Chest ACCP Education Calendar
HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
QUICK SEARCH:   [advanced]


     

Guest Access | Sign In via User Name/Password
doi:10.1378/chest.06-2251
(Chest. 2007; 131:1363-1371)
© 2007 American College of Chest Physicians
This Article
Right arrow Abstract Freely available
Right arrow Full Text (PDF) Free
Right arrow Submit a response
Right arrow Alert me when this article is cited
Right arrow Alert me when eLetters are posted
Right arrow Alert me if a correction is posted
Right arrow Citation Map
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Similar articles in ISI Web of Science
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Add to My Personal Article Archive
Right arrow Download to citation manager
Right arrow reprints & permissions
Citing Articles
Right arrow Citing Articles via ISI Web of Science (1)
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Ma, S.
Right arrow Articles by Turino, G. M.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Ma, S.
Right arrow Articles by Turino, G. M.

Measurements of Desmosine and Isodesmosine by Mass Spectrometry in COPD*

Shuren Ma, PhD; Yong Y. Lin, PhD and Gerard M. Turino, MD

* From the James P. Mara Center for Lung Disease, Department of Medicine, St. Luke’s-Roosevelt Hospital Center, Columbia University College of Physicians & Surgeons, New York, NY.

Correspondence to: Gerard M. Turino, MD, St. Luke’s-Roosevelt Hospital, Department of Medicine, 1000 Tenth Ave, Mara Center, 3rd Floor, New York, NY 10019; e-mail: gmt1{at}columbia.edu

Abstract

Objectives: Application of mass spectrometry (MS) for direct measurements of desmosine (D) and isodesmosine (I) in urine, plasma, and sputum as markers of elastin degradation in patients with {alpha}1-antitrypsin deficiency (AATD) and non-AATD-related COPD.

Background: In COPD patients, the lungs undergo elastin injury, which can be monitored by measurements of D and I in body fluids as specific markers of elastin degradation using the specificity and sensitivity of MS.

Methods: Acid hydrolysis of blood plasma, 24-h urine and sputum measurements, followed by chromatographic separation for mass spectrometric analysis.

Results: Each patient group had levels of plasma D and I that were statistically significantly higher than those of control subjects. AATD patients had higher levels than COPD patients with normal {alpha}1-antitrypsin (AAT) levels. Twenty-four-hour urine measurements demonstrated no significant difference in total levels of D and I among control subjects and patients but showed a free (unbound) concentration of D and I in urine, which was statistically significantly higher in patients with COPD with and without AAT. The D and I levels in the sputum of patients with AATD exceeded the levels in COPD patients with normal AAT levels.

Conclusions: MS allows a sensitive and specific analysis of D and I in body fluids. The quantification of D and I in sputum, along with increases of D and I in plasma and an elevated free component of D and I in urine provide indexes that characterize patients with COPD and can be followed in relation to the course of the disease and/or therapy.

Key Words: {alpha}1-antitrypsin deficiency • COPD • desmosine • elastin • emphysema • isodesmosine • liquid chromatography • mass spectrometry

Lung elastin degradation occurs with the development of pulmonary emphysema in patients with COPD related to smoking or related to {alpha}1-antitrypsin deficiency (AATD).12

Desmosine (D) and isodesmosine (I), the cross-linking amino acids that are present only in elastin in human beings, offer the prospect of assessing elastin degradation in patients with disease by measuring them in certain body fluids.3 Thus far, D and I have been measured in the urine of patients with COPD and have been found to be statistically significantly elevated compared to healthy control subjects.4567 One study8 demonstrated the daily variability of the excretion of D and I and did not show a statistically significantly elevated excretion of these amino acids in patients in 24-h collections. In this same study, statistically significantly increased excretion of D and I was found in patients with cystic fibrosis.

Peptides of elastin have been measured in plasma by radioimmunoassay and were found to be elevated in patients with COPD.79 Because of the variability of the specificity of antibodies to elastin peptides, the quantitation of peptides has varied among various studies.10 Direct measurements of D and I in plasma have not been recorded in healthy subjects or patients with COPD, and measurements of D and I in sputum have only been reported in 2003.11 We now report measurements of D and I in plasma as well as in urine and sputum. The results demonstrate a statistically significant difference between healthy control subjects and patients in whom COPD has been diagnosed, and further suggest that measurements of D and I in plasma may be a discriminating index distinguishing patients with COPD from healthy subjects. D and I were measured in plasma, urine, and sputum in a cohort of patients in whom COPD related to smoking had been diagnosed and in a second cohort of patients in whom COPD was related to Z-phenotype AATD as well as smoking.

Materials and Methods

Preparation of specimens of urine and sputum and measurements by liquid chromatography (LC)/mass spectrometry (MS) has been described previously.11

Chemicals
D and I standard (mixed 50% D and 50% I) were purchased from Elastin Products (Owensville, MI), and all other reagents were from Sigma (St. Louis, MO). MCX cation exchange cartridges (3 mL) were obtained from Waters (Milford, MA), and CF1 cellulose powders were purchased from Whatman (Clifton, NJ).

Urine Specimens:
Twenty-four hour samples were collected and analyzed as previously described.11

Preparation of Plasma Samples:
Samples were obtained after centrifuging venous blood specimens at 2,500 revolutions per minute for 25 min. Samples were stored at –20°C until used. One milliliter of plasma and 1 mL of concentrated HCl (37%) were placed in a glass vial. After air in the sample was displaced with a stream of nitrogen, the sample was acid hydrolyzed for 24 h in 6N HCl. After evaporation to dryness, the residue was dissolved in 2 mL of a mixed solution of n-butanol/acetic acid/6 N HCl (4:1:1, by volume). The sample solution was loaded onto a 3-mL CF1 cartridge. The CF1 cartridge was prepared by introducing 3 mL of the slurry of 5% CF1 cellulose powder in a mixture of n-butanol/acetic acid/water (4:1:1, by volume). The cartridge was washed three times with 3 mL of the n-butanol/acetic acid/water mixture, and the D and I adsorbed in the CF1 cartridge were eluted with 3 mL of water. The eluate was evaporated to dryness under vacuum at 45°C, and the residue was dissolved in 0.1 mL of the high-performance LC (HPLC) mobile phase for LC/MS analysis. For analysis in plasma, samples were processed and measured in duplicate, and the results were averaged.

Sputum samples were processed as previously described11 with the following modification: the acid-hydrolyzed samples underwent chromatography using a CF1 cartridge as described in the section on the treatment of plasma samples. Each sputum sample was processed and measured in duplicate, and the results were averaged. Sputum was obtained from 3-h morning collections of spontaneously produced sputum. When subjects could not voluntarily produce sputum, sputum was induced by the inhalation of a 3% saline solution for 20 min as previously described.11

Recovery of D and I in Urine and Plasma
Using D and I as the external standards, we performed studies to ensure the recovery and reproducibility of the analysis in urine and plasma. Triplicates of two urine samples were spiked with 0.4 and 2.0 pmol each of D and I standards, and were carried through HCl hydrolysis and LC procedures as described. The mean (± SEM) amounts of D and I recovered from one urine sample spiked with 2.0 pmol of D and I were 91 ± 4% and 88 ± 1%, respectively, and those from a urine sample spiked with 0.4 pmol of D and I were 92 ± 3% and 93 ± 8%, respectively. The mean amounts of D and I recovered from the other urine sample spiked with 2.0 pmol of D and I were 88 ± 1% and 93 ± 3%, respectively, and those from a urine sample spiked with 0.4 pmol of D and I were 93 ± 6% and 93 ± 15%, respectively. The reproducibility of the repeated sample analysis ranged from 91 to 99%.

Similar recovery studies were carried out with four plasma samples. The mean amounts of D and I recovered with 0.05-ng standards were 65 ± 4% and 74 ± 13%, respectively, and those recovered with 0.1-ng standards were 67 ± 1 and 72 ± 4%, respectively. The reproducibility of the repeated sample analysis was 83 to 99%. Values in urine and plasma were corrected for recovery losses.

Creatinine and protein measurement were carried out as previously described.11 LC/MS analysis was performed as previously described11 with slight modification (Fig 1 , top, A)


Figure 1
View larger version (18K):
[in this window]
[in a new window]
[Download PPT slide]
  		Figure 1. Top, A: the LC/MS ionchromatogram. HPLC separation of D and I was achieved by an Atlantis dC18 column (2.1 x 150 mm, 3 µm) [Waters]. The mobile phase A is aqueous 7 mmol/L heptafluorobutyric acid and 5 mmol/L ammonium acetate, and the mobile phase B is a solution of 7 mmol/L heptafluorobutyric acid and 5 mmol/L ammonium acetate in a acetonitrile/water (8:2 ratio). HPLC was performed using a 12-min linear gradient flow of the mobile phase A from 100 to 88% and mobile phase B from 0 to 12% at a flow rate of 0.3 mL/min. The temperature of the HPLC column was set at 30°C. Under these chromatographic conditions, D and I were detected at 8.95 and 9.90 min, respectively. The mass spectrometer was operated in the positive-ion mode with the following spectrometric parameters: capillary voltage, 3.20 kV; sample cone voltage, 55 V; ion energy, 0.5 eV; amplifier voltage, 650 V; temperature of the desolvation, 400°C; and temperature of the source, 120°C. Bottom, B: quantification of D and I was achieved by a single ion record of D and I molecular ions, both at a mass/charge ratio of 526.25 (two isomeric molecules), which were produced from the LC/MS analysis. Peak areas of the single ion record obtained by D and I standards gives good linearity between 0.05 and 5 ng.

 
Statistical Analysis
A t test adjusted for unequal variance was used to test the null hypothesis. The level of significance was 0.05. The p values were calculated based on the summed values of D and I using the unpaired t test with Welch correction.

Patients
COPD was diagnosed in study patients and adhere to Global Initiative for Chronic Obstructive Lung Disease grades 1 to 4.12 All patients were screened for AATD by measuring serum levels and phenotyping. Patients were divided into the following two groups: (1) patients with normal levels of {alpha}1-antitrypsin (AAT) in serum; and (2) patients with ZZ-homozygous AATD. Patients gave informed consent for the study. The study was approved by the institutional review board.

All patients with normal levels of AAT had significant smoking histories of 10 to 60 pack-years. Many patients had stopped smoking in the previous 10 years, and none were current smokers when they entered the study. Among these patients, the age range was 44 to 85 years. Five were men and two were women.

Among patients with AATD, all but one had a significant smoking history exceeding 10 pack-years. All patients had ceased smoking for at least 10 years by the time of the study. All AATD patients were being treated with AAT protein replacement, were in a stable clinical state, and exhibited no evidence of an exacerbation. Control subjects were selected by a clinical history free of any specific known disease or significant symptoms, including respiratory symptoms, and none had ever smoked.

Results

Results in healthy subjects are presented in Table 1 . The mean (± SEM) levels of D and I measured in plasma in 13 subjects were 0.10 ± 0.01 and 0.09 ± 0.01 ng/mL, respectively, and were 1.91 ± 0.11 and 1.62 ± 0.14 ng/g protein, respectively.


View this table:
[in this window]
[in a new window]

  		Table 1. Control Subjects Without Lung Disease*

 
The levels of D and I measured in the plasma of patients with COPD with normal levels of AAT are presented in Table 2 and Figure 2 . The mean levels of D and I in plasma were 0.39 ± 0.07 and 0.26 ± 0.07 ng/mL, respectively, and 6.60 ± 0.84 and 4.36 ± 1.04 ng/g protein, respectively, which were statistically significantly higher levels than those found in control subjects.


View this table:
[in this window]
[in a new window]

  		Table 2. Patients With COPD With Normal AAT Levels*

 

Figure 2
View larger version (16K):
[in this window]
[in a new window]
[Download PPT slide]
  		Figure 2. The mean and SEM levels of D and I in plasma for healthy control subjects, patients with COPD without AATD, and patients with COPD with AATD are shown. The differences among all three groups are statistically significant. The p values were calculated based on the summed values of D and I using the unpaired t test with Welch correction.

 
The levels of D and I measured in the plasma of patients with COPD related to AATD are shown in Table 3 and Figure 2. The mean levels measured in plasma were 0.78 ± 0.19 and 0.62 ± 0.14 ng/mL, respectively, and were 19.24 ± 5.22 and 15.03 ± 3.71 ng/g protein, respectively, which were statistically significantly higher levels than those found in control subjects and in patients with COPD not related to AATD when calculated per gram of protein in plasma.


View this table:
[in this window]
[in a new window]

  		Table 3. Patients With AATD-Related COPD*

 
It is noteworthy that no overlap of levels of plasma D and I exists between control subjects and the groups of patients with COPD; the levels in patients with COPD were consistently higher. The levels of D and I in the urine of control subjects and patients with and without AATD are shown in Tables 1, 2, and 3, and in Figure 3 . The mean levels of free D and I were 3.66 ± 0.26 and 2.72 ± 0.21 ng/g creatinine, respectively, in COPD patients with normal levels of AAT, and 2.97 ± 0.30 and 2.15 ± 0.29, respectively, in patients with AATD, which were statistically significantly higher levels than those found in control subjects (1.42 ± 0.31 and 1.10 ± 0.22 ng/g creatinine, respectively). As shown in Figure 3, the percentage of free D and I over total D and I excretion was statistically significantly higher in both groups of patients with COPD, but were highest in COPD patients with normal AAT levels. The mean total 24 h excretion of D and I was not statistically significantly increased in both COPD groups compared to that in control subjects.


Figure 3
View larger version (20K):
[in this window]
[in a new window]
[Download PPT slide]
  		Figure 3. The mean levels and SEM of D and I in the urine of healthy control subjects, patients with COPD without AATD, and patients with COPD with AATD are shown. The mean differences among the groups are statistically significant for the free D and I and the percentage of free/total D and I urinary excretion. The p values were calculated as in Figure 1.

 
Levels of D and I in sputum are shown in Tables 2 and 3, and in Figure 4 . The levels of D and I were below the level of detection by MS in three control subjects,11 whereas both groups of COPD patients showed significantly increased mean levels of D and I of 1.08 ± 0.26 and 0.74 ± 0.15 ng/mL, respectively, and 0.30 ± 0.10 and 0.25 ± 0.09 ng/mL, respectively, in the sputum of COPD patients with and without AATD. The levels of D and I were 312 ± 115 and 212 ± 77.9 per gram of protein, respectively, and 49.9 ± 33.4 and 43.9 ± 31.5 per gram of protein, respectively, in patients with and without AATD. D and I levels in sputum were statistically significantly higher in patients with AATD.


Figure 4
View larger version (14K):
[in this window]
[in a new window]
[Download PPT slide]
  		Figure 4. The mean levels and SEM of D and I in the sputum of patients with COPD without AATD and patients with COPD with AATD are shown. Control subjects did not have detectable D or I levels in induced sputum.11 The content of D and I in the sputum of patients with COPD and AATD is statistically significantly higher than in those with COPD and without AATD. The p values were calculated as in Figure 1.

 
Shown in Table 4 are the results of repeat measurements of plasma D and I in one control subject, in one patient with AATD-related COPD, and in one patient with COPD without AATD. The intervals between repeat measurements were days in subjects with AATD and COPD, to weeks and months for the other two subjects. During these intervals, each patient was in a stable clinical state without exacerbations. The results varied between 10% and 15%, which suggests a stable metabolic state with respect to elastin turnover in each individual’s normal or abnormal levels. Levels of D and I in plasma and urine were analyzed for possible correlation with age, sex, racial origin, or physiologic parameters of FEV1 and residual volume/total lung capacity, and no statistically significant correlations were determined.


View this table:
[in this window]
[in a new window]

  		Table 4. Repeat Measurements of D and I in Plasma

 
Discussion

An early insight into the mechanisms leading to alveolar disruption in patients with pulmonary emphysema is that lung matrix elastin is a target for chemical degradation from cellular elastases.1314 Lung elastin content, determined chemically, has been demonstrated to be low in patients with pulmonary emphysema related to smoking or in those with Z-phenotype AATD2; morphologically, lung elastin fibers have been shown to be fragmented and disordered.1 Also the intratracheal administration of elastases has produced unique animal models of pulmonary emphysema.1516 In addition, elastin peptides have been shown to be chemotactic for neutrophils and macrophages and could be a factor in the progression of human pulmonary emphysema once elastin degradation has occurred.17

Current methods of measuring elastin peptides in blood plasma require radioimmunoassay techniques that depend on antibodies to elastin peptides varying in specificity and sensitivity, which affects the standardization and quantification of the peptides.18 Also, measurements of D and I in urine require a relatively extensive chemical procedure using isotope dilution corrections and HPLC, which can be an arduous methodology.4

Recognizing these limitations, MS, with its ability to detect specific molecular species with high sensitivity, accuracy, and specificity, is a readily applicable method for use in complex body fluids. The increased sensitivity of MS has permitted the measurement of a free component unbound to protein or other matrix constituents of D and I in urine, which are increased statistically significantly in patients with COPD compared with healthy control subjects. Similarly, MS has allowed measurements of D and I in blood plasma and sputum, which are both chemically complex media. Attempts to detect a free vs bound component of D and I in plasma were unsuccessful. The concentration of D and I in a single small sample of plasma may be too low for detection compared to the concentration of D and I in a 24-h collection of urine.

The increased free component of D and I in urine in COPD patients, we believe, may reflect an increased neutrophil elastase concentration in circulating neutrophils, which has been demonstrated by previous measurements as an increase in lysosomal elastase in the neutrophils of COPD patients compared with healthy control subjects.19 This increased elastase concentration may reflect a generalized immunologic hyperreactivity resulting from the chronic inflammatory state of the lung in COPD patients, which is manifested by increased elastase activity in neutrophils and macrophages.20212223

The difference in the levels of D and I in plasma between control subjects and patients with COPD in this study suggests that the levels of D and I in plasma may be one of the sensitive indicators of the presence of lung elastin breakdown in COPD patients, especially since the entire cardiac output constantly circulates through the lung. While changes in the levels of D and I in plasma cannot be assumed to reflect D and I from lung parenchyma per se, the demonstrated presence of D and I in the sputum of patients with COPD indicates that the increased degradation, and probably turnover, of elastin is occurring in the lung, since healthy subjects do not have detectable amounts of D and I in induced sputum samples.11

In the limited number of control subjects in our study, we did not find any correlation between the ages of the subjects and urinary excretion or plasma levels of D and I. In other studies456789 of adult subjects that have included similar measurements, no correlations with age have been reported.

Measurements of the total excretion of D and I in 24-h urine collection did not demonstrate statistically significant differences between patients and healthy control subjects. This result is consistent with the results of the study by Bode et al,8 who showed marked variability in the daily excretion of D and I in COPD patients, and no statistically significant difference in the total excretion between the two cohorts. Also, Starcher and Peterson24 have demonstrated a failure of urine to reflect the rapid degradation of lung elastin produced by intratracheal porcine pancreatic elastase in mice. Their studies demonstrated a sequestering of elastin peptides in renal parenchyma following lung elastin breakdown and a continued slow urinary excretion of D-containing peptides over several days following acute elastase injury.24 Other studies45 have shown significant increases of urinary D in COPD patients compared to healthy control subjects. Possibly, the individual patient population in the present study varied from those previously studied. In that regard, none of the patients in this study were actively smoking, which has been shown to increase urinary D excretion.4

When elastin degradation is mildly increased, or even moderately increased, above the turnover in healthy control subjects, it may be difficult to reflect this increase in urine, even with 24-h collections.25 However, the percentage of the free component of D and I in urine is consistently elevated in both groups of patients with COPD.

It has long been demonstrated that elastin in elastin fibers, once formed, cross-linked and insoluble, is extremely stable and undergoes little metabolic turnover.26 This slow metabolic turnover in healthy humans is consistent with the very low levels of D and I in the plasma of healthy subjects. It is noteworthy that studies27 of elastase injury to lung elastin in vivo in rats and mice have demonstrated that the rapid degradation of elastin occurs when exposed to elastases, with rapidly ascending concentrations of elastin peptides in blood and urine within hours of protease administration. Notable also is the rapid resynthesis of elastin after proteolytic breakdown.28 The stability of plasma and urine levels of D with repeat measurements over a 44-day interval in patients with AATD was reported by Stolk et al,29 which is consistent with the measurements made in this study. Thus, any increase in elastase activity in lungs, which includes bronchial and blood vessel elastin as well as alveolar elastin, may well be reflected in the levels found in blood circulating to and from the lung.

The persistence of elevated levels of D and I in the plasma of patients with COPD in both patient cohorts long after smoking cessation is consistent with continued inflammation of the lung in COPD patients2122 and progression of matrix tissue injury. The levels of D and I in the blood of COPD patients may therefore prove to be a sensitive index of the metabolic state of elastin degradation and possibly resynthesis in the lung. Since elastin is a significant structural constituent of alveoli, bronchial walls, and blood vessels, the levels of D and I in the earliest phases of COPD deserve to be evaluated. Also, the responses to therapeutic agents that may reduce the lung inflammatory state and thereby reduce elastin degradation may be assessed by measurements of D and I in plasma, and by the proportion of free D and I in urine.

It is noteworthy that the ATTD-related COPD patients had higher levels of D and I in plasma than did COPD patients without AATD, along with higher levels in sputum, which is consistent with the loss of lung mass in patients with the emphysematous form of COPD found in ATTD patients. All patients with AATD were receiving AAT augmentation therapy at the time of study. Since levels of D and I in body fluids were not obtained prior to the initiation of augmentation therapy, it cannot be assumed that AAT replacement has no beneficial effect. These data suggest that an evaluation of the effect of higher doses of AAT on D and I levels would be worthwhile.

MS allows separate measurements of D and I. The proportion of D and I in the plasma and urine in control subjects shows a slightly lower proportion of I, constituting approximately 80% of the level of D. In one study30 of the amino acid composition of human lung elastin, D exceeded I content by approximately 10 to 15%, which is close to being in agreement with the present study. It is noteworthy that patients with COPD in both groups had proportions of D and I that are similar to those in control subjects, suggesting that the resynthesis of elastin in these groups does not show major structural dissimilarities from that in healthy control subjects.

The results of this study indicate that levels of D and I in urine, which includes an unconjugated fraction, along with levels in plasma and sputum may be useful parameters for characterizing patients with COPD of various phenotypes who are in various phases of the disease. MS, with its increased specificity and sensitivity, should facilitate this characterization.

Acknowledgements

The authors express their deep appreciation to Dr. John Thornton for assistance in the statistical analysis of data, and to Dr. Seymour Lieberman for consultative advice.

Footnotes

Abbreviations: AAT = {alpha}1-antitrypsin; AATD = {alpha}1-antitrypsin deficiency; D = desmosine; I = isodesmosine; HPLC = high-performance liquid chromatography; LC = liquid chromatography; MS = mass spectrometry

This work was supported by funds from the James P. Mara Center for Lung Disease, the Flight Attendants Medical Research Institute, the Charles A. Mastronardi Foundation, the Ned Doyle Foundation, and the Alpha One Foundation, and by funds from Ethel Kennedy, John Kennedy, and Judith Sulzberger.

The authors have reported to the ACCP that no significant conflicts of interest exist with any companies/organizations whose products or services may be discussed in this article.

Received for publication October 2, 2006. Accepted for publication December 26, 2006.

References

  1. Wright, RR (1961) Elastic tissue of normal and emphysematous lungs: a tridimensional histologic study. Am J Pathol 39,355-367[ISI][Medline]
  2. Chrzanowski, P, Keller, S, Cerreta, J, et al Elastin content of normal and emphysematous lung parenchyma. Am J Med 1980;69,351-359[CrossRef][ISI][Medline]
  3. Rosenbloom, J Biochemical/immunologic markers of emphysema. Ann N Y Acad Sci 1991;624(suppl),7-12[Abstract]
  4. Stone, PJ, Gottlieb, DJ, O’Connor, GT, et al Elastin and collagen degradation products in urine of smokers with and without chronic obstructive pulmonary diseases. Am J Respir Crit Care Med 1995;151,952-959[Abstract]
  5. Viglio, S, Iadarola, P, Lupi, A, et al MECK of desmosine and isodesmosine in urine of chronic destructive lung disease patients. Eur Respir J 2000;15,1039-1045[Abstract]
  6. Schriver, EE, Davison, JM, Sutcliff, MC, et al Comparison of elastin peptide concentration in body fluids from healthy volunteers, smokers and patients with chronic obstructive pulmonary disease. Am Rev Respir Dis 1992;145,762-766[ISI][Medline]
  7. Akers, S, Kucich, U, Swartz, M, et al Specificity and sensitivity of the assay for elastin-derived peptides in chronic obstructive pulmonary disease. Exp Lung Res 1992;145,1077-1081
  8. Bode, DC, Pagan, ED, Cuminskey, R, et al Comparison of urinary desmosine excretion in patients with chronic obstructive disease or cystic fibrosis. Pulm Pharmacol Ther 2000;13,175-180[CrossRef][ISI][Medline]
  9. Dillon, T, Waksh, RL, Scicchitano, R, et al Plasma elastin derived peptide involved in normal adults, children, and emphysema subjects. Am Rev Respir Dis 1992;146,1143-1148[ISI][Medline]
  10. Frette, C, Jacob, MP, Kauffman, F Plasma elastin peptide level: a diagnostic test for chronic obstructive lung disease. Am Rev Respir Dis 1993;147,1063-1064[ISI][Medline]
  11. Ma, S, Lieberman, S, Turino, GM, et al The detection and quantitation of free desmosine and isodesmosine in human urine and their peptide-bound forms in sputum. Proc Natl Acad Sci 2003;100,12941-12943[Abstract/Free Full Text]
  12. Pauwels, RA, Buist, AS, Calverley, PM, et al Global strategy for the diagnosis, management and prevention of chronic obstructive pulmonary disease: NHLBI/WHO Global Initiative for Chronic Obstructive Lung Disease (GOLD) Workshop summary. Am J Respir Crit Care Med 2001;163,1256-1276[Free Full Text]
  13. Turino, GM, Senior, RM, Garg, GD, et al Serum elastase inhibitor deficiency and {alpha}1-antitrypsin deficiency in patients with obstructive emphysema. Science 1969;165,709-711[Abstract/Free Full Text]
  14. Kuhn, CH, Englemafn, W, Chraplyvy, M, et al Degradation of elastin in experimental elastase-induced emphysema measured by a radioimmunoassay for desmosine. Exp Lung Res 1983;5,115-123[ISI][Medline]
  15. Johanson, WG, Pierce, VK Effects of elastin, collagenase and papain on structure and function of rat lungs in vitro. J Clin Invest 1972;510,288-293
  16. Kuhn, C, Yu, S-Y, Chraplyvy, M, et al The induction of emphysema with elastase-11: changes in connective tissue. Lab Invest 1976;32,372-380
  17. Senior, RM, Griffen, GL, Mecham, RP Chemotactic activity of elastin-derived peptides. J Clin Invest 1980;66,859-862[ISI][Medline]
  18. Darnule, TV, Darnule, AT, Likhite, V, et al Antigenic determinants in human lung elastin peptides. Connect Tissue Res 1980;7,269-77[ISI][Medline]
  19. Rodriguez, JR, Seals, JE, Radin, A, et al Neutrophil lysosomal elastase activity in normal subjects and in patients with chronic obstructive lung disease. Am Rev Respir Dis 1979;119,409-417[ISI][Medline]
  20. Saetta, M, Mariani, M, Panina-Bordignon, P, et al Increased expression of the chemokine receptor CXCR3 and its ligand CXCL-10 in peripheral airways of smokers with chronic obstructive pulmonary diseases. Am J Respir Crit Care Med 2002;165,1404-1409[Abstract/Free Full Text]
  21. Snider, GL Understanding inflammation in chronic obstructive pulmonary disease: the process begins. Am J Respir Crit Care Med 2003;167,1045-1049[Free Full Text]
  22. Vernooy, JH, Kucukaycan, M, Jacobs, JA, et al Local and systemic inflammation in patients with chronic obstructive pulmonary disease: soluble tumor necrosis factor receptors are increased in sputum. Am J Respir Crit Care Med 2002;166,1218-1224[Abstract/Free Full Text]
  23. deGodoy, I, Donahoe, M, Calhoun, WJ, et al Elevated TNF production by peripheral blood monocytes of weight-losing COPD patients. Am J Respir Crit Care Med 1996;153,633-637[Abstract]
  24. Starcher, B, Peterson, B The kinetics of elastolysis: elastin catabolism during experimentally induced fibrosis. Exp Lung Res 1999;25,407-424[CrossRef][ISI][Medline]
  25. Starcher, B, Green, M, Scott, M Measurement of urinary desmosine as an indicator of acute pulmonary disease. Respiration 1995;62,252-257[ISI][Medline]
  26. Shapiro, SD, Endicott, SK, Province, MA, et al Marked longevity of human lung parenchymal elastic fibers deduced from prevalence of D-aspartate and nuclear weapons related radiocarbon. J Clin Invest 1991;87,1828-1834[ISI][Medline]
  27. Osman, M, Keller, S, Hosannah, Y, et al Impairment of elastin resynthesis in the lungs of hamsters with experimental emphysema induced by sequential administration of elastase and trypsin. J Lab Clin Med 1985;105,254-258[ISI][Medline]
  28. Osman, M, Kaldany, R, Cantor, JO, et al Stimulation of lung lysyloxidase activity in hamsters with elastase-induced emphysema. Am Rev Respir Dis 1985;131,169-170[ISI][Medline]
  29. Stolk, J, Veldhuisen, B, Annovazzi, L, et al Short-term variability of biomarkers of proteinase activity in patients with emphysema associated with type Z {alpha}1-antitrypsin deficiency. Respir Res 2005;6,47[CrossRef][Medline]
  30. Starcher, BC, Galione, MJ Purification and comparisons of elastin from different animal species. Anal Biochem 1976;74,441-447[CrossRef][ISI][Medline]




This Article
Right arrow Abstract Freely available
Right arrow Full Text (PDF) Free
Right arrow Submit a response
Right arrow Alert me when this article is cited
Right arrow Alert me when eLetters are posted
Right arrow Alert me if a correction is posted
Right arrow Citation Map
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Similar articles in ISI Web of Science
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Add to My Personal Article Archive
Right arrow Download to citation manager
Right arrow reprints & permissions
Citing Articles
Right arrow Citing Articles via ISI Web of Science (1)
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Ma, S.
Right arrow Articles by Turino, G. M.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Ma, S.
Right arrow Articles by Turino, G. M.

HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS