Phosphodiesterase-5 inhibition preserves renal hemodynamics and function in mice with diabetic kidney disease by modulating miR-22 and BMP7

Molecular mechanisms of diabetic nephropathy: A narrative review

Diabetic nephropathy (DN) is the predominant secondary nephropathy resulting in global end-stage renal disease. It is attracting significant attention in both domestic and international research due to its widespread occurrence, fast advancement, and limited choices for prevention and treatment. The pathophysiology of this condition is intricate and involves multiple molecular and cellular pathways at various levels. This article provides a concise overview of the molecular processes involved in the development of DN. It discusses various factors, such as signaling pathways, cytokines, inflammatory responses, oxidative stress, cellular damage, autophagy, and epigenetics. The aim is to offer clinicians a valuable reference for DN's diagnosis, treatment, and intervention.

Cyclic Adenosine Monophosphate Signaling in Chronic Kidney Disease: Molecular Targets and Therapeutic Potentials

Chronic kidney disease (CKD) is characterized by a steady decline in kidney function and affects roughly 10% of the world's population. This review focuses on the critical function of cyclic adenosine monophosphate (cAMP) signaling in CKD, specifically how it influences both protective and pathogenic processes in the kidney. cAMP, a critical secondary messenger, controls a variety of cellular functions, including transcription, metabolism, mitochondrial homeostasis, cell proliferation, and apoptosis. Its compartmentalization inside cellular microdomains ensures accurate signaling. In kidney physiology, cAMP is required for hormone-regulated activities, particularly in the collecting duct, where it promotes water reabsorption through vasopressin signaling. Several illnesses, including Fabry disease, renal cell carcinoma, nephrogenic diabetes insipidus, Bartter syndrome, Liddle syndrome, diabetic nephropathy, autosomal dominant polycystic kidney disease, and renal tubular acidosis, have been linked to dysfunction in the cAMP system. Both cAMP analogs and phosphodiesterase inhibitors have the potential to improve kidney function and reduce kidney damage. Future research should focus on developing targeted PDE inhibitors for the treatment of CKD.

Sildenafil and Kidney Function in Heart Failure with Preserved Ejection Fraction

Key Points

Sildenafil induced an acute effect on eGFR without change in the overall eGFR slope after 24 weeks in a heart failure with preserved ejection fraction (HFpEF) cohort. N -terminal pro–brain natriuretic peptide levels and baseline diuretic use were most strongly associated with eGFR decline in this HFpEF cohort. Long-term studies are required to determine sildenafil's influence on kidney function and outcomes in HFpEF.

Background

CKD worsens the prognosis for people with heart failure with preserved ejection fraction (HFpEF). In the Phosphodiesterase-5 Inhibition to Improve Clinical Status and Exercise Capacity in Diastolic HFpEF (RELAX) trial, sildenafil decreased eGFR compared with placebo despite favorable kidney effects in preclinical models. Since acute eGFR decline precedes long-term kidney benefits for select medications, we assessed the influence of sildenafil on acute and chronic eGFR slopes.

Methods

The RELAX trial randomized 216 participants to placebo or sildenafil and assessed 24-week changes in cardiopulmonary exercise testing, cardiovascular imaging, and laboratory data. We applied linear mixed modeling to calculate the total, acute (0–12 weeks), and chronic (3–24 weeks) eGFR slopes by treatment. Using regression modeling, we assessed respective associations between eGFR slope and baseline data and clinical end points. We repeated the analyses using a binary outcome on the basis of a substantial (≥20%) decline in eGFR.

Results

The mean baseline eGFR was 60.8 ml/min per 1.73 m2, and the mean eGFR slope during follow-up was −3.21 ml/min per 1.73 m2 per year. Sildenafil did not alter total eGFR slope compared with placebo (difference +0.47 ml/min per 1.73 m2 per year, 95% confidence interval [CI], −6.63 to 7.57 ml/min per 1.73 m2 per year). Sildenafil users tended to experience a more negative acute eGFR slope (difference −3.15 ml/min per 1.73 m2 per year) and more positive chronic slope (+2.06 ml/min per 1.73 m2 per year) compared with placebo, but neither difference reached statistical significance. Baseline N -terminal pro–B-type natriuretic peptide and loop diuretic use were associated with worse eGFR trajectory regardless of treatment. Substantial eGFR decline was associated with increase in endothelin-1 and a greater risk of hospitalization or death (HR, 2.34, 95% CI, 1.21 to 4.53, P =0.01).

Conclusions

Sildenafil induced an acute effect on eGFR without change in the overall eGFR slope after 24 weeks in an HFpEF cohort, suggesting lack of long-term risk related to early reduction in eGFR after initiating treatment. Long-term studies are needed to determine the effect of sildenafil on kidney function in HFpEF.

Once upon a Testis: The Tale of Cyclic Nucleotide Phosphodiesterase in Testicular Cancers

Phosphodiesterases are key regulators that fine tune the intracellular levels of cyclic nucleotides, given their ability to hydrolyze cAMP and cGMP. They are critical regulators of cAMP/cGMP-mediated signaling pathways, modulating their downstream biological effects such as gene expression, cell proliferation, cell-cycle regulation but also inflammation and metabolic function. Recently, mutations in PDE genes have been identified and linked to human genetic diseases and PDEs have been demonstrated to play a potential role in predisposition to several tumors, especially in cAMP-sensitive tissues. This review summarizes the current knowledge and most relevant findings regarding the expression and regulation of PDE families in the testis focusing on PDEs role in testicular cancer development.

Phosphodiesterase 5a Signalling in Skeletal Muscle Pathophysiology

Phosphodiesterase 5A (PDE5A) is involved in cGMP hydrolysis, regulating many physiological processes. Increased activity of PDE5A has been found in several pathological conditions, and the pharmacological inhibition of PDE5 has been demonstrated to have several therapeutic applications. We have identified the presence of three different Pde5a isoforms in cardiomyocytes, and we have found that the expression of specific Pde5a isoforms may have a causal role in the onset of pathological responses in these cells. In our previous study, we demonstrated that PDE5A inhibition could ameliorate muscular dystrophy by acting at different levels, as assessed by the altered genomic response of muscular cells following treatment with the PDE5A inhibitor tadalafil. Thus, considering the importance of PDE5A in various pathophysiological conditions, we further investigated the regulation of this enzyme. Here, we analysed the expression of Pde5a isoforms in the pathophysiology of skeletal muscle. We found that skeletal muscle tissues and myogenic cells express Pde5a1 and Pde5a2 isoforms, and we observed an increased expression of Pde5a1 in damaged skeletal muscles, while Pde5a2 levels remained unchanged. We also cloned and characterized the promoters that control the transcription of Pde5a isoforms, investigating which of the transcription factors predicted by bioinformatics analysis could be involved in their modulation. In conclusion, we found an overexpression of Pde5a1 in compromised muscle and identified an involvement of MyoD and Runx1 in Pde5a1 transcriptional activity.

The NO/cGMP/PKG pathway in platelets: The therapeutic potential of PDE5 inhibitors in platelet disorders

Platelets are the "guardians" of the blood circulatory system. At sites of vessel injury, they ensure hemostasis and promote immunity and vessel repair. However, their uncontrolled activation is one of the main drivers of thrombosis. To keep circulating platelets in a quiescent state, the endothelium releases platelet antagonists including nitric oxide (NO) that acts by stimulating the intracellular receptor guanylyl cyclase (GC). The latter produces the second messenger cyclic guanosine-3',5'-monophosphate (cGMP) that inhibits platelet activation by stimulating protein kinase G, which phosphorylates hundreds of intracellular targets. Intracellular cGMP pools are tightly regulated by a fine balance between GC and phosphodiesterases (PDEs) that are responsible for the hydrolysis of cyclic nucleotides. Phosphodiesterase type 5 (PDE5) is a cGMP-specific PDE, broadly expressed in most tissues in humans and rodents. In clinical practice, PDE5 inhibitors (PDE5i) are used as first-line therapy for erectile dysfunction, pulmonary artery hypertension, and lower urinary tract symptoms. However, several studies have shown that PDE5i may ameliorate the outcome of various other conditions, like heart failure and stroke. Interestingly, NO donors and cGMP analogs increase the capacity of anti-platelet drugs targeting the purinergic receptor type Y, subtype 12 (P2Y12) receptor to block platelet aggregation, and preclinical studies have shown that PDE5i inhibits platelet functions. This review summarizes the molecular mechanisms underlying the effect of PDE5i on platelet activation and aggregation focusing on the therapeutic potential of PDE5i in platelet disorders, and the outcomes of a combined therapy with PDE5i and NO donors to inhibit platelet activation.

Nutraceutical Prevention of Diabetic Complications—Focus on Dicarbonyl and Oxidative Stress

Oxidative and dicarbonyl stress, driven by excess accumulation of glycolytic intermediates in cells that are highly permeable to glucose in the absence of effective insulin activity, appear to be the chief mediators of the complications of diabetes. The most pathogenically significant dicarbonyl stress reflects spontaneous dephosphorylation of glycolytic triose phosphates, giving rise to highly reactive methylglyoxal. This compound can be converted to harmless lactate by the sequential activity of glyoxalase I and II, employing glutathione as a catalyst. The transcription of glyoxalase I, rate-limiting for this process, is promoted by Nrf2, which can be activated by nutraceutical phase 2 inducers such as lipoic acid and sulforaphane. In cells exposed to hyperglycemia, glycine somehow up-regulates Nrf2 activity. Zinc can likewise promote glyoxalase I transcription, via activation of the metal-responsive transcription factor (MTF) that binds to the glyoxalase promoter. Induction of glyoxalase I and metallothionein may explain the protective impact of zinc in rodent models of diabetic complications. With respect to the contribution of oxidative stress to diabetic complications, promoters of mitophagy and mitochondrial biogenesis, UCP2 inducers, inhibitors of NAPDH oxidase, recouplers of eNOS, glutathione precursors, membrane oxidant scavengers, Nrf2 activators, and correction of diabetic thiamine deficiency should help to quell this.

Effects of furosemide and tadalafil in both conventional and nanoforms against adenine-induced chronic renal failure in rats

BACKGROUND

Chronic renal failure (CRF) is a progressive loss of renal function that lead to reduced sodium filtration and inappropriate suppression of tubular reabsorption that ultimately leads to volume expansion. The aim of this study was to study the efficacy of furosemide and tadalafil nanoforms compared to conventional forms against adenine-induced CRF rat-model.

METHODS

Addition of 0.75% adenine to the diet of rats for 4 weeks gained general acceptance as a model to study kidney damage as this intervention mimicked most of the structural and functional changes seen in human chronic kidney disease Urine analysis, histopathological changes and immunohistochemical expression of caspase-3 and interleukin-1 beta (IL-1β) in renal tissues were performed.

RESULTS

Our results showed that the combination of tadalafil and furosemide using conventional and nanoparticle formulations had better renoprotective effect than individual drugs. This was demonstrated by improvement of urinary, serum and renal tissue markers as indicative of organ damage. This was also reflected on the reduction of tubular expression of kidney injury molecule-1 (KIM-1) and neutrophil gelatinase-associated lipocalin (NGAL). Immunohistochemical studies showed that the deteriorated renal cellular changes indicated by increased expression of caspase-3 and IL-1β were greatly improved by the combined treatment particularly with the nanoforms.

CONCLUSIONS

The nanoforms of both furosemide and tadalafil had greater renopreventive effects compared with conventional forms against adenine-induced CRF in rats.

Sex-specific effects of daily tadalafil on diabetic heart kinetics in RECOGITO, a randomized, double-blind, placebo-controlled trial

Cyclic GMP-phosphodiesterase type 5 (PDE5) inhibition has been shown to counteract maladaptive cardiac changes triggered by diabetes in some but not all studies. We performed a single-center, 20-week, double-blind, randomized, placebo-controlled trial (NCT01803828) to assess sex differences in cardiac remodeling after PDE5 inhibition in patients with diabetic cardiomyopathy. A total of 122 men and women (45 to 80 years) with long-duration (>3 years) and well-controlled type 2 diabetes mellitus (T2DM; HbA1c < 86 mmol/mol) were selected according to echocardiographic signs of cardiac remodeling. Patients were randomly assigned (1:1) to placebo or oral tadalafil (20 mg, once daily). The primary outcome was to evaluate sex differences in cardiac torsion change. Secondary outcomes were changes in cardiovascular, metabolic, immune, and renal function. At 20 weeks, the treatment-by-sex interaction documented an improvement in cardiac torsion (-3.40°, -5.96; -0.84, P = 0.011) and fiber shortening (-1.19%, -2.24; -0.14, P = 0.027) in men but not women. The primary outcome could not be explained by differences in cGMP concentrations or tadalafil pharmacodynamics. In both sexes, tadalafil improved hsa-miR-199-5p expression, biomarkers of cardiovascular remodeling, albuminuria, renal artery resistive index, and circulating Klotho concentrations. Immune cell profiling revealed an improvement in low-grade chronic inflammation: Classic CD14⁺⁺CD16^- monocytes reduced, and Tie2⁺ monocytes increased. Nine patients (14.5%) had minor adverse reactions after tadalafil administration. Continuous PDE5 inhibition could offer a strategy to target cardiorenal complications of T2DM, with sex- and tissue-specific responses. Further studies are needed to confirm Klotho and hsa-miR-199-5p as markers for T2DM complications.

Bone Morphogenetic Protein 7 Gene Delivery Improves Cardiac Structure and Function in a Murine Model of Diabetic Cardiomyopathy

Diabetes is a major contributor to the increasing burden of heart failure prevalence globally, at least in part due to a disease process termed diabetic cardiomyopathy. Diabetic cardiomyopathy is characterised by cardiac structural changes that are caused by chronic exposure to the diabetic milieu. These structural changes are a major cause of left ventricular (LV) wall stiffness and the development of LV dysfunction. In the current study, we investigated the therapeutic potential of a cardiac-targeted bone morphogenetic protein 7 (BMP7) gene therapy, administered once diastolic dysfunction was present, mimicking the timeframe in which clinical management of the cardiomyopathy would likely be desired. Following 18 weeks of untreated diabetes, mice were administered with a single tail-vein injection of recombinant adeno-associated viral vector (AAV), containing the BMP7 gene, or null vector. Our data demonstrated, after 8 weeks of treatment, that rAAV6-BMP7 treatment exerted beneficial effects on LV functional and structural changes. Importantly, diabetes-induced LV dysfunction was significantly attenuated by a single administration of rAAV6-BMP7. This was associated with a reduction in cardiac fibrosis, cardiomyocyte hypertrophy and cardiomyocyte apoptosis. In conclusion, BMP7 gene therapy limited pathological remodelling in the diabetic heart, conferring an improvement in cardiac function. These findings provide insight for the potential development of treatment strategies urgently needed to delay or reverse LV pathological remodelling in the diabetic heart.

The effects of alprostadil combined with α-lipoic acid in the treatment of senile diabetic nephropathy

OBJECTIVE

This study aimed to investigate the clinical efficacy of alprostadil combined with α-Lipoic acid (α-LA) in the treatment of senile diabetic nephropathy (SDN) and the combination's effect on the serum chemerin and neutrophil gelatinase-associated lipocalin (NGAL) expressions.

METHODS

Seventy-six patients with diabetic nephropathy (DN) admitted to our hospital from March 2018 to October 2019 were recruited as the research cohort. Among them, 36 patients who were administered alprostadil monotherapy were placed in the control group (CG), and the remaining 40 patients administered α-LA in addition to the alprostadil were placed in the research group (RG). The treatment effectiveness rate, the incidence of adverse reactions, and the changes in the renal function indexes (BUN, SCr, UAER) and the blood glucose indexes (FPG, 2hPG) were compared between the two groups.

RESULTS

The total effective rate in the RG was significantly higher than the total effective rate in the CG (P < 0.05). The renal function and blood glucose indexes dropped significantly after the treatment (P < 0.001). The chemerin and NGAL levels were significantly reduced in both groups after the treatment (P < 0.05), and the chemerin and NGAL expressions in the RG were significantly lower than they were in the CG (P < 0.05).

CONCLUSION

Alprostadil combined with α-LA is better than alprostadil monotherapy in the treatment of DN because it can improve the effectiveness rate, reduce the blood glucose, and improve the renal function while effectively reducing patients' serum chemerin and NGAL levels.

Priming metabolism with the type 5 phosphodiesterase: the role of cGMP-hydrolyzing enzymes

The cyclic guanosine monophosphate (cGMP) signaling system is one of the most prominent regulators of many physiopathological processes in humans and rodents. It has been strongly established as an accomplished cellular signal involved in the regulation of energy homeostasis and cell metabolism, and pharmacological enhancement of cGMP has shown beneficial effects in metabolic disorders models. cGMP intracellular levels are finely regulated by phosphodiesterases (PDEs). The main enzyme responsible for the degradation of cGMP is PDE5. Preclinical and clinical studies have shown that PDE5 inhibitors (PDE5i) have beneficial effects on improving insulin resistance and glucose metabolism representing a promising therapeutic strategy for the treatment of metabolic disorders. This review aims to describe the molecular basis underlying the use of PDE5i to prompt cell metabolism and summarize current clinical trials assessing the effects of PDE5i on glucose metabolism.

Independent impact of periodontitis and cardiovascular disease on elevated soluble urokinase-type plasminogen activator receptor (suPAR) levels

BACKGROUND

Previous studies have demonstrated that a soluble urokinase-type plasminogen activator receptor (suPAR) plays an essential function in leukocytes and endothelial homeostasis and, therefore, in the development of coronary heart disease (CHD) and periodontitis. The aim of this study was to analyze the impact of gingival health, periodontitis, and CHD on suPAR levels in plasma and saliva and to evaluate suPAR as a biomarker of periodontitis and CHD.

METHODS

Healthy controls (n = 33), patients with periodontitis (n = 31), CHD (n = 29), and a combination of periodontitis + CHD (n = 29) were enrolled in the present study. All patients were clinically and periodontally evaluated and regularly assessed for socioeconomic status, serum lipids, high-sensitivity C-reactive protein (hs-CRP), and for plasma and salivary suPAR levels.

RESULTS

Patients with periodontitis (P <.001) and with periodontitis + CHD (P <.001) presented higher median plasma and salivary suPAR levels compared with CHD and healthy controls. Moreover, univariate regression analysis demonstrated that hs-CRP (P <.001) and periodontitis (P <.001) had a significant negative direct effect on both plasma and salivary suPAR levels. The multivariate regression analysis showed that periodontitis was the only significant predictor of plasma suPAR (P = .035) while hs-CRP was the only significant predictor of salivary suPAR (P <.001).

CONCLUSIONS

The results of the present study demonstrated that patients with periodontitis and periodontitis + CHD presented higher suPAR levels in both plasma and saliva in comparison with healthy controls and CHD. Moreover, periodontitis and hs-CRP were the only significant predictors of the augmented suPAR levels in plasma and saliva, respectively.

Local cyclic adenosine monophosphate signalling cascades-Roles and targets in chronic kidney disease

The molecular mechanisms underlying chronic kidney disease (CKD) are poorly understood and treatment options are limited, a situation underpinning the need for elucidating the causative molecular mechanisms and for identifying innovative treatment options. It is emerging that cyclic 3',5'-adenosine monophosphate (cAMP) signalling occurs in defined cellular compartments within nanometre dimensions in processes whose dysregulation is associated with CKD. cAMP compartmentalization is tightly controlled by a specific set of proteins, including A-kinase anchoring proteins (AKAPs) and phosphodiesterases (PDEs). AKAPs such as AKAP18, AKAP220, AKAP-Lbc and STUB1, and PDE4 coordinate arginine-vasopressin (AVP)-induced water reabsorption by collecting duct principal cells. However, hyperactivation of the AVP system is associated with kidney damage and CKD. Podocyte injury involves aberrant AKAP signalling. cAMP signalling in immune cells can be local and slow the progression of inflammatory processes typical for CKD. A major risk factor of CKD is hypertension. cAMP directs the release of the blood pressure regulator, renin, from juxtaglomerular cells, and plays a role in Na⁺ reabsorption through ENaC, NKCC2 and NCC in the kidney. Mutations in the cAMP hydrolysing PDE3A that cause lowering of cAMP lead to hypertension. Another major risk factor of CKD is diabetes mellitus. AKAP18 and AKAP150 and several PDEs are involved in insulin release. Despite the increasing amount of data, an understanding of functions of compartmentalized cAMP signalling with relevance for CKD is fragmentary. Uncovering functions will improve the understanding of physiological processes and identification of disease-relevant aberrations may guide towards new therapeutic concepts for the treatment of CKD.

Activation of soluble guanylyl cyclase signalling with cinaciguat improves impaired kidney function in diabetic mice

BACKGROUND AND PURPOSE

Diabetic nephropathy is the leading cause for end-stage renal disease worldwide. Until now, there is no specific therapy available. Standard treatment with inhibitors of the renin-angiotensin system just slows down progression. However, targeting the NO/sGC/cGMP pathway using sGC activators does prevent kidney damage. Thus, we investigated if the sGC activator cinaciguat was beneficial in a mouse model of diabetic nephropathy, and we analysed how mesangial cells (MCs) were affected by related conditions in cell culture.

EXPERIMENTAL APPROACH

Type 1 diabetes was induced with streptozotocin in wild-type and endothelial NOS knockout (eNOS KO) mice for 8 or 12 weeks.. Half of these mice received cinaciguat in their chow for the last 4 weeks. Kidneys from the diabetic mice were analysed with histochemical assays and by RT-PCR and western blotting. . Additionally, primary murine MCs under diabetic conditions were stimulated with 8-Br-cGMP or cinaciguat to activate the sGC/cGMP pathway.

KEY RESULTS

The diabetic eNOS KO mice developed most characteristics of diabetic nephropathy, most marked at 12 weeks. Treatment with cinaciguat markedly improved GFR, serum creatinine, mesangial expansion and kidney fibrosis in these animals. We determined expression levels of related signalling proteins. Thrombospondin 1, a key mediator in kidney diseases, was strongly up-regulated under diabetic conditions and this increase was suppressed by activation of sGC/cGMP signalling.

CONCLUSION AND IMPLICATIONS

Activation of the NO/sGC/PKG pathway with cinaciguat was beneficial in a model of diabetic nephropathy. Activators of sGC might be an appropriate therapy option in patients with Type 1 diabetes.

Antiangiogenic therapy in diabetic nephropathy: A double‑edged sword (Review)

Diabetes and the associated complications are becoming a serious global threat and an increasing burden to human health and the healthcare systems. Diabetic nephropathy (DN) is the primary cause of end-stage kidney disease. Abnormal angiogenesis is well established to be implicated in the morphology and pathophysiology of DN. Factors that promote or inhibit angiogenesis serve an important role in DN. In the present review, the current issues associated with the vascular disease in DN are highlighted, and the challenges in the development of treatments are discussed.

Exosomal miR-22-3p Derived from Chronic Rhinosinusitis with Nasal Polyps Regulates Vascular Permeability by Targeting VE-Cadherin

Background

The abnormal vascular permeability is associated with the formation of chronic rhinosinusitis with nasal polyps (CRSwNP). Previously, our study demonstrated that the nasal lavage fluid- (NLF-) derived exosomes from CRSwNP can promote the vascular permeability of human umbilical vein endothelial cells (HUVECs). miR-22-3p, a specific differentiated miRNA, is reported to regulate microvessels in some diseases. This study is purposed to explore the impact of exosomal miR-22-3p derived from CRSwNP on vascular permeability and identify the underlying targets.

Methods

Exosomes were extracted from NLF of 26 CRSwNP patients and 10 control patients. Quantitative real-time PCR (qRT- PCR) was applied to evaluate the relative level of exosomal miR-22-3p. The impact of exosomal miR-22-3p on HUVECs was assessed by permeability assays in vitro. The potential molecular targets of miR-22-3p were investigated by applying such technologies as dual-luciferase reporter assay and western blot.

Results

miR-22-3p was upregulated in NLF-derived exosomes from CRSwNP. Exosomal miR-22-3p derived from CRSwNP enhanced the tubule permeability of HUVECs. Vascular endothelial- (VE-) cadherin (CDH5) was identified as a direct target of miR-22-3p. miR-22-3p regulated the vascular permeability by targeting VE-cadherin in HUVECs.

Conclusions

Exosomal miR-22-3p derived from NLF of CRSwNP plays an important role in regulating vascular permeability by targeting VE-cadherin.

PDE5 Inhibitors in Type 2 Diabetes Cardiovascular Complications

Pharmacological inhibition of Phosphodiesterase type 5 (PDE5) proved its efficacy treating several pathological conditions, such as erectile dysfunction and pulmonary hypertension. Nowadays, its benefits on cardiovascular diseases are well documented, particularly in the treatment of type 2 diabetes (T2DM)-related cardiovascular complications. In this context, treatment of T2DM with PDE5 inhibitors, such as sildenafil, tadalafil or vardenafil ameliorates endothelial dysfunction both in patients and animal models through an augmented flow mediated dilation rate and an up-regulation of endothelial markers; it also reduces the inflammatory state by down-regulating inflammatory cytokines expression and improves diabetic cardiomyopathy and ischemia-reperfusion injury mainly through the activation of NO-cGMP-PKG pathway. The present review summarizes the state of art on PDE5 inhibition in the treatment of cardiovascular complications in T2DM.

Ameliorative effect of phosphodiesterase 4 and 5 inhibitors in deoxycorticosterone acetate-salt hypertensive uni-nephrectomized KKAy mice

Diabetic nephropathy (DN) is a leading cause of end-stage renal disease (ESRD). Hypertension increases kidney stress, which deteriorates function, and leads to peripheral renal vascular resistance. Long-term hypoperfusion promotes interstitial fibrosis and glomerular sclerosis, resulting in nephrosclerosis. Although hypertension and DN are frequent ESRD complications, relevant animal models remain unavailable. We generated a deoxycorticosterone acetate (DOCA)-salt hypertensive uni-nephrectomized (UNx) KKA^y mouse model demonstrating hypertension, hyperglycemia, cardiac hypertrophy, kidney failure, increased urinary albumin creatinine ratio (UACR), and increased renal PDE4D and cardiac PDE5A mRNA levels. We hypothesized that the novel PDE4 selective inhibitor, compound A, and PDE5 inhibitor, sildenafil, exhibit nephroprotective, and cardioprotective effects in this new model. Compound A, sildenafil, and the angiotensin II receptor blocker, irbesartan, significantly reduced ventricular hypertrophy and pleural effusion volume. Meanwhile, compound A and sildenafil significantly suppressed the UACR, urinary kidney injury molecule-1, and monocyte chemoattractant protein-1 levels, as well as that of renal pro-fibrotic marker mRNAs, including collagen 1A1, fibronectin, and transforming growth factor-beta (TGF-β). Moreover, compound A significantly suppressed TGF-β-induced pro-fibrotic mRNA expression in vitro in all major kidney lesions, including within the glomerular mesangial region, podocytes, and epithelial region. Hence, PDE4 and PDE5 inhibitors may be promising treatments, in combination with irbesartan, for DN with hypertension as they demonstrate complementary mechanisms.

Targeting the NO-cGMP-PDE5 pathway in COVID-19 infection. The DEDALO project

Background

A pandemic outbreak of COVID‐19 has been sweeping the world since December. It begins as a respiratory infection that, mainly in men with diabetes or renal impairment, evolves into a systemic disease, with SARDS, progressive endothelial cell damage, abnormal clotting and impaired cardiovascular and liver function. Some clinical trials are testing biological drugs to limit the immune system dysregulation, “cytokines storm,” that causes the systemic complications of COVID‐19. The contraindications of these drugs and their cost raise concerns over the implications of their widespread availability.

Objectives

Numerous clinical and experimental studies have revealed a role for the nitric oxide (NO)‐cyclic GMP‐phosphodiesterase type 5 (PDE5) pathway in modulating low‐grade inflammation in patients with metabolic diseases, offering cardiovascular protection. PDE5 inhibition favors an anti‐inflammatory response by modulating activated T cells, reducing cytokine release, lowering fibrosis, increasing oxygen diffusion, stimulating vascular repair. PDE5 is highly expressed in the lungs, where its inhibition improves pulmonary fibrosis, a complication of severe COVID‐19 disease.

Materials and methods

We performed a systematic review of all evidence documenting any involvement of the NO‐cGMP‐PDE5 axis in the pathophysiology of COVID‐19, presenting the ongoing clinical trials aimed at modulating this axis, including our own “silDEnafil administration in DiAbetic and dysmetaboLic patients with COVID‐19 (DEDALO trial).”

Results

The reviewed evidence suggests that PDE5 inhibitors could offer a new strategy in managing COVID‐19 by (i) counteracting the Ang‐II‐mediated downregulation of AT‐1 receptor; (ii) acting on monocyte switching, thus reducing pro‐inflammatory cytokines, interstitial infiltration and the vessel damage responsible for alveolar hemorrhage‐necrosis; (iii) inhibiting the transition of endothelial and smooth muscle cells to mesenchymal cells in the pulmonary artery, preventing clotting and thrombotic complications.

Discussion and Conclusion

If the ongoing trials presented herein should provide positive findings, the low cost, wide availability and temperature stability of PDE5 inhibitors could make them a major resource to combat COVID‐19 in developing countries.

Type 5 phosphodiesterase (PDE5) and the vascular tree: From embryogenesis to aging and disease

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Vascular development depends on the timely differentiation of endothelial and smooth muscle cells.

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Vascular aging and vascular disease are influenced by endothelial and vascular smooth muscle cell compartments.

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A survey of the literature on the role of PDE5 in vascular development, aging and disease is reported.

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The role of PDE5 on vascular development, aging and disease needs to be further investigated by its genetic ablation.

Vascular tree development depends on the timely differentiation of endothelial and vascular smooth muscle cells. These latter are key players in the formation of the vascular scaffold that offers resistance to the blood flow. This review aims at providing an overview on the role of PDE5, the cGMP-specific phosphodiesterase that historically attracted much attention for its involvement in male impotence, in the regulation of vascular smooth muscle cell function. The overall goal is to underscore the importance of PDE5 expression and activity in this cell type in the context of the organs where its function has been extensively studied.

Phosphodiesterase-5 inhibitors ameliorate structural kidney damage in a rat model of contrast-induced nephropathy

The aim of the study was to investigate the potential of sildenafil and tadalafil to ameliorate structural kidney damage in contrast-induced nephropathy (CIN). A rat model of CIN was developed by dehydration, administration of a nitric oxide inhibitor and a prostaglandin synthesis inhibitor (L-NAME/indomethacin) and contrast media exposure to iopromide. The effect of pre-treatment with sildenafil, tadalafil or N-acetyl cysteine (NAC) for 7 days prior to CIN induction was investigated. All animals were sacrificed at 24 h after CIN induction and both kidneys were collected. Histopathological examination was performed under light microscopy in serial tissue sections stained with hematoxylin and eosin. CIN group showed hydropic changes of the renal tubules (proximal and distal convoluted tubules and Henle's loop), an increased Bowman space with lobulated glomerulus and alteration of macula densa region of distal convolute tubules. The groups pretreated with sildenafil and tadalafil showed nearly normal histological aspects of renal tissue. The group pretreated with NAC showed similar but less intense histopathologic changes compared to CIN group. Sildenafil and tadalafil pre-treatment ameliorates CIN-related structural kidney damage and the protective potential of these agents is superior to NAC.

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.

miR-34b Alleviates High Glucose-Induced Inflammation and Apoptosis in Human HK-2 Cells via IL-6R/JAK2/STAT3 Signaling Pathway

Background

It is well established that inflammation and apoptosis of renal tubular epithelial cells caused by hyperglycemia contribute to the development of diabetic nephropathy (DN). Although microRNAs (miRNAs) are known to have roles in inflammation-related disorders, the exact role of miR-34b in DN has not been defined, and the regulatory mechanism has been unclear. This study aimed to clarify the role of miR-34b in DN pathogenesis.

Material/Methods

Expression of miR-34b, IL-6R, and other key factors of inflammation, apoptosis (TNF-α, IL-1β, IL-6, caspase-3) in high glucose (HG)-induced HK-2 cells were measured by real-time PCR, Western blot, and flow cytometric cell apoptosis assays. We used luciferase reporter assay to detect the target of miR-34b. Moreover, the targeting gene of miR-34b and its downstream JAK2/STAT3 signaling pathway were explored.

Results

It was demonstrated that miR-34b overexpression inhibited apoptosis and expression levels of TNF-α, IL-1β, IL-6, and caspase-3 in HG-treated HK-2 cells. We also found that IL-6R is a direct target of miR-34b, which could rescue inflammation and apoptosis in HG-treated HK-2 cells transfected with miR-34b mimic. Furthermore, we showed that overexpression of miR-34b inhibited the IL-6R/JAK2/STAT3 signaling pathway in HG-treated HK-2 cells.

Conclusions

Our data suggest that overexpression of miR-34b improves inflammation and ameliorates apoptosis in HG-induced HK-2 cells via the IL-6R/JAK2/STAT3 pathway, indicating that miR-34b could be a promising therapeutic target in DN.

PDE5 Inhibition Stimulates Tie2-Expressing Monocytes and Angiopoietin-1 Restoring Angiogenic Homeostasis in Diabetes

CONTEXT

Vascular dysfunction is a common feature in end-organ complications of type 2 diabetes mellitus (T2DM). The endothelium-specific receptor tyrosine kinase Tie2 and its ligand, angiopoietin-1 (Ang1), participate in the processes of vessel repair, renewal, and maturation. However, their dysregulation in T2DM has seldom been investigated.

OBJECTIVES

To examine the relationship between angiogenic Tie2-expressing monocytes (TEMs) and Ang1, and their pharmacological modulation by the phosphodiesterase type 5 inhibitor (PDE5i) sildenafil, in T2DM and in db/db mouse model.

DESIGN AND SETTING

Randomized, double-blind, placebo-controlled study.

PATIENTS AND INTERVENTION

db/db male mice were randomly assigned to receive 8 weeks of sildenafil or vehicle. Diabetic men were randomly assigned to receive 4 weeks of sildenafil or placebo.

MAIN OUTCOMES AND MEASURES

Peripheral blood cells were investigated by flow cytometry to quantify inflammatory myeloid CD11b+ Gr1+ cells and proangiogenic TEMs in mice and classical CD14++CD16neg monocytes and proangiogenic TEMs in humans at baseline and after treatment. In vitro human tube formation assay was used to test serum angiogenic potential.

RESULTS

We show that TEMs and Ang1 are defective in mouse and human models of diabetes and are normalized by PDE5i treatment. Serum angiogenic properties are impaired in diabetes because they do not support the in vitro formation of capillary-like structures, but they are reestablished by in vivo PDE5i treatment.

CONCLUSIONS

Restoring a more physiological Tie2-Ang1 axis with sildenafil reestablishes serum angiogenic properties in diabetes, promoting angiogenic homeostasis.

The combination of a neprilysin inhibitor (sacubitril) and angiotensin-II receptor blocker (valsartan) attenuates glomerular and tubular injury in the Zucker Obese rat

OBJECTIVE

Diabetic nephropathy (DN) is characterized by glomerular and tubulointerstitial injury, proteinuria and remodeling. Here we examined whether the combination of an inhibitor of neprilysin (sacubitril), a natriuretic peptide-degrading enzyme, and an angiotensin II type 1 receptor blocker (valsartan), suppresses renal injury in a pre-clinical model of early DN more effectively than valsartan monotherapy.

METHODS

Sixty-four male Zucker Obese rats (ZO) at 16 weeks of age were distributed into 4 different groups: Group 1: saline control (ZOC); Group 2: sacubitril/valsartan (sac/val) (68 mg kg^-1 day^-1; ZOSV); and Group 3: valsartan (val) (31 mg kg^-1 day^-1; ZOV). Group 4 received hydralazine, an anti-hypertensive drug (30 mg kg^-1 day^-1, ZOH). Six Zucker Lean (ZL) rats received saline (Group 5) and served as lean controls (ZLC). Drugs were administered daily for 10 weeks by oral gavage.

RESULTS

Mean arterial pressure (MAP) increased in ZOC (+ 28%), but not in ZOSV (- 4.2%), ZOV (- 3.9%) or ZOH (- 3.7%), during the 10 week-study period. ZOC were mildly hyperglycemic, hyperinsulinemic and hypercholesterolemic. ZOC exhibited proteinuria, hyperfiltration, elevated renal resistivity index (RRI), glomerular mesangial expansion and podocyte foot process flattening and effacement, reduced nephrin and podocin expression, tubulointerstitial and periarterial fibrosis, increased NOX2, NOX4 and AT₁R expression, glomerular and tubular nitroso-oxidative stress, with associated increases in urinary markers of tubular injury. None of the drugs reduced fasting glucose or HbA1c. Hypercholesterolemia was reduced in ZOSV (- 43%) and ZOV (- 34%) (p < 0.05), but not in ZOH (- 13%) (ZOSV > ZOV > ZOH). Proteinuria was ameliorated in ZOSV (- 47%; p < 0.05) and ZOV (- 30%; p > 0.05), but was exacerbated in ZOH (+ 28%; p > 0.05) (ZOSV > ZOV > ZOH). Compared to ZOC, hyperfiltration was improved in ZOSV (p < 0.05 vs ZOC), but not in ZOV or ZOH. None of the drugs improved RRI. Mesangial expansion was reduced by all 3 treatments (ZOV > ZOSV > ZOH). Importantly, sac/val was more effective in improving podocyte and tubular mitochondrial ultrastructure than val or hydralazine (ZOSV > ZOV > ZOH) and this was associated with increases in nephrin and podocin gene expression in ZOSV (p < 0.05), but not ZOV or ZOH. Periarterial and tubulointerstitial fibrosis and nitroso-oxidative stress were reduced in all 3 treatment groups to a similar extent. Of the eight urinary proximal tubule cell injury markers examined, five were elevated in ZOC (p < 0.05). Clusterin and KIM-1 were reduced in ZOSV (p < 0.05), clusterin alone was reduced in ZOV and no markers were reduced in ZOH (ZOSV > ZOV > ZOH).

CONCLUSIONS

Compared to val monotherapy, sac/val was more effective in reducing proteinuria, renal ultrastructure and tubular injury in a clinically relevant animal model of early DN. More importantly, these renoprotective effects were independent of improvements in blood pressure, glycemia and nitroso-oxidative stress. These novel findings warrant future clinical investigations designed to test whether sac/val may offer renoprotection in the setting of DN.

Urinary Exosome-Derived microRNAs Reflecting the Changes in Renal Function in Cats

Increased incidence of kidney disease (KD) is a common concern in human and companion animals. Cats, in particular, are highly susceptible to KD. Novel KD biomarkers would help to address these problems. Therefore, we are focusing on microRNA, a highly conserved nucleic acid, as a KD biomarker for various animals. We previously reported that altered levels of urinary exosome (UExo)-derived microRNAs indicate renal pathologies in dogs. This study comprehensively examined UExo-derived microRNAs, which reflected the KD status in cats. The examined cats were divided into two groups: normal renal function (NR) and KD. Based on our previous data in dogs and cats, as well as the present data on UExo-derived microRNAs in cats by next-generation sequencing, let-7b, let-7f, miR-10a, miR-10b, miR-21a, miR-22, miR-26a, miR-27b, miR-146a, miR-181a, miR-191, and miR-486a were identified as biomarker candidates. In summary, the levels of UExo-derived let-7b, miR-22, and miR-26a significantly decreased in cats with KD from the early stages of the disease. UExo-derived miRNA levels normalized to urinary creatinine or total RNA of miR-21a was significantly higher in the KD group. Importantly, the ratio of UExo-derived miR-21a to let-7b showed a significant and strongest correlation with serum creatinine (ρ = 0.751), blood urea nitrogen (ρ = 0.754), and urinary creatinine (ρ = −0.421) among all examined indices. Further, the ratio of miR-181a to let-7b or miR-10b significantly correlated with the progression of renal dysfunction in the KD group. Thus, we identified that UExo-derived microRNAs in cats, and their raw and normalized levels could indicate altered renal function.

Glycemic control by the SGLT2 inhibitor empagliflozin decreases aortic stiffness, renal resistivity index and kidney injury

Background

Arterial stiffness is emerging as an independent risk factor for the development of chronic kidney disease. The sodium glucose co-transporter 2 (SGLT2) inhibitors, which lower serum glucose by inhibiting SGLT2-mediated glucose reabsorption in renal proximal tubules, have shown promise in reducing arterial stiffness and the risk of cardiovascular and kidney disease in individuals with type 2 diabetes mellitus. Since hyperglycemia contributes to arterial stiffness, we hypothesized that the SGLT2 inhibitor empagliflozin (EMPA) would improve endothelial function, reduce aortic stiffness, and attenuate kidney disease by lowering hyperglycemia in type 2 diabetic female mice (db/db).

Materials/methods

Ten-week-old female wild-type control (C57BLKS/J) and db/db (BKS.Cg-Dock7m+/+Leprdb/J) mice were divided into three groups: lean untreated controls (CkC, n = 17), untreated db/db (DbC, n = 19) and EMPA-treated db/db mice (DbE, n = 19). EMPA was mixed with normal mouse chow at a concentration to deliver 10 mg kg⁻¹ day⁻¹, and fed for 5 weeks, initiated at 11 weeks of age.

Results

Compared to CkC, DbC showed increased glucose levels, blood pressure, aortic and endothelial cell stiffness, and impaired endothelium-dependent vasorelaxation. Furthermore, DbC exhibited impaired activation of endothelial nitric oxide synthase, increased renal resistivity and pulsatility indexes, enhanced renal expression of advanced glycation end products, and periarterial and tubulointerstitial fibrosis. EMPA promoted glycosuria and blunted these vascular and renal impairments, without affecting increases in blood pressure. In addition, expression of “reversion inducing cysteine rich protein with Kazal motifs” (RECK), an anti-fibrotic mediator, was significantly suppressed in DbC kidneys and partially restored by EMPA. Confirming the in vivo data, EMPA reversed high glucose-induced RECK suppression in human proximal tubule cells.

Conclusions

Empagliflozin ameliorates kidney injury in type 2 diabetic female mice by promoting glycosuria, and possibly by reducing systemic and renal artery stiffness, and reversing RECK suppression.

MicroRNA-22 Promotes Renal Tubulointerstitial Fibrosis by Targeting PTEN and Suppressing Autophagy in Diabetic Nephropathy

Renal tubulointerstitial fibrosis (TIF) is a major feature of diabetic nephropathy (DN). There is increasing evidence demonstrating that microRNAs act as key players in the regulation of autophagy and are involved in DN. However, the exact link among microRNAs, autophagy, and TIF in DN is largely unknown. In this study, our results showed that TIF was observed in DN rats together with obvious autophagy suppression. Moreover, microRNA-22 (miR-22) was upregulated and associated with reduced expression of its target gene phosphatase and tensin homolog (PTEN) in both the kidneys of DN rats and high glucose-cultured NRK-52E cells. Intriguingly, induction of autophagy by rapamycin antagonized high glucose-induced collagen IV (Col IV) and α-SMA expression. In addition, ectopic expression of miR-22 suppressed autophagic flux and induced the expression of Col IV and α-SMA, whereas the inhibition of endogenous miR-22 effectively relieved high glucose-induced autophagy suppression and the expression of Col IV and α-SMA in NRK-52E cells. Overexpression of PTEN protectively antagonized high glucose- and miR-22-induced autophagy suppression and the expression of Col IV. Therefore, our findings indicated that miR-22 may promote TIF by suppressing autophagy partially via targeting PTEN and represents a novel and promising therapeutic target for DN.

Renal Resistive Index as a Novel Indicator for Renal Complications in High-Fat Diet-Fed Mice

BACKGROUND/AIMS

The renal resistive index (RI) is a novel candidate as a renal injury prognostic indicator, but it remains unclear how renal RI levels correspond to renal injury in diabetic nephropathy.

METHODS

To examine this issue, we compared 8-week-old male C57BL/6 mice fed with high-fat diet (HFD) versus chow diet (CHD) for 16 weeks. At 8 and 12 weeks, the glomerular filtration rate (GFR), urinary albumin-to-creatinine ratio (UACR), and inflammatory factors (IL-1β, IL-6, TNFα, and MCP-1) were measured, along with the increase in renal RI.

RESULTS

Our study suggests RI values positively correlate with GFR for the first 12 weeks of HFD feeding. In contrast, the GFR of 16-week HFD feeding is lower than that of 12-week HFD feeding, whereas RI levels are significantly increased. Additionally, our study suggests RI values accurately indicate the renal fibrosis and renal injury in HFD-fed mice treated with lovastatin.

CONCLUSION

This study seems to confirm the utility of a noninvasive and repeatable ultrasound parameter to rapidly evaluate renal fibrosis in a HFD-induced type 2 diabetic mouse model in vivo. This highly sensitive and comparable renal RI measurement could monitor the whole procedure of disease development in real-time. RI measurement of the renal artery is capable of differentiating responses to standard therapy with lovastatin in HFD-fed mice from the CHD group.