Heraldo Possolo de Souza

Oxidative stress as a signaling mechanism of the vascular response to injury: the redox hypothesis of restenosis.

The prominent role of redox processes in tissue injury and in vascular cell signaling suggest their involvement in the repair reaction to vessel injury, which is a key determinant of restenosis post-angioplasty. Experimental studies showed a protective effect of superoxide dismutase or antioxidants on vasospasm, neointimal thickening or remodeling after balloon injury. It was also shown that oxidized thiols induce chelatable metal-dependent amplification of the vascular repair reaction. Ongoing or completed clinical trials show a promising effect of the antioxidant probucol against restenosis. However, few studies addressed the molecular physiological mechanisms underlying the redox hypothesis of restenosis. We recently showed evidence for marked oxidative stress early after balloon injury, with superoxide production mediated primarily by non-endothelial NAD(P)H oxidase-type flavoenzyme(s). This effect was closely related to the degree of injury. There is evidence supporting a role for such early redox processes in apoptotic cell loss and NF-kappa B activation. We present new data on the time course of oxidative stress after balloon injury of intact rabbit iliac arteries. Our data show that despite substantial neointimal growth and lumen narrowing, superoxide production and glutathione levels are unaltered at day 14 and 28 after balloon injury. At day 7 after injury, the peak neointimal proliferation in this model, there was significant decrease of vascular superoxide dismutase activity, without clear evidence of spontaneous superoxide production. Thus, oxidative stress after injury is likely to be an early transient event, which parallels the inflammatory and proliferative phases of the vascular response. We propose that such early redox processes act as dose-dependent signal transducers of gene programs that affect the final repair.

Vascular oxidant stress early after balloon injury: evidence for increased NAD(P)H oxidoreductase activity.

Available evidence for oxidative stress after angioplasty is indirect or ambiguous. We sought to characterize the pattern, time course, and possible sources of free radical generation early after arterial balloon injury. Ex vivo injury performed in arterial rings in buffer with lucigenin yielded a massive oxygen-dependent peak of luminescence that decayed exponentially and was proportional to the degree of injury. Signals for injured vs. control arteries were 207. 1 +/- 17.9 (n = 13) vs 4.1 +/- 0.7 (n = 22) cpm x 10(3)/mg/min (p <. 001). Data obtained with 0.25 mmol/l lucigenin were validated with 0. 005-0.05 mmol/l lucigenin or the novel superoxide-sensitive probe coelenterazine (5 micromol/l). Gentle removal of endothelium prior to injury scarcely affected the amount of luminescence. Lucigenin signals were amplified 5- to 20-fold by exogenous NAD(P)H, and were >85% inhibited by diphenyliodonium (DPI, a flavoenzyme inhibitor). Antagonists of several other potential free radical sources, including xanthine oxidase, nitric oxide synthase, and mitochondrial electron transport, were without effect. Overdistension of intact rabbit iliac arteries in vivo (n = 7) induced 72% fall in intracellular reduced glutathione and 68% increase in oxidized glutathione, so that GSH/GSSG ratio changed from 7.93 +/- 2.14 to 0. 81 +/- 0.16 (p <.005). There was also 28.7% loss of the glutathione pool. Further studies were performed with electron paramagnetic resonance spectroscopy. Rabbit aortas submitted to ex vivo overdistension in the presence of the spin trap DEPMPO (5-diethoxy-phosphoryl-5-methyl-1-pyrroline-N-oxide, 100 mmol/l, n = 5) showed formation of radical adduct spectra, abolished by DPI or superoxide dismutase. Computer simulation indicated a mixture of hydroxyl and carbon-centered radical adducts, likely due to decay of superoxide adduct. Electrical mobility shift assays for NF-kappaB activation were performed in nuclear protein extracts from intact or previously injured rabbit aortas. Balloon injury induced early NF-kappaB activation, which was decreased by DPI. In conclusion, our data show unambiguously that arterial injury induces an immediate profound vascular oxidative stress. Such redox imbalance is likely accounted for by activation of vessel wall NAD(P)H oxidoreductase(s), generating radical species potentially involved in tissue repair.

Liver mitochondrial dysfunction and oxidative stress in the pathogenesis of experimental nonalcoholic fatty liver disease

Oxidative stress and hepatic mitochondria play a role in the pathogenesis of nonalcoholic fatty liver disease. The aim of the present study was to evaluate the role of hepatic mitochondrial dysfunction and oxidative stress in the pathogenesis of the disease. Fatty liver was induced in Wistar rats with a choline-deficient diet (CD; N = 7) or a high-fat diet enriched with PUFAs-omega-3 (H; N = 7) for 4 weeks. The control group (N = 7) was fed a standard diet. Liver mitochondrial oxidation and phosphorylation were measured polarographically and oxidative stress was estimated on the basis of malondialdehyde and glutathione concentrations. Moderate macrovacuolar liver steatosis was observed in the CD group and mild liver steatosis was observed in the periportal area in the H group. There was an increase in the oxygen consumption rate by liver mitochondria in respiratory state 4 (S4) and a decrease in respiratory control rate (RCR) in the CD group (S4: 32.70 +/- 3.35; RCR: 2.55 +/- 0.15 ng atoms of O2 min-1 mg protein-1) when compared to the H and control groups (S4: 23.09 +/- 1.53, 17.04 +/- 2.03, RCR: 3.15 +/- 0.15, 3.68 +/- 0.15 ng atoms of O2 min-1 mg protein-1, respectively), P < 0.05. Hepatic lipoperoxide concentrations were significantly increased and the concentration of reduced glutathione was significantly reduced in the CD group. A choline-deficient diet causes moderate steatosis with disruption of liver mitochondrial function and increased oxidative stress. These data suggest that lipid peroxidation products can impair the flow of electrons along the respiratory chain, causing overreduction of respiratory chain components and enhanced mitochondrial reactive oxygen species. These findings are important in the pathogenesis of nonalcoholic fatty liver disease.

Low-Level Laser Therapy (808 nm) Reduces Inflammatory Response and Oxidative Stress in Rat Tibialis Anterior Muscle After Cryolesion

Muscle regeneration is a complex phenomenon, involving coordinated activation of several cellular responses. During this process, oxidative stress and consequent tissue damage occur with a severity that may depend on the intensity and duration of the inflammatory response. Among the therapeutic approaches to attenuate inflammation and increase tissue repair, low‐level laser therapy (LLLT) may be a safe and effective clinical procedure. The aim of this study was to evaluate the effects of LLLT on oxidative/nitrative stress and inflammatory mediators produced during a cryolesion of the tibialis anterior (TA) muscle in rats.

Low level laser therapy increases angiogenesis in a model of ischemic skin flap in rats mediated by VEGF, HIF-1α and MMP-2

It is known that low level laser therapy is able to improve skin flap viability by increasing angiogenesis. However, the mechanism for new blood vessel formation is not completely understood. Here, we investigated the effects of 660 nm and 780 nm lasers at fluences of 30 and 40 J/cm(2) on three important mediators activated during angiogenesis. Sixty male Wistar rats were used and randomly divided into five groups with twelve animals each. Groups were distributed as follows: skin flap surgery non-irradiated group as a control; skin flap surgery irradiated with 660 nm laser at a fluence of 30 or 40 J/cm(2) and skin flap surgery irradiated with 780 nm laser at a fluence of 30 or 40 J/cm(2). The random skin flap was performed measuring 10×4 cm, with a plastic sheet interposed between the flap and the donor site. Laser irradiation was performed on 24 points covering the flap and surrounding skin immediately after the surgery and for 7 consecutive days thereafter. Tissues were collected, and the number of vessels, angiogenesis markers (vascular endothelial growth factor, VEGF and hypoxia inducible factor, HIF-1α) and a tissue remodeling marker (matrix metalloproteinase, MMP-2) were analyzed. LLLT increased an angiogenesis, HIF-1α and VEGF expression and decrease MMP-2 activity. These phenomena were dependent on the fluences, and wavelengths used. In this study we showed that LLLT may improve the healing of skin flaps by enhancing the amount of new vessels formed in the tissue. Both 660 nm and 780 nm lasers were able to modulate VEGF secretion, MMP-2 activity and HIF-1α expression in a dose dependent manner.

Obesidade e doença arterial coronariana: papel da inflamação vascular

A obesidade vem se tornando uma epidemia global. Cerca de 1,1 bilhoes de adultos e 10% das criancas do mundo sao atualmente considerados portadores de sobrepeso ou obesos. Classicamente associada a fatores de risco para doenca cardiovascular, como diabete melito e hipertensao arterial sistemica, a obesidade vem sendo cada vez mais encarada como fator de risco independente para doenca arterial coronariana (DAC). A aterosclerose coronariana compreende uma serie de respostas inflamatorias em nivel celular e molecular, cujas reacoes se encontram mais exacerbadas em pacientes obesos. Antes considerado mero deposito de gordura, o tecido adiposo e visto hoje em dia como orgao endocrino e paracrino ativo, produtor de diversas citocinas inflamatorias, como as adipocinas. Este artigo visa alertar para o grave problema de saude publica em que a obesidade se tornou nas ultimas decadas e correlacionar o processo inflamatorio exacerbado nos individuos obesos com a maior incidencia de DAC nessa populacao.Obesity is becoming a global epidemic. Around 1.1 billion adults and 10% of the worlds children are currently overweight or considered obese. Generally associated with risk factors for cardiovascular disease, such as Diabetes Mellitus and systemic arterial high blood pressure, the obesity has been more and more seen as an independent risk factor for Coronary Artery Disease (CAD). Coronary arteriosclerosis comprises a series of inflammatory responses at cellular and molecular level, whose reactions are stronger in obese patients. In the past, the adipose tissue was regarded as a mere fat deposition. Now it is seen from a totally different standpoint, as an active endocrine and paracrine organ that produces several inflammatory cytokines, such as the adipokines. This article aims to raise awareness about obesity as an increasingly significant public health issue over the past decades, as well as to relate the intense inflammatory process in obese individuals with an increased tendency for this group of individuals to develop CAD.

A TRβ-selective agonist confers resistance to diet-induced obesity

Thyroid hormone receptor beta (TRbeta also listed as THRB on the MGI Database)-selective agonists activate brown adipose tissue (BAT) thermogenesis, while only minimally affecting cardiac activity or lean body mass. Here, we tested the hypothesis that daily administration of the TRbeta agonist GC-24 prevents the metabolic alterations associated with a hypercaloric diet. Rats were placed on a high-fat diet and after a month exhibited increased body weight (BW) and adiposity, fasting hyperglycemia and glucose intolerance, increased plasma levels of triglycerides, cholesterol, nonesterified fatty acids and interleukin-6. While GC-24 administration to these animals did not affect food ingestion or modified the progression of BW gain, it did increase energy expenditure, eliminating the increase in adiposity without causing cardiac hypertrophy. Fasting hyperglycemia remained unchanged, but treatment with GC-24 improved glucose tolerance by increasing insulin sensitivity, and also normalized plasma triglyceride levels. Plasma cholesterol levels were only partially normalized and liver cholesterol content remained high in the GC-24-treated animals. Gene expression in liver, skeletal muscle, and white adipose tissue was only minimally affected by treatment with GC-24, with the main target being BAT. In conclusion, during high-fat feeding treatment with the TRbeta-selective agonist, GC-24 only partially improves metabolic control probably as a result of accelerating the resting metabolic rate.

[37] Redox aspects of vascular response to injury

Publisher Summary The chapter discusses some specific aspects of vascular injury models and procedures for the assessment of reactive oxygen species (ROS), particularly superoxide, and NAD (P)H oxidase activity at different time points after vascular injury. Vascular response to injury displays all biological processes typical of vascular pathophysiology and thus, constitutes a relevant model for many vascular diseases. Simple de-endothelialization is useful to assess interactions between platelets and the vessel wall or as a means of creating a localized atherosclerotic plaque developed through hyperlipidemic diet. Redox signaling involves oxidizing or reducing electron transfer reactions mediated by independent intermediates such as free radicals, reducing equivalents, or metals, production of ROS as second messengers is the hallmark of redox signaling. A number of vascular injury models in mice have been described, which are useful with the caveat that they may involve peculiar mechanisms. Oxidant stress with superoxide production likely, because of the activation of NAD(P)H oxidase(s) can be documented after vascular injury. These alterations are prominent immediately after injury and are sustained to some undetermined extent throughout the vascular repair. The later stages of neointima formation appear to be associated with an absence or low levels of oxidative stress.

Obesity and coronary artery disease: role of vascular inflammation

A obesidade vem se tornando uma epidemia global. Cerca de 1,1 bilhoes de adultos e 10% das criancas do mundo sao atualmente considerados portadores de sobrepeso ou obesos. Classicamente associada a fatores de risco para doenca cardiovascular, como diabete melito e hipertensao arterial sistemica, a obesidade vem sendo cada vez mais encarada como fator de risco independente para doenca arterial coronariana (DAC). A aterosclerose coronariana compreende uma serie de respostas inflamatorias em nivel celular e molecular, cujas reacoes se encontram mais exacerbadas em pacientes obesos. Antes considerado mero deposito de gordura, o tecido adiposo e visto hoje em dia como orgao endocrino e paracrino ativo, produtor de diversas citocinas inflamatorias, como as adipocinas. Este artigo visa alertar para o grave problema de saude publica em que a obesidade se tornou nas ultimas decadas e correlacionar o processo inflamatorio exacerbado nos individuos obesos com a maior incidencia de DAC nessa populacao.Obesity is becoming a global epidemic. Around 1.1 billion adults and 10% of the worlds children are currently overweight or considered obese. Generally associated with risk factors for cardiovascular disease, such as Diabetes Mellitus and systemic arterial high blood pressure, the obesity has been more and more seen as an independent risk factor for Coronary Artery Disease (CAD). Coronary arteriosclerosis comprises a series of inflammatory responses at cellular and molecular level, whose reactions are stronger in obese patients. In the past, the adipose tissue was regarded as a mere fat deposition. Now it is seen from a totally different standpoint, as an active endocrine and paracrine organ that produces several inflammatory cytokines, such as the adipokines. This article aims to raise awareness about obesity as an increasingly significant public health issue over the past decades, as well as to relate the intense inflammatory process in obese individuals with an increased tendency for this group of individuals to develop CAD.

Prevention and Reversion of Nonalcoholic Steatohepatitis in OB/OB Mice by S-Nitroso-N-Acetylcysteine Treatment

Objective: To evaluate the role oral administration of S-nitroso-N-acetylcysteine (SNAC), a NO donor drug, in the prevention and reversion of NASH in two different animal models. Methods: NASH was induced in male ob/ob mice by methionine-choline deficient (MCD) and high-fat (H) diets. Two animal groups received or not SNAC orally for four weeks since the beginning of the treatment. Two other groups were submitted to MCD and H diets for 60 days receiving SNAC only from the 31st to the 60th day. Results: SNAC administration inhibited the development of NASH in all groups, leading to a marked decrease in macro and microvacuolar steatosis and in hepatic lipid peroxidation in the MCD group. SNAC treatment reversed the development of NASH in animals treated for 60 days with MCD or H diets, which received SNAC only from the 31st to the 60th day. Conclusions: Oral administration of SNAC markedly inhibited and reversed NASH induced by MCD and H diets in ob/ob mice.