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

Accelerated elastin degradation by age-disease interaction: a common feature in age-related diseases

Aging is a major driving force for many diseases but the relationship between chronological age, the aging process and age-related diseases is not fully understood. Fragmentation and loss of ultra-long-lived elastin are key features in aging and several age-related diseases leading to increased mortality. By comparing the relationship between age and elastin turnover with healthy volunteers, we show that accelerated elastin turnover by age-disease interaction is a common feature of age-related diseases.

Exaggerated elastin turnover in young individuals with Marfan syndrome: new insights from the AIMS trial

Aims

The fragmentation and loss of elastic fibre in the tunica media of the aorta are pathological hallmarks of Marfan syndrome (MFS) but the dynamics of elastin degradation and its relationship to aortic size and physiological growth remain poorly understood.

Methods and results

In this post hoc analysis of the AIMS randomized controlled trial, the association of plasma desmosine (pDES)-a specific biomarker of mature elastin degradation-with age and aortic size was analysed in 113 patients with MFS and compared to 109 healthy controls. There was a strong association between age and pDES in both groups, with higher pDES levels in the lower age groups compared to adults. During childhood, pDES increased and peaked during early adolescence, and thereafter decreased to lower adult levels. This trend was exaggerated in young individuals with MFS but in those above 25 years of age, pDES levels were comparable to controls despite the presence of aortic root dilation. In MFS children, increased aortic diameter relative to controls was seen at an early age and although the increase in diameter was less after adolescence, aortic root size continued to increase steadily with age. In MFS participants, there was an indication of a positive association between baseline pDES levels and aortic root dilatation during up to 5 years of follow-up.

Conclusion

This study has shown that developmental age has a significant effect on levels of elastin turnover as measured by pDES in MFS individuals as well as healthy controls. This effect is exaggerated in those with MFS with increased levels seen during the period of physiologic development that plateaus towards adulthood. This suggests an early onset of pathophysiology that may present an important opportunity for disease-modifying intervention.

Plasma desmosine for prediction of outcomes after acute myocardial infarction

Background

Elastin degradation is implicated in the pathology of vulnerable plaque. Recent studies show promising results for plasma desmosine (pDES), an elastin-specific degradation product, as a marker of cardiovascular disease (CVD) outcomes. The aim of this study was to investigate the potential role of pDES as a marker of clinical outcome in patients with acute myocardial infarction (AMI).

Materials and methods

In this case-control study, we studied 236 AMI patients: 79 patients who had death and/or myocardial infarction (MI) at 2 years, and 157 patients who did not have an event at 2 years. pDES was measured using a validated liquid chromatography-tandem mass spectrometry method. Association of pDES with adverse outcomes, and the incremental value of pDES to global registry of acute coronary events (GRACE) score for risk stratification was assessed.

Results

pDES levels were elevated in patients with the composite outcome of death/MI at 2 years (p = 0.002). Logistic regression analyses showed pDES to be associated with death/MI at 2 years [Odds ratio (OR) 5.99 (95% CI 1.81-19.86) p = 0.003]. pDES remained a significant predictor of death/MI at 2 years even after adjustment for age, sex, history of CVD, revascularisation, blood pressure, medications on discharge, Troponin I, and NT-proBNP levels.[OR 5.60 (95% CI 1.04-30.04) p = 0.044]. In another multivariable model including adjustment for eGFR, pDES was significantly associated with the composite outcome at 6 months, but not at 2 years follow up. DES was also able to reclassify risk stratification for death/MI at 6 months, when added to the GRACE risk model [Net Reclassification Index (NRI) 41.2 (95% CI 12.0-70.4) p = 0.006].

Conclusion

pDES concentrations predict clinical outcomes in patients with AMI, demonstrating its potential role as a prognostic marker in AMI.

Free Lung Desmosine: A Potential Biomarker for Elastic Fiber Injury in Pulmonary Emphysema

INTRODUCTION

Desmosine and isodesmosine (DID) are biomarkers for elastic fiber damage in pulmonary emphysema. However, current methods for measuring lung DID involve tissue hydrolysis and lack specificity for those fibers undergoing breakdown. To address this limitation, free (nonpeptide-bound) DID content in unhydrolyzed tissues was evaluated as a more accurate biomarker in an animal model of pulmonary emphysema.

METHODS

Hamsters were treated with either cigarette smoke and lipopolysaccharide (LPS), room air and LPS, or room air alone (controls). Free DID levels in fresh and formalin-fixed lungs were measured by LC-MS/MS and correlated with the mean linear intercept (MLI) measure of airspace size.

RESULTS

There was no significant difference in free DID between fresh and formalin-fixed lungs. Animals treated with smoke and LPS had significantly higher levels of free DID than the LPS only group (359 vs. 93.1 ng/g wet lung, respectively; p = 0.0012) and room air controls (undetectable levels; p = 0.0002). There was a significant positive correlation between free DID and MLI (p < 0.0001).

CONCLUSIONS

The results support the hypothesis that free lung DID is a sensitive indicator of alveolar wall injury that may be used to study the development of pulmonary emphysema in both animal models and post-mortem human lung tissue.

Respiratory and Cardiovascular Outcomes in Survivors of Extremely Preterm Birth at 19 Years

Rationale: Growth and development during adolescence may modify the respiratory and vascular differences seen among extremely preterm (EP) individuals in childhood and early adolescence.Objectives: To assess the trajectory of respiratory and cardiovascular outcomes during transition to adulthood in a national longitudinal cohort study of births before 26 weeks of gestation in the United Kingdom and Ireland.Methods: A total of 129 EP participants and 65 control subjects attended for a center-based evaluation at 19 years of age. Standardized measures of spirometry, hemodynamics, functional capacity, and markers of inflammation were obtained from EP subjects with and without neonatal bronchopulmonary dysplasia and term-born control subjects at 19 years of age and compared with previous assessments.Measurements and Main Results: Compared with the control group, the EP group was significantly impaired on all spirometric parameters (mean FEV₁ z-score, -1.08 SD [95% confidence interval, -1.40 to -0.77]) and had lower fractional exhaled nitric oxide concentrations (13.9 vs. 24.4 ppb; P < 0.001) despite a higher proportion with bronchodilator reversibility (27% vs. 6%). The EP group had significantly impaired exercise capacity. All respiratory parameters were worse after neonatal bronchopulmonary dysplasia, and respiratory function differences were similar at 11 and 19 years. The augmentation index was 6% higher in the EP group and associated with increased total peripheral resistance (difference in means, 96.4 [95% confidence interval, 26.6-166.2] dyne/s/cm^-5) and elevation in central, but not peripheral, blood pressure. Central systolic and diastolic blood pressures increased more quickly during adolescence in the EP group than in the control group.Conclusions: Clinicians should address both cardiovascular and respiratory risks in adult survivors of extremely preterm birth.

Preparation of isodesmosine-KLH conjugate for ELISA system

Chronic obstructive pulmonary disease (COPD) is a degenerative condition with limited diagnostic detection efficiency. Currently with no available cure, COPD is associated with irreversible elastic tissue degradation in lungs, which results in release of unusual amino acids, isodesmosine and desmosine. These biomarkers are potential key elements in enzyme-linked immunosorbent assay (ELISA), an analytical method, which can detect certain compounds including antigens and proteins in easy and affordable manner. In order to target a biomarker with ELISA, it is necessary to prepare its specific antibody, which can be achieved by immunization of host organism with appropriate antigen containing the biomarker. Although preparation of these types of conjugates has been published, desmosine and isodesmosine used by researchers are obtained from natural sources such as animal tissues. Here, we report the first synthetic preparation of isodesmosine and keyhole limpet hemocyanin (KLH) conjugate from commercially available chiral amino acids and carrier protein. Formation of the core pyridinium of isodesmosine was achieved through key reaction-Chichibabin pyridinium synthesis-to deliver a 1,2,3,5-tetrasubstituted pyridinium amino acid selectively. Further modifications involving KLH and maleimide linker provided the target conjugate, which could potentially invoke an immune response to produce anti-isodesmosine antibody for the ELISA system.

Plasma Desmosine and Abdominal Aortic Aneurysm Disease

Background

It is recognized that factors beyond aortic size are important in predicting outcome in abdominal aortic aneurysm (AAA) disease. AAA is characterized by the breakdown of elastin within the aortic tunica media, leading to aortic dilatation and rupture. The aim of this study was to investigate the association of plasma desmosine (pDES), an elastin‐specific degradation product, with disease severity and clinical outcome in patients with AAA.

Methods and Results

We measured pDES and serum biomarker concentrations in 507 patients with AAAs (94% men; mean age, 72.4±6.1 years; mean AAA diameter, 48±8 mm) and 162 control subjects (100% men; mean age, 71.5±4.4 years) from 2 observational cohort studies. In the longitudinal cohort study (n=239), we explored the incremental prognostic value of pDES on AAA events. pDES was higher in patients with AAA compared with control subjects (mean±SD: 0.46±0.22 versus 0.33±0.16 ng/mL; P<0.001) and had the strongest correlation with AAA diameter (r=0.39; P<0.0001) of any serum biomarker. After adjustment for baseline AAA diameter, pDES was associated with an AAA event (hazard ratio, 2.03 per SD increase [95% CI, 1.02–4.02]; P=0.044). In addition to AAA diameter, pDES provided incremental improvement in risk stratification (continuous net reclassification improvement, 34.4% [95% CI, −10.8% to 57.5%; P=0.09]; integrated discrimination improvement, 0.04 [95% CI, 0.00–0.15; P=0.050]).

Conclusions

pDES concentrations predict disease severity and clinical outcomes in patients with AAA.

Clinical Trial Registration

http://www.isrctn.com. Unique identifier: ISRCTN76413758.

Increased circulating desmosine and age-dependent elastinolysis in idiopathic pulmonary fibrosis

Although chronic obstructive pulmonary disease (COPD) and idiopathic pulmonary fibrosis (IPF) seem to be opposite entities from a clinical perspective, common initial pathogenic steps have been suggested in both lung diseases. Emphysema is caused by an elastase/anti-elastase imbalance leading to accelerated elastin degradation. Elastinolysis is however, also accelerated in the IPF patients’ lungs. The amino acids desmosine and isodesmosine (DES) are unique to elastin. During the degradation process, elastases liberate DES from elastin fibers. Blood DES levels consequently reflect the rate of systemic elastinolysis and are increased in COPD. This is the first report describing elevated DES levels in IPF patients. We also demonstrated that the age-related increment of DES concentrations is enhanced in IPF. Our current study suggests that elastinolysis is a shared pathogenic step in both COPD and IPF. Further investigation is required to establish the relevance of accelerated elastin degradation in IPF and to determine whether decelerating this process leads to slower progression of lung fibrosis and better survival for patients with IPF.

Neutrophil elastase in bronchiectasis

The role of neutrophil elastase (NE) is poorly understood in bronchiectasis because of the lack of preclinical data and so most of the assumptions made about NE inhibitor potential benefit is based on data from CF. In this context, NE seems to be a predictor of long-term clinical outcomes and a possible target of treatment. In order to better evaluate the role of NE in bronchiectasis, a systematic search of scientific evidence was performed.Two investigators independently performed the search on PubMed and included studies published up to May 15, 2017 according to predefined criteria. A final pool of 31 studies was included in the systematic review, with a total of 2679 patients. For each paper data of interest were extracted and reported in table.In this review sputum NE has proved useful as an inflammatory marker both in stable state bronchiectasis and during exacerbations and local or systemic antibiotic treatment. NE has also been associated with risk of exacerbation, time to next exacerbation and all-cause mortality. This study reviews also the role of NE as a specific target of treatment in bronchiectasis. Inhibition of NE is at a very early stage and future interventional studies should evaluate safety and efficacy for new molecules and formulations.

Neutrophil Elastase Activity Is Associated with Exacerbations and Lung Function Decline in Bronchiectasis

RATIONALE

Sputum neutrophil elastase and serum desmosine, which is a linked marker of endogenous elastin degradation, are possible biomarkers of disease severity and progression in bronchiectasis. This study aimed to determine the association of elastase activity and desmosine with exacerbations and lung function decline in bronchiectasis.

METHODS

This was a single-center prospective cohort study using the TAYBRIDGE (Tayside Bronchiectasis Registry Integrating Datasets, Genomics, and Enrolment into Clinical Trials) registry in Dundee, UK. A total of 433 patients with high-resolution computed tomography-confirmed bronchiectasis provided blood samples for desmosine measurement, and 381 provided sputum for baseline elastase activity measurements using an activity-based immunosassay and fluorometric substrate assay. Candidate biomarkers were tested for their relationship with cross-sectional markers of disease severity, and with future exacerbations, mortality and lung function decline over 3 years.

MEASUREMENT AND MAIN RESULTS

Elastase activity in sputum was associated with the bronchiectasis severity index (r = 0.49; P < 0.0001) and was also correlated with the Medical Research Council dyspnea score (r = 0.34; P < 0.0001), FEV1% predicted (r = -0.33; P < 0.0001), and the radiological extent of bronchiectasis (r = 0.29; P < 0.0001). During a 3-year follow-up, elevated sputum elastase activity was associated with a higher frequency of exacerbations (P < 0.0001) but was not independently associated with mortality. Sputum elastase activity was independently associated with FEV1 decline (β coefficient, -0.139; P = 0.001). Elastase showed good discrimination for severe exacerbations with an area under the curve of 0.75 (95% confidence interval [CI], 0.72-0.79) and all-cause mortality (area under the curve, 0.70; 95% CI, 0.67-0.73). Sputum elastase activity increased at exacerbations (P = 0.001) and was responsive to treatment with antibiotics. Desmosine was correlated with sputum elastase (r = 0.42; P < 0.0001) and was associated with risk of severe exacerbations (hazard ratio 2.7; 95% CI, 1.42-5.29; P = 0.003) but not lung function decline.

CONCLUSIONS

Sputum neutrophil elastase activity is a biomarker of disease severity and future risk in adults with bronchiectasis.

Advances in Identifying Urine/Serum Biomarkers in Alpha-1 Antitrypsin Deficiency for More Personalized Future Treatment Strategies

Alpha1-antitrypsin deficiency (AATD) is a genetic disorder characterized by reduced serum levels of alpha1-antitrypsin (AAT) and increased risk for developing both early-onset lung emphysema and chronic liver disease. Laboratory diagnosis of AATD is not just a matter of degree, although the AAT serum level is the most important determinant for risk of lung damage. While being a single-gene disease, the clinical phenotype of AATD is heterogeneous. The current standard of care for patients affected by AATD-associated pulmonary emphysema is replacement therapy with weekly i.v. infusions of pooled human purified plasma AAT. Although no treatment for liver disease caused by deposition of abnormal AAT in hepatocytes is available, innovative treatments for this condition are on the horizon. This article aims to provide a critical review of the methodological steps that have marked progress in the detection of indicators described in the literature as being "clinically significant" biomarkers of the disease. The development and routine use of specific biomarkers would help both in identifying which patients and when they are eligible for treatment as well as providing additional parameters for monitoring the disease.

Circulating desmosine levels do not predict emphysema progression but are associated with cardiovascular risk and mortality in COPD

Elastin degradation is a key feature of emphysema and may have a role in the pathogenesis of atherosclerosis associated with chronic obstructive pulmonary disease (COPD). Circulating desmosine is a specific biomarker of elastin degradation. We investigated the association between plasma desmosine (pDES) and emphysema severity/progression, coronary artery calcium score (CACS) and mortality.pDES was measured in 1177 COPD patients and 110 healthy control subjects from two independent cohorts. Emphysema was assessed on chest computed tomography scans. Aortic arterial stiffness was measured as the aortic-femoral pulse wave velocity.pDES was elevated in patients with cardiovascular disease (p<0.005) and correlated with age (rho=0.39, p<0.0005), CACS (rho=0.19, p<0.0005) modified Medical Research Council dyspnoea score (rho=0.15, p<0.0005), 6-min walking distance (rho=-0.17, p<0.0005) and body mass index, airflow obstruction, dyspnoea, exercise capacity index (rho=0.10, p<0.01), but not with emphysema, emphysema progression or forced expiratory volume in 1 s decline. pDES predicted all-cause mortality independently of several confounding factors (p<0.005). In an independent cohort of 186 patients with COPD and 110 control subjects, pDES levels were higher in COPD patients with cardiovascular disease and correlated with arterial stiffness (p<0.05).In COPD, excess elastin degradation relates to cardiovascular comorbidities, atherosclerosis, arterial stiffness, systemic inflammation and mortality, but not to emphysema or emphysema progression. pDES is a good biomarker of cardiovascular risk and mortality in COPD.

Synthesis and LC-MS/MS analysis of desmosine-CH2, a potential internal standard for the degraded elastin biomarker desmosine

Desmosine-CH2, an analog of the elastic tissue degradation biomarker desmosine, can be regarded as a potential internal standard for precise quantification of desmosines by LC-MS/MS. In this study, the chemical synthesis of desmosine-CH2 was completed in 22% overall yield in five steps. The LC-MS/MS analysis of desmosine-CH2 was also achieved.

Elastin degradation product isodesmosine is a chemoattractant for Pseudomonas aeruginosa

Previous studies have demonstrated that Pseudomonas aeruginosa PAO1 is chemotactic towards proteinogenic amino acids, however, the chemotaxis response of this strain towards non-proteinogenic amino acids and the specific chemoreceptors involved in this response are essentially unknown. In this study, we analysed the chemotactic response of PAO1 towards two degradation products of elastin, the lysine-rich, non-proteinogenic amino acids, desmosine and isodesmosine. We observed that isodesmosine, a potential biomarker for different diseases, served as a chemoattractant for PAO1. A screen of 251methyl-accepting chemotaxis proteins mutants of PAO1 identified PctA as the chemoreceptor for isodesmosine. We also showed that the positive chemotactic response to isodesmosine is potentially common by demonstrating chemoattraction in 12 of 15 diverse (in terms of source of isolation) clinical isolates, suggesting that the chemotactic response to this non-proteinogenic amino acid might be a conserved feature of acute infection isolates and thus could influence the colonization of potential infection sites.

[(13)C3,(15)N1]-labeled isodesmosine: A potential internal standard for LC-MS/MS analysis of desmosines in elastin degradation

Isodesmosine and desmosine are crosslinking amino acids that are present only in elastin. They are useful biomarkers for the degradation of elastin, which occurs during the progression of chronic obstructive pulmonary disease (COPD) and related diseases. This Letter describes the synthesis of [(13)C3,(15)N1]-labeled isodesmosine, using Chichibabin pyridine synthesis as a key reaction. The labeled isodesmosine is a potential internal standard for the quantitative LC-MS/MS analysis of desmosines in elastin degradation.

Biomimetic Chichibabin pyridine synthesis of the COPD biomarkers and elastin cross-linkers isodesmosine and desmosine

The tetrasubstituted pyridinium amino acids isodesmosine and desmosine are cross-linkers of elastin and are attractive biomarkers for the diagnosis of chronic obstructive pulmonary disease (COPD). In this study, the biomimetic total synthesis of isodesmosine and desmosine via a lanthanide-promoted Chichibabin pyridine synthesis using the corresponding aldehyde and amine hydrochloride is reported.