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Combined pulmonary fibrosis and emphysema (CPFE) is a distinct syndrome associated with heavy smoking. The fibrotic component of the disease is generally believed to be superimposed on previously existing pulmonary emphysema, but the mechanisms responsible for these changes remain poorly understood. To better understand the pathogenesis of CPFE, we performed a series of experiments that focused on the relationships between lung elastic fibers, cigarette smoke, and secondary lung injury. The results indicate that even brief smoke exposure predisposes the lung to additional forms of lung injury that may cause alveolar wall fibrosis. The proinflammatory activity of smoke-induced structural alterations in elastic fibers may contribute to this process by enhancing secondary lung inflammation, including acute exacerbations of chronic obstructive pulmonary disease. Furthermore, the levels of the unique elastin crosslinks, desmosine and isodesmosine, in blood, urine, and sputum may serve as biomarkers for the transition from pulmonary emphysema to interstitial fibrosis. While the long-term effects of these inflammatory reactions were not examined, the current studies provide insight into the potential relationships between elastic fiber injury, cigarette smoke, and secondary lung injury. Determining the mechanisms involved in combined pulmonary emphysema and fibrosis and developing a sensitive biomarker for this type of lung injury may permit timely therapeutic intervention that could mitigate the high risk of respiratory failure associated with this condition. [ABSTRACT FROM AUTHOR]

Background: In observational studies, high levels of desphospho-uncarboxylated matrix gla protein (dp-ucMGP) that result from vitamin K deficiency were consistently associated with poor clinical outcomes during COVID-19. Vitamin K-activated matrix gla protein (MGP) is required to protect against elastic fibre degradation, and a deficiency may contribute to pathology. However, intervention trials assessing the effects of vitamin K supplementation in COVID-19 are lacking. Methods: This is a single-centre, phase 2, double-blind, randomised, placebo-controlled trial investigating the effects of vitamin K2 supplementation in 40 hospitalised COVID-19 patients requiring supplemental oxygen. Individuals were randomly assigned in a 1:1 ratio to receive 999 mcg of vitamin K2—menaquinone-7 (MK-7)—or a placebo daily until discharge or for a maximum of 14 days. Dp-ucMGP, the rate of elastic fibre degradation quantified by desmosine, and hepatic vitamin K status quantified by PIVKA-II were measured. Grade 3 and 4 adverse events were collected daily. As an exploratory objective, circulating vitamin K2 levels were measured. Results: Vitamin K2 was well tolerated and did not increase the number of adverse events. A linear mixed model analysis showed that dp-ucMGP and PIVKA-II decreased significantly in subjects that received supplementation compared to the controls (p = 0.008 and p = 0.0017, respectively), reflecting improved vitamin K status. The decrease in dp-ucMGP correlated with higher plasma MK-7 levels (p = 0.015). No significant effect on desmosine was found (p = 0.545). Conclusions: These results demonstrate that vitamin K2 supplementation during COVID-19 is safe and decreases dp-ucMGP. However, the current dose of vitamin K2 failed to show a protective effect against elastic fibre degradation. [ABSTRACT FROM AUTHOR]

Aim: In our study, we aimed to investigate the diagnostic value of NE in blood and sputum, blood IL-8, IL-1β and desmosine levels and their relationship with symptoms, frequency of exacerbation, etiology, prevalence of radiological involvement, types of bronchiectasis, as well as sputum cell counts and cultures. Patients and Methods: The study included 46 patients with bronchiectasis aged between 18-90 years, who applied to the Chest Diseases Polyclinic between November 2020 and March 2021 and were followed up by our clinic, and a control group of 45 people. Results: At blood, NE, IL-1β, desmosine were statistically significantly higher in the patient group (p<0.001). ROC analysis was performed for the diagnostic value of biomarkers. When the cut-off value for blood NE was 12.70 ng/mL, the sensitivity was 71.7%, the specificity was 77.8%, for IL 1β the cut-off value was 2.935 pg/mL, the sensitivity was 73.9%, the specificity was 71.1%, for desmosine, the cut-off value was 0.505 ng/mL, the sensitivity was 67.4% and the specif icity was 62.2%. Conclusion: In our study, it was found that NE, IL-1β and desmosine in blood and NE in sputum in patients with bronchiectasis are important inflammatory markers, have significant diagnostic value, and may be an important component of follow-up parameters, since these parameters are significantly correlated with the frequency of exacerbations. [ABSTRACT FROM AUTHOR]

Developing an effective treatment for pulmonary emphysema will require a better understanding of the molecular changes responsible for distention and rupture of alveolar walls. A potentially useful approach to studying this process involves the concept of emergence in which interactions at different levels of scale induce a phase transition comprising a spontaneous reorganization of chemical and physical systems. Recent studies in our laboratory provide evidence of this phenomenon in pulmonary emphysema by relating the emergence of airspace enlargement to the release of elastin-specific desmosine and isodesmosine (DID) crosslinks from damaged elastic fibers. When the mean alveolar diameter exceeded 400 μm, the level of peptide-free DID in human lungs was greatly increased, reflecting rapid acceleration of elastin breakdown, alveolar wall rupture, and a phase transition to an active disease state that is less responsive to treatment. Based on this finding, it is hypothesized that free DID in urine and other body fluids may serve as a biomarker for early detection of airspace enlargement, thereby facilitating timely therapeutic intervention and reducing the risk of respiratory failure.

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. Graphical abstract [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

To achieve the precise quantitation of desmosine (DES) and isodesmosine (IDS) in skipjack tuna "Katsuo" elastin, an isotope dilution liquid chromatography tandem mass spectrometry (LC–MS/MS) method was applied for the samples of elastin-containing products in tablet, drink, jelly, and capsule forms, and the results were compared with data obtained from an amino acid (AA) analyzer. The quantity of DES/IDS was found to be ca. 2860 mg/kg for elastin peptide A, and 1690 mg/kg for elastin peptide B. Thus, the DES/IDS ratio of 100 ± 5% was obtained for the LC–MS/MS values compared to the data provided by the (AA) analyzer excepting jelly and capsule. This work justifies the quantification of DES/IDS in elastin products by LC–MS/MS, contributing to its application in the agro-food industry. [ABSTRACT FROM AUTHOR]

Aims Arterial stiffness is a hallmark of vascular ageing that precedes and strongly predicts the development of cardiovascular diseases. Age-dependent stiffening of large elastic arteries is primarily attributed to increased levels of matrix metalloproteinase-2 (MMP-2). However, the mechanistic link between age-dependent arterial stiffness and MMP-2 remains unclear. Thus, we aimed to investigate the efficacy of MMP-2 knockdown using small-interfering RNA (siRNA) on age-dependent arterial stiffness. Methods and results Pulse wave velocity (PWV) was assessed in right carotid artery of wild-type (WT) mice from different age groups. MMP-2 levels in the carotid artery and plasma of young (3 months) and old (20–25 months) WT mice were determined. Carotid PWV as well as vascular and circulating MMP-2 were elevated with increasing age in mice. Old WT mice (18- to 21-month old) were treated for 4 weeks with either MMP-2 or scrambled (Scr) siRNA via tail vein injection. Carotid PWV was assessed at baseline, 2 and 4 weeks after start of the treatment. MMP-2 knockdown reduced vascular MMP-2 levels and attenuated age-dependent carotid stiffness. siMMP-2-treated mice showed increased elastin-to-collagen ratio, lower plasma desmosine (DES), enhanced phosphorylation of endothelial nitric oxide synthase (eNOS), and higher levels of vascular cyclic guanosine monophosphate (cGMP). An age-dependent increase in direct protein–protein interaction between MMP-2 and eNOS was also observed. Lastly, DES, an elastin breakdown product, was measured in a patient cohort (n  = 64, 23–86 years old), where carotid-femoral PWV was also assessed; here, plasma levels of DES directly correlated with age and arterial stiffness. Conclusion MMP-2 knockdown attenuates age-dependent carotid stiffness by blunting elastin degradation and augmenting eNOS bioavailability. Given the increasing clinical use of siRNA technology, MMP2 knockdown should be investigated further as a possible strategy to mitigate age-dependent arterial stiffness and related CV diseases. [ABSTRACT FROM AUTHOR]

Desmosine and isodesmosine (DID) are biomarkers for elastic fibre damage in pulmonary emphysema. However, current methods for measuring lung DID involve tissue hydrolysis and lack specificity for those fibres 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. 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. 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). 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. [ABSTRACT FROM AUTHOR]

BackgroundPathology during COVID-19 infection arises partly from an excessive inflammatory response with a key role for interleukin (IL)-6. Both vitamin D and K have been proposed as potential modulators of this process.MethodsWe assessed vitamin D and K status by measuring circulating 25-hydroxyvitamin D (25(OH)D) and desphospho-uncarboxylated Matrix Gla-Protein (dp-ucMGP), respectively in 135 hospitalized COVID-19 patients in relation to inflammatory response, elastic fiber degradation and clinical outcomes.ResultsComparing good and poor disease outcomes of COVID-19 patients, vitamin 25(OH)D levels were not significantly different. IL-6 levels, however, were significantly higher in patients with poor outcome, compared to patients with good outcome (30.3 vs. 153.0 pg/mL; p < 0.0001). Dp-ucMGP levels as biomarker of extrahepatic vitamin K status was associated with IL-6 levels (r = 0.35; p < 0.0001). In contrast, 25(OH)D levels were only borderline statistically significant correlated with IL-6 (r = −0.14; p

Amino acid derivatives with a central cationic heterocyclic core (e.g., imidazolium) are biologically relevant cross-linkers of proteins and advanced glycation end (AGE) products. Here, imidazolium-containing cross-linkers were synthesized from imidazole or histidine by N-alkylation employing aspartate- and glutamate-derived mesylates as key step. Biological investigations were carried out to probe the biocompatibility of these compounds. [ABSTRACT FROM AUTHOR]

Rob Janssen,1 Emiel FM Wouters,2 Wim Janssens,3 Willeke F Daamen,4 Paul Hagedoorn,5 Hugo AJM de Wit,6 Jef Serré,3 Ghislaine Gayan-Ramirez,3 Frits ME Franssen,2 Niki L Reynaert,2 Jan H von der Thüsen,7 Henderik W Frijlink5 1Department of Pulmonary Medicine, Canisius-Wilhelmina Hospital, Nijmegen, The Netherlands; 2Department of Respiratory Medicine, Maastricht University Medical Center+, Maastricht, The Netherlands; 3Laboratory of Respiratory Diseases, Department of Chronic Diseases, Metabolism and Ageing (CHROMETA), KU Leuven, Leuven, Belgium; 4Department of Biochemistry, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, Nijmegen, The Netherlands; 5Department of Pharmaceutical Technology and Biopharmacy, Groningen Research Institute of Pharmacy, Groningen, University of Groningen, Groningen, The Netherlands; 6Department of Clinical Pharmacy, Canisius-Wilhelmina Hospital, Nijmegen, The Netherlands; 7Department of Pathology, Erasmus Medical Center, Rotterdam, The NetherlandsCorrespondence: Rob JanssenDepartment of Pulmonary Medicine, Canisius-Wilhelmina Hospital, Weg Door Jonkerbos 100, Nijmegen, SZ 6532, The NetherlandsEmail rob.janssen@cwz.nlAbstract: Current pharmacotherapy of chronic obstructive pulmonary disease (COPD) aims at reducing respiratory symptoms and exacerbation frequency. Effective therapies to reduce disease progression, however, are still lacking. Furthermore, COPD medications showed less favorable effects in emphysema than in other COPD phenotypes. Elastin fibers are reduced and disrupted, whereas collagen levels are increased in emphysematous lungs. Protease/antiprotease imbalance has historically been regarded as the sole cause of emphysema. However, it is nowadays appreciated that emphysema may also be provoked by perturbations in the sequential repair steps following elastolysis. Essentiality of fibulin-5 and lysyl oxidase-like 1 in the elastin restoration process is discussed, and it is argued that copper deficiency is a plausible reason for failing elastin repair in emphysema patients. Since copper-dependent lysyl oxidases crosslink elastin as well as collagen fibers, copper supplementation stimulates accumulation of both proteins in the extracellular matrix. Restoration of abnormal elastin fibers in emphysematous lungs is favorable, whereas stimulating pulmonary fibrosis formation by further increasing collagen concentrations and organization is detrimental. Heparin inhibits collagen crosslinking while stimulating elastin repair and might therefore be the ideal companion of copper for emphysema patients. Efficacy and safety considerations may lead to a preference of pulmonary administration of copper-heparin over systemic administration.Keywords: collagen, copper, desmosine, elastin, emphysema, fibulin-5, heparin, lysyl oxidase, lysyl oxidase-like protein 1, tropoelastin

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 x 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. [ABSTRACT FROM AUTHOR]

Elastic fibers are essential assemblies of vertebrates and confer elasticity and resilience to various organs including blood vessels, lungs, skin, and ligaments. Mature fibers, which comprise a dense and insoluble elastin core and a microfibrillar mantle, are extremely resistant toward intrinsic and extrinsic influences and maintain elastic function over the human lifespan in healthy conditions. The oxidative deamination of peptidyl lysine to peptidyl allysine in elastin's precursor tropoelastin is a crucial posttranslational step in their formation. The modification is catalyzed by members of the family of lysyl oxidases and the starting point for subsequent manifold condensation reactions that eventually lead to the highly cross‐linked elastomer. This review summarizes the current understanding of the formation of cross‐links within and between the monomer molecules, the molecular sites, and cross‐link types involved and the pathological consequences of abnormalities in the cross‐linking process. [ABSTRACT FROM AUTHOR]

Desmosine, a crosslinking pyridinium amino acid found in elastin, is a useful biomarker for the diagnosis of diseases related to elastin degradation, such as chronic obstructive pulmonary disease (COPD). In order to achieve the precise quantitation of this compound using isotope dilution liquid chromatography‐tandem mass spectrometry (LC‐MS/MS) analysis, isotopically‐labeled internal standards including deuterated desmosine are required. We report herein the synthesis of multi‐deuterated desmosine (d3–9) as a potential internal standard. This synthesis involves the preparation of an alkyne via a Sonogashira cross‐coupling, followed by deuterogenation of the triple bond to incorporate deuterium atoms into the substrate. [ABSTRACT FROM AUTHOR]

[Display omitted] Moyamoya disease (MMD) is a cerebrovascular disease which is characterized by the chronic progression of steno-occlusive changes at the terminal portion of internal carotid arteries and the development of "moyamoya vessels." Dysregulation of the extracellular matrix is regarded as a key pathophysiology underlying unique vascular remodeling. Here, we measured the concentration of elastin crosslinkers desmosine and isodesmosine in the plasma of MMD patients. We aimed to reveal its diagnostic values of desmosines in the progression of steno-occlusive lesions. The concentrations of plasma desmosines were determined by liquid chromatography-tandem mass spectrometry. The temporal profiles of steno-occlusive lesions on magnetic resonance angiography were retrospectively evaluated, and the correlation between the progression of steno-occlusive changes in intracranial arteries and plasma desmosines concentrations was further analyzed. Plasma desmosines were significantly higher in MMD patients with disease progression compared to MMD patients without disease progression. Also, the incidence of disease progression was higher in MMD patients with plasma desmosines levels over limit of quantitation (LOQ) than those with plasma desmosines levels below LOQ. In conclusion, plasma desmosines could be potential biomarkers to predict the progression of steno-occlusive changes in MMD patients. [ABSTRACT FROM AUTHOR]

Abstract 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.

Abstract Cardiovascular diseases are prevalent in patients with chronic obstructive pulmonary disease (COPD). Their coexistence implies that many COPD patients require anticoagulation therapy. Although more and more replaced by direct oral anticoagulants, vitamin K antagonists (VKAs) are still widely used. VKAs induce profound deficiency of vitamin K, a key activator in the coagulation pathway. It is recognized however that vitamin K is also an essential cofactor in the activation of other extrahepatic proteins, such as matrix Gla protein (MGP), a potent inhibitor of arterial calcification. No or insufficient MGP activation by the use of VKAs is associated with a rapid progression of vascular calcification, which may enhance the risk for overt cardiovascular disease. Vitamin K consumption, on the other hand, seems to have a protective effect on the mineralization of arteries. Furthermore, vascular calcification mutually relates to elastin degradation, which is accelerated in patients with COPD associating with impaired survival. In this commentary, we hypothesize that vitamin K is a critical determinant to the rate of elastin degradation. We speculate on the potential link between poor vitamin K status and crucial mechanisms of COPD pathogenesis and raise concerns about the use of VKAs in patients with this disease. Future intervention studies are needed to explore if vitamin K supplementation is able to reduce elastin degradation and vascular calcification in COPD patients.

Jerome Cantor,1 Shuren Ma,2 Gerard Turino2 1Department of Pharmaceutical Sciences, St John’s University, 2Department of Medicine, St Luke’s Mount Sinai Hospital Center, New York, NY, USA Abstract: 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. Keywords: hyaluronan, COPD, desmosine, elastin

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

Elastin is an essential structural protein in the extracellular matrix of vertebrates. It is the core component of elastic fibers, which enable connective tissues such as those of the skin, lungs or blood vessels to stretch and recoil. This function is provided by elastin's exceptional properties, which mainly derive from a unique covalent cross‐linking between hydrophilic lysine‐rich motifs of units of the monomeric precursor tropoelastin. To date, elastin's cross‐linking is poorly investigated. Here, we purified elastin from human tissue and cleaved it into soluble peptides using proteases with different specificities. We then analyzed elastin's molecular structure by identifying unmodified residues, post‐translational modifications and cross‐linked peptides by high‐resolution mass spectrometry and amino acid analysis. The data revealed the presence of multiple isoforms in parallel and a complex and heterogeneous molecular interconnection. We discovered that the same lysine residues in different monomers were simultaneously involved in various cross‐link types or remained unmodified. Furthermore, both types of cross‐linking domains, Lys‐Pro and Lys‐Ala domains, participate not only in bifunctional inter‐ but also in intra‐domain cross‐links. We elucidated the sequences of several desmosine‐containing peptides and the contribution of distinct domains such as 6, 14 and 25. In contrast to earlier assumptions proposing that desmosine cross‐links are formed solely between two domains, we elucidated the structure of a peptide that proves a desmosine formation with participation of three Lys‐Ala domains. In summary, these results provide new and detailed insights into the cross‐linking process, which takes place within and between human tropoelastin units in a stochastic manner. [ABSTRACT FROM AUTHOR]

Female reproductive tissues undergo significant alterations during pregnancy, which may compromise the structural integrity of extracellular matrix proteins. Here, we report on modifications of elastic fibers, which are primarily composed of elastin and believed to provide a scaffold to the reproductive tissues, due to parity and parturition. Elastic fibers from the upper vaginal wall of virgin Sprague Dawley rats were investigated and compared to rats having undergone one, three, or more than five pregnancies. Optical microscopy was used to study fiber level changes. Mass spectrometry, 13C and 2H NMR, was applied to study alterations of elastin from the uterine horns. Spectrophotometry was used to measure matrix metalloproteinases-2,9 and tissue inhibitor of metalloproteinase-1 concentration changes in the uterine horns. Elastic fibers were found to exhibit increase in tortuosity and fragmentation with increased pregnancies. Surprisingly, secondary structure, dynamics, and crosslinking of elastin from multiparous cohorts appear similar to healthy mammalian tissues, despite fragmentation observed at the fiber level. In contrast, elastic fibers from virgin and single pregnancy cohorts are less fragmented and comprised of elastin exhibiting structure and dynamics distinguishable from multiparous groups, with reduced crosslinking. These alterations were correlated to matrix metalloproteinases-2,9 and tissue inhibitor of metalloproteinase-1 concentrations. This work indicates that fiber level alterations resulting from pregnancy and/or parturition, such as fragmentation, rather than secondary structure (e.g. elastin crosslinking density), appear to govern scaffolding characteristics in the female reproductive tissues. Image 1 • Female reproductive tissues adapt and stretch during pregnancy and parturition. • Changes in female reproductive tissue elastin arising from pregnancy were studied. • Structural alterations in elastin from virgin and multiparous groups are reported. • Desmosine cross-links increase with increasing number of pregnancies. • Secondary structure alterations were correlated to MMP-9 concentrations. [ABSTRACT FROM AUTHOR]

[Display omitted] Desmosine is a crosslinking amino acid of the extracellular matrix protein elastin that is contained in tissues such as ligamentum, skin, alveoli, and blood vessels. Quantitative LC-MS/MS analysis of desmosine in human dermis, plasma, and skipjack tuna has been employed as a useful biomarker. The aim of this study is to produce desmosine antibodies to develop an ELISA system that is simpler than LC-MS/MS and can measure many samples in a shorter time. In our previous work, the synthesis of isodesmosine with keyhole limpet hemocyanin (KLH) conjugated antigen using Chichibabin pyridinium synthesis was achieved. In this work, synthesis of desmosine with KLH as the conjugated antigen, which is a new model, using isoChichibabin pyridinium synthesis, is reported. [ABSTRACT FROM AUTHOR]

Developing an effective treatment for pulmonary emphysema will require a better understanding of the molecular changes responsible for distention and rupture of alveolar walls. A potentially useful approach to studying this process involves the concept of emergence in which interactions at different levels of scale induce a phase transition comprising a spontaneous reorganization of chemical and physical systems. Recent studies in our laboratory provide evidence of this phenomenon in pulmonary emphysema by relating the emergence of airspace enlargement to the release of elastin-specific desmosine and isodesmosine (DID) crosslinks from damaged elastic fibers. When the mean alveolar diameter exceeded 400 μm, the level of peptide-free DID in human lungs was greatly increased, reflecting rapid acceleration of elastin breakdown, alveolar wall rupture, and a phase transition to an active disease state that is less responsive to treatment. Based on this finding, it is hypothesized that free DID in urine and other body fluids may serve as a biomarker for early detection of airspace enlargement, thereby facilitating timely therapeutic intervention and reducing the risk of respiratory failure., Competing Interests: The author has a financial interest in MatRx Therapeutics, which is developing the use of hyaluronan as a treatment for chronic obstructive pulmonary disease. He also is listed as an inventor on USPTO 17/821,672, which includes a method for measuring desmosine with liquid chromatography and tandem mass spectrometry., (Copyright © 2023 Cantor.)

Leather biotechnology based on enzyme is one of the main directions toward clean technology in the leather manufacturing process. Proteins such as collagen, elastin, and keratin are important components in animal hides or skins, and proteases are most frequently used in the leather manufacturing process for the removal of interfibrillar substance and opening-up of collagen fiber instead of toxic chemicals. Elastin is an important and highly elastic structural protein in the animal hides or skins and significantly affects the properties of the final leather product. For improving the quality of leather product, thorough understanding of the mechanism of action of proteases on elastin is necessary. The action of proteases on elastin has been mostly studied either qualitatively by histological analysis or quantitatively based on substrate casein or stained substrates, such as congo red-elastin and Remazol Brilliant Blue R-elastin; however, the resulting products have not been accurately characterized and thus these methods are not up to the standard. Besides, controlling the hydrolytic action of proteases to elastin has been very difficult, and excessive hydrolytic action of protease damages the elastin, restricting the wide application of proteases in the leather manufacturing process. In order to quantitatively evaluate the hydrolytic action of proteases on elastin in a more accurate manner, in this study, a new method was established by determining the unique amino acid desmosine based on the covalently bonded elastin-desmosine conjugate. Quantitative analysis of desmosine was performed in liquor based on cowhides substrate, and qualitative characterization was accomplished by histological analysis of elastic fiber in hides using an optical microscope. The results of this study indicated that the newly developed method is sensitive, accurate, and reproducible. In addition, the unhairing trials also demonstrated the suitability of newly established method in the leather manufacturing process to evaluate the action of proteases on the elastin in animal hides or skins. [ABSTRACT FROM AUTHOR]

Purpose: While the elastin-specific crosslinks, desmosine and isodesmosine (DID), are increased in blood, urine, and sputum of patients with clinically documented pulmonary emphysema, the usefulness of DID in detecting early lung injury remains untested. To this end, our laboratory has measured DID in a hamster model of smoke-induced emphysema, involving only minimal alveolar wall damage.Methods: Animals were either treated with cigarette smoke for 2 h/day, 5 days/week, or exposed only to room air (controls) for a period of 3 months. DID levels in bronchoalveolar lavage fluid (BALF) and whole lungs were determined at monthly intervals, using liquid chromatography and tandem mass spectrometry. Lung surface area was also determined, as a measure of airspace enlargement.Results: The portion of BALF DID not bound to peptides (free DID) was significantly higher in smoke-exposed animals at 2 months (9.2 vs 4.4 pg/mg protein; p < 0.05), whereas total BALF DID showed no significant increases over the course of the study, and total lung DID remained unchanged. There was a mild, but significant, loss of lung surface area in the smoke-exposed group at 2 months (28.8% vs 25.2%, p < 0.05), which showed no further progression, consistent with the return of free DID to control levels at 3 months.Conclusions: These findings support the hypothesis that free DID are sensitive indicators of smoke-induced lung injury. Measurement of free DID in smokers with minimally decreased lung mass may help determine the utility of this parameter as a test for incipient pulmonary emphysema. [ABSTRACT FROM AUTHOR]

Desmosine (Des) and isodesmosine (Isodes), cross-linking amino acids in the biomolecule elastin, may be used as biomarkers for various pathological conditions associated with elastin degradation. The current study presents a novel approach to quantify Des and Isodes using matrix-assisted laser desorption ionization (MALDI)-tandem mass spectrometry (MS2) in a linear ion trap coupled to a vacuum MALDI source. MALDI-MS2 analyses of Des and Isodes are performed using stable-isotope-labeled desmosine d4 (labeled-Des) as an internal standard in different biological fluids, such as urine and serum. The method demonstrated linearity over two orders of magnitude with a detection limit of 0.02 ng/μL in both urine and serum without enrichment prior to mass spectrometry, and relative standard deviation of < 5%. The method is used to evaluate the time-dependent degradation of Des upon UV irradiation (254 nm) and found to be consistent with quantification by 1H NMR. This is the first characterized MALDI-MS2 method for quantification of Des and Isodes and illustrates the potential of MALDI-ion trap MS2 for effective quantification of biomolecules. The reported method represents improvement over current liquid chromatography-based methods with respect to analysis time and solvent consumption, while maintaining similar analytical characteristics.ᅟ [ABSTRACT FROM AUTHOR]

Insights into the clinical course of COPD indicate the need for new therapies for this condition. The discovery of alpha-1 antitrypsin deficiency (AATD) led to the protease-antiprotease imbalance hypothesis, which was applied to COPD related to AATD as well as COPD not related to AATD. The discovery of AATD brought recognition to the importance of elastin fibers in maintaining lung matrix structure. Two cross-linking amino acids, desmosine and isodesmosine (DI), are unique to mature elastin and can serve as biomarkers of the degradation of elastin. The intravenous augmentation treatment and lung density in severe alpha-1 antitrypsin deficiency (RAPID) study shows a correlation of an anatomic index of COPD (on CT imaging) correlating with a chemical indicator of matrix injury in COPD, DI. The results suggest that preservation of lung elastin structure may slow the progression of COPD. Hyaluronan aerosol decreases the severity of elastase-induced emphysema in animals and has induced reductions in DI levels in preliminary human studies. Hyaluronan deserves further development as a therapy for COPD. [ABSTRACT FROM AUTHOR]

Background: Desmosine (DES), a cross linking amino-acid unique to mature elastin is expected to increase in proportion to the recruitment and activation of the inflammatory cells induced by smoking, exposure to biomass fuel smoke etc., or during acute exacerbations of COPD. Therefore, it could be investigated as a biomarker of the stable disease and during exacerbations. Aim of the study: The study aimed to evaluate blood DES level in COPD exacerbation as well as in the stable state, and to assess its relation to severity of exacerbation. Methods: The study included 20 COPD patients and 20 healthy controls all individuals were subjected to chest radiograph, spirometric pulmonary function, arterial oxygen saturation (SapO2), arterial blood gases (ABG, patients only), and ELISA – based blood DES level assay which was done once in controls and twice – in COPD patients, both during exacerbation and one month later after being stable. Results: DES level was more elevated, with high statistical significance, in COPD patients (both during exacerbation and in the stable state) compared to the control subjects, as well as it was significantly higher in COPD patients during exacerbation than in the same patients’ group after being stable. The DES level showed significant negative correlation with FEV1% in stable COPD and significant positive correlation with the severity of COPD exacerbation. Conclusion: Blood DES level as a marker of elastin degradation was elevated in stable COPD with more rise during exacerbation indicating that exacerbations could add more lung destruction leading to further deterioration of the lung function.

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. [ABSTRACT FROM AUTHOR]

Cardiovascular diseases are prevalent in patients with chronic obstructive pulmonary disease (COPD). Their coexistence implies that many COPD patients require anticoagulation therapy. Although more and more replaced by direct oral anticoagulants, vitamin K antagonists (VKAs) are still widely used. VKAs induce profound deficiency of vitamin K, a key activator in the coagulation pathway. It is recognized however that vitamin K is also an essential cofactor in the activation of other extrahepatic proteins, such as matrix Gla protein (MGP), a potent inhibitor of arterial calcification. No or insufficient MGP activation by the use of VKAs is associated with a rapid progression of vascular calcification, which may enhance the risk for overt cardiovascular disease. Vitamin K consumption, on the other hand, seems to have a protective effect on the mineralization of arteries. Furthermore, vascular calcification mutually relates to elastin degradation, which is accelerated in patients with COPD associating with impaired survival. In this commentary, we hypothesize that vitamin K is a critical determinant to the rate of elastin degradation. We speculate on the potential link between poor vitamin K status and crucial mechanisms of COPD pathogenesis and raise concerns about the use of VKAs in patients with this disease. Future intervention studies are needed to explore if vitamin K supplementation is able to reduce elastin degradation and vascular calcification in COPD patients. [ABSTRACT FROM AUTHOR]

Elastin is a vital extracellular matrix protein, which is known for providing elasticity in numerous tissues. It is formed by the self-assembly and subsequent crosslinking of elastin precursor, tropoelastin. Two tetrafunctional, pyridinium-based amino acids desmosine and isodesmosine are exclusively found in elastin and play an important role as crosslinkers. Structural elucidation of elastin has eluded scientists to date, owing to the highly cross-linked structure and insoluble nature. Therefore, in this study, we aimed to synthesize a desmosine-containing cyclic peptide as a partial elastin mimic, in order to eventually facilitate the elucidation of the crosslinking pattern of elastin by mass spectrometric analysis. [ABSTRACT FROM AUTHOR]

Desmosine is a crosslinking pyridinium amino acid of elastin, which is a useful biomarker for the diagnosis of chronic obstructive pulmonary disease (COPD) by LC–MS/MS analysis. We previously reported a synthesis of desmosine-d 4 , which is useful as an internal standard for quantitative LC–MS/MS analysis of desmosines, by deuterogenation of an alkyne group; however, the isotopic purity of the desmosine-d 4 was only ca . 50%. The present report describes a new synthesis of desmosine-d 4 that improves the isotopic purity to ca . 90% by exchanging the protons of the amino groups to deuterium using deuterogenation. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM PUBLISHER]

Introduction: Desmosine and isodesmosine (DID) are unique elastin crosslinks that may serve as biomarkers for elastic fiber degradation in chronic obstructive pulmonary disease. Previously, our laboratory found that the ratio of free to peptide-bound DID in bronchoalveolar lavage fluid (BALF) showed a significant positive correlation with the extent of airspace enlargement in an elastase model of pulmonary emphysema. To further evaluate this hypothesis, our laboratory measured this ratio in a bleomycin (BLM) model of pulmonary fibrosis, which involved different microarchitectural changes than those associated with pulmonary emphysema. Methods: Syrian hamsters were instilled intratracheally with 1.0 unit BLM in 0.2 ml of normal saline (controls received the vehicle alone), and BALF was analyzed for both free and total DID, using a combination of liquid chromatography and tandem mass spectrometry. Results: Total BALF DID was significantly increased in hamsters receiving BLM at 1 week post-treatment (92 vs 13 pg/ml; p < 0.001), consistent with elastic fiber degradation. However, in contrast to elastase-induced emphysema, free/bound DID was lower in BLM-treated animals compared to controls at both 1 week (0.76 vs 0.84) and 2 weeks post-treatment (0.69 vs 0.86), though the differences were not statistically significant. Conclusions: These results indicate that it may be possible to identify specific pulmonary microarchitecture changes, based on the ratio of free to peptide-bound DID. It is speculated that the proportionate decrease in free DID in BLM-induced fibrosis may be due to preservation of intact elastic fibers as the lung injury progresses. [ABSTRACT FROM AUTHOR]

Chemical cross-linking of structural biopolymers, such as collagen, hyaluronic acid, and cellulose, plays a significant role in the preparation of new materials for bioengineering and directed delivery of medicinal compounds. However, the currently known methods for the modification of biopolymers by using synthetic reagents often lead to derivatives with noticeable toxicity. In order to design biomaterials that are fully compatible with human tissues, many recent studies have relied on the use of natural heterocyclic compounds isolated from plants and animals. Examples of such heterocycles include genipin, flavonoids found in foods (catechins, proanthocyanidins), and desmosine analogs. The applications of heterocycles in bioengineering for linking natural proteins and polysaccharides is a new and very promising direction in the chemistry of heterocyclic compounds, as illustrated by the large number of publications over the last decade. [ABSTRACT FROM AUTHOR]