Assessment of androgen replacement therapy for erectile function in rats with type 2 diabetes mellitus by examining nitric oxide-related and inflammatory factors

A review of experimental techniques for erectile function researches and development of medical technology using animal erectile dysfunction models in sexual and reproductive medicine

Background

Erectile dysfunction (ED) is one of the causes of male infertility and is a disease that requires treatment. The first-line drugs for ED are phosphodiesterase 5 (PDE-5) inhibitors, and further treatment options are currently limited. Medical technologies, such as genetic control and regenerative medicine, are developing rapidly. Research on erectile function is progressing rapidly, coupled with technological innovations in other areas.

Methods

A PubMed search using the keywords "animal (rat, mouse, rabbit, dog, and monkey)" and "erectile" was conducted, and all relevant peer-reviewed English results were evaluated.

Main findings

The methods for evaluating erectile function include intracavernous pressure (ICP) measurements, isometric tension studies, and dynamic infusion cavernosometry. Papers also reported various disease model animals for the study of diabetes mellitus, cavernous nerve injury, and drug-induced ED.

Conclusion

Basic research on ED treatment has progressed rapidly over the past 20 years. In particular, research on the mechanism of ED has been accelerated by the publication of a study on the evaluation of erectile function using ICP measurements in rats. In addition, molecular biological experimental methods such as polymerase chain reaction (PCR) and western blotting have become relatively easy to perform due to technological progress, thus advancing research development.

Effect of High Testosterone Levels on Endothelial Function in Aorta and Erectile Function in Rats

BACKGROUND

Testosterone is an important hormone for the physical and mental health of men; however testosterone administration has also been suggested to adversely affect the cardiovascular system.

AIM

To investigate the effects of excessive testosterone administration on vascular endothelial and erectile function in rats.

METHODS

A total of seventy-five 12-week-old rats were divided into the following groups: Sham, castrated (Cast), castrated with subcutaneous administration of 100 mg/kg/month testosterone (Cast + T1), and castrated with subcutaneous administration of 100 mg/kg/week testosterone (Cast + T4). To observe the changes in testosterone level after the administration, rats were further divided into the following groups: control; T(6.25), wherein the rats were subcutaneously injected with 6.25 mg/kg testosterone; T(25) per week, wherein the rats were subcutaneously injected with 25 mg/kg testosterone per week; and T(100), wherein the rats were subcutaneously injected with 100 mg/kg testosterone per week. The relaxation responses of aorta were measured in these rats using standardized methods, and their erectile function was also evaluated. Statistical analysis of the obtained data was performed using two-way analysis of variance (ANOVA), Tukey-Kramer's multiple comparison test, or Student's t-test.

OUTCOMES

At the end of the study period, endothelial function was evaluated through measurement of isometric tension, while erectile function was assessed using intracavernosal pressure (ICP), mean arterial pressure (MAP), and the expression of endothelial nitric oxide synthase (eNOS), inducible nitric oxide synthase (iNOS), sirtuin 1 (Sirt1) and vascular endothelial growth factor A.

RESULTS

The ICP/MAP ratio in the Cast group (0.42 ± 0.04) was significantly lower than that in the Sham group (0.79 ± 0.07). The ICP/MAP ratio in the Cast + T1 group (0.73 ± 0.06) was significantly higher than that in the Cast group (P < .01) and that of the Cast + T4 (0.38 ± 0.01) group was unchanged (P > .05). The T(25) and T(100) groups exhibited significantly lower responses to ACh than the control group at 4 weeks (P < .01). Meanwhile, the ICP/MAP ratios in the T(25) group (0.44 ± 0.07) and T(100) group (0.47 ± 0.03) were significantly lower than that in the control group (0.67 ± 0.05) at stimulation frequencies of 16 Hz (P < .05). The expression of androgen receptor, Sirt1, and eNOS were significantly lower while that of iNOS was higher in the T(25) group compared with the control group (P < .05).

CLINICAL TRANSLATION

The results based on this animal model indicate that extremely high testosterone levels may affect endothelial and erectile function.

STRENGTHS AND LIMITATIONS

We found that high-dose testosterone administration decreased endothelial function in aorta and erectile function in rats. A major limitation of this study is that the blood concentration may not be representative of that in humans, and further research is needed.

CONCLUSION

The findings suggest that high doses of testosterone may cause endothelial dysfunction in the aorta and erectile dysfunction in rats and that the blood concentration should be monitored after testosterone administration. Kataoka T, Fukamoto A, Hotta Y, et al. Effect of High Testosterone Levels on Endothelial Function in Aorta and Erectile Function in Rats. Sex Med 2022;10:100550.

Gosha-Jinki-Gan Improved Erectile Dysfunction Caused by Anti-Cancer Agent Oxaliplatin by Decreasing Transcriptional Expression of Phosphodiesterase-5 in Rats

Background

A platinum-containing anti-cancer agent, oxaliplatin (L-OHP), is known to induce peripheral neuropathy, including erectile dysfunction (ED) as a side effect, while Gosha-jinki-gan (GJG) is a traditional Japanese herbal medicine mainly used for peripheral neuropathy.

Aim

To investigate the effect of GJG on L-OHP-induced ED in rats.

Methods

Twelve-week-old male Wister/ST rats were categorized into the following groups: Sham, Sham+GJG, L-OHP, and L-OHP+GJG (each n = 10). The L-OHP and L-OHP+GJG groups were injected intravenously with L-OHP (4 mg/kg) for 2 consecutive days in the first week. Statistical significance was determined using Bonferroni's multiple comparison test.

Outcomes

At the end of the study period, erectile function was evaluated by measuring intracavernosal pressure (ICP) and mean arterial pressure (MAP) after cavernous nerve stimulation. Western blot analysis was used to assess the neuronal nitric oxide synthase (nNOS) and endothelial nitric oxide synthase (eNOS) levels, and quantitative polymerase chain reaction was used to assess the expression of phosphodiesterase-5 (PDE-5) and nicotinamide adenine dinucleotide phosphate (NADPH) oxidase-1.

Results

The ICP/MAP ratio of L-OHP rats (0.34 ± 0.06) was significantly lower than that of Sham rats (0.67 ± 0.03, P < .01), however, the ICP/MAP ratio of L-OHP+GJG rats (0.55 ± 0.01) was significantly higher than that of L-OHP rats (P < .01). There were no significant differences in the nNOS and eNOS protein expression between both groups (P > .05). GJG administration significantly decreased PDE-5 and NADPH oxidase-1 messenger RNA expressions in the L-OHP+GJG group.

Clinical Translation

This animal model study suggests that GJG might be effective for erectile function in cancer survivors.

Strengths & limitations

Our study identified that GJG had no notable side effects in the treated group. Further investigation of the cavernous nerve would also help elucidate the mechanism of GJG effect, which is a limitation of this study.

Conclusion

We found that GJG administration improved L-OHP-induced ED by improving transcriptional PDE-5 expression.

Kataoka T, Kawaki Y, Kito Y, et al. Gosha-Jinki-Gan Improved Erectile Dysfunction Caused by Anti-Cancer Agent Oxaliplatin by Decreasing Transcriptional Expression of Phosphodiesterase-5 in Rats. Sex Med 2022;10:100484.

Evaluating the Effects of Low Carbohydrate and High Protein Diet on Erectile Function in Rats

Introduction

Carbohydrate restriction in diet is becoming a popular means of losing weight nowadays, although it has been reported that excessive intake of low-carbohydrate and high-protein (LCHP) diet causes an adverse effect on cardiovascular function.

Aim

To investigate the influence of LCHP on erectile function in rats.

Methods

A total of 48, 12-week-old rats were divided into 2 groups and either fed a LCHP diet (LCHP group) or a normal diet (Control group). Hematological examination, blood pressure evaluation, erectile function assessments as well as evaluations of the relaxation and contractile responses of corpus cavernosum were carried out in these rats by using standardized methods. Statistical analysis using 2-way ANOVA and Welch's t-test was conducted to examine the obtained data.

Main Outcome Measure

At the end of the study period, the evaluated outcomes to assess erectile function were intracavernosal pressure , mean arterial pressure , endothelial functions, nitric oxide (NO)-operated nerve functions and the expressions of endothelial nitric oxide synthase (eNOS), neuronal nitric oxide synthase (nNOS), and sphingosine-1-phosphate receptor 1 (S1P1).

Results

The intracavernosal pressure / mean arterial pressure ratio was significantly lower in the LCHP group (P < .05) at 4 weeks. Compared to the Control group, the LCHP group exhibited significantly lower responses to ACh and EFS and a decreased nNOS mRNA expression. The results based on this animal model indicate that extreme carbohydrate restricted diet may affect erectile function. Our study identified that LCHP decreased erectile function in rats. A major limitation of this study is, due to the extreme condition of completely replacing carbohydrates with protein, that carbohydrate intake will be gradually increased in the future.

Conclusion

Extreme carbohydrate restriction and high protein in diet may cause ED with vascular endothelial dysfunction and a decrease in the relaxation response of the corpus cavernosum smooth muscle via NO-operated nerves.

Kataoka T, Hidaka J, Suzuki J, et al. Evaluating the Effects of Low Carbohydrate and High Protein Diet on Erectile Function in Rats. Sex Med 2021;10:100500.

Influence of anticancer agents on sexual function: an in Vivo study based on the US FDA Adverse Event Reporting System

Background

Patients with cancer are treated with chemotherapeutics that cause adverse effects, including erectile dysfunction (ED).

Objectives

We investigated erectile function in rats after the administration of anticancer agents based on data retrieved through mining of the US Food and Drug Administration (FDA) Adverse Event Reporting System (AERS) database.

Materials and methods

The statistical signal strength for the association between anticancer drugs and ED was calculated using the reporting odds ratio (ROR). A drug–event combination was detected when the lower limit of the 95% confidence interval (CI) of the ROR exceeded 1.00. Rats were administered anticancer agents detected in the FDA AERS analysis. Erectile function was assessed using intracavernous pressure (ICP) and mean arterial pressure (MAP) analysis after electrical stimulation of the cavernous nerve. Statistical significance was determined using Welch's t‐test or two‐way ANOVA.

Results

Melphalan (L‐PAM; ROR = 4.72, 95% CI = 2.78–8.00), vincristine (VCR; ROR = 2.47, 95% CI = 1.54–3.97), docetaxel (DTX; ROR = 2.25, 95% CI = 1.28–3.95), methotrexate (MTX; ROR = 1.96, 95% CI = 1.39–2.75), and doxorubicin (DOX; ROR = 1.82, 95% CI = 1.07–3.19) enhanced ED risk. L‐PAM and MTX decreased the ICP/MAP ratio 1 week after administration. VCR and DOX decreased erectile function 4 weeks after administration. DTX decreased erectile function at all assessed time points.

Discussion and conclusion

Certain anticancer agents should be considered risk factors for ED.

Our results provide possible treatment strategies for maintaining erectile function in cancer survivors, including careful erectile function monitoring after treatment.

Oxaliplatin, an Anticancer Agent, Causes Erectile Dysfunction in Rats due to Endothelial Dysfunction

BACKGROUND

Chemotherapeutics, one of the standard treatment options for cancer worldwide, have various adverse effects, including erectile dysfunction (ED).

AIM

To investigate erectile function in an animal model after administration of the anticancer agent oxaliplatin (L-OHP).

METHODS

Male Wistar/ST rats were divided into 2 groups: L-OHP rats (n = 21), which were intravenously administered L-OHP (4 mg/kg; twice a week for 4 weeks), and Control rats (n = 21), which were injected with the same volume of 5% glucose solution, using the same dosing schedule. At the end of the study period, erectile function was evaluated by measuring intracavernous pressure (ICP) and mean arterial pressure (MAP) after cavernous nerve stimulation (n = 9-10). Endothelial function was evaluated with an isometric tension study using corpus cavernosum strips (n = 11). Western blot analysis was used to assess neuronal nitric oxide (nNOS) and endothelial NO synthase (eNOS) protein levels (n = 7). Real-time quantitative polymerase chain reaction (qRT-PCR) was used to assess the expression of inflammation- and oxidative stress-related markers (nicotinamide adenine dinucleotide phosphate oxidase-1, p22^phox, interleukin [IL]-6, and nuclear factor-kappa B) (n = 6). Statistical significance was determined using the Student's t-test.

OUTCOMES

The L-OHP group had a significantly lower ICP:MAP ratio than the control group (P < .05). Compared to the Control group, the L-OHP group exhibited significantly lower responses to ACh and eNOS protein levels and significantly higher inflammatory biomarker levels.

CLINICAL TRANSLATION

The results based on this animal model indicate that use of the anticancer agent L-OHP should be considered as a risk factor for ED occurring via reduction of NO bioavailability in humans; our results provide possible treatment strategies for maintaining the erectile function of cancer survivors.

STRENGTHS AND LIMITATIONS

Our study showed that the anticancer agent L-OHP has the propensity to cause ED in rats. A major limitation of this study is the lack of an established cure for ED associated with L-OHP and the lack of clinical evidence.

CONCLUSIONS

L-OHP causes ED in rats via reduction of NO bioavailability caused by endothelial dysfunction. Kataoka T, Mori T, Suzuki J, et al. Oxaliplatin, an Anticancer Agent, Causes Erectile Dysfunction in Rats due to Endothelial Dysfunction. J Sex Med 2021;18:1337-1345.

Effect of Late Androgen Replacement Therapy on Erectile Function Through Structural Changes in Castrated Rats

Background

Because androgen replacement therapy (ART) is not performed immediately after the onset of androgen deficiency, the treatment is considered to be late.

Aim

To investigate the effects of late ART, starting 4 weeks after castration of rats, on erectile function and structural changes in the corpus cavernosum.

Methods

Rats were subjected to ART for 4 (Late-ART [4w]) or 8 (Late-ART [8w]) weeks. In either case, rats were assigned to the following groups: castrated (Cast), castrated with subcutaneous administration of testosterone (3 mg/kg/day; Cast+T), and sham (Sham). Cast + T rats received daily subcutaneous doses of testosterone starting 4 weeks after castration for 4 or 8 weeks whereas Sham and Cast rats received only the vehicle.

Outcomes

Erectile function was assessed by evaluating intracavernosal pressure (ICP) and mean arterial pressure (MAP) after electrical stimulation of the cavernous nerve, corporal veno-occlusive function using dynamic infusion cavernosometry, and histology using Masson's trichrome staining.

Results

No increase in the ICP was observed in Cast+T rats in the Late-ART (4w) group (0.47 ± 0.02, P > .05), whereas, in Cast+T rats in the Late-ART (8w) group, there was a significant increase in the ICP/MAP ratio (0.60 ± 0.02, P < .05), drop rate, and smooth muscle/collagen ratio.

Clinical Translation

The present study provides scientific evidence for the effect of late ART on erectile function.

Strengths and Limitations

This study provides insights into the influence of late ART on erectile function through improvements in the structure of corpus cavernosum. The major limitation of this study is the difference in the time required for healing between the humans and rats, which might have a bearing on the translational relevenace of the results.

Conclusions

Late ART could improve erectile function. However, as improvement requires a considerable time period, it is necessary to persist with therapy patiently for optimal results.

Kataoka T, Hotta Y, Yamamoto Y, et al. Effect of Late Androgen Replacement Therapy on Erectile Function Through Structural Changes in Castrated Rats. Sex Med 2021;XX:XX–XXX.

Effects of androgens and estrogens on sirtuin 1 gene expression in human aortic endothelial cells

Objectives:

To investigate the effect of androgens and estrogens on surtuin 1 (SIRT1) expression in human aortic endothelial cells (HAECs).

Methods:

Real-time polymerase chain reaction analysis of SIRT-1 expression over 48 hours (h) was performed in HAECs treated with various concentrations of dehydroepiandrostendione (DHEA), androstenedione and testosterone (androgens), estrone (E1), estradiol (E2), and estriol (E3) (estrogens) to investigate the dose-dependency of time courses. The influence of high glucose on SIRT1 expression induced by the androgens and estrogens was also examined.

Results:

Dehydroepiandrostendione, androstenedione, and testosterone remarkably produced a dose-dependent increase in SIRT1 expression in the range of 10 to 20 μg/ml. High glucose (40mM) medium had significantly inhibitory effects on 10 μg/ml DHEA-induced SIRT1 expression (p=0.024). Estrone and E2, but not E3, caused a marked dose-dependent increase in SIRT1 expression from 10 to 20 μg/ml. Treatment with 20 mM or 40 mM glucose medium did not significantly inhibit E1- and E3-induced SIRT1 expression in control medium; however, both high glucose mediums significantly emphasized E2-induced SIRT1 expression in control medium (p=0.007, p=0.005).

Conclusion:

These results suggest that DHEA, androstenedione, testosterone, E1, and E2 definitely activate SIRT1 expression in HAECs. A high glucose medium is potent to inhibit the basal gene expression; however, it could not reduce powerful androgen- and estrogen-induced SIRT1 expression in HAECs.

Dynamic erectile responses of a novel penile organ model utilizing TPEM†

Male penis is required to become erect during copulation. In the upper (dorsal) part of penis, the erectile tissue termed corpus cavernosum (CC) plays fundamental roles for erection by regulating the inner blood flow. When blood flows into the CC, the microvascular complex termed sinusoidal space is reported to expand during erection. A novel in vitro explant system to analyze the dynamic erectile responses during contraction/relaxation is established. The current data show regulatory contraction/relaxation processes induced by phenylephrine (PE) and nitric oxide (NO) donor mimicking dynamic erectile responses by in vitro CC explants. Two-photon excitation microscopy (TPEM) observation shows the synchronous movement of sinusoidal space and the entire CC. By taking advantages of the CC explant system, tadalafil (Cialis) was shown to increase sinusoidal relaxation. Histopathological changes have been generally reported associating with erection in several pathological conditions. Various stressed statuses have been suggested to occur in the erectile responses by previous studies. The current CC explant model enables to analyze such conditions through directly manipulating CC in the repeated contraction/relaxation processes. Expression of oxidative stress marker and contraction-related genes, Hypoxia-inducible factor 1-alpha (Hif1a), glutathione peroxidase 1 (Gpx1), Ras homolog family member A (RhoA), and Rho-associated protein kinase (Rock), was significantly increased in such repeated contraction/relaxation. Altogether, it is suggested that the system is valuable for analyzing structural changes and physiological responses to several regulators in the field of penile medicine.

The Inflammation Network in the Pathogenesis of Erectile Dysfunction: Attractive Potential Therapeutic Targets

BACKGROUND

Erectile dysfunction (ED) is an evolving health problem in the aging male population. Chronic low-grade inflammation is a critical component of ED pathogenesis and a probable intermediate stage of endothelial dysfunction, especially in metabolic diseases, with the inclusion of obesity, metabolic syndrome, and diabetes.

OBJECTIVE

This review will present an overview of preclinical and clinical data regarding common inflammatory mechanisms involved in the pathogenesis of ED associated with metabolic diseases and the effect of antiinflammatory drugs on ED.

METHODS

A literature search of existing pre-clinical and clinical studies was performed on databases [Pubmed (MEDLINE), Scopus, and Embase] from January 2000 to October 2019.

RESULTS

Low-grade inflammation is a possible pathological role in endothelial dysfunction as a consequence of ED and other related metabolic diseases. Increased inflammation and endothelial/prothrombotic markers can be associated with the presence and degree of ED. Pharmacological therapy and modification of lifestyle and risk factors may have a significant role in the recovery of erectile response through reduction of inflammatory marker levels.

CONCLUSION

Inflammation is the least common denominator in the pathology of ED and metabolic disorders. The inflammatory process of ED includes a shift in the complex interactions of cytokines, chemokines, and adhesion molecules. These data have established that anti-inflammatory agents could be used as a therapeutic opportunity in the prevention and treatment of ED. Further research on inflammation-related mechanisms underlying ED and the effect of therapeutic strategies aimed at reducing inflammation is required for a better understanding of the pathogenesis and successful management of ED.

The near-infrared dye IR-61 restores erectile function in a streptozotocin-induced diabetes model via mitochondrial protection

This study aimed to evaluate the therapeutic effect of IR-61, a novel mitochondrial heptamethine cyanine dye with antioxidant effects, on diabetes mellitus-induced erectile dysfunction (DMED). Eight-week-old male Sprague-Dawley rats were intraperitoneally injected with streptozotocin (STZ) to induce type 1 diabetes. Eight weeks after STZ injection, all rats were divided into three groups: the control group, DM group, and DM + IR-61 group. In the DM + IR-61 group, the rats were administered IR-61 (1.6 mg kg^-1) twice a week by intravenous injection. At week 13, erectile function was evaluated by determining the ratio of the maximal intracavernous pressure to mean arterial pressure, and the penises were then harvested for fluorescent imaging, transmission electron microscopy, histological examinations, and Western blot analysis. Whole-body imaging suggested that IR-61 was highly accumulated in the penis after intravenous injection. IR-61 treatment significantly improved the maximal ICP of diabetic rats. Additionally, IR-61 ameliorated diabetes-induced inflammation, apoptosis, and phenotypic transition of corpus cavernosum smooth muscle cells (CCSMCs) in penile tissue. IR-61 also attenuated mitochondrial damage, reduced reactive oxygen species production in the corpus cavernosum and upregulated sirtuin1 (SIRT1), sirtuin3 (SIRT3), nuclear factor (erythroid-derived 2)-like 2 (Nrf2), and heme oxygenase expression in penile tissue. In conclusion, IR-61 represents a potential therapeutic option for DMED by protecting the mitochondria of CCSMCs, which may be mediated by activation of the SIRT1, SIRT3, and Nrf2 pathways.

Melatonin prevents deterioration of erectile function in streptozotocin-induced diabetic rats via sirtuin-1 expression

A review of the literature indicated that sirtuin-1 expression, a regulator of nitric oxide bioavailability in erectile dysfunction (ED) after melatonin therapy, has not yet been investigated. The objective of this study was to evaluate the protective effects of melatonin for erectile function with sirtuin-1 protein expression in type 1 diabetic rat models. Fifty male Sprague Dawley rats were placed into five groups. Except for those in the control group (C), each animal received a single dose (60 mg/kg) of streptozotocin to induce diabetes. The animals were placed into the diabetes (D) group, insulin (I) group (6 U/kg/day), melatonin (Mel) group (10 mg kg^-1  day^-1 ) and combined treatment (I + Mel) group. Ten weeks later, the serum testosterone levels, intracavernosal pressure (ICP), mean arterial pressure (MAP), malondialdehyde (MDA), cyclic guanosine monophosphate (c-GMP), 8-hydroxydeoxyguanosine (8-OHdG), nitric oxide synthase (NOS), caspase-3 activity, sirtuin-1 and endothelial nitric oxide synthase (eNOS) protein expression and histological findings were assessed. The mean ICP/MAP ratio for the D group was lower than the mean ratios for the other groups. The treatment groups, particularly the I + Mel group, exhibited lower 8-OHdG and MDA levels and caspase-3 activity than the D group. The sirtuin-1 and eNOS expression and cavernosal tissue (CT) histology seemed to have been preserved by the melatonin and/or insulin therapy. These results were indicative of a profound protective effect of melatonin by the activation of sirtuin-1 protein expression against hyperglycemia-induced oxidative CT injury.

Correcting imbalance of sex hormones by a phosphodiesterase 5 inhibitor improves copulatory dysfunction in male rats with type 2 diabetes

INTRODUCTION

Sexual dysfunction is a common complication in men with type 2 diabetes and is often refractory to treatment. This study investigated the long-term influence of the phosphodiesterase 5 inhibitor (PDE5I) tadalafil on the level of sex hormones and sexual function in male Otsuka Long-Evans Tokushima Fatty (OLETF) rats as an animal model of spontaneous type 2 diabetes.

RESEARCH DESIGN AND METHODS

We treated 36-week-old male OLETF and non-diabetic Long-Evans Tokushima Otsuka (LETO) rats with oral tadalafil (100 µg/kg/day) for 12 weeks; sham groups received vehicle for 12 weeks. Before and after tadalafil treatment, serum levels of total and free testosterone, estradiol, luteinizing hormone (LH), follicle-stimulating hormone and proinflammatory cytokines were compared among four treatment groups. Copulatory function was examined by matching each rat to an estrous female. After completion of the experiment, total fat mass in the abdomen was measured.

RESULTS

Testosterone levels were significantly lower in OLETF versus LETO rats at 36 weeks. After 12 weeks of tadalafil treatment, levels of testosterone were significantly increased both in OLETF-tadalafil and LETO-tadalafil groups versus vehicle groups. Tadalafil decreased estradiol levels both in OLETF and LETO rats. Furthermore, tadalafil increased serum LH levels with a reduction of proinflammatory cytokines. Total fat mass was significantly lower in the OLETF-tadalafil group versus the OLETF-vehicle group. A significant suppression of copulatory behavior, that is, elongation of intromission latency was found in OLETF rats. However, tadalafil treatment for 12 weeks shortened the intromission latency.

CONCLUSION

Our results indicate that tadalafil treatment might improve copulatory disorder in the type 2 diabetic model via improvement of an imbalance in sex hormones and an increase in LH levels.

Mesenchymal stem cell-derived exosomes ameliorate erection by reducing oxidative stress damage of corpus cavernosum in a rat model of artery injury

Erectile dysfunction (ED) is a common ageing male's disease, and vascular ED accounts for the largest proportion of all types of ED. One of the mechanisms of vascular ED in the clinic is arterial insufficiency, which mainly caused by atherosclerosis, trauma and surgical. Moreover, oxidative stress damage after tissue ischemia usually aggravated the progress of ED. As a new way of acellular therapy, mesenchymal stem cell-derived exosomes (MSC-Exos) have great potential in ED treatment. In the current study, we have explored the mechanism of MSC-Exos therapy in a rat model of internal iliac artery injury-induced ED. Compared with intracavernous (IC) injection of phosphate-buffered saline after artery injury, of note, we observed that both mesenchymal stem cells (MSCs) and MSC-Exos through IC injection could improve the erectile function to varying degrees. More specifically, IC injection MSC-Exos could promote cavernous sinus endothelial formation, reduce the organization oxidative stress damage, and improve the nitric oxide synthase and smooth muscle content in the corpus cavernosum. With similar potency compared with the stem cell therapy and other unique advantages, IC injection of MSC- Exos could be an effective treatment to ameliorate erectile function in a rat model of arterial injury.

Impact of Immune System Activation and Vascular Impairment on Male and Female Sexual Dysfunction

INTRODUCTION

Male and female sexual dysfunction (SD) is considered a multifactorial condition. Numerous studies have shown the involvement of inflammatory processes in this pathological condition. Sexual intercourse requires healthy and functioning vessels to supply the pelvic region in both males and females, generating penile erection and clitoral and vaginal lubrication, respectively. Cardiovascular diseases and associated risk factors may contribute negatively to pelvic blood flow, possibly through immune system activation.

AIM

The study aimed to address the correlation between vascular inflammation driven by immune system activation and SD in males and females.

METHODS

A literature review was performed to identify articles addressing male and female SD and vascular inflammation. Key words included "male and female sexual dysfunction," "vascular inflammation," "iliac and pudendal arteries dysfunction," "genitourinary tract," and "blood flow."

MAIN OUTCOME MEASURES

Management of systemic and local inflammation may be a useful alternative to improve SD and reduce the risk of cardiovascular diseases in the future.

RESULTS

Increased levels of cytokines and chemokines have been detected in humans and animals with hypertension, obesity, and diabetic conditions. Chronic activation of the innate immune system, especially by pathogen- or damage-associated molecular patterns, and metabolic-related disorders may act as triggers further contributing to an increased inflammatory condition. Due to the reduced size of vessels, SD and retinal vascular impairments have been shown to be predictive factors for cardiovascular diseases. Therefore, considering that blood flow to the genitalia is essential for sexual function, endothelial dysfunction and vascular remodeling, secondary to chronic immune system activation, may be implicated in male and female vasculogenic SD.

CONCLUSIONS

Several conditions appear to play a role in SD. In the present review, we have identified a role for the immune system in generating vascular and tissue impairments contributing to erectile dysfunction and female SD. Calmasini FB, Klee N, Webb RC, et al. Impact of Immune System Activation and Vascular Impairment on Male and Female Sexual Dysfunction. Sex Med Rev 2019;7:604-613.

Aging-induced elevation in circulating complement C1q level is associated with arterial stiffness

Inflammatory cytokines such as tumor necrosis factor alpha (TNF-α) and interleukin 6 (IL-6) are candidate blood biomarkers of cardiovascular disease (CVD). However, no consensus has been reached on the relationships between aging-induced secretion of cytokines and CVD risk. Complement C1q (C1q) secretion increases with aging, and C1q induces proliferation of vascular smooth muscle cells. Therefore, the secretion of C1q with aging may be a risk factor of CVD and reflect arterial stiffening and blood pressures. This study aimed to clarify whether aging-induced increase in serum C1q, TNF-α, and IL-6 levels are associated with arterial stiffness. One hundred twenty-seven healthy subjects participated in this study. Serum C1q, TNF-α, and IL-6 levels and carotid-femoral pulse wave velocity (cfPWV; arterial stiffness index) in middle-aged and older subjects (≥40 years) were significantly increased as compared with those in young subjects (<40 years; P < 0.05). The serum C1q, TNF-α, and IL-6 levels positively correlated with cfPWV (P < 0.05). Furthermore, C1q level contributed independently to the cfPWV variation after adjustment for 11 confounders. Moreover, serum C1q level is associated with cfPWV regardless of sex, but these relationships with TNF-α or IL-6 differed between sex. Importantly, cfPWV gradually increased from the age of 30 years, with simultaneous increase in circulating C1q level. However, TNF-α and IL-6 levels increased after age 50 years, later than the increase in C1q. These results suggest that serum C1q level may reflect the elevation of arterial stiffness that occurs with advancing age and has a potential as a novel biomarker of arterial stiffness.

Translational Perspective on the Role of Testosterone in Sexual Function and Dysfunction

INTRODUCTION

The biological importance of testosterone is generally accepted by the medical community; however, controversy focuses on its relevance to sexual function and the sexual response, and our understanding of the extent of its role in this area is evolving.

AIM

To provide scientific evidence examining the role of testosterone at the cellular and molecular levels as it pertains to normal erectile physiology and the development of erectile dysfunction and to assist in guiding successful therapeutic interventions for androgen-dependent sexual dysfunction.

METHODS

In this White Paper, the Basic Science Committee of the Sexual Medicine Society of North America assessed the current basic science literature examining the role of testosterone in sexual function and dysfunction.

RESULTS

Testosterone plays an important role in sexual function through multiple processes: physiologic (stimulates activity of nitric oxide synthase), developmental (establishes and maintains the structural and functional integrity of the penis), neural (development, maintenance, function, and plasticity of the cavernous nerve and pelvic ganglia), therapeutically for dysfunctional regulation (beneficial effect on aging, diabetes, and prostatectomy), and phosphodiesterase type 5 inhibition (testosterone supplement to counteract phosphodiesterase type 5 inhibitor resistance).

CONCLUSION

Despite controversies concerning testosterone with regard to sexual function, basic science studies provide incontrovertible evidence for a significant role of testosterone in sexual function and suggest that properly administered testosterone therapy is potentially advantageous for treating male sexual dysfunction.

Constitutive NOS uncoupling and NADPH oxidase upregulation in the penis of type 2 diabetic men with erectile dysfunction

Erectile dysfunction (ED) associated with type 2 diabetes mellitus (T2DM) involves dysfunctional nitric oxide (NO) signaling and increased oxidative stress in the penis. However, the mechanisms of endothelial NO synthase (eNOS) and neuronal NO synthase (nNOS) dysregulation, and the sources of oxidative stress, are not well defined, particularly at the human level. The objective of this study was to define whether uncoupled eNOS and nNOS, and NADPH oxidase upregulation, contribute to the pathogenesis of ED in T2DM men. Penile erectile tissue was obtained from 9 T2DM patients with ED who underwent penile prosthesis surgery for ED, and from six control patients without T2DM or ED who underwent penectomy for penile cancer. The dimer-to-monomer protein expression ratio, an indicator of uncoupling for both eNOS and nNOS, total protein expressions of eNOS and nNOS, as well as protein expressions of NADPH oxidase catalytic subunit gp91phox (an enzymatic source of oxidative stress) and 4-hydroxy-2-nonenal [4-HNE] and nitrotyrosine (markers of oxidative stress) were measured by western blot in this tissue. In the erectile tissue of T2DM men, eNOS and nNOS uncoupling and protein expressions of NADPH oxidase subunit gp91phox, 4-HNE- and nitrotyrosine-modified proteins were significantly (p < 0.05) increased compared to control values. Total eNOS and nNOS protein expressions were not significantly different between the groups. In conclusion, mechanisms of T2DM-associated ED in the human penis may involve uncoupled eNOS and nNOS and NADPH oxidase upregulation. Our description of molecular factors contributing to the pathogenesis of T2DM-associated ED at the human level is relevant to advancing clinically therapeutic approaches to restore erectile function in T2DM patients.

Chronic administration of sildenafil improves erectile function in a rat model of chronic renal failure

The relationship between erectile dysfunction (ED) and chronic renal failure (CRF) has been reported in several studies. This study aimed to investigate whether the chronic use of sildenafil could enhance the erectile capacity in CRF-induced rats. In addition, we assessed the effect of that treatment on certain molecules, which have been suggested to play crucial roles in erectile physiology and CRF-related ED as well. Three groups of animals were utilized: (1) age-matched control rats, (2) CRF-induced rats, (3) CRF-induced rats treated with chronic administration of sildenafil (5 mg kg⁻¹ p.o. for 6 weeks [treatment started after 6 weeks of CRF induction]). At 3 months, all animals underwent cavernosal nerve stimulation (CNS) to assess erectile function. Penile tissue advanced glycation end products (AGE's)/5-hydroxymethyl-2-furaldehyde, malondialdehyde (MDA), cGMP (ELISA), inducible nitric oxide synthase (iNOS) and neuronal NOS (nNOS) (Western blot) analyses were performed in all rat groups. CRF-induced rats had a significant decrease in erectile function when compared to control rats (P < 0.05). The increase in both intracavernosal pressure (ICP) and area under the curve of CRF-induced rats treated with sildenafil (Group 3) was greater than CRF-induced rats (Group 2). Additionally, sildenafil treatment decreased AGE, MDA and iNOS levels, while it preserved nNOS and cGMP contents in CRF-induced penile tissue. Decreased AGE, MDA, iNOS and increased nNOS, cGMP levels at the sildenafil-treated group increased both ICP and Total ICP to CNS, which led to improve erectile function in CRF-induced rats. The results of the present study revealed the therapeutic effect of chronic sildenafil administration on erectile function in CRF-induced rats.

Castration impairs erectile organ structure and function by inhibiting autophagy and promoting apoptosis of corpus cavernosum smooth muscle cells in rats

OBJECTIVE

The aim of this study was to determine the changes and underlying mechanisms of erectile organ structure and function in castrated rats. In addition, the regulatory effects of an androgen on autophagy and apoptosis in corpus cavernosum smooth muscle cells (CCSMCs), especially the regulatory effect of androgen on the BECN 1-Bcl-2 interaction, were investigated.

METHODS

Male Sprague-Dawley rats were divided into three groups (30/group): control group, castration group, and castration with testosterone supplementation group. The erectile function was examined both in vivo and in vitro, by electric stimulation of the cavernous nerve and corpus cavernosum strip bath test, respectively. Transmission electron microscopy, TUNEL assay, Masson's trichrome staining, immunohistochemistry, and western blotting were performed to determine the levels of autophagy and apoptosis, and the structural changes in corpus cavernosum.

RESULTS

Compared with control group, the castration group showed (1) lower erectile function: lower intracavernosal pressure/mean arterial pressure ratio, lower systolic and diastolic capability of corporal strips, and reduced expressions of eNOS and nNOS; (2) greater fibrosis: decreased smooth muscle/collagen ratio, lower expression of α-SMA, and higher expression of TGF-β1; (3) inhibited autophagy: decreased autophagosomes, lower expressions of BECN1 and LC3-II; and (4) enhanced apoptosis: higher apoptotic index and decreased Bcl-2/Bax ratio. Testosterone supplementation partially improved the effects of castration.

CONCLUSIONS

Castration attenuates erectile function and induces corporeal fibrosis by inhibiting autophagy and promoting apoptosis of CCSMCs in rats. Therefore, our study highlights the important role of androgens in maintaining the integrity of the structure and function of corpus cavernosum in rats through counter-regulation of autophagy and apoptosis, mainly by regulating BECN 1-Bcl-2 interaction.

Clinical significance and expression of microRNA in diabetic patients with erectile dysfunction

The aim of the present study was to investigate the expression of microRNA (miR)-93, miR-320 and miR-16 and to assess their diagnostic value in diabetic patients with erectile dysfunction (ED). A total of 120 individuals were divided into three groups, which included the diabetics with ED group (ED group), the diabetics without ED group (NED group) and the healthy volunteers group (control group). Each group included 40 individuals. Serum samples were collected and reverse transcription quantitative polymerase chain reaction detection of the three types of miRNA was performed and the sensitivity of ED was analyzed by receiver operating characteristic curves. A negative correlation was identified between the incidence of ED in patients with diabetes and serum total testosterone levels (r=0.302, P<0.05); however, a positive correlation was observed between the incidence of ED in diabetics and the HbA1c level (r=0.231, P<0.05). Additionally, the relative expression levels of the three types of miRNA were higher in the ED group when compared with the NED and control groups (P<0.05). When compared with the control group, the area under the curve (AUC) values for miR-93, miR-320 and miR-16 were 0.793, 0.818 and 0.810, respectively, in the ED group and 0.576, 0.532 and 0.542 in the NED group, respectively. Furthermore, when compared with the NED group, the AUC value for miR-93, miR-320 and miR-16 was 0.707, 0.810 and 0.833, respectively, in the ED group. Therefore, the expression levels of miR-93, miR-320 and miR-16 may be useful for the early diagnosis of ED in patients with diabetes.