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Precision-cut rat lung slices have been employed in combination with an extensive immunohistochemistry of paraffin-embedded slices for monitoring of early pathohistological changes after exposure to CdCl(2)/TGF-beta(1). Three days of CdCl(2) exposure in combination with TGF-beta(1) seem to be sufficient to induce lung injury with alterations similar to changes observed in early lung fibrogenesis: (1) extracellular matrix accumulation and myofibroblast transdifferentiation (Sirius red staining, collagen type IV, alpha-smooth muscle actin), (2) type I cell injury with loss of type I cell antigens (T1alpha antigen, aquaporin-5, RAGE), (3) increased apoptosis of pulmonary cells (active caspase-3, vimentin cleavage product V1 of caspase-9), and (4) activation of microvascular endothelial cells (podocalyxin, caveolin-1). Western blot analysis confirmed the increasing amount of alpha-smooth muscle actin, the loss of T1alpha antigen, and the increase in caveolin-1 immunoreactivity. The explant culture using CdCl(2)/TGF-beta(1) provides a suitable tool for the study of other factors involved in pulmonary pathology including transcription factors, cytokines, and other metabolites involved in early stages of fibrogenesis.

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Cathepsins in bleomycin-induced lung injury in rat. R. Koslowski, K. Knoch, E. Kuhlisch, D. Seidel, M. Kasper. #ERS Journals Ltd 2003. ABSTRACT: Endogenous inhibitors tightly control the activity of proteinases in the extracellular space. Proteinase/antiproteinase imbalance may be caused by predominance of proteinases, resulting in severe tissue damage or abundance of proteinase inhibitors, leading to a shift in the balance of synthesis and degradation of extracellular matrix proteins and accumulation of these matrix components. Lung fibrosis is characterised by accumulation of fibrous matrix proteins in the alveolar interstitium.The activity of cathepsin D and amounts of cathepsins D and B in bleomycin-injured rat lung tissue and alveolar macrophages were examined. In addition, the activities of cathepsins and cysteine proteinase inhibitors (CPIs) in bronchoalveolar lavage fluid (BALF) were determined.No cathepsin but high CPI activity and large amounts of procathepsin B were detected in the BALF. In the alveolar lumen, the disturbed proteinase/antiproteinase balance for cysteine proteinases was clearly dominated by CPIs. In alveolar macrophages, the main source of increased cathepsin levels, large changes in cathepsin B and D content were observed during the inflammatory phase, corresponding to the occurrence of procathepsin B in BALF. With the end of the phase of tissue remodelling, imbalances in cathepsin and CPI activities were largely eliminated. Immunoblot data, revealing an increase in cathepsin D levels in myofibroblast-like cells compared to fibroblasts and in resting fibroblasts compared to proliferating cells, implicate this proteinase in the differentiation and conversion processes occurring at the beginning of the fibrotic phase of lung injury.The results show that cathepsin amounts and activities are increased transiently in lung tissue during regeneration processes in bleomycin-induced lung injury. Imbalances of cathepsin and cysteine proteinase inhibitors activities are also a phenomenon of the phase of tissue remodelling initiated by lung injury.

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