Advances in the development of phosphodiesterase 5 inhibitors

Phosphodiesterase 5 (PDE5) can hydrolyze cyclic guanosine monophosphate (cGMP), which is critical for maintaining various physiological processes in organisms. Currently, clinically approved indications for PDE5 inhibitors encompass therapeutic agents for erectile dysfunction (ED), symptoms associated with lower urinary tract symptoms (LUTS), and pulmonary artery hypertension (PAH). Despite the fact that the development of selective PDE5 inhibitors has been a significant focus in drug development for some time following the proven success of sildenafil as a PDE5 inhibitor for ED treatment, fewer than ten drugs in this therapeutic class have been marketed in the past 25 years, often accompanied by adverse effects. Therefore, the development of novel, isozyme-selective PDE5 inhibitors is highly warranted. In this review, we systematically summarize the research progress of PDE5 inhibitors over the past 20 years, focusing on the meticulously combing and categorizing the structures of PDE5 inhibitors and natural products exhibiting PDE5 inhibitory activities, along with their therapeutic potentials. We hope that this summary will aid in better understanding of PDE5 inhibitors and provide insights for developing novel therapies targeting PDE5.

The use of phosphodiesterase inhibitors in the treatment of female sexual dysfunction: scoping review

Objective

The purpose of this study was to analyze the available evidence regarding the efficacy of iPDE5 in the treatment of female sexual dysfunction (FSD).

Methods

A comprehensive literature search was conducted in March 2023 through the main scientific databases.

Results

A total of 53 articles were identified, out of which, 6 met the predefined inclusion criteria. All of these were randomized controlled trials. Among the included studies, 4 demonstrated the effectiveness of sildenafil in improving sexual response and addressing FSD, while 2 studies failed to establish its efficacy in this context.

Conclusion

Overall, the efficacy of sildenafil in the treatment of FSD remains controversial and inconclusive based on the available evidence. Further research is necessary to clarify the therapeutic potential of iPDE5 in addressing FSD and to better understand the factors that influence treatment outcomes.

The Effect of the Combination of Ginseng, Tribulus Terrestris, and L-arginine on the Sexual Performance of Men with Erectile Dysfunction: a randomized, double-blind, parallel, and placebo-controlled clinical trial

Objectives

Nitric oxide is the most important mediator of penile erection after the onset of sexual excitement. It activates cyclic guanosine monophosphate (cGMP), increasing penile blood flow. Most pharmaceutical medications prevent enzyme phosphodiesterase type 5 (PDE-5) from breaking down cGMP, thus keeping its level high. However, due to the adverse effects of pharmacological therapies, herbal drugs that improve sexual function have gained attention recently. This study aimed to investigate the combined effects of ginseng, Tribulus terrestris, and L-arginine amino acid on the sexual performance of individuals with erectile dysfunction (ED) using the 5-item version of the International Index of Erectile Function (IIEF-5) questionnaire.

Methods

Over three months, 98 men with erectile dysfunction were randomly assigned to receive either 500 mg of herbal supplements or placebo pills. Each herbal tablet contained 100 mg of protodioscin, 35 mg of ginsenosides, and 250 mg of L-arginine.

Results

The results showed that the changes in the average scores of ILEF-5 within each group before and after the intervention indicated that all parameters related to the improvement of sexual function in patients with erectile dysfunction improved in the herbal treatment group (p < 0.001). The herbal group significantly improved IIEF-5 scores in non-diabetics (p < 0.05). However, there was no significant difference in the changes of IIEF-5 scores between the two intervention and control groups in diabetic patients.

Conclusion

In conclusion, ginseng, Tribulus terrestris, and L-arginine have properties that increase energy and strengthen sexual function, making them suitable for patients with sexual disorders.

Dual Strategy with Adipose-Derived Stem Cells and l-arginine Recovered Cavernosal Functions in a Rat Model of Radical Prostatectomy

As standard therapy for prostate cancer, radical prostatectomy causes cavernous nerve (CN) injury and increases fibrosis and hypoxia-induced penile structural alterations. This study aimed to determine the potential beneficial effects of adipose-derived stem cells (ADSCs) and l-arginine alone or in combination on the penile erection in a rat model of erectile dysfunction caused by bilateral cavernous nerve transection (CNT). Male rats (n = 35) were randomized into five groups: Sham-operated; CNT (4-weeks); CNT plus ADSCs (1 × 106 cells by intracavernosal injection); CNT plus l-arginine (4 weeks, 10 mg/kg/day, oral); and ADSCs combined with l-arginine in CNT. In vivo erectile responses and in vitro relaxant responses were measured. Western blot and immunohistochemistry analyses were used to determine the expression and localization of endothelial nitric oxide synthase, neuronal nitric oxide synthase, transforming growth factor-beta 1, hypoxia-inducible factor-1 alpha (HIF-1α), and apoptosis markers (Bax and Bcl-2). The ratio of smooth muscle to collagen and nerve regeneration were calculated using Masson's trichrome and nicotinamide adenine dinucleotide phosphate (NADPH)-diaphorase staining. The combined treatment restored diminished erectile responses, endothelium-dependent acetylcholine, and electrical field stimulation-induced relaxation of the corpus cavernosum in rats with CNT, whereas either monotherapy produced only partial improvements. All treatment regimens restored increases in the protein expression of HIF-1 and Bax in rats with CNT. The decrease in smooth muscle mass and NADPH-diaphorase-positive nerve fibers was partially ameliorated by monotherapy, whereas combined therapy led to recovery. These findings indicate that combined treatment with ADSCs and l-arginine may restore erectile function in rats with CNT by inhibiting hypoxia-induced neurotoxicity and preserving endothelium function and smooth muscle content.

Advancements in Phosphodiesterase 5 Inhibitors: Unveiling Present and Future Perspectives

Phosphodiesterase 5 (PDE5) inhibitors presented themselves as important players in the nitric oxide/cGMP pathway, thus exerting a profound impact on various physiological and pathological processes. Beyond their well-known efficacy in treating male erectile dysfunction (ED) and pulmonary arterial hypertension (PAH), a plethora of studies have unveiled their significance in the treatment of a myriad of other diseases, including cognitive functions, heart failure, multiple drug resistance in cancer therapy, immune diseases, systemic sclerosis and others. This comprehensive review aims to provide an updated assessment of the crucial role played by PDE5 inhibitors (PDE5-Is) as disease-modifying agents taking their limiting side effects into consideration. From a medicinal chemistry and drug discovery perspective, the published PDE5-Is over the last 10 years and their binding characteristics are systemically discussed, and advancement in properties is exposed. A persistent challenge encountered with these agents lies in their limited isozyme selectivity; considering this obstacle, this review also highlights the breakthrough development of the recently reported PDE5 allosteric inhibitors, which exhibit an unparalleled level of selectivity that was rarely achievable by competitive inhibitors. The implications and potential impact of these novel allosteric inhibitors are meticulously explored. Additionally, the concept of multi-targeted ligands is critically evaluated in relation to PDE5-Is by inspecting the broader spectrum of their molecular interactions and effects. The objective of this review is to provide insight into the design of potent, selective PDE5-Is and an overview of their biological function, limitations, challenges, therapeutic potentials, undergoing clinical trials, future prospects and emerging uses, thus guiding upcoming endeavors in both academia and industry within this domain.

Long-term high-dose L-arginine supplementation in patients with vasculogenic erectile dysfunction: a multicentre, double-blind, randomized, placebo-controlled clinical trial

PURPOSE

The current randomized, double-blind, placebo-controlled clinical trial addressed the effects on penile erectile function of relatively high daily oral doses (6 g/day) of L-ARG for 3 months (N = 51) compared to placebo (N = 47), in patients with vasculogenic ED, with comparison between mild-moderate and severe vasculogenic ED.

METHODS

The outcome measures included IIEF-6 score and cavernous arteries peak systolic flow velocity (PSV) at dynamic penile duplex ultrasonography (PDU).

RESULTS

L-ARG supplementation for 3 months significantly increased IIEF-6 score in the overall cohort (p < 0.0001) and in subgroups of patients with mild-moderate (p < 0.0001) and severe (p = 0.007) vasculogenic ED; PSV was significantly increased in the overall cohort (p < 0.0001) and in patients with mild-moderate (p < 0.0001), but not severe vasculogenic ED. At study completion, 74% of patients improved ED degree category, although only 24% of patients, mainly belonging to the baseline category of mild ED, reached IIEF-6 scores compatible with absence of ED; moreover, 20% of patients, exclusively belonging to the baseline category of mild-moderate vasculogenic ED, reached PSV values compatible with absence of ED.

CONCLUSION

The results of the current study demonstrated that supplementation with relatively high doses of L-ARG as a single compound for 3 months significantly improved penile erectile function, assessed by both IIEF-6 score and PSV at dynamic PDU in patients with mild-moderate, and improved IIEF-6 score, but not PSV, in patients with severe vasculogenic ED, therefore suggesting that L-ARG might be an alternative treatment in mild-moderate vasculogenic ED patients experiencing adverse effects or with contraindications for chronic treatment with PDE5i compounds.

Absorption, distribution, metabolism, and excretion of [14C]TPN729 after oral administration to rats

TPN729, a novel phosphodiesterase type 5 (PDE5) inhibitor for the treatment of erectile dysfunction (ED), is in phase II clinical trials in China. Previous studies suggested that TPN729 possesses promising therapeutic value. In previous non-radiolabeled rat excretion studies, the recovery of TPN729 and its major metabolites accounted for approximately 8.58% of the administration dose in urine and feces by 48 h post-dose.To solve this problem and further study the metabolism of TPN729 in rats, we used the radio-isotopic tracing technique for the first time. In this study, the mass balance, tissue distribution, and metabolism of TPN729 were evaluated in rats after a single oral dose of 25 mg/kg [¹⁴C]TPN729 (150 μCi/kg).At 168 h post-dose, the mean total radioactivity recovery of the dose was 92.13%. Feces was the major excretion route, accounting for 74.63% of the dose, and urine excretion accounted for 17.50%. After oral administration of [¹⁴C]TPN729, radioactivity was widely distributed in all examined tissues, and a higher radioactivity concentration was observed in the stomach, large intestine, lung, liver, small intestine, and eyes. The concentration of drug-related materials were similar in plasma and blood cells. A total of 51 metabolites were identified in rat plasma, urine, feces, and bile, and the predominant metabolically susceptible position of TPN729 was the pyrrolidine moiety. The main metabolic pathways were N-dealkylation, oxidation, dehydrogenation, and glucuronidation.In summary, we solved the previous problem of low drug recovery, elucidated the major excretion pathway, determined the tissue distribution patterns, and investigated the metabolism of TPN729 in rats by using a radioisotopic tracing technique.

Comparison of efficacy and safety of daily oral L-arginine and PDE5Is alone or combination in treating erectile dysfunction: A systematic review and meta-analysis of randomised controlled trials

The meta-analysis was performed to assess the efficacy and safety of daily oral L-arginine and phosphodiesterase type 5 inhibitors (PDE5Is) alone or combination in treating patients with erectile dysfunction (ED). We performed a search of randomised controlled trials in the following databases: PubMed, EMBASE and Cochrane Library databases. Four articles including 373 patients were studied. Erectile functions were significantly improved in three therapy groups compared with baseline. Patients who received the combination of L-arginine and PDE5Is showed significant improvement compared to those treated with L-arginine and PDE5Is alone, as assessed by sexual function index (p <0.00001 and p =0.005, respectively) and total testosterone (p <0.00001 and p =0.0007, respectively). Furthermore, patients who treated with PDE5Is alone exhibited the better efficacy than those treated with L-arginine alone in respects of sexual function index (p <0.00001) and total testosterone (p =0.0001). However, the combination of L-arginine and PDE5Is had no obvious difference relative to PDE5Is alone in terms of various adverse events (AEs). Conclusively, compared with monotherapy, the combination of L-arginine and PDE5Is showed a greater improvement of sexual function and total testosterone, and did not significantly increase the AEs. Besides, PDE5Is alone revealed a better effect than those treated with L-arginine alone for patients with ED.

The Daily Therapy With L-Arginine 2,500 mg and Tadalafil 5 mg in Combination and in Monotherapy for the Treatment of Erectile Dysfunction: A Prospective, Randomized Multicentre Study

INTRODUCTION

A synergistic effect of the combination therapy tadalafil plus L-Arginine is conceivable in patients affected by erectile dysfunction (ED).

AIM

To evaluate the effectiveness and tolerability of tadalafil 5 mg and L-Arginine 2.5 grams in monotherapy and combination therapy.

METHODS

Recruited patients completed the International Index of Erectile Function - Erectile Function domain (IIEF-EF) and Sexual Encounter Profile diaries completed at baseline and after treatment. The survey was randomized into 3 groups with an equal allocation ratio. Group A received daily L-Arginine 2,500 mg, group B received daily tadalafil 5 mg, and group C received both daily L-Arginine 2,500 mg plus daily tadalafil 5 mg. The duration of therapy in all 3 groups was 12 weeks. Safety was assessed by evaluating all reported treatment-emergent adverse events.

MAIN OUTCOME MEASURE

The main outcome measure was the change in IIEF-EF score and in per-patient percentage of "yes" responses to Sexual Encounter Profile Question 3 from baseline to after treatment.

RESULTS

300 eligible patients were enrolled, and 100 subjects for each group were allocated. Based on the IIEF-EF score, the participants were divided into 3 categories: severe, moderate, and mild ED. IIEF-EF score increased in group A from 15 ± 7 to 18.1 ± 9.2, in group B from 14.8 ± 6.9 to 20.8 ± 7.3, and in group C from 14.9 ± 7.1 to 22 ± 7.5. In mild ED group, the mean IIEF-EF score increased from 22.1 ± 2.2 to 27.5 ± 2.3 in group A; from 22.1 ± 2.2 to 27.8 ± 2 in group B, and from 22.2 ± 2.2 to 29.3 ± 0.9 in group C. We report a total of 11, 53, and 67 cases of adverse events in group A, B, and C respectively.

CONCLUSIONS

Combination therapy was superior to monotherapies. Gallo L, Pecoraro S, Sarnacchiaro P, et al. The Daily Therapy With L-Arginine 2,500 mg and Tadalafil 5 mg in Combination and in Monotherapy for the Treatment of Erectile Dysfunction: A Prospective, Randomized Multicentre Study. Sex Med 2020;8:178-185.

Phosphodiesterase inhibitors for lower urinary tract symptoms consistent with benign prostatic hyperplasia

BACKGROUND

Benign prostatic hyperplasia (BPH) refers to non-malignant enlargement of the prostate gland that may cause bothersome lower urinary tract symptoms (LUTS). Alpha-blockers (ABs) and 5-alpha reductase inhibitors (5-ARIs) are the mainstay of medical treatment. Recently, phosphodiesterase inhibitors (PDEIs) that so far have been used mainly to treat erectile dysfunction were introduced to treat male LUTS.

OBJECTIVES

To assess the effects of PDEIs compared to placebo and other standard of care drugs (ABs and 5-ARIs) in men with LUTS consistent with BPH.

SEARCH METHODS

We conducted a systematic search of the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, Embase, Web of Science, and clinical trials registries of the World Health Organization (WHO) and the National Institutes of Health (NIH) (updated 2 August 2018). We performed citation tracking and handsearching of abstracts and conference proceedings. We also contacted study authors to ask for additional information.

SELECTION CRITERIA

We considered for inclusion in this systematic review randomised controlled trials (RCTs) comparing PDEIs versus placebo, ABs, or 5-ARIs for at least four weeks in men with BPH-LUTS.

DATA COLLECTION AND ANALYSIS

Three review authors independently screened the literature and extracted data. Primary outcomes were effects on urinary symptoms as assessed by the International Prostate Symptom Score (IPSS-total; score ranging from 0 to 35, with higher values reflecting more symptoms), urinary bother as assessed by the Benign Prostatic Hyperplasia Impact Index (BPHII; score ranging from 0 to 13, with higher values reflecting more bother), and adverse events (AEs). We used GRADE to rate the quality of evidence. We considered short-term (up to 12 weeks) and long-term (12 weeks or longer) results separately.

MAIN RESULTS

We included a total of 16 randomised trials in this review. The results for primary outcomes are as follows.PDEI versus placebo: PDEIs may result in a small improvement in IPSS-total score (mean difference (MD) 1.89 lower, 95% confidence interval (CI) 2.27 lower to 1.50 lower; n = 4293; low-quality evidence) compared to placebo, and may reduce the BPHII score slightly (MD 0.52 lower, 95% CI 0.71 lower to 0.33 lower; n = 3646; low-quality evidence). Rates of AEs may be increased (risk ratio (RR) 1.42, 95% CI 1.21 to 1.67; n = 4386; low-quality evidence). This corresponds to 95 more AEs per 1000 participants (95% CI 47 more to 151 more per 1000). Study results were limited to a treatment duration of six to 12 weeks.PDEI versus AB: PDEIs and ABs probably provide similar improvement in IPSS-total score (MD 0.22 higher, 95% CI 0.49 lower to 0.93 higher; n = 933; moderate-quality evidence) and may have a similar effect on BPHII score (MD 0.03 higher, 95% CI 1.10 lower to 1.16 higher; n = 550; low-quality evidence) and AEs (RR 1.35, 95% CI 0.80 to 2.30; n = 936; low-quality evidence). This corresponds to 71 more AEs per 1000 participants (95% CI 41 fewer to 264 more per 1000). Study results were limited to a treatment duration of six to 12 weeks.PDEI and AB versus AB alone: the combination of PDEI and AB may provide a small improvement in IPSS-total score (MD 2.56 lower, 95% CI 3.92 lower to 1.19 lower; n = 193; low-quality evidence) compared to AB alone. We found no evidence for BPHII scores. AEs may be increased (RR 2.81, 95% CI 1.53 to 5.17; n = 194; moderate-quality evidence). This corresponds to 235 more AEs per 1000 participants (95% CI 69 more to 542 more per 1000). Study results were limited to treatment duration of four to 12 weeks.PDEI and AB versus PDEI alone: the combination of PDEI and AB may provide a small improvement in IPSS-total (MD 2.4 lower, 95% CI 6.47 lower to 1.67 higher; n = 40; low-quality evidence) compared to PDEI alone. We found no data on BPHII or AEs. Study results were limited to a treatment duration of four weeks.PDEI and 5-ARI versus 5-ARI alone: in the short term (up to 12 weeks), the combination of PDEI and 5-ARI probably results in a small improvement in IPSS-total score (MD 1.40 lower, 95% CI 2.24 lower to 0.56 lower; n = 695; moderate-quality evidence) compared to 5-ARI alone. We found no evidence on BPHII scores or AEs. In the long term (13 to 26 weeks), the combination of PDEI and 5-ARI likely results in a small reduction in IPSS-total score (MD 1.00 less, 95% CI 1.83 lower to 0.17 lower; n = 695; moderate-quality evidence). We found no evidence about effects on BPHII scores. There may be no difference in rates of AEs (RR 1.07, 95% CI 0.84 to 1.36; n = 695; low-quality evidence). This corresponds to 19 more AEs per 1000 participants (95% CI 43 fewer to 98 more per 1000).We found no trials comparing other combinations of treatments or comparing different PDEI agents.

AUTHORS' CONCLUSIONS

Compared to placebo, PDEI likely leads to a small reduction in IPSS-total and BPHII sores, with a possible increase in AEs. There may be no differences between PDEI and AB with regards to improvement in IPSS-total, BPHII, and incidence of AEs. There appears to be no added benefit of PDEI combined with AB compared to PDEI or AB alone or PDEI combined with 5-ARI compared to ARI alone with regards to urinary symptoms. Most evidence was limited to short-term treatment up to 12 weeks and of moderate or low certainty.

Possible Drug-nutraceutical Interaction leading to Unexpected Sequelae after Inguinal Hernia Repair

BACKGROUND Nutraceutical formulations are an area in which physicians should be increasingly aware of their side effects. This case study shows the adverse effects that ginkgo biloba can have when combined with tadalafil following an inguinal hernia repair. CASE REPORT A 74-year-old male presented for repair of a recurrent inguinal hernia and for which the procedure was performed without complication. Upon follow-up, it was noted that he had significant ecchymosis not only in the inguinal region but in the ventral aspect of his penis. Upon further questioning, he reported that he had been taking ginkgo biloba that was stopped 5 days prior to the operation and restarted postoperative day 1. This, combined with tadalafil, was thought to be the reason for the unexpected induration and ecchymosis at the shaft of the penis. After discontinuing both medications, the ecchymosis and induration did resolve. CONCLUSIONS While ecchymosis and induration are expected in the inguinal region, the appearance of significant ecchymosis and induration down the shaft of the penis was unexpected in this case, and therefore we thought it could be due to nutraceutical use of ginkgo biloba combined with tadalafil, which were started postoperatively.

The Effect of LUTS/BPH and Treatments on Ejaculatory Function

As men age, there is an increased incidence of lower urinary tract symptoms (LUTS), often from benign prostatic hyperplasia (BPH) which can adversely affect sexual function. There are many different treatments for these symptoms; however, many of the treatments also affect sexual quality of life, specifically in the realm of ejaculation. Our paper will review the medications, surgical procedures, minimally invasive procedures, and even investigational procedures used to treat LUTS/BPH and the effect they have on ejaculation. The aim of this paper is to help practitioners counsel patients more effectively on treatment options when ejaculation is a concern.

Can Impaired Elasticity of Aorta Predict the Success of Vardenafil Treatment in Patients with Erectile Dysfunction?

Objective. Vardenafil is used in treatment of erectile dysfunction (ED) but reveals variable clinical outcomes. Here, we aimed to evaluate the role of aortic elasticity in predicting vardenafil success among patients with ED. Methods. Sixty-one consecutive male subjects with primary ED and indication for vardenafil treatment were included. All subjects fulfilled 5-item version of the International Index of Erectile Function (IIEF-5) before the vardenafil treatment. Pretreatment aortic stiffness index (ASI) and aortic distensibility (AD) were obtained echocardiographically. Following two-month vardenafil treatment, the patients were reevaluated with IIEF-5. Pretreatment, posttreatment, and ΔIIEF-5 scores and ASI values were compared. Results. Average age was 54 ± 8 years. Pretreatment and posttreatment IIEF-5 and ΔIIEF-5 scores were 9.1 ± 2.5; 18.5 ± 2.3; and 9.4 ± 3, respectively. Mean ASI and AD values were 3.10 ± 0.54 and 4.13 ± 2.55 1/(10(3)  ×  mmHg) accordingly. ASI value of severe pretreatment ED (n = 15) was significantly higher than that of mild-moderate pretreatment ED (n = 12) (p < 0.001). All pretreatment IIEF-5 scores increased significantly compared to posttreatment IIEF-5 scores (p < 0.001). ASI values were significantly correlated to pretreatment IIEF-5 scores (p < 0.001) and ΔIIEF-5 value (p < 0.001) but not to posttreatment IIEF-5 score. Conclusion. Aortic elasticity was impaired in accordance with degree of ED. The subjects with higher ASI values obtained more benefits from vardenafil.

Phosphodiesterase type 5 inhibitors for treating erectile dysfunction and lower urinary tract symptoms secondary to benign prostatic hyperplasia: A comprehensive review

Many men have coexistent erectile dysfunction (ED) and lower urinary tract symptoms secondary to benign prostatic hyperplasia (LUTS/BPH). Phosphodiesterase type 5 (PDE5) inhibitors are effective for treating both of these conditions independently. In this review we summarise the evidence supporting a link between ED and LUTS/BPH, and the results from key clinical studies related to the use of PDE5 inhibitors for treating both conditions. The results from these studies suggest that men who have both ED and LUTS/BPH, and are concerned about their sexual dysfunction, might benefit from single-agent, holistic treatment with a PDE5 inhibitor.

Management of benign prostatic hyperplasia: role of phosphodiesterase-5 inhibitors

Several studies have highlighted a strong association between benign prostatic hyperplasia/lower urinary tract symptoms (BPH/LUTS) and erectile dysfunction (ED), particularly in elderly men. Many epidemiological trials, such as in vitro and in vivo studies, have reported the emerging role of metabolic syndrome, including abdominal obesity, impaired glucose metabolism, hypertriglyceridemia, low high-density lipoprotein cholesterol, and hypertension, in the development and progression of urinary and sexual symptoms. Moreover, many authors have focused their studies on the identification of all the shared pathogenetic mechanisms of LUTS/BPH and ED, including alteration of cyclic guanosine monophosphate and RhoA-ROCK pathways or vascular and neurogenic dysfunction. All these are potential targets for proposed phosphodiesterase type 5 inhibitors (PDE5-Is). Therefore, several trials have recently been designed to evaluate the role of PDE5-Is alone or in combination with conventional treatment for BPH, such as α-adrenergic blockers, in men affected by LUTS/BPH, with or without ED. Different PDE5-Is are in clinical use worldwide and currently six of them are licensed for the oral treatment of ED. All these compounds differ in pharmacokinetic factors, with influence on drug action, and subsequently in the overall safety and efficacy profile.

Sildenafil ameliorates oxidative stress and DNA damage in the stenotic kidneys in mice with renovascular hypertension

Background

Oxidative stress and DNA damage have been implicated in the pathogenesis of renovascular hypertension induced by renal artery stenosis in the two-kidney, one-clip (2K1C) Goldblatt model. Considering our previous report indicating that the chronic blockade of phosphodiesterase 5 with sildenafil (Viagra®) has marked beneficial effects on oxidative stress and DNA damage, we tested the hypothesis that sildenafil could also protect the stenotic kidneys of 2K1C hypertensive mice against oxidative stress and genotoxicity.

Methods

The experiments were performed with C57BL6 mice subjected to renovascular hypertension by left renal artery clipping. Two weeks after clipping, the mice were treated with sildenafil (40 mg/kg/day for 2 weeks, 2K1C-sildenafil group) or the vehicle (2K1C). These mice were compared with control mice not subjected to renal artery clipping (Sham). After hemodynamic measurements, the stenotic kidneys were assessed using flow cytometry to evaluate cell viability and the comet assay to evaluate DNA damage. Measurements of intracellular superoxide anions and hydrogen peroxide levels as well as nitric oxide bioavailability were also obtained.

Results

Sildenafil treatment significantly reduced mean arterial pressure (15%), heart rate (8%), intrarenal angiotensin II (50%) and renal atrophy (36%). In addition, it caused a remarkable decrease of reactive oxygen species production. On the other hand, sildenafil increased nitric oxide levels relative to those in the nontreated 2K1C mice. Sildenafil treatment also significantly reduced the high level of kidney DNA damage that is a characteristic of renovascular hypertensive mice.

Conclusions

Our data reveal that sildenafil has a protective effect on the stenotic kidneys of 2K1C mice, suggesting a new use of phosphodiesterase 5 inhibitors for protection against the DNA damage observed in the hypoperfused kidneys of individuals with renovascular hypertension. Further translational research is necessary to delineate the mechanisms involved in the prevention of renal stenosis in the clinical setting.