Mitochondrial reactive oxygen species regulate the temporal activation of nuclear factor kappaB to modulate tumour necrosis factor-induced apoptosis: evidence from mitochondria-targeted antioxidants.

TitleMitochondrial reactive oxygen species regulate the temporal activation of nuclear factor kappaB to modulate tumour necrosis factor-induced apoptosis: evidence from mitochondria-targeted antioxidants.
Publication TypeJournal Article
Year of Publication2005
AuthorsHughes, G, Murphy, MP, Ledgerwood, EC
JournalBiochem J
Volume389
IssuePt 1
Pagination83-9
Date Published2005 Jul 1
ISSN1470-8728
KeywordsAntioxidants, Apoptosis, Gene Expression Regulation, Humans, Hydrogen Peroxide, Jurkat Cells, Mitochondria, NF-kappa B, Reactive Oxygen Species, Signal Transduction, Time Factors, Tumor Necrosis Factor-alpha, U937 Cells
Abstract

ROS (reactive oxygen species) from mitochondrial and non-mitochondrial sources have been implicated in TNFalpha (tumour necrosis factor alpha)-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-kappaB (nuclear factor kappaB) was implicated. TNF caused maximal nuclear translocation of NF-kappaB 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-kappaB activation and NF-kappaB-dependent antiapoptotic signalling.

DOI10.1042/BJ20050078
Alternate JournalBiochem. J.
Citation Key10.1042/BJ20050078
PubMed ID15727562
PubMed Central IDPMC1184540