The Wonders of Phosphodiesterase-5 Inhibitors: A Majestic History

Inflammation in cerebral ischemia reperfusion improved by avanafil via nod-like receptor protein-3 inflammasome: an experimental study in rats

OBJECTIVE

The aim of study was to investigate the effect of avanafil, a second-generation phosphodiesterase-5 (PDE5) inhibitor, on cerebral ischemia reperfusion (CI/R) model.

METHODS

32 male albino Wistar rats were used. Four groups were constituted, as I: the healthy (sham), II: the CI/R group, III: the CI/R +I 10 mg/kg avanafil group, and IV: the CI/R + 20 mg/kg avanafil group. Avanafil was administered twice via oral gavage, first shortly after ischemia reperfusion and once more after 12 h. The rats were euthanized after 24 h. Histopathological and Real Time PCR analyzes were performed on cerebral tissues.

RESULTS

IL-1β, NLRP3 and TNF-α mRNA expressions were statistically higher in the CI/R group when compared to healthy (sham) group. Conversely, the IL-1β, NLRP3, and TNF-α mRNA expressions were significantly decreased in both of the avanafil-treated groups when compared to CI/R group. Histopathological results showed that both doses of avanafil also decreased cellular damage in cerebral tissue that occurred after CI/R.

CONCLUSION

Avanafil, was found to have ameliorated inflammatory response and cellular injury caused by CI/R. The mRNA expression of IL-1β, NLRP3, and TNF-α decreased in the I/R groups and approached the control group levels with a high dose of avanafil.

Bioactive Compounds in Moringa oleifera: Mechanisms of Action, Focus on Their Anti-Inflammatory Properties

Moringa oleifera (M. oleifera) is a tropical tree native to Pakistan, India, Bangladesh, and Afghanistan; it is cultivated for its nutritious leaves, pods, and seeds. This scientific study was conducted to outline the anti-inflammatory properties and mechanisms of action of bioactive compounds from M. oleifera. The existing research has found that the plant is used in traditional medicine due to its bioactive compounds, including phytochemicals: flavonoids and polyphenols. The compounds are thought to exert their anti-inflammatory effects due to: (1) inhibition of pro-inflammatory enzymes: quercetin and kaempferol inhibit the pro-inflammatory enzymes (cyclooxygenase and lipoxygenase); (2) regulation of cytokine production: isothiocyanates modulate signaling pathways involved in inflammation, such as the nuclear factor-kappa B (NF-kappa B) pathway; isothiocyanates inhibit the production of pro-inflammatory cytokines such as TNF-α (tumor necrosis factor α) and IL-1β (interleukin-1β); and (3) antioxidant activity: M. oleifera contains flavonoids, polyphenols, known to reduce oxidative stress and inflammation. The review includes M. oleifera's effects on cardiovascular protection, anti-hypertensive activities, type 2 diabetes, inflammatory bowel disease, and non-alcoholic fatty liver disease (NAFLD). This research could prove valuable for exploring the pharmacological potential of M. oleifera and contributing to the prospects of developing effective medicines for the benefit of human health.

Relaxation effects of Eriobotrya japonica toward tracheal smooth muscle via action mechanism on histamine-1 receptor and phosphodiesterase-5 enzyme

The Eriobotrya japonica leaves have the activity to relax the smooth muscle in the respiratory tract. However, the mechanism of action due to that activity has never been carried out. This study aims to determine the relaxation effects of E. japonica leaves extract in the isolated trachea of the guinea pigs through the inhibition of the histamine-1 (H-1) receptor and the phosphodiesterase-5 (PDE-5) enzyme. The determination of the relaxation effects was carried out by using histamine to contract smooth muscle within the tracheal tract, followed by adding cumulative concentrations of extract. Michaelis–Menten kinetics equation was used to determine the antagonist type of extract toward H-1 receptor. The understanding of mechanism of action of the extract toward PDE-5 enzyme was performed by incubating the smooth muscle using sildenafil. The percentage value of responses, originated from the relaxation effect of the extract toward the trachea was analyzed by using the t-independent test. The result showed that the extract was able to relax the smooth muscle, which was contracted by histamine, and there was a positive correlation between concentration and relaxation effect (P < 0.05; r = 0.973). The extract also antagonized the histamine as a noncompetitive antagonist. The incubation within the trachea with sildenafil demonstrated equal relaxation effect, produced by the extract. It can be concluded that E. japonica extract had relaxation effect within the isolated trachea as antagonist noncompetitive toward H-1 receptor and inhibitor of the PDE-5 enzyme.

Phosphodiesterases in the Liver as Potential Therapeutic Targets of Cirrhotic Portal Hypertension

Liver cirrhosis is a frequent condition with high impact on patients' life expectancy and health care systems. Cirrhotic portal hypertension (PH) gradually develops with deteriorating liver function and can lead to life-threatening complications. Other than an increase in intrahepatic flow resistance due to morphological remodeling of the organ, a functional dysregulation of the sinusoids, the smallest functional units of liver vasculature, plays a pivotal role. Vascular tone is primarily regulated by the nitric oxide-cyclic guanosine monophosphate (NO-cGMP) pathway, wherein soluble guanylate cyclase (sGC) and phosphodiesterase-5 (PDE-5) are key enzymes. Recent data showed characteristic alterations in the expression of these regulatory enzymes or metabolite levels in liver cirrhosis. Additionally, a disturbed zonation of the components of this pathway along the sinusoids was detected. This review describes current knowledge of the pathophysiology of PH with focus on the enzymes regulating cGMP availability, i.e., sGC and PDE-5. The results have primarily been obtained in animal models of liver cirrhosis. However, clinical and histochemical data suggest that the new biochemical model we propose can be applied to human liver cirrhosis. The role of PDE-5 as potential target for medical therapy of PH is discussed.

Phosphodiesterase inhibitors say NO to Alzheimer's disease

Phosphodiesterases (PDEs) consisted of 11 subtypes (PDE1 to PDE11) and over 40 isoforms that regulate levels of cyclic guanosine monophosphate (cGMP) and cyclic adenosine monophosphate (cAMP), the second messengers in cell functions. PDE inhibitors (PDEIs) have been attractive therapeutic targets due to their involvement in diverse medical conditions, e.g. cardiovascular diseases, autoimmune diseases, Alzheimer's disease (AD), etc. Among them; AD with a complex pathology is a progressive neurodegenerative disorder which affect mostly senile people in the world and only symptomatic treatment particularly using cholinesterase inhibitors in clinic is available at the moment for AD. Consequently, novel treatment strategies towards AD are still searched extensively. Since PDEs are broadly expressed in the brain, PDEIs are considered to modulate neurodegenerative conditions through regulating cAMP and cGMP in the brain. In this sense, several synthetic or natural molecules inhibiting various PDE subtypes such as rolipram and roflumilast (PDE4 inhibitors), vinpocetine (PDE1 inhibitor), cilostazol and milrinone (PDE3 inhibitors), sildenafil and tadalafil (PDE5 inhibitors), etc have been reported showing encouraging results for the treatment of AD. In this review, PDE superfamily will be scrutinized from the view point of structural features, isoforms, functions and pharmacology particularly attributed to PDEs as target for AD therapy.

Degree of Planning of Sexual Intercourse Among Men From China, Japan, and Taiwan Taking Medication for Erectile Dysfunction: Findings of an Observational, Cross-Sectional Survey

INTRODUCTION

Management of erectile dysfunction (ED) is beset with assumptions around spontaneity of sexual intercourse, requiring candor between the physician and patient if appropriate treatment is to be implemented.

AIM

To evaluate the degree to which men who take ED medications plan for and have sex.

METHODS

Men from China, Japan, and Taiwan aged 40-70 years who had taken ED medications within the past 3 months were invited to participate anonymously in an online, self-administered survey that enquired about frequency and advance planning of sex, time between taking ED medication and intercourse, and treatment satisfaction. Data were analyzed using descriptive statistics.

MAIN OUTCOME MEASURE

Frequency of planning of sexual intercourse, planning and ED medication dosing interval, and frequency of ED medication use.

RESULTS

Data from 604 respondents (mean age 50.8 years) from China (n = 254), Japan (n = 250), and Taiwan (n = 100) were collected. Men used ED medications a median of ≤4 times per month in all 3 territories. 76% who used ED medication during the past 3 months planned for sex on specific occasions, with 59% and 52% agreeing that they plan for sex on specific days of the week and times of the day, respectively. Most commonly, men planned for sex up to several hours to a day beforehand, with 94% taking ED medication within 4 hours of sex. Satisfaction with ED medication was generally high and related to erection rigidity, speed of onset, and safety.

CONCLUSION

Knowledge of the degree to which individuals with ED plan for sex may have important implications for the appropriate prescription of ED medication. The high degree of planning around sexual activities exhibited by men taking ED medication suggests there is a need for appropriate counseling to ensure that treatment is aligned with patient behavior. Jiann B-P, Nakajima K, Dighe S, et al. Degree of planning of sexual intercourse among men from China, Japan, and Taiwan taking medication for erectile dysfunction: Findings of an observational, cross-sectional survey. Sex Med 2019;7:54-60.

Phosphodiesterase inhibitors: Potential role in the respiratory distress of neonates

Phosphodiesterases (PDEs) are a superfamily of enzymes that catalyze the hydrolysis of phosphodiester bonds of 3',5' cyclic adenosine and guanosine monophosphate (cAMP and cGMP). PDEs control hydrolysis of cyclic nucleotides in many cells and tissues. Inhibition of PDEs by selective or nonselective PDE inhibitors represents an effective targeted strategy for the treatment of various diseases including respiratory disorders. Recent data have demonstrated that PDE inhibitors can also be of benefit in respiratory distress in neonates. This article outlines the pharmacological properties of nonselective and selective PDE inhibitors and provides up-to-date information regarding their use in experimental models of neonatal respiratory distress as well as in clinical studies.

Genetics of guanylyl cyclase pathways in the cochlea and their influence on hearing

Although hearing loss is the most common sensory deficit in Western societies, there are no successful pharmacological treatments for this disorder. Recent experiments have demonstrated that manipulation of intracellular cyclic guanosine monophosphate (cGMP) concentrations can have both beneficial and harmful effects on hearing. In this review, we will examine the role of cGMP as a key second messenger involved in many aspects of cochlear function and discuss the known functions of downstream effectors of cGMP in sound processing. The nitric oxide-stimulated soluble guanylyl cyclase system (sGC) and the two natriuretic peptide-stimulated particulate GCs (pGCs) will be more extensively covered because they have been studied most thoroughly. The cochlear GC systems are attractive targets for medical interventions that improve hearing while simultaneously representing an under investigated source of sensorineural hearing loss.

The effect of phosphodiesterase-5 inhibitors on cerebral blood flow in humans: A systematic review

Agents that augment cerebral blood flow (CBF) could be potential treatments for vascular cognitive impairment. Phosphodiesterase-5 inhibitors are vasodilating drugs established in the treatment of erectile dysfunction (ED) and pulmonary hypertension. We reviewed published data on the effects of phosphodiesterase-5 inhibitors on CBF in adult humans. A systematic review according to PRISMA guidelines was performed. Embase, Medline and Cochrane Library Trials databases were searched. Sixteen studies with 353 participants in total were retrieved. Studies included healthy volunteers and patients with migraine, ED, type 2 diabetes, stroke, pulmonary hypertension, Becker muscular dystrophy and subarachnoid haemorrhage. Most studies used middle cerebral artery flow velocity to estimate CBF. Few studies employed direct measurements of tissue perfusion. Resting CBF velocity was unaffected by phosphodiesterase-5 inhibitors, but cerebrovascular regulation was improved in ED, pulmonary hypertension, diabetes, Becker's and a group of healthy volunteers. This evidence suggests that phosphodiesterase-5 inhibitors improve responsiveness of the cerebral vasculature, particularly in disease states associated with an impaired endothelial dilatory response. This supports the potential therapeutic use of phosphodiesterase-5 inhibitors in vascular cognitive impairment where CBF is reduced. Further studies with better resolution of deep CBF are warranted. The review is registered on the PROSPERO database (registration number CRD42016029668).

Novel methods in pulmonary hypertension phenotyping in the age of precision medicine (2015 Grover Conference series)

Among pulmonary vascular diseases, pulmonary hypertension (PH) is the best studied and has been the focus of our work. The current classification of PH is based on a relatively simple combination of patient characteristics and hemodynamics. This leads to inherent limitations, including the inability to customize treatment and the lack of clarity from a more granular identification based on individual patient phenotypes. Accurate phenotyping of PH can be used in the clinic to select therapies and determine prognosis and in research to increase the homogeneity of study cohorts. Rapid advances in the mechanistic understanding of the disease, improved imaging methods, and innovative biomarkers now provide an opportunity to define novel PH phenotypes. We have recently shown that altered metabolism may affect nitric oxide levels and protein glycosylation, the peripheral circulation (which may provide insights into the response to therapy), and exhaled-breath analysis (which may be useful in disease evaluation). This review is based on a talk presented during the 2015 Grover Conference and highlights the relevant literature describing novel methods to phenotype pulmonary arterial hypertension patients by using approaches that involve the pulmonary and systemic (peripheral) vasculature. In particular, abnormalities in metabolism, the pulmonary and peripheral circulation, and exhaled breath in PH may help identify phenotypes that can be the basis for a precision-medicine approach to PH management. These approaches may also have a broader scope and may contribute to a better understanding of other diseases, such as asthma, diabetes, and cancer.