(Chest. 2000;117:291S-293S.)
© 2000
American College of Chest Physicians
Bronchial Inflammation*
Its Relationship to Colonizing Microbial Load and 
1-Antitrypsin Deficiency
Robert A. Stockley, DSc, MD;
Adam T. Hill, MB ChB;
Susan L. Hill, PhD and
Edward J. Campbell, MD
*
From the Department of Medicine (Drs. Stockley, Hill, and Hill), Queen Elizabeth Hospital, Birmingham B15 2TH, UK; and the University of Utah (Dr. Campbell), Salt Lake City, UT.
Correspondence to: Robert A. Stockley, DSc, MD, Department of Medicine, Queen Elizabeth Hospital, Birmingham B15 2TH, UK
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Abstract
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Neutrophil elastase is capable of generating many of the features
of chronic bronchial disease. In patients with COPD, airways
inflammation with neutrophil recruitment and elastase release is
positively correlated with colonizing bacterial load in the stable
clinical state (p < 0.0005). In addition,
1-antitrypsin deficiency is associated with a greater
neutrophil load, higher elastase activity, leukotriene-B4
concentration, and serum protein leak than matched patients without
deficiency (p < 0.005). These data confirm an effect of bronchial
colonization on airways inflammation in COPD and indicate the role of
1-antitrypsin in its modulation.
Key Words: 1-antitrypsin deficiency • bacteria • COPD • inflammation
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Introduction
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Abbreviations:
1-AT = 1-antitrypsin;
LTB4 = leukotriene B4; MPO = myeloperoxidase;
NE = neutrophil elastase; SLPI = secretory leukoproteinase inhibitor
The
presence of bronchial disease is often a feature of patients with COPD.
It is associated with inflammation, as indicated by the presence of
increased numbers of neutrophils,1
a reduction in
mucociliary clearance, mucus gland hyperplasia, and epithelial
damage,2
all of which may facilitate bacterial
colonization.
Neutrophil elastase (NE) has been shown to produce many of the features
of bronchial disease, including the generation of mucus gland
hyperplasia, active mucus secretion, a decrease in ciliary beat
frequency, and epithelial damage. In addition, there are other changes
to key host defenses within the airway generated by this enzyme, all of
which may result in a facilitation of bacterial colonization. This, in
turn, will drive inflammation and can result in the perpetuation of
airways inflammation, damage, and continued bacterial
colonization.3
Although these features have been studied extensively in
vitro, there have been very few studies in man. In particular, the
degree of inflammation and its relationship to any colonizing bacterial
load is unknown. Furthermore, the role of
1-antitrypsin (1-AT)
in the protection of the airway has previously been considered to be of
less importance than in the interstitium, because secretory
leukoproteinase inhibitor (SLPI) is believed to be the major elastase
inhibitor in the airway. The purposes of the current studies,
therefore, were to assess airways inflammation and to determine the
influence of the colonizing microbial load and the effect of
1-AT deficiency.
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Materials and Methods
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We studied 55 patients with chronic obstructive bronchitis, 64
patients with a similar degree of airflow obstruction related to
1-AT deficiency (phenotype Pi Z), and 43
patients with idiopathic bronchiectasis diagnosed by high-resolution CT
scan. Sputum was collected over a 4-h period from rising from each
patient, and an aliquot was removed and assessed for the colonizing
microbial load as described previously.4
The remaining
sample was ultracentrifuged to obtain the sputum sol phase. These
samples were stored at - 70°C until analyzed for the presence of
myeloperoxidase (MPO; as a marker of neutrophil content); the activity
of NE; the chemoattractants, interleukin-8, and leukotriene
B4 (LTB4); and finally the inhibitors
1-AT and SLPI and albumin. Serum was obtained
at the same time for the measure of serum albumin to determine the
sputum to serum albumin ratio as a measure of protein leakage. These
methods and their validation have been described in detail
elsewhere.5
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Results
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Inflammation in the airway was clearly associated with the
presence and size of colonizing microbial load as indicated by the
positive correlations with MPO (r = 0.58; p < 0.0005),
NE activity (r = 0.43; p < 0.0005), interleukin-8
(r = 0.67; p < 0.0001), LTB4
(r = 0.48; p < 0.0005), sputum-serum albumin ratio
(r = 0.43; p < 0.0005), and a negative correlation with
SLPI (r = - 0.52; p < 0.0005). The relationship
indicated a microbial threshold of 106 cfu below
which inflammation was present but low, but above which it was markedly
enhanced and related to the size of the colonizing load (see Fig 1
).
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Figure 1. The vertical axis indicates the sputum MPO
concentration (a marker of neutrophil influx). Mean values are
indicated for results of samples containing either no positive
bacterial culture or small numbers of mixed normal flora only, together
with results for increasing concentrations of bacterial load for
single organisms. Note the significant increase in the presence of
106 cfu/mL and the progressive rise with increasing
bacterial load.
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The studies indicated that patients with 1-AT
had a greater degree of inflammation than chronic obstructive
bronchitis patients without deficiency even when they were matched for
smoking history, airflow obstruction, and bacterial load. The
1-AT-deficient patients had a greater sputum
MPO concentration (p < 0.001); readily detectable and increased
elastase activity (p < 0.001); LTB4 (p < 0.005); and
sputum-serum protein ratio (p < 0.001). In addition, the SLPI
concentrations were reduced in 1-AT deficiency
(p < 0.05).
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Discussion
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The results presented here confirmed that subjects with chronic
bronchial disease have inflammation present in their airways as
indicated by the presence of neutrophils (quantified by the MPO
concentration) and leakage of the serum protein albumin. It is well
known that patients with chronic bronchial disease can be colonized
with bacteria even in the stable clinical state.6
The
current data confirm that some patients are colonized and that the
bacterial load may vary from 105 to
> 108 cfu/mL. Of importance, the degree of
inflammation in the airway is dependent on the colonizing bacterial
load. In the absence of bacteria or when bacterial load is
105 cfu/mL, inflammation is relatively low.
However, as the colonizing load rises above 106
organisms/mL, inflammation rises increasingly dependent on the size of
the bacterial load. This first demonstration of such a change in human
disease is consistent with previous animal model studies,7
and suggests that such colonization is not a benign feature of patients
with airways disease.
The data also confirm that 1-AT deficiency is
associated with a greater degree of airways inflammation. It is
conventionally believed that the major inhibitor of elastase in the
airway is SLPI. However, patients with 1-AT
deficiency have slightly reduced SLPI concentrations compared to
subjects without deficiency. The mechanisms involved in the airways are
clearly complex. Previous workers have suggested that an increase in
LTB4 in the lungs of patients with
1-AT deficiency is a direct result of failure
to completely inactivate elastase in the airways.8
The
increased LTB4 released results in neutrophil recruitment and
hence delivery of more elastase to the airways. In our current study,
in the presence of bronchial disease, patients with
1-AT deficiency have a greater amount of
elastase activity in their secretions compared to nondeficient
patients. In addition, the LTB4 is high, as is neutrophil
recruitment (indicated by the MPO concentration). The reduction in SLPI
could be a direct effect of free NE activity in the airway, since this
enzyme has been shown to reduced SLPI secretion by epithelial
cells.9
This may explain the lower SLPI concentrations
found in the 1-AT-deficient subjects, and such a change
would clearly facilitate the activity of the elastase. Finally,
elastase activity has been shown to result in protein leakage across
epithelial cells in vitro,10
and this would be
consistent with the increased sputum serum albumin ratio seen in the
current studies as inflammation and elastase activity rise.
In summary, these observations provide further insights into bronchial
inflammation and factors that may influence it. However, the true
interrelationship of all these factors awaits the development of
intervention studies with specific inhibitors.
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Footnotes
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Supported by a noncommercial educational grant from Bayer as part of
the ADAPT Programme.
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References
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Pesci, A, Balbi, B, Majori, M, et al (1998) Inflammatory cells and mediators in bronchial lavage of patients with chronic obstructive pulmonary disease. Eur Respir J 12,380-386[Abstract]
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Stockley, RA (1995) The pathogenesis of chronic obstructive lung diseases: implications for therapy. Q J Med 88,141-146
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Stockley, RA (1994) The role of proteinases in the pathogenesis of chronic bronchitis. Am J Respir Crit Care Med 150(6 part 2),S109-S113
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Pye, A, Stockley, RA, Hill, SL (1995) Simple method for quantifying viable bacterial numbers in sputum. J Clin Pathol 48,719-724[Abstract/Free Full Text]
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Hill, AT, Bayley, D, Stockley, RA (1999) The interrelationship of sputum inflammatory markers in patients with chronic bronchitis. Am J Respir Crit Care Med 160,893-898[Abstract/Free Full Text]
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Monso, E, Ruiz, J, Rosell, A, et al (1995) Bacterial infection in chronic obstructive pulmonary disease: a study of stable and exacerbated out-patients using the protected specimen brush. Am J Respir Crit Care Med 152,1316-1320[Abstract]
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Onofrio, JM, Toews, GB, Lipscombe, MF, et al (1983) Granulocyte-alveolar-macrophage interaction in the pulmonary clearance of Staphylococcus aureus. Am Rev Respir Dis 127,335-341[ISI][Medline]
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Hubbard, RC, Fells, G, Gadek, J, et al (1991) Neutrophil accumulation in the lungs in 1-antitrypsin deficiency: spontaneous release of leukotriene B4 by alveolar macrophages. J Clin Invest 88,891-897
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Sallenave, JM, Schulmann, J, Crossly, J, et al (1994) Regulation of secretory leukocyte proteinase inhibitor (SPLI) and elastase specific inhibitor (ESI-elafin) in human airway epithelial cells by cytokines and neutrophilic enzymes. Am J Respir Cell Mol Biol 11,733-741[Abstract]
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Peterson, MW, Walter, ME, Nygaard, SD (1995) Effect of neutrophil mediators on epithelial permeability. Am J Respir Cell Mol Biol 13,719-727[Abstract]
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Abstract
Introduction
