Objective— In mice that are heterozygous for mitochondrial superoxide dismutase (SOD2^+/−) with apoE deficiency (apoE^−/−), mitochondrial DNA damage increases formation of atherosclerotic lesions. The purpose of this study was to determine whether SOD2 provides protection against increased vascular superoxide and endothelial dysfunction in apoE-deficient mice.

Methods and Results— Four groups of mice [apoE^−/−/SOD2^+/− (apoe/sod2), apoE^−/−/SOD2^+/+ (apoe/SOD2), apoE^+/+/SOD2^+/− (apoE/sod2), and apoE^+/+/SOD2^+/+ (apoE/SOD2)] were fed normal chow diet, and studied at 15 to 17 months of age. Serum cholesterol levels were similar in apoe/sod2 and apoe/SOD2 mice, and also were similar in apoE/sod2 and apoE/SOD2 mice. Intimal area was increased in aorta, but not carotid artery, of apoe/sod2 and apoe/SOD2 mice. In carotid artery, superoxide was increased (67±5.2 relative fluorescence intensity/vessel area [RI] in apoe/sod2 mice, 31±3.1 RI in apoE/SOD2 mice, P<0.05), and relaxation to acetylcholine was impaired in apoe/sod2 mice versus apoe/ SOD2, apoE/sod2, apoE/SOD2 mice. Tiron improved relaxation to acetylcholine. In aorta, superoxide levels were increased and relaxation to acetylcholine was impaired in apoe/sod2 and apoe/SOD2 mice, but responses were similar in apoe/sod2 and apoe/SOD2 mice.

Conclusion— SOD2 protects against oxidative stress and endothelial dysfunction in carotid artery of apoE-deficient mice.