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

5β-Dihydrosteroids: Formation and Properties

5β-Dihydrosteroids are produced by the reduction of Δ4-3-ketosteroids catalyzed by steroid 5β-reductase (AKR1D1). By analogy with steroid 5α-reductase, genetic deficiency exists in AKR1D1 which leads to errors in newborn metabolism and in this case to bile acid deficiency. Also, like the 5α-dihydrosteroids (e.g., 5α-dihydrotestosterone), the 5β-dihydrosteroids produced by AKR1D1 are not inactive but regulate ligand access to nuclear receptors, can act as ligands for nuclear and membrane-bound receptors, and regulate ion-channel opening. For example, 5β-reduction of cortisol and cortisone yields the corresponding 5β-dihydroglucocorticoids which are inactive on the glucocorticoid receptor (GR) and provides an additional mechanism of pre-receptor regulation of ligands for the GR in liver cells. By contrast, 5β-pregnanes can act as neuroactive steroids at the GABAA and NMDA receptors and at low-voltage-activated calcium channels, act as tocolytic agents, have analgesic activity and act as ligands for PXR, while bile acids act as ligands for FXR and thereby control cholesterol homeostasis. The 5β-androstanes also have potent vasodilatory properties and work through blockade of Ca2+ channels. Thus, a preference for 5β-dihydrosteroids to work at the membrane level exists via a variety of mechanisms. This article reviews the field and identifies gaps in knowledge to be addressed in future research.

Relationship between Androgens and Vascular and Placental Function during Pre-eclampsia

Hypertensive disorders of pregnancy (HDP) represent a substantial risk to maternal and fetal health. Emerging evidence suggests an association between testosterone and pre-eclampsia (PE), potentially mediated through androgen receptors (AR). Nevertheless, the mechanism driving this association is yet to be elucidated. On the other hand, reports of transgender men's pregnancies offer a limited and insightful opportunity to understand the role of high androgen levels in the development of HDP. In this sense, a literature review was performed from a little over 2 decades (1998-2022) to address the association of testosterone levels with the development of HDP. Furthermore, this review addresses the case of transgender men for the first time. The main in vitro outcomes reveal placenta samples with greater AR mRNA expression. Moreover, ex vivo studies show that testosterone-induced vasorelaxation impairment promotes hypertension. Epidemiological data point to greater testosterone levels in blood samples during PE. Studies with transgender men allow us to infer that exogenous testosterone administration can be considered a risk factor for PE and that the administration of testosterone does not affect fetal development. Overall, all studies analyzed suggested that high testosterone levels are associated with PE.

Vasodilator Responses of Perivascular Adipose Tissue-Derived Hydrogen Sulfide Stimulated with L-Cysteine in Pregnancy Hypertension-Induced Endothelial Dysfunction in Rats

Endothelium-derived nitric oxide (NO)-induced vasodilation is impaired in pregnancy hypertension. However, the role of perivascular adipose tissue (PVAT)-derived hydrogen sulfide (H2S), as an alternative for counteracting vascular dysfunction, is incompletely clear in hypertensive disorders of pregnancy. Therefore, PVAT-derived H2S-induced vasodilation was investigated in pregnancy hypertension-induced endothelial dysfunction. Non-pregnant (Non-Preg) and pregnant (Preg) rats were submitted (or not) to the deoxycorticosterone (DOCA)-salt protocol and assigned as follows (n = 10/group): Non-Preg, Non-Preg+DOCA, Preg, and Preg+DOCA groups. Systolic blood pressure (SBP), angiogenesis-related factors, determinant levels of H2S (PbS), NO (NOx), and oxidative stress (MDA) were assessed. Vascular changes were recorded in thoracic aortas with PVAT and endothelium (intact and removed layers). Vasorelaxation responses to the substrate (L-cysteine) for the H2S-producing enzyme cystathionine-γ-lyase (CSE) were examined in the absence and presence of CSE-inhibitor DL-propargylglycine (PAG) in thoracic aorta rings pre-incubated with cofactor for CSE (pyridoxal-5 phosphate: PLP) and pre-contracted with phenylephrine. Hypertension was only found in the Preg+DOCA group. Preg+DOCA rats showed angiogenic imbalances and increased levels of MDA. PbS, but not NOx, showed increased levels in the Preg+DOCA group. Pre-incubation with PLP and L-cysteine elevated determinants of H2S in PVAT and placentas of Preg-DOCA rats, whereas no changes were found in the aortas without PVAT. Aortas of Preg-DOCA rats showed that PVAT-derived H2S-dependent vasodilation was greater compared to endothelium-derived H2S, whereas PAG blocked these responses. PVAT-derived H2S endogenously stimulated with the amino acid L-cysteine may be an alternative to induce vasorelaxation in endothelial dysfunction related to pregnancy hypertension.

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.

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.

Hydrogen sulfide ameliorated preeclampsia via suppression of toll-like receptor 4-activated inflammation in the rostral ventrolateral medulla of rats

This study aims to determine whether toll-like receptor 4 (TLR4)-mediated inflammation in rostral ventrolateral medulla (RVLM) causes sympathetic overactivity leading to preeclampsia (PE) and if TLR4 inhibition with hydrogen sulfide (H₂S) would reduce PE severity. Thirty patients with PE and 30 pregnant controls were involved. PE in rats was induced through deoxycorticosterone acetate and normal saline. NaHS (donor of H₂S), lipopolysaccharide (LPS) (TLR4 agonist), and TAK-242 (TLR4 inhibitor) were injected in lateral cerebral ventricle to investigate their effect on microglia-mediated inflammation in RVLM, sympathetic activation, and PE symptoms. In patients with PE, plasma levels of NE, TNF-α, and interleukin-1β were high compared with those of controls, whereas levels of H₂S were low. Rats with PE showed an increased amount of renal sympathetic nerve activity and plasma levels of NE, with decreased H₂S levels in RVLM. Microglia-mediated inflammation was observed in the RVLM of PE rats. Central infusion of LPS in pregnant rats induced microglia-mediated inflammation, sympathetic nervous tension, and PE-like symptoms, whereas TAK-242 reduced PE symptoms. NaHS treatment lessened microglia-mediated inflammation in the RVLM, sympathetic tension, and symptoms of PE both in PE rats and LPS-treating pregnant rats.These results suggest that inflammation in the RVLM caused by microglial activation might contribute to the progression of PE via an overactive sympathetic system. H₂S could reduce PE via inhibiting inflammation in the RVLM. These results might provide a new target for the treatment of PE.

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.

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.

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.