Roles of roflumilast, a selective phosphodiesterase 4 inhibitor, in airway diseases

Endothelial phosphodiesterase 4B inactivation ameliorates endothelial-to-mesenchymal transition and pulmonary hypertension

Pulmonary hypertension (PH) is a fatal disorder characterized by pulmonary vascular remodeling and obstruction. The phosphodiesterase 4 (PDE4) family hydrolyzes cyclic AMP (cAMP) and is comprised of four subtypes (PDE4A-D). Previous studies have shown the beneficial effects of pan-PDE4 inhibitors in rodent PH; however, this class of drugs is associated with side effects owing to the broad inhibition of all four PDE4 isozymes. Here, we demonstrate that PDE4B is the predominant PDE isozyme in lungs and that it was upregulated in rodent and human PH lung tissues. We also confirmed that PDE4B is mainly expressed in the lung endothelial cells (ECs). Evaluation of PH in Pde4b wild type and knockout mice confirmed that Pde4b is important for the vascular remodeling associated with PH. In vivo EC lineage tracing demonstrated that Pde4b induces PH development by driving endothelial-to-mesenchymal transition (EndMT), and mechanistic studies showed that Pde4b regulates EndMT by antagonizing the cAMP-dependent PKA-CREB-BMPRII axis. Finally, treating PH rats with a PDE4B-specific inhibitor validated that PDE4B inhibition has a significant pharmacological effect in the alleviation of PH. Collectively, our findings indicate a critical role for PDE4B in EndMT and PH, prompting further studies of PDE4B-specific inhibitors as a therapeutic strategy for PH.

The PDE4 Inhibitors Roflumilast and Rolipram Rescue ADO2 Osteoclast Resorption Dysfunction

Autosomal Dominant Osteopetrosis type II (ADO2) is a rare bone disease of impaired osteoclastic bone resorption caused by heterozygous missense mutations in the chloride channel 7 (CLCN7). Adenylate cyclase, which catalyzes the formation of cAMP, is critical for lysosomal acidification in osteoclasts. We found reduced cAMP levels in ADO2 osteoclasts compared to wild-type (WT) osteoclasts, leading us to examine whether regulating cAMP would improve ADO2 osteoclast activity. Although forskolin, a known activator of adenylate cyclase and cAMP levels, negatively affected osteoclast number, it led to an overall increase in ADO2 and WT osteoclast resorption activity in vitro. Next, we examined cAMP hydrolysis by the phosphodiesterase 4 (PDE4) proteins in ADO2 versus WT osteoclasts. QPCR analysis revealed higher expression of the three major PDE4 subtypes (4a, 4b, 4d) in ADO2 osteoclasts compared in WT, consistent with reduced cAMP levels in ADO2 osteoclasts. In addition, we found that the PDE4 antagonists, rolipram and roflumilast, stimulated ADO2 and WT osteoclast formation in a dose-dependent manner. Importantly, roflumilast and rolipram displayed a concentration-dependent increase in osteoclast resorption activity which was greater in ADO2 than WT osteoclasts. Moreover, treatment with roflumilast rescued cAMP levels in ADO2 OCLs. The key findings from our studies demonstrate that osteoclasts from ADO2 mice exhibit reduced cAMP levels and PDE4 inhibition rescues cAMP levels and ADO2 osteoclast activity dysfunction in vitro. The mechanism of action of PDE4 inhibitors and their ability to reduce the high bone mass of ADO2 mice in vivo are currently under investigation. Importantly, these studies advance the understanding of the mechanisms underlying the ADO2 osteoclast dysfunction which is critical for the development of therapeutic approaches to treat clinically affected ADO2 patients.

Pharmacological management of neurocognitive impairment in schizophrenia: A narrative review

BACKGROUND

Cognitive impairment are among the core features of schizophrenia, experienced by up to 75% of patients. Available treatment options for schizophrenia including dopamine antagonists and traditional antipsychotic medications have not been shown to confer significant benefits on cognitive deficits. Contrary to the focus on management of positive symptoms in schizophrenia, cognitive abilities are main predictor of independent living skills, functional abilities, employment, engagement in relapse prevention, and patients' subjective sense of well-being and quality of life. This review aims to provide a summary of recent literature on pharmacological options for the treatment of cognitive deficits in schizophrenia.

METHODS

We conducted a literature search of studies from 2011 to 2021 across four electronic databases including PubMed, PsycInfo, MEDLINE, and Embase. Human studies using a pharmacological treatment for cognitive impairment in schizophrenia were included.

RESULTS

Fifty-eight eligible publications, representing 11 pharmacological classes, were included in this review. Major limitations involved small sample size, methodological limitations as well as heterogeneity of participants and outcome measures.

CONCLUSIONS

Overall evidence remains inconclusive for any pharmacological classes studied for the treatment of cognitive deficits in schizophrenia. Methodological limitations in a majority of the studies rendered their findings preliminary. We further discuss possible explanations for these findings that could guide future research.

The Protective Effect of Roflumilast Against Acute Hepatotoxicity Caused by Methotrexate in Wistar Rats: In vivo Evaluation

Introduction

Methotrexate (MTX) is one of the most widely used drugs in cancer chemotherapy and treating rheumatoid arthritis. The hepatotoxicity of MTX is one of its major side effects. Roflumilast (ROF) has been recognized to have antioxidant and anti-inflammatory activity in in-vivo and in-vitro models. The present study aimed to explore the potential protective effects of roflumilast against MTX-induced liver toxicity in male Wistar rats.

Methods

High dose of 5 mg/kg for 4 consecutive days subcutaneous (S.C) injection of methotrexate for induction of acute liver injury. A total of 24 Wistar rats, rats were used in four different groups. The NS injections were given S.C to the control group once a day for 4 consecutive days. SC injections of MTX (5 mg/kg) were given to the MTX group daily for four days. At 5 mg/kg once daily for four days, the roflumilast group was given daily oral roflumilast. An injection of MTX and oral roflumilast were given to the MTX + roflumilast group once daily for four consecutive days.

Results

Administration of high dose MTX (5 mg/kg) today 4 produced a significant decrease in hepatic glutathione (GSH) levels and a significant increase in ALT and AST liver enzymes, hepatic malondialdehyde (MDA), tumor suppressor protein (p53), interleukin 6, interleukin 1 levels compared to the control group. Treatment with roflumilast for 4 days significantly attenuated unfavorable changes in these parameters. According to histopathological findings, Roflumilast significantly reduced MTX-induced inflammation and degeneration in the liver. In conclusion, the findings indicate that roflumilast may have a potential therapeutic benefit in treating rats with MTX-induced liver toxicity by mitigating its effects.

Purpose

The aim of this study is to investigate the potential protective effects of roflumilast against MTX-induced liver toxicity in Wistar rats.

A comprehensive review on therapeutic potentials of photobiomodulation for neurodegenerative disorders

A series of experimental trials over the past two centuries has put forth Photobiomodulation (PBM) as a treatment modality that utilizes colored lights for various conditions. While in its cradle, PBM was used for treating simple conditions such as burns and wounds, advancements in recent years have extended the use of PBM for treating complex neurodegenerative diseases (NDDs). PBM has exhibited the potential to curb several symptoms and signs associated with NDDs. While several of the currently used therapeutics cause adverse side effects alongside being highly invasive, PBM on the contrary, seems to be broad-acting, less toxic, and non-invasive. Despite being projected as an ideal therapeutic for NDDs, PBM still isn't considered a mainstream treatment modality due to some of the challenges and knowledge gaps associated with it. Here, we review the advantages of PBM summarized above with an emphasis on the common mechanisms that underlie major NDDs and how PBM helps tackle them. We also discuss important questions such as whether PBM should be considered a mainstay treatment modality for these conditions and if PBM's properties can be harnessed to develop prophylactic therapies for high-risk individuals and also highlight important animal studies that underscore the importance of PBM and the challenges associated with it. Overall, this review is intended to bring the major advances made in the field to the spotlight alongside addressing the practicalities and caveats to develop PBM as a major therapeutic for NDDs.

Crisaborole efficacy in murine models of skin inflammation and Staphylococcus aureus infection

Phosphodiesterase 4 (PDE4) is highly expressed in keratinocytes and immune cells and promotes pro-inflammatory responses upon activation. The activity of PDE4 has been attributed to various inflammatory conditions, leading to the development and approval of PDE4 inhibitors as host-directed therapeutics in humans. For example, the topical PDE4 inhibitor, crisaborole, is approved for the treatment of mild-to-moderate atopic dermatitis and has shown efficacy in patients with psoriasis. However, the role of crisaborole in regulating the immunopathogenesis of inflammatory skin diseases and infection is not entirely known. Therefore, we evaluated the effects of crisaborole in multiple mouse models, including psoriasis-like dermatitis, AD-like skin inflammation with and without filaggrin mutations, and Staphylococcus aureus skin infection. We discovered that crisaborole dampens myeloid cells and itch in the skin during psoriasis-like dermatitis. Furthermore, crisaborole was effective in reducing skin inflammation in the context of filaggrin deficiency. Importantly, crisaborole reduced S. aureus skin colonization during AD-like skin inflammation. However, crisaborole was not efficacious in treating S. aureus skin infections, even as adjunctive therapy to antibiotics. Taken together, we found that crisaborole reduced itch during psoriasis-like dermatitis and decreased S. aureus skin colonization upon AD-like skin inflammation, which act as additional mechanisms by which crisaborole dampens the immunopathogenesis in mouse models of inflammatory skin diseases. Further examination is warranted to translate these preclinical findings to human disease.

Effect of roflumilast on airway remodeling in asthmatic mice exposed to or not exposed to cigarette smoke: Comparison with the effect of dexamethasone

Cigarette smoking constitutes a risk factor for severe asthma, which is frequently linked to remodeling of the airways. Appropriate drug treatment for smokers with asthma is uncertain because many smokers with asthma are less sensitive to glucocorticoid treatment than non-smokers with asthma. The purpose of this study was to compare the anti-airway remodeling effects of dexamethasone (Dex) and roflumilast (Rof), a selective phosphodiesterases-4 inhibitor, in smoking and non-smoking mice with asthma. BALB/c mice were sensitized with ovalbumin (OVA) and then challenged with OVA for two weeks, either with or without concurrent exposure to cigarette smoke (CS). Dex (1 mg/kg body weight), Rof (5 mg/kg body weight), or vehicle alone was given orally to the mice once daily. To assess the histopathological effects of airway remodeling, lung tissue sections were obtained. Repeated OVA challenges resulted in fibrosis, goblet cell hyperplasia, and thickening of the airway but not the smooth muscle layer. The presence of CS did not have an impact on the degree of airway remodeling brought on by repeated OVA challenges. In mice repeatedly exposed to OVA either with or without CS, Dex treatment reduced the remodeling alterations. In these mice group, the Rof Treatment had a less significant impact than the Dex treatment. Dex was still more effective than Rof at reducing airway remodeling in asthmatic smoking mice. According to the current study's findings, Dex effectively prevented airway remodeling in a two-week asthma model in mice exposed to CS or not. In contrast, we found that Rof had little to no inhibitory effect of Rof on the airway in our mouse model of asthma, whether or not it had been exposed to CS. We were unable to find solid proof to support CS-induced steroid resistance to treat airway remodeling.

cAMP-PDE signaling in COPD: Review of cellular, molecular and clinical features

Chronic obstructive pulmonary disease (COPD) is the fourth leading cause of death among non-contagious diseases in the world. PDE inhibitors are among current medicines prescribed for COPD treatment of which, PDE-4 family is the predominant PDE isoform involved in hydrolyzing cyclic adenosine monophosphate (cAMP) that regulates the inflammatory responses in neutrophils, lymphocytes, macrophages and epithelial cells The aim of this study is to investigate the cellular and molecular mechanisms of cAMP-PDE signaling, as an important pathway in the treatment management of patients with COPD. In this review, a comprehensive literature review was performed about the effect of PDEs in COPD. Generally, PDEs are overexpressed in COPD patients, resulting in cAMP inactivation and decreased cAMP hydrolysis from AMP. At normal amounts, cAMP is one of the essential agents in regulating metabolism and suppressing inflammatory responses. Low amount of cAMP lead to activation of downstream inflammatory signaling pathways. PDE4 and PDE7 mRNA transcript levels were not altered in polymorphonuclear leukocytes and CD8 lymphocytes originating from the peripheral venous blood of stable COPD subjects compared to healthy controls. Therefore, cAMP-PDE signaling pathway is one of the most important signaling pathways involved in COPD. By examining the effects of different drugs in this signaling pathway critical steps can be taken in the treatment of this disease.

Camellia sinensis L. Alleviates Pulmonary Inflammation Induced by Porcine Pancreas Elastase and Cigarette Smoke Extract

Cigarette smoke (CS) is the major factor in the development of chronic obstructive pulmonary disease (COPD), the third leading cause of death worldwide. Furthermore, although Camellia sinensis (CN) has been known as an anti-inflammatory material, the effect of CN has not yet been known on pulmonary inflammation in COPD. Thus, we investigated the protective effects of Camellia sinensis L. extract (CLE) against pulmonary inflammation in porcine pancreas elastase (PPE) and a cigarette smoke extract (CSE)-induced COPD mouse model. Oral administration of CLE suppressed the symptoms such as infiltration of immune cells, cytokines/chemokines secretion, mucus hypersecretion, and injuries of the lung parenchyma. Increased inflammatory responses in COPD are mediated by various immune cells such as airway epithelial cells, neutrophils, and alveolar macrophages. Thus, we investigated the effect and mechanisms of CLE in H292, HL-60, and MH-S cells. The CLE inhibited the expression of IL-6, IL-8, MUC5AC and MUC5B on CSE/LPS-stimulated H292 cells and also suppressed the formation of neutrophil extracellular traps and secretion of neutrophil elastase by inhibiting reactive oxygen species in PMA-induced HL-60 cells. In particular, the CLE suppressed the release of cytokines and chemokines caused by activating the nuclear factor kappa-light-chain-enhancer of activated B via the activation of nuclear factor erythroid-2-related factor 2 and the heme oxygenase-1 pathway in CSE/LPS-stimulated MH-S cells. Therefore, we suggest that the CLE administration be the effective approach for treating or preventing chronic pulmonary diseases such as COPD induced by CS.

Effects of Roflumilast on Patients with Chronic Obstructive Pulmonary Disease Treated with Inhaled Corticosteroid/Long-Acting β2 Agonist: A Meta-analysis

Objective

Roflumilast is a novel therapeutic drug for chronic obstructive pulmonary disease (COPD). This study was designed to evaluate the efficacy and safety of roflumilast combining inhaled corticosteroid (ICS)/long-acting β2 agonist (LABA) in treating COPD patients through the meta-analysis.

Methods

Randomized controlled trials of roflumilast combining ICS/LABA in treating patients with severe and profound COPD were searched from PubMed, Cochrane Library, and Embase databases from their establishment to February 2022. The quality of included studies was assessed by Cochrane risk bias assessment tool. The main outcomes of these studies should include at least one of the following clinical outcome indicators: forced expiratory volume in one second (FEV₁), exacerbation rate, and adverse events (AEs) such as diarrhea, nasopharyngitis, and headache.

Results

Six articles were included in the study, including 9,715 patients. Meta-analysis revealed that compared with placebo, roflumilast gained superiority for severe COPD patients treated with ICS/LABA combinations in FEV₁ before bronchodilator administration (MD = 46.62, 95% CI (30.69, 62.55), P < 0.00001), FEV₁ after bronchodilator administration (MD = 45.62, 95% CI (34.95, 56.28), P < 0.00001), and COPD exacerbation rate (RR = 0.90, 95% CI (0.87, 0.94), P = 0.001). In terms of safety, the incidence of diarrhea, headache, nausea, weight loss, back pain, loss of appetite, and insomnia was notably higher in the roflumilast group than in the placebo group.

Conclusion

Roflumilast is suggested to be significantly effective for severe COPD patients with ICS/LABA combination therapy, which reduces the exacerbation rate but also leads to PDE4 inhibitor-related adverse reactions.

The Role of the Pharmacist in Optimizing Outcomes With Roflumilast, a PDE4 Inhibitor for the Treatment of COPD

PURPOSE

The pharmacology of roflumilast, recent dosing revisions, and the integral roles of pharmacists in effective chronic obstructive pulmonary disease (COPD) management are reviewed here.

SUMMARY

COPD is characterized by progressive airflow limitation and intermittent acute exacerbations of symptoms, which contribute to disease progression, worsening of comorbidities, and reduced health-related quality of life. Patients with COPD may use a variety of pharmacotherapies (in combination with nonpharmacological modalities) to prevent exacerbations, reduce the impact of symptoms, and reduce or prevent COPD progression. Given the complex and multifaceted nature of disease management, pharmacists are uniquely positioned to collaborate with other clinicians to improve treatment adherence and efficacy via a number of diverse avenues in patients with COPD. Central to this endeavor is patient education and counseling regarding their treatment regimen.

CONCLUSION

Recent findings from a phase 3 clinical trial demonstrate improved tolerability and reduced treatment discontinuation resulting from the use of an uptitration regimen in patients with severe COPD who initiate therapy with roflumilast. Pharmacists have a central role in effective COPD management, especially with respect to patient education about treatments.

Phosphodiesterase‑4 inhibitors: a review of current developments (2013-2021)

INTRODUCTION

Cyclic nucleotide phosphodiesterase 4 (PDE4) is responsible for the hydrolysis of cAMP, which has become an attractive therapeutic target for lung, skin, and severe neurological diseases. Here, we review the current status of development of PDE4 inhibitors since 2013 and discuss the applicability of novel medicinal-chemistry strategies for identifying more efficient and safer inhibitors.

AREAS COVERED

This review summarizes the clinical development of PDE4 inhibitors from 2013 to 2021, focused on their pharmacophores, the strategies to reduce the side effects of PDE4 inhibitors and the development of subfamily selective PDE4 inhibitors.

EXPERT OPINION

To date, great efforts have been made in the development of PDE4 inhibitors, and researchers have established a comprehensive preclinical database and collected some promising data from clinical trials. Although four small-molecule PDE4 inhibitors have been approved by FDA for the treatment of human diseases up to now, further development of other reported PDE4 inhibitors with strong potency has been hampered due to the occurrence of severe side effects. There are currently three main strategies for overcoming the dose limitation and systemic side effects, which provide new opportunities for the clinical development of new PDE4 inhibitors.

Differential effects of dexamethasone and roflumilast on asthma in mice with or without short cigarette smoke exposure

Appropriate drug treatment for smoking asthmatics is uncertain because most smokers with asthma are less sensitive to treatment with glucocorticoids compared with non-smokers with asthma. We hypothesized that roflumilast (Rof), a selective phosphodiesterases-4 inhibitor regarded as an add-on therapy for chronic obstructive pulmonary disease, might be more effective than glucocorticoids for improving asthma in smokers. To investigate this hypothesis, we compared the therapeutic effects of dexamethasone (Dex) and Rof in a mouse model of ovalbumin-induced asthma with or without concurrent cigarette smoke (CS) exposure for 2 weeks. We found that recurrent asthma attacks increased lung tissue resistance. CS exposure in asthmatic mice decreased the central airway resistance, increased lung compliance, and attenuated airway hyper-responsiveness (AHR). CS exposure in asthmatic mice also increased the number of neutrophils and macrophages in the bronchoalveolar fluid. Treatment with Dex in asthmatic mice without CS exposure reduced airway resistance, AHR and airway eosinophilia. In asthmatic mice with CS exposure, however, Dex treatment unexpectedly increased lung tissue resistance and restored AHR that had been otherwise suppressed. Dex treatment in asthmatic mice with CS exposure inhibited eosinophilic inflammation but conversely exacerbated neutrophilic inflammation. On the other hand, treatment with Rof in asthmatic mice without CS exposure reduced airway resistance and airway eosinophilia, although the inhibitory effect of Rof on AHR was unremarkable. In asthmatic mice with CS exposure, Rof treatment did not exacerbate lung tissue resistance but modestly restored AHR, without any significant effects on airway inflammation. These results suggest that CS exposure mitigates sensitivity to both Dex and Rof. In asthmatic mice with CS exposure, Dex is still effective in reducing eosinophilic inflammation but increases lung tissue resistance, AHR and neutrophilic inflammation. Rof is ineffective in improving lung function and inflammation in asthmatic mice with CS exposure. This study did not support our initial hypothesis that Rof might be more effective than glucocorticoids for improving asthma in smokers. However, glucocorticoids may have a detrimental effect on smoking asthmatics.

Phosphodiesterase-4 Inhibitors for Non-COPD Respiratory Diseases

Selective phosphodiesterase (PDE) inhibitors are a class of nonsteroid anti-inflammatory drugs for treating chronic inflammatory diseases. Modulation of systemic and airway inflammation is their pivotal mechanism of action. Furthermore, PDE inhibitors modulate cough reflex and inhibit airway mucus secretion. Roflumilast, a selective PDE4 inhibitor, has been extensively studied for the efficacy and safety in chronic obstructive pulmonary disease (COPD) patients. According to the mechanisms of action, the potential roles of PDE inhibitors in treating chronic respiratory diseases including severe asthma, asthma-COPD overlap (ACO), noncystic fibrosis bronchiectasis, and chronic cough are discussed. Since roflumilast inhibits airway eosinophilia and neutrophilia in COPD patients, it reduces COPD exacerbations in the presence of chronic bronchitis in addition to baseline therapies. The clinical studies in asthma patients have shown the comparable efficacy of roflumilast to inhaled corticosteroids for improving lung function. However, the clinical trials of roflumilast in severe asthma have been limited. Although ACO is common and is also associated with poor outcomes, there is no clinical trial regarding its efficacy in patients with ACO despite a promising role in reducing COPD exacerbation. Since mucus hypersecretion is a result of neutrophil secretagogue in patients with chronic bronchitis, experimental studies have shown that PDE4s are regulators of the cystic fibrosis transmembrane conductance regulator (CFTR) in human airway epithelial cells. Besides, goblet cell hyperplasia is associated with an increased expression of PDE. Bronchiectasis and chronic bronchitis are considered neutrophilic airway diseases presenting with mucus hypersecretion. They commonly coexist and thus lead to severe disease. The role of roflumilast in noncystic fibrosis bronchiectasis is under investigation in clinical trials. Lastly, PDE inhibitors have been shown modulating cough from bronchodilation, suppressing transient receptors potential (TRP), and anti-inflammatory properties. Hence, there is the potential role of the drug in the management of unexplained cough. However, clinical trials for examining its antitussive efficacy are pivotal. In conclusion, selective PDE4 inhibitors may be potential treatment options for chronic respiratory diseases apart from COPD due to their promising mechanisms of action.

Impacts of anti-inflammatory phosphodiesterase inhibitors on a murine model of chronic pulmonary inflammation

Chronic obstructive pulmonary disease (COPD) often tends to respond poorly to glucocorticoid (GC) therapy. Reduced Histone deacetylase-2 (HDAC-2) activity is an important mechanism behind this GC insensitivity. In this study, we investigated the effects of three phosphodiesterase inhibitors (PDEIs), with an anti-inflammatory propensity, on cigarette smoke (CS)-induced pulmonary inflammation and HDAC-2 activity. Male C57BL/6 mice were exposed to cigarette smoke (CS) over the course of 30 weeks. Administration of the PDEIs commenced from the 29th week and followed a schedule of once daily treatments, 5 days a week, for 2 weeks. Roflumilast (ROF) was administered intragastrically (5 mg·kg-1 ), while pentoxifylline (PTX) (10 mg·kg-1 ) and theophylline (THEO) (10 mg·kg-1 ) were administered intraperitoneally, either alone or in combination with a GC (triamcinolone acetonide or TRI, 5 mg·kg-1 , i.m., single injection). Lung morphometry, as well as the activity of HDAC-2, pro-inflammatory cytokines and reactive oxygen species (ROS) were assessed at the end of the 30-week course. CS exposure was associated with a reduction in HDAC-2 activity and the up-regulation of ROS expression. PTX, ROF, and THEO administration led to the partial restoration of HDAC-2 activity, which was favorably associated with the reduction of ROS expression. However, combining TRI to any of these PDEIs did not synergistically augment HDAC-2 activity. Inactivation of HDAC-2 due to long-term CS exposure is closely related to exaggerated oxidative stress, and this reduced HDAC-2 activity could partially be restored through the use of PDEIs. This finding provides a potential novel approach for further clinical research.

Gut probiotic Lactobacillus rhamnosus attenuates PDE4B-mediated interleukin-6 induced by SARS-CoV-2 membrane glycoprotein

Membrane glycoprotein is the most abundant protein of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), but its role in coronavirus disease 2019 (COVID-19) has not been fully characterized. Mice intranasally inoculated with membrane glycoprotein substantially increased the interleukin (IL)-6, a hallmark of the cytokine storm, in bronchoalveolar lavage fluid (BALF), compared to mice inoculated with green fluorescent protein (GFP). The high level of IL-6 induced by membrane glycoprotein was significantly diminished in phosphodiesterase 4 (PDE4B) knockout mice, demonstrating the essential role of PDE4B in IL-6 signaling. Mycelium fermentation of Lactobacillus rhamnosus (L. rhamnosus) EH8 strain yielded butyric acid, which can down-regulate the PDE4B expression and IL-6 secretion in macrophages. Feeding mice with mycelia increased the relative abundance of commensal L. rhamnosus. Two-week supplementation of mice with L. rhamnosus plus mycelia considerably decreased membrane glycoprotein-induced PDE4B expression and IL-6 secretion. The probiotic activity of L. rhamnosus plus mycelia against membrane glycoprotein was abolished in mice treated with GLPG-0974, an antagonist of free fatty acid receptor 2 (Ffar2). Activation of Ffar2 in the gut-lung axis for down-regulation of the PDE4B-IL-6 signalling may provide targets for development of modalities including probiotics for treatment of the cytokine storm in COVID-19.

Diabetic Theory in Anti-Alzheimer's Drug Research and Development. Part 2: Therapeutic Potential of cAMP-Specific Phosphodiesterase Inhibitors

Alzheimer's disease (AD) is one of the most prevalent age-related neurodegenerative disease that affects the cognition, behavior, and daily activities of individuals. Studies indicate that this disease is characterized by several pathological mechanisms, including the accumulation of amyloid-beta peptide, hyperphosphorylation of tau protein, impairment of cholinergic neurotransmission, and increase in inflammatory responses within the central nervous system. Chronic neuroinflammation associated with AD is closely related to disturbances in metabolic processes, including insulin release and glucose metabolism. As AD is also called type III diabetes, diverse compounds having antidiabetic effects have been investigated as potential drugs for its symptomatic and disease-modifying treatment. In addition to insulin and oral antidiabetic drugs, scientific attention has been paid to cyclic-3',5'-adenosine monophosphate (cAMP)-specific phosphodiesterase (PDE) inhibitors that can modulate the concentration of glucose and related hormones and exert beneficial effects on memory, mood, and emotional processing. In this review, we present the most recent reports focusing on the involvement of cAMP-specific PDE4, PDE7, and PDE8 in glycemic and inflammatory response controls as well as the potential utility of the PDE inhibitors in the treatment of AD. Besides the results of in vitro and in vivo studies, the review also presents recent reports from clinical trials.

Roflumilast protects from cisplatin-induced testicular toxicity in male rats and enhances its cytotoxicity in prostate cancer cell line. Role of NF-κB-p65, cAMP/PKA and Nrf2/HO-1, NQO1 signaling

Cisplatin (CIS)-induced testicular injury is a major obstacle in its application as antineoplastic agent. In this study, we investigated the protective effect and mechanism of roflumilast (ROF), a PDE4 inhibitor, against CIS-induced testicular toxicity in rats. Besides, the cytotoxic effect of CIS, with and without ROF, was evaluated on PC3 cell line. ROF reversed CIS-induced abnormalities in sperm characteristics, normalized serum testosterone level, and ameliorated CIS-induced alterations in testicular and epidydimal weights and restored normal testicular structure. Moreover, ROF increased intracellular cAMP level, PKA and HO-1 activities and Nrf2, NQO-1 and HO-1 gene expression, improved testicular oxidative stress parameters (TBARS, NO, GSH levels, and CAT activity) and inflammatory mediators (IL-1β and TNF-α, and NF-κβ p65gene expression) and reduced the proapoptotic proteins, caspase-3, Bax and increased Bcl-2. Lastly, in vitro analyses showed that ROF augmented the anticancer efficacy of CIS and enhanced the increase in gene expression of Nrf2, HO-1, and NQO-1 and the inhibition of gene expression of NF-κβ p65 induced by CIS and enhanced its apoptotic effect in PC3 cells. Conclusively, PDE4 inhibition with induction of Nrf2/HO-1, NQO-1 is a potential therapeutic approach to protect male reproductive system from the detrimental effects with augmenting, the antineoplastic effect of CIS.

Reactive oxygen species modulators in pulmonary medicine

Adapted to effectively capture oxygen from inhaled air and deliver it to all other parts of the body, the lungs constitute the organ with the largest surface area. This makes the lungs more susceptible to airborne pathogens and pollutants that mediate pathologies through generation of reactive oxygen species (ROS). One pathological consequence of excessive levels of ROS production is pulmonary diseases that account for a large number of mortality and morbidity in the world. Of the various mechanisms involved in pulmonary disease pathogenesis, mitochondrial dysfunction takes prominent importance. Herein, we briefly describe the significance of oxidative stress caused by ROS in pulmonary diseases and some possible therapeutic strategies.

Roflumilast Reduced the IL-18-Induced Inflammatory Response in Fibroblast-Like Synoviocytes (FLS)

Pro-inflammatory cytokines, such as the IL-18-induced inflammatory response and associated damage in fibroblast-like synoviocytes (FLS), play an important role in the pathogenesis of rheumatoid arthritis (RA). Roflumilast, an inhibitor of phosphodiesterase-4 (PDE-4), has been licensed for the treatment of chronic obstructive pulmonary disease (COPD). However, it is unknown whether roflumilast possesses a protective effect against the IL-18-induced inflammatory response in FLS. We found that roflumilast attenuated IL-18-induced oxidative stress by reducing the production of reactive oxygen species and malondialdehyde (MDA) in MH7A fibroblast-like synoviocytes (FLS). Additionally, roflumilast prevented IL-18-induced expressions and secretions of pro-inflammatory cytokines such as IL-6, IL-8, and TNF-α. Importantly, we found that roflumilast inhibited IL-18-induced expressions of chemokines such as CCL5, CXCL9, and CXCL10. Further, roflumilast inhibited the expression of extracellular matrix degradative enzymes, such as matrix metalloproteinase-3 (MMP-3) and MMP-13. Mechanistically, we found that roflumilast suppressed the activation of the transcriptional factor AP-1 and NF-κB. Our results suggest that roflumilast might be a potential therapeutic agent for the treatment of RA.

Chronic obstructive pulmonary disease - diagnosis and management of stable disease; a personalized approach to care, using the treatable traits concept based on clinical phenotypes. Position paper of the Czech Pneumological and Phthisiological Society

This position paper has been drafted by experts from the Czech national board of diseases with bronchial obstruction, of the Czech Pneumological and Phthisiological Society. The statements and recommendations are based on both the results of randomized controlled trials and data from cross-sectional and prospective real-life studies to ensure they are as close as possible to the context of daily clinical practice and the current health care system of the Czech Republic. Chronic Obstructive Pulmonary Disease (COPD) is a preventable and treatable heterogeneous syndrome with a number of pulmonary and extrapulmonary clinical features and concomitant chronic diseases. The disease is associated with significant mortality, morbidity and reduced quality of life. The main characteristics include persistent respiratory symptoms and only partially reversible airflow obstruction developing due to an abnormal inflammatory response of the lungs to noxious particles and gases. Oxidative stress, protease-antiprotease imbalance and increased numbers of pro-inflammatory cells (mainly neutrophils) are the main drivers of primarily non-infectious inflammation in COPD. Besides smoking, household air pollution, occupational exposure, low birth weight, frequent respiratory infections during childhood and also genetic factors are important risk factors of COPD development. Progressive airflow limitation and airway remodelling leads to air trapping, static and dynamic hyperinflation, gas exchange abnormalities and decreased exercise capacity. Various features of the disease are expressed unequally in individual patients, resulting in various types of disease presentation, emerging as the "clinical phenotypes" (for specific clinical characteristics) and "treatable traits" (for treatable characteristics) concept. The estimated prevalence of COPD in Czechia is around 6.7% with 3,200-3,500 deaths reported annually. The elementary requirements for diagnosis of COPD are spirometric confirmation of post-bronchodilator airflow obstruction (post-BD FEV₁/VCmax <70%) and respiratory symptoms assessement (dyspnoea, exercise limitation, cough and/or sputum production. In order to establish definite COPD diagnosis, a five-step evaluation should be performed, including: 1/ inhalation risk assessment, 2/ symptoms evaluation, 3/ lung function tests, 4/ laboratory tests and 5/ imaging. At the same time, all alternative diagnoses should be excluded. For disease classification, this position paper uses both GOLD stages (1 to 4), GOLD groups (A to D) and evaluation of clinical phenotype(s). Prognosis assessment should be done in each patient. For this purpose, we recommend the use of the BODE or the CADOT index. Six elementary clinical phenotypes are recognized, including chronic bronchitis, frequent exacerbator, emphysematous, asthma/COPD overlap (ACO), bronchiectases with COPD overlap (BCO) and pulmonary cachexia. In our concept, all of these clinical phenotypes are also considered independent treatable traits. For each treatable trait, specific pharmacological and non-pharmacological therapies are defined in this document. The coincidence of two or more clinical phenotypes (i.e., treatable traits) may occur in a single individual, giving the opportunity of fully individualized, phenotype-specific treatment. Treatment of COPD should reflect the complexity and heterogeneity of the disease and be tailored to individual patients. Major goals of COPD treatment are symptom reduction and decreased exacerbation risk. Treatment strategy is divided into five strata: risk elimination, basic treatment, phenotype-specific treatment, treatment of respiratory failure and palliative care, and treatment of comorbidities. Risk elimination includes interventions against tobacco smoking and environmental/occupational exposures. Basic treatment is based on bronchodilator therapy, pulmonary rehabilitation, vaccination, care for appropriate nutrition, inhalation training, education and psychosocial support. Adequate phenotype-specific treatment varies phenotype by phenotype, including more than ten different pharmacological and non-pharmacological strategies. If more than one clinical phenotype is present, treatment strategy should follow the expression of each phenotypic label separately. In such patients, multicomponental therapeutic regimens are needed, resulting in fully individualized care. In the future, stronger measures against smoking, improvements in occupational and environmental health, early diagnosis strategies, as well as biomarker identification for patients responsive to specific treatments are warranted. New classes of treatment (inhaled PDE3/4 inhibitors, single molecule dual bronchodilators, anti-inflammatory drugs, gene editing molecules or new bronchoscopic procedures) are expected to enter the clinical practice in a very few years.

New putative insights into neprilysin (NEP)-dependent pharmacotherapeutic role of roflumilast in treating COVID-19

Nowadays, coronavirus disease 2019 (COVID-19) represents the most serious inflammatory respiratory disease worldwide. Despite many proposed therapies, no effective medication has yet been approved. Neutrophils appear to be the key mediator for COVID-19-associated inflammatory immunopathologic, thromboembolic and fibrotic complications. Thus, for any therapeutic agent to be effective, it should greatly block the neutrophilic component of COVID-19. One of the effective therapeutic approaches investigated to reduce neutrophil-associated inflammatory lung diseases with few adverse effects was roflumilast. Being a highly selective phosphodiesterase-4 inhibitors (PDE4i), roflumilast acts by enhancing the level of cyclic adenosine monophosphate (cAMP), that probably potentiates its anti-inflammatory action via increasing neprilysin (NEP) activity. Because activating NEP was previously reported to mitigate several airway inflammatory ailments; this review thoroughly discusses the proposed NEP-based therapeutic properties of roflumilast, which may be of great importance in curing COVID-19. However, further clinical studies are required to confirm this strategy and to evaluate its in vivo preventive and therapeutic efficacy against COVID-19.

Current insights on clinical efficacy of roflumilast for treatment of COPD, asthma and ACOS

Phosphodiesterase-4 inhibitors (PDE4) are of great interest for the treatment of airway inflammatory diseases due to its broad anti-inflammatory effects. Roflumilast is a selective PDE4 inhibitor that inhibits pulmonary and systemic inflammation and rallies symptoms in airway diseases. Asthma and COPD are common chronic airway inflammatory diseases having incompletely illustrious pathophysiology and clinical manifestations. Recently, the condition called Asthma- COPD Overlap (ACO) has been evolved having the overlapping symptoms of both diseases. The newly discovered PDE4 inhibitor, roflumilast has exposed its potential in the treatment of Asthma, COPD and ACOS. Its mechanism of action in airway inflammatory diseases are said to be exerts by elevating intracellular cAMP and shows its anti-inflammatory action. Roflumilast, a promising therapeutic approach in inflammatory airway diseases, has many significant outcomes. In this review, we have provided various promising clinical evidences of roflumilast in COPD and asthma. However, there is no published clinical evidence to date for the role of roflumilast in ACOS. Nevertheless, there are therapeutic mechanisms that provide a reference for clinical application for ACOS.

Effects of a novel roflumilast and formoterol fumarate dry powder inhaler formulation in experimental allergic asthma

In this study we aimed to develop a roflumilast (R) and formoterol fumarate (F) dry powder inhaler formulation (DPI) incorporating HPβCD by spray drying and evaluated if it attenuates the inflammatory process and improves lung function in a murine model of ovalbumin induced allergic asthma. The DPI was characterized by powder X-ray diffraction, thermal analysis, scanning electron microscopy, particle size, density, specific surface area and dynamic vapor sorption analyses. In vitro deposition studies were performed using a NGI, while transepithelial permeability and in vivo effects on lung mechanics and inflammation in a model of allergic asthma were also assessed. The R:F formulation was amorphous with high glass transition temperatures, comprised of wrinkled particles, had low bulk and tapped densities, high surface area, suitable particle size for pulmonary delivery and exhibited no recrystallization even at high relative humidities. MMAD were statistically similar of 4.22 ± 0.19 and 4.32 ± 0.13 µm for F and R, respectively. Fine particle fractions (<5 µm) were of more than 50% of the emitted dose. The R:F formulation led to reduced eosinophil infiltration and airway collagen fiber content, yielding decreased airway hyperresponsiveness. In the current asthma model, the R:F formulation combination decreased inflammation and remodeling, thus improving lung mechanics.

Roflumilast, a Phosphodiesterases-4 (PDE4) Inhibitor, Alleviates Sepsis‑induced Acute Kidney Injury

BACKGROUND Sepsis causes acute kidney injury (AKI) in critically ill patients. Roflumilast, a phosphodiesterases-4 (PDE4) inhibitor, has been shown to be therapeutically effective in sepsis-induced organ injury. However, the function of roflumilast in sepsis-induced AKI is not clearly understood. The present study aimed to explore the protective effect of roflumilast on sepsis-induced AKI in mice. MATERIAL AND METHODS A sepsis model was established by cecal ligation and puncture surgery. Roflumilast (1 mg/kg and 3 mg/kg) was used once daily for 7 consecutive days for treatment. Kidney tissues were pathologically examined by hematoxylin and eosin (H&E) and periodic acid-Schiff (PAS) staining. The levels of kidney injury markers including blood urea nitrogen (BUN), creatinine (Cre), kidney injury molecule-1 (KIM-1), and neutrophil gelatinase-associated lipocalin (NGAL), and inflammatory cytokines including interleukin (IL)-6, tumor necrosis factor (TNF)-alpha, and IL-1ß were detected by their corresponding test kits. The protein expression was measured using western blot and cell apoptosis of kidney tissue was determined by TUNEL (terminal deoxynucleotidyl transferase dUTP nick end labeling) assay. RESULTS Roflumilast was demonstrated to alleviate sepsis-induced AKI by reducing histopathological changes and decreasing the levels of kidney injury markers in a concentration-dependent way. The production of TNF-alpha, IL-6, and IL-1ß was significantly suppressed by roflumilast. Besides, roflumilast inhibited the activation of NLRP3 (nucleotide-binding domain (NOD)-like receptor protein 3) and NF-kappaB (nuclear factor kappa-light-chain-enhancer of activated B cells). Additionally, roflumilast inhibited cell apoptosis and changes in expression of apoptosis related proteins induced by sepsis. Finally, high concentration of roflumilast (3 mg/kg) did not have an adverse effect on liver, heart, lung, or spleen. CONCLUSIONS Our study indicated that roflumilast could ameliorate AKI induced by sepsis through restraining inflammatory response and apoptosis of the kidney, providing a molecular basis for a novel medical treatment of septic AKI.

Glucocorticoid Receptor α Mediates Roflumilast's Ability to Restore Dexamethasone Sensitivity in COPD

Background

Glucocorticoids are commonly prescribed to treat inflammation of the respiratory system; however, they are mostly ineffective for controlling chronic obstructive pulmonary disease (COPD)-associated inflammation. This study aimed to elucidate the molecular mechanisms responsible for such glucocorticoid inefficacy in COPD, which may be instrumental to providing better patient outcomes. Roflumilast is a selective phosphodiesterase-4 (PDE4) inhibitor with anti-inflammatory properties in severe COPD patients who have a history of exacerbations. Roflumilast has a suggested ability to mitigate glucocorticoid resistance, but the mechanism is unknown.

Methods

To understand the mechanism that mediates roflumilast-induced restoration of glucocorticoid sensitivity in COPD, we tested the role of glucocorticoid receptor α (GRα). Roflumilast's effects on GRα expression and transcriptional activity were assessed in bronchial epithelial cells from COPD patients.

Results

We found that both GRα expression and activity are downregulated in bronchial epithelial cells from COPD patients and that roflumilast stimulates both GRα mRNA synthesis and GRα's transcriptional activity in COPD bronchial epithelial cells. We also demonstrate that roflumilast enhances dexamethasone's ability to suppress pro-inflammatory mediator production, in a GRα-dependent manner.

Discussion

Our findings highlight the significance of roflumilast-induced GRα upregulation for COPD therapeutic strategies by revealing that roflumilast restores glucocorticoid sensitivity by sustaining GRα expression.

New cassane-type diterpenoids from kernels of Caesalpinia bonduc (Linn.) Roxb. and their inhibitory activities on phosphodiesterase (PDE) and nuclear factor-kappa B (NF-κB) expression

In this paper, chemical investigation on the chloroform soluble fraction of seed kernels of Caesalpinia bonduc resulted in the isolation of five new cassane diterpenoids: norcaesalpinin O (1), norcaesalpinin P (2), caesalpinin MQ (3), caesall O/P (4/5) and seven known compounds (6-12). Compounds structures were elucidated by ¹H NMR, ¹³C NMR, 2D NMR, HR-MS and ECD (electronic circular dichroism) spectral analysis. The characters for new compounds with the presence of an aromatized C ring or demethyl group at C-17 position in the structures were found. By means of bioactive screenings, the inhibitory effect on type-4 phosphodiesterase (PDE4, the target protein of asthma disease) and nuclear factor-kappa B (NF-κB) expression were valued. Compound 1 was found to exhibit moderate inhibitory activity on PDE4 and much better binding affinity than other structures by docking studies for interaction analyzing. Compounds 6, 10 and 11 displayed considerable inhibitory strength against NF-κB expression with inhibitory ratio 48.6%, 42.9% and 37.1% at 10 µM, respectively. The isolation of cassane-type diterpenoids with anti-inflammation activity from C. bonduc implied that this plant might be a good source for anti-inflammation agents finding.

Novel phosphodiesterases inhibitors from the group of purine-2,6-dione derivatives as potent modulators of airway smooth muscle cell remodelling

Airway remodelling (AR) is an important pathological feature of chronic asthma and chronic obstructive pulmonary disease. The etiology of AR is complex and involves both lung structural and immune cells. One of the main contributors to airway remodelling is the airway smooth muscle (ASM), which is thickened by asthma, becomes more contractile and produces more extracellular matrix. As a second messenger, adenosine 3',5'-cyclic monophosphate (cAMP) has been shown to contribute to ASM cell (ASMC) relaxation as well as to anti-remodelling effects in ASMC. Phosphodiesterase (PDE) inhibitors have drawn attention as an interesting new group of potential anti-inflammatory and anti-remodelling drugs. Recently, new hydrazide and amide purine-2,6-dione derivatives with anti-inflammatory properties have been synthesized by our team (compounds 1 and 2). We expanded our study of their PDE selectivity profile, ability to increase intracellular cAMP levels, metabolic stability and, above all, their capacity to modulate cell responses associated with ASMC remodelling. The results show that both compounds have subtype specificity for several PDE isoforms (including inhibition of PDE1, PDE3, PDE4 and PDE7). Interestingly, such combined PDE subtype inhibition exerts improved anti-remodelling efficacies against several ASMC-induced responses such as proliferation, contractility, extracellular matrix (ECM) protein expression and migration when compared to other non-selective and selective PDE inhibitors. Our findings open novel perspectives in the search for new chemical entities with dual anti-inflammatory and anti-remodelling profiles in the group of purine-2,6-dione derivatives as broad-spectrum PDE inhibitors.

Experimental and investigational phosphodiesterase inhibitors in development for asthma

INTRODUCTION

Severe, inadequately-controlled asthma remains a clinical challenge. For this reason, clinical trials and preclinical experimental studies on novel agents as an add-on therapies continue emerge. Phosphodiesterases (PDEs) are enzymes that regulate the function of immune cells by hydrolyzing cyclic guanosine monophosphate/cGMP and cyclic adenosine monophosphate/cAMP. PDEs are divided into subfamilies [PDE3, PDE4, PDE5 and PDE7] which are mainly found in the respiratory tract. Inhibitors of PDEs have already been approved for COPD and pulmonary hypertension.

AREAS COVERED

The role of PDE inhibitors in asthma treatment and the possible mechanism of action via their anti-inflammatory and/or bronchodilating effect are discussed.

EXPERT OPINION

Novel PDE inhibitors exhibiting fewer adverse events may have a role as add-on therapies in asthma treatment in the future. More clinical trials are necessary to prove their efficacy and evaluate their safety profile before approval by regulatory bodies is granted.

Reduction of lung inflammation, oxidative stress and apoptosis by the PDE4 inhibitor roflumilast in experimental model of acute lung injury

Damage of alveolar-capillary barrier, inflammation, oxidative injury, and lung cell apoptosis represent the key features of acute lung injury (ALI). This study evaluated if selective phosphodiesterase (PDE)-4 inhibitor roflumilast can reduce the mentioned changes in lavage-induced model of ALI. Rabbits with ALI were divided into 2 groups: ALI without therapy (A group) and ALI treated with roflumilast i.v. (1 mg/kg; A+R group). One group of healthy animals without ALI served as ventilated controls (C group). All animals were oxygen-ventilated for further 4 h. At the end of experiment, total and differential counts of cells in bronchoalveolar lavage fluid (BALF) and total and differential counts of white blood cells were estimated. Lung edema formation was assessed from determination of protein content in BALF. Pro-inflammatory cytokines (TNFalpha, IL-6 and IL-8) and markers of oxidation (3-nitrotyrosine, thiobarbituric-acid reactive substances) were detected in the lung tissue and plasma. Apoptosis of lung cells was investigated immunohistochemically. Treatment with roflumilast reduced leak of cells, particularly of neutrophils, into the lung, decreased concentrations of cytokines and oxidative products in the lung and plasma, and reduced lung cell apoptosis and edema formation. Concluding, PDE4 inhibitor roflumilast showed potent anti-inflammatory actions in this model of ALI.

Phosphodiesterase-4 Inhibitors for the Treatment of Inflammatory Diseases

Phosphodiesterase-4 (PDE4), mainly present in immune cells, epithelial cells, and brain cells, manifests as an intracellular non-receptor enzyme that modulates inflammation and epithelial integrity. Inhibition of PDE4 is predicted to have diverse effects via the elevation of the level of cyclic adenosine monophosphate (cAMP) and the subsequent regulation of a wide array of genes and proteins. It has been identified that PDE4 is a promising therapeutic target for the treatment of diverse pulmonary, dermatological, and severe neurological diseases. Over the past decades, numerous PDE4 inhibitors have been designed and synthesized, among which roflumilast, apremilast, and crisaborole were approved for the treatment of inflammatory airway diseases, psoriatic arthritis, and atopic dermatitis, respectively. It is regrettable that the dramatic efficacies of a drug are often accompanied by adverse effects, such as nausea, emesis, and gastrointestinal reactions. However, substantial advances have been made to mitigate the adverse effects and obtain better benefit-to-risk ratio. This review highlights the dialectical role of PDE4 in drug discovery and the disquisitive details of certain PDE4 inhibitors to provide an overview of the topics that still need to be addressed in the future.

Pharmacological mechanism of roflumilast in the treatment of asthma-COPD overlap

Asthma-COPD overlap (ACO) is a type of incomplete obstructive airway disease that has a high incidence and mortality. Nevertheless, there is currently no clear definition of ACO and no effective intervention. The newly discovered phosphodiesterase-4 inhibitor, roflumilast, has shown initial efficacy for treating asthma, COPD, and ACO. The mechanism of roflumilast, however, remains unclear, and there has been no interpretation through systematic review to date. The determination of a definite mechanism of roflumilast will guide the clinician's decisions regarding medication use, standardized diagnosis, and treatment guidelines. For this reason, we have systematically reviewed the therapeutic mechanism of roflumilast for ACO and provided reference for the clinical application of roflumilast in ACO.

Inhibitors of phosphodiesterases in the treatment of cough

A group of 11 enzyme families of metalophosphohydrolases called phosphodiesterases (PDEs) is responsible for a hydrolysis of intracellular cAMP and cGMP. Xanthine derivatives (methylxanthines) inhibit PDEs without selective action on their single isoforms and lead to many pharmacological effects, e.g. bronchodilation, anti-inflammatory and immunomodulating effects, and thus they can modulate the cough reflex. Contrary, selective PDE inhibitors have been developed to inhibit PDE isoforms with different pharmacological effects based on their tissue expression. In this paper, effects of non-selective PDE inhibitors (e.g. theophylline) are discussed, with a description of other putative mechanisms in their effects on cough. Antitussive effects of selective inhibitors of several PDE isoforms are reviewed, focusing on PDE1, PDE3, PDE4, PDE5 and PDE7. The inhibition of PDEs suggests participation of bronchodilation, suppression of TRPV channels and anti-inflammatory action in cough suppression. Selective PDE3, PDE4 and PDE5 inhibitors have demonstrated the most significant cough suppressive effects, confirming their benefits in chronic inflammatory airway diseases associated with bronchoconstriction and cough.

Dose dependent effects of tadalafil and roflumilast on ovalbumin-induced airway hyperresponsiveness in guinea pigs

INTRODUCTION

Chronic obstructive diseases of airways associated with cough and/or airway smooth muscle hyperresponsiveness are usually treated with bronchodilating and anti-inflammatory drugs. Recently, selective phosphodiesterase (PDE) 4 inhibitors have been introduced into the therapy of chronic obstructive pulmonary disease. Several studies have demonstrated their ability to influence the airway reactivity and eosinophilic inflammation by increasing the intracellular cAMP concentrations also in bronchial asthma. Furthermore, the expression of PDE5 in several immune cells suggests perspectives of PDE5 inhibitors in the therapy of inflammation, as well.

PURPOSE

The aim of this study was to assess the dose-dependent effects of PDE4 and PDE5 inhibitors in allergic inflammation. Therefore, the effects of 7-days administration of PDE4 inhibitor roflumilast and PDE5 inhibitor tadalafil at two different doses in experimentally-induced allergic inflammation were evaluated.

MATERIALS AND METHODS

In the study, male adult guinea pigs were used. Control group was non-sensitized. Other animals were sensitized with ovalbumin over two weeks and thereafter treated intraperitoneally for 7 days with roflumilast or tadalafil (daily dose 0.5 mg/kg or 1.0 mg/kg b.w.), or with vehicle.

RESULTS

Both roflumilast and tadalafil reduced specific airway resistance after nebulization of histamine (marker of in vivo airway reactivity) at both doses used. The in vitro airway reactivity to cumulative doses of acetylcholine was significantly reduced for roflumilast at higher dose, predominantly in the lung tissue strips. Histamine-induced contractile responses were significantly influenced in both lung and tracheal tissue strips, predominantly at the higher doses. Tadalafil led to a decrease in contractile responses induced by both acetylcholine and histamine, with more significant effects in the lung tissue strips. These changes were associated with decreased numbers of circulating leukocytes and eosinophils and concentrations of interleukin (IL)-4, IL-5 and TNF-α in the lung homogenate.

CONCLUSIONS

The selective PDE4 and PDE5 inhibitors alleviated allergic airway inflammation, with more significant effects at the higher doses.