CHARACTERIZATION OF RAT LUNG ICAM-1

Objective and Design: We expressed soluble rat ICAM-1, generated a pol yclonal anti-ICAM-1 antibody, and studied ICAM-1 upregulation in lung inflammatory conditions. Bacterial and baculovirus expression systems were employed. Material: 250 g adult, male Long Evans rats were used. For in vitro studies, rat pulmonary artery endothelial cells (RPAEC), rat alveolar macrophages and aortic rings were stimulated (as describe d below) and evaluated for ICAM-1 expression. Treatment: RPAEC and mac rophages were stimulated with lipopolysaccharide (LPS) and recombinant murine tumour necrosis factor alpha (TNF alpha). In vivo immunoglobul in G (IgG) immune complex-induced lung injury was employed. Methods: E nzyme-linked immunoassay (ELISA) Western and Northern blot analyses an d immunohistochemical evaluations were performed. All experiments were done at least in duplicate. Data were analyzed by two-tailed Student' s t-test. Results: ICAM-1 expression of RPAEC was time- and dose-depen dent, peaking at 6 h after LPS-stimulation. LPS and TNFa each enhanced ICAM-1 expression on alveolar macrophages (reaching a maximum at 2 h) . In IgG immune complex-induced lung injury, ICAM-1 mRNA isolated from whole lung peaked at 4 h, while lung ICAM-1 protein peaked at 6 h. Co nclusions: Quantitation of ICAM-1 expression in vitro and in vivo sugg ests that ICAM-1 plays a central role in two lung inflammatory models. Furthermore, lung ICAM-1 upregulation involves at least two cell type s: vascular endothelial cells and alveolar macrophages.