Luiza Antas Rabelo

Endothelial dysfunction and elevated blood pressure in MAS gene-deleted mice.

Mas codes for a G protein–coupled receptor that is implicated in angiotensin-(1-7) signaling. We studied the cardiovascular phenotype of Mas-deficient mice backcrossed onto the FVB/N genetic background using telemetry and found that they exhibit higher blood pressures compared with controls. These Mas−/− mice also had impaired endothelial function, decreased NO production, and lower endothelial NO synthase expression. Reduced nicotinamide-adenine dinucleotide phosphate oxidase catalytic subunit gp91phox protein content determined by Western blotting was higher in Mas−/− mice than in controls, whereas superoxide dismutase and catalase activities were reduced. The superoxide dismutase mimetic, Tempol, decreased blood pressure in Mas−/− mice but had a minimal effect in control mice. Our results show a major cardiovascular phenotype in Mas−/− mice. Mas-deletion results in increased blood pressure, endothelial dysfunction, and an imbalance between NO and reactive oxygen species. Our animals represent a promising model to study angiotensin-(1-7)–mediated cardiovascular effects and to evaluate Mas agonistic compounds as novel cardioprotective and antihypertensive agents based on their beneficial effects on endothelial function.

Oxidative stress as an underlying contributor in the development of chronic complications in diabetes mellitus.

The high prevalence of diabetes mellitus and its increasing incidence worldwide, coupled with several complications observed in its carriers, have become a public health issue of great relevance. Chronic hyperglycemia is the main feature of such a disease, being considered the responsible for the establishment of micro and macrovascular complications observed in diabetes. Several efforts have been directed in order to better comprehend the pathophysiological mechanisms involved in the course of this endocrine disease. Recently, numerous authors have suggested that excess generation of highly reactive oxygen and nitrogen species is a key component in the development of complications invoked by hyperglycemia. Overproduction and/or insufficient removal of these reactive species result in vascular dysfunction, damage to cellular proteins, membrane lipids and nucleic acids, leading different research groups to search for biomarkers which would be capable of a proper and accurate measurement of the oxidative stress (OS) in diabetic patients, especially in the presence of chronic complications. In the face of this scenario, the present review briefly addresses the role of hyperglycemia in OS, considering basic mechanisms and their effects in diabetes mellitus, describes some of the more commonly used biomarkers of oxidative/nitrosative damage and includes selected examples of studies which evaluated OS biomarkers in patients with diabetes, pointing to the relevance of such biological components in general oxidative stress status of diabetes mellitus carriers.

ACE2–angiotensin-(1–7)–Mas axis and oxidative stress in cardiovascular disease

The renin–angiotensin–aldosterone system (RAAS) is a pivotal regulator of physiological homeostasis and diseases of the cardiovascular system. Recently, new factors have been discovered, such as angiotensin-converting enzyme 2 (ACE2), angiotensin-(1–7) and Mas. This newly defined ACE2–angiotensin-(1–7)–Mas axis was shown to have a critical role in the vasculature and in the heart, exerting mainly protective effects. One important mechanism of the classic and the new RAAS regulate vascular function is through the regulation of redox signaling. Angiotensin II is a classic prooxidant peptide that increases superoxide production through the activation of NAD(P)H oxidases. This review summarizes the current knowledge about the ACE2–angiotensin-(1–7)–Mas axis and redox signaling in the context of cardiovascular regulation and disease. By interacting with its receptor Mas, angiotensin-(1–7) induces the release of nitric oxide from endothelial cells and thereby counteracts the effects of angiotensin II. ACE2 converts angiotensin II to angiotensin-(1–7) and, thus, is a pivotal regulator of the local effects of the RAAS on the vessel wall. Taken together, the ACE2–angiotensin-(1–7)–Mas axis emerges as a novel therapeutic target in the context of cardiovascular and metabolic diseases.

Characterization of blood oxidative stress in type 2 diabetes mellitus patients: increase in lipid peroxidation and SOD activity.

This study evaluated the oxidative stress through enzymatic and nonenzymatic biomarkers in diabetic patients with and without hypertension and prediabetics. The SOD and CAT (in erythrocytes) and GPx (in plasma) enzymatic activities, plasma levels of lipid peroxidation, and total thiols were measured in the blood of 55 subjects with type 2 diabetes and 38 subjects without diabetes (9 pre-diabetics and 29 controls) aged 40–86 years. The total SOD activity and the lipid peroxidation were higher in diabetics compared to nondiabetics. In stratified groups, the total SOD activity was different for the hypertensive diabetics compared to the prediabetics and normotensive controls. Lipid peroxidation was significantly higher in both groups of diabetics (hypertensive and normotensive) compared to prediabetic groups and hypertensive and normotensive controls. There was no significant difference in the CAT and GPx activities, as well as in the concentration of total thiols in the groups studied. Present data strongly suggest the involvement of oxidative stress in the pathophysiology of diabetes, revealing that the increased lipid peroxidation has a close relationship with high glucose levels, as observed by the fasting glucose and HbA1c levels. The results evidence the correlation between lipid peroxidation and DM, irrespective of the presence of hypertension.

Ablation of angiotensin (1-7) receptor Mas in C57Bl/6 mice causes endothelial dysfunction

The Mas gene codes for an angiotensin (1-7) receptor. There is accumulating evidence that Mas is involved in vascular homeostasis. We have recently backcrossed Mas-knockout mice to two different genetic backgrounds, C57Bl/6 and FVB/N. FVB/NMas-deficient mice exhibited elevation in blood pressure (BP) and impaired endothelial function. In the present study, we aimed to address the question whether this phenotype is strain-specific. Therefore, we evaluated endothelial function in C57Bl/6Mas-deficient mice. Similar to FVB/NMas-knockout animals, Mas-deficiency in C57Bl/6 mice leads to endothelial dysfunction evaluated by the acute BP effect of acetylcholine administration. Measurements of nitric oxide (NO) and reactive oxygen species (ROS) and the systems involved in their metabolism revealed an imbalance between these vasoactive factors in C57Bl/6Mas-knockout mice, which may explain the impairment of endothelial function in these animals. However, endothelial dysfunction was less prominent in Mas-deficient mice on a C57Bl/6 background compared to FVB/N. Moreover, C57Bl/6Mas-deficient mice remained normotensive while FVB/N-based animals exhibited elevated BP. The impairment of endothelium-dependent vasodilatory response to acetylcholine in two different mouse strains with Mas deficiency indicates a key role of Mas in endothelial function by its effects on the generation and metabolism of NO and ROS.

Endothelium dysfunction in LDL receptor knockout mice: a role for H2O2.

In this study, the role of endogenous H2O2 as an endothelium‐dependent relaxant factor was characterised in aortas from C57BL/6J and LDL receptor‐deficient mice (LDLR−/−). Aortic rings from LDLR−/− mice showed impaired endothelium‐dependent relaxation to acetylcholine (ACh; 0.001–100 μM) and to the Ca2+ ionophore A23187 (0.001–3 μM) compared with aortic rings from control mice. Endothelium‐independent relaxation produced by the NO donor, 3‐morpholino‐sydnonimine (SIN‐1) was not different between strains. Pretreatment of vessels with L‐NNA (100 μM) or L‐NNA (100 μM) plus L‐NAME (300 μM) plus haemoglobin (10 μM) markedly decreased, but did not abolish the relaxation to ACh in control mice. In the aortas from LDLR−/− mice treated with L‐NNA (100 μM), ACh induced a contractile effect. Catalase (800 and 2400 U ml−1) shifted to the right the endothelium‐dependent relaxation to ACh in aortas from control but not from LDLR−/− mice. Aminotriazole (50 mM), which inhibits catalase, abolished its effect on control mice. Treatment of vessels with L‐NNA and catalase abolished vasorelaxation induced by ACh. Indomethacin (10 μM) did not modify the concentration–response curve to ACh. Superoxide dismutase (300 U ml−1) did not change ACh‐induced relaxation in both strains. Exogenous H2O2 produced a concentration‐dependent relaxation in endothelium‐denuded aortic rings, which was not different between strains. It is concluded that H2O2 greatly contributes to relaxation to ACh in aorta from control mice. Endothelial‐dependent relaxation to ACh is impaired in LDLR−/− mice. Reduced biosynthesis or increased inactivation of H2O2 is the possible mechanism responsible for endothelial dysfunction in aortas of atherosclerosis‐susceptible LDLR−/− mice.

Antioxidant and Cytotoxic Activity of Hydroethanolic Extract from Jacaranda decurrens Leaves

Background and Purpose Leaves of Jacaranda decurrens are used in traditional Brazilian medicine to treat metabolic diseases related to increased reactive oxygen species. The present study evaluated the antioxidant and cytotoxic potential of hydroethanolic extract from the leaves of Jacaranda decurrens subsp. symmetrifoliolata. Experimental Approach Phenolic compounds, flavonoids and saponins were evaluated in an ethanol∶water (80∶20, v/v) extract from the leaves of Jacaranda decurrens subsp. symmetrifoliolata (E-Jds). The antioxidant activity of E-Jds was investigated by assessing the following: 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging activity; protection against 2,2′-azobis (2-amidinopropane) dihydrochloride (AAPH)-induced hemolysis of erythrocytes; in vitro and in vivo malondialdehyde dosage; and the ability to activate antioxidant enzymes. K562 leukemia cells were used for the cytotoxic evaluation of E-Jds and for the assessment of the cell death profile through flow cytometry. Key Results Phenolic and flavonoid compounds were quantified as 14.38% and 2.15%, respectively, of E-Jds. These phenolic and flavonoid compounds proved to be able to scavenge DPPH free radicals with an IC50 of 9.3±3.3 µg/mL, to protect up to 50% of erythrocytes against AAPH-induced hemolysis and to reduce in vitro and in vivo malondialdehyde levels up to 84% and 22%, respectively. E-Jds also increased glutathione peroxidase enzyme activity, with a concomitant decrease in superoxide dismutase and catalase activity, and exhibited dose-dependent cytotoxic activity on K562 erythroleukemia cells with cell death occurring via both late apoptosis and necrosis. Conclusions E-Jds exhibits in vitro and in vivo antioxidant potential, which may be the mechanism mediating the metabolic activities reported in folk medicine. Furthermore, the cytotoxic activity identified in this study contributes with the knowledge of antiproliferative activities that have been described in the literature for the genus Jacaranda.

Aging Increases Susceptibility to High Fat Diet-Induced Metabolic Syndrome in C57BL/6 Mice: Improvement in Glycemic and Lipid Profile after Antioxidant Therapy

Nonalcoholic fatty liver disease (NAFLD) has been considered a novel component of the metabolic syndrome (MetS), with the oxidative stress participating in its progression. This study aimed to evaluate the metabolic profile in young and old mice with MetS, and the effects of apocynin and tempol on glycemic and lipid parameters. Young and old C57BL/6 mice with high fat diet- (HFD-) induced MetS received apocynin and tempol 50 mg·kg−1/day in their drinking water for 10 weeks. After HFD, the young group showed elevated fasting glucose, worsened lipid profile in plasma, steatosis, and hepatic lipid peroxidation. Nevertheless, the old group presented significant increase in fasting insulin levels, insulin resistance, plasma and hepatic lipid peroxidation, and pronounced steatosis. The hepatic superoxide dismutase and catalase activity did not differ between the groups. Tempol and apocynin seemed to prevent hepatic lipid deposition in both groups. Furthermore, apocynin improved glucose tolerance and insulin sensitivity in old mice. In summary, old mice are more susceptible to HFD-induced metabolic changes than their young counterparts. Also, the antioxidant therapy improved insulin sensitivity and glucose tolerance, and in addition, apocynin seemed to prevent the HFD-induced hepatic fat deposition, suggesting an important role of oxidative stress in the induction of NAFLD.

Redox unbalance: NADPH oxidase as therapeutic target in blood pressure control

Several studies refer to reactive oxygen and nitrogen species (RONS) as important agents in the pathogenesis of a number of heart diseases, including high blood pressure, arteriosclerosis and heart failure. Such species are highly bioactive molecules and a short life due chiefly to reduction of molecular oxygen. The enzyme complex of NADPH oxidase is the main source of these reactive species in vascular system. Under physiological conditions, formation and elimination of these substances seem balanced in vascular wall. During redox Unbalance, nonetheless, there is increase in NADPH oxidase activity and predominance of pro-oxidizing agents, surpassing the anti-oxidant capacity of the organism self-defense. Besides this, such enzyme hyperactivity reduces the bioavailability of nitric oxide, capital for vasodilation and maintenance of normal vascular function. In spite of NADPH oxidase being directly connected to the endothelial dysfunction, it was firstly described as for its expression in phagocytes, where its activity determines efficiency of organism defense mechanisms against pathogens. Slight differences between structural units of NADPH oxidases, depending on the type of cell which expresses it, may create therapeutic implications, allowing to selectively inhibiting redox unbalance triggered by NADPH oxidase, without compromising, however, its participation in physiological cellular signaling which make sure protection against micro-organisms.Varios estudos destacam as especies reativas de oxigenio e nitrogenio (ERONs) como importantes contribuintes na patogenese de numerosas doencas cardiovasculares, incluindo hipertensao, aterosclerose e falencia cardiaca. Tais especies sao moleculas altamente bioativas e com vida curta derivadas, principalmente, da reducao do oxigenio molecular. O complexo enzimatico da NADPH oxidase e a maior fonte dessas especies reativas na vasculatura. Sob condicoes fisiologicas, a formacao e eliminacao destas substâncias aparecem balanceadas na parede vascular. Durante o desbalanco redox, entretanto, ha um aumento na atividade da NADPH oxidase e predominio de agentes pro-oxidantes, superando a capacidade de defesa orgânica antioxidante. Alem disso, tal hiperatividade enzimatica reduz a biodisponibilidade do oxido nitrico, crucial para a vasodilatacao e a manutencao da funcao vascular normal. Apesar de a NADPH oxidase relacionar-se diretamente a disfuncao endotelial, foi primeiramente descrita por sua expressao em fagocitos, onde sua atividade determina a eficacia dos mecanismos de defesa orgânica contra patogenos. As sutis diferencas existentes entre as unidades estruturais das NADPH oxidases, a depender do tipo celular que as expressa, podem ter implicacoes terapeuticas, permitindo a inibicao seletiva do desequilibrio redox induzido pela NADPH oxidase, sem comprometer, entretanto, sua participacao nas vias fisiologicas de sinalizacao celular que garantem a protecao contra microorganismos.

Desbalanço redox: NADPH oxidase como um alvo terapêutico no manejo cardiovascular

Several studies refer to reactive oxygen and nitrogen species (RONS) as important agents in the pathogenesis of a number of heart diseases, including high blood pressure, arteriosclerosis and heart failure. Such species are highly bioactive molecules and a short life due chiefly to reduction of molecular oxygen. The enzyme complex of NADPH oxidase is the main source of these reactive species in vascular system. Under physiological conditions, formation and elimination of these substances seem balanced in vascular wall. During redox Unbalance, nonetheless, there is increase in NADPH oxidase activity and predominance of pro-oxidizing agents, surpassing the anti-oxidant capacity of the organism self-defense. Besides this, such enzyme hyperactivity reduces the bioavailability of nitric oxide, capital for vasodilation and maintenance of normal vascular function. In spite of NADPH oxidase being directly connected to the endothelial dysfunction, it was firstly described as for its expression in phagocytes, where its activity determines efficiency of organism defense mechanisms against pathogens. Slight differences between structural units of NADPH oxidases, depending on the type of cell which expresses it, may create therapeutic implications, allowing to selectively inhibiting redox unbalance triggered by NADPH oxidase, without compromising, however, its participation in physiological cellular signaling which make sure protection against micro-organisms.Varios estudos destacam as especies reativas de oxigenio e nitrogenio (ERONs) como importantes contribuintes na patogenese de numerosas doencas cardiovasculares, incluindo hipertensao, aterosclerose e falencia cardiaca. Tais especies sao moleculas altamente bioativas e com vida curta derivadas, principalmente, da reducao do oxigenio molecular. O complexo enzimatico da NADPH oxidase e a maior fonte dessas especies reativas na vasculatura. Sob condicoes fisiologicas, a formacao e eliminacao destas substâncias aparecem balanceadas na parede vascular. Durante o desbalanco redox, entretanto, ha um aumento na atividade da NADPH oxidase e predominio de agentes pro-oxidantes, superando a capacidade de defesa orgânica antioxidante. Alem disso, tal hiperatividade enzimatica reduz a biodisponibilidade do oxido nitrico, crucial para a vasodilatacao e a manutencao da funcao vascular normal. Apesar de a NADPH oxidase relacionar-se diretamente a disfuncao endotelial, foi primeiramente descrita por sua expressao em fagocitos, onde sua atividade determina a eficacia dos mecanismos de defesa orgânica contra patogenos. As sutis diferencas existentes entre as unidades estruturais das NADPH oxidases, a depender do tipo celular que as expressa, podem ter implicacoes terapeuticas, permitindo a inibicao seletiva do desequilibrio redox induzido pela NADPH oxidase, sem comprometer, entretanto, sua participacao nas vias fisiologicas de sinalizacao celular que garantem a protecao contra microorganismos.