Macrolides in cystic fibrosis

Understanding the molecular regulatory mechanisms of autophagy in lung disease pathogenesis

Lung disease development involves multiple cellular processes, including inflammation, cell death, and proliferation. Research increasingly indicates that autophagy and its regulatory proteins can influence inflammation, programmed cell death, cell proliferation, and innate immune responses. Autophagy plays a vital role in the maintenance of homeostasis and the adaptation of eukaryotic cells to stress by enabling the chelation, transport, and degradation of subcellular components, including proteins and organelles. This process is essential for sustaining cellular balance and ensuring the health of the mitochondrial population. Recent studies have begun to explore the connection between autophagy and the development of different lung diseases. This article reviews the latest findings on the molecular regulatory mechanisms of autophagy in lung diseases, with an emphasis on potential targeted therapies for autophagy.

The indispensable role of pharmacy services and medication therapy management in cystic fibrosis

Care for people with cystic fibrosis (PWCF) is highly complex and requires a multidisciplinary approach where the pharmacist plays a vital role. The purpose of this manuscript is to serve as a guideline for pharmacists and pharmacy technicians who provide care for PWCF by providing background and current recommendations for the use of cystic fibrosis (CF)-specific medications in both the acute and ambulatory care settings. The article explores current literature surrounding the role of pharmacists and pharmacy technicians, proven pharmacy models to emulate, and pharmacokinetic idiosyncrasies unique to the CF population while also identifying areas of future research. Clinical recommendations for the use of CF-specific medications are broken down by organ system including mechanism of action, adverse events, dosages, and monitoring parameters. The article also includes quick reference tables essential to the acute and chronic medication therapy management of PWCF.

Autophagy in Pulmonary Diseases

The pathogenesis of pulmonary diseases is often complex and characterized by multiple cellular events, including inflammation, cell death, and cell proliferation. The mechanisms by which these events are regulated in pulmonary diseases remain poorly understood. Autophagy is an essential process for cellular homeostasis and stress adaptation in eukaryotic cells. This highly conserved cellular process involves the sequestration of cytoplasmic components in double-membrane autophagosomes, which are delivered to lysosomes for degradation. The critical roles of autophagy have been demonstrated in a wide range of pathophysiological conditions. Emerging studies have identified that autophagy plays important roles in the pathogenesis of various lung diseases. In addition, autophagy has been shown to selectively degrade subcellular targets, including proteins, organelles, and pathogens. Here, we highlight the recent advances in the molecular regulation and function of autophagy in lung diseases.

The Approach to Pseudomonas aeruginosa in Cystic Fibrosis

There is a high prevalence of Pseudomonas aeruginosa in patients with cystic fibrosis and clear epidemiologic links between chronic infection and morbidity and mortality exist. Prevention and early identification of infection are critical, and stand to improve with the advent of new vaccines and laboratory methods. Once the organism is identified, a variety of treatment options are available. Aggressive use of antipseudomonal antibiotics is the standard of care for acute pulmonary exacerbations in cystic fibrosis, and providers must take into account specific patient characteristics when making treatment decisions related to antibiotic selection, route and duration of administration, and site of care.

Use of macrolides in lung diseases: recent literature controversies

OBJECTIVE

To review the mechanisms of action of macrolides in pediatric respiratory diseases and their clinical indications.

SOURCES

Review in the PubMed database, comprising the following terms in English: "macrolide and asthma"; "macrolide and cystic fibrosis"; "macrolide bronchiolitis and viral acute"; "macrolide and bronchiolitis obliterans" and "macrolide and non-CF bronchiectasis".

SUMMARY OF THE FINDINGS

The spectrum of action of macrolides includes production of inflammatory mediators, control of mucus hypersecretion, and modulation of host-defense mechanisms. The potential benefit of macrolide antibiotics has been studied in a variety of lung diseases, such as cystic fibrosis (CF), bronchiectasis, asthma, acute bronchiolitis, and non-CF bronchiectasis. Several studies have evaluated the benefits of macrolides in asthma refractory to therapy, but the results are controversial and indications should be limited to specific phenotypes. In viral bronchiolitis, there is no consistent benefit in acute conditions, although recent data have shown an effect in recurrent wheezing prevention. In patients with CF results are also contradictory, but the consensus states there is a small clinical benefit, especially for patients infected with P. aeruginosa. There was also no positive action of macrolides in patients with post-infectious bronchiolitis obliterans. Children with non-CF bronchiectasis seem to have clear benefits regarding the use of macrolides, which showed clinical advantages in parenchyma protection and lung function.

CONCLUSIONS

The long-term use of macrolides should be limited to highly selected situations, especially in patients with bronchiectasis. Careful evaluation of the benefits and potential damage are tools for their indication in specific groups.

Tulathromycin exerts proresolving effects in bovine neutrophils by inhibiting phospholipases and altering leukotriene B4, prostaglandin E2, and lipoxin A4 production

The accumulation of neutrophils and proinflammatory mediators, such as leukotriene B4 (LTB4), is a classic marker of inflammatory disease. The clearance of apoptotic neutrophils, inhibition of proinflammatory signaling, and production of proresolving lipids (including lipoxins, such as lipoxin A4 [LXA4]) are imperative for resolving inflammation. Tulathromycin (TUL), a macrolide used to treat bovine respiratory disease, confers immunomodulatory benefits via mechanisms that remain unclear. We recently reported the anti-inflammatory properties of TUL in bovine phagocytes in vitro and in Mannheimia haemolytica-challenged calves. The findings demonstrated that this system offers a powerful model for investigating novel mechanisms of pharmacological immunomodulation. In the present study, we examined the effects of TUL in a nonbacterial model of pulmonary inflammation in vivo and characterized its effects on lipid signaling. In bronchoalveolar lavage (BAL) fluid samples from calves challenged with zymosan particles (50 mg), treatment with TUL (2.5 mg/kg of body weight) significantly reduced pulmonary levels of LTB4 and prostaglandin E2 (PGE2). In calcium ionophore (A23187)-stimulated bovine neutrophils, TUL inhibited phospholipase D (PLD), cytosolic phospholipase A2 (PLA2) activity, and the release of LTB4. In contrast, TUL promoted the secretion of LXA4 in resting and A23187-stimulated neutrophils, while levels of its precursor, 15(S)-hydroxyeicosatetraenoic acid [15(S)-HETE], were significantly lower. These findings indicate that TUL directly modulates lipid signaling by inhibiting the production of proinflammatory eicosanoids and promoting the production of proresolving lipoxins.

Pseudomonas aeruginosa infection in patients with cystic fibrosis: scientific evidence regarding clinical impact, diagnosis, and treatment

Evidence-based techniques have been increasingly used in the creation of clinical guidelines and the development of recommendations for medical practice. The use of levels of evidence allows the reader to identify the quality of scientific information that supports the recommendations made by experts. The objective of this review was to address current concepts related to the clinical impact, diagnosis, and treatment of Pseudomonas aeruginosa infections in patients with cystic fibrosis. For the preparation of this review, the authors defined a group of questions that would be answered in accordance with the principles of PICO-an acronym based on questions regarding the Patients of interest, Intervention being studied, Comparison of the intervention, and Outcome of interest. For each question, a structured review of the literature was performed using the Medline database in order to identify the studies with the methodological design most appropriate to answering the question. The questions were designed so that each of the authors could write a response. A first draft was prepared and discussed by the group. Recommendations were then made on the basis of the level of scientific evidence, in accordance with the classification system devised by the Oxford Centre for Evidence-Based Medicine, as well as the level of agreement among the members of the group.

Anti-inflammatory effects of macrolides in childhood lung diseases

Macrolides are drugs that have antimicrobial effects, especially against intracellular pathogens. Various studies have shown that macrolides might also have anti-inflammatory effects. Macrolides inhibit the production of interleukins and can reduce pulmonary neutrophilic inflammation. Clinical trials have demonstrated beneficial effects of macrolides in various chronic lung diseases. The objective of this study was to review recent data in the medical literature on the anti-inflammatory effects of macrolides in childhood lung diseases by searching the Medline (PubMed) database. We used the following search terms: "macrolide and cystic fibrosis"; "macrolide and asthma"; "macrolide and bronchiolitis obliterans"; and "macrolide and acute bronchiolitis". We selected articles published in international scientific journals between 2001 and 2012. Clinical studies and in vitro evidence have confirmed the anti-inflammatory effect of macrolides in respiratory diseases. Some clinical trials have shown the benefits of the administration of macrolides in patients with cystic fibrosis, although the risk of bacterial resistance should be considered in the analysis of those benefits. Such benefits are controversial in other respiratory diseases, and the routine use of macrolides is not recommended. Further controlled clinical trials are required in order to assess the efficacy of macrolides as anti-inflammatory drugs, so that the benefits in the treatment of each specific clinical condition can be better established.

Effect of clarithromycin in experimental empyema by multidrug-resistant Pseudomonas aeruginosa

Evidence from a recent randomized study of our group suggests that intravenous clarithromycin resulted in earlier resolution of ventilator-associated pneumonia. The need to understand the mechanism of action of clarithromycin guided to the study of a model of experimental empyema by multidrug-resistant Pseudomonas aeruginosa in 40 rabbits. Animals were randomized into controls (group A); treatment with clarithromycin (group B); treatment with piperacillin/tazobactam (group C); and treatment with both agents (group D). Pleural fluid was collected at regular time intervals for quantitative culture, estimation of cell apoptosis and of concentrations of tumour necrosis factor-alpha (TNFα). After 7 days, animals were euthanized for estimation of tissue growth. Bacterial growth in the pleural fluid of group D was significantly decreased compared with the other groups on day 5. Lung growth of group D was lower than group A. That was also the case of cytokine stimulation by pleural fluid samples on U937 monocytes. It is concluded that administration of clarithromycin enhanced the antimicrobial efficacy of piperacillin/tazobactam and decreased bacterial growth in the pleural fluid and in tissues. It also attenuated the pro-inflammatory phenomena induced by the β-lactam.

Nonantibiotic macrolides prevent human neutrophil elastase-induced mucus stasis and airway surface liquid volume depletion

Mucus clearance is an important component of the lung's innate defense system. A failure of this system brought on by mucus dehydration is common to both cystic fibrosis (CF) and chronic obstructive pulmonary disease (COPD). Mucus clearance rates are regulated by the volume of airway surface liquid (ASL) and by ciliary beat frequency (CBF). Chronic treatment with macrolide antibiotics is known to be beneficial to both CF and COPD patients. However, chronic macrolide usage may induce bacterial resistance. We have developed a novel macrolide, 2'-desoxy-9-(S)-erythromycylamine (GS-459755), that has significantly diminished antibiotic activity against Staphylococcus aureus, Streptococcus pneumonia, Moraxella catarrhalis, and Haemophilus influenzae. Since neutrophilia frequently occurs in chronic lung disease and human neutrophil elastase (HNE) induces mucus stasis by activating the epithelial sodium channel (ENaC), we tested the ability of GS-459755 to protect against HNE-induced mucus stasis. GS-459755 had no effect on HNE activity. However, GS-459755 pretreatment protected against HNE-induced ASL volume depletion in human bronchial epithelial cells (HBECs). The effect of GS-459755 on ASL volume was dose dependent (IC₅₀ ~3.9 μM) and comparable to the antibacterial macrolide azithromycin (IC₅₀ ~2.4 μM). Macrolides had no significant effect on CBF or on transepithelial water permeability. However, the amiloride-sensitive transepithelial voltage, a marker of ENaC activity, was diminished by macrolide pretreatment. We conclude that GS-459755 may limit HNE-induced activation of ENaC and may be useful for the treatment of mucus dehydration in CF and COPD without inducing bacterial resistance.

Pathogen- and host-directed anti-inflammatory activities of macrolide antibiotics

Macrolide antibiotics possess several, beneficial, secondary properties which complement their primary antimicrobial activity. In addition to high levels of tissue penetration, which may counteract seemingly macrolide-resistant bacterial pathogens, these agents also possess anti-inflammatory properties, unrelated to their primary antimicrobial activity. Macrolides target cells of both the innate and adaptive immune systems, as well as structural cells, and are beneficial in controlling harmful inflammatory responses during acute and chronic bacterial infection. These secondary anti-inflammatory activities of macrolides appear to be particularly effective in attenuating neutrophil-mediated inflammation. This, in turn, may contribute to the usefulness of these agents in the treatment of acute and chronic inflammatory disorders of both microbial and nonmicrobial origin, predominantly of the airways. This paper is focused on the various mechanisms of macrolide-mediated anti-inflammatory activity which target both microbial pathogens and the cells of the innate and adaptive immune systems, with emphasis on their clinical relevance.

Macrolides: from in vitro anti-inflammatory and immunomodulatory properties to clinical practice in respiratory diseases

BACKGROUND

Macrolides have long been recognised to exert immunomodulary and anti-inflammatory actions. They are able to suppress the "cytokine storm" of inflammation and to confer an additional clinical benefit through their immunomodulatory properties.

METHODS

A search of electronic journal articles was performed using combinations of the following keywords: macrolides, COPD, asthma, bronchitis, bronchiolitis obliterans, cystic fibrosis, immunomodulation, anti-inflammatory effect, diabetes, side effects and systemic diseases.

RESULTS

Macrolide effects are time- and dose-dependent, and the mechanisms underlying these effects remain incompletely understood. Both in vitro and in vivo studies have provided ample evidence of their immunomodulary and anti-inflammatory actions. Importantly, this class of antibiotics is efficacious with respect to controlling exacerbations of underlying respiratory problems, such as cystic fibrosis, asthma, bronchiectasis, panbrochiolitis and cryptogenic organising pneumonia. Macrolides have also been reported to reduce airway hyper-responsiveness and improve pulmonary function.

CONCLUSION

This review provides an overview on the properties of macrolides (erythromycin, clarithromycin, roxithromycin, azithromycin), their efficacy in various respiratory diseases and their adverse effects.

Azithromycin blocks autophagy and may predispose cystic fibrosis patients to mycobacterial infection

Azithromycin is a potent macrolide antibiotic with poorly understood antiinflammatory properties. Long-term use of azithromycin in patients with chronic inflammatory lung diseases, such as cystic fibrosis (CF), results in improved outcomes. Paradoxically, a recent study reported that azithromycin use in patients with CF is associated with increased infection with nontuberculous mycobacteria (NTM). Here, we confirm that long-term azithromycin use by adults with CF is associated with the development of infection with NTM, particularly the multi-drug-resistant species Mycobacterium abscessus, and identify an underlying mechanism. We found that in primary human macrophages, concentrations of azithromycin achieved during therapeutic dosing blocked autophagosome clearance by preventing lysosomal acidification, thereby impairing autophagic and phagosomal degradation. As a consequence, azithromycin treatment inhibited intracellular killing of mycobacteria within macrophages and resulted in chronic infection with NTM in mice. Our findings emphasize the essential role for autophagy in the host response to infection with NTM, reveal why chronic use of azithromycin may predispose to mycobacterial disease, and highlight the dangers of inadvertent pharmacological blockade of autophagy in patients at risk of infection with drug-resistant pathogens.

The Transition from Bronchopulmonary Dysplasia to Childhood Chronic Lung Disease

The impact of a preterm birth on lung function in later life is not always predictable and the variability of lung phenotype in these children can be striking even among children of the same gestational age. Although many children with a history of bronchopulmonary dysplasia (BPD) improve with age, others continue to manifest significant pulmonary abnormalities. Several different lung phenotypes have been described in older children with a history of BPD. These descriptions have been based in part on chronic respiratory symptoms, pulmonary function abnormalities, and response to respiratory illnesses. These lung phenotypes include large and/or small airway dysfunction, impaired alveolar growth characterized by decreased pulmonary reserve, and pulmonary hypertension found primarily in children with severe chronic lung disease. Children with a history of BPD can manifest 1 or more of these lung phenotypes with varying degrees of severity. Currently, treatment of respiratory symptoms is primarily supportive and symptom based. Although many children improve with age, others continue to have chronic respiratory symptoms into adult life. The development of standardized guidelines for the care of children after discharge from the neonatal intensive care unit may help direct appropriate therapy, limit lung injury, and maximize lung growth potential in this vulnerable group of children.

Clarithromycin for prevention of bronchiolitis obliterans syndrome in lung allograft recipients

BACKGROUND

Bronchiolitis obliterans syndrome (BOS) is the major limitation to long-term survival following lung transplantation and strategies to reduce its incidence have remained elusive. Macrolides may stabilize lung function in patients with established BOS. Their role, however, in prevention of BOS remains unexamined.

METHODS

Survival and BOS-free survival of 102 lung allograft recipients (LARs), transplanted at a single center between July 1995 and December 2001 who routinely received clarithromycin, were compared with two different control groups. The first control group consisted of 44 LARs from the same center who were transplanted from January 2002 onwards and did not receive clarithromycin. The second control group consisted of a contemporaneous cohort of 5089 recipients, transplanted between 1995 and 2001, reported to the United Network for Organ Sharing database.

RESULTS

When compared with the first control group, BOS-free survival was reduced in LARs receiving clarithromycin. Univariate (hazard ratio [HR] 3.13, p-value = 0.004) and multivariate (HR 3.49, p-value = 0.04) analyses showed that routine use of clarithromycin was associated with an increased risk of developing BOS. When compared with the second control group, the five-yr survival of clarithromycin group was similar (p-value = 0.24).

CONCLUSIONS

Routine use of clarithromycin does not delay development of BOS or improve survival.

Chronic macrolide therapy in inflammatory airways diseases

Long-term therapy with the macrolide antibiotic erythromycin was shown to alter the clinical course of diffuse panbronchiolitis in the late 1980s. Since that time, macrolides have been found to have a large number of antiinflammatory properties in addition to being antimicrobials. These observations provided the rationale for many studies performed over the last decade to assess the usefulness of macrolides in other inflammatory airways diseases, such as cystic fibrosis, asthma, COPD, and bronchiolitis obliterans syndrome. This review summarizes the immunomodulatory properties of macrolides and the results of these recent studies demonstrating their potential for being disease-modifying agents.

TLR5 as an anti-inflammatory target and modifier gene in cystic fibrosis

New treatments are needed to improve the health of people with cystic fibrosis (CF). Reducing lung-damaging inflammation is likely to be beneficial, but specific anti-inflammatory targets have not been identified. By combining cellular immunology with a population-based genetic modifier study, we examined TLR5 as an anti-inflammatory target and modifier gene in CF. Using two pairs of human CF and control airway epithelial cells, we demonstrated that the TLR5-flagellin interaction is a major mediator of inflammation following exposure to Pseudomonas aeruginosa. To validate TLR5 as an anti-inflammatory target, we analyzed the disease modifying effects of the TLR5 c.1174C>T single nucleotide polymorphism (rs5744168) in a large cohort of CF patients (n = 2219). rs5744168 encodes a premature stop codon and the T allele is associated with a 45.5-76.3% reduction in flagellin responsiveness (p < 0.0001). To test the hypothesis that reduced TLR5 responsiveness would be associated with improved health in CF patients, we examined the relationship between rs5744168 and two clinical phenotypes: lung function and body weight. Adults with CF carrying the TLR5 premature stop codon (CT or TT genotype) had a higher body mass index than did CF patients homozygous for the fully functional allele (CC genotype) (p = 0.044); however, similar improvements in lung function associated with the T allele were not statistically significant. Although follow-up studies are needed to confirm the impact of TLR5 on nutritional status, this translational research provides evidence that genetic variation in TLR5 resulting in reduced flagellin responsiveness is associated with improved health indicators in adults with CF.

Molecular characterization of macrolide resistance determinants [erm(B) and mef(A)] in Streptococcus pneumoniae and viridans group streptococci (VGS) isolated from adult patients with cystic fibrosis (CF)

OBJECTIVES

Although long-term use of azithromycin has shown a significant clinical improvement for patients with cystic fibrosis (CF), its long-term effect on the susceptibility of commensal flora within CF airways has not yet been examined. We therefore suggest that long-term use of azithromycin increases macrolide resistance in commensal streptococci.

METHODS

Erythromycin susceptibility in naturally colonizing viridans group streptococci (VGS) was characterized, as well as macrolide resistance gene determinants through sequence analysis, in pneumococci (n = 15) and VGS [n = 84; i.e. Streptococcus salivarius (n = 30), Streptococcus mitis (n = 17), Streptococcus sanguinis (n = 11), Streptococcus oralis (n = 10), Streptococcus parasanguinis (n = 6), Streptococcus gordonii (n = 3), Streptococcus infantis (n = 3), Streptococcus cristatus (n = 2), Streptococcus anginosus (n = 1) and Streptococcus australis (n = 1)] isolated from sputum from 24 adult CF patients, who were on oral azithromycin therapy for at least the previous 7 months.

RESULTS

Almost three-quarters of isolates (74; 74.7%) were resistant to erythromycin, whilst a further 15 (15.2%) had reduced susceptibility, leaving only 10 (10.1%) isolates susceptible to erythromycin. The majority (89.8%) were not susceptible to erythromycin, as demonstrated by possession of the erm(B) gene in 25/99 (25.3%), the mef(A) gene in 1/99 (1.0%), the mef(E) gene in 75/99 (75.8%) and both erm(B) and mef(E) genes simultaneously in 11/99 (11.1%). These results indicate that genotypic resistance for macrolides is common in VGS in adult CF patients, with efflux being over three times more frequent.

CONCLUSIONS

Long-term treatment with azithromycin in CF patients may reduce antibiotic susceptibility in commensal VGS, where these organisms may potentially act as a reservoir of macrolide resistance determinants for newly acquired and antibiotic-susceptible pathogens.