title: Microglia enhance beta-amyloid peptide-induced toxicity in cortical and mesencephalic neurons by producing reactive oxygen species.
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.
authors.affiliation: Neuropharmacology Section, Laboratory of Pharmacology and Chemistry, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina 27709, USA. qin1@niehs.nih.gov
authors.forename: Liya
authors.initials: L
authors.lastname: Qin
authors.forename: Yuxin
authors.initials: Y
authors.lastname: Liu
authors.forename: Cynthia
authors.initials: C
authors.lastname: Cooper
authors.forename: Bin
authors.initials: B
authors.lastname: Liu
authors.forename: Belinda
authors.initials: B
authors.lastname: Wilson
authors.forename: Jau-Shyong
authors.initials: JS
authors.lastname: Hong
mesh_terms: D016229:Amyloid beta-Peptides / Q000633:toxicity*; D000818:Animals; D002374:Catalase / Q000494:pharmacology; D002478:Cells, Cultured; D002540:Cerebral Cortex / Q000166:cytology*; D018920:Coculture Techniques; D004791:Enzyme Inhibitors / Q000494:pharmacology; D007375:Interleukin-1 / Q000032:analysis; D008636:Mesencephalon / Q000166:cytology*; D051379:Mice; D008810:Mice, Inbred C57BL; D017628:Microglia / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D019255:NADPH Oxidases / Q000037:antagonists & inhibitors / Q000378:metabolism; D009474:Neurons / Q000166:cytology / Q000187:drug effects*; D018696:Neuroprotective Agents / Q000494:pharmacology; D009569:Nitric Oxide / Q000032:analysis; D051381:Rats; D011916:Rats, Inbred F344; D017382:Reactive Oxygen Species / Q000378:metabolism*; D013482:Superoxide Dismutase / Q000494:pharmacology; D013481:Superoxides / Q000032:analysis / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000032:analysis
chemical_list: D016229:Amyloid beta-Peptides; D004791:Enzyme Inhibitors; D007375:Interleukin-1; D018696:Neuroprotective Agents; D017382:Reactive Oxygen Species; D014409:Tumor Necrosis Factor-alpha; D013481:Superoxides; D009569:Nitric Oxide; D002374:Catalase; D013482:Superoxide Dismutase; D019255:NADPH Oxidases