Abstract 892: The Importance of Mitochondrial Oxidative Stress and Integrity of Mitochondrial DNA in Coronary Arteriogenesis
The prediabetic metabolic syndrome (pdMS) leads to many pathological cardiac and vascular phenotypes including impaired arteriogenesis. Mitochondrial (mt) oxidative stress (mtOxStress) is postulated to contribute to the development of such phenotypes, but whether reduction of mtOxStress, or imposition of a maneuver to mimic its effects, would restore or inhibit coronary arteriogenesis (CA), respectively, has not been determined. We tested the hypothesis that in the pdMS, mtOxStress plays a key role in inhibition of coronary arteriogenesis. Lean (LN, n = 6) and obese (OB, n = 6) Zucker obese fatty rats (model of pdMS) were instrumented with a pneumatic snare around the left anterior descending artery (LAD), and subjected to a protocol of repetitive ischemia (RI: 24, 40 sec occlusions/day for 10 days) to stimulate growth. CA was determined from the ratio of flows (radioactive microspheres) measured during LAD occlusion to collateral-dependent and normal zones (CZ/NZ). Prior to RI, CZ/NZ in all groups was less than 0.2 indicating that the native collateral conductance could supply less than 20% of the normally occurring flow during LAD occlusion. After RI, CZ/NZ was 0.82Â ± 0.09 in LN, which was markedly higher (p < 0.05) than that in the OB (0.21Â ± 0.08) indicating impaired CA in the OB rats. To reduce mtOxStress, OB animals (n = 5) were given mito-Quinone (mt-directed free radical scavenger) in drinking water (750 mg/L); this treatment restored CA (CZ/NZ = 0.79Â ± 0.03) comparable to that in LN. Because one manifestation of mt-OxStress is mt-DNA fragmentation, which results in impaired expression of key mt-proteins and compromised mt-function, we determined if administration of a recombinant protein engineered with a TAT sequence to enable intracellular delivery, a mt-localization sequence, and exonuclease ExoIII (mt-tat-ExoIII) to fragment mtDNA would impair coronary arteriogenesis in LN (n = 5). Mt-tat-ExoIII (iv, 0.2 ug/g, every other day) in LN rats impaired CA in response to RI (CZ/NZ = 0.32Â ± 0.09, p < 0.05 vs. LN controls). We conclude that mitochondrial oxidative stress, and its effects on mtDNA integrity, are pivotal in the abrogation of CA in the pdMS.