title: Overexpression of the nuclear factor kappaB inhibitor A20 is neurotoxic after an excitotoxic injury to the immature rat brain.
abstract: BACKGROUND
  The zinc finger protein A20 is an ubiquitinating/deubiquitinating enzyme essential for the termination of inflammatory reactions through the inhibition of nuclear factor kappaB (NF-kappaB) signaling. Moreover, it also shows anti-apoptotic activities in some cell types and proapoptotic/pronecrotic effects in others. Although it is known that the regulation of inflammatory and cell death processes are critical in proper brain functioning and that A20 mRNA is expressed in the CNS, its role in the brain under physiological and pathological conditions is still unknown.
  
  
  METHODS
  In the present study, we have evaluated the effects of A20 overexpression in mixed cortical cultures in basal conditions: the in vivo pattern of endogenous A20 expression in the control and N-methyl-d-aspartate (NMDA) excitotoxically damaged postnatal day 9 immature rat brain, and the post-injury effects of A20 overexpression in the same lesion model.
  
  
  RESULTS
  Our results show that overexpression of A20 in mixed cortical cultures induced significant neuronal death by decreasing neuronal cell counts by 45 ± 9%. in vivo analysis of endogenous A20 expression showed widespread expression in gray matter, mainly in neuronal cells. However, after NMDA-induced excitotoxicity, neuronal A20 was downregulated in the neurodegenerating cortex and striatum at 10-24 hours post-lesion, and it was re-expressed at longer survival times in reactive astrocytes located mainly in the lesion border. When A20 was overexpressed in vivo 2 hours after the excitotoxic damage, the lesion volume at 3 days post-lesion showed a significant increase (20.8 ± 7.0%). No A20-induced changes were observed in the astroglial response to injury.
  
  
  CONCLUSIONS
  A20 is found in neuronal cells in normal conditions and is also expressed in astrocytes after brain damage, and its overexpression is neurotoxic for cortical neurons in basal mixed neuron-glia culture conditions and exacerbates postnatal brain excitotoxic damage.
authors: Insitut Pasteur de Montevideo, Mataojo 2020, Montevideo 11400, Uruguay. hugo.peluffo@pasteur.edu.uy
authors: Hugo
authors: H
authors: Peluffo
authors: Pau
authors: P
authors: Gonzalez
authors: Laia
authors: L
authors: Acarin
authors: Anna
authors: A
authors: Arís
authors: Rudy
authors: R
authors: Beyaert
authors: Antonio
authors: A
authors: Villaverde
authors: Berta
authors: B
authors: Gonzalez
mesh_terms: D000818:Animals; D001253:Astrocytes / Q000378:metabolism; D001927:Brain Diseases / Q000139:chemically induced / Q000378:metabolism* / Q000473:pathology; D002478:Cells, Cultured; D002540:Cerebral Cortex / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000096:biosynthesis*; D004195:Disease Models, Animal; D018690:Excitatory Amino Acid Agonists / Q000633:toxicity; D007150:Immunohistochemistry; D016202:N-Methylaspartate / Q000633:toxicity; D016328:NF-kappa B / Q000378:metabolism; D009474:Neurons / Q000378:metabolism; D051381:Rats; D020318:Rats, Long-Evans; D055647:Rats, Transgenic; D000072598:Tumor Necrosis Factor alpha-Induced Protein 3; D015854:Up-Regulation
chemical_list: D004268:DNA-Binding Proteins; D018690:Excitatory Amino Acid Agonists; D016328:NF-kappa B; D016202:N-Methylaspartate; C000602677:TNFAIP3 protein, rat; D000072598:Tumor Necrosis Factor alpha-Induced Protein 3