Why is Disease Penetration so Variable in Alpha-1 Antitrypsin Deficiency? The Contribution of Environmental Factors

Pulmonary Rehabilitation for Chronic Obstructive Pulmonary Disease Patients with Underlying Alpha-1 Antitrypsin Deficiency: A Systematic Review and Practical Recommendations

Background

Alpha-1 antitrypsin deficiency (AATD) is an often-overlooked genetic condition that makes individuals susceptible to early onset of chronic obstructive pulmonary disease (COPD). The established benefits of exercise-based pulmonary rehabilitation (PR) for usual COPD patients are unclear for those with underlying AATD, especially given potentially differing muscle adaptations to exercise. This review seeks to compare PR outcomes between AATD and usual COPD patients and to consolidate current knowledge on exercise intervention outcomes for the AATD population.

Methods

A thorough search of 4 databases (Ovid, Medline, CINAHL, CENTRAL) was conducted based on 3 search concepts: (1) alpha-1 antitrypsin deficiency, (2) pulmonary rehabilitation OR exercise, and (3) muscle morphology. A dual review process and quality assessment were independently implemented throughout all stages of the review.

Results

Four studies highlighted modest exercise capacity and quality of life in AATD patients undergoing PR. However, one study reported unique muscle and mitochondrial responses compared to usual COPD patients. Additionally, a moderate exercise session did not alter pro-inflammatory cytokine levels in AATD patients, despite higher levels of tumor necrosis factor-α levels in muscle biopsies compared to usual COPD patients.

Conclusions

The current literature base insufficiently addresses the efficacy of PR on AATD, with indications that exercise adaptation may deviate from that of usual COPD patients. Further research is needed to optimize PR, particularly in identifying the most suitable exercise intensity, and delivery setting, and addressing specific educational needs for individuals with AATD.

Chymotrypsin-like Elastase-1 Mediates Progressive Emphysema in Alpha-1 Antitrypsin Deficiency

Chymotrypsin-like elastase 1 (CELA1) is a serine protease that is neutralized by alpha-1antitrypsin (AAT) and prevents emphysema in a murine antisense oligonucleotide model of AAT-deficient emphysema. Mice with genetic ablation of AAT do not have emphysema at baseline but develop emphysema with injury and aging. We tested the role of the CELA1 gene in emphysema development in this genetic model of AAT-deficiency following tracheal lipopolysaccharide (LPS), 10 months of cigarette smoke exposure, aging, and a low-dose tracheal porcine pancreatic elastase (LD-PPE) model we developed. In this last model, we performed proteomic analysis to understand differences in lung protein composition. We were unable to show that AAT-deficient mice developed more emphysema than wild type with escalating doses of LPS. In the LD-PPE model, AAT-deficient mice developed significant and progressive emphysema from which Cela1-/- & AAT-deficient mice were protected. Cela1-/-& AAT-deficient lungs had more matrix-associated proteins than AAT-deficientlungs but also had more leukocyte-associated proteases. With cigarette smoke exposure, Cela1-/- &AAT-deficient mice had more emphysema than AAT-deficient mice but had less myeloperoxidase activity. Cela1-/-&AAT-deficient mice had less age-related airspace simplification than AAT-deficient and were comparable to wild type. While CELA1 promotes inflammation-independent emphysema progression and its absence preserves the lung matrix in multiple models of AAT-deficient emphysema, for unclear reasons Cela1 deficiency is associated with increased emphysema with cigarette smoke. While anti-CELA1 therapies could potentially be used to prevent emphysema progression in AAT deficiency after smoking cessation, an understanding of why and how cigarette smoke exacerbates emphysema in Cela1 deficiency and whether AAT replacement therapy mitigates this effect is needed first.

CELA1 Mediates Progressive Emphysema in Alpha-1 Antitrypsin Deficiency

Chymotrypsin-like elastase 1 ( CELA1 ) is a serine protease that is neutralized by α1-antitrypsin (AAT) and prevents emphysema in a murine antisense oligonucleotide model of AAT-deficient emphysema. Mice with genetic ablation of AAT do not have emphysema at baseline but develop emphysema with injury and aging. We tested the role of CELA1 in emphysema development in this genetic model of AAT -deficiency following tracheal lipopolysacharide (LPS), 8 months of cigarette smoke (CS) exposure, aging, and a low-dose tracheal porcine pancreatic elastase (LD-PPE) model. In this last model, we performed proteomic analysis to understand differences in lung protein composition. We were unable to show that AAT -/ - mice developed more emphysema than wild type with LPS. In the LD-PPE model, AAT -/- mice developed progressive emphysema from which Cela1 -/- &AAT -/- mice were protected. In the CS model, Cela1 -/- &AAT -/- mice had worse emphysema than AAT -/- , and in the aging model, 72-75 week-old Cela1 -/- &AAT -/- mice had less emphysema than AAT -/- mice. Proteomic analysis of AAT -/- vs. wildtype lungs in the LD-PPE model showed reduced amounts of AAT proteins and increased amounts of proteins related to Rho and Rac1 GTPases and protein oxidation. Similar analysis of Cela1 -/- &AAT -/- vs. AAT -/- lungs showed differences in neutrophil degranulation, elastin fiber synthesis, and glutathione metabolism. Thus, Cela1 prevents post-injury emphysema progression in AAT -deficiency, but it has no effect and potentially worsens emphysema in response to chronic inflammation and injury. Prior to developing anti-CELA1 therapies for AAT-deficient emphysema, an understanding of why and how CS exacerbates emphysema in Cela1 deficiency is needed.

Clinical and functional characteristics of individuals with alpha-1 antitrypsin deficiency: EARCO international registry

BACKGROUND

Alpha-1 antitrypsin deficiency (AATD) is a rare disease that is associated with an increased risk of pulmonary emphysema. The European AATD Research Collaboration (EARCO) international registry was founded with the objective of characterising the individuals with AATD and investigating their natural history.

METHODS

The EARCO registry is an international, observational and prospective study of individuals with AATD, defined as AAT serum levels < 11 μM and/or proteinase inhibitor genotypes PI*ZZ, PI*SZ and compound heterozygotes or homozygotes of other rare deficient variants. We describe the characteristics of the individuals included from February 2020 to May 2022.

RESULTS

A total of 1044 individuals from 15 countries were analysed. The most frequent genotype was PI*ZZ (60.2%), followed by PI*SZ (29.2%). Among PI*ZZ patients, emphysema was the most frequent lung disease (57.2%) followed by COPD (57.2%) and bronchiectasis (22%). Up to 76.4% had concordant values of FEV1(%) and KCO(%). Those with impairment in FEV1(%) alone had more frequently bronchiectasis and asthma and those with impairment in KCO(%) alone had more frequent emphysema and liver disease. Multivariate analysis showed that advanced age, male sex, exacerbations, increased blood platelets and neutrophils, augmentation and lower AAT serum levels were associated with worse FEV1(%).

CONCLUSIONS

EARCO has recruited > 1000 individuals with AATD from 15 countries in its first 2 years. Baseline cross sectional data provide relevant information about the clinical phenotypes of the disease, the patterns of functional impairment and factors associated with poor lung function. Trial registration www.

CLINICALTRIALS

gov (ID: NCT04180319).