Oxidative stress associated with middle aging leads to sympathetic hyperactivity and downregulation of soluble guanylyl cyclase in corpus cavernosum

Early manifestation of aging-related vascular dysfunction in human penile vasculature-A potential explanation for the role of erectile dysfunction as a harbinger of systemic vascular disease

Advanced age is related to functional alterations of human vasculature, but erectile dysfunction precedes systemic manifestations of vascular disease. The current study aimed to simultaneously evaluate the influence of aging on vascular function (relaxation and contraction responses) in systemic human vascular territories: aorta (HA) and resistance mesenteric arteries (HMA) and human corpus cavernosum (HCC) and penile resistance arteries (HPRA). Associations of oxidative stress and inflammation circulating biomarkers with age and functional responses were also determined. Vascular specimens were obtained from 76 organ donors (age range 18-87). Four age-groups were established: < 40, 40-55, 56-65 and > 65 years old. Increasing age was associated with a decline in endothelium-dependent relaxation induced by BK in HMA (r = -0.597, p = 0.0001), or by ACh in HCC (r = -0.505, p = 0.0022), and HPRA (r = -0.601, p = 0.0012). Significant impairment was detected at > 65 years old in HMA but earlier in penile vasculature (> 55 years old). Age-related reduction to H2O2-vasodilatory response started before in HCC (56-65 years old) than in HA (> 65 years old). In contrast to relaxation responses, aging-related hypercontractility to adrenergic stimulation was homogeneous: contractions significantly increased in subjects > 55 years old in all tested vessels. Although not significantly age related, circulating levels of ADMA (r = -0.681, p = 0.0052) and TNF-α (r = -0.537, p = 0.0385) were negatively correlated with endothelial vasodilation in HMA but not in HCC or HPRA. Penile vasculature exhibits an early impairment of endothelium-dependent and H2O2-induced vasodilations when compared to mesenteric microcirculation and aorta. Therefore, functional susceptibility of penile vasculature to the aging process may account for anticipation of erectile dysfunction to systemic manifestations of vascular disease.

Efficacy of resveratrol in male urogenital tract dysfunctions: an evaluation of pre-clinical data

Resveratrol is a polyphenol found naturally in fruits and plants. Recently, studies in humans and animal models have suggested beneficial properties of this polyphenol, such as improvements to metabolic and lipid profiles, along with antioxidant, anti-inflammatory and anti-proliferative effects. In the urogenital tract (UGT), resveratrol has also been tested clinically and experimentally as a therapeutic drug in several diseases; however, the translational efficacy of resveratrol, especially in UGT, is still a matter of debate. In the present review, we address the pre-clinical efficacy of resveratrol in UGT-related dysfunctions, focusing on lower urinary tract symptoms, non-cancerous prostatic disease (benign prostatic hyperplasia and prostatitis) and erectile dysfunction. In vitro studies indicate that resveratrol reduces inflammatory markers and oxidative stress, and improves endothelial function in UGT organs and cells isolated from humans and animals. Despite displaying low oral bioavailability, in vivo administration of resveratrol largely improves erectile dysfunction, benign prostatic hyperplasia, prostatitis and voiding impairments, as evidenced in different animal models. Resveratrol also acts as a microbiota modulator, which may explain some of its beneficial effects in vivo. In contrast to the large amount of pre-clinical data, there are insufficient clinical trials to establish resveratrol treatment efficacy in human UGT-related diseases. In summary, we provide an overview of the in vivo and in vitro efficacy of resveratrol in animal and human UGT dysfunctions, which may support future clinical trials.

Ageing-induced hypercontractility is related to functional enhancement of STIM/Orai and upregulation of Orai 3 in rat and human penile tissue

The role of STIM/Orai calcium entry system on vascular ageing has not been elucidated. We aimed to evaluate the influence of ageing on STIM/Orai signalling and its role on ageing-induced alterations of contractile function in rat corpus cavernosum (RCC) and human penile resistance arteries (HPRA) and corpus cavernosum (HCC). RCC was obtained from 3 months-old and 20 months-old animals. HPRA and HCC were obtained from organ donors of varied ages without history of erectile dysfunction. Aging was associated with enhanced norepinephrine (NE)- and thromboxane analogue (U46619)-induced contractions in RCC which were significantly inhibited by the STIM/Orai inhibitor, YM-58483 (20 μM). Other STIM/Orai inhibitor, 2-aminoethyldiphenylborate also reduced NE-induced contractions in RCC from aged rats. YM-58483 significantly reduced neurogenic contractions and potentiated neurogenic relaxations in RCC from aged rats. In HCC and HPRA, NE-induced contractions were significantly enhanced in older subjects (>65 years-old) but YM-58483 completely reversed ageing-related hypercontractility. Ageing did not modify STIM-1 and Orai1 protein expressions but Orai3 was significantly overexpressed in cavernosal tissue from old rats and older subjects. Contribution of STIM/Orai to cavernosal contraction increases with ageing together with increased expression of Orai3. Orai inhibition could be a potential therapeutic strategy to reduce ageing-related impact on vascular/erectile function.

Antithrombotic strategies in elderly patients with acute coronary syndrome

Elderly patients represent a growing proportion of the acute coronary syndrome population in Western countries. However, their frequent atypical symptoms at presentation often lead to delays in management and to misdiagnosis. Furthermore, their prognosis is poorer than that of younger patients because of physiological changes in platelet function, haemostasis and fibrinolysis, but also a higher proportion of comorbidities and frailty, both of which increase the risk of recurrent thrombotic and bleeding events. This complex situation, with ischaemic and haemorrhagic risk factors often being intertwined, may lead to confusion about the required treatment strategy, sometimes resulting in inadequate management or even to therapeutic nihilism. It is therefore critical to provide a comprehensive overview of our understanding of the pathophysiological processes underlying acute coronary syndrome in elderly patients, and to summarise the results from the latest clinical trials to help decision making for these high-risk patients.

Thiol/Disulfide Homeostasis in Patients With Erectile Dysfunction

BACKGROUND

Although there are no sufficient data on association between oxidative stress and erectile dysfunction (ED), numerous studies have reported that imbalance between the formation of reactive oxygen species and body's antioxidant defenses may play a role in the pathogenesis of ED.

AIM

The aim of this study was to determine and compare the oxidant and antioxidant status in patients with ED and healthy controls with a novel automated assay for thiol/disulphide homeostasis test.

METHODS

Our study included 123 patients with ED and 90 healthy individuals. ED was evaluated by asking questions 1-5 and 15 of the International Index of Erectile Function form. In this study, we used Erel and Neselioglu's thiol/disulfide homeostasis test, which is one of the novel methods that can measure both variables of the oxidative/antioxidative balance individually and collectively.

OUTCOMES

This method measured serum antioxidant (total thiol [toSH], native thiol [SH]) and oxidant (disulfide [SS]) levels. The statistical comparisons were performed between patients with ED (ED+ group) and without ED (ED- group) first and then within the ED+ group. After toSH, SH, and SS levels were determined; SS/toSH%, SS/SH%, and SH/toSH% levels were analyzed separately and compared statistically.

RESULTS

We found a significant difference between ED- and ED+ groups in terms of toSH, SH, SS/toSH%, and SS/SH% ratios. SS parameters were increased in patients with ED, but there was no significant difference in terms of SS and SH/toSH% values.

CLINICAL IMPLICATIONS

Clarification of the factors involved in the etiology of ED such as oxidative/antioxidative balance may open new grounds in the early diagnosis and treatment of the disease.

STRENGTHS & LIMITATIONS

It is a prospective, randomized clinical study with the use of a novel, reliable, and fully automated technique. The limitations of the study are use of a subjective tool such as the International Index of Erectile Function, obtaining blood samples from the peripheral vein instead of penile cavernosal tissue, and relatively small sample size.

CONCLUSION

The results of this study showed that thiol/disulfide homeostasis is altered in ED, and this imbalance may be a factor in its pathophysiology. We determined that as ED gets more severe, toSH and SH parameters decrease, whereas SS parameter increases. Micoogullari U, Karatas OF, Kisa E, et al. Thiol/Disulfide Homeostasis in Patients With Erectile Dysfunction. J Sex Med 2020;17:1934-1941.

Potential Therapeutic Role of Dietary Supplementation with Spirulina platensis on the Erectile Function of Obese Rats Fed a Hypercaloric Diet

Spirulina platensis, an important source of bioactive compounds, is a multicellular, filamentous cyanobacterium rich in high-quality proteins, vitamins, minerals, and antioxidants. Due to its nutrient composition, the alga is considered a complete food and is recognized for its anti-inflammatory, antioxidant, antiobesity, and reproprotective effects. All of which are important for prevention and treatment of organic and metabolic disorders such as obesity and erectile dysfunction. The aim of this study was to investigate the modulatory role of Spirulina platensis food supplementation and the mechanisms of action involved in reversing the damage caused by a hypercaloric diet on the erectile function of rats. The animals were divided into a standard diet group (SD, n = 5); a hypercaloric diet group (HCD, n = 5); a hypercaloric diet group supplemented with S. platensis at doses of 25 (HCD+SP25, n = 5), 50 (HCD+SP50, n = 5), and 100 mg/kg (HCD+SP100, n = 5); and a hypercaloric diet group subsequently fed a standard diet (HCD+SD, n = 5). In the rats fed a hypercaloric diet, dietary supplementation with S. platensis effectively increased the number of erections while decreasing latency to initiate penile erection. Additionally, S. platensis increases NO bioavailability, reduces inflammation by reducing the release of contractile prostanoids, enhances the relaxation effect promoted by acetylcholine (ACh), restores contractile reactivity damage and cavernous relaxation, reduces reactive oxygen species (ROS), and increases cavernous total antioxidant capacity (TAC). Food supplementation with S. platensis thus restores erectile function in obese rats, reduces production of contractile prostanoids, reduces oxidative stress, and increases NO bioavailability. Food supplementation with S. platensis thus emerges as a promising new therapeutic alternative for the treatment of erectile dysfunction as induced by obesity.

The Basic Science Behind Low-Intensity Extracorporeal Shockwave Therapy for Erectile Dysfunction: A Systematic Scoping Review of Pre-Clinical Studies

INTRODUCTION

Despite recent promising clinical results, the underlying mechanism of action of low-intensity extracorporeal shockwave therapy (Li-ESWT) for erectile dysfunction (ED) is mostly unclear and currently under investigation.

AIM

To systematically identify and evaluate evidence regarding the basic science behind Li-ESWT for ED, discuss and propose a putative mechanism of action, address the limitations, and imply insights for further investigation in the field.

METHODS

Using Cochrane's methodologic recommendations on scoping studies and systematic reviews, we conducted a systematic scoping review of the literature on experimental research regarding Li-ESWT for ED and other pathologic conditions. The initial systematic search was carried between January and November 2017, with 2 additional searches in April and August 2018. All studies that applied shockwave treatment at an energy flux density >0.25 mJ/mm² were excluded from the final analysis.

MAIN OUTCOME MEASURE

We primarily aimed to clarify the biological responses in erectile tissue after Li-ESWT that could lead to improvement in erectile function.

RESULTS

59 publications were selected for inclusion in this study. 15 experimental research articles were identified on Li-ESWT for ED and 44 on Li-ESWT for other pathologic conditions. Li-ESWT for ED seems to improve erectile function possibly through stimulation of mechanosensors, inducing the activation of neoangiogenesis processes, recruitment and activation of progenitor cells, improving microcirculation, nerve regeneration, remodeling of erectile tissue, and reducing inflammatory and cellular stress responses.

CLINICAL IMPLICATIONS

Improving our understanding of the mechanism of action of Li-ESWT for ED can help us improve our study designs, as well as suggest new avenues of investigation.

STRENGTHS & LIMITATIONS

A common limitation in all these studies is the heterogeneity of the shockwave treatment application and protocol.

CONCLUSION

Li-ESWT for ED, based on current experimental studies, seems to improve erectile function by inducing angiogenesis and reversing pathologic processes in erectile tissue. These studies provide preliminary insights, but no definitive answers, and many questions remain unanswered regarding the mechanism of action, as well as the ideal treatment protocol. Sokolakis I, Dimitriadis F, Teo P, et al. The Basic Science Behind Low-Intensity Extracorporeal Shockwave Therapy for Erectile Dysfunction: A Systematic Scoping Review of Pre-Clinical Studies. J Sex Med 2019;16:168-194.

Mesenchymal stem cell-derived exosomes ameliorate erection by reducing oxidative stress damage of corpus cavernosum in a rat model of artery injury

Erectile dysfunction (ED) is a common ageing male's disease, and vascular ED accounts for the largest proportion of all types of ED. One of the mechanisms of vascular ED in the clinic is arterial insufficiency, which mainly caused by atherosclerosis, trauma and surgical. Moreover, oxidative stress damage after tissue ischemia usually aggravated the progress of ED. As a new way of acellular therapy, mesenchymal stem cell-derived exosomes (MSC-Exos) have great potential in ED treatment. In the current study, we have explored the mechanism of MSC-Exos therapy in a rat model of internal iliac artery injury-induced ED. Compared with intracavernous (IC) injection of phosphate-buffered saline after artery injury, of note, we observed that both mesenchymal stem cells (MSCs) and MSC-Exos through IC injection could improve the erectile function to varying degrees. More specifically, IC injection MSC-Exos could promote cavernous sinus endothelial formation, reduce the organization oxidative stress damage, and improve the nitric oxide synthase and smooth muscle content in the corpus cavernosum. With similar potency compared with the stem cell therapy and other unique advantages, IC injection of MSC- Exos could be an effective treatment to ameliorate erectile function in a rat model of arterial injury.

The sex-specific association between maternal paraben exposure and size at birth

Parabens are a group of esters of parahydroxybenzoic acid and are utilized as antimicrobial preservatives in the majority of personal care products (PCPs). Epidemiological studies regarding the adverse effects of parabens on fetuses are still limited. The aim of this study was to determine the association between maternal paraben exposure and birth outcomes. One hundred and ninety-nine pregnant women were enrolled, and maternal urine was collected in the third trimester. The urine concentrations of four parabens (methyl (MP), ethyl (EP), propyl (PP), and butyl (BP)) were determined by ultra-performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry. Generalized additive model-penalized regression splines and a multivariable regression model were employed to determine the association between paraben exposure levels and birth outcomes. A causal mediation analysis was conducted to determine the mediation effect of oxidative stress on birth outcomes. The geometric means of urinary MP, EP, PP, and BP were 51.79, 1.26, 4.21, and 1.25 μg/g cre., respectively. In the penalized regression splines, sex-specific associations between maternal MP levels and birth outcomes were observed; a downward curvature was observed between the MP level and birth weight, length, head circumference, and thoracic circumference among female newborns. Pregnant women in the group with MP levels above the third quartile had neonates with significantly lower body weight (β = -215.98 g, p value = 0.02) compared to those in the group with MP levels lower than the third quartile. No significant mediation of oxidative stress was observed between maternal MP exposure and female birth weight. The estimated proportion mediated ranged from -6% to 15%. The negative association between maternal paraben exposure and female birth outcomes in relation to child development should be carefully considered.

Tadalafil for the treatment of benign prostatic hyperplasia

INTRODUCTION

In men, lower urinary tract symptoms (LUTS) are primarily attributed to benign prostatic hyperplasia (BPH). Therapeutic options are targeted to relax prostate smooth muscle and/or reduce prostate enlargement. Areas covered: This article reviews the major preclinical and clinical data on PDE5 inhibitors with a specific focus on tadalafil. It includes details of the role of the nitric oxide (NO)-cyclic guanosine monophosphate (cGMP) - PDE5 pathway in the LUT organs (bladder and prostate) in addition to the available data on tadalafil in patients with LUTS secondary to BPH with or without erectile dysfunction (ED). Expert opinion: Preclinical and clinical data have clearly demonstrated that PDE5 inhibitors induce bladder and prostate relaxation, which contributes to the improvement seen in storage symptoms in both animal models of bladder and prostate hypercontractility. Tadalafil is effective both as a monotherapy and add-on therapy in patients with LUTS secondary to BPH. Furthermore, as LUTS-BPH and ED are urological disorders that commonly coexist in aging men, tadalafil is more advantageous than α1-adrenoceptors and should be used as the first option. Tadalafil is a safe and tolerable therapy and unlike α1- adrenoceptors and 5-alpha reductase inhibitors, which can cause sexual dysfunctions, tadalafil improves sexual function.

Genistein Loaded Nanofibers Protect Spinal Cord Tissue Following Experimental Injury in Rats

Innovative drug-delivery systems offer a unique approach to effectively provide therapeutic drug dose over the needed time to achieve better tissue protection and enhanced recovery. The hypothesis of the current study was to test the antioxidant and anti-inflammatory effects of genistein and nanofibers on the spinal cord tissue following experimental spinal cord injury (SCI). Rats were treated post SCI with genistein that is loaded on chitosan/polyvinyl alcohol (CS/PVA) nanofibers as an implantable drug-delivery system. SCI caused marked oxidative damage and inflammation, as is evident by the reduction in the super oxide dismutase (SOD) activity and the level of interleukin-10 (IL-10) in injured spinal cord tissue, as well as the significant increase in the levels of nitric oxide (NO), malondialdehyde (MDA), and tumor necrosis factor-alpha (TNF-α). Treatment of rats post SCI with genistein and CS/PVA nanofibers improved most of the above-mentioned biochemical parameters and shifted them toward the control group values. Genistein induced an increase in the activity of SOD and the level of IL-10, while causing a decrease in NO, MDA, and TNF-α in injured spinal cord tissue. Genistein and CS/PVA nanofibers provide a novel combination for treating inflammatory nervous tissue conditions, especially when combined as an implantable drug-delivery system.

G protein-coupled receptor kinase 2 inhibition improves erectile function through amelioration of endothelial dysfunction and oxidative stress in a rat model of type 2 diabetes

Type 2 diabetes mellitus (T2DM) is a common cause of erectile dysfunction (ED). It has been demonstrated that G protein-coupled receptor kinase 2 (GRK2) overexpression contributes to diabetic endothelial dysfunction and oxidative stress, which also underlies ED in T2DM. We hypothesized that GRK2 overexpressed and attenuated endothelial function of the cavernosal tissue in a rat model of T2DM. T2DM rats were established by feeding with a high-fat diet (HFD) for 2 weeks and then administering two intraperitoneal (IP) injections of a low dose of streptozotocin (STZ), followed by continuous feeding with a HFD for 6 weeks. GRK2 was inhibited by IP injection of paroxetine, a selective GRK2 inhibitor, after STZ injection. Insulin challenge tests, intracavernous pressure (ICP), GRK2 expression, the protein kinase B (Akt)/endothelial nitric oxide synthase (eNOS) pathway, nicotinamide adenine dinucleotide phosphate (NADPH) oxidase subunit gp91phox, nitric oxide (NO), reactive oxygen species (ROS) production, and apoptosis in cavernosal tissue were examined. Less response to insulin injection was observed in T2DM rats 2 weeks after HFD. Markedly increased GRK2 expression, along with impaired Akt/eNOS pathway, reduced NO production, increased gp91phox expression and ROS generation, increased apoptosis and impaired erectile function were found in T2DM rats. Inhibition of GRK2 with paroxetine ameliorated Akt/eNOS signaling, restored NO production, downregulated NADPH oxidase, subsequently inhibited ROS generation and apoptosis, and ultimately preserved erectile function. These results indicated that GRK2 upregulation may be an important mechanism underlying T2DM ED, and GRK2 inhibition may be a potential therapeutic strategy for T2DM ED.

Effects of low-intensity shock wave therapy (LiST) on the erectile tissue of naturally aged rats

Low-intensity shock wave therapy (LiST) improves erectile function in patients with erectile dysfunction (ED), probably by promoting angiogenesis as suggested by studies on animals with comorbidities as disease associated ED models. We aim to investigate the effects of LiST on erectile tissue of healthy, naturally aged rats. Twelve naturally aged male rats were randomized into two groups: control group (n = 6) and LiST-treatment group (n = 6). Young rats (8 weeks) (n = 6) was also used as control. Each rat in treatment group received 300 shock waves with an energy flux density of 0.09 mJ/mm² at 2 Hz. Sessions were repeated three times/week for 2 weeks, followed by a 2-week washout period. Real-time RT-PCR for the expressions of vascular endothelial growth factor (VEGF), endothelial nitric oxide synthase (eNOS), nerve growth factor (NGF), neuronal NOS (nNOS), as well as α1 and α2-adrenergic receptors (α1AR, α2AR) was performed, followed by immunohistochemical analysis (IHC) to evaluate protein expression. The expressions of VEGF, eNOS, and α2AR/α1AR ratio were increased after LiST (p = 0.039, p = 0.008, and p = 0.006 respectively). The increase of VEGF, eNOS, and α2AR was confirmed in IHC (p = 0.013, p = 0.092, and p = 0.096, respectively). The increase of VEGF and eNOS seem to play key role in the mechanism of action of LiST, apparently by inducing angiogenesis. The altered expression of α1/α2-adrenergic receptors could indicate a decrease in sympathetic activity. LiST showed to partially reverse changes associated with aging in erectile tissue of rats, which supports future research for ED prevention.

A novel experimental model of erectile dysfunction in rats with heart failure using volume overload

BACKGROUND

Patients with heart failure (HF) display erectile dysfunction (ED). However, the pathophysiology of ED during HF remains poorly investigated.

OBJECTIVE

This study aimed to characterize the aortocaval fistula (ACF) rat model associated with HF as a novel experimental model of ED. We have undertaken molecular and functional studies to evaluate the alterations of the nitric oxide (NO) pathway, autonomic nervous system and oxidative stress in the penis.

METHODS

Male rats were submitted to ACF for HF induction. Intracavernosal pressure in anesthetized rats was evaluated. Concentration-response curves to contractile (phenylephrine) and relaxant agents (sodium nitroprusside; SNP), as well as to electrical field stimulation (EFS), were obtained in the cavernosal smooth muscle (CSM) strips from sham and HF rats. Protein expression of endothelial NO synthase (eNOS) and neuronal NO synthase (nNOS) and phosphodiestarese-5 in CSM were evaluated, as well as NOX2 (gp91phox) and superoxide dismutase (SOD) mRNA expression. SOD activity and thiobarbituric acid reactive substances (TBARs) were also performed in plasma.

RESULTS

HF rats display erectile dysfunction represented by decreased ICP responses compared to sham rats. The neurogenic contractile responses elicited by EFS were greater in CSM from the HF group. Likewise, phenylephrine-induced contractions were greater in CSM from HF rats. Nitrergic response induced by EFS were decreased in the cavernosal tissue, along with lower eNOS, nNOS and phosphodiestarese-5 protein expressions. An increase of NOX2 and SOD mRNA expression in CSM and plasma TBARs of HF group were detected. Plasma SOD activity was decreased in HF rats.

CONCLUSION

ED in HF rats is associated with decreased NO bioavailability in erectile tissue due to eNOS/nNOS dowregulation and NOX2 upregulation, as well as hypercontractility of the penis. This rat model of ACF could be a useful tool to evaluate the molecular alterations of ED associated with HF.

Erectile Dysfunction in Heme-Deficient Nitric Oxide-Unresponsive Soluble Guanylate Cyclase Knock-In Mice

INTRODUCTION

The nitric oxide (NO), soluble guanylate cyclase (sGC), and cyclic guanosine monophosphate (cGMP) pathway is the leading pathway in penile erection.

AIM

To assess erectile function in a mouse model in which sGC is deficient in heme (apo-sGC) and unresponsive to NO.

METHODS

Mutant mice (sGCβ₁^ki/ki) that express an sGC enzyme that retains basal activity but fails to respond to NO because of heme deficiency (apo-sGC) were used. Isolated corpora cavernosa from sGCβ₁^ki/ki and wild-type mice were mounted in vitro for isometric tension recordings in response to sGC-dependent and -independent vasorelaxant agents. In addition, the erectile effects of some of these agents were tested in vivo at intracavernosal injection.

MAIN OUTCOME MEASURES

In vitro and in vivo recordings of erectile responses in sGCβ₁^ki/ki and wild-type mice after stimulation with sGC-dependent and -independent vasorelaxant agents.

RESULTS

NO-induced responses were abolished in sGCβ₁^ki/ki mice in vitro and in vivo. The ability of the heme-dependent, NO-independent sGC stimulator BAY 41-2272 to relax the corpora cavernosa was markedly attenuated in sGCβ₁^ki/ki mice. In contrast, the relaxation response to the heme- and NO-independent sGC activator BAY 58-2667 was significantly enhanced in sGCβ₁^ki/ki mice. The relaxing effect of sGC-independent vasorelaxant agents was similar in wild-type and sGCβ₁^ki/ki mice, illustrating that the observed alterations in vasorelaxation are limited to NO-sGC-cGMP-mediated processes.

CONCLUSION

Our results suggest that sGC is the sole target of NO in erectile physiology. Furthermore, this study provides indirect evidence that, in addition to sGCα₁β₁, sGCα₂β₁ is important for erectile function. In addition, the significant relaxation observed in sGCβ₁^ki/ki mice with the cumulative addition of the sGC activator BAY 58-2667 indicates that sGC activators might offer value in treating erectile dysfunction.

The Role of Reactive Oxygen and Nitrogen Species in the Expression and Splicing of Nitric Oxide Receptor

SIGNIFICANCE

Nitric oxide (NO)-dependent signaling is critical to many cellular functions and physiological processes. Soluble guanylyl cyclase (sGC) acts as an NO receptor and mediates the majority of NO functions. The signaling between NO and sGC is strongly altered by reactive oxygen and nitrogen species. Recent Advances: Besides NO scavenging, sGC is affected by oxidation/loss of sGC heme, oxidation, or nitrosation of cysteine residues and phosphorylation. Apo-sGC or sGC containing oxidized heme is targeted for degradation. sGC transcription and the stability of sGC mRNA are also affected by oxidative stress.

CRITICAL ISSUES

Studies cited in this review suggest the existence of compensatory processes that adapt cellular processes to diminished sGC function under conditions of short-term or moderate oxidative stress. Alternative splicing of sGC transcripts is discussed as a mechanism with the potential to both enhance and reduce sGC function. The expression of α1 isoform B, a functional and stable splice variant of human α1 sGC subunit, is proposed as one of such compensatory mechanisms. The expression of dysfunctional splice isoforms is discussed as a contributor to decreased sGC function in vascular disease.

FUTURE DIRECTIONS

Targeting the process of sGC splicing may be an important approach to maintain the composition of sGC transcripts that are expressed in healthy tissues under normal conditions. Emerging new strategies that allow for targeted manipulations of RNA splicing offer opportunities to use this approach as a preventive measure and to control the composition of sGC splice isoforms. Rational management of expressed sGC splice forms may be a valuable complementary treatment strategy for existing sGC-directed therapies. Antioxid. Redox Signal. 26, 122-136.

Sympathetic Hyperactivity, Increased Tyrosine Hydroxylase and Exaggerated Corpus Cavernosum Relaxations Associated with Oxidative Stress Plays a Major Role in the Penis Dysfunction in Townes Sickle Cell Mouse

Background

Sickle cell disease patients display priapism that may progress to erectile dysfunction. However, little is known about the pathophysiological alterations of corpus cavernosum in sickle cell disease.

Objective

Thus, this study aimed to evaluate the functional and molecular alterations of sympathetic machinery and nitric oxide—cyclic guanosine monophosphate signaling pathway in Townes transgenic sickle cell disease mice.

Methods

Concentration–response curves to contractile (phenylephrine) and relaxant agents (acetylcholine and sodium nitroprusside) were obtained in corpus cavernosum strips from sickle and C57BL/6 (control) mice. Neurogenic contractions and nitrergic relaxations were obtained using electrical-field stimulation. Measurements of endothelial nitric oxide synthase (eNOS), neuronal nitric oxide synthase (nNOS), phosphodiesterase-5 (PDE5) and α_1A-, α_1B- and α_1D-adrenoceptor mRNA expressions and reactive-oxygen species were performed. Tyrosine hydroxylase phosphorylated at Ser-31 and total tyrosine hydroxylase protein expressions in cavernosal tissues were also measured.

Results

The neurogenic contractions were higher in the sickle cell disease group, in association with elevated tyrosine hydroxylase phosphorylated at Ser-31 and total tyrosine hydroxylase protein expression, as well as increased tyrosine hydroxylase mRNA expression. Likewise, phenylephrine-induced contractions were greater in the sickle mice, whereas α_1A-, α_1B- and α_1D-adrenoceptor mRNA expression remained unchanged. Cavernosal relaxations to acetylcholine, sodium nitroprusside and EFS were higher in sickle mice, accompanied by decreased eNOS and nNOS, along with lower PDE5 mRNA expression. An increase of about 40% in reactive-oxygen species generation in corpus cavernosum from sickle mice was also detected.

Conclusion

Our study shows that decreased nitric oxide bioavailability in erectile tissue due to increased oxidative stress leads to both sympathetic hyperactivity and dysregulation of nitric oxide signaling in corpus cavernosum from Townes sickle mice.

Role of oxidative stress on platelet hyperreactivity during aging

Thrombotic events are common causes of morbidity and mortality in the elderly. Age-accelerated vascular injury is commonly considered to result from increased oxidative stress. There is abundant evidence that oxidative stress regulate several components of thrombotic processes, including platelet activation. Thus oxidative stress can trigger platelet hyperreactivity by decreasing nitric oxide bioavailability. Therefore oxidative stress measurement may help in the early identification of asymptomatic subjects at risk of thrombosis. In addition, oxidative stress inhibitors and platelet-derived nitric oxide may represent a novel anti-aggregation/-activation approach. In this article the relative contribution of oxidative stress and platelet activation in aging is explored.

Treatment With Metformin Improves Erectile Dysfunction in a Murine Model of Obesity Associated With Insulin Resistance

OBJECTIVE

To evaluate the effects of treatment with metformin on a murine model of obesity-associated erectile dysfunction.

MATERIAL AND METHODS

C57BL/6 male mice were fed for 10 weeks with standard chow or high-fat diet. Lean and obese mice were treated with the insulin sensitizer metformin (300 mg/kg/day, 2 weeks). Intracavernosal pressure (ICP) and in vitro corpus cavernosum (CC) relaxations to both acetylcholine and electrical field stimulation, as well as phenylephrine-induced contractions, were obtained. Levels of cyclic guanosine monophosphate in CC were detected by enzyme immunoassay.

RESULTS

High-fat-fed mice exhibited higher body weight and insulin resistance. Cavernous nerve stimulation caused frequency-dependent ICP increases, which were significantly lower in obese compared with lean mice (P <.05). Two-week therapy with metformin reversed the decreased ICP in obese group. The maximal response to acetylcholine in CC was 35% lower (P <.05) in the obese compared to the lean group, which were restored by metformin treatment. Likewise, the impaired electrical field stimulation-induced CC relaxations in obese mice were also partly restored by metformin. Contractile responses to phenylephrine were significantly greater (P <.05) in obese compared to lean mice, which were fully restored by metformin. Basal and stimulated cyclic guanosine monophosphate productions in the erectile tissues were significantly lower (P <.05) in the obese group, an effect fully restored by metformin.

CONCLUSION

Treatment with metformin restored the erectile function in obese mice, through improvement of in vitro endothelial and nitrergic cavernosal relaxations. Therefore, use of metformin may be a good pharmacologic approach to treat insulin resistance-associated erectile dysfunction.

Pharmacological characterisation of the relaxation induced by the soluble guanylate cyclase activator, BAY 60-2770 in rabbit corpus cavernosum

OBJECTIVE

To characterise the relaxation induced by the soluble guanylate cyclase (sGC) activator, BAY 60-2770 (4-({(4-carboxybutyl) [2- (5-fluoro-2-{[4'-(trifluoromethyl) biphenyl-4-yl]methoxy}phenyl)ethyl] amino}methyl)benzoic acid) in rabbit corpus cavernosum (CC).

MATERIAL AND METHODS

The penis from male New Zealand rabbits was removed and fours strips of CC were obtained. Concentration-response curves to BAY 60-2770 were constructed in the absence and presence of inhibitors of nitric oxide synthase, N (G)-nitro-L- arginine methyl ester (L-NAME, 100 μm), sGC, 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ, 10 μm) and phosphodiesterase type 5 (PDE-5), tadalafil (0.1 μm). The potency (pEC50 ) and maximal response (Emax ) values were determined. Then, electrical-field stimulation (EFS)-induced contraction or relaxation was tested in the absence and presence of BAY 60-2770 (0.1 or 1 μm) alone or combined with ODQ (10 μm). For EFS-induced relaxation two protocols were used: (i) ODQ (10 μm) was first incubated for 20 min and then BAY 60-2770 (1 μm) was added for another 20 min (ODQ + BAY 60-2770); (ii) in different CC strips, BAY 60-2770 was incubated for 20 min followed by another 20 min with ODQ (BAY 60-2770 + ODQ). The intracellular levels of cyclic guanosine monophosphate (cGMP) were also determined.

RESULTS

BAY 60-2770 potently relaxed rabbit CC with mean (sem) pEC50 and Emax values of 7.58 (0.19) and 81 (4)%, respectively. The inhibitors ODQ (n = 7) or tadalafil (n = 7) produced 4.2- and 6.3-leftward shifts, respectively in BAY 60-2770-induced relaxation without interfering with the Emax values. The intracellular levels of cGMP were augmented after stimulation with BAY 60-2770 (1 μm) alone, whereas its co-incubation with ODQ produced even higher levels of cGMP. The EFS-induced contraction was reduced in the presence of BAY 60-2770 (1 μm) and this inhibition was even greater when BAY 60-2770 was co-incubated with ODQ. The nitrergic stimulation induced CC relaxation, which was abolished in the presence of ODQ. BAY 60-2770 alone increased the amplitude of relaxation. Co-incubation of ODQ and BAY 60-2770 did not alter the relaxation in comparison with ODQ alone. Interestingly, when BAY 60-2770 was incubated before ODQ, EFS-induced relaxation was partly restored in comparison with ODQ alone or ODQ + BAY 60-2770.

CONCLUSIONS

The relaxation induced by the sGC activator, BAY 60-2770 was increased after sGC oxidation and unaltered in the absence of nitric oxide. Thus, this class of substances may have advantages over sGC stimulators or PDE-5 inhibitors for treating patients with erectile dysfunction and extensive endothelial damage.

Beneficial effect of the soluble guanylyl cyclase stimulator BAY 41-2272 on impaired penile erection in db/db-/- type II diabetic and obese mice

Type 2 diabetes mellitus (DM2) and obesity are major risk factors for erectile dysfunction (ED). In diabetes, increased oxidative stress leads to decreased nitric oxide (NO) bioavailability, and diabetic patients appear to be less responsive to conventional therapy with phosphodiesterase type 5 inhibitors. We investigated whether the soluble guanylyl cyclase stimulator BAY 41-2272 (5-cyclopropyl-2-[1-(2-fluoro-benzyl)-1H-pyrazolo[3,4-b]pyridine-3-yl]pyrimidin-4ylamine) is effective in improving impaired corpus cavernosum (CC) relaxation in obese DM2 mice by reducing oxidative stress. Adult db/db(-/-) mice or their lean db(/+) littermates were used to assess vascular function, cGMP levels, antioxidant status, NADPH oxidase expression, and superoxide formation in the absence or presence of BAY 41-2272. Results showed that BAY 41-2272 (10(-8) to 10(-5) M) potently relaxed CC from db(/+) or db/db(-/-) mice in a similar manner. BAY 41-2272 significantly enhanced both endothelium-dependent and nitrergic relaxation induced by electrical field stimulation (EFS), and improved the impaired relaxation to acetylcholine and EFS in the diabetic animals in a concentration-dependent manner (10(-8) to 10(-7) M). BAY 41-2272 increased cGMP levels and potentiated relaxation responses to exogenous NO in CC. Total antioxidant status was reduced in plasma and urine whereas expression of vascular NADPH oxidase subunits (gp91phox, p22phox, and p47phox) was increased in the CC of db/db(-/-) mice, suggesting a state of oxidative stress. These effects were prevented by BAY 41-2272 in a concentration-dependent manner. These results suggest that BAY 41-2272 improves CC relaxation in db/db(-/-) mice by increasing cGMP and augmenting antioxidant status, making this drug is a potential novel candidate to treat ED.