Neuronal nitric oxide signaling regulates erection recovery after cavernous nerve injury

l-Arginine and COVID-19: An Update

l-Arginine is involved in many different biological processes and recent reports indicate that it could also play a crucial role in the coronavirus disease 2019 (COVID-19), caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Herein, we present an updated systematic overview of the current evidence on the functional contribution of L-Arginine in COVID-19, describing its actions on endothelial cells and the immune system and discussing its potential as a therapeutic tool, emerged from recent clinical experimentations.

Topically delivered nitric oxide acts synergistically with an orally administered PDE5 inhibitor in eliciting an erectile response in a rat model of radical prostatectomy

Patients undergoing radical prostatectomy (RP) have a high incidence of post-operative erectile dysfunction (ED) refractory to treatment by oral phosphodiesterase-type-5-inhibitors (PDE5i). In the present studies, we investigated if a topically applied, nitric oxide microparticle delivery system (NO-MP) might act synergistically with an oral PDE5i (sildenafil) to improve erectile function outcomes in a rat model of RP.

Thirty-five Sprague–Dawley rats underwent bilateral transection of the cavernous nerve (CN) for one week. After one-week, animals were orally administered 0, 0.05 or 0.005 mg sildenafil/kg and the erectile response following topical application to the penile shaft of 250mg or 100mg NO-MP, or blank-MP, was monitored over a two-hour timeframe by recording the intracorporal pressure normalized to systemic blood pressure (ICP/BP, N=5 animals/treatment group).

Oral treatment with sildenafil by itself resulted in no observable erectile response. However, a combination of orally administered 0.05 sildenafil/kg with topical application of 250mg NO-MP, compared to 250 mg NO-MP by itself, resulted in significantly more spontaneous erections (4.6 compared to 2 erections per hour, t-test; p-value = 0.043), with a significantly faster onset for the first erectile response (11 compared to 22 minutes; t-test, p-value = 0.041).

Our results demonstrate a synergistic effect between orally administered PDE5i and topically applied NO-MP in eliciting an erectile response. Furthermore, they suggest a potential novel therapeutic approach to treat men with ED resulting from RP, through combination therapy of a topically applied NO-MP and an orally administered PDE5i.

European Society for Sexual Medicine Consensus Statement on the Use of the Cavernous Nerve Injury Rodent Model to Study Postradical Prostatectomy Erectile Dysfunction

INTRODUCTION

Rodent animal models are currently the most used in vivo model in translational studies looking into the pathophysiology of erectile dysfunction after nerve-sparing radical prostatectomy.

AIM

This European Society for Sexual Medicine (ESSM) statement aims to guide scientists toward utilization of the rodent model in an appropriate, timely, and proficient fashion.

METHODS

MEDLINE and EMBASE databases were searched for basic science studies, using a rodent animal model, looking into the consequence of pelvic nerve injury on erectile function.

MAIN OUTCOME MEASURES

The authors present a consensus on how to best perform experiments with this rodent model, the details of the technique, and highlight possible pitfalls.

RESULTS

Owing to the specific issue-basic science-Oxford 2011 Levels of Evidence criteria cannot be applied. However, ESSM statements on this topic will be provided in which we summarize the ESSM position on various aspects of the model such as the use of the Animal Research Reporting In Vivo Experiments guideline and the of common range parameter for nerve stimulation. We also highlighted the translational limits of the model.

CONCLUSION

The following statements were formulated as a suggestive guidance for scientists using the cavernous nerve injury model. With this, we hope to standardize and further improve the quality of research in this field. It must be noted that this model has its limitations. Weyne E, Ilg MM, Cakir OO, et al. European Society for Sexual Medicine Consensus Statement on the Use of the Cavernous Nerve Injury Rodent Model to Study Postradical Prostatectomy Erectile Dysfunction. Sex Med 2020;8:327-337.

Piper auritum Kunth (Piperaceae) improves the sexual performance of sluggish male rats through enhancing ejaculation

ETHNOPHARMACOLOGICAL RELEVANCE

Piper auritum Kunth is employed as an aphrodisiac in the traditional medicine, but corroborative evidence for such effect is scarce.

AIM OF THE STUDY

The pro-sexual effect of an aqueous extract of P. auritum and its possible mechanisms were analyzed in two paradigms of male sexual function.

MATERIAL AND METHODS

Effects of an aqueous extract of P. auritum (PA, single administration) were investigated in the fictive ejaculation, and copulatory behavior paradigms in sexually sluggish male rats. WAY 100635 (antagonist of 5-HT_1A receptors), atosiban (antagonist of oxytocinergic receptors), L-NAME (inhibitor of the nitric oxide synthase) and baclofen (antagonist of GABA_B receptors) were used as pre-treatments in order to investigate the role of different neurotransmitter systems in PA actions. Chemical profile of PA was determined by Gases Chromatography and Ultra Performance Chromatography-Electrospray Ionization-Masses Spectrometry (UPLC-ESI-MS).

RESULTS

In males with retarded ejaculation, PA stimulated ejaculatory behavior and recovered electromyographic activity of pelvic musculature participating in seminal emission and ejaculation. All pre-treatments blocked stimulating effects of PA on the fictive ejaculation; additionally WAY 100635 interfered with PA actions on ejaculatory behavior. Safrol, apigenin dimethylether, myristicin, vaccihein A, sakuranin and sakuranetin flavonoids, were main constituents of PA, with possible participation in its pro-sexual effects.

CONCLUSIONS

Pro-sexual effects of P. auritum elicited at level of ejaculation were mediated by several neurotransmitter systems, among which serotonin and its 5-HT_1A receptors play an important role. Present findings support P. auritum reputation as an aphrodisiac, with potential use in delayed ejaculation disorder.

cAMP-dependent post-translational modification of neuronal nitric oxide synthase neuroprotects penile erection in rats

OBJECTIVES

To evaluate neuronal nitric oxide (NO) synthase (nNOS) phosphorylation, nNOS uncoupling, and oxidative stress in the penis and major pelvic ganglia (MPG), before and after the administration of the cAMP-dependent protein kinase A (PKA) agonist colforsin in a rat model of bilateral cavernous nerve injury (BCNI),which mimics nerve injury after prostatectomy.

MATERIALS AND METHODS

Adult male Sprague-Dawley rats were divided into BCNI and sham-operated groups. Each group included two subgroups: vehicle and colforsin (0.1 mg/kg/day i.p.). After 3 days, erectile function (intracavernosal pressure) was measured and penis and MPG were collected for molecular analyses of phospho (P)-nNOS (Ser-1412 and Ser-847), total nNOS, nNOS uncoupling, binding of protein inhibitor of nNOS (PIN) to nNOS, gp91^phox subunit of NADPH oxidase, active caspase 3, PKA catalytic subunit α (PKA-Cα; by Western blot) and oxidative stress (hydrogen peroxide [H₂ O₂ ] and superoxide by Western blot and microdialysis method).

RESULTS

Erectile function was decreased 3 days after BCNI and normalized by colforsin. nNOS phosphorylation on both positive (Ser-1412) and negative (Ser-847) regulatory sites, and nNOS uncoupling, were increased after BCNI in the penis and MPG, and normalized by colforsin. H₂ O₂ and total reactive oxygen species production were increased in the penis after BCNI and normalized by colforsin. Protein expression of gp91^phox was increased in the MPG after BCNI and was normalized by colforsin treatment. Binding of PIN to nNOS was increased in the penis after BCNI and was normalized by colforsin treatment. Protein expression of active Caspase 3 was increased in the MPG after BCNI and was normalized by colforsin treatment. Protein expression of PKA-Cα was decreased in the penis after BCNI and normalized by colforsin.

CONCLUSION

Collectively, BCNI impairs nNOS function in the penis and MPG by mechanisms involving its phosphorylation and uncoupling in association with increased oxidative stress, resulting in erectile dysfunction. PKA activation by colforsin reverses these molecular changes and preserves penile erection in the face of BCNI.

Association of nNOS and Rho-kinase with age-associated erectile dysfunction in Sprague-Dawley rats

The present study aimed to investigate the changes of Rho-associated kinase (Rho-kinase) and neuronal nitric oxide synthase (nNOS) expression in age-associated erectile dysfunction (ED) in Sprague-Dawley (SD) rats. A total of 100 intact male SD rats were divided into 20 groups according to their age (5-24 months; rats that were the same age in months were in the same group). Erectile response measurements were performed and the functional index intracavernosal pressure/mean arterial pressure (ICP/MAP) was tested, followed by detection of Rho-kinase and nNOS protein by western blot analysis. Finally, correlation analyses of the association between ICP/MAP and Rho-kinase, nNOS, or nNOS/Rho-kinase, as well as between age and nNOS or Rho-kinase, were performed. The functional index ICP/MAP decreased with age in SD rats. Moreover, the expression of nNOS protein decreased, while Rho-kinase expression increased, indicating that the nNOS/Rho-kinase ratio decreased with age. The Pearson's correlation coefficients for the association between ICP/MAP and Rho-kinase, nNOS and nNOS/Rho-kinase ratio were -0.917, 0.853 and 0.937, respectively (P<0.01). Furthermore, nNOS was found to be significantly negatively correlated with age (r=-0.855; P<0.01), whereas Rho-kinase was positively correlated with age (r=0.943; P<0.01). Age-associated ED was therefore correlated with decreased nNOS and increased Rho-kinase, indicating that the nNOS/Rho-kinase ratio may be used as a candidate indicator of age-associated ED.

Nitric Oxide Synthase is Necessary for Normal Urogenital Development

Introduction

Neuronal nitric oxide synthase (NOS-I) is significantly decreased with Cavernous Nerve (CN) injury in Erectile Dysfunction (ED) models. Increased apoptosis and collagen deposition accompany decreased NOS/CN injury, however these changes are typically attributed to the altered signaling of other factors, and a contribution of NOS in maintenance of urogenital structures has not previously been examined. Morphological changes in the corpora cavernosa occur at the same time as decreased NOS, suggesting a potential connection between decreased/inhibited NOS and morphological changes associated with ED. In this study we propose that NOS impacts urogenital morphology during development and will examine this hypothesis by NOS inhibition with L-NAME.

Methods

Primary outcomes were H&E, western and TUNEL to determine if penis, prostate and bladder morphology were altered with L-NAME treatment of Postnatal day 4 (P4) Sprague Dawley rats for 8 days. Tissue weight and immunohistochemical analysis for NOS were performed. Secondary evaluation of NOS-I regulation by Sonic Hedgehog (SHH) was examined by SHH inhibition in the pelvic ganglia (PG) and NOS-I protein was quantified by western in the PG/CN and penis. Nos abundance was quantified by RT-PCR during urogenital development and after CN injury.

Results

Apoptosis increased and penis, prostate and bladder morphology were altered with L-NAME. NOS inhibition decreased bladder weight 25%. SHH inhibition decreased NOS-I 35% in the PG/CN and 47% in the penis. Nos-III expression spiked within the first two weeks after birth in the penis but remained abundant in the adult. In the prostate, Nos-III was abundant immediately after birth and declined steadily with age. Nos-I expression in the PG/CN decreased sharply with CN injury and returned to baseline by 7 days.

Conclusions

NOS is required for normal urogenital development. Since NOS is decreased with ED, it may contribute to the abnormal morphology observed in ED patients and animal models.

Hyperbaric oxygen therapy provides neuroprotection following spinal cord injury in a rat model

OBJECTIVE

To investigate the effect of hyperbaric oxygen therapy (HBOT) on the iNOS mRNA-iNOS-NO signaling pathway and neurofunction protected in a rat spinal cord injury model.

METHODS

A total of 36 Sprague-Dawley rats were randomly divided into 3 groups: control group (n=12), SCI group (n=12) and SCI + HBOT group (n=12). SCI + HBOT group In the SCI group and SCI + HBOT groups, SCI was performed on rats. In the SCI + HBOT group, rats with SCI underwent HBO treatment 30 min after SCI for 24 sessions. After HBO therapy, measurement of motor evoked potential (MEP), Basso, Beattie, Bresnahan (BBB) scoring and pathological examination were done. RT-PCR and immunohistochemistry were employed to detect the mRNA and protein expression of iNOS, respectively. Diazo colorimetry was performed to detect the serum NO content.

RESULTS

The mRNA and protein expression of iNOS in the spinal cord and the serum NO content were markedly increased in the SCI group as compared to the control group (P<0.05). However, the mRNA and protein expression of iNOS and the serum NO content were dramatically reduced in the SCI + HBOT group as compared to the SCI group (P<0.05).

CONCLUSION

HBO therapy can promote the neuroprotection following SCI, which may be related to the effect of HBO on the iNOS mRNA-iNOS-NO signaling pathway.

Nitric oxide-releasing polymeric microspheres improve diabetes-related erectile dysfunction

INTRODUCTION

We have used a long-acting nitric oxide (NO)-releasing polymer to develop injectable biodegradable microspheres capable of localized NO release over prolonged periods of time.

AIM

The aim of this study was to evaluate the therapeutic potential of these microspheres for diabetes-related erectile dysfunction (ED) in the rat model.

METHODS

NO-releasing microspheres were incubated in physiologic buffer, and in vitro NO release was measured using a Griess assay. To ensure no migration, microspheres were fluorescently tagged and injected into the corpus cavernosum of adult rats, and fluorescent imaging was performed weekly for 4 weeks, at which point rats were sacrificed. To assess physiologic efficacy, diabetes was induced in 40 rats using streptozotocin (STZ), whereas 10 rats were kept as age-matched controls. Diabetic rats were divided into four groups: no treatment, sildenafil, NO-releasing microspheres, and combination therapy. For each rat, the cavernosal nerve (CN) was stimulated at various voltages, and intracavernosal pressure (ICP) and mean arterial pressure (MAP) were measured via corpus cavernosum and carotid artery catheterization, respectively. Long-term efficacy was determined by injecting diabetic rats with microspheres and measuring erectile response at predetermined intervals for up to 5 weeks.

MAIN OUTCOME MEASURES

Erectile response was determined via calculation of mean peak ICP/MAP and area under curve (AUC) for each experimental group.

RESULTS

Under physiologic conditions in vitro, microspheres continued NO release for up to 4 weeks. Fluorescent imaging revealed no detectable signal in tissues besides cavernosal tissue at 4 weeks postinjection. Upon CN stimulation, peak ICP/MAP ratio and AUC of diabetic rats improved significantly (P < 0.05) in microsphere and combination therapy groups compared with no treatment and sildenafil groups. In long-term efficacy studies, microspheres augmented the effect of sildenafil for 3 weeks following injection (P < 0.05).

CONCLUSIONS

NO-releasing microspheres significantly improved erectile response in diabetic rats for 3 weeks and hence offer a promising approach to ED therapy, either as monotherapy or combination therapy.