthesis. Differentiated myoblasts damaged by TNFα were restored by PNF, as evident by the increase in the expression of myogenin (MyoG) and myosin heavy chain 3 (Myh3)—the markers of muscle differentiation. Moreover, diameter of atrophied myotubes was restored by PNF treatment. TNFα-repressed nuclear respiratory factor 1 (NRF1) and mitochondrial transcription factor A (TFAM) (a major regulator of mitochondrial biosynthesis) were restored by PNF, via regulation by estrogen receptor alpha (ERα), an upregulator of NRF1. This mechanism was confirmed in ovariectomized (OVX) mice with a ~40% reduction in the cross-sectional area of the anterior tibialis muscle. OVX mice administered PNF (100, 300 mg/kg/day) for 12 weeks recovered more than ~20%. Behavioral, rotarod, and inverted screen tests showed that PNF enhances reduced muscle function in OVX mice. ERα restored expression of mitofusin 1 (MFN1) and mitofusin 2 (MFN2) (mitochondrial fusion markers) and dynamin-related protein (DRP1) and fission 1 (FIS1) (mitochondrial fission markers). Therefore, PNF can prevent muscle atrophy in postmenopausal women by inhibiting dysfunctional mitochondrial biogenesis.

Behavioral, Oxidative, and Biochemical Effects of Omega-3 on an Ovariectomized Rat Model of Menopause

OBJECTIVES

Menopause induces changes in neuronal transmission, leading to anxiety and depression. Changes in the brain's glutamate levels cause psychological behavior in postmenopausal women. Omega-3 has been studied to improve some of these behaviors.

METHODS

Twenty-four female Wistar rats were divided into four groups: sham-operated treated with water (SO-W), sham-operated treated with omega-3 (SO-O), ovariectomized (OVX) treated with water (OVX-W), and bilateral OVX treated with omega-3 (OVX-O). These treatments were performed for 20 days via gavage, before and after surgery, totaling 40 days.

RESULTS

In the forced swimming, elevated plus-maze, and open field tests to assess behaviors, such as depression and anxiety, omega-3 improved these behaviors in both treated groups. The levels of thiobarbituric acid reactive substances (TBARS) in the brain were not different between the groups; however, there was a significant decrease in the catalase activity in the SO-O group compared with the SO-W group (P < 0.05). The glutamate level in the cerebrospinal fluid (CSF) was elevated in the SO-O group (P < 0.001) but not in the OVX-W or OVX-O groups.

CONCLUSIONS

These results bring novel data when related to the glutamatergic system in the SO-O group. This has suggested that the action mechanism of omega-3 was not dependent on glutamate levels in the CSF of the OVX group, but it played a regulatory role in the sham-operated animals. To confirm this, more studies are needed to explore this field when relating to the estrogen and glutamate receptor changes in specific brain regions.

Medroxyprogesterone opposes estradiol-induced renal damage in midlife ovariectomized Long Evans rats

OBJECTIVE

Our laboratory previously published that long-term administration of estradiol (E2) was detrimental to the kidneys of midlife ovariectomized Long Evans rats, contrasting clinical studies in showing that menopausal hormone therapy is associated with decreased albuminuria. However, it is unknown whether this renal benefit was due to estrogen and/or the combination with progestogen. Therefore, the objective of the current study was to determine the impact of medroxyprogesterone (MPA) on E2-mediated renal damage using a rodent model.

METHODS

Female Long Evans retired breeders underwent ovariectomy at 11 months of age and were treated for 40 days with subcutaneous E2, E2+MPA or vehicle at doses mimicking that of menopausal hormone therapy (N = 5-7 per group). Systolic blood pressure was measured along with indices of renal damage and function to investigate the impact of MPA on E2-mediated renal outcomes. Renal estrogen receptor alpha and G protein-coupled estrogen receptor transcript copy numbers were measured in all treatment groups through droplet digital PCR.

RESULTS

Middle-aged female Long Evans rats displayed spontaneous hypertension with similar systolic blood pressures and heart weights between groups. Even though blood pressure was comparable, E2 reduced glomerular filtration rate and increased proteinuria indicating pressure-independent renal damage. Coadministration with MPA prevented E2-induced glomerular filtration rate impairment and proteinuria by promoting renal hypertrophy and preventing renal interstitial fibrosis. Both E2 and E2+MPA reduced renal estrogen receptor alpha (ERα) and increased renal G protein-coupled estrogen receptor mRNA, but neither ERα nor ERß protein was different between groups.

CONCLUSION

MPA was protective against E2-induced renal damage and dysfunction in middle-aged female Long Evans rats. Assessing the impact of hormone therapy on renal outcomes may be an important clinical factor when considering treatment options for postmenopausal women.

Estrogen receptor agonists protect against acetaminophen-induced hepatorenal toxicity in rats

AIMS

Acetaminophen-induced hepatorenal toxicity varies among sexes with controversial results among species. The aim was to compare the impact of sex and ovarian hormones on hepatorenal toxicity and to elucidate protective effects of estrogen and estrogen receptor (ER) agonists.

MAIN METHODS

Under anesthesia, female rats underwent ovariectomy (OVX) or sham-OVX. Starting at postsurgical 40th day, OVX-rats received subcutaneously (each, 1 mg/kg/day) 17β-estradiol (E₂), ERβ-agonist (DPN) or ERα-agonist (PPT) for 10 days, while male and sham-OVX rats received vehicle for 10 days. Then, rats received either acetaminophen (3 g/kg) or saline by orogastric gavage and were decapitated at 24th h. Blood samples were obtained to measure serum ALT, AST, BUN, creatinine levels. Liver and kidney samples were obtained for histopathologic examination and for analyzing levels of luminol- and lucigenin-chemiluminescence, glutathione and myeloperoxidase activity.

KEY FINDINGS

Compared to their control groups, levels of AST, ALT, BUN, creatinine, hepatic and renal myeloperoxidase activity and chemiluminescence levels were increased, and hepatic glutathione level was decreased in acetaminophen-administered male groups, while ALT and hepatic chemiluminescence levels were not elevated in sham-OVX-rats. Both ER-agonists and E₂ reduced BUN, creatinine and reversed all oxidative parameters in renal tissues of OVX-rats. Additionally, ERα-agonist reversed all hepatic injury parameters, while ERβ-agonist elevated hepatic glutathione level.

SIGNIFICANCE

Acetaminophen toxicity in female rats presented with a more preserved hepatic function, while renal toxicity was not influenced by sex or by the lack of ovarian hormones. Pretreatment with estrogen or ER agonists, via their antioxidant actions, provided protective effects on acetaminophen-induced hepatorenal toxicity.

Potential role of estradiol in ovariectomy-induced derangement of renal endocrine functions

Menopause is an important physiological event associated with structural and functional changes in the kidneys. An animal model of bilateral ovariectomy was used to study the effects of estrogen depletion, replacement and antiestrogen on renal structure and endocrine function. Sixty female rats were divided into six groups; group I was the control group, the remaining five groups underwent ovariectomy: group II received no treatment. The other groups received estradiol in group III, tamoxifen in group IV, estradiol followed by tamoxifen in group V and tamoxifen followed by estradiol in group VI. Serum creatinine, blood urea nitrogen, and endocrine functions of kidney were measured. Tissue samples were examined both microscopically for beta estrogen receptors and ultrastructurally for cell changes. Groups II, IV & VI showed a significant increase in creatinine, blood urea nitrogen, renal malondialdehyde, renal erythropoietin, plasma renin and plasma prostaglandin E2 and a significant decrease in renal antioxidants and serum vitamin D3. Groups III &V had a significant decrease in creatinine, blood urea nitrogen, renal malondialdehyde and renal erythropoietin with an increase in renal antioxidants, plasma prostaglandin E2 and serum vitamin D3. Histopathological and ultrastructural examinations revealed atrophic tubular changes in group II. The changes were less marked in groups III &V and more extensive in groups IV & VI. Estrogen receptor beta staining showed progressively increased expression in the absence of estrogen. Structural and most endocrine functions of the kidney were significantly affected by estradiol deficiency. Estradiol replacement exhibited a protective effect on renal tissue and endocrine functions.

Ovariectomy and obesity have equal impact in causing mitochondrial dysfunction and impaired skeletal muscle contraction in rats

OBJECTIVE

Previous studies have demonstrated that either an obese-insulin resistance condition or a condition involving loss of estrogen impaired skeletal muscle function as indicated by a decrease in muscle contraction. The differing effects of combined estrogen deficiency over obese-insulin resistance on skeletal muscle function have, however, not yet been determined. Our hypothesis was that estrogen deficiency aggravates skeletal muscle dysfunction in obese-insulin resistant rats, via increased muscle oxidative stress and mitochondrial dysfunction.

METHODS

Twenty-four female Wistar rats were divided into 2 groups and animals in each group were fed either a normal diet (ND) or a high-fat diet (HFD) for 24 weeks. At week 13, rats in each group were subdivided into 2 subgroups: sham-operated or ovariectomized (n = 6/subgroup). At the end of the experimental period the contraction of the gastrocnemius muscles was tested before the rats were sacrificed. Skeletal muscle was removed to assess oxidative stress and mitochondrial function.

RESULTS

We found that an obese-insulin resistant condition was observed in sham-operated HFD-fed rats, ovariectomized ND-fed rats, and ovariectomized HFD-fed rats. Skeletal muscle contractile function (peak-force ratio [g/g]; 25.40 ± 2.03 [ovariectomized ND-fed rats], 22.44 ± 0.85 [sham-operated HFD-fed rats] and 25.06 ± 0.61 [ovariectomized HFD-fed rats]), skeletal muscle mitochondrial function, and oxidative stress were equally significantly impaired in all 3 groups, when compared with those of sham-operated ND-fed rats (31.12 ± 1.88 g/g [NDS]; P < 0.05). Surprisingly, loss of estrogen did not aggravate these dysfunctions of skeletal muscles in HFD-fed rats.

CONCLUSIONS

These findings suggest that skeletal muscle dysfunction may occur due to increased muscle oxidative stress and mitochondrial dysfunction as a result of ovariectomy and obese-insulin resistance. Loss of estrogen, however, did not aggravate these impairments in the muscle of rats with obese-insulin resistant condition.

The protective role of G protein-coupled estrogen receptor 1 (GPER-1) on methotrexate-induced nephrotoxicity in human renal epithelium cells

Nephrotoxicity is an important problem during methotrexate (MTX) treatment, which has been widely used for the treatment of several cancer types. Females are less susceptible to kidney diseases; however, the reason for this condition has not to be fully clarified. But sex hormones such as estrogen may have a protective effect on the kidney. We aimed to evaluate the possible protective role of estrogen on the MTX-induced renal epithelial cell death. Primary renal proximal tubular epithelial cells (RPTEC) were incubated with MTX (1, 10 and 100 μM), either alone or in combination with the 17β-estradiol, G protein-coupled estrogen receptor 1 (GPER1) agonist G-1, estrogen receptor alpha agonist propyl pyrazole triol (PPT), estrogen receptor beta agonist diarylpropionitrile (DPN). Cell viability was determined by MTT assays. Interleukin (IL)-1β, IL-6, superoxide dismutase (SOD) and malondialdehyde (MDA) levels were determined in RPTEC. Approximately half of the cell death was observed with 10 μM MTX incubation for 48 h. The cell death was prevented by co-incubating with17β-estradiol, PPT and G-1. MTX was significantly induced IL-1β and IL-6.17β-estradiol, PPT and G-1 significantly decreased effects of MTX. SOD activity was significantly decreased treatment with MTX compared to control group. SOD activity was increased with co-incubation with 17β-estradioland G-1 compared to treatment with MTX. MDA levels significantly increased in treatment with MTX compared with the control group. Increased MDA levels by MTX-induced was decreased significantly by the treatment with 17β-estradiol and G-1. These data indicate that especially 17β-estradiol and G-1 may be useful in preventing undesirable effects of MTX in renal failure.

Generation of an estrogen receptor beta-iCre knock-in mouse

A novel knock-in mouse that expresses codon-improved Cre recombinase (iCre) under regulation of the estrogen receptor beta (Esr2) promoter was developed for conditional deletion of genes and for the spatial and/or temporal localization of Esr2 expression. ESR2 is one of two classical nuclear estrogen receptors and displays a spatiotemporal expression pattern and functions that are different from the other estrogen receptor, ESR1. A cassette was constructed that contained iCre, a polyadenylation sequence, and a neomycin selection marker. This construct was used to insert iCre in front of the endogenous start codon of the Esr2 gene of a C57BL/6J embryonic stem cell line via homologous recombination. Resulting Esr2-iCre mice were bred with ROSA26-lacZ and Ai9-RFP reporter mice to visualize cells of functional iCre expression. Strong expression was observed in the ovary, the pituitary, the interstitium of the testes, the head and tail but not body of the epididymis, skeletal muscle, the coagulation gland (anterior prostate), the lung, and the preputial gland. Additional diffuse or patchy expression was observed in the cerebrum, the hypothalamus, the heart, the adrenal gland, the colon, the bladder, and the pads of the paws. Overall, Esr2-iCre mice will serve as a novel line for conditionally ablating genes in Esr2-expressing tissues, identifying novel Esr2-expressing cells, and differentiating the functions of ESR2 and ESR1.

Estradiol regulates AQP2 expression in the collecting duct: a novel inhibitory role for estrogen receptor α

While there is evidence that sex hormones influence multiple systems involved in salt and water homeostasis, the question of whether sex hormones regulate aquaporin-2 (AQP2) and thus water handling by the collecting duct has been largely ignored. Accordingly, the present study investigated AQP2 expression, localization and renal water handling in intact and ovariectomized (OVX) female rats, with and without estradiol or progesterone replacement. OVX resulted in a significant increase in urine osmolality and increase in p256-AQP2 in the renal cortex at 7 days post-OVX, as well as induced body weight changes. Relative to OVX alone, estradiol repletion produced a significant increase in urine output, normalized urinary osmolality and reduced both total AQP2 (protein and mRNA) and p256-AQP2 expression, whereas progesterone repletion had little effect. Direct effects of estradiol on AQP2 mRNA and protein levels were further tested in vitro using the mpkCCD principal cell line. Estradiol treatment of mpkCCD cells reduced AQP2 at both the mRNA and protein level in the absence of deamino-8-d-AVP (dDAVP) and significantly blunted the dDAVP-induced increase in AQP2 at the protein level only. We determined that mpkCCD and native mouse collecting ducts express both estrogen receptor (ER)α and ERβ and that female mice lacking ERα displayed significant increases in AQP2 protein compared with wild-type littermates, implicating ERα in mediating the inhibitory effect of estradiol on AQP2 expression. These findings suggest that changes in estradiol levels, such as during menopause or following reproductive surgeries, may contribute to dysregulation of water homeostasis in women.

Age-dependent association between sex and renal cell carcinoma mortality: a population-based analysis

Research on sex differences in renal cancer-specific mortality (RCSM), which considered the sex effect to be constant throughout life, has yielded conflicting results. This study hypothesized the sex effect may be modified by age, which is a proxy for hormonal status. Data from the Surveillance, Epidemiology and End Results database (1988-2010) were used to identify 114,539 patients with renal cell carcinoma (RCC). The study cohort was divided into three age groups using cutoffs of 42 and 58 years, which represent the premenopausal and postmenopausal periods. The cumulative incidence function and competing risks analyses were used to examine the effect of covariates on RCSM and other-cause mortality (OCM). In premenopausal period, male sex was a significant predictor of poor RCSM for both localized (adjusted subdistribution hazard ratio [aSHR] = 1.63, P = 0.002) and advanced (aSHR = 1.20, P = 0.041) disease. In postmenopausal period, the sex disparity diminished (aSHR = 1.05, P = 0.16) and reversed (aSHR = 0.95, P = 0.017) in localized and advanced disease, respectively. On the contrary, similar trend was not found for OCM across all age groups. Our results demonstrated the sex effect on RCSM was strongly modified by age. These findings may aid in clinical practice and need further evaluation of underlying biological mechanisms.

Endogenous female sex hormones delay the development of renal dysfunction in apolipoprotein E-deficient mice

Background

Hypercholesterolemia is a well-established risk factor for the development of kidney injury. Considering that female sex hormones may play a preventative role in both cardiovascular and renal diseases, the aim of the present study was to evaluate the effects of female sex hormones on hypercholesterolemia-induced renal dysfunction.

Methods

Apolipoprotein E-deficient (ApoE) and C57 control female mice underwent an ovariectomy (OVX) or sham surgery and after 2 months, creatinine clearance, uremia and proteinuria were determined. Renal oxidative stress and lipid deposition were also quantified. Values are presented as mean ± SEM. Statistical analyses were performed using Two-way ANOVA followed by Tukey’s post hoc test.

Results

Creatinine clearance (μL/min) was similar between C57 (171 ± 17) and ApoE (140 ± 26) mice underwent sham surgery. OVX resulted in a reduced glomerular filtration rate in both C57 (112 ± 8, ~ − 35%, p < 0.05) and ApoE (61 ± 10, ~ − 56%, p < 0.05) animals. Plasma levels of urea (mg/dL) were higher in both ApoE groups (Sham: 73 ± 7; OVX: 73 ± 8, p < 0.05) when compared to C57 animals (Sham: 49 ± 3; OVX: 60 ± 4), with no changes among ovariectomized groups. Proteinuria levels (mg/24 h) were similar between C57 (Sham: 25.1 ± 5.7; OVX: 33.7 ± 4.7) and ApoE sham animals (26.4 ± 3.5), however, 24-h urine protein excretion was augmented in ApoE OVX animals (49.6 ± 5.8, p < 0.05). Histological kidney analysis demonstrated that the absence of female sex hormones resulted in increased oxidative stress, which was more severe in ApoE mice (C57 Sham: 9.2 ± 0.4; C57 OVX: 22.9 ± 1.0; ApoE Sham: 13.9 ± 0.7; ApoE OVX: 34.0 ± 1.4 au x 10³, p < 0.05). As expected, ApoE mice presented higher lipid deposition, which was not affected by OVX (C57 Sham: 0 ± 0; C57 OVX: 0 ± 0; ApoE Sham: 6.8 ± 1.6; ApoE OVX: 5.2 ± 0.8% x 10⁻², p < 0.05). Ovariectomy resulted in a similar reduction in ER-α protein expression in the renal cortex (C57: 0.78 ± 0.04; ApoE: 0.81 ± 0.04 au, p < 0.05) when compared to sham animals (C57:1.00 ± 0.04; ApoE: 1.03 ± 0.03 au).

Conclusion

Taken together these data indicate that female sex hormones may delay hypercholesterolemia-induced renal dysfunction and emphasizes the importance of plasma cholesterol control in post-menopausal women.

Classical estrogen receptors and ERα splice variants in the mouse

Estrogens exert a variety of effects in both reproductive and non-reproductive tissues. With the discovery of ERα splice variants, prior assumptions concerning tissue-specific estrogen signaling need to be re-evaluated. Accordingly, we sought to determine the expression of the classical estrogen receptors and ERα splice variants across reproductive and non-reproductive tissues of male and female mice. Western blotting revealed that the full-length ERα66 was mainly present in female reproductive tissues but was also found in non-reproductive tissues at lower levels. ERα46 was most highly expressed in the heart of both sexes. ERα36 was highly expressed in the kidneys and liver of female mice but not in the kidneys of males. ERβ was most abundant in non-reproductive tissues and in the ovaries. Because the kidney has been reported to be the most estrogenic non-reproductive organ, we sought to elucidate ER renal expression and localization. Immunofluorescence studies revealed ERα66 in the vasculature and the glomerulus. It was also found in the brush border of the proximal tubule and in the cortical collecting duct of female mice. ERα36 was evident in mesangial cells and tubular epithelial cells of both sexes, as well as podocytes of females but not males. ERβ was found primarily in the podocytes in female mice but was also present in the mesangial cells in both sexes. Within the renal cortex, ERα46 and ERα36 were mainly located in the membrane fraction although they were also present in the cytosolic fraction. Given the variability of expression patterns demonstrated herein, identification of the specific estrogen receptors expressed in a tissue is necessary for interpreting estrogenic effects. As this study revealed expression of the ERα splice variants at multiple sites within the kidney, further studies are warranted in order to elucidate the contribution of these receptors to renal estrogen responsiveness.

Sexual dimorphism: the aging kidney, involvement of nitric oxide deficiency, and angiotensin II overactivity

Females develop less age-dependent loss of renal function, which may be in part due to cardiorenal protective effects of estrogens. The impact of androgen level on cardiovascular-renal health is controversial. Estrogen acts through multiple mechanisms, sometimes beneficial, sometimes damaging, which makes it difficult to predict the effect of hormone replacement therapy (HRT) in an aging population. Nitric oxide (NO) deficiency occurs in aging and contributes to age-dependent cardiovascular risk and kidney damage. The increased oxidative stress of aging has effects at multiple sites in the NO biosynthetic pathway to lower NO production/action. Loss of NO together with activated angiotensin promotes some of the decrements in cardiovascular-renal function seen with age, which may be related to actions of the sex steroids.

Dietary phytoestrogens maintain contractile responses to carbachol with age in the female rat isolated bladder

AIMS

Development of urinary incontinence, for many women, occurs following menopause. Dietary phytoestrogens consumed over the long term may affect the contractile function and maintenance of the urinary bladder in post menopausal women. This study examined the muscarinic receptor mediated contractile responses in the rat isolated bladder in response to ovariectomy and long term dietary phytoestrogen consumption.

MAIN METHODS

Ovariectomised or sham-operated female Wistar rats (8 weeks) were fed either normal rat chow (soy, phytoestrogens) or a non-soy (phytoestrogen free) diet. Bladders were dissected from rats at 12, 24 and 52 weeks of age and placed in 25 ml organ baths filled with McEwans solution.

KEY FINDINGS

The contractile response to carbachol, in 12 week old female rats did not change as a result of dietary phytoestrogens or ovariectomy (P>0.05). At 24 weeks of age, detrusor muscle strip responses to carbachol from non-soy fed ovariectomised rats were attenuated (P<0.05). At 52 weeks, bladder detrusor strip responses to carbachol were reduced in all treatment groups with the exception of the soy-fed sham operated rats.

SIGNIFICANCE

These results suggest an age-related reduction in the contractile response of the detrusor to the muscarinic receptor agonist carbachol, which may be prevented by long term dietary phytoestrogen intake.

The expression of estrogen receptors in the tenosynovium of postmenopausal women with idiopathic carpal tunnel syndrome

The purpose of this study was to investigate estrogen receptor (ER) expression in tenosynovial tissues of postmenopausal woman with idiopathic carpal tunnel syndrome (CTS) to determine whether estrogen contributes to the pathogenesis of this condition. Biopsy samples of tenosynovial tissues were collected from 14 postmenopausal women (mean age; 57, range; 46-69 years) undergoing surgery for idiopathic CTS, and control specimens of tenosynovial tissue were collected from 6 postmenopausal women (mean age; 59, range; 48-68 years) without CTS. Histological and immunohistochemical examinations were performed to determine the distributions of ER-α and ER-β in tenosynovial tissues. Histological examinations showed a significant increase in fibroblast cell densities in the specimens from the carpal tunnel syndrome patients. ER-α and ER-β immunoreactivities were observed in fibroblasts and in the synovial lining cells of tenosynovial tissues, and these were significantly greater in patients than in controls. This study suggests that the up-regulations of ERs in the tenosynovial tissue are associated with idiopathic CTS in postmenopausal women.

Sexual dimorphism, the aging kidney, and involvement of nitric oxide deficiency

Females develop less age-dependent loss of renal function, in part because of cardiorenal protective effects of estrogens. The low androgen level in women also may be protective, although the animal and clinical data are controversial. Both estrogen and androgens act through multiple mechanisms, sometimes beneficial, sometimes damaging, which makes it difficult to predict the impact of hormone replacement therapy in an aging population. Nitric oxide (NO) deficiency contributes to age-dependent cardiovascular risk and kidney damage in animal models. The increased oxidative stress of aging impacts at multiple sites in the NO biosynthetic pathway to decrease NO production/action. Endothelial dysfunction develops with aging and is delayed in women, in association with a delayed increase in asymmetric dimethylarginine. Animal data suggest that the aging kidney develops NO deficiency because of changes in the neuronal NO synthase. Relative preservation of NO production in females contributes to the better cardiovascular and renal responses to aging.

Differential effects of 17beta-estradiol and of synthetic progestins on aldosterone-salt-induced kidney disease

Elevated mineralocorticoid levels and female sex hormones have been shown to confer opposing effects on renal injury, but their combined effects are still unknown.

OBJECTIVE

Identify the function of estrogens and of different synthetic progestins on aldosterone salt-mediated renal disease.

METHODS

The role of 17beta-estradiol, medroxyprogesterone acetate (MPA), and drospirenone during renal injury was studied in Wistar rats subjected to uni-nephrectomy plus aldosterone salt treatment.

RESULTS

Aldo-salt treatment of intact, ovariectomized, and estradiol-treated female rats resulted in remnant kidney hypertrophy without structural damage. Co-treatment with MPA, but not with drospirenone, increased kidney hypertrophy, fluid turnover, sodium retention, and potassium excretion. Medroxyprogesterone acetate also caused glomerular, vascular, tubular, and interstitial lesions that were accompanied by increased blood pressure and enhanced NADPH oxidase (p67phox) and sodium channel (alpha-ENaC) expression. Drospirenone, a progestin with anti-mineralocorticoid function, and spironolactone prevented kidney hypertrophy, hypertension, and sodium retention. Drospirenone and spironolactone also increased renal angiotensin II type 2 receptor expression and relieved aldosterone-induced suppression of serum angiotensin II levels.

CONCLUSION

The choice of specific synthetic progestins has profound implications on the development of kidney injury and renal gene expression under conditions of elevated aldosterone serum levels and salt intake.

Sexual dimorphism in the aging kidney: differences in the nitric oxide system

Females-both rats and women-are substantially protected against the age-dependent decrease in renal function that occurs in males of the species. In part, this finding reflects the cardioprotective and renoprotective effects of estrogens, but estrogen has multiple actions, not all of which are beneficial. In addition, the low androgen level in women might be protective against a decline in renal function, but animal and clinical data on possible adverse effects of androgens are controversial. Androgens also have multiple actions, one of which-aromatization to estrogen-is likely to be protective. Sex steroids clearly have many complex actions, which explains the conflicting information on their relative benefits and dangers. Endothelial nitric oxide (NO) deficiency contributes importantly to cardiovascular risk and intrarenal NO deficiency is clearly linked to chronic kidney disease progression in animal models. Endothelial dysfunction develops with increasing age but is delayed in females, correlating with a delayed rise in asymmetric dimethylarginine level. There is no clear link between aging and arginine (the NO synthase substrate) deficiency. Animal data suggest that the aging kidney develops NO deficiency as a result of changes in neuronal NO synthase. The increased oxidative stress that occurs with aging affects multiple stages of the NO biosynthetic pathway and results in decreased production and/or action of NO. NO production is better preserved in females than in males, partly as a result of the actions of estrogens.

Preventive effects of raloxifene, a selective estrogen receptor modulator, on monocrotaline-induced pulmonary hypertension in intact and ovariectomized female rats

We investigated whether the chronic treatment with raloxifene, a selective estrogen receptor modulator, prevents the development of monocrotaline-induced pulmonary hypertension in ovary-intact and ovariectomized female rats. Four weeks after a single subcutaneous injection of monocrotaline (60 mg/kg), right ventricular systolic pressure, right ventricle-to-left ventricle plus septal weight ratio, pulmonary arterial medial thickening and endothelin-1 levels in right ventricular tissue increased significantly in both female rats, compared with saline-treated control rats. These monocrotaline-induced alterations were much greater in ovariectomized rats than the changes in intact females. Daily oral administration of raloxifene (10 mg/kg/day for 4 weeks) significantly attenuated the increase in right ventricular systolic pressure to the same levels in both groups of animals, but raloxifene suppressed the increases in right ventricle-to-left ventricle plus septal weight ratio and pulmonary arterial medial thickness more efficiently in ovariectomized females than the case with intact females. In addition, raloxifene completely suppressed the increase in right ventricular endothelin-1 levels in ovariectomized rats, but not in intact females. These data suggest that chronic treatment with raloxifene effectively prevents the development of monocrotaline-induced pulmonary hypertension in ovariectomized female rats than in intact females, at least in part, by suppressing right ventricular endothelin-1 overproduction.

Sexual dimorphism of the aging kidney: role of nitric oxide deficiency

GFR falls with aging in humans and rats due to renal vasoconstriction and structural damage. The rate of deterioration is influenced by race/genetic background, environment, and sex, with females protected. Part of the female advantage relates to protective effects of estrogens. There is little information on impact of aging on the distribution/cardiovascular actions of the estrogen receptor subtypes. In rats, androgens may contribute to injury, but in men, high testosterone levels predict cardiovascular health. In women, the association is controversial. Nitric oxide deficiency contributes to the hypertension and renal dysfunction of aging, which may be delayed in the female.

Effect of dietary sodium on estrogen regulation of blood pressure in Dahl salt-sensitive rats

The effects of high-sodium (HS) and normal-sodium (NS) diets on ovarian hormone modulation of mean arterial pressure (MAP) were examined in Dahl salt-resistant (DR) and salt-sensitive (DS) rats. Ovariectomy increased MAP (OVX-Sham) to a greater extent in DS rats maintained for 2 wk on a HS (22 mmHg) compared with a NS (6 mmHg) diet. Ovariectomy had no effect on MAP in DR rats on NS but did increase MAP in rats on HS (10 mmHg) diets. On HS diets, glomerular filtration rate (GFR) was 36% less in the DS-Sham than DR-Sham animals; ovariectomy increased GFR in both strains by 1.4-1.5-fold; glomerular angiotensin II type 1 receptor (AT(1)R) densities were 1.6-fold higher in the DS-Sham than in the DR-Sham group; ovariectomy increased glomerular AT(1)R densities by 1.3-fold in DR rats but had no effect in DS rats; 17beta-estradiol (E(2)) downregulated adrenal AT(1)R densities in both strains on either diet; ovariectomy reduced estrogen receptor-alpha (ER-alpha) protein expression in the renal cortex by 40-50% although renal ER-alpha expression was 34% lower in DS than in DR rats. These observed effects of gonadectomy were prevented by E(2) treatment, suggesting that E(2) deficiency mediates the effects of ovariectomy on MAP, GFR, AT(1)R densities, and renal ER-alpha protein expression. In conclusion, ovariectomy-induced increases in MAP are augmented by HS diet in both strains, and this effect is not mediated by a reduction in GFR. Aberrant renal AT(1)R regulation and reduced renal ER-alpha expression are potential contributors to the hypertensive effects of E(2) deficiency in DS rats. These findings have implications for women with salt-sensitive hypertension and women who are E(2) deficient, such as postmenopausal women.