Stimulation of macrophages by mucins through a macrophage scavenger receptor

We found that phorbol ester-primed THP-1 cells (a human monocyte cell line), which express a scavenger receptor, were stimulated by mucins through the macrophage scavenger receptor, resulting in enhanced secretion of IL-1beta. The activity was abolished by treatment of the mucins with sialidase, indicating that sialic acid is involved in binding. (125)I-Labeled ovine submaxillary mucin could bind to COS 7 cells transfected with cDNA encoding the scavenger receptor. Binding was inhibited by mucins, fucoidan, and polyinosinic acid but not by polycytidylic acid, this being consistent with the characteristics of the scavenger receptor. When phorbol ester-primed THP-1 cells were cocultured with colon cancer cells producing mucins, IL-1beta secreted from the THP-1 cells increased significantly. Adhesion between colon cancer cells and a scavenger receptor transfectant was observed, and binding was inhibited partly by mucins and ligands for the scavenger receptor.