ABSTRACT
The pulmonary recruitment and activation of inflammatory cells, in particular, neutrophils is thought to contribute to lung injury resulting from dust exposure. MIP-2 (macrophage inflammatory protein-2) which is a member of C-X-C chemokine plays a key role in neutrophil recruitment to sites of tissue injury. Especially, mineral fiber induced pulmonary response is as a model for the neutrophil recruitment. Therefore, we evaluated the distribution of MIP-2 expression in lung tissue of mineral fiber exposed rat using immunohistochemical study and the relationship between degree of inflammation of lower respiratory tract and MIP-2 expression. Total cell counts in bronchoalveolar lavage (BAL) fluid in mineral fiber-exposed group were markedly increased compared with each control group even not in ceramic fiber group. Number of neutrophil in BAL fluid in mineral fiber-exposed group were markedly increased compared with each control group until 4th week but except ceramic fiber group. In chrysotile group, number of neutrophil in BAL fluid were markedly increased compared with control group at 8th week. Lung tissue instilled with all kinds of mineral fibers showed remarkable developments of bronchus associated lymphoid tissue (BALT) and small multiple granulomas but not for ceramic fiber group. In chrysotile group, multiple granuloma and inflammatory change were more profuse response compared with other groups. MIP-2 was predominently expresses in epithelial cells of bronchioles and bronchus and was express also found in macrophages with lung section at 1 week after fiber instillation. Small amount of epithelial cell associated MIP-2 was present in chrysotile at 8 week group. But MIP-2 was not seen in epithelial cells and macrophages in the lung tissue instilled with crocidolite, ceramic fiber and glass fiber at 8 weeks. Our finding suggest that MIP-2 is predominantly expressed in bronchial epithelial cells of lung from mineral fiber-exposed rat and correlated with inflammatory cell, especially neutrophil, recruitment and tissue reaction. And we documented that MIP-2 expression and neutrophil recruitment in man-made vitreous fiber-exposed rat, especially glass fiber, less than chrysotile.