In vivo administration of doxazosin in rats highly decreases serum circulating levels of testosterone through a mechanism involving the testicular renin–angiotensin system

Cadmium exposure-induced rat testicular dysfunction and its mechanism of chronic stress

Cadmium is a common environmental pollutant in daily life, the toxic mechanisms of chronic cadmium exposure on the testes have not been fully elucidated. This study aimed to explore the effects of cadmium exposure on male reproductive health and its mechanism. The results showed that cadmium exposure led widened interstitial spaces, abnormal seminiferous tubule morphology, and decreased Leydig cell numbers. Moreover, sperm quality was significantly reduced, along with a decrease in fertility rate. And cadmium exposure could activate the hypothalamic-pituitary-adrenal (HPA) axis, elevate blood glucocorticoid levels, subsequently increase glucocorticoid receptor (GR) expression and activation in testicular Leydig cells. Then GR act on the glucocorticoid receptor element (GRE) in the DNA methyltransferase 3 A (DNMT3A) promoter region and upregulate DNMT3A expression. Consequently, this led to an increase in DNA methylation levels in the angiotensin II receptor 2 (AT2R) promoter region, resulting in reduced AT2R expression and inhibiting testicular steroidogenesis. This study systematically elucidated that cadmium exposure could lead to testicular steroidogenesis suppression and decreased fertility through the GR/DNMT3A/AT2R signaling pathway. This research further provides theoretical and experimental evidence for confirming the threat of cadmium exposure to human reproduction, and contributes to the guidance and protection of male reproductive health.

Regulation of Male Fertility by the Renin-Angiotensin System

The renin-angiotensin system (RAS) is a peptidic system known mainly for its roles in the maintenance of blood pressure and electrolyte and fluid homeostasis. However, several tissues and cells have been described to possess an intrinsic RAS that acts locally through different paracrine and autocrine mechanisms. In the male reproductive system, several components of this system have been observed in various organs and tissues, such as the testes, spermatozoa and seminal fluid. Some functions attributed to this local RAS are maintenance of seminal plasma electrolytes, regulation of steroidogenesis and spermatogenesis, and sperm functions. However, their specific actions in these locations are not fully understood. Therefore, a deep knowledge of the functions of the RAS at both the testicular and seminal levels could clarify its roles in male infertility and sperm physiology, and the different RAS elements could be used to design tools enabling the diagnosis and/or treatment of male infertility.

Differential Effects of Doxazosin on Renin-Angiotensin-System- Regulating Aminopeptidase Activities in Neuroblastoma and Glioma Tumoral Cells

Background:

It has been described that doxazosin, an antihypertensive drug, also promotes glioblastoma cells death by inhibiting cell proliferation, arresting cell cycle and inducing apoptosis. Doxazosin has also demonstrated several modulator effects on renin-angiotensin system (RAS)- regulating aminopeptidase activities, which are highly involved in tumor growth in experimental glioma. Therefore, it remains to elucidate if the anti-tumoral effects of doxazosin could also be mediated by the proteolytic regulatory components of the RAS.

Objective:

To analyze the effects of doxazosin on cell growth and on RAS-regulating proteolytic regulatory aspartyl aminopeptidase (ASAP), aminopeptidase A (APA), aminopeptidase N (APN), aminopeptidase B (APB) and insulin-regulated aminopeptidase (IRAP) specific activities in the human neuroblastoma NB69 and astroglioma U373-MG tumoral cell lines.

Methods:

Human neuroblastoma NB69 and astroglioma U373-MG cell lines were treated with doxazosin 50-500 μM for 24h or 48h. The effects on cell growth and on RAS-regulating aminopeptidase specific activities were analyzed.

Results:

Doxazosin treatments promote a concentration-dependent inhibition on cell growth in both NB69 and U373-MG cells, being NB69 cells more sensitive to the drug than U373-MG cells. However, its effects on RAS-regulating aminopeptidase specific activities depend on the concentration used, the duration of the treatment and the cell type. These data confirm the existence of a different dynamic progression of RAS cascade in each tumoral cell line as a consequence of the treatment with doxazosin and time of action, which also implies a very dynamic metabolism of the peptides which participate in each step of RAS cascade.

Conclusion:

Our results indicate that doxazosin modifies the proteolytic regulatory enzymes of RAS cascade, modulating the bioactive efficacy of the different angiotensin peptides, and therefore, of their functional roles as initiators/promoters of cell proliferation as autocrine/paracrine mediators.

Cardiovascular/Pulmonary Medications and Male Reproduction

Cardiovascular and respiratory medications are used by men of reproductive age although use of the former is most prevalent in advanced age. Many of these drugs have been associated with sexual dysfunction, including erectile and ejaculatory dysfunction, but for most there is insufficient evidence to link their use with testicular dysfunction, reduced semen quality or infertility. Some exceptions are the irreversible α₁-adrenergic antagonist phenoxybenzamine, which carries a high risk of retrograde ejaculation; the specific α_1A-adrenergic antagonists silodosin and tamsulosin, used primarily to treat BPH/lower urinary tract symptoms, which can cause retrograde ejaculation; and the peripheral β₁-adrenergic antagonist atenolol, used to treat hypertension, which may decrease testosterone/free-testosterone levels. In this chapter, we review the evidence available regarding adverse reactions on male reproduction of adrenergic receptor agonists/antagonists, calcium channel blockers, angiotensin converting enzyme (ACE) inhibitors, diuretics, digoxin, and hydralazine. For some of these medications, there is some evidence for male reproductive effects, along with some solid work in experimental and companion animal species suggesting negative effects. In contrast, and of special note, are calcium channel blockers, which have long been included on lists of medications with the potential to cause male infertility. This turns out to be a good example of a substance with profound effects on sperm function in vitro, but with limited evidence for in vivo effects on semen quality or fertility, even in experimental species. We hope that the evidence provided in this chapter will stimulate additional studies for these important classes of medications.

In vivo blockade of α1-adrenergic receptors mitigates stress-disturbed cAMP and cGMP signaling in Leydig cells

The molecular mechanism of stress-associated reproductive dysfunction is complex and largely unknown. This study was designed to systematically analyze molecular effects of systemic in vivo blockade of α1-adrenergic receptors (α1-ADRs) on stress-induced disturbance of cAMP/cGMP signaling in testosterone-producing Leydig cells using the following parameters (i) level of circulating stress hormones, LH and testosterone; (ii) level of main molecular markers of Leydig cell functionality (testosterone, Insl3, cAMP); (iii) expression of cAMP signaling (cAMP 'producers'/'effectors'/'removers') and (iv) expression of NO-cGMP signaling (NO-cGMP 'producers'/'effectors'/'removers'). The results showed that oral administration of α1-ADR blocker before stress increased cGMP and diminished stress-reduced cAMP production in Leydig cells. In the same cells, stress-induced effects on cAMP/cGMP signaling pathways elements were changed. Sustained in vivo α1-ADR blockade completely abolished stress-increased transcription of most abundantly expressed phosphodiesterase that remove cAMP (Pde4b) and potentiated stress-increased expression of PRKA, the main stimulator of Leydig cell steroidogenesis. In the same Leydig cells, stress-decreased NOS3 expression was abolished, while stress-increased GUCY1 (cGMP 'producer') and PRKG1 (cGMP 'effector') were potentiated. It is possible that all molecules mentioned could contribute, at least in part, in recovery of Leydig cell testosterone production. Presented data provide new role of α1-ADRs in stress-triggered disturbance of cAMP/cGMP signaling, and new molecular insights into the relationship between stress and mammalian reproduction. Regardless of whether the effects of α1-blocker + stress are direct or indirect, the results are important in terms of human reproductive health and the wide use of α1-ADR antagonists, alone or in combination, to treat post-traumatic stress disorders, hypertension, benign prostatic hyperplasia symptoms and potential drugs for prostate cancer prevention/treatment.

Sustained in vivo blockade of α₁-adrenergic receptors prevented some of stress-triggered effects on steroidogenic machinery in Leydig cells

This study was designed to systematically analyze and evaluate the effects of in vivo blockade of α₁-adrenergic receptors (α₁-ADRs) on the stress-induced disturbance of steroidogenic machinery in Leydig cells. Parameters followed 1) steroidogenic enzymes/proteins, transcription factors, and cAMP/testosterone production; 2) the main hallmarks of stress (epinephrine, glucocorticoids); and 3) transcription profiles of ADRs and oxidases with high affinity to inactivate glucocorticoids. Results showed that sustained blockade of α₁-ADRs prevented stress-induced 1) decrease of the transcripts/proteins for main steroidogenic CYPs (CYP11A1, CYP17A1); 2) decrease of Scarb1 and Hsd3b1 transcripts; 3) decrease of transcript for Nur77, one of the main activator of the steroidogenic expression; and 4) increase of Dax1 and Arr19, the main steroidogenic repressors in Leydig cells. In the same cells, the expression of steroidogenic stimulatory factor Creb1, StAR, and androgen receptor increased. In this signaling scenario, stress-induced stimulation of Adra1a/Adra1b/Adrbk1 and Hsd11b2 (the unidirectional oxidase with high affinity to inactivate glucocorticoids) was not changed. Blockade additionally stimulated stress-increased transcription of the most abundantly expressed ADRs Adra1d/Adrb1/Adrb2 in Leydig cells. In the same cells, stress-decreased testosterone production, the main marker of Leydig cells functionality, was completely prevented, while reduction of cAMP, the main regulator of androgenesis, was partially prevented. Accordingly, the presented data provide a new molecular/transcriptional base for "fight/adaptation" of steroidogenic cells and new molecular insights into the role of α₁-ADRs in stress-impaired Leydig cell steroidogenesis. The results are important in term of wide use of α₁-ADR selective antagonists, alone/in combination, to treat high blood pressure, nightmares associated with posttraumatic stress disorder, and disrupted sexual health.

Orally applied doxazosin disturbed testosterone homeostasis and changed the transcriptional profile of steroidogenic machinery, cAMP/cGMP signalling and adrenergic receptors in Leydig cells of adult rats

Doxazosin (Doxa) is an α1-selective adrenergic receptor (ADR) antagonist widely used, alone or in combination, to treat high blood pressure, benign prostatic hyperplasia symptoms, and recently has been suggested as a potential drug for prostate cancer prevention/treatment. This study was designed to evaluate the effect of in vivo Doxa po-application, in clinically relevant dose, on: (i) steroidogenic machinery homeostasis; (ii) cAMP/cGMP signalling; (iii) transcription profile of ADR in Leydig cells of adult rats. The results showed that po-application of Doxa for once (1×Doxa), or for two (2×Doxa) or 10 (10×Doxa) consecutive days significantly disturbed steroidogenic machinery homeostasis in Leydig cells. Doxa po-application significantly decreased circulating luteinizing hormone and androgens levels. The level of androgens in testicular interstitial fluid and that extracted from testes obtained from 1×Doxa/2×Doxa rats decreased, although it remained unchanged in 10×Doxa rats. Similarly, the ex vivo basal androgen production followed in testes isolated from 1×Doxa/2×Doxa rats decreased, while remained unchanged in 10×Doxa rats. Differently, ex vivo testosterone production and steroidogenic capacity of Leydig cells isolated from 1×Doxa/2×Doxa rats was stimulated, while 10×Doxa had opposite effect. In the same cells, cAMP content/release showed similar stimulatory effect, but back to control level in Leydig cells of 10×Doxa. 1×Doxa/2×Doxa decreased transcripts for cAMP specific phosphodiesterases Pde7b/Pde8b, whereas 10×Doxa increased Pde4d. All types of treatment reduced the expression of genes encoding protein kinase A (PRKA) regulatory subunit (Prkar2b), whereas only 10×Doxa stimulated catalytic subunit (Prkaca). Doxa application more affected cGMP signalling: stimulated transcription of constitutive nitric oxide synthases (Nos1, Nos3) in time-dependent manner, whereas reduced inducible Nos2. 10×Doxa increased guanylyl cyclase 1 transcript and PRKG1 protein in Leydig cells. Orally applied Doxa significantly disturbed the transcriptional 'signature' of steroidogenic machinery, cAMP/cGMP signalling and ADRs and β-ADRs kinases in Leydig cells, thus giving new molecular insights into the role of cAMP/cGMP/adrenalin signalling in Leydig cells homeostasis.

Diet-induced hypercholesterolemia impaired testicular steroidogenesis in mice through the renin-angiotensin system

Hypercholesterolemia and low testosterone concentrations in men are associated with a high risk factor for atherosclerosis. It is known that cholesterol serves as the major precursor for the synthesis of the sex hormones. The bioactive peptides of the renin-angiotensin-system localized in the gonads play a key role in the relation between cholesterol and testosterone by modulating steroidogenesis and inhibiting testosterone production. In the present work, we evaluated the effects of diet-induced hypercholesterolemia on circulating testosterone levels and its relationship with the testicular RAS-regulating specific aminopeptidase activities in male mouse. A significant decrease in serum circulating levels of testosterone was observed after induced hypercholesterolemia. The changes found in aminopeptidase activities suggest a role of Ang III and Ang IV in the regulation of steroidogenesis.

Hypertension, RAS, and gender: what is the role of aminopeptidases?

Hypertension is the major risk factor for coronary heart disease, stroke, and renal disease. Also, it is probably the most important risk factor for peripheral vascular disease and vascular dementia. Although hypertension occurs in both men and women, gender differences have been observed. However, whether sex hormones are responsible for the observed gender-associated differences in arterial blood pressure, and which is their mechanism of action, remains unclear. Local and circulating renin-angiotensin systems (RAS) are examples of systems that may be involved in the pathogenesis of hypertension. Classically, angiotensin II (Ang II) has been considered as the effector peptide of the RAS, but Ang II is not the only active peptide. Several of its degradation products, including angiotensin III (Ang III) and angiotensin IV (Ang IV) also possess biological functions. These peptides are formed via the activity of several aminopeptidases. This review will briefly summarize what is known about gender differences in RAS-regulating aminopeptidase activities, their relationship with sex hormones, and their potential role in controlling blood pressure acting through local and circulating RAS.