PDE4-inhibitors: a novel, targeted therapy for obstructive airways disease

Host cell cAMP-Epac-Rap1b pathway inhibition by hawthorn extract as a potential target against Trypanosoma cruzi infection

Although the two drugs currently available for the treatment of Chagas disease, Benznidazole and Nifurtimox, have proven to be effective in the acute phase of the disease, the 60-90-day treatment leads to high toxicity and unwanted side effects, presenting, in addition, a low efficacy in the chronic phase of the disease. For this reason, new therapies that are more effective are needed. In this regard, we have recently shown that the inhibition of the Epac-Rap1b pathway suppressed the cAMP-mediated host cell invasion by Trypanosoma cruzi. Interestingly, it has been described that vitexin, a natural flavone that protects against ischemia-reperfusion damage, acts by inhibiting the expression of Epac and Rap1 proteins. Vitexin can be found in plants of the genus Crataegus spp., traditionally known as hawthorn, which are of great interest considering their highly documented use as cardio-protectors. Pre-treating cells with an extract of Crataegus oxyacantha produced levels of T. cruzi invasion comparable to the ones observed for the commercially available Epac1-specific inhibitor, ESI-09. In addition, extract-treated cells exhibited a decrease in the activation of Rap1b, suggesting that the effects of the extract would be mediated by the inhibition of the cAMP-Epac-Rap1 signaling pathway. Using HPLC-HRMS2, we could confirm the presence of vitexin, and other flavones that could act as inhibitors of Epac/Rap1b, in the extracts of C. oxyacantha. Most significantly, when cells were treated with the extract of C. oxyacantha in conjunction with Nifurtimox, an increased modulation of invasion was observed.

Effects of intranasal azithromycin on features of cigarette smoke-induced lung inflammation

Airflow limitation in chronic obstructive pulmonary disease (COPD) is the result of exaggerated airway fibrosis and obliteration of the small airways due to persistent inflammation, and an impaired anti-oxidant response. EMT has been implicated as an active signalling process in cigarette smoke (CS)-induced lung pathology, and macrolide Azithromycin (AZT) use has gained interest in treating COPD. Here, we tested effectiveness of intra-nasal AZT alone and in combination with dexamethasone (DEX) on CS-induced acute lung inflammation. Human alveolar epithelial cells (A549) were treated with CS extract (CSE) for 48 h, and male Balb/c mice were exposed to CS (3 cigarettes-3 times/day) for 4 days. The effects of AZT alone (0.25 and 1.25 μM, in vitro; 0.5 and 5 mg/kg, in vivo) or in combination with DEX (1 μM, in vitro; 1 mg/kg, in vivo) on CS-induced cellular cytotoxicity, oxidative stress, inflammation, and lung function were assessed. AZT alone and in combination with DEX significantly inhibited the CS (E)-induced expression of mesenchymal protein markers and the regulatory protein β-catenin. Furthermore, AZT by itself or in combination with DEX significantly suppressed CS-induced expression of the proinflammatory cytokine TNFα and prevented p-NFkB. Mechanistically, AZT restored the CS-induced reduction in anti-oxidant transcription factor NRF2 and upregulated HDAC2 levels, thereby repressing inflammatory gene expression. Beneficial effects of AZT functionally translated in improved lung mechanics in vivo. Further preclinical and clinical studies are warranted to fully establish and validate the therapeutic efficacy of AZT as a mono- or combination therapy for the treatment of COPD.

NCS 613, a Potent PDE4 Inhibitor, Displays Anti-Inflammatory and Anti-Proliferative Properties on A549 Lung Epithelial Cells and Human Lung Adenocarcinoma Explants

Chronic inflammation is a deleterious process occurring in several pulmonary diseases; it is a driving force promoting tumorigenesis. By regulating local cyclic nucleotide concentration, cyclic nucleotide phosphodiesterases (PDE) govern important biological processes, including inflammation and proliferation. The aim of this study was to investigate the anti-inflammatory and anti-proliferative effects of NCS 613, a specific PDE4 inhibitor, on TNFα-treated human lung adenocarcinoma cell line (A549) and on human lung adenocarcinoma explants. PDE4 isoforms and inflammatory pathways mediated by p38 MAPK, ERK1/2, and IκBα were analyzed by Western blot and immunostainings. Proliferation were performed using [³H]-thymidine incorporation under different experimental conditions. TNFα-stimulation increased p38 MAPK phosphorylation and NF-κB translocation into the nucleus, which was abolished by NCS 613 treatment. Concomitantly, NCS 613 restores IκBα detection level in human adenocarcinoma. An IC₅₀ value of 8.5 μM was determined for NCS 613 on anti-proliferative properties while ERK1/2 signaling was down-regulated in A549 cells and lung adenocarcinoma explants. These findings shed light on PDE4 signaling as a key regulator of chronic inflammation and cancer epithelial cell proliferation. It suggests that PDE4 inhibition by NCS 613 represent potential and interesting strategy for therapeutic intervention in tackling chronic inflammation and cell proliferation.

Inhibition of PDE4/PDE4B improves renal function and ameliorates inflammation in cisplatin-induced acute kidney injury

Nephrotoxicity is a known clinical complication of cisplatin that limits the use of this potent antitumor drug. Cyclic nucleotide phosphodiesterases (PDEs) play complex roles in physiology and pathology. PDE4, which is a member of the PDE family, has four subtypes (PDE4A-PDE4D), and PDE4B plays an important role in inflammation. Thus, in the present study, we investigated the effect of PDE4/PDE4B inhibition on renal function and inflammation in a cisplatin nephrotoxicity model. In mice, cisplatin enhanced mRNA and protein expression of PDE4B in renal tubules. After treatment with the PDE4 inhibitor cilomilast, cisplatin-induced renal dysfunction, renal tubular injury, tubular cell apoptosis, and inflammation were all improved. Next, after silencing PDE4B in vivo, we observed a protective effect against cisplatin nephrotoxicity similar to that of the PDE4 inhibitor. In vitro, cisplatin-induced renal tubular cell death was strikingly ameliorated by the PDE4 inhibitor and PDE4B knockdown along with the blockade of the inflammatory response. Considering the known roles of some cell survival pathways in antagonizing insults, we examined levels of PDE4-associated proteins sirtuin 1, phosphatidylinositol 3-kinase, and phosphorylated AKT in cisplatin-treated renal tubular cells with or without cilomilast treatment. Strikingly, cisplatin treatment downregulated the expression of the above proteins, and this effect was largely abolished by the PDE4 inhibitor. Together, these findings indicate the beneficial role of PDE4/PDE4B inhibition in treating cisplatin nephrotoxicity, possibly through antagonizing inflammation and restoring cell survival signaling pathways.

The 'gifted' actinomycete Streptomyces leeuwenhoekii

Streptomyces leeuwenhoekii strains C34^T, C38, C58 and C79 were isolated from a soil sample collected from the Chaxa Lagoon, located in the Salar de Atacama in northern Chile. These streptomycetes produce a variety of new specialised metabolites with antibiotic, anti-cancer and anti-inflammatory activities. Moreover, genome mining performed on two of these strains has revealed the presence of biosynthetic gene clusters with the potential to produce new specialised metabolites. This review focusses on this new clade of Streptomyces strains, summarises the literature and presents new information on strain C34^T.

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.

Glucagon and glucagon-like peptide-1 as novel anti-inflammatory and immunomodulatory compounds

Glucagon and glucagon-like peptide-1 (GLP-1) are polypeptide hormones that are produced by pancreatic α-cells and the intestine, respectively, whose main function is to control glucose homeostasis. The glucagon and GLP-1 levels are imbalanced in diabetes. Furthermore, type 1 diabetic patients and animals present with a diminished inflammatory response, which is related to some morbidities of diabetes, such as a higher incidence of infectious diseases, including sepsis. The focus of this review is to briefly summarize the state of the art concerning the effects of glucagon and GLP-1 on the inflammatory response. Here, we propose that glucagon and GLP-1 have anti-inflammatory properties, making them possible prototypes for the design and synthesis of new compounds to treat inflammatory diseases. In addition, glucagon, GLP-1 or their analogues or new derivatives may not only be important for managing inflammatory diseases but may also have the therapeutic potential to prevent, cure or ameliorate diabetes in patients by counteracting the deleterious effects of pro-inflammatory cytokines on the function and viability of pancreatic β-cells. In addition, GLP-1, its analogues or drugs that inhibit GLP-1 metabolism may have a doubly beneficial effect in diabetic patients by inhibiting the inflammatory response and reducing glycaemia.

Phosphodiesterase 4 inhibitors and drugs of abuse: current knowledge and therapeutic opportunities

BACKGROUND

Long-term exposure to drugs of abuse causes an up-regulation of the cAMP-signaling pathway in the nucleus accumbens and other forebrain regions, this common neuroadaptation is thought to underlie aspects of drug tolerance and dependence. Phosphodiesterase 4 (PDE4) is an enzyme that the selective hydrolyzes intracellular cAMP. It is expressed in several brain regions that regulate the reinforcing effects of drugs of abuse.

OBJECTIVE

Here, we review the current knowledge about central nervous system (CNS) distribution of PDE4 isoforms and the effects of systemic and brain-region specific inhibition of PDE4 on behavioral models of drug addiction.

METHODS

A systematic literature search was performed using the Pubmed.

RESULTS

Using behavioral sensitization, conditioned place preference and drug self-administration as behavioral models, a large number of studies have shown that local or systemic administration of PDE4 inhibitors reduce drug intake and/or drug seeking for psychostimulants, alcohol, and opioids in rats or mice.

CONCLUSIONS

Preclinical studies suggest that PDE4 could be a therapeutic target for several classes of substance use disorder. We conclude by identifying opportunities for the development of subtype-selective PDE4 inhibitors that may reduce addiction liability and minimize the side effects that limit the clinical potential of non-selective PDE4 inhibitors. Several PDE4 inhibitors have been clinically approved for other diseases. There is a promising possibility to repurpose these PDE4 inhibitors for the treatment of drug addiction as they are safe and well-tolerated in patients.

The cAMP Pathway as Therapeutic Target in Autoimmune and Inflammatory Diseases

Nucleotide signaling molecules contribute to the regulation of cellular pathways. In the immune system, cyclic adenosine monophosphate (cAMP) is well established as a potent regulator of innate and adaptive immune cell functions. Therapeutic strategies to interrupt or enhance cAMP generation or effects have immunoregulatory potential in autoimmune and inflammatory disorders. Here, we provide an overview of the cyclic AMP axis and its role as a regulator of immune functions and discuss the clinical and translational relevance of interventions with these processes.

Phosphodiesterase 4 inhibitors for the treatment of chronic obstructive pulmonary disease: a review of current and developing drugs

INTRODUCTION

Phosphodiesterase (PDE) inhibitors modulate lung inflammation and cause bronchodilation by increasing intracellular cyclic adenosine 3', 5'-monophosphate in airway smooth muscle and inflammatory cells. Roflumilast is the only approved PDE-4 inhibitor (PDE4I) for use in chronic obstructive pulmonary disease (COPD). Its beneficial clinical effects occur preferentially in patients with chronic bronchitis and frequent COPD exacerbations. Use of roflumilast as adjunctive or alternate therapy to other COPD medications reduces exacerbations and modestly improves lung function.

AREAS COVERED

This article reviews the current role of PDE4I in COPD treatment emphasizing roflumilast's clinical efficacy and adverse effects. This article also reviews developing PDE4Is in early clinical trials and in preclinical studies.

EXPERT OPINION

After decades of research in drug development, PDE4Is are a welcomed addition to the COPD therapeutic armamentarium. In its current clinical role, the salubrious clinical effects of PDE4I in reducing exacerbations and stabilizing the frequent exacerbator phenotype have to be cautiously balanced with numerous adverse effects. Developing drugs may provide similar or better clinical benefits while minimizing adverse effects by changing the mode of drug delivery to inhaled formulations, combining dual PDE isoenzyme inhibitors (PDE1/4I and PDE3/4I) and by forming hybrid molecules with other bronchodilators (muscarinic receptor antagonist/PDE4I and β2-agonist/PDE4I).

PDE inhibitors currently in early clinical trials for the treatment of asthma

INTRODUCTION

PDE inhibitors could be useful in the treatment of asthma because of their bronchodilator and/or anti-inflammatory activities. Recently, some selective PDE3, PDE4 and PDE3/4 inhibitors have been shown to have beneficial effects in patients with asthma suggesting that such drugs may offer novel therapeutic options for the treatment of this disease.

AREAS COVERED

The authors describe the main PDE families that could be involved in asthma as well as the PDE inhibitors that have been evaluated for the treatment of asthma.

EXPERT OPINION

Although the potential therapeutic utility of PDE inhibitors has been demonstrated in various animal models of asthma, their clinical efficacy have been restricted by the dose-limiting side effects; no PDE inhibitor has yet been approved for the treatment of patients with asthma. Although new PDE inhibitors have been synthesised, most data are from cellular and tissue-level studies with human trials still on the horizon. Apparently, only CHF 6001, an inhaled PDE4 inhibitor, and RPL554, a dual PDE3/4 inhibitor, are still under clinical development. Further data from these new drugs are eagerly anticipated to better understand where these drugs might stand in the future treatment of asthma.

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.

Roflumilast N-oxide prevents cytokine secretion induced by cigarette smoke combined with LPS through JAK/STAT and ERK1/2 inhibition in airway epithelial cells

Cigarette smoke is a major cause of chronic obstructive pulmonary disease (COPD). Airway epithelial cells and macrophages are the first defense cells against cigarette smoke and these cells are an important source of pro-inflammatory cytokines. These cytokines play a role in progressive airflow limitation and chronic airways inflammation. Furthermore, the chronic colonization of airways by Gram-negative bacteria, contributes to the persistent airways inflammation and progression of COPD. The current study addressed the effects of cigarette smoke along with lipolysaccharide (LPS) in airway epithelial cells as a representative in vitro model of COPD exacerbations. Furthermore, we evaluated the effects of PDE4 inhibitor, the roflumilast N-oxide (RNO), in this experimental model. A549 cells were stimulated with cigarette smoke extract (CSE) alone (0.4% to 10%) or in combination with a low concentration of LPS (0.1 µg/ml) for 2 h or 24 h for measurement of chemokine protein and mRNAs and 5-120 min for protein phosphorylation. Cells were also pre-incubated with MAP kinases inhibitors and Prostaglandin E2 alone or combined with RNO, before the addition of CSE+LPS. Production of cytokines was determined by ELISA and protein phosphorylation by western blotting and phospho-kinase array. CSE did not induce production of IL-8/CXCL8 and Gro-α/CXCL1 from A549 cells, but increase production of CCL2/MCP-1. However the combination of LPS 0.1 µg/ml with CSE 2% or 4% induced an important production of these chemokines, that appears to be dependent of ERK1/2 and JAK/STAT pathways but did not require JNK and p38 pathways. Moreover, RNO associated with PGE2 reduced CSE+LPS-induced cytokine release, which can happen by occur through of ERK1/2 and JAK/STAT pathways. We report here an in vitro model that can reflect what happen in airway epithelial cells in COPD exacerbation. We also showed a new pathway where CSE+LPS can induce cytokine release from A549 cells, which is reduced by RNO.

Efficacy and safety of RPL554, a dual PDE3 and PDE4 inhibitor, in healthy volunteers and in patients with asthma or chronic obstructive pulmonary disease: findings from four clinical trials

BACKGROUND

Many patients with asthma or chronic obstructive pulmonary disease (COPD) routinely receive a combination of an inhaled bronchodilator and anti-inflammatory glucocorticosteroid, but those with severe disease often respond poorly to these classes of drug. We assessed the efficacy and safety of a novel inhaled dual phosphodiesterase 3 (PDE3) and PDE4 inhibitor, RPL554 for its ability to act as a bronchodilator and anti-inflammatory drug.

METHODS

Between February, 2009, and January, 2013, we undertook four proof-of-concept clinical trials in the Netherlands, Italy, and the UK. Nebulised RPL554 was examined in study 1 for safety in 18 healthy men who were randomly assigned (1:1:1) to receive an inhaled dose of RPL554 (0·003 mg/kg or 0·009 mg/kg) or placebo by a computer-generated randomisation table. Subsequently, six non-smoking men with mild allergic asthma received single doses of RPL554 (three received 0·009 mg/kg and three received 0·018 mg/kg) in an open-label, adaptive study, and then ten men with mild allergic asthma were randomly assigned to receive placebo or RPL554 (0·018 mg/kg) by a computer-generated randomisation table for an assessment of safety, bronchodilation, and bronchoprotection. Study 2 examined the reproducibility of the bronchodilator response to a daily dose of nebulised RPL554 (0·018 mg/kg) for 6 consecutive days in a single-blind (patients masked), placebo-controlled study in 12 men with clinically stable asthma. The safety and bronchodilator effect of RPL554 (0·018 mg/kg) was assessed in study 3, an open-label, placebo-controlled crossover trial, in 12 men with mild-to-moderate COPD. In study 4, a placebo-controlled crossover trial, the effect of RPL554 (0·018 mg/kg) on lipopolysaccharide-induced inflammatory cell infiltration in induced sputum was investigated in 21 healthy men. In studies 3 and 4, randomisation was done by computer-generated permutation with a block size of two for study 3 and four for study 4. Unless otherwise stated, participants and clinicians were masked to treatment assignment. Analyses were by intention to treat. All trials were registered with EudraCT, numbers 2008-005048-17, 2011-001698-22, 2010-023573-18, and 2012-000742-34.

FINDINGS

Safety was a primary endpoint of studies 1 and 3 and a secondary endpoint of studies 2 and 4. Overall, RPL554 was well tolerated, and adverse events were generally mild and of equal frequency between placebo and active treatment groups. Efficacy was a primary endpoint of study 2 and a secondary endpoint of studies 1 and 3. Study 1 measured change in forced expiratory volume in 1 s (FEV1) and provocative concentration of methacholine causing a 20% fall in FEV1 (PC20MCh) in participants with asthma. RPL554 produced rapid bronchodilation in patients with asthma with an FEV1 increase at 1 h of 520 mL (95% CI 320-720; p<0·0001), which was a 14% increase from placebo, and increased the PC20MCh by 1·5 doubling doses (95% CI 0·63-2·28; p=0·004) compared with placebo. The primary endpoint of study 2 was maximum FEV1 reached during 6 h after dosing with RPL554 in patients with asthma. RPL554 produced a similar maximum mean increase in FEV1 from placebo on day 1 (555 mL, 95% CI 442-668), day 3 (505 mL, 392-618), and day 6 (485 mL, 371-598; overall p<0·0001). A secondary endpoint of study 3 (patients with COPD) was the increase from baseline in FEV1. RPL554 produced bronchodilation with a mean maximum FEV1 increase of 17·2% (SE 5·2). In healthy individuals (study 4), the primary endpoint was percentage change in neutrophil counts in induced sputum 6 h after lipopolysaccharide challenge. RPL554 (0·018 mg/kg) did not significantly reduce the percentage of neutrophils in sputum (80·3% in the RPL554 group vs 84·2% in the placebo group; difference -3·9%, 95% CI -9·4 to 1·6, p=0·15), since RPL554 significantly reduced neutrophils (p=0·002) and total cells (p=0·002) to a similar degree.

INTERPRETATION

In four exploratory studies, inhaled RPL554 is an effective and well tolerated bronchodilator, bronchoprotector, and anti-inflammatory drug and further studies will establish the full potential of this new drug for the treatment of patients with COPD or asthma.

FUNDING

Verona Pharma.

Monitoring phosphodiesterase-4 inhibitors using liquid chromatography/(tandem) mass spectrometry in sports drug testing

RATIONALE

The recent discovery of resveratrol's capability to inhibit cAMP-specific phosphodiesterases (PDEs) and, as a consequence, to enhance particularly the activity of Sirt1 in animal models has reinforced the interest of preventive doping research organizations, especially in PDE4 inhibitors. Among these, the archetypical PDE4-inhibitor rolipram significantly increased the number of mitochondria in laboratory rodents, which further demonstrated a performance increase in a treadmill-test (time-to-exhaustion) of approximately 40%. Besides rolipram, a variety of new PDE4-inhibiting substances including cilomilast, roflumilast, and numerous additional new drug entities were described, with roflumilast being the first-in-class having received clinical approval for the treatment of chronic obstructive pulmonary disease (COPD). Due to the availability of these substances, and the fact that a misuse of such compounds in sport cannot be excluded, it deems relevant to probe for the prevalence of these compounds in sports drug testing programs.

METHODS

Known urinary phase-I metabolites of rolipram, roflumilast, and cilomilast were generated by in vitro incubations employing human liver microsomal preparations. The metabolites obtained were studied by liquid chromatography with high-resolution/high-accuracy tandem mass spectrometry (LC/MS/MS) and the reference product ion mass spectra of established and most relevant metabolites were utilized to provide the information necessary for comprehensive doping controls. The analytical procedure was based on conventional routine doping control assays employing enzymatic hydrolysis followed by liquid-liquid extraction and subsequent LC/MS/MS measurement.

RESULTS

Structures of diagnostic product ions and dissociation pathways of target analytes were elucidated, providing the information required for implementation into an existing test method for routine sports drug testing. The established method allowed for detection limits for the intact drugs of 1-5 ng/mL, and further assay characteristics (intraday precision 1.5-13.7%, interday precision 7.3-18.6%, recovery 20-100%, ion suppression/enhancement, and specificity) were determined. In addition, proof-of-concept analyses concerning roflumilast were conducted with a urine sample obtained from a COPD patient under roflumilast treatment.

cAMP regulation of airway smooth muscle function

Agonists activating β(2)-adrenoceptors (β(2)ARs) on airway smooth muscle (ASM) are the drug of choice for rescue from acute bronchoconstriction in patients with both asthma and chronic obstructive pulmonary disease (COPD). Moreover, the use of long-acting β-agonists combined with inhaled corticosteroids constitutes an important maintenance therapy for these diseases. β-Agonists are effective bronchodilators due primarily to their ability to antagonize ASM contraction. The presumed cellular mechanism of action involves the generation of intracellular cAMP, which in turn can activate the effector molecules cAMP-dependent protein kinase (PKA) and Epac. Other agents such as prostaglandin E(2) and phosphodiesterase inhibitors that also increase intracellular cAMP levels in ASM, can also antagonize ASM contraction, and inhibit other ASM functions including proliferation and migration. Therefore, β(2)ARs and cAMP are key players in combating the pathophysiology of airway narrowing and remodeling. However, limitations of β-agonist therapy due to drug tachyphylaxis related to β(2)AR desensitization, and recent findings regarding the manner in which β(2)ARs and cAMP signal, have raised new and interesting questions about these well-studied molecules. In this review we discuss current concepts regarding β(2)ARs and cAMP in the regulation of ASM cell functions and their therapeutic roles in asthma and COPD.

Distinct PKA and Epac compartmentalization in airway function and plasticity

Asthma and chronic obstructive pulmonary disease (COPD) are obstructive lung diseases characterized by airway obstruction, airway inflammation and airway remodelling. Next to inflammatory cells and airway epithelial cells, airway mesenchymal cells, including airway smooth muscle cells and (myo)fibroblasts, substantially contribute to disease features by the release of inflammatory mediators, smooth muscle contraction, extracellular matrix deposition and structural changes in the airways. Current pharmacological treatment of both diseases intends to target the dynamic features of the endogenous intracellular suppressor cyclic AMP (cAMP). This review will summarize our current knowledge on cAMP and will emphasize on key discoveries and paradigm shifts reflecting the complex spatio-temporal nature of compartmentalized cAMP signalling networks in health and disease. As airway fibroblasts and airway smooth muscle cells are recognized as central players in the development and progression of asthma and COPD, we will focus on the role of cAMP signalling in their function in relation to airway function and plasticity. We will recapture on the recent identification of cAMP-sensing multi-protein complexes maintained by cAMP effectors, including A-kinase anchoring proteins (AKAPs), proteins kinase A (PKA), exchange protein directly activated by cAMP (Epac), cAMP-elevating seven-transmembrane (7TM) receptors and phosphodiesterases (PDEs) and we will report on findings indicating that the pertubation of compartmentalized cAMP signalling correlates with the pathopysiology of obstructive lung diseases. Future challenges include studies on cAMP dynamics and compartmentalization in the lung and the development of novel drugs targeting these systems for therapeutic interventions in chronic obstructive inflammatory diseases.

Phosphodiesterase 4 inhibition impairs cocaine-induced inhibitory synaptic plasticity and conditioned place preference

Endocannabinoid-mediated long-term depression of inhibitory synaptic transmission (I-LTD) in the ventral tegmental area (VTA) is implicated in cocaine-induced inhibitory synaptic plasticity and behavioral effects. It remains poorly understood, however, how this I-LTD is regulated and whether this regulation affects cocaine-seeking behavior. I-LTD requires cyclic adenosine 3', 5'-monophosphate (cAMP)-dependent protein kinase A (PKA) signaling, raising the possibility that modulators of cAMP/PKA signaling may regulate I-LTD and the reinforcement behavior. Phosphodiesterase (PDE) 4 hydrolyses cAMP and terminates cAMP/PKA signaling. Here, we report that selective PDE4 inhibitors rolipram and Ro 20-1724 blocked I-LTD and acute depression of inhibitory postsynaptic currents (IPSCs) induced by D₂ dopamine receptor and cannabinoid CB₁ receptor agonists in VTA dopamine neurons. We also show that intra-VTA microinjections of PDE4 inhibitor rolipram impaired the acquisition, but not the expression, of conditioned place preference (CPP) to cocaine. Systemic administration of rolipram also increased cAMP response element-binding protein (CREB) phosphorylation and activation in the VTA. Together, our results suggest that blockade of cocaine-induced inhibitory synaptic plasticity (I-LTD) and enhancement of CREB activation are two putative cellular mechanisms by which PDE4 inhibition impairs the acquisition of cocaine CPP.

Severe asthma: advances in current management and future therapy

Effective treatment of severe asthma is a major unmet need because patients' symptoms are not controlled on maximum treatment with inhaled therapy. Asthma symptoms can be poorly controlled because of poor adherence to controller therapy, and this might be addressed by using combination inhalers that contain a corticosteroid and long-acting β(2)-agonist as reliever therapy in addition to maintenance treatment. New bronchodilators with a longer duration of action are in development, and recent studies have demonstrated the benefit of a long-acting anticholinergic bronchodilator in addition to β(2)-agonists in patients with severe asthma. Anti-IgE therapy is beneficial in selected patients with severe asthma. Several new blockers of specific mediators, including prostaglandin D(2), IL-5, IL-9, and IL-13, are also in clinical trials and might benefit patients with subtypes of severe asthma. Several broad-spectrum anti-inflammatory therapies that target neutrophilic inflammation are in clinical development for the treatment of severe asthma, but adverse effects after oral administration might necessitate inhaled delivery. Macrolides might benefit some patients with infection by atypical bacteria, but recent results are not encouraging, although there could be an effect in patients with predominant neutrophilic asthma. Corticosteroid resistance is a major problem in patients with severe asthma, and several molecular mechanisms have been described that might lead to novel therapeutic approaches, including drugs that could reverse this resistance, such as theophylline and nortriptyline. In selected patients with severe asthma, bronchial thermoplasty might be beneficial, but thus far, clinical studies have not been encouraging. Finally, several subtypes of severe asthma are now recognized, and in the future, it will be necessary to find biomarkers that predict responses to specific forms of therapy.

Emerging drugs for asthma

INTRODUCTION

Current drug treatments for asthma relieve bronchospasm and airway inflammation but do not offer a cure, and symptoms return when treatment is stopped. Asthma management guidelines emphasize the importance of effective asthma treatment to achieve and maintain asthma control. However, despite widely available and effective treatments, achieving asthma control is still an unmet need for many patients.

AREAS COVERED

Remarkable efforts have been made to identify the characteristic features of difficult-to-control (usually severe) asthma that are different from those described for mild-to-moderate asthma, setting the stage for the development of new and even individualized therapies. The most fascinating options of the new asthma treatments are biologic therapies, in particular monoclonal antibodies. In addition, some novel once-daily combinations of long-acting β(2)-agonist and inhaled corticosteroids are under development.

EXPERT OPINION

Asthma is a complex syndrome made up of a number of disease variants or asthma phenotypes, with different underlying pathophysiology. As different drugs target different pathways, it is necessary to determine the individual profile of pathophysiological abnormalities for each patient. Several cytokines have been implicated in the inflammatory cascades leading to the different asthma phenotypes, and the most relevant ones are discussed. The challenge in treating asthma resides precisely in its heterogeneity.

Pharmacology and therapeutics of bronchodilators

Bronchodilators are central in the treatment of of airways disorders. They are the mainstay of the current management of chronic obstructive pulmonary disease (COPD) and are critical in the symptomatic management of asthma, although controversies around the use of these drugs remain. Bronchodilators work through their direct relaxation effect on airway smooth muscle cells. at present, three major classes of bronchodilators, β(2)-adrenoceptor (AR) agonists, muscarinic receptor antagonists, and xanthines are available and can be used individually or in combination. The use of the inhaled route is currently preferred to minimize systemic effects. Fast- and short-acting agents are best used for rescue of symptoms, whereas long-acting agents are best used for maintenance therapy. It has proven difficult to discover novel classes of bronchodilator drugs, although potential new targets are emerging. Consequently, the logical approach has been to improve the existing bronchodilators, although several novel broncholytic classes are under development. An important step in simplifying asthma and COPD management and improving adherence with prescribed therapy is to reduce the dose frequency to the minimum necessary to maintain disease control. Therefore, the incorporation of once-daily dose administration is an important strategy to improve adherence. Several once-daily β(2)-AR agonists or ultra-long-acting β(2)-AR-agonists (LABAs), such as indacaterol, olodaterol, and vilanterol, are already in the market or under development for the treatment of COPD and asthma, but current recommendations suggest the use of LABAs only in combination with an inhaled corticosteroid. In addition, some new potentially long-acting antimuscarinic agents, such as glycopyrronium bromide (NVA-237), aclidinium bromide, and umeclidinium bromide (GSK573719), are under development, as well as combinations of several classes of long-acting bronchodilator drugs, in an attempt to simplify treatment regimens as much as possible. This review will describe the pharmacology and therapeutics of old, new, and emerging classes of bronchodilator.

Dual role of Toll-like receptors in asthma and chronic obstructive pulmonary disease

During the last decade, significant research has been focused on Toll-like receptors (TLRs) in the pathogenesis of airway diseases. TLRs are pattern recognition receptors that play pivotal roles in the detection of and response to pathogens. Because of the involvement of TLRs in innate and adaptive immunity, these receptors are currently being exploited as possible targets for drug development. Asthma and chronic obstructive pulmonary disease (COPD) are chronic inflammatory airway diseases in which innate and adaptive immunity play an important role. To date, asthma is the most common chronic disease in children aged 5 years and older. COPD is prevalent amongst the elderly and is currently the fifth-leading cause of death worldwide with still-growing prevalence. Both of these inflammatory diseases result in shortness of breath, which is treated, often ineffectively, with bronchodilators and glucocorticosteroids. Symptomatic treatment approaches are similar for both diseases; however, the underlying immunological mechanisms differ greatly. There is a clear need for improved treatment specific for asthma and for COPD. This review provides an update on the role of TLRs in asthma and in COPD and discusses the merits and difficulties of targeting these proteins as novel treatment strategies for airway diseases. TLR agonist, TLR adjuvant, and TLR antagonist therapies could all be argued to be effective in airway disease management. Because of a possible dual role of TLRs in airway diseases with shared symptoms and risk factors but different immunological mechanisms, caution should be taken while designing pulmonary TLR-based therapies.

Additive anti-inflammatory effects of beta 2 adrenoceptor agonists or glucocorticosteroid with roflumilast in human peripheral blood mononuclear cells

The phosphodiesterase 4 inhibitor (PDE4i) roflumilast has been approved in the US and EU for treatment of GOLD stage 3 and 4 chronic obstructive pulmonary disease (COPD). Inhaled β2 adrenoceptor agonist bronchodilators and anti-inflammatory glucocorticosteroids are also used as standard of care in COPD. We investigated the anti-inflammatory interaction of roflumilast in combination with long-acting β2 agonists (LABA), salmeterol or formoterol, or a glucocorticosteroid, dexamethasone, on cytokine production from LPS-stimulated human primary peripheral blood mononuclear cells (PBMC). Salmeterol or formoterol caused a concentration-dependent inhibition of tumor necrosis factor-α (TNFα) secretion with an IC50 of 0.33 pM (C.I. 0.006-19) and 34 pM (C.I. 13-87), respectively. When roflumilast was evaluated, the addition of salmeterol (1 nM) to roflumilast caused the IC50 for roflumilast to shift from 1.8 nM (C.I. 0.8-4) to 4.1 pM (C.I.0.3-69) (p < 0.01), and maximal inhibition increased from 72.5 ± 3.2% to 90.9 ± 3.1%. Addition of formoterol to roflumilast also produced an increased TNFα inhibition more than either drug alone (p < 0.05). The inhibition of TNFα production with salmeterol was both β2 adrenoceptor- and protein kinase A-dependent. Addition of roflumilast (10 nM) in the presence of dexamethasone increased the inhibition of LPS-induced TNFα and CCL3. Roflumilast in combination with salmeterol, formoterol, or dexamethasone increased the inhibition of LPS-induced TNFα from human PBMC, in an additive manner. Addition of roflumilast to either a β2 adrenoceptor agonist or a glucocorticosteroid may provide superior anti-inflammatory activity and greater efficacy in COPD patients and be dose sparing.

Parsimonious discovery of synergistic drug combinations

Combination therapies that enhance efficacy or permit reduced dosages to be administered have seen great success in a variety of therapeutic applications. More fundamentally, the discovery of epistatic pathway interactions not only informs pharmacologic intervention but can be used to better understand the underlying biological system. There is, however, no systematic and efficient method to identify interacting activities as candidates for combination therapy and, in particular, to identify those with synergistic activities. We devised a pooled, self-deconvoluting screening paradigm for the efficient comprehensive interrogation of all pairs of compounds in 1000-compound libraries. We demonstrate the power of the method to recover established synergistic interactions between compounds. We then applied this approach to a cell-based screen for anti-inflammatory activities using an assay for lipopolysaccharide/interferon-induced acute phase response of a monocytic cell line. The described method, which is >20 times as efficient as a naïve approach, was used to test all pairs of 1027 bioactive compounds for interleukin-6 suppression, yielding 11 pairs of compounds that show synergy. These 11 pairs all represent the same two activities: β-adrenergic receptor agonists and phosphodiesterase-4 inhibitors. These activities both act through cyclic AMP elevation and are known to be anti-inflammatory alone and to synergize in combination. Thus we show proof of concept for a robust, efficient technique for the identification of synergistic combinations. Such a tool can enable qualitatively new scales of pharmacological research and chemical genetics.

Atacamycins A-C, 22-membered antitumor macrolactones produced by Streptomyces sp. C38

Three new 22-membered macrolactone antibiotics, atacamycins A-C, were produced by Streptomyces sp. C38, a strain isolated from a hyper-arid soil collected from the Atacama Desert in the north of Chile. The metabolites were discovered in our HPLC-diode array screening and isolated from the mycelium by extraction and chromatographic purification steps. The structures were determined by mass spectrometry and NMR experiments. Atacamycins A, B and C exhibited moderate inhibitory activities against the enzyme phosphodiesterase (PDE-4B2), whereas atacamycin A showed a moderate antiproliferative activity against adeno carcinoma and breast carcinoma cells.

Roflumilast

Each month, subscribers to The Formulary Monograph Service receive 5 to 6 well-documented monographs on drugs that are newly released or are in late phase 3 trials. The monographs are targeted to Pharmacy & Therapeutics Committees. Subscribers also receive monthly 1-page summary monographs on agents that are useful for agendas and pharmacy/nursing in-services. A comprehensive target drug utilization evaluation/medication use evaluation (DUE/MUE) is also provided each month. With a subscription, the monographs are sent in print and are also available on-line. Monographs can be customized to meet the needs of a facility. Subscribers to The Formulary Monograph Service also receive access to a pharmacy bulletin board, The Formulary Information Exchange (The F.I.X.). All topics pertinent to clinical and hospital pharmacy are discussed on The F.I.X. Through the cooperation of The Formulary, Hospital Pharmacy publishes selected reviews in this column. For more information about The Formulary Monograph Service or The F.I.X., call The Formulary at 800-322-4349. The August 2011 monograph topics are on fidaxomicin, boceprevir, telaprevir, rilpivirine hydrochloride, and gabapentin enacarbil. The DUE/MUE is on fidaxomicin.

Nitric oxide/cGMP pathway signaling actively down-regulates α4β1-integrin affinity: an unexpected mechanism for inducing cell de-adhesion

BACKGROUND

Integrin activation in response to inside-out signaling serves as the basis for rapid leukocyte arrest on endothelium, migration, and mobilization of immune cells. Integrin-dependent adhesion is controlled by the conformational state of the molecule, which is regulated by seven-transmembrane Guanine nucleotide binding Protein-Coupled Receptors (GPCRs). α4β1-integrin (CD49d/CD29, Very Late Antigen-4, VLA-4) is expressed on leukocytes, hematopoietic progenitors, stem cells, hematopoietic cancer cells, and others. VLA-4 conformation is rapidly up-regulated by inside-out signaling through Gαi-coupled GPCRs and down-regulated by Gαs-coupled GPCRs. However, other signaling pathways, which include nitric oxide-dependent signaling, have been implicated in the regulation of cell adhesion. The goal of the current report was to study the effect of nitric oxide/cGMP signaling pathway on VLA-4 conformational regulation.

RESULTS

Using fluorescent ligand binding to evaluate the integrin activation state on live cells in real-time, we show that several small molecules, which specifically modulate nitric oxide/cGMP signaling pathway, as well as a cell permeable cGMP analog, can rapidly down-modulate binding of a VLA-4 specific ligand on cells pre-activated through three Gαi-coupled receptors: wild type CXCR4, CXCR2 (IL-8RB), and a non-desensitizing mutant of formyl peptide receptor (FPR ΔST). Upon signaling, we detected rapid changes in the ligand dissociation rate. The dissociation rate after inside-out integrin de-activation was similar to the rate for resting cells. In a VLA-4/VCAM-1-specific myeloid cell adhesion system, inhibition of the VLA-4 affinity change by nitric oxide had a statistically significant effect on real-time cell aggregation.

CONCLUSIONS

We conclude that nitric oxide/cGMP signaling pathway can rapidly down-modulate the affinity state of the VLA-4 binding pocket, especially under the condition of sustained Gαi-coupled GPCR signaling, generated by a non-desensitizing receptor mutant. This suggests a fundamental role of this pathway in de-activation of integrin-dependent cell adhesion.