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Little is known about mechanisms that control vascular aging, particularly at the cell-specific level. PPARγ (peroxisome proliferator–activated receptor-γ) exerts protective effects in the vasculature when activated pharmacologically. To gain insight into the cell-specific impact of PPARγ, we examined the hypothesis that genetic interference with endothelial PPARγ would augment age-induced vascular dysfunction. We studied carotid arteries from adult (11.6±0.3 months) and old (24.7±0.6 months) mice with endothelial-specific expression of a human dominant negative mutation in PPARγ driven by the vascular cadherin promoter (E-V290M), along with age-matched, nontransgenic littermates. Acetylcholine (an endothelium-dependent agonist) produced similar relaxation in arteries from adult nontransgenic and E-V290M mice and old nontransgenic mice. In contrast, responses to acetylcholine were reduced by >50% in old male and female E-V290M mice ( P P

Pharmacological activation of PPAR-γ (peroxisome proliferator–activated receptor-γ) protects the vasculature. Much less is known on the cell-specific impact of PPAR-γ when driven by endogenous ligands. Recently, we found that endothelial PPAR-γ protects against angiotensin II–induced endothelial dysfunction. Here, we explored that concept further examining whether effects were sex dependent along with underlying mechanisms. We studied mice expressing a human dominant–negative mutation in PPAR-γ driven by the endothelial-specific vascular cadherin promoter (E-V290M), using nontransgenic littermates as controls. Acetylcholine (an endothelium-dependent agonist) produced similar relaxation of carotid arteries from nontransgenic and E-V290M mice. Incubation of isolated arteries with angiotensin II (1 nmol/L) overnight had no effect in nontransgenic, but reduced responses to acetylcholine by about 50% in male and female E-V290M mice ( P 50% ( P

Carotid artery disease is a major contributor to stroke and cognitive deficits. Angiotensin II (Ang II) promotes vascular dysfunction and disease through mechanisms that include the IL-6/STAT3 pathway. Here, we investigated the importance of suppressor of cytokine signaling 3 (SOCS3) in models of Ang II-induced vascular dysfunction. We examined direct effects of Ang II on carotid arteries from SOCS3-deficient (SOCS3+/−) mice and wild-type (WT) littermates using organ culture and then tested endothelial function with acetylcholine (ACh). A low concentration of Ang II (1 nmol/l) did not affect ACh-induced vasodilation in WT but reduced that of SOCS3+/−mice by ∼50% ( P < 0.05). In relation to mechanisms, effects of Ang II in SOCS3+/−mice were prevented by inhibitors of STAT3, IL-6, NF-κB, or superoxide. Systemic Ang II (1.4 mg/kg per day for 14 days) also reduced vasodilation to ACh in WT. Surprisingly, SOCS3 deficiency prevented most of the endothelial dysfunction. To examine potential underlying mechanisms, we performed bone marrow transplantation. WT mice reconstituted with SOCS3+/−bone marrow were protected from Ang II-induced endothelial dysfunction, whereas reconstitution of SOCS3+/−mice with WT bone marrow exacerbated Ang II-induced effects. The SOCS3 genotype of bone marrow-derived cells did not influence direct effects of Ang II on vascular function. These data provide new mechanistic insight into the influence of SOCS3 on the vasculature, including divergent effects depending on the source of Ang II. Bone marrow-derived cells deficient in SOCS3 protect against systemic Ang II-induced vascular dysfunction.

Background and Purpose— Obesity is an increasing epidemic worldwide; however, little is known about effects of obesity produced by high-fat diet (HFD) on the cerebral circulation. The purpose of this study was to examine the functional and temporal effects of a HFD on carotid and cerebral vascular function and to identify mechanisms that contribute to such functional alterations. Methods— Responses of cerebral arterioles (in vivo) and carotid arteries (in vitro) were examined in C57Bl/6 (wild-type) and Nox2-deficient ( Nox2 −/− ) mice fed a control (10%) or a HFD (45% or 60% kcal of fat) for 8, 12, 30, or 36 weeks. Results— In wild-type mice, a HFD produced obesity and endothelial dysfunction by 12 and 36 weeks in cerebral arterioles and carotid arteries, respectively. Endothelial function could be significantly improved with Tempol (a superoxide scavenger) treatment in wild-type mice fed a HFD. Despite producing a similar degree of obesity in both wild-type and Nox2 −/− mice, endothelial dysfunction was observed only in wild-type, but not in Nox2 −/− , mice fed a HFD. Conclusions— Endothelial dysfunction produced by a HFD occurs in a temporal manner and appears much earlier in cerebral arterioles than in carotid arteries. Genetic studies revealed that Nox2-derived superoxide plays a major role in endothelial dysfunction produced by a HFD. Such functional changes may serve to predispose blood vessels to reduced vasodilator responses and thus may contribute to alterations in cerebral blood flow associated with obesity.

Levels of reactive oxygen species, including hydrogen peroxide , increase in blood vessels during hypertension and in response to angiotensin II (Ang II). Although glutathione peroxidases are known to metabolize hydrogen peroxide, the role of glutathione peroxidase during hypertension is poorly defined. We tested the hypothesis that glutathione peroxidase-1 protects against Ang II–induced endothelial dysfunction. Responses of carotid arteries from Gpx1 -deficient ( Gpx1 +/− and Gpx1 −/− ) and Gpx1 transgenic mice, and their respective littermate controls, were examined in vitro after overnight incubation with either vehicle or Ang II. Under control conditions, relaxation to acetylcholine (ACh; an endothelium-dependent agonist) was similar in control, Gpx1 +/− , and Gpx1 transgenic mice, whereas in Gpx1 −/− mice, responses to ACh were impaired. In control mice, ACh-induced vasorelaxation was not affected by 1 nmol/L of Ang II. In contrast, relaxation to ACh in arteries from Gpx1 +/− mice was inhibited by ≈60% after treatment with 1 nmol/L of Ang II, indicating that Gpx1 haploinsufficiency markedly enhances Ang II–induced endothelial dysfunction. A higher concentration of Ang II (10 nmol/L) selectively impaired relaxation to ACh in arteries from control mice, and this effect was prevented in arteries from Gpx1 transgenic mice or in arteries from control mice treated with polyethylene glycol-catalase (which degrades hydrogen peroxide). Thus, genetic and pharmacological evidence suggests a major role for glutathione peroxidase-1 and hydrogen peroxide in Ang II–induced effects on vascular function.

Rho kinase (ROCK) has been implicated in physiological and pathophysiological processes, including regulation of vascular function. ROCK signaling is thought to be a critical contributor to cardiovascular disease, including hypertension and effects of angiotensin II (Ang II). Two isoforms of ROCK (1 and 2) have been identified and are expressed in vascular cells. In this study, we examined the importance of ROCK2 in relation to vessel function using several models and a novel inhibitor of ROCK2. First, incubation of carotid arteries with the direct RhoA activator CN-03 or Ang II impaired endothelium-dependent relaxation by ≈40% to 50% ( P

The goal of this study was to test the hypothesis that loss of a single copy of the gene for CuZn superoxide dismutase (CuZnSOD) increases vascular superoxide levels and produces vascular dysfunction with aging. Responses of carotid arteries from young (7 months) and old (22 to 24 months of age) heterozygous CuZnSOD-deficient (CuZnSOD +/− ) mice and their wild-type (CuZnSOD +/+ ) littermates were examined in vitro. Total superoxide dismutase activity in aorta was reduced by ≈30% ( P +/− mice compared with wild-type mice. Responses to acetylcholine (an endothelium-dependent agonist) produced relaxation that was similar ( P >0.05) in carotid arteries from young wild-type, young CuZnSOD +/− , and old wild-type mice. In contrast, relaxation to acetylcholine was markedly impaired in old CuZnSOD +/− mice (eg, 100 μmol/L acetylcholine produced 51±5% and 96±5% relaxation in vessels from old CuZnSOD +/− and old wild-type mice, respectively). This effect was selective, because relaxation to nitroprusside (an endothelium-independent agonist) was not affected by either CuZnSOD genotype or aging. The impaired response to acetylcholine in old CuZnSOD +/− mice was restored toward normal with either tempol (a scavenger of superoxide; 1 mmol/L) or PJ34 (an inhibitor of poly-ADP-ribose polymerase; 3 μmol/L). Vascular superoxide levels were increased in aorta in old CuZnSOD +/+ mice and increased further in CuZnSOD +/− mice with aging. These findings provide the first direct evidence that normal CuZnSOD expression protects endothelial function and that deficiency in a single copy of the gene that encodes CuZnSOD produces increases in superoxide and marked impairment of endothelial function with aging.

Background and Purpose— Inflammation is thought to be a major contributor to carotid artery disease. Lipopolysaccharide (LPS) activates inflammatory mechanisms thought to contribute to endothelial dysfunction by mechanisms that are not well defined. The goal of this study was to determine whether overexpression of CuZn-SOD protects against LPS-induced increases in superoxide and endothelial dysfunction. Methods— Carotid arteries from CuZn-SOD transgenic (SOD-Tg) and nontransgenic (non-Tg) littermates were examined in vitro. Superoxide levels were measured using lucigenin-enhanced chemiluminescence. Results— In non-Tg mice, LPS (0.5 μg/mL for 22 hours) produced marked impairment of vasorelaxation in response to the endothelium-dependent dilator acetylcholine (ACh). For example, 100 μmol/L ACh relaxed carotid arteries from non-Tg mice by 86±6% and 38±8% after treatment with vehicle and LPS, respectively. In contrast, LPS did not significantly impair responses of carotid artery to ACh in SOD-Tg mice, and LPS had no effect on relaxation responses to the endothelium-independent dilator nitroprusside in carotid artery from non-Tg or SOD-Tg mice. LPS-induced increases in superoxide, as measured using lucigenin-enhanced chemiluminescence, were higher in vessels from non-Tg mice than from SOD-Tg mice. Conclusions— These results indicate that LPS increases superoxide and impairs endothelium-dependent relaxation. Overexpression of the CuZn isoform of SOD effectively prevents LPS-induced oxidative stress and endothelial dysfunction in the carotid artery.

Although aging is the greatest risk factor for vascular disease and stroke, very little is known regarding mechanisms that control vascular aging. Endothelial dysfunction - a critical element of carotid artery and cerebrovascular disease - progresses with age, contributing to increased risk for ischemic stroke and cognitive impairment. The nuclear receptor peroxisome proliferator-activated receptor-γ (PPARγ) exerts protective effects in the vasculature when pharmacologically activated. Because endothelial PPARγ may normally protect against vascular disease, we examined the hypothesis that genetic interference with PPARγ in endothelium would promote vascular aging. We studied carotid arteries from adult (11-12 mo) and old (24±1 mo) transgenic mice with endothelial specific expression of a dominant negative mutation in PPARγ driven by the vascular cadherin promoter (designated E-V290M), along with age-matched, non-transgenic (NT) littermates. Acetylcholine (an endothelium-dependent agonist) produced similar relaxation of arteries from adult NT and E-V290M mice as well as old NT mice. In contrast, responses to acetylcholine were reduced by greater than 50% in old E-V290M mice (P

Angiotensin II (Ang II) is known to promote vascular disease and hypertension in part by formation of cytokines, such as interleukin-6. However, the role of signal transducer and activator of transcription 3 (STAT3) in these processes and Ang II/interleukin-6 signaling is unclear. Using 2 models, we tested the hypothesis that STAT3 is essential for Ang II–induced vascular dysfunction and hypertension. Incubation of isolated carotid arteries from C57BL/6J mice with Ang II overnight increased superoxide ≈2-fold and reduced vasodilator responses to the endothelium-dependent agonist acetylcholine by ≈50% versus controls ( P −1 day −1 ) using osmotic minipumps increased arterial pressure by ≈40 mm Hg at day 14 compared with vehicle-treated mice, and this effect was prevented by S3I-201 treatment (5 mg/kg IP, QOD). After systemic treatment with Ang II, dilator responses to acetylcholine were reduced by ≈30% to 50% in carotid artery and basilar arteries, whereas S3I-201 treatment prevented most of this impairment ( P

Vascular disease occurs commonly during aging. Carotid artery and cerebrovascular disease are major causes of stroke and contributors to dementia. Recent evidence suggests that peroxisome proliferator-activated receptor-γ (PPARγ) may play a protective role in the vasculature, but the potential importance of PPARγ in vascular aging is unknown. To examine the hypothesis that PPARγ normally protects against vascular aging, we studied heterozygous knockin mice expressing a human dominant-negative mutation in PPARγ (P465L, designated L/+). Endothelial dysfunction, a major contributor to vascular disease, was studied using carotid arteries from adult (8 ± 1 mo) and old (24 ± 1 mo) L/+ mice and wild-type littermates. In arteries from wild-type mice, responses to the endothelium-dependent agonist ACh were similar in adult and old wild-type mice but were reduced by ∼50% in old L/+ mice ( n = 7–10, P < 0.05). Impaired responses in arteries from old L/+ mice were restored to normal by a scavenger of superoxide. Relaxation of arteries to nitroprusside (an NO donor) was similar in all groups. Contraction of arteries to U46619 was not affected by age or genotype, while maximal responses to endothelin-1 were reduced with age in both wild-type and L/+ mice. Vascular expression (mRNA) of the catalytic component of NADPH oxidase (Nox2) was not altered in wild-type mice but was increased significantly in old L/+ mice. These findings provide the first evidence that interference with PPARγ function accelerates vascular aging, suggesting a novel role for PPARγ in protecting against age-induced oxidative stress and endothelial dysfunction.

Despite the fact that aging is the greatest risk factor for vascular disease and stroke, relatively little is known regarding mechanisms that promote or protect against vascular aging in experimental models or people. Endothelial dysfunction is a key contributor to both the initiation and progression of vascular disease. Atherosclerosis in carotid arteries (carotid artery disease) greatly increases the risk for ischemic stroke and may contribute to dementia (including Alzheimer’s disease). Peroxisome proliferator activated receptor-γ (PPARγ) is a ligand-activated transcription factor that exerts diverse effects depending on the cell type. Recent work suggests that PPARγ can have beneficial effects in the vasculature including protection against oxidative stress. Relatively little is known regarding the potential role of PPARγ in aging. We used transgenic mice expressing a dominant negative mutation in human PPARγ (V290M) under control of the endothelial-specific vascular cadherin promoter (designated E-V290M) to examine the hypothesis that interference with endothelial PPARγ will promote age-induced vascular dysfunction. Responses of carotid arteries from adult (6±1 mo) and old (23±1 mo) E-V290M mice and non-transgenic littermates (controls) were examined in vitro. Acetylcholine (an endothelium-dependent agonist) produced similar relaxation of arteries from adult control and E-V290M mice as well as old control mice. In contrast, responses to acetylcholine in arteries from old E-V290M mice were markedly impaired. For example, relaxation of the carotid artery to 10 µmol/L acetylcholine was 84±3 and 40±6% in old control versus old E-V290M mice, respectively (P

Background and Purpose— Receptors for calcitonin gene-related peptide (CGRP) are composed of the calcitonin-like receptor in association with receptor activity-modifying protein-1 (RAMP1). CGRP is an extremely potent vasodilator and may protect against vascular disease through other mechanisms. Methods— We tested the hypothesis that overexpression of RAMP1 enhances vascular effects of CGRP using transgenic mice with ubiquitous expression of human RAMP1. Because angiotensin II (Ang II) is a key mediator of vascular disease, we also tested the hypothesis that RAMP1 protects against Ang II-induced vascular dysfunction. Results— Responses to CGRP in carotid and basilar arteries in vitro as well as cerebral arterioles in vivo were selectively enhanced in human RAMP1 transgenic mice compared to littermate controls ( P P P Conclusions— RAMP1 overexpression increases CGRP-induced vasodilation and protects against Ang II-induced endothelial dysfunction. These findings suggest that RAMP1 may be a new therapeutic target to regulate CGRP-mediated effects during disease including pathophysiological states in which Ang II plays a major role.

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 −/− ) 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 −/− mice was reduced by >50% by Ang II ( P P IL-10 −/− mice but not in wild-type. After systemic administration of Ang II (1.4 mg/kg per day for 10 days), Ang II produced modest impairment of endothelial function in wild-type mice but marked impairment in IL-10 −/− mice ( P IL-10 −/− mice. These findings provide the first evidence that endogenous IL-10 limits Ang II-mediated oxidative stress and vascular dysfunction both in vitro and in vivo suggesting that at least some of the protective effects of IL-10 may occur within the vessel wall.

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 μmol/L acetylcholine produced 100±4 and 98±4% relaxation in vehicle-treated and 51±4 and 99±4% 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.

The goal of the present study was to test the hypothesis that the CuZn isoform of superoxide dismutase (CuZnSOD) protects against angiotensin II (Ang II)–induced endothelial dysfunction. Vascular responses of carotid arteries from control, CuZnSOD-deficient (CuZnSOD +/− ), and CuZnSOD transgenic mice were examined in vitro after overnight incubation with either vehicle or Ang II (1 or 10 nmol/L). In control mice, acetylcholine produced concentration-dependent relaxation that was not affected by 1 nmol/L Ang II. In contrast, relaxation to acetylcholine in arteries from CuZnSOD+/− mice was markedly and selectively attenuated after incubation with 1 nmol/L Ang II (eg, 100 μmol/L acetylcholine produced 93±6% and 44±15% relaxation in vehicle- and Ang II-treated arteries, respectively). A higher concentration of Ang II (10 nmol/L) selectively impaired relaxation to acetylcholine in arteries from control mice (eg, 100 μmol/L acetylcholine produced 96±4% and 45±7% relaxation in vehicle- and Ang II-treated vessels, respectively). In contrast, 10 nmol/L Ang II had no effect on responses to acetylcholine in carotid arteries from CuZnSOD transgenic mice (or in control mice treated with the superoxide scavenger Tiron [1 mmol/L]). Superoxide levels in control mice were higher in aorta treated with Ang II than with vehicle and were markedly reduced in CuZnSOD transgenic mice. These findings provide the first direct evidence that CuZnSOD limits Ang II-mediated impairment of endothelial function and that loss of 1 copy of the CuZnSOD gene is sufficient to enhance Ang II-induced vascular dysfunction.