Related Experiment Videos
Autooxidation as a basis for altered function by polymorphonuclear leukocytes
Abstract:
To investigate the possibility that human polymorphonuclear leukocytes (PMN) elaborate sufficient amounts of hydrogen peroxide (H2O2) and other radicals of reduced oxygen to be autotoxic and retard directed cell movement and phagocytosis, the rate of ingestion of opsonized lipopolysaccharide-paraffin oil particles and movement through Nuclepore filters were studied. Ingestion rates were increased under anaerobic conditions and in normal aerobic conditions in the presence of extracellular catalase but not superoxide dismutase (SOD) or scavengers of singlet oxygen or hydroxyl radicals. Conversely, ingestion rates were decreased when cells were exposed to H2O2 or a superoxide anion (O2-)-H2O2 generating system of xanthine-xanthine oxidase. Catalase, but not SOD, prevented the effect and also enhanced the directed movement of PMN in normal aerobic conditions. PMN from volunteers administered 1600 U/day of the membrane lipid antioxidant alpha-tocopherol were hyperphagocytic but killed Staphylococcus aureus 502A less effectively than controls, suggesting that less H2O2 was available to damage PMN or kill bacteria. H2O2-dependent stimulation of the hexose monophosphate shunt, H2O2 release from phaogytizing PMN, and fluoresceinated concanavalin A cap formation promoted by H2O2 damage to microtubules were all diminished, but the release of O2- from phagocytizing PMN was not diminished in the vitamin E group. These results support the hypothesis that directed movement and phagocytosis by PMN are attenuated by autooxidative damage to the cell membrane by endogenously derived H2O2 and that the administration in vivo of vitamin E may prevent this damage by scavenging H2O2.
Insights
Human immune cells, polymorphonuclear leukocytes (PMN), may harm themselves with hydrogen peroxide (H2O2), impairing their ability to fight infection. Vitamin E may protect these cells from this self-inflicted damage.
Area of Science:
- Immunology
- Cell Biology
- Biochemistry
Background:
- Human polymorphonuclear leukocytes (PMN) produce reactive oxygen species, including hydrogen peroxide (H2O2), during immune responses.
- The potential for these reactive oxygen species to cause autotoxicity and impair PMN function is not fully understood.
Purpose of the Study:
- To investigate if endogenous hydrogen peroxide (H2O2) production by PMN leads to autotoxicity, hindering directed cell movement and phagocytosis.
- To explore the protective effects of antioxidants, specifically vitamin E (alpha-tocopherol), against H2O2-induced PMN dysfunction.
Main Methods:
- Assessed PMN phagocytosis of opsonized particles and directed migration through filters under various conditions (anaerobic, presence of catalase, superoxide dismutase, H2O2, xanthine-xanthine oxidase).
- Studied PMN function in volunteers supplemented with alpha-tocopherol, measuring phagocytosis, bacterial killing, hexose monophosphate shunt activity, H2O2 release, and microtubule-associated responses.
- Measured superoxide anion (O2-) release from phagocytizing PMN.
Main Results:
- PMN phagocytosis and migration were enhanced by catalase and impaired by H2O2 or a superoxide-generating system, indicating H2O2's inhibitory role.
- Alpha-tocopherol supplementation resulted in hyperphagocytic PMN but reduced bacterial killing, with diminished H2O2-dependent cellular responses, suggesting reduced H2O2 availability.
- H2O2-induced damage to microtubules was reduced in vitamin E supplemented PMN, while O2- release remained unaffected.
Conclusions:
- Endogenously produced H2O2 can cause autotoxic damage to PMN, attenuating their directed movement and phagocytic capacity.
- In vivo administration of vitamin E may protect PMN from H2O2-induced autotoxicity by scavenging H2O2, potentially preserving immune cell function.