title: Detoxification of ammonia in mouse cortical GABAergic cell cultures increases neuronal oxidative metabolism and reveals an emerging role for release of glucose-derived alanine.
abstract: Cerebral hyperammonemia is believed to play a pivotal role in the development of hepatic encephalopathy (HE), a debilitating condition arising due to acute or chronic liver disease. In the brain, ammonia is thought to be detoxified via the activity of glutamine synthetase, an astrocytic enzyme. Moreover, it has been suggested that cerebral tricarboxylic acid (TCA) cycle metabolism is inhibited and glycolysis enhanced during hyperammonemia. The aim of this study was to characterize the ammonia-detoxifying mechanisms as well as the effects of ammonia on energy-generating metabolic pathways in a mouse neuronal-astrocytic co-culture model of the GABAergic system. We found that 5 mM ammonium chloride affected energy metabolism by increasing the neuronal TCA cycle activity and switching the astrocytic TCA cycle toward synthesis of substrate for glutamine synthesis. Furthermore, ammonia exposure enhanced the synthesis and release of alanine. Collectively, our results demonstrate that (1) formation of glutamine is seminal for detoxification of ammonia; (2) neuronal oxidative metabolism is increased in the presence of ammonia; and (3) synthesis and release of alanine is likely to be important for ammonia detoxification as a supplement to formation of glutamine.
authors.affiliation: Department of Biochemistry, ICBS, Federal University of Rio Grande do Sul, Porto Alegre, RS, Brazil.
authors.forename: Renata
authors.initials: R
authors.lastname: Leke
authors.forename: Lasse K
authors.initials: LK
authors.lastname: Bak
authors.forename: Malene
authors.initials: M
authors.lastname: Anker
authors.forename: Torun M
authors.initials: TM
authors.lastname: Melø
authors.forename: Michael
authors.initials: M
authors.lastname: Sørensen
authors.forename: Susanne
authors.initials: S
authors.lastname: Keiding
authors.forename: Hendrik
authors.initials: H
authors.lastname: Vilstrup
authors.forename: Peter
authors.initials: P
authors.lastname: Ott
authors.forename: Luis V
authors.initials: LV
authors.lastname: Portela
authors.forename: Ursula
authors.initials: U
authors.lastname: Sonnewald
authors.forename: Arne
authors.initials: A
authors.lastname: Schousboe
authors.forename: Helle S
authors.initials: HS
authors.lastname: Waagepetersen
mesh_terms: D000409:Alanine / Q000378:metabolism*; D000641:Ammonia / Q000037:antagonists & inhibitors / Q000633:toxicity*; D000818:Animals; D002478:Cells, Cultured; D002540:Cerebral Cortex / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D018920:Coculture Techniques; D005947:Glucose / Q000378:metabolism*; D051379:Mice; D009474:Neurons / Q000187:drug effects / Q000378:metabolism*; D018384:Oxidative Stress / Q000187:drug effects / Q000502:physiology*; D005680:gamma-Aminobutyric Acid / Q000502:physiology*
chemical_list: D005680:gamma-Aminobutyric Acid; D000641:Ammonia; D005947:Glucose; D000409:Alanine