Human alveolar macrophages produce a fibroblast-like collagenase and collagenase inhibitor

Human macrophages have been implicated in connective tissue remodeling; however, little is known about their direct effects upon collagen degradation. We now report that human alveolar macrophages in culture produced both a collagenase and a collagenase inhibitor. The collagenase was secreted in latent form and could be activated by exposure to trypsin. Collagenase production could be increased three- to fourfold by incubating the cells with lipopolysaccharide, but synthesis was largely unaffected by exposure to phorbol myristate acetate. By several criteria, macrophage collagenase was the same as the collagenase secreted by human skin fibroblasts: (a) they were antigenically indistinguishable in double immunodiffusion; (b) both degraded type III collagen preferentially to type I, had little activity against type II collagen, and none against types IV and V, and (c) their affinity for susceptible collagens was equivalent, Michaelis constant = 1-2 microM. Collagenase inhibitory activity was also present in the macrophage-conditioned medium, and was accounted for by an antigen that showed immunologic and functional identity with the collagenase inhibitor secreted by human skin fibroblasts. The amount of inhibitor released by unstimulated cells, approximately 100 ng/10(6) cells per 24 h, was substantially augmented by both phorbol and lipopolysaccharide, although considerable variability in response to these agents was observed between macrophage populations derived from different subjects. As negligible quantities of collagenase or collagenase inhibitor were detectable intracellularly, it appeared that both proteins were secreted rapidly after synthesis. Thus, human macrophages have the capacity to modulate collagen degradation directly by production of collagenase and collagenase inhibitor.

Effect of frequency on perceived magnitude of added loads to breathing

Using open-magnitude scaling, six normal subjects estimated the perceived magnitude of a range of added elastic loads (20-76 cmH2O/l), applied for a sequence of five breaths, at frequencies varying from 5 to 26.4 breaths/min. Two experiments were performed. In the first, frequency was increased by a reduction in expiratory duration (TE), and the duty cycle (ratio of inspiratory duration to total breath duration, TI/TT) ranged between 0.10 and 0.52. The perceived magnitude psi increased significantly with the peak airway pressure (Pm) (P less than 0.0001) but did not reach conventional significance with frequency (fb) (P = 0.15): psi = K0Pm1.23fb0.07 (r = 0.911). However, the sensory magnitude increased significantly as the duty cycle increased (P less than 0.01), but when it was included, the magnitude decreased minimally with frequency (P less than 0.01): psi = K0Pm1.3fb-0.97 TI/TT1.14 (r = 0.92). In the second experiment the duty cycle (TI/TT) was kept constant [(0.43 +/- 0.008 (SE)] and frequency (5-26.4 breaths/min) increased at the expense of shortening both TI and TE. The perceived magnitude of the added elastances decreased with the increase in frequency. However, when the perceived magnitude was corrected for the duration of inspiration, which is known to increase the sensory magnitude, psi = K0Pm1.3TI0.56, the sensory magnitude increased significantly with frequency (P less than 0.001): psi/TI0.56 = K0Pm1.21fb0.28 (r = 0.773). The decrease in inspiratory duration had a greater quantitative effect decreasing sensory magnitude than frequency had on increasing the magnitude. The effect of increasing frequency is complex and depends on the simultaneous intensity, duration of inspiratory pressure, and the duty cycle.

Effect of long-term administration of digoxin on exercise performance in chronic airflow obstruction

We have studied the effect of long-term digoxin on exercise performance in 15 patients with pulmonary heart disease due to severe chronic airflow obstruction (FEV1/VC ratio 29 +/- 6%: mean +/- SD). Digoxin (0.25 mg/day) was given for 8 weeks in a randomized, double-blind crossover, placebo-controlled trial. All patients were ambulatory and had clinical features of right ventricular dysfunction but no clinical evidence of left ventricular dysfunction. Assessments included progressive and steady-state exercise, pulmonary function studies and evaluation of right and left ventricular function. In all patients the right ventricular ejection fraction was reduced; in 4 patients the left ventricular ejection fraction was also reduced. In patients whose left ventricular ejection fraction was initially abnormal, 8 weeks of digoxin increased left ventricular ejection fraction to normal. In spite of the improvement in resting ventricular function, exercise performance, the cardiopulmonary response to exercise, pulmonary function and general health status did not improve. We conclude that in patients with pulmonary heart disease: 1) digoxin improves ventricular function only if left ventricular function is reduced, and 2) despite the improvement in ventricular function digoxin does not improve pulmonary function, cardiopulmonary response to exercise or general feeling of well being.

Alveolar macrophage function and inflammatory stimuli in smokers with and without obstructive lung disease

To explore possible cofactors in the development of chronic obstructive pulmonary disease (COPD) in smokers, we performed bronchoalveolar lavage in 6 smokers with normal pulmonary function, 6 smokers with COPD (FEV1/FVC less than or equal to 65%) matched for smoking history and age, and 9 age-matched nonsmoking control subjects. Elastase release by macrophages from smokers with COPD was significantly higher (p less than 0.016) than was elastase release by macrophages from normal smokers. There were no differences between chemoattractiveness of alveolar macrophage supernatants for one person's polymorphonuclear leukocytes among the groups of smokers and there was no detectable C5/C5a in these supernatants (limit of detection of C5a greater than 1 ng/ml). There were no significant differences in numbers or species of bacteria in aerobically and anaerobically cultured bronchial brushings. There was no difference in alveolar macrophage superoxide anion release with particulate or membrane-perturbing stimuli for the smokers. Alveolar macrophages from the 3 groups of subjects had similar limited microbicidal ability for the obligate intracellular protozoan, Toxoplasma gondii, and similar numbers of elastase receptors and affinity for elastase.

Effect of diuretics on cardiopulmonary performance in severe chronic airflow obstruction. A controlled clinical trial

In a randomized, controlled trial, ten patients with pulmonary heart disease due to severe chronic airflow obstruction were stratified into two groups: group 1 had clinical features of congestive heart failure during respiratory failure and were regularly receiving diuretics; group 2 had no such clinical features and were not receiving diuretics. In group 1, when placebo was substituted for diuretics, pulmonary edema developed in three patients; exercise performance and ventricular function of the remaining two patients deteriorated. In group 2, there was no difference in exercise tolerance or ventricular function between placebo and diuretic therapy. The clinical deterioration in group 1 was related to abnormal left ventricular function. Thus, diuretics benefit only patients who have clinical features of congestive heart failure. In patients with isolated abnormal right ventricular function, diuretics may be harmful.

Effect of increased lung volume on perception of breathlessness, effort, and tension

By the addition of externally added elastic loads at both functional residual capacity (FRC) and increased lung volume, increased respiratory muscle effort, tension, and breathlessness were induced in normal subjects. The magnitude of each of these sensations was estimated using the psychophysical technique of category scaling (Med. Sci. Sports Exercise 14: 377-381, 1982). The tidal volume, inspiratory time, and breathing frequency were kept constant to avoid variability in sensation due to these factors. The perceived magnitude of effort and breathlessness increased significantly as the inspiratory pressure and lung volume increased (P less than 0.05). The magnitude of perceived tension increased as the inspiratory pressure increased (P less than 0.05) but not as lung volume increased. To validate these results, the subjects estimated the perceived magnitude of a series of static inspiratory occlusion pressures at both lung volumes using open-magnitude scaling and sensory matching. The perceived magnitude of effort increased significantly as the pressure increased and as the lung volume increased (P less than 0.05). To match the perceived effort required to produce the target pressures at FRC, the subjects reproduced pressures. These were not significantly different. However, to match the effort required to produce the target pressures at increased lung volume, the pressures reproduced at FRC were significantly greater (P less than 0.05). The results suggest that the sensations of breathlessness and effort are psychophysically the same, whereas tension is perceived by a different sensory mechanism.

Cathepsin G in human mononuclear phagocytes: comparisons between monocytes and U937 monocyte-like cells

Previous studies demonstrating that a continuous line of human monocyte-like cells (U937) and human monocytes contain elastase probably identical to human neutrophil elastase suggested the possibility that mononuclear phagocytes share other proteinases with neutrophils. The present work establishes that U937 cells contain cathepsin G, an enzyme heretofore found only in neutrophils. U937 cells contain approximately 10 micrograms of cathepsin G-like activity per 10(7) cells, about 25% of the cathepsin G activity in human neutrophils. Normal monocytes have minimal cathepsin G-like activity (approximately 0.1 microgram per 10(7) cells). The cathepsin G-like activity of U937 cells appears to be due to an enzyme that is the same as cathepsin G by several criteria: 1) it is a serine proteinase with activity like cathepsin G against a synthetic chymotrypsin substrate, succinyl-ala-ala-pro-phe-p-nitroanilide; 2) the proteolytic fragments it releases from fibronectin match those released by cathepsin G; 3) like cathepsin G, it can be purified by sequential Trasylol-Sepharose affinity chromatography and carboxymethyl-Sephadex ion exchange chromatography; 4) its amino acid composition and migration on SDS-polyacrylamide gel electrophoresis are indistinguishable from cathepsin G; and 5) it binds with antiserum raised to cathepsin G. The presence of cathepsin G in U937 cells, in much higher concentration than in normal monocytes, indicates either that the content of cathepsin G in monocytes decreases markedly during monocyte differentiation or that U937 cells differ from normal immature monocytes with respect to synthesis of this neutral proteinase.

Cathepsin G in human mononuclear phagocytes: comparisons between monocytes and U937 monocyte-like cells

Previous studies demonstrating that a continuous line of human monocyte-like cells (U937) and human monocytes contain elastase probably identical to human neutrophil elastase suggested the possibility that mononuclear phagocytes share other proteinases with neutrophils. The present work establishes that U937 cells contain cathepsin G, an enzyme heretofore found only in neutrophils. U937 cells contain approximately 10 micrograms of cathepsin G-like activity per 10(7) cells, about 25% of the cathepsin G activity in human neutrophils. Normal monocytes have minimal cathepsin G-like activity (approximately 0.1 microgram per 10(7) cells). The cathepsin G-like activity of U937 cells appears to be due to an enzyme that is the same as cathepsin G by several criteria: 1) it is a serine proteinase with activity like cathepsin G against a synthetic chymotrypsin substrate, succinyl-ala-ala-pro-phe-p-nitroanilide; 2) the proteolytic fragments it releases from fibronectin match those released by cathepsin G; 3) like cathepsin G, it can be purified by sequential Trasylol-Sepharose affinity chromatography and carboxymethyl-Sephadex ion exchange chromatography; 4) its amino acid composition and migration on SDS-polyacrylamide gel electrophoresis are indistinguishable from cathepsin G; and 5) it binds with antiserum raised to cathepsin G. The presence of cathepsin G in U937 cells, in much higher concentration than in normal monocytes, indicates either that the content of cathepsin G in monocytes decreases markedly during monocyte differentiation or that U937 cells differ from normal immature monocytes with respect to synthesis of this neutral proteinase.

Detrimental effects of hydralazine in patients with chronic air-flow obstruction and pulmonary hypertension. A combined hemodynamic and radionuclide study

The acute effects of intravenously administered hydralazine on pulmonary hemodynamics and ejection radionuclide angiography were evaluated in 9 patients with chronic airflow obstruction (forced expiratory volume in one second, 1.2 +/- 0.8 L, mean +/- SD), pulmonary hypertension (mean pulmonary artery pressure (PAP), 29 +/- 13 mmHg), and sleep hypoxemia (maximal sleep desaturation, 20 +/- 16%). The effect of hydralazine was measured during both normoxia and hypoxia and compared with the effect of hyperoxia. Hydralazine increased cardiac index from 3.7 +/- 0.2 to 4.5 +/- 0.8 L/min/m2 (mean +/- SE, p less than 0.05, n = 9), but there were no significant changes in PAP (29 +/- 4 to 32 +/- 4 mmHg), mean pulmonary vascular resistance index (PVRI) (390 +/- 80 to 360 +/- 80 dyn.s.cm.-5.m2), mean right ventricular stroke work index (12.7 +/- 2.7 to 15.0 +/- 2.2 g.m/m2), and mean pulmonary capillary wedge pressure (12 +/- 1 to 12 +/- 2 mmHg). Mean right ventricular ejection fraction and mean right ventricular end diastolic volume also were not changed after treatment with hydralazine. Hyperoxia was used to assess the reversibility of pulmonary hypertension and to compare this with hydralazine. Hyperoxia increased arterial oxygen saturation (SaO2) from 91 +/- 1 to 96 +/- 1% and decreased the cardiac index from 3.8 +/- 0.1 to 3.1 +/- 0.2 L/min/m2 (p less than 0.02, n = 6) but, as with hydralazine, there was no significant change in PAP (28 +/- 6 to 25 +/- 6 mmHg) and PVRI (350 +/- 120 to 360 +/- 80 dyn.s.cm-5).m2).(ABSTRACT TRUNCATED AT 250 WORDS)

Nicotine is chemotactic for neutrophils and enhances neutrophil responsiveness to chemotactic peptides

Neutrophils contribute to chronic bronchitis and pulmonary emphysema associated with cigarette smoking. Nicotine was found to be chemotactic for human neutrophils but not monocytes, with a peak activity at approximately 31 micromolar. In lower concentrations (comparable to those in smokers' plasma), nicotine enhanced the response of neutrophils to two chemotactic peptides. In contrast to most other chemoattractants for neutrophils, however, nicotine did not affect degranulation or superoxide production. Nicotine thus may promote inflammation and consequent lung injury in smokers.

Neutral proteinases from human inflammatory cells. A critical review of their role in extracellular matrix degradation

The cell biology and in vitro activity of neutral proteinases derived from inflammatory cells and the mechanisms by which these enzymes might injure connective tissue are outlined. Current work directed toward understanding local control of tissue degradation may lead to effective strategies for assessing and reducing connective tissue injury in human disease.

Hypoxic injury to human alveolar macrophages accelerates release of previously bound neutrophil elastase. Implications for lung connective tissue injury including pulmonary emphysema

Human neutrophil elastase and other neutrophil granule constituents are internalized by human alveolar macrophages in vitro via receptor-mediated endocytosis, and immunoreactive neutrophil elastase is detectable within alveolar macrophages freshly harvested from human smokers. To gain insight into the potential role of neutrophil elastase bound by alveolar macrophages in the pathogenesis of connective tissue proteolysis, we have chosen hypoxia as a model of macrophage injury and have studied its effect upon the fate of bound neutrophil elastase. We found (1) that in a 3-h incubation after brief exposure to neutrophil elastase, control alveolar macrophages partially degraded bound enzyme, but they also released intact, enzymatically active, elastase in small amounts; (2) that release of TCA-insoluble radiolabeled elastase and elastase activity was enhanced fivefold and twofold over control, respectively, by alveolar macrophage injury during a 3-h incubation in humidified nitrogen; (3) that enzymatic activity of bound neutrophil elastase was largely masked by human neutrophil elastase-inhibitory activity of macrophage cell extracts. The data suggest (1) that the fate of neutrophil elastase bound to alveolar macrophages may be modulated by the local tissue environment; (2) that noxious agents may cause proteolytic tissue injury in the vicinity of alveolar macrophages by enhancing release of bound neutrophil elastase; (3) that alveolar macrophages may participate in the pathogenesis of centrilobular pulmonary emphysema by serving as a vector for neutrophil elastase, even if elastase activity is not detectable in alveolar macrophage lysates.

Effect of background loads on the perception of added loads to breathing

Using open-magnitude scaling, we compared the perceived magnitude of externally added resistive and elastic loads to breathing in normal subjects with that perceived when the background load (i.e., the minimum load of the circuit) was increased by the addition of either resistive or elastic loads of increasing magnitude. The study was carried out over four experimental sessions. After a control experiment (no added background load), the background load was increased by the addition of either a resistive or an elastic load for a duration of 3 min. The perceived magnitude of a further series of loads, proportionately increased, was then ascertained. This sequence was then repeated after a further increase in background. The results showed that the perceived magnitude of the load was closely related [mean r = 0.96 +/- 0.01 (SE)] to the magnitude of the physical stimulus expressed as the peak inspiratory pressure by a power function relationship in keeping with Stevens' law. After the increases in background resistance or elastance, there were no significant differences in either exponents or intercepts compared with basal conditions. There was no significant difference in the perceived magnitude of the loads after adaptation. At the smallest load, the perceived magnitude was less than expected from the control experiment. However, this reduction did not reach statistical significance. In the special senses, moderate-to-large stimuli show little change after adaptation, whereas small stimuli are reduced. Although not conclusive, we suggest that the relationship is similar with loaded breathing.

Psychophysics of inspiratory muscle force

The perceived magnitude of static inspiratory muscle pressure was studied in normal subjects using psychophysical techniques. The sensory magnitude of a range of inspiratory pressures increased as the magnitude of the pressure increased. When the duration of the inspiratory pressure was controlled, the sensory magnitude also increased as duration increased. The relationship can be described by a single psychophysical function, psi = k x P1.234 x t0.62, where psi is perceived magnitude, P is inspiratory pressure, t is duration, and k is a constant. Use of different muscle groups and changes in lung volume altered the perceived magnitude of static inspiratory pressures. When static inspiratory pressures were generated by the abdomen-diaphragm, the perceived magnitude was significantly greater (P less than 0.01) than when they were generated by the rib cage. When lung volume was increased, the perceived magnitude of pressure was reduced. The results show that the perceived magnitude of static inspiratory pressures is affected by the pressure itself, pressure duration, the muscles used, and the lung volume at which the pressure is generated.

Fate of human neutrophil elastase following receptor-mediated endocytosis by human alveolar macrophages. Implications for connective tissue injury

AM may be important in the pathogenesis of centrilobular emphysema of cigarette smokers because smokers' AM release elastolytic activity into culture medium and an expanded population of AM is found in lung regions of smokers where destructive lesions occur. AM are capable of receptor-mediated endocytosis of neutrophil elastase in vitro, but little has been known about the fate of the enzyme after endocytosis. We have observed that after brief exposure to HLE in vitro, (1) CEs of cultured human AM contain detectable quantities of neutrophil elastase and elastase activity for days; (2) endocytosed neutrophil elastase is slowly degraded by the macrophages; (3) neutrophil elastase and elastase activity are slowly released into the culture medium conditioned by the macrophages; (4) elastase activity released into CM by the macrophages has catalytic properties of neutrophil elastase; and (5) elastase released into CM during 5 days in culture is fourfold greater than the initial elastase activity of the CEs, suggesting that enzymatic activity of endocytosed elastase is masked by an intracellular inhibitor. Thus macrophages both degrade and release endocytosed neutrophil elastase and may play a very complex role in modulation of neutrophil elastase injury to connective tissue in the lung and other tissues.

The effect of intravenously administered almitrine, a peripheral chemoreceptor agonist, on patients with chronic air-flow obstruction

Almitrine, a peripheral chemoreceptor agonist, was given intravenously in a dose of 0.5 mg/kg/h for 2 h in a randomized double-blind manner with placebo, to 11 patients with severe chronic air-flow obstruction and hypoxemia (SaO2 less than 90%). There was no significant placebo effect. Maximal respiratory effect occurred at the end of the almitrine infusion with an increase in ventilation from 8.2 + 0.9 to 11.6 + 1.5 L/min (mean +/- SEM), and improvements in SaO2 from 83 +/- 3 to 90 +/- 2%, in PaO2 from 48 +/- 2 to 55 +/- 3 mmHg, and in PaCO2 from 54 + 3 to 47 +/- 4 mmHg. Venous admixture was reduced from 38 +/- 4% to 22 +/- 3%. In 4 patients, blood gas values substantially improved, but there was no change in total ventilation for ventilatory pattern. This study of acute effects showed that almitrine improved arterial PO2 and PCO2 in patients with chronic air-flow obstruction both by increasing ventilation and by improving ventilation-perfusion relationships.

Theory of resistive load detection

During normal breathing the brain sets the required muscle pressure to overcome resistance and elastance and presumably monitors the resultant flow (rate of change of volume). The lag in flow compared to the pressure can be described by a phase angle. When a small resistive load is added the resultant flow is delayed further and the phase angle increases. We postulate that if the change in phase angle exceeds a critical phase lag, the added load is detected. Over a wide range of basal resistances, R, the mathematical analysis predicts that detection occurs if the just noticeable added resistance, delta R, is a constant fraction of the basal resistance. Resistive load detection thus obeys the Weber psychophysical law, delta R/R = constant. This is in accord with previous experimental observations. The theory also predicts that delta R/R increases at low basal resistance in accord with recent experimental observations. Further as yet untested predictions of the theory are that breathing frequency and elastance should affect the Weber relationship.

Weber's law and resistive load detection

The threshold of detection for added resistive loads to breathing (delta R50) was measured in 4 normal subjects at 4 different background resistances (Ro). Under normal conditions (Ro = 2.26 +/- 0.16 (SEM) cm H2O/L/s), the mean delta R50 was 0.53 +/- 0.17 cm H2O/L/s and the Weber fraction (delta R50/Ro) was 0.24 +/- 0.07. When the background resistance was increased, the threshold of detection increased proportionately, so that the Weber fraction did not change significantly. The background resistance was also decreased by having the subject breathe heliox. Although this did not result in a change in delta R50 (0.68 +/- 0.1 cm H2O/L/s), the Weber fraction increased to 0.49 +/- 0.08. These results show that although the Weber fraction is relatively constant over a wide range of background resistances, it rises sharply at low levels of background resistance, a finding that is similar to other sensory modalities.

Characterization of the mannose/fucose receptor on human mononuclear phagocytes

Cells of the mononuclear phagocyte system contain a cell surface receptor which mediates the uptake of mannose- and fucose-terminated glycoproteins. We have extended the initial studies to human alveolar and monocyte-derived macrophages in culture using two radiolabelled ligands, the synthetic glycoconjugate mannose-bovine serum albumin and the lysosomal glycosidase, beta-glucuronidase. Uptake (37 degrees C) of 125I-mannose-BSA by freshly isolated alveolar macrophages is saturable with increasing concentrations of ligand. Kuptake values in macrophages of smokers and nonsmokers are similar, and resemble earlier reported values using rabbit alveolar macrophages (Kuptake = 40 nM). Uptake of 125I-mannose-BSA in cultured smoker macrophages is identical to that found in fresh cells, and uptake is stable for 5-10 days in culture. Fucose- and mannose-BSA are the most effective inhibitors of uptake, while N-acetylglucosamine-BSA is inhibitory at slightly higher concentrations. Binding (4 degrees C) of 125I-mannose-BSA is likewise ligand concentration dependent (KD = 30 nM). Freshly isolated human monocytes from healthy subjects and patients with cystic fibrosis do not have mannose-specific uptake. However, after monocytes are in culture for 3 days, mannose-specific uptake appears and Kuptake values and specificity of uptake are identical with the results from the alveolar macrophages. No uptake of mannose-BSA could be found in the human monocyte-like cell line, U937.

The perception of breathlessness in asthma

We studied the perception of breathlessness as a function of air flow obstruction in 45 asthmatic subjects using a category scaling technique. Air flow obstruction and breathlessness were induced by inhalations of histamine acid phosphate in twofold-increasing concentrations from 0.03 to 16 mg/ml. The FEV1 was measured after each inhalation of histamine, and the subject was asked to rate his symptoms of breathlessness. The results showed that breathlessness increased as the FEV1 decreased but, despite a close linear relationship in all subjects (mean r = 0.88 +/- 0.15 SD), there was a considerable variation in the severity of breathlessness for any particular degree of air flow obstruction (mean intercept, 0.50 +/- 0.89 SD). However, the increase in sensory magnitude with increasing air flow obstruction did not show the same degree of variability (mean slope, 0.13 +/- 0.06 SD). The variability in breathlessness in asthmatic patients is likely to have many components. Two of these components were identified. First, we found that there was less respiratory distress in those subjects in whom air flow obstruction was present at the onset of the study. However, the presence of air flow obstruction at this time does not result in a reduction in sensation for further increases in air flow obstruction as might be expected from discrimination studies. Second, there was a significant relationship (p less than 0.01) between bronchial responsiveness and the magnitude of respiratory distress. Those subjects highly responsive to histamine experienced less respiratory distress than the less responsive subjects.