Opportunities for the use of aerosolized alpha 1-antitrypsin for the treatment of cystic fibrosis

Effect of Alpha-1 Antitrypsin on CFTR Levels in Primary Human Airway Epithelial Cells Grown at the Air-Liquid-Interface

The cystic fibrosis transmembrane conductance regulator (CFTR) gene is influenced by the fundamental cellular processes like epithelial differentiation/polarization, regeneration and epithelial–mesenchymal transition. Defects in CFTR protein levels and/or function lead to decreased airway surface liquid layer facilitating microbial colonization and inflammation. The SERPINA1 gene, encoding alpha1-antitrypsin (AAT) protein, is one of the genes implicated in CF, however it remains unknown whether AAT has any influence on CFTR levels. In this study we assessed CFTR protein levels in primary human lung epithelial cells grown at the air-liquid-interface (ALI) alone or pre-incubated with AAT by Western blots and immunohistochemistry. Histological analysis of ALI inserts revealed CFTR- and AAT-positive cells but no AAT-CFTR co-localization. When 0.5 mg/mL of AAT was added to apical or basolateral compartments of pro-inflammatory activated ALI cultures, CFTR levels increased relative to activated ALIs. This finding suggests that AAT is CFTR-modulating protein, albeit its effects may depend on the concentration and the route of administration. Human lung epithelial ALI cultures provide a useful tool for studies in detail how AAT or other pharmaceuticals affect the levels and activity of CFTR.

Role of Cystic Fibrosis Bronchial Epithelium in Neutrophil Chemotaxis

A hallmark of cystic fibrosis (CF) chronic respiratory disease is an extensive neutrophil infiltrate in the mucosa filling the bronchial lumen, starting early in life for CF infants. The genetic defect of the CF Transmembrane conductance Regulator (CFTR) ion channel promotes dehydration of the airway surface liquid, alters mucus properties, and decreases mucociliary clearance, favoring the onset of recurrent and, ultimately, chronic bacterial infection. Neutrophil infiltrates are unable to clear bacterial infection and, as an adverse effect, contribute to mucosal tissue damage by releasing proteases and reactive oxygen species. Moreover, the rapid cellular turnover of lumenal neutrophils releases nucleic acids that further alter the mucus viscosity. A prominent role in the recruitment of neutrophil in bronchial mucosa is played by CF bronchial epithelial cells carrying the defective CFTR protein and are exposed to whole bacteria and bacterial products, making pharmacological approaches to regulate the exaggerated neutrophil chemotaxis in CF a relevant therapeutic target. Here we revise: (a) the major receptors, kinases, and transcription factors leading to the expression, and release of neutrophil chemokines in bronchial epithelial cells; (b) the role of intracellular calcium homeostasis and, in particular, the calcium crosstalk between endoplasmic reticulum and mitochondria; (c) the epigenetic regulation of the key chemokines; (d) the role of mutant CFTR protein as a co-regulator of chemokines together with the host-pathogen interactions; and (e) different pharmacological strategies to regulate the expression of chemokines in CF bronchial epithelial cells through novel drug discovery and drug repurposing.

Delivering drugs to the lungs: The history of repurposing in the treatment of respiratory diseases

The repurposing of drug delivery by the pulmonary route has been applied to treatment and prophylaxis of an increasingly wide range of respiratory diseases. Repurposing has been most successful for the delivery of inhaled bronchodilators and corticosteroids in patients with asthma and chronic obstructive pulmonary disease (COPD). Repurposing utilizes the advantages that the pulmonary route offers in terms of more targeted delivery to the site of action, the use of smaller doses, and a lower incidence of side-effects. Success has been more variable for other drugs and treatment indications. Pulmonary delivery is now well established for delivery of inhaled antibiotics in cystic fibrosis (CF), and in the treatment of pulmonary arterial hypertension (PAH). Other inhaled treatments such as those for idiopathic pulmonary fibrosis (IPF), lung transplant rejection or tuberculosis may also become routine. Repurposing has progressed in parallel with the development of new drugs, inhaler devices and formulations.

Lung deposition of inhaled alpha-1-proteinase inhibitor (alpha 1-PI) - problems and experience of alpha1-PI inhalation therapy in patients with hereditary alpha1-PI deficiency and cystic fibrosis

Alpha-1-proteinase inhibitor (α1-PI) is the most relevant protease inhibitor in the lung. Patients with hereditary deficiency of α1-PI suffer from an impaired hepatic synthesis of α1-PI in the liver and in consequence an insufficient concentration of the protease inhibitor in the lung followed by development of lung emphysema due to an impaired protease antiprotease balance and a local relative excess of neutrophil elastase (NE). In contrast, patients with cystic fibrosis (CF) are characterised by a normal synthesis of α1-PI and a severe pulmonary inflammation with a strong excess of NE in the lung followed by progressive loss of lung function. In principle, both patient groups may benefit from an augmentation of α1-PI. Intravenous augmentation, which is established in patients with α1-PI deficiency only, is very expensive, subject to controversial discussions and only about 2% of the administered protein reaches lung interstitium. Inhalation of α1-PI may serve as an alternative to administer high α1-PI doses into the lungs of both patient groups to restore the impaired protease antiprotease balance and to diminish the detrimental effects of NE. However, prerequisites of this therapy are the reproducible administration of sufficient doses of active α1-PI into the lung without adverse effects. In our review we describe the results of studies investigating the inhalation of α1-PI in patients with α1-PI deficiency and CF. The data demonstrate the feasibility of α1-PI inhalation for restoration of the impaired protease antiprotease balance, attenuation of the inflammation and neutralisation of the excess activity of NE. Likely, inhalation of α1-PI serves as cheaper and more convenient therapy than intravenous augmentation. However, inhalation will be further optimised by use of novel nebulisers and optimised breathing techniques.

Safety and efficacy of recombinant alpha(1)-antitrypsin therapy in cystic fibrosis

Neutrophil elastase (NE) is thought to be the most important protease which damages the cystic fibrosis (CF) lung. Attempts have been made to suppress this activity using the plasma-derived inhibitor, alpha(1)-antitrypsin (AAT). In this pilot study, the safety and efficacy of inhaled recombinant human AAT (rAAT) as a treatment for CF were investigated. Thirty-nine patients participated in a prospective, double-blinded, randomized, placebo-controlled phase II trial to examine the effect of rAAT (500, 250, and 125 mg) on sputum NE activity. Sputum myeloperoxidase (MPO), interleukin-8, tumor necrosis factor receptors, sputum and plasma NE/AAT complexes, and safety parameters were also measured. Subjects were randomized to receive nebulized treatment once a day for 4 weeks, followed by 2-4 weeks with no study treatment, and then a 2-week rechallenge phase. Trends toward a reduction in NE activity were observed in patients treated with 500 mg and 250 mg of rAAT compared to placebo. Sputum NE/AAT complex and MPO levels were lower on rAAT compared to placebo. No major adverse events and, in particular, no allergic reactions to rAAT were observed. Although significant differences between rAAT and placebo for sputum NE activity were not observed, some improvements were found for secondary efficacy variables. This study demonstrated that nebulized rAAT is safe and well-tolerated, but has a limited effect on NE activity and other markers of inflammation.

Antiinflammatory Therapies for Cystic Fibrosis: Past, Present, and Future

Inflammation is a major component of the vicious cycle characterizing cystic fibrosis pulmonary disease. If untreated, this inflammatory process irreversibly damages the airways, leading to bronchiectasis and ultimately respiratory failure. Antiinflammatory drugs for cystic fibrosis lung disease appear to have beneficial effects on disease parameters. These agents include oral corticosteroids and ibuprofen, as well as azithromycin, which, in addition to its antimicrobial effects, also possesses antiinflammatory properties. Inhaled corticosteroids, colchicine, methotrexate, montelukast, pentoxifylline, nutritional supplements, and protease replacement have not had a significant impact on the disease. Therapy with oral corticosteroids, ibuprofen, and fish oil is limited by adverse effects. Azithromycin appears to be safe and effective, and is thus the most promising antiinflammatory therapy available for patients with cystic fibrosis. Pharmacologic therapy with antiinflammatory agents should be started early in the disease course, before extensive irreversible lung damage has occurred.

Circulating markers to assess nutritional therapy in cystic fibrosis

Cystic fibrosis (CF) is the most commonly occurring lethal autosomal recessive disorder. The gene defect causes defective sodium and chloride transport across epithelial cells of the respiratory, hepatobiliary, gastrointestinal and reproductive tracts, resulting in thick mucus secretions. In the respiratory tract, mucus traps bacteria, causing repeated lung infections, progressive bronchiectasis and eventual death due to respiratory failure. In the gastrointestinal tract, mucus prevents pancreatic enzymes reaching the gut, leading to nutrient malabsorption. Careful nutritional management has a dramatic effect on growth and survival rates in CF. Appropriate nutritional support includes pancreatic enzyme replacement therapy, a high-fat/high-energy diet and essential nutrient supplementation, specifically fat-soluble vitamins and essential fatty acids (EFA). Long-term studies are required to examine the effects of nutritional interventions on key clinical outcomes in CF, such as the rate of decline of lung function. The use of circulating markers to assess the influence of nutritional therapy allows short-term intervention studies to predict the potential for clinical improvements. This article provides an overview of the biomarkers useful in the prediction of the efficacy of nutritional therapy on improvements in quality and quantity of life in CF.

Effect of fluticasone on the elastase:antielastase profile of the normal lung

BACKGROUND

Excessive elastolytic activity contributes to the pathogenesis of several inflammatory respiratory diseases. The effect of glucocorticoids, which are potent anti-inflammatory agents, on the elastase:antielastase balance of the human respiratory tract is unclear, as studies on patients and in vitro have yielded inconsistent results.

DESIGN

To clarify this, bronchoalveolar lavage and lavage fluids from the upper and central airways were collected from 10 healthy, nonsmoking volunteers before and after a 2-week course of inhaled fluticasone propionate (2 x 500 micrograms day-1). Concentrations of two neutrophil elastase inhibitors, alpha-1-proteinase inhibitor (PI) and secretory leukoproteinase inhibitor (SLPI), as well as neutrophil elastase (NE) activity and NE inhibitory capacity (NEIC) were quantified in all lavage fluids.

RESULTS

Concentrations of SLPI were highest in the proximal airways and decreased distally. Neutrophil elastase inhibitory capacity activity followed the same gradient and correlated positively and consistently with SLPI, suggesting that this inhibitor makes an important contribution to the regulation of elastolytic activity in the healthy human respiratory tract. Inhaled fluticasone propionate had no effect on any component of the elastase:antielastase balance at any level of the respiratory tract, even though circulating cortisol levels were reduced in all subjects, confirming subject compliance and adequate pulmonary delivery of the drug.

CONCLUSION

This lack of action in the respiratory tract may contribute to the ineffectiveness of inhaled glucocorticoids in respiratory conditions characterised by excessive elastolytic activity.

The Pseudomonas aeruginosa secretory product pyocyanin inactivates alpha1 protease inhibitor: implications for the pathogenesis of cystic fibrosis lung disease

Alpha1 Protease inhibitor (alpha1PI) modulates serine protease activity in the lung. Reactive oxygen species inactivate alpha1PI, and this process has been implicated in the pathogenesis of a variety of forms of lung injury. An imbalance of protease-antiprotease activity is also detected in the airways of patients with cystic fibrosis-associated lung disease who are infected with Pseudomonas aeruginosa. P. aeruginosa secretes pyocyanin, which, through its ability to redox cycle, induces cells to generate reactive oxygen species. We tested the hypothesis that redox cycling of pyocyanin could lead to inactivation of alpha1PI. When alpha1PI was exposed to NADH and pyocyanin, a combination that results in superoxide production, alpha1PI lost its ability to form an inhibitory complex with both porcine pancreatic elastase (PPE) and trypsin. Similarly, addition of pyocyanin to cultures of human airway epithelial cells to which alpha1PI was also added resulted in a loss of the ability of alpha1PI to form a complex with PPE or trypsin. Neither superoxide dismutase, catalase, nor dimethylthiourea nor depletion of the media of O2 to prevent formation of reactive oxygen species blocked pyocyanin-mediated inactivation of alpha1PI. These data raise the possibility that a direct interaction between reduced pyocyanin and alpha1PI is involved in the process. Consistent with this possibility, pretreatment of alpha1PI with the reducing agent beta-mercaptoethanol also inhibited binding of trypsin to alpha1PI. These data suggest that pyocyanin could contribute to lung injury in the P. aeruginosa-infected airway of cystic fibrosis patients by decreasing the ability of alpha1PI to control the local activity of serine proteases.