The integrin alpha v beta 6 binds and activates latent TGF beta 1: a mechanism for regulating pulmonary inflammation and fibrosis.
Transforming growth factor beta (TGF beta) family members are secreted in inactive complexes with a latency-associated peptide (LAP), a protein derived from the N-terminal region of the TGF beta gene product. Extracellular activation of these complexes is a critical but incompletely understood step in regulation of TGF beta function in vivo. We show that TGF beta 1 LAP is a ligand for the integrin alpha v beta 6 and that alpha v beta 6-expressing cells induce spatially restricted activation of TGF beta 1. This finding explains why mice lacking this integrin develop exaggerated inflammation and, as we show, are protected from pulmonary fibrosis. These data identify a novel mechanism for locally regulating TGF beta 1 function in vivo by regulating expression of the alpha v beta 6 integrin. (+info)
Idiopathic pulmonary haemosiderosis. Epidemiology, pathogenic aspects and diagnosis.
Idiopathic pulmonary haemosiderosis (IPH) is a rare clinical entity characterized by recurrent episodes of diffuse alveolar haemorrhage, often presenting with haemoptysis. Many patients have iron deficiency anaemia due to deposition of haemosiderin iron in the alveoli, and eventually develop moderate pulmonary fibrosis. Typically, intensive search for an aetiology ends up negative. There is no evidence of pulmonary vasculitis or capillaritis. The aetiology is obscure, but may be an immunological or toxic mechanism causing a defect in the basement membrane of the pulmonary capillary. IPH affects both children and adults. During an acute episode, a chest X-ray demonstrates bilateral, alveolar infiltrates. Sputum examination discloses haemosiderin-laden alveolar macrophages. Diagnosis is established by lung biopsy (fiber-optic or thoracoscopic), showing large numbers of haemosiderin-laden macrophages in the alveoli and without evidence of capillaritis or deposition of immunoglobulins. Corticosteroids and/or immunosuppressive drugs may be effective during an acute bleeding episode, and may in some patients improve symptoms and prognosis on the long-term, but the response to treatment displays great interindividual variation. (+info)
Pulmonary expression of interleukin-13 causes inflammation, mucus hypersecretion, subepithelial fibrosis, physiologic abnormalities, and eotaxin production.
Interleukin (IL)-13 is a pleiotropic cytokine produced in large quantities by activated CD4(+) Th2 lymphocytes. To define further its potential in vivo effector functions, the Clara cell 10-kDa protein promoter was used to express IL-13 selectively in the lung, and the phenotype of the resulting transgenic mice was characterized. In contrast to transgene-negative littermates, the lungs of transgene-positive mice contained an inflammatory response around small and large airways and in the surrounding parenchyma. It was mononuclear in nature and contained significant numbers of eosinophils and enlarged and occasionally multinucleated macrophages. Airway epithelial cell hypertrophy, mucus cell metaplasia, the hyperproduction of neutral and acidic mucus, the deposition of Charcot-Leyden-like crystals, and subepithelial airway fibrosis were also prominently noted. Eotaxin protein and mRNA were also present in large quantities in the lungs of the transgene-positive, but not the transgene-negative, mice. IL-4, IL-5, granulocyte-macrophage colony-stimulating factor, and monocyte chemoattractant protein-5 were not similarly detected. Physiological evaluations revealed significant increases in baseline airways resistance and airways hyperresponsiveness (AHR) to methacholine in transgene-positive animals. Thus, the targeted pulmonary expression of IL-13 causes a mononuclear and eosinophilic inflammatory response, mucus cell metaplasia, the deposition of Charcot-Leyden-like crystals, airway fibrosis, eotaxin production, airways obstruction, and nonspecific AHR. IL-13 may play an important role in the pathogenesis of similar responses in asthma or other Th2-polarized tissue responses. (+info)
Reduced tumor necrosis factor-alpha and transforming growth factor-beta1 expression in the lungs of inbred mice that fail to develop fibroproliferative lesions consequent to asbestos exposure.
Tumor necrosis factor (TNF)-alpha and transforming growth factor (TGF)-beta mRNA and protein expression and the degree of fibroproliferative response to inhaled asbestos fibers are clearly reduced in the 129 inbred mouse strain as compared with typical fibrogenesis observed in the C57BL/6 inbred strain. The C57BL/6 mice showed prominent lesions at bronchiolar-alveolar duct (BAD) junctions where asbestos fibers deposit and responding macrophages accumulate. The 129 mice, however, were generally indistinguishable from controls even though the numbers of asbestos fibers deposited in the lungs of all exposed animals were the same. Quantitative morphometry of H&E-stained lung sections comparing the C57BL/6 and 129 mice showed significantly less mean cross-sectional area of the BAD junctions in the 129 animals, apparent at both 48 hours and 4 weeks after exposure. In addition, fewer macrophages had accumulated at these sites in the 129 mice. Nuclear bromodeoxyuridine immunostaining demonstrated that the number of proliferating cells at first alveolar duct bifurcations and in adjacent terminal bronchioles was significantly reduced in the 129 strain compared with C57BL/6 mice at 48 hours after exposure (P < 0.01). TNF-alpha and TGF-beta1 gene expression, as measured by in situ hybridization, was reduced in the 129 mice at 48 hours after exposure, and expression of TNF-alpha and TGF-beta1 protein, as measured by immunohistochemistry, was similarly reduced or absent in the 129 animals. We postulate that the protection afforded the 129 mice is related to reduction of growth factor expression by the bronchiolar-alveolar epithelium and lung macrophages. (+info)
Effects of pirfenidone on procollagen gene expression at the transcriptional level in bleomycin hamster model of lung fibrosis.
A time course study was carried out to elucidate the mechanisms for antifibrotic effect of pirfenidone (PD). Hamsters were intratracheally (i.t.) instilled with saline (SA) or bleomycin (BL) (7.5 units/kg/5 ml). The animals were fed a diet containing 0.5% PD or the same control diet (CD) without the drug 2 days before and throughout the study. The animals were sacrificed at various times after instillation. The lung hydroxyproline level in BL + CD groups was gradually increased and peaked at 21 days to 181% of the SA + CD control. The BL + PD-treated groups showed a gradual decrease in their lung collagen content, showing a maximum reduction of 40% at day 21. The lung malondialdehyde levels of the BL + CD groups were increased by several-fold of the corresponding SA + CD groups at various times. The lung prolyl hydroxylase (PH) activities in the BL + CD groups were also increased by several-fold of the corresponding SA + CD groups at these time points. The hamsters in the BL + PD showed a gradual decrease in the lung malondialdehyde levels from 10 to 21days compared with their corresponding BL + CD groups. Treatment with PD also reduced the lung PH activities in the BL + PD groups compared with the corresponding BL + CD groups. However, PD failed to manifest any direct inhibitory effect on PH activity in vitro. BL treatment increased the lung procollagen I and III gene expressions in the BL + CD groups by several-fold at varying times compared with the corresponding SA + CD, and treatment with PD in the BL + PD groups significantly down-regulated the BL-induced overexpression of these genes. Studies evaluating the regulation of these genes at the transcriptional level revealed PD significantly reduced the transcription of PC I at 14 days. Our results indicate that the antifibrotic effect of PD was partly due to suppression of the BL-induced inflammatory events and partly due to down-regulation of BL-induced overexpression of lung procollagen I and III genes. (+info)
T cell independence of bleomycin-induced pulmonary fibrosis.
The role of T cells and cytokines in bleomycin (BLM)-induced fibrosis was evaluated in susceptible and resistant strains of normal and SCID mice. Histology and hydroxyproline analysis showed that BLM induced pulmonary fibrosis in C57BL/6 and (C57BL/6 x BALB/c)F1 mice, whereas BALB/c mice were resistant to the disease. To test whether lymphocytes were required for the induction of BLM-induced pulmonary fibrosis, SCID mice were injected intratracheally with BLM and evaluated for the development of pulmonary inflammation and fibrosis. Similar morphological changes and increases in hydroxyproline were observed in both C57BL/6 SCID and (C57BL/6 x CB.17)F1 SCID animals compared to those seen in wild-type C57BL/6 and (C57BL/6 x BALB/c)F1 mice. In contrast, CB.17 SCID mice, which are genetically similar to BALB/c mice, were resistant to disease induction. Analysis of the cellular infiltrate in BLM-treated C57Bl/6 SCID mice confirmed a lack of T cells in the lungs of SCID mice and demonstrated a pronounced accumulation of eosinophils in areas of developing pulmonary fibrosis. NK cells were significantly elevated in untreated SCID mice and did not increase further after BLM treatment. Analysis of selected cytokines 1 day after initiation of BLM-induced pulmonary fibrosis indicated that the levels of TNF-alpha and IFN-gamma appeared to segregate with fibrosis in both the SCID and wild-type mice. The data demonstrate that T cells are not required for the induction of fibrosis by BLM and suggest that responses by non-lymphoid cells may be sufficient for the induction of fibrosis. (+info)
Structural elucidation of a novel exopolysaccharide produced by a mucoid clinical isolate of Burkholderia cepacia. Characterization of a trisubstituted glucuronic acid residue in a heptasaccharide repeating unit.
The structure of the exopolysaccharide (EPS) produced by a clinical isolate of Burkholderia cepacia isolated from a patient with fibrocystic lung disease has been investigated. By means of methylation analyses, carboxyl reduction, partial depolymerization by fuming HCl and chemical degradations such as Smith degradation, lithiumethylenediamine degradation and beta-elimination, supported by GC/MS and NMR spectroscopic analyses, the repeat unit of the EPS has been identified and was shown to correspond to the acidic branched heptasaccharide with the following structure: [formula: see text]. This partially acetylated acidic polymer, distinguished by the presence of the less usual D-isomer of rhamnose and of a trisubstituted glucuronic acid residue, could represent the main EPS produced by this bacterial species. (+info)
In search of a cause of cryptogenic fibrosing alveolitis (CFA): one initiating factor or many?
The history of patients with idiopathic pulmonary fibrosis (IPF) shows that the disease may be preceded by a viral-like illness. Although viruses have not been demonstrated, it is possible that viruses were not detected in culture because they do not replicate during latency. We investigated the presence of adenovirus in IPF and interstitial pneumonia associated with collagen vascular disease (CVD-IP), using the nested polymerase chain reaction (PCR) and in situ hybridization (ISH) for the E1A region of the adenovirus genome. Studies were performed on lung tissues obtained by transbronchial lung biopsy from 19 patients with IPF, 10 patients with CVD-IP and, for comparison, 20 patients with sarcoidosis. The E1A DNA was present in 3 out of 19 (16%) cases of IPF, in 5 of 10 (50%) cases of CVD-IP, and in 2 of 20 (10%) cases of sarcoidosis. The incidence of E1A DNA in CVD-IP was significantly higher than that in sarcoidosis (p < 0.05). In patients with IPF and CVD-IP, E1A DNA was more prevalent in patients treated with corticosteroids (6 out of 9 cases; 67%) than in those without it (2 out of 20 cases; 10%) (p < 0.01). ISH studies showed that 1 out of 8 cases of IPF and CVD-IP, in which E1A DNA was detected by PCR, was positive for E1A DNA. We conclude that adenovirus E1A is unlikely to be aetiologically involved in the pathogenesis of idiopathic pulmonary fibrosis or interstitial pneumonia associated with collagen vascular disease. However, a latent adenovirus infection may be reactivated or may newly infect the host following corticosteroid administration. (+info)