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Role of oxidative stress in the ammonia‐induced mitochondrial permeability transition in cultured astrocytes
Author(s) -
Jayakumar A. R.,
Rama Rao K. V.,
Bai G.,
Norenberg M. D.
Publication year - 2002
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1046/j.1471-4159.81.s1.42_8.x
Subject(s) - oxidative stress , mitochondrial permeability transition pore , reactive oxygen species , chemistry , superoxide dismutase , mitochondrion , mitochondrial ros , biochemistry , biophysics , ammonia , biology , programmed cell death , apoptosis
Ammonia is the principal neurotoxin implicated in the pathogenesis of hepatic encephalopathy (HE). The mechanisms of ammonia toxicity are unclear, but appear to involve oxidative stress and mitochondrial dysfunction. Astrocytes appear to be cell mainly affected. We have previously shown that ammonia increases the production of reactive oxygen species (ROS), and that it also induces the mitochondrial permeability transition (MPT) in cultured astrocytes. Since ROS is a factor commonly implicated in the induction of the MPT, we investigated the role of oxidative stress in the induction of the MPT by ammonia. We therefore examined the effects of various antioxidants on the induction by ammonia of the MPT in cultured astrocytes. Astrocytes were subjected to NH 4 Cl (5 m m ) treatment for two days alone or with various antioxidants. The MPT was assessed by 2‐deoxyglucose (2‐DG) permeability into mitochondria, and by changes in the mitochondrial membrane potential (ΔΨ m ) by confocal microscopy using the potentiometric dye JC‐1. Astrocytes treated with ammonia significantly increased 2‐DG permeability (90%, p < 0.01) and concomitantly dissipated the ΔΨ m (60%, p < 0.01), consistent with the induction of the MPT. The antioxidants superoxide dismutase (by 50%, p < 0.05), vitamin E (by 80%, p < 0.01), and the spin trapping agent PBN (by 80%, p < 0.01), all significantly blocked the increase in 2‐DG permeability and the dissipation of the ΔΨ m produced by ammonia. These data demonstrate the induction of the MPT by ammonia and suggest the involvement of ROS in this process. Increased oxidative stress and subsequent induction of the MPT by ammonia in astrocytes may contribute to the pathogenesis of HE.