Cyclic Guanosine Monophosphate Levels Research Articles

Malakoplakia: A rare cause of hematochezia in pediatric patients

AbstractMalakoplakia is a rare inflammatory condition characterized by impaired macrophages unable to completely digest and kill phagocytized bacteria, resulting in partially digested bacterial components accumulating within the phagolysosome. Malakoplakia typically presents in immunocompromised individuals due to underlying disease or to medication effects and is rarely diagnosed in the pediatric population. The urinary tract is the most commonly involved site, followed by the gastrointestinal (GI) tract, mainly affecting the descending colon, sigmoid colon, and rectum. Treatment focuses on the use of antibiotics that concentrate in macrophages such as quinolones and trimethoprim‐sulfamethoxazole as well as cholinergic agents such as bethanechol, which raise intracellular levels of cyclic guanosine monophosphate in macrophages to improve bactericidal activity. We report a rare case of GI tract malakoplakia in a pediatric patient undergoing treatment for leukemia.

Possible retinotoxicity of long-term vardenafil treatment

Phosphodiesterase (PDE) inhibitors – such as vardenafil – are used primarily for treating erectile dysfunction via increasing cyclic guanosine monophosphate (cGMP) levels. Recent studies have also demonstrated their significant cardioprotective effects in several diseases, including diabetes, upon long-term, continuous application. However, PDE inhibitors are not specific for PDE5 and also inhibit the retinal isoform. A sustained rise in cGMP in photoreceptors is known to be toxic; therefore, we hypothesized that long-term vardenafil treatment might result in retinotoxicity. The hypothesis was tested in a clinically relevant animal model of type 2 diabetes mellitus. Histological experiments were performed on lean and diabetic Zucker Diabetic Fatty rats. Half of the animals were treated with vardenafil for six months, and the retinal effects were evaluated. Vardenafil treatment alleviated rod outer segment degeneration but decreased rod numbers in some positions and induced changes in the interphotoreceptor matrix, even in control animals. Vardenafil treatment decreased total retinal thickness in the control and diabetic groups and reduced the number of nuclei in the outer nuclear layer. Müller cell activation was detectable even in the vardenafil-treated control animals, and vardenafil did not improve gliosis in the diabetic group. Vardenafil-treated animals showed complex retinal alterations with improvements in some parameters while deterioration in others. Our results point towards the retinotoxicity of vardenafil, even without diabetes, which raises doubts about the retinal safety of long-term continuous vardenafil administration. This effect needs to be considered when approving PDE inhibitors for alternative indications.

Placenta-anchored tadalafil liposomes rescues intrauterine growth restriction through continuous placental blood perfusion improvement

Physiological or pathological hypoperfusion of the placenta is one of the main causes of intrauterine growth restriction (IUGR) which poses a significant risk to the health of the fetus and newborn. Tadalafil, a 5-type phosphodiesterase inhibitor, has previously been found to improve the symptoms of IUGR in various clinical studies. Unfortunately, its clinical utility is hindered by its limited water solubility, rapid metabolism, and lack of specific distribution in target tissues rendering tadalafil unable to maintain long-term placental perfusion. In this study, iRGD-modified tadalafil-loaded liposomes (iRGD-lipo@Tad) featuring a size of approximately 480 nm were designed to rectify the shortcomings of tadalafil. The prepared iRGD-lipo@Tad exhibited superior stability, sustained drug release capacity, and low cytotoxicity. The fluorescence study, tissue slice study, and drug biodistribution study together demonstrated the placenta-anchored ability of iRGD-modified liposomes. This was achieved by a dual approach consisting of the iRGD-mediated placenta-targeting effect and special particle size-mediated placenta resident effect. The pharmacokinetic study revealed a significant improvement in the in vivo process of tadalafil encapsulated by the iRGD-modified liposomes. In comparison to the tadalafil solution, the peak plasma concentration of iRGD-lipo@Tad was significantly increased, and the area under the curve was increased by about 7.88 times. In the pharmacodynamic study, iRGD-lipo@Tad achieved a continuous and efficient improvement of placental blood perfusion. This was achieved by decreasing the ratio of plasma soluble fms-like tyrosine kinase to placental growth factor and increasing the levels of cyclic guanosine monophosphate and nitric oxide. Consequently, iRGD-lipo@Tad resulted in a significant increase in embryo weight and a reduction in the miscarriage rate of N-Nitro-L-arginine methyl ester-induced IUGR pregnant mice without detectable toxicity. In summary, the nanotechnology-assisted therapy strategy presented here not only overcomes the limitations of tadalafil in the clinical treatment of IUGR but also offers new avenues to address the treatment of other placenta-originated diseases.

Effective AAV-mediated gene replacement therapy in retinal organoids modeling AIPL1-associated LCA4

Biallelic variations in the aryl hydrocarbon receptor interacting protein-like 1 (AIPL1) gene cause Leber congenital amaurosis subtype 4 (LCA4), an autosomal recessive early-onset severe retinal dystrophy that leads to the rapid degeneration of retinal photoreceptors and the severe impairment of sight within the first few years of life. Currently, there is no treatment or cure for AIPL1-associated LCA4. In this study, we investigated the potential of adeno-associated virus-mediated AIPL1 gene replacement therapy in two previously validated human retinal organoid (RO) models of LCA4. We report here that photoreceptor-specific AIPL1 gene replacement therapy, currently being tested in a first-in-human application, effectively rescued molecular features of AIPL1-associated LCA4 in these models. Notably, the loss of retinal phosphodiesterase 6 was rescued and elevated cyclic guanosine monophosphate (cGMP) levels were reduced following treatment. Transcriptomic analysis of untreated and AAV-transduced ROs revealed transcriptomic changes in response to elevated cGMP levels and viral infection, respectively. Overall, this study supports AIPL1 gene therapy as a promising therapeutic intervention for LCA4.

The impact of phosphodiesterase-5 inhibition or angiotensin-converting enzyme inhibition on right and left ventricular remodeling in heart failure due to chronic volume overload.

While phosphodiesterase-5 inhibition (PED5i) may prevent hypertrophy and failure in pressure-overloaded heart in an experimental model, the impact of PDE5i on volume-overload (VO)-induced hypertrophy is unknown. It is also unclear whether the hypertrophied right ventricle (RV) and left ventricle (LV) differ in their responsiveness to long-term PDE5i and if this therapy affects renal function. The goal of this study was to elucidate the effect of PDE5i treatment in VO due to aorto-caval fistula (ACF) and to compare PDE5i treatment with standard heart failure (HF) therapy with angiotensin-converting enzyme inhibitor (ACEi). ACF/sham procedure was performed on male HanSD rats aged 8 weeks. ACF animals were randomized for PDE5i sildenafil, ACEi trandolapril, or placebo treatments. After 20 weeks, RV and LV function (echocardiography, pressure-volume analysis), myocardial gene expression, and renal function were studied. Separate rat cohorts served for survival analysis. ACF led to biventricular eccentric hypertrophy (LV: +68%, RV: +145%), increased stroke work (LV: 3.6-fold, RV: 6.7-fold), and reduced load-independent systolic function (PRSW, LV: -54%, RV: -51%). Both ACF ventricles exhibited upregulation of the genes of myocardial stress and glucose metabolism. ACEi but not PDE5i attenuated pulmonary congestion, LV remodeling, albuminuria, and improved survival (median survival in ACF/ACEi was 41 weeks vs. 35 weeks in ACF/placebo, p = .02). PDE5i increased cyclic guanosine monophosphate levels in the lungs, but not in the RV, LV, or kidney. PDE5i did not improve survival rate and cardiac and renal function in ACF rats, in contrast to ACEi. VO-induced HF is not responsive to PDE5i therapy.

Evaluation of the effectiveness of Tadalafil on improving pulmonary function and asthma severity in severe asthmatic patients: a randomized controlled trial study

Phosphodiesterase inhibitors elevate the levels of cyclic adenosine monophosphate and cyclic guanosine monophosphate, which have been associated with various anti-inflammatory effects that can help alleviate asthma symptoms. This study aims to assess the impact of Tadalafil, a selective phosphodiesterase inhibitor, on pulmonary function in patients with asthma. This study was a randomized, double-blind clinical trial conducted in 2021 at Imam Khomeini Hospital in Ahvaz, Iran. The study enrolled 44 patients with severe asthma, who were divided equally into a Tadalafil group and a placebo group. The Tadalafil group received 20 mg/day of Tadalafil, while the placebo group received a placebo at the same dose. The patients' spirometry tests, asthma quality of life questionnaire, 6-minute walk distance, and quality of life were measured at the beginning of the study and one month later. The study results indicated that there was no statistically significant difference between the Tadalafil group and the placebo group in terms of pulmonary parameters (p>0.05). Furthermore, the scores for patients' quality of life (p=0.167) and the 6-minute walk test (p=0.148) at the end of the study did not show any statistically significant improvement compared to the placebo group. Results showed that the use of Tadalafil (20 mg) once daily for one month in patients with severe asthma did not affect clinical and laboratory outcomes.

Liuwei Dihuang Pills alleviates postmenopausal osteoporosis and fatigue in rats by inhibiting the epigenetic regulatory molecule BRD4 pathway

To explore the role of epigenetic signal molecule bromodomain protein 4 (BRD4) in mediating the therapeutic effect of Liuwei Dihuang (LWDH) Pills on postmenopausal osteoporosis (PMOP) and fatigue. Thirty rat models of PMOP induced by bilateral ovariectomy were randomized equally into two groups for treatment with normal saline (model group) or LWDH Pills (385.7 mg/kg), with another 15 sham-operated rats as the sham operation group. After 12 weeks of treatment, femoral samples were taken to determine the bone density and BRD4 protein expression. The weight-bearing exhaustive swimming time of the rat models was recorded, and serum levels of cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP) were measured using enzyme-linked immunosorbent assay. In cultured primary osteoblasts the changes in the expressions of BRD4, MAPK and NF-κB proteins were detected by immunofluorescence staining following treatment with LWDH Pills. The rat models of PMOP showed significantly up-regulated expression of BRD4 protein in the femoral tissue (P < 0.05), which was obviously lowered by treatment with LWDH Pills. The rats treated with LWDH Pills also showed significant improvement of fatigue. Immunofluorescent staining of the osteoblasts showed that treatment with LWDH Pills significantly decreased the protein expressions of BRD4, MAPK and NF-κB. Analysis of the GSE56116 dataset revealed that that patients with kidney-yin deficiency had significantly higher BRD4 expression than those in the kidney-yang-deficiency group and non-kidney-deficiency group (P < 0.05). The upregulation of BRD4 expression involved multiple signaling pathways including neural ligand receptor response, cytoskeleton rearrangement, cytokine interaction, and granulocyte colony-stimulating factor chemotaxis pathways. LWDH can alleviate PMOP and fatigue by decreasing BRD4 signaling pathway, suggesting that potential of BRD4 as a promising therapeutic target for PMOP.

Exploring the Multifaceted Potential of Sildenafil in Medicine.

Phosphodiesterase type 5 (PDE5) is pivotal in cellular signalling, regulating cyclic guanosine monophosphate (cGMP) levels crucial for smooth muscle relaxation and vasodilation. By targeting cGMP for degradation, PDE5 inhibits sustained vasodilation. PDE5 operates in diverse anatomical regions, with its upregulation linked to various pathologies, including cancer and neurodegenerative diseases. Sildenafil, a selective PDE5 inhibitor, is prescribed for erectile dysfunction and pulmonary arterial hypertension. However, considering the extensive roles of PDE5, sildenafil might be useful in other pathologies. This review aims to comprehensively explore sildenafil's therapeutic potential across medicine, addressing a gap in the current literature. Recognising sildenafil's broader potential may unveil new treatment avenues, optimising existing approaches and broadening its clinical application.

Inhaled nitric oxide suppresses neuroinflammation in experimental ischemic stroke

Ischemic stroke is a major global health issue and characterized by acute vascular dysfunction and subsequent neuroinflammation. However, the relationship between these processes remains elusive. In the current study, we investigated whether alleviating vascular dysfunction by restoring vascular nitric oxide (NO) reduces post-stroke inflammation. Mice were subjected to experimental stroke and received inhaled NO (iNO; 50 ppm) after reperfusion. iNO normalized vascular cyclic guanosine monophosphate (cGMP) levels, reduced the elevated expression of intercellular adhesion molecule-1 (ICAM-1), and returned leukocyte adhesion to baseline levels. Reduction of vascular pathology significantly reduced the inflammatory cytokines interleukin-1β (Il-1β), interleukin-6 (Il-6), and tumor necrosis factor-α (TNF-α), within the brain parenchyma. These findings suggest that vascular dysfunction is responsible for leukocyte adhesion and that these processes drive parenchymal inflammation. Reversing vascular dysfunction may therefore emerge as a novel approach to diminish neuroinflammation after ischemic stroke and possibly other ischemic disorders.

Cis-DA-dependent dispersion by Pseudomonas aeruginosa biofilm and identification of cis-DA-sensory protein DspS.

Dispersion is an essential stage of the biofilm life cycle resulting in the release of bacteria from a biofilm into the surrounding environment. Dispersion contributes to bacterial survival by relieving overcrowding within a biofilm and allowing dissemination of cells into new habitats for colonization. Thus, dispersion can contribute to biofilm survival as well as disease progression and transmission. Cells dispersed from a biofilm rapidly lose their recalcitrant antimicrobial-tolerant biofilm phenotype and transition to a state that is susceptible to antibiotics. However, much of what is known about this biofilm developmental stage has been inferred from exogenously induced dispersion. Our findings provide the first evidence that native dispersion is coincident with reduced cyclic dimeric guanosine monophosphate levels, while also relying on at least some of the same factors that are central to the environmentally induced dispersion response, namely, BdlA, DipA, RbdA, and AmrZ. Additionally, we demonstrate for the first time that cis-DA signaling to induce dispersion is attributed to the two-component sensor/response regulator DspS, a homolog of the DSF sensor RpfC. Our findings also provide a path toward manipulating the native dispersion response as a novel and highly promising therapeutic intervention.

Stimulation of soluble guanylyl cyclase in erythrocytes induces export of cGMP and cardioprotection in type 2 diabetes

Abstract Background Red blood cells (RBCs) are known to export cardioprotective nitric oxide (NO) bioactivity. Although, RBCs contain a functional soluble guanylyl cyclase (sGC), the signalling behind the export of NO bioactivity remains unclear. Impairment of NO signalling in RBCs has been suggested to contribute to augmented cardiac ischemia-reperfusion injury in type 2 diabetes (T2D). We hypothesized that increased NO signaling by stimulation of sGC in RBCs protects from myocardial ischemia-reperfusion injury by release of a cardioprotective signal. Purpose To investigate whether stimulation of sGC, the intracellular NO receptor, in RBCs from T2D patients induces export of a cardioprotective factor and to determine its nature. Methods RBCs were collected from patients with T2D and from gender- and age-matched healthy subjects and incubated with different pharmacological compounds affecting the NO-signalling pathway. The RBCs or their supernatant were then administered to isolated Langendorff-perfused rat hearts subjected to 25 min global ischemia and 60 min reperfusion. Left ventricular developed pressure and infarct size were measured. ELISA and immunofluorescence were used to determine levels of cyclic guanosine monophosphate (cGMP) and substrate of protein kinase G activation. All animal experiments and procedures were performed according to the guidelines by the U.S National Institutes of Health (NIH publication no 85-23, revised 1996). The present study was performed following The Code of Ethics of the World Medical Association outlined in the Declaration of Helsinki of 1975 and revised in 1983 for experiments that involve human subjects. Results RBCs from T2D patients impaired post-ischemic cardiac function and increased infarct size compared to RBCs from healthy subjects, and these effects were prevented by pre-incubation of the RBCs with the sGC stimulator CYR715. Administration of the supernatant from RBCs incubated with the sGC stimulator resulted in similar cardioprotection, indicating release of a cardioprotective factor from the RBCs (Figure 1A and B). The cardioprotection was abolished by inhibition of transport of cGMP with MK571, an inhibitor of cyclic nucleotide transport. Extracellular cGMP levels in the supernatant from RBCs were increased following sGC stimulation, and administration of exogenous cGMP induced cardioprotection (Figure 1C and D). Expression of protein kinase G-dependent phosphorylated vasodilator-specific phosphoprotein in cardiomyocytes was increased following administration of supernatant from RBCs incubated with the sGC stimulator (Figure 1E). Conclusions This study shows that stimulation of sGC in RBCs leads to release of a cardioprotective mediator, identified as cGMP, that activates cardiac protein kinase G and protects from ischemia-reperfusion injury. It further identifies RBC sGC as a novel therapeutic target to prevent cardiovascular injury in T2D.Figure 1

Prediction of molecular interaction of Phosphodiesterase 10A inhibition by natural compounds: insights from structure-based screening and molecular dynamics simulations

Phosphodiesterase 10 A (PDE10A) is an enzyme that regulates cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP) levels in the brain, particularly in the striatum, which plays a critical role in movement control and reward processing. Inhibition of PDE10A can increase cAMP and cGMP levels, improving neuronal signaling and reducing symptoms of neuropsychiatric disorders such as schizophrenia, Huntington’s disease, and Parkinson’s disease. In this study, a structure-based virtual screening was conducted to identify potential anti-neuropsychiatric disorders compounds from phytoconstituents in the IMPPAT database. The ligands were docked against PDE10A, resulting in 40 compounds with appreciable docking scores. These 40 compounds underwent further ADMET predictions and drug likeliness, resulting in five potential compounds. Finally, based on the specific interactions, two compounds (Colladonin and Isopongachromene), were subjected to molecular dynamics (MD) simulation and MM-PBSA studies. The MM-PBSA analysis validated and captured the intermolecular interactions, indicating that Colladonin and Isopongachromene had appreciable binding affinities of −155.60 kJ.mol−1 and −108.28 kJ.mol−1, respectively and were promising candidates against neuropsychiatric disorders, targeting PDE10A. Overall, this study provides insight into the potential of PDE10A inhibitors as therapeutic agents for treating neuropsychiatric disorders, and Colladonin and Isopongachromene are promising compounds for further development. Communicated by Ramaswamy H. Sarma

Extract of Pfaffia glomerata Ameliorates Paroxetine-Induced Sexual Dysfunction in Male Mice and the Characterization of Its Phytoconstituents by UPLC-MS.

Pfaffia glomerata extract (PGE) has a variety of biological activities. However, its ameliorative effect on and exact working mechanism in male sexual dysfunction are still poorly understood. This study aims to evaluate the ameliorative effect of PGE on paroxetine (PRX)-induced sexual dysfunction in male mice and uses molecular docking technology to investigate its underlying mechanism. In this work, PRX-induced sexual dysfunction was caused and PGE was gavaged in mice for 28 days. The results show that PGE significantly improved the sexual performance of mice and reduced the damage to testicular tissues. Further studies showed that PGE restored serum sex hormones to normal levels and increased nitric oxide (NO) and cyclic guanosine monophosphate (cGMP) levels as well as nitric oxide synthase (NOS) activity in penile tissues, while also decreasing phosphodiesterase-5 (PDE-5) activity, thereby maintaining normal penile erection in mice. In addition, PGE improved the activities of enzymes (LDH, ACP, and ALP) related to energy metabolism in the testis and significantly increased sperm count and viability in mice. Furthermore, the molecular docking results show that all eight compounds in PGE could form a stable complex with PDE-5 and inhibit the activity of PDE-5. In conclusion, PGE had an ameliorative effect on PRX-induced sexual dysfunction, suggesting that PGE has a potential protective effect on male sexual health.

Effects of transplantation of umbilical cord blood mononuclear cells into the scrotum on sexual function in elderly mice.

Aim: This study investigated the effect of allografting umbilical cord blood mononuclear cells (UCBMCs) into the scrotum on sexual function in male elderly mice. Methods: UCBMCs were injected once into the scrotal sheath cavity of elderly mice. Results: The transplanted UCBMCs survived in the scrotal sheath cavity for 1month. The micehad significantly increased blood testosterone concentrations, cyclic guanosine monophosphate (cGMP) levels and total nitric oxide synthase (T-NOS) activity in the corpus cavernosum and an increase inthe number of mouse matings within 30min (all p=0.000). Conclusion: Scrotum-implanted UCBMCs improve the sexual function of male elderly mice through testosterone production and the NOS/cGMP pathway, which may provide an innovative transplantation approach for thetreatment of erectile dysfunction.

Neuromodulatory effect of vardenafil on aluminium chloride/d-galactose induced Alzheimer’s disease in rats: emphasis on amyloid-beta, p-tau, PI3K/Akt/p53 pathway, endoplasmic reticulum stress, and cellular senescence

Dysregulation of protein homeostasis, proteostasis, is a distinctive hallmark of many neurodegenerative disorders and aging. Deleteriously, the accumulation of aberrant proteins in Alzheimer’s disease (AD) is accompanied with a marked collapse in proteostasis network. The current study explored the potential therapeutic effect of vardenafil (VAR), a phosphodiesterase-5 inhibitor, in AlCl3/d-galactose (d-gal)-induced AD in rats and its possible underlying mechanisms. The impact of VAR treatment on neurobehavioral function, hippocampal tissue architecture, and the activity of the cholinergic system main enzymes were assessed utilizing VAR at doses of 0.3 mg/kg and 1 mg/kg. Additionally, the expression level of amyloid-beta and phosphorylated tau proteins in the hippocampus were figured out. Accordingly, VAR higher dose was selected to contemplate the possible underlying mechanisms. Intriguingly, VAR elevated the cyclic guanosine monophosphate level in the hippocampus and averted the repressed proteasome activity by AlCl3/d-gal; hence, VAR might alleviate the burden of toxic protein aggregates in AD. In addition, a substantial reduction in the activating transcription factor 6-mediated endoplasmic reticulum stress was demonstrated with VAR treatment. Notably, VAR counteracted the AlCl3/d-gal-induced depletion of nuclear factor erythroid 2-related factor 2 level. Moreover, the anti-senescence activity of VAR was demonstrated via its ability to restore the balance of the redox circuit. The modulation of phosphatidylinositol-3-kinase/protein kinase B/p53 pathway and the reduction of nuclear factor kappa B level, the key regulator of senescence-associated secretory phenotype mediators release, with VAR treatment were also elucidated. Altogether, these findings insinuate the possible therapeutic benefits of VAR in AD management.Graphic abstract

Adrenomedullin in paraventricular nucleus attenuates adipose afferent reflex and sympathoexcitation via receptors mediated nitric oxide-gamma-aminobutyric acid A type receptor pathway in rats with obesity-related hypertension.

Hypothalamic paraventricular nucleus (PVN) is an important central site for the control of the adipose afferent reflex (AAR) that increases sympathetic outflow and blood pressure in obesity-related hypertension (OH). In this study, we investigated the effects of nitric oxide (NO) and cardiovascular bioactive polypeptide adrenomedullin (ADM) in the PVN on AAR and sympathetic nerve activity (SNA) in OH rats induced by a high-fat diet. The results showed that ADM, total neuronal NO synthase (nNOS) and phosphorylated-nNOS protein expression levels in the PVN of the OH rats were down-regulated compared to the control rats. The enhanced AAR in OH rats was attenuated by PVN acute application of NO donor sodium nitroprusside (SNP), but was strengthened by the nNOS inhibitor nNOS-I, guanylyl cyclase inhibitor (1H-[1,2,4]Oxadiazolo[4,3-a]quinoxalin-1-one, ODQ) and gamma-aminobutyric acid A type receptor (GABAA) antagonist Bicuculline. Moreover, PVN ADM microinjection not only decreased basal SNA but also attenuated the enhanced AAR in OH rats, which were effectively inhibited by ADM receptor antagonist ADM22-52, nNOS-I, ODQ or Bicuculline pretreatment. Bilateral PVN acute microinjection of ADM also caused greater increases in NO and cyclic guanosine monophosphate (cGMP) levels, and nNOS phosphorylation. Adeno-associated virus vectors encoding ADM (AAV-ADM) transfection in the PVN of OH rats not only decreased the elevated AAR, basal SNA and blood pressure (BP), but also increased the expression and activation of nNOS. Furthermore, AAV-ADM transfection improved vascular remodeling in OH rats. Taken together, our data highlight the roles of ADM in improving sympathetic overactivation, enhanced AAR and hypertension, and its related mechanisms associated with receptors mediated NO-cGMP-GABAA pathway in OH condition.

Icariin ameliorates oxidative stress-induced inflammation, apoptosis, and heart failure in isoproterenol-challenged Wistar rats.

Cardiovascular diseases are widespread across the globe, and heart failure (HF) accounts for the majority of heart-associated deaths. Target-based drug therapy is much needed for the management of heart failure. We have designed this study to evaluate icariin for its cardioprotective activity in the isoproterenol (ISO) induced postinfarction model. We have randomly distributed Wistar rats into seven groups, i.e., vehicle control; isoproterenol-treated; icariin per se; sildenafil per se; ISO + icariin 5; ISO + icariin 10; and ISO + sildenafil groups. ISO (85 mg/kg, subcutaneous) was administered at 24 hr for two consecutive days to produce cardiac injury, followed by icariin administration at 5 mg/kg and 10 mg/kg orally for 56 days. Rats were subjected to hemodynamic measurements biweekly. After 24 hr of the completion of dosing, animals were sacrificed, and markers for oxidative stress, fibrosis, inflammation, and cell death were measured. Transmission electron microscopy (TEM), histopathology, and MT staining of cardiac tissue were also done to assess the pathological and fibrotic architectural damage. A significant decline in hemodynamics and an anti-oxidant collapse were found in ISO-intoxicated rats. Alterations in the levels of cyclic guanosine monophosphate (cGMP), interleukin-10 (IL-10), Tumor necrosis factor (TNF-α), and brain natriuretic peptide (BNP) were also observed in serum. Up-regulation of caspase-3, nuclear factor (NF-ĸB), and decline in expression of nuclear factor (NrF-2) contribute to cardiac damage. The treatment with icariin and sildenafil considerably reversed the toxic changes toward normal. Increased cGMP and Nrf2 expression and suppressed NF-ĸB-caspase-3 signaling play a pivotal role in icariin-mediated cardioprotection.

Elevated retinal cGMP is not associated with elevated circulating cGMP levels in a canine model of retinitis pigmentosa.

To investigate whether raised levels of retinal cyclic guanosine monophosphate (cGMP) was reflected in plasma levels in PDE6A-/- dogs. Retina was collected from 2-month-old wildtype dogs (PDE6A+/+, N = 6), heterozygous dogs (PDE6A+/-, N = 4) and affected dogs (PDE6A-/-, N = 3) and plasma was collected from 2-month-old wildtype dogs (PDE6A+/+, N = 5), heterozygous dogs (PDE6A+/-, N = 5) and affected dogs (PDE6A-/-, N = 5). Retina and plasma samples were measured by ELISA. cGMP levels in retinal samples of PDE6A-/- dogs at 2 months of age were significantly elevated. There was no significant difference in plasma cGMP levels between wildtype and PDE6A-/- or PDE6A+/- puppies. However, the plasma cGMP levels of the PDE6A-/- puppies were significantly lower than that of PDE6A+/- puppies. cGMP levels in the plasma from PDE6A-/- was not elevated when compared to control dogs. At the 2-month timepoint, cGMP plasma levels would not be a useful biomarker for disease.

BAY-7081: A Potent, Selective, and Orally Bioavailable Cyanopyridone-Based PDE9A Inhibitor.

Despite advances in the treatment of heart failure in recent years, options for patients are still limited and the disease is associated with considerable morbidity and mortality. Modulating cyclic guanosine monophosphate levels within the natriuretic peptide signaling pathway by inhibiting PDE9A has been associated with beneficial effects in preclinical heart failure models. We herein report the identification of BAY-7081, a potent, selective, and orally bioavailable PDE9A inhibitor with very good aqueous solubility starting from a high-throughput screening hit. Key aspect of the optimization was a switch in metabolism of our lead structures from glucuronidation to oxidation. The switch proved being essential for the identification of compounds with improved pharmacokinetic profiles. By studying a tool compound in a transverse aortic constriction mouse model, we were able to substantiate the relevance of PDE9A inhibition in heart diseases.

Inhibition of multidrug resistance proteins by MK571 restored the erectile function in obese mice through cGMP accumulation.

Intracellular levels of cyclic nucleotides can also be controlled by the action of multidrug resistance protein types 4 (MRP4) and 5 (MRP5). To date, no studies evaluated the role of their inhibition in an animal model of erectile dysfunction (ED). To evaluate the effect of a 2-week treatment with MK571, an inhibitor of the efflux of cyclic nucleotides in the ED of obese mice. Mice were divided in three groups: (i) lean, (ii) obese, and (iii) obese+MK571. The corpus cavernosum (CC) were isolated, and concentration-response curves to acetylcholine (ACh), sodium nitroprusside (SNP), and tadalafil in addition to electrical field stimulation (EFS) were carried out in phenylephrine pre-contracted tissues. Expression of ABCC4 and ABCC5, intracellular levels of cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP), the protein levels for pVASPSer157 and pVASPSer239 , and the intracavernous pressure (ICP) were also determined. The intracellular and extracellular (supernatant) ratios in CC from obese and lean stimulated with a cGMP-increasing substance (BAY 58-2667) in the absence and presence of MK571 (20μM, 30min) were also assessed. The treatment with MK571 completely reversed the lower relaxing responses induced by EFS, ACh, SNP, and tadalafil observed in obese mice CC in comparison with untreated obese mice. Cyclic GMP and p-VASPSer239 expression were significantly reduced in CC from obese groups. MK571 promoted a sixfold increase in cGMP without interfering in the protein expression of p-VASPSer239 . Neither the cAMP levels nor p-VASPSer157 were altered in MK571-treated animals. The ICP was ∼50% lower in obese than in the lean mice; however, the treatment with MK571 fully reversed this response. Expressions of ABCC4 and ABCC5 were not different between groups. The intra/extracellular ratio of cGMP was similar in CC from obese and lean mice stimulated with BAY 58-2667. The MRPs inhibition by MK571 favored the accumulation of cGMP in the smooth muscle cells, thus improving the smooth muscle relaxation and the erectile function in obese mice.