Expression of Monocyte Chemoattractant Protein-1 (MCP-1) by Rat Alveolar Macrophages during Chronic Lung Injury

Using a well-characterized model of bleomycin-induced pulmonary fibrosis in the rat, we determined that there was a time-dependent elaboration of monocyte chemotactic activity in bronchoalveolar lavage fluid. Northern hybridization analysis revealed markedly increased expression of rat monocyte chemoattractant protein-1 (MCP-1) mRNA in alveolar macrophages (AMs) from rats following induction of pulmonary fibrosis. Monocyte chemotactic activity was also significantly increased in conditioned media from AMs retrieved from injured rat lungs. These data suggest that one important role of AMs in the pathogenesis of chronic inflammatory lung injury and pulmonary fibrosis is the regulation of monocyte recruitment and activation within the lung secondary to secretion of monocyte chemoattractants including MCP-1.