Involvement of the endothelin ET(B) receptor in gender differences in deoxycorticosterone acetate-salt-induced hypertension

Heart remodelling affects ECG in rat DOCA/salt model

Myocardial remodelling involves structural and functional changes in the heart, potentially leading to heart failure. The deoxycorticosterone acetate (DOCA)/salt model is a widely used experimental approach to study hypertension-induced cardiac remodelling. It allows to investigate the mechanisms underlying myocardial fibrosis and hypertrophy, which are key contributors to impaired cardiac function. In this study, myocardial remodelling in rat deoxycorticosterone acetate/salt model was examined over a three-week period. The experiment involved 11 male Sprague-Dawley rats, divided into two groups: fibrosis (n=6) and control (n=5). Myocardial remodelling was induced in the fibrosis group through unilateral nephrectomy, deoxyco-rticosterone acetate administration, and increased salt intake. The results revealed significant structural changes, including increased left ventricular wall thickness, myocardial fractional volume, and development of myocardial fibrosis. Despite these changes, left ventricular ejection fraction was preserved and even increased. ECG analysis showed significant prolongation of the PR interval and widening of the QRS complex in the fibrosis group, indicating disrupted atrioventricular and ventricular conduction, likely due to fibrosis and hypertrophy. Correlation analysis suggested a potential relationship between QRS duration and myocardial hypertrophy, although no significant correlations were found among other ECG parameters and structural changes detected by MRI. The study highlights the advantage of the DOCA/salt model in exploring the impact of myocardial remodelling on electrophysiological properties. Notably, this study is among the first to show that early myocardial remodelling in this model is accompanied by distinct electrophysiological changes, suggesting that advanced methods combined with established animal models can open new opportunities for research in this field. Key words Myocardial fibrosis, Remodelling, Animal model, DOCA-salt, Magnetic resonance imaging.

Sex-Specific Differences in Kidney Function and Blood Pressure Regulation

Premenopausal women generally exhibit lower blood pressure and a lower prevalence of hypertension than men of the same age, but these differences reverse postmenopause due to estrogen withdrawal. Sexual dimorphism has been described in different components of kidney physiology and pathophysiology, including the renin-angiotensin-aldosterone system, endothelin system, and tubular transporters. This review explores the sex-specific differences in kidney function and blood pressure regulation. Understanding these differences provides insights into potential therapeutic targets for managing hypertension and kidney diseases, considering the patient's sex and hormonal status.

Sex differences in blood pressure regulation and hypertension: renal, hemodynamic, and hormonal mechanisms

The teleology of sex differences has been argued since at least as early as Aristotle's controversial Generation of Animals more than 300 years BC, which reflects the sex bias of the time to contemporary readers. Although the question "why are the sexes different" remains a topic of debate in the present day in metaphysics, the recent emphasis on sex comparison in research studies has led to the question "how are the sexes different" being addressed in health science through numerous observational studies in both health and disease susceptibility, including blood pressure regulation and hypertension. These efforts have resulted in better understanding of differences in males and females at the molecular level that partially explain their differences in vascular function and renal sodium handling and hence blood pressure and the consequential cardiovascular and kidney disease risks in hypertension. This review focuses on clinical studies comparing differences between men and women in blood pressure over the life span and response to dietary sodium and highlights experimental models investigating sexual dimorphism in the renin-angiotensin-aldosterone, vascular, sympathetic nervous, and immune systems, endothelin, the major renal sodium transporters/exchangers/channels, and the impact of sex hormones on these systems in blood pressure homeostasis. Understanding the mechanisms governing sex differences in blood pressure regulation could guide novel therapeutic approaches in a sex-specific manner to lower cardiovascular risks in hypertension and advance personalized medicine.

Case report: 17α- hydroxylase deficiency due to a hotspot variant and a novel compound heterozygous variant in the CYP17A1 gene of five Chinese patients

17α-Hydroxylase deficiency (17OHD) is a rare form of congenital adrenal hyperplasia caused by mutations in the CYP17A1 gene. It is characterized by impaired adrenal and gonad steroid biosynthesis. Affected patients present with hypertension, hypokalemia, and disorders of sexual development. Here, we describe the genotypes and phenotypes of five patients from three families with this rare disease. Most patients had the hotspot variant, c.985_987delTACinsAA, in CYP17A1, which may be caused by a founder effect. However, the patients in our study were younger than the typical age of onset of 17OHD, and there was a pair of twins with the karyotypes 46, XX and 46, XY, but they both had a female phenotype. Meanwhile, we identified a novel compound heterozygous variant, c.1243+6T>G (p.Y329fs/splicing) in the CYP17A1 gene.

Modulation by antenatal therapies of cardiovascular and renal programming in male and female offspring of preeclamptic rats

Morbidity and mortality risks are enhanced in preeclamptic (PE) mothers and their offspring. Here, we asked if sexual dimorphism exists in (i) cardiovascular and renal damage evolved in offspring of PE mothers, and (ii) offspring responsiveness to antenatal therapies. PE was induced by administering N^G-nitro-L-arginine methyl ester (L-NAME, 50 mg/kg/day, oral gavage) to pregnant rats for 7 days starting from gestational day 14. Three therapies were co-administered orally with L-NAME, atrasentan (endothelin ETA receptor antagonist), terutroban (thromboxane A2 receptor antagonist, TXA2), or α-methyldopa (α-MD, central sympatholytic drug). Cardiovascular and renal profiles were assessed in 3-month-old offspring. Compared with offspring of non-PE rats, PE offspring exhibited elevated systolic blood pressure and proteinuria and reduced heart rate and creatinine clearance (CrCl). Apart from a greater bradycardia in male offspring, similar PE effects were noted in male and female offspring. While terutroban, atrasentan, or α-MD partially and similarly blunted the PE-evoked changes in CrCl and proteinuria, terutroban was the only drug that virtually abolished PE hypertension. Rises in cardiorenal inflammatory (tumor necrosis factor alpha, TNFα) and oxidative (isoprostane) markers were mostly and equally eliminated by all therapies in the two sexes, except for a greater dampening action of atrasentan, compared with α-MD, on tissue TNFα in female offspring only. Histopathologically, antenatal terutroban or atrasentan was more effective than α-MD in rectifying cardiac structural damage, myofiber separation, and cytoplasmic alterations, in PE offspring. The repair by antenatal terutroban or atrasentan of cardiovascular and renal anomalies in PE offspring is mostly sex-independent and surpasses the protection offered by α-MD, the conventional PE therapy.

A rare cause of delayed puberty in two cases with 46,XX and 46,XY karyotype: 17 α-hydroxylase deficiency due to a novel variant in CYP17A1 gene

Aims: 17α-hydroxylase deficiency is a rare form of congenital adrenal hyperplasia (CAH) which is inherited autosomal recessive. It occurs result of a mutations in gene cytochrome (CYP)17A1, which encodes both 17α-hydroxylase and 17,20-lyase enzymes. The main clinical findings of the disease are delayed puberty, primary amenorrhea in females, and disorders of sex development (DSD) in males. Also, hypertension and hypokalemia can be seen in both sexes. In this paper, we describe the clinical and genetic changes of two patients with 46,XY and 46,XX karyotypes from two different families who were diagnosed with complete 17α-hydroxylase enzyme deficiency.Methods: In this study various methods including clinical, hormonal, radiological and genetic analyzes were used. Blood samples were obtained for genetic tests. Genomic DNA was extracted from peripheral blood leukocytes, and coding sequence abnormalities of the CYP17 gene were assessed by polymerase chain reaction and direct sequencing analysis.Results: 17α-hydroxylase deficiency was diagnosed in 2 patients with 46,XX and 46,XY karyotype who presented with hypertension and delayed puberty. The pQ80 * (c.238C > T) mutation detected in both cases was evaluated as a novel variant.

Greater T Regulatory Cells in Females Attenuate DOCA-Salt-Induced Increases in Blood Pressure Versus Males

Hypertension is the most common risk factor for cardiovascular disease, causing over 18 million deaths a year. Although the mechanisms controlling blood pressure (BP) in either sex remain largely unknown, T cells play a critical role in the development of hypertension. Further evidence supports a role for the immune system in contributing to sex differences in hypertension. The goal of the current study was to first, determine the impact of sex on the renal T-cell profiles in DOCA-salt hypertensive males and females and second, test the hypothesis that greater numbers of T regulatory cells (Tregs) in females protect against DOCA-salt-induced increases in BP and kidney injury. Male rats displayed greater increases in BP than females following 3 weeks of DOCA-salt treatment, although increases in renal injury were comparable between the sexes. DOCA-salt treatment resulted in an increase in proinflammatory T cells in both sexes; however, females had more anti-inflammatory Tregs than males. Additional male and female DOCA-salt rats were treated with anti-CD25 to decrease Tregs. Decreasing Tregs significantly increased BP only in females, thereby abolishing the sex difference in the BP response to DOCA-salt. This data supports the hypothesis that Tregs protect against the development of hypertension and are particularly important for the control of BP in females.

Afferent arteriole responsiveness to endothelin receptor activation: does sex matter?

BACKGROUND

The pathogenesis of hypertension is distinct between men and women. Endothelin-1 (ET-1) is a potential contributor to sex differences in the pathophysiology of hypertension. ET-1 participates in blood pressure regulation through activation of endothelin A (ET_A) and endothelin B (ET_B) receptors including those in the vasculature. Previous studies demonstrated that sex and sex hormones evoke discrepancies in ET-1-mediated control of vascular tone in different vascular beds. However, little is known about sex- and sex hormone-related differences in ET-1-dependent renal microvascular reactivity. Accordingly, we hypothesized that loss of sex hormones impairs afferent arteriole reactivity to ET-1.

METHODS

Male and female Sprague Dawley rats were subjected to gonadectomy or sham surgery (n = 6/group). After 3 weeks, kidneys from those rats were prepared for assessment of renal microvascular responses to ET-1 (ET_A and ET_B agonist, 10^-12 to 10^-8 M) and sarafotoxin 6c (S6c, ET_B agonist, 10^-12 to 10^-8 M) using the blood-perfused juxtamedullary nephron preparation.

RESULTS

Control afferent arteriole diameters at 100 mmHg were similar between sham male and female rats averaging 14.6 ± 0.3 and 15.3 ± 0.3 μm, respectively. Gonadectomy had no significant effect on control arteriole diameter. In sham males, ET-1 produced significant concentration-dependent decreases in afferent arteriole diameter, with 10^-8 M ET-1 decreasing diameter by 84 ± 1%. ET-1 induced similar concentration-dependent vasoconstrictor responses in sham female rats, with 10^-8 M ET-1 decreasing the diameter by 82 ± 1%. The afferent arteriolar vasoconstrictor responses to ET-1 were unchanged by ovariectomy or orchiectomy. Selective ET_B receptor activation by S6c induced a concentration-dependent decline in afferent arteriole diameter, with 10^-8 M S6c decreasing diameter by 77 ± 3 and 76 ± 3% in sham male and female rats, respectively. Notably, ovariectomy augmented the vasoconstrictor response to S6c (10^-12 to 10^-9 M), whereas orchiectomy had no significant impact on the responsiveness to ET_B receptor activation.

CONCLUSION

These data demonstrate that sex does not significantly influence afferent arteriole reactivity to ET receptor activation. Gonadectomy potentiated the responsiveness of the afferent arteriole to ET_B-induced vasoconstriction in females, but not males, suggesting that female sex hormones influence ET_B-mediated vasoconstriction in the renal microcirculation.

Sex differences in endothelial function important to vascular health and overall cardiovascular disease risk across the lifespan

Diseases of the cardiovascular system are the leading cause of morbidity and mortality in men and women in developed countries, and cardiovascular disease (CVD) is becoming more prevalent in developing countries. The prevalence of atherosclerotic CVD in men is greater than in women until menopause, when the prevalence of CVD increases in women until it exceeds that of men. Endothelial function is a barometer of vascular health and a predictor of atherosclerosis that may provide insights into sex differences in CVD as well as how and why the CVD risk drastically changes with menopause. Studies of sex differences in endothelial function are conflicting, with some studies showing earlier decrements in endothelial function in men compared with women, whereas others show similar age-related declines between the sexes. Because the increase in CVD risk coincides with menopause, it is generally thought that female hormones, estrogens in particular, are cardioprotective. Moreover, it is often proposed that androgens are detrimental. In truth, the relationships are more complex. This review first addresses female and male sex hormones and their receptors and how these interact with the cardiovascular system, particularly the endothelium, in healthy young women and men. Second, we address sex differences in sex steroid receptor-independent mechanisms controlling endothelial function, focusing on vascular endothelin and the renin-angiotensin systems, in healthy young women and men. Finally, we discuss sex differences in age-associated endothelial dysfunction, focusing on the role of attenuated circulating sex hormones in these effects.

The chemerin knockout rat reveals chemerin dependence in female, but not male, experimental hypertension

Measures of the adipokine chemerin are elevated in multiple cardiovascular diseases, including hypertension, but little mechanistic work has been done to implicate chemerin as being causative in such diseases. The chemerin knockout (KO) rat was created to test the hypothesis that removal of chemerin would reduce pressure in the normal and hypertensive state. Western analyses confirmed loss of chemerin in the plasma and tissues of the KO vs. wild-type (WT) rats. Chemerin concentration in plasma and tissues was lower in WT females than in WT males, as determined by Western analysis. Conscious male and female KO rats had modest differences in baseline measures vs. the WT that included systolic, diastolic, mean arterial and pulse pressures, and heart rate, all measured telemetrically. The mineralocorticoid deoxycorticosterone acetate (DOCA) and salt water, combined with uninephrectomy as a hypertensive stimulus, elevated mean and systolic blood pressures of the male KO higher than the male WT. By contrast, all pressures in the female KO were lower than their WT throughout DOCA-salt treatment. These results revealed an unexpected sex difference in chemerin expression and the ability of chemerin to modify blood pressure in response to a hypertensive challenge.-Watts, S. W., Darios, E. S., Mullick, A. E., Garver, H., Saunders, T. L., Hughes, E. D., Filipiak, W. E., Zeidler, M. G., McMullen, N., Sinal, C. J., Kumar, R. K., Ferland, D. J., Fink, G. D. The chemerin knockout rat reveals chemerin dependence in female, but not male, experimental hypertension.

Loss of endothelin B receptor function impairs sodium excretion in a time- and sex-dependent manner

Recent studies suggested a direct link between circadian rhythms and regulation of sodium excretion. Endothelin-1 (ET-1) regulates sodium balance by promoting natriuresis through the endothelin B receptor (ET_B) in response to increased salt in the diet, but the effect that the time of day has on this natriuretic response is not known. Therefore, this study was designed to test the hypothesis that ET_B receptor activation contributes to the diurnal control of sodium excretion and that sex differences contribute to this control as well. Twelve-hour urine collections were used to measure sodium excretion. On day 3 of the experiment, a NaCl load (900 μeq) was given by oral gavage either at Zeitgeber time [ZT] 0 (inactive period) or ZT12 (active period) to examine the natriuretic response to the acute salt load. Male and female ET_B-deficient (ET_B def) rats showed an impaired natriuretic response to a salt load at ZT0 compared with their respective transgenic controls (Tg cont). Male ET_B def rats showed a delayed natriuretic response to a salt load given at ZT12 compared with male Tg cont, a contrast to the prompt response shown by female ET_B def rats. Treatment with ABT-627, an ET_A receptor antagonist, improved the natriuretic response seen within the first 12 h of a ZT0 salt load in both sexes. These findings demonstrate that diurnal excretion of an acute salt load 1) requires ET-1 and the ET_B receptor, 2) is more evident in male vs. female rats, and 3) is opposed by the ET_A receptor.

Role of the endothelin system in sexual dimorphism in cardiovascular and renal diseases

Epidemiological studies of blood pressure in men and women and in experimental animal models point to substantial sex differences in the occurrence of arterial hypertension as well as in the various manifestations of arterial hypertension, including myocardial infarction, stroke, retinopathy, chronic kidney failure, as well as hypertension-associated diseases (e.g. diabetes mellitus). Increasing evidence demonstrates that the endothelin (ET) system is a major player in the genesis of sex differences in cardiovascular and renal physiology and diseases. Sex differences in the ET system have been described in the vasculature, heart and kidney of humans and experimental animals. In the current review, we briefly describe the role of the ET system in the cardiovascular and renal systems. We also update information on sex differences at different levels of the ET system including synthesis, circulating and tissue levels, receptors, signaling pathways, ET actions, and responses to antagonists in different organs that contribute to blood pressure regulation. Knowledge of the mechanisms underlying sex differences in arterial hypertension can impact therapeutic strategies. Sex-targeted and/or sex-tailored approaches may improve treatment of cardiovascular and renal diseases.

Endothelin, sex, and pregnancy: unique considerations for blood pressure control in females

Endothelin-1 (ET-1) is a potent vasoconstrictor, and dysregulation of the endothelin (ET) system has been implicated in the development of hypertension. Sex differences in the ET system have been identified in ET receptor expression and activation, levels of ET-1, and downstream mediators of the ET system. More specifically, males have greater ET-1/ETA receptor activation, whereas females exhibit greater ETB receptor activation. These differences have been suggested to contribute to the sex differences observed in blood pressure control, with greater ETB receptor activation in females potentially acting as an important pathway contributing to the lower prevalence of hypertension in young females compared with age-matched males. This hypothesis is further supported by studies in pregnancy; the role of the ET system is enhanced during pregnancy, with dysregulation of the ET system resulting in preeclampsia. Further research is necessary to elucidate the relative roles of the ET system in blood pressure control in both sexes and to further explore the potential benefits of pharmacological ET blockade in women.

Endothelin ET(B) receptors contribute to sex differences in blood pressure elevation in angiotensin II hypertensive rats on a high-salt diet

Female rats are more resistant to blood pressure increases induced by high salt (HS) intake or angiotensin (Ang) II infusion. Because endothelin ET(B) receptors on endothelial and epithelial cells mediate tonic vasodilation and sodium excretion, we hypothesized that ET(B) receptors limit the hypertensive response and renal injury induced by HS diet alone or with chronic AngII infusion (AngII/HS) in female compared with male rats. A 4 week HS diet (4% NaCl) did not significantly change blood pressure (measured by telemetry) in either male or female Sprague-Dawley rats. Administration of the ET(B) receptor antagonist A-192621 (1, 3 and 10 mg/kg per day in food) during HS feeding caused a dose-dependent increase in blood pressure in both sexes. In AngII/HS rats, males had a larger increase in blood pressure than females. The increase in blood pressure produced by ET(B) receptor blockade in male AngII/HS rats was not significant. However, A-192621 treatment resulted in a significant further increase in blood pressure in female AngII/HS rats. Male rats had consistently higher protein excretion rates before and during AngII/HS, but this was not significantly affected by ET(B) receptor blockade in either sex. In conclusion, ET(B) receptors play a significantly greater beneficial role in protecting female compared with male rats against AngII-induced hypertension and may contribute to the sex differences in AngII-induced hypertension.

Vasoprotective effects of an endothelin receptor antagonist in ovariectomized female rats

AIMS

The effects of hormone replacement therapy with estrogen on cardiovascular disease in postmenopausal women are still controversial. In the present study, we examined the effects of an endothelin (ET) receptor antagonist (ERA) and/or angiotensin receptor blocker (ARB) on neointimal formation following vascular injury in ovariectomized (OVX) female rats.

MAIN METHODS

Female rats were divided into intact female and OVX groups. The right carotid artery was subjected to balloon injury, and harvested 2 weeks later.

KEY FINDINGS

In the intact female groups, treatment with ARB (L-158809; 1 mg/kg/day) for two weeks after the injury significantly decreased neointimal formation, whereas treatment with the ERA (J-104132; 10 mg/kg/day) did not affect neointimal formation. On the other hand, the ERA markedly decreased neointimal formation after the injury in the OVX groups; however, neointimal formation was not significantly improved by the ARB treatment. In addition, the combined treatment with 17β-estradiol (20 μg/kg/day) or the ERA and ARB markedly suppressed neointimal formation after the balloon injury in the OVX groups, whereas no combinational effects were observed due to the combined treatment with 17β-estradiol and the ERA.

SIGNIFICANCE

These results suggest that ERAs have estrogen-like vasoprotective effects on neointimal formation following balloon injury in OVX rats. ERAs may be useful as an alternative therapy to prevent vascular disease in postmenopausal women.

Hypertension: what's sex got to do with it?

Hypertension is a complex and multifaceted disease, and there are well established sex differences in many aspects of blood pressure (BP) control. The intent of this review is to highlight recent work examining sex differences in the molecular mechanisms of BP control in hypertension to assess whether the "one-size-fits-all" approach to BP control is appropriate with regard to sex.

ET-1 actions in the kidney: evidence for sex differences

Hypertension and chronic kidney disease are more common in men than in premenopausal women at the same age. In animal models, females are relatively protected against genetic or pharmacological procedures that produce high blood pressure and renal injury. Overactivation or dysfunction of the endothelin (ET) system modulates the progression of hypertension or kidney diseases with the ET(A) receptor primarily mediating vasoconstriction, injury and anti-natriuresis, and ET(B) receptors having opposite effects. The purpose of this review is to examine the role of the ET system in the kidney with a focus on the inequality between the sexes associated with the susceptibility to and progression of hypertension and kidney diseases. In most animal models, males have higher renal ET-1 mRNA expression, greater ET(A) -mediated responses, including renal medullary vasoconstriction, and increased renal injury. These differences are reduced following gonadectomy suggesting a role for sex hormones, mainly testosterone. In contrast, females are relatively protected from high blood pressure and kidney damage via increased ET(B) versus ET(A) receptor function. Furthermore, ET(A) receptors may have a favourable effect on sodium excretion and reducing renal damage in females. In human studies, the genetic polymorphisms of the ET system are more associated with hypertension and renal injury in women. However, the knowledge of sex differences in the efficacy or adverse events of ET(A) antagonists in the treatment of hypertension and kidney disease is poorly described. Increased understanding how the ET system acts differently in the kidneys between sexes, especially with regard to receptor subtype function, could lead to better treatments for hypertension and renal disease. LINKED ARTICLES This article is part of a themed section on Endothelin. To view the other articles in this section visit http://dx.doi.org/10.1111/bph.2013.168.issue-1.

Pathological Importance of the Endothelin-1/ET(B) Receptor System on Vascular Diseases

Activation of the endothelin (ET)-1/ET receptor system is involved in the development of vascular diseases such as atherosclerosis, vascular hypertrophy, and restenosis. Some issues still remain unresolved including whether ET receptor antagonists are expected to become the new therapeutic tools for the treatment of vascular diseases. One of the unresolved critical points is the functional role of ET receptor subtypes on each vascular disease, in particular the pathophysiological roles of the ET_B receptor. We recently demonstrated that selective inhibition of the ET_B receptor system showed harmful effects in the development of neointimal formation after vascular injury. However, there was no apparent difference in the therapeutic effects between a nonselective ET_A/ET_B receptor antagonist and selective ET_A receptor antagonist. These findings indicate that antagonism of the ET_A receptor system is essential for suppressing vascular remodeling, irrespective of the presence of ET_B-receptor-mediated actions, although the selective ET_B receptor antagonist worsens vascular remodeling. In addition, we found that ET receptor systems contribute to sex differences in the severity of vascular disease, thereby suggesting that the efficacy of ET receptor antagonists for vascular diseases may differ between sexes. In this paper, we outline the roles of the ET-1/ET_B receptor system on vascular diseases and its sex differences.

New concepts in endothelin control of sodium balance

1. Endothelin (ET)-1, which was originally found to be secreted by the vascular endothelium, is highly expressed in the kidney, particularly in the renal medulla. 2. Recent studies using genetic models have provided significant breakthroughs in the role of ET-1 in the kidney. For example, ET-1 in the medullary collecting duct physiologically regulates water and salt reabsorption, thereby controlling blood pressure. Surprisingly, to explain the blood pressure regulation both ET(A) and ET(B) receptors are necessary in collecting duct. In fact, we recently revealed that ET(A) receptor stimulation in the renal medulla was natriuretic and diuretic. 3. The expression and secretion of ET-1 in the renal medulla are regulated by multiple mechanisms, such as changes in osmolality, exaggerated renin-angiotensin system activity and hypoxia. The changes in the renal medullary ET system are likely to work as compensatory 'protective' natriuretic factors in response to high sodium exposure in the kidney. 4. In the present review, we focus on recent publications that describe our current knowledge of the functional role of renal medullary ET-1, including the recently characterized actions of ET(A) receptors, the second messenger systems, mechanisms of stimulating ET-1 production and how the ET system is involved in the development of hypertension.

Phenotypic variation in a Chinese family with 46,XY and 46,XX 17α-hydroxylase deficiency

BACKGROUND

17α-hydroxylase deficiency is a rare autosomal recessive disorder characterized by sexual infantilism, amenorrhea, hypertension and hypokalemia, which is caused by mutations in the CYP17A1 gene. To date, more than 50 mutations in this gene have been described.

METHODS

The clinical features and biochemical data of a pair of 46,XY and 46,XX Chinese siblings with 17α-hydroxylase deficiency from Singapore were studied. Direct DNA sequence analysis of the CYP17A1 gene was performed.

RESULTS

There was significant phenotypic variation between the siblings. The proband (46,XY) presented classically with sexual infantilism, amenorrhea and hypertension. The younger sibling (46,XX) also presented with amenorrhea, but she had breast development and absence of hypokalemic hypertension. The same compound heterozygous mutations in CYP17A1 gene were identified in both patients. A missense mutation (P409R) was detected in exon 7, and a 9-bp deletion (D487-S488-F489del) was detected in exon 8.

CONCLUSION

We confirmed the diagnosis of 17α-hydroxylase deficiency in these two patients. Both P409R and D487-S488-F489del have been described previously and are widely propagated in the Chinese population in East and Southeast Asia. We propose that the phenotypic expression of affected individuals with 17α-hydroxylase deficiency is karyotype-dependent, with individuals having the 46,XX karyotype having less pronounced clinical symptoms.

Sex differences in renal medullary endothelin receptor function in angiotensin II hypertensive rats

We hypothesized that angiotensin (Ang) II hypertensive rats have impaired natriuresis after renal medullary endothelin (ET) B receptor stimulation that would be more evident in male versus female rats. Acute intramedullary infusion of the ET(B) agonist sarafotoxin 6c in normotensive male rats increased sodium excretion from 0.51±0.11 μmol/min during baseline to 1.64±0.19 μmol/min (P<0.05) after S6c. After 2 weeks of Ang II infusion (260 ng/kg per minute SC), male rats had an attenuated natriuretic response to S6c of 0.62±0.16 μmol/min during baseline versus 0.95±0.07 μmol/min after S6c. In contrast, ET(B)-dependent natriuresis was similar in female hypertensive rats (0.48±0.07 versus 1.5±0.18 μmol/min; P<0.05) compared with normotensive controls (1.05±0.07 versus 2.14±0.24 μmol/min; P<0.05). Because ET(A) receptors also mediate natriuresis in normotensive female rats, we examined ET(A) receptor function in female Ang II hypertensive rats. Intramedullary infusion of ET-1 increased sodium excretion in both hypertensive and normotensive female rats, which was partially blocked by the ET(A) antagonist BQ-123. Maximum ET(B) receptor binding in inner medullary membrane preparations was comparable between vehicle and Ang II hypertensive females; however, maximum ET(B) binding was significantly lower in male hypertensive rats (1952±251 versus 985±176 fmol/mg; P<0.05). These results indicate that renal ET(B) function is impaired in male Ang II hypertension attributed, at least in part, to a reduced number of ET(B) binding sites. Furthermore, renal ET receptor function is preserved in female rats during chronic Ang II infusion, suggesting that renal ET receptor function could serve to limit hypertension in females compared with males.

Absence of thrombospondin-2 increases cardiomyocyte damage and matrix disruption in doxorubicin-induced cardiomyopathy

Clinical use of the antineoplastic agent doxorubicin (DOX) is limited by its cardiomyocyte toxicity. Attempts to decrease cardiomyocyte injury showed promising results in vitro, but failed to reduce the adverse effects of DOX in vivo, suggesting that other mechanisms contribute to its cardiotoxicity as well. Evidence that DOX also induces cardiac injury by compromising extracellular matrix integrity is lacking. The matricellular protein thrombospondin-2 (TSP-2) is known for its matrix-preserving function, and for modulating cellular function. Here, we investigated whether TSP-2 modulates the process of doxorubicin-induced cardiomyopathy (DOX-CMP). TSP-2-knockout (TSP-2-KO) and wild-type (WT) mice were treated with DOX (2 mg/kg/week) for 12 weeks to induce DOX-CMP. Mortality was significantly increased in TSP-2-KO compared to WT mice. Surviving DOX-treated TSP-2-KO mice had depressed cardiac function compared to WT animals, accompanied by increased cardiomyocyte apoptosis and matrix damage. Enhanced myocyte damage in the absence of TSP-2 was associated with impaired activation of the Akt signaling pathway in TSP-2-KO compared to WT. The absence of TSP-2, in vivo and in vitro, reduced Akt activation both under non-treated conditions and after DOX. Importantly, inhibition of Akt phosphorylation in cardiomyocytes significantly reduced TSP-2 expression, unveiling a unique feedback loop between Akt and TSP-2. Finally, enhanced matrix disruption in DOX-treated TSP-2-KO hearts went along with increased matrix metalloproteinase-2 levels. Taken together, this study is the first to provide evidence for the implication of the matrix element TSP-2 in protecting against DOX-induced cardiac injury and dysfunction.

Endothelin ETB receptor is involved in sex differences in the development of balloon injury-induced neointimal formation

The purpose of this study was to evaluate the involvement of endothelin (ET)(B) receptor-mediated action in the sex differences in balloon injury-induced neointimal formation using the spotting-lethal rat, which carries a naturally occurring deletion in its ET(B) receptor gene. Male and female ET(B)-deficient and wild-type rats underwent balloon injury of the carotid artery. In the wild-type rats, the neointima/media ratio was significantly lower in females than in males, but this sex difference was attenuated by ovariectomy and restored by treatment with 17β-estradiol (20 μg/kg/day). In the ET(B)-deficient rats, the neointima/media ratio of the male and female rats was markedly increased to the same level, and this increase was not affected by ovariectomy or 17β-estradiol treatment. Treatment with (+)-(5S,6R,7R)-2-butyl-7-[2-((2S)-2-carboxypropyl)-4-methoxyphenyl]-5-(3,4-methylenedioxyphenyl)cyclopenteno[1,2-b]pyridine-6-carboxylic acid (J-104132) (10 mg/kg/day), an ET(A)/ET(B) dual receptor antagonist, markedly decreased the neointima/media ratio of the male wild-type rats and the male and female ET(B)-deficient rats, but not the female wild-type rats. In addition, 2R-(4-propoxyphenyl)-4S-(1,3-benzodioxol-5-yl)-1-(N-(2,6-diethylphenyl)aminocarbonyl-methyl)-pyrrolidine-3R-carboxylic acid (A-192621) (30 mg/kg/day), a selective ET(B) receptor antagonist, abolished the sex difference of balloon injury-induced neointimal formation. 2R-(4-methoxyphenyl)-4S-(1,3-benzodioxol-5-yl)-1-(N,N-di(n-butyl)aminocarbonyl-methyl)-pyrrolidine-3R-carboxylic acid (ABT-627) (10 mg/kg/day), a selective ET(A) receptor antagonist, and J-104132 (10 mg/kg/day) markedly decreased the neointima/media ratio to the same extent in males but not intact females. These results indicate that the sex difference in balloon injury-induced neointimal formation was abolished by genetic ET(B) receptor deficiency or its pharmacological blockade. The lack of a vasoprotective effect of estrogen and the augmentation of ET(A) receptor-mediated action seem to be responsible for the abolition of sex differences in the ET(B) receptor-inhibited condition.

Attenuation of experimental hepatopulmonary syndrome in endothelin B receptor-deficient rats

Experimental hepatopulmonary syndrome (HPS) after common bile duct ligation (CBDL) in rat is accompanied by increased lung vascular endothelial endothelin B (ETB) receptor expression and increased circulating levels of endothelin-1 (ET-1). The onset of HPS is hypothesized to be triggered by ET-1/ETB receptor activation of endothelial nitric oxide synthase (eNOS)-derived NO production in the pulmonary endothelium. However, whether functional pulmonary vascular ETB receptors are required for the development of experimental HPS is not defined. We evaluated the effects of vascular ETB receptor deficiency on the development of experimental HPS. The molecular and physiological alterations of HPS were compared in 2-wk CBDL wild-type and ETB receptor-deficient (transgenic sl/sl) rats. Relative to wild-type rats, basal hepatic and plasma ET-1 levels were elevated in sl/sl controls although, unlike wild-type animals circulating ET-1 levels, did not increase further after CBDL in sl/sl animals. In contrast to wild-type animals, ETB receptor-deficient rats did not develop increased Akt and eNOS expression and activation and did not develop gas exchange abnormalities of HPS after CBDL. There was a similar degree of pulmonary intravascular monocyte accumulation in both 2-wk CBDL sl/sl and wild-type animals. In conclusion, ETB receptor deficiency inhibits lung Akt/eNOS activation and prevents the onset of experimental HPS after CBDL. This effect is independent of inhibition of pulmonary intravascular monocyte accumulation. These results demonstrate that ET-1/ETB receptor signaling plays a key role in the initiation of experimental HPS.

Contribution of endothelin A receptors in endothelin 1-dependent natriuresis in female rats

Renal medullary endothelin B receptors contribute to blood pressure regulation by facilitating salt excretion. Premenopausal females have relatively less hypertension than males; therefore, we examined whether there is a sex difference in the natriuretic response to renal medullary infusion of endothelin peptides in the rat. All of the experiments were conducted in anesthetized wild-type (wt) or endothelin B-deficient (sl/sl) rats. Infusion of endothelin 1 (ET-1) significantly increased sodium excretion (U(Na)V) in female, but not male, wt rats (Delta U(Na)V: 0.41+/-0.07 versus -0.04+/-0.06 micromol/min, respectively). The endothelin B receptor agonist sarafotoxin 6c produced similar increases in U(Na)V in both male (Delta 0.58+/-0.15 micromol/min) and female (Delta 0.67+/-0.18 micromol/min) wt rats. Surprisingly, ET-1 markedly increased U(Na)V in female (Delta 0.70+/-0.11 micromol/min) but not male sl/sl rats (Delta 0.00+/-0.05 micromol/min). ET-1 had no effect on medullary blood flow in females, although medullary blood flow was significantly reduced to a similar extent in males of both strains. These results suggest that the lack of a natriuretic response to ET-1 in male rats is because of reductions in medullary blood flow. Treatment with ABT-627, an endothelin A receptor antagonist, or N(G)-propyl-L-arginine, an NO synthase 1 inhibitor, prevented the increase in U(Na)V observed in female rats. Gonadectomy eliminated the sex difference in the U(Na)V and medullary blood flow response to ET-1. These findings demonstrate that there is no sex difference in endothelin B-dependent natriuresis, and the endothelin A receptor contributes to ET-1-dependent natriuresis in female rats, an effect that requires NO synthase 1. These findings provide a possible mechanism for why premenopausal women are more resistant to salt-dependent hypertension.

Sex differences in control of blood pressure: role of oxidative stress in hypertension in females

In general, blood pressure is higher in normotensive men than in age-matched women, and the prevalence of hypertension in men is also higher until after menopause, when the prevalence of hypertension increases for women. It is likely then that the mechanisms by which blood pressure increases in men and women with aging may be different. Although clinical trials to reduce blood pressure with antioxidants have typically not been successful in human cohorts, studies in male rats suggest that oxidative stress plays an important role in mediating hypertension. The exact mechanisms by which oxidative stress increases blood pressure have not been completely elucidated. There may be several reasons for the discrepancies between clinical and animal studies. In this review, the data obtained in selected clinical and animal studies are discussed, and the hypothesis is put forward that oxidative stress may not be as important in mediating hypertension in females as has been shown previously in male rats. Furthermore, it is likely that differences in genetics, age, length of time with hypertension, endothelial dysfunction, and sex are all factored in to modulate the responses to antioxidants in humans. As such, future clinical trials should be designed and powered to evaluate the effects of oxidative stress on blood pressure separately in men and women.

Reactive oxygen species participate in acute renal vasoconstrictor responses induced by ETAand ETBreceptors

Reactive oxygen species (ROS) play important roles in renal vasoconstrictor responses to acute and chronic stimulation by angiotensin II and norepinephrine, as well as in long-term effects of endothelin-1 (ET-1). Little is known about participation of ROS in acute vasoconstriction produced by ET-1. We tested the influence of NAD(P)H oxidase inhibition by apocynin [4 mg·kg−1·min−1, infused into the renal artery (ira)] on ETAand ETBreceptor signaling in the renal microcirculation. Both receptors were stimulated by ET-1, ETAreceptors by ET-1 during ETBantagonist BQ-788, and ETBby ETBagonist sarafotoxin 6C. ET-1 (1.5 pmol injected ira) reduced renal blood flow (RBF) 17 ± 4%. Apocynin raised baseline RBF (+10 ± 1%, P < 0.001) and attenuated the ET-1 response to 10 ± 2%, i.e., 35 ± 9% inhibition ( P < 0.05). Apocynin reduced ETA-induced vasoconstriction by 42 ± 12% ( P < 0.05) and that of ETBstimulation by 50 ± 8% ( P < 0.001). During nitric oxide (NO) synthase inhibition ( Nω-nitro-l-arginine methyl ester), apocynin blunted ETA-mediated vasoconstriction by 60 ± 8% ( P < 0.01), whereas its effect on the ETBresponse (by 87 ± 8%, P < 0.001) was even larger without than with NO present ( P < 0.05). The cell-permeable superoxide dismutase mimetic tempol (5 mg·kg−1·min−1ira), which reduces O2−and may elevate H2O2, attenuated ET-1 responses similar to apocynin (by 38 ± 6%, P < 0.01). We conclude that ROS, O2−rather than H2O2, contribute substantially to acute renal vasoconstriction elicited by both ETAand ETBreceptors and to basal renal vasomotor tone in vivo. This physiological constrictor action of ROS does not depend on scavenging of NO. In contrast, scavenging of O2−by NO seems to be more important during ETBstimulation.

Sex differences in the pressor response to angiotensin II when the endogenous renin-angiotensin system is blocked

The present study determined whether there are sex differences in the pressor response to angiotensin II (Ang II) when the endogenous renin-angiotensin system (RAS) is blocked by enalapril (ACEI), and whether this pressor response is changed in the presence of high salt (HS). Telemetry BP was measured in rats treated with ACEI (250 mg/L drinking water) (n=6 to 7/grp), or with ACEI and Ang II (150 ng/kg/min, sc; n=5 to 6/grp), for 3 wk. For the last 2 wk of the study, rats received HS (4% NaCl). MAP was lower in females during baseline (100.8+/-1.1 versus 105.2+/-1.3; P<0.05), and with ACEI the last 3 days on normal salt diet (78.8+/-1.2 versus 88.5+/-0.9; P<0.05), but increased to higher levels than in males on day 6 of Ang II (129.0+/-2.2 versus 117.3+/-2.9; P<0.05). One week of Ang II increased albuminuria in males, but not females, and urinary 8-iso-PGF2alpha (F2-isoP) was not increased in either males or females. MAP was salt-sensitive in both sexes receiving ACEI, but was only salt-sensitive in males with Ang II (129.3+/-3.7 versus 145.1+/-5.7; P<0.05). Albuminuria continued to increase with HS and Ang II in males, but not in females. F2-isoP excretion increased with MAP during the last week of HS and Ang II in males but was independent of MAP in females. With ACEI, MAP in females on normal salt is more responsive to Ang II but is independent of oxidative stress or renal injury. MAP in males is salt-sensitive with Ang II, which may be mediated by oxidative stress and renal injury.

Endothelin, sex and hypertension

The ETs (endothelins) comprise a family of three 21-amino-acid peptides (ET-1, ET-2 and ET-3) and 31-amino-acid ETs (ET-1(1-31), ET-2(1-31) and ET-3(1-31)). ET-1 is synthesized from a biologically inactive precursor, big ET-1, by ECEs (ET-converting enzymes). The actions of ET-1 are mediated through activation of the G-protein-coupled ET(A) and ET(B) receptors, which are found in a variety of cells in the cardiovascular and renal systems. ET-1 has potent vasoconstrictor, mitogenic, pro-inflammatory and antinatriuretic properties, which have been implicated in the pathophysiology of a number of cardiovascular diseases. Overexpression of ET-1 has been consistently described in salt-sensitive models of hypertension and in models of renal failure, and has been associated with disease progression. Sex differences are observed in many aspects of mammalian cardiovascular function and pathology. Hypertension, as well as other cardiovascular diseases, is more common in men than in women of similar age. In experimental models of hypertension, males develop an earlier and more severe form of hypertension than do females. Although the reasons for these differences are not well established, the effects of gonadal hormones on arterial, neural and renal mechanisms that control blood pressure are considered contributing factors. Sex differences in the ET-1 pathway, with males displaying higher ET-1 levels, greater ET-1-mediated vasoconstrictor and enhanced pressor responses in comparison with females, are addressed in the present review. Sex-associated differences in the number and function of ET(B) receptors appear to be particularly important in the specific characteristics of hypertension between females and males. Although the gonadal hormones modulate some of the differences in the ET pathway in the cardiovascular system, a better understanding of the exact mechanisms involved in sex-related differences in this peptidergic system is needed. With further insights into these differences, we may learn that men and women could require different antihypertensive regimens.