Analysis of erectile responses to H2S donors in the anesthetized rat

The functions of hydrogen sulfide on the urogenital system of both males and females: from inception to the present

Hydrogen sulfide (H2S) is known as a chemical gas in nature with both enzymatic and non-enzymatic biosynthesis in different human organs. A couple of studies have demonstrated the function of H2S in regulating the homeostasis of the human body. Additionally, they have shown its synthesis, measurement, chemistry, protective effects, and interaction in various aspects of scientific evidence. Furthermore, many researches have demonstrated the beneficial impacts of H2S on genital organs and systems. According to various studies, it is recognized that H2S-producing enzymes and the endogenous production of H2S are expressed in male and female reproductive systems in different mammalian species. The main goal of this comprehensive review is to assess the potential therapeutic impacts of this gasotransmitter in the male and female urogenital system and find underlying mechanisms of this agent. This narrative review investigated the articles that were published from the 1970s to 2022. The review's primary focus is the impacts of H2S on the male and female urogenital system. Medline, CINAHL, PubMed, and Google scholar databases were searched. Keywords used in this review were "Hydrogen sulfide," "H2S," "urogenital system," and "urogenital tract". Numerous studies have demonstrated the therapeutic and protective effects of sodium hydrosulfide (Na-HS) as an H2S donor on male and female infertility disorders. Furthermore, it has been observed that H2S plays a significant role in improving different diseases such as ameliorating sperm parameters. The specific localization of H2S enzymes in the urogenital system provides an excellent opportunity to comprehend its function and role in various disorders related to this system. It is noteworthy that H2S has been demonstrated to be produced in endocrine organs and exhibit diverse activities. Moreover, it is important to recognize that alterations in H2S biosynthesis are closely linked to endocrine disorders. Therefore, hormones can be pivotal in regulating H2S production, and H2S synthesis pathways may aid in establishing novel therapeutic strategies. H2S possesses pharmacological effects on essential disorders, such as anti-inflammation, anti-apoptosis, and anti-oxidant activities, which render it a valuable therapeutic agent for human urogenital disease. Furthermore, this agent shows promise in ameliorating the detrimental effects of various male and female diseases. Despite the limited clinical research, studies have demonstrated that applying H2S as an anti-oxidant source could ameliorate adverse effects of different conditions in the urogenital system. More clinical studies are required to confirm the role of this component in clinical settings.

Prospective, randomized, placebo-controlled, two-arm study to evaluate the efficacy of coadministration of garlic as a hydrogen sulfide donor and tadalafil in patients with erectile dysfunction not responding to tadalafil alone - A pilot study

OBJECTIVE

The objective is to evaluate the efficacy of coadministration of garlic (as a hydrogen sulfide [H2S] donor) and tadalafil for patients with ED using a placebo-controlled, prospective, randomized, two-arm pilot study in patients responding poorly to tadalafil alone.

MATERIALS AND METHODS

The patients with complaints of ED (with normal penile Doppler) who failed to maintain sustained improvement in erectile function with tadalafil were recruited after excluding those with comorbidities. The study sample was randomized into two groups. Group A received garlic 5 g twice a day orally and Group B received a placebo twice daily orally for 4 weeks. Both groups continued tadalafil 5 mg in the night for 4 weeks. Their erectile function was assessed at the beginning and at the end of 4 weeks using the International Index of Erectile Function (IIEF-EF), erectile function domain and compared. A value of P ≤ 0.05 was considered statistically significant.

RESULTS

Nineteen patients in Group A (mean age 37.5 ± 10.6 years) and 16 patients in Group B (mean age 39.6 ± 9.6 years) participated in the pilot study conducted from May 2022 to August 2022. The participants treated with garlic (as an H2S donor) as a coadministrant had statistically significant improvement in IIEF-EF score (P ≤ 0.0001) at the end of 4 weeks compared to placebo.

CONCLUSIONS

Garlic (as an H2S donor) as adjunctive therapy was beneficial in our study participants responding poorly to tadalafil alone.

Role of hydrogen sulfide in the male reproductive system

As an important gas signaling molecule, hydrogen sulfide (H2S) affects multiple organ systems, including the nervous, cardiovascular, digestive, and genitourinary, reproductive systems. In particular, H2S not only regulates female reproductive function but also holds great promise in the treatment of male reproductive diseases and disorders, such as erectile dysfunction, prostate cancer, varicocele, and infertility. In this review, we summarize the relationship between H2S and male reproductive organs, including the penis, testis, prostate, vas deferens, and epididymis. As lower urinary tract symptoms have a significant impact on penile erection disorders, we also address the potential ameliorative effects of H2S in erectile dysfunction resulting from bladder disease. Additionally, we discuss the regulatory role of H2S in cavernous smooth muscle relaxation, which involves the NO/cGMP pathway, the RhoA/Rho-kinase pathway, and K+ channel activation. Recently, various compounds that can alleviate erectile dysfunction have been reported to be at least partly dependent on H2S. Therefore, understanding the role of H2S in the male reproductive system may help develop novel strategies for the clinical treatment of male reproductive system diseases.

Therapeutic Potential of Hydrogen Sulfide in Reproductive System Disorders

Hydrogen sulfide (H2S), previously regarded as a toxic exhaust and atmospheric pollutant, has emerged as the third gaseous signaling molecule following nitric oxide (NO) and carbon monoxide (CO). Recent research has revealed significant biological effects of H2S in a variety of systems, such as the nervous, cardiovascular, and digestive systems. Additionally, H2S has been found to impact reproductive system function and may have therapeutic implications for reproductive disorders. This paper explores the relationship between H2S and male reproductive disorders, specifically erectile dysfunction, prostate cancer, male infertility, and testicular damage. Additionally, it examines the impact of H2S regulation on the pathophysiology of the female reproductive system, including improvements in preterm birth, endometriosis, pre-eclampsia, fetal growth restriction, unexplained recurrent spontaneous abortion, placental oxidative damage, embryo implantation, recovery of myometrium post-delivery, and ovulation. The study delves into the regulatory functions of H2S within the reproductive systems of both genders, including its impact on the NO/cGMP pathway, the activation of K+ channels, and the relaxation mechanism of the spongy smooth muscle through the ROCK pathway, aiming to broaden the scope of potential therapeutic strategies for treating reproductive system disorders in clinical settings.

Icarifil® in Association with Daily Use of Tadalafil (5 mg) versus Standard Tadalafil Daily Dose (5 mg) or Alone: Results from a Controlled, Randomized Clinical Trial

Background: The management of erectile dysfunction (ED) shows several grey zones and new treatments are required to reduce the percentage of patients discontinuing treatment. Here, we aim to evaluate the role of a natural mixture named Icarifil® (L-Citrulline, L-Carnitine, Eruca vesicaria, Panax ginseng, Tribulus terrestris, Turnera diffusa, Taurine, Vitamin E, Zinc) in the management of patients with ED. Methods: From September 2022 to March 2023, all patients attending 3 urological institutions due to ED were randomized to receive the following for 3 months: Icarifil® 1 sachet every 24 h (Group 1) or Icarifil® 1 sachet + tadalafil 5 mg 1 tablet every 24 h (Group 2) or tadalafil 5 mg 1 tablet daily (Group 3). All patients underwent urologic visits and dedicated questionnaires (IIEF-5, SEP-2, SEP-3) at enrollment and at the follow-up evaluation (3 months). Patient-Reported Outcomes (PROs) at the follow-up evaluation were used. The primary endpoint was the difference in the questionnaires at the follow-up visit compared to the one at enrollment among the study groups. Results: In the per-protocol analysis, 52 patients in Group 1, 55 in Group 2 and 57 in Group 3 were analyzed. At the follow-up evaluation, IIEF-5 scores improved in all the 3 groups between enrollment and the follow-up evaluation, but a statistically significant difference was reported between Group 2 (+7.4) and Group 1 (+4.1) or Group 3 (+5.1), (p < 0.001; p < 0.001). Moreover, 47 patients (94.0%) in Group 2 showed an improvement in the SEP questionnaires, when compared with the baseline, while 29 in Group 1 (56.9%) and 42 in Group 3 (82.3%) showed a statistically significant difference (p = 0.004; p = 0.003) among the groups. The PRO analysis reported better efficacy and patient satisfaction in Group 2 when compared with Group 1 or Group 3. Conclusions: In conclusion, Icarifil® is able to improve penile erectile function in mild-moderate ED and significantly improve the clinical efficacy of daily used tadalafil 5 mg. Icarifil® could represent an interesting alternative treatment in patients experiencing adverse effects or with contraindications for chronic treatment with PDE5-is.

Erectile dysfunction is associated with defective L-cysteine/hydrogen sulfide pathway in human corpus cavernosum and penile arteries

H₂S signaling was proposed to participate in erectile physiology. L-cysteine (CYS)/H₂S pathway stimulation causes cGMP-dependent relaxation of human corpus cavernosum (HCC) and penile arteries (HPRA). The aim was to evaluate the impact of ED on CYS/H₂S pathway at functional and molecular level in human penile vascular tissues. NaHS- and CYS-induced responses were evaluated in HCC and HPRA from organ donors without ED (NoED, n = 29) and from ED patients undergoing penile prosthesis insertion (n = 45). cGMP accumulation and cystathionine β-synthase and cystathionine γ-lyase expression were also determined. NaHS-induced relaxations were slightly but significantly impaired in HCC but not in HPRA from ED patients. In contrast, CYS-induced relaxations were markedly impaired in HCC (E_max 67.6 ± 4.9% vs 46.2 ± 4.6%, P < 0.01) and HPRA (E_max 80.8 ± 4.0% vs 48.1 ± 8.6%, P < 0.05) from men with ED. Impairment of CYS-induced responses was observed even after separating diabetic ED patients. In HPRA from ED patients, CYS- but not NaHS-induced vasodilation was significantly associated to endothelial function measured as vasodilatory capacity of acetylcholine (ACh) in these preparations (r² = 0.481, P < 0.01). Impairment of CYS-induced relaxations was related to significant reduction in CYS-induced accumulation of cGMP in cavernosal tissue. Furthermore, the expression of H₂S synthesizing enzymes was significantly reduced in HCC from ED patients with respect to NoED. This was confirmed by immunofluorescence in HCC and HPRA sections. ED involves impairment of CYS/H₂S pathway in penile vascular tissues associated with decreased expression of H₂S generating enzymes, CBS and CSE. These evidences support a therapeutic potential for modulation of CYS/H₂S signaling in the management of ED.

Evaluation of combined therapeutic effects of hydrogen sulfide donor sodium hydrogen sulfide and phosphodiesterase type-5 inhibitor tadalafil on erectile dysfunction in a partially bladder outlet obstructed rat model

AIMS

To evaluate the impacts of hydrogen sulfide (H₂ S) donor, sodium hydrogen sulfide (NaHS), and phosphodiesterase type-5 inhibitor (PDE5i), tadalafil per se and their combination treatment on partial bladder outlet obstruction (PBOO)-induced erectile dysfunction (ED).

METHODS

Sprague-Dawley rats were equally divided into five groups: (a) sham-operated control; (b) PBOO; (c) PBOO-treated with NaHS (5.6 mg/kg/day, ip); (d) PBOO-treated with tadalafil (2 mg/kg/day, oral); and (e) PBOO-treated with combination of NaHS and tadalafil. The obstruction was created by urethral ligation for 6 weeks. In vivo erectile responses, in vitro relaxant and contractile responses in penile tissue as well as protein expression of nitric oxide synthases (NOS), H₂ S synthesis enzymes, oxidative stress, hypoxia, fibrosis markers, and the smooth muscle/collagen ratio and apoptosis were analyzed.

RESULTS

Combined treatment entirely returned increased bladder mass, reduced erectile responses, relaxation responses to acetylcholine, and electrical field stimulation in obstructed rats, while partial amelioration was observed after mono-treatment. Decreased neuronal NOS and 3-mercaptopiruvate transferase enzyme expressions in penile tissue from obstructed rats were also entirely restored by the combined treatment. Mono-treatment partially improved increased hypoxia, oxidative stress, fibrosis markers, decreased smooth muscle mass, and H₂ S levels, while combined therapy completely recovered.

CONCLUSIONS

The combination therapy with H₂ S donor and PDE5i had positive effects on erectile responses through the improvement of ischemia-induced morphological and functional penile alterations in obstruction. H₂ S and NO may likely play a synergistic role in the regulation of erectile function and have constructive effects on clinical outcomes in male patients with ED and benign prostatic hyperplasia/lower urinary tract symptoms.

Sodium Tanshinone IIA Sulfonate Attenuates Erectile Dysfunction in Rats with Hyperlipidemia

Hyperlipidemia is considered one of the most important risk factors for erectile dysfunction (ED). To determine the effect of sodium tanshinone IIA sulfonate (STS) as an antioxidant agent on ED in high-fat diet- (HFD-) induced hyperlipidemia in rats and to investigate if STS administration could improve erectile function via hydrogen sulfide (H₂S) production by inhibition of oxidative stress. Hyperlipidemia was induced in Sprague-Dawley rats by feeding HFD for 16 weeks. The rats were randomly divided into 3 groups: control, HFD, and HFD treated with STS (10 mg/kg/day for 12 weeks, intraperitoneal injection). Erectile function including intracavernosal pressure (ICP), H₂S production, and antioxidant capacity was assessed. In addition, cavernosal smooth muscle cells (CSMC) isolated from SD rats were pretreated with STS in vitro and exposed to H₂O₂. Expressions of nuclear factor erythroid 2-related factor 2 (Nrf2)/heme oxygenase-1 (HO-1), activity of antioxidant enzymes, and H₂S-generating enzymes within CSMC were examined. ICP was significantly decreased in HFD rats compared with control. In addition, decreased H₂S production and expression of cystathionine ɣ-lyase (CSE) and cystathionine β-synthase (CBS) associated with increased oxidative stress were observed in the penile tissue of HFD rats. However, all these changes were reversed by 16 weeks after STS administration. STS also increased antioxidant defense as evidenced by increased expression of Nrf2/HO-1 in the penile tissue of HFD rats. In CSMC, pretreatment with STS attenuated the decreased expression of CSE and CBS and H₂S production by H₂O₂. STS exerted similar protective antioxidative effect as shown in the in vivo hyperlipidemia model. The present study demonstrated the redox effect of STS treatment on ED via increased H₂S production in HFD-induced hyperlipidemia rat model by increased antioxidant capacity via activation of the Nrf2/HO-1 pathway, which provides STS potential clinical application in the treatment of hyperlipidemia-related ED.

The Relaxant Mechanisms of Hydrogen Sulfide in Corpus Cavernosum

In several animal and human studies, the contribution of the endothelium, nitric oxide/soluble guanosine monophosphate (NO/cGMP) pathway, adenylyl cyclase, phosphodiesterase (PDE), potassium (K⁺) channels, L-type calcium channels, Na⁺-K⁺-ATPase, muscarinic acetylcholine receptors, RhoA/Rho-kinase pathway, and cyclooxygenase (COX)/arachidonic acid cascade on the relaxant mechanism of L-cysteine/H₂S pathway in corpus cavernosum has been investigated. In this chapter the relaxant mechanisms of H₂S in corpus cavernosum is discussed with data available in the current relevant literature. Also, in vitro experimental procedure for mice corpus cavernosum which used to investigate the relaxant effect of H₂S is given in detail.

Cavernosal hydrogen sulfide levels are associated with nitric oxide and hemeoxygenase levels in diabetic rats

Penile erection is a neuromuscular event modulated by psyche, hormones as well as neurotransmitters. This pre-clinical study aimed to assess hydrogen sulfide (H₂S) relationship with nitric oxide (NO) and hemeoxygenase (HO) in the cavernous tissues of diabetic rats. Overall, 90 adult male rats were investigated (6 groups, n = 15 each). They were subdivided into the following groups; untreated rats, rats treated with H₂S donor/inhibitor, induced diabetic rats, diabetic rats treated with H₂S donor/inhibitor. At the 6th week, the rats were killed to assess cavernous tissue cGMP, NO, H₂S, HO enzyme activity levels. The rats treated with H₂S donor showed increased mean cavernous tissue cGMP, NO, H₂S, and HO enzyme activity levels whereas induced diabetic rats and rats treated with H₂S inhibitor showed significant decreases in these parameters compared with the untreated rats. On the other hands, diabetic rats treated with H₂S donor showed elevated mean cavernous tissue cGMP, NO, H₂S, and HO enzyme activity levels whereas diabetic rats treated with H₂S inhibitor showed significant decreases in these parameters compared with diabetic rats. Cavernous tissue H₂S levels exhibited significant positive correlations with the cavernous tissue levels cGMP, NO, and HO enzyme activity levels. From these results, it could be concluded that cavernous tissues H₂S plays a role of male sexual health by affecting cavernous tissues NO and HO enzyme activity in general and in diabetics in particular.

Regulation of Aqueous Humor Dynamics by Hydrogen Sulfide: Potential Role in Glaucoma Pharmacotherapy

Hydrogen sulfide (H₂S) is a gaseous transmitter with well-known biological actions in a wide variety of tissues and organs. The potential involvement of this gas in physiological and pathological processes in the eye has led to several in vitro, ex vivo, and in vivo studies to understand its pharmacological role in some mammalian species. Evidence from literature demonstrates that 4 enzymes responsible for the biosynthesis of this gas (cystathionine β-synthase, CBS; cystathionine γ-lyase, CSE; 3-mercaptopyruvate sulfurtransferase, 3MST; and d-amino acid oxidase) are present in the cornea, iris, ciliary body, lens, and retina. Studies of the pharmacological actions of H₂S (using several compounds as fast- and slow-releasing gas donors) on anterior uveal tissues reveal an effect on sympathetic neurotransmission and the ability of the gas to relax precontracted iris and ocular vascular smooth muscles, responses that were blocked by inhibitors of CSE, CBS, and K_ATP channels. In the retina, there is evidence that H₂S can inhibit excitatory amino acid neurotransmission and can also protect this tissue from a wide variety of insults. Furthermore, exogenous application of H₂S-releasing compounds was reported to increase aqueous humor outflow facility in an ex vivo model of the porcine ocular anterior segment and lowered intraocular pressure (IOP) in both normotensive and glaucomatous rabbits. Taken together, the finding that H₂S-releasing compounds can lower IOP and can serve a neuroprotective role in the retina suggests that H₂S prodrugs could be used as tools or therapeutic agents in diseases such as glaucoma.

Drugs in preclinical to phase II clinical development for the treatment of erectile dysfunction

INTRODUCTION

Erectile function is an important aspect in the quality of life of many men. For men with erectile dysfunction (ED), a spectrum of treatment options exists. Novel therapies for ED are currently being developed in order to delay surgical placement of a penile prosthesis - the final step in the management of treatment-refractory ED. Areas covered: This review examines innovative treatments such as alternative vasoactive agents, trophic factors and bio-compounds as well as gene and stem cell therapy. All therapies are currently in some phase of development for the management of ED. Using the MedLine and FDA Clinical Trials Registry, recent developments in treatment of ED were queried. Expert opinion: Recent studies have demonstrated the potential for multiple, novel therapies in the treatment of ED. Much of the work requires further experimentation in large-scale, blinded, placebo-controlled studies. This will require a concerted effort to bring these products to market.

Emerging role of hydrogen sulfide-microRNA crosstalk in cardiovascular diseases

Despite an obnoxious smell and toxicity at a high dose, hydrogen sulfide (H2S) is emerging as a cardioprotective gasotransmitter. H2S mitigates pathological cardiac remodeling by regulating several cellular processes including fibrosis, hypertrophy, apoptosis, and inflammation. These encouraging findings in rodents led to initiation of a clinical trial using a H2S donor in heart failure patients. However, the underlying molecular mechanisms by which H2S mitigates cardiac remodeling are not completely understood. Empirical evidence suggest that H2S may regulate signaling pathways either by directly influencing a gene in the cascade or interacting with nitric oxide (another cardioprotective gasotransmitter) or both. Recent studies revealed that H2S may ameliorate cardiac dysfunction by up- or downregulating specific microRNAs. MicroRNAs are noncoding, conserved, regulatory RNAs that modulate gene expression mostly by translational inhibition and are emerging as a therapeutic target for cardiovascular disease (CVD). Few microRNAs also regulate H2S biosynthesis. The inter-regulation of microRNAs and H2S opens a new avenue for exploring the H2S-microRNA crosstalk in CVD. This review embodies regulatory mechanisms that maintain the physiological level of H2S, exogenous H2S donors used for increasing the tissue levels of H2S, H2S-mediated regulation of CVD, H2S-microRNAs crosstalk in relation to the pathophysiology of heart disease, clinical trials on H2S, and future perspectives for H2S as a therapeutic agent for heart failure.