Production of fibronectin by the human alveolar macrophage: mechanism for the recruitment of fibroblasts to sites of tissue injury in interstitial lung diseases

Connective matrix organization in chronic granulomas of experimental paracoccidioidomycosis

The histological and ultrastructural aspects of chronic granulomas from rats infected intraperitoneally with Paracoccidioides brasiliensis are described with special emphasis on the composition of the extracellular matrix. The granulomas were structurally arranged in two zones, one central containing fungi, and the other peripheral. The extracellular matrix was composed of collagen types I and III, proteoglycans, glycoprotein, and an undefined amorphous substance. The main cellular population was represented by macrophages, epithelioid cells, and giant cells in the central zone, and fibroblasts in the peripheral zone. The fibrotic process was a critical event in this stage of the infection, and showed a centrifugal direction. This might be provoked by direct stimulus from the fungi or by macrophage-fibroblastic interaction.

Reaction of macrophages activated by agents in vivo to quartz dust in vitro

A comparative study was made of the cytotoxic action of quartz dust in vitro on macrophages activated in vivo by intraperitoneal inoculation of physiological saline, thioglycolate and starch. The liberation of lactate dehydrogenase (LDH) into the supernatant culture medium, adherence to a plastic surface, extent of acid dye exclusion and ultrastructural alteration in the surface morphology of macrophages were taken as parameters of the cytotoxic action of the dusts. Thioglycolate and starch stimulated cells when exposed in vitro to quartz dust released more LDH into the supernatant culture medium and resulted in a greater decrease in macrophage adherence than similarly exposed cells derived from saline stimulated animals. No difference was observed between cells obtained from differently stimulated animals in increased acid dye uptake, loss of surface filopodia and rounding of cells which phagocytosed quartz particles. The results show that quartz is cytotoxic for macrophages, irrespective of their degree of activation and the extent of damage induced is related to the chemical agent used for activation of macrophages in vivo.

Decline of fibroblast chemotaxis with age of donor and cell passage number

Human dermal fibroblasts have a limited life span in culture, which is manifested by a progressive decline of their proliferative activity. Here we show by the Boyden Chamber assay that the chemotactic response of human fibroblasts to fibroblast-conditioned medium and fibronectin declines during cellular aging in vitro and in vivo. The chemotactic response of human embryonic fibroblasts (HEF) declined progressively after the 25th passage. Virtually no chemotactic activity could be observed after the 40th passage in culture. Fibroblasts cultures from donors aged between 70-90 years had lost chemotactic activity by the 15th passage. Cells from patients suffering from progeroid syndromes of premature aging showed, even in early passages, a very low chemotactic response (20% of the HEF) and lost their chemotactic activity after a few subcultures. The response to the chemoattractant fibronectin also decreased with aging. Immunofluorescence studies indicated that the decline in chemotactic activity was accompanied by the formation of a thicker fibronectin network in the extracellular matrix of senescent human fibroblasts and progeroid cells than that observed in early passage embryonic cultures. Since fibroblast chemotaxis and synthesis of connective tissue components probably play an important role in tissue repair, our results could contribute to an understanding of age-related differences in the healing of skin wounds.

Spectrum of alveolitis in quartz-exposed human subjects

To characterize silica-induced alveolitis in human subjects, we studied 22 workers in the granite stone cutting industry of Quebec and compared results with those of 22 manual workers without quartz exposure (group 1). All were nonsmokers and were of comparable age. On the basis of chest roentgenogram, seven were without disease (group 2), nine had silicosis without coalescence/conglomeration (group 3), and six had silicosis with coalescence/conglomeration (group 4). The alveolitis in subsets of silica-exposed workers with distinct clinical stages of disease was found to have distinct biologic characteristics.

A controlled study of oxygen metabolite release by alveolar macrophages from children with interstitial lung disease

The ability of alveolar macrophages (AM) to release O2 metabolites was studied in 8 children with interstitial lung disease (ILD), and in 11 children without lung parenchyma disorder. AM were collected by bronchoalveolar lavage. The experiments were performed on unstimulated AM and on AM stimulated by phorbol myristate acetate (PMA) or zymosan. Our results indicated that, with or without triggering agent, the amount of O2 metabolites release was a linear function pattern with time. The accumulation of superoxide anion (O2-) and hydrogen peroxide (H2O2) into the extracellular medium differed depending on the triggering agent used: with PMA, the amount of O2- released was threefold the amount of H2O2 detected in the medium, whereas with zymosan the O2- accumulation was tenfold higher than the amount of H2O2 measured. In patients with ILD, a significant increase in the amount of H2O2 release was observed for both unstimulated and stimulated AM (p less than 0.001). In this group, the measurement was repeated after a 2-month steroid treatment: prednisone had markedly improved the clinical, radiologic, and functional status of the patients, and this improvement was in good correlation with the decrease of O2 metabolite production. The amount of H2O2 release in each case was within the range of control values. Evaluation of O2 metabolite release by AM could be a useful parameter in the assessment of the activity of ILD.

Unilateral paraquat-induced lung fibrosis: evolution of changes in lung fibronectin and collagen after graded degrees of lung injury

We describe a model of pulmonary fibrosis in which doses of paraquat ranging from 0.001 mg/kg to 1.0 mg/kg were instilled into the right lung of rats. Lung injury, as measured by right lung lavage albumin content and differential neutrophil count, ranged from undetectable to extremely severe, depending on the dose. Lung fibrosis, as assessed by collagen content and electron microscopy, showed similar dose-response effects. Mortality was minimal. Lavage fibronectin increased after high doses of paraquat, peaked at 2 d postinjury, decreased sharply after 3 d and was normal by 7 d. The temporal pattern was similar to that for albumin. Cultured alveolar macrophages obtained at 4 d postinjury did not have significant increases in fibronectin release. Tissue fibronectin content increased more slowly than lavage fibronectin, peaking at 4 d postinjury, and was still elevated at 7 and 14 d postinjury. Incorporation of [35S]methionine into tissue fibronectin by lung explants obtained at different times postinjury showed a similar time course. Lung collagen content increased steadily between 4 and 14 d postinjury. We conclude that, in our model, graded degrees of lung injury and fibrosis can be produced by varying the dose of unilaterally instilled paraquat and that the increases in lavage fibronectin were related mainly to capillary permeability whereas increases in tissue fibronectin represented parenchymal synthesis. The time course of changes in lung tissue fibronectin and collagen was consistent with the proposed roles of fibronectin in tissue repair and fibrosis. The ability of our model to produce graduated degrees of lung injury and fibrosis should be useful in further studies on the pathogenesis of postinjury lung fibrosis.

Modulation of fibronectin gene expression in human mononuclear phagocytes

Under some conditions, mononuclear phagocytes spontaneously synthesize and release fibronectin, an extracellular matrix glycoprotein with versatile effects on cell-matrix interactions. To gain insight into the processes that modulate the level of fibronectin secretion by these cells, we used monocytes, in vitro matured monocytes and alveolar macrophages as models to compare fibronectin mRNA levels and fibronectin secretion in a variety of circumstances. Using Northern analysis and dot-blot analysis with a 32P-labeled human fibronectin cDNA probe, we evaluated steady-state mRNA levels and a human fibronectin-specific ELISA was used to evaluate fibronectin secretion. In all cases the amounts of fibronectin secreted paralleled fibronectin mRNA levels. Specifically (a) when fibronectin mRNA was undetectable, as in the case of normal blood monocytes, no fibronectin was secreted, but whenever fibronectin mRNA was present, as in normal alveolar macrophages, fibronectin was secreted by the cells; (b) as monocytes matured into macrophages in vitro, the cells began to express fibronectin mRNA and the cells secreted fibronectin; (c) when alveolar macrophages were activated with surface stimuli such as lipopolysaccharide (LPS) or immune complexes, fibronectin mRNA levels decreased and in parallel, the cells secreted less fibronectin; (d) in idiopathic pulmonary fibrosis (IPF), alveolar macrophages contained severalfold more fibronectin mRNA transcripts that normal and the cells spontaneously secreted severalfold more fibronectin than normal; and (e) when IPF alveolar macrophages were placed in culture the fibronectin mRNA levels in the cells decreased with time, and concurrently the amounts of fibronectin produced per unit time continually decreased. The observation of a strict concordance of fibronectin mRNA levels and fibronectin release by mononuclear phagocytes suggests that, at least in many circumstances, fibronectin secretion by mononuclear phagocytes is controlled by steady-state levels of fibronectin mRNA.

Chemotaxis of 3T3 and SV3T3 cells to fibronectin is mediated through the cell-attachment site in fibronectin and a fibronectin cell surface receptor

Fibronectin (FN) is a multidomain extracellular matrix protein that induces attachment and chemotactic migration of fibroblastic cells. In this study we analyzed the molecular determinants involved in the FN-induced chemotactic migration of normal and SV40-transformed 3T3 cells. Two different monoclonal antibodies to the cell-binding site of FN blocked chemotaxis to a 140-kD FN fragment (Ca 140) containing the cell-binding domain. A monoclonal antibody to a determinant distant from the cell-binding site did not affect chemotaxis. A synthetic tetrapeptide, RGDS, which represents the major cell-attachment sequence, was able to compete with FN and the Ca 140 fragment in chemotaxis assays, but this peptide itself had no significant chemotactic activity. A larger peptide encompassing this sequence, GRGDSP, was chemotactic, while the peptide GRGESP, where a glutamic acid residue was substituted for aspartic acid, was inactive. Chemotactic migration could be prevented in a dose-dependent manner by a rabbit polyclonal antiserum to a 140-kD cell surface FN receptor. This antibody was more effective on normal than on transformed 3T3 cells. Neither the anti-FN receptor antiserum nor a monoclonal antibody to the cell-binding site of FN blocked migration induced by another potent chemoattractant, platelet-derived growth factor. These data indicate that FN-induced chemotaxis of 3T3 and SV3T3 cells is mediated via the RGDS cell-attachment site of FN and the 140-kD cell surface FN receptor. The interaction is specific and can be altered by transformation.

A light microscopic and biochemical study of carbon tetrachloride-induced pulmonary fibrosis in rats: the preventive effect of malotilate

Orally administered malotilate was studied as a protective anti-fibrotic agent with respect to experimentally induced pulmonary fibrosis in rats. Intraperitoneally-injected carbon tetrachloride (CCI4) significantly increased the lung weight to body weight ratio, lung total protein and total hydroxyproline content, while the relative protein content of the lungs decreased. CCI4) induction caused diffuse alveolar damage and inflammatory changes mimicking usual interstitial pneumonia with interstitial fibrosis. The morphological findings suggest a primary toxic effect on the lungs. Treatment with malotilate completely normalized the lung weight to body weight ratio, lung total and relative protein content and total hydroxyproline content. Morphologically, malotilate seemed to prevent the exudative inflammatory changes and interstitial fibrosis, but not the primary toxic effect of CCI4 on the capillary endothelium or the alveolar epithelium, the result of which was diffuse alveolar damage. It is concluded that malotilate may be a useful drug for the prevention of pulmonary fibrosis.

Exaggerated spontaneous release of platelet-derived growth factor by alveolar macrophages from patients with idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis is a fibrotic lung disease characterized by an increased number of mesenchymal cells in the alveolar walls. Alveolar macrophages constitutively express low levels of c-sis, the protooncogene coding for the B chain of platelet-derived growth factor, a protein with chemotactic and mitogenic activity toward mesenchymal cells. We therefore hypothesized that alveolar macrophages in patients with idiopathic pulmonary fibrosis may release increased amounts of platelet-derived growth factor, which might help to explain the accumulation of mesenchymal cells and the fibrosis of the lower respiratory tract in the disease. Evaluation of alveolar macrophages recovered from the lungs of patients with idiopathic pulmonary fibrosis demonstrated that these cells spontaneously released four times more platelet-derived growth factor than did alveolar macrophages recovered from normal persons (P less than 0.01). That the platelet-derived growth factor molecules were potentially active was shown by their chemotactic activity for smooth-muscle cells and their ability to act as a "competence" factor for fibroblast growth. These observations suggest the possibility that the accumulation of mesenchymal cells within the alveolar walls in patients with idiopathic pulmonary fibrosis may result partly from the exaggerated release of the potent mitogen platelet-derived growth factor by mononuclear phagocytes in the lower respiratory tract.

Asbestos-induced changes in rat lung parenchyma

Fischer 344 rats have been exposed to UICC crocidolite by whole-body inhalation procedures for periods of 1 d to 12 mo. Material was obtained from the same location in the left lung, and the numbers of cells in the parenchyma were identified and determined by transmission electron microscopy. An immediate increase (1 d of exposure) was evident in the number of type II cells, suggesting a direct action of the dust on these cells. The number of interstitial and alveolar macrophages showed a significant increase after 3 mo of exposure. The number of alveolar macrophages containing dust particles after a 1-d exposure was 49%, and the corresponding value after 12 mo of exposure was 92%. The longer periods of exposure were associated with an increase in the number of particles per macrophage. Polymorphs appeared in the interstitium at airway bifurcations, prior to their appearance in the alveolar space. These bifurcations were also the initial sites where evidence of cell damage and collagen deposition was seen. In this experiment crocidolite appears to be weakly fibrogenic, and other factors may be needed to produce the marked lesions seen in human asbestosis.

Quantitative gallium 67 lung scan to assess the inflammatory activity in the pneumoconioses

Gallium 67 lung scan has recently become increasingly used to evaluate the biological activity of alveolitis of interstitial lung diseases and to stage the disease process. In order to have a more precise and objective indicator of the inflammatory activity in the lung, we and others have developed computer-based quantitative techniques to process the 67Ga scan. In this report, we compare the results of three such computer-based methods of analysis of the scans of 38 normal humans and 60 patients suspected to have pneumoconiosis. Results of previous investigations on the mechanisms of 67Ga uptake in interstitial lung disease are reviewed. These data strengthen the view that quantitative 67Ga lung scan has become a standard technique to assess inflammatory activity in the interstitial lung diseases and that computer-based method of analysis of the scan provides an index of inflammatory activity of the lung disease that correlates with lung lavage and biopsy indices of inflammation in the lung tissue.

The role of intraalveolar fibrosis in the process of pulmonary structural remodeling in patients with diffuse alveolar damage

For a study of the processes and mechanisms of pulmonary structural remodeling in fibrotic lungs and metaplastic squamous epithelial cells in fibrotic alveoli, immunohistochemical, ultrastructural, and light-microscopic morphometric observations were made of the lungs in acute and proliferative stages of diffuse alveolar damage (n = 40) obtained from biopsies and autopsies. Morphometry showed that intraalveolar fibrosis developed in the early proliferative stage and was more prominent than interstitial fibrosis. In the early proliferative stage, activated myofibroblasts migrated into intraalveolar spaces through gaps in the epithelial basement membrane. They then attached to the luminal side of epithelial basement membrane and produced intraalveolar fibrosis and coalescence of alveolar walls. This intraalveolar fibrosis was the essential factor in the remodeled lungs. Albumin, fibrinogen, immunoglobulins, and surfactant apoprotein were present throughout the hyaline membrane. Fibronectin was not found in hyaline membrane of the lesions in early acute stage but was demonstrated in later stages in outer layers of hyaline membranes and in the areas of intraalveolar fibrosis. Fibronectin may be responsible for the migration and proliferation of myofibroblasts in intraalveolar spaces. Metaplastic single-layered and stratified squamous epithelial cells were keratin-positive and surfactant apoprotein-negative. These metaplastic epithelial cells were frequently found in the alveoli with minimal Type II epithelial cell proliferation and in the grossly scarred alveoli.

Tumor necrosis factor production by human sarcoid alveolar macrophages

Tumor necrosis factor (TNF) is an oncolytic peptide that may also exert many other biologic effects. Experimentally, immunologically activated mononuclear phagocytes stimulated with endotoxin (LPS) produce TNF, while resting mononuclear phagocytes stimulated with LPS produce little TNF. To date, the ability of human alveolar macrophages (AMs) to produce TNF has not been clearly delineated. As pulmonary sarcoidosis is a granulomatous inflammatory disorder characterized by immunologically activated AMs, we investigated the production of TNF by AMs obtained by bronchoalveolar lavage from 7 normal volunteers and 13 patients with pulmonary sarcoidosis. The AMs were cultured with and without LPS, and TNF production was assessed by an in vitro cytotoxicity assay. Unstimulated sarcoid and normal AMs produced little TNF, but LPS stimulation enhanced TNF production by both normal and sarcoid AMs. Furthermore, LPS-stimulated sarcoid AMs produced more TNF than normal AMs (84.9 +/- 16.7 versus 32.5 +/- 10.2 units/million cells, P less than 0.05). It is concluded that human AMs can produce TNF and that sarcoid AMs are primed and can produce significantly more TNF, compared with normal AMs.

Inhibition of bleomycin-induced pulmonary fibrosis by nordihydroguaiaretic acid. The role of alveolar macrophage activation and mediator production

The role of alveolar macrophage activation and release of mediators remains unclear. In this study, this role is examined with respect to the effects of relatively selective inhibitors of arachidonate metabolism on the pathogenesis of pulmonary fibrosis. CBA/J mice were administered bleomycin (0.037 units) endotracheally to induce pulmonary fibrosis. Daily intraperitoneal injections of a lipoxygenase inhibitor, nordihydroguaiaretic acid (NDGA) inhibited pulmonary fibrosis in a dose-dependent manner (15-25 mg/kg body weight), as assessed by both lung collagen synthesis and total lung hydroxyproline content. The less specific inhibitor BW755c was also effective at a dose of 25 mg/kg. In contrast, the cyclooxygenase inhibitor, ibuprofen (15 mg/kg), was completely ineffective. Correlated with this antifibrogenic activity of NDGA was the inhibition of several other parameters of bleomycin-induced pulmonary fibrosis. Bleomycin treatment caused a greater than threefold increase in the percentage of alveolar macrophages expressing Ia antigen (from 7.7% +/- 1.07% to 29.9% +/- 4.16% of total recoverable alveolar macrophages). NDGA, but not ibuprofen, inhibited this increase in a dose-dependent manner. Associated with this indication of macrophage stimulation was an increase in spontaneous macrophage production of fibroblast growth factor (MDGF) activity as a result of bleomycin instillation. This increase was also inhibited by NDGA treatment. In contrast, bleomycin treatment caused a reduction in alveolar macrophage interleukin-1 (IL-1) production, and NDGA treatment did not alter this reduction, which suggests that MDGF is separate from IL-1 in this case, and that MDGF played a more dominant role, at least in this model of pulmonary fibrosis. This antifibrogenic activity of NDGA was accomplished without any reduction in spontaneous macrophage prostaglandin (PG)E2 production, which suggests the selectivity (versus cyclooxygenase pathway) of NDGA inhibition and the relative lack of importance of macrophage-derived PGE2 in modulating fibrogenesis in this model. The results of this study have thus demonstrated the importance of alveolar macrophage stimulation and increased production of MDGF in the pathogenesis of bleomycin-induced pulmonary fibrosis. The data also suggest that both macrophage parameters are subject to regulation by arachidonate metabolites.

Spontaneous expression of the c-sis gene and release of a platelet-derived growth factorlike molecule by human alveolar macrophages

Alveolar macrophages from normal individuals and patients with interstitial lung diseases spontaneously expressed a 4.2-kilobase mRNA complementary to the c-sis gene, a proto-oncogene coding for one of the chains of platelet-derived growth factor (PDGF). Concomitantly, these cells released a mediator with the properties of PDGF, including: chemotactic factor for smooth muscle cells whose activity was resistant to heat and acid, but sensitive to reduction; mitogenic (competence) activity for fibroblasts; ability to compete with PDGF for its receptor; and precipitated by an anti-PDGF antibody. While blood monocytes did not contain c-sis mRNA transcripts, monocytes matured in vitro expressed c-sis, consistent with the concept that expression of c-sis occurs during the differentiation of monocytes into alveolar macrophages. Together with the known actions of PDGF, these observations suggest that the c-sis proto-oncogene and its PDGF product are part of the armamentarium available to the alveolar macrophages for normal lung defense and participation in lung inflammation.

Activated alveolar macrophage and lymphocyte alveolitis in extrathoracic sarcoidosis without radiological mediastinopulmonary involvement

Cellular characteristics of BAL were investigated in 18 patients with proved extrathoracic sarcoidosis (that is, sarcoidosis that affected the skin, eyes, parotid glands, stomach, nose, kidneys, or meninges) without clinical or radiological mediastinopulmonary involvement. Computed tomography of the thorax was performed on five patients: four patients were normal, and one had enlarged lymph nodes (these enlargements were not detectable on the patient's chest roentgenogram). The results of pulmonary function tests were normal in all patients. The total BAL cell count did not differ significantly between controls and patients. Abnormal percentages of alveolar lymphocytes (from 18 to 87%) were noted in 15 out of 18 patients. SACE levels were normal in 15 patients. No pulmonary gallium uptake was detected. The chemiluminescence of AM's, whether spontaneous or PMA induced, was increased in five out of seven patients. The percentages of T3+ lymphocytes in sarcoidosis patients did not significantly differ from those in controls. The T4+:T8+ ratio was normal in four patients and slightly increased in one. Follow-up of patients showed that alveolar lymphocytosis is as lasting as extrathoracic involvement. Our data demonstrate increased percentages of lymphocytes and activated AM's in the BAL of patients with extrathoracic sarcoidosis. This may be due to the initial involvement of the respiratory tract in extrathoracic sarcoidosis or to the diffusion of activated macrophages and lymphocytes from an extrathoracic site into the lung.

Phenytoin-induced connective tissue growth in the rat

Rats were treated daily for 9 days with 100, 50, or 25 mg/kg phenytoin i.p. This treatment resulted in a significant increase in the thickness of the connective tissue capsules of the liver, spleen, and pancreas, and of the subepithelial connective tissue of the mesentery but not the epicardium or visceral pleura of the lung where exposure to the drug was via the vascular route. Many areas of connective tissue growth exhibited obvious proliferation of fibroblasts and in some areas contained seemingly large numbers of macrophages and an increase in vascularity. It was demonstrated by electron microscopy that the macrophages occasionally were seen in intimate contact with the fibroblasts. Our observations clearly showed that intraperitoneal exposure of visceral connective tissues of the rat to phenytoin rapidly resulted in a dose-related proliferation of that tissue. The presence of numerous macrophages leads to the suggestion that macrophage-derived growth factor could be responsible for the increased growth.

Organization of the connective matrix of the sarcoid granuloma. Evolution and cell-matrix interactions

The connective matrix of sarcoid granulomas is polymorphic. Immunolabeling techniques show that it is partly composed of fibronectin and collagen types I and III and is found at all stages of the granulomas' evolution. This suggests that the process known as hyalinization is not due to changes in the composition of the matrix but results from a gradual accumulation of connective tissue components. Fibronectin seems to play an essential role as mediator between different cell populations during the evolution of the granulomas.

Familial idiopathic pulmonary fibrosis. Evidence of lung inflammation in unaffected family members

We evaluated 17 clinically unaffected members of three families with an autosomal dominant form of idiopathic pulmonary fibrosis for evidence of alveolar inflammation. Each person in the study was examined by gallium-67 scanning for a general estimate of pulmonary inflammation, and by bronchoalveolar lavage for characterization of the types of recovered cells and their state of activation. Eight of the 17 subjects had evidence of alveolar inflammation on the lavage studies. Supporting data included increased numbers of neutrophils and activated macrophages that released one or more neutrophil chemoattractants, and growth factors for lung fibroblasts--findings similar to those observed in patients with overt idiopathic pulmonary fibrosis. Four of these eight also had a positive gallium scan; in all the other clinically unaffected subjects the scan was normal. During a follow-up of two to four years in seven of the eight subjects who had evidence of inflammation, no clinical evidence of pulmonary fibrosis has appeared. These results indicate that alveolar inflammation occurs in approximately half the clinically unaffected family members at risk of inheriting autosomal dominant idiopathic pulmonary fibrosis. Whether these persons with evidence of pulmonary inflammation but no fibrosis will proceed to have clinically evident pulmonary fibrosis is not yet known.

Toxicity of mycotoxins for the rat pulmonary macrophage in vitro

The presence of mycotoxins in grains is well documented. Workers in grain handling occupations are commonly exposed to grain dust aerosols. Work in our laboratory has shown that T-2 toxin is highly toxic to rat alveolar macrophages in vitro, causing loss of viability, release of radiolabeled chromium, inhibition of macromolecular synthesis, inhibition of phagocytosis, and inhibition of macrophage activation. Similarly, patulin caused a significant release of radiolabeled chromium, decrease in ATP levels, significant inhibition of protein and RNA synthesis, and inhibition of phagocytosis. The data show that both T-2 toxin and patulin are highly toxic to rat alveolar macrophages in vitro. The data further suggest that the presence of these mycotoxins in airborne respirable dust might present a hazard to exposed workers.

Tracheal lavage and plasma fibronectin: relationship to respiratory distress syndrome and development of bronchopulmonary dysplasia

Plasma for fibronectin determinations was obtained from 39 neonates with uncomplicated respiratory distress syndrome (RDS) and from 15 infants with RDS who developed bronchopulmonary dysplasia (BPD). Tracheal lavage fibronectin and albumin concentrations were measured in 15 infants with RDS and 15 with BPD. Control plasma fibronectin values were obtained from 20 healthy preterm infants on days 1, 2, 3, 14, and 30 of life. Control tracheal lavage fibronectin and albumin concentrations were measured in 17 neonates of various gestational ages who required tracheal intubation for nonpulmonary indications. Mean plasma fibronectin concentrations from patients with RDS was 121 +/- 11 micrograms/ml on days 1, 2, and 3, versus control level of 163 +/- 12 micrograms/ml (P less than 0.01). Mean tracheal lavage fibronectin/albumin ratio was 3.8 +/- 0.6 ng per microgram of albumin on days 1 to 5 for infants with RDS, versus control level of 5.6 +/- 3.6 (P = NS). Tracheal lavage fibronectin/albumin ratio from patients with BPD was elevated at 16.3 +/- 5.0 ng fibronectin per microgram of albumin on days 14 to 21, and 23.6 +/- 7.4 on day 30 (P less than 0.05 versus control and and versus RDS days 1 to 10). Low plasma fibronectin concentrations early in RDS may contribute to the development of pulmonary capillary leak. High tracheal lavage fibronectin levels may foster the development of pulmonary fibrosis in patients with BPD.

Modulation of alveolar macrophage-driven fibroblast proliferation by alternative macrophage mediators

Tissue fibrosis results, in part, from an interaction between growth regulatory molecules released by mononuclear phagocytes and fibroblasts. In the chronic interstitial lung disorders, alveolar macrophages, the mononuclear phagocytes of the lung, are known to spontaneously release two growth factors for fibroblasts, fibronectin and alveolar macrophage-derived growth factor (AMDGF) that together stimulate nonreplicating lung fibroblasts to divide. In addition to these two primary growth promoting signals, alveolar macrophages are able to release other mediators that may have a potential role in modulating lung fibroblast replication in response to these primary signals, including interferon gamma (IFN gamma), prostaglandin E2 (PGE2), and interleukin 1 (IL-1). To evaluate this possibility, we examined the effect of each of these other mediators on lung fibroblast replication in response to fibronectin and AMDGF in serum-free, defined medium. IFN gamma had no effect on fibroblast replication. In contrast, PGE2 resulted in a dose-dependent inhibition of fibroblast replication in response to fibronectin and AMDGF with 50% of the maximum inhibition observed at a PGE2 concentration of less than 10 ng/ml. IL-1, while not active as a primary growth promoting signal, at concentrations of 4-10 U/ml, augmented fibroblast replication in response to fibronectin and AMDGF by 10 to 15%. Temporally, the growth augmenting effect of IL-1 occurred early in the G1 phase of the cell cycle. These data indicate that lung fibroblast replication in response to two of the primary growth promoting signals spontaneously released by alveolar macrophages in the interstitial lung disorders, while uninfluenced by IFN gamma, can be inhibited by PGE2 and modestly augmented by IL-1. Understanding the relevant fibroblast growth modulatory signals within the alveolar microenvironment in the chronic interstitial disorders may lead to rational therapeutic strategies designed to interrupt the fibrotic process.

Fibronectin and procollagen 3 levels in bronchoalveolar lavage of asbestos-exposed human subjects and sheep

To evaluate the potential interest of levels of fibronectin and procollagen 3 in bronchoalveolar lavage fluid as markers of fibrogenic activity, we characterized the time course of changes in fibronectin and procollagen 3 levels in the tracheal lobe of sheep exposed to nonfibrogenic and fibrogenic materials. We correlated these observations with those of bronchoalveolar lavage in long-term asbestos workers in various stages of disease activity. Following studies before exposure, the tracheal lobe of three groups of 24 sheep were exposed once to 100 ml of phosphate-buffered saline solution (PBS), to 100 mg of latex beads in 100 ml of PBS, or to 100 mg of chrysotile fibers in 100 ml of PBS. Bronchoalveolar lavages were obtained at 0, 1, 2, 4, 8, and 12 months after exposure, and four or five sheep per group were killed after each lavage for histopathologic analysis. Fibronectin in bronchoalveolar lavage fluid increased significantly only in the asbestos-exposed sheep to values two to three times above controls or latex-exposed sheep and remained elevated during the 12 months of the study. Levels of procollagen 3 in bronchoalveolar lavage fluid were increased significantly only during the first two months following exposure in the asbestos-exposed sheep only. In the asbestos workers without disease, levels of fibronectin and procollagen 3 in bronchoalveolar lavage fluid were comparable to controls, but these levels were significantly elevated in those with asbestos-associated alveolitis or asbestosis. This study documents that the measurement of levels of fibronectin and procollagen 3 in bronchoalveolar lavage fluid assesses fibrogenic activity of alveolitis and should be useful to predict its progression in a fibrotic process. In asbestos workers the potential use of these markers is primarily related to early detection of asbestos-induced pulmonary injury.

Biochemical markers in sarcoidosis

The clinical course of sarcoidosis is varying and unpredictable. Once the diagnosis has been made, the clinician needs simple tests to detect and predict remission or progression, to determine whether treatment is effective or not, and to assess the clinical activity of the disease. Sarcoidosis is a multisystem disease, but the lungs are almost always involved. Traditionally, the clinical management has therefore included chest X-rays and lung function studies. Extrapulmonary lesions have been followed in different ways. Sensitive and reproducible biochemical tests would be helpful in evaluating the clinical course of patients with sarcoidosis, if they measure functions related to the granulomatous inflammation. This review will deal with measurements of serum and urinary calcium, and 1,25-dihydroxyvitamin D. The usefulness of single and serial determinations of lysozyme, angiotensin converting enzyme, beta 2-microglobulin, collagenase, carboxypeptidase and glucuronidase in serum, bronchoalveolar lavage fluid, and other biological fluids will be discussed.

Early cellular events in pulmonary fibrosis

In this review we have surveyed recent investigations of early cellular events in pulmonary fibrosis both in animal models and in human diseases. Analysis of the interactions of the numerous cell types in the lung following injury is an almost overwhelmingly complex enterprise. In the animal models experimental design has a profound effect on results, making it difficult to compare studies when species, fibrogenic agent, dose, route of exposure, schedule of administration, time course, and analytical methods may not be equivalent. In human diseases we are rarely able to obtain data at precisely the same time point in the course of the disease even among patients in the same study, and possible confounding variables present are legion. Transcending these difficulties for the moment, can we draw any conclusions from our current knowledge of early cellular interactions in pulmonary fibrosis? What is striking is not that there are so many agents that can potentially induce pulmonary fibrosis, but that the lung has such capabilities for recovery. Although the major effector cells may all initially participate in damaging the lung and initiating fibrosis, there is evidence that they may also have the capacity to participate in subsequent repair. Macrophages may initially recruit fibroblasts and stimulate them to proliferate, only to suppress them subsequently. Macrophage production of prostaglandins can lead to suppression of macrophage, neutrophil and lymphocyte responses, thus attenuating tissue injury and the development of fibrosis. Neutrophils may initially release toxic metabolites and enzymes that damage parenchyma. However, there is evidence that they may later play a role in attenuating fibrosis, perhaps through collagenase secretion, or through as yet unknown mechanisms. Lymphocytes may initially participate in a number of damaging ways by secreting chemoattractants for other cells and participating in destructive autoimmune processes. However, there is evidence that subpopulations of T cells may dramatically shift during the course of fibrosis, leading to attenuation of the process. It may thus be useful to consider irreversible pulmonary fibrosis as the end result of a process in which the balance of normal injury/repair mechanisms is disrupted. There is clearly no single "fibrogenic event." Rather, there seem to be a number of places where disruption of balance/repair processes may begin. In diseases of unknown etiology such as sarcoidosis or IPF, loss of control may occur at the genetic level, leading to the destructive alveolitis that is the apparent precursor of fibrosis.(ABSTRACT TRUNCATED AT 400 WORDS)

Characterization of a macrophage-derived plasminogen-activator inhibitor. Similarities with placental urokinase inhibitor

Human and mouse macrophages release a fibrinolytic inhibitor after stimulation by endotoxin in vitro. The released mouse inhibitor was indistinguishable in size by molecular-sieve chromatography from an intracellular form (approx. 50 kDa), and both inhibitors blocked urokinase directly as judged by a 125I-plasminogen conversion assay. The intracellular inhibitor was found mostly to dissociate from 125I-urokinase during sodium dodecyl sulphate/polyacrylamide-gel electrophoresis under reduced conditions, but a dodecyl sulphate-stable complex at 65-67 kDa was observed. Because of similarities in the reported size, stability and urokinase-binding properties of a placental urokinase inhibitor, the kinetic properties of the two inhibitors were compared. Under the reaction conditions employed (37 degrees C at pH7.4 in the presence of 0.2% Triton X-100), the association rate constants and equilibrium dissociation constants of the two inhibitors were indistinguishable, 3 X 10(5) M-1 X s-1 and 4 X 10(-10) M respectively. These data show that peritoneal macrophages contain a plasminogen-activator very similar to a previously recognized placental inhibitor. Although the inhibitor appears to be a trace protein in macrophages, placental macrophages may account for the accumulation of the inhibitor in placental tissue.

Gamma interferon is spontaneously released by alveolar macrophages and lung T lymphocytes in patients with pulmonary sarcoidosis

Gamma interferon (IFN gamma) is a potent immune mediator that plays a central role in enhancing cellular immune processes. This study demonstrates that while lung mononuclear cells from normal individuals spontaneously release little or no interferon (less than 10 U/10(6) cells per 24 h), those from patients with pulmonary sarcoidosis spontaneously release considerable amounts (65 +/- 20 U/10(6) cells per 24 h, P less than 0.02 compared to normals). Furthermore, cells from patients with active disease release far more interferon than those from patients with inactive disease (101 +/- 36 compared to 24 +/- 8 U/10(6) cells per 24 h, P less than 0.02). Characterization of this interferon using acid sensitivity, specific antibody inhibition, and target cell specificity criteria demonstrated that it was almost entirely IFN gamma. This spontaneous release of IFN gamma appeared to be compartmentalized to the lung of these patients in that their blood mononuclear cells spontaneously released little or no IFN gamma (P less than 0.02, compared to sarcoidosis lung mononuclear cells) and no IFN gamma was detected in their serum. Both lung T lymphocytes and alveolar macrophages contributed to the spontaneous release of IFN gamma by lung mononuclear cells from sarcoid patients; purified preparations of T lymphocytes and alveolar macrophages from these patients spontaneously released similar amounts of IFN gamma (56 +/- 21 and 32 +/- 11 U/10(6) cells per 24 h, respectively, P greater than 0.3). At least one role for IFN gamma in the pathogenesis of sarcoidosis appeared to be related to activation of alveolar macrophages, as alveolar macrophages recovered from patients with active disease spontaneously killed [3H]uridine-labeled tumor cell targets (17.7 +/- 4.5% cytotoxicity compared with 2.8 +/- 0.9% in normals, P less than 0.02) and purified IFN gamma enhanced the ability of alveolar macrophages from sarcoidosis patients with inactive disease to kill similar targets (P less than 0.001, compared to alveolar macrophages cultured in medium alone). Treatment of sarcoid patients with corticosteroids, a therapy known to suppress the activity of the disease, caused a marked reduction in the level of spontaneous IFN gamma release by lung mononuclear cells compared with untreated patients (P less than 0.02), which suggests that the effectiveness of corticosteroid therapy in controlling active pulmonary sarcoidosis may, at least in part, be due to suppression of IFN gamma release.

[Importance of fibroblast chemotaxis in wound healing and tumor cell evasion]

Fibroblast are responsible for the synthesis of the structural proteins of the connective tissue. A further property of these cells, their migratory ability, could be analyzed in the last years. A special form of migration is chemotaxis, which can be quantitatively measured in a modified Boyden chamber in-vitro. Using this method chemoattractive substances could be characterized, which are able to stimulate fibroblasts and tumorcells to chemotactic migration. Furthermore it could be proved, that benign and transformed cell lines react in a different manner towards these chemoattractive substances. The in-vitro results allow some hypotheses about both fibroblast migration in wound healing or chronic inflammation, and the mechanisms of tumor cell evasion in the tumor surrounding tissue or the metastasizing process in other organs.

Fibronectin production by synovial intimal cells

The distribution of fibronectin in the inflamed synovium has been described previously using immunohistochemical methods. Under favourable conditions, it is possible to demonstrate apparent cytoplasmic staining of the intimal cell layer. We have further investigated the localisation of fibronectin in the synovial intimal cells using higher resolution techniques with peroxidase-antiperoxidase staining and high power light microscopy of semi-thin Araldite sections and immunoelectron microscopy using a protein A-gold technique. Synovia from 11 mechanical/traumatic, or osteoarthritic joints; 12 seropositive rheumatoid arthritis and nine cases from other joint diseases made a total of 32 cases examined in semi-thin sections, while six rheumatoid and two osteoarthritis synovia were studied by immunoelectron microscopy. Fibronectin was demonstrated in individual cells of the synovial intimal layer in 22 out of 32 samples examined by the light microscope method, and electron microscopy of adjacent sections showed that the positively staining cells were type B synoviocytes. Immunoelectron microscopy confirmed the presence of fibronectin within the rough endoplasmic reticulum of type B synoviocytes in all but one of the eight samples examined. The results provide evidence that the type B synoviocyte is responsible for fibronectin production.

Clinical features to stage alveolitis in asbestos workers

To analyze the clinical features of asbestos-induced alveolitis and stage its activity, we evaluated 217 asbestos workers by the usual clinical, radiological, and functional parameters and computerized gallium 67(Ga) lung scan; we obtained bronchoalveolar lavage (BAL) in 33 and lung biopsy in 6. In addition, we scored the profusion of lung rales and correlated it with other parameters of severity of asbestosis. In the 55 workers without asbestosis and normal 67Ga scan, BAL analyses were comparable to those of controls. Of the 56 without asbestosis but increased 67Ga lung uptake, BAL analyses in 8 documented a predominantly macrophagic alveolitis (confirmed on lung biopsy in 3), with the highest levels of BAL fibronectin. In the 106 workers with asbestosis, 67Ga lung uptake was increased in 75; BAL in 17 demonstrated a macrophagic and neutrophilic alveolitis with elevated fibronectin levels. Lung biopsy in 3 of the latter workers documented peribronchiolar fibrosing alveolitis. Rale scores in all workers or in those without asbestosis did not correlate with 67Ga scores; they correlated fairly well with profusion of parenchymal opacities (Rs = 0.42) and rigidity of the lung pressure-volume curve (Rs = 0.39). Thus, 67Ga lung uptake is an early indicator of chronic macrophagic alveolitis in asbestos workers, which usually progresses to asbestosis. In the disease, profusion of lung rales constitutes a simple clinical mode of assessment of disease severity that correlates better with radiological and functional parameters than with parameters of alveolitis.

Normal human alveolar macrophages obtained by bronchoalveolar lavage have a limited capacity to release interleukin-1

Interleukin-1 (IL-1) is a mediator released by stimulated mononuclear phagocytes that is thought to play an important role in modulating T and B lymphocyte activation as well as in contributing to the febrile response and other inflammatory processes. Circulating mononuclear phagocytes, blood monocytes, readily release IL-1 when stimulated. However, the ability of lung mononuclear phagocytes, alveolar macrophages, to dispose of the large daily burden of inhaled antigens without stimulating an inflammatory response suggests that the release of IL-1 by alveolar macrophages may differ significantly from that of blood monocytes. To evaluate this hypothesis, normal autologous alveolar macrophages, obtained by bronchoalveolar lavage, were compared with blood monocytes for their ability to release IL-1 in response to a standard stimulus, lipopolysaccharide (LPS). Alveolar macrophages were found to be at least 1,000 times less sensitive to LPS than blood monocytes. Furthermore, alveolar macrophages released significantly less IL-1 than blood monocytes (26 +/- 11 vs. 128 +/- 21 U/10(6) cells X 24 h, respectively, after stimulation with 10 micrograms/ml of LPS, P less than 0.001). This difference was not due to the release of substances by macrophages, which inhibited lymphocyte proliferation in response to IL-1, or to degradation of IL-1 by macrophages. Culturing macrophages in the presence of indomethacin and dialysis of macrophage supernatants did not affect the difference, and culturing macrophages with monocytes did not decrease detectable IL-1 activity from the monocytes. The IL-1 produced by the two cell types was indistinguishable by anion-exchange chromatography, gel filtration, and isoelectric focusing. In addition, consistent with the findings for alveolar macrophages, macrophages generated by the in vitro maturation of blood monocytes were also deficient in their ability to release IL-1. These findings suggest that if the population of alveolar macrophages obtained by bronchoalveolar lavage represents the total in vivo population of alveolar macrophages, although normal human macrophages are capable of IL-1 release, they are relatively limited in this ability, and this limitation seems to be linked to the maturational state of the mononuclear phagocyte. These observations may explain, in part, the ability of alveolar macrophages to clear the airspaces of foreign antigens without extensive activation of other pulmonary inflammatory and immune effector cells.

Alveolar macrophage replication. One mechanism for the expansion of the mononuclear phagocyte population in the chronically inflamed lung

Within any chronically inflamed tissue, there is an increased number of macrophages, pluripotential phagocytic cells that, while critical to host defenses, are also able to profoundly damage parenchymal structure and function. Because of their central role in the inflammatory response, considerable attention has been focused on the mechanisms resulting in an expansion of the macrophage population within an inflamed tissue. Although recruitment of precursor monocytes from the circulation into inflamed tissues clearly plays an important role in macrophage accumulation, it is also possible that replication of tissue macrophages contributes to the expansion of macrophage numbers in inflammation. Because of the accessibility of tissue macrophages with the technique of bronchoalveolar lavage, the lung provides an ideal opportunity to test this hypothesis in humans. To accomplish this, bronchoalveolar lavage was performed to obtain alveolar macrophages from normals (n = 5) and individuals with chronic lung inflammation (normal smokers [n = 5], idiopathic pulmonary fibrosis [n = 13], sarcoidosis [n = 18], and other chronic interstitial lung disorders [n = 11]). Alveolar macrophage replication was quantified by three independent methods: (a) DNA synthesis, assessed by autoradiographic analysis of macrophages cultured for 16 h in the presence of [3H]thymidine; (b) DNA content, assessed by flow cytometric analysis of macrophages fixed immediately after recovery from the lower respiratory tract; and (c) cell division, assessed by cluster formation in semisolid medium. While the proportion of replicating macrophages in normals was very low, there was a 2- to 15-fold increase in this proportion in patients with chronic lung inflammation. In addition, morphologic evaluation demonstrated that individuals with chronic lung inflammation had alveolar macrophages undergoing mitosis. These results suggest that local tissue macrophage replication may play a role in the expansion of the macrophage population in chronic inflammation.

Effect of vitamin A and its derivatives on collagen production and chemotactic response of fibroblasts

Vitamin A and several other retinoids were added to fibroblast cultures in order to study possible alterations in biochemical properties and cellular responsiveness. The proliferation of cells was inhibited as the concentration of retinoids increased from 10(-9) to 10(-5) mol/l. Synthesis of non-collagenous proteins and production of both type I and type III collagen were decreased. The onset of type III collagen synthesis by tendon fibroblasts in culture was delayed. Furthermore, the chemotactic response of fibroblasts to fibroblast-conditioned medium was markedly reduced in the presence of retinoids (10(-6) to 10(-12) mol/l).

The pulmonary extracellular lining

The extracellular lining of the lungs is reviewed. The pulmonary extracellular lining is a complex mixture of phospholipids, proteins and carbohydrates which is absolutely essential for the maintenance of normal pulmonary functions such as gas exchange. Without the lining the lungs would collapse. Alterations in the pulmonary extracellular lining may underlie some disease conditions induced by toxic agents, especially those which interfere with the formation of pulmonary surfactant. The extracellular lining could be used to detect and monitor damage and disease caused by agents toxic to the lungs. The lining contains many hydrolytic enzymes which may act to detoxify certain toxic agents such as those which contain ester groups. The pulmonary extracellular lining could play a significant role mediating the toxic action of inhaled agents as well as the removal of those agents from the lungs.