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Inhibition of astrocyte TNFalpha expression by extracellular potassium
1Department of Pathology (F-717), Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, NY 10461, USA.
Abstract:
TNFalpha and IL-6 are cytokines of great interest, given the numerous biological activities and the documented expression in several central nervous system (CNS) pathologies. In this report, we have examined cultures of IL-1- or IL-1/IFNgamma-activated human fetal astrocytes as a model to study mechanisms of cytokine regulation in the inflamed CNS. Since one of the major functions of astrocytes is spatial buffering of K(+) ions, we examined the effect of high extracellular KCl on astrocyte cytokine expression by ribonuclease protection assay and ELISA. Results demonstrate that astrocyte TNFalpha production was potently inhibited by K(+) with 44 and 89% inhibition at 25 and 55 mM K+, respectively. In contrast, astrocyte IL-6 inhibition required higher concentrations of K+ (>/=75 mM). These results demonstrate a novel role for astrocyte potassium channel activity in modulation of glial cytokine production.
Insights
High potassium levels inhibit astrocyte production of tumor necrosis factor-alpha (TNFalpha) and interleukin-6 (IL-6), revealing a novel mechanism for regulating glial cytokine expression in the central nervous system (CNS).
Area of Science:
- Neuroscience
- Immunology
- Cell Biology
Background:
- Tumor necrosis factor-alpha (TNFalpha) and interleukin-6 (IL-6) are key cytokines implicated in central nervous system (CNS) pathologies.
- Astrocytes play a crucial role in CNS homeostasis, including spatial buffering of potassium (K+) ions.
- Understanding astrocyte cytokine regulation is vital for studying neuroinflammation.
Purpose of the Study:
- To investigate the effect of elevated extracellular potassium (K+) on cytokine production by human fetal astrocytes.
- To explore the role of astrocyte potassium channel activity in modulating glial cytokine expression.
- To model cytokine regulation mechanisms within an inflamed CNS environment.
Main Methods:
- Primary human fetal astrocyte cultures were activated with interleukin-1 (IL-1) or IL-1/interferon-gamma (IFNgamma).
- High extracellular potassium chloride (KCl) concentrations were applied to assess effects on cytokine expression.
- Ribonuclease protection assay and ELISA were utilized to quantify TNFalpha and IL-6 levels.
Main Results:
- Astrocyte TNFalpha production was significantly inhibited by physiological K+ concentrations (44% at 25 mM, 89% at 55 mM).
- Astrocyte IL-6 production required higher K+ concentrations (>=75 mM) for comparable inhibition.
- These findings highlight differential K+ sensitivity for TNFalpha and IL-6 production in astrocytes.
Conclusions:
- Astrocyte potassium channel activity represents a novel mechanism for modulating glial cytokine production in the CNS.
- Potassium ion regulation offers a potential therapeutic target for neuroinflammatory conditions.
- This study provides new insights into the interplay between astrocyte ion transport and neuroinflammation.