Abstract 347: eNOS Deficiency Ameliorates Vascular Remodeling Induced by Periadventitial Injury in SOD1 Knock-Out Mice
Background: Copper/zinc SOD (SOD1) is a major enzyme which deactivates superoxide radicals (O2−), and endothelial nitric oxide synthase (eNOS) synthesizes nitric oxide (NO) in endothelial cells. Reduction of each enzyme can increase oxidative stress, leading to cardiovascular dysfunction. Herein, we established SOD1 and eNOS double deficient mice, and examined their physiological and pathological cardiovascular phenotypes to clarify the function of eNOS in cardiovascular system in the case of SOD1 deficiency.
Methods and Results:
SOD1 deficient mice (SOD-KO) were crossbred with eNOS deficient mice (eNOS-KO), and SOD1 and eNOS double-deficient mice (Do-KO) were established. Do-KO had significantly higher blood pressure (BP) than SOD-KO (129.6 ± 4.7 vs. 102.1 ± 1.2 mmHg, p<0.0001). Do-KO had significantly higher heart weights than SOD-KO (3.12 ± 0.09 vs. 2.89 ± 0.03 mg/g, p<0.01). Relaxation of carotid arteries due to acetylcholine was mildly impaired in SOD-KO when compared with wild type mice (WT), while relaxation to acetylcholine was completely ablated in Do-KO. These data indicated that targeted ablation of eNOS in SOD-KO impaired their vascular relaxation, and caused hypertension.
Next, we examined vascular remodeling induced by periadventitial cuff-injuries. Four weeks after cuff replacement, marked neointimal formation was induced in SOD-KO; however, eNOS deficiency in SOD-KO ameliorated the vascular remodeling of SOD-KO, and significantly decreased the ratio of intimal to medial areas (1.23 ± 0.23 vs. 2.23 ± 0.38, p<0.05). This data shows that eNOS enhances the vascular remodeling of SOD-KO caused by cuff injury. NO and O2− react to form the strong oxidant peroxynitrite, which is involved in vascular injury. The levels of 3-nitrotyrosine, a marker of peroxynitrite generation, were significantly elevated in the injured arteries of SOD-KO, while their elevation were attenuated in Do-KO. This indicates that NO derived from eNOS enhances the peroxynitrite formation in injured arteries of SOD-KO, so that vascular remodeling may be markedly enhanced.
Conclusion: Our results demonstrate that peroxynitrite, generated from O2− and eNOS derived-NO, plays a key role in vascular remodeling induced by periadventitial injury.