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Voltage-gated proton currents in microglia of distinct morphology and functional state
1Department of Neurophysiology, Institute of Physiology, Humboldt University, Berlin, Germany.
Abstract:
Whole-cell patch-clamp measurements were performed to investigate voltage-gated proton currents (I(PR)) in cultured murine microglia of distinct morphology and functional state. We studied I(PR) in ameboid microglia of untreated cultures, in ameboid microglia which had been activated by lipopolysaccharide, and in ramified microglia which had been exposed to astrocyte-conditioned medium. Proton currents of these three microglia populations did not differ regarding their activation threshold or the voltage dependence of steady-state activation. Moreover, pharmacological properties of I(PR) were similar: proton currents were sensitive to extracellularly applied Zn2+ or La3+, and could be abolished by each of those at a concentration of 100 microM. In the presence of extracellular Na+, I(PR) was decreased to a similar small extent due to activity of the Na+/H+ exchanger in all microglial populations. In contrast, proton currents of microglia differed between the three cell populations with respect to their current density and their time-course of activation: in comparison with untreated microglia, the current density of I(PR) was reduced by about 50% in microglia after their treatment with either lipopolysaccharide or astrocyte-conditioned medium. Moreover, I(PR) activated significantly more slowly in cells exposed to lipopolysaccharide or astrocyte-conditioned medium than in untreated cells. It can be concluded that the distinct H+ current characteristics of the three microglial populations do not correlate with the functional state of the cells.
Insights
Voltage-gated proton currents (I(PR)) in microglia showed similar activation and pharmacology across different cell states. However, current density and activation speed varied, suggesting functional state does not correlate with these proton current characteristics.
Area of Science:
- Neuroscience
- Cell Biology
- Physiology
Background:
- Microglia are key immune cells in the central nervous system.
- Voltage-gated proton currents (I(PR)) play roles in cellular functions.
- Understanding I(PR) in microglia is crucial for neuroinflammation research.
Purpose of the Study:
- To investigate voltage-gated proton currents (I(PR)) in cultured murine microglia.
- To compare I(PR) characteristics in microglia of distinct morphologies and functional states.
- To determine if I(PR) properties correlate with microglial functional states.
Main Methods:
- Whole-cell patch-clamp electrophysiology was used.
- Murine microglia cultures were utilized, including untreated, lipopolysaccharide-activated, and astrocyte-conditioned medium-exposed cells.
- Pharmacological sensitivity to Zn2+ and La3+ was assessed.
Main Results:
- Proton currents (I(PR)) showed no differences in activation threshold or voltage dependence across the three microglial populations.
- Pharmacological properties, including sensitivity to Zn2+ and La3+, were similar among all groups.
- Current density of I(PR) was reduced by approximately 50% in activated and medium-exposed microglia compared to untreated cells.
- I(PR) activation kinetics were significantly slower in lipopolysaccharide-activated and medium-exposed microglia.
Conclusions:
- Distinct H+ current characteristics were observed in different microglial populations.
- These observed differences in current density and activation kinetics do not correlate with the functional state of the microglia.
- Further research is needed to elucidate the precise roles of I(PR) in microglial function.