Phosphodiesterase Type 5 Inhibitor Sildenafil Decreases the Proinflammatory Chemokine CXCL10 in Human Cardiomyocytes and in Subjects with Diabetic Cardiomyopathy

Phosphodiesterase in heart and vessels: from physiology to diseases

Phosphodiesterases (PDEs) are a superfamily of enzymes that hydrolyze cyclic nucleotides, including cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP). Both cyclic nucleotides are critical secondary messengers in the neurohormonal regulation in the cardiovascular system. PDEs precisely control spatiotemporal subcellular distribution of cyclic nucleotides in a cell- and tissue-specific manner, playing critical roles in physiological responses to hormone stimulation in the heart and vessels. Dysregulation of PDEs has been linked to the development of several cardiovascular diseases, such as hypertension, aneurysm, atherosclerosis, arrhythmia, and heart failure. Targeting these enzymes has been proven effective in treating cardiovascular diseases and is an attractive and promising strategy for the development of new drugs. In this review, we discuss the current understanding of the complex regulation of PDE isoforms in cardiovascular function, highlighting the divergent and even opposing roles of PDE isoforms in different pathogenesis.

Mitochondrial transplantation: opportunities and challenges in the treatment of obesity, diabetes, and nonalcoholic fatty liver disease

Metabolic diseases, including obesity, diabetes, and nonalcoholic fatty liver disease (NAFLD), are rising in both incidence and prevalence and remain a major global health and socioeconomic burden in the twenty-first century. Despite an increasing understanding of these diseases, the lack of effective treatments remains an ongoing challenge. Mitochondria are key players in intracellular energy production, calcium homeostasis, signaling, and apoptosis. Emerging evidence shows that mitochondrial dysfunction participates in the pathogeneses of metabolic diseases. Exogenous supplementation with healthy mitochondria is emerging as a promising therapeutic approach to treating these diseases. This article reviews recent advances in the use of mitochondrial transplantation therapy (MRT) in such treatment.

Inflammatory plasma proteins predict short-term mortality in patients with an acute myocardial infarction

BACKGROUND

The aim of this study was to investigate the association between inflammatory markers and 28-day mortality in patients with ST-elevation myocardial infarction (STEMI).

METHODS

In 398 STEMI patients recorded between 2009 and 2013 by the population-based Myocardial Infarction Registry Augsburg, 92 protein biomarkers were measured in admission arterial blood samples using the OLINK inflammatory panel. In multivariable-adjusted logistic regression models, the association between each marker and 28-day mortality was investigated. The values of the biomarkers most significantly associated with mortality were standardized and summarized to obtain a prediction score for 28-day mortality. The predictive ability of this biomarker score was compared to the established GRACE score using ROC analysis. Finally, a combined total score was generated by adding the standardized biomarker score to the standardized GRACE score.

RESULTS

The markers IL-6, IL-8, IL-10, FGF-21, FGF-23, ST1A1, MCP-1, 4E-BP1, and CST5 were most significantly associated with 28-day mortality, each with FDR-adjusted (false discovery rate adjusted) p-values of < 0.01 in the multivariable logistic regression model. In a ROC analysis, the biomarker score and the GRACE score showed comparable predictive ability for 28-day mortality (biomarker score AUC: 0.7859 [CI: 0.6735-0.89], GRACE score AUC: 0.7961 [CI: 0.6965-0.8802]). By combining the biomarker score and the Grace score, the predictive ability improved with an AUC of 0.8305 [CI: 0.7269-0.9187]. A continuous Net Reclassification Improvement (cNRI) of 0.566 (CI: 0.192-0.94, p-value: 0.003) and an Integrated Discrimination Improvement (IDI) of 0.083 ((CI: 0.016-0.149, p-value: 0.015) confirmed the superiority of the combined score over the GARCE score.

CONCLUSIONS

Inflammatory biomarkers may play a significant role in the pathophysiology of acute myocardial infarction (AMI) and AMI-related mortality and might be a promising starting point for personalized medicine, which aims to provide each patient with tailored therapy.

The Prostacyclin Analogue Iloprost Modulates CXCL10 in Systemic Sclerosis

The prostacyclin analogue iloprost is used to treat vascular alterations and digital ulcers, the early derangements manifesting in systemic sclerosis (SSc), an autoimmune disease leading to skin and organ fibrosis. Bioindicator(s) of SSc onset and progress are still lacking and the therapeutic approach remains a challenge. The T helper 1 (Th1) chemokine interferon (IFN)γ-induced protein 10 (IP-10/CXCL10) associates with disease progression and worse prognosis. Endothelial cells and fibroblasts, under Th1-dominance, release CXCL10, further enhancing SSc’s detrimental status. We analyzed the effect of iloprost on CXCL10 in endothelial cells, dermal fibroblasts, and in the serum of SSc patients. Human endothelial cells and dermal fibroblasts activated with IFNγ/Tumor Necrosis Factor (TNF)α, with/without iloprost, were investigated for CXCL10 secretion/expression and for intracellular signaling cascade underlying chemokine release (Signal Transducer and Activator of Transcription 1, STAT1; Nuclear Factor kappa-light-chain-enhancer of activated B cells, NF-kB; c-Jun NH₂-terminal kinase, JNK: Phosphatidyl-Inositol 3-kinase (PI3K)/protein kinase B, AKT; Extracellular signal-Regulated Kinase 1/2, ERK1/2). CXCL10 was quantified in sera from 25 patients taking iloprost, satisfying the American College of Rheumatology (ACR)/European Alliance of Associations for Rheumatology (EULAR) 2013 classification criteria for SSc, and in sera from 20 SSc sex/age-matched subjects without therapy, previously collected. In human endothelial cells and fibroblasts, iloprost targeted CXCL10, almost preventing IFNγ/TNFα-dependent cascade activation in endothelial cells. In SSc subjects taking iloprost, serum CXCL10 was lower. These in vitro and in vivo data suggest a potential role of iloprost to limit CXCL10 at local vascular/dermal and systemic levels in SSc and warrant further translational research aimed to ameliorate SSc understanding/management.

Heart Failure with Preserved Ejection Fraction and Pulmonary Hypertension: Focus on Phosphodiesterase Inhibitors

Pulmonary hypertension (PH) is common in patients with heart failure with preserved ejection fraction (HFpEF). A chronic increase in mean left atrial pressure leads to passive remodeling in pulmonary veins and capillaries and modest PH (isolated postcapillary PH, Ipc-PH) and is not associated with significant right ventricular dysfunction. In approximately 20% of patients with HFpEF, "precapillary" alterations of pulmonary vasculature occur with the development of the combined pre- and post-capillary PH (Cpc-PH), pertaining to a poor prognosis. Current data indicate that pulmonary vasculopathy may be at least partially reversible and thus serves as a therapeutic target in HFpEF. Pulmonary vascular targeted therapies, including phosphodiesterase (PDE) inhibitors, may have a valuable role in the management of patients with PH-HFpEF. In studies of Cpc-PH and HFpEF, PDE type 5 inhibitors were effective in long-term follow-up, decreasing pulmonary artery pressure and improving RV contractility, whereas studies of Ipc-PH did not show any benefit. Randomized trials are essential to elucidate the actual value of PDE inhibition in selected patients with PH-HFpEF, especially in those with invasively confirmed Cpc-PH who are most likely to benefit from such treatment.

Serum trimethylamine-N-oxide is associated with incident type 2 diabetes in middle-aged and older adults: a prospective cohort study

Background

The role of trimethylamine-N-oxide (TMAO) in the development of diabetes remains controversial, and prospective data are few. We aimed to investigate the association between serum TMAO and incident type 2 diabetes in middle-aged and older adults.

Methods

This study was based on the Guangzhou Nutrition and Health Study (GNHS), a community-based prospective cohort study in China. A total of 2088 diabetes-free participants aged 40–75 years were included from 2008 to 2010. Incident type 2 diabetes was ascertained during follow-up visits. Baseline serum TMAO was measured by high-performance liquid chromatography with online electrospray ionization tandem mass spectrometry. Hazard ratios (HRs) and 95% confidence intervals (95% CIs) for diabetes across tertiles of serum TMAO were calculated using Cox proportional hazard models. Prospective associations of serum TMAO with changes in glycemic traits (fasting glucose, HbA1c, insulin, HOMA-IR) over time were estimated using linear mixed-effects models (LMEMs).

Results

We ascertained 254 incident type 2 diabetes cases during a median follow-up of 8.9 years. The median (interquartile range) of serum TMAO was 1.54 (0.86–2.91) μmol/L. From the first to the third tertile of serum TMAO, the multivariable-adjusted HRs for diabetes were 1.00 (reference), 1.17 (95% CI: 0.84–1.61), and 1.42 (95% CI: 1.03–1.96) (P-trend = 0.031). LMEMs showed that the estimated yearly change in fasting glucose was 0.011 (0.001–0.022) mmol/L/y in the highest tertile of serum TMAO, compared with the lowest tertile (P-interaction = 0.044). Serum TMAO was not associated with longitudinal changes in HbA1c, insulin or HOMA-IR.

Conclusions

Our findings suggested that higher serum TMAO was associated with a higher risk of type 2 diabetes and an increase in fasting glucose among middle-aged and older Chinese adults.

Trial registration: NCT03179657. https://clinicaltrials.gov/ct2/show/NCT03179657?term=NCT03179657&draw=2&rank=1

Supplementary Information

The online version contains supplementary material available at 10.1186/s12967-022-03581-7.

Cell-Target-Specific Anti-Inflammatory Effect of Empagliflozin: In Vitro Evidence in Human Cardiomyocytes

The antidiabetic sodium–glucose cotransporter type 2 inhibitor (SGLT2i) empagliflozin efficiently reduces heart failure (HF) hospitalization and cardiovascular death in type 2 diabetes (T2D). Empagliflozin-cardioprotection likely includes anti-inflammatory effects, regardless glucose lowering, but the underlying mechanisms remain unclear. Inflammation is a primary event in diabetic cardiomyopathy (DCM) and HF development. The interferon (IFN)γ-induced 10-kDa protein (IP-10/CXCL10), a T helper 1 (Th1)-type chemokine, promotes cardiac inflammation, fibrosis, and diseases, including DCM, ideally representing a therapeutic target. This preliminary study aims to explore whether empagliflozin directly affects Th1-challenged human cardiomyocytes, in terms of CXCL10 targeting. To this purpose, empagliflozin dose–response curves were performed in cultured human cardiomyocytes maintained within a Th1-dominant inflammatory microenvironment (IFNγ/TNFα), and CXCL10 release with the intracellular IFNγ-dependent signaling pathway (Stat-1) was investigated. To verify possible drug–cell-target specificity, the same assays were run in human skeletal muscle cells. Empagliflozin dose dependently inhibited CXCL10 secretion (IC50 = 76,14 × 10-9 M) in association with Stat-1 pathway impairment only in Th1-induced human cardiomyocytes, suggesting drug-selective cell-type-targeting. As CXCL10 plays multifaceted functions in cardiac remodeling toward HF and currently there is no effective method to prevent it, these preliminary data might be hypothesis generating to open new scenarios in the translational approach to SGLT2i-dependent cardioprotection.

Pulmonary artery targeted therapy in treatment of COVID-19 related ARDS. Literature review

INTRODUCTION

The most grievous complication of the COVID-19 is the acute respiratory distress syndrome. A specific, rescue treatment for rapidly deteriorating patients should emerge to improve respiratory function and help patients to survive the most challenging period. Drugs used in targeted therapy of pulmonary arterial hypertension (PAH) appears to be suitable for this task and this article describes their potential for treatment of severe cases of COVID-19.

METHODS

The authors reviewed the following databases for randomized controlled trials, reviews and meta-analyses published up to July 2020: Pubmed, Scopus, Google Scholar, Cochrane Database and ClinicalKey. The authors included every study contributory to the assessment of the potential of drugs used in targeted PAH therapy in treatment of COVID-19.

RESULTS

Endothelin receptor antagonists, phosphodiesterase 5 inhibitors, riociguat and prostacyclin have proven ani-inflammatory effect and reduce pulmonary artery blood pressure, lung oedema and remodelling. Bosentan shows antiviral properties and sildenafil, as well as epoprostenol, inhibits apoptosis of lung epithelial cells. Among patients with lung lesions the decrease of pulmonary blood pressure can lead to increase of ventilation/perfusion mismatch and decrease of blood oxygenation.

CONCLUSIONS

Among all assessed drugs bosentan, sildenafil and epoprostenol appear to be most promising and a combination of these drugs should be considered due to synergism. The targeted PAH therapy in treatment of COVID-19 associated ARDS could be a useful tool saving lives of patients with severe SARS-CoV-2 infection, however, its introduction should be investigated and monitored very carefully as it can lead to transient deterioration of patient condition.

Human cell-based anti-inflammatory effects of rosiglitazone

PURPOSE

The C-X-C motif chemokine ligand 10 (CXCL10) participates in diabetes and diabetic cardiomyopathy development from the early stages. Rosiglitazone (RGZ) exhibits anti-inflammatory properties and can target cardiomyocytes secreting CXCL10, under interferon (IFN)γ and tumor necrosis factor (TNF)α challenge. Cardiomyocyte remodeling, CD4 + T cells and dendritic cells (DCs) significantly contribute to the inflammatory milieu underlying and promoting disease development. We aimed to study the effect of RGZ onto inflammation-induced secretion of CXCL10, IFNγ, TNFα, interleukin (IL)-6 and IL-8 by human CD4 + T and DCs, and onto IFNγ/TNFα-dependent signaling in human cardiomyocytes associated with chemokine release.

METHODS

Cells maintained within an inflammatory-like microenvironment were exposed to RGZ at near therapy dose (5 µM). ELISA quantified cytokine secretion; qPCR measured mRNA expression; Western blot analyzed protein expression and activation; immunofluorescent analysis detected intracellular IFNγ/TNFα-dependent trafficking.

RESULTS

In human CD4 + T cells and DCs, RGZ inhibited CXCL10 release likely with a transcriptional mechanism, and reduced TNFα only in CD4 + T cells. In human cardiomyocytes, RGZ impaired IFNγ/TNFα signal transduction, blocking the phosphorylation/nuclear translocation of signal transducer and activator of transcription 1 (Stat1) and nuclear factor-kB (NF-kB), in association with a significant decrease in CXCL10 expression, IL-6 and IL-8 release.

CONCLUSION

As the combination of Th1 biomarkers like CXCL10, IL-8, IL-6 with classical cardiovascular risk factors seems to improve the accuracy in predicting T2D and coronary events, future studies might be desirable to further investigate the anti-Th1 effect of RGZ.

cAMP-specific phosphodiesterase 8A and 8B isoforms are differentially expressed in human testis and Leydig cell tumor

Cyclic adenosine monophosphate/Protein kinase A (cAMP/PKA) signaling pathway is the master regulator of endocrine tissue function. The level, compartmentalization and amplitude of cAMP response are finely regulated by phosphodiesterases (PDEs). PDE8 is responsible of cAMP hydrolysis and its expression has been characterized in all steroidogenic cell types in rodents including adrenal and Leydig cells in rodents however scarce data are currently available in humans. Here we demonstrate that human Leydig cells express both PDE8A and PDE8B isoforms. Interestingly, we found that the expression of PDE8B but not of PDE8A is increased in transformed Leydig cells (Leydig cell tumors-LCTs) compared to non-tumoral cells. Immunofluorescence analyses further reveals that PDE8A is also highly expressed in specific spermatogenic stages. While the protein is not detected in spermatogonia it accumulates nearby the forming acrosome, in the trans-Golgi apparatus of spermatocytes and spermatids and it follows the fate of this organelle in the later stages translocating to the caudal part of the cell. Taken together our findings suggest that 1) a specific pool(s) of cAMP is/are regulated by PDE8A during spermiogenesis pointing out a possible new role of this PDE8 isoform in key events governing the differentiation and maturation of human sperm and 2) PDE8B can be involved in Leydig cell transformation.

Environmental Contaminants Acting as Endocrine Disruptors Modulate Atherogenic Processes: New Risk Factors for Cardiovascular Diseases in Women?

The number of aged individuals is increasing worldwide, rendering essential the comprehension of pathophysiological mechanisms of age-related alterations, which could facilitate the development of interventions contributing to “successful aging” and improving quality of life. Cardiovascular diseases (CVD) include pathologies affecting the heart or blood vessels, such as hypertension, peripheral artery disease and coronary heart disease. Indeed, age-associated modifications in body composition, hormonal, nutritional and metabolic factors, as well as a decline in physical activity are all involved in the increased risk of developing atherogenic alterations that raise the risk of CVD development. Several factors have been reported to play a role in the alterations observed in muscle and endothelial cells and that lead to increased CVD, such as genetic pattern, smoking and unhealthy lifestyle. Moreover, a difference in the risk of these diseases in women and men has been reported. Interestingly, in the past decades attention has been focused on a potential role of several pollutants that disrupt human health by interfering with hormonal pathways, and more specifically in non-communicable diseases such as obesity, diabetes and CVD. This review will focus on the potential alteration induced by Endocrine Disruptors (Eds) in the attempt to characterize a potential role in the cellular and molecular mechanisms involved in the atheromatous degeneration process and CVD progression.

The Involvement of CXC Motif Chemokine Ligand 10 (CXCL10) and Its Related Chemokines in the Pathogenesis of Coronary Artery Disease and in the COVID-19 Vaccination: A Narrative Review

Coronary artery disease (CAD) and coronary heart disease (CHD) constitute two of the leading causes of death in Europe, USA and the rest of the world. According to the latest reports of the Iranian National Health Ministry, CAD is the main cause of death in Iranian patients with an age over 35 years despite a significant reduction in mortality due to early interventional treatments in the context of an acute coronary syndrome (ACS). Inflammation plays a fundamental role in coronary atherogenesis, atherosclerotic plaque formation, acute coronary thrombosis and CAD establishment. Chemokines are well-recognized mediators of inflammation involved in several bio-functions such as leucocyte migration in response to inflammatory signals and oxidative vascular injury. Different chemokines serve as chemo-attractants for a wide variety of cell types including immune cells. CXC motif chemokine ligand 10 (CXCL10), also known as interferon gamma-induced protein 10 (IP-10/CXLC10), is a chemokine with inflammatory features whereas CXC chemokine receptor 3 (CXCR3) serves as a shared receptor for CXCL9, 10 and 11. These chemokines mediate immune responses through the activation and recruitment of leukocytes, eosinophils, monocytes and natural killer (NK) cells. CXCL10, interleukin (IL-15) and interferon (IFN-g) are increased after a COVID-19 vaccination with a BNT162b2 mRNA (Pfizer/BioNTech) vaccine and are enriched by tumor necrosis factor alpha (TNF-α) and IL-6 after the second vaccination. The aim of the present study is the presentation of the elucidation of the crucial role of CXCL10 in the patho-physiology and pathogenesis of CAD and in identifying markers associated with the vaccination resulting in antibody development.

Decreased Production of TNF-α and IL-6 Inflammatory Cytokines in Non-Pregnant Idiopathic RPL Women Immunomodulatory Effect of Sildenafil Citrate on the Cellular Response of Idiopathic RPL Women

Sildenafil citrate (SC), a PDE5 inhibitor, a drug for erectile dysfunction (ED) and pulmonary hypertension (PAH), was found to exert a positive effect on pregnancy outcomes when administered intravaginally before conception. In our previous studies, sildenafil increased endometrial thickness and significantly decreased peripheral blood NK cell activity after the intravaginal administration in women with recurrent pregnancy loss (RPL). No data are available to confirm the effect of sildenafil on maternal T cell populations involved in shaping fetal-maternal tolerance and NK cell activity. Thus, the present study aimed to establish if SC influences NKT cells or the axis of Th17/Treg cells and Th1/Th2 cytokine production. Materials and methods: Twenty-one healthy fertile women and twenty-two nonpregnant women with idiopathic RPL were studied. The ELISA method was used to evaluate the production of cytokines, including IL-2, IL-12p40, IL-4, IL-10, IL-6, IL-17, IL-21, TGF-β, TNF-α, and IFN-γ in PBMC culture supernatants before and after supplementation with the physiological concentration of SC. The percentages of NKT (CD56⁺CD3⁺CD44⁺CD161⁺), Treg (CD4⁺CD25⁺FOXP3⁺) and Th17 (CD4⁺CD25⁺IL-17A⁺) cells were determined with flow cytometry method. Results: Unexpectedly, we found that the PBMCs of patients with RPL produced a significantly lower level of inflammatory cytokines (TNF-α and IL-6) and a higher level of anti-inflammatory cytokines (TGF-β and IL-10). SC significantly decreased IL-6, IL-12 and increased TGF-β cytokine concentration in fertile women. In the case of RPL patients’ PBMCs, SC improved the production of TNF-α and IL-10. Conclusions: Lower concentration of proinflammatory cytokines in idiopathic RPL women compared to fertile women might suggest the exhaustion of the immune system. The emphasized production of IL-10 by SC partially explains the previously observed downregulation of NK cell activity in RPL patients. The immunomodulatory effect of the drug might be utilized in anti-inflammatory therapies and help achieve positive pregnancy outcomes in women with reproductive failure due to a Th1/Th2 imbalance.

Sildenafil Counteracts the In Vitro Activation of CXCL-9, CXCL-10 and CXCL-11/CXCR3 Axis Induced by Reactive Oxygen Species in Scleroderma Fibroblasts

Oxidative stress plays a key role in systemic sclerosis (SSc) pathogenesis, and an altered redox homeostasis might be responsible for abnormal inflammatory status, fibrosis and tissue damage extension. In this study, we explored the effect of the phosphodiesterase type 5 inhibitor sildenafil in modulating the activation of the CXCL-9, -10, -11/CXCR3 axis, which is fundamental in the perpetuation of inflammation in different autoimmune diseases, in the cell culture of SSc human dermal fibroblasts exposed to a pro-oxidant environment. We observed that sildenafil significantly reduced gene expression and release of CXCL-9, -10 and -11, inhibited the CXCR3 action and suppressed the activation of STAT1-, JNK- and p38MAPK pathways. This in vitro study on dermal fibroblasts supports clinical studies to consider the efficacy of sildenafil in preventing tissue damage and fibrosis in SSc by targeting central biomarkers of disease progression, vascular injuries and fibrosis and reducing the pro-inflammatory activation induced by oxidative stress.

Muscle Damage in Systemic Sclerosis and CXCL10: The Potential Therapeutic Role of PDE5 Inhibition

Skeletal muscle damage is a common clinical manifestation of systemic sclerosis (SSc). C-X-C chemokine ligand 10 (CXCL10) is involved in myopathy and cardiomyopathy development and is associated with a more severe SSc prognosis. Interestingly, the phosphodiesterase type 5 inhibitor (PDE5i) sildenafil reduces CXCL10 sera levels of patients with diabetic cardiomyopathy and in cardiomyocytes. Here, we analyzed the levels of CXCL10 in the sera of 116 SSc vs. 35 healthy subjects and explored differences in 17 SSc patients on stable treatment with sildenafil. CXCL10 sera levels were three-fold higher in SSc vs. healthy controls, independent of subset and antibody positivity. Sildenafil treatment was associated with lower CXCL10 sera levels. Serum CXCL10 strongly correlated with the clinical severity of muscle involvement and with creatine kinase (CK) serum concentration, suggesting a potential involvement in muscle damage in SSc. In vitro, sildenafil dose-dependently reduced CXCL10 release by activated myocytes and impaired cytokine-induced Signal transducer and activator of transcription 1 (STAT1), Nuclear factor-κB (NFκB) and c-Jun N-terminal kinase (JNK) phosphorylation. This was also seen in cardiomyocytes. Sildenafil-induced CXCL10 inhibition at the systemic and human muscle cell level supports the hypothesis that PDE5i could be a potential therapeutic therapy to prevent and treat muscle damage in SSc.

Anti-infection mechanism of phosphodiesterase-5 inhibitors and their roles in coronavirus disease 2019 (Review)

Coronavirus disease 2019 (COVID-19) has a variety of impacts on the human body. Severe acute respiratory syndrome coronavirus 2 is the pathogen that causes COVID-19. It invades human tissues through the receptor angiotensin-converting enzyme 2, resulting in an imbalance in the angiotensin II (AngII) level and upregulation of renin-angiotensin system/AngII pathway activity. Furthermore, the binding of AngII to its receptor leads to vasoconstriction, endothelial injury and intravascular thrombosis. In addition, COVID-19 may have adverse effects on male reproductive organs and a marked impact on male reproductive health. Phosphodiesterase-5 inhibitors (PDE5Is) may improve vascular endothelial function, promote testicular and systemic blood circulation and testosterone secretion and enhance epididymal function, as well as sperm maturation and capacitation. PDE5Is may also be of use in the treatment of infectious diseases by enhancing immunity and anti-inflammatory responses and improving vascular endothelial function. Based on the pharmacological mechanism of PDE5Is, they are of unique value in the fight against infectious diseases and may be effective in combination with direct antiviral drugs. The anti-infection mechanisms of PDE5Is and their roles in COVID-19 were reviewed in the present study.

Phosphodiesterase-5a Knock-out Suppresses Inflammation by Down-Regulating Adhesion Molecules in Cardiac Rupture Following Myocardial Infarction

Cardiac rupture is a fatal complication of acute myocardial infarction (MI), associated with increased inflammation and damaged extracellular matrix. C57BL/6 J wild type (WT) and Pde5a knockout (Pde5a^-/-) mice were selected to establish MI model. The rupture rate of Pde5a^-/- mice was significantly reduced (P < 0.01) within 7 days post MI. The cardiac function of Pde5a^-/- mice was better than WT mice both at day 3 and 7 post MI. Immunohistochemical staining and flow cytometry showed neutrophils and macrophages were decreased in Pde5a^-/- mouse hearts. Inflammatory factors expression such as IL-1β, IL-6, IL-8, Mcp-1, TNF-α significantly decreased in Pde5a^-/- mice post MI. Moreover, western blot showed the inhibition of inflammatory response was accompanied by down-regulation of intercellular adhesion molecule-1(ICAM-1) and vascular cell adhesion molecule-1(VCAM-1) in Pde5a^-/- mice. Knockout of Pde5a reduced inflammatory cells infiltration by down-regulating the expression of ICAM-1 and VCAM-1, and prevented early cardiac rupture after MI. All authors declare that they have no conflicts of interest. This article does not contain any studies with human participants performed by any of the authors. All applicable international, national, and institutional guidelines for the care and use of animals were followed.

Role of Phosphodiesterase in the Biology and Pathology of Diabetes

Glucose metabolism is the initiator of a large number of molecular secretory processes in β cells. Cyclic nucleotides as a second messenger are the main physiological regulators of these processes and are functionally divided into compartments in pancreatic cells. Their intracellular concentration is limited by hydrolysis led by one or more phosphodiesterase (PDE) isoenzymes. Literature data confirmed multiple expressions of PDEs subtypes, but the specific roles of each in pancreatic β-cell function, particularly in humans, are still unclear. Isoforms present in the pancreas are also found in various tissues of the body. Normoglycemia and its strict control are supported by the appropriate release of insulin from the pancreas and the action of insulin in peripheral tissues, including processes related to homeostasis, the regulation of which is based on the PDE- cyclic AMP (cAMP) signaling pathway. The challenge in developing a therapeutic solution based on GSIS (glucose-stimulated insulin secretion) enhancers targeted at PDEs is the selective inhibition of their activity only within β cells. Undeniably, PDEs inhibitors have therapeutic potential, but some of them are burdened with certain adverse effects. Therefore, the chance to use knowledge in this field for diabetes treatment has been postulated for a long time.

The Phosphodiesterase-5 Inhibitor Vardenafil Improves the Activation of BMP Signaling in Response to Hydrogen Peroxide

PURPOSE

The pleiotropic roles of phosphodiesterase-5 inhibitors (PDE5is) in cardiovascular diseases have attracted attention. The effect of vardenafil (a PDE5i) is partly mediated through reduced oxidative stress, but it is unclear whether vardenafil protects against hydrogen peroxide (H₂O₂)-induced endothelial cell injury, and the molecular mechanisms that are involved remain unknown. We determined the protective role of vardenafil on H₂O₂-induced endothelial cell injury in cultured human umbilical vein endothelial cells (HUVECs).

METHODS AND RESULTS

Vardenafil decreased the number of TUNEL-positive cells, increased the Bcl2/Bax ratio, and ameliorated the numbers of BrdU-positive cells in H₂O₂-treated HUVECs. The bone morphogenetic protein receptor (BMPR)/p-Smad/MSX2 pathway was enhanced in response to H₂O₂, and vardenafil treatment could normalize this pathway. To determine whether the BMP pathway is involved, we blocked the BMP pathway using dorsomorphin, which abolished the protective effects of vardenafil. We found that vardenafil improved the H₂O₂-induced downregulation of BMP-binding endothelial regulator protein (BMPER), which possibly intersects with the BMP pathway in the regulation of endothelial cell injury in response to oxidative stress.

CONCLUSIONS

We demonstrated for the first time that exogenous H₂O₂ activates BMPR expression and promotes Smad1/5/8 phosphorylation. Additionally, vardenafil can attenuate H₂O₂-induced endothelial cell injury in HUVECs. Vardenafil decreases apoptosis through an improved Bcl-2/Bax ratio and increases cell proliferation. Vardenafil protects against endothelial cell injury through ameliorating the intracellular oxidative stress level and BMPER expression. The protective role of vardenafil on H₂O₂-induced endothelial cell injury is mediated through BMPR/p-Smad/MSX2 in HUVECs.

Pluripotent stem cell-based screening identifies CUDC-907 as an effective compound for restoring the in vitro phenotype of Nakajo-Nishimura syndrome

Nakajo-Nishimura syndrome (NNS) is an autoinflammatory disorder caused by a homozygous mutations in the PSMB8 gene. The administration of systemic corticosteroids is partially effective, but continuous treatment causes severe side effects. We previously established a pluripotent stem cell (PSC)-derived NNS disease model that reproduces several inflammatory phenotypes, including the overproduction of monocyte chemoattractant protein-1 (MCP-1) and interferon gamma-induced protein-10 (IP-10). Here we performed high-throughput compound screening (HTS) using this PSC-derived NNS model to find potential therapeutic candidates and identified CUDC-907 as an effective inhibitor of the release of MCP-1 and IP-10. Short-term treatment of CUDC-907 did not induce cell death within therapeutic concentrations and was also effective on primary patient cells. Further analysis indicated that the inhibitory effect was post-transcriptional. These findings suggest that HTS with PSC-derived disease models is useful for finding drug candidates for autoinflammatory diseases.

Mechanisms of diabetic cardiomyopathy and potential therapeutic strategies: preclinical and clinical evidence

The pathogenesis and clinical features of diabetic cardiomyopathy have been well-studied in the past decade, but effective approaches to prevent and treat this disease are limited. Diabetic cardiomyopathy occurs as a result of the dysregulated glucose and lipid metabolism associated with diabetes mellitus, which leads to increased oxidative stress and the activation of multiple inflammatory pathways that mediate cellular and extracellular injury, pathological cardiac remodelling, and diastolic and systolic dysfunction. Preclinical studies in animal models of diabetes have identified multiple intracellular pathways involved in the pathogenesis of diabetic cardiomyopathy and potential cardioprotective strategies to prevent and treat the disease, including antifibrotic agents, anti-inflammatory agents and antioxidants. Some of these interventions have been tested in clinical trials and have shown favourable initial results. In this Review, we discuss the mechanisms underlying the development of diabetic cardiomyopathy and heart failure in type 1 and type 2 diabetes mellitus, and we summarize the evidence from preclinical and clinical studies that might provide guidance for the development of targeted strategies. We also highlight some of the novel pharmacological therapeutic strategies for the treatment and prevention of diabetic cardiomyopathy.

Phosphodiesterase Type 5 Inhibitors Synergize Vincristine in Killing Castration-Resistant Prostate Cancer Through Amplifying Mitotic Arrest Signaling

Combination therapies that display cancer-killing activities through either coexistent targeting of several cellular factors or more efficient suppression of a specific pathway are generally used in cancer treatment. Sildenafil, a specific phosphodiesterase type 5 (PDE5) inhibitor, has been suggested to display both cardioprotective and neuroprotective activities that provide a rationale for the combination with vincristine on the treatment against castration-resistant prostate cancer (CRPC). In the present work, vincristine arrested cells in the metaphase stage of mitosis. Vincristine-induced mitotic arrest was identified by Cdk1 activation (i.e., increased Cdk1^Thr161 phosphorylation and decreased Cdk1^Tyr15 phosphorylation), cyclin B1 upregulation, and increased phosphorylation of multiple mitotic proteins and stathmin. Sildenafil synergistically potentiated vincristine-induced mitotic arrest and a dramatic increase of mitotic index. Furthermore, sildenafil potentiated vincristine-induced mitochondrial damage, including Mcl-1 downregulation, Bcl-2 phosphorylation and downregulation, Bak upregulation and loss of mitochondrial membrane potential, and sensitized caspase-dependent apoptotic cell death. Sildenafil-mediated synergistic effects were mimicked by other PDE5 inhibitors including vardenafil and tadalafil, and also by PDE5A knockdown in cells, suggesting PDE5-involved mechanism. Notably, sildenafil amplified vincristine-induced phosphorylation and cleavage of BUBR1, a protein kinase in spindle assembly checkpoint (SAC) function and chromosome segregation. Sildenafil also significantly decreased kinetochore tension during SAC activation. Moreover, sildenafil synergized with vincristine on suppressing tumor growth in an in vivo model. In conclusion, the data suggest that sildenafil, in a PDE5-dependent manner, potentiates vincristine-induced mitotic arrest signaling, and sensitizes mitochondria damage–involved apoptosis in CRPC. Both in vitro and in vivo data suggest the combination potential of PDE5 inhibitors and vincristine on CRPC treatment.

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.

Advantages of Phosphodiesterase Type 5 Inhibitors in the Management of Glucose Metabolism Disorders: A Clinical and Translational Issue

Among metabolic diseases, carbohydrate metabolism disorders are the most widespread. The most common glucose pathological conditions are acquired and may increase the risk of type 2 diabetes, obesity, heart diseases, stroke, and kidney insufficiency. Phosphodiesterase type 5 inhibitors (PDE5i) have long been used as an effective therapeutic option for the treatment of erectile dysfunction (ED). Different studies have demonstrated that PDE5i, by sensitizing insulin target tissues to insulin, play an important role in controlling the action of insulin and glucose metabolism, highlighting the protective action of these drugs against metabolic diseases. In this review, we report the latest knowledge about the role of PDE5i in the metabolic diseases of insulin resistance and type 2 diabetes, highlighting clinical aspects and potential treatment approaches. Although various encouraging data are available, further in vivo and in vitro studies are required to elucidate the mechanism of action and their clinical application in humans.

Therapeutic targeting of 3',5'-cyclic nucleotide phosphodiesterases: inhibition and beyond

Phosphodiesterases (PDEs), enzymes that degrade 3',5'-cyclic nucleotides, are being pursued as therapeutic targets for several diseases, including those affecting the nervous system, the cardiovascular system, fertility, immunity, cancer and metabolism. Clinical development programmes have focused exclusively on catalytic inhibition, which continues to be a strong focus of ongoing drug discovery efforts. However, emerging evidence supports novel strategies to therapeutically target PDE function, including enhancing catalytic activity, normalizing altered compartmentalization and modulating post-translational modifications, as well as the potential use of PDEs as disease biomarkers. Importantly, a more refined appreciation of the intramolecular mechanisms regulating PDE function and trafficking is emerging, making these pioneering drug discovery efforts tractable.

Cardiomyopathy Associated with Diabetes: The Central Role of the Cardiomyocyte

The term diabetic cardiomyopathy (DCM) labels an abnormal cardiac structure and performance due to intrinsic heart muscle malfunction, independently of other vascular co-morbidity. DCM, accounting for 50%–80% of deaths in diabetic patients, represents a worldwide problem for human health and related economics. Optimal glycemic control is not sufficient to prevent DCM, which derives from heart remodeling and geometrical changes, with both consequences of critical events initially occurring at the cardiomyocyte level. Cardiac cells, under hyperglycemia, very early undergo metabolic abnormalities and contribute to T helper (Th)-driven inflammatory perturbation, behaving as immunoactive units capable of releasing critical biomediators, such as cytokines and chemokines. This paper aims to focus onto the role of cardiomyocytes, no longer considered as “passive” targets but as “active” units participating in the inflammatory dialogue between local and systemic counterparts underlying DCM development and maintenance. Some of the main biomolecular/metabolic/inflammatory processes triggered within cardiac cells by high glucose are overviewed; particular attention is addressed to early inflammatory cytokines and chemokines, representing potential therapeutic targets for a prompt early intervention when no signs or symptoms of DCM are manifesting yet. DCM clinical management still represents a challenge and further translational investigations, including studies at female/male cell level, are warranted.

Activation of cGMP/PKG/p65 signaling associated with PDE5-Is downregulates CCL5 secretion by CD8 + T cells in benign prostatic hyperplasia

BACKGROUND

Benign prostatic hyperplasia (BPH) is the most common urological disease in elderly men, but the underlying pathophysiological mechanisms are complex and not fully understood. Phosphodiesterase type 5 inhibitors (PDE5-Is) used to treat BPH could upregulate the cyclic guanosine monophosphate (cGMP)-dependent protein kinase G (PKG) signaling, which was shown to blunt inflammation in the prostate. Our previous findings indicate that CD8⁺ T cells promote the proliferation of BPH epithelial cells (BECs) in low androgen conditions through secretion of CCL5; however, the role of the cGMP/PKG pathway in the process is unclear.

METHODS

Paraffin-embedded tissues were used for expression quantity of CD8⁺ T cells, CCL5, cyclin D1, and PDE5 protein by immunohistology in prostate specimens which were/were not treated with finasteride 5 mg daily for at least 6 months before surgery. BPH-1 cells were cocultured with or without CD8 ⁺ T cells or PDE5-Is in low androgen conditions for 4 days. The conditioned media, BPH-1 cells, and CD8 ⁺ T cells were harvested for the subsequent experiments. The quantitative polymerase chain reaction was used for assaying the level of messenger RNA expression of CCL5. CCL5 in the conditioned media was detected by the enzyme-linked immunosorbent assay. The effect of PDE5-Is on cocultured BPH-1/CD8 ⁺ T-cell proliferation was detected by the cell counting kit-8. A high-fat diet (HFD)-induced prostatic hyperplasia rat model was used to investigate the effect of cGMP/PKG activation in CD8 ⁺ T cells in vivo.

RESULTS

CD8⁺ T-cell infiltration into human BPH tissues was positively correlated with the expression of CCL5, cyclin D1, and PDE5, whereas in an HFD-induced prostatic hyperplasia rat model, the activation of the cGMP/PKG signaling by a PDE5-I could suppress the CD8 ⁺ T-cell infiltration and the CCL5 and cyclin D1 expression. Furthermore, the activation of the cGMP/PKG pathway inhibited CCL5 secretion by CD8 ⁺ T cells by downregulating nuclear factor-κB p65 phosphorylation, which reduced the growth of BPH-1 through CCL5/STAT5/CCND1 signaling.

CONCLUSIONS

Our results indicate that the upregulation of the cGMP/PKG/p65 signaling reduces CCL5 secretion in CD8 ⁺ T cells, which in turn decreases the proliferation of BECs in low androgen conditions, suggesting that the combination of 5α reductase inhibitors lowering androgen levels and PDE5-Is may be a novel, more effective treatment for BPH patients.

The phosphodiesterase 5 inhibitor sildenafil decreases the proinflammatory chemokine IL-8 in diabetic cardiomyopathy: in vivo and in vitro evidence

PURPOSE

Interleukin (IL)-8 is a proinflammatory C-X-C chemokine involved in inflammation underling cardiac diseases, primary or in comorbid condition, such diabetic cardiomyopathy (DCM). The phosphodiesterase type 5 inhibitor sildenafil can ameliorate cardiac conditions by counteracting inflammation. The study aim is to evaluate the effect of sildenafil on serum IL-8 in DCM subjects vs. placebo, and on IL-8 release in human endothelial cells (Hfaec) and peripheral blood mononuclear cells (PBMC) under inflammatory stimuli.

METHODS

IL-8 was quantified: in sera of (30) DCM subjects before (baseline) and after sildenafil (100 mg/day, 3-months) vs. (16) placebo and (15) healthy subjects, by multiplatform array; in supernatants from inflammation-challenged cells after sildenafil (1 µM), by ELISA.

RESULTS

Baseline IL-8 was higher in DCM vs. healthy subjects (149.14 ± 46.89 vs. 16.17 ± 5.38 pg/ml, p < 0.01). Sildenafil, not placebo, significantly reduced serum IL-8 (23.7 ± 5.9 pg/ml, p < 0.05 vs. baseline). Receiver operating characteristic (ROC) curve for IL-8 was 0.945 (95% confidence interval of 0.772 to 1.0, p < 0.01), showing good capacity of discriminating the response in terms of drug-induced IL-8 decrease (sensitivity of 0.93, specificity of 0.90). Sildenafil significantly decreased IL-8 protein release by inflammation-induced Hfaec and PBMC and downregulated IL-8 mRNA in PBMC, without affecting cell number or PDE5 expression.

CONCLUSION

Sildenafil might be suggested as potential novel pharmacological tool to control DCM progression through IL-8 targeting at systemic and cellular level.

Sildenafil ameliorates right ventricular early molecular derangement during left ventricular pressure overload

Right ventricular (RV) dysfunction following left ventricular (LV) failure is associated with poor prognosis. RV remodeling is thought initiated by the increase in the afterload of RV due to secondary pulmonary hypertension (PH) to impaired LV function; however, RV molecular changes might occur in earlier stages of the disease. cGMP (cyclic guanosine monophosphate)-phosphodiesterase 5 (PDE5) inhibitors, widely used to treat PH through their pulmonary vasorelaxation properties, have shown direct cardiac benefits, but their impacts on the RV in LV diseases are not fully determined. Here we show that RV molecular alterations occur early in the absence of RV hemodynamic changes during LV pressure-overload and are ameliorated by PDE5 inhibition. Two-day moderate LV pressure-overload (transverse aortic constriction) neither altered RV pressure/ function nor RV weight in mice, while it induced only mild LV hypertrophy. Importantly, pathological molecular features were already induced in the RV free wall myocardium, including up-regulation of gene markers for hypertrophy and inflammation, and activation of extracellular signal-regulated kinase (ERK) and calcineurin. Concomitant PDE5 inhibition (sildenafil) prevented induction of such pathological genes and activation of ERK and calcineurin in the RV as well as in the LV. Importantly, dexamethasone also prevented these RV molecular changes, similarly to sildenafil treatment. These results suggest the contributory role of inflammation to the early pathological interventricular interaction between RV and LV. The current study provides the first evidence for the novel early molecular cross-talk between RV and LV, preceding RV hemodynamic changes in LV disease, and supports the therapeutic strategy of enhancing cGMP signaling pathway to treat heart diseases.

Phosphodiesterase-5 inhibitors and the heart: compound cardioprotection?

Novel cardioprotective agents are needed in both heart failure (HF) and myocardial infarction. Increasing evidence from cellular studies and animal models indicate protective effects of phosphodiesterase-5 (PDE5) inhibitors, drugs usually reserved as treatments of erectile dysfunction and pulmonary arterial hypertension. PDE5 inhibitors have been shown to improve contractile function in systolic HF, regress left ventricular hypertrophy, reduce myocardial infarct size and suppress ischaemia-induced ventricular arrhythmias. Underpinning these actions are complex but increasingly understood cellular mechanisms involving the cyclic GMP activation of protein kinase-G in both cardiac myocytes and the vasculature. In clinical trials, PDE5 inhibitors improve symptoms and ventricular function in systolic HF, and accumulating epidemiological data indicate a reduction in cardiovascular events and mortality in PDE5 inhibitor users at high cardiovascular risk. Here, we focus on the translation of underpinning basic science to clinical studies and report that PDE5 inhibitors act through a number of cardioprotective mechanisms, including a direct myocardial action independent of the vasculature. We conclude that future clinical trials should be designed with these mechanisms in mind to identify patient subsets that derive greatest treatment benefit from these novel cardioprotective agents.

miR-503 Is Involved in the Protective Effect of Phase II Enzyme Inducer (CPDT) in Diabetic Cardiomyopathy via Nrf2/ARE Signaling Pathway

Diabetic cardiomyopathy (DCM) is a common heart disease. The Phase II enzyme inducer (CPDT) is a complex enzyme that promotes the expression of antioxidant enzymes through activating nuclear factor erythroid 2-related factor 2 (Nrf2); these compounds have been shown to protect against oxidative stress. However, whether these compounds have similar protective effects in DCM still remains unclear. The purpose of this study is to investigate the protective effects and potential mechanism of CPDT in diabetic cardiomyopathy. In the results, firstly, compared with control rats, myocardial cell size, left ventricular mass index, and myocardial apoptosis index were increased, miR-503 was increased, and Nrf2, malondialdehyde (MDA), and heme oxygenase 1 (HO-1) were decreased in diabetic cardiomyopathy rats. Furthermore, compared with diabetic cardiomyopathy rats, these above parameters show the opposite change in CPDT treatment rats. In addition, the bioinformatics and luciferase reporter assay demonstrated that Nrf2 is a direct target of miR-503. Finally, the miR-503 could also regulate Nrf2 in the myocardial cells. Therefore, miR-503 is involved in the protective effect of CPDT in diabetic cardiomyopathy via Nrf2/ARE signaling pathway; miR-503 and Nrf2 may be a promising therapeutic target for the management of diabetic cardiomyopathy.

Profiling of selenium absorption and accumulation in healthy subjects after prolonged L-selenomethionine supplementation

PURPOSE

Autoimmune thyroiditis and its complications for the reproductive system are a growing problem. Selenium is a common ingredient in numerous food supplements recommended for thyroiditis and pregnancy. A fast, simple method to measure serum selenium concentration will improve knowledge of its pharmacokinetics and toxicity.

AIM

To validate a useful method to measure serum selenium concentration and to study selenium absorption and accumulation in a prospective interventional study of prolonged treatment.

METHODS

Thirty healthy volunteers received a single dose of L-selenomethionine one tablet (83 mcg) (Phase 1), a single dose of two tablets (Phase 2), and two tablets daily for 14 days (Phase 3). Total selenium and selenium time profiles were generated by serial sampling (T0, T3, T6, T12, and T24 hours after ingestion-Phases 1 and 2; and T0 and T24 hours-Phase 3). Selenium concentration was investigated by open-vessel acid digestion of small serum volumes followed by hydride generation atomic fluorescence spectroscopy analysis.

RESULTS

There was a significant increase in serum selenium concentration (mcg/L) in all treatment phases. Significantly increased levels were reached at T3 in Phase 1 (baseline: 76.5 ± 2.47; T3: 82.8 ± 3.28) and at T6 in Phase 2 (83.8 ± 3.46). They remained significantly increased at T12 in Phase 1 and T24 in Phase 2 (79.03 ± 2.69). There was significant selenium accumulation after prolonged intake (14 days) (102.13 ± 5.61).

CONCLUSIONS

Prolonged selenomethionine administration increases circulating blood selenium concentration and hydride generation atomic fluorescence spectroscopy enables its accurate quantification.

Sildenafil Transiently Delays Early Alveolar Healing of Tooth Extraction Sockets

Bone is a unique tissue that has the ability to repair itself and return to full function. Bone regeneration is a well synchronized biological process that recapitulates embryonic bone development. The establishment of a functional vascular supply has been shown to be essential for proper ossification of newly deposited bone, and impaired angiogenesis as in advanced age, diabetes, and anti-cancer treatments affect bone repair. Endothelial Guanosine, 3', 5'-Cyclic Monophophate(cGMP) is known to support angiogenesis, and sildenafil, a Phosphodiesterase 5 (PDE5) antagonist, prevents cGMP hydrolysis and thereby, promotes the formation of new blood vessels. Since the development of functional vascular networks is critical to bone repair, we investigated the effects of sildenafil on early alveolar bone regeneration following exodontia. Our results demonstrate that per-oral administration of sildenafil (10 mg/kg/day) in rats delays the dissolution and replacement of the sanguine clot with granulation tissue. As a result, the number of replicating cells, a hallmark of regenerating tissue, observed on day 4 was remarkably lower in sildenafil-treated animals than their control counterparts (mean±SD; control: 47.35±9.21; sildenafil: 11.47±5.14). Similarly, cells expressing transcription factor Cbfa-1/Runx2 and osteopontin, markers of differentiating osteoblasts, were fewer in treated animals (mean±SD; control: 83.18 ± 4.60; sildenafil: 13.77 ± 4.63). Treatment with hydrolysis-resistant cyclic GMP (cGMP) showed findings similar to sildenafil-treated animals suggesting a negative impact of cGMP on early inflammatory phase of bone healing. However, histological differences were not significant between the 2 groups on day 8. Based on these findings, we conclude that sildenafil temporarily retards early events in alveolar bone healing.

Sildenafil, a Phosphodiesterase Type 5 Inhibitor, Downregulates Osteopontin in Human Peripheral Blood Mononuclear Cells

The aim of this study was to investigate the ability of sildenafil to regulate osteopontin (OPN) gene and protein in peripheral blood mononuclear cells (PBMCs) from healthy blood donors. OPN is expressed by a wide variety of cell types, including immune cells. OPN functions are linked to various physiological and pathological conditions. Sildenafil is a selective inhibitor of type 5 phosphodiesterase. Sildenafil has recently been found to have immunomodulatory effects in animal models and in studies performed in humans. PMA-stimulated and unstimulated PBMCs from 16 healthy blood donors (men) were cultured with sildenafil (at concentrations of 400 ng/ml and 4 µg/ml). OPN level in culture supernatants was measured by enzyme-linked immunosorbent assay. The analysis of OPN gene expression was performed by real-time PCR. Cell viability was assessed by trypan blue staining. PMA plus ionomycin stimulation of PBMCs resulted in a significant increase of OPN production and gene expression (p < 0.001). Sildenafil significantly decreased OPN secretion (p < 0.05) and gene expression (p < 0.05) in stimulated PBMCs; however, had no effect on OPN in unstimulated PBMCs. Sildenafil did not affect PBMCs viability. Sildenafil downregulates OPN in PBMCs from healthy men. Despite accumulating evidence for the immunomodulatory effects of sildenafil on human immune system cells, further studies are needed to determine if this drug affects the level of cGMP and NF-κB in PBMCs. In addition, it is needed to evaluate sildenafil’s activity in PBMCs from patients with elevated OPN levels.

Angiopoietin-1 and Angiopoietin-2 in metabolic disorders: therapeutic strategies to restore the highs and lows of angiogenesis in diabetes

The morbidity and mortality of diabetes mellitus are mostly attributed to cardiovascular complications. Despite tremendous advancement in glycemic control, anti-diabetic medications have failed to revert vascular impairment once triggered by the metabolic disorder. The angiogenic growth factors, Angiopoietin-1 (Ang1) and Angiopoietin-2 (Ang2), are crucial regulators of vessel formation and maintenance starting with embryonic development and continuing through life. In mature vessels, angiopoietins control vascular permeability, inflammation and remodeling. A crucial role of angiopoietins is to drive vascular inflammation from the active to the quiescent state, enabling restoration of tissue homeostasis. The mechanism is of particular importance for healing and repair after damage, two conditions typically impaired in metabolic disorders. There is an emerging body of evidences suggesting that the imbalance of Ang1 and Ang2 regulation, leading to an increased Ang2/Ang1 ratio, represents a culprit of the vascular alterations of patients with type-2 diabetes mellitus. Pharmacological modulation of Ang1 or Ang2 actions may help prevent or delay the onset of diabetic vascular complications by restoring vessel function, favoring tissue repair and maintaining endothelial quiescence. In this review, we present a summary of the role of Ang1 and Ang2, their involvement in diabetic complications, and novel therapeutic strategies targeting angiopoietins to ameliorate vascular health in metabolic disorders.

The CXCL10/CXCR3 Axis and Cardiac Inflammation: Implications for Immunotherapy to Treat Infectious and Noninfectious Diseases of the Heart

Accumulating evidence reveals involvement of T lymphocytes and adaptive immunity in the chronic inflammation associated with infectious and noninfectious diseases of the heart, including coronary artery disease, Kawasaki disease, myocarditis, dilated cardiomyopathies, Chagas, hypertensive left ventricular (LV) hypertrophy, and nonischemic heart failure. Chemokine CXCL10 is elevated in cardiovascular diseases, along with increased cardiac infiltration of proinflammatory Th1 and cytotoxic T cells. CXCL10 is a chemoattractant for these T cells and polarizing factor for the proinflammatory phenotype. Thus, targeting the CXCL10 receptor CXCR3 is a promising therapeutic approach to treating cardiac inflammation. Due to biased signaling CXCR3 also couples to anti-inflammatory signaling and immunosuppressive regulatory T cell formation when activated by CXCL11. Numbers and functionality of regulatory T cells are reduced in patients with cardiac inflammation, supporting the utility of biased agonists or biologicals to simultaneously block the pro-inflammatory and activate the anti-inflammatory actions of CXCR3. Other immunotherapy strategies to boost regulatory T cell actions include intravenous immunoglobulin (IVIG) therapy, adoptive transfer, immunoadsorption, and low-dose interleukin-2/interleukin-2 antibody complexes. Pharmacological approaches include sphingosine 1-phosphate receptor 1 agonists and vitamin D supplementation. A combined strategy of switching CXCR3 signaling from pro- to anti-inflammatory and improving Treg functionality is predicted to synergistically lessen adverse cardiac remodeling.