Differential regulation by cytokines of human astrocyte nitric oxide production

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Abstract
Reactive nitrogen intermediates, such as nitric oxide (NO), play an important role in host-defense and injury. Human astrocytes released abundant NO upon stimulation with the pro-inflammatory cytokine interleukin (IL)-1β, which was potentiated by interferon (IFN)-γ and tumor necrosis factor (TNF)-α. IL-1 receptor antagonist protein markedly attenuated astrocyte NO production. The anti-inflammatory cytokines IL-4 and IL-10 potently suppressed IL-1β plus IFN-γ-stimulated NO, while transforming growth factor-β preferentially inhibited IL-1β plus TNF-α-stimulated production of NO. These findings suggest that while IL-1 plays a key role in inducing astrocyte NO production, anti-inflammatory cytokines have the capacity to downregulate NO production by IL-1-stimulated astrocytes.