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It has been proposed that the development of lung fibrosis is associated with a T helper type 2 response, mainly characterized by IL-4 and IL-13 production. We investigated the potential role of type 2 immune polarization in the silicotic process and examined the pulmonary response to silica particles in mice genetically deficient for IL-4. We found that [IL-4.sup.-/-] mice were not protected against the development of silicosis, suggesting that IL-4 is not essential for the development of this fibrotic disease. By evaluating the intensity of silica-induced lung fibrosis in mice deficient for IL-4 receptor [alpha] (IL-4R[alpha]), we showed that the establishment of pulmonary fibrosis was independent of both IL-4 and IL-13. Strong impairment of the type 2 immune response (Ig[G.sub.1]) in the lungs of [IL-4.sup.-/-] and IL-4R[[alpha].sup.-/-] mice did not affect the development of the disease. Measurement of IL-13[alpha]2 receptor expression and Ig[G.sub.2]a, IL-12p70, and IFN-[gamma] levels in silica-treated [IL-4.sup.-/-] and IL-4R[[alpha].sup.-/-] animals showed that the development of silicosis was not related to an IL-13 signaling pathway or a switch to a type 1 response in deficient animals. Our data clearly indicate that the type 2 immune response associated with silicosis in mice is not required for the development of this inflammatory and fibrotic disease. inflammation; T helper type 2; lung fibrosis; cytokines

Chronic inflammation and proinflammatory cytokines as well as T helper type 2 (Th2) cytokines have been involved in the pathogenesis of pulmonary injury and lung fibrosis. The actual role of IL-10 in lung fibrosis is still unclear because this cytokine has been identified as Th2 but possesses strong anti-inflammatory properties. To better dissect the potential role of IL-10 in silica-induced lung librosis, IL-10 was overexpressed in the lung of mice by adenoviral gene transfer during the inflammatory (administered at day -1) or the fibrotic (administered at day +30) stages of the disease. Pulmonary overexpression of IL-10 during both silica-induced lung inflammation and fibrosis exacerbated the fibrotic lesions as estimated by the measurement of hydroxyproline and other biochemical and histological markers. Increased expression of IL-10 significantly enhanced the number of lung lymphocytes and bronchoalveolar lavage fluid IgG1 but not IgG2a levels, indicating the induction of a Th2-like immune response. In addition, the production of the profibrotic Th2 cytokines IL-4 and IL-13 was also significantly increased upon IL-10 overexpression. No difference in transforming growth factor-[beta] or PG[E.sub.2] production was noted after adenoviral IL-10 treatment of silica-treated mice. Together, these data indicate that the increased expression of IL-10 significantly contributed to silica-induced lung fibrosis by exacerbating the Th2 response and the production of the profibrotic cytokines IL-4 and IL-13. inflammation; T helper 2 cytokines; interleukin-10

Abstract Background It has been generally well accepted that chronic inflammation is a necessary component of lung fibrosis but this concept has recently been challenged. Methods Using biochemical, histological, immunohistochemistry, and cellular analyses, we compared the lung responses (inflammation and fibrosis) to fibrogenic silica particles (2.5 and 25 mg/g lung) in Sprague-Dawley rats and NMRI mice. Results Rats treated with silica particles developed chronic and progressive inflammation accompanied by an overproduction of TNF-α as well as an intense lung fibrosis. Dexamethasone or pioglitazone limited the amplitude of the lung fibrotic reaction to silica in rats, supporting the paradigm that inflammation drives lung fibrosis. In striking contrast, in mice, silica induced only a limited and transient inflammation without TNF-α overproduction. However, mice developed lung fibrosis of a similar intensity than rats. The fibrotic response in mice was accompanied by a high expression of the anti-inflammatory and fibrotic cytokine IL-10 by silica-activated lung macrophages. In mice, IL-10 was induced only by fibrotic particles and significantly expressed in the lung of silica-sensitive but not silica-resistant strains of mice. Anti-inflammatory treatments did not control lung fibrosis in mice. Conclusion These results indicate that, beside chronic lung inflammation, a pronounced anti-inflammatory reaction may also contribute to the extension of silica-induced lung fibrosis and represents an alternative pathway leading to lung fibrosis.

Hypersensitivity pneumonitis (HP) represents the immunologically mediated lung disease induced by repeated inhalations of a wide variety of certain finely dispersed organic antigens. In susceptible subjects, these inhalations provoke a hypersensitivity reaction characterized by intense inflammation of the terminal bronchioles, the interstitium and the alveolar tree. The inflammation often organizes into granulomas and may progress to pulmonary fibrosis. Our previous work indicated that cell extract of gram-negative bacteria Pantoea agglomerans (SE-PA) causes, in young C57BL/6J mice, pulmonary changes that are very similar to the clinical manifestations of HP in men. The purpose of presented studies was to describe the response of mice immune system while exposed to SE-PA. Particular attention was paid to examine the age influence on SE-PA induced inflammation and fibrosis in lung tissue. We used 3- and 18-month-old C57BL/6J mice. Lung samples were collected from untreated mice and animals exposed to harmful agent for 7 and 28 days. HP development was monitored by histological and biochemical evaluation. Using ELISA tests, we examined concentration of pro- and anti-inflammatory cytokines in lung homogenates. Our study demonstrated again that SE-PA provokes in mice changes typical for the clinical picture of HP, and that successive stages of disease (acute, subacute and chronic) might be obtained by modulation of time exposure. Furthermore, we found that animals' age at the time of sensitization influences the nature of observed changes (cytokine expression pattern) and the final outcome (reaction intensity and scale of fibrosis). [ABSTRACT FROM AUTHOR]

Since tumor growth factor beta (TGF- ) and its receptor are ubiquitously expressed and because latent TGF- cannot bind to the cell surface receptor, the ability of a cell to activate latent TGF- upon secretion represents an important regulatory mechanism of TGF- action. In vivo, the protease plasm in is considered to be one of the main enzymes operative in the proteolytic cleavage of the latency-associated peptide moiety from TGF- , which converts it into the biologically active form. The TGF- response was characterized in alveolar macrophages during pulmonary inflammation (d 3) and fibrosis (d 120) induced by a single intratracheal instillation of silica particles ( 5 mg/ mouse). To appreciate the role of urokinase-type plasminogen activator (uPA) in the activation of TGF- , the production of total, active and latent TGF- by explanted alveolar macrophages was compared in uPA-deficient (uPA-/-) mice and their normal counterparts (uPA+/ +) . At d 3 and 120 after silica treatment, a significant increase in cell-associated PA activity was found in uPA+/ + mice compared to that of saline controls. As expected, this response was almost totally absent in uPA-/- mice. Alveolar macrophages from uPA+/ + controls were found to release TGF- mainly expressed in a biologically active form. In response to silica treatment, inflammatory cells were found to upregulate, especially at the fibrotic stage, their secretion of total and bioactive TGF- . No significant difference was found between uPA-/- and uPA+/ + silica-treated animals for the expression of total, active, or latent TGF- . Although it has previously been reported that macrophage surface activation of TGF- is dependent on both plasmin generation and uPA cell surface receptor, no evidence was found to support this hypothesis in the present study. [ABSTRACT FROM AUTHOR]

The aim of this study was to reproduce in laboratory conditions hypersensitivity pneumonitis (HP) pathogenesis in a new animal model predictive of the human response, and to select the microbial antigen associated with organic dust that exerts the strongest pathogenic effect on the respiratory organ. To achieve this goal, mice of the strain C57BL/6J prone to fibrosis were exposed for 1 hour daily up to 28 days to the inhalation of aerosols of each of the 5 microbial components of organic dusts whose conjunction with the occurrence of HP has been confirmed by numerous authors: Pantoea agglomerans saline extract (SE), P. agglomerans microvesicle-bound endotoxin, Saccharopolyspora rectivirgula SE, Aspergillus fumigatus SE, saline extract of dust from a grain sample overgrown with S. rectivirgula and Thermoactinomyces vulgaris, and a saline solvent (PBS) was used as a control. Exposure of the animals to organic dust components was conducted using a novel inhalation challenge set. Lung samples were collected from untreated mice and from mice exposed for 7 and 28 days, and examined by digitalized histopathology and biochemistry for the presence of inflammatory changes and fibrosis. P. agglomerans SE appeared to be the sole antigen which evoked a statistically significant fibrosis and a significant increase of hydroxyproline in the lungs of mice exposed for 28 days to this extract, both compared to the mice untreated and to those exposed to the solvent. P. agglomerans SE also evoked the strongest and statistically significant inflammatory response in the lungs of the mice, both after 7 and 28 days of exposure. After 7 days, significant inflammatory changes were also found in mice exposed to A. fumigatus SE, and after 28 days in mice exposed to all antigens. In conclusion, our results allow us to define a useful animal model of HP which can be a supplement for now commonly used bleomycin model. This model should comprise: present set of instruments for inhalation, mice of the line C57BL/6J and the saline extract of P. agglomerans as the antigen. For a better understanding of the presented results, a detailed study covering immunological investigations, focused on the mechanism of antigen action, are needed.