Erythrocyte Membranes Inhibit Respiratory Burst and Protein Nitration during Phagocytosis by Macrophages

J. WILHELM, A. SKOUMALOVÁ, R. VYTÁŠEK, B. FIŠÁRKOVÁ1, P. HITKA1, L. VAJNER2

Department of Medical Chemistry and Biochemistry, 1Department of Pathophysiology, 2Department of Embryology and Histology, Second Faculty of Medicine, Charles University, and Center for Experimental Cardiovascular Research, Prague, Czech Republic

Received June 2, 2004
Accepted November 25, 2004
On-line available January 10, 2005


Summary
Phagocytosis is associated with respiratory burst producing reactive oxygen and nitrogen species. Several studies imply that erythrocytes can inhibit the respiratory burst during erythrophagocytosis. In this work we studied the mechanisms of this effect using control and in vitro peroxidized erythrocyte membranes. We demonstrated that autofluorescence of peroxidation products can be used for visualization of phagocytozed membranes by fluorescence microscopy. We also found that respiratory burst induced by a phorbol ester was inhibited by control membranes (5 mg/ml) to 63 % (P0.001), and to 40 % by peroxidized membranes (P0.001). We proved that this effect is not caused by the direct interaction of membranes with free radicals or by the interference with luminol chemiluminescence used for the detection of respiratory burst. There are indications of the inhibitory effects of iron ions and free radical products. Macrophages containing ingested erythrocyte membranes do not contain protein-bound nitrotyrosine. These observations imply a specific mechanism of erythrocyte phagocytosis.


Key words
Phagocytosis • Macrophages • Erythrocyte membranes • Respiratory burst • Nitrotyrosine