Objective-The goal of this study was to test the hypothesis that IL-6 mediates the increases in superoxide, vascular hypertrophy, and endothelial dysfunction in response to angiotensin II (Ang II). Methods and Results-Responses of carotid arteries from control and IL-6 -deficient mice were examined after acute (22-hour) incubation with Ang II (10 nmol/L) or chronic infusion of Ang II (1.4 mg/kg/d for 14 days). The hypertrophic response and endothelial dysfunction produced by Ang II infusion was markedly less in carotid arteries from IL-6 -deficient mice than that in control mice. IL-6 deficiency also protected against endothelial dysfunction in response to acute (local) Ang II treatment (eg, 100 mol/L acetylcholine produced 100Ϯ4 and 98Ϯ4% relaxation in vehicle-treated and 51Ϯ4 and 99Ϯ4% relaxation in Ang II-treated, control, and IL-6 -deficient vessels, respectively). Endothelial dysfunction could be reproduced in vessels from IL-6 -deficient mice with combined Ang II plus IL-6 (0.1 nmol/L) treatment. Increases in vascular superoxide and IL-6, as well as reductions in endothelial nitric oxide synthase mRNA expression, produced by Ang II were absent in IL-6 -deficient mice. Conclusions-These data demonstrate that IL-6 is essential for Ang II-induced increases in superoxide, endothelial dysfunction, and vascular hypertrophy. (Arterioscler Thromb Vasc Biol.

Abstract-Increased superoxide is thought to play a major role in vascular dysfunction in a variety of disease states.Superoxide dismutase (SOD) limits increases in superoxide; however, the functional significance of selected isoforms of SOD within the vessel wall are unknown. We tested the hypothesis that selective loss of CuZnSOD results in increased superoxide and altered vascular responsiveness in CuZnSOD-deficient (CuZnSOD Ϫ/Ϫ ) mice compared with wild-type (CuZnSOD ϩ/ϩ ) littermates. Total SOD activity was reduced (PϽ0.05) by approximately 60% and CuZnSOD protein was absent in aorta from CuZnSOD Ϫ/Ϫ as compared with wild-type mice. Vascular superoxide levels, measured using lucigenin (5 mol/L)-enhanced chemiluminescence and hydroethidine (2 mol/L)-based confocal microscopy, were increased (approximately 2-fold; PϽ0.05) in CuZnSOD Ϫ/Ϫ mice as compared with wild-type mice. Relaxation of the carotid artery in response to acetylcholine and authentic nitric oxide was impaired (PϽ0.05) in CuZnSOD Ϫ/Ϫ mice. For example, maximal relaxation to acetylcholine (100 mol/L) was 50Ϯ6% and 69Ϯ5% in CuZnSOD Ϫ/Ϫ and wild-type mice, respectively. Contractile responses of the carotid artery were enhanced (PϽ0.05) in CuZnSOD Ϫ/Ϫ mice in response to phenylephrine and serotonin, but not to potassium chloride or U46619. In vivo, dilatation of cerebral arterioles (baseline diameterϭ31Ϯ1 m) to acetylcholine was reduced by approximately 50% in CuZnSOD Ϫ/Ϫ mice as compared with wild-type mice (PϽ0.05). These findings provide the first direct insight into the functional importance of CuZnSOD in blood vessels and indicate that this specific isoform of SOD limits increases in superoxide under basal conditions. CuZnSOD-deficiency results in altered responsiveness in both large arteries and microvessels.

Abstract-Blood vessels express 3 isoforms of superoxide dismutase (SOD): cytosolic or copper-zinc SOD (CuZn-SOD), manganese SOD (Mn-SOD) localized in mitochondria, and an extracellular form of CuZn-SOD (EC-SOD). Because there are no selective pharmacological inhibitors of individual SOD isoforms, the functional importance of the different SODs has been difficult to define. Recent molecular approaches, primarily the use of genetically-altered mice and viral-mediated gene transfer, have allowed investigators to begin to define the role of specific SOD isoforms in vascular biology. This review will focus mainly on the role of individual SODs in relation to endothelium under normal conditions and in disease states. This area is important because reactive oxygen species and superoxide anion are thought to play major roles in changes in vascular structure and function in pathophysiology. Key Words: reactive oxygen species Ⅲ endothelium Ⅲ nitric oxide Ⅲ superoxide dismutase Ⅲ peroxynitrite S uperoxide anion (O 2 Ϫ ) and other reactive oxygen species (ROS) play a major role in vascular biology. In general, relatively low concentrations of ROS are thought to act as mediators or modulators of cell signaling and contribute to other key functions, such as regulation of activity of transcription factors and gene expression. [1][2][3] In contrast, higher levels of ROS contribute to vascular dysfunction and abnormal cell growth including hypertrophy of vascular muscle. Superoxide levels are increased in blood vessels in many pathophysiological conditions including hypertension, atherosclerosis, diabetes, hyperhomocysteinemia, heart failure, sepsis, subarachnoid hemorrhage, and Alzheimer disease, as well as during aging. Since the initial evidence that superoxide or other ROS inactivate nitric oxide (NO) or endothelium-derived relaxing factor (EDRF), 4 many studies have suggested that inactivation of NO by superoxide contributes to vascular dysfunction under pathophysiological conditions. Steady-state levels of superoxide are dependent on both its rate of production as well as activity of the various superoxide dismutases (SODs). The goal of this review is to briefly summarize the role of SODs in relation to vascular biology with an emphasis on endothelium. This summary will mainly focus on highlighting recent work from an emerging field, the functional importance of specific SOD isoforms in vascular protection. Superoxide Dismutases: Basic Characteristics and FunctionsIn mammals, there are 3 isoforms of SOD, 5 and each are products of distinct genes but catalyze the same reaction: As indicated above, SODs dismute superoxide into hydrogen peroxide plus molecular oxygen. There are several functional consequences of this enzymatic activity. First, SODs protect against superoxide-mediated cytotoxicity, such as inactivation of mitochondrial proteins containing ironsulfur (Fe-S) centers (eg, aconitase and fumarase) ( Figure 2). 5 Such interactions are of potential importance, as damage to such complexes results in release of free i...

Abstract-Angiotensin II (Ang II) produces inflammation and endothelial dysfunction in blood vessels. We tested the hypothesis that interleukin 10 (IL-10), an antiinflammatory cytokine, protects against Ang II-induced vascular dysfunction. Responses of carotid arteries from wild-type and IL-10 -deficient mice (IL-10 Ϫ/Ϫ ) were examined in vitro after overnight incubation with vehicle or Ang II (1 nmol/L). In arteries from wild-type mice, acetylcholine (an endothelium-dependent agonist) produced relaxation that was not affected by Ang II. In contrast, relaxation to acetylcholine in arteries from IL-10 Ϫ/Ϫ mice was reduced by Ͼ50% by Ang II (PϽ0.05) and this effect was prevented by a scavenger of superoxide. Vascular superoxide increased Ϸ2-fold (PϽ0.05) after treatment with Ang II in IL-10

Abstract-The peroxisome proliferator activated receptor (PPAR␥) agonist rosiglitazone has been reported to yield cardiovascular benefits in patients by a mechanism that is not completely understood. We tested whether oral rosiglitazone (25 mg/kg per day, 21 days) treatment improves blood pressure and vascular function in a transgenic mouse expressing both human renin and human angiotensinogen transgenes (R ϩ A ϩ ). Rosiglitazone decreased systolic (138Ϯ5 versus 128Ϯ5 mm Hg) and mean blood pressure (145Ϯ5 versus 126Ϯ7 mm Hg) of R ϩ A ϩ mice as measured by tail-cuff and indwelling carotid catheters, respectively. Relaxation of carotid arteries to acetylcholine and authentic nitric oxide, but not papaverine, was impaired in R ϩ A ϩ mice when compared with littermate controls (RA Ϫ ). There were no effects of rosiglitazone on RA Ϫ mice; however, relaxation to acetylcholine (49Ϯ10 versus 82Ϯ9% at 100 mol/L) and nitric oxide (51Ϯ11 versus 72Ϯ6% at 10 mol/L) was significantly improved in treated R ϩ A ϩ mice. Rosiglitazone treatment of R ϩ A ϩ mice did not alter the expression of genes, including endothelial nitric oxide synthase (eNOS), angiotensin 1 receptors, and preproendothelin-1, nor did it alter the levels of eNOS or soluble guanylyl cyclase protein.In separate studies, carotid arteries from R ϩ A ϩ and RA Ϫ mice relaxed in a concentration-dependent manner to rosiglitazone, suggesting possible PPAR␥-independent effects in the vasculature. This response was not inhibited with the nitric oxide synthase inhibitor N -nitro-L-arginine methyl ester (200 mol/L) or the PPAR␥ antagonist bisphenol A diglycidyl ether; 4,4Ј-isopropylidenediphenol diglycidyl ether (100 mol/L). These data suggest that in addition to potential genomic regulation caused by PPAR␥ activation, the direct effect of rosiglitazone in blood vessels may contribute to the improved blood pressure and vessel function. Key Words: nitric oxide Ⅲ angiotensin Ⅲ endothelin Ⅲ carotid P eroxisome proliferator activated receptors (PPARs) are members of the nuclear hormone receptor superfamily and bind to DNA as a heterodimer with retinoid x receptor to regulate transcription. Three genes encode different PPARs (␣, ␤/␦, and ␥), and the gene products are differentially expressed in a variety of tissues. 1 PPARs have been most widely characterized with respect to their role in adipocyte growth and differentiation. 2 More recently, PPAR␥ has become the focus of attention for the treatment of noninsulin-dependent diabetes mellitus, due largely to successful treatment with the thiazolidinedione (TZD) class of drugs that act as specific PPAR␥ ligands. TZDs (ie, troglitazone, ciglitazone, pioglitazone, and rosiglitazone) activate PPAR␥, leading to improved insulin sensitivity and reduced blood pressure in both humans and animals through a mechanism that has not been completely elucidated. [3][4][5][6] These findings, coupled with the observation that PPAR␥ is expressed in both vascular muscle 7 and endothelium, 8 suggest that it may play an important role in the regulati...