Leukocyte elastase inhibition therapy in cystic fibrosis: role of glycosylation on the distribution of alpha-1-proteinase inhibitor in blood versus lung

Recombinant Alpha-1 Antitrypsin as Dry Powder for Pulmonary Administration: A Formulative Proof of Concept

Alpha-1 antitrypsin (AAT) deficiency is a genetic disorder associated with pulmonary emphysema and bronchiectasis. Its management currently consists of weekly infusions of plasma-purified human AAT, which poses several issues regarding plasma supplies, possible pathogen transmission, purification costs, and parenteral administration. Here, we investigated an alternative administration strategy for augmentation therapy by combining recombinant expression of AAT in bacteria and the production of a respirable powder by spray drying. The same formulation approach was then applied to plasma-derived AAT for comparison. Purified, active, and endotoxin-free recombinant AAT was produced at high yields and formulated using L-leucine and mannitol as excipients after identifying compromise conditions for protein activity and good aerodynamic performances. An oxygen-free atmosphere, both during formulation and powder storage, slowed down methionine-specific oxidation and AAT inactivation. This work is the first peer-reviewed report of AAT formulated as a dry powder, which could represent an alternative to current treatments.

Bioengineering of an elastase inhibitor from Caesalpinia echinata (Brazil wood) seeds

Protease inhibitors have been widely used in several therapeutic applications such as in the treatment of bleeding disorders, hypertension, cancer and pulmonary diseases. In a previous work, we demonstrated that a Kunitz-type serine protease inhibitor isolated from the seeds of Caesalpinia echinata (CeEI) exhibits pharmacological potential in lung inflammatory diseases in which neutrophil elastase plays a crucial role. However, an important challenge in the use of natural products is to ensure a commercially viable production. In this work, we report the cloning, expression and purification of two recombinant CeEI isoinhibitors with 700 base pairs encoding two proteins with 181 amino acid residues (rCeEI-4 and rCeEI-5). After the expression, each yielding 22 mg/L of active protein, both isoinhibitors presented a molecular mass of about 23.0 kDa, evaluated by SDS-PAGE. The inhibition constants for human neutrophil elastase (HNE) were 0.67 nM (rCeEI-4) and 0.57 nM (rCeEI-5), i.e., similar to the native inhibitor (1.90 nM). Furthermore, rCeEI-4 was used as a template to design smaller functional peptides flanking the inhibitor reactive site: rCeEI-36, delimited between the amino acid residues N³⁶ and S⁸⁸ containing a disulfide bond in the reactive-site loop, and rCeEI-46, delimited between S⁴⁶ and L⁷⁵ without the disulfide bond. The yields were 18 mg/L (rCeEI-36) and 12 mg/L (rCeEI-46). Both peptides inhibit HNE in the nanomolar range (K_i 0.30 ± 0.01 and 8.80 ± 0.23, respectively). Considering their size and the inhibitory efficiency, these peptides may be considered in strategies for the development of drugs targeting pulmonary disorders where elastase is involved.

Circulating Truncated Alpha-1 Antitrypsin Glycoprotein in Patient Plasma Retains Anti-Inflammatory Capacity

Alpha-1 antitrypsin (AAT) is an acute phase protein that possesses immune-regulatory and anti-inflammatory functions independent of antiprotease activity. AAT deficiency (AATD) is associated with early-onset emphysema and chronic obstructive pulmonary disease. Of interest are the AATD nonsense mutations (termed null or Q0), the majority of which arise from premature termination codons in the mRNA coding region. We have recently demonstrated that plasma from an AATD patient homozygous for the Null Bolton allele (Q0bolton ) contains AAT protein of truncated size. Although the potential to alleviate the phenotypic consequences of AATD by increasing levels of truncated protein holds therapeutic promise, protein functionality is key. The goal of this study was to evaluate the structural features and anti-inflammatory capacity of Q0bolton-AAT. A low-abundance, truncated AAT protein was confirmed in plasma of a Q0bolton-AATD patient and was secreted by patient-derived induced pluripotent stem cell-hepatic cells. Functional assays confirmed the ability of purified Q0bolton-AAT protein to bind neutrophil elastase and to inhibit protease activity. Q0bolton-AAT bound IL-8 and leukotriene B4, comparable to healthy control M-AAT, and significantly decreased leukotriene B4-induced neutrophil adhesion (p = 0.04). Through a mechanism involving increased mRNA stability (p = 0.007), ataluren treatment of HEK-293 significantly increased Q0bolton-AAT mRNA expression (p = 0.03) and Q0bolton-AAT truncated protein secretion (p = 0.04). Results support the rationale for treatment with pharmacological agents that augment levels of functional Q0bolton-AAT protein, thus offering a potential therapeutic option for AATD patients with rare mutations of similar theratype.

Oxidation-resistant and thermostable forms of alpha-1 antitrypsin from Escherichia coli inclusion bodies

Native α1‐antitrypsin (AAT) is a 52‐kDa glycoprotein that acts as an antiprotease and is the physiological inhibitor of neutrophil serine proteases. The main function of AAT is to protect the lung from proteolytic damage induced by inflammation. AAT deficiency (AATD) is a codominant autosomal disorder caused by pathogenic mutations in SERPINA1 gene, leading to reduced levels of serum AAT. The deficiency is known to increase the risk of pulmonary emphysema and chronic obstructive pulmonary disease as a consequence of proteolytic imbalance induced by inflammation, associated in many instances with cigarette smoking and other environmental hazards. Currently, the available therapy for lung disease associated with AATD is serum purified human AAT injected into patients on a weekly basis. It would be advantageous to replace serum‐derived AAT with a recombinant version which is stable and resistant to oxidation. We have expressed AAT in Escherichia coli as inclusion bodies and developed a highly efficient refolding and purification process. We engineered a series of mutant forms of AAT to achieve enhance thermostability and oxidation resistance. Moreover, we synthesized an active form of AAT via cysteine‐pegylation to achieve a markedly extended half‐life in vivo. The resulting molecule, which retains comparable activity to the wild‐type form, is expected to be an improved therapeutic agent for treating hereditary emphysema. In addition, the molecule may also be used to treat other types of emphysema caused by smoking, cystic fibrosis, pulmonary hypertension, pulmonary fibrosis, and chronic obstructive pulmonary disease.

Transepithelial migration of neutrophils: mechanisms and implications for acute lung injury

The primary function of neutrophils in host defense is to contain and eradicate invading microbial pathogens. This is achieved through a series of swift and highly coordinated responses culminating in ingestion (phagocytosis) and killing of invading microbes. While these tasks are usually performed without injury to host tissues, in pathologic circumstances such as sepsis, potent antimicrobial compounds can be released extracellularly, inducing a spectrum of responses in host cells ranging from activation to injury and death. In the lung, such inflammatory damage is believed to contribute to the pathogenesis of diverse lung diseases, including acute lung injury and the acute respiratory distress syndrome, chronic obstructive lung disease, and cystic fibrosis. In these disorders, epithelial cells are targets of leukocyte-derived antimicrobial products, including proteinases and oxidants. Herein, we review the mechanisms involved in the physiologic process of neutrophil transepithelial migration, including the role of specific adhesion molecules on the leukocyte and epithelial cells. We examine the responses of the epithelial cells to the itinerant leukocytes and their cytotoxic products and the consequences of this for lung injury and repair. This paradigm has important clinical implications because of the potential for selective blockade of these pathways to prevent or attenuate lung injury.

Stability and activity in sputum of G10KHc, a potent anti-Pseudomonas antimicrobial peptide

G10KHc, a specifically targeted antimicrobial peptide developed in our laboratory, has shown rapid and selective killing activity against Pseudomonas aeruginosa in culture medium. Because of the major role played by this pathogen in cystic fibrosis, we sought to evaluate the utility of G10KHc under more physiologic conditions in vitro. In the current study, we found that robust G10KHc activity could be maintained in expectorated sputum if serine protease-dependent digestion associated with this fluid was inhibited, either by chemical antagonists or by the construction of a D-amino acid enantiomer of G10KHc. Further investigations revealed that specifically targeted antimicrobial peptide activity in sputum could be further enhanced when samples were treated with a combination of peptide and recombinant human DNase. Our results illustrate the importance of investigating combination therapy to treat cystic fibrosis, especially if protease-sensitive peptide-based agents, such as G10KHc, are to be developed as alternatives to, or in conjunction with, conventional small-molecule antibiotics.

Inhaled recombinant alpha 1-antitrypsin ameliorates cigarette smoke-induced emphysema in the mouse

In alpha 1-antitrypsin deficiency in humans, inadequately regulated activity of serine protease activity is responsible for the chronic lung tissue degeneration and irreversible loss of pulmonary function seen in those individuals with emphysema. Typically, disease symptoms in this patient population are exacerbated by cigarette smoke. Here we show that inhaled recombinant alpha 1-antitrypsin (rAAT) can provide significant protection against the development of emphysema in cigarette smoke-treated mice. As has been reported previously, cigarette smoke was seen to increase significantly the recruitment of neutrophils and macrophages into the lungs of these animals, leading to concomitant alveolar airspace enlargement and emphysema. In smoking animals treated for 6 months with inhaled rAAT, effects on lavage levels of neutrophils and macrophages were only moderate when compared with untreated animals. Furthermore, neutralizing antibodies to rAAT were generated in all rAAT-treated animals. Despite this, however, reductions in airspace enlargement of up to 73% were observed. These findings demonstrate that delivery of rAAT directly to the lungs of smoke-treated mice can inhibit lung tissue damage mediated by proteases, suggesting that rAAT inhalation therapy might represent a practical approach towards treating emphysema in humans, by modifying the course of the disease.

Recombinant human alpha-1 proteinase inhibitor: towards therapeutic use

Human alpha-1-proteinase inhibitor is a well-characterized protease inhibitor with a wide spectrum of anti-protease activity. Its major physiological role is inhibition of neutrophil elastase in the lungs, and its deficiency is associated with progressive ultimately fatal emphysema. Currently in the US, only plasma-derived human alpha-1-proteinase inhibitor is available for augmentation therapy, which appears to be insufficient to meet the anticipated clinical demand. Moreover, despite effective viral clearance steps in the manufacturing process, the potential risk of contamination with new and unknown pathogens still exists. In response, multiple efforts to develop recombinant versions of human alpha-1-proteinase inhibitor, as an alternative to the plasma-derived protein, have been reported. Over the last two decades, various systems have been used to express the human gene for alpha-1-proteinase inhibitor. This paper reviews the recombinant versions of human alpha-1-proteinase inhibitor produced in various hosts, considers current major safety and efficacy issues regarding recombinant glycoproteins as potential therapeutics, and the factors that are impeding progress in this area(1).

Acute phase mediator oncostatin M regulates affinity of α1-protease inhibitor for concanavalin A in hepatoma-derived but not lung-derived epithelial cells

Quantitative changes in plasma protein concentrations during tissue injury or inflammation (acute phase response) are often accompanied by specific alterations in the carbohydrate moieties of these proteins. The glycosylation changes comprise alterations in the type of branching of the carbohydrate structures as revealed by modulated reactivity of acute phase glycoproteins with the lectin concanavalin A. Interestingly, inflammation-induced changes in the glycosylation of acute phase proteins have been shown to affect the functional properties of these proteins. In this study we demonstrate that synthesis of acute phase protein alpha(1)-PI, the controlling inhibitor of neutrophil elastase, is significantly up-regulated in hepatic and lung-derived epithelial cells by the inflammatory mediator oncostatin M. Although oncostatin M markedly altered the concanavalin A reactivity of hepatic alpha(1)-PI, lung-derived epithelial cells did not change the pattern of alpha(1)-PI glycan branching upon stimulation with oncostatin M. These results indicate that inflammation-induced changes in glycosylation of alpha(1)-PI may have different impacts on functional properties of liver and lung-synthesized alpha(1)-PI.

Leukocyte elastase induces epithelial apoptosis: role of mitochondial permeability changes and Akt

During acute inflammation, neutrophil-mediated injury to epithelium may lead to disruption of epithelial function, including the induction of epithelial apoptosis. Herein, we report the effects of neutrophil transmigration and of purified leukocyte elastase on epithelial cell survival. Neutrophil transmigration induced apoptosis of epithelial cells [control monolayers: 5 +/- 1 cells/25 high-power fields (HPF) vs. neutrophil-treated monolayers: 29 +/- 10 cells/HPF, P < 0.05, n = 3 as determined by terminal deoxynucleotidyl transferase dUTP nick-end labeling assay] as did low concentrations (0.1 U/ml) of purified leukocyte elastase (control monolayers: 6.4 +/- 2.5% apoptotic vs. elastase: 26.2 +/- 2.9% apoptotic, P < 0.05, as determined by cytokeratin 18 cleavage). Treatment with elastase resulted in decreased mitochondrial membrane potential, release of cytochrome c to the cytosol, and cleavage of caspases-9 and -3 as determined by Western blot analysis, implicating altered mitochondrial membrane permeability as a primary mechanism for elastase-induced apoptosis. Additionally, incubation of epithelial cells with leukocyte elastase resulted in an early increase followed by a decrease in the phosphorylation of epithelial Akt, a serine/threonine kinase important in cell survival. Inhibition of epithelial Akt before elastase treatment potentiated epithelial cell apoptosis, suggesting that the initial activation of Akt represents a protective response by the epithelial cells to the proapoptotic effects of leukocyte elastase. Taken together, these observations suggest that epithelial cells exhibit a dual response to cellular stress imposed by leukocyte elastase with a proapoptotic response mediated via early alterations in mitochondrial membrane permeability countered by activation of the survival pathway involving Akt.