Role of oxidative stress in the ammonia-induced mitochondrial permeability transition in cultured astrocytes

K. V. Rama Rao, A. R. Jayakumar, Michael D Norenberg

Research output: Contribution to journalArticle

61 Citations (Scopus)

Abstract

Ammonia is a neurotoxin that has been strongly implicated in the pathogenesis of hepatic encephalopathy (HE) and other neurological disorders, and astrocytes are thought to be the principal target of ammonia toxicity. While the precise mechanisms of ammonia neurotoxicity remain to be more clearly defined, altered bioenergetics and oxidative stress appear to be critical factors in its pathogenesis. It has recently been demonstrated that pathophysiological concentrations of ammonia induce the mitochondrial permeability transition (MPT) in cultured astrocytes, a process associated with mitochondrial dysfunction, and frequently caused by oxidative stress. This study investigated the potential role of oxidative stress in the induction of the MPT by ammonia. Accordingly, the effect of various antioxidants on the induction of the MPT by ammonia in cultured astrocytes was examined. Astrocytes were subjected to NH4Cl (5 mM) treatment for 2 days with or without various antioxidants. The MPT was assessed by quantitative fluorescence imaging for the mitochondrial membrane potential (ΔΨm), employing the potentiometric dye TMRE; by changes in mitochondrial calcein fluorescence and by 2-deoxyglucose-6-phosphate (2-DG-6-P) changes in mitochondrial permeability. Astrocytes treated with ammonia significantly dissipated the ΔΨm, which was blocked by the MPT inhibitor, cyclosporin A, caused a decrease in mitochondrial calcein fluorescence and increased 2-DG-6-P permeability into mitochondria. All of these findings are consistent with induction of the MPT. Pretreatment with SOD, catalase, desferroxamine, Vitamin E, PBN and the nitric oxide synthase inhibitor, NG-nitro-l-arginine methyl ester (l-NAME), completely blocked the ammonia-induced MPT. These data provide strong evidence that oxidative stress is involved in the induction of the MPT by ammonia, and suggest that oxidative stress and the subsequent induction of the MPT contribute to the pathogenesis of HE and other hyperammonemic disorders.

Original languageEnglish
Pages (from-to)31-38
Number of pages8
JournalNeurochemistry International
Volume47
Issue number1-2 SPEC. ISS.
DOIs
StatePublished - Jul 1 2005

Fingerprint

Ammonia
Astrocytes
Permeability
Oxidative Stress
Hepatic Encephalopathy
Antioxidants
Fluorescence
Deferoxamine
Mitochondrial Membrane Potential
Optical Imaging
Neurotoxins
Nervous System Diseases
Vitamin E
Nitric Oxide Synthase
Catalase
Energy Metabolism
Cyclosporine
Mitochondria
Coloring Agents

Keywords

  • Ammonia
  • Antioxidants
  • Astrocytes
  • Hepatic encephalopathy
  • Mitochondrial permeability transition
  • Nitric oxide
  • Oxidative stress

ASJC Scopus subject areas

  • Cell Biology
  • Molecular Biology
  • Cellular and Molecular Neuroscience

Cite this

Role of oxidative stress in the ammonia-induced mitochondrial permeability transition in cultured astrocytes. / Rama Rao, K. V.; Jayakumar, A. R.; Norenberg, Michael D.

In: Neurochemistry International, Vol. 47, No. 1-2 SPEC. ISS., 01.07.2005, p. 31-38.

Research output: Contribution to journalArticle

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