Expression of a tumor necrosis factor-alpha transgene in murine lung causes lymphocytic and fibrosing alveolitis. A mouse model of progressive pulmonary fibrosis

Preferential activation of the p46 isoform of JNK/SAPK in mouse macrophages by TNF alpha

A pleiotropic cytokine, tumor necrosis factor-alpha (TNF alpha), regulates the expression of multiple macrophage gene products and thus contributes a key role in host defense. In this study, we have investigated the specificity and mechanism of activation of members of the c-Jun-NH2-terminal kinase/stress-activated protein kinase (JNK/SAPK) subfamily of mitogen-activated protein kinases (MAPKs) in mouse macrophages in response to stimulation with TNF alpha. Exposure of macrophages to TNF alpha stimulated a preferential increase in catalytic activity of the p46 JNK/SAPK isoform compared with the p54 JNK/SAPK isoform as determined by: (i) separation of p46 and p54 JNK/SAPKs by anion exchange liquid chromatography and (ii) selective immunodepletion of the p46 JNK/SAPK from macrophage lysates. To investigate the level of regulation of p46 JNK/SAPK activation, we determined the ability of MKK4/SEK1/JNKK, an upstream regulator of JNK/SAPKs, to phosphorylate recombinant kinase-inactive p46 and p54 JNK/SAPKs. Endogenous MKK4 was able to transphosphorylate both isoforms. In addition, both the p46 and p54 JNK/SAPK isoforms were phosphorylated on their TPY motif in response to TNF alpha stimulation as reflected by immunoblotting with a phospho-specific antibody that recognizes both kinases. Collectively, these results suggest that the level of control of p46 JNK/SAPK activation is distal not only to MKK4 but also to the p54 JNK/SAPK. Preferential isoform activation within the JNK/SAPK subfamily of MAPKs may be an important mechanism through which TNF alpha regulates macrophage phenotypic heterogeneity and differentiation.

Regulated overexpression of interleukin 11 in the lung. Use to dissociate development-dependent and -independent phenotypes

Standard overexpression transgenic approaches are limited in their ability to model waxing and waning diseases and frequently superimpose development-dependent and -independent phenotypic manifestations. We used the clara cell 10-kD protein (CC10) promoter and the reverse tetracycline transactivator (rtTA) to create a lung-specific, externally regulatable, overexpression transgenic system and used this system to express human interleukin 11 (IL-11) in respiratory structures. Gene induction could be achieved in utero, in neonates and in adult animals. Moreover, gene expression could be turned off by removal of the inducing stimulus. When gene activation was initiated in utero and continued into adulthood, subepithelial airway fibrosis, peribronchiolar mononuclear nodules, and alveolar enlargement (emphysema) were noted. Induction in the mature lung caused airway remodeling and peribronchiolar nodules, but alveolar enlargement was not appreciated. In contrast, induction in utero and during the first 14 d of life caused alveolar enlargement without airway remodeling or peribronchiolar nodules. Thus, IL-11 overexpression causes abnormalities that are dependent (large alveoli) and independent (airway remodeling, peribronchiolar nodules) of lung growth and development, and the CC10-rtTA system can be used to differentiate among these effector functions. The CC10-rtTA transgenic system can be used to model waxing and waning, childhood and growth and development-related biologic processes with enhanced fidelity.

Mice Lacking Both Granulocyte Colony-Stimulating Factor (CSF) and Granulocyte-Macrophage CSF Have Impaired Reproductive Capacity, Perturbed Neonatal Granulopoiesis, Lung Disease, Amyloidosis, and Reduced Long-Term Survival

Mice lacking granulocyte colony-stimulating factor (G-CSF) are neutropenic with reduced hematopoietic progenitors in the bone marrow and spleen, whereas those lacking granulocyte-macrophage colony-stimulating factor (GM-CSF) have impaired pulmonary homeostasis and increased splenic hematopoietic progenitors, but unimpaired steady-state hematopoiesis. These contrasting phenotypes establish unique roles for these factors in vivo, but do not exclude the existence of additional redundant functions. To investigate this issue, we generated animals lacking both G-CSF and GM-CSF. In the process of characterizing the phenotype of these animals, we further analyzed G-CSF– and GM-CSF–deficient mice, expanding the recognized spectrum of defects in both. G-CSF–deficient animals have a marked predisposition to spontaneous infections, a reduced long-term survival, and a high incidence of reactive type AA amyloidosis. GM-CSF–deficient mice have a modest impairment of reproductive capacity, a propensity to develop lung and soft-tissue infections, and a similarly reduced survival as in G-CSF–deficient animals. The phenotype of mice lacking both G-CSF and GM-CSF was additive to the features of the constituent genotypes, with three novel additional features: a greater degree of neutropenia among newborn mice than in those lacking G-CSF alone, an increased neonatal mortality rate, and a dominant influence of the lack of G-CSF on splenic hematopoiesis resulting in significantly reduced numbers of splenic progenitors. In contrast to newborn animals, adult mice lacking both G-CSF and GM-CSF exhibited similar neutrophil levels as G-CSF–deficient animals. These findings demonstrate that the additional lack of GM-CSF in G-CSF–deficient animals further impairs steady-state granulopoiesis in vivo selectively during the early postnatal period, expand the recognized roles of both G-CSF and GM-CSF in vivo, and emphasize the utility of studying multiply deficient mouse strains in the investigation of functional redundancy.

Early role of Fsp1 in epithelial-mesenchymal transformation

A seamless plasticity exists among cells shifting between epithelial and mesenchymal phenotypes during early development and again later, in adult tissues, following wound repair or organ remodeling in response to injury. Fsp1, a gene encoding a fibroblast-specific protein associated with mesenchymal cell morphology and motility, is expressed during epithelial-mesenchymal transformations (EMT) in vivo. In the current study, we identified several cytokines that induce Fsp1 in cultured epithelial cells. A combination of these factors, however, was most efficacious at completing the process of EMT. The optimal combination identified were two of the cytokines classically associated with fibrosis, i.e., transforming growth factor-beta1 (TGF-beta1) and epidermal growth factor (EGF). To confirm that it was the induction of Fsp1 by these cytokines mediating EMT, we used antisense oligomers to block Fsp1 production and subsequently measured cell motility and markers of EMT phenotype. The antisense oligomers suppressed Fsp1 expresison and epithelial transformation; therefore, we conclude that the appearance of Fsp1 is an important early event in the pathway toward EMT.

Induction of apoptosis and pulmonary fibrosis in mice in response to ligation of Fas antigen

Fas antigen is a cell surface protein that mediates apoptosis, and it is expressed in various cells and tissues. Fas ligand binds to its receptor Fas, thus inducing apoptosis of Fas-bearing cells. Malfunction of the Fas-Fas ligand system causes lymphoproliferative disorders and autoimmune diseases, whereas its exacerbation may cause tissue destruction. We hypothesize that excessive apoptosis mediated by Fas-Fas ligand interaction may damage alveolar epithelial cells and result in pulmonary fibrosis. Mice were allowed to inhale repeatedly an aerosolized anti-Fas antibody for 14 days. The nuclei of bronchial and alveolar epithelial cells were positively stained by in situ DNA nick end labeling. Electron microscopy demonstrated apoptotic changes in bronchial and alveolar epithelial cells. Histologic findings and hydroxyproline content showed the development of pulmonary fibrosis, which was dependent on the dose of anti-Fas antibody. The repeated inhalation of control antibody (isotype-matched control hamster IgG) did not induce apoptosis of epithelial cells or pulmonary fibrosis. The expression of TGF-beta mRNA was upregulated from day 7 to day 28 in lung tissues of anti-Fas antibody-treated mice but not in those of control mice. In this report, we present the evidence that repeated inhalation of anti-Fas antibody mimicking Fas-Fas ligand crosslinking induces excessive apoptosis and inflammation, which results in pulmonary fibrosis in mice.

Effects of mineral fibers on the expression of genes whose product may play a role in fiber pathogenesis

To determine which factors are useful for the risk assessment of man-made fibers, we examined the gene expression of proinflammatory cytokines, growth factors, manganese superoxide dismutase (MnSOD), and inducible nitric oxide synthase (iNOS) in mineral fiber-exposed rats by means of reverse transcription-polymerase chain reaction (RT-PCR). Male Wistar rats received a single intratracheal instillation of either saline (control) or two types of fibers (2 mg of Union Internationale Centre le Cancer (UICC) chrysotile or alumina silicate refractory ceramic fiber [RCF]). Expression of interleukin-1 alpha (IL-1 alpha), interleukin-6 (IL-6), tumor necrosis factor alpha (TNF-alpha), platelet-deriving growth factor-A, (PDGF-A), platelet-deriving growth factor-B (PDGF-B), transforming growth factor beta 1 (TGF-beta 1), basic fibroblast growth factor (bFGF), MnSOD, and iNOS mRNA from lung and lipopolysaccharide (LPS)-stimulated alveolar macrophages (AM) were assessed by RT-PCR. Among these factors, IL-1 alpha, TNF-alpha, IL-6, bFGF, and iNOS would be the possible parameters for the risk assessment of fibers. In a follow-up study, we investigated the time course (3 days, 1 week, 1 month, and 3 months) of expression of IL-1 alpha and TNF-alpha by LPS-stimulated AM exposed to mineral fibers in vivo. Male Wistar rats were instilled intratracheally with saline or fibers (2 mg of Union Internationale Contre le Cancer UICC crocidolite or potassium octatitanate whisker [TW]). The expression of IL-1 alpha mRNA by fibers was greatest in TW, crocidolite, chrysotile, and RCF-instilled rat AM, in that order. The increase of IL-1 alpha and TNF-alpha mRNA in AM peaked at 1 month and 3 days after exposure to crocidolite or TW, respectively. The expression of IL-1 alpha by fibers (crocidolite, chrysotile, TW, and RCF) may be a good indicator of the pathologic potential of fibers.

Cardiac-specific overexpression of tumor necrosis factor-alpha causes lethal myocarditis in transgenic mice

BACKGROUND

Tumor necrosis factor (TNF)-alpha, a proinflammatory cytokine with negative inotropic effects, can be detected in myocardium with end-stage heart failure, after endotoxin administration, and during transplant rejection. Various studies suggest that TNF-alpha participates in the pathogenesis of cardiac dysfunction. To test this hypothesis, transgenic mice were made that selectively overexpress TNF-alpha in cardiomyocytes.

METHODS AND RESULTS

A transgene construct was made containing the murine alpha-myosin heavy chain promoter and the coding sequence of murine TNF-alpha, followed by the simian virus 40 T-antigen intron and polyadenylation signals. Injection of this construct into fertilized eggs yielded three transgenic mice, all of which died spontaneously before the completion of weaning. Gross pathologic analysis of these mice demonstrated a decrease in body weight with markedly increased heart weight. Histologic examination of the heart revealed a substantial, diffuse lymphohistiocytic inflammatory infiltrate, associated with interstitial edema. Reverse transcriptase polymerase chain reaction showed that the transgene was expressed in the heart. Enzyme-linked immunosorbent assay demonstrated a substantial amount of TNF-alpha protein in the transgenic heart.

CONCLUSION

Overexpression of TNF-alpha in the heart leads to severe myocarditis and cardiomegaly. These results support the hypothesis that myocardial expression of TNF-alpha can contribute to the pathogenesis of cardiac dysfunction.

Interstitial lung disease in an adult with Fanconi anemia: clues to the pathogenesis

We have studied a 38-year-old man with a prior diagnosis of Holt-Oram syndrome, who presented with diabetes mellitus. He had recently taken prednisone for idiopathic interstitial lung disease and trimethoprim-sulfamethoxazole for sinusitis. Thrombocytopenia progressed to pancytopenia. The patient had skeletal, cardiac, renal, cutaneous, endocrine, hepatic, neurologic, and hematologic manifestations of Fanconi anemia (FA). Chest radiographs showed increased interstitial markings at age 25, dyspnea began in his late 20s, and he stopped smoking at age 32. At age 38, computerized tomography showed bilateral upper lobe fibrosis, lower lobe honeycombing, and bronchiectasis. Pulmonary function tests, compromised at age 29, showed a moderately severe obstructive and restrictive pattern by age 38. Serum alpha-1 antitrypsin level was 224 (normal 85-213) mg/dL and PI phenotype was M1. Karyotype was 46,XY with a marked increase in chromosome aberrations induced in vitro by diepoxybutane. The early onset and degree of pulmonary disease in this patient cannot be fully explained by environmental or known genetic causes. The International Fanconi Anemia Registry (IFAR) contains no example of a similar pulmonary presentation. Gene-environment (ecogenetic) interactions in FA seem evident in the final phenotype. The pathogenic mechanism of lung involvement in FA may relate to oxidative injury and cytokine anomalies.

Anticytokine approaches in pulmonary fibrosis: bringing factors into focus

The prognosis of pulmonary fibrosis is poor and current therapies inadequate. Recent progress in understanding the mechanisms underlying the pathogenesis of this disease leads us to expect that inhibitors of cytokine and polypeptide growth factor will provide novel therapeutic agents. This paper outlines the role of cytokines in the pathogenesis of pulmonary fibrosis and concludes that there are compelling reasons to explore anticytokine therapeutic approaches. It also proposes criteria that will enable us to evaluate such agents in vivo and suggests approaches which might overcome the obstacles presented by control mechanisms which recruit a multiplicity of factors.

Overexpression of granulocyte-macrophage colony-stimulating factor induces pulmonary granulation tissue formation and fibrosis by induction of transforming growth factor-beta 1 and myofibroblast accumulation

We have previously reported that transfer to rat lung of the granulocyte-macrophage colony-stimulating factor (GM-CSF) gene leads to high expression of GM-CSF between days 1 and 4 and granulation tissue formation followed by an irreversible fibrotic response starting from day 12 onward. In the current study, we investigated the underlying mechanisms. We found that GM-CSF overexpression did not enhance production of tumor necrosis factor-alpha in a significant manner at any time after GM-CSF gene transfer. However, the content of transforming growth factor-beta 1 in bronchoalveolar lavage fluid was markedly induced at day 4 and appeared to be maximal around day 7 and remained high at day 12. Macrophages purified from bronchoalveolar lavage fluid 7 days after GM-CSF gene transfer spontaneously released significant quantities of transforming growth factor-beta 1 protein in vitro. After peak transforming growth factor-beta 1 production was the emergence of alpha-smooth muscle actin-rich myofibroblasts. Accumulation of these cells was most prominent at day 12 within the granulation tissues and they were still present in fibrotic areas between days 12 and 24 and diminished markedly afterward. Thus, we provide the first in vivo evidence that tumor necrosis factor-alpha may be dissociated from participation in a fibrotic process in the lung and GM-CSF may play a more direct role in pulmonary fibrogenesis at least in part through its capability to induce transforming growth factor-beta 1 in macrophages and the subsequent emergence of myofibroblast phenotypes. This GM-CSF transgene lung model is useful for a stepwise dissection of both cellular and molecular events involved in pulmonary fibrosis.

Scleroderma. Clinical problems. The lungs

A recent follow-up study found that patients with pulmonary involvement (with no renal or cardiac involvement) survived a median of 78 +/- 17 months. Another study found death from SSc was most frequently due to pulmonary hypertension. Improved diagnostic modalities and better understanding of the pathophysiology of SSc lung disease are essential, because mortality from this SSc lung disease remains high. During the past decade, advances have been made in the understanding of the alveolitis of SSc lung disease. Although the inciting injury remains uncertain, a cascade of inflammatory and fibrosing mediators culminates in a chronic state of interstitial lung disease. There is increasing evidence that the fibrogenic cytokines PDGF and TGF-beta are major contributors to the pathophysiology of interstitial lung disease, including that of SSc. Future research aimed at modifying the biologic response to such cytokines may yield novel therapeutic approaches to the management of this type of lung disease. Similarly, improved understanding of mediators of vascular tone, such as endothelin and nitric oxide, may yield much-needed treatments for pulmonary hypertension.

Adenovirus-vector-mediated cytokine gene transfer to lung tissue

In summary, we have been able to demonstrate that adenovirus vectors are valuable tools in examining the roles played by individual cytokines in lung responses and inflammation. These viral vectors have marked trophism for the epithelial cells of the lung and are highly efficient in transferring the genes into these lining cells. This results in significant expression of cytokines both within the lumen and the parenchyma of the lung. As a result of an individual cytokine being overexpressed, there are cytokine-specific changes seen-IL-6 resulting in lymphocytosis, MIP2 resulting in neutrophil accumulation, RANTES resulting in monocyte accumulation, TGF beta resulting in monocytosis but no fibrosis, and GM-CSF most surprisingly resulting in tissue eosinophilia, granuloma formation, and subsequently the onset of fibrosis. These vectors have helped pinpoint the role of a number of the cytokines in inducing chronic inflammatory changes to the lung and imply that a single cytokine may not be the only trigger resulting in chronic changes within the lung parenchyma.

Early production of macrophage inflammatory protein-1 alpha occurs in respiratory distress syndrome and is associated with poor outcome

Although progression to pulmonary fibrosis in preterm infants with respiratory distress syndrome (RDS) is related to the inflammatory response, the nature of this response remains controversial. We have therefore performed sequential bronchoalveolar lavages in 30 infants with RDS (13 of whom developed bronchopulmonary dysplasia) and 7 ventilated control infants, characterizing the cells obtained by immunohistochemical analysis of lineage-specific markers and assaying macrophage-associated chemokines and cytokines in supernatant fluid. At all ages from birth, lavage supernatants demonstrated highly significant increase over controls of the beta-chemokine macrophage inflammatory protein (MIP)-1 alpha, although not of regulated upon activation, normal T cell expressed and secreted (RANTES), of the cytokines tumor necrosis factor (TNF)-alpha and IL-1 beta, and of elastase/alpha-1 antitrypsin. Significantly higher concentrations of MIP-1 alpha in particular were associated with the later development of fibrosis. Increased numbers of macrophages expressing the activation marker RM/3-1 were found at all ages in bronchopulmonary dysplasic infants, whereas neutrophil numbers were increased from d 3. Dexamethasone administered to 10 infants induced rapid decrease in inflammatory cell numbers and concentrations of MIP-1 alpha, tumor necrosis factor-alpha, IL-1 beta, and elastase/alpha-1 antitrypsin. The inflammatory response in neonatal RDS begins within the first day of life. Long-term outcome is associated with the magnitude of this early response, in particular production of MIP-1 alpha. The early introduction of specific therapy is thus likely to be beneficial.

Tumor necrosis factor-alpha inhibits collagen alpha1(I) gene expression and wound healing in a murine model of cachexia

The mechanisms responsible for impaired wound healing in patients with cachexia-associated infection, inflammation, and cancer are unknown. As tumor necrosis factor (TNF)-alpha is elevated in these diseases, and TNF-alpha inhibits collagen alpha1(I) gene expression in cultured fibroblasts, we analyzed whether chronically elevated serum TNF-alpha affects collagen metabolism in vivo by inoculating nude mice with Chinese hamster ovary cells secreting TNF-alpha (TNF-alpha mice) or control Chinese hamster ovary cells (control mice). Before the onset of weight loss, TNF-alpha mice had a selective decrease in collagen synthesis and collagen alpha1(I) mRNA in the skin. In addition, TNF-alpha mice displayed impaired healing of incisional and excisional skin wounds, compared with control animals, before the onset of cachexia. The expression of transforming growth factor-beta1, a potent fibrogenic factor, was inhibited by TNF-alpha in the skin. In studies with transgenic mice expressing the human growth hormone under the direction of 5' regulatory regions of the human collagen alpha1(I) gene, TNF-alpha treatment inhibited the expression of the collagen alpha1(I) human growth hormone transgene containing -2.3 kb of the 5' region, whereas transgene expression directed by -0.44 kb of the 5' region was not affected. These experiments suggest that TNF-alpha may play an important role in the impaired wound healing of chronic diseases that are characterized by a high production of this cytokine and provide insights for potential therapeutic approaches.

Cytokines and production of surfactant components

The production of pulmonary surfactant, a complex of lipids and proteins that reduces surface tension at the alveolar air-liquid interface, is developmentally regulated. Several hormones, most notably glucocorticoids, are known to accelerate maturation of the surfactant system. Cytokines are polypeptides that act mostly in a paracrine fashion and possess a wide spectrum of activities on multiple types of cells. Many cytokines are produced by different lung cells a various stages of fetal development or under pathological conditions affecting the fetus. In addition, cytokines present in amniotic fluid or in the blood stream may reach the fetal lungs. Some cytokines, including epidermal growth factor, transforming growth factor-alpha, and interferon-gamma have been shown to stimulate the production of surfactant components. On the other hand, tumor necrosis factor and transforming growth factor-beta downregulate the production of surfactant lipids and proteins. We have recently shown that the proinflammatory cytokine interleukin-1 (IL-I) enhances the expression of surfactant protein A (SP-A) in fetal rabbit lung explants. In addition, injection of IL-I into the amniotic fluid of fetal rabbits enhances the expression of surfactant proteins and improves the lung compliance of preterm animals. Preterm delivery is often associated with subclinical intraamniotic infection. In these cases, amniotic fluid concentrations of IL-I are often elevated. We propose that this cytokine accelerates maturation of the surfactant system in fetal lungs and thus prepares the fetus for extrauterine life.