Background— Enhanced production of reactive oxygen species (ROS) has been recognized as the major determinant of age-related endothelial dysfunction. The p66^shc protein controls cellular responses to oxidative stress. Mice lacking p66^shc (p66^shc−/−) have increased resistance to ROS and a 30% prolonged life span. The present study investigates age-dependent changes of endothelial function in this model.

Methods and Results— Aortic rings from young and old p66^shc−/− or wild-type (WT) mice were suspended for isometric tension recording. Nitric oxide (NO) release was measured by a porphyrinic microsensor. Expression of endothelial NO synthase (eNOS), inducible NOS (iNOS), superoxide dismutase, and nitrotyrosine-containing proteins was assessed by Western blotting. Nitrotyrosine residues were also identified by immunohistochemistry. Superoxide (O₂⁻) production was determined by coelenterazine-enhanced chemiluminescence. Endothelium-dependent relaxation in response to acetylcholine was age-dependently impaired in WT mice but not in p66^shc−/− mice. Accordingly, an age-related decline of NO release was found in WT but not in p66^shc−/− mice. The expression of eNOS and manganese superoxide dismutase was not affected by aging either in WT or in p66^shc−/− mice, whereas iNOS was upregulated only in old WT mice. It is interesting that old WT mice displayed a significant increase of O₂⁻ production as well as of nitrotyrosine expression compared with young animals. Such age-dependent changes were not found in p66^shc−/− mice.

Conclusions— We report that inactivation of the p66^shc gene protects against age-dependent, ROS-mediated endothelial dysfunction. These findings suggest that the p66^shc is part of a signal transduction pathway also relevant to endothelial integrity and may represent a novel target to prevent vascular aging.