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

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

Building Elastin. Incorporation of recombinant human tropoelastin into extracellular matrices using nonelastogenic rat-1 fibroblasts as a source for lysyl oxidase

The purpose of this study was to assess the feasibility of crosslinking exogenously produced tropoelastin, the precursor of insoluble elastin, into existing elastin. Tritiated recombinant human tropoelastin (rhTE) was added to neonatal rat aorta smooth-muscle cell (NNRSMC) cultures. As much as 12% of the added rhTE was incorporated into the NNRSMC-derived insoluble elastin with the formation of the elastin crosslinks desmosine (DES) and isodesmosine (IDES) in a time-dependent fashion. The ratio of radioactivity found in DES and IDES crosslinks to that found in lysyl residues increased from 0.18 immediately after incubation with rhTE to 0.76 after 14 d. Crosslinking of rhTE into elastin and the accompanying formation of tritiated water was inhibited by beta-aminoproprionitrile, a potent inhibitor of lysyl oxidase, an enzyme critical for the post-translational processing of elastin and collagen. Acellular NNRSMC matrices were produced and replated with Rat-1 fibroblasts, cells that were found to express lysyl oxidase but not tropoelastin. At 14 d after incubation with rhTE, the ratio of DES and IDES radioactivity to that of lysine in the insoluble elastin was 0.38. We show for the first time that cells expressing lysyl oxidase, but not elastin, as well as elastogenic cells can incorporate rhTE into insoluble elastin with the formation of elastin crosslinks. This novel approach might be used to augment elastin repair in certain pathologic states.

Water deficit effects on sweet corn. II. Canopy development

The response of sweet corn canopy development to timing and severity of water deficit was determined in an experiment using a mobile rainshelter. Six irrigation treatments were applied such that plots experienced: (1) no water deficit; (2) full water deficit; (3) moderate pre-silking deficit; (4) severe pre-silking deficit; (5) moderate post-silking deficit; or (6) severe post-silking deficit. Soil moisture content profiles were measured using neutron moisture probes and water deficit was quantified using the concept of ‘potential soil moisture deficit’ (Dp), which was calculated from climatic data. Water deficit reduced leaf area, and the effect varied depending on its timing and severity. Early water deficit reduced the rate of leaf expansion (but not duration of expansion) and, consequently, the maximum area of individual leaves; it therefore reduced the maximum leaf area index (LAI). Moderate post-silking water deficit did not significantly reduce maximum LAI, but it hastened leaf senescence. Severe water deficit late in crop growth reduced canopy development by decreasing maximum LAI and advancing leaf senescence. A model was developed which accounted for these effects. Two measures of Dp were defined which related to both short-term transient responses and those integrated over longer times. The model made it possible to simply and mechanistically describe the effects of water deficit on canopy development.

Water deficit effects on sweet corn. I. Water use, radiation use efficiency, growth, and yield

The responses of sweet corn biomass and yield to timing and severity of water deficit were determined in an experiment using a mobile rainshelter. Six irrigation treatments were applied such that plots experienced: (1) no water deficit; (2) full water deficit; (3) moderate pre-silking deficit; (4) severe pre-silking deficit; (5) moderate post-silking deficit; or (6) severe post-silking deficit. Drought was quantified using the concept of potential soil moisture deficit, which was calculated from climatic data. Potential soil moisture deficit can be related simply to a wide range of plant performance variables, making it possible to compare the relative importance of variables in determining the overall response of the crop to drought. For all treatments, yield was related strongly to biomass, especially that accumulated after silking. Biomass, in turn, was reduced by water deficit, mainly because of reduced radiation use efficiency, but also because of reduced total radiation interception, particularly in early deficit treatments. Both water use efficiency and transpiration efficiency increased with water deficit, even though soil evaporation as a proportion of total water use also increased with deficit. There was no stage of crop development at which yield was particularly sensitive to water deficit, although yield components changed with timing of deficit. Importantly, measures of potential soil moisture deficit integrated the effects of timing and severity of drought, making it possible to simply and mechanistically account for the effects of water deficit on biomass and particularly yield.

Azorhizobium caulinodans ORS571 colonizes the xylem of Arabidopsis thaliana

Improved conditions were used for the aseptic growth of Arabidopsis thaliana to investigate whether xylem colonization of A. thaliana by Azorhizobium caulinodans ORS571 might occur. When seedlings were inoculated with ORS571 (pXLGD4) tagged with the lacZ reporter gene, nearly all of the plants showed blue regions of ORS571 colonization at lateral root cracks (LRC). The flavonoids naringenin and liquiritigenin significantly stimulated colonization of LRC by ORS571. Blue bands of ORS571 (pXLGD4) bacteria were observed histochemically in the xylem of intact roots of inoculated plants. Detailed microscopic analysis of sections of primary and lateral roots from inoculated A. thaliana confirmed xylem colonization. Xylem colonization also occurred with an ORS571 nodC mutant deficient in nodulation factors. There was no significant difference in the percentage of plants with xylem colonization or in the mean length of xylem colonized per plant between plants inoculated with either ORS571 (pXLGD4) or ORS571::nodC (pXLGD4), with or without naringenin.

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.

Effects of glucosinolates and flavonoids on colonization of the roots of Brassica napus by Azorhizobium caulinodans ORS571

Plants of Brassica napus were assessed quantitatively for their susceptibility to lateral root crack colonization by Azorhizobium caulinodans ORS571(pXLGD4) (a rhizobial strain carrying the lacZ reporter gene) and for the concentration of glucosinolates in their roots by high-pressure liquid chromatography (HPLC). High- and low-glucosinolate-seed (HGS and LGS) varieties exhibited a relatively low and high percentage of colonized lateral roots, respectively. HPLC showed that roots of HGS plants contained a higher concentration of glucosinolates than roots of LGS plants. One LGS variety showing fewer colonized lateral roots than other LGS varieties contained a higher concentration of glucosinolates than other LGS plants. Inoculated HGS plants treated with the flavonoid naringenin showed significantly more colonization than untreated HGS plants. This increase was not mediated by a naringenin-induced lowering of the glucosinolate content of HGS plant roots, nor did naringenin induce bacterial resistance to glucosinolates or increase the growth of bacteria. The erucic acid content of seed did not appear to influence colonization by azorhizobia. Frequently, leaf assays are used to study glucosinolates and plant defense; this study provides data on glucosinolates and bacterial colonization in roots and describes a bacterial reporter gene assay tailored easily to the study of ecologically important phytochemicals that influence bacterial colonization. These data also form a basis for future assessments of the benefits to oilseed rape plants of interaction with plant growth-promoting bacteria, especially diazotrophic bacteria potentially able to extend the benefits of nitrogen fixation to nonlegumes.

The role of the carboxy terminus of tropoelastin in its assembly into the elastic fiber

Tropoelastin, the soluble precursor protein of insoluble amorphous elastin, contains repeating segments that are important for the characteristic elasticity and crosslinking sites of mature elastin. In addition, there is a unique carboxy terminal domain that is encoded by exon 36 of the elastin gene, and it has been suggested that this region may play a role in the process of insolubilization. The contribution of exon 36 to the maturation of tropoelastin into insoluble elastin was probed in these studies. Neonatal rat aortic smooth muscle cells were cultured and the fate of [3H] Lys labeled human recombinant tropoelastin (hrTE) molecules added to the cultures was monitored. In comparison to the hrTE containing the region encoded by exon 36, hrTE molecules lacking this domain were less efficiently incorporated into elastin, as evidenced by a decrease in NaOH insoluble radioactivity. Specific residues within the domain encoded by exon 36 were targeted for further study in experiments in which the two Cys residues were reduced and alkylated, and/or the four basic Arg-Lys-Arg-Lys residues at the carboxy terminus were removed. Both of these modifications resulted in decreased incorporation into elastin equivalent to the complete removal of the carboxy terminus. Prior treatment of the cell layer with elastase reduced the efficiency of insolubilization of hrTE containing the domain encoded by exon 36, but had no effect on the processing of molecules lacking this region. These data suggest that exon 36 of the elastin gene contributes to normal efficient incorporation of tropoelastin into the elastin fiber.

The zebrafish swimbladder: A simple model for lung elastin injury and repair

In this communication we offer data to suggest that the zebrafish swimbladder may provide a simple model of elastin injury and repair which is amenable to genetic analysis and pertinent to lung physiology. In situ hybridization of zebrafish embryos illustrated that elastin gene expression is evident in the developing gut tract prior to swimbladder morphogenesis. Northern blot analysis demonstrated that the major zebrafish elastin mRNA is 2.0 kb which is significantly smaller than its higher vertebrate counterpart. Amino acid analysis of alkali-resistant protein from the anterior chamber of the adult zebrafish swimbladder showed a composition similar to higher vertebrate elastins including significant amounts of desmosine crosslinks. Electron microscopic investigations of the swimbladder wall indicate a simple structure with an inner layer of elastin fibers. Elastase delivery to the swimbladder in vitro resulted in significant fragmentation of elastin in the anterior chamber providing an environment for studying elastin repair within the tissue.

Remodeling of alveolar walls after elastase treatment of hamsters. Results of elastin and collagen mRNA in situ hybridization

Treatment of hamster lungs with porcine pancreatic elastase (PPE) causes emphysema and a decrease in lung elastin content, which returns to control level by Day 30. To explore the mechanism of alveolar wall remodeling after elastolytic injury, we examined the expression of elastin and alpha1(I) collagen mRNAs by in situ hybridization at 1, 2, 3, 5, 7, and 30 d after intratracheal PPE. The lungs of control animals displayed weak signals for elastin and alpha1(I) collagen mRNA in pleura, large arteries, veins, and airways. There was little or no signal in respiratory air space walls. Increased expression of elastin and alpha1(I) collagen mRNA began by Day 1 after PPE and reached an asymptote by Day 3 that was maintained by elastin until Day 7; expression of alpha1(I) collagen mRNA waned earlier. Elastin and, to a lesser extent, alpha1(I) collagen mRNA were heavily expressed in pleura, blood vessels, and airways. Analysis of serial sections showed elastin message was minimal in the walls of respiratory air spaces and when present, at 3, 5, and 7 d, was primarily found at the free margins of alveolar septa. Collagen message was very sparse in respiratory air space walls. By 30 d, elastin mRNA expression was reduced but still above control levels and emphysema was widespread and severe. Rank score of elastin mRNA expression in individual subpleural air spaces showed a positive correlation with air space size. In conclusion, most expression of elastin and alpha1(I) collagen mRNA occurs in the pleura, airway, and vascular walls. In respiratory air space walls, expression of elastin mRNAs occurs in damaged tissue at free septal margins.

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.

Degradation and repair of elastic fibers in rat lung interstitial fibroblast cultures

BACKGROUND

Evidence from in vitro and in vivo studies indicates that damaged elastic fibers can be repaired.

METHODS

Lipid interstitial pulmonary fibroblasts were cultured for 6 weeks. Cultures were then exposed to 25 microg of porcine pancreatic elastase and fixed in pairs (control, elastase-treated) immediately after exposure and at 1, 2, 3, 4, 7, 10, 14, and 22 days for ultrastructural examination. Elastin was also analyzed biochemically for resistance to hot alkali, an indicator of repair. Steady-state levels of tropoelastin and lysyl oxidase mRNA at 2, 4, and 7 days after elastase treatment were determined by Northern blot analysis.

RESULTS

Immediately after exposure to elastase, damaged elastic fibers exhibited a frayed, porous appearance and a granular texture. Through day 4, fibers showed no evidence of repair. By day 7, the granular texture of damaged fibers was no longer evident and a gradual filling-in of porous areas appeared to be taking place. By 22 days, elastic fibers were indistinguishable from elastic fibers in control cultures. The ultrastructural changes were paralleled by changes in hot alkali resistance. Through day 4, there was no change in the level of hot alkali resistant elastin. Between day 4 and day 7, resistance to hot alkali increased sharply and continued to increase at a slower rate, reaching 84% of the control level by day 22. Steady-state levels of tropoelastin and lysyl oxidase mRNA showed no increase over control levels at 2, 4, and 7 days after elastase treatment.

CONCLUSIONS

Elastic fibers synthesized by lipid interstitial pulmonary fibroblasts in culture were repaired after damage by elastase. This type of repair may have relevance to the prevention of pathological conditions, such as emphysema.

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.

Repair of elastase-digested elastic fibers in acellular matrices by replating with neonatal rat-lung lipid interstitial fibroblasts or other elastogenic cell types

Disruption of elastic fibers is a major factor in the pathogenesis of pulmonary emphysema. Elastic fibers in culture, injured by exposure to elastase, undergo repair in the presence of elastogenic cells that restores the fibers toward normal as determined by biochemical and ultrastructural methods. The repair appears to be the result of both salvage and de novo repair mechanisms. The evidence for salvage repair is that hot-alkali resistance, lost as a result of elastase treatment, is restored to previously radiolabeled elastic fibers. This repair mechanism has been shown in aortic smooth muscle cell cultures. In order to determine the potential relevance of this mechanism for elastic fiber repair in the lungs, experiments were carried out using neonatal rat lung lipid interstitial fibroblasts (LIF). Treatment of the LIF cultures with elastase, in the absence of serum, caused solubilization of 12% of elastin; however, 81% of the elastin protein and 80% of the elastin-associated radioactivity (EAR) were solubilized by subsequent hot-alkali treatment, indicating that most of the elastin was retained in the matrix but was damaged. Ultrastructurally, the elastic fibers were frayed. After 6 additional wk in culture, hot-alkali resistant elastin protein and EAR were restored to 88 and 62% of control values, respectively, and the ultrastructural appearance of elastic fibers was restored to normal. We calculate that about 42% of the restored elastin represented salvage repair; the remainder was new elastin. No repair occurred in matrices rendered acellular by azide treatment; however, when acellular matrices were replated with LIF, repair was complete at 6 wk. No repair was seen when acellular matrices were replated with a transformed mouse macrophage cell line. We conclude that lung LIF are capable of mounting a robust repair process after elastolytic injury of elastin and that the repair is the result of both salvage and de novo repair mechanisms.

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.

Responses of grain growth and malting quality of barley to short periods of high temperature in field studies using portable chambers

Although environmental conditions during grain filling are often cited as the reason for decreases in malting quality of barley, little is actually known about the specific effects of different environmental conditions on grain yield and quality of barley. In the present study, an attempt was made to assess in the field the effects of short periods of high temperature (>35�C), using portable chambers with thermostatically controlled electric heaters, on grain yield and quality of barley. Two experiments were carried out in 2 consecutive years, involving the malting barley cultivars Schooner (first year) and Parwan (second year). The treatments were (i) control (no chamber, no heating) during the whole grain-filling period, (ii) plots with chambers heated to ca. 40�C for 6 h per day over 5 days starting 17 days after anthesis, and (iii) plots with non-heated chambers for 5 days from 17 days after anthesis. High temperature treatments reduced individual grain weight by 14% in Schooner and 25% in Parwan. There was a reduction in starch content and an increase in nitrogen content in the heat treatments compared to the control, but the G-glucan content was similar to the control. The resulting malt extract was reduced from 79 to 73% in Schooner and from 68.4 to 66.2% in Parwan in ,the heat stress treatment. The starch granule size distribution was also measured. Results indicate that decreases in grain dry matter were due to reductions in number rather than size of starch granules. It is concluded that high temperature reduced the amount of 'maltable' grain by reducing grain size and increasing the screening percentage, and also reduced malt extract by 3-7%, which represents a large decrease for the malting industry.

Immunocytochemical study of the degradation of elastic fibers in a living extracellular matrix

We used ultrastructural and immunocytochemical technique to follow the movement of human neutrophil elastase (HNE) and porcine pancreatic elastase (PPE) through a living extracellular matrix produced by cultured smooth muscle cells and to compare the effect of the two elastases on elastic fibers in situ. Although both enzymes solubilize elastin purified from these cultures at similar rates, PPE solubilized 11.5 times more elastin from the intact cultures than did HNE. The difference in the rate of elastin solubilization from the cultures parallels the degree of elastic fiber degradation and the emphysema-inducing potency of the two elastases when they are instilled into animal lungs. Immunohistochemical studies employing antibodies to HNE and PPE revealed that PPE penetrates the smooth muscle cell cultures more readily than does HNE. Because the amount of elastin in these cultures increases with increasing distance from the free surface, the lesser amounts of elastin solubilized by HNE may be partly due to poor penetration of HNE into the living extracellular matrix, resulting in limited access to elastin substrate. Ultrastructural and immunocytochemical studies indicated, however, that even when HNE does have access to elastin substrate, it is less efficient than PPE at penetrating and degrading individual elastic fibers.

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.

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.

A survey of the effects of high temperature during grain filling on yield and quality of 75 wheat cultivars

The responses of 75 cultivars of wheat to a short (3 day) period of very high temperature (40�C max.) applied at either 10 or 30 days after anthesis were examined under controlled conditions. The effect of high temperature on a number of yield (grain number, individual kernel mass and N per kernel) and quality components (protein composition, apparent amylose content and noodle swelling power) is described for the sample population and for a number of varieties which were either particularly heat tolerant or sensitive. Genotypic variation of response to high temperature of the order of 20% was recorded for the majority of yield and quality components. The fact that responses of this magnitude were caused by exposure to high temperatures lasting only 5 to 6% of the grain filling period demonstrates the extent to which short periods of very high temperature may affect wheat yield and quality.

Pitfalls in antiprotease therapy of emphysema

Many individuals with emphysema are unable to stop smoking despite the best efforts of specialists in smoking cessation. Because emphysema is a slowly progressive disease, it is rational to attempt to develop drugs for it. The hope is that drug therapy will slow the rate of decline of lung function, thereby delaying the onset of disability and prolonging life. The major emphasis in drug development has been on antiproteases having the ability to inhibit neutrophil elastase. There are a number of potential pitfalls in the development of such drugs. Although there is gathering evidence that elastin degradation is a part of the development of human emphysema, it is evident from studies in experimental emphysema that protease-antiprotease imbalance is not the only pathogenetic mechanism that gives rise to emphysema. There is strong evidence that human centrilobular and panacinar emphysema are different in pathogenesis. Indeed, airspace enlargement may be considered one of the stereotyped ways that the lung heals after a variety of injuries. There is accumulating evidence that macrophages as well as neutrophils may participate in elastolysis; antiproteases designed to inhibit neutrophil elastase may not inhibit the metalloproteases produced by macrophages. Some antiproteases may serve to transport elastase into the interstitium of the lung and actually increase the risk of emphysema. A process study of antiprotease therapy, using a measure of alteration of elastase burden of the lungs and urinary elastin peptides and desmosine measurements as markers of elastin degradation is now feasible. An outcome study of antiprotease therapy of emphysema should not be undertaken unless there is evidence from a process study that an antiprotease has biochemical efficacy and no unacceptable side effects.

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)

Neutrophil proteases associated with amyloid fibrils

We found significant amounts of enzymatic activity characteristic of the human neutrophil proteases, elastase and cathepsin G, associated with isolated amyloid fibrils from patients with five different types of systemic amyloidosis. Amyloid deposits in tissue sections from the patients with amyloid A, amyloid transthyretin and amyloid beta 2-microglobulin amyloidosis also stained positive with antiserum to elastase and cathepsin G. Elastase and cathepsin G, found in the azurophilic granules of the neutrophil and, to a lesser extent, the monocyte, may become associated with amyloid precursor proteins before or during the formation of amyloid fibrils. This may occur in an extracellular inflammatory microenvironment or in a phagolysosome and play a role in the formation of the fibrils.

Cloning and sequence analysis of the glucoamylase gene of Neurospora crassa

A 1.0-kb DNA fragment, corresponding to an internal region of the Neurospora crassa glucoamylase gene, gla-1, was generated from genomic DNA by the polymerase chain reaction, using oligonucleotide primers which had been deduced from the known N-terminal amino-acid sequence or from consensus regions within the aligned amino-acid sequences of other fungal glucoamylases. The fragment was used to screen an N. crassa genomic DNA library. One clone contained the gene together with flanking regions and its sequence was determined. The gene was found to code for a preproprotein of 626 amino acids, 35 of which constitute a signal and propeptide region. The protein and the gene are compared with corresponding sequences in other fungi.

Electron microscopic study of human lung tissue after in vitro exposure to elastase

Much of the experimental evidence supporting the hypothesis that pulmonary emphysema results from an imbalance between elastases and anti-elastases in the lung comes from animal models. The present study was designed to examine the effects on human lung tissue of the two elastases that have been most widely used to produce these animal models. Lung tissue was exposed in vitro to human neutrophil elastase (HNE) or porcine pancreatic elastase (PPE). Although both enzymes solubilized protein at similar rates, PPE solubilized elastin five times faster than did HNE. Ultrastructurally, HNE-exposed tissue exhibited fewer damaged elastic fibers as well as some fibers that were damaged at the edges, whereas the interior of the fiber appeared intact. Elastic fibers showing damage only at the periphery were not seen in tissue exposed to PPE. Immunocytochemical studies in which antibodies to HNE and PPE were applied to thin sections of Lowicryl-embedded tissue indicated that both of these elastases could be detected in association with elastic fibers, but only in areas of the fiber that showed morphological evidence of elastase injury. Both HNE and PPE removed fibronectin from basement membranes (as determined by loss of binding of fibronectin antibodies after exposure to elastase), but neither elastase was detected on basement membrane. Loss of epithelial cells usually accompanied elastic fiber damage by HNE but not PPE.

Relationship of secretory granule content and proliferative intensity in the secretory compartment of the hamster bronchial epithelium

We have previously shown that normal hamster airway epithelial secretory cells have a lower proliferative intensity than basal cells, but because of their high frequency are a major contributor to cell renewal (Am. J. Respir. Cell Mol. Biol. 1990; 2:51-58). In the present experiment, the relation between proliferative intensity and secretory granule content in bronchial epithelial cells is studied. [3H]thymidine (2 microCi/g wt) was given intraperitoneally, 1 h before killing, to 5 hamsters treated 21 days earlier with intratracheal saline and to six hamsters in which secretory cell metaplasia had been induced by intratracheal treatment with 300 micrograms of human neutrophil elastase given 21 days earlier. Light microscopic autoradiograms were prepared from 2-microns-thick Epon sections of left intrapulmonary hilar bronchi. Cells were categorized as basal, ciliated, secretory, or indeterminate. Secretory cells were classified as either: S1, with 0 to 4 granules; S2, with > or = 5 granules with intervening cytoplasm; or S3, with abundant granules and no apparent supranuclear cytoplasm. Proliferative intensity was defined by the categorical labeling index (LIc) at 1 h after [3H]thymidine injection. LIc was determined by the number of labeled cells in a category as the percent of labeled and unlabeled cells of that category. LIc of each of the cell categories were similar in the elastase and saline groups. LIc was highest for basal cells, reflecting their proliferative intensity, and lowest for ciliated cells. In the saline group, LIc of S1 (0.25%) was significantly higher compared with S2 (0.13%); S3 cells were rare (0.2%) and none were labeled.(ABSTRACT TRUNCATED AT 250 WORDS)

Elastase causes secretory discharge in bronchi of hamsters with elastase-induced secretory cell metaplasia

A single intratracheal instillation of human neutrophil elastase (HNE) into hamsters causes granule discharge from bronchial secretory cells followed by marked accumulation of granules, visible by light microscopy at 21 days and persisting through 18 months. To determine whether persistence of this secretory cell metaplasia (SCM) is due to inability of the metaplastic secretory cells to secrete their granules, hamsters having HNE-induced SCM were challenged with the potent secretagogue HNE. Four groups of 10 hamsters each received 300 micrograms HNE intratracheally. Twenty-one days later, hamsters were intratracheally treated with HNE or saline; the groups were designated HNE-HNE and HNE-SAL, respectively. Hamsters were killed 2 h or 21 days following the second treatment. Using light microscopy, nucleated epithelial cells were counted in plastic sections of the left main intrapulmonary bronchus. Cells were classified as ciliated (C), basal (B), indeterminate (IN), or secretory. Secretory cells were subcategorized as S0 (0 granules), S1 (1-4 granules), S2 (> or = 5 granules with intervening cytoplasm), and S3 (abundant granules completely filling the cytoplasm). At 2 h, S3 cell frequency in the HNE-HNE group was 13.0 +/- 2.2 (% mean +/- SE), significantly lower than in the 2 h HNE-SAL group (31.1 +/- 4.5). Concomitantly, higher cell frequencies were seen in the other secretory categories of the HNE-HNE group compared to the HNE-SAL group; S2 17.1 +/- 1.9 compared to 9.4 +/- 1.9, S1 2.4 +/- 0.4 compared to 1.1 +/- 0.5, and S0 2.4 +/- 0.5 compared to 1.1 +/- 0.5, respectively. The S3 cell frequency of the 21-day HNE-HNE group was 25.4 +/- 4.7, increased significantly compared to the 2 h HNE-HNE group; this change was concomitant with significant decrease in the frequency of the S0 secretory cells. Cell frequencies of C, B, and IN were not affected by treatment or time. It is concluded that metaplastic secretory cells discharge their granules in response to HNE; SCM returns to its original state after HNE rechallenge; persistent SCM is not due to the inability of metaplastic secretory cells to discharge their granules.

Oxidants from neutrophil myeloperoxidase do not enhance elastase-induced emphysema in the hamster

Alpha-1-protease inhibitor is susceptible to oxidative impairment by the neutrophil myeloperoxidase (MPO) system. The purpose of this study was to assess the effect of the MPO oxidant system on elastase-induced emphysema in the hamster. Intratracheal instillation of 200 micrograms of human neutrophil elastase (HNE) induced a significant secretory cell metaplasia (SCM) and airspace enlargement [23% increase in mean linear intercept (MLI) as compared with control values]. Instillation of MPO system components [0.6 international units (U) of MPO, 5.5 U of glucose oxidase and glucose (0.02 M)] along with 200 micrograms HNE failed to enhance the severity of the SCM or emphysema induced by HNE alone. A second experiment was carried out using 50 micrograms of porcine pancreatic elastase (PPE) to induce emphysema. PPE produced a significant 45% increase in MLI, but the MPO system combined with PPE failed to enhance the emphysema induced by PPE alone. The MPO system alone had no measurable effect on airspace size or SCM. In vitro studies showed that PPE was partially inactivated by the MPO system; a 56% loss of elastolytic activity occurred during a 6-min incubation of PPE with the MPO system. This may explain why the MPO system did not exacerbate PPE-induced injury, but it does not explain the lack of enhancement for HNE. A 6-minute incubation of HNE with the MPO system resulted in a nonsignificant 10% decrease of elastolytic activity.(ABSTRACT TRUNCATED AT 250 WORDS)

Isolation of hydroxylysyl pyridinoline, a mature collagen crosslink from neonatal rat aorta smooth muscle cell cultures

Hydroxylysyl pyridinoline (HP) is a nonreducible collagen crosslink derived from three posttranslationally modified lysyl residues. Neonatal rat aorta smooth muscle cell cultures (NNRSMC) produce mg amounts of insoluble collagen. The purpose of the present study was to evaluate the capability of NNRSMC to produce collagen containing HP crosslinks. Cultures were pulsed with [14C]-lysine and then chased for five weeks. Insoluble collagen was prepared by digestion of the cell layer material with porcine pancreatic elastase and trypsin. After acid hydrolysis and cation-exchange chromatography, purified HP was isolated by reversed phase ion-paired chromatography. The material eluting from the HPLC was monitored continuously at 295 nm and the ultraviolet absorption spectrum was recorded every 21 msec. The ultraviolet spectrum of the HP peak was virtually identical to that of standard HP run on the HPLC. The HP exhibited a homogeneity of 97.3% when the ultraviolet spectrum of the apex of the peak was compared with the spectra of the shoulders of the peak. The radioactive HP also exhibited the expected fluorescence emission spectrum. We calculate a mean of 0.40 +/- 0.03 nmol HP/nmol collagen in the three experiments as compared with reported values of 0.57 +/- 0.1 for rabbit aorta. This is the first report of cell culture biosynthesis of chemically measurable amounts of HP. Using such pulse-chase techniques one can study the maturation of intermediate collagen crosslinks into HP. HP can also be used as a marker to study the metabolism of mature collagen molecules during normal and pathologic states.

Covalently linking a peptidyl carbamate elastase inhibitor to a hydrophilic polymer increases its effectiveness in preventing emphysema and secretory cell metaplasia in the hamster

A peptidyl carbamate, p-nitrophenyl N-(succinyl-L-alanyl-L-alanyl-L-prolyl-methyl)-N-isopropylcarbamate++ + (PCI) was tested for its ability to inhibit the elastolytic activity of human neutrophil elastase (HNE) and to prevent HNE-induced emphysema and secretory cell metaplasia in the hamster. In vitro, 50% of the elastolytic activity of 10 micrograms of HNE was inhibited by 0.9 micrograms of PCI, a molar ratio of PCI to HNE of 4.5. Bronchoalveolar lavage of hamsters receiving PCI intratracheally showed a rapid decrease in HNE inhibitory activity (4 min for 50% decrease), suggesting rapid clearance, binding, or inactivation of the PCI. Instillation of 300 micrograms of HNE combined with 100, 500, or 3,000 micrograms PCI, a 16-, 83-, and 503-fold molar excess of PCI, respectively (molar ratios of 17, 84, and 504), suppressed HNE-induced lung hemorrhage, but it did not moderate HNE-induced emphysema despite the large molar excess of inhibitor. When PCI was covalently bound to a linear hydrophilic polymer of alpha,beta-poly[N(2-hydroxyethyl)-D,L-aspartamide], producing a polymer-bound carbamate inhibitor (PPCI) of HNE, the time for a 50% decrease of PPCI functional activity from the hamster lung lavage was 421 min. Instillation of 100 micrograms of PPCI 1 h before instillation of 300 micrograms HNE resulted in significant amelioration of emphysema; 900 micrograms of PPCI was required to obtain amelioration of bronchial secretory cell metaplasia. The larger dose of PPCI also provided significant amelioration of emphysema when the interval between PPCI and HNE administration was 8 h.(ABSTRACT TRUNCATED AT 250 WORDS)

Alterations of tropoelastin biosynthesis by elastase damage to smooth muscle cell matrices

The effect of porcine pancreatic elastase (PPE)-induced proteolysis of the extracellular matrix on elastin biosynthesis in neonatal rat aortic smooth muscle cell cultures (NRSMC) was examined. The quantity of insoluble elastin remaining in the damaged cultures decreased with increasing amounts of enzyme used, however no significant cell damage was demonstrated. The accumulation of soluble elastin (tropoelastin) was examined in enzyme injured and control cultures by radiolabelling with [3H]-valine for 4 hours. The tropoelastin content of both the cell layer and media were less in injured cultures on the day of injury and up to one week later when compared to control cultures. In addition, experiments in which cultures were radiolabelled for 15 minutes demonstrated that the biosynthesis of tropoelastin was decreased in the enzyme treated cultures. Moreover, the incorporation of radiolabelled elastin into the insoluble matrix also decreased. Steady-state levels of elastin mRNA showed no differences between injured and control cultures, which suggested that elastin synthesis is affected at a translational or post-translational level.

Resistance of hamster bronchiolar epithelium to neutrophil elastase: investigation by cell surface lectin cytochemistry

An intratracheal instillation of human neutrophil elastase (HNE) causes accumulation of an excess number of secretory granules in the epithelial secretory cells lining the hamster bronchus. This chronic lesion, which we refer to as secretory cell metaplasia (SCM), is not seen in the trachea or bronchioles. Because luminal cell surface lectin binding is much higher in the trachea than in the bronchus, we concluded that tracheal resistance may be due to a protective glycoconjugate coat. In the present ultrastructural study, we analyzed the lectin-binding capability of bronchiolar epithelial cells to determine whether their luminal cell surface glycoconjugate layer is similar to tracheal epithelial cells. None of the six ferritin-conjugated lectins showed higher binding in bronchioles compared to the bronchus, suggesting that a high level of surface oligosaccharides is not necessary for resistance to the metaplastic effects of HNE. HNE caused a significant reduction in bronchiolar surface binding of the gold-labeled, secretory cell-specific lectin, Helix pomatia agglutinin. The principal granulated secretory cell type in bronchioles was ultrastructurally similar to a form of bronchial Clara cell that converts to a mucous cell phenotype in response to HNE. The results suggest that absence of bronchiolar SCM is not attributable to a protective layer of cell surface oligosaccharides, a lack of cellular contact by HNE, or the presence of a morphologically distinct population of epithelial cells in bronchioles.

A cytosolic inhibitor of human neutrophil elastase and cathepsin G

The neutrophil serine proteinases elastase and cathepsin G produce connective tissue injury, the extent of which depends on the balance between these enzymes and their inhibitors. The most important of these inhibitors is alpha 1-proteinase inhibitor, a member of a superfamily of homologous proteins known as serpins. Neutrophil cytosol inhibited the activities of human neutrophil elastase and cathepsin G in a dose-dependent fashion. To demonstrate formation of an enzyme-inhibitor complex, we combined 125I-elastase or 125I-cathepsin G with neutrophil cytosol or alpha 1-proteinase inhibitor and analyzed the products by polyacrylamide gel electrophoresis. Unbound elastase and cathepsin G each migrated to an apparent molecular weight of 25 kDa. In the presence of cytosol from neutrophils both radiolabeled enzymes migrated with a relative size of 68 kDa, whereas in the presence of alpha 1-proteinase inhibitor the relative size was 85 kDa. Enzyme-inhibitor complexes were stable in sodium dodecyl sulfate at 100 degrees C but were dissociated by hydrolysis in ammonium hydroxide (1.5 mol/L) at 37 degrees C. Formation of each complex was prevented by pretreatment of elastase or cathepsin G with diisopropylfluorophosphate, indicating that the inhibitor binds to the active site of the enzyme. Exposure of either alpha 1-proteinase inhibitor or neutrophil cytosol to the myeloperoxidase-H2O2-halide system prevented complex formation, suggesting the presence of an oxidizable amino acid at the binding site of the inhibitor. By electrophoretic analysis, the molecular weight of the cytosolic inhibitor was 43 kDa and neutrophils contained approximately 1 attomol of inhibitor per cell. The isoelectric points of the elastase and cathepsin G inhibitor were 5.5-5.9 and inhibitors of the two proteinases coeluted using size exclusion chromatography. These data demonstrate that human neutrophil cytosol contains a single serpinlike protein that inhibits elastase and cathepsin G. The inhibitor may be important in protecting the intracellular environment from proteolytic injury during degranulation.

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)

Putative role of neutrophil elastase in the pathogenesis of emphysema

Emphysema in humans takes several different forms: centrilobular, panacinar, paraseptal, and airspace enlargement with fibrosis. The varying morphologic and background features of these forms of emphysema suggest that they differ in pathogenesis. Elastic fiber rupture and fraying are a feature of emphysema. Experimental emphysema may be induced by human neutrophil elastase and other elastolytic enzymes but not by nonelastolytic proteases. Disruption of elastic fibers also appears to be the underlying feature of lathyrogen-induced airspace enlargement and of the emphysema in the blotchy mouse. However, there is no evidence of elastic fiber destruction in cadmium-induced airspace enlargement with fibrosis or in emphysema associated with hyperoxia or severe starvation. Thus, elastic fiber disruption is not common to all forms of experimental emphysema. We posit that airspace enlargement may be a stereotyped response of the lungs to different injuries. Emphysema can be induced in experimental animals by repeated induction of pulmonary neutrophilia. However, the evidence for involvement of neutrophil elastase in human emphysema is not clear: there are studies using a variety of approaches that weigh on both sides of the question. There is also in vitro evidence that alveolar macrophages can degrade elastin or elastic fibers with which they are in contact by means of a metalloelastase or the cooperative action of plasminogen activator and an acid cysteine protease. We conclude that the pathogenesis of emphysema is complex. Neutrophil elastase likely plays a major role in the development of some forms of emphysema, but our understanding of the interactions between the alveolar walls and neutrophils is still fragmentary.

Lectin cytochemistry reveals differences between hamster trachea and bronchus in the composition of epithelial surface glycoconjugates and in the response of secretory cells to neutrophil elastase

Hamsters exposed to an intratracheal instillation of human neutrophil elastase (HNE) accumulate an abnormally high number of secretory granules in bronchial but not tracheal epithelial cells. We employed lectin cytochemistry to investigate possible differences in the epithelial cell surface glycoconjugate layer in trachea compared to bronchus which might explain the regional dissimilarity in response to HNE. Portions of glutaraldehyde-fixed trachea and bronchi were incubated in one of several ferritin-labeled lectins prior to embedding for transmission electron microscopy. Lectins from Ricinus communis, Helix pomatia, and Triticum vulgaris bound to the surface of tracheal secretory cells in moderate to profuse amounts, while most bronchial secretory cells showed little or no label with these lectins. Gold-labeled Helix pomatia agglutinin (HPA), a lectin specific for secretory cells, showed a decrease in surface binding to all tracheal secretory cell types within 2 h of HNE instillation, compared to saline controls. In contrast, the majority of bronchial secretory cells showed an HNE-induced increase in surface label from extremely low levels in saline controls. The low levels of lectin binding to bronchial cells, in contrast to the trachea, may indicate the lack of a protective surface glycoconjugate coat, thus explaining the vulnerability of these cells to HNE. The rise in number of accessible HPA binding sites on the surface of bronchial secretory cells exposed to HNE may represent an important event in the pathologic accumulation of secretory granules by these cells.

Alpha 1-protease inhibitor moderates human neutrophil elastase-induced emphysema and secretory cell metaplasia in hamsters

A study was undertaken to determine whether emphysema and airway secretory cell metaplasia, induced in hamsters by intratracheal treatment with human neutrophil elastase (HNE), could be moderated by pretreatment with human alpha 1-protease inhibitor (API). API (4.9 mg) was given intratracheally to hamsters 1 h before 0.3 mg HNE. Eight weeks later, lung volumes and pressure-volume relationships were measured in the anaesthetized animals. Mean linear intercepts and secretory cell indices were measured in lung sections. API given 1 h before HNE moderated the development of bronchial secretory cell metaplasia. The severity of emphysema was reduced by 75%. Clearance studies indicated that 80% of the functional activity of instilled API could be lavaged from the lungs after 1 h, indicating a 4 h half-life in the lavageable compartment of the lungs. We calculate that for 50% protection from emphysema the molar ratio of lavageable API to HNE at the time of HNE instillation was 4.8 as compared with 0.78 for 50% inhibition of elastolytic activity in vitro, indicating that API is only 16% as efficient in vivo as compared with its in vitro HNE inhibitory effectiveness. Nevertheless, we conclude that human API given intratracheally is efficacious against HNE-induced emphysema and secretory cell metaplasia.

Alpha 1-protease inhibitor moderates human neutrophil elastase-induced emphysema and secretory cell metaplasia in hamsters

A study was undertaken to determine whether emphysema and airway secretory cell metaplasia, induced in hamsters by intratracheal treatment with human neutrophil elastase (HNE), could be moderated by pretreatment with human alpha 1-protease inhibitor (API). API (4.9 mg) was given intratracheally to hamsters 1 h before 0.3 mg HNE. Eight weeks later, lung volumes and pressure-volume relationships were measured in the anaesthetized animals. Mean linear intercepts and secretory cell indices were measured in lung sections. API given 1 h before HNE moderated the development of bronchial secretory cell metaplasia. The severity of emphysema was reduced by 75%. Clearance studies indicated that 80% of the functional activity of instilled API could be lavaged from the lungs after 1 h, indicating a 4 h half-life in the lavageable compartment of the lungs. We calculate that for 50% protection from emphysema the molar ratio of lavageable API to HNE at the time of HNE instillation was 4.8 as compared with 0.78 for 50% inhibition of elastolytic activity in vitro, indicating that API is only 16% as efficient in vivo as compared with its in vitro HNE inhibitory effectiveness. Nevertheless, we conclude that human API given intratracheally is efficacious against HNE-induced emphysema and secretory cell metaplasia.

The specific treatment of emphysema

Cigarette smoking is the major risk factor for development of emphysema. Many people are unable to stop smoking despite skilled support. The elastase-antielastase imbalance hypothesis for the pathogenesis of emphysema suggests that treatment with a supplemental elastase inhibitor might prevent development of emphysema in susceptible people. Many elastase inhibitors have been developed. Poorly soluble inhibitors do not prevent emphysema when tested in an animal model of elastase-induced emphysema. Irreversible inhibitors are effective in a dose-response manner. Reversible but tight-binding large molecular weight inhibitors, which clear slowly from the lungs, are effective in vivo. Small molecular weight, reversible inhibitors prevent haemorrhage after human neutrophil elastase instillation into the lungs but may potentiate emphysema. Only 15% of long-term smokers are susceptible to the development of emphysema. Susceptible smokers can be identified by the development of airflow obstruction. An outcome study of efficacy of elastase inhibitor therapy would be prohibitively expensive. However, a study of the process of development of elastase-induced emphysema is feasible. Measurement of alterations in elastase load of the lungs, elastase derived fibrinopeptides, circulating elastin peptides and urinary desmosines could be used for this purpose.

Recombinant human secretory leukocyte-protease inhibitor: in vitro properties, and amelioration of human neutrophil elastase-induced emphysema and secretory cell metaplasia in the hamster

Studies were undertaken to evaluate the in vitro properties of recombinant human secretory leukocyte-protease inhibitor (rSLPI) that had been made in Escherichia coli in an inactive form and refolded, and to determine whether emphysema and bronchial secretory cell metaplasia, induced in hamsters by intratracheal treatment with human neutrophil elastase (HNE), could be amelio-rated by prior intratracheal instillation of rSLPI. Chromatographic studies indicated that 3H-rSLPI formed a 1:1 complex with HNE. Blockage of the active site of HNE by a covalently bound tetrapeptide chloromethyl ketone reduced complex formation with 3H-rSLPI by more than 98%. Incubation of 3H-rSLPI-HNE complex with alpha 1-protease inhibitor for 3 hours at 37 degrees C decreased the amount of complex compared with incubation in the presence of bovine serum albumin (70% vs 27% dissociated). The calculated dissociation rate constant was 1.1 x 10(-4) sec-1, indicating a 1.8 hour dissociation half-life. Dissociated 3H-rSLPI retained its ability to recombine with HNE. rSLPI was as effective at inhibiting HNE released from stimulated neutrophils as 3H-rSLPI was at inhibiting purified HNE. Intratracheal pretreatment of hamsters with 3000 micrograms of rSLPI as long as 8 hours before the intratracheal instillation of 250 micrograms of HNE, resulted in significant protection against induction of emphysema and secretory cell metaplasia. One and 4 hours after instillation of rSLPI, 59% and 44%, respectively, of the initial functional activity was recovered in lung lavage supernatant, indicating a half-life of approximately 2 hours.(ABSTRACT TRUNCATED AT 250 WORDS)

Induction and exacerbation of emphysema in hamsters with human neutrophil elastase inactivated reversibly by a peptide boronic acid

In solution, MeO-Suc-Ala-Ala-Pro-D,L-boro-Val pinacol ester (Boroval) is a highly effective but reversible inhibitor of both porcine pancreatic elastase and human neutrophil elastase (HNE) (50% inhibition with a 1.5 M ratio of Boroval to elastase). Boroval has been shown to prevent porcine-pancreatic-elastase-induced emphysema in hamsters. But with HNE-induced emphysema in hamsters, pretreatment with as much as a 170-fold M excess of Boroval, given intratracheally 1 h before 0.3 mg HNE, did not prevent emphysema. Indeed, lung volumes were larger after Boroval pretreatment than after HNE alone. Emphysema was also induced by instilling HNE that had been mixed with and inactivated by a 41-fold M excess of Boroval (a molar ratio of 42). When 0.25 or 0.5 mg of HNE were given mixed with a 41-fold M excess of Boroval, the emphysema was much more severe with the 0.5 mg dose. Two hours after instillation of 0.3 mg HNE inactivated with a 34-fold M excess of Boroval, bronchoalveolar lavage contained elastolytic activity but no evidence of hemorrhage. In contrast, hemorrhage was severe in hamsters that had been instilled with 0.3 mg HNE alone. We conclude that Boroval can enhance HNE-induced emphysema. We postulate that Boroval suppresses HNE-induced hemorrhage and the resultant influx of plasma protease inhibitors; the HNE-Boroval complex is transported into the alveolar interstitium, followed by dissociation of the inhibitor from the active site of HNE. Because of its small size, free Boroval is rapidly cleared, and the reactivated HNE attacks elastic fibers, giving rise to emphysema.