Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0034067 (emphysema)
 11,506 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

It is clear that alpha 1AT deficiency leads to early onset pulmonary emphysema. With the lead provided by the deficiency state, studies aimed at the linkage between alpha 1AT and its target enzyme, neutrophil elastase, have provided useful information about the pathogenesis of emphysema due to cigarette smoking. alpha 1AT represents the predominant antielastase of the lower respiratory tract. This observation implicates neutrophil elastase as the enzyme responsible for lung destruction, since affinity studies demonstrate that alpha 1ATs physiologically relevant function is the inhibition of neutrophil elastase. However, because of the inexorably slow nature of the emphysema process, demonstration of the protease-antiprotease imbalance in the lungs of smokers has been difficult. Studies using sensitive assays for alpha 1AT function and for neutrophil elastase's presence have added new support for the protease-antiprotease theory, and evaluation of related disorders such as the adult respiratory distress syndrome and cystic fibrosis have provided corraborative evidence. Finally, studies that have indicated that the major site of the protease-antiprotease imbalance is the microenvironment of protease-producing cells offer a new direction for future research into the pathogenesis of emphysema.
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PMID:Pathogenesis of emphysema. Assessment of basic science concepts through clinical investigation. 278 6

Alpha 1-Antitrypsin (alpha 1AT) deficiency is characterized by insufficient amounts of alpha 1AT to protect the lower respiratory tract from neutrophil elastase, resulting in emphysema. Yeast-produced recombinant alpha 1AT (rAAT) has normal antielastase function but is associated with high renal clearance, thus obviating chronic intravenous administration. As an alternative, we evaluated aerosol administration of rAAT to alpha 1AT-deficient individuals. After aerosol administration of single doses of 10-200 mg of rAAT, epithelial lining fluid (ELF) alpha 1AT antineutrophil elastase defenses were augmented in proportion to the dose of rAAT administered. ELF alpha 1AT levels and antineutrophil elastase capacity 4 h after 200 mg rAAT aerosol were increased 40-fold over preaerosol levels, and were fivefold increased over baseline at 24 h after aerosol administration. rAAT was detectable in serum after aerosol, indicating that the lower respiratory tract epithelium may be permeable to rAAT, and that aerosolized rAAT is capable of gaining access to lung interstitium. No adverse clinical effects were noted. These observations demonstrate that aerosol administration of rAAT is safe and results in significant augmentation of lung antineutrophil elastase defenses, suggesting this method is a feasible approach to therapy. Because this approach is clinically unproven, further studies will be necessary to establish the long-term clinical efficacy of aerosol therapy in alpha 1AT deficiency.
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PMID:Recombinant DNA-produced alpha 1-antitrypsin administered by aerosol augments lower respiratory tract antineutrophil elastase defenses in individuals with alpha 1-antitrypsin deficiency. 279 66

Cigarette smoke-induced emphysema is thought to involve reduction of antielastolytic capacity, resulting in elevated elastase activity and lung tissue damage. Peripheral lavage collected from ten asymptomatic subjects immediately before and 20 min after smoking two high tar cigarettes was analysed for neutrophil elastase (NE) inhibitory capacity (IC), alpha 1-proteinase inhibitor (PI) function, elastolytic activity and immunoreactive levels of PI and bronchial inhibitor (BI). The only change found was a small fall in mol immunoreactive PI/mol albumin after smoking (approximately 17%, p less than 0.05) which did not affect NEIC, since PI contributed less than 50% of the NEIC. There was often more NEIC than mol BI + functional PI, suggesting the presence of other NE inhibitors. Thoracic computerized tomography scans of eight of these subjects highlighted two with emphysematous regions of lung; lavage from these two subjects contained either undetectable BI or inactive BI and this suggests a protective role for BI in emphysema.
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PMID:The acute effect of cigarette smoking on the neutrophil elastase inhibitory capacity of peripheral lung lavage from asymptomatic volunteers. 280 3

Current concepts relating to the pathogenesis of emphysema associated with cigarette smoking is that an imbalance exists within the lower respiratory tract between neutrophil elastase and the local anti-neutrophil elastase screen, enabling uninhibited neutrophil elastase to destroy the alveolar structures over time. The possible role of alveolar macrophages in contributing to this imbalance was investigated by evaluating the ability of cigarette smokers' alveolar macrophages to inactivate alpha 1-antitrypsin (alpha 1AT), the major anti-neutrophil elastase of the human lower respiratory tract. In vitro, alveolar macrophages of smokers spontaneously released 2.5-fold more superoxide anion and eightfold more H2O2 than macrophages of nonsmokers (P less than 0.01, both comparisons). Using a model system that reproduced the relative amounts of alveolar macrophages and alpha 1AT found in the epithelial lining fluid of the lower respiratory tract, we observed that smokers' macrophages caused a 60 +/- 5% reduction in the ability of alpha 1AT to inhibit neutrophil elastase. In marked contrast, under the same conditions, nonsmokers' macrophages had no effect upon the anti-neutrophil elastase function of alpha 1AT. Addition of superoxide dismutase, catalase, mannitol, and methionine prevented inactivation of alpha 1AT by smokers' macrophages, implying that the release of oxidants mediated the inactivation of alpha 1AT. In addition, by utilizing a recombinant DNA produced modified form of alpha 1AT containing an active site substitution (met358----val), the inactivation of alpha 1AT by smokers' alveolar macrophages was prevented, suggesting that the smokers' macrophages inactivate alpha 1AT by oxidizing the active site of the alpha 1AT molecule. These results suggest that in cigarette smokers, the alveolar macrophage can modulate the activity of alpha 1AT as an inhibitor of neutrophil elastase and thus play a role in the pathogenesis of emphysema associated with cigarette smoking.
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PMID:Oxidants spontaneously released by alveolar macrophages of cigarette smokers can inactivate the active site of alpha 1-antitrypsin, rendering it ineffective as an inhibitor of neutrophil elastase. 282 59

Human neutrophil elastase (HNE) has been implicated as a major contributor to tissue destruction in various disease states, including emphysema. The structure of HNE, at neutral pH, in complex with methoxysuccinyl-Ala-Ala-Pro-Ala chloromethyl ketone (MSACK), has been solved and refined to an R factor of 16.4% at 1.84-A resolution. Results are consistent with the currently accepted mechanism of peptide chloromethyl ketone inhibition of serine proteases, in that MSACK cross-links the catalytic residues His-57 and Ser-195. The structure of the HNE-MSACK complex is compared with that of porcine pancreatic elastase in complex with L-647,957, a beta-lactam inhibitor of both elastases. The distribution of positively charged residues on HNE is highly asymmetric and may play a role in its specific association with the underlying negatively charged proteoglycan matrix of the neutrophil granules in which the enzyme is stored.
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PMID:Structure of human neutrophil elastase in complex with a peptide chloromethyl ketone inhibitor at 1.84-A resolution. 291 84

Emphysema is a chronic pulmonary disorder characterized by a permanent enlargement of the air spaces distal to the terminal bronchioles consequent to destruction of the alveolar walls, including the epithelial and endothelial cells and the connective tissue matrix. There is increasing evidence that an imbalance of oxidants and antioxidants in the lower respiratory tract contributes to this process. Oxidants such as O2-., H2O2, OH, OCl- are generated in the lower respiratory tract as a result of normal biochemical processes, activation of inflammatory cells and inhaled toxic gases. Under normal circumstances, the parenchymal cells are protected by intracellular antioxidants and membrane radical scavengers. In addition, the fluid lining the epithelial surface contains a catalase-like antioxidant that protects the epithelial cells from oxidants. If the oxidant burden overcomes these defenses, the parenchymal cells may be injured, the connective tissue matrix may be partially degraded, the antiprotease screen that protects the lower respiratory tract from attack by neutrophil elastase may be rendered impotent. The alveolar wall then becomes highly vulnerable to elastolytic attack, with a complete destruction of the interstitial connective tissue matrix. In this regard, it is reasonable to hypothesize that reestablishment of the oxidant-antioxidant balance in favor of the antioxidants would be useful as a therapeutic strategy to suppress the emphysematous process.
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PMID:Oxidants, antioxidants and the pathogenesis of emphysema. 299 6

Chronic obstructive pulmonary disease (COPD) is equated with chronic bronchitis and emphysema as one disease entity. In COPD airflow limitation is relatively persistent--unlike asthma. Tests for "small-airways disease" form no part of routine practice, for their accuracy in detecting pathological change is debatable. The proteolytic theory of the pathogenesis of emphysema highlights the role of neutrophil elastase, antielastases, oxidants, antioxidants, and thus of potential new treatments. Clinical features of COPD include breathlessness, cough, and sputum, with airflow obstruction and lung hyperinflation. The differential diagnosis includes bronchiectasis, cystic fibrosis, and pulmonary hypertension, but pulmonary fibrosis, etc., is distinguished by radiological infiltrates. Plain chest radiography cannot reliably diagnose emphysema in life, but a new method measuring lung density from the computed tomographic (CT) scan allows location, quantitation, and diagnosis of emphysema (defined by enlargement of distal air spaces) in humans in life. "Pink puffers" with breathlessness, hyperinflation, mild hypoxemia, and a low PCO2 are contrasted with "blue bloaters" with hypoxemia, secondary polycythemia, CO2 retention, and pulmonary hypertension and cor pulmonale. Antismoking measures are a major aim in management. A bronchodilator regimen combining a slow-release oral theophylline with an inhaled beta 2-agonist, ipratropium, and high-dose inhaled steroids is proposed because even modest improvement in obstruction can help these patients. In acute exacerbations with purulent sputum, antimicrobials against Streptococcus pneumoniae and Hemophilus influenzae are used with controlled oxygen therapy aiming to keep the arterial PO2 over 50 mm Hg without the pH falling below 7.25. Influenza prophylaxis is recommended, but pneumococcal vaccination remains debatable. Chronic under-nutrition in "emphysema" implies controlled trials of feeding regimens--but these remain to be assessed. Long-term oxygen therapy is the only treatment known to prolong life in blue bloaters, and oxygen concentrators and transtracheal oxygen delivery are discussed. Pulmonary vasodilators (e.g., beta 2-agonists, hydralazine, nifedipine, angiotensin-converting enzyme [ACE] inhibitors, etc.) have not yet been proved to provide long-term reduction in pulmonary arterial pressure. Blue bloaters have severe nocturnal hypoxemia in rapid eye movement (REM) sleep that is corrected by oxygen or the investigational drug almitrine.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Chronic obstructive pulmonary disease. 304 40

A study was made of the evolution of emphysema and airway injury induced in the lungs of male golden Syrian hamsters by a single intratracheal injection of 350 micrograms human neutrophil elastase (HNE). Saline control and HNE-treated groups of 8 animals were studied 1, 3, 6, 12, and 18 months posttreatment. HNE treatment caused a significant increase in all lung volumes and a significant decrease in maximum expiratory flows at all study times. The mean linear intercept (MLI) values of the left lung were significantly increased over control values. There was no progression with time in MLI values, lung volumes, or lung compliance. Secretory-cell metaplasia was present at 1 month and persisted throughout the study. The HNE-treated lungs showed clusters of ferric iron-containing macrophages in the terminal airspaces. The amount of iron in the lungs, determined morphometrically, was greatest at 1 month, was decreased by 6 months, and then did not change further to 18 months. At 18 months the amount of iron was still significantly above control amounts. We conclude that the airway and parenchymal lesions induced by HNE persist without progression for 18 months. Clearance of ferric iron, which was probably a result of the hemorrhage induced by HNE treatment, continued for 6 months with no evident subsequent clearance.
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PMID:An 18-month study of the effects on hamster lungs of intratracheally administered human neutrophil elastase. 322 98

Homozygous inheritance of the null bellingham alpha 1-antitrypsin (alpha 1AT) gene is associated with early-onset emphysema, resulting from the lack of alpha 1AT to protect the lung from neutrophil elastase. Cloning and sequencing of the null bellingham gene demonstrated that the promoter region, coding exons, and all exon-intron junctions were normal except for a single base substitution in exon III, causing the normal lys217 (AAG) to become a stop codon (TAG). Evaluation of genomic DNA of family members by using oligonucleotides directed toward this region demonstrated that the index case had inherited this mutation in a homozygous fashion. Although the consequences to the individual (i.e., emphysema) are identical to those associated with the common homozygous Z mutation, the homozygous null bellingham form of alpha 1AT deficiency has a very different genetic basis.
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PMID:Emphysema associated with complete absence of alpha 1- antitrypsin in serum and the homozygous inheritance [corrected] of a stop codon in an alpha 1-antitrypsin-coding exon. 325 51

The major physiological role of the serine protease inhibitor alpha 1-antitrypsin (alpha 1-AT) is to protect elastic fibers in the lung from excessive hydrolysis by neutrophil elastase. Genetic deficiency of alpha 1-AT predisposes individuals toward the development of emphysema. We have cloned and characterized a mutant alpha 1-AT gene from an individual exhibiting a total absence of immunoreactive alpha 1-AT in serum. Nucleotide sequence analysis of this "null" allele has demonstrated a TC dinucleotide deletion within the codon for Leu318 in exon IV. This frame-shift mutation results in the generation of a premature termination codon at residue 334, which is upstream of the active inhibitory site. To determine the biochemical basis of the null phenotype, the mutant and normal genes were transferred into mouse hepatoma cells for expression analysis. Pulse-chase experiments demonstrated that the mutant gene is expressed into a truncated protein of 45 kDa, which is retained within the rough endoplasmic reticulum. The complete lack of secretion of the truncated protein is consistent with the absence of immunoreactive alpha 1-AT in the patient's serum. In addition, a G to A transition was identified in exon II of the mutant gene, changing the codon for Arg101 to His101. Finally, an A to C transversion was identified in exon V changing the codon for Glu376 to Asp376. Since the latter conservative amino acid substitution has previously been identified in the common PiM2 variant, the frame-shift mutation might have occurred on a PiM2 background chromosome. Using the birthplace of this index case, this mutant alpha 1-AT allele has been designated "nullHong Kong."
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PMID:A frameshift mutation results in a truncated alpha 1-antitrypsin that is retained within the rough endoplasmic reticulum. 325 32


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