title: Astrocytic phospholipase A2 contributes to neuronal glutamate toxicity.
abstract: The role of astrocytes in glutamate toxicity has been controversial. Here, we show that astrocytes in neuron-astrocyte co-cultures increased neuronal sensitivity to chronic glutamate exposure but not to acute exposure. Enhanced neuronal toxicity by chronic exposure was dependent on astrocyte cell numbers. A reduced generation of extracellular H2O2 induced by glutamate was observed in co-cultures. Further, neuronal glutamate toxicity was not suppressed by NADPH oxidase (Nox) inhibitors, catalase or Nox4 knockdown in co-cultures, whereas these compounds effectively reduced the toxicity in pure neuron cultures. Instead, the intracellular scavenger of reactive oxygen species, N-acetylcysteine (NAC), reduced neuronal cytotoxicity in co-cultures, whereas catalase worked in pure neuron cultures. Lipoxygenase (LOX) inhibitors attenuated neuronal glutamate toxicity in co-cultures but not in pure neuron cultures. Neuronal 5-LOX activity was increased only in co-cultures, whereas 12-LOX activity was increased in both types of cultures. The cyclooxygenase (COX) inhibitors, indomethacin and NS-398, and the phospholipase A2 (PLA2) inhibitors, LY311727 and MAFP, more effectively reduced neuronal glutamate toxicity in co-cultures than in pure neuron cultures. However, in co-cultures, pre-treating neurons and astrocytes with the same inhibitors generated opposite results. COX inhibitors suppressed neuronal glutamate toxicity in pre-treated neurons rather than astrocytes, whereas PLA2 inhibitors reduced the toxicity in pre-treated astrocytes rather than neurons. Gene-specific knockdown of PLA2 confirmed these results. Knockdown of cPLA2α and/or sPLA2-V in astrocytes rather than in neurons more effectively reduced glutamate toxicity in co-cultures. These findings suggest that astrocytic PLA2 activity increases neuronal sensitivity to chronic glutamate exposure in neuron-astrocyte co-cultures.
authors.affiliation: Aging Intervention Research Center, Korea Research Institute of Bioscience and Biotechnology (KRIBB), 125 Gwahak-ro, Yuseong-gu, Daejeon 305-806, Republic of Korea.
authors.forename: Jong Seong
authors.initials: JS
authors.lastname: Ha
authors.affiliation: Aging Intervention Research Center, Korea Research Institute of Bioscience and Biotechnology (KRIBB), 125 Gwahak-ro, Yuseong-gu, Daejeon 305-806, Republic of Korea.
authors.forename: So Hee
authors.initials: SH
authors.lastname: Dho
authors.affiliation: Aging Intervention Research Center, Korea Research Institute of Bioscience and Biotechnology (KRIBB), 125 Gwahak-ro, Yuseong-gu, Daejeon 305-806, Republic of Korea.
authors.forename: Tae Hyun
authors.initials: TH
authors.lastname: Youm
authors.affiliation: Aging Intervention Research Center, Korea Research Institute of Bioscience and Biotechnology (KRIBB), 125 Gwahak-ro, Yuseong-gu, Daejeon 305-806, Republic of Korea.
authors.forename: Ki-Sun
authors.initials: KS
authors.lastname: Kwon
authors.affiliation: Aging Intervention Research Center, Korea Research Institute of Bioscience and Biotechnology (KRIBB), 125 Gwahak-ro, Yuseong-gu, Daejeon 305-806, Republic of Korea. Electronic address: sspark@kribb.re.kr.
authors.forename: Sung Sup
authors.initials: SS
authors.lastname: Park
mesh_terms: D000818:Animals; D001253:Astrocytes / Q000201:enzymology*; D002470:Cell Survival / Q000187:drug effects; D018920:Coculture Techniques; D055785:Gene Knockdown Techniques; D018698:Glutamic Acid / Q000633:toxicity*; D006861:Hydrogen Peroxide / Q000633:toxicity; D008084:Lipoxygenase / Q000378:metabolism; D051379:Mice; D008813:Mice, Inbred ICR; D009474:Neurons / Q000187:drug effects*; D016877:Oxidants / Q000633:toxicity; D054467:Phospholipases A2 / Q000235:genetics / Q000378:metabolism*; D061251:Primary Cell Culture; D011451:Prostaglandin-Endoperoxide Synthases / Q000378:metabolism
chemical_list: D016877:Oxidants; D018698:Glutamic Acid; D006861:Hydrogen Peroxide; D008084:Lipoxygenase; D011451:Prostaglandin-Endoperoxide Synthases; D054467:Phospholipases A2
keywords: Chronic glutamate toxicity; Neuron–astrocyte co-culture; Phospholipase A2 (PLA2); Pure neuron culture