Increased adherence of monocytes to fibronectin in bronchiectasis. Regulatory effects of bacterial lipopolysaccharide and role of CD11/CD18 integrins

Regulated adherence of monocytes to extracellular matrix is a prerequisite for accumulation of mononuclear phagocytes during pulmonary infection and inflammation. We have obtained monocytes from patients with an inflammatory lung disease (bronchiectasis) and from control subjects and have compared their adherence to fibronectin. Spontaneous adherence of monocytes from the control subjects was 20 +/- 2%, whereas that of patients' cells was markedly higher and correlated with the severity of airway inflammation: 65 +/- 5% and 40 +/- 8% in patients with purulent and mucoid sputum, respectively. Endotoxin and cytokines from areas of airway disease are likely to be responsible for the observed monocyte activation, since: (1) endotoxin was detectable in all of the patients but in none of the control subjects; (2) LPS produced a dose-related increase in adherence of normal monocytes in vitro (maximal 65 +/- 2% adherence at 1 microgram/ml of LPS); (3) recombinant cytokines and LPS produced additive effects on monocyte adherence in vitro. The adherence of the patients' monocytes to fibronectin was substantially mediated by CD11/CD18 integrins, via both RGD-dependent and RGD-independent mechanisms. These data indicate that signals arising from foci of infection and inflammation can influence the adherence of monocytes, and they are likely to be determinants of the accumulation of mononuclear phagocytes in the lungs of patients with bronchiectasis.

Family study of alpha 1-antitrypsin deficiency: effects of cigarette smoking, measured genotype, and their interaction on pulmonary function and biochemical traits

To gain insight into the variable expression of lung disease in alpha 1-antitrypsin (alpha 1AT) deficiency, five quantitative variables including forced expiratory volume at 1 sec (FEV1), forced expiratory flow rate between 25 and 75% of forced vital capacity (FEF25-75), total serum alpha 1AT, oxidized serum alpha 1AT, and total serum immunoglobulin E (IgE) were measured in alpha 1AT deficient individuals and their families. The effect of a known, measured genotype (the Pi type) was estimated for each quantitative trait; the influence of mode of case ascertainment on the measured genotype effect was also assessed. These analyses showed that total alpha 1AT levels are strongly influenced by Pi type; IgE levels are unaffected by Pi type; and FEV1, FEF25-75, and oxidized alpha 1AT are moderately influenced by Pi type. The effect of genotype-by-environment interaction between Pi type and pack-years of cigarette smoking on the five quantitative phenotypes was studied using an analysis of covariance. Significant Pi x pack-years interaction was evident for FEV1, but this effect is confounded in this data set with the Pi x age interaction. Probands who were ascertained because they had chronic obstructive pulmonary disease (COPD) do not demonstrate the significant Pi x pack-years interaction effect of the Pi x pack-years subjects ascertained for other reasons demonstrate. The effect of the Pi x pack-years interaction on FEV1 was no longer significant on a transformed scale, (FEVf12,) thus providing an additive scale for future data analysis. The increased sensitivity of Pi MZ individuals in our sample to cigarette smoking reduced the Pi x packs-years interaction effect on FEF25-75 to borderline significance. This investigation has provided an opportunity to incorporate both measured genotype and genotype-by-environment interaction analyses into the study of the variable expression of lung disease in Pi Z individuals.

Breathing during prolonged exercise in humans

1. Six normal subjects cycled to endurance or for 60 min at four work rates (WR 1-4): mean of 34% working capacity (93 watts for 60 min); 43% (120 watts for 56 min); 63% (177 watts for 37 min); and 84% (233 watts for 12 min), to determine how breathing pattern and dyspnoea change during prolonged activity. Four to six minutes were allowed to establish steady state and subsequent changes were considered to be endurance related. 2. Dyspnoea (Borg scale, 0-10) increased with the duration of activity at all work rates. 3. Ventilation (VE) did not change at WR1; increased from 44 to 47 l min-1 at WR2; from 60 to 88 l min-1 at WR3; and from 111 to 132 l min-1 at WR4. Dyspnoea was significantly and independently related to ventilation and duration of activity: dyspnoea = 0.004 VE1.36 time 0.25 (r = 0.81; partial F 202 and 26 respectively). 4. Inspiratory resistance did not increase at any work rate. Dynamic elastance remained constant during WR1, WR2 and WR3 but increased from 7.4 to 9.1 cmH2O l-1 during WR4. 5. Peak inspiratory pressure did not increase, and the increase in VE was accomplished by an increased breathing frequency without change in duty cycle. 6. Duration of activity is an important contributor to dyspnoea independent of changes in respiratory muscle contractile activity.

Effort and dyspnoea during work of varying intensity and duration

This study quantified the separate contributions of the intensity of exercise and its duration to muscular effort and dyspnoea during cycle ergometry. Six normal subjects estimated the perceived intensity (Borg scale 0-10) of peripheral muscular effort and dyspnoea during incremental exercise to their maximum work capacity (Wcap). On separate days, the same subjects exercised to endurance or 60 min at work rates rated for leg effort on the initial incremental test as: 2 ("slight", 33.1 +/- 1.45% Wcap) (mean +/- SE); 3 ("moderate", omission 83.6 +/- 3.87% Wcap). Perceived leg effort increased by a factor of 4.4 (2(2.13)) with a doubling of work rate and by 1.3 (2(0.39)) with a doubling of duration, as expressed by: Leg effort = k x %Wcap2.13 x Time0.39 (r2 = 0.87) Perceived dysponea increased 5.3-fold with a doubling of work rate and by 1.4-fold with a doubling of duration: Dysponea = k x %Wcap2.41 x Time0.47 (r2 = 0.75) Changes in work intensity, rather than duration, dominated symptom magnitudes such that in the performance of a given task, halving the intensity and doubling the duration of activity reduces the maximal intensity of muscular effort and dyspnoea to less than a third.

Effort and dyspnoea during work of varying intensity and duration

This study quantified the separate contributions of the intensity of exercise and its duration to muscular effort and dyspnoea during cycle ergometry. Six normal subjects estimated the perceived intensity (Borg scale 0-10) of peripheral muscular effort and dyspnoea during incremental exercise to their maximum work capacity (Wcap). On separate days, the same subjects exercised to endurance or 60 min at work rates rated for leg effort on the initial incremental test as: 2 ("slight", 33.1 +/- 1.45% Wcap) (mean +/- SE); 3 ("moderate", omission 83.6 +/- 3.87% Wcap). Perceived leg effort increased by a factor of 4.4 (2(2.13)) with a doubling of work rate and by 1.3 (2(0.39)) with a doubling of duration, as expressed by: Leg effort = k x %Wcap2.13 x Time0.39 (r2 = 0.87) Perceived dysponea increased 5.3-fold with a doubling of work rate and by 1.4-fold with a doubling of duration: Dysponea = k x %Wcap2.41 x Time0.47 (r2 = 0.75) Changes in work intensity, rather than duration, dominated symptom magnitudes such that in the performance of a given task, halving the intensity and doubling the duration of activity reduces the maximal intensity of muscular effort and dyspnoea to less than a third.

Elastin degradation by mononuclear phagocytes

During their development, mononuclear phagocytes express a changing profile of proteinases that may participate in the degradation of elastin and other extracellular matrix components. Neutrophil elastase is produced and stored in azurophil-like granules in immature mononuclear phagocytes. Monocytes contain small amounts of neutrophil elastase but do not synthesize the enzyme. Macrophages neither synthesize nor contain neutrophil elastase, but they can internalize and secrete scavenged neutrophil elastase. Human alveolar macrophages synthesize cysteine proteinases including cathepsin L, a lysosomal enzyme with elastolytic activity at an acidic pH. Macrophages from several animal species synthesize an approximately 22-kD metalloelastase that, in the mouse, is secreted as a zymogen of about 36 kD. In addition to its direct elastolytic properties, this metalloelastase may also promote elastolysis by cleaving alpha 1-antiproteinase and thus protecting neutrophil elastase from inhibition. A human counterpart of this enzyme has not yet been purified; however, the elastolytic activity of human macrophages appears to depend predominantly on the activity of one or more metalloproteinases. Because elastin is intertwined with other matrix components in natural matrices, degradation of elastin in vivo probably involves cooperation of multiple proteinases to uncover macromolecules that mask the elastic fibers. Degradation of matrix may be localized to pericellular sites, where proteinases are protected from inhibitors and where potentially surface-bound enzymes may be concentrated. Complete breakdown of matrix may be completed within the cells after partially cleaved molecules are internalized. Growth and remodeling of the extracellular matrix must involve highly coordinated interactions between cells, cytokines, proteinases, proteinase activators and inhibitors, as well as the matrix itself. The intrapulmonary process resulting in emphysema probably involves equally complex interactions. Mononuclear phagocytes accumulate in large numbers in the lung in response to cigarette smoking, and they may play a role in the pathogenesis of the alveolar septal injury that characterizes pulmonary emphysema.

Marked longevity of human lung parenchymal elastic fibers deduced from prevalence of D-aspartate and nuclear weapons-related radiocarbon

Normal structure and function of the lung parenchyma depend upon elastic fibers. Amorphous elastin is biochemically stable in vitro, and may provide a metabolically stable structural framework for the lung parenchyma. To test the metabolic stability of elastin in the normal human lung parenchyma, we have (a) estimated the time elapsed since the synthesis of the protein through measurement of aspartic acid racemization and (b) modeled the elastin turnover through measurement of the prevalence of nuclear weapons-related 14C. Elastin purified by a new technique from normal lung parenchyma was hydrolyzed; then the prevalences of D-aspartate and 14C were measured by gas chromatography and accelerator-mass spectrometry, respectively. D-aspartate increased linearly with age; Kasp (1.76 x 10(-3) yr(-1) was similar to that previously found for extraordinarily stable human tissues, indicating that the age of lung parenchymal elastin corresponded with the age of the subject. Radiocarbon prevalence data also were consistent with extraordinary metabolic stability of elastin; the calculated mean carbon residence time in elastin was 74 yr (95% confidence limits, 40-174 yr). These results indicate that airspace enlargement characteristic of "aging lung" is not associated with appreciable new synthesis of lung parenchymal elastin. The present study provides the first tissue-specific evaluation of turnover of an extracellular matrix component in humans and underscores the potential importance of elastin for maintenance of normal lung structure. Most importantly, the present work provides a foundation for strategies to directly evaluate extracellular matrix injury and repair in diseases of lung (especially pulmonary emphysema), vascular tissue, and skin.

Dexamethasone selectively modulates basal and lipopolysaccharide-induced metalloproteinase and tissue inhibitor of metalloproteinase production by human alveolar macrophages

To define the capacity of glucocorticoids to regulate tissue damage associated with inflammation more clearly, we have studied the effects of dexamethasone on human alveolar macrophage secretion of both a variety of metalloproteinases and also the counter-regulatory tissue inhibitor of metalloproteinases (TIMP). We found that dexamethasone selectively and coordinately inhibited expression of the following human metalloproteinases: interstitial collagenase, stromelysin, and the 92-kDa type IV collagenase, as well as TIMP. Both basal and LPS-stimulated cells exhibited similar degrees of inhibition, with greater than 50% decrease in secretion of all enzymes and TIMP observed at dexamethasone concentrations of greater than or equal to 10(-8) M in serum-containing medium. The effects of dexamethasone were mediated at a pretranslational level. In summary, our results indicate that glucocorticoids suppress the matrix-degrading phenotype that is characteristic of mature human mononuclear phagocytes, and block the effects of the most potent known signal for upregulation of metalloproteinase secretion. Similar actions in vivo would serve to limit tissue damage associated with the inflammatory response.

Dexamethasone selectively modulates basal and lipopolysaccharide-induced metalloproteinase and tissue inhibitor of metalloproteinase production by human alveolar macrophages

To define the capacity of glucocorticoids to regulate tissue damage associated with inflammation more clearly, we have studied the effects of dexamethasone on human alveolar macrophage secretion of both a variety of metalloproteinases and also the counter-regulatory tissue inhibitor of metalloproteinases (TIMP). We found that dexamethasone selectively and coordinately inhibited expression of the following human metalloproteinases: interstitial collagenase, stromelysin, and the 92-kDa type IV collagenase, as well as TIMP. Both basal and LPS-stimulated cells exhibited similar degrees of inhibition, with greater than 50% decrease in secretion of all enzymes and TIMP observed at dexamethasone concentrations of greater than or equal to 10(-8) M in serum-containing medium. The effects of dexamethasone were mediated at a pretranslational level. In summary, our results indicate that glucocorticoids suppress the matrix-degrading phenotype that is characteristic of mature human mononuclear phagocytes, and block the effects of the most potent known signal for upregulation of metalloproteinase secretion. Similar actions in vivo would serve to limit tissue damage associated with the inflammatory response.

Neutral proteinases of human mononuclear phagocytes. Cellular differentiation markedly alters cell phenotype for serine proteinases, metalloproteinases, and tissue inhibitor of metalloproteinases

Mononuclear phagocytes have the capacity to directly participate in extracellular matrix turnover via secretion of neutral proteinases. We have studied the effects of in vivo and in vitro differentiation upon cellular content or secretion of a spectrum of neutral proteinases, along with a counter-regulatory metalloproteinase inhibitor (TIMP). We found 1) matrix-degradative serine proteinases (leukocyte elastase and cathepsin G) were lost during cellular maturation and/or differentiation; 2) the 92-kDa type IV/type V collagenase and TIMP were secreted earliest in mononuclear phagocyte differentiation, whereas stromelysin secretion was observed only by LPS-stimulated alveolar macrophages; 3) exposure of alveolar macrophages, but not monocytes, to phorbol esters and LPS resulted in markedly augmented secretion of all studied metalloproteinases and TIMP; 4) monocyte-derived macrophages partially (but not completely) mimicked the metalloproteinase secretory phenotype of alveolar macrophages; and 5) the secretory phenotype of alveolar macrophages for interstitial collagenase (but not TIMP) was largely lost during in vitro culture. These results underscore the complexity of the process of differentiation in human mononuclear phagocytes, and provide insights into the variable capacity of mononuclear phagocytes to degrade extracellular matrix components. Moreover, we anticipate that human mononuclear phagocytes at various stages of differentiation will provide a useful model system for study of the variable regulation of secretion of human matrix-degrading metalloproteinases.

Neutral proteinases of human mononuclear phagocytes. Cellular differentiation markedly alters cell phenotype for serine proteinases, metalloproteinases, and tissue inhibitor of metalloproteinases

Mononuclear phagocytes have the capacity to directly participate in extracellular matrix turnover via secretion of neutral proteinases. We have studied the effects of in vivo and in vitro differentiation upon cellular content or secretion of a spectrum of neutral proteinases, along with a counter-regulatory metalloproteinase inhibitor (TIMP). We found 1) matrix-degradative serine proteinases (leukocyte elastase and cathepsin G) were lost during cellular maturation and/or differentiation; 2) the 92-kDa type IV/type V collagenase and TIMP were secreted earliest in mononuclear phagocyte differentiation, whereas stromelysin secretion was observed only by LPS-stimulated alveolar macrophages; 3) exposure of alveolar macrophages, but not monocytes, to phorbol esters and LPS resulted in markedly augmented secretion of all studied metalloproteinases and TIMP; 4) monocyte-derived macrophages partially (but not completely) mimicked the metalloproteinase secretory phenotype of alveolar macrophages; and 5) the secretory phenotype of alveolar macrophages for interstitial collagenase (but not TIMP) was largely lost during in vitro culture. These results underscore the complexity of the process of differentiation in human mononuclear phagocytes, and provide insights into the variable capacity of mononuclear phagocytes to degrade extracellular matrix components. Moreover, we anticipate that human mononuclear phagocytes at various stages of differentiation will provide a useful model system for study of the variable regulation of secretion of human matrix-degrading metalloproteinases.

Proteinases secreted by human mononuclear phagocytes

Human mononuclear phagocytes express an array of serine and metal dependent proteinases that are under complex developmental control and are also highly regulated by physiologic and pharmacologic stimuli. Monocytes contain the intracellular serine proteinases, elastase and cathepsin G, but have little metalloproteinase secretory capacity. Macrophages, on the other hand, produce predominantly metalloproteinases. Phorbol induced differentiation of promonocyte-like U937 cells into more mature mononuclear phagocytes results in transcriptional suppression of cathepsin G and temporally delayed onset of collagenase transcription. Mature macrophages upregulate metalloproteinase synthesis in response to lipopolysaccharide and phorbol myristic acetate; expression is downregulated with interferon gamma and dexamethasone. Thus, during the development of the mononuclear phagocyte, stores of serine proteinases are replaced by regulated secretion of metalloproteinases. These alterations may reflect changing roles of these cells in extracellular matrix degradation.

Enzyme techniques in blood group serology: the effect of ionic strength

Lowering the ionic strength of the solution in which red blood cells were suspended for blood grouping was shown to increase sensitivity and the incidence of 'false' positive results in various papain techniques. A reduction in ionic strength of the solution in which cells were pre-modified increased the titration scores for 'enzyme-only' anti-c, anti-e, anti-E and anti-D. Suspension of papain pre-modified cells in lower strength solutions for antigen/antibody reactions had the same effect.

A family study of the variability of pulmonary function in alpha 1-antitrypsin deficiency. Quantitative phenotypes

A group of 52 alpha 1-antitrypsin-deficient individuals of phenotype Pi Z and 117 of their relatives underwent a protocol including pulmonary function testing, completion of a questionnaire, and blood donation. Our population permitted a minimum frequency estimate (7 x 10(-4)) for Pi null alleles. Five quantitative phenotypes were measured, including FEV1, FEF25-75, total serum alpha 1AT, oxidized serum alpha 1AT, and total serum IgE. We found that (1) total alpha 1AT levels were higher in Pi Z subjects with lung function impairment (FEV1 less than or equal to 65% of predicted) than in Pi Z subjects who were not impaired; (2) Pi Z subjects with lung function impairment had elevated serum levels of oxidized alpha 1AT; and (3) IgE levels were relatively elevated in first-degree Pi MZ relatives of impaired Pi Z subjects. Moreover, FEV1 tended to be relatively reduced in heterozygous parents of impaired Pi Z subjects, suggesting that a subset of Pi MZ individuals are at risk for development of lung disease because of familial factors. These results represent an initial step toward the development of intermediate phenotypes that will be predictive of a severe course in alpha 1AT deficiency; they suggest that, in addition to cigarette smoking, atopic predisposition and undetermined familial factors may be important codeterminants of lung disease progression.

Neutral metalloproteinases produced by human mononuclear phagocytes. Enzyme profile, regulation, and expression during cellular development

Mononuclear phagocytes are developmentally and functionally complex cells that play critical roles in extracellular matrix remodeling. We hypothesized that differentiated mononuclear phagocytes, typified by alveolar macrophages, use a spectrum of metalloproteinases to degrade various matrix macromolecules. To test this hypothesis, we have evaluated synthesis and secretion of four metalloproteinases (interstitial collagenase, stromelysin, 72-kD type IV collagenase, and 92-kD type IV collagenase) by human mononuclear phagocytes with regard to (a) the effect of cellular differentiation, (b) regulation of secretion, and (c) comparisons/contrasts with a prototype metalloproteinase-secretory cell, the human fibroblast. We found that regulated secretion of greater quantities and a wider spectrum of metalloenzymes correlated with a more differentiated cellular phenotype. As extreme examples, the 92-kD type IV collagenase was released by peripheral blood monocytes and uninduced U937 monocyte-like cells, whereas stromelysin was secreted only by lipopolysaccharide-stimulated alveolar macrophages. Macrophage production of interstitial collagenase, stromelysin, and 72-kD type IV collagenase was approximately 20%, 10%, and 1-2%, respectively, of that from equal numbers of fibroblasts; secretion of the 92-kD type IV collagenase was not shared by fibroblasts. This work confirms the potential of macrophages to directly degrade extracellular matrix via secreted metalloproteinases in a manner that differs both qualitatively and quantitatively from that of fibroblasts. Moreover, varying regulation of metalloenzyme synthesis, evidenced by distinct patterns of basal and stimulated secretion during differentiation, can be studied at a molecular level in this model system.

Immune modulation of metalloproteinase production in human macrophages. Selective pretranslational suppression of interstitial collagenase and stromelysin biosynthesis by interferon-gamma

Interferon-gamma (IFN-gamma) is a lymphokine that activates mononuclear phagocytes. To test the hypothesis that IFN-gamma might have important effects upon the ability of human mononuclear phagocytes to degrade extracellular matrix, we have studied the action of this cytokine on the production of metalloproteinases and the counterregulatory tissue inhibitor of metalloproteinases (TIMP) by the human alveolar macrophage. We have found that IFN-gamma potently and selectively suppresses the lipopolysaccharide-induced production of two metalloproteinases--interstitial collagenase and stromelysin--by 50-90% at doses greater than or equal to 10 U/ml. The synthesis of TIMP and 92-kD type IV collagenase was also diminished by IFN-gamma, but these responses required 50- to 100-fold higher concentrations of the cytokine. All doses of IFN-gamma increased total and secreted protein synthesis slightly, indicating a highly specific effect on metalloenzyme biosynthesis. Inhibition of metalloproteinase expression occurred at a pretranslational level, as evidenced by parallel reductions in enzyme biosynthesis and collagenase-specific steady-state mRNA levels. Interestingly, the effect of IFN-gamma on metalloenzyme production was not readily reversible. Therefore, while IFN-gamma activates the macrophage and renders it tumoricidal, this enhanced function appears to be attained at the expense of the cell's capacity to degrade extracellular matrix.

Prospective study of long-term pulmonary manifestations of mantle irradiation

Given the high cure rate of patients with Hodgkin's disease, the complications related to therapy take on great significance. Mantle irradiation to the thorax is used in virtually all patients with early stage Hodgkin's disease. Prior studies of patients receiving mantle irradiation demonstrated short-term (up to 24 months) abnormalities of pulmonary function. In the present study, we prospectively studied 13 patients for up to 60 months after irradiation only with serial pulmonary function tests, arterial blood gas tests, diffusing capacity of carbon monoxide, chest radiographs, and ventilation-perfusion scans. No respiratory symptoms attributable to therapy were noted. Frequent radiographic changes (62%) were found consisting of apical fibrosis, paramediastinal fibrosis, or pleural thickening. Two patients developed an asymptomatic spontaneous pneumothorax that resolved with conservative management. Ventilation-perfusion scans often (73%) revealed decreased perfusion to the lung apices with associated ventilatory deficits in one-half of these patients. Patients with intrathoracic disease had decreased lung volumes prior to therapy, and lung volumes did not change following irradiation. Lung mechanics were normal throughout the study. Gas exchange at rest was normal in patients with extrathoracic disease. Patients with intrathoracic disease often presented with an abnormal arterial PO2 and widened alveolar-arterial partial pressure gradient for oxygen. However, these parameters normalized by 9 months after therapy. Despite the frequent development of radiographic and V/Q scan abnormalities in the lung apices, patients tolerated mantle radiotherapy remarkably well. In fact, patients with intrathoracic disease demonstrated improved gas exchange at rest following therapy.

Elastase and cathepsin G of human monocytes: heterogeneity and subcellular localization to peroxidase-positive granules

We used antibodies to human leukocyte ("neutrophil") elastase and cathepsin G to localize the corresponding antigens in human neutrophils, monocytes, and alveolar macrophages by immunohistochemistry. Furthermore, we combined immunogold localization with enzyme histochemistry to localize proteinase antigens and endogenous peroxidase activity in the same sections. As expected, all neutrophils contained both elastase and cathepsin G, and the proteinases localized to granules with peroxidase activity. In contrast, marked heterogeneity in monocyte staining for elastase, cathepsin G, and endogenous peroxidase was found. Sixty percent or more were unstained, while the remainder varied greatly in staining intensity. The elastase and cathepsin G in monocytes were localized by immunoelectron microscopy, combined with histochemistry, to cytoplasmic granules which had peroxidase activity. Alveolar macrophages were unstained. Therefore, a subpopulation of peripheral blood monocytes contains leukocyte elastase and cathepsin G in a cell compartment from which these enzymes may potentially be released into the extracellular space. The occurrence of peroxidase and neutral proteinases in the same granules in monocytes could permit the H2O2-myeloperoxidase-halide system and the neutral proteinases to act in concert in such functions as microbe killing and extracellular proteolysis.

Inhibition of human leukocyte elastase bound to elastin: relative ineffectiveness and two mechanisms of inhibitory activity

Human leukocyte elastase (HLE) has been demonstrated on lung elastic fibers in areas of pulmonary emphysema. In vitro studies in our laboratory have shown that HLE-elastin complexes may be remarkably stable. We tested the possibility that elastin-bound HLE may retain catalytic activity in the presence of inhibitors that are effective against free HLE and found: (1) alpha-1-proteinase inhibitor (alpha 1PI), antileukoprotease (ALP), and eglin C inhibited free HLE on an approximately 1:1 molar basis, measured with either 3H-elastin or a synthetic peptide substrate; (2) the ability of each inhibitor to control catalytic activity of HLE when complexed with elastin was impaired (e.g., in a 24-h assay, a 70-fold molar excess of alpha 1PI gave only 93% inhibition of HLE); and (3) a chloromethyl ketone inhibitor of HLE gave qualitatively similar results, although at the low enzyme concentrations used it was a less effective inhibitor of free and elastin-bound enzyme than were the polypeptide inhibitors. Further, we found evidence for two distinct mechanisms of inhibition of elastin-bound HLE. alpha 1PI and eglin C prevented elastin solubilization largely by enhancing net dissociation of HLE from the complexes; enzyme remaining bound to the substrate retained essentially full activity. In contrast, ALP and the chloromethyl ketone prevented elastin solubilization by binding to the complexes and inhibiting the enzyme in situ. These results may have implications regarding progressive elastin solubilization in vivo and should stimulate further investigation of enzyme activity in heterogeneous systems in which one or more reactants are insoluble.

Developmental regulation of the human cathepsin G gene in myelomonocytic cells

Cathepsin G is a neutral serine protease that is found in the azurophil granules of neutrophils and monocytes. Previous experiments had demonstrated that cathepsin G is actively produced by the promonocytic U937 cell line, and that 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced differentiation of these cells toward macrophages resulted in a reduction of cathepsin G activity. In this study, we have analyzed the mechanism of this TPA-induced down-regulatory event. Using in situ hybridization techniques, we demonstrated that cathepsin G mRNA is detectable only at the promyelocytic stage of myeloid development. Using U937 promonocytic cells as a model, we demonstrated; 1) cathepsin G protein levels decline in TPA-treated cells; 2) this decline was due to a nearly complete loss of cathepsin G mRNA in cells treated with TPA for 24 h; and 3) the rate of cathepsin G mRNA loss with TPA treatment was similar to that with actinomycin D. These results suggested that cathepsin G transcription was down-regulated within several hours of TPA addition. This was directly tested by performing nuclear run-off assays of TPA-treated U937 cells; cathepsin G transcription was shown to be strand-specific, and declined within 4 h of TPA addition. Cathepsin G transcription was essentially undetectable 8 or more hours after TPA treatment, suggesting that down-regulation is predominantly transcriptional. Cycloheximide treatment of U937 cells resulted in a partial block of TPA-mediated cathepsin G down-regulation, indicating that continuous protein synthesis is required for down-regulation to occur. A newly synthesized protein or proteins may therefore be required for the transcriptional down-regulation of cathepsin G during the normal development of promyelocytes or promonocytes.

Biochemical intermediates in alpha 1-antitrypsin deficiency: residual family resemblance for total alpha 1-antitrypsin, oxidized alpha 1-antitrypsin, and immunoglobulin E after adjustment for the effect of the Pi locus

alpha 1-antitrypsin (alpha 1 AT) deficiency is variably associated with the development of pulmonary emphysema. To gain insight into the process which begins the Z point mutation at the Protease Inhibitor (Pi) locus and results in the variable development of emphysema, three quantitative phenotypes, including total alpha 1 AT, oxidized alpha 1 AT, and total immunoglobulin E (IgE), were measured in sera from alpha 1-antitrypsin-deficient individuals and their families. The mean and variance effects of the Pi locus on these biochemical phenotypes were removed, and path analysis of the residual phenotypes was performed by using a TAU model to investigate whether there was any additional multifactorial transmission. Significant transmission was demonstrated for total serum IgE and serum-oxidized alpha 1 AT, which could be due to major genes other than the Pi locus, polygenes, or familial environment. Segregation analysis of the residual phenotypes was performed to determine whether additional major gene effects, other than the Pi effect, influence these quantitative phenotypes. Convincing evidence for an additional major gene was not found for oxidized alpha 1 AT, total alpha 1 AT, or IgE.

Variability of pulmonary function in alpha-1-antitrypsin deficiency: residual family resemblance beyond the effect of the Pi locus

To gain insight into the variable expression of lung disease in alpha 1-antitrypsin deficiency, two pulmonary function tests, FEV1 and FEF25-75, were examined in alpha 1-antitrypsin-deficient individuals and their families. The mean and variance effects of Pi type, age, and sex on the pulmonary function variables were removed by stepwise multiple regression, and the residual phenotypes were analyzed. Path analysis of the residual phenotypes with environmental indices in 46 nuclear families demonstrated highly significant cultural inheritance. Significant polygenic inheritance was not demonstrated for FEV1 but was shown for FEF25-75. For FEV1, adjustment for the significant interaction between Pi type and pack-years of smoking tended to increase the estimated contribution of polygenic inheritance and to decrease the estimated contribution of cultural inheritance. Segregation analysis of the residual phenotypes in 44 nuclear families was carried out to determine whether another major gene, other than the Pi locus, may be influencing pulmonary function in this population. Statistical evidence was found for an additional major gene influencing FEV1; however, the evidence diminished after adjusting for the effects of pack-years and the interaction between Pi type and pack-years. This apparent drop in the importance of genetic factors would not be surprising if the effect of the putative major gene is to enhance susceptibility to effects of cigarette smoking. Finally, our investigation demonstrates the feasibility of dissecting residual familial effects on complex multifactorial traits.

Variability of pulmonary function in alpha-1-antitrypsin deficiency: clinical correlates

STUDY OBJECTIVE

To determine the range of pulmonary function variability in alpha-1-antitrypsin-deficient persons and to identify epidemiologic factors and pulmonary symptoms and conditions associated with this variability.

DESIGN

Case series ascertained through investigation of extant obstructive lung disease (index cases, 22 subjects) or by other means (non-index cases, 30 subjects).

SETTING

Referral-based pulmonary division at a tertiary care medical center.

PARTICIPANTS

Fifty-two alpha-1-antitrypsin-deficient persons of type Pi Z ascertained by: extant chronic obstructive pulmonary disease (22 cases), family studies (20 cases), liver disease (4 cases), population screening (4 cases), and other pulmonary problems (2 cases).

MEASUREMENTS AND MAIN RESULTS

Pulmonary function tests and a version of the American Thoracic Society 1978 standard respiratory epidemiology questionnaire were used. Persons of type Pi Z who were not specifically ascertained with chronic obstructive pulmonary disease had values of forced expiratory volume in 1 second over 65% of predicted in 20 out of 30 cases and frequently had normal lung function. Univariate and multivariate analyses of possible causes of lung disease showed that the following factors were significant (P less than 0.05): pulmonary symptoms (effects associated with chronic obstructive pulmonary disease), including dyspnea and chronic cough; age and pack-years of smoking (epidemiologic correlates); and other pulmonary conditions (potential causes or effects) including asthma, pneumonia, and episodes of increased cough and phlegm. Finally, we found a striking excess of questionnaire-reported parental emphysema in families of type Pi Z persons with chronic obstructive pulmonary disease compared with families of type Pi Z persons without disease.

CONCLUSIONS

Many persons with alpha-1-antitrypsin deficiency do not have clinically significant lung function impairment: the perceived natural history of antitrypsin deficiency has been distorted by ascertainment bias. In addition to cigarette smoking, it appears that asthma, lower respiratory infections, and possibly some familial factors contribute to a severe clinical course. Follow-up of our cohort with widely varying lung function will provide insights into the natural history of the emphysema associated with alpha-1-antitrypsin deficiency.