Increased Expression of Intercellular Adhesion Molecule 1, CD11/CD18 Cell Surface Adhesion Glycoproteins and α4β1 Integrin in a Rat Model of Chronic Interstitial Lung Fibrosis

Abstract

The expression of the intercellular adhesion molecule 1 (ICAM-1), and the integrins CD49, CD1 Vole, and CD1 la (LFA-1α chain) was analyzed in an experimental model of pulmonary fibrosis. Adult rats were exposed to 75% oxygen during 10 weeks, and to 2.0 mg/kg of paraquat twice weekly. Rats were sacrificed at 2 days, and at 2 and 10 weeks after the first injection of paraquat. Lungs were fixed in 4% paraformaldehyde and used for histology and immunohistochemistry. At 2 days the lungs showed a diffuse inflammation composed of a mixed polymorphonuclear and mononuclear cell infiltrate. Afterwards, the inflammatory process was predominantly mononuclear, and an increasing fibroblast proliferation was observed. Early inflammatory events (48 h) correlated with a moderate increased expression of ICAM-1, LFA, and CD1 lb/c in epithelial cells as well as a pronounced expression of ICAM-1 and CD1 lb/c in macrophages. At 2 and 10 weeks, there was a progressive increased expression of CD1 lb/c and ICAM-1 by macrophages, as well as of LFA in epithelial cells, and of ICAM-1 and CD49 by epithelial and interstitial cells. Lymphocytes showed a slight increased expression of LFA at 2 weeks, and of CD49 at 2 and 10 weeks. These results suggest that macrophages expressing ICAM-1, CD1 lb/c, and CD49 are involved in the earlier and late phases of the disease whereas fibroblast and epithelial cells expressing ICAM-1 and CD49 might play a role in the cell interactions involved in the fibrotic phase.