Phosphodiesterase-5 Research Articles

Structural optimization and bioactivity evaluation of 2-(Methylcarbonylamino) thiazole derivatives as novel PDE4B inhibitors

Phosphodiesterase-4 (PDE4) is a protease belonging to the phosphodiesterase family, with a specific function of hydrolyzing intracellular cyclic adenosine monophosphate (cAMP). PDE4 is widely distributed across various human tissues and cells, where it plays a pivotal role in modulating intracellular cAMP levels, particularly in immune and inflammatory cells. Consequently, PDE4 inhibitors have been proven to effectively dampen inflammatory responses in these cells, leading to a reduction in the release of pro-inflammatory factors such as lipid mediators, reactive oxygen species (ROS) hydrolases, cytokines, and chemokines. Despite the considerable interest from both academia and pharmaceutical industries in exploiting this target for drug development, only a handful of PDE4 inhibitors are available in the market. The aim of this study was to identify novel PDE4B inhibitors through a combined approach of computer-aided drug design, synthesis, and activity evaluation. The study implemented three phases of structure optimization from the hit compound MR9, which was previously obtained by virtual screening, with reference to structure-based drug design (SBDD) and ligand-based drug design (LBDD) approaches. The optimized compound MR9-302 (PDE4B IC50=2.02±0.2888 μM) exhibited enhanced inhibitory activity compared to MR9.

VP3.15 reduces acute cerebellum damage after germinal matrix-intraventricular hemorrhage of the preterm newborn

Germinal matrix-intraventricular hemorrhage (GM-IVH) is one of the most common complications of the preterm newborn. The pathology of the GM-IVH is not completely understood and even regions distant from the lesion area are severely affected. It has been suggested that cerebellar diaschisis may underlie the neurodevelopmental problems that many of these kids show, including cerebral palsy, attention deficit disorders or hyperactivity. Additionally, GM-IVH has no successful treatment. VP3.15 is a dual action phosphodiesterase 7 (PDE7) and glycogen synthase kinase-3β (GSK-3β) inhibitor that limits neuroinflammation and neuronal loss. Therefore, it might also provide a relevant tool to reduce complications associated with GM-IVH. We have used a murine model of GM-IVH to analyze the short and long-term effects of VP3.15 in brain pathology and behavioral complications. In our hands, the induction of unilateral GM-IVH to P7 CD1 mice results in a short-term (P14) compromise of the cerebellar neuronal population and Purkinje cells arborization, an increase of microglia burden in the nuclei and an overall increase of punctuate cerebellar hemorrhages. Whereas brain alterations are no longer observed in the long term (P110), these animals present overt hyperactivity when analyzed in the adulthood, supporting the long-term behavioral impairment. Also, hyperactivity significantly correlates with ipsi and contralateral cerebellar sizes, neuronal densities and myelin basic protein levels. Importantly, treatment with VP3.15 significantly reduces neuronal loss, Purkinje cells simplification, the presence of cerebellar hemorrhages, as well as hyperactivity. Altogether, our data support the neuroprotective effects of VP3.15 in GM-IVH of the PT.

Development of selective heterocyclic PDE4 inhibitors for treatment of psoriasis

Psoriasis is a chronic autoimmune disease that badly affects the life quality of patients and their families. Inadequate efficacy, safety risks, high cost and low compliance of current psoriasis drugs urge development of novel small molecular drugs. In this study, two series of 37 novel compounds were designed and synthesized as inhibitors of phosphodiesterase 4 (PDE4) that specifically hydrolyzes second messenger cAMP and is an effective target for treatment of inflammatory diseases. Comprehensive structural-activity optimization led to finding of inhibitor 2e with IC50 = 2.4 nM for PDE4D and >4100-fold selectivity over other PDE families. Compound 2e inhibited the release of TNF-α (IC50 = 21.36 μM) and IL-6 (IC50 = 29.22 μM) in the LPS-stimulated Raw264.7 cells. Topical application of 2e exhibited remarkable therapeutic efficacy in imiquimod-induced psoriasis mice model, suggesting that 2e is a strong drug candidate for treatment of psoriasis.

7360 An Overlooked Cause of Hypoglycemia and Weight Loss: Phosphodiesterase-4 Inhibitors

Abstract Disclosure: J. Aurora: None. K. Cappetta: None. R.M. Lechan: None. Background: Phosphodiesterase-4 (PDE-4) inhibitors, apremilast and roflumilast, are anti-inflammatory agents used to treat psoriasis, psoriatic arthritis, and COPD. These agents are commonly associated with gastrointestinal intolerance. However, patients may also experience profound weight loss (>10%). We present a case of a patient with T2DM who developed significant hypoglycemia and weight loss on apremilast. Clinical Case: A 57-year-old female with T2DM, obesity, psoriasis, and postsurgical hypothyroidism due to papillary thyroid cancer developed symptoms of hypoglycemia and weight loss over 1 month. Prior to this, her A1c was 7.8% and weight 104 kg on stable doses of metformin, repaglinide, and insulin glargine. Insulin glargine and repaglinide were both discontinued given her symptoms, yet hypoglycemia persisted, and she continued to lose weight. Further investigations into the cause of this sudden change were carried out. Initial fasting labs: BG 53 mg/dL, C-peptide 4.48 ng/mL (RR 0.8-3.85 ng/mL), insulin 12.8 uIU/mL (RR <18.4 uIU/mL), proinsulin 29.8 pmol/L (RR <18.8 pmol/L), A1c 6.8%, cortisol 24.9 mcg/dL (RR 4-22 mcg/dL), IGF-1 95 ng/mL (Z-score -0.7), and IGF-2 434 ng/mL (RR 267-616 ng/mL). 1 month later, hypoglycemia symptoms improved but she continued to lose weight. Fasting labs were repeated: BG 84 mg/dL, C-peptide 5.62 ng/mL, insulin 24.3 uIU/mL, proinsulin 35 pmol/L, and beta-hydroxybutyrate (BHB) 0.17 mmol/L (RR <0.28 mmol/L); metformin was subsequently stopped. A MR abdomen revealed a 2 cm cystic pancreatic lesion that showed atypical mucinous epithelium by biopsy under endoscopic ultrasound guidance. Gallium-68 DOTATATE-PET scan was unremarkable for an insulin-producing tumor. Two months off metformin, she had no further episodes of hypoglycemia, but her weight loss continued. Fasting labs were repeated: BG 129 mg/dL, C-peptide 5.15 ng/mL, insulin 18.2 uIU/mL, proinsulin 40.5 pmol/L, and BHB 0.27 mmol/L. Review of her medications identified apremilast as a potential culprit contributing to both her hypoglycemia and weight loss, as her symptoms started 1 month after starting apremilast. Over 9 months using apremilast, her A1c decreased by 1% and weight decreased by 27%. Hypoglycemia resolved off all glucose-lowering agents. Conclusion: Significant weight loss with apremilast may be explained by PDE-4 inhibition increasing cyclic AMP, which triggers the release of GLP-1 with subsequent effects on pancreatic beta cells. Apremilast has also been shown to significantly increase fasting insulin levels in patients without insulin resistance, as seen in our patient (1). Given these effects, patients may be at higher risk of hypoglycemia with concurrent glucose-lowering agents, particularly secretagogues. BG and weight need careful monitoring for patients with T2DM using PDE-4 inhibitors. Reference: 1. Ikumi K, et al. J Dermatol. 2022;49(4):e125-e126. Presentation: 6/3/2024

A Brief Overview of Cholinergic and Phosphodiesterase-5 Inhibitors in Diabetic Bladder Dysfunction.

Diabetic bladder dysfunction (DBD) comprises a wide spectrum of lower urinary tract symptoms that impact diabetic patients' lives, including urinary frequency, urgency, incontinence, and incomplete bladder emptying. To relieve symptoms, anticholinergics have been widely prescribed and are considered an effective treatment. There is increasing evidence that diabetic patients may benefit from the use of phosphodiesterase 5 (PDE5) inhibitors. This narrative review aims to provide a brief overview of the pathophysiology of DBD along with a focus on cholinergic and phosphodiesterase inhibitors as therapies that benefit DBD. An examination of the literature suggests compelling avenues of research and underscores critical gaps in understanding the mechanisms underlying DBD. New tools and models, especially rodent models, are required to further elucidate the mechanisms of action of current therapies in the treatment of DBS.

Diminished nuclear-localized β-adrenoceptor signalling activates YAP to promote kidney fibrosis in diabetic nephropathy.

Diabetic nephropathy (DN) is a leading cause of chronic kidney disease (CKD), which is characterized by mesangial matrix expansion that involves dysfunctional mesangial cells (MCs). However, the underlying mechanisms remain unclear. This study aims to delineate the spatiotemporal contribution of adrenergic signalling in diabetic kidney fibrosis to reveal potential therapeutic targets. A model of diabetic nephropathy was induced by in db/db mice. Gene expression in kidneys was profiled by RNA-seq analyses, western blot and immunostaining. Subcellular-localized fluorescence resonance energy transfer (FRET) biosensors determined adrenergic signalling microdomains in MCs. Effects of oral rolipram, a phosphodiesterase 4 (PDE4) inhibitor, on the model were measured. Our model exhibited impaired kidney function with elevated expression of adrenergic and fibrotic genes, including Adrb1, PDEs, Acta2 and Tgfβ. RNA-seq analysis revealed that MCs with dysregulated YAP pathway were crucial to the extracellular matrix secretion in kidneys from diabetic nephropathy patients. In cultured MCs, TGF-β promoted profibrotic gene transcription, which was regulated by nuclear-localized β-adrenoceptor signalling. Mechanistically, TGF-β treatment diminished nuclear-specific cAMP signalling in MCs and reduced PKA-dependent phosphorylation of YAP, leading to its activation. In parallel, db/db mouse kidneys showed increased expressions of PDE4B and PDE4D. Treatment with oral rolipram alleviated kidney fibrosis in db/db mice. Diabetic nephropathy impaired nuclear-localized β1-adrenoceptor-cAMP signalling microdomain through upregulating PDE4 expression, promoting fibrosis in MCs via PKA dephosphorylation-dependent YAP activation. Our results suggest PDE4 inhibition as a promising strategy for alleviating kidney fibrosis in diabetic nephropathy.

Phosphodiesterase4 inhibitors in dermatology : Role in the treatment of skin diseases

Chronic inflammatory skin diseases are of great social and medical importance and require effective drug therapy. Phosphodiesterase4 (PDE4) inhibitors represent apossible therapeutic option by regulating inflammatory processes. PDEs cause the release of proinflammatory cytokines by interfering with signaling pathways. The PDE4 inhibitors apremilast (treatment of psoriasis and Behçet's disease), roflumilast (treatment of chronic obstructive pulmonary disease), and crisaborole (treatment of atopic dermatitis) are currently approved in Europe. Apremilast is used for second-line treatment of plaque psoriasis and psoriatic arthritis and has afavorable side effect profile. Topical PDE4 inhibitors are currently being researched and have not yet been approved by the European Medicines Agency (EMA). The topical PDE4 inhibitor crisaborole was approved by the EMA in 2020 as atopical treatment alternative to glucocorticoids and calcineurin inhibitors. Although the substance has shown good tolerability in studies and also alleviates the accompanying itching, it did not find its way onto the German market. BEHçET'S DISEASE: Apremilast is approved for the treatment of Behçet's disease in adults with refractory, severe oral ulcers. Case studies have also demonstrated the efficacy of systemic PDE4 inhibition in other skin diseases (including blistering autoimmune dermatoses, lichen planus, and acantholytic genodermatoses). The substances are also being researched and used to treat extracutaneous inflammatory diseases.

Safety, pharmacokinetics, and pharmacodynamics of ART-648, a PDE4 inhibitor in healthy subjects: A randomized, placebo-controlled phase I study.

Phosphodiesterase 4 (PDE4) inhibitor is associated with a broad-spectrum anti-inflammatory mechanism. However, securing clinically efficacious doses with sufficient safety margins remains challenging due to class specific adverse events that are often unavoidable in the clinic. ART-648 is an orally available PDE4 inhibitor being developed for the treatment of inflammatory diseases. According to the estimated clinical doses based on an invitro whole-blood assay, a phase I study was designed. The purpose of this phase I study was to assess the safety, tolerability, pharmacokinetics (PK), and pharmacodynamics (PD) following single and multiple administration of ART-648 in healthy subjects. PD was assessed by suppression of lipopolysaccharide-induced TNFα release in exvivo whole-blood assay. In the single rising dose study, ART-648 was safe and well tolerated with a dose-proportional increase in exposures up to 4 mg. Single doses of ART-648 demonstrated dose-dependent PD response, indicating target engagement at 2-8 mg doses. In the multiple rising dose study, doses up to 4 mg BID after careful titration were well tolerated, while doses up to 6 mg BID were tolerated not in all but the majority of subjects. In conclusion, ART-648 exhibits a favorable PK profile with robust target engagement at clinically safe and tolerated doses identified in healthy subjects.

Investigation of the effects of tadalafil on the myocardium via electrical and isometric contractions and cardiac markers in Wistar rats

Purpose: Tadalafil, a long-acting phosphodiesterase-5 (PDE-5) inhibitor, is commonly used in the treatment of erectile dysfunction. This study investigates the contribution of tadalafil in cardiac function by measuring isometric and electrical contractions of myocardium in rats. Materials and Methods: Thirty rats were divided into five groups. Basal electrical contractions were recorded via electrocardiogram (ECG) for intervals PR (ms), QRS (ms), QT (ms), Tp (ms), Te (ms), pathological Q and heart beats/min. Then group 1 received saline for 7 days (control); group 2 received tadalafil 1 mg/kg; group 3 received tadalafil 10 mg/kg; group 4 received tadalafil 1 mg/kg for 7 days; group 5 received tadalafil 10 mg/kg for 7 days. After treatments, electrical contractions were re-performed to analyze the differences in ECG. For isometric contractions, hearts were connected to isometric power transducer to determine myocardial contractile forces (g), durations (ms) and frequencies (Hz). Serum samples were collected for cardiac creatine kinase (CK-MB) and cardiac troponin I via ELISA. Results: We found a significant decrease in CK-MB in Group 2 (395.56±124.38 pg/ml) and 3 (377.81±79.61 pg/ml), compared to Group 1 (575.32±83.54 pg/ml). The differences in cardiac contractile forces, contraction durations or frequencies were not statistically significant. Conclusion: Tadalafil did not exert obvious distruption on myocardial electrical or isometrical contractions. It is noteworthy that tadalafil 1 and 10 mg/kg reduced serum CK-MB. Shortening in QT and decrease in heart rate may have important implications on myocardial functions.

Roflumilast-loaded nanostructured lipid carriers attenuate oxidative stress and neuroinflammation in Parkinson’s disease model

Parkinson’s disease (PD) is a progressive neurodegenerative disorder with limited symptomatic treatment options. Targeting phosphodiesterase 4 (PDE4) has shown a promising result in several preclinical studies. In our study, we aim to repurpose US FDA-approved PDE4 inhibitor for PD. Through in-silico study, we identified roflumilast (ROF) as the potential candidate targeting PDE4B2. In Drosophila PD expressing the A30P mutant α-synuclein model, ROF exhibited anti-PD effects as indicated by negative geotaxis and antioxidant activities. Given the low brain distribution of ROF (<50%) at clinical doses, incorporation into nanostructured lipid carriers (NLCs) was carried out to enhanced blood-brain barrier permeability. In vitro release studies indicated sustained ROF release from NLCs (≈75%) over 24 h. Single-dose oral toxicity studies reported no mortality or toxicity signs. ROF-loaded NLCs significantly alleviated behavioural deficits, increased antioxidant parameters (p < 0.05), and reduced TNF-α and IL-6 levels (p < 0.5) in the striatum compared to pure ROF. ROF-loaded NLCs demonstrated potential anti-PD effects with high efficacy than pure ROF. Our study suggests that nanostructured lipid carriers (NLCs) can be a promising drug delivery system to overcome limitations associated with poor brain bioavailability of lipophilic drugs like ROF for PD treatment. Further investigation related to brain occupancy and underlying mechanisms of our formulation is warranted to confirm and strengthen our current findings.

Equine metabolic investigation of the phosphodiesterase-4 inhibitor ibudilast as a potential performance enhancer.

Phosphodiesterase 4 (PDE4) inhibitors are a newer class of drugs that induce bronchodilation and have anti-inflammatory effects, making them susceptible to misuse as performance enhancers in competitive sports. This study explores the metabolic conversion of PDE4 inhibitor ibudilast in thoroughbred horses after oral administration and in vitro using equine liver microsomes and Cunninghamella elegans. A liquid chromatography-high resolution mass spectrometry method was used to postulate the plausible structures of the detected metabolites. A total of 20 in vivo metabolites were identified under experimental conditions, including 12 Phase I and 8 Phase II conjugated metabolites. Phase I metabolites were predominantly formed through hydroxylation (mono-, di-, and tri-hydroxylation). Demethylated metabolites were also identified during this investigation. Additionally, the research detected Phase II metabolites conjugated with glucuronic and sulfonic acids. The data presented here can assist in detecting the PDE4 inhibitor ibudilast and uncover its illicit use in competitive sports.

PDE5 inhibitor potentially improves polyuria and bladder storage and voiding dysfunctions in type 2 diabetic rats.

Bladder dysfunction associated with type 2 diabetes mellitus (T2DM) includes urine storage and voiding disorders. We examined pathological conditions of the bladder wall in a rat T2DM model and evaluated the effects of the phosphodiesterase-5 (PDE-5) inhibitor tadalafil. Male Otsuka Long-Evans Tokushima Fatty (OLETF) rats and Long-Evans Tokushima Otsuka (LETO) rats were used as the T2DM and control groups, respectively. Tadalafil was orally administered for 12 weeks. Micturition behavior was monitored using metabolic cages, and bladder function was evaluated by cystometry. Bladder blood flow was evaluated by laser speckle imaging, and an organ bath bladder distention test was used to measure adenosine triphosphate (ATP) release from the bladder urothelium. The expression levels of vesicular nucleotide transporter (VNUT), hypoxia markers, pro-inflammatory cytokines and growth factors in the bladder wall were measured using real-time polymerase chain reaction and enzyme-linked immunosorbent assay. Bladder wall contractions in response to KCl and carbachol were monitored using bladder-strip tests. With aging, OLETF rats had higher micturition frequency and greater urine volume than LETO rats. Although bladder capacity was not significantly different, non-voiding bladder contraction occurred more frequently in OLETF rats than in LETO rats. Bladder blood flow was decreased and ATP release was increased with higher VNUT expression in OLETF rats than in LETO rats. These effects were suppressed by tadalafil administration, with accompanying decreased HIF-1α, 8-OHdG, IL-6, TNF-α, IGF-1, and bFGF expression. The impaired contractile responses of bladder strips to KCl and carbachol in OLETF rats with aging were restored by tadalafil administration. The T2DM rats had polyuria, increased ATP release induced by decreased bladder blood flow and impaired contractile function. PDE5 inhibition improved these changes and may prevent T2DM-associated urinary frequency and bladder storage and voiding dysfunctions.

Inhibition of Phosphodiesterase 4 Suppresses Neuronal Ferroptosis After Cerebral Ischemia/Reperfusion.

We have previously shown that inhibition of phosphodiesterase 4 (PDE4) protects against cerebral ischemia/reperfusion injury. However, it remains unclear whether and how PDE4 affects ferroptosis under cerebral ischemia/reperfusion conditions. In this study, we found that overexpression of PDE4B in HT-22 cells exacerbated the detrimental effects of oxygen-glucose deprivation/reoxygenation (OGD/R), including a decrease in cell viability and glutathione (GSH) levels and an increase in Fe2+ content. PDE4B knockdown mitigated the effects of OGD/R, as evidenced by decreased oxidative stress, lactate dehydrogenase (LDH) release, Fe2+ content, and nuclear receptor coactivator 4 (NCOA4) expression. PDE4B knockdown also enhanced the levels of GSH, ferroportin (FPN), and ferritin heavy chain 1 (FTH1). Consistently, inhibition of PDE4 by roflumilast (Roflu) produced similar effects as PDE4B knockdown. Roflu also ameliorated the morphology and membrane potential of the mitochondria. Glutathione peroxidase 4 (GPX4) knockdown blocked the effects of Roflu on cell viability and lipid peroxidation. Moreover, we found that nuclear factor erythroid 2-related factor 2 (Nrf-2) knockdown decreased GPX4 expression. In addition, Nrf-2 knockdown led to enhanced lipid peroxidation, LDH release, and iron levels, while the GSH and FPN levels decreased. More crucially, PDE4 inhibition decreased infarct volume, alleviated oxidative stress, and restored the expression levels of ferroptosis-associated proteins in middle cerebral artery occlusion/reperfusion (MCAO/R) rats. Interestingly, the GPX4 inhibitor RSL3 blocked the neuroprotective effects of Roflu in rats subjected to MCAO/R. Thus, PDE4 inhibition significantly inhibits neuronal ferroptosis by activating the Nrf-2/GPX4 pathway. These data indicate the existence of a novel mechanism underlying the neuroprotective effects of PDE4 inhibition.

PET imaging in rat brain shows opposite effects of acute and chronic alcohol exposure on phosphodiesterase-4B, an indirect biomarker of cAMP activity.

The cyclic adenosine monophosphate (cAMP) cascade is thought to play an important role in regulating alcohol-dependent behaviors, with potentially opposite effects following acute versus chronic administration. Phosphodiesterase 4 (PDE4) is the primary brain enzyme that metabolizes cAMP, thereby terminating its signal. Radioligand binding to PDE4 serves as an indirect biomarker of cAMP activity, as cAMP-protein kinase A (PKA)-mediated phosphorylation of PDE4 increases its affinity for radioligand binding ~10-fold. Of the four PDE4 subtypes, PDE4B polymorphisms are known to be strongly associated with alcohol and substance use disorders. This study imaged rats with the PDE4B-preferring positron emission tomography (PET) radioligand [18F]PF-06445974 following acute and chronic ethanol administration, aiming to explore the potential of PDE4B PET imaging for future human studies. Compared to the control group treated with saline, acute alcohol administration (i.p. ethanol 0.5 g/kg) significantly increased whole brain uptake of [18F]PF-06445974 as early as 30 minutes post-exposure. This effect persisted at 2 hours, peaked at 4 hours, and diminished at 6 hours and 24 hours post-exposure. In contrast, in a rat model of alcohol dependence, [18F]PF-06445974 brain uptake was significantly reduced at 5 hours post-exposure and was normalized by 3 days. This reduction may reflect long-term adaptation to repeated alcohol-induced activation of cAMP signaling with chronic exposure. Taken together, the results suggest that PET imaging of PDE4B in individuals with alcohol use disorder (AUD) should be considered in conjunction with ongoing trials of PDE4 inhibitors to treat alcohol withdrawal and reduce alcohol consumption.

Roflumilast cream (Zoryve) for atopic dermatitis.

The FDA has approved a 0.15% cream formulation of the phosphodiesterase-4 (PDE4) inhibitor roflumilast (Zoryve – Arcutis) for topical treatment of mild to moderate atopic dermatitis (AD) in patients ≥6 years old. Roflumilast is the second PDE4 inhibitor to be approved in the US for treatment of AD; crisaborole (Eucrisa), which can be used in patients ≥3 months old, was the first.

The Effect of Chronic Treatment with the Inhibitor of Phosphodiesterase 5 (PDE5), Sildenafil, in Combination with L-DOPA on Asymmetric Behavior and Monoamine Catabolism in the Striatum and Substantia Nigra of Unilaterally 6-OHDA-Lesioned Rats.

The use of phosphodiesterase inhibitors in the treatment of Parkinson's disease is currently widely discussed. The study aimed to investigate the impact of acute and chronic treatment with the phosphodiesterase 5 inhibitor, sildenafil, at low and moderate doses of 2 mg/kg and 6 mg/kg, and L-DOPA (12.5 mg/kg), alone or in combination, on asymmetric behavior and dopamine (DA) and serotonin metabolism in the striatum and substantia nigra of unilaterally 6-OHDA-lesioned rats. Acute administration of sildenafil at both tested doses jointly with L-DOPA significantly increased the number of contralateral rotations during a 2 h measurement compared to L-DOPA alone. The effect of a lower dose of sildenafil combined with L-DOPA was much greater in the second hour of measurement. However, the acute combined administration of a higher dose of sildenafil with L-DOPA resulted in an immediate and much stronger increase in the number of contralateral rotations compared to L-DOPA alone, already visible in the first hour of measurement. Interestingly, the chronic combined administration of 2 mg/kg of sildenafil and L-DOPA significantly reduced the number of contralateral rotations, especially during the first hour of measurement, compared to the long-term treatment with L-DOPA alone. Such an effect was not observed after the long-term combined treatment of a higher dose of sildenafil and L-DOPA compared to L-DOPA alone. The concentration of DA in the ipsilateral striatum and substantia nigra after the last combined chronic dose of sildenafil (2 or 6 mg/kg) and L-DOPA (12.5 mg/kg) was significantly higher than after L-DOPA alone. In spite of much stronger increases in the DA concentration in the ipsilateral striatum and substantia nigra, the number of contralateral rotations was reduced in the group of rats treated with the combination of 2 mg/kg sildenafil and L-DOPA compared to the group receiving L-DOPA alone. Moreover, the combined treatment with a low dose of sildenafil and L-DOPA had an opposite effect on DA catabolism, as assessed by DOPAC/DA and HVA/DA indexes, and these indexes were reduced in the ipsilateral striatum but increased in the contralateral striatum and substantia nigra compared to the treatment with L-DOPA alone. The results of the present study show that the addition of a low dose of a PDE5 inhibitor to the standard L-DOPA therapy differently modulates rotational behavior, the tissue DA concentration and its catabolism in the striatum and substantia nigra.

Phosphodiesterase 4 is overexpressed in keloid epidermal scars and its inhibition reduces keratinocyte fibrotic alterations

BackgroundEpidermal remodeling and hypertrophy are hallmarks of skin fibrotic disorders, and keratinocyte to mesenchymal (EMT)-like transformations drive epidermis alteration in skin fibrosis such as keloids and hypertrophic scars (HTS). While phosphodiesterase 4 (PDE4) inhibitors have shown effectiveness in various fibrotic disorders, their role in skin fibrosis is not fully understood. This study aimed to explore the specific role of PDE4B in epidermal remodeling and hypertrophy seen in skin fibrosis.MethodsIn vitro experiments examined the effects of inhibiting PDE4A-D (with Roflumilast) or PDE4B (with siRNA) on TGFβ1-induced EMT differentiation and dedifferentiation in human 3D epidermis. In vivo studies investigated the impact of PDE4 inhibition on HOCl-induced skin fibrosis and epidermal hypertrophy in mice, employing both preventive and therapeutic approaches.ResultsThe study found increased levels of PDE4B (mRNA, protein) in keloids > HTS compared to healthy epidermis, as well as in TGFβ-stimulated 3D epidermis. Keloids and HTS epidermis exhibited elevated levels of collagen Iα1, fibronectin, αSMA, N-cadherin, and NOX4 mRNA, along with decreased levels of E-cadherin and ZO-1, confirming an EMT process. Inhibition of both PDE4A-D and PDE4B prevented TGFβ1-induced Smad3 and ERK1/2 phosphorylation and mesenchymal differentiation in vitro. PDE4A-D inhibition also promoted mesenchymal dedifferentiation and reduced TGFβ1-induced ROS and keratinocyte senescence by rescuing PPM1A, a Smad3 phosphatase. In vivo, PDE4 inhibition mitigated HOCl-induced epidermal hypertrophy in mice in both preventive and therapeutic settings.ConclusionsOverall, the study supports the potential of PDE4 inhibitors, particularly PDE4B, in treating skin fibrosis, including keloids and HTS, shedding light on their functional role in this condition.

Abstract P224: RbFox2 is a Rho-related BTB Domain Containing 1 (RhoBTB1)-Cullin 3 (CUL3) Pathway Target that Regulates the Actin Cytoskeleton

Blood pressure (BP) is controlled by an array of cellular pathways. Our prior research revealed that endothelial nitric oxide (NO)-dependent vessel tone and BP are regulated through the RhoBTB1-CUL3 mediated proteasomal degradation of Phosphodiesterase 5 (PDE5). RhoBTB1 is an adaptor protein which delivers protein substrates to the CUL3 E3 ubiquitin ligase for proteasomal degradation. However, the range of protein targets of RhoBTB1 remains unknown. We employed the ascorbate peroxidase (APEX2) proximity labelling system coupled with mass spectroscopy to identify RhoBTB1 targets in A7r5 smooth muscle cells. This analysis identified nearly 75 proteins which putatively bind to the C terminal half of RhoBTB1 (known as B1B2C), the region we previously identified was essential for adaptor function. One of these proteins was RNA binding motif protein 9, known as RBM9 and RbFox2, a key regulator of splicing events. Subsequent co-immunoprecipitation (Co-IP) assays validated the interaction of RbFox2 with RhoBTB1 and its B1B2C domains. Expression of Rbfox2 was increased in response to treatment of A7r5 cells with either MG132, an inhibitor of the proteasome, and MLN4924, an inhibitor of the CUL family. Similarly, RbFox2 expression was increased in CRISPR-Cas9 generated CUL3-deficient HEK293 cells, in aorta isolated from SMC-specific CUL3-deficient mice, and in A7r5 cells expressing an siRNA targeting RhoBTB1. Ang-II treatment of mice, which raised blood pressure by 40 mmHg, also increased RbFox2 expression, presumably through down regulation of RhoBTB1. Targeting RbFox2 by siRNA in A7r5 cells resulted in a decrease in actin fiber formation detected by phalloidin staining. In summary, our findings suggest that RbFox2 regulation may occur through the RhoBTB1-CUL3 proteasomal pathway and may potentially play a mechanistic role in actin cytoskeleton organization and thus arterial stiffness associated with hypertension.

Investigation of Cissus populnea as a Potential Therapeutic Agent for Erectile Dysfunction.

Cissus populnea (CP) is a plant reported to possess an erection-enhancing ability, though mechanisms remain unclear. Drugs targeting phosphodiesterase 5 (PDE5) inhibition, such as sildenafil, have been employed to treat erectile dysfunction (EDRF), but they are associated with several complications. This study investigated the effect of C. populnea extracts (aqueous and saponin-rich) on the activity and gene expressions of proteins related to erection. PDE5, Nitric oxide synthase (NOS) and androgen receptor (AR) genes were studied using RT-PCR on CP-treated paroxetine-induced ERDF-rats. It also employed Schrödinger suites for investigations such as molecular and induced-fit docking, MMGBSA, ADMET, and QSAR profiling of CP-phytocompounds. C. populnea extracts reduce the activity and downregulate the expression of the PDE5 gene while upregulating the expressions of AR and NOS genes in the ERDF-rats relative to the control group. Five (leading) compounds with induced-fit docking (IFD) scores in kcal/mol, namely, stigmasterol (-638.73), daucosterol (-644.73), furostanol (-639.29), papaverine (-639.03), and capsaicin (-642.88), had better docking scores of -9.936, -9.824, -9.064, -8.863, and -8.736 kcal/mol, respectively, compared with those of sildenafil (-8.611 kcal/mol). They also showed an excellent ADMET profile, satisfying Lipinski's rule of five. The MMGBSA predictions revealed that stigmasterol, daucosterol, papaverine, and capsaicin had binding free energies of -45.29, -59.14, -50.63, and -50.47 kcal/mol, respectively, suggesting that they are significant inhibitors of PDE5. The QSAR model revealed that lead compounds possess good pIC50 values. These results indicate that C. populnea is a more promising possible treatment for controlling EDRF and deserves further research.

Phosphodiesterase 4 is overexpressed in human keloids and its inhibition reduces fibroblast activation and skin fibrosis

There is a pressing medical need for improved treatments in skin fibrosis including keloids and hypertrophic scars (HTS). This study aimed to characterize the role of phosphodiesterase 4 (PDE4), specifically PDE4B in fibrotic skin remodeling in vitro and in vivo.In vitro, effects of PDE4A-D (Roflumilast) or PDE4B (siRNA) inhibition on TGFβ1-induced myofibroblast differentiation and dedifferentiation were studied in normal (NHDF) and keloid (KF) human dermal fibroblasts. In vivo, the role of PDE4 on HOCl-induced skin fibrosis in mice was addressed in preventive and therapeutic protocols.PDE4B (mRNA, protein) was increased in Keloid > HTS compared to healthy skin and in TGFβ-stimulated NHDF and KF. In Keloid > HTS, collagen Iα1, αSMA, TGFβ1 and NOX4 mRNA were all elevated compared to healthy skin confirming skin fibrosis.In vitro, inhibition of PDE4A-D and PDE4B similarly prevented TGFβ1-induced Smad3 and ERK1/2 phosphorylation and myofibroblast differentiation, elevated NOX4 protein and proliferation in NHDF. PDE4A-D inhibition enabled myofibroblast dedifferentiation and curbed TGFβ1-induced reactive oxygen species and fibroblast senescence. In KF PDE4A-D inhibition restrained TGFβ1-induced Smad3 and ERK1/2 phosphorylation, myofibroblast differentiation and senescence. Mechanistically, PDE4A-D inhibition rescued from TGFβ1-induced loss in PPM1A, a Smad3 phosphatase. In vivo, PDE4 inhibition mitigated HOCl-induced skin fibrosis in mice in preventive and therapeutic protocols.The current study provides novel evidence evolving rationale for PDE4 inhibitors in skin fibrosis (including keloids and HTS) and delivered evidence for a functional role of PDE4B in this fibrotic condition.