Oxidative Stress Mediates Tumor Necrosis Factor-α–Induced Mitochondrial DNA Damage and Dysfunction in Cardiac Myocytes

Abstract

Background-Tumor necrosis factor-␣ (TNF-␣) and angiotensin II (Ang II) are implicated in the development and further progression of heart failure, which might be, at least in part, mediated by the production of reactive oxygen species (ROS). However, the cause and consequences of this agonist-mediated ROS production in cardiac myocytes have not been well defined. Recently, we demonstrated that increased ROS production was associated with mitochondrial DNA (mtDNA) damage and dysfunction in failing hearts. We thus investigated whether the direct exposure of cardiac myocytes to TNF-␣ and Ang II in vitro could induce mtDNA damage via production of ROS. Methods and Results-TNF-␣ increased ROS production within cultured neonatal rat ventricular myocytes after 1 hour, as assessed by 2Ј,7Ј-dichlorofluorescin diacetate fluorescence microscopy. TNF-␣ also decreased mtDNA copy number by Southern blot analysis in association with complex III activity, which was prevented in the presence of the antioxidant ␣-tocopherol. A direct exposure of myocytes to H 2 O 2 caused a similar decrease in mtDNA copy number. In contrast, Ang II did not affect mtDNA copy number, despite the similar increase in ROS production. TNF-␣-mediated ROS production and a decrease in mtDNA copy number were inhibited by the sphingomyelinase inhibitor D609. Furthermore, N-acetylsphingosine (C2-ceramide), a synthetic cell-permeable ceramide analogue, increased myocyte ROS production, suggesting that TNF-␣-mediated ROS production and subsequent mtDNA damage were mediated by the sphingomyelin-ceramide signaling pathway. Conclusions-The intimate link between TNF-␣, ROS, and mtDNA damage might play an important role in myocardial remodeling and failure.

Regulation of mitochondrial DNA content and cancer

“…Given these observations, it is likely that the inhibition of the repair system for ROSmediated damage to mtDNA, detoxification of ROS, or increase in ROS generation might be possible causes for point mutations of mtDNA, accumulation of large-deletion mutant mtDNA, and the depletion of mtDNA. Additionally, the report indicates that oxidative stress generated by myocardial infraction (Ide et al, 2001) and TNF (Suematsu et al, 2003) rapidly and directly induced depletion of mtDNA. It is likely that mtDNA depletion can be induced independent of mtDNA mutation.…”

Association between Mitochondrial DNA Copy Number in Peripheral Blood and Incident CKD in the Atherosclerosis Risk in Communities Study

“…19,20 Exposure to TNF-a, an inflammatory cytokine, also generated reactive oxygen species and reduced mtDNA copy number in myocytes. 21 Cross-sectional studies of patients with CKD have shown that lower mitochondrial function, indicated by metabolites from urine and gene expression from peripheral blood, correlated with more severe CKD. 22,23 In this study, the association between mtDNA copy number and incident CKD was slightly attenuated after controlling for WBC count, a marker of systematic inflammation, but remained independent of WBC count and hsCRP.…”

Mitochondrial network in the heart

“…Hydrogen peroxide can induce the translocation of Bax and Bad from cytosol to mitochondria (von Harsdorf et al, 1999). ROS induce the production of TNF-α, which is elevated in many cardiac diseases and cardiomyocyte apoptosis (Suematsu et al, 2003), and ROS may be the direct cause of Cytochrome c release (Atlante et al, 2000). The two recently found ROS generators p66 Shc and MAO-A are important regulators in ischemia induced cardiomyocyte apoptosis.…”