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High extracellular potassium modulates nitric oxide synthase expression in human astrocytes
A C Morgan1, H Y Chang, J S Liu
1Department of Pathology, Albert Einstein College of Medicine, Bronx, New York 10461, USA.
Journal of Neurochemistry
|May 9, 2000
Summary
High extracellular potassium (KCI) and potassium channel inhibitors reduce inducible nitric oxide synthase (iNOS) expression in human astrocytes. This suggests neural-specific mechanisms regulate glial iNOS in the central nervous system (CNS).
Area of Science:
- Neuroscience
- Cell Biology
- Immunology
Background:
- Inducible nitric oxide synthase (iNOS) plays a role in central nervous system (CNS) pathologies.
- Regulation of iNOS expression is species- and CNS-specific.
- Astrocytes are key glial cells in the CNS involved in ion homeostasis.
Purpose of the Study:
- To investigate the mechanisms regulating iNOS expression in primary human astrocytes.
- To examine the effect of extracellular potassium (K+) on astrocyte iNOS expression.
- To determine the role of astrocyte potassium channel activity in iNOS regulation.
Main Methods:
- Primary human astrocytes were cultured and activated with cytokines (IL-1/IFNγ).
- The effect of high extracellular KCl (25-75 mM) on nitrite production (a marker of iNOS activity) was measured.
- The impact of various potassium channel inhibitors (CsCl, tetraethylammonium, 4-aminopyridine, nigericin) on iNOS expression was assessed.
Main Results:
- High extracellular KCl significantly inhibited IL-1/IFNγ-stimulated nitrite production in astrocytes.
- Potassium channel inhibitors also suppressed IL-1/IFNγ-induced astrocyte iNOS expression.
- These findings indicate a direct modulation of iNOS by potassium levels and channel activity.
Conclusions:
- Astrocyte potassium channel activity plays a novel role in modulating astrocyte function.
- Neural-specific mechanisms likely govern glial iNOS regulation in the CNS.
- This study provides insights into the neuro-immune interactions within the CNS.