4.7 Article

Perturbation of astroglial Slc38 glutamine transporters by NH4 + contributes to neurophysiologic manifestations in acute liver failure

期刊

FASEB JOURNAL
卷 35, 期 7, 页码 -

出版社

WILEY
DOI: 10.1096/fj.202001712RR

关键词

hepatic encephalopathy; NH4; (+); Slc38; Slc38a3; SNAT3

资金

  1. National Centre for Research (NCBiR) Polish Norwegian Research Program [Pol-Nor/196190/23/2013]
  2. South-Eastern Norway Regional Health Authority [21561/2017052]
  3. UiO:Life Science

向作者/读者索取更多资源

The study investigates the impact of ammonia on Slc38 transporters, including competition with glutamine binding and effects on intracellular pH, membrane potential, and K+ buffering; Knocking out the Slc38a3 gene in mice results in cerebral cortical edema and disrupted neurotransmitter synthesis; A mouse model of acute liver failure shows downregulation of Slc38a3 protein, inhibited astroglial glutamine release, and cytotoxic edema.
Ammonia is considered the main pathogenic toxin in hepatic encephalopathy (HE). However, the molecular mechanisms involved have been disputed. As altered glutamatergic and GABAergic neurotransmission has been reported in HE, we investigated whether four members of the solute carrier 38 (Slc38) family of amino acid transporters-involved in the replenishment of glutamate and GABA-contribute to ammonia neurotoxicity in HE. We show that ammonium ion exerts multiple actions on the Slc38 transporters: It competes with glutamine for the binding to the system N transporters Slc38a3 and Slc38a5, consequently inhibiting bidirectional astroglial glutamine transport. It also competes with H+, Na+, and K+ for uncoupled permeation through the same transporters, which may perturb astroglial intracellular pH, membrane potential, and K+-buffering. Knockdown of Slc38a3 in mice results in cerebral cortical edema and disrupted neurotransmitter synthesis mimicking events contributing to HE development. Finally, in a mouse model of acute liver failure (ALF), we demonstrate the downregulation of Slc38a3 protein, impeded astroglial glutamine release, and cytotoxic edema. Altogether, we demonstrate contribution of Slc38 transporters to the ammonia-induced impairment of glutamine recycling between astrocytes and neurons, a phenomenon underlying acute ammonia neurotoxicity in the setting of ALF.

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