ROS (reactive oxygen species) from mitochondrial and non-mitochondrial sources have been implicated in TNFα (tumour necrosis factor α)-mediated signalling. In the present study, a new class of specific mitochondria-targeted antioxidants were used to explore directly the role of mitochondrial ROS in TNF-induced apoptosis. MitoVit E {[2-(3,4-dihydro-6-hydroxy-2,5,7,8-tetramethyl-2H-1-benzopyran-2-yl)ethyl]triphenylphosphonium bromide} (vitamin E attached to a lipophilic cation that facilitates accumulation of the antioxidant in the mitochondrial matrix) enhanced TNF-induced apoptosis of U937 cells. In time course analyses, cleavage and activation of caspase 8 in response to TNF were not affected by MitoVit E, whereas the activation of caspase 3 was significantly increased. Furthermore, there was an increased cleavage of the proapoptotic Bcl-2 family member Bid and an increased release of cytochrome c from mitochondria, in cells treated with TNF in the presence of MitoVit E. We considered several mechanisms by which MitoVit E might accelerate TNF-induced apoptosis including mitochondrial integrity (ATP/ADP levels and permeability transition), alterations in calcium homoeostasis and transcription factor activation. Of these, only the transcription factor NF-κB (nuclear factor κB) was implicated. TNF caused maximal nuclear translocation of NF-κB within 15 min, compared with 1 h in cells pretreated with MitoVit E. Thus the accumulation of an antioxidant within the mitochondrial matrix enhances TNF-induced apoptosis by decreasing or delaying the expression of the protective antiapoptotic proteins. These results demonstrate that mitochondrial ROS production is a physiologically relevant component of the TNF signal-transduction pathway during apoptosis, and reveal a novel functional role for mitochondrial ROS as a temporal regulator of NF-κB activation and NF-κB-dependent antiapoptotic signalling.
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Research Article|
June 21 2005
Mitochondrial reactive oxygen species regulate the temporal activation of nuclear factor κB to modulate tumour necrosis factor-induced apoptosis: evidence from mitochondria-targeted antioxidants
Gillian HUGHES;
Gillian HUGHES
*Department of Biochemistry, University of Otago, P.O. Box 56, Dunedin, New Zealand
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Michael P. MURPHY;
Michael P. MURPHY
†Medical Research Council Dunn Human Nutrition Unit, Wellcome Trust–MRC Building, Hills Road, Cambridge CB2 2XY, U.K.
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Elizabeth C. LEDGERWOOD
Elizabeth C. LEDGERWOOD
1
*Department of Biochemistry, University of Otago, P.O. Box 56, Dunedin, New Zealand
1To whom correspondence should be addressed (email liz.ledgerwood@stonebow.otago.ac.nz).
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Publisher: Portland Press Ltd
Received:
January 12 2005
Revision Received:
February 21 2005
Accepted:
February 23 2005
Accepted Manuscript online:
February 23 2005
Online ISSN: 1470-8728
Print ISSN: 0264-6021
The Biochemical Society, London
2005
Biochem J (2005) 389 (1): 83–89.
Article history
Received:
January 12 2005
Revision Received:
February 21 2005
Accepted:
February 23 2005
Accepted Manuscript online:
February 23 2005
Citation
Gillian HUGHES, Michael P. MURPHY, Elizabeth C. LEDGERWOOD; Mitochondrial reactive oxygen species regulate the temporal activation of nuclear factor κB to modulate tumour necrosis factor-induced apoptosis: evidence from mitochondria-targeted antioxidants. Biochem J 1 July 2005; 389 (1): 83–89. doi: https://doi.org/10.1042/BJ20050078
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