The relationship between elastin cross linking and alveolar wall rupture in human pulmonary emphysema

To better define the role of mechanical forces in pulmonary emphysema, we employed methods recently developed in our laboratory to identify microscopic level relationships between airspace size and elastin-specific desmosine and isodesmosine (DID) cross links in normal and emphysematous human lungs. Free DID in wet tissue (a biomarker for elastin degradation) and total DID in formalin-fixed, paraffin-embedded (FFPE) tissue sections were measured using liquid chromatography-tandem mass spectrometry and correlated with alveolar diameter, as determined by the mean linear intercept (MLI) method. There was a positive correlation between free lung DID and MLI (P < 0.0001) in formalin-fixed lungs, and elastin breakdown was greatly accelerated when airspace diameter exceeded 400 µm. In FFPE tissue, DID density was markedly increased beyond 300 µm (P < 0.0001) and leveled off around 400 µm. Elastic fiber surface area similarly peaked at around 400 µm, but to a much lesser extent than DID density, indicating that elastin cross linking is markedly increased in response to early changes in airspace size. These findings support the hypothesis that airspace enlargement is an emergent phenomenon in which initial proliferation of DID cross links to counteract alveolar wall distention is followed by a phase transition involving rapid acceleration of elastin breakdown, alveolar wall rupture, and progression to an active disease state that is less amenable to therapeutic intervention.NEW & NOTEWORTHY The current findings support the hypothesis that airspace enlargement is an emergent phenomenon in which initial proliferation of DID cross links to counteract alveolar wall distention is followed by a phase transition involving rapid acceleration of elastin breakdown, alveolar wall rupture, and progression to an active disease state that is less amenable to therapeutic intervention.

The Proinflammatory Activity of Structurally Altered Elastic Fibers

The mechanisms responsible for the increased loss of pulmonary function following acute lung inflammation in chronic obstructive pulmonary disease remain poorly understood. To investigate this process, our laboratory developed a hamster model that uses a single intratracheal instillation of LPS to superimpose an inflammatory response on lungs treated with intratracheal elastase 1 week earlier. Parameters measured at 2 days after LPS included total leukocyte content and percent neutrophils in BAL fluid (BALF), and BALF levels of both total and peptide-free elastin-specific crosslinks, desmosine and isodesmosine (DID). Airspace enlargement, measured by the mean linear intercept method, and relative interstitial elastic fiber surface area were determined at 1 week after LPS. Compared with animals only treated with elastase, those receiving elastase/LPS showed statistically significant increases in mean linear intercept (156.2 vs. 85.5 μm), BALF leukocytes (187 vs. 37.3 × 10⁴ cells), neutrophils (39% vs. 3.4%), and free DID (182% vs. 97% of controls), which exceeded the sum of the individual effects of the two agents. Despite increased elastin breakdown, the elastase/LPS group had significantly greater elastic fiber surface area than controls (49% vs. 26%) owing to fragmentation and splaying of the fibers. Additional experiments showed that the combination of elastin peptides and LPS significantly enhanced their separate effects on BALF neutrophils and BALF DID in vivo and leukocyte chemotaxis in vitro. The results suggest that structural changes in elastic fibers have proinflammatory activity and may contribute to the decline in pulmonary function related to chronic obstructive pulmonary disease exacerbations.

A pilot clinical trial to determine the safety and efficacy of aerosolized hyaluronan as a treatment for COPD

A novel therapy for COPD involving the use of aerosolized hyaluronan (HA) was tested on a small cohort of COPD patients to determine both its safety and efficacy in reducing levels of desmosine and isodesmosine (DID), biomarkers for elastin degradation. In a 2-week, randomized, double-blind trial, 8 patients receiving 150 kDa HA (mean molecular weight) and 3 others given placebo did not show significant adverse effects with regard to spirometry, electrocardiograms, and hematological indices. Furthermore, measurements of DID in plasma from HA-treated patients indicated a progressive decrease over a 3-week period following initiation of treatment (r=−0.98; p=0.02), whereas patients receiving placebo showed no reduction in DID (r=−0.70; p=0.30). Measurements of sputum in the HA-treated group also revealed a progressive decrease in DID (r=−0.97; p=0.03), but this finding was limited by the absence of similar measurements in the placebo group. Nevertheless, the results of this small, pilot study support a longer-term trial of HA in a larger population of COPD patients.

Pharmacotherapy for Non-Cystic Fibrosis Bronchiectasis: Results From an NTM Info & Research Patient Survey and the Bronchiectasis and NTM Research Registry

BACKGROUND

Non-cystic fibrosis bronchiectasis ("bronchiectasis") is a chronic inflammatory lung disease often associated with nontuberculous mycobacteria (NTM) infection. Very little data exist to guide bronchiectasis management decisions. We sought to describe patterns of inhaled corticosteroid (ICS) and antibiotic therapy in the United States.

METHODS

We invited 2,000 patients through NTM Info & Research (NTMir) to complete an anonymous electronic survey. We separately queried baseline clinical and laboratory data from the US Bronchiectasis and NTM Research Registry (BRR).

RESULTS

Among 511 NTMir survey responders with bronchiectasis, whose median age was 67 years, 85 (17%) reported asthma and 99 (19%) reported COPD. History of ICS use was reported by 282 (55%), 171 (61%) of whom were treated 1 year or longer, and 150 (53%) were currently taking ICSs. Fewer reported ever taking azithromycin for non-NTM bronchiectasis (203 responders [40%]) or inhaled tobramycin (78 responders [15%]). The median age of 1,912 BRR patients was 69 years; 528 (28%) had asthma and 360 (19%) had COPD. Among 740 patients (42%) without NTM, 314 were taking ICSs at baseline. Among patients without NTM who were taking ICSs, only 178 (57%) had a concurrent diagnosis of COPD or asthma that could explain ICS use. Fewer were taking suppressive macrolides (96 patients [13%]), and of the 70 patients (10%) taking inhaled suppressive antibiotics, 48 (68%) had chronic Pseudomonas aeruginosa infection.

CONCLUSIONS

ICS use was common in two national samples of patients with bronchiectasis, with relatively few patients taking suppressive antibiotic therapies. Further research is needed to clarify the safety and effectiveness of these therapies in patients with bronchiectasis.

Adult Patients With Bronchiectasis: A First Look at the US Bronchiectasis Research Registry

OBJECTIVES

We sought to describe the characteristics of adult patients with bronchiectasis enrolled in the US Bronchiectasis Research Registry (BRR).

METHODS

The BRR is a database of patients with non-cystic-fibrosis bronchiectasis (NCFB) enrolled at 13 sites in the United States. Baseline demographic, spirometric, imaging, microbiological, and therapeutic data were entered into a central Internet-based database. Patients were subsequently analyzed by the presence of NTM.

RESULTS

We enrolled 1,826 patients between 2008 and 2014. Patients were predominantly women (79%), white (89%), and never smokers (60%), with a mean age of 64 ± 14 years. Sixty-three percent of the patients had a history of NTM disease or NTM isolated at baseline evaluation for entry into the BRR. Patients with NTM were older, predominantly women, and had bronchiectasis diagnosed at a later age than those without NTM. Gastroesophageal reflux disease (GERD) was more common in those with NTM, whereas asthma, primary immunodeficiency, and primary ciliary dyskinesia were more common in those without NTM. Fifty-one percent of patients had spirometric evidence of airflow obstruction. Patients with NTM were more likely to have diffusely dilated airways and tree-in-bud abnormalities. Pseudomonas and Staphylococcus aureus isolates were cultured less commonly in patients with NTM. Bronchial hygiene measures were used more often in those with NTM, whereas antibiotics used for exacerbations, rotating oral antibiotics, steroid use, and inhaled bronchodilators were more commonly used in those without NTM.

CONCLUSIONS

Adult patients with bronchiectasis enrolled in the US BRR are described, with differences noted in demographic, radiographic, microbiological, and treatment variables based on stratification of the presence of NTM.

The Diagnosis and Management of Alpha-1 Antitrypsin Deficiency in the Adult

Background: The diagnosis and clinical management of adults with alpha-1 antitrypsin deficiency (AATD) have been the subject of ongoing debate, ever since the publication of the first American Thoracic Society guideline statement in 1989.¹ In 2003, the "American Thoracic Society (ATS)/European Respiratory Society (ERS) Statement: Standards for the Diagnosis and Management of Individuals with Alpha-1 Antitrypsin Deficiency" made a series of evidence-based recommendations, including a strong recommendation for broad-based diagnostic testing of all symptomatic adults with chronic obstructive pulmonary disease (COPD).² Even so, AATD remains widely under-recognized. To update the 2003 systematic review and clinical guidance, the Alpha-1 Foundation sponsored a committee of experts to examine all relevant, recent literature in order to provide concise recommendations for the diagnosis and management of individuals with AATD. Purpose: To provide recommendations for: (1) the performance and interpretation of diagnostic testing for AATD, and (2) the current management of adults with AATD and its associated medical conditions. Methods: A systematic review addressing the most pressing questions asked by clinicians (clinician-centric) was performed to identify citations related to AATD that were published since the 2003 comprehensive review, specifically evaluating publications between January 2002 and December 2014. Important, more recent publications were solicited from the writing committee members as well. The combined comprehensive literature reviews of the 2003 document and this current review comprise the evidence upon which the committee's conclusions and recommendations are based. Results: Recommendations for the diagnosis and management of AATD were formulated by the committee. Conclusions: The major recommendations continue to endorse and reinforce the importance of testing for AATD in all adults with symptomatic fixed airflow obstruction, whether clinically labeled as COPD or asthma. Individuals with unexplained bronchiectasis or liver disease also should be tested. Family testing of first-degree relatives is currently the most efficient detection technique. In general, individuals with AATD and emphysema, bronchiectasis, and/or liver disease should be managed according to usual guidelines for these clinical conditions. In countries where intravenous augmentation therapy with purified pooled human plasma-derived alpha-1 antitrypsin is available, recent evidence now provides strong support for its use in appropriate individuals with lung disease due to AATD.

Lung hyaluronan levels are decreased in alpha-1 antiprotease deficiency COPD

INTRODUCTION

Hyaluronan (HA), a long-chain polysaccharide, is currently being evaluated as a potential therapeutic agent for pulmonary emphysema, based on previous studies from this laboratory indicating its protective effect against elastic fiber breakdown. To determine whether exogenously administered HA might replace a loss of this extracellular matrix component in this disease, we measured the content of HA in lung biopsies from both healthy individuals and alpha-1 antiprotease-deficient (AAPD) COPD patients with pulmonary emphysema.

METHODS

Tissue samples (9 from COPD patients, 5 from controls) were digested with papain to isolate glycosaminoglycans, and lung HA was quantified with an enzyme-linked immunoabsorbent assay.

RESULTS

HA was significantly decreased in the AAPDCOPD population compared to normal individuals (13.5 vs 21.7 ng/mg wet lung; p < 0.01). Furthermore, there was a positive correlation between HA levels and the following parameters: 1) percent predicted FEV1 (r = 0.78; p < 0.001), 2) percent predicted DLCO (r = 0.74; p < 0.05), and 3) serum levels of AAP (r = 0.61; p < 0.05).

CONCLUSIONS

These findings support the hypothesis that depletion of lung HA plays a role in the pathogenesis of pulmonary emphysema, and that replacement of this matrix component could slow the progression of the disease.

The Ratio of Free to Bound Desmosine and Isodesmosine May Reflect Emphysematous Changes in COPD

BACKGROUND

The unique elastin crosslinks, desmosine and isodesmosine (DID) are significantly elevated in blood, urine, and sputum from patients with COPD, and may decline following treatment of the disease. However, the large degree of variance in this biomarker among COPD patients with similar levels of disease suggests that it has limited prognostic value with regard to the degree of lung disease in a given individual. As an alternative to measuring the total amount of DID, we propose using the ratio of free to peptide-bound DID, which may provide a better indication of overall lung disease.

METHODS

To test this hypothesis, the free/bound DID ratio was measured in bronchoalveolar lavage fluid (BALF) from both hamsters with elastase-induced emphysema and controls not given the enzyme, using a combination of liquid chromatography and tandem mass spectroscopy. This ratio was then correlated with airspace enlargement, as measured by the mean percentage of lung surface area at ×100 microscopic magnification.

RESULTS

There was a significant negative correlation between the free/bound DID ratio in BALF and lung surface area. However, there was no correlation between this ratio and total BALF DID, suggesting that free/bound DID is unrelated to the immediate rate of breakdown of elastic fibers, and may instead measure the cumulative effect of elastase injury in the lung.

CONCLUSIONS

The free/bound DID ratio may be a useful measure of emphysematous changes in the lung and might also serve as a screening procedure for healthy smokers and other individuals at risk for developing COPD.

Neutrophil elastase-mediated lung disease

Elastases of both the neutrophil and macrophage have been implicated in lung disease initiation and progression. Although it is unlikely that these proteases evolved for the purpose of injuring lung tissue, the elastin-rich connective tissue framework of the lungs appears to be particularly susceptible to the action of elastolytic proteases. Assuming that neutrophil elastase most likely plays a role in the migration of neutrophils toward a site of inflammation and degradation of proteins from invading organisms or other products of the inflammatory response, it is the role of inhibitors of this protease to protect normal tissues from its effects. In alpha-1 antitrypsin deficiency we find an experiment of nature that disrupts this protease-anti-protease balance, resulting in an increased risk of destructive lung disease.

Development of predictive models for airflow obstruction in alpha-1-antitrypsin deficiency

Alpha-1-antitrypsin deficiency is a genetic condition associated with severe, early-onset chronic obstructive pulmonary disease (COPD). However, there is significant variability in lung function impairment among persons with the protease inhibitor ZZ genotype. Early identification of persons at highest risk of developing lung disease could be beneficial in guiding monitoring and treatment decisions. Using a multicenter, family-based study sample (2002-2005) of 372 persons with the protease inhibitor ZZ genotype, the authors developed prediction models for forced expiratory volume in 1 second (FEV(1)) and the presence of severe COPD using demographic, clinical, and genetic variables. Half of the data sample was used for model development, and the other half was used for model validation. In the training sample, variables found to be predictive of both FEV(1) and severe COPD were age, sex, pack-years of smoking, bronchodilator responsiveness, chronic bronchitis symptoms, and index case status. In the validation sample, the predictive model for FEV(1) explained 50% of the variance in FEV(1), and the model for severe COPD exhibited excellent discrimination (c statistic = 0.88).

Heritability of lung function in severe alpha-1 antitrypsin deficiency

Severe alpha-1 antitrypsin (AAT) deficiency is a proven genetic risk factor for COPD, but there is marked variation in the development of COPD among AAT deficient subjects. To investigate familial aggregation of lung function in subjects with AAT deficiency, we estimated heritability for forced expiratory volume in 1 s (FEV1) and FEV1/forced vital capacity (FVC) in 378 AAT deficient subjects from 167 families in the AAT Genetic Modifiers Study; all subjects were verified homozygous for the Z AAT deficiency allele. Heritability was evaluated for models that included and excluded an ascertainment correction, as well as for models that excluded, included and were stratified by a cigarette smoking covariate. In models without an ascertainment correction, and in all models without a covariate for smoking, no evidence for familial aggregation of lung function was observed. In models conditioned on the index proband with covariates for smoking, post-bronchodilator FEV1/FVC demonstrated significant heritability (0.26 +/- 0.14, p = 0.03). When we limited the analysis to subjects with a smoking history, post-bronchodilator FEV1 demonstrated significant heritability (0.47 +/- 0.21, p = 0.02). Severity rate phenotypes were also assessed as potential phenotypes for genetic modifier studies. Significant heritability was found with all age-of-onset threshold models that included smoking and ascertainment adjustments. Using the t-distribution, the heritability estimates ranged from 0.43 to 0.64, depending on the age-of-onset of FEV1 decline used for the severity rate calculation. Correction for ascertainment and consideration of gene-by-smoking interactions will be crucial for the identification of genes that may modify susceptibility for COPD in families with AAT deficiency.

IL10 polymorphisms are associated with airflow obstruction in severe alpha1-antitrypsin deficiency

Severe alpha(1)-antitrypsin (AAT) deficiency is a proven genetic risk factor for chronic obstructive pulmonary disease (COPD), especially in individuals who smoke. There is marked variability in the development of lung disease in individuals homozygous (PI ZZ) for this autosomal recessive condition, suggesting that modifier genes could be important. We hypothesized that genetic determinants of obstructive lung disease may be modifiers of airflow obstruction in individuals with severe AAT deficiency. To identify modifier genes, we performed family-based association analyses for 10 genes previously associated with asthma and/or COPD, including IL10, TNF, GSTP1, NOS1, NOS3, SERPINA3, SERPINE2, SFTPB, TGFB1, and EPHX1. All analyses were performed in a cohort of 378 PI ZZ individuals from 167 families. Quantitative spirometric phenotypes included forced expiratory volume in one second (FEV(1)) and the ratio of FEV(1)/forced vital capacity (FVC). A qualitative phenotype of moderate-to-severe COPD was defined for individuals with FEV(1) </= 50 percent predicted. Six of 11 single-nucleotide polymorphisms (SNPs) in IL10 (P = 0.0005-0.05) and 3 of 5 SNPs in TNF (P = 0.01-0.05) were associated with FEV(1) and/or FEV(1)/FVC. IL10 SNPs also demonstrated association with the qualitative COPD phenotype. When phenotypes of individuals with a physician's diagnosis of asthma were excluded, IL10 SNPs remained significantly associated, suggesting that the association with airflow obstruction was independent of an association with asthma. Haplotype analysis of IL10 SNPs suggested the strongest association with IL10 promoter SNPs. IL10 is likely an important modifier gene for the development of COPD in individuals with severe AAT deficiency.

Delay in diagnosis of alpha1-antitrypsin deficiency: a continuing problem

BACKGROUND AND STUDY OBJECTIVES

Alpha1-antitrypsin (AAT) deficiency is common but under-recognized. A 1994 mail survey showed a long delay between the onset of symptoms and the initial diagnosis of AAT deficiency. In 2003, we carried out a similar mail survey of AAT-deficient individuals to determine whether any delay in diagnosis experienced by individuals with a more recent diagnosis had become shorter. We also determined whether individuals living near medical centers with an expressed interest in AAT deficiency experienced shorter diagnostic delays than those living at a distance.

METHODS

Results from mail surveys of two different cohorts were compared: a 1994 survey of 304 individuals with severe AAT deficiency and a 2003 survey of 1,953 AAT-deficient individuals. In the 2003 survey cohort, diagnostic delay intervals were analyzed by calendar year of initial diagnosis, rural vs urban residence, visit to a liver or lung specialist within the last year, and living within 50 miles of a medical center with particular expertise in AAT deficiency. One thousand nine hundred fifty-three individuals responded to the 2003 mail survey (37.4%).

RESULTS

In the 2003 cohort, the mean +/- SD diagnostic delay was 5.6 +/- 8.5 years, compared with 7.2 +/- 8.3 years for the 1994 cohort (p = 0.002). In the 2003 cohort, younger patients and male patients experienced shorter diagnostic delays than older patients and female patients (p < 0.0001 and p = 0.007, respectively). For example, the delay was 6.5 +/- 8.8 years for those born in the 1940s, as compared with 0.43 +/- 1.08 years for those born after 1980. Neither urban residence nor living near a center with expertise in AAT deficiency were associated with a shortened diagnostic delay interval.

CONCLUSIONS

Although these results show some improvement in the mean diagnostic delay in the 9-year period separating the two studies, under-recognition of AAT deficiency persists. Diagnostic delay of AAT deficiency is longer in women and in older individuals. Educational efforts are underway to enhance clinicians' diagnostic suspicion of AAT deficiency and permit earlier diagnosis and attendant benefits.

Results of a survey of patients with alpha-1 antitrypsin deficiency

BACKGROUND

alpha(1)-Antitrypsin deficiency (AATD) is an uncommon genetic disease which occurs in 1-2.5% of Americans with chronic obstructive pulmonary disease (COPD). Little is known about current demographics of AATD.

OBJECTIVES

This survey study reviews the clinical characteristics of diseased individuals in North America.

METHODS

A survey of members from the mailing lists of US AATD patient support organizations was commissioned with duplicate persons omitted. The survey was mailed to 5,222 unique individuals with AATD. Questionnaires were returned by 1,953 individuals, including 1,810 with severe deficiency, 93 with the carrier state and 41 who were caregivers of others.

RESULTS

The majority (81%) of participants reported COPD with symptoms of asthma, chronic bronchitis, and emphysema, usually in combination. The mean age of respondents [53.1 +/- 13.2 (SD) years] is older than the general US population. Lung or liver transplantation was reported by 9% of all respondents (n = 175), including 66 single lung transplants, 68 double lung transplants, and 47 liver transplants. Another 6.6% (n = 128) reported that they were currently on a transplant list. Twenty-one percent of lung transplants report continuing augmentation therapy use. Augmentation use is reported by 75% of those with obstructive lung disease. The majority of patients with liver disease also have COPD.

CONCLUSIONS

AATD remains a devastating illness for many of those affected as reflected in a high incidence of transplantation for liver and lung disease.