Phosphodiesterase-5 Activity Research Articles

From Antipsychotic to Neuroprotective: Computational Repurposing of Fluspirilene as a Potential PDE5 Inhibitor for Alzheimer's Disease.

Phosphodiesterase 5 (PDE5) inhibitors have shown great potential in treating Alzheimer's disease by improving memory and cognitive function. In this study, we evaluated fluspirilene, a drug commonly used to treat schizophrenia, as a potential PDE5 inhibitor using computational methods. Molecular docking revealed that fluspirilene binds strongly to PDE5, supported by hydrophobic and aromatic interactions. Molecular dynamics simulations confirmed that the fluspirilene-PDE5 complex is stable and maintains its structural integrity over time. Binding energy calculations further highlighted favorable interactions, indicating that the drug forms a strong and stable bond with PDE5. Additional analyses, including studies of protein dynamics and energy landscape mapping, revealed how the drug interacts dynamically with PDE5, adapting to different conformations and maintaining stability. These findings suggest that fluspirilene may modulate PDE5 activity, potentially offering therapeutic benefits for Alzheimer's disease. This study provides strong evidence for repurposing fluspirilene as a treatment for Alzheimer's and lays the foundation for further experimental and clinical investigations.

Prosopis africana extract inhibits critical enzymes associated with hypertension in vitro and in cyclosporine-induced hypertensive rats

ObjectiveThis study evaluated the antihypertensive properties of leaf extracts of Prosopis africana (PA) in vitro and in hypertensive rats. MethodsEthanol (ELPA) and differential solvent fractions [ethyl-acetate (EAPA), butanol (BLPA), and aqueous (ALPA)] were prepared using standard protocols. Hypertension was induced in female albino Wistar rats intraperitoneally using cyclosporine (25 mg/kg/day) while extracts were administered via oral route. Forty female rats were grouped into 5 (n = 8). Group 1 received 2 ml distilled water, Group 2: (cyclosporine + 2 ml distilled water); Group 3: cyclosporine + captopril (10 mg/kg/day); Group 4: cyclosporine + 1000 mg/kg ELPA and Group 5: cyclosporine + 1500 mg/kg ELPA. The blood pressure of anesthetized rats was measured using LabScribe coupled to a Lab-Trax-4/24T, and the activities of angiotensin-converting enzyme (ACE), arginase, phosphodiesterase-5 (PDE-5), acetylcholinesterase (AChE) and adenosine deaminase (ADA) were evaluated using standard methods. ResultsAll the fractions exerted significantly (p < 0.05) higher ACE inhibitory effect (ELPA = 64.36 ± 0.50%; EAPA = 86.31 ± 0.60%; BLPA= 85.28 ± 2.30 % ; ALPA= 82.27 ± 2.10 % ) than the reference, lisinopril (40.22±0.50 % ); while the butanol fraction (67.05±0.40 % ) showed higher PDE-5 inhibition than the reference, sildenafil (23.06±0.70 % ). Administration of cyclosporine caused notable (p < 0.05) elevation of systolic/diastolic blood (131.00 ± 1.22/93.25 ± 1.49 mmHg) pressure plus elevated heart rate when in comparison with the normotensive rats (106.25 ± 1.65/85.25 ± 1.18 mmHg). Treatment of hypertensive rats with ELPA significantly reduced elevated activities of ACE, PDE-5, AChE, and arginase to values that are not significantly (p < 0.05) different from those of the rats treated with the reference drug. ConclusionThis result could validate the use of P. africana as an antihypertensive agent in folklore.

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.

Coupling of conformational dynamics and inhibitor binding in the phosphodiesterase-5 family.

Phosphodiesterase-5 (PDE5) is responsible for regulating the concentration of the second messenger molecule cGMP by hydrolyzing it into 5'-GMP. PDE5 is implicated in erectile dysfunction and cardiovascular diseases. The substrate binding site in the catalytic domain of PDE5 is surrounded by several dynamic structural motifs (including the α14 helix, M-loop, and H-loop) that are known to switch between inactive and active conformational states via currently unresolved structural intermediates. We evaluated the conformational dynamics of these structural motifs in the apo state and upon binding of an allosteric inhibitor (evodiamine) or avanafil, a competitive inhibitor. We employed enhanced sampling-based replica exchange solute scaling (REST2) method, principal component analysis (PCA), time-lagged independent component analysis (tICA), molecular dynamics (MD) simulations, and well-tempered metadynamics simulations to probe the conformational changes in these structural motifs. Our results support a regulatory mechanism for PDE5, where the α14 helix alternates between an inward (lower activity) conformation and an outward (higher activity) conformation that is accompanied by the folding/unfolding of the α8' and α8″ helices of the H-loop. When the allosteric inhibitor evodiamine is bound to PDE5, the inward (inactive) state of the α14 helix is preferred, thus preventing substrate access to the catalytic site. In contrast, competitive inhibitors of PDE5 block catalysis by occupying the active site accompanied by stabilization of the outward conformation of the α14 helix. Defining the conformational dynamics underlying regulation of PDE5 activation will be helpful in rational design of next-generation small molecules modulators of PDE5 activity.

Almond-citrus peel enriched short bread modulates sexual behaviour and enzymes linked with erectle dysfunction in hypertensive rats

Almond nut (Terminalia catappa) and orange peel (Citrus sinensis) are commonly used as nutraceuticals in folklore for the treatment of degenerative diseases. Erectile dysfunction is a pathology with various predisposing factors such as hypertension and hypercholesterolemia. This study aim to evaluate the effect of almond-citrus peel enriched shortbread on sexual function and biochemical parameters linked with erectile dysfunction in high fat diet (HFD)/Nω-nitro-l-arginine methyl ester hydrochloride (l-NAME)- induced male rats. The experimental rats were distributed into eight groups and fed with shortbread enriched with varying inclusions of almond and citrus peel. Sexual behavioral assessments (mounting number, mounting latency, intromission number and intromission latency) were evaluated. Thereafter, the activities of phosphodiesterase-5 (PDE-5),arginase, malondialdehyde (MDA), reactive oxygen species (ROS), antioxidant indices and nitric oxide (NO) level were evaluated. The result showed significant elevation in mounting latency, intromission latency, MDA level as well as arginase and PDE-5 activities in the penile tissue of the untreated rats. Conversely, the mounting number, intromission number, antioxidant status and NO level were significantly decreased in the untreated groups. Notably, the treatment with almond-citrus peel enriched shortbread and the individual effect of almond (50%) and citrus peel (0.2%) all reversed these trends in the hypertensive rats. However, treatment with the almond (50%)-citrus peel (0.2%) shortbread reinstated the altered sexual behaviour in male rats, enhanced antioxidant status and suppressedphosphodiesterase-5 and arginase activities in HFD/l-NAME-induced rats. The results suggest that almond and citrus peel offer potentials as therapeutic agent in the prevention and management of erectile dysfunction associated with hypertension. Intriguingly, the almond (50%)-citrus (0.2%) formulated shortbread had the best antioxidative and erectogenic effects.However, further in vivo experiments and clinical trials are recommended.

Ameliorative Sexual Behavior and Phosphodiesterase-5 Inhibitory Effects of Spondias mangifera Fruit Extract in Rodents: In Silico, In Vitro, and In Vivo Study.

The ethanolic extracts of Spondias mangifera fruit (SMFE) were evaluated for aphrodisiac activity. The in-vitro phosphodiesterase-5 (PDE-5) inhibition was assessed based on in-silico molecular docking and simulation studies. In addition, the in-vivo sexual behavior was analyzed in the form of mount (MF, ML), intromission (IF, IL), and ejaculation (EF, EL) frequencies and latencies to validate the in-vitro results. Some biochemical parameters, including PDE-5, nitric oxide, and testosterone, were also observed. The above extract constituted β-amyrin, β-sitosterol, and oleanolic acid and showed tremendous binding with phosphodiesterase-5 and sildenafil. Both the sildenafil and ethanolic extracts (200 and 400 mg/kg/d bodyweight) significantly (p < 0.1, p < 0.05) increased MF, IF, and EF, respectively. In contrast, ML and IL significantly (p < 0.1) decreased, and EL significantly (p < 0.1) increased compared with a normal group of animals. The ethanolic extracts (200 and 400 mg/kg/d bodyweight) and sildenafil further significantly (p < 0.05, p < 0.1) diminished PDE-5 activity significantly (p < 0.05, p < 0.1) and enhanced nitric oxide and testosterone levels, as compared with normal rodents. Therefore, the S. mangifera ethanolic extract might be a valuable alternate aphrodisiac for erectile dysfunction.

PDE-5 inhibitors in selected herbal supplements from the Ghanaian market for better erectile function as tested by a bioassay

Herbal supplements sold as ‘all natural’ on various markets in Accra (Ghana) and advertised as highly efficacious in treating erectile dysfunction (ED) were bought and analysed by a PDE-5 enzyme inhibition assay. The claimed efficacy of these products could be the result of inherent plant constituents, but also of intentionally added pharmaceuticals. Medically, ED is treated with potent inhibitors of the phosphodiesterase-5 (PDE-5) enzyme, as in the case of sildenafil. To test the efficacy of the Ghanaian supplements, extracts were made and tested using a PDE-Glo phosphodiesterase assay, a luminescent high-throughput screening (HTS) method.Results revealed that about 90% of the selected samples were able to inhibit PDE-5 activity to a high extent. Estimated concentrations in sildenafil equivalents ranged from traces to very high, with 25 samples (62.5%) pointing at daily doses higher than 25 mg sildenafil equivalents and 9 (22.5%) of these at doses higher than the maximal recommended daily intake of 100 mg sildenafil equivalents. Further investigations are needed to confirm if the observed effects are due to inherent plant constituents or merely the result of added synthetic PDE-5 enzyme inhibitors, especially because doses above 100 mg sildenafil equivalents per day may result in severe health risks.

Diketopiperazine-Based, Flexible Tadalafil Analogues: Synthesis, Crystal Structures and Biological Activity Profile.

Phosphodiesterase 5 (PDE5) is one of the most extensively studied phosphodiesterases that is highly specific for cyclic-GMP hydrolysis. PDE5 became a target for drug development based on its efficacy for treatment of erectile dysfunction. In the present study, we synthesized four novel analogues of the phosphodiesterase type 5 (PDE5) inhibitor—tadalafil, which differs in (i) ligand flexibility (rigid structure of tadalafil vs. conformational flexibility of newly synthesized compounds), (ii) stereochemistry associated with applied amino acid building blocks, and (iii) substitution with bromine atom in the piperonyl moiety. For both the intermediate and final compounds as well as for the parent molecule, we have established the crystal structures and performed a detailed analysis of their structural features. The initial screening of the cytotoxic effect on 16 different human cancer and non-cancer derived cell lines revealed that in most cases, the parent compound exhibited a stronger cytotoxic effect than new derivatives, except for two cell lines: HEK 293T (derived from a normal embryonic kidney, that expresses a mutant version of SV40 large T antigen) and MCF7 (breast adenocarcinoma). Two independent studies on the inhibition of PDE5 activity, based on both pure enzyme assay and modulation of the release of nitric oxide from platelets under the influence of tadalafil and its analogues revealed that, unlike a reference compound that showed strong PDE5 inhibitory activity, the newly obtained compounds did not have a noticeable effect on PDE5 activity in the range of concentrations tested. Finally, we performed an investigation of the toxicological effect of synthesized compounds on Caenorhabditis elegans in the highest applied concentration of 6a,b and 7a,b (160 μM) and did not find any effect that would suggest disturbance to the life cycle of Caenorhabditis elegans. The lack of toxicity observed in Caenorhabditis elegans and enhanced, strengthened selectivity and activity toward the MCF7 cell line made 7a,b good leading structures for further structure activity optimization and makes 7a,b a reasonable starting point for the search of new, selective cytotoxic agents.

β-caryophyllene improves sexual performance via modulation of crucial enzymes relevant to erectile dysfunction in rats.

This study sought to investigate the effect of β-caryophyllene (BCP) on sexual performance, crucial enzymes linked to erectile function as well as lipid peroxidation in the penile tissue of paroxetine (PD)-induced rats. Animals were randomly divided into ten groups of five animals each: normal control (NC), BCP (10mg/kg), BCP (20mg/kg), sildenafil citrate (SD) (20mg/kg), BCP + SD (20mg/kg), PD (20mg/kg), PD + BCP (10mg/kg), PD + BCP (20mg/kg), PD + SD (20mg/kg) and PD + BCP (20mg/kg) + SD (20mg/kg). Oral administration of 20mg/kg body weight of PD for the first 7days was done while treatment with BCP and SD were performed between 8 and 14days prior to euthanasia. The sexual performance study revealed that PD caused erectile dysfuction. Elevated activities of phosphodiesterase-5' (PDE-5'), arginase, adenosine deaminase (ADA), acetylcholinesterase (AChE) and angiotensin-I converting enzyme (ACE) as well as lipid peroxidation level were observed in PD-induced rats when compared to the NC group. However, treatment with sildenafil and/ or β-Caryophyllene significantly reduced the activities of AChE, PDE-5', arginase, ADA, and ACE in penile tissues of PD-induced rats. In addition, co-administration of β-caryophyllene and sildenafil citrate showed better modulatory effects. Thus, β-caryophyllene could represent a potential nutraceutical in the management of erectile dysfunction.

Icariside II, a PDE5 Inhibitor, Suppresses Oxygen-Glucose Deprivation/Reperfusion-Induced Primary Hippocampal Neuronal Death Through Activating the PKG/CREB/BDNF/TrkB Signaling Pathway.

BackgroundIschemic stroke remains the leading cause of death and adult disability. Cerebral ischemic/reperfusion (I/R) injury is caused by ischemic stroke thereafter aggravates overwhelming neuronal apoptosis and even the death of neurons. Of note, hippocampus is more susceptive to cerebral I/R injury than the other brain region. This study was designed to explore the effects and mechanism of icariside II (ICS II), a pharmacologically active compound exists in herbal Epimedii with previous study-proved as a phosphodiesterase 5 (PDE5) inhibitor, on the oxygen glucose deprivation/reoxygenation (OGD/R)-induced primary hippocampal neurons injury.MethodsEffects of ICS II on primary hippocampal neuronal impairment and apoptosis induced by OGD/R were examined by MTT, lactate dehydrogenase (LDH) release, TUNEL staining, and flow cytometry, respectively. Activation of memory-related signaling pathways was measured using Western blot analysis. The direct interaction between ICS II and PDE5 was further evaluated by molecular docking.ResultsICS II (12.5, 25, 50 μM) markedly abrogated OGD/R-induced hippocampal neuronal death as suggested by the increase in neurons viability and the decrease in cellular LDH release. Furthermore, ICS II not only effectively decreased the protein expression and activity of PDE5, restored the 3′5′-cyclic guanosine monophosphate (cGMP) level and its downstream target protein kinase G (PKG) activity but also increased the phosphorylation of cAMP response element binding protein (CREB) level, expressions of brain derived neurotrophic factor (BDNF), and tyrosine protein kinase B (TrkB). Mechanistically, the inhibitory effects of ICS II were abrogated by Rp-8-Br-cGMP (a PKG inhibitor) or ANA-12 (a TrkB inhibitor), which further confirmed that the favorable effects of ICS II were attributed to its activation of the PKG/CREB/BDNF signaling pathways. Intriguingly, ICS II might effectively bind and inhibited PDE5 activity as demonstrated by relatively high binding scores (−6.52 kcal/mol).ConclusionsICS II significantly rescues OGD/R-induced hippocampal neuronal injury. The mechanism is, at least partly, due to inhibition of PDE5 and activation of PKG/CREB/BDNF/TrkB signaling pathway. Hence it is thought that ICS II might be a potential naturally PDE5 inhibitor to combat cerebral I/R injury.

In vitro antioxidant and enzyme inhibitory properties of the n-butanol fraction of Senna podocarpa (Guill. and Perr.) leaf.

Background This study evaluates the antioxidant activity and enzyme inhibitory properties of the n-butanol fraction of Senna podocarpa leaves on α-amylase, α-glucosidase, acetylcholinesterase (AChE), butyrylcholinesterase (BChE), tyrosinase, arginase, phosphodiesterase 5 (PDE-5), and angiotensin converting enzyme (ACE). Methods The total phenol and flavonoids, iron (Fe) chelation, and 2,2-azino-bis-3-ethylbenzothiazoline-6-sulfonic acid (ABTS) free radical scavenging were used to determine the antioxidant activity, and the inhibitory activities of α-glucosidase, α-amylase, AChE, BChE, tyrosinase, arginase, PDE-5 and ACE were also assessed. Results The n-butanol fraction of S. podocarpa shows high total phenol and total flavonoid contents. The n-butanol fraction of S. podocarpa leaves also chelates Fe2+ and ABTS radicals. The n-butanol fraction of S. podocarpa leaves also inhibited α-glucosidase, α-amylase, AChE, BChE, tyrosinase, arginase, PDE-5, and ACE at the concentration tested. Chromatographic analysis displayed the presence of β-elemene, phytol and caryophyllene oxide chrysophanol, 3-oxo-methyl ester, α-humulene, β-caryophyllene, rhein, emodin, and α-copaene. Conclusions Hence, the n-butanol fraction of S. podocarpa leaves demonstrates encouraging feat in controlling and/or managing cognitive dysfunction such as Alzheimer's disease and also hypertension, diabetes, erectile dysfunction, endothelial dysfunction, and hyperpigmentation.

Almond-supplemented diet improves sexual functions beyond Phosphodiesterase-5 inhibition in diabetic male rats

Hyperglycemia, an important feature of diabetes, can cause oxidative stress, which is associated with varieties of diabetic complications including erectile dysfunction. Therefore, this study sought to investigate the effect of almond-supplemented diet on some biochemical indices relevant to erection in diabetic male rats. Forty-two male rats were divided into two groups: A (n = 6) and B (n = 36). Diabetes was induced in Group B via injection of a single dose of STZ (50 mg/kg) intraperitoneally and confirmed 72 h after induction. Diabetic rats (blood glucose ≥250 mg/dL) were subsequently divided into six groups (n = 6). Fourteen days after confirmation of diabetes, rats were fed with diets containing almond drupe and seeds (10 and 20% inclusion) for fourteen days. The effects of the diets on blood glucose, sexual behavior, sexual hormones, phosphodiesterase-5 activity, nitric oxide, H2S, and AGEs levels were evaluated. Significant increase in blood glucose level, phosphodiesterase-5 activity, and glycated hemoglobin was observed in diabetic rats. Furthermore, diabetes caused a significant decrease in nitric oxide, H2S, sexual hormones (testosterone, follicle-stimulating hormone and luteinizing hormone) levels, and sexual behavioral indices. However, treatment with diets supplemented with almond drupe and seeds significantly reversed these effects in diabetic rats. Findings in this study revealed that almond-supplemented diets enhance some important biomarkers relevant to erection in diabetic rats. Thus, dietary inclusion of almond (drupe and seeds) could serve as a cheap and readily available nutraceutical in the management of erectile dysfunction associated with diabetes.

Developing a phosphodiesterase-5 inhibitor assay to detect counterfeit drugs containing phosphodiesterase-5 inhibitors using spectrophotometry

Background: Phosphodiesterase-5 inhibitors (PDE5i) are the first line of drugs used for the treatment of erectile dysfunction. PDE5i inhibits the activities of phosphodiesterase-5 (PDE5) found in corpus cavernosum reducing production of guanosine monophosphate (GMP) that results in vasodilation of blood vessels thereby prolonging penile erection. Various counterfeit drugs adulterated with unknown levels of PDE5i pose a danger with reported undesirable adverse effects on patients. Methods: We developed an assay to detect counterfeit drugs containing PDE5i using spectrophotometry based on a colour change of malachite green from blue to green when exposed to inorganic phosphate (Pi) measured at 630 nm. Initially, a standard graph of a known Pi concentration was established ranging from 0 to 20 µM followed by a dual biochemical reaction system of converting GMP from cGMP by PDE5, generating Pi from the first reaction’s product by calf intestinal alkaline phosphatase (CIAP), and then measuring Pi using an equation derived from the generated standard curve. Dilutions of CX1A, a counterfeit drug sample adulterated with the PDE5i sildenafil, were prepared via ultrasonication and filtration for assay testing and evaluation. Results: Sil was detected from the two separate samples comprised of low and high dilutions of CX1A quantified as 0.673% and 0.407%, respectively, based on a standard curve of pure sildenafil established from 0.1 nM to 300 µM. Conclusions: This PDE5i assay that we developed has the potential to become an alternative analytical method for detecting PDE5i showing comparable results when evaluated using HPLC.

Abstract 120: Protective Role of Vascular Smooth Muscle Rho-Related BTB Domain Containing Protein 1 in Hypertension and Arterial Stiffness

Rho-related BTB domain containing protein 1 (RhoBTB1) is an atypical GTPase associated with human hypertension. RhoBTB1 was decreased in aorta from mice expressing a hypertension (HT)-causing PPARγ mutation (P467L) specifically in vascular smooth muscle (VSM, S-P467L mice). Restoration of VSM RhoBTB1 improved vasodilation, reversed arterial stiffness and HT by suppressing phosphodiesterase 5 (PDE5) activity. Here we sought to reveal the molecular function of RhoBTB1 and study its protective role in Angiotensin II (Ang II) induced hypertension. PDE5 and RhoBTB1 reciprocally co-immunoprecipitated in HEK293 cells; and notably, endogenous Cullin3 from HEK293 cells was also present in RhoBTB1/PDE5 immunoprecipitant. Whereas, RhoBTB1 was not sufficient to inhibit PDE5 activity in vitro (1.9±0.2 vs 1.7 ±0.2 nmol/min/mg, n=3), it was required for PDE5 ubiquitination in HEK293 cells. RhoBTB1-mediated PDE5 ubiquitination was blunted by pan-Cullin inhibitor MLN4924 treatment, and MLN4924 increased PDE5 activity in aorta. Thus, RhoBTB1 serves as a substrate adaptor for Cullin3-Ring ubiquitin ligase (CRL3) complex. Like mutation in PPARγ, Ang II infusion also reduced aortic RhoBTB1 expression. We generated mice with VSM specific, tamoxifen inducible RhoBTB1 (S-RhoBTB1) expression. Activation of RhoBTB1 expression with tamoxifen partially prevented Ang II induced HT and vascular dysfunction. However, activation of the RhoBTB1 transgene after 2-week of Ang II infusion did not reverse established Ang II HT and failed to reverse impaired vasodilation to acetylcholine and sodium nitroprusside in aorta and carotid artery. Remarkably however, arterial stiffness as measured by aortic Pulse Wave Velocity was decreased in S-RhoBTB1 compared to non-transgenic mice receiving Ang II infusion (4.6±0.4 vs 3.2±0.3 mm/ms, p&lt;0.05, n=5-7). In conclusion, RhoBTB1 serves as CRL3 substrate adaptor and promotes PDE5 ubiquitination. Pretreatment with RhoBTB1 partially prevents Ang II HT, while restoration of VSM RhoBTB1 was not sufficient to reverse Ang II mediated HT but showed a potential in reducing arterial stiffness.

Intervening with the Nitric Oxide Pathway to Alleviate Pulmonary Hypertension in Pulmonary Vein Stenosis.

Pulmonary hypertension (PH) as a result of pulmonary vein stenosis (PVS) is extremely difficult to treat. The ideal therapy should not target the high-pressure/low-flow (HP/LF) vasculature that drains into stenotic veins, but only the high-pressure/high-flow (HP/HF) vasculature draining into unaffected pulmonary veins, reducing vascular resistance and pressure without risk of pulmonary oedema. We aimed to assess the activity of the nitric oxide (NO) pathway in PVS during the development of PH, and investigate whether interventions in the NO pathway differentially affect vasodilation in the HP/HF vs. HP/LF territories. Swine underwent pulmonary vein banding (PVB; n = 7) or sham surgery (n = 6) and were chronically instrumented to assess progression of PH. Pulmonary sensitivity to exogenous NO (sodium nitroprusside, SNP) and the contribution of endogenous NO were assessed bi-weekly. The pulmonary vasodilator response to phosphodiesterase-5 (PDE5) inhibition was assessed 12 weeks after PVB or sham surgery. After sacrifice, 12 weeks post-surgery, interventions in the NO pathway on pulmonary small arteries isolated from HP/LF and HP/HF territories were further investigated. There were no differences in the in vivo pulmonary vasodilator response to SNP and the pulmonary vasoconstrictor response to endothelial nitric oxide synthase (eNOS) inhibition up to 8 weeks after PVB as compared to the sham group. However, at 10 and 12 weeks post-PVB, the in vivo pulmonary vasodilation in response to SNP was larger in the PVB group. Similarly, the vasoconstriction to eNOS inhibition was larger in the PVB group, particularly during exercise, while pulmonary vasodilation in response to PDE5 inhibition was larger in the PVB group both at rest and during exercise. In isolated pulmonary small arteries, sensitivity to NO donor SNP was similar in PVB vs. sham groups irrespective of HP/LF and HP/HF, while sensitivity to the PDE5 inhibitor sildenafil was lower in PVB HP/HF and sensitivity to bradykinin was lower in PVB HP/LF. In conclusion, both NO availability and sensitivity were increased in the PVB group. The increased nitric oxide sensitivity was not the result of a decreased PDE5 activity, as PDE5 activity was even increased. Some vasodilators differentially effect HP/HF vs. HP/LF vasculature.

Comparative effects of horseradish (Moringa oleifera) leaves and seeds on blood pressure and crucial enzymes relevant to hypertension in rat

Horseradish (Moringa oleifera) is consumed as a vegetable and used for medicinal purposes. The effects of horseradish (Moringa oleifera) leaves and seeds on blood pressure measurement, enzymatic and non-enzymatic antioxidant status and critical enzymes [angiotensin-1 converting enzyme (ACE), acetylcholinesterase (AChE), arginase, phosphodiesterase-5 (PDE-5)] relevant to hypertension in vivo were determined. Hypertensive rats (HYP) were placed on dietary regimen containing 2% and 4% horseradish leaves and seeds. The result revealed that there were significant (p < 0.05) significant (p < 0.05) reductions in the systolic and diastolic blood pressure levels of HYP fed horseradish leaves and seeds supplemented diets when compared to the elevated levels of HYP. Furthermore, there were significant (p < 0.05) reductions in the activities of arginase, AChE, PDE-5 and ACE of HYP fed horseradish seeds and leaves supplemented diets when compared to HYP. In addition, HYP fed horseradish seeds and leaves supplemented diet had significantly (p < 0.05) higher antioxidant effect when compared to HYP. Thus, the observed salutary effects of the seeds and leaves could be part of the possible biochemical mechanisms behind their folkloric use as antihypertensive plants. However, horseradish leaves showed higher antihypertensive effects than the seeds.

Exogenous l-ARGININE does not stimulate production OF NO or cGMP within the rat corporal smooth muscle cells in culture

Background and aimNitric oxide (NO) is the intracellular chemical responsible for initiating a penile erection. Despite conflicting clinical data, it continues to be publicized and promoted that orally administered l-arginine, the putative substrate for NO, enhances the erectile response presumably by stimulating NO production by the corporal tissues resulting in an increase in cGMP production. To shed light on this issue, an in vitro study was conducted to explore the effect of direct exogenous administration of l-arginine as well as its precursor and metabolite, l-citrulline, on the NO-cGMP pathway within the cavernosal smooth muscle (CSM) cell. Materials and methodsCSM cells obtained from 8 to 10 week old Sprague-Dawley rats were grown in Dulbecco media with 20% fetal calf serum and then incubated with or without l-arginine (L-ARG) or l-citrulline (L-CIT) in a time course and dose-response manner. Sildenafil (0.4 mM), IBMX (1 mM), l-NAME (3 μM), ODQ (5 μM) and Deta Nonoate (10 μM) were used as either inhibitors or stimulators of the NO-cGMP pathway. mRNA and protein were extracted and used for the determination of the phosphodiesterase 5 (PDE5). PDE5 activity was determined by luminometry. cGMP content was determined by ELISA. Nitrite formation, an indicator of NO production, was measured in the cell culture media by a colorimetric assay. The cationic (CAT-1) and neutral (SNAT-1) amino acid transporters for L-ARG and L-CIT, respectively, were determined by Western blot. ResultsWhen compared to untreated CSM cells, incubation with 0.25–4.0 mM of L-ARG or 0.3–4.8 mM of L-CIT anywhere between 3 and 24 h did not result in any additional nitrite or cGMP production. The addition of l-NAME, IBMX or ODQ to these L-ARG and L-CIT treated cells did not alter these results. L-CIT but not L-ARG increased PDE5 mRNA and protein content as well as the activity of the PDE5 enzyme. Both CAT-1 and SNAT-1 were expressed in the CSM cells. ConclusionsThis in vitro study demonstrates that exogenous administration of L-ARG or L-CIT failed to stimulate production of either NO or cGMP by the corporal CSM cells. A re-evaluation of the presumptive role of the exogenous administration of L-ARG in improving the synthesis of NO at least at the level of the CSM cells appears warranted.

Hunteria umbellata seed extract administration modulates activities of phosphodiesterase-5 and purinergic enzymes relevant to erection in normal male rats

Hunteria umbellata is used in Nigerian traditional medicine for the treatment of erectile dysfunction and other male sexual related diseases but the basis remain unclear. This study investigated the effects of H. umbellata on phosphodiesterase-5, ectonucleotidases, adenosine deaminase and acetylcholinesterase activities in experimental animals. Twenty-four male rats were divided into four groups of six animals each; control group, Viagra administered group, 50 and 100 mg/kg body weight H. umbellata treated group. After 28 days of treatment, the animals were sacrificed and the effect of H. umbellata on the activities of enzymes mentioned above was evaluated. The results revealed a significant increase in PDE-5, ATPDase, adenosine deaminase and AChE activities in control group. However, treatment with H. umbellata caused a significant decrease in PDE-5, ATPDase, adenosine deaminase and AChE activities with concomitant increase in 5′-nucleotidase activity. Findings presented in this study revealed that H. umbellata could prevent the impairment of enzymes that regulate purinergic and NO/cGMP signaling and thereby be of biological importance in the management of erectile dysfunction.

Ocimum gratissimum Linn. Leaves reduce the key enzymes activities relevant to erectile dysfunction in isolated penile and testicular tissues of rats

BackgroundOcimum gratissimum L. is a medicinal plant widely grown in tropical and subtropical regions with the leaf decoction usually taken in folk medicine to enhance erectile performance in men although the probable mechanism of actions remains undetermined. This study examined the inhibitory potentials of Ocimum gratissimum leaves on some key enzymes associated with erectile dysfunction in penile and testicular tissues of the rat.MethodsInhibitory effect of aqueous extract (1:10 w/v) of O. gratissimum leaves on the activities of phosphodiesterase-5 (PDE-5), arginase, angiotensin I –converting enzyme (ACE), and acetylcholinesterase (AChE) in penile and testicular tissues were assessed. Also, the extract was investigated for ferric reducing antioxidant property(FRAP) and 1,1-diphenyl-2-picryl-hydrazil (DPPH) radical scavenging abilities.ResultsThe extract showed higher PDE-5 (IC50 = 43.19 μg/mL), ACE (IC50 = 44.23 μg/mL), AChE (IC50 = 55.51 μg/mL) and arginase (IC50 = 46.12 μg/mL) inhibitory activity in the penile tissue than PDE-5 (IC50 = 44.67 μg/mL), ACE (IC50 = 53.99 μg/mL), AChE (IC50 = 60.03 μg/mL) and arginase (IC50 = 49.12 μg/mL) inhibitory activity in the testicular tissue homogenate. Furthermore, the extract scavenged free radicals and in a dose-dependent manner.ConclusionThe enzyme activities displayed might be associated with the bioactive compounds present in the extract which could possibly explain its use in the management of erectile dysfunction (ED).

Icariin and Its Metabolites as Potential Protective Phytochemicals Against Alzheimer's Disease.

Alzheimer’s disease (AD) is a neurodegenerative disorder affecting more than 35 million people worldwide. As the prevalence of AD is dramatically rising, there is an earnest need for the identification of effective therapies. Available drug treatments only target the symptoms and do not halt the progression of this disorder; thus, the use of natural compounds has been proposed as an alternative intervention strategy. Icariin, a prenylated flavonoid, has several therapeutic effects, including osteoporosis prevention, sexual dysfunction amelioration, immune system modulation, and improvement of cardiovascular function. Substantial studies indicate that icariin may be beneficial to AD by reducing the production of extracellular amyloid plaques and intracellular neurofibrillary tangles and inhibiting phosphodiesterase-5 activity. Moreover, increasing evidence has indicated that icariin exerts a protective role in AD also by limiting inflammation, oxidative stress and reducing potential risk factors for AD such as atherosclerosis. This mini-review discusses the multiple potential mechanisms of action of icariin on the pathobiology of AD including explanation regarding its bioavailability, metabolism and pharmacokinetic.