Neuronal death in cytokine-activated primary human brain cell culture: Role of tumor necrosis factor-α

We examined cytokine-mediated neuronal death in neuron-astrocyte cultures from second trimester human fetal cerebrum. In these cultures, high-output inducible nitric oxide synthase (NOS) and tumor necrosis factor-α (TNFα) are expressed in astrocytes after exposure to IL-1β/IFNγ. Neuronal cell death was evident at ≥48 h following cytokine stimulation. Neutralizing anti-TNFα antiserum inhibited (≃48%) neurotoxicity in IL-1β/IFNγ-treated cultures, demonstrating a role for endogenously produced TNFα. Interestingly, the degree of neuroprotection conferred by superoxide dismutase or N-methyl D-aspartate (NMDA) receptor antagonists in these cultures was smaller and variable. Similarly, the effect of the NOS inhibitor, N(G)-monomethyl L-arginine (NMMA) on IL-1β/IFNγ-induced neuronal death was variable, showing no statistically significant effect when results from more than 30 independent cultures were averaged. Neurons die by apoptosis in cytokine-treated human fetal CNS cultures as shown by the characteristic nuclear morphology as well as positive labeling for TUNEL. Our results demonstrate a potent neurotoxicity mediated by the cytokine combination IL-1β/IFNγ in primary human neuron-astrocyte cultures and a crucial role for endogenous TNFα in mediating neurotoxicity in this system. These results firmly establish the neurotoxic potential of the inflammatory cytokines IL-1β and TNFα in the human CNS.