Peripheral Mechanisms of Erectile Dysfunction in a Rat Model of Chronic Cocaine Use

Artificial intelligence based identification of the functional role of hirudin in diabetic erectile dysfunction treatment

Diabetic erectile dysfunction (DED) hugely affected the patients' sexual life quality. However, there are no satisfactory therapeutic methods and intervention targets for this subtype of erectile dysfunction (ED). Inspired by the clinical practice of traditional Chinese medicine (TCM), we found that hirudin, the main active ingredient in the leech, could ameliorate the ED symptoms of the DED mouse model. To further reveal the underlying mechanism of hirudin, we designed a novel strategy to discover potential targets based on the diagnostic system of TCM, and found that myeloperoxidase (MPO) was a promising target of hirudin. Hirudin directly interacts with MPO and inhibits its activity, thus further decreases the content of oxidized low-density lipoprotein (ox-LDL) in serum. Our results demonstrated that the hirudin could ameliorate the symptoms of DED, and revealed the underlying mechanism of hirudin in regulating the activity of MPO.

Atorvastatin reduces the proadhesive and prothrombotic endothelial cell phenotype induced by cocaine and plasma from cocaine consumers in vitro

OBJECTIVE

Cocaine consumption is a risk factor for vascular ischemic complications. Although endothelial dysfunction and accelerated atherosclerosis have been observed in cocaine consumers, the mechanisms underlying their pathogenesis are not fully understood. This study aimed at identifying the effects of atorvastatin in relation to a proadhesive and prothrombotic phenotype induced by cocaine and plasma from chronic cocaine users on endothelial cells.

APPROACH AND RESULTS

Human umbilical vein endothelial cells were exposed to either cocaine or platelet-free plasma (PFP) from chronic cocaine consumers in the presence or absence of 10 μmol/L of atorvastatin. Atorvastatin significantly reduced the enhanced platelet adhesion that was induced by cocaine and PFP from chronic cocaine consumers, as well as the release of the von Willebrand factor. Atorvastatin also avoided striking alterations on cell monolayer structure triggered by both stimuli and enhanced NO reduction because of cocaine stimulation through disrupting interactions between endothelial nitric oxide synthase (eNOS) and caveolin-1, thus increasing eNOS bioavailability. Cocaine-increased tissue factor-dependent procoagulant activity and reactive oxygen species generation were not counteracted by atorvastatin. Although monocyte chemoattractant protein-1 levels were not significantly higher than controls either under cocaine or PFP stimulation, atorvastatin completely avoided monocyte chemoattractant protein-1 release in both conditions. Platelets stimulated with cocaine or PFP did not express P-selectin, glycoprotein IIb/IIIa, or CD40L and failed to adhere to resting human umbilical vein endothelial cell.

CONCLUSIONS

Cocaine and patient plasma equally induced a proadhesive and prothrombotic phenotype in endothelial cells, except for von Willebrand Factor release, which was only induced by PFP from chronic cocaine consumers. Atorvastatin improved endothelial cell function by reducing cocaine-induced and PFP from chronic cocaine consumer-induced effects on platelet adhesion, cell architecture, and NO production.

A novel method to establish a rat ED model using internal iliac artery ligation combined with hyperlipidemia

Objective

To investigate a novel method, namely using bilateral internal iliac artery ligation combined with a high-fat diet (BCH), for establishing a rat model of erectile dysfunction (ED) that, compared to classical approaches, more closely mimics the chronic pathophysiology of human ED after acute ischemic insult.

Materials and Methods

Forty 4-month-old male Sprague Dawley rats were randomly placed into five groups (n = 8 per group): normal control (NC), bilateral internal iliac artery ligation (BIIAL), high-fat diet (HFD), BCH, and mock surgery (MS). All rats were induced for 12 weeks. Copulatory behavior, intracavernosal pressure (ICP), ICP/mean arterial pressure, hematoxylin-eosin staining, Masson's trichrome staining, serum lipid levels, and endothelial and neuronal nitric oxide synthase immunohistochemical staining of the cavernous smooth muscle and endothelium were assessed. Data were analyzed by SAS 8.0 for Windows.

Results

Serum total cholesterol and triglyceride levels were significantly higher in the HFD and BCH groups than the NC and MS groups. High density lipoprotein levels were significantly lower in the HFD and BCH groups than the NC and MS groups. The ICP values and mount and intromission numbers were significantly lower in the BIIAL, HFD, and BCH groups than in the NC and MS groups. ICP was significantly lower in the BCH group than in the BIIAL and HFD groups. Cavernous smooth muscle and endothelial damage increased in the HFD and BCH groups. Cavernous smooth muscle to collagen ratio, nNOS and eNOS staining decreased significantly in the BIIAL, HFD, and BCH groups compared to the NC and MS groups.

Conclusions

The novel BCH model mimics the chronic pathophysiology of ED in humans and avoids the drawbacks of traditional ED models.

The effect of methamphetamine on an animal model of erectile function

In the US methamphetamine is considered a first-line treatment for attention-deficit hyperactivity disorder. It is also a common drug of abuse. Reports in patients and abusers suggest its use results in impotence. The efficacy of phosphodiesterase-5 inhibitors (PDE5i) to restore erectile function in these patient groups also has not been determined. In these studies, we determined if the rat is a suitable animal model for the physiological effects of methamphetamine on erectile function, and if a PDE5i (tadalafil) has an effect on erectile function following methamphetamine treatment. In acute phase studies, erectile function was measured in male Sprague-Dawley rats, before and after administration of 10 mg/kg methamphetamine i.p. Chronically treated animals received escalating doses of methamphetamine [2.5 mg/kg (1st week), 5 mg/kg (2nd week), and 10 mg/kg (3rd week)] i.p. daily for 3 weeks and erectile function compared with untreated controls. The effect of co-administration of tadalafil was also investigated in rats acutely and chronically treated with methamphetamine. Erectile function was determined by measuring the intracorporal pressure/blood pressure ratio (ICP/BP) following cavernous nerve stimulation. In both acute and chronic phase studies, we observed a significant increase in the rates of spontaneous erections after methamphetamine administration. In addition, following stimulation of the cavernous nerve at 4 and 6 mA, there was a significant decrease in the ICP/BP ratio (approximately 50%), indicative of impaired erectile function. Tadalafil treatment reversed this effect. In chronically treated animals, the ICP/BP ratio following 4 and 6 mA stimulation decreased by approximately 50% compared with untreated animals and erectile dysfunction (ED) was also reversed by tadalafil. Overall, our data suggest that the rat is a suitable animal model to study the physiological effect of methamphetamine on erectile function. Our work also provides a rationale for treating patients that report ED associated with therapeutics-containing methamphetamine or amphetamine with PDE5i.

Mechanisms of penile erection and basis for pharmacological treatment of erectile dysfunction

Erection is basically a spinal reflex that can be initiated by recruitment of penile afferents, both autonomic and somatic, and supraspinal influences from visual, olfactory, and imaginary stimuli. Several central transmitters are involved in the erectile control. Dopamine, acetylcholine, nitric oxide (NO), and peptides, such as oxytocin and adrenocorticotropin/α-melanocyte-stimulating hormone, have a facilitatory role, whereas serotonin may be either facilitatory or inhibitory, and enkephalins are inhibitory. The balance between contractant and relaxant factors controls the degree of contraction of the smooth muscle of the corpora cavernosa (CC) and determines the functional state of the penis. Noradrenaline contracts both CC and penile vessels via stimulation of α₁-adrenoceptors. Neurogenic NO is considered the most important factor for relaxation of penile vessels and CC. The role of other mediators, released from nerves or endothelium, has not been definitely established. Erectile dysfunction (ED), defined as the "inability to achieve or maintain an erection adequate for sexual satisfaction," may have multiple causes and can be classified as psychogenic, vasculogenic or organic, neurologic, and endocrinologic. Many patients with ED respond well to the pharmacological treatments that are currently available, but there are still groups of patients in whom the response is unsatisfactory. The drugs used are able to substitute, partially or completely, the malfunctioning endogenous mechanisms that control penile erection. Most drugs have a direct action on penile tissue facilitating penile smooth muscle relaxation, including oral phosphodiesterase inhibitors and intracavernosal injections of prostaglandin E₁. Irrespective of the underlying cause, these drugs are effective in the majority of cases. Drugs with a central site of action have so far not been very successful. There is a need for therapeutic alternatives. This requires identification of new therapeutic targets and design of new approaches. Research in the field is expanding, and several promising new targets for future drugs have been identified.

Future sexual medicine physiological treatment targets

INTRODUCTION

Sexual function in men and women incorporates physiologic processes and regulation of the central and peripheral nervous systems, the vascular system, and the endocrine system. There is need for state-of-the-art information as there is an evolving research understanding of the underlying molecular biological factors and mechanisms governing sexual physiologic functions.

AIM

To develop an evidence-based, state-of-the-art consensus report on the current knowledge of the major cellular and molecular targets of biologic systems responsible for sexual physiologic function.

METHODS

State-of-the-art knowledge representing the opinions of seven experts from four countries was developed in a consensus process over a 2-year period.

MAIN OUTCOME MEASURES

Expert opinion was based on the grading of evidence-based medical literature, widespread internal committee discussion, public presentation, and debate.

RESULTS

Scientific investigation in this field is needed to increase knowledge and foster development of the future line of treatments for all forms of biological-based sexual dysfunction. This article addresses the current knowledge of the major cellular and molecular targets of biological systems responsible for sexual physiologic function. Future treatment targets include growth factor therapy, gene therapy, stem and cell-based therapies, and regenerative medicine.

CONCLUSIONS

Scientific discovery is critically important for developing new and increasingly effective treatments in sexual medicine. Broad physiologic directions should be vigorously explored and considered for future management of sexual disorders.

Low doses of cocaine decrease, and high doses increase, anxiety-like behavior and brain progestogen levels among intact rats

There are sex and hormonal differences in response to cocaine that have been demonstrated in people and animal models. Cocaine can alter secretion of progestogens, such as progesterone (P), and its neuroactive metabolite, 5alpha-pregnan-3alpha-ol-20-one (3alpha,5alpha-THP). However, little research has been done on the neuroendocrine effects in the initiation phase of cocaine use. We hypothesize that some sex/hormonal differences in initiation phase responses to cocaine may be related to formation of progestogens. To investigate the role of progestogens in sex differences in response to acute cocaine, male and female rats in the high (proestrous) or low (diestrous) progestogen phase of the estrous cycle were administered cocaine (0, 5, 10, or 20mg/kg, IP). We examined cocaine's acute neuroendocrine effects on P and 3alpha,5alpha-THP levels, as well as its effects on acute psychomotor stimulation, anxiety, and sexual behaviors. Among rats that had P and/or 3alpha,5alpha-THP levels increased in response to cocaine, enhanced acute psychomotor stimulation was observed. Results suggest that cocaine produces U-shaped curves for progestogens, and anxiety-like behaviors. Male rats were less susceptible to these effects of cocaine than were proestrous or diestrous female rats. However, cocaine's disruption of sexual behaviors was similar among males and proestrous females. These data suggest a complex interaction between hormonal milieu and the neuroendocrine and behavioral effects of cocaine.

Molecular analysis of cocaine-induced endothelial dysfunction: role of endothelin-1 and nitric oxide

Cocaine remains the most frequently used illicit substance. Although cocaine-induced atherosclerosis is well documented, its mechanism of action on human vascular endothelial cells has not been determined. Nitric oxide (NO) and endothelin-1 (ET-1) are involved in endothelial cell activation and leukocyte recruitment. The present study monitored the effects of cocaine on NO and ET-1 production in human aortic endothelial cells (HAECs) and the effects of sodium nitroprusside (SNP) and BQ-123 on leukocyte adhesion to HAECs. Acute exposure to cocaine (1 and 3 muM) significantly increased ET-1 production (2-fold) and ET-1 receptor type-A (ET(A)R) protein expression, within 6-12 h. Cocaine exposure for a longer duration (24-72 h) showed a temporal decrease in both NO production and endothelial NO-synthase (eNOS) expression. The cocaine-mediated suppression of NO was ameliorated by co-treatment of cells with the ET(A)R blocker, BQ-123 (5 muM). Furthermore, both short-term (24 h) and long-term (72 h) exposure to cocaine increased endothelial adhesion of monocytes (U937 cells) by 20% and 40%, respectively, which were also suppressed by BQ-123 and SNP co-treatment. These data suggest that a concomitant increase in both ET-1 and ET(A)R expression in cocaine exposed HAECs may enhance signaling via the ET(A)R which decreases eNOS expression and NO production, and ultimately results in endothelial activation and leukocyte adhesion. Our findings implicate a molecular mechanism of action of cocaine and a therapeutic effect of ET(A)R-specific inhibitor in suppressing the cocaine-induced endothelial dysfunction.