Na-K-Cl cotransporter-1 in the mechanism of ammonia-induced astrocyte swelling

Arumugam R. Jayakumar, Mingli Liu, Mitsuaki Moriyama, Ramugounder Ramakrishnan, Bliss Forbush, Pichili V B Reddy, Michael D Norenberg

Research output: Contribution to journalArticle

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Abstract

Brain edema and the consequent increase in intracranial pressure and brain herniation are major complications of acute liver failure (fulminant hepatic failure) and a major cause of death in this condition. Ammonia has been strongly implicated as an important factor, and astrocyte swelling appears to be primarily responsible for the edema. Ammonia is known to cause cell swelling in cultured astrocytes, although the means by which this occurs has not been fully elucidated. A disturbance in one or more of these systems may result in loss of ion homeostasis and cell swelling. In particular, activation of the Na-K-Cl cotransporter (NKCC1) has been shown to be involved in cell swelling in several neurological disorders. We therefore examined the effect of ammonia on NKCC activity and its potential role in the swelling of astrocytes. Cultured astrocytes were exposed to ammonia (NH4Cl; 5 mM), and NKCC activity was measured. Ammonia increased NKCC activity at 24 h. Inhibition of this activity by bumetanide diminished ammonia-induced astrocyte swelling. Ammonia also increased total as well as phosphorylated NKCC1. Treatment with cyclohexamide, a potent inhibitor of protein synthesis, diminished NKCC1 protein expression and NKCC activity. Since ammonia is known to induce oxidative/nitrosative stress, and antioxidants and nitric-oxide synthase inhibition diminish astrocyte swelling, we also examined whether ammonia caused oxidation and/or nitration of NKCC1. Cultures exposed to ammonia increased the state of oxidation and nitration of NKCC1, whereas the antioxidants N-nitro-L-arginine methyl ester and uric acid all significantly diminished NKCC activity. These agents also reduced phosphorylated NKCC1 expression. These results suggest that activation of NKCC1 is an important factor in the mediation of astrocyte swelling by ammonia and that such activation appears to be mediated by NKCC1 abundance as well as by its oxidation/nitration and phosphorylation.

Original languageEnglish
Pages (from-to)33874-33882
Number of pages9
JournalJournal of Biological Chemistry
Volume283
Issue number49
DOIs
StatePublished - Dec 5 2008

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Sodium-Potassium-Chloride Symporters
Ammonia
Astrocytes
Swelling
Nitration
Acute Liver Failure
Chemical activation
Oxidation
Member 2 Solute Carrier Family 12
Brain
Antioxidants
Bumetanide
Phosphorylation
Protein Synthesis Inhibitors
Oxidative stress
Intracranial Hypertension
Brain Edema
Uric Acid
Nervous System Diseases
Nitric Oxide Synthase

ASJC Scopus subject areas

  • Biochemistry
  • Cell Biology
  • Molecular Biology

Cite this

Jayakumar, A. R., Liu, M., Moriyama, M., Ramakrishnan, R., Forbush, B., Reddy, P. V. B., & Norenberg, M. D. (2008). Na-K-Cl cotransporter-1 in the mechanism of ammonia-induced astrocyte swelling. Journal of Biological Chemistry, 283(49), 33874-33882. https://doi.org/10.1074/jbc.M804016200

Na-K-Cl cotransporter-1 in the mechanism of ammonia-induced astrocyte swelling. / Jayakumar, Arumugam R.; Liu, Mingli; Moriyama, Mitsuaki; Ramakrishnan, Ramugounder; Forbush, Bliss; Reddy, Pichili V B; Norenberg, Michael D.

In: Journal of Biological Chemistry, Vol. 283, No. 49, 05.12.2008, p. 33874-33882.

Research output: Contribution to journalArticle

Jayakumar, AR, Liu, M, Moriyama, M, Ramakrishnan, R, Forbush, B, Reddy, PVB & Norenberg, MD 2008, 'Na-K-Cl cotransporter-1 in the mechanism of ammonia-induced astrocyte swelling', Journal of Biological Chemistry, vol. 283, no. 49, pp. 33874-33882. https://doi.org/10.1074/jbc.M804016200
Jayakumar AR, Liu M, Moriyama M, Ramakrishnan R, Forbush B, Reddy PVB et al. Na-K-Cl cotransporter-1 in the mechanism of ammonia-induced astrocyte swelling. Journal of Biological Chemistry. 2008 Dec 5;283(49):33874-33882. https://doi.org/10.1074/jbc.M804016200
Jayakumar, Arumugam R. ; Liu, Mingli ; Moriyama, Mitsuaki ; Ramakrishnan, Ramugounder ; Forbush, Bliss ; Reddy, Pichili V B ; Norenberg, Michael D. / Na-K-Cl cotransporter-1 in the mechanism of ammonia-induced astrocyte swelling. In: Journal of Biological Chemistry. 2008 ; Vol. 283, No. 49. pp. 33874-33882.
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