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Superoxide release is involved in membrane potential changes in mouse peritoneal macrophages
I A Gamaley1, K M Kirpichnikova, I V Klyubin
1Institute of Cytology, Russian Academy of Sciences, St. Petersburg. igamaley@link.cytspb.rssi.ru
Abstract:
Participation of reactive oxygen species (ROS) in the changes in macrophage membrane potential resulted from effects of different agonists has been studied. Treatment of macrophages with chemotactic peptide fMLP or platelet-activating factor (PAF) caused a brief depolarization followed by a long-lasting hyperpolarization. Lipopolysaccharide and interferon-gamma only depolarized the plasma membrane. Chemiluminescence measurements indicated that only fMLP and PAF activated macrophages to release ROS. The hyperpolarization response of the cell was significantly decreased in the presence of superoxide dismutase (but not catalase). Moreover, the O2.- -generating system, xanthine plus xanthine oxidase, caused a marked hyperpolarization. In all the cases, the hyperpolarization induced by fMLP, PAF and O2.- -generating system was found to depend on the concentration of intracellular Ca2+ and extracellular K+. Furthermore, in the presence of quinidine, a blocker of Ca2+-dependent K+ conductance fMLP and PAF caused only prolonged depolarization while the effect of O2.- was reduced to a minimum. These data suggest that the macrophage hyperpolarization response to fMLP and PAF involves superoxide-mediated Ca2+-dependent alteration of the relative membrane permeability to K+.
Insights
Reactive oxygen species (ROS) mediate macrophage hyperpolarization. Superoxide release, triggered by fMLP and PAF, influences membrane potential changes, dependent on calcium and potassium levels.
Area of Science:
- Immunology
- Cellular Physiology
Background:
- Macrophages play a crucial role in immune responses.
- Membrane potential changes are critical for macrophage function.
- Reactive oxygen species (ROS) are implicated in cellular signaling.
Purpose of the Study:
- To investigate the role of ROS in modulating macrophage membrane potential.
- To elucidate the mechanisms underlying membrane potential changes induced by various agonists.
Main Methods:
- Macrophage treatment with agonists (fMLP, PAF, LPS, IFN-γ).
- Measurement of membrane potential using electrophysiological techniques.
- Chemiluminescence assays to detect ROS production.
- Pharmacological inhibition of ROS and ion channels.
Main Results:
- fMLP and PAF induced depolarization followed by hyperpolarization, associated with ROS release.
- LPS and IFN-γ caused only depolarization.
- Superoxide dismutase, but not catalase, reduced hyperpolarization.
- A xanthine/xanthine oxidase system mimicked hyperpolarization.
- Hyperpolarization was dependent on intracellular Ca2+ and extracellular K+.
- Quinidine blocked Ca2+-dependent K+ channels, altering depolarization and reducing ROS effects.
Conclusions:
- Macrophage hyperpolarization induced by fMLP and PAF is mediated by superoxide.
- This process involves a Ca2+-dependent alteration in K+ permeability.
- ROS play a significant role in regulating macrophage membrane potential and function.