Effects of diabetes on nitric oxide synthase and growth factor genes and protein expression in an animal model

Synthesis and secretion of Nerve Growth Factor is regulated by Nitric Oxide in bladder cells in vitro under a hyperglycemic environment

Urine samples of female patients with overactive bladder (OAB) are characterized by low levels of nerve growth factor (NGF) and elevated concentrations of nitric oxide (NO) compared to healthy controls. We therefore examined how NO might regulate NGF synthesis using rat bladder smooth muscle (SMCs) and urothelial (UROs) cells in culture. In UROs, incubation in hyperglycemic conditions to mimic insulin insensitivity present in the OAB cohort increased secretion of NO and concomitantly decreased NGF, except when the NO synthase inhibitor, l-NAME (1 mM) was present. Sodium nitroprusside (SNP) (300 μM, 24 h), a NO generator, decreased NGF levels and decreased cyclic GMP (cGMP) content, a process validated by the cGMP synthase inhibitor ODQ (100 μM). Alternatively, SNP increased mRNA of both NGF and matrix metalloproteinase-9 (MMP-9). MMP-9 knockout of UROs by Crispr-Cas9 potently decreased the effect of SNP on NGF, implying a dependent role of NO on MMP-9. On the other hand, matrix metalloproteinase-7 (MMP-7) activity was increased by SNP, which taken together with increase in NGF mRNA, suggests a compensatory mechanism. In SMCs, hyperglycemic conditions had the same effect on extracellular content of NO and NGF than in UROs. SNP also decreased NGF secretion but increased cGMP content. Stable permeable analogs of cGMP 8-(4-Chlorophenylthio)-cGMP (1 mM) and N2,2'-O-Dibutyryl-cGMP (3 mM) inhibited NGF release. NGF and MMP-9 mRNA expression was unchanged by SNP. Deletion of MMP-9 in SMCs by Crispr-Cas9 did not alter the effect of SNP. Finally, SNP decreased MMP-7 activity, diminishing the conversion of proNGF to NGF. These results demonstrate that enhanced NO secretion triggered by high glucose decreases NGF secretion through pathways unique for each cell type that involve cGMP and proteases MMP-7 and MMP-9. These results might help to explain our observations from the urine from patients with OAB associated with metabolic syndrome.

Role of adipose-derived stem cells in healing surgically induced trauma of the rat's tunica albuginea

Background

Injection of adipose-derived stem cells (ADSCs) into the injured tunica albuginea (TA) may prevent fibrosis, restore the balance between pro- and antifibrotic pathways, and potentially mitigate erectile dysfunction caused by abnormal TA healing.

Aim

To assess the potential role of ADSC injection on structural, ultrastructural, functional, and molecular changes in surgically induced trauma of the rat's TA.

Methods

Forty adult male albino Wistar rats were divided into 5 groups of 8 rats each: group 1, sham; group 2, injury to TA without treatment; group 3, injury to TA and suture repair; group 4, injury to TA and injection of ADSCs without suture repair; group 5, injury to TA followed by injection of ADSCs and suture repair.

Outcomes

After 6 weeks, all groups were subjected to functional, histologic, and ultrastructural examination and molecular expression of healing growth factors.

Results

The intracavernous pressure (ICP; mean ± SD) was 114 ± 2, 32 ± 2, 65 ± 2, 68 ± 2, and 111 ± 2 mm Hg in groups 1 to 5, respectively. There were significant differences in ICP between each of groups 3 to 5 and group 2 (P < .05), and groups 3 and 4 each had significant differences with group 1 (P < .05). No significant difference in ICP occurred between groups 3 and 4 (P > .05). There were significant histologic and ultrastructural alterations in tunical tissues from group 2; however, these changes were markedly less in group 5 in terms of lower levels of fibrotic changes, elastosis, and superior overall neuroendothelial expression. Groups 3 and 4 showed improved structural and ultrastructural parameters when compared with group 2. Group 5 demonstrated lower levels of transforming growth factor β1 and basic fibroblast growth factor expression.

Clinical Implications

This experimental model may encourage administration of ADSCs to prevent the deleterious effects of trauma to the TA.

Strengths and Limitations

Injecting ADSCs can improve the healing process and erectile dysfunction in a rat model following TA injury, and combining ADSC injection with surgical suturing resulted in superior outcomes. The main limitation was the absence of long-term ICP measurements and a longer follow-up period that may provide further insight into the chronic phase of the healing process.

Conclusion

ADSC injection may prevent structural, ultrastructural, functional, and molecular alterations in surgically induced trauma of the rat's TA and enhance the effect of tunical suturing after trauma.

Nitrergic perivascular innervation in health and diseases: Focus on vascular tone regulation

For a long time, the vascular tone was considered to be regulated exclusively by tonic innervation of vasoconstrictor adrenergic nerves. However, accumulating experimental evidence has revealed the existence of nerves mediating vasodilatation, including perivascular nitrergic nerves (PNN), in a wide variety of mammalian species. Functioning of nitrergic vasodilator nerves is evidenced in several territories, including cerebral, mesenteric, pulmonary, renal, penile, uterine and cutaneous arteries. Nitric oxide (NO) is the main neurogenic vasodilator in cerebral arteries and acts as a counter-regulatory mechanism for adrenergic vasoconstriction in other vascular territories. In the penis, NO relaxes the vascular and cavernous smooth muscles leading to penile erection. Furthermore, when interacting with other perivascular nerves, NO can act as a neuromodulator. PNN dysfunction is involved in the genesis and maintenance of vascular disorders associated with arterial and portal hypertension, diabetes, ageing, obesity, cirrhosis and hormonal changes. For example defective nitrergic function contributes to enhanced sympathetic neurotransmission, vasoconstriction and blood pressure in some animal models of hypertension. In diabetic animals and humans, dysfunctional nitrergic neurotransmission in the corpus cavernosum is associated with erectile dysfunction. However, in some vascular beds of hypertensive and diabetic animals, an increased PNN function has been described as a compensatory mechanism to the increased vascular resistance. The present review summarizes current understanding on the role of PNN in control of vascular tone, its alterations under different conditions and the associated mechanisms. The knowledge of these changes can serve to better understand the mechanisms involved in these disorders and help in planning new treatments.

Early administration of phosphodiesterase 5 inhibitors after induction of diabetes in a rat model may prevent erectile dysfunction

BACKGROUND

The possible role of phosphodiesterase 5 inhibitors (PDE5Is) in prevention of negative effect of diabetes mellitus (DM) on erectile function is not well settled.

OBJECTIVES

To investigate the effect of early administration of vardenafil on erectile function, cavernosal structure, and genes expression in a rat model of DM.

MATERIALS AND METHODS

This experimental study was carried out at Suez Canal University's research laboratory. This study was conducted on a total of 60 adult male Albino Wistar rats, aged 60-80 days and weighing an average of 200 g. Rats were equally divided into six groups of 10 rats each: Group I (sham); Group II (DM with no treatment); Groups III, IV, V, and VI received vardenafil started at day 1, week 4, week 8, and week 12 after induction of DM, respectively. Functional study assessment of all groups was performed before euthanization, and then tissues were harvested for histopathological, ultrastructural, and molecular examinations.

RESULTS

There was a significant difference of intracavernosal pressure between early (94 ± 2.18) and late (40.5 ± 1.94) treatment groups (p = 0.011). Histopathological and ultrastructural changes of DM with no treatment and late treatment groups showed distorted cavernous architecture and extensive fibrosis. There was significant difference of smooth muscle to collagen ratio between early and late treatment groups (p = 0.035). There was significant upregulation of nNOS(p = 0.021) and iNOS (p = 0.047) in early vs. late treatment group. The difference was insignificant in eNOS (p = 0.386) or TGF-β1(p = 0.149).

DISCUSSION AND CONCLUSION

Early treated rats with vardenafil had preserved erection and normal cavernosal structure, ultrastructure and gene expression of iNOS, nNOS, eNOS, and TGF-β1. Quantification of gene expression would improve our knowledge regarding cytokines expression and molecular background of DM-associated ED. Clinical application of this result may encourage early administration of PDE5I to prevent deleterious effects of DM on erectile function in newly diagnosed DM patients with probable uncontrolled blood glucose.

Pharmacotherapy for erectile dysfunction in diabetic males

INTRODUCTION

Numerous studies have highlighted the intimate association between erectile dysfunction (ED) and diabetes mellitus (DM). However, the true pathogenesis of ED among diabetic men has not yet been fully discovered. The treatment of ED in diabetic patients remains an interesting area of research. The last two decades have witnessed phenomenal advances in the management of ED with the efficacy of pharmacotherapy for ED in diabetic patients encouraging, especially with introduction of innovative conservative tools for treatment.

AREAS COVERED

The aim of this review is to discuss the currently available information on ED pharmacotherapy in diabetic males and provide an expert perspective on the current treatment strategies.

EXPERT OPINION

Conservative treatment remains the initial step for the treatment of ED in diabetic patients. This kind of therapy consists of different modalities including: oral treatments, intracavernosal pharmacotherapy, and evolving modalities such as soluble guanylate cyclase activators, stem cells (SCs), and alternative treatments such as herbal treatment and transdermal/topical pharmacotherapy. However, it should be noted that the currently available pharmacotherapy is still far from ideal. One hopes to witness new drugs and technologies that may revolutionize ED treatment in the future, especially in such complex cases as DM.

Relationship between Response to PDE5 Inhibitors and Penile Duplex Doppler Ultrasound in Erectile Dysfunction

The relationship between the results of penile duplex Doppler ultrasound (PDDU) and response to vardenafil was investigated in patients diagnosed with erectile dysfunction (ED). Data from 148 patients with ED were analyzed retrospectively. Patients who did not respond to therapy were classified in to Group I (n = 32), those who responded partially were classified into Group II (n = 40), and complete responders were classified into Group III (n = 76). Age, comorbidities, and vascular and penile pathologies were compared among the three groups. While diabetes mellitus (DM) and dyslipidemia positivity adversely affected the response to treatment, the presence of hypertension (HT), Peyronie’s disease and priapism increased the therapeutic response to the treatment (p < 0.05). Arterial insufficiency was present in 20 (30.3%), 25 (37.9%) and 21 (31.8%) of the patients in Group I, Group II and Group III, respectively (p = 0.001). Venous insufficiency was observed in three (14.3%) patients in Group I and in eight (85.7%) patients in Group III (p = 0.001). Arterial/venous insufficiency was seen in 9 (30%), 14 (46.7%) and 7 (23.3%) of the patients in Group I, Group II and Group III, respectively (p = 0.001). The response rate to treatment was highest in normal patients according to PDDU, followed by patients with venous insufficiency. In addition, it was found that DM decreased the response to treatment, whereas the response increased in cases with HT, priapism and Peyronie’s disease.

Differentially expressed microRNAs in the corpus cavernosum from a murine model with type 2 diabetes mellitus-associated erectile dysfunction

To better understand the molecular aetiology of type 2 diabetes mellitus-associated erectile dysfunction (T2DMED) and to provide candidates for further study of its diagnosis and treatment, this study was designed to investigate differentially expressed microRNAs (miRNAs) in the corpus cavernosum (CC) of mice with T2DMED using GeneChip array techniques (Affymetrix miRNA 4.0 Array) and to predict target genes and signalling pathways regulated by these miRNAs based on bioinformatic analysis using TargetScan, the DAIAN web platform and DAVID. In the initial screening, 21 miRNAs appeared distinctly expressed in the T2DMED group (fold change ≥3, p ≤ 0.01). Among them, the differential expression of miR-18a, miR-206, miR-122, and miR-133 were confirmed by qRT-PCR (p < 0.05 and FDR <5 %). According to bioinformatic analysis, the four miRNAs were speculated to play potential roles in the mechanisms of T2DMED via regulating 28 different genes and several pathways, including apoptosis, fibrosis, eNOS/cGMP/PKG, and vascular smooth muscle contraction processes, which mainly focused on influencing the functions of the endothelium and smooth muscle in the CC. IGF-1, as one of the target genes, was verified to decrease in the CCs of T2DMED animals via ELISA and was confirmed as the target of miR-18a or miR-206 via luciferase assay. Finally, these four miRNAs deserve further confirmation as biomarkers of T2DMED in larger studies. Additionally, miR-18a and/or miR-206 may provide new preventive/therapeutic targets for ED management by targeting IGF-1.

Short hairpin rna targeting insulin-like growth fator binding protein-3 restores the bioavailability of insulin-like growth factor-1 in diabetic rats

Purpose

To investigate whether intracavernosal injection of short hairpin RNA for IGFBP-3 could improve erectile function in streptozotocin-induced diabetic rats.

Materials and methods

After 12 weeks of IGFBP-3 short hairpin RNA injection treatment, intracavernous pressure responses to electrical stimulation of cavernous nerves were evaluated. The expression of IGFBP-3 and IGF-1 at mRNA and protein levels were detected by quantitative real-time PCR analysis and Western blot, respectively. The concentration of cavernous cyclic guanosine monophosphate was detected by enzyme-linked immunosorbent assay.

Results

At 12 weeks after intracavernous administration of IGFBP-3 shRNA, the cavernosal pressure was significantly increased in response to the cavernous nerves stimulation compared to the diabetic group (P<0.05). Cavernous IGFBP-3 expression at both mRNA and protein levels was significantly inhibited. At the same time, cavernous IGF-1 expression was significantly increased in the IGFBP-3 shRNA treatment group compared to the diabetic group (P<0.01). Cavernous cyclic guanosine monophosphate concentration was significantly increased in the IGFBP-3 shRNA treatment group compared to the diabetic group (P<0.01).

Conclusions

Gene transfer of IGFBP-3 shRNA could improve erectile function via the restoration of cavernous IGF-1 bioavailability and an increase of cavernous cGMP concentration in the pathogenesis of erectile dysfunction in streptozotocin-induced diabetic rats.

Mesenchymal stem cell-based gene therapy for erectile dysfunction

Despite the overwhelming success of PDE5 inhibitor (PDE5I), the demand for novel pharmacotherapeutic and surgical options for ED continues to rise owing to the increased proportion of elderly individuals in the population, in addition to the growing percentage of ED patients who do not respond to PDE5I. Surgical treatment of ED is associated with many complications, thus warranting the need for nonsurgical therapies. Moreover, none of the above-mentioned treatments essentially corrects, cures or prevents ED. Although gene therapy is a promising option, many challenges and obstacles such as local inflammatory response and random transgene expression, in addition to other safety issues, limit its use at the clinical level. The use of stem cell therapy alone also has many shortcomings. To overcome these inadequacies, many scientists and clinicians are investigating new gene and stem cell therapies.

Low serum insulin-like growth factor-1 in patients with erectile dysfunction

OBJECTIVE

Endothelial dysfunction and microvascular damage play a crurical role in the pathogenesis of erectile dysfunction (ED). Insulin-like growth factor-1 (IGF-1) is one of the growth factors that have a wide range of biologic effects. IGF-1 is an important mediator of cell growth, differentiation and transformation in various tissues. The purpose of the current study was to determine the association between IGF-1 levels and ED.

MATERIALS AND METHODS

All men were evaluated for ED and divided into two groups: 80 patients suffering from ED for > 1 year and 80 subjects without ED were enrolled as a control group in this study. Diagnosis of ED was based on the International Index of Erectile Function Score-5. IGF-1 levels were measured in serum by an automated chemiluminescence immunoassay. The relationship between IGF-1 levels and ED scores in patients was statistically evaluated.

RESULTS

The mean age of patients in ED group was 60.4 ± 11.3 years and 55.4 ± 9.6 in control group. The plasma IGF-1 levels were significantly lower in ED than in control group (96.5 ± 38.3 and 132.5 ± 53.3 ng/ mL, respectively, P < 0.001). The IGF-1 levels were positively correlated with ED score (r = 0.623, P < 0.01).

CONCLUSION

In this study serum IGF-1 levels were found to be associated with endothelial dysfunction that predicts ED. Serum IGF-1 level appears to be a specific predictor of ED, and it might be used in early prediction of ED in male population.

Pharmacogenetics of erectile dysfunction: navigating into uncharted waters

Sildenafil and other PDE-5 inhibitors have revolutionized erectile dysfunction (ED) treatment. However, a significant number of patients do not respond or present adverse reactions to these drugs. While genetic polymorphisms may underlie this phenomenon, very little research has been undertaken in this research field. Most of the current knowledge is based on sildenafil, thus almost completely ignoring other important pharmacological therapies. Currently, the most promising genes with pharmacogenetic implications in ED are related to the nitric oxide and cGMP pathway, although other genes are likely to affect the responsiveness to treatment of ED. Nevertheless, the small number of studies available opens the possibility of further exploring other genes and phenotypes related to ED. This article provides a comprehensive overview of the genes being tested for their pharmacogenetic relevance in the therapy of ED.

Effects of insulin-like growth factor-1 on the relaxation responses of the cavernous smooth muscle from aged rats

OBJECTIVE

The aim of this study was determine whether intracavernosal injection (ICI) of insulin-like growth factor-1 (IGF-1) protein can improve corpus cavernosal smooth muscle relaxation in aging rats.

MATERIALS AND METHODS

Ten young (4-month-old) and 30 old (24-month-old) Sprague-Dawley male rats were enrolled in the study. The old rats were divided into three groups: vehicle-only (n = 10), IGF-1 1 µg/kg (n = 10) and IGF-1 10 µg/kg treatment groups (n = 10). After 4 weeks of single IGF-1 injection treatment, strips of corporal tissue were precontracted with phenylephrine, and dose-response curves were generated to evaluate endothelial-dependent [acetylcholine (ACh)], endothelial-independent [sodium nitroprusside (SNP)] and electrical field stimulation (EFS) vasoreactivity. The changes in percentage of cavernosal smooth muscle and the concentration of nitric oxide (NO) in penile tissue were also evaluated.

RESULTS

After IGF-1 treatment, the vasoreactivity was significantly improved in both the 1 µg/kg and the 10 µg/kg treatment groups compared with the vehicle-only group at 4 weeks in response to ACh, SNP and EFS (all p < 0.05). The percentage of cavernosal smooth muscle was increased in the IGF-1 treatment groups. The NO concentrations were increased after IGF-1 treatment.

CONCLUSIONS

These data demonstrate that ICI of IGF-1 can improve vasoreactivity via endothelium-dependent and endothelial-independent mechanisms in the corpus cavernosum of the aging rat.

nNOS polymorphisms are associated with responsiveness to sildenafil in clinical and postoperative erectile dysfunction

AIM

Sildenafil potentiates the nitric oxide (NO) signaling pathway. Since neuronal NOS is very important in the penis, we assessed whether NOS1 polymorphisms are associated with altered responsiveness to sildenafil in erectile dysfunction (ED).

MATERIALS & METHODS

Patients (n = 137) were divided as clinical ED or postoperative ED. They were subdivided as good responders or poor responders to sildenafil, and genotypes for rs41279104 and rs2682826 NOS1 polymorphisms were determined.

RESULTS

We found that the rs41279104 CT genotype was associated with good responders in postoperative ED patients, while rs2682826 CT genotype was associated with good responders in postoperative ED, and the TT genotype associated with good responders in both groups. Finally, the CT haplotype was associated with good responders in postoperative ED.

CONCLUSION

NOS1 polymorphisms are associated with responsiveness to sildenafil in ED. Original submitted 20 November 2013; Revision submitted 31 January 2014.

Hydroxyl fasudil, an inhibitor of Rho signaling, improves erectile function in diabetic rats: a role for neuronal ROCK

INTRODUCTION

The pathogenesis of diabetic erectile dysfunction (ED) includes neuropathy, but the molecular basis for neurogenic ED is incompletely understood. The RhoA/ROCK pathway has been implicated in diabetic neuropathy and in ED, but its role in diabetic neurogenic ED is not known.

AIMS

The aim of this study was to determine whether hydroxyl fasudil, a ROCK inhibitor, affects diabetic neuropathy-related ED.

METHODS

Type 1 diabetes mellitus was induced in male rats by streptozotocin (75 mg/kg, intraperitoneally). After 8 weeks, diabetic rats were administered hydroxyl fasudil, a selective ROCK inhibitor (10 mg/kg/day, intraperitoneally) or vehicle, for 4 weeks. Age-matched control, nondiabetic, rats were treated intraperitoneally for 4 weeks with saline. At week 12, after a 2 day washout, neuro-stimulated erectile function was evaluated. Major pelvic ganglia (MPG) were collected for Western blot analysis of RhoA, ROCK-1, ROCK-2, phospho (P)-AKT (Ser(473) ), and P-phosphatase and tensin homolog (P-PTEN) (Ser(380) /Thr(382/383) ).

MAIN OUTCOME MEASURES

Effect of ROCK inhibitor hydroxyl fasudil on erectile function and ROCK/P-AKT/P-PTEN pathway in the MPG of diabetic rats.

RESULTS

Erectile response was significantly (P < 0.05) reduced in diabetic rats compared with nondiabetic rats and was preserved (P < 0.05) in diabetic rats treated with hydroxyl fasudil. In diabetic rats, RhoA and ROCK-2 protein expressions in MPG were increased (P < 0.05) and remained increased in hydroxyl fasudil-treated rats. P-AKT (Ser(473) ) expression was decreased (P < 0.05), whereas P-PTEN (Ser(380) /Thr(382/383) ) expression was increased (P < 0.05) in MPG of diabetic rats compared with nondiabetic rats, and both were reversed (P < 0.05) in diabetic rats treated with hydroxyl fasudil.

CONCLUSION

Improved erectile function and restored P-AKT and P-PTEN in the MPG with hydroxyl fasudil treatment suggest the role of Rho signaling via PTEN/AKT pathway in neurogenic diabetic ED.

Long-term high-fat consumption leads to downregulation of Akt phosphorylation of eNOS at Ser1177 and upregulation of Sirtuin-1 expression in rat cavernous tissue

Long-term consumption of high-fat diets negatively interferes with metabolic status and promotes endothelial dysfunction and inflammation. In the cavernous tissue, these outcomes become conspicuous in the elderly and strongly affect penile erection, a vascular process highly dependent on local nitric oxide bioavailability. Although epidemiological data links erectile dysfunction to nutritional patterns, the underlying molecular mechanisms remain unclear. Therefore, we investigated the effects of long-term high-fat diet on endothelial nitric oxide synthase (eNOS)-Sirtuin-1 axis and Akt/eNOS phosphorylation in the cavernous tissue of Sprague-Dawley rats, and compared with energy-restricted animals. We demonstrated that high-fat diet intake led to a noteworthy decrease in eNOS phosphorylation at Ser1177 residue through the Akt pathway, which seems to be compensated by upregulation of phosphorylation at Ser615, but without an increment in nitric oxide production. These results are accompanied by an increase of systemic inflammatory markers and upregulation of the inducible NOS and of the deacetylase Sirtuin-1 in the cavernous tissue to levels apparently detrimental to cells and to metabolic homeostasis. Conversely, in long-term energy-restricted animals, the rate of phosphorylation of eNOS at Ser1177 diminished, but the activation of the enzyme increased through phosphorylation of eNOS at Ser615, resulting in an enhancement in nitric oxide bioavailability. Taken together, our results demonstrate that long-term nutritional conditions override the influence of age on the eNOS expression and activation in rat cavernous tissue.

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.

Differential expression of nerve injury-induced protein 1 (ninjurin 1) in in vivo and in vitro models for diabetic erectile dysfunction

Purpose

Endothelial dysfunction and peripheral neuropathy are important mechanisms responsible for diabetes-induced erectile dysfunction (ED). Nerve injury-induced protein 1 (Ninjurin 1) is known to be related to neuroinflammatory processes and is also reported to induce vascular regression during the developmental period. In the present study, we determined the differential expression of Ninjurin 1 in penile tissue of streptozotocin (STZ)-induced diabetic mice with ED.

Materials and Methods

Diabetes was induced in 8-week-old C57BL/6J mice by intraperitoneal injections of STZ (50 mg/kg for 5 days). Eight weeks later, erectile function was measured by electrical stimulation of the cavernous nerve (n=6 per group). The penis was then harvested for immunohistochemical analysis and Western blot analysis for Ninjurin 1 (n=4 per group). We also determined Ninjurin 1 expression in primary cultured mouse cavernous endothelial cells (MCECs) incubated under the following conditions: normal glucose condition (5 mM), high-glucose condition (30 mM), and high-glucose condition (30 mM)+insulin (1 nM).

Results

The expression of Ninjurin 1 protein was significantly higher in both cavernous endothelial cells and the dorsal nerve bundle of diabetic mice than in those of controls. In the in vitro study in MCECs, Ninjurin 1 expression was also significantly increased by the high-glucose condition and was returned to baseline levels by treatment with insulin.

Conclusions

Regarding the role of Ninjurin 1 in neuropathy and vascular regression, it would be interesting to examine the effects of inhibition of Ninjurin 1 on erectile function in animal models of ED with a vascular or neurogenic cause.

Gene therapy as future treatment of erectile dysfunction

IMPORTANCE OF THE FIELD

Erectile dysfunction (ED) is a major men's health problem. Although the high success rate of treating ED by phosphodiesterase 5 (PDE5) inhibitors has been reported, there are a significant number of ED patients who do not respond to currently available treatment modalities.

AREAS COVERED IN THIS REVIEW

To elucidate the current status of gene therapy applications for ED, gene therapy approaches for ED treatment are reviewed.

WHAT THE READER WILL GAIN

Gene therapy strategies that can enhance nitric oxide (NO) production or NO-mediated signaling pathways, growth factor-mediated nerve regeneration or K(+) channel activity in the smooth muscle could be promising approaches for the treatment of ED. Although the majority of gene therapy studies are still in the preclinical phase, the first clinical trial using non-viral gene transfer of Ca(2+)-activated, large-conductance K(+) channels into the corpus cavernosum of ED patients showed positive results.

TAKE HOME MESSAGE

Gene therapy represents an exciting future treatment option for ED, especially for people with severe ED unresponsive to current first-line therapies such as PDE5 inhibitors although the long-term safety of both viral and non-viral gene therapies should be established.

Farnesoid X receptor activation improves erectile dysfunction in models of metabolic syndrome and diabetes

The metabolic syndrome (MetS) is an insulin-resistant state characterized by a cluster of cardiovascular risk factors, including abdominal obesity, hyperglycemia, elevated blood pressure and combined dyslipidemia. In this review, we discuss the potential of farnesoid X receptor (FXR) agonists in the treatment of erectile dysfunction (ED), a multifactorial disorder often comorbid with MetS. FXR not only regulates lipid and glucose homeostasis but also influences endothelial function and atherosclerosis, suggesting a regulatory role for this hormone nuclear receptor in the cardiovascular complications associated with the MetS, including ED. MetS induces ED via several mechanisms, and in particular through endothelial dysfunction in penile vessels. In a high-fat diet rabbit model of MetS, a 3-month treatment with the potent and selective FXR agonist INT-747 restores endothelium-dependent relaxation in isolated cavernous tissue, normalizing responsiveness to acetylcholine and to electrical field stimulation. Accordingly, eNOS expression in the penis is greatly up-regulated by INT-747 treatment. Experiments in a rat model of chemically-induced type 1 diabetes further demonstrate that INT-747 treatment preserves erectile function induced by electrical stimulation of the cavernous nerve. These results add a new facet to the pleiotropic activities mediated by FXR, and reveal novel beneficial effects of FXR activation with potential clinical relevance. This article is part of a Special Issue entitled: Translating nuclear receptors from health to disease.

Change of erectile function and responsiveness to phosphodiesterase type 5 inhibitors at different stages of streptozotocin-induced diabetes in rats

INTRODUCTION

It has been suggested that risk of erectile dysfunction (ED) increases with duration of diabetes and phosphodiesterase type 5 inhibitors (PDE5I) are not as effective in treatment of diabetes-associated ED. However, few studies have investigated time-dependent change in erectile function during the course of diabetes.

AIM

To investigate time-dependent change in erectile function and responsiveness to PDE5I in streptozotocin-induced diabetic rats and to understand the pathophysiology of diabetic ED.

MAIN OUTCOME MEASURES

At 6, 8, 10, 12, and 14 weeks after diabetic induction, erectile function was assessed by cavernous nerve stimulation before and after administration of DA-8159, a novel PDE5I. Penile tissue was assessed for apoptosis with immunohistochemistry. Protein expression of Rho-kinase 2 (ROCK2), myosin phosphatase targeting subunit 1 (MYPT1), and endothelial nitric oxide synthase (eNOS) was evaluated by Western blot.

METHODS

Streptozotocin was injected into 50 8-week-old male Sprague-Dawley rats, which were then classified into five diabetic groups according to the observation period.

RESULTS

Diabetic rats maintained normal erectile responses until 6 weeks of diabetes. Following 8 weeks, the rats showed lower erectile responses at higher frequencies of nerve stimulation, which were normalized to control by administration of DA-8159. In contrast, erectile responses were significantly decreased in 10-week diabetic rats, and administration of DA-8159 resulted in partial recovery of normal responses. At more than 12 weeks, rats demonstrated severe deterioration of erectile function, which did not fully respond to PDE5I. Corporal apoptosis was significantly increased after 10 weeks. Upregulation of ROCK2 was found at 6 weeks, and was followed by an increase of MYPT1 phosphorylation. Phosphorylation of eNOS showed marked suppression at 6 weeks and remained lower during the experimental period.

CONCLUSIONS

Impairment of erectile function was followed by decreased responsiveness to PDE5I during the course of diabetes. The RhoA/ROCK pathway played an important role in diabetes-associated ED.

Farnesoid X receptor activation improves erectile function in animal models of metabolic syndrome and diabetes

INTRODUCTION

The farnesoid X receptor (FXR) is critically involved in the regulation of the hepato-biliary system. Recent data suggest a role for FXR in modulating other metabolic pathways and vascular function.

AIM

To investigate whether long-term administration of the selective FXR agonist INT-747 ameliorates erectile function, we tested it in two animal models of metabolic derangements: a rabbit model of high-fat diet (HFD)-induced metabolic syndrome (MetS) and a rat model of streptozotocin (STZ)-induced type 1 diabetes.

METHODS

HFD rabbit or STZ rats with or without chronic INT-747 dosing (10 mg/kg/day for 12 weeks). INT-747 addition to rabbit penile smooth muscle cells (rpSMCs).

MAIN OUTCOME MEASURE

Effects of INT-747 on metabolic features and erectile function in animal models and clarification of mechanism of action in isolated cells.

RESULTS

INT-747 dosing normalized visceral adiposity and glucose intolerance in HFD rabbits. INT-747 increased penile FXR expression and partially restored endothelial nitric oxide synthase and dimethylarginine dimethylaminohydrolase 1 expression as well as impaired nitric oxide (NO)-dependent relaxation (improved responsiveness to acetylcholine and electrical field stimulation). INT-747 was also effective in regulating NO downstream events, as shown by increased sodium nitroprusside-induced relaxation. Because phosphodiesterase type 5 and protein kinase G (PKG) were unaltered by INT-747, we analyzed the calcium-sensitizing RhoA/ROCK pathway. HFD increased, and INT-747 normalized, RhoA membrane translocation/activation. RhoA/ROCK signaling inhibition by INT-747 was confirmed in rpSMCs by confocal microscopy, MYPT1-phosphorylation, cytoskeleton remodeling, cell migration, and smooth muscle-related genes expression. In STZ rats, FXR penile expression was not altered but was significantly upregulated by INT-747 dosing. In this model, INT-747 improved penile erection induced by electrical stimulation of cavernous nerve and hypersensitivity to intracavernous injection of a ROCK-inhibitor, Y-27632, without improving hyperglycemia.

CONCLUSION

In HFD rabbits, INT-747 dosing improved glucose sensitivity and MetS-associated erectile dysfunction, via upregulation of NO transmission and inhibition of RhoA/ROCK pathway. In STZ rats, INT-747 restored in vivo penile erection and sensitivity to ROCK inhibition, independently of effects on glycemia.

A once-daily dose of tadalafil for erectile dysfunction: compliance and efficacy

Selective phosphodiesterase type 5 inhibitors (PDE5Is) have revolutionized the treatment of erectile dysfunction (ED) in men. As an on-demand treatment, PDE5Is have excellent efficacy and safety in the treatment of ED due to a broad spectrum of etiologies. Nevertheless, these drugs do have side-effect profiles that are troublesome to some patients, eg, headache, dyspepsia, myalgia, etc. Furthermore, many patients and their partners dislike the necessity of on-demand treatment for ED, citing a desire for greater spontaneity with sexual interactions. In 2008, approximately 10 years after the release of the first commercially available PDE5I, a paradigm shift in the management of ED occurred with the approval of once-daily dose of tadalafil by the US Food and Drug Administration for the management of ED. The prolonged half-life of tadalafil lends itself well to this dosing regimen and conveys the advantage of separating medication from sexual interactions; lower dose therapy also carries the theoretical benefit of lower incidence of side effects. In this study, we review the current state of the art with respect to this new management strategy for ED, highlighting published reports of the efficacy and tolerability of the daily dose tadalafil regimen.

Treatment of type 1 diabetes with adipose tissue-derived stem cells expressing pancreatic duodenal homeobox 1

Due to the limited supply of donor pancreas, it is imperative that we identify alternative cell sources that can be used to treat diabetes mellitus (DM). Multipotent adipose tissue-derived stem cells (ADSC) can be abundantly and safely isolated for autologous transplantation and therefore are an ideal candidate. Here, we report the derivation of insulin-producing cells from human or rat ADSC by transduction with the pancreatic duodenal homeobox 1 (Pdx1) gene. RT-PCR analyses showed that native ADSC expressed insulin, glucagon, and NeuroD genes that were up-regulated following Pdx1 transduction. ELISA analyses showed that the transduced cells secreted increasing amount of insulin in response to increasing concentration of glucose. Transplantation of these cells under the renal capsule of streptozotocin-induced diabetic rats resulted in lowered blood glucose, higher glucose tolerance, smoother fur, and less cataract. Histological examination showed that the transplanted cells formed tissue-like structures and expressed insulin. Thus, ADSC-expressing Pdx1 appear to be suitable for treatment of DM.

Emerging gene and stem cell therapies for the treatment of erectile dysfunction

Erectile dysfunction is a prevalent condition that leads to significant morbidity and distress, not just for affected men but also for their partners. Very few currently available treatments ameliorate the underlying causes of the disorder and 'cure' the disease state. Much recent effort has been focused on the development of gene and cell-based approaches to rectify the molecular and tissue defects responsible for ED. Gene therapy has been investigated in animal models as a means to restore normal function to the penis; at this time, however, only one human trial has been published in the peer-reviewed literature. Recent gene therapy studies have focused on the modulation of enzymes associated with the NOS/cGMP pathway, and supplementation of trophic factors, peptides and potassium channels. Stem cell therapy has been a topic of interest in more recent years but there are currently very few published reports in animal models and none in human men. Although stem cell therapy offers the potential for restoration of functional tissues, legitimate concerns remain regarding the long-term fate of stem cells. The long-term safety of both gene and stem cell therapy must be thoroughly investigated before large-scale human studies can be considered.

Functional and morphologic characterizations of the diabetic mouse corpus cavernosum: comparison of a multiple low-dose and a single high-dose streptozotocin protocols

INTRODUCTION

With the advent of genetically modified mice, it seems particularly advantageous to develop a mouse model of diabetic erectile dysfunction.

AIM

To establish a mouse model of type I diabetes by implementation of either multiple low-dose streptozotocin (STZ) protocol or single high-dose STZ protocol and to evaluate morphologic alterations in the cavernous tissue and subsequent derangements in penile hemodynamics in vivo.

METHODS

Eight-week-old C57BL/6J mice were divided into three groups: a control group, a group administered the multiple low-dose STZ protocol (50 mg/kg x 5 days), and a group administered the single high-dose STZ protocol (200 mg/kg).

MAIN OUTCOME MEASURES

After 8 weeks, erectile function was measured by electrical stimulation of the cavernous nerve. The penis was then harvested and stained with hydroethidine (in situ analysis of superoxide anion), TUNEL, or antibodies to nitrotyrosine (marker of peroxynitrite formation), PECAM-1, smooth muscle alpha-actin, and phospho-eNOS. Penis specimens from a separate group of animals were used for phospho-eNOS and eNOS western blot or cGMP determination.

RESULTS

Erectile function was significantly less in diabetic groups than in control group. The generation of superoxide anion and nitrotyrosine and the number of apoptotic cells in both cavernous endothelial and smooth muscle cells were significantly higher in diabetic groups than in control group. Cavernous tissue phospho-eNOS and cGMP expression and the number of endothelial and smooth muscle cells were lower in diabetic groups than in control group. Both diabetic models resulted in similar structural and functional derangements in the corpus cavernosum; however, the mortality rate was higher in mice receiving single high-dose of STZ than in those receiving multiple low-doses.

CONCLUSION

The mouse model of type I diabetes is useful and technically feasible for the study of the pathophysiologic mechanisms involved in diabetic erectile dysfunction.

eNOS, metabolic syndrome and cardiovascular disease

Large epidemiologic studies have established that diabetes, hyperlipidemia and obesity all increase the risk for cardiovascular disease. However, the precise mechanisms by which these metabolic disorders increase the propensity to develop atherosclerosis are not known. Recently, the concept of the metabolic syndrome - a constellation of conditions including obesity, hypertension, hyperlipidemia and insulin resistance - has received much attention. Studies on the metabolic syndrome might enable a better understanding of the underlying biological mechanisms that lead to cardiovascular disease. This review focuses on endothelial nitric oxide synthase and summarizes evidence that a reduction in the bioavailability of endothelium-derived nitric oxide serves as a key link between metabolic disorders and cardiovascular risk.

Increased expression of the nitric oxide synthase gene and protein in corpus cavernosum by repeated dosing of udenafil in a rat model of chemical diabetogenesis

Erectile dysfunction (ED) is a major complication of diabetes mellitus (DM). This study investigates the relationship between ED and the downregulation of constitutive nitric oxide synthase (cNOS) in the corpus cavernosum (CC) of diabetic rats. It also examines the effects of udenafil, a phosphodiesterase type 5 (PDE5) inhibitor, on ED and cNOS expression levels. After 16 weeks of daily oral treatment with udenafil in diabetic rats, the intracavernous pressure/mean arterial pressure (ICP/MAP) ratio was recorded to measure erectile function, and cNOS expression was measured using reverse transcriptase (RT)-PCR and immunoblots. Although the ICP/MAP ratio and the expression levels of endothelial NOS (eNOS) and neuronal NOS (nNOS) in the CC were markedly decreased in diabetic rats, long-term udenafil treatment improved the erectile function and increased cNOS expression compared with diabetic controls. These findings suggest that ED in DM is closely related to decreased cNOS expression in the CC and that udenafil has the ability to compensate for this pathological change by modulating cNOS expression. Udenafil also has an inhibitory role in cGMP (cyclic guanosine monophosphate) degradation.

Estradiol ameliorates diabetes-induced changes in vaginal structure of db/db mouse model

INTRODUCTION

Women with diabetes experience diminished genital arousal, reduced vaginal lubrication, vaginal atrophy, dyspareunia, and increased infections. Limited studies are available investigating the effects of diabetic complications on the vagina.

AIMS

The goals of this study were to investigate type 2 diabetes-induced changes in vaginal structure, and to determine if estradiol treatment ameliorates these changes.

METHODS

Eight-week-old female diabetic (db/db) mice (strain BKS*Cg-m+/+Lepr(db)/J) and age-matched control normoglycemic female littermates were used to investigate the effects of type 2 diabetes on vaginal tissue structural integrity. Diabetic animals were divided into two subgroups: diabetic treated with vehicle only and diabetic treated with pellets containing estradiol. At 16 weeks, the animals were sacrificed, and the vaginal tissues were excised and analyzed by histological and immunohistochemical methods to assess diabetes-induced changes in vaginal tissue and the extent by which these parameters are restored by estradiol treatment.

MAIN OUTCOME MEASURES

The effects of type 2 diabetes and estradiol supplementation were investigated on vaginal histoarchitecture.

RESULTS

Diabetic animals exhibited high blood glucose levels (>600 mg/dL), increased body weight (43.0 +/- 6.0 g vs. 24.4 +/- 2.0 g), and reduced plasma estradiol levels (65.5 +/- 6.6 pg/mL vs. 80.77 +/- 13.2 pg/mL) when compared to control animals. Diabetes resulted in significant thinning of the epithelium (P <or= 0.05), marked decrease in the muscularis area (P </= 0.05), distinct truncation of elastic fibers, and significant reduction of the nitrergic immunoreactive nerve fibers (P <or= 0.05). Treatment of diabetic animals with estradiol restored epithelial thickness (P <or= 0.05), muscularis area (P <or= 0.05), and elastic fiber distribution, and partially restored the density of nitrergic nerve fibers.

CONCLUSIONS

The data in this study demonstrate that type 2 diabetes disrupts vaginal structural integrity and that estradiol supplementation ameliorates the diabetes-induced vaginal pathology.

Inducible nitric oxide synthase gene deficiency counteracts multiple manifestations of peripheral neuropathy in a streptozotocin-induced mouse model of diabetes

AIMS/HYPOTHESIS

Evidence for the importance of peroxynitrite, a product of superoxide anion radical reaction with nitric oxide, in peripheral diabetic neuropathy is emerging. The role of specific nitric oxide synthase isoforms in diabetes-associated nitrosative stress and nerve fibre dysfunction and degeneration remains unknown. This study evaluated the contribution of inducible nitric oxide synthase (iNOS) to peroxynitrite injury to peripheral nerve and dorsal root ganglia and development of peripheral diabetic neuropathy.

METHODS

Control mice and mice with iNos (also known as Nos2) gene deficiency (iNos ( -/- )) were made diabetic with streptozotocin, and maintained for 6 weeks. Peroxynitrite injury was assessed by nitrotyrosine and poly(ADP-ribose) accumulation (immunohistochemistry). Thermal algesia was evaluated by paw withdrawal, tail-flick and hot plate tests, mechanical algesia by the Randall-Selitto test, and tactile allodynia by a von Frey filament test.

RESULTS

Diabetic wild-type mice displayed peroxynitrite injury in peripheral nerve and dorsal root ganglion neurons. They also developed motor and sensory nerve conduction velocity deficits, thermal and mechanical hypoalgesia, tactile allodynia and approximately 36% loss of intraepidermal nerve fibres. Diabetic iNos ( -/- ) mice did not display nitrotyrosine and poly(ADP-ribose) accumulation in peripheral nerve, but were not protected from nitrosative stress in dorsal root ganglia. Despite this latter circumstance, diabetic iNos ( -/- ) mice preserved normal nerve conduction velocities. Small-fibre sensory neuropathy was also less severe in diabetic iNos ( -/- ) than in wild-type mice.

CONCLUSIONS/INTERPRETATION

iNOS plays a key role in peroxynitrite injury to peripheral nerve, and functional and structural changes of diabetic neuropathy. Nitrosative stress in axons and Schwann cells, rather than dorsal root ganglion neurons, underlies peripheral nerve dysfunction and degeneration.

Insulin-like growth factor-1 restores erectile function in aged rats: modulation the integrity of smooth muscle and nitric oxide-cyclic guanosine monophosphate signaling activity

INTRODUCTION

Insulin-like growth factor-1 (IGF-1) is one of the growth factors that have a wide range of biologic effects. We have confirmed that gene transfer of IGF-1 to the penis could improve erectile capacity. However, there are some limitations in gene therapies, such as toxicity or a risk of insertional mutagenesis. Protein treatment may be another choice for decreasing these risks.

AIM

To investigate whether intracavernosal injection of IGF-1 protein can restore erectile function in the aging rat.

MAIN OUTCOME MEASURES

Erectile responses, morphological changes, and nitric oxide-cyclic guanosine monophosphate (NO-cGMP) signaling pathways-related marker were determined.

METHODS

Ten young (4 months) and 30 old (24 months) Sprague-Dawley male rats were enrolled in this study. The old rats were divided into three groups: vehicle-only (N = 10), IGF-1 1 microg/kg (N = 10) and IGF-1 10 microg/kg treatment group (N = 10). After 4 and 8 weeks of single IGF-1 injection treatment, intracavernous pressure (ICP) responses with electrical stimulation to the cavernous nerve were evaluated. The percent of smooth muscle in corpus cavernosum tissue, the expression of mRNA and protein of endothelial nitric oxide synthase (eNOS) were also evaluated. The activity of nitric oxide synthase (NOS) and concentration of guanosine 3',5'-cyclic-monophosphate (cGMP) that act upon the major NO-cGMP signaling pathways in penile tissue were also analyzed.

RESULTS

After IGF-1 treatment, the ICP responses was significantly increased as the young control group in both the IGF-1 1 microg/kg and the IGF-1 10 microg/kg group compared with the vehicle-only group at 4 and 8 weeks (P < 0.05). Masson's trichrom staining showed the percentage of cavernosal smooth muscle was increased in IGF-1 treatment group. IGF-1 increased e-NOS expression. NOS activities and cGMP concentrations were also significantly increased in IGF-1 treatment rats.

CONCLUSIONS

IGF-1 improved erectile function in aged rats via restoration the integrity of smooth muscle of corpus cavernosum and modulation of NO-cGMP pathways.

Localization of increased insulin-like growth factor binding protein-3 in diabetic rat penis: implications for erectile dysfunction

OBJECTIVES

Diabetes-induced erectile dysfunction (ED) is assumed to result from neurovascular abnormalities. However, the entire picture of the molecular mechanisms underlying ED has not yet been clarified. To elucidate the possible elements involved in ED in diabetes mellitus, we performed broad-scale gene expression profiling using cDNA array in the penis of streptozotocin-induced diabetic rats.

METHODS

Northern blot analysis was performed to examine the course of the mRNA expression encoded by the identified gene. Immunohistochemistry was performed to identify the cellular localization of the encoded protein.

RESULTS

Of the genes investigated, the expression level of insulin-like growth factor binding protein 3 (IGFBP-3) was greatly increased at 12 weeks after streptozotocin treatment. The levels of ErbB3 epidermal growth factor receptor-related proto-oncogene, G1/S-specific cyclin D2, hepatic neutral cholesteryl ester hydrolase precursor, UDP-galactose ceramide galactosyltransferase, and serine protease RNK-Met-1 were markedly decreased. Increased levels of IGFBP-3 mRNA were demonstrated as early as 2 weeks after induction of hyperglycemia. Increased IGFBP-3 protein was localized to the epithelium of the urethra, penile endothelium, and smooth muscle in the corpus cavernosum. Significant depletion of the smooth muscle density relative to the connective tissue was first observed in the penis of the 8-week diabetic rats, and a significant reduction in the intracavernous pressure was demonstrated only at 12 weeks after the induction of hyperglycemia.

CONCLUSIONS

These results suggest that the increased expression of IGFBP-3 during hyperglycemia might play an important role in the development of ED.

Anandamide improves the impaired nitric oxide-mediated neurogenic relaxation of the corpus cavernosum in diabetic rats: involvement of cannabinoid CB1and vanilloid VR1receptors

OBJECTIVE

To investigate the ability of acute administration of the endogenous cannabinoid, anandamide, in vitro to alter the nonadrenegic noncholinergic (NANC)-mediated relaxation of corpus cavernosum (CC) in diabetic rats and the possible role of nitric oxide (NO), as it is well known that erectile dysfunction (ED) affects 35-75% of men with diabetes mellitus and several studies have been conducted to find appropriate strategies for treating diabetes-induced ED.

MATERIALS AND METHODS

Diabetes was induced in rats by streptozotocin administration and was maintained for 8 weeks. The CC were removed and isolated in organ baths for pharmacological studies. Agonist-evoked or electrical-field stimulation (EFS)-evoked smooth muscle tensions in CC strips from control and diabetic rats were measured.

RESULTS

The neurogenic relaxation of phenylephrine (7.5 microm)-precontracted isolated CC strips was impaired in diabetic rats. Anandamide (0.3, 1 and 3 microm) enhanced the relaxant responses to EFS in diabetic CC strips in a dose-dependent manner. This effect was antagonized by the selective cannabinoid CB(1) receptor antagonist AM251 (1 microm) and the selective vanilloid receptor antagonist capsazepine (3 microm). Concurrent administration of partially effective doses of l-arginine (10 microm) and anandamide (0.3 microm) exerted a synergistic improvement in EFS-induced relaxation of diabetic CC strips (P < 0.001). The relaxant responses to the NO donor, sodium nitroprusside, were similar between diabetic and control groups. CONCLUSION; For the first time, we show that acute administration of anandamide, an endogenous cannabinoid, alone or combined with l-arginine can improve nitrergic nerve-mediated relaxation of the CC in diabetic rats. This effect was mediated by cannabinoid CB(1) and vanilloid VR(1) receptors within the CC.

ORIGINAL RESEARCH—ERECTILE DYSFUNCTION: Association of Risk Factors and Medical Comorbidities with Male Sexual Dysfunctions

INTRODUCTION

Conventionally, little attention has been given to the association of risk factors and medical comorbidities with male sexual dysfunctions. Although that association has been recently shown in many studies, it is not yet well investigated in the Saudi community.

AIM

To investigate the association of risk factors and medical comorbidities with male sexual dysfunctions in the Saudi community.

METHODS

A total of 1,464 male patients with a clinical diagnosis of sexual dysfunctions were enrolled in this study. All patients were assessed for sexual functions using different domains of the International Index for Erectile Function. Patients were also interviewed for sociodemographic data, medical history, and risk factors for erectile dysfunction (ED). Routine laboratory investigations, plus total testosterone and prolactin assessments, were offered to all patients. Assessments of penile vasculature using Doppler ultrasonography and rigidometer were performed.

RESULTS

A total of 92.6% of the patients had ED, 50.8% had premature ejaculation (PE), and 7.6% had low sexual desire. There was a significant association between increased age and increased severity of ED. In total, 20% had psychogenic cause, whereas 80% had organic cause of ED. Of the patients, 10.2% had mild, 41% had moderate, and 48.8% had severe ED. There were significant associations between endocrinopathy and both low sexual desire and PE (P < 0.05). There were significant associations between increased severity of ED and presence of diabetes, hypertension, dyslipidemia, ischemic heart disease, myocardial infarction, and psychological disorders. There were significant associations between increased severity of ED and increased values of end diastolic velocity, decreased values of peak systolic velocity, resistive index, rigidometer, and decreased response to intracavernosal injection (P < 0.001).

CONCLUSION

This study provides an assessment of the association of risk factors and medical comorbidities with male sexual dysfunctions in ambulatory service in this community.

Using gene chips to identify organ-specific, smooth muscle responses to experimental diabetes: potential applications to urological diseases

OBJECTIVE

To identify early diabetes-related alterations in gene expression in bladder and erectile tissue that would provide novel diagnostic and therapeutic treatment targets to prevent, delay or ameliorate the ensuing bladder and erectile dysfunction.

MATERIALS AND METHODS

The RG-U34A rat GeneChip (Affymetrix Inc., Sunnyvale, CA, USA) oligonucleotide microarray (containing approximately 8799 genes) was used to evaluate gene expression in corporal and male bladder tissue excised from rats 1 week after confirmation of a diabetic state, but before demonstrable changes in organ function in vivo. A conservative analytical approach was used to detect alterations in gene expression, and gene ontology (GO) classifications were used to identify biological themes/pathways involved in the aetiology of the organ dysfunction.

RESULTS

In all, 320 and 313 genes were differentially expressed in bladder and corporal tissue, respectively. GO analysis in bladder tissue showed prominent increases in biological pathways involved in cell proliferation, metabolism, actin cytoskeleton and myosin, as well as decreases in cell motility, and regulation of muscle contraction. GO analysis in corpora showed increases in pathways related to ion channel transport and ion channel activity, while there were decreases in collagen I and actin genes.

CONCLUSIONS

The changes in gene expression in these initial experiments are consistent with the pathophysiological characteristics of the bladder and erectile dysfunction seen later in the diabetic disease process. Thus, the observed changes in gene expression might be harbingers or biomarkers of impending organ dysfunction, and could provide useful diagnostic and therapeutic targets for a variety of progressive urological diseases/conditions (i.e. lower urinary tract symptoms related to benign prostatic hyperplasia, erectile dysfunction, etc.).

Improvement in erectile dysfunction after insulin-like growth factor-1 gene therapy in diabetic rats

AIM

To determine whether adenoviral gene transfer of insulin like growth factor-1 (IGF-1) to the penis of streptozotocin (STZ)-induced diabetic rats could improve erectile capacity.

METHODS

THE STZ diabetic rats were transfected with AdCMV-betagal or AdCMV-IGF-1. These rats underwent cavernous nerve stimulation to assess erectile function and their responses were compared with those of age-matched control rats 1 to 2 days after transfection. In control and transfected STZ diabetic rats, IGF-1 expression were examined by reverse transcription polymerase chain reaction (RT-PCR), Western blot and histology. The penis beta-galactosidase activity and localization of the STZ diabetic rats were also determined.

RESULTS

One to two days after transfection, the beta-galactosidase was found in the smooth muscle cells of the diabetic rat penis transfected with AdCMV-betagal. One to 2 days after administration of AdCMV-IGF-1, the cavernosal pressure, as determined by the ratio of maximal intracavernous pressure-to-mean arterial pressure (ICP/MAP) and total intracavernous pressure (ICP), was increased in response to cavernous nerve stimulation. Transgene expression was confirmed by RT-PCR, Western blot and histology.

CONCLUSION

Gene transfer of IGF-1 significantly increased erectile function in the STZ diabetic rats. These results suggest that in vivo gene transfer of IGF-1 might be a new therapeutic intervention for the treatment of erectile dysfunction (ED) in the STZ diabetic rats.

Mesenchymal stem cells alone or ex vivo gene modified with endothelial nitric oxide synthase reverse age-associated erectile dysfunction

Mesenchymal stem cells (MSCs) can be used in adult stem cell-based gene therapy for vascular diseases. To test the hypothesis that MSCs alone or endothelial nitric oxide synthase (eNOS)-modified MSCs can be used for treatment of erectile dysfunction (ED), syngeneic rat MSCs (rMSCs) were isolated, ex vivo expanded, transduced with adenovirus containing eNOS, and injected into the penis of aged rats. Histological analysis demonstrated that rMSCs survived for at least 21 days in corporal tissue after intracavernous injection, and an inflammatory response was not induced. Intracavernous administration of eNOS-modified rMSCs improved the erectile response in aged rats at 7 and 21 days after injection. The increase in erectile function was associated with increased eNOS protein, NOS activity, and cGMP levels. rMSCs alone increased erectile function of aged rats at day 21, but not at day 7, with the transplanted cells exhibiting positive immunostaining for several endothelial and smooth muscle cell markers. This change in rMSC phenotype was accompanied by upregulation of penile eNOS protein expression/activity and elevated cGMP levels. These findings demonstrate that an adenovirus can be used to transduce ex vivo expanded rMSCs to express eNOS and that eNOS-modified rMSCs improve erectile function in the aged rat. Intracavernous injection of unmodified wildtype rMSCs improved erectile function 21 days after injection through mechanisms involving improved endothelium-derived NO/cGMP signaling and rMSC differentiation into penile cells expressing endothelial and smooth muscle markers. These data highlight the potential clinical use of adult stem cell-based therapy for the treatment of ED.

Endothelial dysfunction in diabetic erectile dysfunction

Erectile dysfunction (ED) is highly prevalent in diabetes mellitus. Pathophysiological mechanisms underlying diabetes-associated ED are in large part due to endothelial dysfunction, which functionally refers to the inability of the endothelium to produce vasorelaxing messengers and to maintain vasodilation and vascular homeostasis. The precise mechanisms leading to endothelial dysfunction in the diabetic vasculature, including the penis, are not yet fully understood. Hyperglycemia affects endothelial nitric oxide synthase activity and nitric oxide production/bioavailability, nitric oxide-independent relaxing factors, oxidative stress, production and/or action of hormones, growth factors and/or cytokines, and generation and activity of opposing vasoconstrictors. Considering recent advances in the field of vascular biology and diabetes, the emphasis in this review is placed on the mechanisms of hyperglycemia-induced endothelial dysfunction in the pathophysiology of diabetes-associated ED.

Effects of streptozotocin-induced diabetes on bladder and erectile (dys)function in the same rat in vivo

OBJECTIVE

To establish the methods, feasibility and utility of evaluating the impact of diabetes on bladder and erectile function in the same rat, as more than half of diabetic patients have bladder dysfunction, and half of diabetic men have erectile dysfunction, but the severity of coincident disease has not been rigorously assessed.

MATERIALS AND METHODS

In all, 16 F-344 rats had diabetes induced by streptozotocin (STZ), and were divided into insulin-treated (five) and untreated (11), and compared with age-matched controls (10), all assessed in parallel. All STZ rats were diabetic for 8-11 weeks. Cystometric studies were conducted on all rats, with cavernosometric studies conducted on a subset of rats.

RESULTS

There were insulin-reversible increases in the following cystometric variables; bladder weight, bladder capacity, micturition volume, residual volume, micturition pressure and spontaneous activity (P < 0.05, in all, one-way analysis of variance, anova). Cavernosometry showed a diabetes-related, insulin-reversible decline in the cavernosal nerve-stimulated intracavernosal pressure (ICP) response at all levels of current stimulation (P < 0.05, in all one-way anova). Plotting erectile capacity (i.e. ICP) against bladder capacity showed no correlation between the extent of the decline in erectile capacity and the magnitude of the increase in bladder capacity.

CONCLUSIONS

These studies extend previous work to indicate that the extent of diabetes-related bladder and erectile dysfunction can vary in the same rat. As such, these findings highlight the importance of evaluating the impact of diabetes on multiple organ systems in the lower urinary tract. Future studies using this model system should lead to a better understanding of the initiation, development, progression and coincidence of these common diabetic complications.

Testosterone Restores Diabetes‐Induced Erectile Dysfunction and Sildenafil Responsiveness in Two Distinct Animal Models of Chemical Diabetes

INTRODUCTION

Hypogonadism is often associated with diabetes and both conditions represent major risk factors for erectile dysfunction (ED).

AIM

To investigate the role of hypogonadism on phosphodiesterase type 5 (PDE5) expression and sildenafil responsiveness in diabetes.

METHODS

Two different models of experimental diabetes were used: (i) alloxan-induced diabetic rabbit; and (ii) streptozotocin (STZ)-induced diabetic rat. In both experimental models, animals were separated into three groups: control, diabetic, diabetic supplemented with testosterone (T) enanthate. Rabbits were used for "in vitro" experiments. Conversely, each rats group was further subdivided: no further treatment or acute sildenafil dosing (25 mg/kg, 1 hour before "in vivo" electrical stimulation [ES]).

MAIN OUTCOME MEASURE

Erectile capacity was evaluated either by "in vitro" contractility study (alloxan-induced diabetic rabbit) and "in vivo" evaluation of erectile response elicited by ES of cavernous nerve (STZ-induced diabetic rats). Also endothelial nitric oxide synthase, neural nitric oxide synthase (nNOS), and PDE5 protein (Western blot) and mRNA (quantitative real-time reverse transcriptase polymerase chain reaction [RT-PCR]) expression were measured in rat penile samples of each group.

RESULTS

In both models, hypogonadism was observed, characterized by reduced T and atrophy of androgen-dependent accessory glands. T substitution completely reverted hypogonadism and diabetes-induced penile hyposensitivity to "in vitro" (acetylcholine, rabbit) or "in vivo" (ES, rat) relaxant stimuli, along with nNOS expression, which was reduced (P < 0.05) in STZ rats. In diabetic animals, T substitution reinstated sildenafil-induced enhancement of both "in vitro" nitric oxide donor (NCX 4040) relaxant effect (rabbit) and "in vivo" ES-induced erection (rat). PDE5 was reduced in diabetic STZ rats (P < 0.05) and normalized by T. In STZ rats, sodium nitroprusside (SNP) intracavernous injection induced a more sustained erection than in control rats, which was no further enhanced by sildenafil. T substitution normalized both hyper-responsiveness to SNP and sildenafil efficacy.

CONCLUSION

In two models of diabetes T deficiency underlies biochemical alterations leading to ED. Normalizing T in diabetes restores nNOS and PDE5, and reinstates sensitivity to relaxant stimuli and responsiveness to sildenafil.

Vascular endothelial growth factor restores erectile function through modulation of the insulin-like growth factor system and sex hormone receptors in diabetic rat

Previous studies have shown that intracavernous injection of vascular endothelial growth factor (VEGF) restored erectile function in diabetic rats. However, the mechanism of VEGF in diabetes-related erectile dysfunction (ED) has not been fully investigated. We hypothesize that intracavernous injection of VEGF may reverse diabetes-related ED through modulation of the insulin-like growth factor system and sex hormone receptors. To test this hypothesis the erectile function of treated and control rats was analyzed by measurement of intracavernous pressure (ICP) following electrostimulation of the cavernous nerves. Mean ICP was significantly lower in non-treated diabetic rats compared to controls. After VEGF injection, ICP was significantly higher than in non-treated diabetic rats. IGFBP-3 mRNA and protein expression was significantly higher in non-treated diabetic rat crura than controls, while VEGF-treated animals had control levels. ER-beta and PR mRNA and protein expression was significantly lower in non-treated diabetic rat crura. After VEGF injection, ER-beta and PR mRNA and protein expression was similar to control levels. Expression of AR and ER-alpha was the same in all groups. These findings suggest that orthotopic injection of VEGF may improve the functional recovery of diabetes-related ED through modulation of the insulin-like growth factor system and sex hormone receptors. To our knowledge, this is the first study demonstrating that VEGF treatment restores erectile function through restoration of the insulin-like growth factor system and sex hormone receptor genes at the mRNA and protein levels in diabetic rat crura. These results may be important in understanding the pathogenesis of diabetes-related ED and also in providing better strategies for management of this disease.