Ammonia induces the mitochondrial permeability transition in primary cultures of rat astrocytes

G. Bai, K. V. Rama Rao, Ch R K Murthy, K. S. Panickar, A. R. Jayakumar, Michael D Norenberg

Research output: Contribution to journalArticle

125 Citations (Scopus)

Abstract

Ammonia is a toxin that has been strongly implicated in the pathogenesis of hepatic encephalopathy (HE), and the astrocyte appears to be the principal target of ammonia toxicity. The specific neurochemical mechanisms underlying HE, however, remain elusive. One of the suggested mechanisms for ammonia toxicity is impaired cellular bioenergetics. Because there is evidence that the mitochondrial permeability transition (MPT) is associated with mitochondrial dysfunction, we determined whether the MPT might be involved in the bioenergetic alterations related to ammonia toxicity. Accordingly, we examined the mitochondrial membrane potential (Δψm) in cultured astrocytes and neurons using laser-scanning confocal microscopy after loading the cells with the voltage-sensitive dye JC-1. We found that ammonia induced a dissipation of the Δψm in a time- and concentration-dependent manner. These findings were supported by flow cytometry using the voltage-sensitive dye tetramethylrhodamine ethyl ester (TMRE). Cyclosporin A, a specific inhibitor of the MPT, completely blocked the ammonia-induced dissipation of the Δψm. We also found an increase in the mitochondrial permeability to 2-deoxyglucose in astrocytes that had been exposed to 5 mM NH4Cl, further supporting the concept that ammonia induces the MPT in these cells. Pretreatment with methionine sulfoximine, an inhibitor of glutamine synthetase, blocked the ammonia-induced collapse of Δψm, suggesting a role of glutamine in this process. Over a 24-hr period, ammonia had no effect on the Δψm in cultured neurons. Collectively, our data indicate that ammonia induces the MPT in cultured astrocytes, which may be a factor in the mitochondrial dysfunction associated with HE and other hyperammonemic states.

Original languageEnglish
Pages (from-to)981-991
Number of pages11
JournalJournal of Neuroscience Research
Volume66
Issue number5
DOIs
StatePublished - Dec 1 2001

Fingerprint

Ammonia
Astrocytes
Permeability
Hepatic Encephalopathy
Energy Metabolism
Coloring Agents
Methionine Sulfoximine
Neurons
Glutamate-Ammonia Ligase
Mitochondrial Membrane Potential
Deoxyglucose
Glutamine
Confocal Microscopy
Cyclosporine
Flow Cytometry
Esters

Keywords

  • Ammonia
  • Astrocytes
  • Cyclosporin A
  • Glutamine
  • Hepatic encephalopathy
  • Mitochondrial permeability transition

ASJC Scopus subject areas

  • Neuroscience(all)

Cite this

Ammonia induces the mitochondrial permeability transition in primary cultures of rat astrocytes. / Bai, G.; Rama Rao, K. V.; Murthy, Ch R K; Panickar, K. S.; Jayakumar, A. R.; Norenberg, Michael D.

In: Journal of Neuroscience Research, Vol. 66, No. 5, 01.12.2001, p. 981-991.

Research output: Contribution to journalArticle

Bai, G. ; Rama Rao, K. V. ; Murthy, Ch R K ; Panickar, K. S. ; Jayakumar, A. R. ; Norenberg, Michael D. / Ammonia induces the mitochondrial permeability transition in primary cultures of rat astrocytes. In: Journal of Neuroscience Research. 2001 ; Vol. 66, No. 5. pp. 981-991.
@article{cf669a1c359f4c488cba386f5fdd227d,
title = "Ammonia induces the mitochondrial permeability transition in primary cultures of rat astrocytes",
abstract = "Ammonia is a toxin that has been strongly implicated in the pathogenesis of hepatic encephalopathy (HE), and the astrocyte appears to be the principal target of ammonia toxicity. The specific neurochemical mechanisms underlying HE, however, remain elusive. One of the suggested mechanisms for ammonia toxicity is impaired cellular bioenergetics. Because there is evidence that the mitochondrial permeability transition (MPT) is associated with mitochondrial dysfunction, we determined whether the MPT might be involved in the bioenergetic alterations related to ammonia toxicity. Accordingly, we examined the mitochondrial membrane potential (Δψm) in cultured astrocytes and neurons using laser-scanning confocal microscopy after loading the cells with the voltage-sensitive dye JC-1. We found that ammonia induced a dissipation of the Δψm in a time- and concentration-dependent manner. These findings were supported by flow cytometry using the voltage-sensitive dye tetramethylrhodamine ethyl ester (TMRE). Cyclosporin A, a specific inhibitor of the MPT, completely blocked the ammonia-induced dissipation of the Δψm. We also found an increase in the mitochondrial permeability to 2-deoxyglucose in astrocytes that had been exposed to 5 mM NH4Cl, further supporting the concept that ammonia induces the MPT in these cells. Pretreatment with methionine sulfoximine, an inhibitor of glutamine synthetase, blocked the ammonia-induced collapse of Δψm, suggesting a role of glutamine in this process. Over a 24-hr period, ammonia had no effect on the Δψm in cultured neurons. Collectively, our data indicate that ammonia induces the MPT in cultured astrocytes, which may be a factor in the mitochondrial dysfunction associated with HE and other hyperammonemic states.",
keywords = "Ammonia, Astrocytes, Cyclosporin A, Glutamine, Hepatic encephalopathy, Mitochondrial permeability transition",
author = "G. Bai and {Rama Rao}, {K. V.} and Murthy, {Ch R K} and Panickar, {K. S.} and Jayakumar, {A. R.} and Norenberg, {Michael D}",
year = "2001",
month = "12",
day = "1",
doi = "10.1002/jnr.10056",
language = "English",
volume = "66",
pages = "981--991",
journal = "Journal of Neuroscience Research",
issn = "0360-4012",
publisher = "Wiley-Liss Inc.",
number = "5",

}

TY - JOUR

T1 - Ammonia induces the mitochondrial permeability transition in primary cultures of rat astrocytes

AU - Bai, G.

AU - Rama Rao, K. V.

AU - Murthy, Ch R K

AU - Panickar, K. S.

AU - Jayakumar, A. R.

AU - Norenberg, Michael D

PY - 2001/12/1

Y1 - 2001/12/1

N2 - Ammonia is a toxin that has been strongly implicated in the pathogenesis of hepatic encephalopathy (HE), and the astrocyte appears to be the principal target of ammonia toxicity. The specific neurochemical mechanisms underlying HE, however, remain elusive. One of the suggested mechanisms for ammonia toxicity is impaired cellular bioenergetics. Because there is evidence that the mitochondrial permeability transition (MPT) is associated with mitochondrial dysfunction, we determined whether the MPT might be involved in the bioenergetic alterations related to ammonia toxicity. Accordingly, we examined the mitochondrial membrane potential (Δψm) in cultured astrocytes and neurons using laser-scanning confocal microscopy after loading the cells with the voltage-sensitive dye JC-1. We found that ammonia induced a dissipation of the Δψm in a time- and concentration-dependent manner. These findings were supported by flow cytometry using the voltage-sensitive dye tetramethylrhodamine ethyl ester (TMRE). Cyclosporin A, a specific inhibitor of the MPT, completely blocked the ammonia-induced dissipation of the Δψm. We also found an increase in the mitochondrial permeability to 2-deoxyglucose in astrocytes that had been exposed to 5 mM NH4Cl, further supporting the concept that ammonia induces the MPT in these cells. Pretreatment with methionine sulfoximine, an inhibitor of glutamine synthetase, blocked the ammonia-induced collapse of Δψm, suggesting a role of glutamine in this process. Over a 24-hr period, ammonia had no effect on the Δψm in cultured neurons. Collectively, our data indicate that ammonia induces the MPT in cultured astrocytes, which may be a factor in the mitochondrial dysfunction associated with HE and other hyperammonemic states.

AB - Ammonia is a toxin that has been strongly implicated in the pathogenesis of hepatic encephalopathy (HE), and the astrocyte appears to be the principal target of ammonia toxicity. The specific neurochemical mechanisms underlying HE, however, remain elusive. One of the suggested mechanisms for ammonia toxicity is impaired cellular bioenergetics. Because there is evidence that the mitochondrial permeability transition (MPT) is associated with mitochondrial dysfunction, we determined whether the MPT might be involved in the bioenergetic alterations related to ammonia toxicity. Accordingly, we examined the mitochondrial membrane potential (Δψm) in cultured astrocytes and neurons using laser-scanning confocal microscopy after loading the cells with the voltage-sensitive dye JC-1. We found that ammonia induced a dissipation of the Δψm in a time- and concentration-dependent manner. These findings were supported by flow cytometry using the voltage-sensitive dye tetramethylrhodamine ethyl ester (TMRE). Cyclosporin A, a specific inhibitor of the MPT, completely blocked the ammonia-induced dissipation of the Δψm. We also found an increase in the mitochondrial permeability to 2-deoxyglucose in astrocytes that had been exposed to 5 mM NH4Cl, further supporting the concept that ammonia induces the MPT in these cells. Pretreatment with methionine sulfoximine, an inhibitor of glutamine synthetase, blocked the ammonia-induced collapse of Δψm, suggesting a role of glutamine in this process. Over a 24-hr period, ammonia had no effect on the Δψm in cultured neurons. Collectively, our data indicate that ammonia induces the MPT in cultured astrocytes, which may be a factor in the mitochondrial dysfunction associated with HE and other hyperammonemic states.

KW - Ammonia

KW - Astrocytes

KW - Cyclosporin A

KW - Glutamine

KW - Hepatic encephalopathy

KW - Mitochondrial permeability transition

UR - http://www.scopus.com/inward/record.url?scp=0035577916&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0035577916&partnerID=8YFLogxK

U2 - 10.1002/jnr.10056

DO - 10.1002/jnr.10056

M3 - Article

C2 - 11746427

AN - SCOPUS:0035577916

VL - 66

SP - 981

EP - 991

JO - Journal of Neuroscience Research

JF - Journal of Neuroscience Research

SN - 0360-4012

IS - 5

ER -