Microglia enhance beta-amyloid peptide-induced toxicity in cortical and mesencephalic neurons by producing reactive oxygen species

J Neurochem. 2002 Nov;83(4):973-83. doi: 10.1046/j.1471-4159.2002.01210.x.

Abstract

The purpose of this study was to assess and compare the toxicity of beta-amyloid (Abeta) on primary cortical and mesencephalic neurons cultured with and without microglia in order to determine the mechanism underlying microglia-mediated Abeta-induced neurotoxicity. Incubation of cortical or mesencephalic neuron-enriched and mixed neuron-glia cultures with Abeta(1-42) over the concentration range 0.1-6.0 microm caused concentration-dependent neurotoxicity. High concentrations of Abeta (6.0 microm for cortex and 1.5-2.0 microm for mesencephalon) directly injured neurons in neuron-enriched cultures. In contrast, lower concentrations of Abeta (1.0-3.0 microm for cortex and 0.25-1.0 microm for mesencephalon) caused significant neurotoxicity in mixed neuron-glia cultures, but not in neuron- enriched cultures. Several lines of evidence indicated that microglia mediated the potentiated neurotoxicity of Abeta, including the observations that low concentrations of Abeta activated microglia morphologically in neuron-glia cultures and that addition of microglia to cortical neuron-glia cultures enhanced Abeta-induced neurotoxicity. To search for the mechanism underlying the microglia-mediated effects, several proinflammatory factors were examined in neuron-glia cultures. Low doses of Abeta significantly increased the production of superoxide anions, but not of tumor necrosis factor-alpha, interleukin-1beta or nitric oxide. Catalase and superoxide dismutase significantly protected neurons from Abeta toxicity in the presence of microglia. Inhibition of NADPH oxidase activity by diphenyleneiodonium also prevented Abeta-induced neurotoxicity in neuron-glia mixed cultures. The role of NADPH oxidase-generated superoxide in mediating Abeta-induced neurotoxicity was further substantiated by a study which showed that Abeta caused less of a decrease in dopamine uptake in mesencephalic neuron-glia cultures from NADPH oxidase-deficient mutant mice than in that from wild-type controls. This study demonstrates that one of the mechanisms by which microglia can enhance the neurotoxicity of Abeta is via the production of reactive oxygen species.

MeSH terms

  • Amyloid beta-Peptides / toxicity*
  • Animals
  • Catalase / pharmacology
  • Cells, Cultured
  • Cerebral Cortex / cytology*
  • Coculture Techniques
  • Enzyme Inhibitors / pharmacology
  • Interleukin-1 / analysis
  • Mesencephalon / cytology*
  • Mice
  • Mice, Inbred C57BL
  • Microglia / cytology
  • Microglia / drug effects
  • Microglia / metabolism*
  • NADPH Oxidases / antagonists & inhibitors
  • NADPH Oxidases / metabolism
  • Neurons / cytology
  • Neurons / drug effects*
  • Neuroprotective Agents / pharmacology
  • Nitric Oxide / analysis
  • Rats
  • Rats, Inbred F344
  • Reactive Oxygen Species / metabolism*
  • Superoxide Dismutase / pharmacology
  • Superoxides / analysis
  • Superoxides / metabolism
  • Tumor Necrosis Factor-alpha / analysis

Substances

  • Amyloid beta-Peptides
  • Enzyme Inhibitors
  • Interleukin-1
  • Neuroprotective Agents
  • Reactive Oxygen Species
  • Tumor Necrosis Factor-alpha
  • Superoxides
  • Nitric Oxide
  • Catalase
  • Superoxide Dismutase
  • NADPH Oxidases