Lymphocyte transendothelial migration toward smooth muscle cells in interleukin-1 ?-stimulated co-cultures is related to fibronectin interactions with ?4?1 and ?5?1 integrins

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Abstract
We previously reported infiltration of immune-inflammatory cells in coronary arteries from cardiac allografts, associated with increased endothelial and smooth muscle cell fibronectin synthesis regulated by interleukin (IL)-1b̃. We now investigate, using a porcine endothelial-smooth muscle cell co-culture system, whether IL-1b̃-stimulated fibronectin production is functionally important in lymphocyte transendothelial migration. Lymphocytes were harvested from porcine peripheral blood and, in the unactivated state or following activation with phorbol myristic acetate (PMA) and IL-2, were characterized by fluorescence-activated cell sorter (FACS) analysis and added to a confluent endothelial monolayer on the upper chamber of a transwell system. Endothelial cells, as well as smooth muscle cells (in the bottom of the chamber), were stimulated with IL-1b̃. Then transendothelial lymphocyte migration was determined in the presence of CS1 and RGD (fibronectin) peptides, blocking α4b̃1 and α5b̃1 integrin receptors on lymphocyte surfaces, respectively. A 55-70% inhibition of lymphocyte migration was observed when compared to control peptides. The combination of CS1 and RGD peptides did not significantly enhance the inhibitory effect of either peptide alone. A similar decrease in lymphocyte transendothelial migration toward smooth muscle cells was documented using a monoclonal antibody to cellular fibronectin. Furthermore, using smooth muscle cell conditioned medium; we reproduced the enhanced transendothelial lymphocyte migration as well as the inhibition with blocking peptides or fibronectin antibodies. Our data suggest that cytokine-mediated fibronectin synthesis in vascular cells recruits inflammatory cells through interactions of specific peptides with cell surface α4b̃1 α5b̃1 integrins.