Sildenafil protects epithelial cell through the inhibition of xanthine oxidase and the impairment of ROS production

PDE5 inhibitors: breaking new grounds in the treatment of COVID-19

INTRODUCTION

Despite the ever-increasing occurrences of the coronavirus disease (COVID-19) cases around the world, very few medications have been validated in the clinical trials to combat COVID-19. Although several vaccines have been developed in the past quarter, the time elapsed between deployment and administration remains a major impediment.

CONTENT

Repurposing of pre-approved drugs, such as phosphodiesterase 5 (PDE5) inhibitors, could be a game-changer while lessening the burden on the current healthcare system. Repurposing and developing phosphodiesterase 5 (PDE5) inhibitors could extrapolate their utility to combat the SARS-CoV-2 infection, and potentially aid in the management of the symptoms associated with its newer variants such as BF.7, BQ.1, BQ.1.1, XBB.1.5, and XBB.1.16.

SUMMARY

Administration of PDE5 inhibitors via the oral and intravenous route demonstrates other potential off-label benefits, including anti-apoptotic, anti-inflammatory, antioxidant, and immunomodulatory effects, by intercepting several pathways. These effects can not only be of clinical importance in mild-to-moderate, but also moderate-to-severe SARS-CoV-2 infections. This article explores the various mechanisms by which PDE5 inhibitors alleviates the symptoms associated with COVID-19 as well as well as highlights recent studies and findings.

OUTLOOK

These benefits of PDE5 inhibitors make it a potential drug in the physicians' armamentarium in alleviating symptoms associated with SARS-CoV-2 infection. However, adequate clinical studies must be instituted to eliminate any untoward adverse events.

PDE5 inhibitors: breaking new grounds in the treatment of COVID-19

INTRODUCTION

Despite the ever-increasing occurrences of the coronavirus disease (COVID-19) cases around the world, very few medications have been validated in the clinical trials to combat COVID-19. Although several vaccines have been developed in the past quarter, the time elapsed between deployment and administration remains a major impediment.

CONTENT

Repurposing of pre-approved drugs, such as phosphodiesterase 5 (PDE5) inhibitors, could be a game-changer while lessening the burden on the current healthcare system. Repurposing and developing phosphodiesterase 5 (PDE5) inhibitors could extrapolate their utility to combat the SARS-CoV-2 infection, and potentially aid in the management of the symptoms associated with its newer variants such as BF.7, BQ.1, BQ.1.1, XBB.1.5, and XBB.1.16.

SUMMARY

Administration of PDE5 inhibitors via the oral and intravenous route demonstrates other potential off-label benefits, including anti-apoptotic, anti-inflammatory, antioxidant, and immunomodulatory effects, by intercepting several pathways. These effects can not only be of clinical importance in mild-to-moderate, but also moderate-to-severe SARS-CoV-2 infections. This article explores the various mechanisms by which PDE5 inhibitors alleviates the symptoms associated with COVID-19 as well as well as highlights recent studies and findings.

OUTLOOK

These benefits of PDE5 inhibitors make it a potential drug in the physicians' armamentarium in alleviating symptoms associated with SARS-CoV-2 infection. However, adequate clinical studies must be instituted to eliminate any untoward adverse events.

Xanthine oxidase/NADPH oxidase inhibition by hydralazine attenuates acute kidney injury and prevents the transition of acute kidney injury to chronic kidney disease

AIMS

The enhancement of inflammation and reactive oxygen species leads to the damage of renal tubular cells in acute kidney injury (AKI), and the upregulation of inflammation increases the risk of AKI being converted into chronic kidney disease (CKD). Hydralazine has shown renoprotective effects in multiple kidney diseases and was shown to be a potent xanthine oxidase (XO) inhibitor. This study aimed to investigate the mechanisms of hydralazine in ischemia-reperfusion (I/R)-stimulated renal proximal tubular epithelial cells in vitro and in AKI animals in vivo.

MAIN METHODS

The effects of hydralazine in AKI-to-CKD transition were also evaluated. Human renal proximal tubular epithelial cells were stimulated by I/R conditions in vitro. To generate a mouse model of AKI, a right nephrectomy was performed, followed by left renal pedicle I/R using a small atraumatic clamp.

KEY FINDINGS

In the in vitro part, hydralazine could protect renal proximal tubular epithelial cells against insults from the I/R injury through XO/NADPH oxidase inhibition. In the in vivo part, hydralazine preserved renal function in AKI mice and improved the AKI-to-CKD transition by decreasing renal glomerulosclerosis and fibrosis independently of blood pressure lowering. Furthermore, hydralazine exerted antioxidant, anti-inflammatory, and anti-fibrotic effects both in vitro and in vivo.

SIGNIFICANCE

Hydralazine, as a XO/NADPH oxidase inhibitor, could protect renal proximal tubular epithelial cells from the insults of I/R and prevent kidney damage in AKI and AKI-to-CKD. The above experimental studies strengthen the possibility of repurposing hydralazine as a potential renoprotective agent through its antioxidative mechanisms.

Sildenafil citrate ameliorates the adverse effects of cryopreservation on sperm quality in asthenozoospermic men

In this study, the effects of Sildenafil Citrate on the sperm quality during cryopreservation in the asthenozoospermic patients were investigated for the first time. Thirty semen samples were collected from asthenozoospermic patients and each sample was divided into 3 groups: Control (fresh), Freeze and Freeze + Sildenafil. In each groups the sperm parameters, DNA fragmentation, acrosome integrity, protamine deficiency, mitochondrial membrane potential, plasma membrane integrity, the expression of Bcl-2 and HSP70 genes, as well as the level of Tumor necrosis factor-alpha, Malondialdehyde and antioxidants (Catalase, Glutathione, and Superoxide dismutase) in sperm were assessed. Data were analyzed statistically using Repeated Measure Analysis. The level of Malondialdehyde and Tumor necrosis factor-alpha, morphological abnormalities, DNA fragmentation, protamine deficiency and the expression of Bcl-2 and HSP70 genes increased significantly in the Freeze group compared to the Control, while the level of sperm parameters and antioxidants, plasma membrane integrity, mitochondrial membrane potential and acrosomal integrity significantly decreased. In the Freeze + Sildenafil group, compared to the Freeze group, all the mentioned parameters were significantly reversed except for the acrosomal integrity (decreased even more) and the expression of Bcl-2 (increased even more) and HSP70 genes (with no change). Although adding Sildenafil to the freezing medium decreased the adverse effects of freezing on the sperm of asthenozoospermic patients and improved sperm quality, but it also caused premature acrosome reaction. Therefore, we suggest the consumption of Sildenafil along with another antioxidant, to benefit from the favorable effects of Sildenafil as well as to maintain the integrity of the sperm acrosome.

Could Oral Phosphodiesterase 5 Inhibitors Have a Potential Adjuvant Role in Combating COVID-19 Infection?

INTRODUCTION

The recent global outbreak of coronavirus disease 2019 (COVID-19) has become a pandemic with a lot of sufferers. Excessive inflammation, exaggerated immune response, with ultimate apoptosis contribute to COVID-19 pathology that progress to acute lung acute respiratory distress.

OBJECTIVE

To shed a light on the likely benefits of the oral phosphodiesterase 5 (PDE5) inhibitor adjuvant role in combating COVID-19 infection.

METHODS

A literature review was performed in the PubMed/Medline database, Scopus, Cochrane Library, EMBASE, Academic Search Complete, Google Scholar, and CINAHL databases using the keywords COVID-19; phosphodiesterase-5 inhibitors; cytokine storm; respiratory distress.

RESULTS

Despite the worsening trends of COVID-19, still no drugs are validated to have significant clinical efficacy in the treatment of patients with COVID-19 in large-scale studies. While the progress toward a curative agent and/or vaccine is certainly hopeful, the principal limiting factor in such public health emergencies is always the time. Therefore, a preexisting licensed therapeutic(s) might offer a reprieve to the healthcare systems operating at the edge of capacity. In this context, the innovation of oral PDE5 inhibitors with their valuable effects on erection have provided a breakthrough in the treatment of erectile dysfunction and opened new fields of clinical application for this class of drugs. Oral PDE5 inhibitors have been demonstrated to possess many beneficial useful additional implications with acknowledged anti-inflammatory, antioxidant, immune response regulation, and antiapoptotic properties. These properties have been elucidated through the nitric oxide/soluble guanylyl cyclase/cyclic guanylate monophosphate pathway in addition to the emerged hemeoxygenase-1 enzyme as well as hydrogen sulfide pathways. These properties could support repurposing oral PDE5 inhibitors' potential adjuvant use in targeting different aspects of COVID-19 infection.

CONCLUSION

Oral PDE5 inhibitors retain several acknowledged off-labeled useful implications with anti-inflammatory, antioxidant, immune response regulation, and antiapoptotic properties. These properties may support repurposing oral PDE5 inhibitors' potential adjuvant use in the protocols combating COVID-19 manifestations. Mostafa T. Could Oral Phosphodiesterase 5 Inhibitors Have a Potential Adjuvant Role in Combating Coronavirus Disease 2019 Infection? Sex Med Rev 2021;9:15-22.

Could Oral Phosphodiesterase 5 Inhibitors Have a Potential Adjuvant Role in Combating COVID-19 Infection?

INTRODUCTION

The recent global outbreak of coronavirus disease 2019 (COVID-19) has become a pandemic with a lot of sufferers. Excessive inflammation, exaggerated immune response, with ultimate apoptosis contribute to COVID-19 pathology that progress to acute lung acute respiratory distress.

OBJECTIVE

To shed a light on the likely benefits of the oral phosphodiesterase 5 (PDE5) inhibitor adjuvant role in combating COVID-19 infection.

METHODS

A literature review was performed in the PubMed/Medline database, Scopus, Cochrane Library, EMBASE, Academic Search Complete, Google Scholar, and CINAHL databases using the keywords COVID-19; phosphodiesterase-5 inhibitors; cytokine storm; respiratory distress.

RESULTS

Despite the worsening trends of COVID-19, still no drugs are validated to have significant clinical efficacy in the treatment of patients with COVID-19 in large-scale studies. While the progress toward a curative agent and/or vaccine is certainly hopeful, the principal limiting factor in such public health emergencies is always the time. Therefore, a preexisting licensed therapeutic(s) might offer a reprieve to the healthcare systems operating at the edge of capacity. In this context, the innovation of oral PDE5 inhibitors with their valuable effects on erection have provided a breakthrough in the treatment of erectile dysfunction and opened new fields of clinical application for this class of drugs. Oral PDE5 inhibitors have been demonstrated to possess many beneficial useful additional implications with acknowledged anti-inflammatory, antioxidant, immune response regulation, and antiapoptotic properties. These properties have been elucidated through the nitric oxide/soluble guanylyl cyclase/cyclic guanylate monophosphate pathway in addition to the emerged hemeoxygenase-1 enzyme as well as hydrogen sulfide pathways. These properties could support repurposing oral PDE5 inhibitors' potential adjuvant use in targeting different aspects of COVID-19 infection.

CONCLUSION

Oral PDE5 inhibitors retain several acknowledged off-labeled useful implications with anti-inflammatory, antioxidant, immune response regulation, and antiapoptotic properties. These properties may support repurposing oral PDE5 inhibitors' potential adjuvant use in the protocols combating COVID-19 manifestations. Mostafa T. Could Oral Phosphodiesterase 5 Inhibitors Have a Potential Adjuvant Role in Combating Coronavirus Disease 2019 Infection? Sex Med Rev 2021;9:15-22.

Carnosine protects pancreatic beta cells and islets against oxidative stress damage

Islet transplantation is a valid therapeutic option for type 1 diabetes treatment. However, in this procedure one of the major problems is the oxidative stress produced during pancreatic islet isolation. The aim of our study was to evaluate potential protective effects of L-carnosine and its isomer D-carnosine against oxidative stress. We evaluated the carnosine effect on cell growth, cell death, insulin production, and the main markers of oxidative stress in rat and murine stressed beta cell lines as well as in human pancreatic islets. Both isomers clearly inhibited hydrogen peroxide induced cytotoxicity, with a decrease in intracellular reactive oxygen and nitrogen species, prevented hydrogen peroxide induced apoptosis/necrosis, nitrite production, and reduced glucose-induced insulin secretion. In addition, NF-κB expression/translocation and nitrated protein induced in stressed cells was significantly reduced. Furthermore, both isomers improved survival and function, and decreased reactive oxygen and nitrogen species, and nitrite and nitrotyrosine production in human islets cultured for 1, 3, and 7 days. These results seem to indicate that both L and D-carnosine have a significant cytoprotective effect by reducing oxidative stress in beta cell lines and human islets, suggesting their potential use to improve islet survival during the islet transplantation procedure.

Effects of Sildenafil and Tadalafil on Edema and Reactive Oxygen Species Production in an Experimental Model of Lung Ischemia-Reperfusion Injury

BACKGROUND

Lung ischemia-reperfusion injury is characterized by formation of reactive oxygen species and cellular swelling leading to pulmonary edema and primary graft dysfunction. Phosphodiesterase 5 inhibitors could ameliorate lung ischemia-reperfusion injury by interfering in many molecular pathways. The aim of this work was to evaluate and compare the effects of sildenafil and tadalafil on edema and reactive oxygen species formation in an ex vivo nonhuman animal model of lung ischemia-reperfusion injury.

METHODS

Thirty-two Wistar rats were distributed, treated, perfused and the cardiopulmonary blocks were managed as follows: control group: immediate excision and reperfusion without pretreatment; ischemia reperfusion group: treatment with dimethylsulfoxide 0.9% and excision 1 hour later; sildenafil group: treatment with sildenafil (0.7 mg/kg) and excision 1 hour later; and tadalafil group: treatment with tadalafil (0.15 mg/kg) and excision 2 hours later. All cardiopulmonary blocks except control group were preserved for 8 hours and then reperfused. Pulmonary arterial pressure, pulmonary venous pressure, and capillary filtration coefficient were measured. Reactive oxygen species were measured.

RESULTS

Edema was similar between control and sildenafil groups, but significantly greater in the ischemia-reperfusion (P ≤ .04) and tadalafil (P ≤ .003) groups compared with the sildenafil group. The malondialdehyde levels were significantly lower in the sildenafil (P ≤ .001) and tadalafil (P ≤ .001) groups than the ischemia-reperfusion group.

CONCLUSIONS

Administration of sildenafil, but not tadalafil, decreased edema in lung ischemia-reperfusion injury. Both drugs decreased reactive oxygen species formation in a lung ischemia-reperfusion injury model.

Sildenafil reduces signs of oxidative stress in pulmonary arterial hypertension: Evaluation by fatty acid composition, level of hydroxynonenal and heart rate variability

Pulmonary arterial hypertension (PAH) is a rare multifactorial disease with an unfavorable prognosis. Sildenafil therapy can improve functional capacity and pulmonary hemodynamics in PAH patients. Nowadays, it is increasingly recognized that the effects of sildenafil are pleiotropic and may also involve changes of the pro-/antioxidant balance, lipid peroxidation and autonomic control. In present study we aimed to assess the effects of sildenafil on the fatty acids (FAs) status, level of hydroxynonenal (HNE) and heart rate variability (HRV) in PAH patients. Patients with PAH were characterized by an increase in HNE and changes in the FAs composition with elevation of linoleic, oleic, docosahexanoic acids in phospholipids as well as reduced HRV with sympathetic predominance. Sildenafil therapy improved exercise capacity and pulmonary hemodynamics and reduced NT-proBNP level in PAH. Antioxidant and anti-inflammatory effects of sildenafil were noted from the significant lowering of HNE level and reduction of the phopholipid derived oleic, linoleic, docosahexanoic, docosapentanoic FAs. That was also associated with some improvement of HRV on account of the activation of the neurohumoral regulatory component. Incomplete recovery of the functional metabolic disorders in PAH patients may be assumed from the persistent increase in free FAs, reduced HRV with the sympathetic predominance in the spectral structure after treatment comparing to control group. The possibilities to improve PAH treatment efficacy through mild stimulation of free radical reactions and formation of hormetic reaction in the context of improved NO signaling are discussed.

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Sildenafil showed antioxidant and anti-inflammatory effects in pulmonary hypertension.

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Sildenafil reduced hydroxynonenal level and improved fatty acid profile in serum.

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Improvement of heart rate variability and functional capacity was noted after therapy.

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Mild prooxidant activity is suggested as the mechanism to improve sildenafil efficacy.

PDE-5 inhibition improves skin flap viability in rats that are exposed to nicotine

INTRODUCTION

Nicotine causes ischemia and necrosis of skin flaps. Phosphodiesterase-5 (PDE-5) inhibition enhances blood flow and vasculogenesis. This study examines skin flap survival in rats exposed to nicotine that are treated with and without PDE-5 inhibition.

MATERIALS AND METHODS

Eighty six rats were divided into five groups. Group 1 received saline subcutaneous (SC) once per day. Group 2 received nicotine SC 2 mg/kg day. Group 3 received sildenafil intraperitoneal (IP) 10 mg/kg day. Group 4 received nicotine SC 2 mg/kg and sildenafil IP 10 mg/kg day. Group 5 received nicotine SC 2 mg/kg day and sildenafil IP 10 mg/kg two times daily. After 28 days of treatment, modified McFarlane flaps were created, silicone sheets were interposed, and flaps were sutured. Photographs were taken on postoperative days 1, 3, and 7 and fluorescence angiography was used on day 7, both to evaluate for skin flap necrosis. Rats were euthanized and flaps were harvested for Vascular Endothelial Growth Factor (VEGF) Western blot analysis. Images were analyzed by three blinded observers using ImageJ, and necrotic indices were calculated.

RESULTS

The nicotine and PDE-5 inhibition twice-daily group showed a 46% reduction in flap necrosis when compared to saline only (P < 0.05) and a 54% reduction when compared to nicotine only (P < 0.01). Fluorescence angiographic image analysis revealed reductions in flap necrosis (P < 0.01). VEGF analysis trended toward increased VEGF for all sildenafil-treated groups (P > 0.05).

CONCLUSIONS

PDE-5 inhibition exhibits a dose-dependent reduction in skin flap necrosis in rats exposed to nicotine. This suggests that PDE-5 inhibition may mitigate the ill effects of smoking on skin flaps.

Phytoagents for cancer management: regulation of nucleic acid oxidation, ROS, and related mechanisms

Accumulation of oxidized nucleic acids causes genomic instability leading to senescence, apoptosis, and tumorigenesis. Phytoagents are known to reduce the risk of cancer development; whether such effects are through regulating the extent of nucleic acid oxidation remains unclear. Here, we outlined the role of reactive oxygen species in nucleic acid oxidation as a driving force in cancer progression. The consequential relationship between genome instability and cancer progression highlights the importance of modulation of cellular redox level in cancer management. Current epidemiological and experimental evidence demonstrate the effects and modes of action of phytoagents in nucleic acid oxidation and provide rationales for the use of phytoagents as chemopreventive or therapeutic agents. Vitamins and various phytoagents antagonize carcinogen-triggered oxidative stress by scavenging free radicals and/or activating endogenous defence systems such as Nrf2-regulated antioxidant genes or pathways. Moreover, metal ion chelation by phytoagents helps to attenuate oxidative DNA damage caused by transition metal ions. Besides, the prooxidant effects of some phytoagents pose selective cytotoxicity on cancer cells and shed light on a new strategy of cancer therapy. The “double-edged sword” role of phytoagents as redox regulators in nucleic acid oxidation and their possible roles in cancer prevention or therapy are discussed in this review.

Sildenafil protects human mammary epithelial cells against ROS production induced by estradiol

Several studies suggest that xanthine dehydrogenase (XDH) and its oxidase form (XO) play an important role in various types of ischemic and vascular injuries. Recently, we have demonstrated that estradiol (E2) induces a significant decrease of the expression and activity of XDH and of its conversion to XO in human mammary epithelial cells. E2 is known to induce upregulation of eNOS gene expression in aortic endothelial cells. Because the XO-derived O2·- combines with ·NO to yield ONOO-, and considering that ONOO- converts XDH to XO, the resulting increase of XO activity and reactive oxygen species production would eventually lead to a further increase of ONOO- production, thus creating a vicious cycle of oxidative stress. Our previous study has indicated that sildenafil has a protective effect on human mammary epithelial cells as a consequence of XO inhibition and of the resulting decrease of free oxygen radicals that can impair the expression of NADPH oxidase and type 5 phosphodiesterase (PDE-5). In the present study, we report that the dual inhibitory effect exerted by sildenafil on both XO and PDE-5 is a consequence of a structural modification induced by O2·-, also consisting of the release of a piperazine group that could in turn inhibit the XO enzyme.