Determination of free desmosine in human plasma and its application in two experimental medicine studies.

Elastin is one of the major extracellular matrix proteins associated with connective tissue. Its degradation leads to the liberation of the unique amino acids desmosine and isodesmosine. These have shown utility as biomarkers of elastin breakdown for disease progression, patient stratification, and drug efficacy. So far, the quantitation of desmosines in plasma is hampered by complex sample preparation. Here we demonstrate an improved and simplified procedure for detecting both free and total desmosines. The method is based on spiking with a deuterium-labeled desmosine standard, ethanol precipitation, propionylation, high-performance liquid chromatography (HPLC) separation, and selected reaction monitoring (SRM) mass spectrometry. The performance of the assay is illustrated by comparing the levels of free and total desmosines in normal healthy plasma and those from patients diagnosed with chronic obstructive pulmonary disease (COPD). A conserved ratio of 1:3 for free to total desmosine was found. The determination of free desmosine has higher accuracy than that of total desmosine; therefore, it is the method of choice when plasma volume is limiting. Finally, we show that the plasma desmosine concentration correlates with age and body mass index.

Stable deuterium internal standard for the isotope-dilution LC-MS/MS analysis of elastin degradation.

Chemical synthesis of the deuterium isotope desmosine-d4 has been achieved. This isotopic compound possesses all four deuterium atoms at the alkanyl carbons of the alkyl amino acid substitution in the desmosine molecule and is stable toward acid hydrolysis; this is required in the measurement of two crosslinking molecules, desmosine and isodesmosine, as biomarkers of elastic tissue degradation. The degradation of elastin occurs in several widely prevalent diseases. The synthesized desmosine-d4 is used as the internal standard to develop an accurate and sensitive isotope-dilution liquid chromatography-tandem mass spectrometry analysis, which can serve as a generalized method for an accurate analysis of desmosine and isodesmosine as biomarkers in many types of biological tissues involving elastin degradation.

Alpha-1 antitrypsin augmentation therapy and biomarkers of elastin degradation.

BACKGROUND: Intravenous alpha-1 antitrypsin protein (AAT) augmentation is a prescribed therapy for severe, genetically determined, alpha-1 antitrypsin deficiency (AATD), a genetic basis for pulmonary emphysema. AAT, a predominant systemic inhibitor of neutrophil elastase thus far has not been shown to decrease elastin degradation in a significant number of patients on this therapy. The objective of this study was to compare levels of biomarkers of elastin degradation in plasma, bronchoalveolar lavage (BALF) fluid and urine before and after beginning AAT augmentation therapy in patients with AATD. METHODS: Desmosine and isodesmosine (DI), which occur only in elastin, are amino acid cross-links in mature elastin. Levels of DI in body fluids measure degradation of elastin and can be measured more specifically by mass spectrometry. This method was used to measure DI levels in plasma, bronchoalveolar lavage fluid and urine in cohorts of severe AATD patients on augmentation, not on augmentation and before and after the initiation of augmentation therapy. RESULTS: Statistically significant reductions in plasma DI and in BALF DI were demonstrated in AATD patients receiving intravenous (IV) augmentation therapy as compared with those not receiving it. Administration by aerosol also produced statistically significant reductions in levels of DI in BALF. CONCLUSIONS: Results indicate that the currently prescribed doses of AAT augmentation inhibit neutrophil elastase adequately to reduce elastin degradation, both systemically and in the lung per se. The currently prescribed doses did not reduce elastin degradation to control levels, which may be possible with higher doses.

Total desmosines in plasma and urine correlate with lung function.

The aim of the present study was to evaluate the relationship between the matrix degradation biomarkers, desmosine and isodesmosine (desmosines), and lung function. Plasma and creatinine-corrected urinary total desmosines (P- and U-desmosines, respectively), lung function and diffusing capacity of the lung for carbon monoxide (D(L,CO)) were measured in a cohort of subjects from the Swedish Twin Registry. Concentrations of U- and P-desmosines were measured in 349 and 318 subjects, respectively; approximately one-third of subjects had chronic obstructive pulmonary disease (COPD). Age, female sex, body mass index (BMI) and smoking were significantly associated with U-desmosines in a multiple linear regression analysis. In the overall population, after adjustments for age, sex, height, BMI and smoking, concentrations of U-desmosines were significantly correlated with all lung function measures, and P-desmosines with forced expiratory volume in 1 s and D(L,CO) (p<0.05). With the exception of residual volume versus P-desmosines, relationships between concentrations of desmosines and lung function measures were markedly stronger in subjects with COPD compared with those without COPD. These cross-sectional data showing associations between desmosines and several lung function variables suggest that desmosines, particularly U-desmosines, could be a useful biomarker of COPD status.

Matrix elastin: a promising biomarker for chronic obstructive pulmonary disease.

Chronic obstructive pulmonary disease (COPD) is a major health problem worldwide and is now the third leading cause of death in the United States. There is a lack of therapies that can stop progression of the disease and improve survival. New drug discovery can be aided by the development of biomarkers, which can act as indicators of severity in the course of the disease and responses to therapy. This perspective brings together the laboratory and clinical evidence, which suggest that elastin degradation products can fulfill the need for such a biomarker. Elastin is a recognized target for injury in COPD. The amino acids desmosine and isodesmosine exist only in matrix elastin; can be measured specifically and sensitively in plasma, urine, and sputum; and indicate changes in the systemic balance between elastase activity and elastase inhibition brought on by the systemic inflammatory state. The biomarker levels in sputum reflect the state of elastin degradation in the lung specifically. Clinical data accumulated over several decades indicate correlations of desmosine and isodesmosine levels with COPD of varying severity and responses to therapy.

Long-term variability of desmosine/isodesmosine as biomarker in alpha-1-antritrypsin deficiency-related COPD.

Desmosine and isodesmosine are products of elastin breakdown which are candidate biomarkers to measure lung destruction in COPD. Data exist on the burden of desmosines in urine and plasma in COPD but long-term changes have never been investigated. We determined the changes of desmosine levels over 14 months in urine and plasma of patients with type ZZ alpha-1-antitryspsin deficiency-related COPD. Urines and plasma for determination of desmosines were collected from 11 ex-smokers with moderate/severe emphysema at monthly intervals for 14 months. Spirometry and gas transfer were assessed at baseline and 6-month intervals. At baseline and month 14, eleven healthy partners of patients volunteered to give a blood sample for detection of desmosines. Desmosines were determined by capillary electrophoresis combined with laser-induced fluorescence. Urine and plasma desmosines were significantly increased after 14 months in patients (p = 0.027 and p = 0.0005, respectively). Plasma desmosines of healthy partners at baseline were 4-fold lower than from patients and not significantly different from values at month 14. Only a significant decline in lung gas transfer occurred in patients (p = 0.015). The variability of desmosines was higher in urine than in plasma (coefficient of variation 0.17 and 0.087, respectively). As longitudinal desmosine changes likely reflect the elevated elastic fiber turnover associated with the progression of lung damage and destruction in COPD, they appear to be a suitable marker for application in long-term studies. Plasma desmosines were more stable long-term biomarkers than desmosines in urine.

The effect of tiotropium therapy on markers of elastin degradation in COPD.

BACKGROUND: Desmosine and Isodesmosine (D/I) are cross-linking amino acids which are present only in mature elastin. Changes in their concentration in body fluids indicate changes in elastin degradation and can be a reflection of tissue elastase activity. This study was undertaken to determine whether continuous therapy with the long-acting bronchodilator Tiotropium bromide (TTP) could result in reductions in D/I as measured by mass spectrometry in plasma, urine and sputum. METHODS: Twelve not currently smoking patients with chronic obstructive pulmonary disease (COPD), never on TTP, were selected for study. Levels of D/I, along with measurements of FVC, FEV1 and FEV1/FVC. were determined before starting TTP daily, and then one and two months after. RESULTS: D/I decreased in plasma (10 of 12 patients), in sputum all (12 of 12), and in the percentage of free D/I in urine (10 of 12). Most patients showed slight increases in FVC and FEV1 percent predicted over two months. CONCLUSION: The results are consistent with an effect of prolonged bronchodilitation by anti-cholinergic blockade to also result in reduced lung elastin degradation.

Desmosine as a biomarker of elastin degradation in COPD: current status and future directions.

Desmosine (DES) and isodesmosine (IDES) are two unusual, tetrafunctional, pyridinium ring-containing amino acids involved in elastin cross-linking. Being amino acids unique to mature, cross-linked elastin, they are useful for discriminating peptides derived from elastin breakdown from precursor elastin peptides. According to these features, DES and IDES have been extensively discussed as potentially attractive indicators of elevated lung elastic fibre turnover and markers of the effectiveness of agents with the potential to reduce elastin breakdown. In the present manuscript, immunology-based and separation methods for the evaluation of DES and IDES are discussed, along with studies reporting increased levels of urine excretion in chronic obstructive pulmonary disease (COPD) patients with and without alpha(1)-antitrypsin deficiency. The results of the application of DES and IDES as surrogate end-points in early clinical trials in COPD are also reported. Finally, recent advances in detection techniques, including liquid chromatography tandem mass spectrometry and high-performance capillary electrophoresis with laser-induced fluorescence, are discussed. These techniques allow detection of DES and IDES at very low concentration in body fluids other than urine, such as plasma or sputum, and will help the understanding of whether DES and IDES are potentially useful in monitoring therapeutic intervention in COPD.

Vitamin K deficit and elastolysis theory in pulmonary elasto-degenerative diseases.

Elastin is a unique protein providing deformability and resilience to dynamic tissues, such as arteries and lungs. It is an absolute basic requirement for circulation and respiration. Elastin can be degraded by elastases and has a high calcium affinity. Elastin calcification and elastin degradation are two pathological processes that impair elastin's functioning. Furthermore, elastin degradation can be associated to elastin calcification. Matrix Gla Protein (MGP) is probably the most potent natural inhibitor of elastin calcification and requires vitamin K for its activation. Measuring circulating levels of inactive MGP (dp-ucMGP) is a frequently used method to assess vitamin K status. Dp-ucMGP reflects the burden of vitamin K-dependent proteins that have not been activated by vitamin K and could therefore best be regarded as a biomarker of a vitamin K deficit. Dp-ucMGP levels decrease after vitamin K supplementation. Since the amino acids desmosine and isodesmosine (DES) are unique to crosslinked elastin fibers, systemic elastin degradation can be assessed with the plasma DES assay. Recently, we discovered a strong correlation between plasma dp-ucMGP and plasma DES levels in both patients with chronic obstructive pulmonary disease (COPD) and controls. The 'Vitamin K deficit and elastolysis theory' posits that elastin degradation causes a rise in the vitamin K deficit and implies that vitamin K supplementation could be preventing elastin degradation. If this hypothesis holds true and is universally found in every state and condition, it will have an unprecedented impact on the management of every single pulmonary disease characterized by accelerated elastin degradation, such as alpha-1 antitrypsin deficiency, bronchiectasis, COPD and cystic fibrosis. Theoretically, a plasma dp-ucMGP concentration of zero would be associated with a near-complete standstill of elastin degradation and disease progression in patients with any of these debilitating conditions.

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.

Characterization and validation of an isotope-dilution LC-MS/MS method for quantification of total desmosine and isodesmosine in plasma and serum.

BACKGROUND: Desmosine/isodesmosine (DES/IDS) is a promising biomarker for estimating activity of elastin degradation. RESULTS/METHODOLOGY: A stable isotope dilution LC-MS/MS method for measuring serum/plasma DES/IDS was developed and validated. The reportable range of this assay was 0.1-160 ng/ml. Serum/plasma DES/IDS level was stable at room temperature or 4°C for 20 h, and for three freeze-thaw cycles. Interferences from endogenous compounds and ion suppression/enhancing effect were also evaluated. Our results suggest the absolute necessity of using an IS in the measurement. We found that serum/plasma DES/IDS levels from patients with chronic obstructive pulmonary disease and cystic fibrosis were significantly higher compared with healthy smokers. CONCLUSION: These results demonstrate that the LC-MS/MS method provides sensitive, reproducible and accurate quantification of total serum/plasma DES/IDS.

Quantitation of desmosine and isodesmosine in urine, plasma, and sputum by LC-MS/MS as biomarkers for elastin degradation.

The aim of this study is to develop a standardized LC-MS/MS method for accurate measurement of desmosine (DES) and isodesmosine (IDS) in all body fluids as biomarkers for in vivo degradation of matrix tissue elastin in man and animals. A reproducible three-step analytical procedure: (1) sample hydrolysis in 6N HCl, (2) SPE by a CF1 cartridge with addition of acetylated pyridinoline as internal standard (IS), and (3) LC/MSMS analysis by SRM monitoring of transition ions; DES or IDS (m/z 526-481+397) and IS (m/z 471-128) was developed. The method achieves accurate measurements of DES/IDS in accessible body fluids (i.e. urine, plasma, and sputum). LOQ of DES/IDS in body fluids is 0.1 ng/ml. The % recoveries and reproducibility from urine, plasma, and sputum samples are above 99 ± 8% (n = 3), 94 ± 9% (n = 3) and 87 ± 11% (n = 3), with imprecision 8%, 9% and 10%, respectively. The proposed method was applied to measure DES/IDS in body fluids of patients with chronic obstructive pulmonary disease (COPD) and healthy controls. Total DES/IDS in sputum and plasma is increased over normal controls along with the free DES/IDS in urine in patients. DES/IDS can be used to study the course of COPD and the response to therapy. This practical and reliable LC-MS/MS method is proposed as a standardized method to measure DES and IDS in body fluids. This method can have wide application for investigating diseases which involve elastic tissue degradation.

The effect of secondhand smoke exposure on markers of elastin degradation.

BACKGROUND: Tobacco smoke is a major risk factor in the development of COPD. Secondhand smoke (SHS) exposure is a known risk factor in asthma, bronchitis, and coronary artery disease. Elastin is a recognized target for injury in COPD, and the amino acids desmosine and isodesmosine (D/I), which are specific for elastin degradation, are elevated in COPD. This study determined whether exposure to SHS affects elastin degradation in asymptomatic individuals. METHODS: Two cohorts of asymptomatic individuals without evidence of respiratory or circulatory disease, exposed to SHS, were studied. Both cohorts comprised normal nonsmokers, active smokers, and those exposed to SHS. D/I were measured in plasma and quantified by high-performance liquid chromatography and tandem mass spectrometry by published methods. Plasma cotinine, a metabolite of nicotine, was also measured. RESULTS: In each cohort, the levels of D/I in plasma were statistically significantly higher in secondhand-smoke-exposed subjects than in the normal nonexposed subjects. Smokers had the highest levels of D/I but their levels were not statistically significantly higher than those of the secondhand-smoke-exposed. Cotinine levels were elevated in secondhand-smoke-exposed subjects and active smokers but not in most nonsmoking control subjects. CONCLUSIONS: Results indicate a tissue matrix effect of degradation of body elastin from SHS exposure and possible lung structure injury, which may result in COPD. Long-term studies of individuals exposed to SHS for the development of COPD are warranted.