Matrix protein regulation of PMN oxidative metabolism during ischemia

Matrix proteins upregulate polymorphonuclear neutrophil (PMN) oxidative metabolism in a normoxic environment. We sought to investigate the relationship between matrix proteins and adherent PMN oxidative metabolism during acute ischemia. PMN adherent to buffer, fibronectin, Arg-Gly-Asp-Ser (RGDS), or laminin were placed in either normoxic or ischemic media. PMN adherence, superoxide anion production, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) formazan production, and surface receptor expression (CD64, CD32w, CD16, CD35, and CD11b/CD18) using monoclonal antibodies directed against these receptors were assayed. Ischemia increased PMN adherence unless the PMN were adhered to fibronectin or RGDS. Ischemia reduced PMN superoxide anion, MTT formazan, and H2O2 production unless the PMN were adhered to fibronectin or RGDS. Fibronectin and RGDS prevented ischemic-induced suppression of FcR expression. Immunofluorescent studies demonstrated capping and clustering of PMN Fc and complement receptors during ischemia while adhered on matrix proteins. These results demonstrate that 1) ischemia suppresses matrix protein upregulation of PMN oxidative metabolism, which is restored by fibronectin; 2) fibronectin-mediated restoration of PMN oxidative metabolism involves the binding epitope of fibronectin; and 3) fibronectin maintains PMN oxidative metabolism during ischemia in part by maintaining PMN FcR on the cell surface and by recruiting a new population of PMN capable of undergoing oxidative metabolism.