Modulation of human microglial cell superoxide production by cytokines.

Reactive oxygen intermediates (e.g., superoxide [O2-]) generated by microglia may play a role in host defense and injury within the central nervous system. We investigated the effect of cytokines on human microglial cell O2- production on stimulation with phorbol myristate acetate. Priming of microglial cell cultures with interferon-gamma or tumor necrosis factor-alpha resulted in a dose- and time-dependent enhancement of O2- production. The priming effects of these cytokines were mediated through a protein kinase C signal transduction pathway. In contrast, astrocytes did not generate detectable O2- on phorbol myristate acetate stimulation. Treatment of microglia with transforming growth factor-beta, interleukin-4, or interleukin-10 suppressed in a dose-dependent manner the priming effects of tumor necrosis factor-alpha and interferon-gamma. The results of this study have implications for understanding the mechanisms by which cytokines and microglia contribute to processes of host defense and neurodegeneration via generation of reactive oxygen intermediates.