Selective Targeting of a Redox-active Ubiquinone to Mitochondria within Cells

Abstract

With the recognition of the central role of mitochondria in apoptosis, there is a need to develop specific tools to manipulate mitochondrial function within cells. Here we report on the development of a novel antioxidant that selectively blocks mitochondrial oxidative damage, enabling the roles of mitochondrial oxidative stress in different types of cell death to be inferred. This antioxidant, named mitoQ, is a ubiquinone derivative targeted to mitochondria by covalent attachment to a lipophilic triphenylphosphonium cation through an aliphatic carbon chain. Due to the large mitochondrial membrane potential, the cation was accumulated within mitochondria inside cells, where the ubiquinone moiety inserted into the lipid bilayer and was reduced by the respiratory chain. The ubiquinol derivative thus formed was an effective antioxidant that prevented lipid peroxidation and protected mitochondria from oxidative damage. After detoxifying a reactive oxygen species, the ubiquinol moiety was regenerated by the respiratory chain enabling its antioxidant activity to be recycled. In cell culture studies, the mitochondrially localized antioxidant protected mammalian cells from hydrogen peroxide-induced apoptosis but not from apoptosis induced by staurosporine or tumor necrosis factor-␣. This was compared with untargeted ubiquinone analogs, which were ineffective in preventing apoptosis. These results suggest that mitochondrial oxidative stress may be a critical step in apoptosis induced by hydrogen peroxide but not for apoptosis induced by staurosporine or tumor necrosis factor-␣. We have shown that selectively manipulating mitochondrial antioxidant status with targeted and recyclable antioxidants is a feasible approach to investigate the role of mitochondrial oxidative damage in apoptotic cell death. This approach will have further applications in investigating mitochondrial dysfunction in a range of experimental models.

Granzyme B-induced mitochondrial ROS are required for apoptosis

“…Moreover, MnTBAP significantly protects the B-cell line 721.221 from YT-Indy human NK cell line that mainly abundantly expresses GB (Figure 1b), indicating that GB induces ROS-dependent apoptosis. The mitochondria-targeted ROS scavenger MitoQ 21 completely scavenges GB-induced ROS and inhibits cell death, suggesting that GB induces mitochondrial ROSdependent apoptosis (Figure 1c). By 2D gel electrophoresis and mass spectrometry analysis of the mitochondria treated or not with GB or GA, we identified NDUFV1 as a putative GB target (Figure 1d).…”

α-Tocopheryl succinate induces apoptosis by targeting ubiquinone-binding sites in mitochondrial respiratory complex II

“…With high succinate levels as the substrate driving CII-mediated MTT reduction in whole cells, treatment with 3BP, a-TOS or TTFA inhibited MTT reduction in a dose-dependent manner (Figures 2b-d). Pre-incubation of cells with MitoQ , a form of UbQ that preferentially localizes to mitochondria where it binds to CII but not CIII (Kelso et al, 2001;James et al, 2005James et al, , 2007, overcame the inhibition in MTT reduction by TTFA and a-TOS, but not by 3BP (Figures 2b-d). These results indicate that a-TOS inhibits SDH activity in a similar manner to TTFA.…”

Role of oxidative stress in the induction of metallothionein-2A and heme oxygenase-1 gene expression by the antineoplastic agent gallium nitrate in human lymphoma cells

“…Gallium nitrate (100 or 300 µM) was then added to each flask. In separate flasks, 10 µM mito-Q, a mitochondria-targeted antioxidant [27], was added to cells incubated with 300 µM gallium nitrate. After 1-4 h of incubation, 1 mL of cell suspension (10 6 cells) was removed and centrifuged.…”