Increased Sensitivity to H2O2 in Glutathione Peroxidase-Deficient Rat Granulocytes

Abstract

The role of glutathione peroxidase (GSH-Px) in protecting phagocytic function of peritoneal granulocytes (PMN) was assessed using selenium (Se)-deficient rats. Rats fed an Se-deficient diet for 12–15 weeks developed profound Se deficiency. Their PMN were found to contain 11% of control levels of GSH-Px. Previous studies have shown that at this level of enzyme activity, the metabolism of H₂O₂ via the glutathione cycle was impaired. Despite this, the initial rate of phagocytosis, as measured by the ingestion of opsonized oil red O particles, was normal. Prior incubation of PMN in an H₂O₂-generating system resulted in a time-dependent loss in the ability of the cells to ingest. GSH-Px-deficient PMN were affected to a greater degree than control PMN. Degranulation, as measured by the release of β-glucuronidase into the extracellular medium after stimulation of PMN by opsonized zymosan in the presence of cytochalasin B, was unaffected by GSH-Px deficiency. Prior incubation of PMN in an H₂O₂ generating system resulted in decreased degranulation in both control and GSH-Px-deficient PMN, with GSH-Px-deficient PMN being affected to a greater degree. The killing of Staphylococcus aureus 502A by both control and GSH-Px-deficient PMN was the same. There was no effect of prior H₂O₂ incubation on bacterial killing in either control or GSH-Px-deficient PMN. Thus, GSH-Px appears to be important in protecting those aspects of phagocytic function that are sensitive to the destructive properties of exogenous H₂O₂.