Urine Desmosine as a Novel Biomarker for Bronchopulmonary Dysplasia and Postprematurity Respiratory Disease in Extremely Preterm or Low Birth Weight Infants

OBJECTIVE

 This study aimed to evaluate whether elevated urine desmosine levels at 3 weeks of age were associated with severe radiological findings, bronchopulmonary dysplasia (BPD), and post-prematurity respiratory disease (PRD) in extremely preterm (EP) or extremely low birth weight (ELBW) infants.

STUDY DESIGN

 This study recruited 37 EP (22-27 completed weeks) or ELBW (<1,000 g) infants. Urine was collected between 21 and 28 postnatal days, and desmosine was measured using an enzyme-linked immunosorbent assay kit; the urine creatinine level was also measured. Bubbly/cystic lungs were characterized by emphysematous chest X-rays on postnatal day 28. Furthermore, provision of supplemental oxygen or positive-pressure respiratory support at 40 weeks' postmenstrual age defined BPD, and increased medical utilization at 18 months of corrected age defined PRD. The desmosine/creatinine threshold was determined by receiver operating characteristic analysis. The adjusted risk and 95% confidence interval (CI) for elevated urine desmosine/creatinine levels were estimated by logistic regression analysis.

RESULTS

 Elevated urine desmosine/creatinine levels higher than the threshold were significantly associated with bubbly/cystic lungs (8/13 [61.5%] vs. 2/24 [8.3%], p = 0.001), BPD (10/13 [76.9%] vs. 8/24 [33.3%], p = 0.02), and PRD (6/13 [46.2%] vs. 2/24 [8.3%], p = 0.01). After adjusting for gestational age, birth weight, and sex, the urine desmosine/creatinine levels were significantly higher in those who were highly at risk of bubbly/cystic lungs (odds ratio [OR], 13.2; 95% CI, 1.67-105) and PRD (OR, 13.8; 95% CI, 1.31-144).

CONCLUSION

 Elevated urine desmosine/creatinine levels on the third postnatal week were associated with bubbly/cystic lungs on day 28 and PRD at 18 months of corrected age in EP or ELBW infants.

KEY POINTS

· Urine desmosine was prospectively measured in 3-week-old EP/ELBW infants.. · Elevated urine desmosine levels were associated with emphysematous radiological findings on day 28, PRD at 18 months of corrected age.. · Urine desmosine may be a promising biomarker indicating lung damage in EP/ELBW infants..

Repeatability of and relationship between potential COPD biomarkers in bronchoalveolar lavage, bronchial biopsies, serum, and induced sputum

Chronic Obstructive Pulmonary Disease (COPD) is a chronic inflammatory disease, primarily affecting the airways. Stable biomarkers characterizing the inflammatory phenotype of the disease, relevant for disease activity and suited to predict disease progression are needed to monitor the efficacy and safety of drug interventions. We therefore analyzed a large panel of markers in bronchoalveolar lavage, bronchial biopsies, serum and induced sputum of 23 healthy smokers and 24 smoking COPD patients (GOLD II) matched for age and gender. Sample collection was performed twice within a period of 6 weeks. Assays for over 100 different markers were validated for the respective matrices prior to analysis. In our study, we found 51 markers with a sufficient repeatability (intraclass correlation coefficient >0.6), most of these in serum. Differences between groups were observed for markers from all compartments, which extends (von-Willebrand-factor) and confirms (e.g. C-reactive-protein, interleukin-6) previous findings. No correlations between lung and serum markers were observed, including A1AT. Airway inflammation defined by sputum neutrophils showed only a moderate repeatability. This could be improved, when a combination of neutrophils and four sputum fluid phase markers was used to define the inflammatory phenotype.In summary, our study provides comprehensive information on the repeatability and interrelationship of pulmonary and systemic COPD-related markers. These results are relevant for ongoing large clinical trials and future COPD research. While serum markers can discriminate between smokers with and without COPD, they do not seem to sufficiently reflect the disease-associated inflammatory processes within the airways.

Urinary desmosine: a biomarker of structural lung injury during CF pulmonary exacerbation

RATIONALE

Cystic fibrosis (CF) lung disease is characterized by structural changes and remodeling in airway architecture and lung parenchyma. Neutrophilic inflammation and infection lead to injury and breakdown of airway matrix constituents, including elastin. The non-invasive measurement of urinary desmosine (UDes), a breakdown product of elastin, may be reflective of ongoing lung injury and may serve as a biomarker of active short-term damage during pulmonary exacerbation. Our objectives were to measure desmosine in the urine of CF patients hospitalized for treatment of a pulmonary exacerbation and to explore the correlation between desmosine concentration and other markers of clinical improvement, including lung function and inflammatory mediators.

METHODS

Urine and blood samples plus lung function measurements were collected at up to three points during hospitalization for treatment of a CF pulmonary exacerbation. We used a repeated measures model, adjusted for age and time between measurements, to compare log transformed urine desmosine concentrations across multiple time points and to correlate those concentrations with related clinical variables. Change in UDes concentration was investigated using a statistical model that incorporated normalization factors to account for variations in urinary concentration.

RESULTS

Desmosine was measured by radioimmunoassay (RIA) in 155 spot urine samples from 53 CF patients hospitalized for 63 pulmonary exacerbations (range of results: 0-235 pmol Des/ml). Specific gravity (SG) adjusted UDes concentration decreased significantly during admission for CF pulmonary exacerbation, P < 0.01 (average length of stay = 11 days). No correlation was observed between UDes concentration and lung function or inflammatory markers.

CONCLUSIONS

UDes decreased significantly following treatment for an acute pulmonary exacerbation and may be a useful biomarker of short-term injury to the CF lung. Further investigation is needed to evaluate the utility of UDes concentration in the long-term progression of CF lung disease.

High-sensitivity nanoLC-MS/MS analysis of urinary desmosine and isodesmosine

Chronic obstructive pulmonary disease (COPD) is characterized by the degradation of elastin, the major insoluble protein of lung tissues. The degradation of elastin gives rise to desmosine (DES) and isodesmosine (IDES), two major urinary products typified by a hydrophilic pyridinium-based cross-linker structure. A high sensitivity method based on nanoflow liquid chromatography tandem mass spectrometry with multiple reaction monitoring was developed for the analysis of urinary DES and IDES. The analytes were derivatized with propionic anhydride and deuterated DES (D(4)-DES) was used as an internal standard. This method enables the quantification of DES and IDES in as little as 50 microL of urine and provides a detection limit of 0.10 ng/mL (0.95 fmol on-column). We report the analysis of DES and IDES in a cohort of 40 urine specimens from four groups of individuals: (a) COPD rapid decliners (11.8 +/- 3.7 ng/mg creatine (crea)), (b) COPD slow decliners (16.0 +/- 3.1 ng/mg crea), (c) healthy smokers (13.2 +/- 1.9 ng/mg crea), and (d) healthy nonsmokers (14.9 +/- 2.9 ng/mg crea). Our analysis reveals a statistically significant decrease in the level of urinary DES and IDES in COPD rapid decliner patients compared to healthy nonsmoker controls and COPD slow decliner patients. This methodology may be useful for monitoring DES and IDES levels in well controlled animal models for COPD or for longitudinal studies in COPD patients.

Urinary desmosine as a biomarker in acute lung injury

Acute lung injury (ALI) is a complex disorder associated with an acute inflammatory response thought to contribute to tissue injury. Desmosine, a cross-linking amino acid present in elastin, is released during matrix degradation and cleared by the kidney. Results from animal models and human disease studies have suggested that ALI is associated with the release of desmosine, resulting in increased urinary desmosine. A radioimmunoassay was used to monitor urinary desmosine levels over 10 days in ten patients with ALI. The concentration of desmosine was measured with and without acid hydrolysis. Baseline urinary desmosine was increased in two of ten patients. The concentration of desmosine at baseline did not appear to be related to age, gender, neutrophil elastase (NE)/alpha(1)-antiprotease complex concentration or P(a)O(2)/F(i)O(2) ratio. No meaningful changes in desmosine levels were noted after removal from mechanical ventilation. Baseline desmosine concentrations did not appear to correlate with the risk of death. The limited sensitivity, predictive correlations and dynamic modulation would suggest that urine desmosine has a limited role as a biomarker for ALI. Hydrolysis of urine samples appears necessary for optimal measurement of urine desmosine.

Higher urine desmosine levels are associated with mortality in patients with acute lung injury

Desmosine is a stable breakdown product of elastin that can be reliably measured in urine samples. We tested the hypothesis that higher baseline urine desmosine would be associated with higher mortality in 579 of 861 patients included in the recent Acute Respiratory Distress Syndrome Network trial of lower tidal volume ventilation (1). We also correlated urine desmosine levels with indexes of disease severity. Finally, we assessed whether urine desmosine was lower in patients who received lower tidal volumes. Desmosine was measured by radioimmunoassay in urine samples from days 0, 1, and 3 of the study. The data were expressed as a ratio of urine desmosine to urine creatinine to control for renal dilution. The results show that higher baseline (day 0) urine desmosine-to-creatinine concentration was associated with a higher risk of death on adjusted analysis (odds ratio 1.36, 95% confidence interval 1.02-1.82, P=0.03). Urine desmosine increased in both ventilator groups from day 0 to day 3, but the average rise was higher in the 12-ml/kg predicted body weight group compared with the 6-ml/kg predicted body weight group (P=0.053, repeated-measures model). In conclusion, patients with acute lung injury ventilated with lower tidal volumes have lower urine desmosine levels, a finding that may reflect reduced extracellular matrix breakdown. These results illustrate the value of evaluating urinary biological markers that may have prognostic and pathogenetic significance in acute lung injury.

Assay for urinary desmosines in a healthy pre-pubertal population using an improved extraction technique

BACKGROUND

Current evidence indicates that increased desmosine excretion reflects the active inflammatory status of some connective tissue diseases. Our goal was to establish a reliable method of detection and to investigate the normal distribution of urinary desmosine excretion in a healthy pre-pubertal population.

METHOD

Urine was collected from healthy volunteers aged four weeks to 12 years old. We modified a published high-performance liquid chromatography (HPLC) method by (a) increasing hydrolysis time and temperature and (b) increasing cellulose column size.

RESULTS

Our modified method had small inter- and intra-assay variability, with coefficients of variation of <6.4% and 5.3%, respectively. There was positive correlation between isodesmosine and desmosine (r(2) = 0.91). There was no significant diurnal or day-to-day variability in total desmosine levels. A reference range for healthy pre-pubertal children aged four weeks to 12 years was established.

CONCLUSION

The modified HPLC method is reliable with low variability. The technique can now be applied as a non-invasive research or diagnostic tool for children with chronic lung disease.

Capillary electrophoresis with laser-induced fluorescence detection as a novel sensitive approach for the analysis of desmosines in real samples

Among various biomarkers believed to behave as descriptors of the disease process in chronic obstructive pulmonary disease (COPD), urinary desmosines are commonly used for monitoring elastin degradation. Given the low concentrations of urinary desmosines, their quantitative determination in this biological matrix often requires preconcentration steps. To minimize both solute losses and effects of sample matrix, and to decrease data variability related to the above-mentioned manipulation processes, we have developed a capillary electrophoresis approach combined with laser-induced fluorescence (CE-LIF) detection system using urine samples not submitted to any pretreatment procedure other than filtering the sample. Urines were hydrolyzed, derivatized with fluorescein isothiocyanate (FITC) and endogenous desmosines were identified by addition of standard analytes and submitting to mass spectrometry (MS) analysis the material collected from micropreparative runs. The assay showed good linearity, reproducibility and precision, allowing to detect amounts of desmosines as low as 10(-8) M (equivalent to 0.1 fmol on column). We conclude that CE-LIF technique is a highly sensitive method for detecting urinary desmosines.

High levels of desmosines in urine and plasma of patients with pseudoxanthoma elasticum

BACKGROUND

Pseudoxanthoma elasticum (PXE), a rare heritable disorder caused by mutations of the ABCC6 gene, is characterized by fragmentation and mineralization of elastic fibres. We determined the extent of degradation of elastin by measuring and comparing the amount of desmosines in plasma and urine of PXE patients, healthy carriers and normal subjects.

METHODS

Using capillary electrophoresis with laser-induced fluorescence detection (CE-LIF) we measured the amount of desmosines in the urine of 46 individuals (14 PXE patients, 17 healthy carriers and 15 controls) and in the plasma of 56 subjects (18 PXE patients, 23 healthy carriers and 15 controls). Pseudoxanthoma elasticum patients and carriers were identified by clinical, structural and molecular biology analyses.

RESULTS

The urinary excretion of desmosines was two-fold higher in PXE patients than in controls (P < 0.01); the values for healthy carriers were intermediate between those of PXE patients and controls. A very similar trend between patients and their relatives was observed for plasma desmosines. There was a significant correlation between the amount of the desmosines in plasma and urine. Moreover, a positive correlation was observed between urinary desmosine content and age of the patients as well as between urinary desmosine content and severity of clinical manifestations.

CONCLUSIONS

Both the urinary and plasma desmosine concentrations indicate that elastin degradation is higher in PXE patients and, to a lesser extent, in healthy carriers than in normal subjects. Data seem to indicate that the amount of elastin breakdown products correlates with the age of patients as well as with the severity of the disease.

The detection and quantitation of free desmosine and isodesmosine in human urine and their peptide-bound forms in sputum

Desmosine (D) and isodesmosine (I), the intramolecular crosslinking amino acids that occur in chains of elastin, have now been found in free form in human urine. Until now, these amino acids (M(r) = 526) were found to occur in urine only as higher molecular weight (M (r) = 1,000-1,500) peptides. Thus, the previously used analytical methods required, as the first step, acid hydrolysis of the urine at elevated temperature to liberate D and I from their peptides. The analytical method described here uses HPLC followed by electrospray ionization MS for the detection and quantitation of free D and I in unhydrolyzed urine. Identities of both D and I were established by their retention times on LC and by their mass ion at 526 atomic mass units, characteristic of each compound. The sensitivity of the method is 0.10 ng. The average values of free D and I in the urine of seven healthy subjects were 1.42 +/- 1.16 and 1.39 +/- 1.04 microg/g of creatinine, respectively. After acid hydrolysis of the urine, the amounts of D and I were 8.67 +/- 3.75 and 6.28+/-2.87 microg/g of creatinine, respectively. The method was also successfully used to measure peptide-bound D and I levels in the sputum of patients with chronic obstructive pulmonary disease.

Urinary desmosine excretion is inversely correlated with the extent of emphysema in patients with chronic obstructive pulmonary disease

An enhanced proteolysis of lung interstitium is key event in the pathogenesis of emphysema, a major constituent of chronic obstructive pulmonary disease. To assess whether urinary desmosine and/or hydroxyproline may be used as a marker of lung destruction we studied urinary excretions of these products in 20 patients with chronic obstructive pulmonary disease and in 19 appropriate controls in 24h urine collection samples. For desmosine measurements, we developed a new indirect competitive enzyme-linked immunosorbent assay. The extent of emphysema was measured in high resolution computed tomography (CT) scans, by considering lung area with CT numbers <-950 Hounsfield units (HU). Urinary desmosine excretion was significantly higher in patients with chronic obstructive pulmonary disease than in controls (294+/-121 microg versus 183+/-93 microg, P=0.003), and was unrelated with both age and smoking habits. In patients with no evidence or only mild emphysema, desmosine excretion values were significantly higher (P=0.006) than those of patients with moderate to severe emphysema. In patients with chronic obstructive pulmonary disease, urinary hydroxyproline excretion was positively correlated with urinary desmosine excretion but on the average, it was not different from that of controls. These data indicate that urinary desmosine is a sensitive biological marker of lung elastin catabolism. The relatively low levels of urinary desmosine observed in patients with severe emphysema may be accounted for a decrease in elastin catabolism due to reduced lung elastin mass. Urinary desmosine may be used to identify subjects at risk of developing emphysema and to assess the efficacy of therapeutic interventions.

Urinary desmosine excretion in acute exacerbations of COPD: a preliminary report

Desmosine (DES) is an elastin-derived, cross-link amino acid, which is not metabolized; hence, its urinary levels reflect elastin breakdown. We hypothesized that elastin degradation should increase as a result of increased lung inflammation during an acute exacerbation of COPD and should decrease after recovery. To test this hypothesis we measured DES in three urine samples from nine COPD subjects during the first 5 days of an acute exacerbation and at 2 months after recovery. We also measured forced expiratory volume in 1 sec (FEV1) to monitor the effects ofthe exacerbation on ventilatory function. The mean (SD) FEV1 was 45 (15)% predicted during the exacerbation and 57.8 (16)% predicted 2 months later (P=0.00001). The mean (SD) DES excretion was 25.3 (9) microg g(-1) creatinine at day 1;23.5 (9) at day 3 and 24 (9) at day 5 of the exacerbation. The mean (SD) urinary DES excretion 60 days after discharge was 20.9 (7) microg g(-1) creatinine (P=0.049) in comparison with the mean of the three acute-phase values. The size of the increase in desmosine excretion during exacerbation is small, 3.2 microg g(-1) creatinine or 16% of the recovery desmosine value. We conclude that there is a small but statistically significant increase in lung elastin breakdown in the body during an acute exacerbation of COPD.

Short-term supplementation therapy does not affect elastin degradation in severe alpha(1)-antitrypsin deficiency. The American-Italian AATD Study Group

We evaluated the ability of intravenous supplementation therapy with alpha(1)-antitrypsin (AAT) to reduce the rate of urinary excretion of desmosine (DES), a specific marker of elastin degradation, in eight men and four women with emphysema due to severe, congenital deficiency of AAT (range 17-69 mg/dl). Nine were former cigarette smokers, two were current smokers, and one reported never smoking; their mean age was 54 (SD 12) yr and their mean FEV(1) was 41 (18%) of predicted. Urinary DES was measured by isotope dilution and HPLC. Prior to the start of AAT supplementation, mean DES excretion was 13.0 (5.0) microg/g creatinine, 73% higher than in healthy nonsmokers. During 8 wk of supplementation therapy, mean urinary DES excretion was 13.0 (5.9) microg/g creatinine, unchanged from the baseline period (p = 0.85 by repeated measures ANOVA). We conclude that baseline levels of elastin degradation in emphysematous patients with severe AAT deficiency were abnormally high and that 8 wk of AAT supplementation therapy did not appreciably reduce the rate of elastin degradation. These findings raise the possibilities that protective levels of AAT in the lungs are insufficient or that elastin degradation in the lungs of these subjects is not dependent upon neutrophil elastase at this time.

Potential use of collagen and elastin degradation markers for monitoring liver fibrosis in schistosomiasis

Liver fibrosis is a serious complication of schistosomiasis infection, is associated with increased amounts of collagen and the collagen cross-link, pyridinoline. Non-invasive markers of liver fibrosis have been developed. Serum and urinary markers of collagen synthesis and degradation have been studied to assess the balance between collagen synthesis, measured with markers of collagen synthesis such as amino-terminal propeptide of type III procollagen (PIIINP), and markers of degradation such as pyridinoline or pyridinoline cross-linked carboxyterminal telopeptide of type I collagen (ICTP). It has been shown that mice infected with Schistosomiasis mansoni excrete excess pyridinoline cross links in urine and this was correlated with the collagen content of granulomas from the liver. Treatment of infected mice with an anti-parasitic drug, praziquantel, decreased the collagen content of parenchyma and excretion of pyridinoline in the urine. Although the connective tissue protein, elastin, is present in the liver, the role of elastin in liver fibrosis has not been investigated. However, it has been shown that the urinary concentration of elastin specific crosslinks, desmosine and isodesmosine, as well as the urinary concentration of the collagen crosslink, pyridinoline, correlated well with liver fibrosis score in biopsy specimens from patients with liver disease secondary to hepatitis C virus and alcohol. Each biopsy specimen was reviewed by two pathologists who were blinded as to the clinical data. The pathological evaluation generated scores for both inflammation and fibrosis. No correlation was seen between the urinary markers and inflammation scores. The measurement of non-invasive markers of collagen synthesis and degradation may be useful in monitoring the reversal of fibrosis following therapeutic intervention in schistosome infections.

Comparison of urinary desmosine excretion in patients with chronic obstructive pulmonary disease or cystic fibrosis

Neutrophil elastase is involved in the pathogenesis of several pulmonary diseases; a strategy for monitoring in vivo elastase activity is to measure changes in biochemical markers. The objective of this study was to determine whether differences in the urinary excretion of the elastin crosslinks, desmosine and isodesmosine (which are unique amino acid products of elastase activity), could be discerned between groups of patients with chronic obstructive pulmonary disease (COPD) or cystic fibrosis (CF), and non-diseased, age-matched controls. Twenty-four-hour urine collections were analysed to eliminate variations in excretion throughout the day, and urine was collected on four separate days in 29-31 subjects/group to investigate the variability in desmosines excretion among the groups. Both sets of patient populations had significantly more variable desmosines readings (higher standard deviations) relative to their respective age-matched control group. The means for three adult groups (COPD, controls and a COPD-smoker subset) ranged from 28.4 to 35.5 pmol desmosines/mg creatinine and there were no differences among the groups. Values in children were higher: 55 pmol desmosines/mg creatinine in the non-CF children and 77 pmol desmosines/mg creatinine for the CF group (P<0.01 vs. age-matched controls). The results of this study show that urinary desmosines, as a surrogate marker for enhanced elastase activity, are more highly variant in both patient populations relative to age-matched controls, and an overall increase in the mean value is further observed in patients with cystic fibrosis.

MEKC of desmosine and isodesmosine in urine of chronic destructive lung disease patients

Degradation of extracellular matrix components is central to many pathological features of chronic destructive lung disorders. Desmosine and isodesmosine are elastin-derived cross-linked amino acids whose urine levels are considered representative of elastin breakdown. The aim of this study was to apply a novel methodology, based on high-performance capillary electrophoresis, to the quantification of desmosine and isodesmosine in 11 patients with stable chronic obstructive pulmonary disease (COPD), 10 with an exacerbation of COPD, nine with alpha1-antitrypsin deficiency, 13 with bronchiectasis, and 11 adults with cystic fibrosis, in comparison to 24 controls. It was found that, in patients with stable COPD, urinary desmosine levels were higher than in controls (p=0.03), but lower than in COPD subjects with an exacerbation (p< or =0.05). The highest desmosine levels were found in subjects with alpha1-antitrypsin deficiency, bronchiectasis and cystic fibrosis (p<0.001 versus stable COPD). In a short-term longitudinal study, five stable COPD patients showed a constant rate of desmosine excretion (mean coefficient of variation <8% over three consecutive days). In conclusion, the present method is simple and suitable for the determination of elastin-derived cross-linked amino acid excretion in urine, giving results similar to those obtained using other separation methods. In addition, evidence is presented that urinary desmosine excretion is increased in conditions characterized by airway inflammation, such as exacerbations of chronic obstructive pulmonary disease, bronchiectasis and cystic fibrosis. Results obtained in subjects with alphal-antitrypsin deficiency suggest that this method might be used to evaluate the putative efficacy of replacement therapy.

Characteristic change of urinary elastin peptides and desmosine in the aortic aneurysm

To estimate elastin metabolism in aneurysm, urinary levels of desmosine and elastin peptide in patients (n=23, range 54 to 85 years old) with aneurysm were measured by ELISA and compared between two control groups divided by age (<10 years old and >20 years old). The amounts of urinary desmosine and elastin peptide in the aneurysm group were significantly increased compared with those in the older control group (>20 years old). There was a correlation between urinary desmosine and elastin peptide in the young group. On the other hand, no such correlation was observed in the aneurysm group and the older control group. The distribution of the ratio (desmosine/elastin peptide) in the aneurysm group was different from that of the young control group. We conclude that assay of elastin peptide and desmosine in urine are useful in characterizing elastin degradation in a patient with aneurysm.

Micellar electrokinetic chromatography for the determination of urinary desmosine and isodesmosine in patients affected by chronic obstructive pulmonary disease

The presence in urine of desmosine (DES) and isodesmosine (IDES), two crosslinked amino acids unique to the elastic fiber network, can be used as a specific indicator of degradation of mature elastin. Compared to methodologies so far available, the capillary electrophoretic technique reported here seems to be suitable and convenient for determining desmosines in urine of patients affected by chronic obstructive pulmonary disease (COPD). By using 35 mM sodium tetraborate pH 9.3 containing 65 mM SDS as the background electrolyte, the peaks of DES and IDES could be detected in hydrolyzed urine samples from controls and patients. Owing to the simultaneous determination of endogenous urinary creatinine used as appropriate internal standard, the amount of these amino acids could be accurately quantified. The results obtained were of the same order of magnitude as the data already reported in the literature for COPD patients. Thus micellar electrokinetic chromatography (MEKC) may be considered as a reliable technique for studying the turnover of the elastic fiber in clinical conditions.

Circadian variation of urinary excretion of elastin and collagen crosslinks

Urinary levels of collagen- and elastin-crosslink amino acids have been used as biologic markers for degradation of collagen and elastin in the body. Circadian variation of collagen-crosslink amino acids is well known. The current study was undertaken to determine whether there is also circadian variation in excretion of elastin-crosslink amino acids. We used an isotope dilution-HPLC assay to measure the elastin-crosslink amino acids, desmosine (DES) and isodesmosine (IDES), and the collagen-crosslink amino acids, hydroxylysyl pyridinoline (HP) and lysyl pyridinoline (LP), in urine. Sixteen apparently healthy subjects collected urine from 5:00 to 7:00 AM, and from 5:00 to 7:00 PM. Mean urinary excretion of DES and IDES in women was 56% and 41% higher (P < 0.001), respectively, in AM versus PM specimens when normalized by the creatinine content of the urine specimen. For men, the corresponding values were 11% and 13% higher (not statistically significant). Mean urinary excretion of HP and LP in women was 61% and 71% higher (P < 0.001), respectively, in AM versus PM specimens. For men, the corresponding values were 11% and 19% higher (not statistically significant). Differences were not found in the AM versus PM rates of excretion of creatinine in men or women. These findings demonstrate the occurrence of circadian variation in HP, LP, DES and IDES in women but not in men. We conclude that the time of collection of urine specimens, especially from women, must be taken into consideration in using the urinary levels of these crosslink amino acids as biologic markers for collagen or elastin degradation.

Urinary assays for desmosine and hydroxylysylpyridinoline in the detection of cirrhosis

BACKGROUND/AIMS

Non-invasive markers of liver fibrosis have great potential for both the diagnosis and therapy of liver disease and cirrhosis. The aim of this study was to evaluate the potential of urinary amino acids desmosine (DES) and isodesmosine (IDES) derived from the breakdown of elastin and hydroxylysylpyridinoline (HP) and lysylpyridinoline (LP) derived from fibrillar collagen in diagnosing chronic liver disease.

METHODS

We studied 48 patients with chronic liver disease who had varying degrees of liver fibrosis, graded 0-6 using a modified Knodell score, and 20 control subjects without liver disease. Urinary DES (microg/g creatinine) and HP (nmol/mmol creatinine) were measured by an isotope dilution, high performance liquid chromatography method. For liver disease patients, aminoterminal propeptide of type III procollagen (PIIINP) and alanine aminotransferase were determined. The urine and serum markers were correlated to degree of fibrosis and inflammation on liver biopsies. Differences between groups were analyzed by ANOVA and multiple linear regression was applied to determine independence of variables. Sensitivity, specificity and receiver operating curves were derived for each marker.

RESULTS

In the 17 patients with liver fibrosis score of 5-6, mean urinary DES, IDES, HP and LP were all significantly greater than in the control group (p<0.05). Urinary DES and IDES correlated best with fibrosis score, r=0.61 for both markers. The correlation coefficient between serum PIIINP and fibrosis score was 0.47. Urinary DES and HP each had an overall diagnostic accuracy of 77% for fibrosis. Combining markers improved accuracy to over 80%. No correlation was seen between the urinary markers and inflammation scores.

CONCLUSIONS

Urinary DES and HP are potentially useful clinical markers for liver fibrosis, especially when used in combination or in association with PIIINP.

Distribution of elastin in hamsters and the turnover rates of different elastin pools

Desmosine (DES) and isodesmosine (IDES) concentration in the urine can be used as a noninvasive method of assessing degradation of mature elastin in normal and pathologic states. The present study was undertaken to determine the distribution of elastin among organs and tissues of normal hamsters, and to determine the turnover rates of two elastin-containing organs (lung, thoracic aorta) as a reflection of their contributions to DES and IDES excretion in the urine. Hamsters were metabolically labeled at 5 days of age with 14C-lysine and studied at 1.5, 4.5, 8, and 12 months of age. The aorta DES + IDES-associated radioactivity did not change significantly over the age span of 1.5-12 months. Lung DES + IDES-associated radioactivity decreased with a half-life of 420 days. Measurement of DES + IDES pools in other tissues, with relatively low concentrations of elastin, was carried out by the isotope dilution technique. At 12 months of age, the head and paws pool, skin, skeletal muscle, gastrointestinal tract, heart-liver-kidney-spleen pool, lungs, and thoracic aorta represented 37%, 28%, 13%, 11%, 6%, 4%, and 1%, respectively, of total body DES + IDES. The organs with the highest DES + IDES-specific radioactivity at 12 months were heart-liver-kidney-spleen, lung, and gastrointestinal tract, with 310, 217, and 217 dpm/nmol, respectively. Skin had the lowest specific radioactivity, with 90 dpm/nmol. The specific radioactivity of DES + IDES in urine was 62 dpm/nmol at 12 months, down from 251 dpm/nmol at 1.5 months. These data clearly indicate that non-lung tissues contain a high proportion of the total body DES + IDES and suggest that pathology in these other pools of DES + IDES could result in significant elevation of urinary DES + IDES. Nevertheless, the relatively high specific radioactivity of DES + IDES in lung elastin as compared with urine makes monitoring labeled urinary DES + IDES in this animal model a sensitive tool for assessing elastin degradation in experimental lung disease.

Urinary desmosine excretion in smokers with and without rapid decline of lung function: the Normative Aging Study

It is hypothesized that smoking-related chronic obstructive pulmonary disease (COPD) results in part from excess lung elastin degradation. Taking advantage of spirometry performed over a 12-yr period at the Normative Aging Study, we conducted a nested case-control study of elastin and collagen degradation rates in current smokers with (n = 10) and without (n = 8) rapid decline of lung function, using a biochemical assay for urinary desmosine (DES), a specific marker for mature elastin degradation, and hydroxylysylpyridinoline (HP), a specific marker for mature fibrillar collagen degradation. Mean urinary excretion of DES in rapid decliners was 36% greater than in slow decliners (9.8 +/- 0.7 [mean +/- SE] versus 7.2 +/- 0.4 microg/g creatinine, p < 0.01); after adjustment for age and lean body mass (LBM), DES excretion in rapid decliners was 30% greater than in slow decliners (9.6 +/- 0.6 versus 7.4 +/- 0.7 microg/g creatinine, p = 0.06). Among rapid decliners, there was no difference in DES excretion between those with and those without computed tomogaphic evidence of emphysema. There was no significant difference between rapid and slow decliners in mean urinary excretion of HP (24.7 +/- 1.4 versus 21.6 +/- 1.8 nmol/mmol creatinine, p = 0.18). Among all subjects, rate of decline of FEV1 was significantly correlated with DES excretion (r = 0.61, p < 0.01). In a linear regression model adjusting for age and LBM, an increase in DES excretion of 1 microg/g creatinine was associated with an excess decline of FEV1 of 10.6 ml/yr (p = 0.04). This study provides further evidence in support of the elastase-antielastase hypothesis of the pathogenesis of COPD, and it suggests a role for elastin degradation in both emphysema and small airways disease. Moreover, it suggests that urinary DES excretion may be a useful biochemical marker for the study of interventions designed to prevent the development or progression of COPD.

MR889, a neutrophil elastase inhibitor, in patients with chronic obstructive pulmonary disease: a double-blind, randomized, placebo-controlled clinical trial

We investigated whether MR889, a synthetic cyclic thiolic elastase inhibitor, administered for a period of 4 weeks to chronic obstructive pulmonary disease (COPD) patients, is well-tolerated, and whether it modifies biochemical indices of lung destruction. The study was a double-blind, randomized, placebo-controlled clinical trial in COPD patients. Thirty subjects were administered MR889 orally at a dose of 500 mg b.i.d. for 4 weeks, and 30 received placebo following the same schedule. In addition to safety parameters, MR889 efficacy was checked by a pretreatment/postreatment evaluation of levels of plasma elastin-derived peptides and urinary desmosine. There were no statistically significant differences between pretreatment and posttreatment efficacy parameter levels either in the control group or in the treated group. However, in a subset of treated patients with a short disease duration, the level of urinary desmosine dropped significantly with respect to pretreatment values (p = 0.004). We conclude that MR889 is safe to administer to COPD patients for a period of at least 4 weeks. During this time, MR889 does not modify biochemical markers of lung destruction in unselected COPD patients. Nevertheless, a subset of treated patients with fairly short disease duration showed a post-treatment reduction of desmosine urine levels, thus justifying the need for further studies to prove the efficacy of MR889 in modulating indices of lung destruction in COPD.

Increase in urinary desmosine and pyridinoline during postpartum involution of the uterus in humans

One of the most rapid changes in collagen and elastin content of a tissue occurs in the uterus following postpartum involution. We measured the urinary excretion of specific amino acid markers for mature elastin (desmosine [DES] and isodesmosine [IDES]) and fibrillar collagen (hydroxylysyl pyridinoline [HP] and lysyl pyridinoline [LP]) before and after parturition in three gravid subjects. For that purpose, we used an isotope dilution method coupled with gel filtration and HPLC. The highest DES values were found 2-5 weeks postpartum and were 18-45 micrograms/g creatinine or two to six times those found for healthy neversmoking nongravid females (7.7 +/- 0.3 micrograms/g creatinine, mean +/- SE). The highest levels of urinary HP for each subject were found 2-3 weeks after parturition and were 115-607 nmol/mmol creatinine or 4-21 times those found for healthy neversmoking nongravid females (28.1 +/- 1.3 nmol/mmol creatinine). For the gravid subjects as a group and also for each subject, the mean values for urinary DES, IDES, HP, and HP/LP during the first 6 weeks postpartum were significantly greater than the mean baseline values beginning 27 weeks postpartum. For the gravid subjects as a group, the mean value for urinary HP/LP during the first 6 weeks postpartum was significantly greater than the value during the 20 weeks preceding parturition. This suggested that the tissue(s) of origin of the excess HP, during the 6 weeks following parturition, was not bony and was consistent with a uterine origin.

Elastin and collagen degradation products in urine of patients with cystic fibrosis

Elastin degradation has been reported to be increased in patients with cystic fibrosis (CF). In order to further explore evidence for elastin degradation in a group of 18 patients with CF with a wide range of disease severity, we used an isotope dilution method to measure urinary desmosine (DES) and isodesmosine (IDES), amino acids derived exclusively from cross-linked elastin, and hydroxylysylpyridinoline (HP) and lysylpyridinoline (LP), amino acids derived exclusively from cross-linked collagen. Urinary DES and IDES (mean +/- SD) were 23.9 +/- 30.7 and 18.5 +/- 22.4 micrograms/g creatinine, respectively, in the patients with CF versus 7.5 +/- 1.7 and 6.8 +/- 1.4 micrograms/g creatinine, respectively, in 10 healthy control subjects (p < 0.001); only two patients with CF had DES values within the control range. The values of urinary HP and LP in the CF group were 54.9 +/- 39.1 and 12.3 +/- 8.6 nmol/mmol creatinine, respectively, versus 24.5 +/- 5.8 and 5.1 +/- 2.7 nmol/mmol creatinine, respectively, in the controls (p < 0.005). Both HP and LP were highly correlated (r = 0.71, p < 0.0001). Patients with CF had active pulmonary inflammation; neutrophils were abundant in the bronchoalveolar lavage fluid of the CF group and correlated with elastase activity measured with methoxysuccinyl Ala-Ala-Pro-Val paranitroanilide (r = 0.61, p < 0.05). Airway neutrophils had decreased expression of the complement receptor CR1 (CR1/CR3 of 0.17 +/- 0.15 versus 1.0 for blood neutrophils), a change known to be caused by uninhibited neutrophil elastase. We conclude that lung elastin is the most likely source of the increased DES and IDES in CF.

Enrichment and analysis of desmosine and isodesmosine in biological fluids

A method has been developed for the enrichment and analysis of the elastin crosslinks, desmosine and isodesmosine, in biological fluids and tissues. It is adapted from published methods, offering improved recovery, sensitivity, resolution, and speed of analysis. Samples were hydrolyzed in 6 M HCl, after which the desmosines were enriched by CF1 cellulose chromatography and analyzed by HPLC with a C18 column. Isodesmosine and desmosine were quantitated based on absorbance at 275 nm, with a limit of detection of approximately 30 pmol and recovery of approximately 66% in urine. Their tR values on our HPLC system were approximately 9 and 12 min, respectively. This method was used to evaluate the daily and weekly variation in the concentrations of desmosine and isodesmosine in human urine. The results suggest that this method can be used to process large numbers of biological samples for analysis of desmosine and isodesmosine.

Cross-linked elastin and collagen degradation products in the urine of patients with scleroderma

OBJECTIVE

To measure the urinary excretion of specific cross-link amino acid markers for mature elastin (desmosine [DES] and isodesmosine [IDES]) and fibrillar collagen (hydroxylysylpyridinoline [HP] and lysylpyridinoline [LP]) in systemic sclerosis (SSc) patients and healthy controls.

METHODS

Urine specimens from 20 patients with SSc and 22 controls were assessed for DES, IDES, HP, and LP using high performance liquid chromatography and ultraviolet absorption spectroscopy, in combination with an isotope dilution technique in which the urine specimen was spiked with isotopically labeled cross-link amino acids.

RESULTS

Mean +/- SD levels of urinary DES and IDES were elevated in SSc patients by 2-3-fold, and urinary HP and LP by 3-4-fold, compared with controls (DES 21.0 +/- 9.4 versus 7.5 +/- 1.4 micrograms/gm creatinine; HP 109.0 +/- 72.9 versus 24.9 +/- 5.7 nmoles/mmole creatinine). Nineteen of the 20 SSc patients had urinary DES and HP values that were > 3 SD above the control mean. A significant elevation in the HP:LP ratio in SSc patients as compared with controls (mean +/- SD 6.9 +/- 1.5 versus 5.5 +/- 1.3) indicated a soft tissue origin for much of the increased HP.

CONCLUSION

Patients with SSc have higher levels of urinary cross-link amino acids specific for the degradation of mature collagen and elastin. These markers distinguish most SSc patients from healthy controls.

Elastin and collagen degradation products in urine of smokers with and without chronic obstructive pulmonary disease

It has been hypothesized that emphysema results from damage to the elastic fiber network of the lungs as a result of elastase-antielastase imbalance. We used a new assay for urinary desmosine (DES) and isodesmosine (IDES), specific markers for the degradation of mature crosslinked elastin, and hydroxylysylpyridinoline (HP) and lysylpyridinoline (LP), specific markers for the degradation of mature crosslinked collagen, in order to examine elastin and collagen degradation in relation to current cigarette smoking and the presence of chronic obstructive pulmonary disease (COPD). The study sample consisted of 22 never-smokers (NSM group), 13 current smokers without airflow obstruction (SM group), and 21 patients with COPD (COPD group), including both current and former smokers. The relation between the creatinine-height index and FEV1 was used to correct for possible loss of muscle mass and decreased excretion of creatinine in the COPD group. Mean urinary excretion of elastin-derived crosslinks in the COPD group (DES, 11.8 +/- 5.1 [mean +/- SD]; IDES, 11.3 +/- 5.0 micrograms/g creatinine) and in the SM group (DES, 11.0 +/- 4.2; IDES, 10.2 +/- 2.5 micrograms/g creatinine) was significantly higher than in the NSM group (DES, 7.5 +/- 1.4; IDES, 6.9 +/- 1.3 micrograms/g creatinine). In multivariate analysis, current smoking and the presence of COPD were significantly and independently associated with higher urinary excretion of elastin degradation products, and there was no significant interaction between current smoking and the presence of COPD.(ABSTRACT TRUNCATED AT 250 WORDS)

Preliminary evidence that augmentation therapy diminishes degradation of cross-linked elastin in alpha-1-antitrypsin-deficient humans

It is hypothesized that emphysema develops in some severely alpha 1-antitrypsin (AAT)-deficient persons because endogenous elastases are not adequately controlled by AAT, and accelerated elastin degradation occurs. It is not known whether augmentation therapy with AAT diminishes degradation of lung elastin in severely deficient persons with lung disease. Two severely deficient, PiZ patients were studied, a 63-year-old never-smoking woman with bronchiectasis and a 41-year-old smoking man with emphysema. Urinary desmosine (DES) was determined before and after augmentation therapy with AAT, 260 mg/kg/month. Mean +/- SEM pretreatment urinary DES was elevated in both patients, 19.7 +/- 0.9 (n = 2) and 10.8 +/- 0.2 (n = 2) micrograms/g creatinine, respectively, compared to normal values of 7.5 +/- 0.3 (n = 22) micrograms/g creatinine. Following augmentation therapy, urinary DES values decreased 40 and 36%, respectively, to 11.9 +/- 0.3 (n = 8) and 6.9 +/- 0.4 (n = 7) microgram/g creatinine (p < 0.05). We conclude that monthly AAT augmentation therapy decreased DES excretion in the urine of these PiZ patients. We speculate that since there was lung disease in both patients, a decrease in degradation of lung elastin is the most likely explanation for this observation.

Measurement of urinary desmosine as an indicator of acute pulmonary disease

A modified radioimmunoassay (RIA) for desmosine in the urine was investigated as a tool for the rapid estimation of lung elastin catabolism. Cystic fibrosis (CF) and oxygen toxicity were chosen as conditions that might show altered elastin destruction. Using an antibody bound to magnetic particles the RIA was adapted to handle large numbers of samples requiring only 50 microliters or urine. The experiments show that it was not necessary to hydrolyze or extract the urine prior to assay and that collecting spot urines and normalizing the data to urine creatinine gives the same interpretation of the data as total desmosine in a 24-hour collection. Urine desmosine levels were elevated in 10 of 16 patients with CF; however, daily fluctuations were considerable in some subjects, varying as much as 5-fold and underlining the importance of assaying several consecutive days of urine in acute disorders for an accurate estimate of desmosine excretion. The RIA for desmosine is a rapid and sensitive assay that requires no sample preparation and could be applied to clinical situations that require large numbers of samples.

Effect of diet on urinary excretion of desmosine and hydroxylysyl pyridinoline

To help validate the use of urinary desmosine (DES), isodesmosine (IDES), and hydroxylysyl pyridinoline (HP) as specific markers of host elastin and collagen degradation, respectively, a study was carried out on the effect of dietary elastin and collagen on urinary DES, IDES, and HP. Ingestion of a meal of calf ligamentum nuchae containing 33 g elastin, 500 mg DES, and 400 mg IDES produced a 10-fold increase in urinary DES and an 8-fold increase in IDES. The urinary DES values remained elevated for more than 10 days following the ingestion. We estimate that about 0.3 mg, or < 0.1%, of the ingested DES was excreted in the urine. Since ligamentum nuchae is not a usual ingredient of human diets, we also determined whether a more typical source and amount of DES, IDES, and HP might affect urinary DES, IDES, or HP values. Lean ground beef (454 g) was ingested. Our analysis showed that this meal contained 4 mg DES, 2 mg IDES, and 0.9 mg HP. The meat-rich diet caused a significant increase of 16 and 34% in the creatinine and DES content of the urine, respectively. When DES, IDES, and HP values were normalized for the urine creatinine content, diet had no effect on the measured amounts. The baseline values (mean +/- SE) for the volunteers before ingestion of the beef were 8.3 +/- 0.7 micrograms DES/24 h, 8.3 +/- 0.6 micrograms IDES/24 h, and 340 +/- 48 nmol HP/24 h; 5.7 +/- 0.5 micrograms DES/g creatinine, 5.6 +/- 0.4 micrograms IDES/g creatinine, and 26.9 +/- 2.2 nmol HP/mmol creatinine.(ABSTRACT TRUNCATED AT 250 WORDS)

Nitrogen dioxide exposure and urinary excretion of hydroxyproline and desmosine

The relationship between average and peak personal exposure to nitrogen dioxide and urinary excretion of hydroxyproline and desmosine was investigated in a population of preschool children and their mothers. Weekly average personal nitrogen dioxide exposures for subjects who resided in homes with one or more potential nitrogen dioxide source (e.g., a kerosene space heater, gas stove, or tobacco smoke) ranged between 16.3 and 50.6 ppb (30.6 and 95.1 micrograms/m3) for children and between 16.9 and 44.1 ppb (12.8 and 82.9 micrograms/m3) for mothers. In these individuals, the hydroxyproline-to-creatinine and desmosine-to-creatinine ratios were unrelated to personal nitrogen dioxide exposure--even though continuous monitoring documented home nitrogen dioxide concentration peaks of 100-475 ppb lasting up to 100 h in duration. Significantly higher hydroxyproline-to-creatinine and desmosine-to-creatinine ratios were observed in children, compared with mothers (p < .001 and .003, respectively).

Influence of nifedipine on aortal cholesterol content, blood coagulation and elastin metabolism in cholesterol-fed rabbits

Our studies showed that the nifedipine in daily doses of 30 mg/kg given to rabbits treated with a diet containing 1% cholesterol for 6 months, decreased cholesterol content in aorta homogenates, urine excretion of desmosines and prolonged partial thromboplastin time, while it did not alter serum lipids. These results may have some value for understanding of the antiatherogenic mechanism of nifedipine.

Risk factors for the degradation of lung elastic fibers in the ventilated neonate. Implications for impaired lung development in bronchopulmonary dysplasia

In order to evaluate the risk for proteolytic destruction of lung parenchymal elastic fibers in ventilated premature infants, the concentrations of elastase were determined in tracheal aspirates of 65 infants from whom we obtained a total of 327 sequential samples. Elastase was detected at least once in 39 of the 65 infants studied. Eleven of these infants were ventilated with greater than 60% oxygen for greater than 5 days. In 19 infants, the presence of elastase was associated with positive bacterial and/or viral cultures and/or elevated ratios (greater than 0.22) of immature neutrophils to total neutrophils. Elastase was not detected in the lung secretions of 26 infants ventilated with greater than 60% oxygen for less than 3 days, suggesting minimal risk for elastic fiber destruction in the intubated infant who neither has pneumonia nor requires prolonged hyperoxic ventilation. The risk for elastic fiber destruction was further evaluated by analyzing sequential urine and tracheal aspirate samples for the presence of an elastolytic degradation product of elastin (desmosine). The biochemical data indicated a potential risk for proteolytic destruction of elastic fibers in association with infection and/or prolonged hyperoxic exposure. In addition, autopsy specimens obtained from three of the infants revealed structurally abnormal lung parenchymal elastic fibers. Because elastic fibers are believed to provide the structural support for alveolar septal development, proteolytic degradation of these fibers may be a significant factor in the impaired lung development that occurs in infants with bronchopulmonary dysplasia.

Fractionation of urine to allow desmosine analysis by radioimmunoassay

The present study was designed to re-evaluate the radioimmunoassay for desmosine in urine, which is currently used as a measure of elastin metabolism. Using ion exchange chromatography, gel filtration and affinity chromatography it was shown that at least five other compounds in hydrolysates of human urine competed for desmosine in the RIA. Fractionating the urine prior to hydrolysis with acetone removed one of the major contaminants. The other contaminants could subsequently be removed by extracting the urine hydrolysate with a mixture of chloroform/ethanol (60:40). Samples from nine normal adult urines showed that an average of 45% of the RIA competing material in unfractionated urine was not desmosine. The final extracted residue retained all of the desmosine and only 16% of the original solids. The average adult urine contains approximately 50 pmol desmosine/mg creatinine, reflecting a daily turnover of between 3 and 4 mg of elastin per day.

Urinary desmosine excretion as a marker of lung injury in the adult respiratory distress syndrome

Desmosine, the intermolecular and intramolecular cross link between the chains of elastin polypeptide, may be useful as a marker of a lung injury in adult respiratory distress syndrome (ARDS). A radioimmunoassay for rabbit antibody developed against desmosine, conjugated to bovine serum albumin, can detect as little as 100 pg of desmosine in plasma or urine. Desmosine is not metabolically absorbed, reused, or catabolized by the body, but rather eliminated unchanged in the urine as low molecular weight peptides. The lung is relatively rich in elastin, and we reasoned that a timed collection could be used as an index of elastin degradation in vivo. A 2-h collection of urine for desmosine assay was obtained at the time of Swan-Ganz catheter insertion in 41 consecutive patients. On the basis of clinical and initial Swan-Ganz catheter data, the patients were assigned to one of three groups: an ARDS group (n = 12); a cardiogenic pulmonary edema (CPE) group (n = 12); and a critically ill, nonpulmonary edema group (NPE, n = 17). The mean urine desmosine concentration (mg/L) for the ARDS group (0.728 +/- 0.22 SE) differed from the CPE group (0.149 +/- 0.07; p less than 0.001). The total excretion (microgram/2 h) was 64.95 +/- 24.7 in the ARDS group and 24.71 +/- 11.7 in the CPE group (p less than 0.05). Urine desmosine concentration/serum creatinine index for the ARDS group (0.78 +/- 0.28) was greater than in the CPE group (0.07 +/- 0.04; p = 0.019). Desmosine excretion was increased in the NPE group compared with CPE and ARDS groups, possibly reflecting heterogeneity in this group. In the differentiation of ARDS from CPE, we conclude that substantial increases in urinary desmosine excretion favor a diagnosis of ARDS.

Measurement of urinary desmosine by isotope dilution and high performance liquid chromatography. Correlation between elastase-induced air-space enlargement in the hamster and elevation of urinary desmosine

The accuracy of methods employed to measure the elastin-specific crosslinks, desmosine (DES) and isodesmosine (IDES), has been called into question because contaminants in the urine may cause elevated values. In the present study urine samples were spiked with a known amount of [14C]DES and refluxed in 6 N HCl. Sephadex G-15 chromatography of the hydrolyzed urine employed to remove contaminants. DES and IDES were quantified by high performance liquid chromatography (HPLC) as well as by amino acid analysis. The amount of isotope recovered was used to determine losses during the overall procedure and the isotope dilution to calculate the amounts of endogenous DES and IDES originally present in the urine. Because similar values were obtained by both methods, the more rapid HPLC method was used for all succeeding analyses. In one experiment, the DES amounts in urine collected from hamsters for 3 days after intratracheal treatment with human neutrophil elastase (300 micrograms) or porcine pancreatic elastase (300 micrograms) were 0.212 +/- 0.012 (mean +/- SEM, two measurements on a single pool) and 0.816 +/- 0.005 (two measurements) microgram per hamster per day, respectively. Urine from control hamsters had a mean value of 0.074 +/- 0.008 (eight measurements) microgram per hamster per day. The HNE- and PPE-treated hamsters had mean linear intercept values of 119 and 159% of control values, respectively, giving a positive correlation between increase in airspace size and elevation of urinary DES.(ABSTRACT TRUNCATED AT 250 WORDS)

Urinary desmosine, elastolysis, and lung disease

Desmosine is an amino acid specific to elastin. Animal studies suggest that urinary desmosine (UD) represents endogenous elastin degradation. Therefore, UD has previously been used to investigate endogenous elastolysis, but was not elevated in subjects with chronic obstructive airways disease (COAD), although accelerated pulmonary elastolysis is thought to contribute to COAD. We have investigated whether this reflects large day-to-day and between-subject variation in UD and whether, in man, dietary desmosine contributes significantly to that in urine. Mean 24-hour UD output (over 5 consecutive days) from 10 asymptomatic subjects (5 males) was higher in males than females (77.4 +/- 9.6 and 40.2 +/- 5.0 nmol/24 hours, respectively; mean +/- SD, P less than .001), but not significantly different when expressed in terms of creatinine (micrograms desmosine/100 mg creatinine: males, 2.5 +/- 0.4; females, 3.1 +/- 0.8; mean +/- SD). The lowest between-subject variation was observed when the mean of 5 days' 24-hour UD values was analyzed on the basis of gender (coefficient of variation [CV], 12.5%); when gender was not considered, the least between-subject variation was found for the mean of 5 days' desmosine/creatinine analysis (CV, 24.5%). Approximately 1% of dietary desmosine (ingested as [3H]elastin and [3H] desmosine) was excreted in the urine within 24 hours, contributing approximately 15% of UD while on a normal diet. Although ingestion of a low elastin diet (less than 1/10 desmosine/24 hours than a normal diet) resulted in lower within-subject variation in 24-hour UD excretion (mean CV decreased from 31.5% to 20.2%), the between-subject CV and UD levels did not alter.(ABSTRACT TRUNCATED AT 250 WORDS)

[An enzyme-linked immunosorbent assay for measuring desmosine in vivo]

Pulmonary emphysema may be a disease in which some elastin in lung is lost. In order to evaluate lung elastin degradation, we developed an enzyme-linked immunosorbent assay for desmosine and measured urinary desmosine excretion and serum desmosine levels in healthy individuals and patients with pulmonary emphysema and other chronic pulmonary disorders. The measurement was performed by the inhibition technique of ELISA so that the samples had to be applied to CF11 cellulose mini-column for partial purification of desmosine. Total urinary excretion of desmosine was uniformly low in healthy individuals and patients with lung cancer, but urinary desmosine was elevated in some cases of pulmonary emphysema and diffuse panbronchiolitis. Using this ELISA method, more than 0.06 micrograms/ml serum desmosine concentration could be measured in 3 out of 25 healthy subjects who had never smoked (13.6%), 4/9 healthy current smokers (44.4%) and 19/26 patients with pulmonary emphysema (73.1%). Mean serum desmosine levels of meseared 19 cases of empysema were 0.182 micrograms/ml. It has been reported that approximately 15% of smokers develop pulmonary emphysema. The most important problem now is whether smokers with elevated urinary desmosine or with high serum desmosine will eventuality develop pulmonary emphysema.

An enzyme-linked immunosorbent assay (ELISA) for the quantitation of urinary desmosine

An enzyme-linked immunosorbent assay (ELISA) method has been developed for the quantitation of the elastin cross-link desmosine in urine. The system employs Rabbit antisera directed to the conjugate of desmosine and bovine serum albumin which was conjugated using carbodiimide reagent. The ELISA was done in microtiter plates which were coated with a desmosine-gelatin conjugate. And the assay system is based on an inhibition immunoassay. With this assay system, desmosine could be detected in a range between 0.4-400 ng/ml. Recovery of desmosine (DES) added to urine was 90.6-117.0% as measured by this method. Anti-DES antisera obtained from rabbits, showed no cross-reaction to 19 standard amino acids, two elastines nor mouse acetone liver power (which contained degradated elastin). But iso-desmosine cross-reacted with the antisera 13-45% at the isodesmosine concentration range of 40-400 ng/ml. Column purification of the urinary desmosine with CF-1 cellulose will not be necessary for desmosine measurement in ELISA assay. This paper described the detail procedures for sample preparation and the desmosine measurement in urine. Desmosine measurement can be an effective marker for screening the lung elastin degradation caused by cigarette smoking and environmental pollution to human lung.

Urinary excretion of connective tissue protein markers in arterial disease

In diseases of major arteries there is an increased turnover of connective tissue components. This implies a greater excretion of fragments of collagen and elastin. The changes for each of these may be useful in further delineating the nature of the disease. In a preliminary study, the urine of 10 Marfan's syndrome patients was analyzed. The hydroxyproline (collagen) concentration was up to eight times higher than that of control subjects. The desmosine (elastin) crosslink concentration was either normal or slightly reduced in these patients. The mean of the ratio of hydroxyproline to desmosine was nearly seven times higher in the patients.

Early markers of lung injury

The goal of this study was to develop an early marker of lung injury that might change in response to exposure to a mobile source emission. Nitrogen dioxide (NO2)2 was chosen as an example of an atmospheric pollutant that is related to automobile emissions. Since reorganization of the connective tissue matrix of the lung occurs in response to injury, markers of connective tissue metabolism were selected as targets. Hydroxylysine became the marker of choice. It is an amino acid that is virtually exclusive to collagen, although it does occur in minimal amounts in other proteins. Furthermore, it is excreted in the urine, which makes it readily available for analysis using noninvasive techniques. Other markers evaluated as part of the study included angiotensin-converting enzyme as a marker of lung injury, desmosine as a marker of elastin degradation, and hydroxyproline as another marker of collagen metabolism. Male Fischer-344 rats were exposed in whole-body chambers to controlled concentrations of NO2 for various doses and periods of time. The concentrations of NO2 ranged from 0.5 to 30 parts per million (ppm); the rats were exposed for six hours per day for periods of two days to four weeks. Urine and bronchoalveolar lavage samples were collected and analyzed for the appropriate marker. In addition, pulmonary function studies and histologic examinations of the lungs were completed at selected time points. Urinary hydroxylysine concentration increased as a function of NO2 concentration during six-hour-per-day exposures for two days. This short-term exposure required relatively high doses to achieve significant changes in the hydroxylysine output. During one-week exposures to either 25 or 30 ppm NO2, there was an increase in urinary hydroxylysine associated with changes in lavage concentrations of angiotensin-converting enzyme and hydroxylysine. The lungs of these animals demonstrated histologic changes typical of oxidant injury. Four-week exposure protocols using 0.5 and 1 ppm NO2 were most interesting in terms of the sensitivity of the marker. There was minimal damage revealed by the histology and function studies, yet there were significant increases in the excretion of hydroxylysine. It appears that hydroxylysine can be indicative of exposure when other parameters are normal. It will require long-term follow-up of exposed rats to determine whether or not the change in marker concentration is predictive of damage. Hydroxylysine may be an excellent marker of exposure to oxidants in the human population. Controlled studies to establish base-line values are needed, followed by carefully controlled studies in individuals with connective tissue abnormalities of the lung.

Experience with an enzyme-linked immuno sorbent assay for the quantitation of urinary desmosine

An enzyme-linked immuno sorbent assay has been set up for the quantitation of the elastin crosslink desmosine. With the assay desmosine could be detected in the range 0.01-10 ng (the amount is corresponding to 0.4-400 ng/ml) in standard solutions. One hundred percent crossreactivity with isodesmosine was found. The low titer rabbit antiserum used in this inhibition immunoassay was less suitable for the measurement of desmosine in urinary hydrolysates, because a number of unknown urinary substances interfered with the measurement. Interfering substances could not be removed completely with a column purification method. Future research is needed to determine the applicability of the higher titer anti-desmosine antiserum from a second rabbit.

Pulmonary penetration of alpha 1-proteinase inhibitor administered parenterally to dogs

To study the penetration of alpha 1-proteinase inhibitor (A1Pl) into the lungs of healthy dogs, 83 mg/kg of active A1Pl was administered intravenously over 30 min followed by a bolus of 131I-A1Pl. Animals were lavaged 2 to 72 h after infusion, sequential gamma camera scans were acquired, and urine was analyzed for the excretion of desmosine. After a distribution phase, infused A1Pl left the bloodstream with a half-life of 103 +/- 24 h. Analysis of plasma antiprotease activity demonstrated preservation of function of the infused A1Pl. Lavage fluid A1Pl concentration and activity were significantly increased 24 h after infusion. Gamma camera scans demonstrated that lung, liver, and spleen acquired 131I-A1Pl similarly; radioactivities per gram of tissue of these organs were similar at autopsy. Excretion of desmosine did not decrease from a baseline of 157 +/- 59 nmol/24 h after A1Pl infusion, indicating no effect of A1Pl infusion on background elastolysis. These data suggest that intravenous administration of A1Pl can raise lung antiproteinase levels within 24 h despite the absence of preferential uptake by the lung of the infused protein.

Urinary excretion of desmosine (elastin cross-links) in subjects with PiZZ alpha-1-antitrypsin deficiency, a phenotype associated with hereditary predisposition to pulmonary emphysema

To evaluate the concept that lung elastin degradation is accelerated in homozygous alpha-1-antitrypsin (AAT) deficient persons, we prepared acid hydrolysates of urine and used a radioimmunoassay for desmosine to measure urine concentrations of this elastin-specific cross-link in such persons and in control subjects. Excretion of desmosine in 17 homozygous AAT-deficient (PiZZ) patients with emphysema was compared with that in 27 patients with interstitial lung diseases (16 sarcoid, 5 idiopathic pulmonary fibrosis, 6 other interstitial lung diseases) and 26 healthy subjects. Both smokers and nonsmokers were present in all groups. Urinary desmosine concentration (microgram/100 mg creatinine) was 2.35 +/- 0.93 in the PiZZ patients, 2.49 +/- 1.01 in those with interstitial lung disease, and 2.05 +/- 0.54 in the healthy control subjects (p greater than 0.1, all comparisons). Because abnormal pulmonary elastolysis may be largely completed before symptoms of emphysema develop in AAT-deficient persons, we also tested 6 asymptomatic adults with homozygous AAT deficiency (PiZZ) and 5 PiZZ children. Urine desmosine (microgram/100 mg creatinine) was not significantly elevated in either group compared with that in the age-matched control subjects, although children (PiZZ and age-matched controls) showed higher excretions than did adults (6 asymptomatic PiZZ adults, 2.60 +/- 0.91; 5 PiZZ children, 3.27 +/- 0.62; 10 control children, 3.61 +/- 0.62). These data suggest that pathologic lung elastolysis in the PiZZ subject may constitute too small a fraction of total-body elastin turnover to be detected by this method.(ABSTRACT TRUNCATED AT 250 WORDS)