Oxidative stress increases M1dG, a major peroxidation-derived DNA adduct, in mitochondrial DNA

Reactive oxygen species (ROS) are formed in mitochondria during electron transport and energy generation. Elevated levels of ROS lead to increased amounts of mitochondrial DNA (mtDNA) damage. We report that levels of M(1)dG, a major endogenous peroxidation-derived DNA adduct, are 50-100-fold higher in mtDNA than in nuclear DNA in several different human cell lines. Treatment of cells with agents that either increase or decrease mitochondrial superoxide levels leads to increased or decreased levels of M(1)dG in mtDNA, respectively. Sequence analysis of adducted mtDNA suggests that M(1)dG residues are randomly distributed throughout the mitochondrial genome. Basal levels of M(1)dG in mtDNA from pulmonary microvascular endothelial cells (PMVECs) from transgenic bone morphogenetic protein receptor 2 mutant mice (BMPR2(R899X)) (four adducts per 10(6) dG) are twice as high as adduct levels in wild-type cells. A similar increase was observed in mtDNA from heterozygous null (BMPR2(+/-)) compared to wildtype PMVECs. Pulmonary arterial hypertension is observed in the presence of BMPR2 signaling disruptions, which are also associated with mitochondrial dysfunction and oxidant injury to endothelial tissue. Persistence of M(1)dG adducts in mtDNA could have implications for mutagenesis and mitochondrial gene expression, thereby contributing to the role of mitochondrial dysfunction in diseases.