The investigation of putative agents, using anin vitromodel, to prevent cavernosal smooth muscle dysfunction during low-flow priapism

Conservative and medical treatments of non-sickle cell disease-related ischemic priapism: a systematic review by the EAU Sexual and Reproductive Health Panel

Conservative and medical treatments are considered the first step in ischemic priapism (IP) management, although there is no clear evidence regarding their efficacy. We conducted a systematic review on behalf of the EAU Guidelines panel on Sexual and Reproductive health to analyse the available evidence on the efficacy and safety of conservative and medical treatment for non-sickle cell disease-related IP. Databases searched for relevant literature investigating efficacy and safety of conservative measures and medical treatment for IP included Medline, EMBASE, Cochrane Libraries and clinicaltrial.gov published up to September 2021. Overall, 41 retrospective, 3 prospective single-arm studies and 3 randomized controlled trials met the inclusion criteria. Intracavernous injection with sympathomimetic (ICIs) agents were the most frequently utilized treatment with efficacy ranging from 0 to 100% of cases. The combination of ICIs with corporeal aspiration with or without irrigation with saline was successful in 70 to 100% of cases. Oral treatment with β2 receptor agonist (e.g., terbutaline) showed mild to moderate efficacy. Conservative methods including ice pack, exercise, cold enema and ejaculation depicted lower effectiveness in resolving priapism (1-55%). Longer time interval from the onset to the resolution of IP was associated with higher rate of erectile dysfunction at follow-up (30-70%), especially after 24 h.

Mechanisms underlying priapism in sickle cell disease: targeting and key innovations on the preclinical landscape

Introduction: Priapism is prolonged penile erection in the absence of sexual arousal or desire and is a devastating condition affecting millions of patients with sickle cell disease (SCD) globally. Available drug treatments for SCD-related priapism remain limited and have been primarily reactive rather than preventive. Hence, there is an unmet need for new drug targets and pharmacologic therapies.Areas covered: We examine the molecular mechanisms underlying SCD-associated priapism evaluated mostly in animal models. In mouse models of SCD, molecular defects of priapism operating at the cavernous tissue level include reduced tonic NO/cGMP signaling, elevated oxidative/nitrosative stress, vascular adhesion molecule derangements, excessive adenosine and opiorphin signaling, dysregulated vasoconstrictive RhoA/ROCK signaling, and testosterone deficiency. We discuss the consequences of downregulated cGMP-dependent phosphodiesterase type 5 (PDE5) activity in response to these molecular signaling derangements, as the main effector mechanism causing unrestrained cavernous tissue relaxation that results in priapism.Expert opinion: Basic science studies are crucial for understanding the underlying pathophysiology of SCD-associated priapism. Understanding the molecular mechanisms could unearth new therapeutic targets for this condition based on these mechanisms. Treatment options should aim to improve deranged erection physiology regulatory signaling to prevent priapism and potentially restore or preserve erectile function.

The Case Report of Priapus and a Modern Approach to an Ancient Affliction

INTRODUCTION

Priapism, taking its name from God Priapus, is total or partial erection lasting longer than 4 hours independent of sexual stimulus and can result in erectile dysfunction. There are three subtypes of priapism.

AIM

To review the three subtypes of priapism, their pathophysiology, current treatment options, and complications.

METHODS

The literature including priapism guidelines, review articles, and current trial studies was reviewed and the priapism type of God Priapus was investigated according to the mythology.

MAIN OUTCOME MEASURES

All three types of priapism were reviewed for etiology, diagnosis, and management. Medical and surgical treatment options were reviewed in relation to the current literature. Special emphasis concerned current treatment strategies and controversial surgical topics.

RESULTS

Ischemic priapism is the most common type, constituting 95% of all cases, and is an emergency. First-line treatments are blood aspiration and intracavernosal sympathomimetic drug injections. If these fail, then surgical shunt operations are recommended. A T-shunt combined with corporal tunneling is the currently popular option. Immediate penile prosthesis implantation is recommended for patients who present 48 to 72 hours after the onset of a priapism episode. High-flow priapism is caused by irregular arterial cavernosal blood flow, which usually occurs after a blunt perineal trauma. Antiandrogens and selective arterial embolization are the treatment options. Stuttering priapism is repetitive, self-limiting ischemic priapism and frequent in patients with sickle cell anemia. Ketoconazole is safe, cheap, and effective and appears to be a logical and suitable current treatment option to prevent further episodes, which is the primary treatment goal of stuttering priapism.

CONCLUSION

Priapism is a relatively common condition but not well known by clinicians. The lack and delay of treatment result in irreversible complications such as erectile dysfunction. Each type of priapism should be diagnosed and treated correctly with caution.

Management of priapism: an update for clinicians

Priapism is a prolonged erection that persists beyond or is unrelated to sexual stimulation. It is associated with significant morbidity: psychological, socioeconomic, and physical, including pain and potentially irreversible compromise of erectile function. There are three major types of priapism: ischemic, nonischemic, and stuttering. Establishing the type of priapism is paramount to safely and effectively treating these episodes. Ischemic priapism represents a urological emergency. Its treatment may involve aspiration/irrigation with sympathomimetic injections, surgical shunts, and as a last resort, penile prosthesis implantation. Nonischemic priapism results from continuous flow of arterial blood into the penis, most commonly related to penile trauma. This is not an emergency and may be managed conservatively initially, as most of these episodes are self-limiting. Stuttering priapism involves recurrent self-limiting episodes of ischemic priapism. The primary goal of therapy is prevention, but acute episodes should be managed in accordance with guidelines for ischemic priapism. In this paper we review the diagnosis and treatment of the three priapism variants, as well as discuss future targets of therapy and novel targets on the horizon.

Targeting NADPH oxidase decreases oxidative stress in the transgenic sickle cell mouse penis

INTRODUCTION

Sickle cell disease (SCD) is a state of chronic vasculopathy characterized by endothelial dysfunction and increased oxidative stress, but the sources and mechanisms responsible for reactive oxygen species (ROS) production in the penis are unknown.

AIMS

We evaluated whether SCD activates NADPH oxidase, induces endothelial nitric oxide synthase (eNOS) uncoupling, and decreases antioxidants in the SCD mouse penis. We further tested the hypothesis that targeting NADPH oxidase decreases oxidative stress in the SCD mouse penis.

METHODS

SCD transgenic (sickle) mice were used as an animal model of SCD. Hemizygous (hemi) mice served as controls. Mice received an NADPH oxidase inhibitor apocynin (10 mM in drinking water) or vehicle. Penes were excised at baseline for molecular studies. Markers of oxidative stress (4-hydroxy-2-nonenal [HNE]), sources of ROS (eNOS uncoupling and NADPH oxidase subunits p67(phox) , p47(phox) , and gp91(phox) ), and enzymatic antioxidants (superoxide dismutase [SOD]1, SOD2, catalase, and glutathione peroxidase-1 [GPx1]) were measured by Western blot in penes.

MAIN OUTCOME MEASURES

Sources of ROS, oxidative stress, and enzymatic antioxidants in the SCD penis.

RESULTS

Relative to hemi mice, SCD increased (P<0.05) protein expression of NADPH oxidase subunits p67(phox) , p47(phox) , and gp91(phox) , 4-HNE-modified proteins, induced eNOS uncoupling, and reduced Gpx1 expression in the penis. Apocynin treatment of sickle mice reversed (P<0.05) the abnormalities in protein expressions of p47(phox) , gp91(phox) (but not p67(phox) ) and 4-HNE, but only slightly (P>0.05) prevented eNOS uncoupling in the penis. Apocynin treatment of hemi mice did not affect any of these parameters.

CONCLUSION

NADPH oxidase and eNOS uncoupling are sources of oxidative stress in the SCD penis; decreased GPx1 further contributes to oxidative stress. Inhibition of NADPH oxidase upregulation decreases oxidative stress, implying a major role for NADPH oxidase as a ROS source and a potential target for improving vascular function in the SCD mouse penis.

Experimental priapism is associated with increased oxidative stress and activation of protein degradation pathways in corporal tissue

Priapism is a debilitating disease for which there is at present no clinically accepted pharmacologic intervention. It has been estimated that priapism lasting more than 24 hours in patients is associated with a 44–90% rate of erectile dysfunction (ED). In this investigation we determined in two animal models of priapism (opiorpin-induced priapism in the rat and priapism in a mouse model of sickle cell disease) if there is evidence for an increase in markers of oxidative stress in corporal tissue. In both animal models we demonstrate that priapism results in increased levels of lipid peroxidation, glutathione S-transferase activity, and oxidatively damaged proteins in corporal tissue. Using Western blot analysis we demonstrated there is up regulation of the ubiquitination ligase proteins, Nedd-4 and Mdm-2, and the lysososomal autophage protein, LC3. The anti-apoptotic protein, Bcl-2, was also up regulated. Overall, we demonstrate that priapism is associated with increased oxidative stress in corporal tissue and the activation of protein degradation pathways. Since oxidative stress is known to mediate the development of ED resulting from several etiologies (for example ED resulting from diabetes and aging) we suggest that damage to erectile tissue resulting from priapism might be prevented by treatments targeting oxidative stress.

In vitro and in vivo animal models in priapism research

INTRODUCTION

Priapism is an enigmatic yet devastating clinical phenomenon. In the last two decades, the use of various animal models to study this disorder has dramatically advanced our understanding of this mysterious disorder.

AIM

This report reviews various animal models used to study ischemic priapism and informs basic science researchers the broad view of priapism research.

METHODS

Retrospective review of pertinent literature from the last two decades via PubMed search using the keywords "ischemic priapism" and "priapism model."

MAIN OUTCOME MEASURES

  Findings on the animal models used in ischemic priapism research and its advantages and limitations.

RESULTS

In vitro and in vivo animal models varying from dogs, cats, rabbits, rats to mice were used in priapism research. In vitro models included: (i) corpora cavernosa smooth muscle (CCSM) strip in organ bath; (ii) corporal tissue binding assay; (iii) CCSM cell culture under hypoxia/anoxia. In vivo models could be categorized as: (i) pharmacologically induced by corpus cavernosum medicine injection; (ii) ventilation induced by tidal volume control; (iii) mechanical induced by a constrictor band placed around the base of the penis combined with induced erection; (iv) genetic engineered by intracorporal gene transfer, transgenic, or gene knock-out.

CONCLUSIONS

The ischemic priapism animal models are shifting from pharmaceutically or mechanically induced to genetically engineered. The knowledge generated by those models is enhancing our understanding and management of this clinical challenge.