Potentiation of erectile response and cAMP accumulation by combination of prostaglandin E1 and rolipram, a selective inhibitor of the type 4 phosphodiesterase (PDE 4)

PURPOSE

Phosphodiesterases (PDEs) are an important component of the signal transduction pathway during the erectile response. To determine the PDE isoforms in the corpora cavernosa in the cat and to establish the functional presence of PDE 4 in human cavernosal tissue, the erectile response to intracavernosal phosphodiesterase (PDE) inhibitors alone and the combination of PDE inhibitors and prostaglandin E1 (PGE1) was evaluated in the anesthetized cat. The in vitro formation of cAMP and cGMP in human cavernosal smooth muscle cells (HCSMCs) treated with PGE1 and rolipram in primary culture was also measured.

MATERIALS AND METHODS

In pentobarbital-anesthetized cats, increases in intracavernosal pressure, penile length, and duration of erectile response were determined after intracavernosal injections of (i) the type 3 cAMP-specific, cGMP-inhibitable PDE inhibitor, milrinone, (ii) the type 4 cAMP-specific PDE inhibitor, rolipram, (iii) the type 5 cGMP-specific PDE inhibitor, zaprinast, and (iv) the combination of rolipram and PGE1. Systemic arterial pressure was concurrently assessed in these experiments. All responses to PDE inhibitors were compared with a control triple-drug combination comprised of papaverine (1.65 mg.), PGE1 (0.5 microg.), and phentolamine (25 microg.). HCSMCs were incubated with PGE1 (3 microM) and rolipram (10 microM) individually or in combination up to 2 hours at 37C. The intracellular cAMP and cGMP was extracted by cold absolute ethanol and measured (pmol./10(6) cells) by a commercially available EIA kit.

RESULTS

Milrinone (3 to 100 microg.), rolipram (3 to 100 microg.), and zaprinast (3 to 100 microg.) induced dose-dependent increases in intracavernosal pressure and penile length (p <0.05) when administered intracavernosally. The maximum increase in cavernosal pressure in response to zaprinast was associated with no significant change in systemic arterial pressure. When rolipram was combined with PGE1 (0.1 microg.), the increases in intracavernosal pressure and the duration of erectile response were significantly higher (p <0.05) and longer (p <0.05) than those observed when rolipram alone was injected intracavernosally. PGE1 (3 microM) and rolipram (10 microM) produced significant increases (p <0.05) in the accumulation of intracellular cAMP levels in HCSMCs in primary culture above those of the baseline values while intracellular levels of cGMP did not change.

CONCLUSIONS

PDE inhibitors administered intracavernosally caused dose-dependent increases in cavernosal pressure in the cat. When a specific cAMP PDE inhibitor was combined with PGE1, the erectile response was enhanced and intracellular levels of cAMP were increased in HCSMCs in primary culture. These data suggest further exploration of the combination of various PDE inhibitors and PGE1 in the pharmacologic treatment of erectile dysfunction and provide functional evidence for the presence of PDE 4 isoenzyme in human penile cavernosal cells.

Male infertility and erectile dysfunction in spinal cord injury: a review

OBJECTIVE

To review the pathophysiology, evaluation, and management of erectile dysfunction and infertility in spinal cord injury (SCI).

STUDY SELECTIONS

Studies that covered various treatment options and their contraindications, complications, or side effects, including sildenafil (Viagra), intracavernosal injection therapy, topical medications and a urethral delivery system, a vacuum erection device, and penile prostheses. Other studies covered the effects of SCI on reproduction: spermatogenesis and testicular function, and seminal constituents. In addition, assisted reproductive techniques were compared: external vibratory stimulation, electroejaculation, testicular sperm aspiration, and intracytoplasmic sperm injection.

CONCLUSION

Goal-directed therapy is the mainstay of treatment of erectile dysfunction in men with or without SCI. The choice of therapy is often defined more by the needs of the patient's sexual relationship than by his erectile dysfunction. The majority of men with SCI are infertile because of a combination of ejaculatory dysfunction, impaired spermatogenesis, and poor semen quality. Although many technological advances have evolved to overcome ejaculatory dysfunction, the sperm density, motility, and function remain poor. Until these parameters are improved, men with SCI will have to pursue more financially and emotionally taxing procedures. Further studies to elucidate the cellular and molecular mechanisms of diminished sperm quality are needed. Addressing the issues of erectile dysfunction and male infertility may help to preserve the relationship between the patient and his partner.

Characterization of reactive oxygen species induced effects on human spermatozoa movement and energy metabolism

Reactive oxygen species (ROS) inhibit sperm movement and have been implicated in male infertility. In this study, we determined the effects of specific ROS produced by activated leukocytes on human spermatozoa and investigated their metabolic site of action. We used chemiluminescence and electron paramagnetic resonance (EPR) to characterize the ROS generated by both blood and seminal leukocytes. We also determined the effects of these ROS on sperm energy metabolism using biochemical analyses and flow cytometry. Both blood and seminal leukocytes produced the same characteristic ROS which were determined to be hydrogen peroxide (H2O2) and superoxide radicals (O2*-). EPR using the spin trapping technique indicated that superoxide radical-dependent hydroxyl radicals (HO.) were also generated. ROS generated by PMA-stimulated blood leukocytes (2-5 x 10(6)/ml) caused inhibition of sperm movement in 2 h (p < .01). Using the hypoxanthine/ xanthine oxidase (0.5 U/ml) system to generate ROS, we determined that spermatozoa ATP levels, after ROS treatment, were reduced approximately eight-fold in 30 min (0.10 x 10(10) moles/10(6) sperm cells) compared to control (0.84 X 10(-10) moles/10(6) sperm cells) (p < .01). Sperm ATP reduction paralleled the inhibition of sperm forward progression. Neither superoxide dismutase (100 U/ml) nor dimethyl sulfoxide (100 mM) reversed these effects; however, protection was observed with catalase (4 X 10(3) U/ml). Flow cytometric analyses of sperm treated with various doses of H2O2 (0.3 mM-20.0 mM) showed a dose-dependent decrease in sperm mitochondrial membrane potential (MMP); however, at low concentrations of H2O2, sperm MMP was not significantly inhibited. Also, sperm MMP uncoupling with CCClP had no effect on either sperm ATP levels or forward progression. These results indicate that H2O2 is the toxic ROS produced by activated leukocytes causing the inhibition of both sperm movement and ATP production. O2*- and HO. do not play a significant role in these processes. Low concentrations of H2O2 causing complete inhibition of sperm movement and ATP levels inhibit sperm energy metabolism at a site independent of mitochondrial oxidative phosphorylation.

Ex vivo expression of nitric oxide synthase isoforms (eNOS/iNOS) and calmodulin in human penile cavernosal cells

PURPOSE

Nitric oxide (NO) synthesized by nitric oxide synthase (NOS) is recognized as the central mediator of penile erection. This process appears to be mediated mainly by neuronal NOS (nNOS), which is localized to the nonadrenergic, noncholinergic innervation of the penis. However, the role of non-neuronal penile constituents (specifically the cavernosal smooth muscle), as well as other NOS isoforms in NO production in the human penis is not well understood. The present study evaluates the expression of non-neuronal (inducible and endothelial) isoforms of NOS in human penile cavernosal smooth muscle cells in culture.

MATERIALS AND METHODS

Primary culture was initiated with explants of human corpora cavernosa. For gene expression studies, total RNA was extracted from cavernosal cells and subjected to reverse transcriptase polymerase chain reaction (RT-PCR). For NADPH-diaphorase histochemistry, the cells were incubated with 1 mM beta-NADPH and 0.5 mM nitrobluetetrazolium at 37C for 3 hours. For indirect immunofluorescence and electron microscopy, cells were incubated overnight at 4C with specific primary (eNOS; calmodulin) and secondary antibodies. A conventional avidin biotin complex technique was used for electron microscopy.

RESULTS

The mRNA expression studies revealed that these cells express both endothelial (eNOS) and inducible (iNOS) forms. Localization studies showed positive signals for NADPH-diaphorase, eNOS, and calmodulin. The electron microscopic evaluation confirmed the localization of eNOS to the cytoplasm and small vesicles in the cells.

CONCLUSIONS

These findings support the hypothesis that human cavernosal smooth muscle cells express both endothelial and inducible forms of NOS, which may significantly contribute to NO production in the penile architecture during the erectile process.

The influence of castration on pharmacologically induced penile erection in the cat

The purpose of this study was to investigate the in vivo effects of intracavernosal injections of adrenomedullin (ADM), calcitonin gene-related peptide (CGRP), nociceptin, vasoactive intestinal polypeptide (VIP), sodium nitroprusside (SNP), and prostaglandin E1 (PGE1) on penile erection in castrated and intact (control) anesthetized cats. Erectile responses to ADM, CGRP, nociceptin, VIP, SNP, and PGE1 were compared with responses to a standard triple-drug combination (1.65 mg of papaverine, 25 microg of phentolamine, and 0.5 microg of PGE1) in both castrated and control cats. In control animals, ADM, CGRP, nociceptin, VIP, SNP, and PGE1 induced penile erections similar to those elicited by the triple-drug combination. However, in castrated animals, there was a significant decrease in erectile response; the response to intracavernosal injection of the standard triple-drug combination in castrated cats was 28% of that of the control group of animals. Serum testosterone levels demonstrated a significant (P < 0.0001) positive correlation (r = 0.52) with intracavernosal pressure in response to the standard combination. A marked reduction in serum testosterone levels was observed in castrated cats when measured by radioimmunoassay (0.34 +/- 0.1 ng/dl in castrated cats, compared with 31.15 +/- 6 ng/dl in control cats). These data suggest that the presence of testosterone is a necessary prerequisite to sustain a pharmacologically induced penile erection in the cat.

Antioxidant potential of human serum albumin: role in the recovery of high quality human spermatozoa for assisted reproductive technology

Human serum albumin (HSA) is being considered as an alternate media for sperm enrichment in assisted reproductive technology (ART) because of recent concern with the use of Percoll. In this study, we compared HSA and Percoll for 1) sperm recovery, 2) reactive oxygen species scavenging potential, and 3) effects on total oxidative stress to spermatozoa. The spermatozoa-enriched fractions obtained from Percoll (80%:40%) and HSA (12%) were monitored for sperm motility, viability, hypoosmotic swelling test (HOST), and adenosine triphosphate (ATP) levels. The effect of superoxide anions (O2.-) on donor human spermatozoa was observed in the presence of either HSA or Percoll media. A combination of luminol and the Cypridina luciferin analog 2-methyl-6-(4-methoxyphenyl)-3,7-dihydroimidazo(1,2-alpha)pyraz in-3-one hydrochloride was used as a highly sensitive chemiluminescence probe in our hypoxanthine and xanthine oxidase-based assay for O2.-. Sperm membrane total oxidative stress was determined by measuring levels of the prostanoid 8-iso-Prostaglandin F2alpha (8-iso-PGF2alpha). Significant differences in sperm parameters between the Percoll-enriched spermatozoa (motility 60%+/-4%, viability 56%+/-6%, and HOST 73%+/-7%) and those enriched with HSA (motility 84%+/-5%, viability 85%+/-4%, and HOST 84%+/-3%; P < 0.01) were observed. Adenosine triphosphate levels were significantly higher, by almost 50%, in samples processed with HSA than with Percoll (P=0.03). The dismutation rate of O2.- in HSA (slope -6.8) was significantly lower than in Percoll (slope -87.0; P < 0.01). Sperm motility and ATP levels decreased at a slower rate after treatment with O2.- in the presence of HSA when compared to Percoll; moreover, spermatozoa in HSA regained partial motility after 2 hours, whereas spermatozoa in Percoll were immobilized. No significant differences in 8-iso-PGF2alpha levels in spermatozoa enriched by either HSA or Percoll were observed. We conclude that the HSA sperm enrichment procedure improves the recovery of higher quality spermatozoa compared to Percoll and, because of its antioxidant properties, may be useful in processing high leukospermia semen samples for ART purposes.

Effect of tumour necrosis factor-alpha (TNF-alpha) and interferon-gamma (IFN-gamma) on human sperm motility, viability and motion parameters

Male genital tract infections and non-specific inflammatory conditions may be associated with unexplained infertility. Previous studies have shown the presence of cytokines such as tumour necrosis factor-alpha (TNF-alpha) and interferon-gamma (IFN-gamma) in the semen of infertile men. However, the mechanism of effect of these cytokines on human sperm function is still controversial. The present study was undertaken to investigate the in-vitro effects of TNF-alpha and IFN-gamma on human sperm motion, viability and the hypoosmotic swelling test (HOST). Washed spermatozoa from normal volunteers (n = 9) were incubated in the presence/absence of TNF-alpha (1 microgram/mL) plus IFN-gamma (0.1 microgram/mL). Sperm motility, viability, HOST, and video sequences were recorded at different time intervals (0, 30, 60 and 180 min). Sperm motion parameters were analysed using computer-assisted semen analysis. There was a time-dependent negative effect of TNF-alpha plus IFN-gamma on sperm motility, viability, HOST, and lateral-head displacement (ALH). The maximum decrease was observed between 60 and 180 min for sperm motility (50.8 +/- 5.6%), viability (52.8 +/- 4.0%), HOST (38 +/- 2%) and ALH (4.7 +/- 0.1 microns) compared to control samples (62.2 +/- 2.8, 62.4 +/- 2.9, 58 +/- 4, and 5.3 +/- 0.4, respectively; All p < 0.05). There was no significant effect on sperm straight-line velocity and mean linearity when compared to control. These data suggest that the common inflammatory cytokines TNF-alpha plus IFN-gamma have only partial detrimental effects on sperm motility, viability, membrane integrity and lateral head displacement, which may contribute to the poor fertilizing potential of human spermatozoa during inflammatory conditions.

Effects of luminal nutrients and small bowel transplants on congenital indirect hyperbilirubinemia

The Gunn rat is an excellent model of Crigler-Najjar syndrome, type 1. In previous studies we demonstrated that heterotopic 15-20-cm jejunal transplants from Wistar rats lowered serum bilirubin levels by 40%, and the reduction was transient (6 weeks). In contrast, orthotopic transplants decreased bilirubin levels by 60% and the effect persisted throughout the 8-week study. This study was initiated to identify the luminal substance(s) which are responsible for the persistent bilirubin-lowering effect of jejunal transplants. Thirty-one Wistar to Gunn 15-20-cm jejunal transplants were randomized to receive daily Thiry-Vella graft irrigation with 5 ml of normal saline (n = 8); bile salts (cholate + deoxycholate, 40 mg/ml, n = 5; fats (Microlipid, 20 mg/ml, n = 5); proteins (Casec caseinate, 40 mg/ml, n = 5); and sugars (Moducal + Polycose, 40 mg/ml, n = 8). Bilirubin levels were measured spectrophotometrically at weekly intervals. At 4 and 8 weeks, enzyme-induced bilirubin conjugation activity was measured using added known amounts of added bilirubin. Irrigation of the transplants with saline, protein, and sugar resulted in moderate (40%) lowering of serum total and indirect bilirubin levels. Fat was significantly more effective, lowering mean total bilirubin levels from 9.6 +/- 0.4 to 1.6 +/- 0.2 mg/dl at 6 weeks. After this time, bilirubin levels increased slightly. Bile salts were slightly less effective, lowering bilirubin levels at 6 weeks by only 75%. However, this effect persisted and at 8 weeks levels averaged 2.4 +/- 0.2 mg/dl. Conjugating enzyme activity in the transplants increased from 1.4 +/- 0.3 to 2.5 +/- 0.5 mg bilirubin conjugated/mg tissue/hr. Luminal fats and bile salts appear to augment enzyme-induced bilirubin conjugation in heterotopic jejunal transplant recipients.

Quantitative assessment of cytokines (GRO alpha and IL-10) in human seminal plasma during genitourinary inflammation

PROBLEM

Mechanisms involved in infertility due to genitourinary (GU) inflammation are unknown. The production of pro-inflammatory (GRO alpha) and anti-inflammatory (IL-10) cytokines in seminal plasma is monitored in this study.

METHOD

GRO alpha, IL-10, and granulocyte elastase were evaluated in semen from I) normal, II) infertile patients, and III) infertile patients with leukocytospermia.

RESULTS

GRO alpha in infertile patients with GU inflammation was 1.5-fold higher compared to group II and 2.5-fold higher compared to group I patients. The IL-10 was higher in group III than the other two groups. A positive correlation was observed between granulocyte elastase and GRO alpha in all groups. Group III patients exhibited poor sperm parameters.

CONCLUSIONS

A shift towards increased production of pro-inflammatory chemokine GRO alpha may have a potential role in male infertility associated with GU inflammation.

Role of oxidative stress and antioxidants in male infertility

Oxygen toxicity is an inherent challenge to aerobic life, including spermatozoa, the cells responsible for propagation of the species. How this toxicity affects the spermatozoan in its interactions with the ovum is still unknown. An increase in oxidative damage to sperm membranes, proteins, and DNA is associated with alterations in signal transduction mechanisms that affect fertility. Recent evidence suggests that spermatozoa and oocytes possess an inherent but limited capacity to generate ROS to aid in the fertilization process. Though a variety of defense mechanisms encompassing antioxidant enzymes (SOD, catalase, and GSH peroxidase and reductase), vitamins (E, C, and carotenoids), and biomolecules (GSH and ubiquinol) are available, a balance of the benefits and risks from ROS and antioxidants appears to be necessary for the survival and functioning of spermatozoa. An assay system for the evaluation of OSS needs to be developed. Such an assay will assist the clinician in the assessment of fertility status of both male and female partners. The determination of this OSS value will also theoretically identify the subgroups of responders and nonresponders to any putative antioxidant therapy. Though the therapeutic use of antioxidants appears attractive, clinicians need to be aware of exaggerated claims of antioxidant benefits by various commercial supplements for fertility purposes until proper multicenter clinical trial have been completed.

Oxidative stress and interleukins in seminal plasma during leukocytospermia

OBJECTIVE

To quantify the levels of reactive oxygen species, superoxide dismutase (SOD), and interleukins (IL) 2 and 8 in seminal plasma of infertile patients as well as to examine the possible relationship between oxidative stress and proinflammatory cytokines.

DESIGN

Semen collected from normal fertile donors, infertile men without symptoms of genitourinary (GU) inflammation, and infertile men with symptoms of infection-inflammation of the GU tract was evaluated for the levels of granulocyte elastase, reactive oxygen species, SOD, IL-2, and IL-8. Any correlation between the levels of reactive oxygen species and other parameters in these population was analyzed statistically.

RESULTS

Significantly high levels of granulocyte elastase (18.32 +/- 1.52 U/L), reactive oxygen species (6 x 10(5) cpm), IL-8 (3.7 +/- 0.10 microgram/L), and IL-2 (18.32 +/- 1.47 ng/L) were observed in semen of infertile patients with leukocytospermia compared with the other two groups. In leukocytospermic samples, the activity of SOD was significantly lower (624.89 +/- 41.16 NU/mL) compared with nonleukocytospermic samples (787.85 +/- 24.26 NU/mL) or fertile donors (816.29 +/- 50.16 NU/mL). A significant positive correlation was observed between the levels of reactive oxygen species and IL-8.

CONCLUSIONS

These findings suggest that increased oxidative stress observed during leukocytospermia may modulate the level of proinflammatory cytokines. The increased oxidative stress may be due to a defect in the reactive oxygen species scavenging system.

Sperm-damaging effects of electric current: possible role of free radicals

The generation of reactive oxygen species (ROS) and sperm damage was evaluated in (a) samples obtained during electroejaculation (EE) of men with spinal cord injury and (b) in electrolyzed HAM's F-10 medium subjected to electric current in vitro. Chemiluminescence data showed a significant increase in ROS in the ejaculates (6 x 10(7) photons/ml) collected immediately after EE and in the electrolyzed medium (3 to 7 x 10(6) photons/ml) when compared to the control (4 to 7 x 10(4) photons/ml). Incubation of normal human sperm with the electrolyzed medium resulted in a significant threefold decrease in percent motility and a twofold decrease in percent viability. Sperm subjected to direct electric stimulation in vitro exhibited a significant twofold decrease in percent motility and percent viability. Superoxide dismutase (SOD) activity decreased significantly in sperm subjected to direct electric current in comparison to the control or the sample incubated with electrolyzed medium. These studies indicate that in vitro and in vivo electrical stimulation generate reactive oxygen species and affect SOD activity, which in part are responsible for decreased sperm motion and viability.

Spermicidal activity of an antifungal saponin obtained from the tropical herb Mollugo pentaphylla

The ethyl acetate fraction of Mollugo pentaphylla, a tropical herb, contains an antifungal saponin (mollugogenol-A). We report here the spermicidal effects of this saponin. Washed sperm (> 100 x 10(6) with > 50% motility) from normal volunteers were incubated with varying concentrations (0-300 micrograms/ml) of mollugogenol-A at 30 degrees C. Sperm motility, velocity and viability were assessed at 0, 30, 60 minutes both manually and by using computer assisted semen analysis (CASA). Samples collected at 0 and 60 minutes were evaluated for membrane lipid peroxidation, superoxide dismutase (SOD) activity and transmission electron microscopy. A dose- and time-dependent effect of this saponin on sperm motion and viability was observed. The maximal spermicidal effect (4-5 fold decrease in motility and viability) was observed with 300 micrograms/ml dose of saponin. A three-fold increase in sperm membrane lipid peroxidation with corresponding inhibition of SOD activity were observed after 60 minutes incubation with this spermicidal agent. Transmission electron microscopy of saponin-treated samples revealed significant damage to the sperm membrane in both head and tail regions, and the acrosomal membranes were notably swollen and disrupted. These results indicate that this natural saponin has a potential spermicidal effect besides its known antifungal activity. The likely mechanism of its action involves sperm membrane damage by increased lipid peroxidation.

Time course of hydrogen peroxide induced changes in the lipid peroxidation of human sperm membranes

The present study evaluates the changes in sperm motility due to H202 induced membrane damage. Washed human sperm suspended in HAM's F-10 (20-30 x 10 6/ml) were incubated (37 degrees Celsius) with varying concentrations (0-0.05%) of H202 for up to 15 minutes. Sperm were analyzed for % motility, % viability, the ratio of cholesterol to phospholipids (C/PL), and the degree of lipid peroxidation (LPO). Motility was monitored manually and viability was evaluated by the Eosin Y staining method. Total lipids were extracted with chloroform:methanol (1:2) and used in colorimetric determination of cholesterol and phospholipid contents (mcmol/106 sperm). Lipid peroxidation was measured by the production of malondialdehyde (nmol MDA/108 sperm). The results (mean +or- SEM, n=8) indicate a dose a time-dependent effect on % motility during the 15 minute incubation period. In comparison to control (8 +or- 4%), samples incubated with 0.01% H202 exhibited a 25 +or- 3% decrease in % motility, while a complete loss of motility was observed with 0.05% H202. No significant differences in decrease in sperm viability were observed between control (211 +or- 4) and H202 (0.01%) treated samples (14 +or- 2%). An increase of (54 +or- 5%) in lipid peroxidation was observed with 0.01% H202, as compared with an 18 +or- 1% increase in control samples at 15 minutes. The C/PL ratio increased by 46 +or- 4% at 15 minutes in H202 treated samples while showing a 34.3% decrease in control samples. H202 inhibited sperm motility while increasing membrane LPO and C/PL, without altering sperm viability. It would appear that lipid peroxidation and alteration of sperm membrane composition lead to the loss of sperm motility.

Pre-clinical toxicity of IDPH-791: a new centrally acting muscle relaxant in rats

IDPH-791, a novel centrally acting muscle relaxant, in doses up to 500 mg/kg (po) for 14 days did not result in any appreciable adverse effect on body weight gain, food or water consumption including biochemical and haematologica parameters in rats. Variations observed in the biochemistry and haematology were either comparable to controls or were within normal limits.