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Background: Extract of the wild orchid, Eulophia macrobulbon (EM) inhibits phosphodiesterase5 (PDE5) suggesting it could preferentially dilate the pulmonary vasculature.Purpose and Study Design: To pharmacologically characterize the vascular actions of EM ethanolic extract and its active compound, 1-(4'-hydroxybenzyl)-4,8-dimethoxyphenanthrene-2,7-diol using isolated pulmonary arteries (PA) from rats having pulmonary arterial hypertension (PAH) induced by monocrotaline (MCT). PA were fixed and prepared for histology.Results: EM extract relaxed PA (EC50 = 0.17  mg/ml, Emax ∼ 94%) but less so for aorta (EC50 = 0.51 mg/ml, Emax ∼ 62%), suggesting some selectivity towards the pulmonary circulation. PA vasorelaxation was reduced by endothelial removal or NG-nitro-L-arginine methyl ester, but unaffected by indomethacin, apamin +charybdotoxin, 4-aminopyridine, glibenclamide, iberiotoxin, or 1H - [1,2,4]oxadiazolo[4,3-a]quinoxalin -1- one. Sodium nitroprusside-induced relaxation was enhanced by EM extract, probably via PDE5 inhibition. EM extract reduced contractions evoked by extracellular Ca2+application, and inhibited intracellular Ca2+release activated by phenylephrine. The phenanthrene relaxed PA independently of the endothelium. MCT thickened walls and decreased lumens of PA, and hypertrophied right ventricular myocytes, effects ameliorated by 3 weeks of oral sildenafil (20  mg/kg) or EM extract (15, 450 or 1000  mg/kg).Conclusion: PAH is improved by EM extract acting through PA relaxation mediated through endothelial NO, reduced Ca2+-mobilization, and reduced PA wall thickness and right ventricular hypertrophy. [ABSTRACT FROM AUTHOR]

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

Idiopathic pulmonary arterial hypertension (IPAH) is a progressive and fatal disease of the pulmonary artery resulting from currently unidentified etiology. IPAH is pathologically characterized as sustained vasoconstriction and vascular remodeling of the pulmonary artery. Phosphodiesterase type 5 (PDE5) inhibitors have been clinically used in the treatment of IPAH. Recently, we have shown that Ca 2+ -sensing receptor (CaSR) antagonists, or calcilytics, inhibit excessive cell proliferation of pulmonary arterial smooth muscle cells (PASMCs) from IPAH patients. In this study, the additive or synergistic effect of calcilytics on antiproliferation following PDE5 inhibition was examined in IPAH-PASMCs by MTT assay. Treatment with sildenafil blocked the excessive cell proliferation of IPAH-PASMCs in a concentration-dependent manner with an IC 50 value of 16.9 μM. However, sildenafil (0.03–100 μM) did not affect the cell growth of PASMCs from normal subjects and patients with chronic thromboembolic pulmonary hypertension (CTEPH). Co-treatment with 0.3 μM NPS2143, a calcilytic, additively enhanced the antiproliferative effect induced by sildenafil (3 or 30 μM) in IPAH-PASMCs. Additionally, the inhibitory effect of calcilytics, NPS2143 or Calhex 231 (1 or 10 μM), on excessive cell proliferation of IPAH-PASMCs was synergistic increased in the presence of 1 μM sildenafil. Similar results were obtained by BrdU incorporation assay. These findings reveal that calcilytics additively/synergistically enhance the antiproliferative activity mediated by PDE5 inhibition, suggesting that a combination therapy of a PDE5 inhibitor with a calcilytic may be useful as a novel therapeutic approach for IPAH. [ABSTRACT FROM AUTHOR]

Abstract: A concise enantioselective strategy for the synthesis of key PDE5 inhibitor 2 was developed in 5 and 6 steps using asymmetric hydrogenation and one-pot chiral auxiliary approaches, respectively. The synthesis features the use of imine 6 obtained through Bischler–Napieralsky reaction from amide 5. Absolute R configuration was introduced in (+)-7 by asymmetric transfer-hydrogenation reaction with Ru(II) catalyst followed by establishing the tricyclic pyrroloquinalone core using the Winterfeldt oxidation. Another alternative synthetic approach for the introduction of chirality in the molecule employed imine 6 and chloroformates of different chiral auxiliaries, which achieved N-acyliminium ion intermediates that were reduced in situ using PdCl2/Et3SiH protocol. These synthetic routes were applied in the total synthesis of promising male erectile dysfunction (MED) PDE5 inhibitor 1. [Copyright &y& Elsevier]

Abstract: Berberine is an isoquinoline alkaloid isolated from Berberis aristata, a major herb widely used in Indian and Chinese systems of medicine. Berberine possessed a wide range of biological activity including antidiarrheal, antimicrobial, anti-inflammatory effects and some central nervous system activity as well. The present study was designed to explore the antidepressant activity and its possible mechanism of action. Further, the involvement of l-arginine-nitric oxide (NO)-cyclic guanosine monophosphate (cGMP) signaling pathway in the antidepressant action of berberine chloride was investigated. The antidepressant activity was assessed in forced-swim and tail-suspension tests. Total immobility period was recorded during a six-min test. Berberine (5-20 mg/kg, i.p.) produced a reduction in immobility period in both the tests. When berberine (5 mg/kg, i.p.) was co-administered with other antidepressant drugs, it enhanced the anti-immobility effect of subeffective doses of imipramine (2 mg/kg, i.p.), desipramine (5 mg/kg, i.p.), tranylcypromine (4 mg/kg, i.p.), fluoxetine (5 mg/kg, i.p.), venlafaxine (2 mg/kg, i.p.) or bupropion (10 mg/kg, i.p.) in forced-swim test. However, berberine did not modify the effects of mianserine (32 mg/kg, i.p.) or trazodone (2 mg/kg, i.p.), the two atypical antidepressant drugs. The neurochemical analysis revealed that berberine (5 mg/kg, i.p.) increased the levels of norepinephrine, serotonin or dopamine in the mouse whole brain. The antidepressant-like effect of berberine (5 mg/kg, i.p.) in forced-swim test was prevented by pretreatment with l-arginine (750 mg/kg, i.p.) [substrate for nitric oxide synthase (NOS)]. Pretreatment of mice with 7-nitroindazole (25 mg/kg, i.p.) [a specific neuronal nitric oxide synthase (nNOS) inhibitor] produced potentiation of the action of subeffective dose of berberine (2 mg/kg, i.p.). In addition, treatment of mice with methylene blue (10 mg/kg, i.p.) [direct inhibitor of both nitric oxide synthase (NOS) and soluble guanylate cyclase (sGC)] potentiated the effect of berberine (2 mg/kg, i.p.) in the forced-swim test. Furthermore, the reduction in the immobility period elicited by berberine (5 mg/kg, i.p.) was also inhibited by pretreatment with sildenafil (5 mg/kg, i.p.) [phosphodiesterase 5 inhibitor]. The various modulators and their combination with berberine did not produce any changes in locomotor activity. Our findings demonstrated that berberine exerted antidepressant-like effect in various behavioural paradigms of despair possibly by modulating brain biogenic amines (norepinephrine, serotonin or dopamine) and further, the antidepressant-like effect of berberine in the forced-swim test involved an interaction with the l-arginine-NO-cGMP pathway. [Copyright &y& Elsevier]

Abstract: Objectives: Phosphodiesterase 5 (PDE5) inhibitors improve smooth muscle relaxation and therefore are considered for pharmacotherapy of benign prostatic hyperplasia (BPH) and lower urinary tract symptoms (LUTS). Cyclic guanosine monophosphate (cGMP)-dependent protein kinase-1 (cGKI) has been identified as one of the downstream targets for cGMP. The aim of the present study was to evaluate, by means of immunohistochemistry and Western blot analysis, the expression and localization of cGKI isoforms in relation to smooth muscle α-actin and cGMP in the human prostate. Methods: Cryostat sections of tissue segments excised from the transition zone of human prostates from 11 patients (aged 54–68 yr) were incubated with primary antibodies directed against smooth muscle α-actin, cGMP, cGKI, cGKIα, and cGKIβ. Visualization of double-labelled immunofluorescent staining was achieved by laser microscopy. Western blot analysis was performed to confirm the expression of cGKI isoforms. Results: Immunoreactivities specific for cGKI, cGKIα, and cGKIβ were observed in the smooth musculature of the transition zone. Double-staining revealed the colocalization of smooth muscle α-actin, cGMP, and cGKI isoforms in smooth muscle cells of the fibromuscular stroma. The expression of cGKI isoforms was confirmed by Western blot analysis. Conclusions: Our results confirm the presence of cGKI isoforms α and β in the transition zone of human prostate tissue. In addition, the colocalization of α-actin, cGMP, and cGKI isoforms provides further evidence for a significant role of the nitric oxide/cGMP pathway in the regulation of smooth muscle contractility in human prostate tissue and therefore could provide additional targets for pharmacotherapy of BPH and LUTS. [Copyright &y& Elsevier]

Abstract: The involvement of l-arginine–nitric oxide (NO)–cyclic guanosine monophosphate (cGMP) signaling pathway in the antidepressant action of venlafaxine (dual serotonin and norepinephrine reuptake inhibitor) was investigated in mice. The antidepressant activity was assessed in forced swim test (FST) behavioral paradigm. Total immobility time was registered during the period of 6 min. Venlafaxine produced dose-dependent (4–16 mg/kg, i.p.) reduction in immobility period. The antidepressant-like effect of venlafaxine (8 mg/kg, i.p.) was prevented by pretreatment with l-arginine (750 mg/kg, i.p.) [substrate for nitric oxide synthase (NOS)]. Pretreatment of mice with 7-nitroindazole (7-NI) (25 mg/kg, i.p.) [a specific neuronal nitric oxide synthase (nNOS) inhibitor] produced potentiation of the action of subeffective dose of venlafaxine (2 mg/kg, i.p.). In addition, treatment of mice with methylene blue (10 mg/kg, i.p.) [direct inhibitor of both nitric oxide synthase (NOS) and soluble guanylate cyclase (sGC)] potentiated the effect of venlafaxine (2 mg/kg, i.p.) in the FST. Furthermore, the reduction in the immobility time elicited by venlafaxine (8 mg/kg, i.p.) was also inhibited by pretreatment with sildenafil (5 mg/kg, i.p.) [phosphodiesterase 5 inhibitor]. The various modulators used in the study did not produce any changes in locomotor activity per se. The results demonstrated that the antidepressant-like effect of venlafaxine in the FST involved an interaction with the l-arginine–NO–cGMP pathway. [Copyright &y& Elsevier]

Abstract: Gene expression changes in the corpus cavernosum of hypercholesterolemic rats were not fully assessed, which were not previously known to be associated with hypercholesterolemia-related erectile dysfunction (ED). To provide molecular insight into pathophysiology of hypercholesterolemia-related ED and to investigate the effects of Udenafil, a phosphodiesterase type 5 (PDE5) inhibitor, on gene expression, we performed microarray gene expression analysis via gene discovery methods using GenoCheck platinum cDNA chip (Ansan, S. Korea). Sixteen male Sprague-Dawley rats were fed 2% cholesterol diet for 5 months. Half of them were orally treated with Udenafil (20 mg/kg/day) simultaneously. Eight age-matched rats fed normal diet were served as normal control. RNA was extracted from corpus cavernosum and microarray analysis was performed. Decreased erectile responses and hypercholesterolemia were observed in hypercholesterolemic control group. In microarray analysis, 122 candidate genes were noted to be altered based on the magnitude of expression changes, which includes 44 down-regulated and 78 up-regulated genes compared with the age-matched normal controls. These changes were, however, significantly attenuated by treatment with Udenafil. Out of the 78 up-regulated genes, 8 genes were significantly decreased by the chronic treatment with Udenafil. The altered genes were cytochrome oxidase biogenesis protein OXA1, skeletal muscle myosin heavy chain, lipophilin, fast skeletal muscle isoforms beta/alpha, myosin light chain 3, cytochrome c oxidase, adipocyte fatty acid binding protein and one EST gene. In contrast, among the 44 down-regulated genes, Kruppel-like factor 5 and cyclin D1 genes were increased after the Udenafil treatment. These results provide the molecular basis for understanding the pathogenesis of hypercholesterolemia-related ED and offer clues on determining the underlying action mechanism of a PDE5 inhibitor. [Copyright &y& Elsevier]

Abstract: This work presents a chemometric classification for a set of phosphodiesterase 5 inhibitors, based on a pattern recognition method widely used in quantitative structure–activity (QSAR) studies, hierarchical cluster analysis (HCA) and principal component analysis (PCA), aiming to access the most relevant structural and physicochemical variables related to phosphodiesterase 5 inhibition and to quantify the similarity of the structures within the set of inhibitors. Our model is capable of classifying a test set of 26 known phosphodiesterase 5 inhibitors in terms of similarity, the results being consistent with published experimental data. [Copyright &y& Elsevier]

Summary: Obesity hypoventilation syndrome (OHS) is often associated with pulmonary hypertension (PH), and noninvasive bi-level positive airway pressure therapy is indicated as first-line treatment. However, its effect in reducing pulmonary arterial pressure is insufficient in many cases, thus adjunctive therapies should be evaluated. In this report, we present a patient with OHS-associated PH who was successfully treated by tadalafil in conjunction with weight reduction and bi-level positive airway pressure therapy. [ABSTRACT FROM AUTHOR]