Nuclear factor erythroid 2-related factor 2 and autophagy regulation in cancer development.

Nuclear factor erythroid 2-related factor 2 (Nrf2) mitigates cell damage due to stress, environmental xenobiotics, and toxic chemicals. Nrf2 is present in the cytoplasm bound to its cysteine-rich Kelch domain-containing partner, Kelch-like ECH-associated protein 1 (Keap1), where is ubiquitinated and degraded. In addition to inducers that disrupt the Keap1-Nrf2 complex, defective autophagy has recently been shown to upregulate endogenous p62, which interacts with Keap1 triggering transcriptional activation of Nrf2 in several cancers. This regulation by Nrf2-dependent transactivation of cytoprotective genes needs to be validated by clinical trials in view of its persistent activation in a p62-dependent manner when there is deregulation of autophagy.

Measurement of Reactive Oxygen and Nitrogen Species in Living Cells Using the Probe 2',7'-Dichlorodihydrofluorescein.

Reactive oxygen species and reactive nitrogen species (RONS) are involved in programmed cell death in the context of numerous degenerative and chronic diseases. In particular, the ability of cells to maintain redox homeostasis is necessary for an adaptive cellular response to adverse conditions that can cause damage to proteins and DNA, resulting in apoptosis and genetic mutations. Here, we focus on the 2',7'-dichlorodihydrofluorescein diacetate (DCFH2-DA) assay to detect RONS. Although this fluorescence-based assay is widely utilized due to its high sensitivity to detect changes in cellular redox status that allow measuring alterations in RONS over time, its validity has been a matter of controversy. If correctly carried out, its limitations are understood and results are correctly interpreted, the DCFH2-DA assay is a valuable tool for cell-based studies.

Mitochondrial oxidative injury: a key player in nonalcoholic fatty liver disease.

Nonalcoholic fatty liver disease (NAFLD) has become the most prevalent liver disease worldwide. NAFLD is tightly linked to the metabolic syndrome, insulin resistance, and oxidative stress. Globally, its inflammatory form, nonalcoholic steatohepatitis (NASH), has become the main cause of liver-related morbidity and mortality, mainly due to liver cirrhosis and primary liver cancer. One hallmark of NASH is the presence of changes in mitochondrial morphology and function that are accompanied by a blocked flow of electrons in the respiratory chain, which increases formation of mitochondrial reactive oxygen species in a self-perpetuating vicious cycle. Consequences are oxidation of DNA bases and mitochondrial DNA depletion that are coupled with genetic and acquired mitochondrial DNA mutations, all impairing the resynthesis of respiratory chain polypeptides. In general, several maladaptations of pathways that usually maintain energy homeostasis occur with the early and late excess metabolic stress in NAFLD and NASH. We discuss the interplay between hepatocyte mitochondrial stress and inflammatory responses, focusing primarily on events initiated and maintained by mitochondrial free radical-induced damage in NAFLD. Importantly, mitochondrial oxidative stress and dysfunction are modulated by key pharmacological targets that are related to excess production of reactive oxygen species, mitochondrial turnover and the mitochondrial unfolded protein response, mitophagy, and mitochondrial biogenesis. However, the efficacy of such interventions depends on NAFLD/NASH disease stage.

Intestinally derived bacterial products stimulate development of nonalcoholic steatohepatitis.

Fatty livers are susceptible to factors that cause inflammation and fibrosis, but fat deposition and the inflammatory response can be dissociated. While nonalcoholic fatty liver disease (NAFLD), caused by pathologic fat accumulation inside the liver, can remain stable for several years, in other cases NAFLD progresses to nonalcoholic steatohepatitis (NASH), which is characterized by fat accumulation and inflammation and is not a benign condition. In this review, we discuss the NASH host cells and microbial mechanisms that stimulate inflammation and predispose the liver to hepatocyte injury and fibrotic stages via increased lipid deposition. We highlight the interactions between intestine-derived bacterial products, such as lipopolysaccharide, and nutritional models of NAFLD and/or obese individuals. The results of modulating enteric microbiota suggest that gut-derived endotoxins may be essential determinants of fibrotic progression and regression in NASH.

Endotoxin regulates matrix genes increasing reactive oxygen species generation by intercellular communication between palmitate-treated hepatocyte and stellate cell.

Previous studies have shown that gut-derived bacterial endotoxins contribute in the progression of simple steatosis to steatohepatitis, although the mechanism(s) remains inaccurate to date. As hepatic stellate cells (HSC) play a pivotal role in the accumulation of excessive extracellular matrix (ECM), leading to collagen deposition, fibrosis, and perpetuation of inflammatory response, an in vitro model was developed to investigate the crosstalk between HSC and hepatocytes (human hepatoma cell) pretreated with palmitate. Bacterial lipopolysaccharide (LPS) stimulated HSC with phosphorylation of the p38 mitogen-activated protein kinase/NF-κB pathway, while several important pro-inflammatory cytokines were upregulated in the presence of hepatocyte-HSC. Concurrently, fibrosis-related genes were regulated by palmitate and the inflammatory effect of endotoxin where cells were more exposed or sensitive to reactive oxygen species (ROS). This interaction was accompanied by increased expression of the mitochondrial master regulator, proliferator-activated receptor gamma coactivator alpha, and a cytoprotective effect of the agent N-acetylcysteine suppressing ROS production, transforming growth factor-ß1, and tissue inhibitor of metalloproteinase-1. In summary, our results demonstrate that pro-inflammatory mediators LPS-induced promote ECM rearrangement in hepatic cells transcriptionally committed to the regulation of genes encoding enzymes for fatty acid metabolism in light of differences that might require an alternative therapeutic approach targeting ROS regulation.

Oxidative stress causes hypertension and activation of nuclear factor-κB after high-fructose and salt treatments.

There is evidence that diets rich in salt or simple sugars as fructose are associated with abnormalities in blood pressure regulation. However, the mechanisms underlying pathogenesis of salt- and fructose-induced kidney damage and/or consequent hypertension yet remain largely unexplored. Here, we tested the role of oxidative state as an essential factor along with high salt and fructose treatment in causing hypertension. Fischer male rats were supplemented with a high-fructose diet (20% in water) for 20 weeks and maintained on high-salt diet (8%) associate in the last 10 weeks. Fructose-fed rats exhibited a salt-dependent hypertension accompanied by decrease in renal superoxide dismutase activity, which is the first footprint of antioxidant inactivation by reactive oxygen species (ROS). Metabolic changes and the hypertensive effect of the combined fructose-salt diet (20 weeks) were markedly reversed by a superoxide scavenger, Tempol (10 mg/kg, gavage); moreover, Tempol (50 mM) potentially reduced ROS production and abolished nuclear factor-kappa B (NF-κB) activation in human embryonic kidney HEK293 cells incubated with L-fructose (30 mM) and NaCl (500 mosmol/kg added). Taken together, our data suggested a possible role of oxygen radicals and ROS-induced activation of NF-κB in the fructose- and salt-induced hypertension associated with the progression of the renal disease.

Health implications of high-fructose intake and current research.

Although fructose consumption has dramatically increased and is suspected to be causally linked to metabolic abnormalities, the mechanisms involved are still only partially understood. We discuss the available data and investigate the effects of dietary fructose on risk factors associated with metabolic disorders. The evidence suggests that fructose may be a predisposing cause in the development of insulin resistance in association with the induction of hypertriglyceridemia. Experiments in animals have shown this relation when they are fed diets very high in fructose or sucrose, and human studies also show this relation, although with conflicting results due to the heterogeneity of the studies. The link between increased fructose consumption and increases in uric acid also has been confirmed as a potential risk factor for metabolic syndrome, and insulin resistance/hyperinsulinemia may be causally related to the development of hypertension. Collectively, these results suggest a link between high fructose intake and insulin resistance, although future studies must be of reasonable duration, use defined populations, and improve comparisons regarding the effects of relevant doses of nutrients on specific endpoints to fully understand the effect of fructose intake in the absence of potential confounding factors.

Efficacy of the superoxide dismutase mimetic tempol in animal hypertension models: a meta-analysis.

OBJECTIVE: Considering the growing body of evidence that indicates the contribution of superoxide anions (O2) and other reactive oxygen species (ROS) to the development of hypertension, we assessed whether animal models of hypertension have a benefic effect with tempol, a superoxide dismutase mimetic, to help augment the design of future studies. METHODS: Studies published between July 1998 and December 2012 on blood pressure (BP) in different hypertensive models were obtained after an electronic and manual search of PubMed. In-depth analyses of the methodological quality of the studies and the mean arterial pressure (MAP) changes after treatment with tempol were performed, as well as the subgroup analyses on the route of tempol delivery. RESULTS: Out of the 144 identified studies, 28 were included after screening. The data showed that tempol reduced MAP by computing the standardized mean difference with the value of 4.622 (95% confidence interval 3.24-5.99). The quality of studies included in the meta-analysis was category II; however, omission of details in the trials might have biased the results. There was substantial heterogeneity in the results with an I of 94.45%, which persisted after stratifying for the route of tempol delivery. CONCLUSION: In conclusion, this analysis shows that antioxidant treatment with tempol can reduce BP, suggesting that ROS plays a role in the pathogenesis of increased BP in the hypertension models used in the current research practice.

Iron toxicity mediated by oxidative stress enhances tissue damage in an animal model of diabetes.

Although iron is a first-line pro-oxidant that modulates clinical manifestations of various systemic diseases, including diabetes, the individual tissue damage generated by active oxidant insults has not been demonstrated in current animal models of diabetes. We tested the hypothesis that oxidative stress is involved in the severity of the tissues injury when iron supplementation is administered in a model of type 1 diabetes. Streptozotocin (Stz)-induced diabetic and non-diabetic Fischer rats were maintained with or without a treatment consisting of iron dextran ip at 0.1 mL day(-1) doses administered for 4 days at intervals of 5 days. After 3 weeks, an extensive increase (p < 0.001) in the production of reactive oxygen species (ROS) in neutrophils of the diabetic animals on iron overload was observed. Histological analysis revealed that this treatment also resulted in higher (p < 0.05) tissue iron deposits, a higher (p < 0.001) number of inflammatory cells in the pancreas, and apparent cardiac fibrosis, as shown by an increase (p < 0.05) in type III collagen levels, which result in dysfunctional myocardial. Carbonyl protein modification, a marker of oxidative stress, was consistently higher (p < 0.01) in the tissues of the iron-treated rats with diabetes. Moreover, a significant positive correlation was found between ROS production and iron pancreas stores (r = 0.42, p < 0.04), iron heart stores (r = 0.54, p < 0.04), and change of the carbonyl protein content in pancreas (r = 0.49, p < 0.009), and heart (r = 0.48, p < 0.02). A negative correlation was still found between ROS production and total glutathione content in pancreas (r = -0.50, p < 0.03) and heart (r = -0.45, p < 0.04). In conclusion, our results suggest that amplified toxicity in pancreatic and cardiac tissues in rats with diabetes on iron overload might be attributed to increased oxidative stress.

High dietary salt decreases antioxidant defenses in the liver of fructose-fed insulin-resistant rats.

In this study we investigated the hypothesis that a high-salt diet to hyperinsulinemic rats might impair antioxidant defense owing to its involvement in the activation of sodium reabsorption to lead to higher oxidative stress. Rats were fed a standard (CON), a high-salt (HS), or a high-fructose (HF) diet for 10 weeks after which, 50% of the animals belonging to the HF group were switched to a regimen of high-fructose and high-salt diet (HFS) for 10 more weeks, while the other groups were fed with their respective diets. Animals were then euthanized and their blood and liver were examined. Fasting plasma glucose was found to be significantly higher (approximately 50%) in fructose-fed rats than in the control and HS rats, whereas fat liver also differed in these animals, producing steatosis. Feeding fructose-fed rats with the high-salt diet triggered hyperinsulinemia and lowered insulin sensitivity, which led to increased levels of serum sodium compared to the HS group. This resulted in membrane perturbation, which in the presence of steatosis potentially enhanced hepatic lipid peroxidation, thereby decreasing the level of antioxidant defenses, as shown by GSH/GSSG ratio (HFS rats, 7.098±2.1 versus CON rats, 13.2±6.1) and superoxide dismutase (HFS rats, 2.1±0.05 versus CON rats, 2.3±0.1%), and catalase (HFS rats, 526.6±88.6 versus CON rats, 745.8±228.7 U/mg ptn) activities. Our results indicate that consumption of a salt-rich diet by insulin-resistant rats may lead to regulation of sodium reabsorption, worsening hepatic lipid peroxidation associated with impaired antioxidant defenses.

Salt overload in fructose-fed insulin-resistant rats decreases paraoxonase-1 activity.

Paraoxonase 1 (PON1) is a HDL-associated esterase/lactonase and its activity is inversely related to the risk of cardiovascular diseases. The aim of the present study was to evaluate the effect of a high-salt diet on serum PON1 activity in fructose-fed insulin-resistant rats. Adult male Fischer rats were initially divided into two groups. Control (CON), which received a normal salt diet and drinking water throughout the study; high fructose (HF), which received a normal salt diet and 20% fructose supplemented drinking water. After 10 weeks, half of the animals from HF group were randomly switched to a high-salt diet and 20% fructose supplemented drinking water (HFS) for more 10 weeks. Serum PON1 activity was determined by synthetic substrate phenyl acetate. HFS rats showed markedly decreased PON1 activity (HFS rats, 44.3 ± 14.4 g/dL versus CON rats, 64.4 ± 13.3 g/dL, P < 0.05) as compared to controls. In parallel, the level of oxidative stress, as indicated by thiobarbituric acid reactive substances (TBARS), was increased in HFS rats by 1.2-fold in the liver in relation to controls and was negatively correlated with PON activity. Differential leukocyte counts in blood showed a significant change in lymphocytes and monocytes profile. In conclusion, these results show that PON1 activity is decreased in fructose-fed insulin-resistant rats on a high-salt diet, which may be associated with increased oxidative stress, leading to inflammation.

Animal models for the study of arterial hypertension.

Hypertension is one of the leading causes of disability or death due to stroke, heart attack and kidney failure. Because the etiology of essential hypertension is not known and may be multifactorial, the use of experimental animal models has provided valuable information regarding many aspects of the disease, which include etiology, pathophysiology, complications and treatment. The models of hypertension are various, and in this review, we provide a brief overview of the most widely used animal models, their features and their importance.

Exercício físico e diabetes mellitus tipo 2 / Physical exercise and type 2 diabetes mellitus (exercise and diabetes)

Um estilo de vida sedentário deve ser considerado um importante fator de risco capaz de ser modificado para indivíduos com diabetes mellitus (DM) tipo 2, já que atividade física regular oferece múltiplos benefícios que incluem melhora da sensibilidade à insulina e do controle glicêmico, aumento do condicionamento cardiorespiratório e redução do risco de mortalidade cardiovascular. Entretanto, o estabelecimento de programas de treinamentos e de guias práticos para o manejo adequado na diabetes tipo 2 não têm sido sugeridos num consenso único. Dessa forma, o presente estudo selecionou publicações realizadas a partir de dados Pubmed, objetivando discutir informações que estão sendo descritas na literatura de forma a reforçar bases que representem uma resposta adaptativa às demandas do treinamento, apoiando uma positiva função da atividade física no cuidado da diabetes tipo 2.

A sedentary lifestyle should be considered an important modifiable risk factor for individuals with type 2 diabetes mellitus (DM) already that regular physical activity offers many benefits including improved insulin sensitivity and glycemic control, increased cardiorespiratory fitness and reduced risk of cardiovascular mortality. However, the establishment of training programs and practical guidelines for management of type 2 diabetes has not been suggested in a single consensus. Thus, this study through of the selection of publications was performed on Pubmed aims to discuss the data being reported in the literature in order to reinforce the base that represent an adaptative response to the demands of training, supporting a positive role of physical activity in the management of type 2 diabetes.

Experimental atherosclerosis in rabbits.

Many researches have been conducted in experimental models in order to study the development of atherosclerosis from hyperlipidemia-inducing diets. Since rabbits are very sensitive to cholesterol-rich diets and accumulate large amounts of cholesterol in their plasma, their use as experimental models to evaluate the development of atherosclerosis is highly relevant and brings information on factors that contribute to the progression and regression of this condition that can be applied to humans. As such, this review includes studies on the atherogenic function of cholesterol based on rabbits as the experimental model, since they have become the most largely used experimental model of atherosclerosis.

Aterosclerose experimental em coelhos / Experimental atherosclerosis in rabbits

Numerosas pesquisas têm sido realizadas utilizando modelos experimentais para estudar o desenvolvimento da aterosclerose com dieta induzindo hiperlipidemia. Devido ao fato de que coelhos são muito sensíveis a dietas ricas em colesterol e acumulam grandes quantidades no plasma, a utilização destes animais como modelo experimental para avaliar o desenvolvimento de aterosclerose é de grande relevância, trazendo informação sobre fatores que contribuem para progressão e regressão aplicadas a situações humanas. Sendo assim, nessa revisão a função aterogênica do colesterol é mostrada em trabalhos que incluem o coelho como modelo experimental, uma vez que este animal tornou-se o mais popular modelo experimental de aterosclerose.

Many researches have been conducted in experimental models in order to study the development of atherosclerosis from hyperlipidemia-inducing diets. Since rabbits are very sensitive to cholesterol-rich diets and accumulate large amounts of cholesterol in their plasma, their use as experimental models to evaluate the development of atherosclerosis is highly relevant and brings information on factors that contribute to the progression and regression of this condition that can be applied to humans. As such, this review includes studies on the atherogenic function of cholesterol based on rabbits as the experimental model, since they have become the most largely used experimental model of atherosclerosis.

Flavonóides e aterosclerose / Flavonoids and atherosclerosis

Dentre as enfermidades pertencentes ao grupo das doenças cardiovasculares, a aterosclerose têm sido, atualmente, considerada problema de saúde pública no Brasil. tendo em vista o seu papel no perfil de mortalidade e das alterações tatológicas que acarretam. Pesquisas têm demonstrado associações entre o consumo de gordura saturada, nível de coleterol e doenças coronárias, no entanto, medidas dietéticas isoladas mostram-se, frqquentemente, insuficientes, tornando-se necessária à associação dessas com fármacos hipolipidêmicos capazes de reduzir a síntese endógena de colesterol ou melhorar a eficiência de sua remoção do plasma. Durante os últimos anos, um número crescente de estudos tem relacionado flavonóides a promissores fármacos naturais, uma vez que têm sido atribuidos a esses a capacidade de modificar a biossíntese de eicosanóides (resposta anti-prostanóide e antiinflamatória), proteger colesterol LDL da oxidação (inibindo formação de placa aterosclerótica), prevenir agregação plaquetária (efeitos anti-trombóticos) e promover relaxamento de músculo liso (efeito anti-hipertensivo e anti-isquêmico). Sendo assim, essa revisão sugere que a proteção contra doenças cardiovasculares associadas por meio de dietas ricas em flavonóides pode resultar em uma variedade de efeitos produzidos por diferentes mecanismos, necessitando, portanto, de maiores investigações e entendimewntos científicos.

Efeitos antidiabéticos de plantas medicinais / Antidiabetic effects of the medicinal plants

Diabetes mellitus (DM) é uma doença metabólica crônica caracterizada por hipeglicemia que tem impacto significante em seus pacientes. Sua incidência está crescendo rapidamente conduzindo para aumento no custo dos cuidados da doença e de suas complicações. O tratamento envolve, além de controle dietético e atividade física, o uso de fármacos que ocasionam efeitos colaterais para atingir ações farmacológicas desejadas. Entretanto, produtos de plantas são, freqüentemente, considerados menos tóxicos e com menos efeitos colaterais que drogas sintéticas e amplamente utilizadas pela população. Nesse trabalho várias espécies de plantas utilizadas experimentalmente ou na medicina popular, agindo de diferentes formas de modo a controlar glicemia e/ou inibir sintomas e complicações características da diabetes serão revisadas para avaliação de seus supostos efeitos terapêuticos.

Diabetes mellitus (DM) is a chronic metabolic disease characterized by hyperglycemy that has a significant impact for their patients. Its incidence is raising leading to an increase in the cost of the cares of the disease and of its complications. The treatment involves, besides dietary control and physical activity, the use of drugs that cause side effects to reach wanted pharmacological actions. However, products of plants are, frequently, considered less poisonous and with fewer side effects than synthetic drugs and widely used by the population. In this paper, several species of plants, used experimentally or in the popular medicine, acting by different ways to control glycemia and/or to inhibit symptoms and characteristic complications of the diabetes, they will be reviewed for evaluation of their supposed therapeutic effects.