Cyclic Guanosine Monophosphate-specific Phosphodiesterase Research Articles

Stress-induced impairment of parasympathetic NO-mediated inhibition of sympathetic vasoconstriction in submucosal arteriole of rat rectum.

In the gastrointestinal tract, nitrergic inhibition of the arteriolar contractility has not been demonstrated. Here, we explored whether neurally-released nitric oxide (NO) inhibits sympathetic vasoconstrictions in the rat rectal arterioles. Changes in sympathetic vasoconstrictions and their nitrergic modulation in rats exposed to water avoidance stress (WAS, 10days, 1h per day) were also examined. In rectal submucosal preparations, changes in arteriolar diameter were monitored using video microscopy. In control or sham-treated rats, electrical field stimulation (EFS)-induced sympathetic vasoconstrictions were increased by the neuronal nitric oxide synthase (nNOS) inhibitor L-NPA (1μM) and diminished by the cyclic guanosine monophosphate-specific phosphodiesterase 5 (PDE5) inhibitor tadalafil (10nM). In phenylephrine-constricted, guanethidine-treated arterioles, EFS-induced vasodilatations were inhibited by the calcitonin gene-related peptide (CGRP) receptor antagonist BIBN-4096 (1μM) but not L-NPA. Perivascular nNOS-immunoreactive nitrergic fibres co-expressing the parasympathetic marker vesicular acetylcholine transporter (VAChT) were intermingled with tyrosine hydroxylase (TH)-immunoreactive sympathetic fibres expressing soluble guanylate cyclase (sGC), a receptor for NO. In WAS rats in which augmented sympathetic vasoconstrictions were developed, L-NPA failed to further increase the vasoconstrictions, while tadalafil-induced inhibition of the vasoconstrictions was attenuated. Phenylephrine- or α,β-methylene ATP-induced vasoconstrictions and acetylcholine-induced vasodilatations were unaltered by WAS. Thus, in arterioles of the rat rectal submucosa, NO released from parasympathetic nerves appears to inhibit sympathetic vasoconstrictions presumably by reducing sympathetic transmitter release. In WAS rats, sympathetic vasoconstrictions are augmented at least partly due to the diminished pre-junctional nitrergic inhibition of transmitter release without changing α-adrenoceptor or P2X-purinoctor mediated vasoconstriction and endothelium-dependent vasodilatation.

Polygonatum sibiricum (Huang Jing) polysaccharide reduces diabetic cardiomyopathy through increasing cyclic guanosine monophosphate-protein kinase G signaling in diabetic mice.

Diabetic cardiomyopathy (DCM) is a prevalent condition among individuals with diabetes, and is associated with a high mortality rate. The anti-oxidant properties of Jing Huang or Polygonatum sibiricum polysaccharide (PSP) have been extensively used to treat diabetes-related disorders; however, its potential effectiveness against DCM remains unknown. This study aimed to investigate PSP's therapeutic effects on DCM in an experimental diabetic mouse model. To induce insulin resistance, mice were fed a high-fat diet for 3 months, followed by intraperitoneal streptozotocin injection to induce slight hyperglycemia and develop DCM. Both DCM and control mice were given PSP orally for 3 weeks. Western blotting was used to detect the protein expressions of protein kinase G, C/EBP homologous protein, glucose-regulated protein 78, phosphodiesterase type 5, protein kinase R-like endoplasmic reticulum (ER) kinase, and phospho-protein kinase R-like endoplasmic reticulum kinase in heart tissue. The results showed a reduction in bodyweight and blood glucose levels in the PSP therapy group compared with DCM group. PSP also improved cardiac function and had a negligible effect on malondialdehyde activity. Furthermore, the findings showed that PSP alleviated ER and oxidative stress observed in DCM mice hearts, leading to the inhibition of cyclic guanosine monophosphate-specific phosphodiesterase type 5 and cardiac cyclic guanosine monophosphate reactivation. Phosphodiesterase type 5 inhibition reduced high-fat diet-induced cardiac dysfunction and decreased ER stress. PSP could effectively protect diabetic myocardium by inhibiting endoplasmic reticulum stress. These findings provide crucial insights into the potential of PSP to ameliorate DCM conditions in diabetic mice by decreasing ER and oxidative stress, and enhancing cyclic guanosine monophosphate protein kinase G signaling.

Safety, tolerability, and pharmacokinetics of aildenafil citrate tablets, a novel oral PDE5 inhibitor, in healthy Chinese volunteers after multiple-dose administration.

Aildenafil citrate is a potent and selective inhibitor of cyclic guanosine monophosphate-specific phosphodiesterase type 5, developed for the treatment of erectile dysfunction (ED). This study aimed to assess the pharmacokinetics, safety, and tolerability of aildenafil citrate tablets after multiple doses in healthy Chinese males. Twenty participants were divided into 2 groups, 10 participants each. Participants were administered multiple doses of aildenafil citrate tablets at 30and 60mg. The safety evaluation was based on clinical symptoms and adverse events. Concentrations of aildenafil and its key metabolites (M1, M5, and M12) in human serum were measured by liquid chromatography-tandem mass spectrometry. Pharmacokinetic analysis showed rapid absorption and elimination of aildenafil, with a median time to maximum serum concentration of 1hour and mean terminal half-lives of 2.75and 3.26hours in the respective dose groups. The mean maximum concentration was proportional to the aildenafil dose in the range of 30to 60mg, although the area under the curve was not proportional for serum concentration vs time 0 to the last measurable time point (24 hours). Multiple doses of aildenafil were well tolerated, with 60.0% of men experiencing treatment-emergent adverse events, notably myalgia and fatigue, particularly in the 60-mg group. Aildenafil citrate tablets demonstrated favorable tolerability with once-daily administration over the clinical dose range. The occurrence of myalgia and fatigue was more prevalent in the 60-mg group. From a pharmacokinetic perspective, optimal administration of aildenafil citrate tablets appears to be 1hour before sexual intercourse in men with ED. This study presents robust safety and pharmacokinetic data at expected therapeutic doses, unaffected by clinical factors. The efficacy of aildenafil citrate tablets warrants further validation in individuals with ED. Aildenafil citrate tablets exhibited good tolerability in healthy Chinese males following multiple doses at 30and 60mg. The 60-mg group showed an increased incidence of myalgia and fatigue, suggesting the need for heightened clinical vigilance. The mean maximum concentration, but not the area under the curve, displayed dose proportionality within the 30- to 60-mg dose range, and no significant drug accumulation was observed with repeated daily administration. CTR20192473 (http://www.chinadrugtrials.org.cn).

A Comprehensive Review: Transdermal Drug Delivery System: A Tool For Novel Drug Delivery System

In the recent decade, skin delivery (topical and transdermal) has gained an unprecedented popularity, especially due to increased incidences of chronic skin diseases, demand for targeted and patient compliant delivery and interest in life cycle management strategies among pharmaceutical companies. Transdermal drug delivery system was presented to overcome the difficulties of drug delivery especially oral route. Transdermal drug delivery refers to a means of delivering drugs through the surface of the skin for local or systemic treatment. The drug functions after absorption through the skin into the systemic circulation via capillary action at a certain rate. Transdermal patches are now widely used as cosmetic, topical and transdermal delivery systems. These patches represent a key outcome from the growth in skin science, technology and expertise developed through trial and error, clinical observation and evidence-based studies that date back to the first existing human records. A transdermal patch is a medicated adhesive patch that is placed on the skin to deliver a specific dose of medication through skin and into the bloodstream. An advantage of a transdermal drug delivery route over other types of delivery system such as oral, topical, intravenous (i.v.), intramuscular (i.m.), etc. is that the patch provides a controlled release of the medication into the patient, usually through either a porous membrane covering a reservoir of medication or through body heat melting thin layers of medication embedded in the adhesive. The main disadvantage to transdermal delivery systems stems from the fact that the skin composition offers very effective barrier that allow only small molecule based drugs to penetrate the skin and pass through the barrier. Sildenafil citrate (SLD) is a selective cyclic guanosine monophosphate-specific phosphodiesterase type 5 inhibitor used for the oral treatment of erectile dysfunction and more recently, it has been used for the treatment of pulmonary arterial hypertension and the enhancement of uteroplacental perfusion in case of fetal growth retardation. The challenges facing the oral administration of the drug include poor bioavailability and short duration of action that requires frequent administration. The main objective of transdermal drug delivery system is to deliver drugs into systemic circulation through skin at predetermined rate with minimal inter and intrapatient variations. Keyword: Skin delivery, Transdermal drug delivery, Oral rout, Sildenafil citrate, Pulmonary arterial hypertension

Optimized nano-transfersomal films for enhanced sildenafil citrate transdermal delivery: ex vivo and in vivo evaluation.

Sildenafil citrate (SLD) is a selective cyclic guanosine monophosphate-specific phosphodiesterase type 5 inhibitor used for the oral treatment of erectile dysfunction and, more recently, for other indications, including pulmonary hypertension. The challenges facing the oral administration of the drug include poor bioavailability and short duration of action that requires frequent administration. Thus, the objective of this work is to formulate optimized SLD nano-transfersomal transdermal films with enhanced and controlled permeation aiming at surmounting the previously mentioned challenges and hence improving the drug bioavailability. SLD nano-transfersomes were prepared using modified lipid hydration technique. Central composite design was applied for the optimization of SLD nano-transfersomes with minimized vesicular size. The independent variables studied were drug-to-phospholipid molar ratio, surfactant hydrophilic lipophilic balance, and hydration medium pH. The optimized SLD nano-transfersomes were developed and evaluated for vesicular size and morphology and then incorporated into hydroxypropyl methyl cellulose transdermal films. The optimized transfersomes were unilamellar and spherical in shape with vesicular size of 130 nm. The optimized SLD nano-transfersomal films exhibited enhanced ex vivo permeation parameters with controlled profile compared to SLD control films. Furthermore, enhanced bioavailability and extended absorption were demonstrated by SLD nano-transfersomal films as reflected by their significantly higher maximum plasma concentration (Cmax) and area under the curve and longer time to maxi mum plasma concentration (Tmax) compared to control films. These results highlighted the potentiality of optimized SLD nano-transfersomal films to enhance the transdermal permeation and the bioavailability of the drug with the possible consequence of reducing the dose and administration frequency.

Chronic inhibition of cyclic guanosine monophosphate-specific phosphodiesterase 5 prevented cardiac fibrosis through inhibition of transforming growth factor β-induced Smad signaling.

Recent evidences suggested that cyclic guanosine monophosphate-specific phosphodiesterase 5 (PDE5) inhibitor represents an important therapeutic target for cardiovascular diseases. Whether and how it ameliorates cardiac fibrosis, a major cause of diastolic dysfunction and heart failure, is unknown. The purpose of this study was to investigate the effects of PDE5 inhibitor on cardiac fibrosis. We assessed cardiac fibrosis and pathology in mice subjected to transverse aortic constriction (TAC). Oral sildenafil, a PDE5 inhibitor, was administered in the therapy group. In control mice, 4 weeks of TAC induced significant cardiac dysfunction, cardiac fibrosis, and cardiac fibroblast activation (proliferation and transformation to myofibroblasts). Sildenafil treatment markedly prevented TAC-induced cardiac dysfunction, cardiac fibrosis and cardiac fibroblast activation but did not block TAC-induced transforming growth factor-β1 (TGF-β1) production and phosphorylation of Smad2/3. In isolated cardiac fibroblasts, sildenafil blocked TGF-β1-induced cardiac fibroblast transformation, proliferation and collagen synthesis. Furthermore, we found that sildenafil induced phosphorylated cAMP response element binding protein (CREB) and reduced CREB-binding protein 1 (CBP1) recruitment to Smad transcriptional complexes. PDE5 inhibition prevents cardiac fibrosis by reducing CBP1 recruitment to Smad transcriptional complexes through CREB activation in cardiac fibroblasts.

Effects of tadalafil—Type-V phosphodiesterase enzyme inhibitor—On rats with spinal trauma

In this research, the effect of tadalafil, a selective inhibitor of cyclic guanosine monophosphate-specific phosphodiesterase type 5, on rats with spinal trauma was evaluated. The evaluation consisted of neurological examination and biochemical parameters. Twenty healthy male Wistar albino rats were used in this study. They were separated into three groups: tadalafil-receiving (TD) group (n = 7), laminectomy and trauma (LT) group (n = 7), and just laminectomy group (n = 6). The TD group received daily dose of tadalafil (10 mg/kg) for a week along with bait and water. Each rat's spinal cord was dissected with utter caution. The spinal cord was traumatized by Allen's weight-drop method. Using a standard apparatus, 5 g of weight was dropped from a height of 10 cm on the spinal cords of the TD and LT (laminectomy + trauma) group. No extra maneuvers were conducted on the laminectomy group. A day later, the rat's functional neurological status was examined followed by re-exploration of the spinal cord for sampling 1 cm of tissue. The Tarlov scale was used to evaluate the functional neurological status. The modified Tarlov scale was rated to be significantly higher in the TD group than that in the LT group. For the biochemical parameters, malondialdehyde (MDA) and cytokines such as interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α) involved in the inflammatory process were examined. MDA—an indicator of lipid peroxidation—was found to be significantly lower in the TD group compared with that in the LT group. TNF-α and IL-6 levels were also found to be lower in the TD group compared with those in the LT group. Shortly, this research showed that the use of TD group in spinal trauma resulted in better neurological outcome and significant improvement in biochemical parameters.

Tadalafil

Tadalafil is a selective cyclic guanosine monophosphate-specific phosphodiesterase type 5 inhibitor. Once-daily tadalafil 5 mg was effective in treating the signs and symptoms of benign prostatic hyperplasia (BPH). In phase III trials in men with BPH, the mean change from baseline to week 12 in the total International Prostate Symptom Score (IPSS; primary endpoint) was significantly greater in those treated with once-daily tadalafil 5 mg than with placebo. Improvements in total IPSS that occurred over the initial 12 weeks of tadalafil treatment were maintained with continued treatment over a 1-year period in an open-label extension study. Moreover, tadalafil was effective in treating both erectile dysfunction (ED) and the signs and symptoms of BPH in a phase III trial that specifically enrolled men with both indications. Both the International Index of Erectile Function-Erectile Function domain score and the total IPSS (co-primary endpoints) were significantly improved from baseline to week 12 after treatment with once-daily tadalafil 5 mg compared with placebo. Tadalafil was generally well tolerated (for a period of up to 1 year) in patients with BPH, including those with ED, with adverse events being of mild to moderate intensity.

Identification of phosphodiesterase 9A as a cyclic guanosine monophosphate–specific phosphodiesterase in germinal vesicle oocytes: a proposed role in the resumption of meiosis

To identify a cyclic guanosine monophosphate (cGMP)-specific phosphodiesterase (PDE) in nonhuman primate germinal vesicle (GV) oocytes and establish a proposed effect on oocyte maturation through preliminary experiments in mouse GV oocytes. Controlled nonhuman primate and rodent experiments. Academic research institution. Rhesus macaques and B6/129F1 mice. Stimulation of Rhesus macaques with follicle-stimulating hormone (FSH) to collect GV oocytes and cumulus for gene expression analysis, and stimulation of female mice with pregnant mare serum gonadotropin to collect GV oocytes. Expression of PDE transcript in primate GV oocytes and cumulus cells, measurement of fluorescence polarization of phosphodiesterase 3A (PDE3A) activity, and analysis of spontaneous resumption of meiosis in mouse GV oocytes. Of five PDE transcripts detected in Rhesus GV oocytes, only PDE9A was cGMP-specific. The fluorescence polarization assays indicated cGMP has an inhibitory effect on PDE3A while the phosphodiesterase 9A (PDE9) inhibitor, BAY73-6691, does not. Similarly, BAY73-6691 had little effect on preventing spontaneous maturation in oocytes, but did augment the inhibitory effects of cGMP. Inclusion of 0 μM (control), 10 μM, 100 μM, and 1 mM BAY73-6691 statistically significantly increased the proportion of mouse oocytes maintaining GV arrest in the presence of the cGMP analog 8-Br-cGMP at 100 μM (8.8%, 11.4%, 18.8%, and 28%), 500 μM (21.1%, 38.1%, 74.5%, and 66.5%), and 1 mM (57.8%, 74.5%, 93.9%, and 94.0%), respectively. Phosphodiesterase 9A (PDE9A) is a cGMP-specific hydrolyzing enzyme present in primate oocytes, and PDE9 antagonists augment the inhibitory effect of cGMP during spontaneous in vitro maturation of GV mouse oocytes.

Preparation and Evaluation of Sildenafil Rapidly Disintegrating Tablets

Sildenafil citrate is an oral therapy for erectile dysfunction (ED). Sildenafil, a selective inhibitor of cyclic guanosine monophosphate-specific phosphodiesterase type 5 (PDE5), has been reported to be effective in men with ED associated with diabetes and prostate cancer, and in psychogenic ED. The main objective of this study is to prepare more effective, rapidly disintegrating and rapid onset of action sildenafil oral tablets. Sildenafil tablets were prepared using the newly introduced Pharmaburst® as a direct compression vehicle in comparison with the well-known excipients, namely mannitol, anhydrous lactose and primojel. The formula containing Pharmaburst® showed the most rapidly-disintegrating effect (15 sec) compared to the other formulations. Thus, Pharmaburst® can be utilized as an effective direct compression vehicle as well as a superdisintegrant with very rapid disintegration time in vitro and in the oral cavity. The rapidly-disintegrating sildenafil tablets showed maximum serum concentration within only two minutes (Cmax of 0.76 µg) by applying the tablets to the oral cavity of rabbits, whereas, the conventional sildenafil tablets have a comparatively lower Cmax (0.56µg) through about 45 minutes. 

Tadalafil

Tadalafil is a selective cyclic guanosine monophosphate-specific phosphodiesterase type 5 inhibitor that is effective in improving exercise ability, the time to clinical worsening and health-related quality of life (HR-QOL) scores in patients with pulmonary arterial hypertension (PAH). In a large, 16-week, randomized, double-blind, placebo-controlled, multicentre, phase III trial (PHIRST) in patients aged >or=14 years with PAH (WHO group I), tadalafil 40 mg once daily (the recommended dosage) significantly increased the mean placebo-corrected 6-minute walk distance (6MWD) by 33 m from baseline (primary endpoint). In treatment-naive patients, tadalafil 40 mg once daily significantly increased the mean placebo-corrected 6MWD by 44 m at week 16, whereas in patients receiving bosentan 125 mg twice daily as background therapy there was a mean change of 23 m, which was not significant. Both the time to the first occurrence of clinical worsening and the incidence of clinical worsening were significantly reduced in recipients of tadalafil 40 mg once daily compared with recipients of placebo. Furthermore, at week 16, tadalafil improved most HR-QOL outcomes from baseline to a significantly greater extent than placebo. Preliminary data from an extension of the PHIRST trial suggest that the improvements in 6MWD are maintained for up to 1 year in recipients of tadalafil 20 or 40 mg once daily. Treatment with tadalafil was generally well tolerated, with adverse events that were transient in nature and of mild to moderate intensity.

Up-Regulation of 3′5′-Cyclic Guanosine Monophosphate-Specific Phosphodiesterase in the Porcine Cumulus-Oocyte Complex Affects Steroidogenesis during in Vitro Maturation

The 3'5'-cyclic GMP (cGMP) pathway is known to influence ovarian functions, including steroidogenesis, ovulation, and granulosa cell proliferation. We show here that cGMP-phosphodiesterase (PDE) activity increased in a gonadotropin-dependent manner more than 3-fold in the cumulus-oocyte complex (COC) after 24 h in vitro maturation (IVM) and up to 5-fold after 48 h. Further characterization of this increase demonstrated that the activity was located primarily in cumulus cells, and was sensitive to sildenafil and zaprinast, two inhibitors specific to both type 5 and 6 PDEs. RT-PCR experiments showed that the mRNAs for cGMP-degrading PDEs 5A and 6C are present in the COC before and after 30 h IVM. Western blotting confirmed the presence of PDE 5A in the COC. Western blotting of PDE 6C revealed a significant up-regulation in the COC during IVM. Isolation and analysis of detergent-resistant membranes suggested that PDE 6C protein, along with half of the total sildenafil-sensitive cGMP-degradation activity, is associated with detergent-resistant membrane in the COC after 30 h IVM. Treatment of porcine COC with sildenafil during IVM caused a significant decrease in gonadotropin-stimulated progesterone secretion. Together, these results constitute the first report exploring the contribution of cGMP-PDE activity in mammalian COC, supporting a functional clustering of the enzyme, and providing the first evidence of its role in steroidogenesis.

Cyclic GMP/Protein Kinase G Phosphorylation of Smad3 Blocks Transforming Growth Factor-β–Induced Nuclear Smad Translocation

See related article, pages 185–192 In response to hemodynamic overload, the heart undergoes a complex adaptive remodeling process that involves cardiac myocyte hypertrophy, transformation of fibroblast into myofibroblast, high-level expression of extracellular matrix (ECM) proteins, interstitial fibrosis, and cell death.1 Differentiation of cardiac fibroblasts into myofibroblasts is critical to the production and deposition of collagens and plays a decisive role in myocardial fibrosis and morphological alterations during the progression of adaptive myocardial hypertrophy to decompensation and heart failure.1,2 Among the plethora of identified fibrogenic factors, transforming growth factor (TGF)-β3 plays a fundamental role in hypertrophic and fibrotic remodeling of the heart, where it regulates cardiomyocyte growth, fibroblast activation, and ECM deposition.4,5 The expression of ventricular TGF-β mRNA and protein is increased in numerous models of pathological cardiac hypertrophy and in cardiac cells in response to putative hypertrophic stimuli.6,7 In vitro, TGF-β activates myofibroblast transformation and increases ECM production.7 Blockade of TGF-β signaling is predicted to blunt fibrosis.5 Recent studies from Chen et al8 convincingly demonstrated that disruption of TGF-β signaling by inducible dominant-negative mutation of the TGF-β receptor type II (TβRII) gene significantly reduced the pressure overload–induced myofibroblast transformation and interstitial fibrosis in mouse heart. Thus, there is considerable interest in understanding how signaling by TGF-β receptors is transduced and how the inevitable damage produced could be mitigated. Of the 3 isoforms of TGF-β expressed in mammals,9,10 TGF-β1 is expressed in the adult heart, where it is secreted by cardiomyocytes and myofibroblasts and retained in significant amounts in ECM as a latent cytokine. Recent advances have led to clear description of downstream of TGF-β signal transduction pathways initiated by binding of TGF-β to membrane-bound heteromeric receptor kinases (TβRI and TβRII) that transduce intracellular signals via both Smad and non-Smad pathways …

Inhibition of N-Type Calcium Channels by Activation of GPR35, an Orphan Receptor, Heterologously Expressed in Rat Sympathetic Neurons

GPR35 is a G protein-coupled receptor recently "de-orphanized" using high-throughput intracellular calcium measurements in clonal cell lines expressing a chimeric G-protein alpha-subunit. From these screens, kynurenic acid, an endogenous metabolite of tryptophan, and zaprinast, a synthetic inhibitor of cyclic guanosine monophosphate-specific phosphodiesterase, emerged as potential agonists for GPR35. To investigate the coupling of GPR35 to natively expressed neuronal signaling pathways and effectors, we heterologously expressed GPR35 in rat sympathetic neurons and examined the modulation of N-type (Ca(V)2.2) calcium channels. In neurons expressing GPR35, calcium channels were inhibited in the absence of overt agonists, indicating a tonic receptor activity. Application of kynurenic acid or zaprinast resulted in robust voltage-dependent calcium current inhibition characteristic of Gbetagamma-mediated modulation. Both agonist-independent and -dependent effects of GPR35 were blocked by Bordetella pertussis toxin pretreatment indicating the involvement of G(i/o) proteins. In neurons expressing GPR35a, a short splice variant of GPR35, zaprinast was more potent (EC(50) = 1 microM) than kynurenic acid (58 microM) but had a similar efficacy (approximately 60% maximal calcium current inhibition). Expression of GPR35b, which has an additional 31 residues at the N terminus, produced similar results but with much greater variability. Both GPR35a and GPR35b appeared to have similar expression patterns when fused to fluorescent proteins. These results suggest a potential role for GPR35 in regulating neuronal excitability and synaptic release.

A Double-blind, Placebo-Controlled, Crossover Study of Sildenafil in Obstructive Sleep Apnea

Sildenafil prolongs the action of cyclic guanosine monophosphate and nitric oxide by inhibiting cyclic guanosine monophosphate-specific phosphodiesterase 5. It is largely used for erectile dysfunction, a highly prevalent condition in obstructive sleep apnea. Because nitric oxide promotes upper airway congestion, muscle relaxation, and pulmonary vasodilation, the aim of this study was to establish the impact of a single 50-mg dose of sildenafil on the sleep of patients with severe obstructive sleep apnea. Thirteen [corrected] middle-aged men with severe obstructive sleep apnea were consecutively selected for this double-blind, placebo-controlled, crossover study. Exclusion criteria were obesity, cardiovascular and/or respiratory disease, and conditions that interfere with sleep. All-night polysomnography was preceded by a single 50-mg dose of sildenafil or matching placebo randomly administered at bedtime, after a washout period of 1 week. In comparison to placebo, a single 50-mg dose of sildenafil significantly increased the percentage of total sleep time with an arterial oxygen saturation of less than 90% (mean +/- SD, 15.6% +/- 9.6% vs 7.9% +/- 3.3%, [corrected] P < .01), without a difference in the nadir of oxygen desaturation. The mean arterial oxygen saturation also decreased (92.1% +/- 1.9% vs 93.8% +/- 1.3%, P = .03), [corrected] and the desaturation index increased (30.3 +/- 14.5 [corrected] events per hour vs 18.5 +/- 9.1 [corrected] events per hour, P < .001). There was an increase in apnea-hypopnea index (48.1 +/- 20.8 [corrected] events per hour vs 32.3 +/- 11.3 [corrected] events per hour, P = .001), [corrected] involving mostly obstructive events. In patients with severe obstructive sleep apnea, a single 50-mg dose of sildenafil at bedtime worsens respiratory and desaturation events.

Zaprinast, a well-known cyclic guanosine monophosphate-specific phosphodiesterase inhibitor, is an agonist for GPR35

We found that zaprinast, a well-known cyclic guanosine monophosphate-specific phosphodiesterase inhibitor, acted as an agonist for a G protein-coupled receptor, GPR35. In our intracellular calcium mobilization assay, zaprinast activated rat GPR35 strongly (geometric mean EC 50 value of 16 nM), whereas it activated human GPR35 moderately (geometric mean EC 50 value of 840 nM). We also demonstrated that GPR35 acted as a Gα i/o- and Gα 16-coupled receptor for zaprinast when heterologously expressed in human embryonic kidney 293 (HEK 293) cells. These findings will facilitate the research on GPR35 and the drug discovery of the GPR35 modulators.

Hemodynamic effects of inhaled nitric oxide and phosphodiesterase inhibitor (dipyridamole) on secondary pulmonary hypertension following heart valve surgery in adults

Background Inhaled nitric oxide (iNO) is proposed in the management of pulmonary hypertension (PH) in patients undergoing cardiac surgery. Secondary PH related to a long-standing heart valve disease however may be refractory to iNO. Aim of this prospective study was to determine whether the combination of iNO plus dipyridamole (DP), a cyclic guanosine monophosphate-specific phosphodiesterase inhibitor (PDE5), may enhance and/or prolong the response to iNO in adult patients with secondary valve-related PH undergoing cardiac surgery, and attenuate rebound events related to its discontinuation. Methods Responses in 27 patients, 11 male, mean age 72±11 years, with PH due to mitral and/or aortic valve disease, were studied in the Intensive Care Unit after cardiac surgery, during sedation and stable hemodynamic conditions. The effect of isolated iNO administration (40 ppm), iNO combined with DP (0.2 mg/kg i.v.), and DP alone (1 mg/kg/24 h) on pulmonary vascular resistance, mean pulmonary artery pressure, cardiac index, mixed venous O2Sat%, and mean arterial pressure were determined. Results All patients showed at least a 10% decrease in pulmonary vascular resistance vs. baseline after administration of iNO [responders]. Inhaled NO and the combination of iNO/DP produced a reduction of pulmonary vascular resistance and mean pulmonary artery pressure ( p<0.05). Cardiac index improved with a significant difference between iNO and the association iNO/DP versus baseline ( p<0.05). This significant hemodynamic improvement versus baseline was maintained during isolated DP administration ( p<0.05), but not during isolated iNO discontinuation. Mixed venous oxygen saturation showed an overall improvement of 17% ( p<0.05). Conclusions Inhaled NO and DP infusion might represent a valuable association in the management of PH secondary to a heart valve disease in patients undergoing cardiac surgery. Their beneficial hemodynamic effects might be particularly valuable in the management of patients with associated right ventricular dysfunction.

Role of ATP-sensitive K + channels in relaxation of penile resistance arteries

Objectives To investigate the functional presence of adenosine triphosphate (ATP)-sensitive potassium (K +) channels (K ATP) in penile resistance arteries by evaluating the relaxant effects of the selective K ATP channel openers, cromakalim and levcromakalim, and also the involvement of K ATP channels in the relaxation of two drugs currently used in the treatment of erectile dysfunction (ie, prostaglandin E 1 [PGE 1] and sildenafil). Methods Penile resistance arteries were dissected from the horse corpus cavernosum and mounted in microvascular myographs for isometric tension recording. The arteries were precontracted with phenylephrine, and the responses to several vasodilators were tested in the absence and presence of K + channel blockers. Results Cromakalim and levcromakalim evoked complete concentration-dependent relaxations that were blocked by 3 μm of the selective K ATP channel inhibitor glibenclamide. Raising extracellular K + (25 mM) inhibited the relaxations to PGE 1 and to the selective inhibitor of the cyclic adenosine monophosphate-specific phosphodiesterase (PDE 4) rolipram. At a concentration selective for calcium-activated K +(K Ca) channels (3 mM), tetraethylammonium inhibited rolipram responses but not those of PGE 1. However, glibenclamide significantly reduced the relaxation to both PGE 1 and rolipram, but not those induced by the selective inhibitor of the type 5 cyclic guanosine monophosphate-specific phosphodiesterase (PDE 5). Conclusions The present results suggest a functional role for K ATP channels in the relaxation of penile resistance arteries, as well as their differential involvement in the vasodilation to drugs used in the treatment of organic erectile dysfunction. They mediated relaxation to PGE 1 and cyclic adenosine monophosphate-elevating agents, but not those of cyclic guanosine monophosphate-elevating agents such as sildenafil.

Incidence of erectile dysfunction and characteristics of patients before and after the introduction of sildenafil in the United Kingdom: cross sectional study with comparison patients

Erectile dysfunction, the consistent inability to achieve or maintain an erection sufficient for satisfactory sexual performance, is reported to occur in association with cardiovascular disease, diabetes, hypertension, hypercholesterolaemia, smoking, spinal...

Exclusion of the PDE6A gene for generalised progressive retinal atrophy in 11 breeds of dog.

The cyclic guanosine monophosphate specific phosphodiesterase (cGMP-specific PDE) is a key enzyme in the phototransduction cascade of the vertebrate retina. This enzyme consists of two catalytic alpha and beta subunits, two identical inhibitory gamma subunits as well as a delta subunit. Mutations in PDE6A and the PDE6B genes lead to autosomal recessive (ar) forms of retinitis pigmentosa (RP) in human and to the homologous disease in dogs, designated generalised progressive retinal atrophy (gPRA). We investigated the PDE6A gene in 13 gPRA-affected dog breeds including healthy animals, obligate gPRA carriers and gPRA-affected dogs. In the coding region of PDE6A only a rare sequence variation (G103A; Asp35Asn) was found in exon 1 of two healthy Tibet Terriers and one affected Cocker Spaniel. Using single-stranded conformation polymorphism (SSCP) analyses we detected several sequence variations in eight of the PDE6A introns in different investigated breeds. Most informative for excluding the PDE6A gene as a cause for gPRA was a polymorphic microsatellite ((GT)10CG(GT)2CG(GT)12) in intron 14 and four sequence variations in intron 18 for almost all breeds investigated. The sequence variations of PDE6A did not segregate together with gPRA in 11 breeds. Since diseased animals were heterozygous for the polymorphisms, the PDE6A gene is unlikely to harbour the critical mutation causing gPRA in the following breeds: Chesapeake Bay Retriever. Entlebucher Sennenhund, Labrador Retriever. Tibet Mastiff, Dachshund (long- and wire-haired), Tibetan Terrier, Miniature Poodle. Australian Cattle Dog, Cocker Spaniel, Saarloos/Wolfshound, Sloughi.