Cyclic nucleotide phosphodiesterase (PDE) inhibitors and immunomodulation

Contribution of Visceral Systems to the Development of Substance Use Disorders: Translational Aspects of Interaction between Central and Peripheral Mechanisms

Substance use disorders are associated with structural and functional changes in the neuroendocrine, neuromediator, and neuromodulator systems in brain areas involved in the reward and stress response circuits. Chronic intoxication provokes emergence of somatic diseases and aggravates existing pathologies. Substance use disorders and somatic diseases often exacerbate the clinical courses of each other. Elucidation of biochemical pathways common for comorbidities may serve as a basis for the development of new effective pharmacotherapy agents, as well as drug repurposing. Here, we discussed molecular mechanisms underlying integration of visceral systems into the central mechanisms of drug dependence.

Protective effect of PDE4B subtype-specific inhibition in an App knock-in mouse model for Alzheimer's disease

Meta-analysis of genome-wide association study data has implicated PDE4B in the pathogenesis of Alzheimer's disease (AD), the leading cause of senile dementia. PDE4B encodes one of four subtypes of cyclic adenosine monophosphate (cAMP)-specific phosphodiesterase-4 (PDE4A-D). To interrogate the involvement of PDE4B in the manifestation of AD-related phenotypes, the effects of a hypomorphic mutation (Pde4bY358C) that decreases PDE4B's cAMP hydrolytic activity were evaluated in the AppNL-G-F knock-in mouse model of AD using the Barnes maze test of spatial memory, 14C-2-deoxyglucose autoradiography, thioflavin-S staining of β-amyloid (Aβ) plaques, and inflammatory marker assay and transcriptomic analysis (RNA sequencing) of cerebral cortical tissue. At 12 months of age, AppNL-G-F mice exhibited spatial memory and brain metabolism deficits, which were prevented by the hypomorphic PDE4B in AppNL-G-F/Pde4bY358C mice, without a decrease in Aβ plaque burden. RNA sequencing revealed that, among the 531 transcripts differentially expressed in AppNL-G-F versus wild-type mice, only 13 transcripts from four genes - Ide, Btaf1, Padi2, and C1qb - were differentially expressed in AppNL-G-F/Pde4bY358C versus AppNL-G-F mice, identifying their potential involvement in the protective effect of hypomorphic PDE4B. Our data demonstrate that spatial memory and cerebral glucose metabolism deficits exhibited by 12-month-old AppNL-G-F mice are prevented by targeted inhibition of PDE4B. To our knowledge, this is the first demonstration of a protective effect of PDE4B subtype-specific inhibition in a preclinical model of AD. It thus identifies PDE4B as a key regulator of disease manifestation in the AppNL-G-F model and a promising therapeutic target for AD.

Safety, Tolerability, and Pharmacokinetics of a Novel Oral Phosphodiesterase 4 Inhibitor, ME3183: First-in-Human Phase 1 Study

A novel, oral phosphodiesterase 4 (PDE4) inhibitor, ME3183, is under development for the treatment of psoriasis, atopic dermatitis, and other inflammatory diseases. To evaluate its safety, tolerability, and pharmacokinetics, double-blind, placebo-controlled, single ascending dose (SAD), and multiple ascending dose (MAD) phase 1 studies were conducted in 126 healthy adults. The food effect was evaluated in a randomized, open-label, crossover manner (n = 5). ME3183 was safe and tolerable up to 25 mg in the SAD part and up to 10 mg twice daily in the MAD part. Frequently observed treatment-emergent adverse events included diarrhea and headache, as commonly reported for approved PDE4 inhibitors, providing no novel safety concerns. Pharmacokinetic analysis showed dose-dependent increases in Cmax and AUC, with later tmax and longer t1/2 than apremilast, an approved PDE4 inhibitor. The food effect study showed slightly decreased systemic exposure. In the MAD part, plasma exposure levels of ME3183 were higher even at the minimal dose (2.5 mg twice daily) than the estimated therapeutically effective level. These results show the safe profile of ME3183 and support further studies to confirm the safety and efficacy of the drug in patients with psoriasis and other inflammatory diseases.

Promising advances in treatments for the management of idiopathic pulmonary fibrosis

INTRODUCTION

Following the INPULSIS and ASCEND studies, leading to the first two approved antifibrotic therapies for patients with IPF, ongoing investigations are firmly exploring novel agents for a targeted effective and better tolerated therapy able to improve the natural history of the disease.

AREAS COVERED

This review aims to analyze recent advances in pharmacological research of IPF, discussing the currently available treatments and the novel drugs under investigation in phase 3 trials, with particular emphasis on BI 1015550 and inhaled treprostinil. The literature search utilized Medline and Clinicaltrials.org databases. Critical aspects of clinical trial design in IPF are discussed in light of recently completed phase III studies.

EXPERT OPINION

While randomized clinical trials in IPF are currently underway, future objectives should explore potential synergistic benefits when combining novel molecules with the existing therapies and identify more specific molecular targets. Moreover, refining the study design represent another crucial goal. The aim of the pharmacological research will be not only stabilizing but also potentially reversing the fibrotic changes in IPF.

PDE9A polymorphism and association analysis with growth performance and gastrointestinal weight of Hu sheep

Phosphodiesterase 9A (PDE9A) plays a crucial role in activating the cGMP-dependent signaling pathway and may have important effects on the growth and development of the gastrointestinal tract in Hu sheep. In this study, we analyzed the single nucleotide polymorphisms of PDE9A in 988 Hu sheep and their correlation with growth performance, feed efficiency, and gastrointestinal development. Additionally, we examined the expression level of different PDE9A genotypes in the gastrointestinal tract of Hu sheep by using fluorescence quantitative PCR. The results revealed a moderate level of polymorphism (0.25 < PIC < 0.50) at the g.286248617 T > C mutation site located in the first intron of PDE9A in Hu sheep, with three genotypes: CC, CT, and TT. The weights of the omasum, colon, and cecum were significantly greater in the CC genotype than in the TT genotype (P < 0.05), and the expression level of PDE9A in the tissues of the rumen, ileum, cecum, and colon was notably lower in the CC genotype individuals (P < 0.05). These findings suggest that the polymorphism of PDE9A affects the weight of the stomach, colon, and cecum in Hu sheep through expression regulation. Overall, the results of this study suggest that the g.286248617 T > C mutation site in the first intron of PDE9A can serve as a potential molecular marker for breeding practices related to the gastrointestinal weight of Hu sheep.

An update on emerging drugs for the treatment of idiopathic pulmonary fibrosis: a look towards 2023 and beyond

INTRODUCTION

Currently approved drug treatments for idiopathic pulmonary fibrosis (IPF), pirfenidone and nintedanib, have been shown to slow lung function decline and improve clinical outcomes. Since significant advances in the understanding of pathogenetic mechanisms in IPF, novel potential agents are being tested to identify new targeted and better tolerated therapeutic strategies.

AREAS COVERED

This review describes the evidence from IPF phase II and III clinical trials that have been completed or are ongoing in recent years. The literature search was performed using Medline and Clinicaltrials.org databases. Particular attention is paid to the new inhibitor of phosphodiesterase 4B (BI 1015550), being studied in a more advanced research phase. Some emerging critical issues of the pharmacological research are highlighted considering the recent outstanding failures of several phase III trials.

EXPERT OPINION

An exponential number of randomized clinical trials are underway testing promising new molecules to increase treatment choices for patients with IPF and improve patients' quality of life. The next goals should aim at a deeper understanding of the pathogenic pathways of the disease with the challenging goal of being able not only to stabilize but also to reverse the ongoing fibrotic process in patients with IPF.

The phosphodiesterase 4 inhibitor AA6216 suppresses activity of fibrosis-specific macrophages

Background

Idiopathic pulmonary fibrosis (IPF) is a form of chronic, progressive fibrosing interstitial pneumonia of unknown cause, with a poor prognosis. We previously showed the antifibrotic effects of a novel phosphodiesterase 4 (PDE4) inhibitor, AA6216. In this study, we examined the effect of AA6216 on the pulmonary accumulation of segregated-nucleus-containing atypical monocytes (SatMs), which produce tumor necrosis factor (TNF)-α and are involved in murine lung fibrosis.

Methods

Mice were treated with bleomycin intratracheally at day 0 and either 10 mg/kg AA6216, 100 mg/kg nintedanib, or vehicle orally once daily from day 0 to 8. On day 9, we isolated the bronchoalveolar lavage fluid and analyzed the SatM ratio. In addition, we evaluated the effect of AA6216 on TNF-α production from SatMs isolated from murine bone marrow.

Results

AA6216, and not the antifibrotic agent nintedanib, significantly suppressed the pulmonary accumulation of SatMs (AA6216: 68.3 ± 5.4%, Nintedanib: 129.8 ± 19.7%). Furthermore, AA6216 dose-dependently inhibited the production of TNF-α by SatMs.

Conclusions

AA6216 suppresses pathogenic SatMs in the lung, which contributes to its antifibrotic effects.

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Fibrosis-specific macrophages are critical for the development of lung fibrosis.

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The PDE4 inhibitor, AA6216, suppresses the pro-fibrotic activity of macrophages.

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AA6216 inhibits the pulmonary accumulation of fibrosis-specific macrophages.

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AA6216 inhibits the production of TNF-α by fibrosis-specific macrophages.

Nonclinical genotoxicity and carcinogenicity profile of apremilast, an oral selective inhibitor of PDE4

Apremilast is an oral, selective small molecule inhibitor of phosphodiesterase-4 (PDE4) that has been approved for the treatment of active psoriatic arthritis, moderate to severe plaque psoriasis, and for patients with oral ulcers associated with Behçet's disease. Apremilast modulates the inflammatory cascade in cells by inhibiting PDE4, thus preventing the degradation of cyclic adenosine monophosphate, resulting in the upregulation of interleukin (IL)-10 and the downregulation of proinflammatory cytokines, including IL-23, interferon gamma (IFNγ), and tumor necrosis factor alpha (TNFα). Here, we evaluated the genotoxic and carcinogenic potential of apremilast using Good Laboratory Practice (GLP)-compliant in vitro and in vivo studies. Apremilast was not genotoxic in the genetic toxicology battery, as evaluated for mutagenicity in the Ames test up to concentrations of 5000 μg/plate, clastogenicity in cultured human peripheral blood lymphocytes up to concentrations of 700 ug/mL was in excess of the solubility limit in culture medium and not able to assess; and negative for the induction of micronuclei in the bone marrow micronucleus test in mice up to doses of 2000 mg/kg/day. Furthermore, apremilast did not increase the incidence of tumors in lifetime rat or mouse carcinogenicity studies up to the maximum tolerated dose. In summary, in non-clinical studies, apremilast is not genotoxic and is not carcinogenic.

Anti-inflammatory effects of a novel phosphodiesterase-4 inhibitor, AA6216, in mouse dermatitis models

Atopic dermatitis (AD) is a chronic inflammatory skin disease that is commonly treated with corticosteroids. However, these drugs have long-term adverse effects, representing an unmet need for new treatments. AD is associated with dysregulation of phosphodiesterase 4 (PDE4) activity in inflammatory cells and the topical PDE4 inhibitor, crisaborole, is approved by the US FDA for mild-to-moderate AD. In this study, we compared the effects of a novel PDE4 inhibitor, AA6216, with those of crisaborole on skin inflammation. We found that AA6216 is a more potent inhibitor of PDE4 and of cytokine production (TNF-α, IL-12/23p40, IL-4, IL-13, and IFN-γ) by human peripheral blood mononuclear cells (PBMCs) stimulated by phytohemagglutinin (PHA) or anti-CD3 antibodies, with IC₅₀ values ranging from 5.9 to 47 nM. AA6216 also significantly suppressed skin inflammation in three mouse models of dermatitis. In acute and chronic oxazolone-induced dermatitis models, topical AA6216 exhibited stronger inhibitory effects on ear inflammation and cytokine production (TNFα, IL-1β, and IL-4) in skin lesions compared with crisaborole. In a Dermatophagoides farinae-induced dermatitis model, AA6216 significantly reduced the dermatitis score, based on the development of erythema/hemorrhage, scarring/dryness, edema, and excoriation/erosion, compared with a clinically used topical AD drug, tacrolimus. These results suggest the possibility that AA6216 is a novel and effective topical therapeutic agent for the treatment of dermatitis including AD.

Oximes: Novel Therapeutics with Anticancer and Anti-Inflammatory Potential

Oximes have been studied for decades because of their significant roles as acetylcholinesterase reactivators. Over the last twenty years, a large number of oximes have been reported with useful pharmaceutical properties, including compounds with antibacterial, anticancer, anti-arthritis, and anti-stroke activities. Many oximes are kinase inhibitors and have been shown to inhibit over 40 different kinases, including AMP-activated protein kinase (AMPK), phosphatidylinositol 3-kinase (PI3K), cyclin-dependent kinase (CDK), serine/threonine kinases glycogen synthase kinase 3 α/β (GSK-3α/β), Aurora A, B-Raf, Chk1, death-associated protein-kinase-related 2 (DRAK2), phosphorylase kinase (PhK), serum and glucocorticoid-regulated kinase (SGK), Janus tyrosine kinase (JAK), and multiple receptor and non-receptor tyrosine kinases. Some oximes are inhibitors of lipoxygenase 5, human neutrophil elastase, and proteinase 3. The oxime group contains two H-bond acceptors (nitrogen and oxygen atoms) and one H-bond donor (OH group), versus only one H-bond acceptor present in carbonyl groups. This feature, together with the high polarity of oxime groups, may lead to a significantly different mode of interaction with receptor binding sites compared to corresponding carbonyl compounds, despite small changes in the total size and shape of the compound. In addition, oximes can generate nitric oxide. This review is focused on oximes as kinase inhibitors with anticancer and anti-inflammatory activities. Oximes with non-kinase targets or mechanisms of anti-inflammatory activity are also discussed.

A novel phosphodiesterase 4 inhibitor, AA6216, reduces macrophage activity and fibrosis in the lung

Idiopathic pulmonary fibrosis (IPF) is an intractable disease with poor prognosis, and therapeutic options are limited. While the pathogenic mechanism is unknown, cytokines, such as transforming growth factor (TGF)-β, and immune cells, such as monocytes and macrophages, that produce them, seem to be involved in fibrosis. Some phosphodiesterase 4 (PDE4) inhibitors reportedly have anti-fibrotic potential by acting on these disease-related factors. Therefore, we evaluated the effect of a novel PDE4 inhibitor, AA6216, on nonclinical IPF-related models and samples from IPF patients. First, we examined the inhibitory effect of AA6216 on the production of TGF-β1 from a human monocytic cell line, THP-1. Second, we analyzed the impact of AA6216 on TNF-α production by human alveolar macrophages collected from patients with IPF. Finally, we investigated the anti-fibrotic potency of AA6216 on bleomycin-induced lung fibrosis in mice. We found that AA6216 significantly inhibited TGF-β1 production by THP-1 cells. It also significantly suppressed TNF-α production by alveolar macrophages from patients with IPF. In the mouse model of bleomycin-induced pulmonary fibrosis, therapeutic administration of AA6216 significantly reduced fibrosis scores, collagen-stained areas, and TGF-β1 in bronchoalveolar lavage fluid. AA6216 may represent a new agent for the treatment of IPF with a distinct mechanism of action from that of conventional anti-fibrotic agents.

Phosphodiesterase 4B: Master Regulator of Brain Signaling

Phosphodiesterases (PDEs) are the only superfamily of enzymes that have the ability to break down cyclic nucleotides and, as such, they have a pivotal role in neurological disease and brain development. PDEs have a modular structure that allows targeting of individual isoforms to discrete brain locations and it is often the location of a PDE that shapes its cellular function. Many of the eleven different families of PDEs have been associated with specific diseases. However, we evaluate the evidence, which suggests the activity from a sub-family of the PDE4 family, namely PDE4B, underpins a range of important functions in the brain that positions the PDE4B enzymes as a therapeutic target for a diverse collection of indications, such as, schizophrenia, neuroinflammation, and cognitive function.

Involvement of the myeloid cell compartment in fibrogenesis and systemic sclerosis

Systemic sclerosis (SSc) is an autoimmune fibrotic disease of unknown aetiology that is characterized by vascular changes in the skin and visceral organs. Autologous haematopoietic stem cell transplantation can improve skin and organ fibrosis in patients with progressive disease and a high risk of organ failure, indicating that cells originating in the bone marrow are important contributors to the pathogenesis of SSc. Animal studies also indicate a pivotal function of myeloid cells in the development of fibrosis leading to changes in the tissue architecture and dysfunction in multiple organs such as the heart, lungs, liver and kidney. In this Review, we summarize current knowledge about the function of myeloid cells in fibrogenesis that occurs in patients with SSc. Targeted therapies currently in clinical studies for SSc might affect myeloid cell-related pathways. Therefore, myeloid cells might be used as cellular biomarkers of disease through the application of high-dimensional techniques such as mass cytometry and single-cell RNA sequencing.

From bench to bedside: evolving therapeutic targets in autoimmune blistering disease

Autoimmune blistering diseases comprise a group of heterogenous conditions characterized by the loss of tolerance and subsequent development of autoantibodies targeting epidermal and subepidermal adhesion proteins. Blisters and erosions form on the skin and mucous membranes leading to significant morbidity and mortality. Traditional therapies rely on systemic immunosuppression. Advancements in our understanding of the pathophysiology of pemphigus and pemphigoid have led to the development of molecules which target specific pathways involved in induction and perpetuation of disease. In this review, we outline the novel therapeutic strategies including B-cell depletion, T-regulatory cell repletion, cell signalling inhibitors and small molecular inhibitors, inhibitory monoclonal antibodies, as well as complement inhibition. We additionally review their current level of clinical evidence. We lastly review therapeutics targets gleaned from the experimental epidermolysis bullosa acquisita mouse model. These emerging treatments offer an exciting progression from basic science discoveries that have the potential to transform the treatment paradigm in autoimmune blistering diseases.

PDE4 inhibitor rolipram inhibits the expression of microsomal prostaglandin E synthase-1 by a mechanism dependent on MAP kinase phosphatase-1

Phosphodiesterase‐4 (PDE4) inhibitors have recently been introduced to the treatment of COPD and psoriatic arthritis. Microsomal prostaglandin E synthase‐1 (mPGES‐1) is an inducible enzyme synthesizing PGE₂, the most abundant prostanoid related to inflammation and inflammatory pain. mPGES‐1 is a potential drug target for novel anti‐inflammatory treatments aiming at an improved safety profile as compared to NSAIDs. Here we investigated the effect of the PDE4 inhibitor rolipram on the expression of mPGES‐1 in macrophages; and a potential mediator role in the process for MAP kinase phosphatase‐1 (MKP‐1) which is an endogenous factor limiting the activity of the proinflammatory MAP kinases p38 and JNK. The expression of mPGES‐1 was decreased, whereas that of MKP‐1 was enhanced by rolipram in wild‐type murine macrophages. Interestingly, rolipram did not reduce mPGES‐1 expression in peritoneal macrophages from MKP‐1‐deficient mice. A reduced phosphorylation of JNK, but not p38 MAP kinase, was specifically associated with the decreased expression of mPGES‐1. Accordingly, mPGES‐1 expression was suppressed by JNK but not p38 inhibitor. These findings underline the significance of the increased MKP‐1 expression and decreased JNK phosphorylation associated with the downregulated expression of mPGES‐1 by PDE4 inhibitors in inflammation.

Efficacy and safety of phosphodiesterase 4 inhibitors in patients with asthma: A systematic review and meta-analysis

Phosphodiesterase 4 (PDE4) inhibitors are a novel medication approved for airway inflammatory diseases including chronic obstructive pulmonary disease. Their role and application in asthma are controversial and not defined. A comprehensive search was performed in major databases (1946-2016) using the keywords: 'phosphodiesterase 4 inhibitor' or 'roflumilast' and 'asthma'. Placebo-controlled trials reporting lung function, airway hyperresponsiveness by direct challenge, asthma control and exacerbations, and adverse events were included. Random or fixed-effects models were used to calculate odds ratios (OR) and mean differences between the two treatment groups. Statistical analyses were conducted using Mann-Whitney U-tests and Cochrane systematic review software, Review Manager. Seventeen studies were included in the systematic review, of which 14 studies were included in the meta-analysis. Except for significant statistical heterogeneity in pre- and post-challenge predicted percentage of forced expiratory volume in 1 s (FEV₁ %; I²  = 72%, χ²  = 3.35, P = 0.06), there was no heterogeneity in outcome measures. Roflumilast (500 μg) significantly improved FEV₁ (mean difference: 0.05, 95% CI: 0.01-0.09, Z = 2.50, P = 0.01), peak expiratory flow, asthma control and exacerbations, but showed variable effects on airway responsiveness to methacholine and a 20% fall in FEV₁ .Of note, PDE4 inhibitors were accompanied with significantly higher adverse events such as headache (OR: 3.99, 95% CI: 1.65-9.66, Z = 3.07, P = 0.002) and nausea (OR: 5.53, 95% CI: 1.38-22.17, Z = 2.41, P = 0.02). In patients with mild asthma, oral PDE4 inhibitors can be considered as an alternative treatment to regular bronchodilators and inhaled controllers.

JAK/STAT inhibitors and other small molecule cytokine antagonists for the treatment of allergic disease

OBJECTIVE

To provide an overview of janus kinase (JAK), chemoattractant receptor homologous molecule expressed on T_H2 cells (CRTH2), and phosphodiesterase 4 (PDE4) inhibitors in allergic disorders.

DATA SOURCES

PubMed literature review.

STUDY SELECTIONS

Articles included in this review discuss the emerging mechanism of action of small molecule inhibitors and their use in the treatment of atopic dermatitis (AD), asthma, and allergic rhinitis (AR).

RESULTS

Allergic diseases represent a spectrum of diseases, including AD, asthma, and AR. For decades, these diseases have been primarily characterized by increased T_H2 signaling and downstream inflammation. In recent years, additional research has identified disease phenotypes and subsets of patients with non-Th2 mediated inflammation. The increasing heterogeneity of disease has prompted investigators to move away from wide-ranging treatment approaches with immunosuppressive agents, such as corticosteroids, to consider more targeted immunomodulatory approaches focused on specific pathways. In the past decade, inhibitors that target JAK signaling, PDE4, and CRTH2 have been explored for their potential activity in models of allergic disease and therapeutic benefit in clinical trials. Interestingly, although JAK inhibitors provide an opportunity to interfere with cytokine signaling and could be beneficial in a broad range of allergic diseases, current clinical trials are focused on the treatment of AD. Conversely, both PDE4 and CRTH2 inhibitors have been evaluated in a spectrum of allergic diseases. This review summarizes the varying degrees of success that these small molecules have demonstrated across allergic diseases.

CONCLUSION

Emerging therapies currently in development may provide more consistent benefit to patients with allergic diseases by specifically targeting inflammatory pathways important for disease pathogenesis.

Phosphodiesterase type 5 and cancers: progress and challenges

Cancers are an extraordinarily heterogeneous collection of diseases with distinct genetic profiles and biological features that directly influence response patterns to various treatment strategies as well as clinical outcomes. Nevertheless, our growing understanding of cancer cell biology and tumor progression is gradually leading towards rational, tailored medical treatments designed to destroy cancer cells by exploiting the unique cellular pathways that distinguish them from normal healthy counterparts. Recently, inhibition of the activity of phosphodiesterase type 5 (PDE5) is emerging as a promising approach to restore normal intracellular cyclic guanosine monophosphate (cGMP) signalling, and thereby resulting into the activation of various downstream molecules to inhibit proliferation, motility and invasion of certain cancer cells. In this review, we present an overview of the experimental and clinical evidences highlighting the role of PDE5 in the pathogenesis and prevention of various malignancies. Current data are still not sufficient to draw conclusive statements for cancer patient management, but could provide further rational for testing PDE5-targeting drugs as anticancer agents in clinical settings.

Treatment of obesity-associated overactive bladder by the phosphodiesterase type-4 inhibitor roflumilast

PURPOSE

To prove that phosphodiesterase type-4 inhibitors could potentially treat obesity-associated overactive bladder through modulation of the systemic inflammatory response.

METHODS

In this 12-week study, 90 female Sprague-Dawley rats were divided into three groups: (1) vehicle-treated normal diet (ND)-fed rats; (2) vehicle-treated high-fat diet (HFD)-fed rats; and (3) roflumilast-treated HFD-fed rats. Oral roflumilast (5 mg/kg/day) was administered during the last 4 weeks of HFD feeding in the test group. At 12 weeks, a urodynamic study was performed in ten rats of each group. Bladder tissue was extracted, the bladder mucosa was separated under microscopy, and bladder detrusor smooth muscle (DSM) expression of TNF-α, interleukin (IL)-6, IL-1β, and nuclear factor kappa B (NF-κB) were analyzed using Western blotting and quantitative reverse transcription-polymerase chain reaction (qRT-PCR).

RESULTS

Bodyweights of the HFD-fed rats significantly increased and were not ameliorated by roflumilast treatment. Cystometry evidenced augmented frequency and non-void contractions in obese rats that were also prevented by roflumilast. These alterations were accompanied by a markedly increased expression of TNF-α, IL-6, IL-1β, and NF-κB in DSM of obese rats. Furthermore, roflumilast decreased expression of inflammatory factors in DSM.

CONCLUSIONS

Oral treatment with roflumilast in rats fed an HFD restores normal bladder function and downregulates expression of inflammatory factors in the bladder.

New and cost effective cell-based assay for Dialyzed Leukocyte Extract (DLE)-induced Jurkat cells proliferation under azathioprine treatment

The human Dialyzed Leukocyte Extract (DLE) is a heterogeneous mix of oligopeptides of <10kDa, extracted from leukocytes of healthy donors. There is significant clinical evidence of improvement using DLE during treatment of allergies, cancer,immunodeficiencies, and in mycotic and viral infections. Nevertheless, the DLE exact nature and mechanism of action have been elusive for more than 50 years. DLE biological activity testing is necessary in DLE production and quality control. Both in vitro and in vivo assays exist: E-rosette test, induction of delayed type hypersensitivity in mice, leukocyte migration and IFN-γ secretion. The animal-origin materials and in vivo assays convey a considerable logistic, ethic and economic burden, meanwhile the available in vitro assays have been reported with limited reproducibility and sometimes contradictory results. Here we are reporting a new DLE biological activity cell-based assay. The A20 and Jurkat cell lines were treated with (+Aza) or without (-Aza) azathioprine, DLE (+DLE) or both (+Aza/+DLE). After 72h, the cell proliferation was analyzed by the MTT or BrdU incorporation assays. In +Aza/+DLE treated cells, we observed a significant higher proliferation, when compared with +Aza/-DLE. In the absence of Aza, cells did not present any proliferation difference between -DLE or +DLE treatments. Both assays, MTT and BrdU showed similar results, being the MTT test more cost effective and we select it for validation as DLE biological assay using Jurkat cells only. We tested three different lyophilized DLE batches and we found consistent results with acceptable assay reproducibility and linearity. The DLE capacity for rescuing Jurkat cell proliferation during +Aza treatment was consistent using different liquid and lyophilized DLE batches, presenting also consistent chromatographic profiles. Finally, DLE treatment in Jurkat cells did not result into significant IL-2 of IFN-γ secretion, and known lymphocyte proliferative drugs failed to rescue Jurkat cells viability in presence of +Aza, as +DLE treatment did in our MTT assay. In conclusion, our new cell-based MTT assay has excellent DLE biological activity consistency, robustness and is cost effective, presenting important advantages over previous DLE activity in vitro and in vivo assays.

Effect of bucladesine, pentoxifylline, and H-89 as cyclic adenosine monophosphate analog, phosphodiesterase, and protein kinase A inhibitor on acute pain

The aim of this study was to determine the effects of cyclic adenosine monophosphate (cAMP) and its dependent pathway on thermal nociception in a mouse model of acute pain. Here, we studied the effect of H-89 (protein kinase A inhibitor), bucladesine (Db-cAMP) (membrane-permeable analog of cAMP), and pentoxifylline (PTX; nonspecific phosphodiesterase (PDE) inhibitor) on pain sensation. Different doses of H-89 (0.05, 0.1, and 0.5 mg/100 g), PTX (5, 10, and 20 mg/100 g), and Db-cAMP (50, 100, and 300 nm/mouse) were administered intraperitoneally (I.p.) 15 min before a tail-flick test. In combination groups, we injected the first and the second compounds 30 and 15 min before the tail-flick test, respectively. I.p. administration of H-89 and PTX significantly decreased the thermal-induced pain sensation in their low applied doses. Db-cAMP, however, decreased the pain sensation in a dose-dependent manner. The highest applied dose of H-89 (0.5 mg/100 g) attenuated the antinociceptive effect of Db-cAMP in doses of 50 and 100 nm/mouse. Surprisingly, Db-cAMP decreased the antinociceptive effect of the lowest dose of H-89 (0.05 mg/100 g). All applied doses of PTX reduced the effect of 0.05 mg/100 g H-89 on pain sensation; however, the highest dose of H-89 compromised the antinociceptive effect of 20 mg/100 g dose of PTX. Co-administration of Db-cAMP and PTX increased the antinociceptive effect of each compound on thermal-induced pain. In conclusion, PTX, H-89, and Db-cAMP affect the thermal-induced pain by probably interacting with intracellular cAMP and cGMP signaling pathways and cyclic nucleotide-dependent protein kinases.

Inhibition of phosphodiesterase 4 (PDE4) reduces dermal fibrosis by interfering with the release of interleukin-6 from M2 macrophages

OBJECTIVES

To investigate the disease-modifying effects of phosphodiesterase 4 (PDE4) inhibition in preclinical models of systemic sclerosis (SSc).

METHODS

We studied the effects of PDE4 inhibition in a prevention and a treatment model of bleomycin-induced skin fibrosis, in the topoisomerase mouse model as well as in a model of sclerodermatous chronic graft-versus-host disease. To better understand the mode of action of PDE4 blockade in preclinical models of SSc, we investigated fibrosis-relevant mediators in fibroblasts and macrophages from healthy individuals and patients suffering from diffuse-cutaneous SSc on blockade of PDE4.

RESULTS

Specific inhibition of PDE4 by rolipram and apremilast had potent antifibrotic effects in bleomycin-induced skin fibrosis models, in the topoisomerase I mouse model and in murine sclerodermatous chronic graft-versus-host disease. Fibroblasts were not the direct targets of the antifibrotic effects of PDE4 blockade. Reduced leucocyte infiltration in lesional skin on PDE4 blockade suggested an immune-mediated mechanism. Further analysis revealed that PDE4 inhibition decreased the differentiation of M2 macrophages and the release of several profibrotic cytokines, resulting in reduced fibroblast activation and collagen release. Within these profibrotic mediators, interleukin-6 appeared to play a central role.

CONCLUSIONS

PDE4 inhibition reduces inflammatory cell activity and the release of profibrotic cytokines from M2 macrophages, leading to decreased fibroblast activation and collagen release. Importantly, apremilast is already approved for the treatment of psoriasis and psoriatic arthritis. Therefore, PDE4 inhibitors might be further developed as potential antifibrotic therapies for patients with SSc. Our findings suggest that particularly patients with inflammation-driven fibrosis might benefit from PDE4 blockade.

In vivo effective dibenzo[b,d]furan-1-yl-thiazoles as novel PDE-4 inhibitors

Herein we report the synthesis, PDE-4B and TNF-α inhibitory activities of a few dibenzo[b,d]furan-1-yl-thiazole derivatives. The hydroxycyclohexanol amide derivatives 14, 18, 24, 29, 31 and 33 exhibited promising in vitro PDE-4B and TNF-α inhibitory activities. Compound 24 showed good systemic availability in preclinical animal models and was also found to be non-toxic (exploratory mutagenicity test). Further it exhibited promising results in in vivo asthma/COPD and Uveitis models.

Roflumilast combined with montelukast versus montelukast alone as add-on treatment in patients with moderate-to-severe asthma

BACKGROUND

Roflumilast, a selective phosphodiesterase 4 inhibitor, has been shown to provide modest improvements in lung function in patients with mild-to-moderate asthma, but its efficacy in patients with moderate-to-severe asthma has not been assessed. We hypothesized that this drug might provide benefit if combined with montelukast, a leukotriene receptor antagonist, in patients whose symptoms are uncontrolled by inhaled corticosteroids and long-acting β-agonists.

OBJECTIVE

We sought to examine the efficacy, safety, and mode of action of the addition of roflumilast and montelukast versus montelukast alone in patients with moderate-to-severe asthma.

METHODS

In a phase 2, randomized, double-blind, placebo-controlled, multiple-dose, 2-sequence, crossover study, 64 patients were randomized to receive 500 μg of roflumilast plus montelukast followed by placebo plus 10 mg of montelukast (sequence AB) or placebo plus 10 mg of montelukast followed by 500 μg of roflumilast plus 10 mg of montelukast (sequence BA). All patients had a diagnosis of bronchial asthma inadequately controlled by at least a medium-dose inhaled corticosteroid plus a long-acting β-agonist.

RESULTS

The analysis of FEV1 change from baseline to week 4 showed a statistically significant and clinically meaningful treatment difference of 100 mL for roflumilast plus montelukast versus placebo plus montelukast. Also, improvements in patient-reported outcomes and a reduction in urinary leukotriene E4 levels were observed during roflumilast plus montelukast treatment compared with placebo plus montelukast treatment. Adverse events were consistent with the known safety profile of roflumilast.

CONCLUSION

The combination of roflumilast with montelukast compared with montelukast alone improved lung function and asthma control in patients with moderate-to-severe asthma and deserves further study for this indication.

The role of phosphodiesterase-5 inhibitors in prostatic inflammation: a review

Clinical and basic experimental evidence indicates that chronic inflammation is the greatest factor in benign prostatic hyperplasia (BPH) progression, which is the most common cause of Lower Urinary Tract Symptoms (LUTS). The use of anti-inflammatory agents such as steroids, cyclooxygenase-2 (COX-2) and phytotherapics have been investigated as forms of treatment for various prostate diseases. Recent evidence has demonstrated that PDE5 inhibitors (PDE5Is) improve symptoms of BPH/LUTS, possibly as a result of the relaxing of the smooth muscle fibers of the bladder and prostate by NO/cGMPc signaling, or by improving RhoA/Rho-kinase (ROCK), and reduction of the hyperactivity of the autonomic nervous system. However, some results have suggested that besides vasodilatation and their anti-proliferative effect, PDE5Is exert a direct anti-inflammatory effect, by raising cGMP. Given that inflammation is major factor in benign prostatic hyperplasia (BPH) progression, PDE5Is could act also restore prostatic function as they act as potent anti-inflammatory drugs. This review aims to provide a comprehensive summary of the use of phosphodiesterase-5 inhibitors to treat prostatic inflammation.

Apremilast, a novel phosphodiesterase 4 (PDE4) inhibitor, regulates inflammation through multiple cAMP downstream effectors

Introduction

This work was undertaken to delineate intracellular signaling pathways for the PDE4 inhibitor apremilast and to examine interactions between apremilast, methotrexate and adenosine A_2A receptors (A_2AR).

Methods

After apremilast and LPS incubation, intracellular cAMP, TNF-α, IL-10, IL-6 and IL-1α were measured in the Raw264.7 monocytic murine cell line. PKA, Epac1/2 (signaling intermediates for cAMP) and A_2AR knockdowns were performed by shRNA transfection and interactions with A2AR and A2BR, as well as with methotrexate were tested in vitro and in the murine air pouch model. Statistical differences were determined using one or two-way ANOVA or Student’s t test. The alpha nominal level was set at 0.05 in all cases. A P value of < 0.05 was considered significant.

Results

In vitro, apremilast increased intracellular cAMP and inhibited TNF-α release (IC₅₀=104nM) and the specific A_2AR-agonist CGS21680 (1μM) increased apremilast potency (IC₅₀=25nM). In this cell line, apremilast increased IL-10 production. PKA, Epac1 and Epac2 knockdowns prevented TNF-α inhibition and IL-10 stimulation by apremilast. In the murine air pouch model, both apremilast and MTX significantly inhibited leukocyte infiltration, while apremilast, but not MTX, significantly inhibited TNF-α release. The addition of MTX (1 mg/kg) to apremilast (5 mg/kg) yielded no more inhibition of leukocyte infiltration or TNF-α release than with apremilast alone.

Conclusions

The immunoregulatory effects of apremilast appear to be mediated by cAMP through the downstream effectors PKA, Epac1, and Epac2. A2AR agonism potentiated TNF-α inhibition by apremilast, consistent with the cAMP-elevating effects of that receptor. Because the A2AR is also involved in the anti-inflammatory effects of MTX, the mechanism of action of both drugs involves cAMP-dependent pathways and is therefore partially overlapping in nature.

Electronic supplementary material

The online version of this article (doi:10.1186/s13075-015-0771-6) contains supplementary material, which is available to authorized users.

Adenosine 2A Receptor Antagonists for the Treatment of Motor Symptoms in Parkinson's Disease

Background

Treatment of motor fluctuations in Parkinson's disease (PD) remains an unmet challenge. Adenosine 2A (A_2A) receptors are located along the indirect pathway and represent a potential target to enhance l-3,4-dihydroxyphenylalanine (l-DOPA) antiparkinsonian action.

Methods

This article summarizes the preclinical and clinical literature on A_2A antagonists in PD, with a specific focus on their effect on off time, on time, and dyskinesia.

Findings

Several A_2A receptor antagonists have been tested in preclinical studies and clinical trials. In preclinical studies, A_2A antagonists enhanced l-DOPA antiparkinsonian action without exacerbating dyskinesia, but A_2A antagonists were generally administered in combination with a subthreshold dose of l-DOPA, which is different to the paradigms used in clinical trials, where A_2A antagonists were usually added to an optimal antiparkinsonian regimen. In clinical settings, A_2A antagonists generally reduced duration of off time, by as much as 25% in some studies. The effect of on time duration is less clear, and in a few studies an exacerbation of dyskinesia was reported. Two A_2A antagonists have been tested in phase III settings: istradefylline and preladenant. Istradefylline was effective in two phase III trials, but ineffective in another; the drug has been commercially available in Japan since 2013. In contrast, preladenant was ineffective in a phase III trial and the drug was discontinued. A phase III study with tozadenant will begin in 2015; the drug was effective at reducing off time in a phase IIb study. Other A_2A antagonists are in development at the preclinical and early clinical levels.

Roflumilast, a phosphodiesterase-4 inhibitor, induces phagocytic activity in Greek COPD patients

Background

A new approach to the treatment of COPD includes controlling inflammation because of its important role in exacerbation of the disease. Recently, roflumilast has been added as a therapeutic option for COPD. Roflumilast is an oral phosphodiesterase-4 inhibitor that targets inflammatory cells involved in triggering exacerbations of COPD. The objective of the current study was to evaluate roflumilast for its contribution to phagocytic activity in COPD patients.

Methods

Twenty-one patients diagnosed with COPD received roflumilast once daily for 6 months in combination with fluticasone (an inhaled corticosteroid), salmeterol (a long-acting β2-agonist), and tiotropium (a long-acting muscarinic antagonist) or combinations of these agents. The main inclusion criterion was stable disease for at least the previous 30 days. Neutrophils and spirometric changes, ie, forced expiratory volume in 1 second (FEV₁) and forced vital capacity (FVC), were measured in the COPD patients at indicated time points. The first sample was taken before receiving roflumilast, the second 3 months later, and the third after 6 months. Examination of defective phagocytosis was done by flow cytometry using a FagoFlowEx^® kit. The statistical analysis was performed using Statistica software.

Results

Our results indicate that phagocytic activity was increased after 3 and 6 months of treatment when compared with baseline (P<0.001). Similarly, FVC and FEV₁ were also increased during the 6-month period, but only FVC differed significantly from baseline (P<0.001).

Conclusion

Although the number of patients in this study was limited, our results indicate that roflumilast induces phagocytic activity, which improves lung function.

Clinical and molecular genetics of the phosphodiesterases (PDEs)

Cyclic nucleotide phosphodiesterases (PDEs) are enzymes that have the unique function of terminating cyclic nucleotide signaling by catalyzing the hydrolysis of cAMP and GMP. They are critical regulators of the intracellular concentrations of cAMP and cGMP as well as of their signaling pathways and downstream biological effects. PDEs have been exploited pharmacologically for more than half a century, and some of the most successful drugs worldwide today affect PDE function. Recently, mutations in PDE genes have been identified as causative of certain human genetic diseases; even more recently, functional variants of PDE genes have been suggested to play a potential role in predisposition to tumors and/or cancer, especially in cAMP-sensitive tissues. Mouse models have been developed that point to wide developmental effects of PDEs from heart function to reproduction, to tumors, and beyond. This review brings together knowledge from a variety of disciplines (biochemistry and pharmacology, oncology, endocrinology, and reproductive sciences) with emphasis on recent research on PDEs, how PDEs affect cAMP and cGMP signaling in health and disease, and what pharmacological exploitations of PDEs may be useful in modulating cyclic nucleotide signaling in a way that prevents or treats certain human diseases.

Design, synthesis and evaluation of dual pharmacology β2-adrenoceptor agonists and PDE4 inhibitors

A novel series of formoterol-phthalazinone hybrids were synthesised and evaluated as dual pharmacology β2-adrenoceptor agonists and PDE4 inhibitors. Most of the hybrids displayed high β2-adrenoceptor agonist and moderate PDE4 inhibitory activities. The most potent compound, (R,R)-11c, exhibited agonist (EC50=1.05nM, pEC50=9.0) and potent PDE4B2 inhibitory activities (IC50=0.092μM).

Overactive bladder syndrome and the potential role of prostaglandins and phosphodiesterases: an introduction

In this paper, a general introduction is given, presenting the overactive bladder syndrome (OAB) and its impact on the quality of life and economical burden in patients affected. Moreover, the anatomy, physiology and histology of the lower urinary tract are discussed, followed by a brief overview on the possible role of prostaglandin (PG) and phosphodiesterase type 5 (PDE5) in the urinary bladder. The current literature on the role and distribution of PGE2 and its receptors in the urinary bladder is discussed. In both animal models and in human studies, high levels of signaling molecules such as PG and cGMP have been implicated, in decreased functional bladder capacity and micturition volume, as well as in increased voiding contraction amplitude. As a consequence, inhibition of prostanoid production, the use of prostanoid receptor antagonists, or PDE inhibitors might be a rational way to treat patients with detrusor overactivity. Similarly, prostanoid receptor agonists, or agents that stimulate their production, might have a function in treating bladder underactivity.

The absence of mrp4 has no effect on the recruitment of neutrophils and eosinophils into the lung after LPS, cigarette smoke or allergen challenge

The multidrug resistance protein 4 (Mrp4) is an ATP-binding cassette transporter that is capable of exporting the second messenger cAMP from cells, a process that might regulate cAMP-mediated anti-inflammatory processes. However, using LPS- or cigarette smoke (CS)-inflammation models, we found that neutrophil numbers in the bronchoalveolar lavage fluid (BALF) were similar in Mrp4^−/− and Mrp4^+/+ mice treated with LPS or CS. Similarly, neutrophil numbers were not reduced in the BALF of LPS-challenged wt mice after treatment with 10 or 30 mg/kg of the Mrp1/4 inhibitor MK571. The absence of Mrp4 also had no impact on the influx of eosinophils or IL-4 and IL-5 levels in the BALF after OVA airway challenge in mice sensitized with OVA/alum. LPS-induced cytokine release in whole blood ex vivo was also not affected by the absence of Mrp4. These data clearly suggest that Mrp4 deficiency alone is not sufficient to reduce inflammatory processes in vivo. We hypothesized that in combination with PDE4 inhibitors, used at suboptimal concentrations, the anti-inflammatory effect would be more pronounced. However, LPS-induced neutrophil recruitment into the lung was no different between Mrp4^−/− and Mrp4^+/+ mice treated with 3 mg/kg Roflumilast. Finally, the single and combined administration of 10 and 30 mg/kg MK571 and the specific breast cancer resistance protein (BCRP) inhibitor KO143 showed no reduction of LPS-induced TNFα release into the BALF compared to vehicle treated control animals. Similarly, LPS-induced TNFα release in murine whole blood of Mrp4^+/+ or Mrp4^−/− mice was not reduced by KO143 (1, 10 µM). Thus, BCRP seems not to be able to compensate for the absence or inhibition of Mrp4 in the used models. Taken together, our data suggest that Mrp4 is not essential for the recruitment of neutrophils into the lung after LPS or CS exposure or of eosinophils after allergen exposure.

Phosphodiesterase 4-targeted treatments for autoimmune diseases

Advancements in phosphodiesterase (PDE)-targeted therapies have shown promise in recent years for treating patients with a variety of autoimmune diseases. This review summarizes the development of PDE4 inhibitors and the associated literature with a focus on treatments for autoimmune diseases. After the initial investigations of the prototypic PDE inhibitor, rolipram, more selective inhibitors targeting the PDE4 isozyme have been developed. With phase II and phase III clinical trials currently underway to evaluate the safety and efficacy of the latest generation of PDE4 inhibitors, namely apremilast, a new class of treatments may be around the corner for patients suffering from chronic, autoimmune diseases.

Determination of 2-aryl-7(3',4'-dialkoxyphenyl)-pyrazolo [1,5-alpha] pyrimidine, a novel phosphodiesterase-4 inhibitor, in rat plasma by liquid chromatography-tandem mass spectrometry

A method for assaying a novel phosphodiesterase-4 inhibitor, 2-aryl-7(3',4'-dialkoxyphenyl)-pyrazolo [1,5-alpha] pyrimidine (PDE-310), was developed and validated in rat plasma using liquid chromatography-tandem mass spectrometry (LC-MS-MS). Rat plasma samples were processed by liquid-liquid extraction with ethyl acetate and injected onto the LC-MS-MS system for quantification. PDE-310 and imipramine (i.e., internal standard) were separated using a Gemini C18 column with mixture of acetonitrile and 0.1% formic acid (70:30, v/v) as the mobile phase. The ion transitions monitored were m/z 425.0 → 331.0 for PDE-310 and m/z 281.3 → 86.1 for imipramine in the multiple-reaction monitoring mode. The detector response was specific and linear for PDE-310 concentrations in the range of 0.1-50 µg/mL. The intra-day and inter-day precision and accuracy of the method were determined to be within the acceptance criteria for assay validation guidelines. The recoveries were approximately 85.7 and 88.2% from rat plasma for PDE-310 and imipramine, respectively. PDE-310 was stable under various processing and handling conditions. PDE-310 concentrations were readily measured in rat plasma samples up to 8 h after an intravenous administration of PDE-310, suggesting that the assay is practically useful.

Myelin-derived lipids modulate macrophage activity by liver X receptor activation

Multiple sclerosis is a chronic, inflammatory, demyelinating disease of the central nervous system in which macrophages and microglia play a central role. Foamy macrophages and microglia, containing degenerated myelin, are abundantly found in active multiple sclerosis lesions. Recent studies have described an altered macrophage phenotype after myelin internalization. However, it is unclear by which mechanisms myelin affects the phenotype of macrophages and how this phenotype can influence lesion progression. Here we demonstrate, by using genome wide gene expression analysis, that myelin-phagocytosing macrophages have an enhanced expression of genes involved in migration, phagocytosis and inflammation. Interestingly, myelin internalization also induced the expression of genes involved in liver-X-receptor signaling and cholesterol efflux. In vitro validation shows that myelin-phagocytosing macrophages indeed have an increased capacity to dispose intracellular cholesterol. In addition, myelin suppresses the secretion of the pro-inflammatory mediator IL-6 by macrophages, which was mediated by activation of liver-X-receptor β. Our data show that myelin modulates the phenotype of macrophages by nuclear receptor activation, which may subsequently affect lesion progression in demyelinating diseases such as multiple sclerosis.

Zaprinast activates MAPKs, NFκB, and Akt and induces the expressions of inflammatory genes in microglia

Previously, the authors reported that zaprinast, an inhibitor of cGMP-selective phosphodiesterases, induced the secretions of TNF-α and IL-1β by microglia and enhanced the induction of iNOS by lipopolysaccharide (LPS). In this study, the signaling mechanism responsible for microglial activation by zaprinast was investigated and the effects of zaprinast and LPS on microglial activation were compared. Zaprinast was found to activate ERK1/2, p38 MAPK, JNK, NFκB, and PI3K/Akt, and subsequently, induce the mRNA expressions of IL-1α, IL-1β, TNF-α, CCL2, CCL4, CXCL1, CXCL2, and CD14. Associations between signaling pathways and gene expressions were examined by treating microglia with signal inhibitors. PDTC inhibited the induction of all the above genes by zaprinast, and SB203580 inhibited all genes except CXCL1. SP600125, PD98059, and LY294002 inhibited the induction of at least CCL2. Microglial activation by zaprinast was then compared with full-blown activation by LPS. The zaprinast-induced phosphorylations of MAPKs and IκB were less prompt than LPS-induced phosphorylations. IκB degradation by LPS was significant at 10min and did not return to normal, whereas zaprinast induced a later, transient degradation. LPS induced the mRNA expressions of IL-1β, TNF-α, IL-6, CCL2, iNOS, and COX-2, and although zaprinast significantly induced the expressions of all except IL-6 and iNOS, these inductions were far less than those induced by LPS. Collectively, zaprinast was found to upregulate microglial activity mainly via NFκB and p38 MAPK signaling and the subsequent expressions of inflammatory genes. Although, zaprinast was found to have obvious effects on microglia, these were weaker than the effects of LPS.

Effect of phosphodiesterase 7 (PDE7) inhibitors in experimental autoimmune encephalomyelitis mice. Discovery of a new chemically diverse family of compounds

Phosphodiesterase (PDE) 7 is involved in proinflammatory processes, being widely expressed both on lymphocytes and on certain brain regions. Specific inhibitors of PDE7 have been recently reported as potential new drugs for the treatment of neurological disorders because of their ability to increase intracellular levels of cAMP and thus to modulate the inflammatory process, as a neuroprotective well-established strategy. Multiple sclerosis is an unmet disease in which pathologies on the immune system, T-cells, and specific neural cells are involved simultaneously. Therefore, PDE7 inhibitors able to interfere with all these targets may represent an innovative therapy for this pathology. Here, we report a new chemically diverse family of heterocyclic PDE7 inhibitors, discovered and optimized by using molecular modeling studies, able to increase cAMP levels in cells, decrease inflammatory activation on primary neural cultures, and also attenuate the clinical symptoms in the experimental autoimmune encephalomyelitis (EAE) mouse model. These results led us to propose the use of PDE7 inhibitors as innovative therapeutic agents for the treatment of multiple sclerosis.

Kaempferia parviflora, a plant used in traditional medicine to enhance sexual performance contains large amounts of low affinity PDE5 inhibitors

AIM OF THE STUDY

A number of medicinal plants are used in traditional medicine to treat erectile dysfunction. Since cyclic nucleotide PDEs inhibitors underlie several current treatments for this condition, we sought to show whether these plants might contain substantial amounts of PDE5 inhibitors.

MATERIALS AND METHODS

Forty one plant extracts and eight 7-methoxyflavones from Kaempferia parviflora Wall. ex Baker were screened for PDE5 and PDE6 inhibitory activities using the two-step radioactive assay. The PDE5 and PDE6 were prepared from mice lung and chicken retinas, respectively. All plant extracts were tested at 50 μg/ml whereas the pure compounds were tested at 10 μM.

RESULTS

From forty one plant extracts tested, four showed the PDE5 inhibitory effect. The chemical constituents isolated from rhizomes of Kaempferia parviflora were further investigated on inhibitory activity against PDE5 and PDE6. The results showed that 7-methoxyflavones from this plant showed inhibition toward both enzymes. The most potent PDE5 inhibitor was 5,7-dimethoxyflavone (IC(50) = 10.64 ± 2.09 μM, selectivity on PDE5 over PDE6 = 3.71). Structure activity relationship showed that the methoxyl group at C-5 position of 7-methoxyflavones was necessary for PDE5 inhibition.

CONCLUSIONS

Kaempferia parviflora rhizome extract and its 7-methoxyflavone constituents had moderate inhibitory activity against PDE5. This finding provides an explanation for enhancing sexual performance in the traditional use of Kaempferia parviflora. Moreover, 5,7-dimethoxyflavones should make a useful lead compound to further develop clinically efficacious PDE5 inhibitors.

Effects of pentoxifylline and H-89 on epileptogenic activity of bucladesine in pentylenetetrazol-treated mice

The present study shows interactive effects of pentoxifylline (PTX) as a phosphodiesterase (PDE) inhibitor, H-89 as a protein kinase A (PKA) inhibitor and bucladesine (db-cAMP) as a cAMP agonist on pentylenetetrazol (PTZ)-induced seizure in mice. Different doses of pentoxifylline (25, 50, 100 mg/kg), bucladesine (50, 100, 300 nM/mouse), and H-89 (0.05, 0.1, 0.2 mg/100g) were administered intraperitoneally (i.p.), 30 min before intravenous (i.v.) infusion of PTZ (0.5% w/v). In combination groups, the first and second components were injected 45 and 30 min before PTZ infusion. In all groups, the control animals received an appropriate volume of vehicle. Single administration of PTX had no significant effect on both seizure latency and threshold. Bucladesine significantly decreased seizure latency and threshold only at a high concentration (300 nM/mouse). Intraperitoneal administration of H-89 (0.2 mg/100g) significantly increased seizure latency and threshold in PTZ-treated animals. All applied doses of bucladesine in combination with PTX (50 mg/kg) caused a significant reduction in seizure latency. Pretreatment of animals with PTX (50 and 100 mg/kg) attenuated the anticonvulsant effect of H-89 (0.2 mg/100g) in PTZ-exposed animals. H-89 (0.05, 0.2 mg/100g) prevented the epileptogenic activity of bucladesine (300 nM) with significant increase of seizure latency and seizure threshold. In conclusion, we showed that seizure activities were affected by pentoxifylline, H-89 and bucladesine via interactions with intracellular cAMP and cGMP signaling pathways, cyclic nucleotide-dependent protein kinases, and related neurotransmitters.