Kininogen binding to the surfaces of macrophages

Kinin generation may be initiated on the cell surfaces via a primary kininogen docking which has been characterized for endothelial cells, platelets, neutrophils, astrocytes and smooth muscle cells. In this work we describe the adsorption of biotin-labeled human kininogens by murine RAW 264.7 macrophages and human U-937 monocytes/macrophages. Both cell types strongly bound high molecular mass kininogen (HK) in a zinc-ion dependent manner with the dissociation constants of 9.1 nM and 3.3 nM, respectively, and the binding capacities of 46 fmol and 71 fmol per million of respective cells. The HK binding was quenched by 50% by antibodies against Mac-1, gC1qR and uPAR proteins indicating that these macrophage surface receptors are involved in the HK adsorption. A significant increase of HK binding was observed after cell activation with phorbol myristate acetate. Our results suggest that macrophages, similarly to neutrophils, may supply kininogens to the inflammatory foci to support the local kinin production at these sites.