title: Hyperammonemia induces glial activation, neuroinflammation and alters neurotransmitter receptors in hippocampus, impairing spatial learning: reversal by sulforaphane.
abstract: BACKGROUND
  Patients with liver cirrhosis and minimal hepatic encephalopathy (MHE) show mild cognitive impairment and spatial learning dysfunction. Hyperammonemia acts synergistically with inflammation to induce cognitive impairment in MHE. Hyperammonemia-induced neuroinflammation in hippocampus could contribute to spatial learning impairment in MHE. Two main aims of this work were: (1) to assess whether chronic hyperammonemia increases inflammatory factors in the hippocampus and if this is associated with microglia and/or astrocytes activation and (2) to assess whether hyperammonemia-induced neuroinflammation in the hippocampus is associated with altered membrane expression of glutamate and GABA receptors and spatial learning impairment. There are no specific treatments for cognitive alterations in patients with MHE. A third aim was to assess whether treatment with sulforaphane enhances endogenous the anti-inflammatory system, reduces neuroinflammation in the hippocampus of hyperammonemic rats, and restores spatial learning and if normalization of receptor membrane expression is associated with learning improvement.
  
  
  METHODS
  We analyzed the following in control and hyperammonemic rats, treated or not with sulforaphane: (1) microglia and astrocytes activation by immunohistochemistry, (2) markers of pro-inflammatory (M1) (IL-1β, IL-6) and anti-inflammatory (M2) microglia (Arg1, YM-1) by Western blot, (3) membrane expression of GABA, AMPA, and NMDA receptors using the BS3 cross-linker, and (4) spatial learning using the radial maze.
  
  
  RESULTS
  The results reported show that hyperammonemia induces astrocytes and microglia activation in the hippocampus, increasing pro-inflammatory cytokines IL-1β and IL-6. This is associated with altered membrane expression of AMPA, NMDA, and GABA receptors which would be responsible for altered neurotransmission and impairment of spatial learning in the radial maze. Treatment with sulforaphane promotes microglia differentiation from pro-inflammatory M1 to anti-inflammatory M2 phenotype and reduces activation of astrocytes in hyperammonemic rats. This reduces neuroinflammation, normalizes membrane expression of glutamate and GABA receptors, and restores spatial learning in hyperammonemic rats.
  
  
  CONCLUSIONS
  Hyperammonemia-induced neuroinflammation impairs glutamatergic and GABAergic neurotransmission by altering membrane expression of glutamate and GABA receptors, resulting in impaired spatial learning. Sulforaphane reverses all these effects. Treatment with sulforaphane could be useful to improve cognitive function in cirrhotic patients with minimal or clinical hepatic encephalopathy.
authors.affiliation: Laboratorio de Neurobiología, Centro de Investigación Príncipe Felipe, Valencia, Spain.
authors.forename: Vicente
authors.initials: V
authors.lastname: Hernández-Rabaza
authors.affiliation: Laboratorio de Neurobiología, Centro de Investigación Príncipe Felipe, Valencia, Spain.
authors.forename: Andrea
authors.initials: A
authors.lastname: Cabrera-Pastor
authors.affiliation: Laboratorio de Neurobiología, Centro de Investigación Príncipe Felipe, Valencia, Spain.
authors.forename: Lucas
authors.initials: L
authors.lastname: Taoro-González
authors.affiliation: Laboratorio de Neurobiología, Centro de Investigación Príncipe Felipe, Valencia, Spain.
authors.forename: Michele
authors.initials: M
authors.lastname: Malaguarnera
authors.affiliation: Laboratorio de Neurobiología, Centro de Investigación Príncipe Felipe, Valencia, Spain.
authors.forename: Ana
authors.initials: A
authors.lastname: Agustí
authors.affiliation: Laboratorio de Neurobiología, Centro de Investigación Príncipe Felipe, Valencia, Spain.
authors.forename: Marta
authors.initials: M
authors.lastname: Llansola
authors.affiliation: Laboratorio de Neurobiología, Centro de Investigación Príncipe Felipe, Valencia, Spain. vfelipo@cipf.es.
authors.forename: Vicente
authors.initials: V
authors.lastname: Felipo
mesh_terms: D000818:Animals; D000893:Anti-Inflammatory Agents / Q000494:pharmacology / Q000627:therapeutic use*; D001835:Body Weight / Q000187:drug effects; D016207:Cytokines / Q000378:metabolism; D004195:Disease Models, Animal; D004660:Encephalitis / Q000188:drug therapy / Q000209:etiology*; D005786:Gene Expression Regulation / Q000187:drug effects; D005904:Glial Fibrillary Acidic Protein / Q000378:metabolism; D006624:Hippocampus / Q000378:metabolism* / Q000473:pathology; D022124:Hyperammonemia / Q000150:complications* / Q000473:pathology; D066298:In Vitro Techniques; D017879:Isothiocyanates / Q000494:pharmacology / Q000627:therapeutic use*; D007859:Learning Disabilities / Q000188:drug therapy / Q000209:etiology / Q000473:pathology; D008297:Male; D018782:Maze Learning / Q000187:drug effects; D009457:Neuroglia / Q000187:drug effects / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D017981:Receptors, Neurotransmitter / Q000378:metabolism*; D065853:Spatial Learning / Q000187:drug effects / Q000502:physiology; D013454:Sulfoxides
chemical_list: D000893:Anti-Inflammatory Agents; D016207:Cytokines; D005904:Glial Fibrillary Acidic Protein; D017879:Isothiocyanates; D017981:Receptors, Neurotransmitter; D013454:Sulfoxides; C016766:sulforaphane