Sildenafil activates antioxidant and antiapoptotic genes and inhibits proinflammatory cytokine genes in a rat model of renal ischemia/reperfusion injury

Anti-inflammatory and anti-oxidant action of tadalafil in testicular regeneration process after heat stress

Tadalafil, a potent phosphodiesterase inhibitor 5 (PDE-5), is commonly used for the management of erectile dysfunction. However, its therapeutic potential extends beyond this indication. This study aimed to investigate the impact of tadalafil on the recovery of testicular parenchyma in male Wistar rats exposed to testicular thermal stress. Fifty-four Wistar rats were subjected to testicular thermal stress and randomly assigned to receive either tadalafil treatment (TAD) or no treatment (control). TAD was administered intraperitoneally at a dose of either 0.9 mg/kg or 1.8 mg/kg. Biometric parameters, histopathological assessment of the testis, serum testosterone levels, oxidative stress, and interleukin levels were evaluated on days 7, 15, and 30 after thermal shock. The animals were euthanized at the end of each experimental period, and samples were collected. TAD treatment maintained testicular weight and reduced the testicular degenerative process up to day 7 post-injury. However, despite TAD therapy, serum testosterone levels were decreased in the treated groups at days 7 and 15 post-thermal stress. TAD also decreased TNF-α and NO levels at different doses but had no effect on IL-6. The treatment with TAD after heat shock demonstrated anti-inflammatory and antioxidant properties but did not prevent the aggravation of testicular lesions in subsequent periods, even with the systematic reduction in TNF-α and NO levels. Therefore, this selective PDE-5 inhibitor, at the dosages used, did not have a positive impact on testosterone levels during the post-thermal stress period, which could compromise the resumption of the spermatogenic process.

The effect of Sildenafil, a phosphodiesterase-5 inhibitor, on tendon healing: an experimental study in rat model of achilles tendon injury

INTRODUCTION

Sildenafil Citrate has various effects on the body, including widening blood vessels, inhibiting platelet aggregation, promoting the growth of blood vessels, stimulating apoptosis and adhesion of fibroblasts, and reducing inflammation. This research aims to explore how Sildenafil Citrate affects surgically treated Achilles tendons, both in terms of tissue structure and mechanical properties.

MATERIALS AND METHODS

Forty-eight Wistar-albino rats weighing 350-400 g were randomly divided into groups, 6 in each group, as the study group was given Sildenafil Citrate and the control group given saline, respectively. The Achilles tendon rupture model was created under ketamine and xylazine anesthesia. During the entire experiment, rats were housed in eight separate cages, six of them each. The study group and control group of the first group were sacrificed at the end of 1 week, and Achilles tendon samples were taken. After that, Achilles tendon samples were taken after sacrificing the second group at 14 days, the third group at 21 days, and the fourth group at 28 days, respectively. Neovascularization, inflammation, fibrosis and fibroblastic activities of the harvested Achilles tendons were evaluated histopathologically. Biomechanically, stretching was applied to the Achilles tendons and continued until the tendon ruptured. the maximum force values at the moment of rupture were calculated.

RESULTS

The mean maximum strength value of group T21, which was given sildenafil citrate for 21 days, was 31.1 ± 4.36 N, and the mean maximum strength value of group C21, which was the control group, was 20.56 ± 6.92 N. A significant difference was observed between the groups (p: 0.008). Group T28 (45.17 ± 5.54 N) also demonstrated greater strength than group C28 (34.62 ± 3.21 N) in the comparison (p: 0.004). The study also noted significant differences between the groups in neovascularization, in the first week, 1 mild, 3 moderate and 2 prominent neovascularization was observed in group T7, in group T28, moderate neovascularization was observed in 4 specimens and prominent neovascularization was observed in 2 specimens (p: 0.001). Furthermore, the groups showed significant differences in their levels of fibrosis, inflammation and fibroblastic proliferation (p: 0.017, p: 0.036, (p: 0.035) respectively).

CONCLUSIONS

Study has demonstrated that sildenafil citrate can enhance the biomechanical and histopathological aspects of tendon healing, resulting in a stronger tendon.

Histopathology and electron microscopy evaluation of the sildenafil effect on diabetic rats' retinae

PURPOSE

Although there is increasing evidence that phosphodiesterase-5 (PDE-5) inhibitors modify the effect of diabetes on different tissues, its effect on diabetic retinopathy is not well studied.

METHODS

Forty male Sprague-Dawley (SD) rats were divided into four groups: group I = control group that received no treatment; group II (diabetic group), in which diabetes was induced by a single streptozotocin injection; group III (sildenafil small dose, SSD), in which diabetes was similarly introduced (however, rats received daily oral 1 mg/kg sildenafil citrate (SC) for 3 months); and group IV (sildenafil large dose, SLD), which was as in group 3, but SC was 2.5 mg/kg. After 3 months, globes were removed and retinae were dissected; one globe from each rat was examined by light microscopy (LM), and the other by electron microscopy (EM).

RESULTS

In contrast to the control group, diabetic rats in group II demonstrated well-established diabetic changes in the form of capillary congestion, decreased cell population, hyaline changes of capillary walls, and degenerated nerve fiber layer by LM. Similarly, EM demonstrated photoreceptor degeneration, mitochondrial cristolysis, and vacuolated depleted cells among other features in group II. These diabetic features were less prominent in group III and nearly absent in group IV.

CONCLUSION

SC use in the early stages of DR may prevent/delay diabetic retinopathy development or progression in diabetic rat models, an effect that seems to be dose-related.

Impaired NRF2 Inhibits Recovery from Ischemic Reperfusion Injury in the Aging Kidney

Deteriorating kidney function is frequently observed in the elderly population, as well as vulnerability to acute kidney failure, such as ischemic/reperfusion injury (IRI), and inadequate recovery from IRI is one of the mechanisms of kidney dysfunction in the elderly. The potential mediators in the progression of kidney dysfunction in the aging kidney have not yet been clearly revealed. In this study, we investigated the role of nuclear factor erythroid 2-related factor 2 (NRF2), which is an essential regulator of cellular redox homeostasis, in restoring kidney function after IRI in the aging kidney. NRF2 expression decreased significantly in the kidneys of old mice, as well as histologic and functional renal recovery after IRI; 45-min renal pedicle clamping was retarded in old compared with young mice. Persistent renal injury during the recovery phase after IRI was aggravated in NRF2 knockout (KO) mice compared to wild-type mice. Oxidative stress occurred in NRF2 KO old mice during the IRI recovery phase along with decreased expression of mitochondrial OXPHOS-related proteins and a reduction in mitochondrial ATP content. In vitro, hypoxia/reoxygenation (H/R) injury was aggravated in senescent human proximal tubuloepithelial cells after NRF2 restriction using NRF2 siRNA, which also increased the level of oxidative stress and deteriorated mitochondrial dysfunction. Treating the mice with an NRF2 activator, CDDO-Me, alleviated the injury. These results suggest that NRF2 may be a therapeutic target for the aging kidney.

Role of Iberin as an anti-apoptotic agent on renal ischemia-reperfusion injury in rats

Ischemia-reperfusion injury (IRI) is a major contributor to acute and chronic kidney failure, heart failure, and ischemic stroke. This study aimed to investigate the therapeutic potential of Iberin, known for its anti-inflammatory, antioxidant, and antiapoptotic properties, in a rat model of renal IRI. Twenty-four adult male rats were randomly divided into four groups: Group I (Sham group) underwent laparotomy without IRI induction; Group II (Control group) underwent laparotomy followed by renal artery clamping for 30 minutes to induce ischemia, followed by 2 hours of reperfusion; Group III (Iberin treatment group) received a pre-injection of Iberin (15 mg/kg) and underwent 30 minutes of ischemia followed by 2 hours of reperfusion; and Group IV (Vehicle-treated group) received the vehicle (ethanol) 1 hour prior to ischemia and reperfusion induction. Iberin was diluted with ethanol. Biomarkers associated with inflammation, oxidative stress, and apoptosis were measured using enzyme-linked immunosorbent assay. Iberin treatment significantly reduced levels of inflammatory cytokines interleukin-1β (IL-1β) and IL-6, Bcl-2-associated X protein (BAX), tumor necrosis factor α (TNF-α), nuclear factor kappa p56, high mobility group B1, and neutrophil gelatinase-associated lipocalin. Moreover, Iberin increased levels of heat shock protein and Bcl2 compared to the control and vehicle groups. Iberin treatment prolonged the ischemic tolerance of renal tissue, potentially preventing or delaying irreversible injuries. These findings highlight the potential of Iberin as a promising candidate for mitigating renal injury caused by ischemia-reperfusion, due to its ability to modulate inflammatory markers.

Hepatoprotective Effects of Hyaluronic Acid-Preconditioned Bone Marrow Mesenchymal Stem Cells against Liver Toxicity via the Inhibition of Apoptosis and the Wnt/β-Catenin Signaling Pathway

BACKGROUND

Doxorubicin (DOX) is widely used to treat a variety of malignancies in both adults and children, including those of the bladder, breast, stomach, and ovaries. Despite this, it has been reported to cause hepatotoxicity. The recent discovery of bone marrow-derived mesenchymal stem cells' (BMSCs) therapeutic effects in the context of liver diseases suggests that their administration plays a part in the mitigation and rehabilitation of drug-induced toxicities.

OBJECTIVES

This study investigated whether bone BMSCs could reduce DOX-induced liver damage by blocking the Wnt/β-catenin pathway that causes fibrotic liver.

MATERIALS AND METHODS

BMSCs were isolated and treated with hyaluronic acid (HA) for 14 days before injection. Thirty-five mature male SD rats were categorized into four groups; group one (control) rats were supplemented with saline 0.9% for 28 days, group two (DOX) rats were injected with DOX (20 mg/kg), group three (DOX + BMSCs) rats were injected with 2 × 106 BMSCs after 4 days of DOX injection, group four (DOX + BMSCs + HA) rats were injected with 0.1 mL BMSCs pretreated with HA after 4 days of DOX. After 28 days the rats were sacrificed, and blood and liver tissue samples were subjected to biochemical and molecular analysis. Morphological and immunohistochemical observations were also carried out.

RESULTS

In terms of liver function and antioxidant findings, cells treated with HA showed considerable improvement compared to the DOX group (p < 0.05). Moreover, the expression of inflammatory markers (TGFβ1, iNos), apoptotic markers (Bax, Bcl2), cell tracking markers (SDF1α), fibrotic markers (β-catenin, Wnt7b, FN1, VEGF, and Col-1), and ROS markers (Nrf2, HO-1) was improved in BMSCs conditioned with HA in contrast to BMSCs alone (p < 0.05).

CONCLUSION

Our findings proved that BMSCs treated with HA exert their paracrine therapeutic effects via their secretome, suggesting that cell-based regenerative therapies conditioned with HA may be a viable alternative to reduce hepatotoxicity.

Immunomodulatory, apoptotic and anti-proliferative potentials of sildenafil in Ehrlich ascites carcinoma murine model: In vivo and in silico insights

Sildenafil is a potent phosphodiesterase-5 (PDE5) inhibitor that effectively inhibits cGMP and increases the strength of nitric oxide. PDE5 was overexpressed in several carcinomas, including breast cancer, which inhibited tumor growth and cell division. The current research aims to investigate the in vivo sildenafil's immunomodulatory and antineoplastic potentials against Ehrlich Ascites Carcinoma. This study looked at the effects of sildenafil mono-treatment and co-treatment with cisplatin; tumor cell count, viability and the inhibition rate were determined. Apoptosis, cell cycle distribution, alterations in tumor cells and splenocytes proliferation, changes in splenocytes immunophenotyping using flowcytometry, plasma levels of malondialdehyde (MDA), reduced glutathione (GSH), interferone (IFN)-γ, granzyme B, alanine aminotransferase (ALT), aspartate aminotransferase (AST), urea, creatinine and hematological alterations were detected. Additionally, docking study was conducted to get further insights on how Sildenafil exerts its activity. Sildenafil mono-treatment and co-treatment with cisplatin markedly reduced tumor cell count, viability, growth rate and proliferative capability accompanied by apoptosis enhancement and G₀/G₁ and sub G₁ cells cycle arrest. Fortunately, sildenafil evoked efficient cellular immune response by increasing plasma levels of granzyme B and IFN-γ, proportion of splenic T cytotoxic (CD3⁺CD8⁺) and T helper (CD3⁺CD4⁺), accompanied by decrease in the proportion of splenic regulatory T cells. . Moreover, in silico data suggest LcK and MAPKs as the potential targets of sildenafil. Furthermore, sildenafil rebalanced the oxidant-antioxidant status by decreasing MDA and increasing GSH plasma levels. Sildenafil successfully retrieved various hematological values besides renal and hepatic functions in EAC-bearing animals. In conclusion, our results suggest that sildenafil could be potential safe anti-tumor agent with immuno-modulatory properties against Ehrlich ascites carcinoma.

The PDE5 inhibitor, vardenafil, ameliorates progressive pathological changes in a focal segmental glomerulosclerosis mouse model

AIMS

Phosphodiesterase 5 inhibitors (PDE5is) inhibit the hydrolysis of cyclic guanosine 5'-monophosphate in smooth muscle cells and are a widely known treatment for erectile dysfunction. Accumulating evidence also suggests that PDE5is exhibit potential benefits in cardiovascular and chronic kidney diseases. In this study, we examined the therapeutic effects of a PDE5i, vardenafil (VAR), in a focal segmental glomerulosclerosis (FSGS) mouse model.

MATERIALS AND METHODS

FSGS was induced in BALB/c mice by the intravenous administration of Adriamycin (AD, 11 mg/kg of body weight). After 24 h, VAR (at 12.5 μg/ml) was given in drinking water ad libitum until the animals were sacrificed. At the end of the experiment, plasma and kidney samples were harvested to evaluate clinical parameters, histopathological changes, and alterations in transcriptome and protein expressions.

KEY FINDINGS

In this study, VAR treatment attenuated the deterioration of proteinuria, renal dysfunction, and hypercholesterolemia in AD-induced FSGS. Treatment with VAR exhibited reductions in the severity of both glomerulosclerosis and tubulointerstitial injury in the histological analysis. In addition to relieving AD-induced podocyte loss, VAR also preserved endothelial cells in glomerular capillaries and ameliorated the accumulation of collagen fibers in the mesangial area and Bowman's capsule basement membrane. In addition, VAR showed an ability to suppress transforming growth factor-β-induced fibroblast-to-myofibroblast transdifferentiation.

SIGNIFICANCE

Our data suggest that VAR exhibited reno-therapeutic effects via attenuating podocyte loss, preserving the integrity of the glomerular vasculature, and ameliorating fibrotic changes. These findings suggest that PDE5is might be a promising treatment modality for nephrotic syndrome.

The emerging coloprotective effect of sildenafil against ulcerative colitis in rats via exerting counterbalance between NF-κB signaling and Nrf-2/HO-1 pathway

The current work explored the influences of time dependent Sildenafil (SILD) administration, and the possible outcomes from its concomitant administration with dexamethasone against acetic acid-induced ulcerative colitis in rats. Rats were assigned into six random groups: diseased group (AA), injected once with 2 ml acetic acid (3%) intrarectally, 2 days before sacrification. SILD + AA, received sildenafil (25 mg/kg, orally) for 6 days starting 3 days pre-injection of AA; SILD-t + AA, received sildenafil (25 mg/kg, orally), starting at time of AA injection and continued for 3 days; DEXA + AA, received dexamethasone (2 mg/kg, i.p.) for 3 days, starting at time of AA injection; SILD-t + DEXA + AA, received sildenafil (25 mg/kg, orally) and dexamethasone (2 mg/kg, i.p.), as mentioned. Sildenafil markedly ameliorated disease activity index (DAI), ulcer scores, colon length shortening and colonic histopathological changes. Mechanistically, Sildenafil markedly attenuated immunoexpression of NF-κB p65/ TNF-α and COX-2, diminished oxidative stress (↓ MDA/NO levels and ↑ GSH level and SOD activity), increased levels of Nrf-2/HO-1, compared to untreated group. Taken together, Sildenafil treatment suppressed acetic acid-induced ulcerative colitis, probably via inhibiting NF-κB/TNF-α signaling dependent of Nrf-2/HO-1 pathway, reducing oxidative stress and attenuating inflammation. Surprisingly, effects of sildenafil were unpromoted in a time dependant manner. Short term treatment with sildenafil was sufficient to exert its coloprotective effect, while longer term pretreatment was only superior among other treatments in the macroscopical changes. Moreover, concurrent administration of sildenafil and dexamethasone had the preference in boosting the antioxidant defense and anti-inflammatory mechanisms, visualized by histopathological/immunohistochemical changes.

Protective effects of sildenafil administration on chemotherapeutic-induced ovarian damage in rats

Agents to reduce the gonadotoxic effects of chemotherapeutics are still under investigation. In this context, we aimed to investigate the protective effect of sildenafil against chemotherapeutic-induced gonadotoxicity in a rat model. A total of 62 female rats were divided into eight groups as control, sildenafil (1.4 mg/kg, orally), doxorubicin (3 mg/kg, i.p.), cisplatin (5 mg/kg, i.p.), cyclophosphamide (200 mg/kg, i.p.), doxorubicin+sildenafil, cisplatin+sildenafil, and cyclophosphamide+sildenafil (1.4 mg/kg orally sildenafil in addition to the same dose of chemotherapeutics). The groups were compared in terms of follicle count, ovarian size, and anti-müllerian hormone (AMH) levels. Use of sildenafil with cyclophosphamide was effective only in preserving primary follicle count (p = 0.026) and had no significant change in the secondary follicle count, ovarian size, or AMH level. Adding sildenafil to cisplatin had a significant protective effect on primary follicle count (p = 0.011), secondary follicle count (p = 0.009), and ovarian size (p = 0.001), but this effect could not be demonstrated at AMH level. Sildenafil was not effective on any parameter in the doxorubicin group. Sildenafil may be effective in reducing the gonadotoxicity associated with the use of cisplatin and cyclophosphamide.

Altered mRNA Expression of Interleukin-1 Receptors in Myocardial Tissue of Patients with Left Ventricular Assist Device Support

Serum levels of cytokines interleukin 1 beta ( IL-1β) and interleukin 33 (IL-33) are highly abnormal in heart failure and remain elevated after mechanical circulatory support (MCS). However, local cytokine signaling induction remains elusive. Left (LV) and right ventricular (RV) myocardial tissue specimens of end-stage heart failure (HF) patients without (n = 24) and with MCS (n = 39; 594 ± 57 days) were analyzed for cytokine mRNA expression level of IL-1B, interleukin 1 receptor 1/2 (IL-1R1/2), interleukin 1 receptor-like 1 (IL-1RL1), IL-33 and interleukin-1 receptor accessory protein (IL-1RaP). MCS patients showed significantly elevated IL-1B expression levels (LV: 2.0 fold, p = 0.0058; RV: 3.3 fold, p < 0.0001). Moreover, IL-1R1, IL-1RaP and IL-33 expression levels strongly correlated with each other. IL-1RL1 and IL-1R2 expression levels were significantly higher in RV myocardial tissue (RV/LV ratio IL-1R2 HF: 4.400 ± 1.359; MCS: 4.657 ± 0.655; IL-1RL1 HF: 3.697 ± 0.876; MCS: 4.529 ± 0.5839). In addition, IL1-RaP and IL-33 RV expression levels were significantly elevated in MCS. Furthermore, IL-33 expression correlates with C-reactive protein (CRP) plasma levels in HF, but not in MCS patients. Increased expression of IL-1B and altered correlation patterns of IL-1 receptors indicate enhanced IL-1β signaling in MCS patients. Correlation of IL-1 receptor expression with IL-33 may hint towards a link between both pathways. Moreover, diverging expression in LV and RV suggests specific regulation of local cytokine signaling.

Cyclic nucleotide phosphodiesterase inhibition as a potential therapeutic target in renal ischemia reperfusion injury

AIMS

Ischemia/reperfusion (I/R) occurs in renal artery stenosis, partial nephrectomy and most commonly during kidney transplantation. It brings serious consequences such as DGF (Delayed Graft Function) or organ dysfunction leading to renal failure and ultimate death. There is no effective therapy to handle the consequences of Renal Ischemia/Reperfusion (I/R) injury. Cyclic nucleotides, cAMP and cGMP are the important second messengers that stimulate intracellular signal transduction for cell survival in response to growth factors and peptide hormones in normal tissues and in kidneys plays significant role that involves vascular tone regulation, inflammation and proliferation of parenchymal cells. Renal ischemia and subsequent reperfusion injury stimulate signal transduction pathways involved in oxidative stress, inflammation, alteration in renal blood flow leading to necrosis and apoptosis of renal cell.

MATERIALS AND METHODS

An extensive literature review of various search engines like PubMed, Medline, Bentham, Scopus, and EMBASE (Elsevier) databases was carried out. To understand the functioning of Phosphodiesterases (PDEs) and its pharmacological modulation in Renal Ischemia-Reperfusion Injury.

KEY FINDINGS

Current therapeutic options may not be enough to treat renal I/R injury in group of patients and therefore, the current review has discussed the general characteristics and physiology of PDEs and preclinical-studies defining the relationship between PDEs expression in renal injury due to I/R and its outcome on renal function.

SIGNIFICANCE

The role of PDE inhibitors in renal I/R injury and the clinical status of drugs for various renal diseases have been summarized in this review.

Effect of zinc oxide nanoparticles and ferulic acid on renal ischemia/reperfusion injury: possible underlying mechanisms

OBJECTIVES

The present study examined the effects of ferulic acid (FA) and Zinc oxide nanoparticles (ZnO-NPs) and a combination of both on renal ischemia/reperfusion injury (IRI) in rats and their possible underlying mechanisms.

METHODS

two-hundreds male Sprague Dawley rats were randomly allocated into the 5 groups; i) sham group, ii) control (IRI) group (occlusion of the left renal pedicle for 45 min), iii) FA group as IRI group with FA (100 mg/Kg oral 24 hrs before ischemia), iv) ZnO-NPs group as IRI group with ZnO-NPs single 5 mg/Kg i.p. 2 hrs before ischemia and v) FA + ZnO-NPs group as IRI group with both FA and ZnO-NPs in the same previous doses. According to the reperfusion times, each group was further subdivided into 4 hr, 24 hr, 48 hr and 7 days reperfusion subgroups.

RESULTS

administration of either FA or ZnO-NPs caused significant improvement in the elevated serum creatinine and BUN and malondialdehyde (MDA) concentrations and expression of TNF-α, Bax, caspase-3 in kidney tissues with significant rise in the creatinine clearance, the activities of catalase (CAT) and superoxide dismutase (SOD) and the expression of HO-1, HIF-1α genes and proliferation marker (ki67) in kidney tissues compared to IRI group (p < 0.05). Moreover, a combination of both agents produced more significant improvement in the studied parameters than each agent did alone (p < 0.05).

CONCLUSIONS

Both FA and ZnO-NPs exerted cytoprotective effects against ischemic kidney injury and a combination of both exhibited more powerful renoprotective effect. This renoprotective effect might be due to suppression of oxidative stress, enhancement of cell proliferation (ki67), upregulation of antioxidant genes (Nrf2, HO-1 and HIF-1α) and downregulation of inflammatory cytokine (TNF-α) and apoptotic genes (caspase-3 and Bax).

Experimental isolation and preservation of solid organs before transplantation: effects of pretreatment using four different molecules

OBJECTIVES

In transplantation surgery, the ischaemic organ and reperfusion impairment after cold storage remains a considerable risk factor for impaired function and potential failure of the grafted organ. Substantial logistical efforts have been undertaken to reduce the cold ischaemic time because the demand for available transplant organs and the periods of cold ischaemia are increasing.

METHODS

Four molecules were investigated (erythropoietin, sildenafil, lazaroid [U74389G], octreotide) in individual intravenous infusions 1 hour before the organ was harvested. This study was performed in 30 healthy landrace/large-white pigs (male; >10 weeks old; average weight, 22 ± 2 kg) in groups of six. The organs were studied at harvest, and at 8 and 24 hours post-harvest.

RESULTS

The lazaroid molecule increased malondialdehyde (MDA) levels in the liver and pancreas at 8 hours. Hepatic lazaroid molecules improved liver histology at 8 and 24 hours. For kidneys, erythropoietin had a positive effect at 24 hours post-harvest. For the pancreas, octreotide showed better performance. In the lungs, there was less interstitial oedema with erythropoietin and lazaroid compared with the control group at 8 hours post-harvest.

CONCLUSION

All molecules had a positive effect and decreased ischaemia/reperfusion graft injury. Thus, pretreatment before organ harvest has a beneficial role.

Reno-protective effects of Phosphodiesterase 5 inhibitors

The kidneys are vital organs that play an important role in removing waste materials from the blood, electrolyte balance, blood pressure regulation, and red blood cell genesis. Kidney disease can be caused by various factors, including diabetes, ischemia/reperfusion injury, and nephrotoxic agents. Inflammation and oxidative stress play a key role in the progression and pathogenesis of kidney diseases. Acute kidney injury (AKI) and chronic kidney disease (CKD) are important health problems worldwide, as they are associated with a long-term hospital stay, and increased morbidity and mortality in high-risk patients. Current standard therapeutic options are not sufficient to delay or stop the loss of kidney function. Therefore, it is necessary to develop new therapeutic options. Phosphodiesterase 5 inhibitors (PDE5Is) are a currently available class of drugs that are used to treat erectile dysfunction and pulmonary hypertension in humans. However, recent evidence suggests that PDE5Is have beneficial renoprotective effects via a variety of mechanisms. In this review, the benefits of PDE5 inhibitors in clinical conditions associated with kidney disease, such as diabetic nephropathy, ischemia-reperfusion injury, and acute and chronic kidney injury, are summarized.

Possible mechanisms for the renoprotective action of adipose-derived mesenchymal stem cells with CD44-targeted hyaluronic acid against renal ischemia

The present study aimed to investigate the invitro preconditioning of adipose-derived mesenchymal stem cells (ADMSCs) with CD44-targeted hyalournic acid (HA) on ischemic kidney injury in rats. Ninety male Sprague Dawley rats were randomly allocated into the following groups; i) sham group, ii) control group: rats exposed to 45 min left renal ischemia with saline treatment, iii) HA group as control group but rats treated with HA, iv) ADMSCs group as control but rats treated with ADMSCs v) HA + ADMSCs group as ADMSCs but rats treated with ADMSCs preconditioned with CD44-tageted HA for 14 days. We found that treattment with either ADMSCs or HA + ADMSCs caused significant decrease in the elevated serum creatinine and BUN and malondialdehyde (MDA) concentrations and expression of TGF-β1, fibronectin, collagen type I, inducible nitric oxide synthease (iNOS) and microRNAs (miR-21, miR-17-5p, miR-10a) in kidney and significant increase in creatinine clearance, superoxide dismutase (SOD), reduced glutathione (GSH) and the expression of Bcl2, vascular endothelial growth factor (VEGF), Wnt/β-catenin pathway genes in kidney compared to control group (p < 0.05). Moreover, HA + ADMSCs group caused more significant improvement in these parameters than ADMSCs group (p < 0.05), while HA group did not cause any significant improvement in these parameters compared to control group. These results suggest that preconditioning of ADMSCs preconditioned with CD44-targted HA enhanced their cytoprotective effect against ischemic kidney injury. This renoprotective effect might be due to activation of angiogenesis, Wnt/β-catenin pathway proteins, and suppression of oxidative stress, apoptosis, inflammation and fibrosis.

Sildenafil beyond erectile dysfunction and pulmonary arterial hypertension: Thinking about new indications

Sildenafil, approved two decades ago, is the inhibitor of phosphodiesterase 5 (PDE5). First of all, it was designated for angina pectoris, but soon it showed a wonderful efficacy in erectile dysfunction (ED) and then pulmonary arterial hypertension (PAH). Due to the distribution of phosphodiesterase (PDE) in almost all organs, maybe it effects other diseases. Hence, a great number of investigations began to understand the role of PDEi in different organs. Preliminary research on sildenafil in cell culture and animal models has yielded promising results. Soon, a greater number of animal researches and clinical trials joined them. The results disclosed sildenafil can have beneficial effects in each organ such as heart, liver, kidney, brain, and intestines. Furthermore, it has significantly improved the prognosis of organ ischemia in various animal models. Clinical trials in several diseases, such as recurrent spontaneous miscarriage, fatty liver disease, bronchopulmonary dysplasia (BPD), heart failure, and premature ejaculation (PE) brought promising results. Although some clinical trials are available on the effects of sildenafil on various diseases, further studies on humans are needed to consolidate the ultimate effects of sildenafil. The aim of this review was to describe the effects of sildenafil on each organ and explain its mechanisms of action. Further, other PDE inhibitors such as tadalafil and vardenafil have been briefly discussed in parts of this review.

The role of Nrf2 in acute kidney injury: Novel molecular mechanisms and therapeutic approaches

Acute kidney injury (AKI) is a common clinical syndrome that is related to high morbidity and mortality. Oxidative stress, including the production of reactive oxygen species (ROS), appears to be the main element in the occurrence of AKI and the cause of the progression of chronic kidney disease (CKD) into end-stage renal disease (ESRD). Nuclear factor erythroid 2 related factor 2 (Nrf2) is a significant regulator of redox balance that has been shown to improve kidney disease by eliminating ROS. To date, researchers have found that the use of Nrf2-activated compounds can effectively reduce ROS, thereby preventing or retarding the progression of various types of AKI. In this review, we summarized the molecular mechanisms of Nrf2 and ROS in AKI and described the latest findings on the therapeutic potential of Nrf2 activators in various types of AKI.

Berberine ameliorates renal injury in a rat model of D-galactose-induced aging through a PTEN/Akt-dependent mechanism

This study aimed to investigate the protective effects of berberine (BBR) against D-galactose (D-gal)-induced renal aging in rats, pointing to its ability to modulate phosphatase and tensin homolog deleted on chromosome ten (PTEN)/Akt signalling, and to attenuate oxidative stress, inflammation and apoptosis. Renal aging was induced by subcutaneous injection of D-gal for six consecutive weeks along with simultaneous oral administration of BBR and compared to control rats and rats received individual doses of either drug. BBR treatment significantly reduced the serum levels of urea and creatinine, retrieved the alterations in kidney histopathology, and restored redox balance evidenced by alleviations of the level of malondialdehyde, 8-hydroxy-2'-deoxyguanosine and activating heme oxygenase-1 enzyme. Moreover, it markedly reduced the serum levels of pro-inflammatory mediators, along with down-regulation of PTEN expression, enhanced Akt activity, as well as significantly higher immunostaining of the anti-apoptotic marker (Bcl-2). These findings hold a great promise for the use of BBR as a protecting agent against renal aging.

Current Concepts on the Reno-Protective Effects of Phosphodiesterase 5 Inhibitors in Acute Kidney Injury: Systematic Search and Review

Acute kidney injury (AKI) is associated with increased morbidity, prolonged hospitalization, and mortality, especially in high risk patients. Phosphodiesterase 5 inhibitors (PDE5Is), currently available as first-line therapy of erectile dysfunction in humans, have shown a beneficial potential of reno-protection through various reno-protective mechanisms. The aim of this work is to provide a comprehensive overview of the available literature on the reno-protective properties of PDE5Is in the various forms of AKI. Medline was systematically searched from 1946 to November 2019 to detect all relevant animal and human studies in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) statement. In total, 83 studies were included for qualitative synthesis. Sildenafil is the most widely investigated compound (42 studies), followed by tadalafil (20 studies), icariin (10 studies), vardenafil (7 studies), zaprinast (4 studies), and udenafil (2 studies). Even though data are limited, especially in humans with inconclusive or negative results of only two clinically relevant studies available at present, the results of animal studies are promising. The reno-protective action of PDE5Is was evident in the vast majority of studies, independently of the AKI type and the agent applied. PDE5Is appear to improve the renal functional/histopathological alternations of AKI through various mechanisms, mainly by affecting regional hemodynamics, cell expression, and mitochondrial response to oxidative stress and inflammation.

Effects of sildenafil on inflammatory injury of the lung in sodium taurocholate-induced severe acute pancreatitis rats

BACKGROUND

Inflammatory response and acute lung injury (ALI) occur in sodium taurocholate-induced severe acute pancreatitis (SAP). Because sildenafil has anti-inflammatory, anti-oxidant and immune-modulating effects, we investigated its effect on inflammatory and lung injury in sodium taurocholate-induced SAP-associated ALI rat lung.

METHODS

Sodium taurocholate-induced SAP rats received sildenafil (100 mg/kg) or not and were compared to age-matched normal control animals. We evaluated inflammatory response by detecting the expression of inflammatory factors including IL-1β, IL-6 and TNF-α, and detected the level of lung injury through histopathological evaluation. Moreover, we also tested the protein expression of PCNA, P21, Bcl-2 and Bax in the lung.

RESULTS

Sildenafil administration rats had a low level of lung injury and inflammation. In addition, sildenafil significantly increased the expression of proliferation-related markers and decreased the expression of apoptosis-related markers in lung tissue.

CONCLUSIONS

Sildenafil administration may attenuate inflammation and lung injury by promoting proliferation and suppressing apoptosis in SAP rats.

Sildenafil reduces aortic endothelial dysfunction and structural damage in spontaneously hypertensive rats: Role of NO, NADPH and COX-1 pathways

Arterial hypertension is a condition associated with endothelial dysfunction, accompanied by an imbalance in the production of reactive oxygen species (ROS) and NO. The aim of this study was to investigate and elucidate the possible mechanisms of sildenafil, a selective phosphodiesterase-5 inhibitor, actions on endothelial function in aortas from spontaneously hypertensive rats (SHR). SHR treated with sildenafil (40 mg/kg/day, p.o., 3 weeks) were compared to untreated SHR and Wistar-Kyoto (WKY) rats. Systolic blood pressure (SBP) was measured by tail-cuff plethysmography and vascular reactivity was determined in isolated rat aortic rings. Circulating endothelial progenitor cells and systemic ROS were measured by flow cytometry. Plasmatic total antioxidant capacity, NO production and aorta lipid peroxidation were determined by spectrophotometry. Scanning electron microscopy was used for structural analysis of the endothelial surface. Sildenafil reduced high SBP and partially restored the vasodilator response to acetylcholine and sodium nitroprusside in SHR aortic rings. Using selective inhibitors, our experiments revealed an augmented participation of NO, with a simultaneous decrease of oxidative stress and of cyclooxygenase-1 (COX-1)-derived prostanoids contribution in the endothelium-dependent vasodilation in sildenafil-treated SHR compared to non-treated SHR. Also, the relaxant responses to sildenafil and 8-Br-cGMP were normalized in sildenafil-treated SHR and sildenafil restored the pro-oxidant/antioxidant balance and the endothelial architecture. In conclusion, sildenafil reverses endothelial dysfunction in SHR by improving vascular relaxation to acetylcholine with increased NO bioavailability, reducing the oxidative stress and COX-1 prostanoids, and improving cGMP/PKG signaling. Also, sildenafil reduces structural endothelial damage. Thus, sildenafil is a promising novel pharmacologic strategy to treat endothelial dysfunction in hypertensive states reinforcing its potential role as adjuvant in the pharmacotherapy of cardiovascular diseases.

Anti-inflammatory and nephroprotective activity of Juglans mollis against renal ischemia-reperfusion damage in a Wistar rat model

BACKGROUND

Oxidative stress and the inflammatory process are involved in ischemia-reperfusion (I/R) injury. Juglans mollis has been reported as having antioxidant activity, which could attenuate the damage caused by I/R. We evaluated whether a methanolic extract of Juglans mollis (JM) exhibits nephroprotective activity in a Wistar rat model of I/R injury.

METHODS

Four groups of six rats were used: Sham, I/R, JM, and JM + I/R. Two groups were dosed with JM (300 mg/kg) for 7 days before I/R. I/R injury was induced by clamping the renal hilums for 45 min and then reperfusing the kidneys for 15 h. Blood samples were taken to evaluate the levels of alanine aminotransferase (ALT), blood urea nitrogen, creatinine, superoxide dismutase (SOD), malondialdehyde (MDA), interleukin 1β (IL-1β), IL-6, and tumor necrosis factor α (TNF-α).

RESULTS

The levels of creatinine, ALT, MDA, IL-1β, IL-6, and TNF-α were lower in JM + I/R than in I/R rats, whereas SOD level only was higher in JM + I/R than in Sham rats. No biochemical or histological damage was observed in JM rats compared with Sham rats; however, less histological damage was observed in JM + I/R rats compared with I/R rats.

CONCLUSIONS

To our knowledge, this is the first report of nephroprotective activity of J. mollis against damage induced by I/R. This activity may be related to decreased levels of proinflammatory cytokines (IL-1β, IL-6, and TNF-α) and modulation of oxidative stress markers (SOD and MDA) observed in the present study.

Renoprotective effect of local sildenafil administration in renal ischaemia-reperfusion injury: A randomised controlled canine study

Objectives: To design a new canine model to assess the renoprotective effect of local sildenafil administration, as the renoprotective effect of systemic sildenafil administration in renal ischaemia-reperfusion (IR) injury in animal models has been shown but its local effects have not been established to date. Materials and methods: In all, 120 dogs were assigned to five groups: sham, oral control (OC) group (right nephrectomy + left renal ischaemia for 60 min), oral sildenafil (OS) group (oral sildenafil 1 mg/kg, 60 min before ischaemia), local control (LC) group (local renal perfusion with saline and heparin for 5 min) and local sildenafil (LS) group (perfusion with sildenafil 0.5 mg/kg). Renal functions, histopathological changes, expression of caspase-3, nuclear factor erythroid 2-related factor 2 (Nrf2), inflammatory cytokines (intracellular adhesion molecule 1, tumour necrosis factor α and interleukin 1β) and endothelial nitric oxide synthase (eNOS) in renal tissues were assessed in all groups at 1, 3, 7 and 14 days. Results: There were significant improvements in renal functions and cortical and medullary damage scores in the sildenafil-treated groups compared to their control groups (P < 0.05). Also, the LS group showed significantly better improvement of renal functions and cortical and medullary damage scores than the OS group (P < 0.05). Moreover, sildenafil significantly decreased the expression of caspase-3 and inflammatory cytokines and increased the expression of Nrf2 and eNOS in renal tissue, which were statistically significant in the LS group. Conclusion: LS has a greater renoprotective effect against renal IR injury than systemic administration via anti-inflammatory, antioxidant and anti-apoptotic pathways. Abbreviations: BUN: blood urea nitrogen; Ct: cycle threshold; eNOS: endothelial nitric oxide synthase; GAPDH: glyceraldehyde 3-phosphate dehydrogenase; H&E: haematoxylin and eosin; IL-1β: interleukin 1β; NO: nitric oxide; Nrf2: nuclear factor erythroid 2-related factor 2; OC: oral control; OS: oral sildenafil; LC: local control; LS: local sildenafil.

Analysis of Flavonoids Bioactivity for Cholestatic Liver Disease: Systematic Literature Search and Experimental Approaches

Flavonoids are naturally occurring compounds that show health benefits on the liver. However, there is little investigation about identification and evaluation of new flavonoid-containing drugs for cholestatic liver disease, one of the most common liver illnesses. We aimed to a systematic search regarding efficacy of flavonoids for treatment of cholestatic liver disease, and then evaluate naringenin (NG) as representative flavonoid in an obstructive cholestasis model. We searched for information of experimental and clinical studies in four major databases without time and language limits. Intervention was defined as any flavonoid derivate compared with other flavonoid, placebo, or without comparator. In addition, we evaluated NG on a bile duct-ligated model in order to contribute evidence of its actions. Eleven experimental reports that support the efficacy of flavonoids in cholestatic liver disease were identified. However, there was no homogeneity in efficacy endpoints evaluated and methodology. On the other hand, NG showed beneficial effects by improving specific metabolic (cholesterol and lipoproteins) and liver damage (bilirubin and alkaline phosphatase) biomarkers. The review lacks homogeneous evidence about efficacy of flavonoids in experimental settings, and is susceptible to risk for bias. NG only showed improvements in specific disease biomarkers. More investigation is still needed to determine its potential for drug development.

Effect of combination sildenafil and gemfibrozil on cisplatin-induced nephrotoxicity; role of heme oxygenase-1

Background/aim: Cisplatin-induced nephrotoxicity in large proportion of patients. The aim of this work is to clarify the effect of combination of sildenafil and gemfibrozil on cisplatin-induced nephrotoxicity either before or after cisplatin treatment and determination of nephrotoxicity predictors among the measured tissue markers.

Methods: Thirty two adult male albino rats were divided into four equal groups (G) GI control, GII received cisplatin, GIII received sildenafil and gemfibrozil before cisplatin, GIV received sildenafil and gemfibrozil after cisplatin. Creatinine and urea were measured and animals were sacrificed and kidney was taken for histopathology. The following tissue markers were measured, heme oxygenase-1 (HO-1) activity, reduced glutathione, quantitative (real-time polymerase chain reaction) RT-PCR for gene expression of tumor necrosis factor alpha (TNF-α) and endothelial nitric oxide synthase (ENOS) level.

Results: GII developed AKI demonstrated by significantly high urea and creatinine and severe diffuse (80–90%) tubular necrosis. TNF-α was highly and significantly elevated while the rest of tissue markers were significantly reduced in GI1 compared to other groups. GIV showed better results compared to GIII. There was a significant positive correlation between creatinine and TNF-α when combining GI and GII while there were significant negative correlation between creatinine and other tissue markers in same groups. Linear regression analysis demonstrated that HO-1 was the independent predictor of AKI demonstrated by elevated creatinine among GI and GII.

Conclusions: Combination of sildenafil and gemfibrozil can be used in treatment of cisplatin-induced nephrotoxicity. HO-1 is a promising target for prevention and/or treatment of cisplatin-induced nephrotoxicity.

Frontiers in pediatric testicular torsion: An integrated review of prevailing trends and management outcomes

Testicular torsion remains the most frequent cause of testicular ischemia, especially in adolescents and young adults. Timely diagnosis and intervention are keys to saving the affected testicle. This review presents current trends in the diagnosis and treatment of torsion, potential pitfalls and consequent outcomes. Additionally, other salient issues surrounding testicular torsion are also discussed, including: pathogenesis of injury, legal ramifications, fertility outcomes, novel management techniques, and recent advances in diagnostic technology.

Chronical treatment with sildenafil causes Achilles tendinopathy in rats

AIMS

The primary goal was to assess the effects of chronic sildenafil treatment over the Achilles tendons in rats.

MAIN METHODS

Animals were divided into two groups, control and sildenafil administration (n = 5). After 60 days, the tendons were subject to biochemical and image analysis to compare tendons between the groups: collagen I and decorin content, polarisation microscopy and birefringence analysis, and tissue zymography.

KEY FINDINGS

The animals exposed to sildenafil presented a much less organised tendon matrix, with reduced collagen I and non-collagenous protein content and a much higher decorin content.

SIGNIFICANCE

The results observed in the animals can be characterised as tendinopathy, a condition not yet described as a sildenafil side effect.

Protective Effect of Nicotinamide Adenine Dinucleotide Phosphate on Renal Ischemia-Reperfusion Injury

BACKGROUND/AIMS

Renal ischemia-reperfusion injury (IRI) is a common consequence of acute kidney injury. Nicotinamide adenine dinucleotide phosphate (NADPH), which is derived from the pentose phosphate pathway, is essential for the proper functioning of essential redox and antioxidant defense systems. Previous studies have indicated that NADPH is responsible for protecting the brain from ischemic injury. The goal of this study was to analyze the protective function of NADPH in renal IRI.

METHODS

The IRI animal model was generated through a midline laparotomy surgery that clamped both sides of the renal pedicles for 40 min to induce renal ischemia. The in vitro model was generated by removing oxygen and glucose from human kidney epithelial cells (HK-2 cells), followed by reoxygenation to imitate IRI. Renal function and histopathological changes were observed and evaluated. Additionally, malondialdehyde and glutathione levels were determined in renal tissue homogenate as indicators of oxidative stress. ROS production in cells was determined by DHE staining. Protein biomarker expression was evaluated by western blot, apoptosis was analyzed by TUNEL staining, and p65 nuclear translocation was visualized by immunofluorescence.

RESULTS

Our data indicated that NADPH safeguarded the kidneys from histological and functional damage, and significantly reduce cell injury along with preventing potential increases in blood urea nitrogen and creatinine levels. Furthermore, we observed that NADPH increased glutathione levels, while reducing levels of malondialdehyde and reactive oxygen species. Additionally, our results suggested that NADPH treatment may alleviate IRI-induced apoptosis and inflammation.

CONCLUSION

NADPH treatment may protect against renal IRI and should be further developed as a new treatment for acute kidney injury.

Olprinone protects the liver from ischemia–reperfusion injury through oxidative stress prevention and protein kinase Akt activation

Liver ischemia–reperfusion (IR) injury is inevitable in surgical procedures such as hepatic resection and liver transplantation. It represents a leading cause of liver graft dysfunction and primary nonfunction after transplantation. Phosphodiesterase (PDE) inhibitors are emerging as effective drugs able to reduce IR damage. The aim of this study was to investigate the effect of selective PDE-3 inhibitor olprinone (Olp) against liver IR injury. Male Wistar rats were subjected to 1 h of partial warm ischemia (70%) followed by 6 h of reperfusion. Before ischemia, rats were treated with saline (IR group), Olp (Olp group), or Olp with Akt inhibitor LY294002 (Olp plus LY group). After reperfusion, hepatic injury (transaminase activities), mitochondrial damage (glutamate dehydrogenase activity), oxidative stress (malondialdehyde and glutathione concentrations and catalase and superoxide dismutase activities), and protein kinase Akt activation were evaluated. Rat treatment with Olp reduced liver injury, prevented mitochondrial damage, decreased lipid peroxidation, and enhanced antioxidant enzymes. Also, Olp induced a significant activation in protein kinase Akt. Inhibition of Akt with LY294002 abolished all of the protective effects of Olp. In conclusion, Olp treatment may be an effective strategy in reducing liver IR injury through oxidative stress prevention and Akt activation.

The mechanism of attenuation of epithelial-mesenchymal transition by a phosphodiesterase 5 inhibitor via renal klotho expression

Phosphodiesterase-5 (PDE-5) inhibitors induces vasodilation in several organs by blocking cyclic GMP (guanosine monophosphate) degradation. However, the existence of alternative mechanism of action in case of an impaired nitric oxide (NO) system remains controversial. Previous studies suggested that decreased NO bioavailability may result in the downregulation of klotho expression, but the relationship between klotho and NO remains obscure. Therefore, we investigated whether a PDE-5 inhibitor could preserve epithelial-mesenchymal transition (EMT) and relationship exists between the NO and renal klotho expression. Ten-week-old SD rats (N = 24, 200 g, male) were divided (N = 6) into four groups, which received: A LSD, L-NAME 1 mg/mL in drinking water, Udenafil 5 mg/kg subcutaneously and both for 4 weeks. Urine nitrate/nitrite, NGAL (Neutrophil gelatinase-associated lipocalin), and cGMP were measured using ELISA. Kidney was subjected to evaluate PCNA (proliferative cell nuclear antigen), α-SMA (smooth muscle cell antigen), E-cadherin, and klotho expression. Urine cGMP decreased after treatment of PDE-5 inhibitor compared with control due to blocking degradation of cGMP (P < .05, control vs Udenafil and L-NAME with Udenafil groups). Urine NGAL increased after treating of L-NAME and attenuated after using PDE-5 inhibitor (P < .05, control vs L-NAME and L-NAME with Udenafil). PCNA, α-SMA, and E-cadherin (EMT markers) increased after L-NAME treatment and normalized after using PDE-5 inhibitor. Klotho expression showed trend to increase in the L-NAME with PDE-5 inhibitor group compared with the L-NAME group, however, eNOS expression did not change after treatment of L-NAME or PDE-5 inhibitor compared with control. PDE-5 inhibitor alleviates EMT in the kidney via klotho modulation independent of the NO system.

Phosphodiesterase 5 inhibition as a therapeutic target for ischemic stroke: A systematic review of preclinical studies

Phosphodiesterase 5 inhibitors (PDE5i), such as sildenafil (Viagra®) are widely used for erectile dysfunction and pulmonary hypertension. Preclinical studies suggest that PDE5i may improve functional outcome following ischemic stroke. In this systematic review we aimed to evaluate the effects of selective PDE5i in animal models of brain ischaemia. A systematic search in Medline, Embase, and The Cochrane Library was performed including studies in English assessing the effects of selective PDE5i. 32 publications were included describing outcome in 3646 animals. Neuroprotective effects of PDE5i were dependent on the NO-cGMP-PKG-pathway. These included reduced neuronal apoptosis (n=3 studies), oxidative stress (n=5), and neuroinflammation (n=2). PDE5i increased angiogenesis and elevated regional cerebral blood flow in the ischemic penumbra, and improved functional recovery. Some studies found that PDE5i treatment reduced lesion volume (n=9), others found no effect (n=9). Treatment was effective when administered within 24h post-ischemia, though treatment delayed to seven days improved outcome in one study. This review demonstrates both neuroprotective and neurorestorative effects of PDE5i in animal models of stroke, though the specific underlying signaling pathways relating to PDE5 inhibition and cGMP may remain serendipitous in some studies. There is currently limited evidence on the effects of selective PDE5i in human stroke patients, hence translation of preclinical results into clinical trials may be warranted.

Sildenafil Can Affect Innate and Adaptive Immune System in Both Experimental Animals and Patients

Sildenafil, a type 5 phosphodiesterase inhibitor (PDE5-I), is primarily used for treating erectile dysfunction. Sildenafil inhibits the degradation of cyclic guanosine monophosphate (cGMP) by competing with cGMP for binding site of PDE5. cGMP is a secondary messenger activating protein kinases and a common regulator of ion channel conductance, glycogenolysis, and cellular apoptosis. PDE5 inhibitors (PDE-Is) found application in cardiology, nephrology, urology, dermatology, oncology, and gynecology. Positive result of sildenafil treatment is closely connected with its immunomodulatory effects. Sildenafil influences angiogenesis, platelet activation, proliferation of regulatory T cells, and production of proinflammatory cytokines and autoantibodies. Sildenafil action in humans and animals appears to be different. Surprisingly, it also acts differently in males and females organisms. Although the immunomodulatory effects of PDE5 inhibitors appear to be promising, none of them reached the point of being tested in clinical trials. Data on the influence of selective PDE5-Is on the human immune system are limited. The main objective of this review is to discuss the immunomodulatory effects of sildenafil in both patients and experimental animals. This is the first review of the current state of knowledge about the effects of sildenafil on the immune system.

Sildenafil potentiates the antitumor activity of cisplatin by induction of apoptosis and inhibition of proliferation and angiogenesis

Sildenafil is the first phosphodiesterase-5 inhibitor used for the treatment of erectile dysfunction. However, recent studies have been suggesting an antitumor effect of sildenafil. The current study assessed the aforementioned activity of sildenafil in vivo and in vitro in solid-tumor-bearing mice and in a human cell line MCF-7, respectively. Moreover, we investigated the impact of sildenafil on cisplatin antitumor activity. The solid tumor was induced by inoculation of Ehrlich ascites carcinoma cells in female mice. The tumor-bearing mice were assigned randomly to control (saline), sildenafil (sildenafil 5 mg/kg/d, PO daily for 15 days), cisplatin (cisplatin 7.5 mg/kg, IP once on the 12th day of Ehrlich ascites carcinoma inoculation), and combination therapy (cisplatin and sildenafil) groups. The tumor volume was measured at the end of the treatment period along with the following parameters: angiogenin, vascular endothelial growth factor, tumor necrosis factor-α, Ki-67, caspase-3, DNA-flow cytometry analysis, and histopathological examination. The study results showed that sildenafil has significantly decreased the tumor volume by 30.4%, angiogenin and tumor necrosis factor-α contents, as well as vascular endothelial growth factor expression. Additionally, caspase-3 level significantly increased with sildenafil treatment, whereas Ki-67 expression failed to show any significant changes. Furthermore, the cell cycle analysis revealed that sildenafil was capable of improving the category of tumor activity from moderate to low proliferative. Sildenafil induced necrosis in the tumor. Moreover, the drug of interest showed cytotoxic activity against MCF-7 in vitro as well as potentiated cisplatin antitumor activity in vivo and in vitro. These findings shed light on the antitumor activity of sildenafil and its possible impact on potentiating the antitumor effect of conventional chemotherapeutic agents such as cisplatin. These effects might be related to antiangiogenic, antiproliferative, and apoptotic activities of sildenafil.

Sildenafil prevents renal dysfunction in contrast media-induced nephropathy in Wistar rats

Contrast-induced nephropathy (CIN) is an iatrogenic medical event in stable cardiology patients that may lead to acute renal failure. There is no current successful therapy to manage CIN. Increasing evidence in experimental models and humans has suggested that this disease is associated with renal tubular and vascular injury triggered by oxidative stress. Considering the importance of reactive oxygen species (ROS) generation in the pathogenesis of CIN, the goal of the present study was to evaluate the effects of sildenafil on CIN development. Male Wistar rats were divided into control, CIN, and CIN pretreated with sildenafil (50 mg/kg/day). CIN was induced by water deprivation, NG-nitro-L-arginine methyl ester + indomethacin injections (10 mg/kg, intraperitoneally) and intravenous iohexol administration (3 g/kg). Renal function was evaluated through glomerular filtration rate (GFR), renal blood flow (RBF), plasma creatinine, uremia, and proteinuria. Oxidative stress was assessed by flow cytometry for intracellular ROS. Treatment with sildenafil attenuated the marked reduction of GFR and RBF in the CIN group. Moreover, sildenafil treatment in CIN rats reduced plasma creatinine, uremia, and proteinuria. Flow cytometry demonstrated that sildenafil attenuated the ROS production in the CIN group. These data suggest that sildenafil may be a new therapeutic agent to prevent CIN through its ability to preserve renal function and attenuate oxidative stress.