Endothelial dysfunction of resistance vessels in female apolipoprotein E-deficient mice

<p>Abstract</p> <p>Background</p> <p>The effects of hypercholesterolemia on vasomotricity in apolipoprotein E-deficient (ApoE) mice, a murine model of spontaneous atherosclerosis, are still unclear. The studies were mostly performed in conductance vessels from male mice fed a high-fat diet. In the present study, we evaluated the endothelial function of resistance vessels from normal C57BL/6 (C57) and hypercholesterolemic (ApoE) female mice in both normal and ovariectomized conditions.</p> <p>Methods</p> <p>Twenty week-old C57 and ApoE mice underwent ovariectomy or sham surgery and were studied 30 days later. The vascular reactivities to norepinephrine (NE, 10^-9to 2 × 10^-3mol/L), acetylcholine (ACh) and sodium nitroprusside (SNP) (10^-10to 10^-3mol/L) were evaluated in the isolated mesenteric arteriolar bed through dose-response curves.</p> <p>Results</p> <p>ACh-induced relaxation was significantly reduced (P < 0.05) in ApoE compared with C57 animals, as indicated by both the maximal response (37 ± 4% vs. 72 ± 1%) and the LogEC₅₀(-5.67 ± 0.18 vs. -6.23 ± 0.09 mol/L). Ovariectomy caused a significant impairment in ACh-induced relaxation in the C57 group (maximal response: 61 ± 4%) but did not worsen the deficient state of relaxation in ApoE animals (maximal response: 39 ± 5%). SNP-induced vasorelaxation and NE-induced vasoconstriction were similar in ApoE and C57 female mice.</p> <p>Conclusion</p> <p>These data show an impairment of endothelial function in the resistance vessels of spontaneously atherosclerotic (ApoE-deficient) female mice compared with normal (C57) female mice. The endothelial dysfunction in hypercholesterolemic animals was so marked that ovariectomy, which impaired endothelial function in C57 mice, did not cause additional vascular damage in ApoE-deficient mice.</p

Cardiac and vascular phenotypes in the apolipoprotein E-deficient mouse

Cardiovascular death is frequently associated with atherosclerosis, a chronic multifactorial disease and a leading cause of death worldwide. Genetically engineered mouse models have proven useful for the study of the mechanisms underlying cardiovascular diseases. The apolipoprotein E-deficient mouse has been the most widely used animal model of atherosclerosis because it rapidly develops severe hypercholesterolemia and spontaneous atherosclerotic lesions similar to those observed in humans. In this review, we provide an overview of the cardiac and vascular phenotypes and discuss the interplay among nitric oxide, reactive oxygen species, aging and diet in the impairment of cardiovascular function in this mouse model

Hypercholesterolemia promotes early renal dysfunction in apolipoprotein E-deficient mice

<p>Abstract</p> <p>Background</p> <p>Aging and dyslipidemia are processes which can lead to deleterious consequences to renal function. Therefore, the aim of this study was to determine the effects of both hypercholesterolemia and aging on renal function in mice.</p> <p>Methods</p> <p>Male hypercholesterolemic apolipoprotein E-deficient mice (ApoE, n = 13) and age-matched C57BL/6 control mice (C57, n = 15) were studied at 2 (young) and 8 (adult) month-old. At each time point, animals were placed in metabolic cages for 24 hours to urine volume and urinary creatinine quantification. Blood samples were collected for serum cholesterol, urea and creatinine measurements. Glomerular filtration rate (GFR) was estimated through creatinine clearance determination. Mesangial expansion was evaluated by Periodic Acid Schiff staining, renal fibrosis was determined through Masson's trichrome staining and neuronal nitric oxide synthase (nNOS) expression in the kidney was performed by Western Blotting. To statistical analysis two-way ANOVA followed by Fisher's <it>post hoc </it>test was used.</p> <p>Results</p> <p>Total plasma cholesterol was increased about 5-fold in ApoE mice at both time points compared to C57 animals. At 2-month-old, GFR was already markedly reduced in ApoE compared to C57 mice (187 ± 28 vs 358 ± 92 μL/min, p < 0.05). Adult C57 (-77%) and ApoE (-50%) mice also presented a significant reduction of GFR. In addition, serum urea was significantly increased in young ApoE animals compared to C57 mice (11 ± 1.3 vs 7 ± 0.9 mmol/L, p < 0.01). A significant mesangial expansion was observed at 2-month old ApoE mice compared to C57 mice (35 ± 0.6 vs 30 ± 0.9%, respectively, p < 0.05), which was aggravated at 8-month old animals (40 ± 3 and 35 ± 3%, respectively). Tubulointersticial fibrosis was augmented at both young (17 ± 2%, p < 0.05) and adult (20 ± 1%, p < 0.05) ApoE mice compared to respective C57 age controls (8 ± 1 and 12 ± 2%, respectively). The expression of nNOS was markedly reduced in a time-dependent manner in both strains.</p> <p>Conclusions</p> <p>These data show that both hypercholesterolemia and aging contribute to the loss of renal function in mice.</p

Sildenafil ameliorates oxidative stress and DNA damage in the stenotic kidneys in mice with renovascular hypertension

Background: Oxidative stress and DNA damage have been implicated in the pathogenesis of renovascular hypertension induced by renal artery stenosis in the two-kidney, one-clip (2K1C) Goldblatt model. Considering our previous report indicating that the chronic blockade of phosphodiesterase 5 with sildenafil (Viagra (R)) has marked beneficial effects on oxidative stress and DNA damage, we tested the hypothesis that sildenafil could also protect the stenotic kidneys of 2K1C hypertensive mice against oxidative stress and genotoxicity.Methods: the experiments were performed with C57BL6 mice subjected to renovascular hypertension by left renal artery clipping. Two weeks after clipping, the mice were treated with sildenafil (40 mg/kg/ day for 2 weeks, 2K1C-sildenafil group) or the vehicle (2K1C). These mice were compared with control mice not subjected to renal artery clipping (Sham). After hemodynamic measurements, the stenotic kidneys were assessed using flow cytometry to evaluate cell viability and the comet assay to evaluate DNA damage. Measurements of intracellular superoxide anions and hydrogen peroxide levels as well as nitric oxide bioavailability were also obtained.Results: Sildenafil treatment significantly reduced mean arterial pressure (15%), heart rate (8%), intrarenal angiotensin II (50%) and renal atrophy (36%). in addition, it caused a remarkable decrease of reactive oxygen species production. On the other hand, sildenafil increased nitric oxide levels relative to those in the nontreated 2K1C mice. Sildenafil treatment also significantly reduced the high level of kidney DNA damage that is a characteristic of renovascular hypertensive mice.Conclusions: Our data reveal that sildenafil has a protective effect on the stenotic kidneys of 2K1C mice, suggesting a new use of phosphodiesterase 5 inhibitors for protection against the DNA damage observed in the hypoperfused kidneys of individuals with renovascular hypertension. Further translational research is necessary to delineate the mechanisms involved in the prevention of renal stenosis in the clinical setting.Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)State Agency for the Development of Science and Technology (FAPES)Univ Fed Espirito Santo, Hlth Sci Ctr, Lab Translat Physiol, Vitoria, ES, BrazilUniv Fed Paraiba, Hlth Sci Ctr, Dept Physiol & Pathol, BR-58059900 Joao Pessoa, Paraiba, BrazilUniversidade Federal de São Paulo, Dept Med, Div Nephrol, São Paulo, BrazilUniv Vila Velha, Pharmaceut Sci Grad Program, Vila Velha, ES, BrazilFed Inst Educ Sci & Technol IFES, Vila Velha, ES, BrazilUniversidade Federal de São Paulo, Dept Med, Div Nephrol, São Paulo, BrazilCNPq: 302582/2011-8CNPq: 476525/2012-8CNPq: 305188/2012-7CNPq: 473177/2013-7State Agency for the Development of Science and Technology (FAPES): 54498465CNPq: 012/2009Web of Scienc

Inhibition of phosphodiesterase 5 restores endothelial function in renovascular hypertension

Background: the clipping of an artery supplying one of the two kidneys (2K1C) activates the renin-angiotensin (Ang) system (RAS), resulting in hypertension and endothelial dysfunction. Recently, we demonstrated the intrarenal beneficial effects of sildenafil on the high levels of Ang II and reactive oxygen species (ROS) and on high blood pressure (BP) in 2K1C mice. Thus, in the present study, we tested the hypothesis that sildenafil improves endothelial function in hypertensive 2K1C mice by improving the NO/ROS balance.Methods: 2K1C hypertension was induced in C57BL/6 mice. Two weeks later, they were treated with sildenafil (40 mg/kg/day, via oral) or vehicle for 2 weeks and compared with sham mice. At the end of the treatment, the levels of plasma and intrarenal Ang peptides were measured. Endothelial function and ROS production were assessed in mesenteric arterial bed (MAB).Results: the 2K1C mice exhibited normal plasma levels of Ang I, II and 1-7, whereas the intrarenal Ang I and II were increased (similar to 35% and similar to 140%) compared with the Sham mice. Sildenafil normalized the intrarenal Ang I and II and increased the plasma (similar to 45%) and intrarenal (+15%) Ang 1-7. the 2K1C mice exhibited endothelial dysfunction, primarily due to increased ROS and decreased NO productions by endothelial cells, which were ameliorated by treatment with sildenafil.Conclusion: These data suggest that the effects of sildenafil on endothelial dysfunction in 2K1C mice may be due to interaction with RAS and restoring NO/ROS balance in the endothelial cells from MAB. Thus, sildenafil is a promising candidate drug for the treatment of hypertension accompanied by endothelial dysfunction and kidney disease.Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)State Agency for the Development of Science and Technology (FAPES/Universal)Univ Fed Espirito Santo, Hlth Sci Ctr, Lab Translat Physiol, Vitoria, ES, BrazilEmescam Sch Hlth Sci, Vitoria, ES, BrazilUniversidade Federal de São Paulo, Dept Med, Div Nephrol, São Paulo, BrazilUniv Fed Espirito Santo, Hlth Sci Ctr, Pharmaceut Sci Grad Program, Vitoria, ES, BrazilUniv Fed Paraiba, Hlth Sci Ctr, Dept Physiol & Pathol, BR-58059900 Joao Pessoa, PB, BrazilUVV, Pharmaceut Sci Grad Program, Vila Velha, ES, BrazilFed Inst Educ Sci & Technol IFES, Vila Velha, ES, BrazilUniversidade Federal de São Paulo, Dept Med, Div Nephrol, São Paulo, BrazilCNPq: 302582/2011-8CNPq: 476525/2012-8CNPq: 305188/2012-7CNPq: 473177/2013-7State Agency for the Development of Science and Technology (FAPES/Universal): 012/2011State Agency for the Development of Science and Technology (FAPES/Universal): 54498465CNPq: 012/2009Web of Scienc

Cardiac-Autonomic Imbalance and Baroreflex Dysfunction in the Renovascular Angiotensin-Dependent Hypertensive Mouse

Mouse models provide powerful tools for studying the mechanisms underlying the dysfunction of the autonomic reflex control of cardiovascular function and those involved in cardiovascular diseases. The established murine model of two-kidney, one-clip (2K1C) angiotensin II-dependent hypertension represents a useful tool for studying the neural control of cardiovascular function. In this paper, we discuss the main contributions from our laboratory and others regarding cardiac-autonomic imbalance and baroreflex dysfunction. We show recent data from the angiotensin-dependent hypertensive mouse demonstrating DNA damage and oxidative stress using the comet assay and flow cytometry, respectively. Finally, we highlight the relationships between angiotensin and peripheral and central nervous system areas of cardiovascular control and oxidative stress in the 2K1C hypertensive mouse

Sildenafil restores endothelial function in the apolipoprotein E knockout mouse

Abstract Background Atherosclerosis is an inflammatory process of the arterial walls and is initiated by endothelial dysfunction accompanied by an imbalance in the production of reactive oxygen species (ROS) and nitric oxide (NO). Sildenafil, a selective phosphodiesterase-5 (PDE5) inhibitor used for erectile dysfunction, exerts its cardiovascular effects by enhancing the effects of NO. The aim of this study was to investigate the influence of sildenafil on endothelial function and atherosclerosis progression in apolipoprotein E knockout (apoE−/−) mice. Methods ApoE−/− mice treated with sildenafil (Viagra®, 40 mg/kg/day, for 3 weeks, by oral gavage) were compared to the untreated apoE−/− and the wild-type (WT) mice. Aortic rings were used to evaluate the relaxation responses to acetylcholine (ACh) in all of the groups. In a separate set of experiments, the roles of NO and ROS in the relaxation response to ACh were evaluated by incubating the aortic rings with L-NAME (NO synthase inhibitor) or apocynin (NADPH oxidase inhibitor). In addition, the atherosclerotic lesions were quantified and superoxide production was assessed. Results Sildenafil restored the vasodilator response to acetylcholine (ACh) in the aortic rings of the apoE−/− mice. Treatment with L-NAME abolished the vasodilator responses to ACh in all three groups of mice and revealed an augmented participation of NO in the endothelium-dependent vasodilation in the sildenafil-treated animals. The normalized endothelial function in sildenafil-treated apoE−/− mice was unaffected by apocynin highlighting the low levels of ROS production in these animals. Moreover, morphological analysis showed that sildenafil treatment caused approximately a 40% decrease in plaque deposition in the aorta. Conclusion This is the first study demonstrating the beneficial effects of chronic treatment with sildenafil on endothelial dysfunction and atherosclerosis in a model of spontaneous hypercholesterolemia. These data indicate that the main mechanism of the beneficial effect of sildenafil on the endothelial function appears to involve an enhancement of the NO pathway along with a reduction in oxidative stress.</p