The vasodilatory action of testosterone: a potassium-channel opening or a calcium antagonistic action?

Cardiovascular Outcomes of Hypogonadal Men Receiving Testosterone Replacement Therapy: A Meta-analysis of Randomized Controlled Trials

OBJECTIVE

To investigate the impact of testosterone replacement therapy (TRT) on cardiovascular outcomes in hypogonadal men.

METHODS

A meta-analysis of 26 randomized controlled trials involving 10 941 participants was conducted. Various clinical outcomes, including all-cause mortality, cardiovascular-related mortality, myocardial infarction, stroke, congestive heart failure, atrial fibrillation, pulmonary embolism, and venous thrombosis, were assessed.

RESULTS

No statistically significant differences were observed between the TRT group and the control group in terms of these clinical outcomes. Sensitivity analysis and publication bias assessment supported the robustness of the findings. Meta-regression analysis found no significant associations between clinical outcomes and potential covariates, including age, diabetes, hypertension, dyslipidemia, and smoking.

DISCUSSION

Previous research on TRT and cardiovascular events, with comparisons to studies like the Testosterone Trials and the studies conducted by Vigen et al, Finkle et al, Layton et al, and Wallis et al, is provided. The significance of the systematic review and meta-analysis approach is emphasized, particularly its exclusive focus on hypogonadal patients.

CONCLUSION

This study offers reassurance that TRT does not increase mortality risk or worsen cardiovascular outcomes in hypogonadal men. However, further research, especially long-term studies involving diverse populations, is essential to strengthen the evidence base and broaden the applicability of these findings.

Cycling matters: Sex hormone regulation of vascular potassium channels

Sex hormones and the reproductive cycle (estrus in rodents and menstrual in humans) have a known impact on arterial function. In spite of this, sex hormones and the estrus/menstrual cycle are often neglected experimental factors in vascular basic preclinical scientific research. Recent research by our own laboratory indicates that cyclical changes in serum concentrations of sex -hormones across the rat estrus cycle, primary estradiol, have significant consequences for the subcellular trafficking and function of KV. Vascular potassium channels, including KV, are essential components of vascular reactivity. Our study represents a small part of a growing field of literature aimed at determining the role of sex hormones in regulating arterial ion channel function. This review covers key findings describing the current understanding of sex hormone regulation of vascular potassium channels, with a focus on KV channels. Further, we highlight areas of research where the estrus cycle should be considered in future studies to determine the consequences of physiological oscillations in concentrations of sex hormones on vascular potassium channel function.

PFI-3 induces vasorelaxation with potency to reduce extracellular calcium influx in rat mesenteric artery

Background

PFI-3 is a small-molecule inhibitor that targets the bromodomains (BRDs) of Brahma-related gene 1 (BRG1). This monomeric compound, which has high selectivity and potent cellular effects, has recently been developed. Although PFI-3 has been reported as a potential therapeutic agent targeting thrombomodulin, its role in the regulation of vascular function remains unknown. Therefore, we aimed to investigate the impact of PFI-3 on arterial vessel tone.

Methods

A microvascular tension measurement device (DMT) was utilized to identify alterations in vascular tension within the mesenteric artery. To detect variations in cytosolic [Ca²⁺]_i, a Fluo-3/AM fluorescent probe and fluorescence microscope were employed. Additionally, whole-cell patch clamp techniques were utilized to evaluate the activity of L-type voltage-dependent calcium channels (VDCCs) in cultured arterial smooth muscle cells (A10 cells).

Results

PFI-3 exerted a dose-dependent relaxation effect on rat mesenteric arteries with both intact and denuded endothelium after phenylephrine (PE)- and high-K⁺-induced constriction. PFI-3-induced vasorelaxation was not affected by the presence of L-NAME/ODQ or K⁺ channel blockers (Gli/TEA). PFI-3 abolished Ca²⁺-induced contraction on endothelium-denuded mesenteric arteries preincubated by PE in Ca²⁺-free solution. Incubation with TG had no impact on PFI-3-induced vasorelaxation pre-contracted by PE. PFI-3 reduced Ca²⁺-induced contraction on endothelium-denuded mesenteric arteries pre-incubated by KCl (60 mM) in Ca²⁺-free solution. PFI-3 declined extracellular calcium influx in A10 cells detected by Fluo-3/AM fluorescent probe and fluorescence microscope. Furthermore, we observed that PFI-3 decreased the current densities of L-type VDCC by whole-cell patch clamp techniques.

Conclusions

PFI-3 blunted PE and high K⁺-induced vasoconstriction independent of endothelium on rat mesenteric artery. The vasodilatory effect of PFI-3 may be attributed to its inhibition of VDCCs and receptor-operated calcium channels (ROCCs) on vascular smooth muscle cells (VSMCs).

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.

Testosterone Deficiency as One of the Major Endocrine Disorders in Chronic Kidney Disease

Reduced testosterone concentration is nowadays thought to be one of the main endocrine disorders in chronic kidney disease (CKD). It is caused by the dysfunction of the hypothalamic-pituitary-gonadal axis. The role of testosterone is multifactorial. Testosterone is responsible not only for reproductive processes, but it is a hormone which increases bone and muscle mass, improves lipid profile, insulin sensitivity, erythropoiesis, reduces blood pressure, and ameliorates mood and perception. The implications of hypogonadism in CKD are infertility and loss of libido, reduction of muscle mass and strength, disorders in bone mineralization, the development of sarcopenia and protein energy wasting (PEW), progression of atherosclerosis, increased visceral adiposity, insulin resistance, and anaemia. Reduced testosterone serum concentrations in CKD are associated with increased mortality rate. Testosterone supplementation improves sexual functions, reduces the level of inflammatory markers and blood pressure, stimulates muscle protein synthesis, improves insulin sensitivity and lipid profile, and increases muscle mass, bone mineral density, and haemoglobin concentration. It positively affects mood and well-being. The modes of testosterone supplementation are intramuscular injections, subcutaneous pellets, and percutaneous methods—patches and gels. Successful kidney transplantation may improve gonadal function and testosterone production, however, half of men with low testosterone concentrations before kidney transplantation do not restore hormonal function.

Effects of long-term testosterone treatment on cardiovascular outcomes in men with hypogonadism: Rationale and design of the TRAVERSE study

BACKGROUND

Testosterone exerts some effects on the cardiovascular system that could be considered beneficial; some other effects may potentially increase the risk of cardiovascular (CV) events. Neither the long-term efficacy nor safety of testosterone treatment has been studied in an adequately-powered randomized trial.

METHODS

The Testosterone Replacement therapy for Assessment of long-term Vascular Events and efficacy ResponSE in hypogonadal men (TRAVERSE) study is a randomized, double-blind, placebo-controlled, parallel group, non-inferiority, multicenter study. Eligible participants are men, 45 to 80 years, with serum testosterone concentration <300 ng/dL and hypogonadal symptoms, who have evidence pre-existing CV disease or increased risk of CV disease. Approximately 6,000 subjects will be randomized to either 1.62% transdermal testosterone gel or a matching placebo gel daily for an anticipated duration of up to 5 years. The primary outcome is CV safety defined by the major adverse CV event composite of nonfatal myocardial infarction, nonfatal stroke, or death due to CV causes. The trial will continue until at least 256 adjudicated major adverse CV event endpoints have occurred to assess whether the 95% (2-sided) upper confidence limit for a hazard ratio of 1.5 can be ruled out. Secondary endpoints include prostate safety defined as the incidence of adjudicated high grade prostate cancer and efficacy in domains of sexual function, bone fractures, depression, anemia, and diabetes.

RESULTS

As of July 1, 2021, 5,076 subjects had been randomized.

CONCLUSIONS

The TRAVERSE study will determine the CV safety and long-term efficacy of testosterone treatment in middle-aged and older men with hypogonadism with or at increased risk of CV disease.

Testosterone Supplementation Induces Age-Dependent Augmentation of the Hypoxic Ventilatory Response in Male Rats With Contributions From the Carotid Bodies

Excessive carotid body responsiveness to O₂ and/or CO₂/H⁺ stimuli contributes to respiratory instability and apneas during sleep. In hypogonadal men, testosterone supplementation may increase the risk of sleep-disordered breathing; however, the site of action is unknown. The present study tested the hypothesis that testosterone supplementation potentiates carotid body responsiveness to hypoxia in adult male rats. Because testosterone levels decline with age, we also determined whether these effects were age-dependent. In situ hybridization determined that androgen receptor mRNA was present in the carotid bodies and caudal nucleus of the solitary tract of adult (69 days old) and aging (193–206 days old) male rats. In urethane-anesthetized rats injected with testosterone propionate (2 mg/kg; i.p.), peak breathing frequency measured during hypoxia (FiO₂ = 0.12) was 11% greater vs. the vehicle treatment group. Interestingly, response intensity following testosterone treatment was positively correlated with animal age. Exposing ex vivo carotid body preparations from young and aging rats to testosterone (5 nM, free testosterone) 90–120 min prior to testing showed that the carotid sinus nerve firing rate during hypoxia (5% CO₂ + 95% N₂; 15 min) was augmented in both age groups as compared to vehicle (<0.001% DMSO). Ventilatory measurements performed using whole body plethysmography revealed that testosterone supplementation (2 mg/kg; i.p.) 2 h prior reduced apnea frequency during sleep. We conclude that in healthy rats, age-dependent potentiation of the carotid body’s response to hypoxia by acute testosterone supplementation does not favor the occurrence of apneas but rather appears to stabilize breathing during sleep.

Daily variation of the cortisol and insulin concentration, glycemia, surface temperature, and behavior patterns due the administration of equine Chorionic Gonadotropin in rams

Sex steroids can modulate the circadian rhythmicity of some physiological and behavioral functions of sheep. During the non-breeding season, Corriedale rams have a low testosterone concentration, but the administration of equine Chorionic Gonadotropin (eCG) stimulates its secretion. Therefore, the daily variation of cortisol and insulin concentrations, glycemia, behavioral pattern (eating, ruminating, standing, lying, and sleeping), and rostral and eye surface temperatures were compared in rams treated or not treated with eCG during the non-breeding season [between August (late winter) and September (early spring)]. Twenty Corriedale adult rams (BW 63.4 ± 7.3 kg; BCS: 3.5 ± 0.5; mean ± SD; age: 2-3 years old) were randomly assigned to 1 of 2 treatments: a) Treated: administration of 1000 IU of eCG intramuscularly and b) Control: control, without application of eCG. All the rams were managed under the same feeding and environmental conditions (individual pens outdoors). All variables were measured each hour for 26 h, except testosterone and insulin that were measured at 09:00, 10:00, 12:00, 15:00, 18:00, 21:00, 22:00, 24:00, 03:00, 06:00, 09:00 and 11:00 h. Testosterone and cortisol concentration were greater in Treated than Control rams (testosterone: 32.7 ± 0.7 nmol/L vs 5.8 ± 0.7 nmol/L; P <0.0001; cortisol: 11.3 ± 0.6 nmol/L vs 9.9 ± 0.6 nmol/L; P =0.02). The eye surface temperature was 0.9°C lower in the Treated than in the Control rams (P =0.004). The characteristics of the daily variation pattern of cortisol, glycemia, glycemia:insulin ratio, and surface temperature were not affected by the treatment, the acrophases being at ∼06:00 h, ∼18:00 h, ∼08:00 h, and ∼11:00 h, respectively. The acrophase of insulin concentration was observed earlier in Treated than in Control rams (13:02 ± 0:56 vs 15:47 ± 0:53; P =0.04). Additionally, the acrophase of the time spent eating was advanced in Treated rams (09:48 ± 00:16 vs 10:20 ± 00:16; P =0.04) and sleeping (21:39 ± 00:57 vs 02:02 ± 01:06; P <0.0001). Treated rams slept less time than Control rams (P =0.04). In conclusion, the administration of eCG modulated the daily variation pattern of insulin concentration and the behavioral pattern (period in which rams were observed eating and sleeping). Nevertheless, although there was a greater cortisol concentration and reduced eye surface temperature, the administration of eCG did not modify their daily variation pattern, suggesting that this is robust, limiting the effect of testosterone on their basal pattern.

Cardiovascular Health of Youth During Gender-Affirming Testosterone Treatment: A Review

PURPOSE

Many birth-assigned female/transgender male and nonbinary people (identified as masculine spectrum here) begin gender-affirming testosterone therapy by the age of 24 years. Few data inform assessment of cardiovascular health of masculine spectrum youth as a specific subgroup of the 1.5 million transgender people in the United States. The purpose of this review is to help youth-serving practitioners consider, understand, and evaluate cardiovascular health in adolescent and young adult masculine spectrum patients receiving gender-affirming testosterone treatment.

METHODS

This is a narrative review intended to synthesize a broad body of clinical and research literature.

RESULTS

Common cardiovascular health changes associated with testosterone include increased red blood cell mass and likely insignificant changes in high-density lipoprotein and low-density lipoprotein levels. Changes in heart mass, heart electrophysiology, and endothelial reactivity are likely, based on extrapolation of data from adults. Testosterone may have indirect effects on cardiovascular health through influences on depression, anxiety, stress, and anorexia nervosa as well as on behaviors such as tobacco use.

CONCLUSIONS

Testosterone contributes importantly to the cardiovascular health and well-being of masculine spectrum gender-diverse youth. We need to do a better job of supporting these young people with data on cardiovascular health over the life span.

Changes in Proximate Chemical and Mineral Compositions of Different Sex Categories of Mutton during the Dry-Curing Process

The aim of this research was to determine the effect of sex, castration, and processing on the chemical properties of mutton in the production of kaštradina-a traditional Dalmatian dry-cured meat product. Therefore, the carcasses of 20 ewes (E), 20 rams (R), and 20 wethers (W) of the Dalmatian pramenka breed were processed by dry-curing. On the 1st, 35th, and 60th days of processing, the samples from the scapulae were taken, then the proximate chemical, NaCl, and mineral analyses were performed, and significant differences between most of the parameters were found. Unlike W, the R samples contained significantly more proteins (p < 0.01), NaCl (p < 0.05), and potassium (p < 0.05) and less fat (p < 0.05). Furthermore, compared to the W and R categories, the E category of kaštradina contained significantly more calcium (p < 0.05). The higher contents of intramuscular fat, potassium, and calcium and lower content of NaCl could positively affect the sensory (marbling, flavor, juiciness, and tenderness) and chemical (fatty acid profile) properties of kaštradina. These findings suggest that the W and E raw mutton could be a better-quality raw material for production of kaštradina than could the R, but further research is needed for a more comprehensive picture of its quality.

Testosterone therapy and cardiovascular diseases

Since it was first synthesised in 1935, testosterone (T) has been viewed as the mythical Fountain of Youth, promising rejuvenation, restoring sexual appetites, growing stronger muscles, and quicker thinking. T is endowed with direct effects on myocardial and vascular structure and function, as well as on risk factors for cardiovascular (CV) disease. Indeed, low serum T levels are a risk factor for diabetes, metabolic syndrome, inflammation, and dyslipidaemia. Moreover, many studies have shown that T deficiency per se is an independent risk factor of CV and all-cause mortality. On this background and due to direct-to-patient marketing by drug companies, we have witnessed to the widespread use of T replacement therapy (TT) without clear indications particularly in late-life onset hypogonadism. The current review will dwell upon current evidence and controversies surrounding the role of T in the pathophysiology of CV diseases, the link between circulating T levels and CV risk, and the use of replacing T as a possible adjuvant treatment in specific CV disorders. Specifically, recent findings suggest that heart failure and type 2 diabetes mellitus represent two potential targets of T therapy once that a state of hypogonadism is diagnosed. However, only if ongoing studies solve the CV safety issue the T orchid may eventually 'bloom'.

Vasodilatory action of trans-4-methoxy-β-nitrostyrene in rat isolated pulmonary artery

Trans-4-methoxy-β-nitrostyrene (T4MN) induced more potent vasorelaxant effects in resistance arteries from hypertensive rats than its parent drug, β-nitrostyrene 1-nitro-2-phenylethene (NPe). To better understand the influence of insertion of the electron-releasing methoxy group in the aromatic ring of NPe, we investigated vasorelaxant effects of T4MN in isolated pulmonary artery and compared them with those of NPe in view of the potential interest of T4MN in pulmonary arterial hypertension. T4MN and NPe both caused concentration-dependent vasorelaxation in pulmonary artery rings pre-contracted with either phenylephrine (1 µmol/L) or KCl (60 mmol/L), an effect unaffected by endothelium removal. In endothelium-intact preparations pre-contracted with phenylephrine, the vasorelaxant effect of T4MN was more potent than that of NPe. However, unlike NPe, this effect was significantly reduced following pretreatment with 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ) (10 µmol/L, a guanylate cyclase inhibitor) or tetraethylammonium (5 mmol/L, a potassium channel blocker). T4MN abolished the CaCl2 -induced contractions in pulmonary artery preparations stimulated with phenylephrine (PHE) under Ca2+ -free conditions in the presence of verapamil, to preferentially activate receptor-operated calcium channels. From these findings, we propose that T4MN evokes endothelium-independent vasorelaxant effects in isolated rat pulmonary artery, partially by inhibiting Ca2+ influx through L-type Ca2+ channels, as well as by activating soluble guanylate cyclase and potassium channels. The present results suggest the therapeutic potential of T4MN in treating pulmonary arterial hypertension.

Late-onset hypogonadism: Reductio ad absurdum of the cardiovascular risk-benefit of testosterone replacement therapy

BACKGROUND

Low testosterone (T) level is considered a marker of poor cardiovascular health. Ten years ago, the Testosterone in Older Men with Mobility Limitations (TOM) trial was discontinued due to a higher number of adverse events in men receiving T compared with placebo. Since then, several studies have investigated the risks of T replacement therapy (TRT) in late-onset hypogonadism (LOH).

OBJECTIVE

To review the mechanism by which TRT could damage the cardiovascular system.

MATERIALS AND METHODS

Comprehensive literature search of recent clinical and experimental studies.

RESULTS

The mechanisms of T-mediated coronary vasodilation were reviewed with emphasis on calcium-activated and ATP-sensitive potassium ion channels. We showed how T regulates endothelial nitric oxide synthase (eNOS) and phosphoinositide 3-kinase/protein kinase B/eNOS signaling pathways in vessel walls and its direct effects on cardiomyocytes via β1-adrenergic and ryanodine receptors and provided data on myocardial infarction and heart failure. Vascular smooth muscle senescence could be explained by the modulation of growth factors, matrix metalloproteinase-2, and angiotensin II by T. Furthermore, leukocyte trafficking, facilitated by changes in TNF-α, could explain some of the effects of T on atheromatous plaques. Conflicting data on prothrombotic risk linked to platelet aggregation inhibition via NO-triggered arachidonate synthesis or increased aggregability due to enhanced thromboxane A in human platelets provide evidence regarding the hypotheses on plaque maturation and rupture risk. The effects of T on cardiac electrophysiology and oxygen delivery were also reviewed.

DISCUSSION

The effects of TRT on the cardiovascular system are complex. Although molecular studies suggest a potential benefit, several clinical observations reveal neutral or occasionally detrimental effects, mostly due to confounding factors.

CONCLUSIONS

Attempts to demonstrate that TRT damages the cardiovascular system via systematic analysis of the putative mechanisms led to the contradiction of the initial hypothesis. Current evidence indicates that TRT is safe once other comorbidities are addressed.

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.

Sex, Gender, and Sex Hormones in Pulmonary Hypertension and Right Ventricular Failure

Pulmonary hypertension (PH) encompasses a syndrome of diseases that are characterized by elevated pulmonary artery pressure and pulmonary vascular remodeling and that frequently lead to right ventricular (RV) failure and death. Several types of PH exhibit sexually dimorphic features in disease penetrance, presentation, and progression. Most sexually dimorphic features in PH have been described in pulmonary arterial hypertension (PAH), a devastating and progressive pulmonary vasculopathy with a 3-year survival rate <60%. While patient registries show that women are more susceptible to development of PAH, female PAH patients display better RV function and increased survival compared to their male counterparts, a phenomenon referred to as the "estrogen paradox" or "estrogen puzzle" of PAH. Recent advances in the field have demonstrated that multiple sex hormones, receptors, and metabolites play a role in the estrogen puzzle and that the effects of hormone signaling may be time and compartment specific. While the underlying physiological mechanisms are complex, unraveling the estrogen puzzle may reveal novel therapeutic strategies to treat and reverse the effects of PAH/PH. In this article, we (i) review PH classification and pathophysiology; (ii) discuss sex/gender differences observed in patients and animal models; (iii) review sex hormone synthesis and metabolism; (iv) review in detail the scientific literature of sex hormone signaling in PAH/PH, particularly estrogen-, testosterone-, progesterone-, and dehydroepiandrosterone (DHEA)-mediated effects in the pulmonary vasculature and RV; (v) discuss hormone-independent variables contributing to sexually dimorphic disease presentation; and (vi) identify knowledge gaps and pathways forward. © 2020 American Physiological Society. Compr Physiol 10:125-170, 2020.

Testosterone Induces Relaxation of Human Corpus Cavernosum Tissue of Patients With Erectile Dysfunction

Introduction

Previous research in the field of cardiovascular diseases suggests a relaxing effect of testosterone (T) on smooth muscle cells. Therefore, it was hypothesized that T could play a significant role in erection development.

Aim

To investigate the relaxing effect of T and other molecules of the T signaling pathway on human corpus cavernosum (HCC) tissue.

Methods

Samples of the HCC tissue were obtained from men who underwent penile prosthesis implantation (n = 33) for erectile dysfunction. Samples were used for isometric tension measurement in Ex Vivo experiments. Following standardized precontraction with phenylephrine, increasing doses of T or dihydrotestosterone were administered and blocked by NO/H₂S synthesis inhibitors, a K_ATP blocker, and flutamide (androgen receptor inhibitor).

Main Outcome Measure

The outcome was relaxation of the HCC tissue, normalized to a maximum precontraction achieved by phenylephrine.

Results

A dose-dependent relaxing effect of dihydrotestosterone and T was observed with a relaxation of, respectively, 24.9% ± 23.4% (P < .0001) and 41.7% ± 19.1% (P = .01) compared with 6.8% ± 15.9% for vehicle (dimethylsulfoxide) at 300 μM. The relaxing effect of T was not countered by blocking NO synthesis, H₂S synthesis, K_ATP channels, or the androgen receptor.

Clinical Implications

By understanding the underlying mechanisms of T-induced HCC relaxation, potential new therapeutic targets can be identified.

Strengths & Limitations

The strength of the study is the use of fresh HCC tissues with reproducible results. The limitation is the need for supraphysiological T levels to induce the observed effect.

Conclusion

Rapid androgen-induced relaxation of HCC is likely to occur via nongenomic mechanisms. Previously suggested mechanisms of action by which T modulates HCC relaxation have been excluded.

Van den Broeck T, Soebadi MA, Falter A, et al. Testosterone Induces Relaxation of Human Corpus Cavernosum Tissue of Patients With Erectile Dysfunction. J Sex Med 2019; 8:114–119.

Chronic testosterone administration improves cardiac contractility and has a beneficial effect on the haemostatic system by enhancing fibrinolytic activity and inducing hypocoagulation in healthy rats

This study investigated the effects of chronic supraphysiological dose of testosterone propionate administration cardiovascular function in rats from the perspective of haemostatic function including platelet functions, coagulation, and fibrinolysis. Testosterone significantly enhanced cardiac contractility by enhancing LVSP (10%), dp/dt_max (36.7%), dp/dt_min (14.6%) without altering heart rate, diastolic function, and serum lipid profile. While it has no effect on platelets count, thromboxane B2 levels, and platelet aggregation, testosterone significantly enhanced bleeding time and increased circulatory and thoracic aorta mRNA and protein levels of tPA (46.5%, 58.2%, and 74.3%, respectively) and significantly decreased those of PAI-1 (29.3%, 26.4%, and 32.8%, respectively). While there were no significant changes in PT and aPTT, mRNA and protein levels of prothrombin and factor VII were downregulated in the livers of the testosterone-treated rats (57.7% and 64.9%, respectively). Overall, chronic testosterone administration in rats may act as a cardio-protective agent by modulating haemostasis in rats.

Randomized controlled trials - mechanistic studies of testosterone and the cardiovascular system

Testosterone deficiency is common in men with cardiovascular disease (CVD), and randomized placebo-controlled trials (RCTs) have reported beneficial effects of testosterone therapy on exercise-induced cardiac ischemia in chronic stable angina, functional exercise capacity, maximum oxygen consumption during exercise (VO_2max) and muscle strength in chronic heart failure (CHF), shortening of the Q-T interval, and improvement of some cardiovascular risk factors. Testosterone deficiency is associated with an adverse CV risk profile and mortality. Clinical and scientific studies have provided mechanistic evidence to support and explain the findings of the RCTs. Testosterone is a rapid-onset arterial vasodilator within the coronary circulation and other vascular beds including the pulmonary vasculature and can reduce the overall peripheral systemic vascular resistance. Evidence has demonstrated that testosterone mediates this effect on vascular reactivity through calcium channel blockade (L-calcium channel) and stimulates potassium channel opening by direct nongenomic mechanisms. Testosterone also stimulates repolarization of cardiac myocytes by stimulating the ultra-rapid potassium channel-operated current. Testosterone improves cardiac output, functional exercise capacity, VO_2max and vagally mediated arterial baroreceptor cardiac reflex sensitivity in CHF, and other mechanisms. Independent of the benefit of testosterone on cardiac function, testosterone substitution may also increase skeletal muscle glucose metabolism and enhance muscular strength, both factors that could contribute to the improvement in functional exercise capacity may include improved glucose metabolism and muscle strength. Testosterone improves metabolic CV risk factors including body composition, insulin resistance, and hypercholesterolemia by improving both glucose utilization and lipid metabolism by a combination of genomic and nongenomic actions of glucose uptake and utilization expression of the insulin receptor, glucose transporters, and expression on regulatory enzymes of key metabolic pathways. The effect on high-density lipoprotein-cholesterol (HDL-C) differs between studies in that it has been found to fall, rise, or have no change in levels. Testosterone replacement can suppress the levels of circulating pro-inflammatory cytokines and stimulate the production of interleukin-10 (IL-10) which has anti-inflammatory and anti-atherogenic actions in men with CVD. No effect on C-reactive protein has been detected. No adverse effects on clotting factors have been detected. RCTs have not clearly demonstrated any significant evidence that testosterone improves or adversely affects the surrogate markers of atherosclerosis such as reduction in carotid intima thickness or coronary calcium deposition. Any effect of testosterone on prevention or amelioration of atherosclerosis is likely to occur over years as shown in statin therapy trials and not months as used in testosterone RCTs. The weight of evidence from long-term epidemiological studies supports a protective effect as evidenced by a reduction in major adverse CV events (MACEs) and mortality in studies which have treated men with testosterone deficiency. No RCT where testosterone has been replaced to the normal healthy range has reported a significant benefit or adverse effect on MACE nor has any recent meta-analysis.

Potential of phloroglucinol to improve erectile dysfunction associated with streptozotocin-induced diabetes in rats

OBJECTIVE

Diabetes is a common metabolic disease with several complications in its patients. Often, people living with diabetes develop erectile dysfunction (ED). The primary aim of this work was to investigate the effect of phloroglucinol in diabetes-induced ED in rats.

METHODS

Male Wistar rats were given 52 mg/kg of streptozotocin, by intraperitoneal injection, to induce diabetes and ED. Subsequently, animals were grouped into three groups: group 1, diabetic control; group 2, low-dose phloroglucinol (150 mg/kg body weight); and group 3, high-dose phloroglucinol (250 mg/kg body weight). A group of six normal rats served as a normal control. The rats were treated with phloroglucinol for six weeks and then were assessed for treatment effects. Sexual behavior, glycosylated hemoglobin A1c (HbA1c) values, serum testosterone, serum nitric oxide (NO), blood pressure and sperm count were measured after the end of treatment.

RESULTS

After a 6-week treatment period, the high dose of phloroglucinol significantly decreased HbA1c values in diabetic rats. Rats treated with phloroglucinol had increased serum testosterone, NO and sperm count. Animals treated with 250 mg/kg phloroglucinol performed similar to normal rats in the sexual behavioral study, suggesting the reversal of complications of ED. Conversely, a decrease in the blood pressure in treated groups was observed.

CONCLUSION

The results highlight the protective effect of phloroglucinol in diabetes-induced ED in rats warranting further studies.

Contributions of sex to cerebrovascular function and pathology

Sex differences exist in how cerebral blood vessels function under both physiological and pathological conditions, contributing to observed sex differences in risk and outcomes of cerebrovascular diseases (CBVDs), such as vascular contributions to cognitive impairment and dementia (VCID) and stroke. Throughout most of the lifespan, women are protected from CBVDs; however, risk increases following menopause, suggesting sex hormones may play a significant role in this protection. The cerebrovasculature is a target for sex hormones, including estrogens, progestins, and androgens, where they can influence numerous vascular functions and pathologies. While there is a plethora of information on estrogen, the effects of progestins and androgens on the cerebrovasculature are less well-defined. Estrogen decreases cerebral tone and increases cerebral blood flow, while androgens increase tone. Both estrogens and androgens enhance angiogenesis/cerebrovascular remodeling. While both estrogens and androgens attenuate cerebrovascular inflammation, pro-inflammatory effects of androgens under physiological conditions have also been demonstrated. Sex hormones exert additional neuroprotective effects by attenuating oxidative stress and maintaining integrity and function of the blood brain barrier. Most animal studies utilize young, healthy, gonadectomized animals, which do not mimic the clinical conditions of aging individuals likely to get CBVDs. This is also concerning, as sex hormones appear to mediate cerebrovascular function differently based on age and disease state (e.g. metabolic syndrome). Through this review, we hope to inspire others to consider sex as a key biological variable in cerebrovascular research, as greater understanding of sex differences in cerebrovascular function will assist in developing personalized approaches to prevent and treat CBVDs.

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 impact of testosterone replacement therapy on glycemic control, vascular function, and components of the metabolic syndrome in obese hypogonadal men with type 2 diabetes

OBJECTIVE

This study set out to assess effects of testosterone replacement therapy (TRT) on parameters of metabolic syndrome and vascular function in obese hypogonadal males with type 2 diabetes mellitus (DM2).

STUDY DESIGN

Fifty-five obese hypogonadal diabetic males on oral hypoglycemic treatment were enrolled into this one-year, double-blind, randomized, placebo-controlled clinical study. Group T (n = 28) was treated with testosterone undecanoate (1000 mg i.m. every 10 weeks) while group P (n = 27) received placebo.

METHODS

Anthropometrical and vascular measurements - flow-mediated dilatation (FMD) and intima media thickness (IMT) - biochemical and hormonal blood sample analyses were performed at the start of the study and after one year. Derived parameters (BMI, HOMA-IR, calculated free testosterone (cFT) and bioavailable testosterone (BT)) were calculated.

RESULTS

TRT resulted in reduction of HOMA-IR by 4.64 ± 4.25 (p < .001), HbA1c by 0.94 ± 0.88% points (p < .001), and an increase in FMD by 2.40 ± 4.16% points (p = .005).

CONCLUSION

TRT normalized serum testosterone levels, improved glycemic control and endothelial function while exerting no ill effects on the study population.

α-Terpineol, a natural monoterpene: A review of its biological properties

Terpineols are monocyclic monoterpene tertiary alcohols which are naturally present in plant species. There are five common isomers of terpineols, alpha-, beta-, gamma-, delta- and terpinen-4-ol, of which α-terpineol and its isomer terpinen-4-ol are the most common terpineols found in nature. α-Terpineol plays an important role in the industrial field. It has a pleasant odor similar to lilacs and it is a common ingredient in perfumes, cosmetics, and aromatic scents.

In addition, α-terpineol attracts a great interest as it has a wide range of biological applications as an antioxidant, anticancer, anticonvulsant, antiulcer, antihypertensive, anti-nociceptive compound. It is also used to enhance skin penetration, and also has insecticidal properties. This study reviews the relevance of α-terpineol based on scientific findings on Google Scholar, Pubmed, Web of Science, Scopus and Chemical Abstracts.

Collectively, the use of α-terpineol in medicine and in the pharmaceutical industry plays an important role in therapeutic applications. This review will, therefore, support future research in the utilization of α-terpineol.

High-throughput proteome analysis reveals targeted TRPM8 degradation in prostate cancer

The Ca²⁺-permeable ion channel TRPM8 is a hallmark of the prostate epithelium. We recently discovered that TRPM8 is an ionotropic testosterone receptor. This finding suggested that testosterone-induced TRPM8 activity regulates Ca²⁺ homeostasis in the prostate epithelium. Since androgens are significantly implicated in prostate cancer development, the role of the novel testosterone receptor TRPM8 in cancer was assessed in our study. Although TRPM8 mRNA levels increase at the early prostate cancer stages, we found that it is not proportionally translated into TRPM8 protein levels. High-throughput proteome analysis revealed that TRPM8 degradation is enhanced in human prostate cancer cells. This degradation is executed via a dual degradation mechanism with the involvement of both lysosomal and proteasomal proteolytic pathways. The evaluation of the TRPM8 expression pattern in prostate cancer patients further confirmed the incidence of TRPM8 removal from the plasma membrane and its internalization pattern coincided with the severity of the tumor. Together, our results indicate that enhanced TRPM8 hydrolysis in prostate cancer could present an adaptation mechanism, sustained via bypassing testosterone-induced rapid Ca²⁺ uptake through TRPM8, thus, diminishing the rates of apoptosis. In this light, recovery of TRPM8 may pose a novel therapeutic strategy for an anti-tumor defense mechanism.

Association of admission testosterone level with ST-segment resolution in male patients with ST-segment elevation myocardial infarction undergoing primary percutaneous coronary intervention

Background

Low level of testosterone may be associated with cardiovascular diseases in men, as some evidence suggests a protective role for testosterone in cardiovascular system. Little is known about the possible role of serum testosterone in response to reperfusion therapy in ST-elevation myocardial infarction (STEMI) and its relationship with ST-segment recovery. The present study was conducted to evaluate the association of serum testosterone levels with ST-segment resolution following primary percutaneous coronary intervention (PPCI) in male patients with acute STEMI.

Methods

Forty-eight men (mean age 54.55 ± 12.20) with STEMI undergoing PPCI were enrolled prospectively. Single-lead ST segment resolution in the lead with maximum baseline ST-elevation was measured and patients were divided into two groups according to the degree of ST-segment resolution: complete (> or =50%) or incomplete (<50%). The basic and demographic data of all patients, their left ventricular ejection fraction (LVEF) and laboratory findings including serum levels of free testosterone and cardiac enzymes were recorded along with angiographic finding and baseline TIMI (Thrombolysis in Myocardial Infarction) flow and also in-hospital complications and then these variables were compared between two groups.

Results

A complete ST-resolution (≥50%) was observed in 72.9% of the patients. The serum levels of free testosterone (P = 0.04), peak cardiac troponin (P = 0.03) were significantly higher and hs-CRP (P = 0.02) were lower in patients with complete ST-resolution compared to those with incomplete ST-resolution. In-hospital complications were observed in 31.2% of patients. The patients with a lower baseline TIMI flow (P = 0.03) and those who developed complications (P = 0.04) had lower levels of free testosterone. A significant positive correlation was observed between the left ventricular function and serum levels of free testosterone (P = 0.01 and r = +0.362).

Conclusion

This study suggests that in men with STEMI undergoing PPCI, higher serum levels of testosterone are associated with a better reperfusion response, fewer complications and a better left ventricular function.

Electronic supplementary material

The online version of this article (doi:10.1186/s12610-017-0058-7) contains supplementary material, which is available to authorized users.

Recent Progress in Vascular Aging: Mechanisms and Its Role in Age-related Diseases

As with many age-related diseases including vascular dysfunction, age is considered an independent and crucial risk factor. Complicated alterations of structure and function in the vasculature are linked with aging hence, understanding the underlying mechanisms of age-induced vascular pathophysiological changes holds possibilities for developing clinical diagnostic methods and new therapeutic strategies. Here, we discuss the underlying molecular mediators that could be involved in vascular aging, e.g., the renin-angiotensin system and pro-inflammatory factors, metalloproteinases, calpain-1, monocyte chemoattractant protein-1 (MCP-1) and TGFβ-1 as well as the potential roles of testosterone and estrogen. We then relate all of these to clinical manifestations such as vascular dementia and stroke in addition to reviewing the existing clinical measurements and potential interventions for age-related vascular dysfunction.

Hormonal changes in hemodialysis patients: Novel risk factors for mortality?

Patients with end-stage renal disease undergoing dialysis commonly experience derangements in the hypothalamic-pituitary-gonadal axis together with alterations at the level of synthesis and clearance of many hormones. This hormonal imbalance, even if asymptomatic, has recently been associated with increased mortality in these patients. In this review, we summarize observational and mechanistic evidence linking hormonal alterations at the level of the thyroid and sex-hormone systems with this mortality risks.

Regulated expression of the prostacyclin receptor (IP) gene by androgens within the vasculature: Combined role for androgens and serum cholesterol

The prostanoid prostacyclin plays a key cardioprotective role within the vasculature. There is increasing evidence that androgens may also confer cardioprotection but through unknown mechanisms. This study investigated whether the androgen dihydrotestosterone (DHT) may regulate expression of the prostacyclin/I prostanoid receptor or, in short, the IP in platelet-progenitor megakaryoblastic and vascular endothelial cells. DHT significantly increased IP mRNA and protein expression, IP-induced cAMP generation and promoter (PrmIP)-directed gene expression in all cell types examined. The androgen-responsive region was localised to a cis-acting androgen response element (ARE), which lies in close proximity to a functional sterol response element (SRE) within the core promoter. In normal serum conditions, DHT increased IP expression through classic androgen receptor (AR) binding to the functional ARE within the PrmIP. However, under conditions of low-cholesterol, DHT led to further increases in IP expression through an indirect mechanism involving AR-dependent upregulation of SCAP expression and enhanced SREBP1 processing & binding to the SRE within the PrmIP. Chromatin immunoprecipitation assays confirmed DHT-induced AR binding to the ARE in vivo in cells cultured in normal serum while, in conditions of low cholesterol, DHT led to increased AR and SREBP1 binding to the functional ARE and SRE cis-acting elements, respectively, within the core PrmIP resulting in further increases in IP expression. Collectively, these data establish that the human IP gene is under the transcriptional regulation of DHT, where this regulation is further influenced by serum-cholesterol levels. This may explain, in part, some of the protective actions of androgens within the vasculature.

Investigation of testosterone-mediated non-transcriptional inhibition of Ca2+ in vascular smooth muscle cells

The aim of the present study was to observe the effect of short-term testosterone treatment on Ca²⁺ in vascular smooth muscle cells (VSMCs) of male rats. Cells were loaded with the Ca²⁺-sensitive fluorescent indicator Fura-2 and intracellular Ca²⁺ signals of VSMCs were measured using a Nikon TE2000-E live cell imaging workstation. The baseline level of cytosolic Ca²⁺ concentration ([Ca²⁺]_i) in resting state VSMCs was ~100 nmol/l. Testosterone alone led to a slow increase in [Ca²⁺]_i, but there was no significant difference compared with the ethanol vehicle control. When VSMCs were stimulated with a high-potassium solution (containing 42 mmol/l of K⁺), [Ca²⁺]_i rose rapidly and remained at a high plateau level. Short-term treatment using physiological (40 nmol/l) or supraphysiological (4 µmol/l) levels of testosterone at either the plateau phase or the pretreatment stage could significantly inhibit the [Ca²⁺]_i increase induced by high-potassium solutions. Testosterone coupled to bovine serum albumin also had a similar effect and repetitive testosterone interventions over a short time-frame led to inhibition. Testosterone has a non-transcriptional inhibition effect on the [Ca²⁺]_i of VSMCs and acts with the cell membranes of VSMCs to inhibit voltage-gated Ca²⁺ channel-mediated Ca²⁺ influx, which may be one of the mechanisms underlying testosterone-mediated vasodilation.

Molecular effects of supraphysiological doses of doping agents on health

Supraphysiological doses of doping agents, such as T/DHT and GH/IGF-1, affect cellular pathways associated with apoptosis and inflammation.

The TRPM8 protein is a testosterone receptor: II. Functional evidence for an ionotropic effect of testosterone on TRPM8

Testosterone is a key steroid hormone in the development of male reproductive tissues and the regulation of the central nervous system. The rapid signaling mechanism induced by testosterone affects numerous behavioral traits, including sexual drive, aggressiveness, and fear conditioning. However, the currently identified testosterone receptor(s) is not believed to underlie the fast signaling, suggesting an orphan pathway. Here we report that an ion channel from the transient receptor potential family, TRPM8, commonly known as the cold and menthol receptor is the major component of testosterone-induced rapid actions. Using cultured and primary cell lines along with the purified TRPM8 protein, we demonstrate that testosterone directly activates TRPM8 channel at low picomolar range. Specifically, testosterone induced TRPM8 responses in primary human prostate cells, PC3 prostate cancer cells, dorsal root ganglion neurons, and hippocampal neurons. Picomolar concentrations of testosterone resulted in full openings of the purified TRPM8 channel in planar lipid bilayers. Furthermore, acute applications of testosterone on human skin elicited a cooling sensation. Our data conclusively demonstrate that testosterone is an endogenous and highly potent agonist of TRPM8, suggesting a role of TRPM8 channels well beyond their well established function in somatosensory neurons. This discovery may further imply TRPM8 channel function in testosterone-dependent behavioral traits.

An evaluation of vardenafil as a calcium channel blocker in pulmonary artery in rats

OBJECTIVE

Vardenafil was reported to relax rat pulmonary artery through endothelium-dependent mechanisms. The aim of this in vitro study was to investigate other related mechanisms for this effect.

MATERIALS AND METHODS

Endothelium-intact and denuded artery rings were suspended in order to record isometric tension. In the rings with or without endothelium, the concentration-response curves for vardenafil were generated. In the rings without endothelium the contractile response induced by phenylephrine (Phe) or KCl was assessed in the presence or absence of vardenafil. In the last set of experiments, pulmonary artery rings were exposed to calcium-free isotonic depolarizing solution and the contractile response induced by the addition of calcium was evaluated in the presence or absence of vardenafil, nifedipine, verapamil or 1H-[1,2,4] oxadiazolo[4,3-a] quinoxalin-1-one (ODQ).

RESULTS

Vardenafil attenuated pulmonary artery contraction induced by phenylephrine in the presence and absence of endothelium. In addition, vardenafil attenuated both Phe or KCl-induced contraction but, it's effect on the KCl dose-response curve was more significant. Vardenafil also inhibited the contractile response induced by calcium in a dose-dependent manner. Addition of nifedipine or verapamil did not significantly alter this effect while ODQ incubation significantly inhibited vardenafil-induced relaxation.

CONCLUSION

From these findings, it was proposed that vardenafil relaxed rat pulmonary artery through inhibiting calcium influx.

Attenuation of cerebral vasospasm and secondary injury by testosterone following experimental subarachnoid hemorrhage in rabbit

BACKGROUND

The vasodilatator effects of testosterone have been widely studied and demonstrated. Based on previous studies of these vasodilatatory activities, we hypothesized that testosterone might have potential effects on subarachnoid hemorrhage-induced cerebral vasospasm.

METHODS

Thirty-two adult male New Zealand white rabbits were randomly divided into four groups of eight rabbits in each group: group 1 (control); group 2 (subarachnoid hemorrhage); group 3 (subarachnoid hemorrhage + vehicle); and group 4 (subarachnoid hemorrhage + testosterone). Testosterone (15 mg/kg, intraperitoneally) was administered 5 min after the intracisternal blood injection and continued for 72 h once per day in the same dose for group 4. Animals were killed 72 h after subarachnoid hemorrhage. Basilar artery cross-sectional areas, arterial wall thicknesses, and hippocampal degeneration scores were evaluated in all groups.

RESULTS

Intraperitoneal administration of testosterone was found to attenuate cerebral vasospasm and provide neuroprotection after subarachnoid hemorrhage in rabbits. Testosterone treatment was determined to be effective at increasing the luminal area and reducing the wall thickness of the basilar artery.

CONCLUSIONS

Our findings show that testosterone has some preventive effects on SAH-induced vasospasm and secondary neuronal injury in rabbits. We propose that the vasodilatatory activity of testosterone is due to its effects on inhibiting calcium channels, activating potassium channels, augmenting nitric oxide synthesis, and inhibiting oxidant stress and inflammation.

Relaxation of rat aorta by farrerol correlates with potency to reduce intracellular calcium of VSMCs

Farrerol, isolated from Rhododendron dauricum L., has been proven to be an important multifunctional physiologically active component, but its vasoactive mechanism is not clear. The present study was performed to observe the vasoactive effects of farrerol on rat aorta and to investigate the possible underlying mechanisms. Isolated aortic rings of rat were mounted in an organ bath system and the myogenic effects stimulated by farrerol were studied. Intracellular Ca²⁺ ([Ca²⁺]_in) was measured by molecular probe fluo-4-AM and the activities of L-type voltage-gated Ca²⁺ channels (LVGC) were studied with whole-cell patch clamp in cultured vascular smooth muscle cells (VSMCs). The results showed that farrerol significantly induced dose-dependent relaxation on aortic rings, while this vasorelaxation was not affected by N^G-nitro-l-arginine methylester ester or endothelium denudation. In endothelium-denuded aortas, farrerol also reduced Ca²⁺-induced contraction on the basis of the stable contraction induced by KCl or phenylephrine (PE) in Ca²⁺-free solution. Moreover, after incubation with verapamil, farrerol can induce relaxation in endothelium-denuded aortas precontracted by PE, and this effect can be enhanced by ruthenium red, but not by heparin. With laser scanning confocal microscopy method, the farrerol-induced decline of [Ca²⁺]_in in cultured VSMCs was observed. Furthermore, we found that farrerol could suppress Ca²⁺ influx via LVGC by patch clamp technology. These findings suggested that farrerol can regulate the vascular tension and could be developed as a practicable vasorelaxation drug.

Polyamines transduce the nongenomic, androgen-induced calcium sensitization in intestinal smooth muscle

Androgens regulate body development and differentiation through a variety of genotropic mechanisms, mostly in reproductive organs. In recent years a different scenario for sex hormone actions has emerged: the intestinal muscle. Thus, although estrogens relax intestinal muscle, androgens are powerful inducers of mechanical potentiation. This effect of androgens was intriguing because it is observed at physiological concentrations, is mediated by nongenomic mechanisms, and involves a phenomenon of calcium sensitization of contractile machinery by stimulating phosphorylation of 20 kDa myosin light chain by Rho-associated kinase. Here we have deciphered the molecular mechanisms underlying calcium sensitization and mechanical potentiation by androgens in male intestinal muscle as well as its tight relationship to polyamine metabolism. Thus, androgens stimulate polyamine synthesis, and the inhibition of polyamine synthesis abolishes androgen-induced calcium sensitization and 20 kDa myosin light chain phosphorylation. We demonstrate that the first molecular step in the induction of calcium sensitization is a nonconventional activation of the adaptor protein RhoA, triggered by a transglutaminase-catalyzed polyamination of RhoA, which is then targeted to the membrane to activate Rho-associated kinase. Altogether, these results demonstrate that the physiological levels of androgens, through the modulation of polyamine metabolism and posttanslational modification of RhoA, activate a new signal transduction pathway in the intestinal smooth muscle to induce calcium sensitization. Furthermore, apart from being one of the few physiologically relevant nongenomic effects of androgens, these results might underlie the well-known gender differences in intestinal transits, thus expanding the nature's inventory of sex hormones effects.

Testosterone: a vascular hormone in health and disease

Coronary heart disease is a leading cause of premature death in men. Epidemiological studies have shown a high prevalence of low serum testosterone levels in men with cardiovascular disease (CVD). Furthermore, a low testosterone level is associated in some but not in all observational studies with an increase in cardiovascular events and mortality. Testosterone has beneficial effects on several cardiovascular risk factors, which include cholesterol, endothelial dysfunction and inflammation: key mediators of atherosclerosis. A bidirectional relationship between low endogenous testosterone levels and concurrent illness complicates attempts to validate causality in this association and potential mechanistic actions are complex. Testosterone is a vasoactive hormone that predominantly has vasodilatory actions on several vascular beds, although some studies have reported conflicting effects. In clinical studies, acute and chronic testosterone administration increases coronary artery diameter and flow, improves cardiac ischaemia and symptoms in men with chronic stable angina and reduces peripheral vascular resistance in chronic heart failure. Although the mechanism of the action of testosterone on vascular tone in vivo is not understood, laboratory research has found that testosterone is an L-calcium channel blocker and induces potassium channel activation in vascular smooth muscle cells. Animal studies have consistently demonstrated that testosterone is atheroprotective, whereas testosterone deficiency promotes the early stages of atherogenesis. The translational effects of testosterone between in vitro animal and human studies, some of which have conflicting effects, will be discussed in this review. We review the evidence for a role of testosterone in vascular health, its therapeutic potential and safety in hypogonadal men with CVD, and some of the possible underlying mechanisms.

Vasorelaxant and antihypertensive effects of methanolic fraction of the essential oil of Alpinia zerumbet

Alpinia zerumbet is used in folk medicine in Brazil to treat hypertension. However, several pathways involved in the mechanism of vasorelaxation are still unclear. This study was designed to verify the antihypertensive effect of the methanolic fraction of the essential oil of A. zerumbet (MFEOAz) and to characterize its mechanism of action. The thoracic aortic rings from the Wistar rats were perfused in the organ chambers filled with Kreb's solution, where the tension of each ring was measured. The antihypertensive effect of MFEOAz was assessed in rats submitted to chronic hypertension by inhibition of nitric oxide synthesis by indirect measurement of blood pressure with indirect tail cuff method. MFEOAz relaxed phenylephrine and KCl-induced contraction of either endothelium-intact or endothelium-denuded rat aortic rings in a concentration-dependent manner. Pre-incubation with MFEOAz (100 and 300 μg/mL) in Ca(2+)-free Krebs solution attenuated phenylephrine- or caffeine-induced contraction. Pre-incubation with L-NAME, ODQ, wortmannin, atropine, indomethacin, catalase, SOD, TEA, 4-aminopyridine, glibenclamide, apamin, charybdotoxin, or iberiotoxin did not affect MFEOAz-induced relaxation. The intragastric administration of MFEOAz induced an antihypertensive effect. MFEOAz it seems inhibited the calcium influx via voltage-operated calcium channels and receptor-operated calcium channels, as well as inhibition of calcium mobilization from intracellular stores.

Differential effects of androgens on coronary blood flow regulation and arteriolar diameter in intact and castrated swine

Background

Low endogenous testosterone levels have been shown to be a risk factor for the development of cardiovascular disease and cardiovascular benefits associated with testosterone replacement therapy are being advocated; however, the effects of endogenous testosterone levels on acute coronary vasomotor responses to androgen administration are not clear. The objective of this study was to compare the effects of acute androgen administration on in vivo coronary conductance and in vitro coronary microvascular diameter in intact and castrated male swine.

Methods

Pigs received intracoronary infusions of physiologic levels (1–100 nM) of testosterone, the metabolite 5α-dihydrotestosterone, and the epimer epitestosterone while left anterior descending coronary blood flow and mean arterial pressure were continuously monitored. Following sacrifice, coronary arterioles were isolated, cannulated, and exposed to physiologic concentrations (1–100 nM) of testosterone, 5α-dihydrotestosterone, and epitestosterone. To evaluate effects of the androgen receptor on acute androgen dilation responses, real-time PCR and immunohistochemistry for androgen receptor were performed on conduit and resistance coronary vessels.

Results

In vivo, testosterone and 5α-dihydrotestosterone produced greater increases in coronary conductance in the intact compared to the castrated males. In vitro, percent maximal dilation of microvessels was similar between intact and castrated males for testosterone and 5α-dihydrotestosterone. In both studies epitestosterone produced significant increases in conductance and microvessel diameter from baseline in the intact males. Androgen receptor mRNA expression and immunohistochemical staining were similar in intact and castrated males.

Conclusions

Acute coronary vascular responses to exogenous androgen administration are increased by endogenous testosterone, an effect unrelated to changes in androgen receptor expression.

Testosterone deficiency in older men: a problem worth treating

Testosterone levels decrease with normal aging, and researchers estimate that more than 4.5 million American men may have symptoms related to low testosterone. Termed late-onset hypogonadism (LOH), low testosterone levels in older men may be associated not only with symptoms such as depressed mood and fatigue, but also comorbidities such as diabetes and heart failure. Understanding the symptoms, diagnosis, and treatment of LOH is important for all practitioners who care for older men.

Mechanisms involved in testosterone-induced relaxation to the pig urinary bladder neck

OBJECTIVES

Testosterone replacement therapy improves bladder capacity in urinary tract dysfunction. There is no information, however, about the role of this steroid hormone on the muscle tension of the bladder outflow region. The current study investigated the mechanisms underlying the testosterone-induced action in the pig bladder neck.

METHODS

Urothelium-denuded bladder neck strips were mounted in myographs for isometric force recordings and for simultaneous measurements of intracellular Ca(2+) concentration ([Ca(2+)](i)) and tension. The relaxations to testosterone, the non-aromatizable metabolite 4,5α-dihydrotestosterone (DHT) and electrical field stimulation (EFS) were carried out on phenylephrine (PhE)-precontracted strips.

RESULTS

Testosterone and DHT evoked similar concentration-dependent relaxations only at very high pharmacological concentrations. The presence of the urothelium and the inhibition of intracellular androgenic receptor (AR), aromatase, 5α-reductase, nitric oxide (NO) synthase, guanylyl cyclase, cyclooxygenase (COX), large-, intermediate- and small-Ca(2+)-activated K(+) channels or ATP-dependent K(+) channels failed to modify the testosterone relaxations. Neuronal voltage-gated Ca(2+) (VOC) channels and voltage-gated K(+) (K(V)) channel blockers potentiated these responses. EFS evoked frequency-dependent relaxations, which were not changed by threshold concentrations of testosterone. In Ca(2+)-free potassium rich physiological saline solution, testosterone inhibited the contractions induced by CaCl(2) and the L-type VOC channel activator (±)-BAY K 8644. Relaxations elicited by testosterone were accompanied by simultaneous decreases in smooth muscle [Ca(2+)](i).

CONCLUSIONS

Testosterone produces relaxation of the pig urinary bladder neck through mechanisms independent of urothelium, AR, aromatase, 5α-reductase, NO synthase, guanylyl cyclase, COX and K(+) channels. Testosterone-induced relaxation is produced via the inhibition of the extracellular Ca(2+) entry through L-type VOC channels.

Regional differences in the vasorelaxing effects of testosterone and its 5-reduced metabolites in the canine vasculature

Although the vasorelaxing effects of testosterone (T) and various androgen metabolites have been observed in a variety of blood vessels and species, previous studies have not systematically compared the vasorelaxing effects of androgen metabolites in different vascular beds within the same species. Therefore, we studied the vasorelaxing effects of T and its 5-reduced metabolites (5α- and 5β-DHT) on KCl-induced contractions of the canine left coronary artery, femoral artery and saphenous vein, using standard isometric recordings. KCl contractions were inhibited by each androgen in a concentration-dependent manner from 1.8 to 310μM. Vascular sensitivity and efficacy were expressed as inhibitory concentration 50 (IC₅₀) and maximal relaxation (R(max)), respectively. The coronary artery was significantly more sensitive to androgen-induced vasorelaxation than the saphenous vein or femoral artery. These vasorelaxing responses were unaffected by an antiandrogen (Flutamide) or the sulfhydryl reagent, N-ethylmaleimide, suggesting a nongenomic mechanism independent of signaling mediated by the androgen receptor or G proteins. Concentration-response curves were unchanged in endothelium-denuded preparations; thus, the endothelium appears to have no role in androgen-induced vasorelaxation. 5β-DHT was the most potent androgen in both coronary and femoral artery, but all three androgens were equipotent in the saphenous vein. It is concluded that: 1) significant regional differences exist in vasorelaxing effects of androgen metabolites in the canine vasculature; 2) structural differences in these androgens determine their vasorelaxing efficacy; and 3) regional differences in androgen-induced vasorelaxation may account for some of the conflicting findings reported on the vasorelaxing effects of the androgens.

Alterations in vasomotor systems and mechanics of resistance-sized mesenteric arteries from SHR and WKY male rats following in vivo testosterone manipulation

Background

Testosterone (T) and the sympathetic nervous system each contribute to the pathology of hypertension. Altered blood vessel reactivity is also associated with the pathology of high blood pressure. The purpose of this study was to examine the effects of T manipulation in the regulation of resistance-sized blood vessel reactivity.

Methods

Adult spontaneously hypertensive (SHR) and Wistar Kyoto (WKY) male rats at 8 weeks of age were used. The rats were divided into groups consisting of gonadally intact controls (CONT), castrate with sham implant (CAST) and castrate with T implant (CAST + T) (n = 6 to 12 per group). Following a short-term period of T treatment (approximately 4 weeks), plasma norepinephrine (NE) and plasma T were assessed by performing high-performance liquid chromatography and RIA, respectively. Resistance-sized mesenteric artery reactivity was assessed on a pressurized arteriograph for myogenic reactivity (MYO), phenylephrine (PE) responsiveness and passive structural mechanics.

Results

SHR and WKY males exhibited similar physiological trends in T manipulation, with castration significantly lowering plasma T and NE and T replacement significantly increasing plasma T and NE. T manipulation in general resulted in significant alterations in MYO of second-order mesenteric arteries, with T replacement decreasing MYO in SHR (P < 0.05) compared to CONT, T replacement increasing MYO, and CAST decreasing MYO in WKY rats (P < 0.001) compared to CONT rats. Additionally, PE-induced constriction was significantly altered in both strains following T treatment, with the effective concentration of PE to constrict the vessel to 50% of the total diameter significantly increased in the CAST + T SHR compared to CONT (P < 0.05). Comparisons of passive structural mechanics between SHR and WKY treatment groups indicated in SHR a significantly increased wall-to-lumen ratio and decreased circumferential wall stress compared to WKY treatment groups.

Conclusions

These data suggest that T and NE are involved in a complex interaction with both myogenic reactivity and structural alterations of resistance-sized blood vessels and that these factors likely contribute to the development and maintenance of hypertension.

Diagnosis and treatment of sexual dysfunctions in late-onset hypogonadism

Testosterone is the principal androgen in the human male. The decline of testosterone with aging was recognized to be associated with a number of symptoms and signs that reduce the quality of life and that may even have severe, debilitating consequences. Clinically, late-onset hypogonadism (LOH) is diagnosed by use of biochemical and clinical measures. Despite published guidelines and recommendations, however, uncertainty surrounds the profile of clinical symptoms as well as the biochemical threshold of diagnosis. Clinicians should be aware of these shortcomings while adhering to the guidelines. Current treatment methods are centered on restoring testosterone to mid to lower levels of young men with natural testosterone replacements. Although recent studies have highlighted possible additional benefits involving improvement of systemic disorders, the goal of treatment is to improve sexual function, while observing for adverse effects in the prostate. Overall, the problem of LOH in debilitating the quality of life and well-being is real, and by following proper guidelines with attentiveness to the results of treatment trials, testosterone replacement therapy presents a safe and effective treatment option.