The Role of Strain Variation in BAX and BCL-2 Expression in Murine Bleomycin-Induced Pulmonary Fibrosis

This study hypothesized that the expression of apoptosis-regulatory genes, such as BCL-2 and BAX may be affected by genetic variation in bleomycin-induced pulmonary fibrosis in C57BL/6 and NMRI mice. Pulmonary fibrosis induced by single intratracheal dose of bleomycin (3 U kg(-1)). After 2 weeks, lung samples were analyzed for collagen deposition, pathological changes and expression of BCL-2 and BAX. The fibrotic lung changes were similar in both strains. The immunohistochemical assay using a biotin-streptavidin technique showed no significant difference in immunoreactivity for BCL-2 protein between the controls and bleomycin-treated C57BL/6 mice. However, in NMRI mice, the expression of BCL-2 was significantly (p<0.05) upregulated in myofibroblasts and neutrophils. The expression of BAX protein was significantly (p<0.05) upregulated in alveolar epithelial cells of both strains and downregulated in myofibroblasts and lymphocytes of the lung tissues of C57BL/6 mice and also in lymphocytes of NMRI mice at 2 weeks after bleomycin instillation. These results confirm the role of BCL-2 and BAX proteins in the pathogenesis of pulmonary fibrosis and suggest that the expression of apoptotic regulatory genes may be specific in different cell types in various strains.