Citations

Objective—The ubiquitin-proteasome system is the principal degradation route of intracellular and oxidized proteins, thus regulating many cellular processes conceivably important for atherosclerosis. The aim of this study was to evaluate the activity of ubiquitin-proteasome system in human carotid artery plaques in relation to oxidative stress and clinical manifestation.Methods and Results—In carotid endarterectomy specimens from 83 asymptomatic and 94 symptomatic patients, content of ubiquitin, ubiquitin conjugates, matrix metalloproteases, and NADPH-oxidase-p67 was evaluated by immunoblotting; proteolytic proteasome activity by fluorometric assay; single and double immunostaining for ubiquitin conjugates, 3-nitrotyrosine, apoptosis, smooth muscle α-actin, and macrophage CD-68, as well as Sirius Red staining for collagen were performed. Compared with asymptomatic patients, symptomatic patients showed a more unstable plaque phenotype, an increased degree of apoptosis, a significantly higher ubiquitin conjugates content (17.72±1.36 versus 10.99±1.04;P<0.001), and lower proteasome activity (5.01±0.70 versus 9.41±1.19 nmol AMC/mg protein/min;P<0.01). Ubiquitin conjugates content was directly correlated to NADPH-p67 and degree of apoptosis. Immunostaining revealed colocalization of ubiquitin conjugates and 3-nitrotyrosine, and accumulation of ubiquitin conjugates in smooth muscle cells and macrophages.Conclusions—In human carotid plaques increased oxidative stress is associated with inhibition of the proteasome activity and accumulation of ubiquitin conjugates, particularly in symptomatic patients. These results suggest a possible role of the ubiquitin-proteasome system in influencing plaque stability.

Objective— Intima-media remodeling, as frequently assessed by changes in the external elastic lamina-to-lumen area (EELLA), is well-described in coronary artery disease in contrast to adventitial remodeling, especially in the early disease stage. Method and Results— Female domestic pigs were randomized to one of the following 12-week treatment groups: normal diet (N; n=6), high-cholesterol diet (HC; n=6), or renovascular hypertension (HT; n=4). Low-density lipoprotein (LDL) cholesterol serum concentration was higher in HC than in N and HT (395.5±106 versus 38.6±14 and 37.2±6.8 mg/dL; P <0.05 for both). Mean arterial pressure was higher in HT than in N and HC (141.3±21 versus 107.4±8.9 and 109.4±7.8 mm Hg; P <0.05 for both). EELLA ratio, as assessed by morphometry, was similar in N, HC, and HTN (1.03±0.32 versus 0.95±0.29 and 1.01±0.09; P <0.05 for both). Coronary vasa vasorum density, as assessed by 3-dimensional micro-computed tomography, was higher in HC than in N and HT (3.4±1.0 versus 1.9±0.3 and 2.0±1.2; P <0.05 for both). In contrast, immunostaining showed a higher collagen III content and the presence of adventitial myofibroblasts in HT compared with N and HC. Conclusions— The current study suggests that adventitial remodeling precedes intima and media remodeling of coronary arteries early after exposure to hypercholesterolemia and hypertension, with distinct qualitative differences between them.

Renal artery stenosis (RAS) may lead to renal injury, partly mediated through increased oxidative stress. However, the potential effects of chronic oral antioxidant intervention on the stenotic kidney remain unknown. This study was designed to test the hypothesis that chronic antioxidant vitamin supplementation in RAS would preserve renal function and structure. Single-kidney hemodynamics and function were quantified in vivo in pigs using electron-beam CT after 12 weeks of unilateral RAS (n=7), a similar degree of RAS orally supplemented with vitamins C (1 g) and E (100 IU/kg) (RAS+Vitamins, n=7), or controls (normal, n=7). Renal tissue was studied ex vivo using Western blotting and immunohistochemistry. Mean arterial pressure was similarly elevated in both RAS groups, while ischemic renal volume and glomerular filtration rate were similarly reduced. Renal blood flow was decreased in RAS compared with normal (326.5±99.9 versus 553.4±48.7 mL/min, respectively, P =0.01), but preserved in RAS+Vitamins (485.2±104.1 mL/min, P =0.3 versus normal). The marked increase in the expression of the NADPH-oxidase subunits p47phox and p67phox, nitrotyrosine, endothelial and inducible nitric oxide synthase, and nuclear factor-κB observed in RAS ( P <0.05 versus normal) was normalized in RAS+Vitamins ( P >0.1). Furthermore, trichrome staining and the expression of transforming growth factor-β and tissue inhibitor of matrix-metalloproteinase-1 were also decreased in RAS+Vitamins. In conclusion, chronic blockade of the oxidative stress pathway in RAS using antioxidant vitamins improved renal hemodynamics and decreased oxidative stress, inflammation, and fibrosis in the ischemic kidney. These observations underscore the involvement of oxidative stress in renal injury in RAS and support a role for antioxidant vitamins in preserving the ischemic kidney.

ABSTRACT The ubiquitin‐proteasome system (UPS) is involved in the removal of damaged proteins and the activation of transcription factors, such as nuclear‐factor‐κB. Recent reports, however, questioned the functional activity of the UPS under conditions of increased oxidative stress, such as experimental hypercholesterolemia, which was the objective of our study. Pigs were placed on a normal chow diet (N) or on a hypercholesterolemic diet without (HC) or with vitamin C and E supplementation (HC+VIT) for 12 weeks. Compared with N, plasma concentration of total cholesterol increased in both HC and HC+VIT [76 ± 21 vs. 400 ± 148 ( P <0.05) and 329 ± 102 ( P <0.05) mg/dL], whereas increase in lipid peroxidation, as assessed by LDL‐malondialdehyde plasma concentration, was found in HC but not in HC+VIT [6.6 ± 0.7 vs. 8.5 ± 0.3 ( P <0.05) and 6.8 ± 0.7 nmol/mg protein]. In comparison with N, the level of ubiquitin conjugates in the coronary artery, as assessed by immunoblotting, increased by 42% in HC but not in HC+VIT and was localized predominantly to media vascular smooth muscle cells by immunostaining. There was no difference in proteasome proteolytic activity among the study groups. These results demonstrate that the UPS is functionally active in early atherogenesis despite increase in oxidative stress with important repercussions in the pathophysiology and therapy of cardiovascular diseases.

Objective— Coronary endothelial dysfunction is associated with an increase in cardiac events. Hypercholesterolemia (HC) and hypertension (HT) are both associated with endothelial dysfunction, and their coexistence is associated with an increased incidence of cardiac events in epidemiological studies. However, pathogenic mechanisms are poorly understood. Here we studied the effects of coexisting HC and HT on coronary endothelial function. Methods and Results— Four groups of pigs were studied after 12 weeks of a normal diet (n=9), a 2% HC diet (n=9), HT (achieved by unilateral renal artery stenosis, n=8), or HC+HT (n=6). Coronary endothelial function was tested, in epicardial arteries and arterioles, by using organ chamber techniques. Oxidative stress was measured in coronary artery tissue. Vasodilatory response to bradykinin and calcium ionophore was significantly impaired in animals with HC+HT compared with each risk factor alone ( P <0.05 for both). In animals with coexistent HC and HT, the increase in oxidative stress was more pronounced compared with each risk factor alone ( P <0.05). Furthermore, chronic antioxidant supplementation significantly improved coronary artery vasoreactivity. Conclusions— These results suggest that HC and HT have a synergistic deleterious effect on coronary endothelial function, associated with increased oxidative stress. This interaction may contribute to the increased incidence of coronary heart disease and cardiac events seen when HC and HT coexist.

Objective— C-reactive protein (CRP) is a sensitive marker of inflammation and a prognostic marker in cardiovascular disease. Evidence suggests direct biological activities of CRP within the vascular wall. The study was designed to examine the vasoreactive effects of CRP. Methods and Results— Human internal mammary artery rings were obtained during cardiovascular bypass surgery and suspended in an organ bath chamber. The rings were precontracted with endothelin-1, and response to cumulative concentrations of CRP was obtained. Experiments were repeated after initial incubation with 20, 40, and 60 mmol/L KCl, the potassium channel blockers BaCl, tetraethylammonium chloride, and glibenclamide, and the NO synthase inhibitor N -monomethyl- l -arginine and also after removal of the endothelium. CRP caused dose-dependent relaxation of human internal mammary artery rings, which was not affected by preincubation with N -monomethyl- l -arginine or removal of the endothelium. Maximum relaxation response to CRP (79.5±10%) was attenuated by KCl (2.5±11.5%, P <0.001), BaCl (24.5±7.5%, P <0.001), and tetraethylammonium chloride (34.9±8.25%, P <0.01) but not by glibenclamide. Conclusions– The present study demonstrates that CRP exerts an endothelium-independent vasorelaxing effect via potassium channels. Thus, the study suggests a role of CRP in the regulation of vascular tone.

Background— Stenting-related myocardial injury has been recognized as a frequent and prognostically important event, the extent of which depends on microcirculatory impairment in association with platelet aggregation, inflammation, and increased oxidative stress. Recent studies underscored the non–lipid-lowering effects of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors (statins) with antithrombotic, antiinflammatory, and antioxidative aspects. Thus, we tested the hypothesis that preprocedural statin therapy is associated with a reduction in the extent of stenting-related myocardial injury. Methods and Results— We stratified 296 consecutive patients who were undergoing stenting of a de novo stenosis according to the preprocedural status of statin therapy (229 statin-treated and 67 control patients). Incidence of periprocedural myocardial injury was assessed by analysis of creatine kinase (CK; upper limit of normal [ULN] 70 IU/L for women, 80 IU/L for men) and cardiac troponin T (cTnT; bedside test; threshold 0.1 ng/mL) before and 6, 12, and 24 hours after the intervention. Relative to control patients, the incidence of CK elevation >3× ULN was more than 90% lower in statin-treated patients (0.4% versus 6.0%, P =0.01). Statin therapy was the only factor independently associated with a lower risk of CK elevation >3× ULN (OR: 0.08, 95% CI: 0.01 to 0.75; P =0.03). The overall incidences of CK and cardiac troponin T elevation were slightly lower in statin-treated than in control patients (14.4% versus 20.9%, P =0.3, and 17.9% versus 22.4%, P =0.5, respectively). Conclusions— Preprocedural statin therapy is associated with a reduction in the incidence of larger-sized, stenting-related myocardial infarctions. Prospective, randomized trials are warranted to further assess this cardioprotective effect of statins in coronary intervention.

Background — Previous studies have demonstrated that experimental hypercholesterolemia leads to neovascularization in the coronary artery vasa vasorum (VV). Recent evidence suggests that HMG-CoA reductase inhibitors (statins) have beneficial effects independent of lipid lowering. We aimed to determine the effect of simvastatin on coronary VV neovascularization, in the absence of cholesterol lowering. Methods and Results — Pigs were randomized to 3 groups fed a normal (N), high cholesterol (HC), or HC+simvastatin (HC+S) diet for 12 weeks. The proximal left anterior descending artery was isolated, scanned with micro-CT, and reconstructed. Quantification of the VV density in serial cross-sections along the vessel was then performed. LDL cholesterol was similarly increased in HC and HC+S compared with N. There was an increase in both VV density (4.7±0.3 versus 2.7±0.2 n/mm 2 ; P <0.05) and vessel wall area (3.1±0.2 versus 1.8±0.1 mm 2 ; P <0.05) in HC compared with N. The VV density in HC+S was preserved compared with HC (3.0±0.2 n/mm 2 ; P <0.05), despite similar increase in vessel wall area compared with N (2.5±0.1 mm 2 ; P <0.05). Coronary artery tissue expression of VEGF was increased in HC but not in HC+S compared with N. In parallel, immunoreactivity for HIF-1α, VEGF, MMP-2, and MMP-9 was accentuated in the outer media in HC but not in HC+S compared with N. Conclusions — This study demonstrates that simvastatin attenuates hypoxia in the coronary artery wall and VV neovascularization in experimental hypercholesterolemia, despite no change in plasma lipids. These data are consistent with an additional mechanism for the vascular effects of the statins, independent of cholesterol lowering.