title: Astrogliosis is a possible player in preventing delayed neuronal death.
abstract: Mitigating secondary delayed neuronal injury has been a therapeutic strategy for minimizing neurological symptoms after several types of brain injury. Interestingly, secondary neuronal loss appeared to be closely related to functional loss and/or death of astrocytes. In the brain damage induced by agonists of two glutamate receptors, N-ethyl-D-aspartic acid (NMDA) and kainic acid (KA), NMDA induced neuronal death within 3 h, but did not increase further thereafter. However, in the KA-injected brain, neuronal death was not obviously detectable even at injection sites at 3 h, but extensively increased to encompass the entire hemisphere at 7 days. Brain inflammation, a possible cause of secondary neuronal damage, showed little differences between the two models. Importantly, however, astrocyte behavior was completely different. In the NMDA-injected cortex, the loss of glial fibrillary acidic protein-expressing (GFAP+) astrocytes was confined to the injection site until 7 days after the injection, and astrocytes around the damage sites showed extensive gliosis and appeared to isolate the damage sites. In contrast, in the KA-injected brain, GFAP+ astrocytes, like neurons, slowly, but progressively, disappeared across the entire hemisphere. Other markers of astrocytes, including S100β, glutamate transporter EAAT2, the potassium channel Kir4.1 and glutamine synthase, showed patterns similar to that of GFAP in both NMDA- and KA-injected cortexes. More importantly, astrocyte disappearance and/or functional loss preceded neuronal death in the KA-injected brain. Taken together, these results suggest that loss of astrocyte support to neurons may be a critical cause of delayed neuronal death in the injured brain.
authors.affiliation: Department of Pharmacology, Ajou University School of Medicine, Suwon 442-721, Korea.
authors.forename: Hey-Kyeong
authors.initials: HK
authors.lastname: Jeong
authors.affiliation: Department of Biomedical Sciences Neuroscience Graduate Program, Ajou University School of Medicine, Suwon 442-721, Korea.
authors.forename: Kyung-Min
authors.initials: KM
authors.lastname: Ji
authors.affiliation: Brain Disease Research Center, Ajou University School of Medicine, Suwon 442-721, Korea.
authors.forename: Kyoung-Jin
authors.initials: KJ
authors.lastname: Min
authors.affiliation: Department of Brain Science, Ajou University School of Medicine, Suwon 442-721, Korea.
authors.forename: Insup
authors.initials: I
authors.lastname: Choi
authors.affiliation: Chronic Inflammatory Disease Research Center, Ajou University School of Medicine, Suwon 442-721, Korea.
authors.forename: Dong-Joo
authors.initials: DJ
authors.lastname: Choi
authors.forename: Ilo
authors.initials: I
authors.lastname: Jou
authors.forename: Eun-Hye
authors.initials: EH
authors.lastname: Joe
mesh_terms: D000818:Animals; D001253:Astrocytes / Q000187:drug effects* / Q000502:physiology; D015415:Biomarkers / Q000378:metabolism; D001930:Brain Injuries / Q000188:drug therapy*; D002450:Cell Communication / Q000187:drug effects; D016923:Cell Death / Q000187:drug effects; D002540:Cerebral Cortex / Q000187:drug effects*; D027342:Excitatory Amino Acid Transporter 2 / Q000378:metabolism; D005904:Glial Fibrillary Acidic Protein / Q000378:metabolism; D005911:Gliosis / Q000188:drug therapy*; D005974:Glutamate-Ammonia Ligase / Q000378:metabolism; D007608:Kainic Acid / Q000008:administration & dosage*; D008297:Male; D016202:N-Methylaspartate / Q000008:administration & dosage*; D009474:Neurons / Q000187:drug effects / Q000502:physiology; D024661:Potassium Channels, Inwardly Rectifying / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D017470:Receptors, Glutamate / Q000378:metabolism; D064568:S100 Calcium Binding Protein beta Subunit / Q000378:metabolism; D000098854:Kcnj10 Channel
chemical_list: D015415:Biomarkers; D027342:Excitatory Amino Acid Transporter 2; D005904:Glial Fibrillary Acidic Protein; D000098854:Kcnj10 Channel; D024661:Potassium Channels, Inwardly Rectifying; D017470:Receptors, Glutamate; D064568:S100 Calcium Binding Protein beta Subunit; D016202:N-Methylaspartate; D005974:Glutamate-Ammonia Ligase; D007608:Kainic Acid