The role for reactive oxygen species in membrane potential changes in macrophages and astrocytes

Involvement of reactive oxygen species (ROS) in changes of the plasma membrane potential of mouse peritoneal macrophages and astrocytes (U118 cell line) under the action of different agents has been studied, Membrane potential was measured using the voltage-dependent fluorescent oxonol dye DiBAC(4)(3), Agonists that stimulate macrophages to release ROS (the fMLP peptide and platelet-activating factor) cause prolonged hyperpolarization. Experiments with the fluorescent probe 2',7'-dichlorofluorescin diacetate have shown that astrocytes released ROS upon the action of C5a complement anaphylatoxin (but not C3a). The effect of C5a is accompanied by hyperpolarization of the astrocyte plasma membrane. Treatment of the cells with agents that do not induce ROS generation (C3a, lipopolysaccharide, interferon-gamma) depolarizes the plasma membrane. Hyperpolarization of both cell types was significantly decreased in the presence of superoxide dismutase (but not catalase). Moreover, the O-2(radical) (anion)-generating system caused a marked hyperpolarization of both cell types. The data obtained permit the conclusion that O-2(radical anion) is involved in the macrophage and astrocyte hyperpolarization response.