Background-Prostaglandins generated by cyclooxygenase (COX) have been implicated in hyperglycemia-induced endothelial dysfunction. However, the role of individual COX isoenzymes as well as the molecular mechanisms linking oxidative stress and endothelial dysfunction in diabetes remains to be clarified. Methods and Results-Human aortic endothelial cells were exposed to normal (5.5 mmol/L) and high (22.2 mmol/L) glucose. Glucose selectively increased mRNA and protein expression of COX-2. Its upregulation was associated with an increase of thromboxane A 2 and a reduction of prostacyclin (PGI 2 ) release. Glucose-induced activation of PKC resulted in the formation of peroxynitrite and tyrosine nitration of PGI 2 synthase. NO release was reduced despite 2-fold increase of endothelial NO synthase expression. Phorbol ester caused an increase of COX-2 and endothelial NO synthase expression similar to that elicited by glucose. These effects were prevented by the PKC inhibitor calphostin C. N-acetylcysteine, vitamin C, and calphostin C prevented ROS formation, restored NO release, and reduced colocalization of nitrotyrosine and PGI 2 synthase. Expression of p22 phox , a subunit of NAD(P)H oxidase, was increased, and diphenyleneiodonium inhibited ROS formation. By contrast, indomethacin did not affect glucose-induced ROS generation. Conclusions-Thus, high glucose, via PKC signaling, induces oxidative stress and upregulation of COX-2, resulting in reduced NO availability and altered prostanoid profile.

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 shcϪ/Ϫ ) 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 p66shcϪ/Ϫ 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 (O 2 Ϫ ) production was determined by coelenterazine-enhanced chemiluminescence. Endothelium-dependent relaxation in response to acetylcholine was age-dependently impaired in WT mice but not in p66shcϪ/Ϫ mice. Accordingly, an age-related decline of NO release was found in WT but not in p66shcϪ/Ϫ mice. The expression of eNOS and manganese superoxide dismutase was not affected by aging either in WT or in p66shcϪ/Ϫ mice, whereas iNOS was upregulated only in old WT mice. It is interesting that old WT mice displayed a significant increase of O 2 Ϫ production as well as of nitrotyrosine expression compared with young animals. Such age-dependent changes were not found in p66shcϪ/Ϫ mice. Conclusions-We report that inactivation of the p66shc 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. Key Words: aging Ⅲ endothelium Ⅲ free radicals Ⅲ nitric oxide Ⅲ genes S hc proteins are adaptor proteins that exist in 3 different isoforms with relative molecular masses of 46, 52, and 66 kDa. P52shc /p46 shc is involved in the transmission of mitogenic signals from tyrosine kinases to Ras. 1 p66 shc has the same modular structure of p52 shc /p46 shc (SH2-CH1-PTB) and contains a unique N-terminal region (CH2); however, it is not involved in Ras regulation but rather functions in the intracellular pathway that converts oxidative signals into apoptosis. Indeed, embryo fibroblasts from mice carrying a targeted mutation of p66 shc (p66 shcϪ/Ϫ ) are more resistant to oxidative stress-induced apoptosis. 2 p66 shcϪ/Ϫ mice have an approximately 30% increase in life span and reduced early atherogenesis after long-term consumption of a high-fat diet, 3 suggesting that p66shc is implicated in aging and in the pathogenesis of aging-associated diseases in mammals. The biochemical function of p66 shc remains, however, largely unknown. Recent reports demonstrated that p66 shc acts as a downstream target of the tumor suppressor p53 and is indispensable to the ability of activated p53 to induce elevation of intra...