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PubMed1989

Silica-induced pulmonary fibrosis involves the reaction of particles with interstitial rather than alveolar macrophages.

Macrophage-derived products have been implicated in fibroblast stimulation following particle deposition in the lung. To assess the role of macrophages in the alveolus versus those in the interstitium in the induction of pulmonary fibrosis, we compared the pulmonary response to silica when phagocytosis occurred predominantly in each of these compartments. One group of mice received intratracheal silica which was phagocytosed largely by alveolar macrophages (AM). A second group was exposed to whole body irradiation prior to receiving the same dose of silica. This prevented the usual efflux of PMN and monocytes into the air sacs, allowing passage of silica particles across the alveolar epithelium to reach the interstitial macrophages (IM). In the irradiation plus silica group, many large interstitial granulomas were formed at 2-4 weeks, and collagen levels were significantly greater than in all other groups at 16 weeks. More silica was found in a lung tissue residue and in lymph nodes of these animals. Pulmonary fibrosis was limited to interstitial areas where there was a high level of retained silica, whereas peripheral regions of the lung, where free AM containing silica were found, did not show fibrosis of the alveolar walls. The results suggest that factors secreted by IM in response to silica are more effective in stimulating fibrogenesis than secretions made by the AM into the alveolar space.

Animals↗

PubMed1988

Smoking and pulmonary fibrosis.

A review of the relevant literature provides evidence that cigarette smoking causes microscopic diffuse interstitial pulmonary fibrosis in humans at autopsy. The association shows a dose-response relationship and the fibrosis is often severe. Experimental animal studies have confirmed these observations when the exposure to inhaled smoke was prolonged or heavy. Six published and one unpublished cross-sectional chest x-ray surveys of adults have shown low profusion of small irregular opacities related to smoking with a dose-response relationship when this has been studied. Although information on radiographic-pathologic correlation is deficient, these studies support the hypothesis that smoking causes diffuse interstitial pulmonary fibrosis which is radiologically visible with low profusion in low prevalence. The x-ray manifestations may be confused with early pneumoconiosis such as asbestosis.

Age Factors↗

PubMed2000

Idiopathic pulmonary fibrosis: molecular mechanisms and possible therapeutic strategies.

Idiopathic pulmonary fibrosis (IPF) is a devastating disease with an almost universally terminal outcome. In recent years much insight has been gained into the pathogenesis of IPF from both a bleomycin mice-model as well as ex vivo human tissue studies. Alveolar damage and inflammation of unknown etiology, eventually leading to interstitial fibrosis, characterize IPF. Apoptosis has emerged as an important factor in the pathogenesis of IPF. This review will outline the current understanding of the immunological and molecular mechanisms underlying IPF and discuss new therapeutic strategies.

Animals↗

PubMed2000

Involvement of collagen-binding heat shock protein 47 and procollagen type I synthesis in idiopathic pulmonary fibrosis: contribution of type II pneumocytes to fibrosis.

The most common pathologic form of idiopathic pulmonary fibrosis is usual interstitial pneumonia, which is characterized by patchy fibrotic areas, marked increase in the number of fibroblasts and type II pneumocytes, and excessive deposition of extracellular matrix proteins, especially collagen. Heat shock protein 47 is a collagen-binding stress protein and has a specific role in intracellular processing of procollagen molecules as a collagen-specific molecular chaperone. However, its role in the causation of fibrosis in usual interstitial pneumonia is unknown. In this study, we examined the expression of heat shock protein 47 and type I procollagen in 12 patients with usual interstitial pneumonia by immunohistochemistry on sequential sections. Heat shock protein 47 was localized predominantly in alpha-smooth muscle actin-positive myofibroblasts and surfactant protein-A-positive type II pneumocytes in active fibrotic areas of usual interstitial pneumonia. Type I procollagen was also expressed in those cells. In contrast, heat shock protein 47 and type I procollagen were weakly or not at all expressed in myofibroblasts and type II pneumocytes in bronchiolitis obliterans organizing pneumonia and normal lung tissue samples obtained from excised lung cancer tissues. The numbers of heat shock protein 47- and type I procollagen-positive cells to type II pneumocytes or myofibroblasts were significantly higher in usual interstitial pneumonia than in bronchiolitis obliterans organizing pneumonia and normal lung tissue specimens. Our results suggest that myofibroblasts and type II pneumocytes play an important role in the progression of fibrosis through the induction of heat shock protein 47, which regulates the synthesis/assembly of type I procollagen in usual interstitial pneumonia. HUM PATHOL 31:1498-1505.

Actins↗

PubMed2001

A new direction in the pathogenesis of idiopathic pulmonary fibrosis?

A recent review article suggested that idiopathic pulmonary fibrosis (IPF) is a disease that is associated more with abnormal wound healing than with inflammation. Data derived from transgenic and gene transfer rodent models suggest that lung inflammation may be a necessary but insufficient component of IPF, and that at some point in the natural history of the disease IPF becomes no longer dependent on the inflammatory response for propagation. Altered microenvironment and involvement of epithelial cell/mesenchymal cell interaction are the most likely contributors to the pathogenesis of this chronic progressive disorder.

Animals↗

PubMed1989

[The effect of foamy alveolar macrophages presented in bleomycin-injured rat lungs in pulmonary fibrosis].

Foamy alveolar macrophages (FAM) are observed in lungs injured by Bleomycin (BLM), but their relation to pulmonary fibrosis is not clearly understood. We purified FAM from BLM-instilled rat lungs by density gradient centrifugation on Percoll, and studied the effect of FAM on pulmonary fibrosis. The cells lavaged from the rat lungs 14 days after the administration of BLM (B) or saline (S), were applied on Percoll. After centrifugation, the cells layered on each interface were collected and named as SI, SII, SIII, and BI, BII, BIII in order of gravity. The BI layer included 8.5% of unfractionated cells (U). These BI cells were viable (88%), significantly larger than the others, nonspecific esterase positive cells, and included much ferritin and lysozyme, and were morphologically identified as alveolar macrophages (AM). Therefore, we called the BI cells FAM. We estimated the capacity of FAM (2.5 X 10(5] to synthesize DNA (3H-thymidine uptake) and RNA (3H-uridine uptake), and the activities of silica-stimulated FAM to cause proliferation of mouse thymocytes (IL-1 activity) and rat lung fibroblasts (FP activity), and to produce PGE2. FAM has a lower mitogenic activity but did not have been protein synthetic activity as compared with the others. Silica-stimulated FAM released less IL-1 than BII or BIII, and induced less fibroblast growth than BII, but induced as much as BIII, possibly because of the increased capacity of BIII cells to produce PGE2, which is known to inhibit fibroblast growth. In this way, FAM were considered to be "already activated" rather than "highly activated" cells, but the presence of FAM suggested that smaller or denser AM might receive bleomycin stimulation and release fibrogenic mediators (IL-1 or MDGF) into the alveolar spaces during FAM formation, and that AM might participate in the fibrogenic responses.

Animals↗

PubMed1979

Changes in transglutaminase activity in an experimental model of pulmonary fibrosis induced by paraquat.

An experimental model of pulmonary fibrosis has been developed by dosing rats with one-fifth the LD50 dose of the herbicide paraquat on 5 consecutive days. Approximately 50% of the rats died within 4 days of the completion of dosing, showing macroscopic changes and wet weight increases in the lung consistent with severe oedema. Those animals which died between Days 4 and 10 had markedly increased levels of hydroxyproline in the lung, maximum at Day 6, and increased prolyl hydroxylase activity, maximum at Day 4. These changes, together with an increase in thymidine incorporation into DNA, and increased lung DNA content, were consistent with the development of fibrosis. Measurement of transglutaminase activity in the lung showed marked increases at Days 4 and 10 after completion of dosing. This activity paralleled closely the changes in prolyl hydroxylase activity and became increasingly associated with particulate protein present in the "nuclear pellet" fraction. The presence of zymogen plasma transglutaminase trapped in lung homogenates could not be demonstrated but the contribution by the active plasma transglutaminase (Factor XIIIa) to increases shown at Day 4 cannot be ruled out.

Animals↗

PubMed2006

Lower occurrence of idiopathic pulmonary fibrosis in Maori and Pacific Islanders.

OBJECTIVE: Idiopathic pulmonary fibrosis (IPF), a chronic fibro-proliferative interstitial pneumonia, has not been reported to occur more frequently in any particular race. We have observed that our patients with IPF comprise a proportionately lower number of Maori and Pacific Islanders and set out to evaluate this further. METHODS: Retrospective analysis of an IPF database from a single tertiary respiratory institution was undertaken. Demographic and survival data were collected. Ethnicity was compared with 2001 New Zealand census data from the same catchment area. RESULTS: Eighty-seven cases of IPF were identified. Overall median survival was 46 months. Ethnicity data were available for 84 of the 87 cases. 76/84 (90%) were European, 6/84 (7%) were Asian or Indian, 2/84 (2%) were Maori, and 0/84 (0%) were Pacific Islanders. For Maori and Pacific Islanders, this represented a significant trend in difference when compared with ethnicity data from the hospital catchment population (P < 0.001). CONCLUSIONS: Our department is the tertiary referral centre for pulmonary disease in the upper North Island of New Zealand, and therefore referral centre bias is likely to be low. The preliminary observation that the occurrence of IPF is lower in those of Maori or Polynesian ethnicity warrants further study. This may, in part, help in our understanding of the pathogenic mechanisms in IPF.

Aged↗

PubMed2006

Role of epithelial cells in idiopathic pulmonary fibrosis: from innocent targets to serial killers.

Idiopathic pulmonary fibrosis (IPF), a progressive and relentless lung scarring of unknown etiology, has been recognized as the most lethal interstitial lung disease. Despite the growing interest in IPF, the precise molecular mechanisms underlying the development of fibrosis and leading to the irreversible destruction of the lung are still unknown. Recently, it has been proposed that IPF, instead of being a chronic inflammatory disorder, results from multiple cycles of epithelial cell injury and activation. In turn, active alveolar epithelial cells provoke the migration, proliferation, and activation of mesenchymal cells with the formation of fibroblastic/myofibroblastic foci and the exaggerated accumulation of extracellular matrix, mirroring abnormal wound repair. In this article, some characteristics of the alveolar epithelium are briefly outlined, and the fibrogenic mechanisms specifically operated by active abnormal epithelial cells are examined.

Apoptosis↗

PubMed1989

[Experimental studies on the pathogenesis and development of interstitial pneumonia and pulmonary fibrosis].

In order to elucidate the mechanism of pulmonary fibrosis development, analysis of bronchoalveolar lavage fluid (BALF), alveolar macrophage function and histological examination were performed in bleomycin (BLM) treated mice and MRL/lpr mice. In the BLM-treated group, swelling of type II alveolar cells, increase of phospholipids and total cell counts in BALF were observed at the early stage following BLM administration. Lysosomal enzyme activities, total protein volume, superoxide production and IL-1 production of alveolar macrophages peaked at the second week after completing BLM administration. In MRL/lpr mice, lymphocytes infiltration in the interstitium, perivascular and peribronchial granuloma formation were observed at 24 weeks old. Analysis of BALF revealed the increase of total cell counts, lymphocyte counts, and fibronectin volume. No significant difference was observed in total protein and phospholipid volume between MRL/lpr mice and MRL/n mice (control mice).

Animals↗

PubMed2004

Idiopathic pulmonary fibrosis: misunderstandings between epithelial cells and fibroblasts?

Idiopathic pulmonary fibrosis is a complex disease of unknown etiology which produces a progressive and irreversible destruction of the alveolar-capillary units leading ultimately to death from respiratory failure. For a long time the pathogenesis of the disease was attributed to an unresolved chronic alveolitis. However, a growing body of evidence suggests that inflammation does not play a major role in this disease, and that the pivotal pathogenic mechanisms include epithelial cell microinjuries/activation, and fibroblast migration, proliferation, and differentiation in myofibroblasts forming discrete foci in the injured areas. Active fibroblasts/myofibroblasts from these foci may in turn disturb alveolar re-epithelialization, by provoking basement membrane disruption and epithelial cell apoptosis finally resulting in exaggerated extracellular matrix accumulation. This aberrant repair process annihilates the lung architecture leading to the honeycomb remodeling.

Apoptosis↗

PubMed1986

Extensive laminin and basement membrane accumulation occurs at the onset of bleomycin-induced rodent pulmonary fibrosis.

The distribution of laminin was studied during pulmonary fibrosis induced in rodents by bleomycin sulfate. Large accumulations of laminin associated with basement membranes were seen in thickened lung interstitial spaces by immunofluorescence microscopy, starting at 7 days (32-75% increases) and persisting through 28 days (66-79% increase). By electron microscopy, these laminin concentrations were skeinlike masses of reduplicated basement membranes localized at the surface of alveolar capillary endothelial cells. Numerous macrophages were also associated with this basement membrane material. These findings suggest that bleomycin-induced damage to lung cells causes massive local accumulations of basement membranes, which might be involved in the expansion of the interstitial stroma by stimulating attachment and activation of certain inflammatory cells.

Animals↗

PubMed2003

Idiopathic pulmonary fibrosis--a disorder of alveolar wound repair?

Idiopathic pulmonary fibrosis (IPF) is a chronic and usually progressive lung disorder of unknown aetiology. Conventional management of patients with IPF has been primarily based on the concept that suppressing inflammation would prevent progression to fibrosis. Although the pathogenesis is incompletely understood, it is here suggested that IPF is a disease of abnormal wound repair and remodelling in the lung rather than an inflammatory disease. Therefore, treatment strategies are no longer aimed at reducing inflammation, but rather at preventing or inhibiting the fibroproliferative responses and enhancing efficient alveolar epithelial repair. So far, no cell-specific drugs for these purposes are clinically available. However, novel promising molecules or drugs are being studied in experimental models or ongoing clinical trials in patients with IPF. Evolving hypotheses on the pathogenesis of IPF are reviewed, focusing on possible implications for future therapies. A better understanding of the sequence of the pathogenic mechanisms that control the fibrotic response will hopefully lead to efficient therapies and finally a favourable outcome in patients with this disease.

Animals↗

PubMed1983

Nitrofurantoin-induced interstitial pulmonary fibrosis. Presentation and outcome.

Four cases of interstitial pulmonary fibrosis associated with nitrofurantoin therapy are analysed along with 45 other reported cases of this disease in order to review the presenting features and outcome and to determine the role of steroid therapy. Most patients were elderly (mean age, 66 years); women were more commonly affected (71%). All patients had been treated with nitrofurantoin for longer than six months (mean, 31 months). The usual presenting symptoms were dyspnoea and non-productive cough which had been present for periods for two weeks to six years (mean, 9.4 months). After cessation of nitrofurantoin therapy, the condition of 32 patients improved. In seven patients the symptoms remained unchanged. In one case, progressive deterioration of the condition ensued. There was no difference in outcome between patients who were treated with steroids and those who were not. Steroid therapy is probably not indicated in mild cases.

Aged↗

PubMed1984

Sex hormone suppression and sexual impotence in hypoxic pulmonary fibrosis.

Eight men with hypoxia associated with idiopathic pulmonary fibrosis were studied. Serum testosterone concentrations were low in two subjects and fell to subnormal levels in two others as the clinical condition and arterial oxygen tension deteriorated. There was a significant correlation between serum testosterone concentrations and arterial oxygen tensions (p less than 0.05). Three patients showed evidence of suppression of luteinising hormone secretion at the pituitary level. Only occasional abnormalities of thyroid and prolactin concentrations were noted. Most of the men suffered from organic sexual impotence, which is considered to be due at least in part to endocrine disturbance. These findings are similar to observations in patients with hypoxic chronic obstructive airways disease and support the hypothesis that hypoxia of lung disease suppresses the hypothalamo-pituitary-testicular axis.

Adult↗

PubMed2006

DNA microarray analysis of pulmonary fibrosis three months after exposure to paraquat in rats.

Although paraquat (PQ) is known to induce pulmonary fibrosis, how it does so is not entirely clear. To elucidate the mechanisms involved, the profile of gene expression in the lung at three months after exposure to PQ (7 mg/kg, s.c., daily for eight administrations) was investigated in rats using a DNA microarray. Changes in gene expression that were considered to reflect damage to the lung, a change in the balance of electrolytes and fluid, and alveolar remodeling were observed. The products of these genes were: CSF-1 receptor, which is a receptor of inflammatory cytokines that activates monocyte/macrophages; TGF-beta type II receptor, which is a receptor of TGF-betas involved in wound healing and fibrosis; a subunit of Na+/K(+)-ATPase, an amiloride-sensitive cation channel, and a subunit of the potassium channel, all of which regulate the alveolar fluid balance and play a role in clearing lung edema; the adenosine A2a receptor, which has a protective function in the lung and interacts with dopamine D1 and D2 receptors to regulate the function of amiloride-sensitive cation channels; cofilin, which is involved in the depolymerization and cleavage of actin filaments; LIM motif-containing protein kinase 1, which negatively regulates the activity of cofilin; SHPS-1, which regulates the integrin-mediated reorganization of the cytoskeleton; and sodium channel beta 2, which is involved in cell adhesion and migration. These results indicate that PQ-induced pulmonary fibrosis does not merely terminate as cicatrices three months after the discontinuation of PQ treatment, but that dynamic functional change continues in the lung.

Animals↗

PubMed2001

Cryptogenic fibrosing alveolitis/idiopathic pulmonary fibrosis.

Cryptogenic fibrosing alveolitis (CFA), synonymous with idiopathic pulmonary fibrosis (IPF), remains a life-threatening disease: 50% of patients die within 5 yrs. Historically, many diseases that are now considered to be quite distinct have been "labelled" as CFA. More recently, high-resolution computed tomography and new appreciation of the histopathological patterns of idiopathic interstitial pneumonias have enabled disease variants to be defined according to their different responses to therapy and survival. CFA is believed to be induced by an external agent, although it is not clear whether CFA represents the final common outcome of numerous pathogenetic mechanisms or has a single cause. In addition, there are currently no prospective double-blind, placebo-controlled trials of treatment showing superiority of one drug regimen over another. This review attempts to dissect the different patterns of cryptogenic fibrosing alveolitis, illustrate the major features of each, and refine the clinico-radiological-pathological descriptors that together define cryptogenic fibrosing alveolitis as it is understood today.

Humans↗

PubMed1980

Pentose pathway in pulmonary fibrosis due to chronic paraquat poisoning.

In 14 beagle dogs, paraquat was infused in fractional doses to produce pulmonary fibrosis while avoiding fatal liver and kidney lesions. Activity of the three enzymes of the pentose pathway: glucose-6-phosphate dehydrogenase (G-6-PDH), glutathione reductase (GR) and glutathione peroxidase (GSH Px), which supply reduced equivalents against oxidant agents, were measured in the mediastinal lobe of the lung. After a single low dose (2-3 mg/kg body weight), GR and GSH Px activities were reduced. After repeated paraquat doses, pentose pathway enzyme activities were higher than after a single low dose; however, they did not significantly exceed the normal values as determined in control dogs. The activities of G-6-PDH, GR and GSH Px correlated with the total paraquat dose and with the extent of pulmonary fibrosis measured with an electronic image analyzer. The activity of pulmonary lactate dehydrogenase, which was also reduced after a single low dose of paraquat, did not show the same correlations.

Animals↗