Antihypertensive effects of androgens in conscious, spontaneously hypertensive rats

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

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

Hyperandrogenism Protects Against High Blood Pressure by Nongenomic Mechanisms and Obesity Causes Hypertension in Females with Polycystic Ovary Syndrome

BACKGROUND

Androgens induce vasorelaxation and reduce blood pressure in different mammals, including humans. Most women with polycystic ovary syndrome (PCOS), with hyperandrogenism, are obese and exhibit hypertension; thus, the fact that androgens increase blood pressure (BP) is controversial. Our aim was to determine whether hypertension is produced by androgen excess and/or obesity.

METHODS

Experiments were performed in dehydroepiandrosterone; (DHEA, s.c)-induced PCOS model. BP from nonobese and obese rats with PCOS (fed a normal or high-fat diet, respectively) was evaluated weekly for 10 weeks by plethysmography and compared between them. We determined whether androgen receptors are responsible for androgen action on BP in rats with PCOS; a group of DHEA-treated rats was implanted with pellets of an antiandrogen and was compared with nonobese rats with PCOS. Isometric tension from aortas of nonobese and obese rats was recorded and compared to explore the integrity of the vascular endothelium when acetylcholine-induced endothelium-dependent vascular relaxation on phenylephrine contraction. Additionally, BP was obtained from 30 women diagnosed with PCOS: nonobese (BMI ≤25) and obese women (BMI ≥35) and compared with healthy counterparts; 15 obese and 15 nonobese women.

RESULTS

Nonobese rats and women with PCOS showed hypotension, while obese rats and women with PCOS displayed hypertension. Healthy obese women were hypertensive and nonobese women remained normotensive. Antiandrogen did not modify the BP values in nonobese rats with PCOS, and obese rats with PCOS revealed marked endothelial dysfunction.

CONCLUSIONS

Our findings show that obesity is responsible for hypertension in PCOS and partial endothelial damage was observed, which may contribute to elevated BP. Remarkably, hyperandrogenism is capable of regulating BP to low values that are androgen receptor-independent.

Cardiovascular and metabolic actions of the androgens: Is testosterone a Janus-faced molecule?

Cardiovascular disease (CVD) is a major cause of morbidity and mortality worldwide and in the Western world, one-third of all deaths are attributed to CVD. A conspicuous characteristic of this healthcare epidemic is that most CVD is higher in men than in age-matched premenopausal women, yet reasons for these obvious sex differences remain poorly understood. Driven by clinical case and epidemiological studies and supported by animal experiments, a strong dogma emerged early on that testosterone (TES) exerts deleterious effects on cardiovascular health and exacerbates development of CVD and metabolic dysfunctions in men. In this review, earlier and more recent clinical and experimental animal evidence of cardiovascular and metabolic effects of androgens are discussed. The more recent evidence overwhelmingly suggests that it is progressive, age-dependent declines in TES levels in men that exacerbate CVD and metabolic dysfunctions, while TES exerts beneficial systemic hypotensive effects and protects against metabolic syndrome (MetS) and type2 diabetes mellitus (T2DM). Recent findings reveal existence of bi-directional modulation of glucose and fat homeostasis by TES in females vs males, such that age-dependent declines in TES levels in males and abnormal increases in normally low TES levels in females both result in similar dysfunction in glucose and fat homeostasis, resulting in development of MetS and T2DM, central risk factors for development of CVD, in men as well as women. These findings suggest that the long-held view that TES is detrimental to male health should be discarded in favor of the view that, at least in men, TES is beneficial to cardiovascular and metabolic health.

Sex hormones and vascular reactivity: a temporal evaluation in resistance arteries of male rats

The role of androgens in vascular reactivity is controversial, particularly regarding their age-related actions. The objective of this study was to conduct a temporal evaluation of the vascular reactivity of resistance arteries of young male rats, as well as to understand how male sex hormones can influence the vascular function of these animals. Endothelium-mediated relaxation was characterized in third-order mesenteric arteries of 10-, 12-, 16-, and 18w (week-old) male rats. Concentration-response curves to acetylcholine (ACh, 0.1 nmol/L-10 µmol/L) were constructed in arteries previously contracted with phenylephrine (PE, 3 µmol/L), before and after the use of nitric oxide synthase or cyclooxygenase inhibitors. PE concentration-response curves (1 nmol/L-100 μmol/L) were also built. The levels of vascular nitric oxide, superoxide anion, and hydrogen peroxide were assessed and histomorphometry analysis was performed. The 18w group had impaired endothelium-dependent relaxation. All groups showed prostanoid-independent and nitric oxide-dependent vasodilatory response, although this dependence seems to be smaller in the 18w group. The 18w group had the lowest nitric oxide and hydrogen peroxide production, in addition to the highest superoxide anion levels. Besides functional impairment, 18w animals showed morphological differences in third-order mesenteric arteries compared with the other groups. Our data show that time-dependent exposure to male sex hormones appears to play an important role in the development of vascular changes that can lead to impaired vascular reactivity in mesenteric arteries, which could be related to the onset of age-related cardiovascular changes in males.

Additive damage in the thromboxane related vasoconstriction and bradykinin relaxation of intramural coronary resistance arterioles in a rodent model of andropausal hypertension

Hypertension and andropause both accelerate age–related vascular deterioration. We aimed to evaluate the effects of angiotensin-II induced hypertension and deficiency of testosterone combined regarding the resistance coronaries found intramurally.

Four male groups were formed from the animals: control group (Co, n = 10); the group that underwenr orchidectomy (ORC, n = 13), those that received an infusion of angiotensin-II (AII, n = 10) and a grous that received AII infusion and were also surgically orchidectomized (AII + ORC, n = 8). AII and AII + ORC animals were infused with infusing angiotensin-II (100 ng/min/kg) using osmotic minipumps. Orchidectomy was perfomed in the ORC and the AII + ORC groupsto establish deficiency regarding testosterone. Following four weeks of treatment, pressure-arteriography was performed in vitro, and the tone induced by administration of thromboxane-agonist (U46619) and bradykinin during analysis of the intramural coronaries (well-known to be resistance arterioles) was studied.

U46619-induced vasoconstriction poved to be significantly decreased in the ORC and AII + ORC groups when compared with Co and AII animals. In ORC and AII + ORC groups, the bradykinin-induced relaxation was also significantly reduced to a greater extent compared to Co and AII rats. Following orchidectomy, the vasocontraction and vasodilatation capacity of blood vessels is reduced. The effect of testosterone deficiency on constrictor tone and relaxation remains pronounced even in AII hypertension: testosterone deficiency further narrows adaptation range in the double noxa (AII + ORC) group. Our studies suggest that vascular changes caused by high blood pressure and testosterone deficiency together may significantly increase age-related cardiovascular risk.

Androgens and Non-Genomic vascular responses in hypertension

Arterial hypertension is a global public health concern. In the last few years, the interest in androgen deficiency has been growing, and the association between androgens and high blood pressure (BP) is still controversial. One purpose of this review was to summarize the available findings in order to clarify whether male sex steroid hormones have beneficial or harmful effect on BP. The second purpose was to enhance the recognition of the acute non-genomic sex-independent vasorelaxing effect of androgens. Remarkably, BP variation is expected to be a consequence of the androgen-induced vasorelaxation which reduces systemic BP; hence the in vivo vasodepressor, hypotensive, and antihypertensive responses of androgens were also analyzed. This article reviews the current understanding of the physiological regulation of vascular smooth muscle contractility by androgens. Additionally, it summarizes older and more recent data on androgens, and some of the possible underlying mechanisms of relaxation, structural-functional differences in the androgen molecules, and their designing ability to induce vasorelaxation. The clinical relevance of these findings in terms of designing future therapeutics mainly the 5-reduced metabolite of testosterone, 5β-dihydrotestosterone, is also highlighted. Literature collected through a PubMed database search, as well as our experimental work, was used for the present review.

The correlation between testosterone and stroke and the mediating role of blood pressure: The Henan rural cohort study

AIMS

We aimed to investigate the association of serum testosterone with stroke and calculate the proportion explained by blood pressure on this association.

MATERIALS AND METHODS

A total of 6175 subjects were included in this study. Serum testosterone was quantified by liquid chromatography-tandem mass spectrometry. The logistic regression model was used to evaluate the association between serum testosterone and stroke. Linear regression analysis was used to assess the associations of serum testosterone with blood pressure. In addition, mediation analysis was performed to identify the mediation effects of blood pressure on the association of serum testosterone with stroke. Sex-stratified analysis was employed throughout the research.

RESULTS

After adjusting for multiple variables, serum testosterone levels were negatively associated with stroke in males (per 1 unit natural log-transformed, odds ratio (OR) = 0.81, 95% confidence interval (CI): 0.69-0.94; Tertile 3 vs Tertile 1, OR = 0.65, 95% CI:0.44-0.96). Furthermore, blood pressure played a partial mediating role in the relationship between testosterone and stroke in males. The indirect effect/total effect of systolic blood pressure, diastolic blood pressure and mean arterial pressure were 7.37%, 9.54% and 9.22%, respectively. Notably, the relationship between testosterone and stroke and the role of blood pressure in regulating them was not observed in females.

CONCLUSION

This study describes that in rural Chinese males, testosterone can reduce the risk of stroke by affecting blood pressure. To some extent, we provide a new epidemiological evidence for the relationship between testosterone and stroke.

Does Patient-Applied Testosterone Replacement Therapy Pose Risk for Blood Pressure Elevation? Circadian Medicine Perspectives

We reviewed medication package inserts, US Food and Drug Administration (FDA) reports, and journal publications concerning the 10 nonbiosimilar patient-applied (PA) testosterone (T) replacement therapies (TRTs) for intraday serum T patterning and blood pressure (BP) effects. Blood T concentration is circadian rhythmic in young adult eugonadal males, being highest around awakening and lowest before bedtime. T level and 24 h variation are blunted in primary and secondary hypogonadism. Utilized as recommended, most PA-TRTs achieve nonphysiologic T 24 h patterning. Only Androderm^® , an evening PA transdermal patch, closely replicates the normal T circadian rhythmicity. Accurate determination of risk for BP elevation and hypertension (HTN) by PA-TRTs is difficult due to limitations of office BP measurements (OBPM) and suboptimal methods and endpoints of ambulatory BP monitoring (ABPM). OBPM is subject to "White Coat" pressor effect resulting in unrepresentative BP values plus masked normotension and masked HTN, causing misclassification of approximately 45% of trial participants, both before and during treatment. Change in guideline-recommended diagnostic thresholds over time causes misclassification of an additional approximately 15% of participants. ABPM is improperly incorporated into TRT safety trials. It is done for 24 h rather than preferred 48 h; BP is oversampled during wakefulness, biasing derived 24 h mean values; 24 h mean systolic and diastolic BP (SBP, DBP) are inappropriate primary outcomes, because of not being best predictors of risk for major acute cardiovascular events (MACE); "daytime" and "nighttime" BP means referenced to clock time are reported rather than biologically relevant wake-time and sleep-time BP means; most importantly, asleep SBP mean and dipping, strongest predictors of MACE, are disregarded. © 2022 American Physiological Society. Compr Physiol 12: 1-20, 2022.

Could Lower Testosterone in Older Men Explain Higher COVID-19 Morbidity and Mortalities?

The health scourge imposed on humanity by the COVID-19 pandemic seems not to recede. This fact warrants refined and novel ideas analyzing different aspects of the illness. One such aspect is related to the observation that most COVID-19 casualties were older males, a tendency also noticed in the epidemics of SARS-CoV in 2003 and the Middle East respiratory syndrome in 2012. This gender-related difference in the COVID-19 death toll might be directly involved with testosterone (TEST) and its plasmatic concentration in men. TEST has been demonstrated to provide men with anti-inflammatory and immunological advantages. As the plasmatic concentration of this androgen decreases with age, the health benefit it confers also diminishes. Low plasmatic levels of TEST can be determinant in the infection’s outcome and might be related to a dysfunctional cell Ca²⁺ homeostasis. Not only does TEST modulate the activity of diverse proteins that regulate cellular calcium concentrations, but these proteins have also been proven to be necessary for the replication of many viruses. Therefore, we discuss herein how TEST regulates different Ca²⁺-handling proteins in healthy tissues and propose how low TEST concentrations might facilitate the replication of the SARS-CoV-2 virus through the lack of modulation of the mechanisms that regulate intracellular Ca²⁺ concentrations.

Toward the Development of Personalized Syndrome Discriminant Systems: A Discriminant System for Hypertension with Liver Yang Hyperactivity Syndrome

Traditional Chinese medicine has shown promising results in treating the symptoms of hypertension, a major global health concern not yet fully managed by modern medicine. It is, therefore, of high priority to clarify the altered pathophysiology of hypertension in individuals with liver Yang hyperactivity syndrome (HLYH) in response to effective treatments to better understand this disorder. The primary aim of this study was to construct a personalized syndrome discriminant system based on data capable of informing management strategies prior to the initiation of antihypertensive therapy or the implementation of screening strategies in at-risk HLYH. Based on the successful replication of HLYH rat models, we extracted the core discriminant factors of the disorder through the integration of physical signs, biochemical indicators, and metabolic markers. Macro and micro information was correlated to construct a syndrome discriminant system. At the macroscopic level, HLYH rat models characterized by elevated blood pressure were found to be associated with significant changes in water intake, pain threshold, retention time on a rotating platform, and body surface temperature. A total of 27 potential biomarkers and 14 metabolic pathways appeared to reflect the primary metabolic characteristics. Through the integration of these data, we successfully constructed a combined macro-micro personalized syndrome discriminant system, which provides a foundation for research regarding the risk loci of HLYH. Our findings also broaden our understanding of the biological pathways involved in HLYH.

SWIM TRAINING REVERSES SOME EFFECTS OF NANDROLONE DECANOATE IN WISTAR RATS

ABSTRACT Introduction: The indiscriminate use of androgenic steroids may have deleterious effects on human tissue. Objectives: Evaluate the effects of chronic administration of the steroid nandrolone decanoate (DECA) on autonomic cardiovascular modulation, kidney morphometry and the association between these variables in Wistar rats subjected to physical training with swimming. Methods: Thirty-two male Wistar rats aged 20 weeks were distributed among four experimental groups according to the training received: sedentary control (SC), sedentary treated with DECA (SD), trained control (TC) and trained treated with DECA (TD). The hemodynamic parameters, including blood pressure and variations in systolic blood pressure (SBPV) and diastolic blood pressure (DBPV), and kidney morphometry were evaluated. The level of significance adopted was 5%. Results: The SD group had higher baseline SBP and DBP values when compared to the SC, TC and TD groups, which were similar to each other. The rats in the SD group had higher systolic blood pressure (SBPV) and diastolic blood pressure (DBPV) variation values and higher absolute and normalized values in the LF band of the DBPV when compared to the animals in the SC, TC and TD groups. The animals in the SD group had a significantly higher rate of kidney fibrosis compared to the SC, TC and TD groups. There were no significant differences between the sympathetic modulation of SBPV through the LF component and kidney fibrosis. Conclusions: Physical training with swimming was effective in preventing the increase in blood pressure levels and lowering the occurrence of kidney fibrosis in animals treated with anabolic steroids. Level of Evidence IV; Series of cases .

Vasomotor action of androgens in the mesenteric artery of hypertensive rats. Role of perivascular innervation

Androgens may exert cardiovascular protective actions by regulating the release and function of different vascular factors. In addition, testosterone (TES) and its 5-reduced metabolites, 5α- and 5β-dihydrotestosterone (5α- and 5β-DHT) induce vasorelaxant and hypotensive effects. Furthermore, hypertension has been reported to alter the release and function of the neurotransmitters nitric oxide (NO), calcitonin gene-related peptide (CGRP) and noradrenaline (NA). Since the mesenteric arteries possess a dense perivascular innervation and significantly regulate total peripheral vascular resistance, the objective of this study was to analyze the effect of TES, 5α- and 5β-DHT on the neurogenic release and vasomotor function of NO, CGRP and NA. For this purpose, the superior mesenteric artery from male spontaneously hypertensive rats (SHR) and normotensive Wistar Kyoto (WKY) rats was used to analyze: (i) the effect of androgens (10 nM, incubated for 30 min) on the neurogenic release of NO, CGRP and NA and (ii) the vasoconstrictor-response to NA and the vasodilator responses to the NO donor, sodium nitroprusside (SNP) and exogenous CGRP. The results showed that TES, 5α- or 5β-DHT did not modify the release of NO, CGRP or NA induced by electrical field stimulation (EFS) in the arteries of SHR; however, in the arteries of WKY rats androgens only caused an increase in EFS-induced NO release. Moreover, TES, and especially 5β-DHT, increased the vasodilator response induced by SNP and CGRP in the arteries of SHR. These findings could be contributing to the hypotensive/antihypertensive efficacy of 5β-DHT previously described in conscious SHR and WKY rats, pointing to 5β- DHT as a potential drug for the treatment of hypertension.

Testosterone Therapy and Cardiovascular Risk: A Critical Analysis of Studies Reporting Increased Risk

BACKGROUND

Treatment of "adult-onset hypogonadism" (AOH) with exogenous testosterone therapy (TTh) to raise serum testosterone (T) levels may influence cardiovascular (CV) risk factors in patients with AOH, whereas low endogenous T levels are associated with an increased CV risk and mortality.

AIM

To critically evaluate studies reporting increased CV risk associated with TTh and to provide an overview of the risks and benefits of restoring T levels through exogenous TTh.

METHODS

A review of publications focusing on the association between TTh and increased CV risk was conducted, and the study methodologies and conclusions of each were critically evaluated. Further, recent clinical and epidemiological studies associating AOH or TTh with a change in CV risk, and pertinent hematologic and vascular effects noted in animal studies and in vitro, as well as in clinical practice were also reviewed.

OUTCOMES

A review of the literature shows that untreated testosterone deficiency and/or low T is associated with an increase in CV risk and adverse outcomes, with numerous studies and meta-analyses to support a positive association between exogenous TTh and an improvement in CV risk factors in men with AOH.

RESULTS

Numerous studies in the literature demonstrate the positive benefits of using TTh; however, since 2013, some publications have suggested a link to increased CV risk associated with TTh. A number of these studies retrospectively analyzed insurance claims databases using diagnosis codes, procedures codes, and prescription information. Many reviews published since have pointed out the methodological flaws and debatable conclusions of these studies.

CLINICAL IMPLICATIONS

A careful assessment of the patient's current health status and CV risk factors should be weighed against the benefits and possible risks resulting from TTh, and consideration should be given to deferring treatment pending resolution or stabilization of CV disease or risk factors.

STRENGTHS & LIMITATIONS

In this review, we provide an in-depth analysis of studies reporting increased CV risk with TTh. Many of the studies were not well-designed, randomized, double-blind, prospective clinical trials but rather post hoc analyses of cohort data. These studies may reflect bias in how treatment and nontreatment decisions are made or reflect conclusions based on widely cited methodological flaws.

CONCLUSION

Appropriate patient selection supported by low pre-treatment T levels and monitoring T levels during treatment with the goal of achieving and maintaining physiologic levels all contribute to the safe and effective use of TTh in men with AOH. Khera M, Miner M, Jaffe J, et al. Testosterone Therapy and Cardiovascular Risk: A Critical Analysis of Studies Reporting Increased Risk. J Sex med 2021;18:83-98.

Non-genomic actions of sex hormones on pregnant uterine contractility in rats: An in vitro study at term

AIMS

The non-genomic (prompt) actions of sex steroids on pregnant uterine contractility are not fully explored yet, the aim of our study was to clarify such effects of 17-β estradiol (E2), progesterone (P4) and testosterone (T) on late (22-day) pregnant uterine contractions together with the signaling pathways in rats in vitro.

METHODS

The uterine effects of sex steroids on KCl-stimulated contractions were examined in the presence of genomic pathway blocker actinomycin D and cycloheximide, sex hormone receptor antagonists (flutamide, fulvestrant, mifepristone) and also after removing the endometrium. The modifications in uterine G-protein activation and cAMP levels were also detected.

RESULTS

T and E2 both relaxed the uterine contractions in the concentration range of 10^-8-10^-3 M with an increase in the activated G-protein and cAMP levels of the uterus, while P4 was ineffective. Cycloheximide, actinomycin D, antagonist for T and E2 were not able to modify the responses along with the endothelium removal. Mifepristone blocked the relaxing effects of T and E2 and reduced the activation of G-protein and the formation of cAMP.

SIGNIFICANCE

T and E2 can inhibit KCl-stimulated contractions in the late pregnant uterus in high concentrations and in a non-genomic manner. Their actions are mediated by a G-protein coupled receptor that can be blocked by mifepristone. A single and high dose of T or E2 might be considered in premature contractions, however, further preclinical and clinical studies are required for the approval of such a therapeutic intervention.

Hypogonadal hypertension in male Sprague-Dawley rats is renin-angiotensin system-dependent: role of endogenous androgens

Background

Acutely, testosterone (TES) and other androgens are efficacious vasodilators, both in vitro and in vivo; however, their long-term effects on arterial blood pressure (BP) remain unclear. It was hypothesized that endogenous androgens exert long-term anti-hypertensive effects on systemic BP through a combination of genomic and nongenomic effects to enhance vasodilation of the systemic vasculature.

Methods

The long-term effects of endogenous TES and exogenous TES replacement therapy (TRT) on BP were studied in intact (InT) and castrated (CsX) male Sprague-Dawley (SD) and testicular-feminized male (Tfm, androgen receptor defective) rats (12 weeks old). Systolic BP (tail-cuff plethysmography) was determined weekly for 15 weeks in InT-control and CsX rats. Some CsX-SD rats received androgen replacement therapy at 10-15 weeks with TES-enanthate (TRT; 1.75 mg/kg, 2x/week) or DHT-enanthate (DRT; 1.00 mg/kg. 2x/week) and a separate group of CsX-SD rats received losartan-potassium in drinking water (LST, 250 mg/L) for the entire 15 week period. Expression of renin, angiotensinogen (Agt), angiotensin converting enzyme (ACE), and angiotensin II type I receptor (AT₁R) mRNA in kidney and aorta were determined by real-time PCR (rt-PCR) and plasma renin levels were determined by radioimmunoassay.

Results

There was a progressive rise in BP over 10 weeks in CsX (109 ± 3.3 vs. 143 ± 3.5 mmHg), while BP remained stable in InT-control (109 ± 3.0 vs. 113 ± 0.3). BP gradually declined to normal in CsX-TRT rats (113 ± 1.3), while BP remained elevated in CsX (140 ± 1.2) and normal in InT-control (113 ± 0.3). LST prevented the development of hypertension in CsX at 10 weeks (100 ± 1.5 in CsX + LST vs. 143 ± 3.5 in CsX). During the next 5 weeks with TES-RT, BP declined in CsX-TRT (113 ± 1.3) and remained lower in CsX + LST (99 ± 0.4). DHT-RT reduced BP in CxS to a similar extent. In Tfm, CsX resulted in a similar rise in BP (109 ± 0.7 vs. 139 ± 0.4 mmHg), but TRT reduced BP more rapidly and to a greater extent (106 ± 2.8). rt-PCR of the kidney revealed that CsX increased expression of mRNA for renin (92%), ACE (58%), and AT₁R (80%) compared to InT, while TES RT normalized expression of renin, AT1R, and ACE mRNA to levels of InT rats. Plasma renin levels exhibited changes similar to those observed for renin mRNA expression.

Conclusions

This is the first study to examine the long-term effects of endogenous and exogenous androgens on BP in male SD and Tfm rats. These data reveal that endogenous androgens (TES) exert anti-hypertensive effects that appear to involve non-genomic and possibly genomic mechanism(s), resulting in reductions in RAS expression in the kidney and enhanced systemic vasodilation.

Vascular mechanisms of testosterone: The non-genomic point of view

Testosterone (T) is the predominant endogenous androgen in the bloodstream. At the vascular level, T presents genomic and non-genomic effects, and both effects may overlap. The genomic actions assume that androgens can freely cross the plasma membrane of target cells and bind to nuclear androgen receptors, inducing gene transcription and protein synthesis. The non-genomic effects have a more rapid onset and may be related to the interaction with protein/receptor/ion channels of the plasma membrane. The key T effect at the vascular level is vasorelaxation, which is primarily due to its rapid effect. Thus, the main purpose of this review is to discuss the T non-genomic effects at the vascular level and the molecular pathways involved in its vasodilator effect observed in in vivo and in vitro studies. In this sense, the nuclear receptor activation, the influence of vascular endothelium and the activation or inhibition of ion channels (potassium and calcium channels, respectively) will be reviewed regarding all the data that corroborated or not. Moreover, this review also provides a brief update on the association of T with the risk factors for cardiovascular diseases, namely metabolic syndrome, type 2 diabetes mellitus, obesity, atherosclerosis, dyslipidaemia, and hypertension. In summary, in this paper we consider the non-genomic vascular mode of action of androgen in physiological conditions and the main risk factors for cardiovascular diseases.

Gonadal function protects against organ culture-induced vascular damage. Involvement of prostanoids

Androgen deprivation induces vascular dysfunction in which altered release and action of prostanoids has been extensively studied. On the other hand, the vascular organ-culture system has been reported as a valid model for phenotypic changes that occur in several cardiovascular pathologies. Since there are no studies analyzing the impact of androgenic loss on vascular vulnerability during induced vascular damage, the objective of this study was to analyze the possible preventive role of male sex hormones on the organ culture-induced vascular damage in rat aorta. The link to possible changes in gross structure was also analyzed. For this purpose, fresh and 20 h-cultured aortic arterial segments from intact and orchidectomized rats were used to analyze: (i) the release and vasomotor effect of the thromboxane A₂ (TXA₂), prostaglandin (PG) E₂, PGF_2α and PGI₂; (ii) the vasodilator response induced by acetylcholine (ACh) as well as the involvement of prostanoids, in particular TXA₂, in the ACh-induced response; (iii) the effect of activation of thromboxane/prostaglandin (TP) receptors on the ACh-induced response; and (iv) the vascular structure. The results showed that organ culture: i) increased production of prostanoids; ii) increased prostanoids-induced vasomotor responses; iii) decreased ACh-induced relaxation after incubation with indomethacin, a blocker of cyclooxygenases; iv) increased the ACh-induced relaxation after incubation with the TXA₂ synthase inhibitor, furegrelate, more in arteries from orchidectomized rats than in those of intact rats; v) diminished ACh-induced relaxation after U-46619 incubation only in arteries from orchidectomized rats; and vi) preserved the integrity of the different vascular layers. These results showed the protective role of male sex hormones against the induced vascular damage, since a decreased deleterious effect of prostanoids, in particular that of TXA₂, was observed in arteries from rats with intact gonadal function.

Systemic effects of the hormonal treatment of male hypogonadism with preliminary indications for the management of COVID-19 patients

Male hypogonadism, defined as an inadequate production of testosterone (T), is associated with a greater morbidity and mortality. Epidemiological studies identified T deficiency as a risk factor for cardiovascular disease. Also, low serum T levels impact on glucose homeostasis through a worse glucose uptake, utilization, and disposal, and the general negative impact on metabolism. The aim of this review is to provide a comprehensive and updated overview of the effects of T replacement therapy on metabolic and cardiovascular systems and prostate tissue in patients with hypogonadism, including molecular mechanisms through which T exerts its actions. Furthermore, recent findings on novel coronavirus disease (COVID-19) epidemiology have shown a greater mortality in male compared with female patients and a role of T in promoting the severe acute respiratory syndrome coronavirus 2 (SARS-CoV2) infection of the host cells has been demonstrated. Hence, the secondary aim of this review is to provide preliminary indications on the management in patients with COVID-19.

Hypotestosteronemia is an important factor for the development of hypertension: elevated blood pressure in orchidectomized conscious rats is reversed by different androgens

PURPOSE

Hypotestosteronemia is an aging-associated disease. Little is known about experimental evidence linking androgen deficiency to hypertension. Various androgens are acute vasodilators, both in vitro and in vivo. We aimed to systematically investigate blood pressure (BP) in male normotensive intact or orchidectomized (ORX) Wistar and Wistar-Kyoto rats. Furthermore, we studied the acute antihypertensive responses of testosterone (TES), its precursor (DHEA), or its 5β-reduced metabolite (5β-DHT) in conscious, unrestrained, hypertensive Wistar rats caused by orchidectomy to determine their potency and efficacy. Similarly, the mechanism of their action mediated by nitric oxide (NO) was studied in vivo.

METHODS

BP of ORX rats was evaluated weekly for 18 weeks by tail cuff plethysmography. Subsequently, BP of ORX Wistar rats was measured by chronic indwelling vascular catheters, arterial, and venous catheters were implanted under anesthesia for BP recording and androgen administration, respectively. Then, a dose-response curve of each androgen was performed. Likewise, the dose-response curve of 5β-DHT, the most potent androgen, was repeated in the presence of a nonselective NO synthase inhibitor (L-NAME) or an inhibitor of endothelial NO synthesis (Endothelin-1).

RESULTS

ORX rats progressively increased systolic/diastolic BP (167 ± 2.8/141 ± 3.3 mmHg) over 18 weeks. No difference was found between strains. The BP was reduced in a dose-dependent manner caused by i.v. bolus injection of each androgen, with a rank order of potency of: 5β-DHT = DHEA>>TES. Dose-dependent antihypertension induced by 5β-DHT in ORX rats was not abolished in the presence of L-NAME or Endothelin-1.

CONCLUSIONS

These in vivo experimental findings reveal that hypotestosteronemia is a determining factor for the development of hypertension which is powerfully reduced by androgen administration, and 5β-DHT induces a potent and effective antihypertensive response by a NO-independent mechanism.

Association of total testosterone, free testosterone, bioavailable testosterone, sex hormone-binding globulin, and hypertension

Low testosterone has been inversely associated with hypertension. Our objective was to determine the associations between total testosterone (TT), free testosterone (FT), bioavailable testosterone (BioT), sex hormone-binding globulin (SHBG), and hypertension. Two hundred fifty-three men were enrolled in this study. TT and SHBG were measured by chemiluminescent immunoassay, and FT and BioT were calculated. Hypertension was defined as systolic blood pressure (SBP) ≥140 mm Hg and/or diastolic blood pressure (DBP) ≥90 mm Hg. Our results showed that hypertensive men had higher SHBG levels, and lower FT and BioT, compared to normotensive men. FT and BioT were inversely associated with SBP and DBP after adjusting for covariates (age, smoking, alcohol consumption, and physical activity). Furthermore, there was a significant decrease in the odds ratios for hypertension in the third and fourth quartiles of BioT and FT, compared to the lowest quartile before and after adjusting for covariates. In contrast, the OR for hypertension in the third quartile of SHBG was lower than the highest quartile. Our data show that FT and BioT are inversely correlated with SBP, DBP, and hypertension in men.

Sex differences in the central and peripheral manifestations of ischemia-induced heart failure in rats

Sex differences in the presentation, outcome, and responses to treatment of systolic heart failure (HF) have been reported. In the present study, we examined the effect of sex on central neural mechanisms contributing to neurohumoral excitation and its peripheral manifestations in rats with HF. Male and female Sprague-Dawley rats underwent coronary artery ligation (CL) to induce HF. Age-matched rats served as controls. Ischemic zone and left ventricular function were similar 24 h and 4 wk after CL. Female rats with HF had a lower mortality rate and less hemodynamic compromise, pulmonary congestion, and right ventricular remodeling 4 wk after CL. Plasma angiotensin II (ANG II), arginine vasopressin (AVP), and norepinephrine levels were increased in HF rats in both sexes, but AVP and norepinephrine levels increased less in female rats. In the hypothalamic paraventricular nucleus, a key cardiovascular-related nucleus contributing to neurohumoral excitation in HF, mRNA levels for the proinflammatory cytokines tumor necrosis factor-α and interleukin-1β as well as cyclooxygenase-2 and the ANG II type 1a receptor were increased in HF rats of both sexes, but less so in female rats. Angiotensin-converting enzyme 2 protein levels increased in female HF rats but decreased in male HF rats. mRNA levels of AVP were lower in female rats in both control and HF groups compared with the respective male groups. Activation of extracellular signal-regulated protein kinases 1 and 2 increased similarly in both sexes in HF. The results suggest that female HF rats have less central neural excitation and less associated hemodynamic compromise than male HF rats with the same degree of initial ischemic cardiac injury. NEW & NOTEWORTHY Sex differences in the presentation and responses to treatment of heart failure (HF) are widely recognized, but the underlying mechanisms are poorly understood. The present study describes sex differences in the central nervous system mechanisms that drive neurohumoral excitation in ischemia-induced HF. Female rats had a less intense central neurochemical response to HF and experienced less hemodynamic compromise. Sex hormones may contribute to these differences in the central and peripheral adaptations to HF.

Mechanisms of Sex Disparities in Cardiovascular Function and Remodeling

Epidemiological studies demonstrate disparities between men and women in cardiovascular disease prevalence, clinical symptoms, treatments, and outcomes. Enrollment of women in clinical trials is lower than men, and experimental studies investigating molecular mechanisms and efficacy of certain therapeutics in cardiovascular disease have been primarily conducted in male animals. These practices bias data interpretation and limit the implication of research findings in female clinical populations. This review will focus on the biological origins of sex differences in cardiovascular physiology, health, and disease, with an emphasis on the sex hormones, estrogen and testosterone. First, we will briefly discuss epidemiological evidence of sex disparities in cardiovascular disease prevalence and clinical manifestation. Second, we will describe studies suggesting sexual dimorphism in normal cardiovascular function from fetal life to older age. Third, we will summarize and critically discuss the current literature regarding the molecular mechanisms underlying the effects of estrogens and androgens on cardiac and vascular physiology and the contribution of these hormones to sex differences in cardiovascular disease. Fourth, we will present cardiovascular disease risk factors that are positively associated with the female sex, and thus, contributing to increased cardiovascular risk in women. We conclude that inclusion of both men and women in the investigation of the role of estrogens and androgens in cardiovascular physiology will advance our understanding of the mechanisms underlying sex differences in cardiovascular disease. In addition, investigating the role of sex-specific factors in the development of cardiovascular disease will reduce sex and gender disparities in the treatment and diagnosis of cardiovascular disease. © 2019 American Physiological Society. Compr Physiol 9:375-411, 2019.

Vasoactive androgens: Vasorelaxing effects and their potential regulation of blood pressure

BACKGROUND

Testosterone, 5α- and 5β-dihydrotestosterone (-DHT) induce an acute in vitro vasorelaxation and in vivo vasodepressor, hypotensive and antihypertensive responses. Our aim was to study whether androgen-induced blood pressure (BP) reduction is involved with a blockade of Ca²⁺ influx through L-type voltage-operated calcium channels (L-VOCCs) and/or the signaling pathways of α₁-adrenoceptors to induce vasoconstriction, which are one of the major mechanisms of BP maintenance.

MATERIALS AND METHODS

The relaxing potency and efficacy of each androgen in large conduit (thoracic aorta) and resistance (mesenteric) arteries from male hypertensive (SHR) and normotensive (WKY) rats were established. Blood vessels were isometrically recorded and precontracted with KCl or phenylephrine (Phe).

RESULTS

Androgens induced concentration-dependent vasorelaxation in precontracted arteries from SHR and WKY rats. 5β-DHT was always the most potent vasorelaxant in arteries from SHR. The KCl-induced contraction resulted significantly more sensitive to androgen-induced vasorelaxation than the Phe-induced contraction. On Phe-induced contraction, 5β-DHT was more potent in the mesenteric artery than in the thoracic aorta.

CONCLUSIONS

The vasorelaxation induced by androgens is mainly mediated by blocking L-VOCCs and in lesser extent by the blockade of multiple signaling pathways operative during α-adrenoceptor-induced vasoconstriction. 5β-DHT regulates vascular resistance and BP by mainly acting in the mesenteric arterial bed, which may explain its outstanding antihypertensive response previously reported.

Antihypertensive responses of vasoactive androgens in an in vivo experimental model of preeclampsia

Dehydroepiandrosterone (DHEA), testosterone (TES) and its 5-reduced metabolites induce a nongenomic vasorelaxation in several vascular beds of mammals; similarly these hormones produce systemic hypotensive and antihypertensive responses in normotensive and hypertensive male rats. Thus, it was hypothesized that the antihypertensive response of androgens, whose levels are elevated during gestation, protect against gestational hypertension. An animal model of preeclampsia was induced in female Wistar rats using DOCA-salt-treated pregnant (PT) and normal pregnant (NP) rats. In vivo experiments in conscious rats revealed that bolus intravenous injections of DHEA, TES, 5α- or 5β-dihydrotestosterone (-DHT) log -1.0 to 2.0μmolk^-1min^-1, produced substantial transient reductions in arterial blood pressure (BP), without significant changes in heart rate (HR). Mean arterial blood pressure (MAP) was reduced significantly in both groups. PT rats were more sensitive to the antihypertensive responses of androgens than NP. DHEA and 5β-DHT were the most potent to reduce MAP: 66±07 and 69±2.0mmHg in PT but only 33±0.5 and 35±1.2mmHg in NP rats, respectively. In isolated aortas of PT and NP, the concentration-response curves to each androgen (0.1-100μM) indicated that KCl-induced pre-contraction is more sensitive to all androgens than phenylephrine (Phe) pre-contractions. Notably, 5β-DHT is the greatest vasorelaxant with KCl-induced contraction than with Phe contraction of both groups, suggesting a preferential blockade on L-VOCCs. TES exhibited minor vasorelaxing effect of aortas pre-contracted with KCl, compared to its precursor DHEA and its 5-reduced metabolites. These data show that these androgens exert acute vasorelaxing effects in vitro and remarkably, reduce the BP in vivo in PT and NP at term pregnancy. Moreover, a deficit in feto-placental androgen production during pregnancy may trigger the development of preeclampsia or gestational hypertension.

Cardiovascular and Metabolic Consequences of Testosterone Supplements in Young and Old Male Spontaneously Hypertensive Rats: Implications for Testosterone Supplements in Men

BACKGROUND

The safety of testosterone supplements in men remains unclear. In the present study, we tested the hypothesis that in young and old male spontaneously hypertensive rats (SHR), long-term testosterone supplements increase blood pressure and that the mechanism is mediated in part by activation of the renin-angiotensin system.

METHODS AND RESULTS

In untreated males, serum testosterone exhibited a sustained decrease after 5 months of age, reaching a nadir by 18 to 22 months of age. The reductions in serum testosterone were accompanied by an increase in body weight until very old age (18 months). Testosterone supplements were given for 6 weeks to young (12 weeks-YMSHR) and old (21-22 months-OMSHR) male SHR that increased serum testosterone by 2-fold in young males and by 4-fold in old males. Testosterone supplements decreased body weight, fat mass, lean mass, and plasma leptin, and increased plasma estradiol in YMSHR but had no effect in OMSHR. Mean arterial pressure (MAP) was significantly higher in OMSHR than in YMSHR and testosterone supplements decreased MAP in OMSHR, but significantly increased MAP in YMSHR. Enalapril, the angiotensin-converting enzyme inhibitor, reduced MAP in both control and testosterone-supplemented YMSHR, but had a greater effect on MAP in testosterone-treated rats, suggesting the mechanism responsible for the increase in MAP in YMSHR is mediated at least in part by activation of the renin-angiotensin system.

CONCLUSIONS

Taken together with previous studies, these data suggest that testosterone supplements may have differential effects on men depending on age, cardiovascular and metabolic status, and dose and whether given long-term or short-term.

Testosterone rapidly increases Ca2+-activated K+ currents causing hyperpolarization in human coronary artery endothelial cells

Testosterone has endothelium-dependent vasodilatory effects on the coronary artery, with some reports suggesting endothelial ion channel involvement. This study employed the whole-cell patch clamp technique to investigate the effect of testosterone on ion channels in human coronary artery endothelial cells (HCAECs) and the mechanisms involved. We found that 0.03-3μM testosterone significantly induced a rapid, concentration-dependent increase in total HCAEC current (EC₅₀, 71.96±1.66nM; maximum increase, 59.13±8.37%; mean±SEM). The testosterone-enhanced currents consisted of small- and large-conductance Ca²⁺-activated K⁺ currents (SK_Ca and BK_Ca currents), but not Cl^- and nonselective cation currents. Either a non-permeant testosterone conjugate or the non-aromatizable androgen dihydrotestosterone (DHT) could increase HCAEC currents as well. The androgen receptor antagonist flutamide prevented this testosterone, testosterone conjugate, and DHT effect, while the estrogen receptor antagonist fulvestrant did not. Incubating HCAECs with pertussis toxin or protein kinase A inhibitor H-89 largely inhibited the testosterone effect, while pre-incubation with phospholipase C inhibitor U-73122, prostacyclin inhibitor indomethacin, nitric oxide synthase inhibitor L-NAME or cytochrome P450 inhibitor MS-PPOH, did not. Finally, testosterone application induced HCAEC hyperpolarization within minutes; this effect was prevented by SK_Ca and BK_Ca current inhibitors apamin and iberiotoxin. This is the first electrophysiological demonstration of androgen-induced K_Ca current increase, leading to hyperpolarization, in any endothelial cell, and the first report of SK_Ca as a testosterone target. Our data show that testosterone rapidly increased whole-cell HCAEC SK_Ca and BK_Ca currents via a surface androgen receptor, G_i/o protein, and protein kinase A. This mechanism may explain rapid testosterone-induced coronary vasodilation seen in vivo.