Hydrogen Peroxide– and Peroxynitrite-Induced Mitochondrial DNA Damage and Dysfunction in Vascular Endothelial and Smooth Muscle Cells

Abstract

The mechanisms by which reactive species (RS) participate in the development of atherosclerosis remain incompletely understood. The present study was designed to test the hypothesis that RS produced in the vascular environment cause mitochondrial damage and dysfunction in vitro and, thus, may contribute to the initiating events of atherogenesis. DNA damage was assessed in vascular cells exposed to superoxide, hydrogen peroxide, nitric oxide, and peroxynitrite. In both vascular endothelial and smooth muscle cells, the mitochondrial DNA (mtDNA) was preferentially damaged relative to the transcriptionally inactive nuclear beta-globin gene. Similarly, a dose-dependent decrease in mtDNA-encoded mRNA transcripts was associated with RS treatment. Mitochondrial protein synthesis was also inhibited in a dose-dependent manner by ONOO(-), resulting in decreased cellular ATP levels and mitochondrial redox function. Overall, endothelial cells were more sensitive to RS-mediated damage than were smooth muscle cells. Together, these data link RS-mediated mtDNA damage, altered gene expression, and mitochondrial dysfunction in cell culture and reveal how RS may mediate vascular cell dysfunction in the setting of atherogenesis.

Mitochondrial DNA depletion in prostate epithelial cells promotes anoikis resistance and invasion through activation of PI3K/Akt2

“…For instance, H 2 O 2 treatment has been shown to promote extensive mtDNA damage through generation of apurinic sites, strand breaks and base modifications. 19,20 To investigate whether mtDNA chemical damage would also activate Akt2 signaling thus mirroring the effects of mtDNA depletion, we treated wild-type PNT1A cells with either 2.5 or 5 mM H 2 O 2 for up to 1 h, after which H 2 O 2 -containing medium was replaced with fresh medium. Higher H 2 O 2 concentrations proved to be cytotoxic (not shown).…”

Oxidative Stress in Heart Failure: The Role of Mitochondria.

“…As opposed to nuclear-encoded genes, mitochondrial-encoded gene expression is largely regulated by the copy number of mtDNA (12). Therefore, mitochondrial injury is reflected by mtDNAdamage as well as by a decline in the mitochondrial RNA(mtRNA) transcripts, protein synthesis, and mitochondrial function (13,14). Wehave recently shown that the increased generation of ROSwas associated with mitochondrial damage and a dysfunction in the failing hearts, which were characterized by an increased lipid peroxidation in the mitochondria, a decreased mtDNAcopy number, a decrease in the numberof mtRNA transcripts, and a reduced oxidative capacity due to low complex enzyme activities (15).…”

Inhibition of mitochondrial protein synthesis results in increased endothelial cell susceptibility to nitric oxide-induced apoptosis

“…NO induces cell death through mechanisms involving cytochrome c release and caspase activation (7,8). Furthermore, ROS can induce mitochondrial DNA damage in endothelial cells, and this damage is accompanied by a decrease in mitochondrial RNA (mtRNA) transcripts, mitochondrial protein synthesis, and cellular ATP levels (9). Mitochondria have been recognized to play a pivotal role in the signaling cascade of apoptosis (10) and have been implicated in atherosclerosis-induced damage in endothelial cells (11,12).…”