Theophylline's effect on neutrophil function and the late asthmatic response

Xanthines and Phosphodiesterase Inhibitors

Theophylline is an orally acting xanthine that has been used since 1937 for the treatment of respiratory diseases including asthma and chronic obstructive pulmonary disease (COPD). However, in most treatment guidelines, xanthines have now been consigned to third-line therapy because of their narrow therapeutic window and propensity for drug-drug interactions. However, lower than conventional doses of theophylline considered to be bronchodilator are now known to have anti-inflammatory actions of relevance to the treatment of respiratory disease. The molecular mechanism(s) of action of theophylline are not well understood, but several potential targets have been suggested including non-selective inhibition of phosphodiesterases (PDE), inhibition of phosphoinositide 3-kinase, adenosine receptor antagonism and increased activity of certain histone deacetylases. Although theophylline has a narrow therapeutic window, other xanthines are in clinical use that are claimed to have a better tolerability such as doxofylline and bamifylline. Nonetheless, xanthines still play an important role in the treatment of asthma and COPD as they can show clinical benefit in patients who are refractory to glucocorticosteroid therapy, and withdrawal of xanthines from patients causes worsening of disease, even in patients taking concomitant glucocorticosteroids.More recently the orally active selective PDE4 inhibitor, roflumilast, has been introduced into clinical practice for the treatment of severe COPD on top of gold standard treatment. This drug has been shown to improve lung function in patients with severe COPD and to reduce exacerbations, but is dose limited by a range side effect, particularly gastrointestinal side effects.

Neutrophilic inflammation in asthma: mechanisms and therapeutic considerations

INTRODUCTION

Neutrophilic airway inflammation represents a pathologically distinct form of asthma and frequently appears in symptomatic adulthood asthmatics. However, clinical impacts and mechanisms of the neutrophilic inflammation have not been thoroughly evaluated up to date. Areas covered: Currently, distinct clinical manifestations, triggers, and molecular mechanisms of the neutrophilic inflammation (namely Toll-like receptor, Th1, Th17, inflammasome) are under investigation in asthma. Furthermore, possible role of the neutrophilic inflammation is being investigated in respect to the airway remodeling. We searched the related literatures published during the past 10 years on the website of Pub Med under the title of asthma and neutrophilic inflammation in human. Expert commentary: Epidemiologic and experimental studies have revealed that the neutrophilic airway inflammation is induced by a wide variety of stimuli including ozone, particulate matters, cigarette smoke, occupational irritants, endotoxins, microbial infection and colonization, and aeroallergens. These triggers provoke diverse immune and inflammatory responses leading to progressive and sometimes irreversible airway obstruction. Clinically, neutrophilic airway inflammation is frequently associated with severe asthma and poor response to glucocorticoid therapy, indicating the need for other treatment strategies. Accordingly, therapeutics will be targeted against the main mediators behind the underlying molecular mechanisms of the neutrophilic inflammation.

Theophylline inhibits the differentiation of human monocyte into dendritic cell potentially via adenosine receptor antagonism

BACKGROUND

Theophylline has an anti-inflammatory action that may account for its clinical effectiveness in the reduction of inflammatory cells in the airways. Dendritic cells (DCs) are professional antigen-presenting cells, capable of priming naïve T cells, and play key roles in the activation of immune responses in asthma.

OBJECTIVE

The purpose of this study was to investigate the effects of theophylline on human monocyte differentiation into DCs and whether this involved antagonism of adenosine receptors.

METHODS

Peripheral human blood monocytes were cultured in the presence of granulocyte/macrophage-colony stimulating factor and IL-4 to induce DC differentiation. The cells were incubated with theophylline, KF17837 (a selective A2a receptor antagonist) and enprofylline (A2b receptor antagonist) and co-incubated with selective adenosine A1 and A2a receptor agonists, a phosphodiesterase inhibitor (rolipram) and adenosine deaminase (ADA) to determine their effects on DC differentiation. In addition, depletion of adenosine receptors by small interfering RNA (siRNA) was also examined.

RESULTS

Monocytes differentiated into myeloid DCs in the culture system. The number of DCs was remarkably reduced by 60-70% when theophylline was administered at a therapeutic concentration. This effect was concentration-dependently exacerbated, was partly mediated by cellular apoptosis and was effectively reversed by the addition of the A1 agonists [2-chloro-N(6)-cyclopentyladenosin, N(6)-cyclohexyladenosine, and N-ethylcarboxamidoadenosine (NECA)] or the A2a agonist (CGS-21680, NECA). The depletion of the adenosine A1 receptor by siRNA and addition of ADA remarkably reduced DC differentiation. Meanwhile, both enprofylline and rolipram had little effect.

CONCLUSION

Our findings suggest that the adenosine A1 (and possibly coordinated with A2a) receptors contribute to DC differentiation and survival. These findings provide further evidence that theophylline has an anti-inflammatory action in bronchial asthma.

Theophylline

Theophylline (3-methyxanthine) has been used to treat airway diseases for over 70 years. It was originally used as a bronchodilator but the relatively high doses required are associated with frequent side effects, so its use declined as inhaled β₂-agonists became more widely used. More recently it has been shown to have anti-inflammatory effects in asthma and COPD at lower concentrations. The molecular mechanism of bronchodilatation is inhibition of phosphodiesterase(PDE)3 and PDE4, but the anti-inflammatory effect may be due to histone deacetylase (HDAC) activation, resulting in switching off of activated inflammatory genes. Through this mechanism theophylline also reverses corticosteroid resistance and this may be of particular value in severe asthma and COPD where HDAC2 activity is markedly reduced. Theophylline is given systemically (orally as slow-release preparations for chronic treatment and intravenously for acute exacerbations of asthma) and blood concentrations are determined mainly by hepatic metabolism, which may be increased or decreased in several diseases and by concomitant drug therapy. Theophylline is now usually used as an add-on therapy in asthma patients not well controlled on inhaled corticosteroids and in COPD patients with severe disease not controlled by bronchodilator therapy. Side effects are related to plasma concentrations and include nausea, vomiting and headaches due to PDE inhibition and at higher concentrations to cardiac arrhythmias and seizures due to adenosine A₁-receptor antagonism.

Allergen-induced airway inflammation and its therapeutic intervention

Allergen inhalation challenge has been useful for examining the mechanisms of allergen-induced airway inflammation and the associated physiological changes and for documenting the efficacy of drugs to treat asthma. Allergen inhalation by a sensitized subject results in acute bronchoconstriction, beginning within 15-30 min and lasting 1-3 hr, which can be followed by the development of a late asthmatic response. Individuals who develop both an early and late response after allergen have more marked increases in airway hyperresponsiveness, and greater increases in allergen-induced airway inflammation, particularly in airway eosinophils and basophils. All of the currently available and effective treatments for asthma modify some aspects of allergen-induced responses. These medications include short-acting and long-acting inhaled β₂-agonists, inhaled corticosteroids, cromones, methylxanthines, leukotriene inhibitors, and anti-IgE monoclonal antibody. In addition, allergen inhalation challenge has become a useful method which can, in a very limited number of patients, provide key information on the therapeutic potential of new drugs being developed to treat asthma.

Novel chronotherapeutic rectal aminophylline delivery system for therapy of asthma

The aim of this study was to develop a new chronotherapeutic pharmaceutical preparation as a sustained-release suppository for prevention and therapeutic use against bronchial asthma in the early morning. Sustained-release hollow-type (SR-HT) suppositories using sodium alginate (Alg-Na), sodium polyacrylate (PANa) or polyacrylate-PANa co-polymer (PA-PANa) as gelling polymers (gel agent) were prepared and pharmaceutical characteristics of these suppositories were investigated. Type A SR-HT suppositories comprised a suppository shell prepared with oleaginous base and containing aminophylline only or aminophylline with Alg-Na or PANa in the cavity (hollow space). Type B SR-HT suppositories comprised a suppository shell prepared with oleaginous base and gel agent (30%), with aminophylline in the hollow space. In drug-release studies, the acrylate polymer-containing suppositories showed linearity of delayed release rate, providing significantly decreased the highest concentration of theophylline in plasma (C(max)) and delayed the time required to reach C(max) (t(max)) and the mean residence time (MRT) after rectal administrated in rabbits. In particular, suppositories containing PA-PANa maintained significantly higher theophylline concentrations than control suppositories at 12h after rectal administration. Furthermore, histopathological examination indicated that these suppositories using acrylate polymers did not result in rectal lesions. The SR-HT suppository, particularly using PA-PANa as a gel agent, may thus be useful against nocturnal symptoms of asthma. In this study, we confirmed new formulation of sustained-release suppository for chronotherapy of theophylline using oily base material in combination with polymer such as PA-PANa. The hollow-type suppository containing oleaginous base and hydrophilic polymer in the shell could be useful device for rectal administration of various drugs with prolongation of plasma concentration.

The allergen bronchoprovocation model: an important tool for the investigation of new asthma anti-inflammatory therapies

Allergen bronchoprovocation tests have been used for more than two decades in the investigation of respiratory allergic diseases such as asthma and rhinitis. These bronchial challenges are now well standardized and can offer key information on the therapeutic potential of new agents and on their anti-inflammatory effects on the airways. Both standard and low-dose allergen provocations are safe when performed by experienced investigators and do not lead to persistent worsening of asthma or change in airway function. The evaluation of new therapeutic agents by these methods can also provide important information on the mechanisms of development and persistence of airway diseases.

Association between neutrophilic and eosinophilic inflammation in patients with severe persistent asthma

BACKGROUND

Eosinophils are generally recognized as effector cells in asthma. Recently, neutrophils have been suggested to contribute to the development of chronic severe asthma. The mechanisms by which neutrophils contribute to the pathophysiology of asthma remain to be elucidated; however, neutrophils may affect either accumulation or functional status of eosinophils via the generation of inflammatory mediators. The objective of this study was to evaluate whether neutrophilic inflammation is associated with eosinophilic inflammation in severe asthma.

METHODS

Following the inhalation of hypertonic saline, induced sputum was obtained from 12 healthy controls, 10 mild persistent asthmatics who were treated with low-dose inhaled corticosteroids, and 8 severe persistent asthmatics who were treated with combinations of drugs including high-dose inhaled corticosteroids and oral prednisolone. Subsequently, differential inflammatory cell counts were evaluated.

RESULTS

The percentage of eosinophils in induced sputum was significantly higher in patients who showed airway neutrophilia. In severe persistent asthmatics, the percentage of neutrophils was significantly correlated with the percentage of eosinophils in induced sputum.

CONCLUSIONS

The results of the present study suggest that accumulated neutrophils may contribute to the development of eosinophilic inflammation in severe persistent asthmatics who were treated with oral and high-dose inhaled corticosteroids. This effect may contribute to the eventual manifestation of airway inflammation in severe asthma.

Effects of piclamilast, a selective phosphodiesterase-4 inhibitor, on oxidative burst of sputum cells from mild asthmatics and stable COPD patients

Oxidative stress associated with increased presence of neutrophils is an important feature of inflammatory airways diseases like asthma or chronic obstructive pulmonary disease. We studied the in vitro effect of piclamilast (RP73401), a selective phosphodiesterase (PDE)-4 inhibitor, compared to theophylline and prednisolone, on respiratory burst of sputum cells from mild asthmatics and COPD patients. Sputum cells were harvested from mild asthmatics and stable COPD patients and treated with piclamilast, theophylline or prednisolone. Respiratory burst was assessed by luminol-dependent chemoluminescence after stimulation with 10 microM n-formyl-met-leu-phe (FMLP). Piclamilast inhibited FMLP-induced respiratory burst of sputum cells in a concentration-dependent manner (asthma: EC50 approximately 100 nM, max. inhibition: 97.5+/-5% at 100 microM; COPD: EC50 approximately 1 microM, max. inhibition: 70.6+/-4.5% at 100 microM), whereas maximal inhibition observed with theophylline (asthma: max. inhib. 27+/-15%; COPD: 6+/-2%, both p < 0.05 vs. piclamilast) and prednisolone (asthma: 16+/-6%; COPD: 7.8+/-6.2%, both p < 0.05 vs. piclamilast) was weaker. Inhibition by piclamilast was largely reversed through pretreatment of cells with the adenylcyclase inhibitor SQ22536. We concluded that piclamilast, a selective PDE-4 inhibitor, attenuates the respiratory burst of sputum cells from mild asthmatics and COPD patients in vitro. These data underline the potential of PDE-4 inhibition as a novel therapeutic approach to inflammatory airway diseases like asthma or COPD.

Neutrophil-mediated inflammation in respiratory syncytial viral bronchiolitis

BACKGROUND

The involvement of neutrophil-mediated inflammation may play an important role in the pathogenesis of acute respiratory syncytial virus bronchiolitis. However, no measurable marker is sensitive enough to assess neutrophil-mediated inflammation in the airways. Released neutrophil elastase (NE) in intraluminal airways has been reported to induce pulmonary inflammation. The aim of this study was to determine whether the amount of urinary trypsin inhibitor (UTI) in serum, a degenerate induced by NE, reflects the degree of airway inflammation in children with respiratory syncytial viral (RSV) bronchiolitis and whether the severity of inflammation is evaluated. The pre-alpha-/inter-alpha-trypsin inhibitor is assumed to be precursors of the UTI. When NE degrades these inhibitors, UTI is liberated.

METHODS

Serum UTI concentrations in infants admitted with RSV bronchiolitis, other viral infections, bacterial pneumonia and control subjects were measured by means of one-step sandwich-type enzyme immunoassay.

RESULTS

Serum UTI concentrations in 25 patients on admission were significantly higher than the 15 infantile control values (mean +/- SEM, 22.126 +/- 2.317 and 6.701 +/- 0.719 U/mL, respectively; P < 0.0001). The elevated levels returned to baseline values with improvement in the respiratory symptoms. Higher levels of serum UTI with RSV infection were consistently associated with clinical symptoms and artificial ventilation. Serum NE concentrations of patients were elevated in some patients but not significantly different from controls in the patients who showed only upper respiratory symptoms with RSV infections.

CONCLUSION

The findings strongly suggested that neutrophil-mediated events are involved in the pathogenesis of RSV bronchiolitis, and the monitoring of UTI concentrations might be useful for evaluating the neutrophil-mediated airway inflammation.

Low-dose theophylline in childhood asthma: a placebo-controlled, double-blind study

Regular anti-inflammatory treatment is essential in treating persistent asthma. Most commonly, inhaled corticosteroids (ICS) are used. However, especially in children, there is concern about the long-term safety of ICS such that doses should be kept to a minimum. The use of theophylline has decreased because of frequent side-effects in therapeutic doses. In adults, there have been reports about an immunomodulatory effect of low-dose theophylline. To study the clinical and immunomodulatory effect in children, 36 patients (mean age 12.5 SD 2.4 years) with moderate, persistent asthma on regular ICS were recruited into a placebo-controlled, double-blind study. After a 6-week run-in period, patients received either theophylline 10 mg/kg bodyweight or placebo for 12 weeks. Diary cards, lung function, peripheral blood lymphocyte subpopulations and serum eosinophil cationic protein (sECP) were assessed. In the treatment group, mean serum theophylline was 7.1 mg/l. There was no change in symptoms or use of rescue medication. Mean (SD) peak expiratory flow (PEF) increased from 86% (24) to 95% (18) predicted. sECP decreased from 43.2 microg/l (32.5) to 26.5 microg/l (16.9) (p = 0.02). Lymphocyte subpopulations did not change. The study failed to show a beneficial clinical or an immunomodulatory effect of theophylline when used in low doses. These results do not support a more important role of theophylline in the long-term treatment of moderate childhood asthma.

Theophylline. A review of its potential steroid sparing effects in asthma

Theophylline is generally considered to be a bronchodilatory drug. However, recent pharmacodynamic studies indicate that it has anti-inflammatory effects. It reduced eosinophil survival rates in vitro, and reduced eosinophil accumulation in bronchial tissue in patients with atopic asthma. Theophylline has also been shown to reduce T cell proliferation and accumulation. These changes were mirrored by improved pulmonary function in patients with asthma in studies that evaluated this parameter. Three randomised double-blind studies have evaluated the potential role of theophylline as an anti-inflammatory treatment in patients with asthma not controlled by low doses of inhaled corticosteroids. Patients were randomised to receive low dose theophylline (400 to 750 mg daily) plus low dose inhaled corticosteroids, or an increased dose of inhaled corticosteroids. Clinical pulmonary function improved to the same or a greater extent in patients who received low dose inhaled corticosteroids plus theophylline than in those treated with high dose inhaled corticosteroids plus placebo. Where reported, the dosages of theophylline used in these studies resulted in serum theophylline concentrations of approximately 9 to 10 mg/L. Approximate monthly costs were provided in one study: these were $60 (year and currency not specified) for theophylline plus budesonide 800 micrograms/day, compared with $100 for budesonide 1600 micrograms/day, and $155 for a regimen of budesonide 800 micrograms/day and salmeterol 100 micrograms/day.

CONCLUSIONS

Low dose theophylline has been shown to reduce requirements for inhaled corticosteroid therapy in patients with asthma and may reduce overall treatment costs.

Theophylline inhibits the late asthmatic response to nighttime antigen challenge in patients with mild atopic asthma

BACKGROUND

Inhaled antigen at night causes a more pronounced late asthmatic response (LAR) when compared with daytime challenges. Chronopharmacology with controlled-release theophylline given in the evening leads to a peak serum theophylline concentration (STC) in early morning which coincides with LAR that follows an evening challenge.

OBJECTIVE

To evaluate the effect of controlled-release theophylline given with the evening meal on the immediate asthmatic response (IAR) and LAR following nighttime antigen challenge in patients with mild atopic asthma.

METHODS

To qualify, subjects underwent antigen bronchoprovocation by graded nebulization until the IAR (fall in FEV1 of > or =20%) occurred; spirometry was then measured hourly for 8 hours to establish the presence of LAR (fall in FEV1 > or =15%). After 2 weeks of randomized, double-blind crossover treatment with either theophylline (target STC of 10 to 15 mg/L, (56 to 83 micromol/L)) or placebo, inhaled antigen challenge was performed at 10 PM in each subject. FEV1 values were measured immediately and then hourly for 8 hours following antigen challenge.

RESULTS

Twelve subjects completed the study. During the placebo phase, the maximal fall in FEV1 during LAR was 39 +/- 3% (mean +/- SEM) compared with 31 +/- 4% fall during theophylline treatment phase (P = .01). A reduction in LAR occurred despite higher dose (P <.05) of inhaled antigen during theophylline phase, which would have been expected to result in a more pronounced LAR. Serum theophylline concentration at 8 AM on the day following antigen challenge was 9.6 +/- 1.1 mg/L (53 +/- 6 micromol/L).

CONCLUSION

Nocturnal administration of controlled-release theophylline increases the tolerance to inhaled antigen and reduces severity of LAR. Because the LAR is linked to airway inflammation, these data support the possibility of antiinflammatory effects associated with theophylline use.