Hydrogen peroxide induced chemokine production in the glia-rich cultured cerebellar granule cells under acidosis

Abstract

We have documented the time-dependent production of chemotactic cytokine, i.e., IL-8, in the extracellular fluid of astrocyte-rich cultured rat cerebellar granule cells under acidified conditions. In this paper, the mechanism of this production was evaluated based on the production of hydrogen peroxide (H 2O 2). Significant and time-dependent increases of cytosolic H 2O 2 were detected under acidosis in astrocyte-rich cultured cell. Upon exposure to 10 μM H 2O 2, significant levels of IL-8 appeared in the extracellular fluid of astrocyte-rich cells, although an initial transient increase of IL-8 was also seen in the intracellular space. Concurrently, after H 2O 2 exposure cell injury and a delayed increase of cytosolic Ca 2+ levels were detected in astrocyte-rich cells. However, in the absence of extracellular Ca 2+, the cell injury and the increase of IL-8 production were significantly attenuated. A synergistic effect of cyclosporine A (an inhibitor of the Ca 2+/calmodulin-regulated protein phosphatase) and trifluoperazine (an inhibitor of phospholipase A 2) on the suppression of H 2O 2-induced IL-8 production was clearly evident. These results suggest that extracellular acidosis induced Ca 2+-dependent H 2O 2 production, which in turn stimulated IL-8 expression, which is regulated by the cytosolic Ca 2+ cascade. Thus, the production of IL-8 from glia cells may have a role in regulating in the process of cell injury.