Inhibition of astrocyte TNFalpha expression by extracellular potassium

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.