Aerobic Swim Training Restores Aortic Endothelial Function by Decreasing Superoxide Levels in Spontaneously Hypertensive Rats.

OBJECTIVE:: We aimed to determine whether aerobic training decreases superoxide levels, increases nitric oxide levels, and improves endothelium-dependent vasodilation in the aortas of spontaneously hypertensive rats. METHODS:: Spontaneously hypertensive rats (SHR) and Wistar Kyoto rats (WKY) were distributed into 2 groups: sedentary (SHRsd and WKYsd, n=10 each) and swimming-trained (SHRtr, n=10 and WKYtr, n=10, respectively). The trained group participated in training sessions 5 days/week for 1 h/day with an additional work load of 4% of the animal's body weight. After a 10-week sedentary or aerobic training period, the rats were euthanized. The thoracic aortas were removed to evaluate the vasodilator response to acetylcholine (10-10 to 10-4 M) with or without preincubation with L-NG-nitro-L-arginine methyl ester hydrochloride (L-NAME; 10-4 M) in vitro. The aortic tissue was also used to assess the levels of the endothelial nitric oxide synthase and nicotinamide adenine dinucleotide oxidase subunit isoforms 1 and 4 proteins, as well as the superoxide and nitrite contents. Blood pressure was measured using a computerized tail-cuff system. RESULTS:: Aerobic training significantly increased the acetylcholine-induced maximum vasodilation observed in the SHRtr group compared with the SHRsd group (85.9±4.3 vs. 71.6±5.2%). Additionally, in the SHRtr group, superoxide levels were significantly decreased, nitric oxide bioavailability was improved, and the levels of the nicotinamide adenine dinucleotide oxidase subunit isoform 4 protein were decreased compared to the SHRsd group. Moreover, after training, the blood pressure of the SHRtr group decreased compared to the SHRsd group. Exercise training had no effect on the blood pressure of the WKYtr group. CONCLUSIONS:: In SHR, aerobic swim training decreased vascular superoxide generation by nicotinamide adenine dinucleotide oxidase subunit isoform 4 and increased nitric oxide bioavailability, thereby improving endothelial function.

Aerobic Swim Training Restores Aortic Endothelial Function by Decreasing Superoxide Levels in Spontaneously Hypertensive Rats

OBJECTIVE: We aimed to determine whether aerobic training decreases superoxide levels, increases nitric oxide levels, and improves endothelium-dependent vasodilation in the aortas of spontaneously hypertensive rats. METHODS: Spontaneously hypertensive rats (SHR) and Wistar Kyoto rats (WKY) were distributed into 2 groups: sedentary (SHRsd and WKYsd, n=10 each) and swimming-trained (SHRtr, n=10 and WKYtr, n=10, respectively). The trained group participated in training sessions 5 days/week for 1 h/day with an additional work load of 4% of the animal’s body weight. After a 10-week sedentary or aerobic training period, the rats were euthanized. The thoracic aortas were removed to evaluate the vasodilator response to acetylcholine (10-10 to 10-4 M) with or without preincubation with L-NG-nitro-L-arginine methyl ester hydrochloride (L-NAME; 10-4 M) in vitro. The aortic tissue was also used to assess the levels of the endothelial nitric oxide synthase and nicotinamide adenine dinucleotide oxidase subunit isoforms 1 and 4 proteins, as well as the superoxide and nitrite contents. Blood pressure was measured using a computerized tail-cuff system. RESULTS: Aerobic training significantly increased the acetylcholine-induced maximum vasodilation observed in the SHRtr group compared with the SHRsd group (85.9±4.3 vs. 71.6±5.2%). Additionally, in the SHRtr group, superoxide levels were significantly decreased, nitric oxide bioavailability was improved, and the levels of the nicotinamide adenine dinucleotide oxidase subunit isoform 4 protein were decreased compared to the SHRsd group. Moreover, after training, the blood pressure of the SHRtr group decreased compared to the SHRsd group. Exercise training had no effect on the blood pressure of the WKYtr group. CONCLUSIONS: In SHR, aerobic swim training decreased vascular superoxide generation by nicotinamide adenine dinucleotide oxidase subunit isoform 4 and increased nitric oxide bioavailability, thereby improving endothelial function.

The importance of animal studies in exercise science

Abstract The validity and relevance of research with animals for the development of knowledge in Exercise Science have for long been discussed. Given the complexity of the biological systems, the use of animal models offers a significant contribution to uncover new findings about acute and chronic effects of exercise, particularly when these studies in humans have limitations and ethical implications. There have been notable findings using experimental animals either in basic sciences or in clinical studies involving physiology, pharmacology, genetic, biochemistry, urology, endocrinology and cancer. This article presents a brief review of scientific research using animal models with a focus on exercise training as an effective tool for the prophylaxis and treatment of different pathological processes, which are the basis of many concepts taught and used in undergraduate courses and graduate programs, as well as in new researches showed in scientific conference meetings in numerous areas of science.(AU)

Loss of strength capacity is associated with mortality, but resistance exercise training promotes only modest effects during cachexia progression.

AIMS: Resistance exercise training (RET) has been adopted as non-pharmacological anti-catabolic strategy. However, the role of RET to counteract cancer cachexia is still speculative. This study aimed to verify whether short-term RET would counteract skeletal muscle wasting in a severe cancer cachexia rat model. MAIN METHODS: Wistar rats were randomly allocated into four experimental groups; 1) untrained control rats (control), 2) rats submitted to RET (control+RET), 3) untrained rats injected with Walker 256 tumor cells in the bone marrow (tumor) and 4) rats injected with Walker 256 tumor cells in the bone marrow and submitted to RET (tumor+RET). KEY FINDINGS: Tumor group displayed skeletal muscle atrophy fifteen days post tumor cells injection as assessed by plantaris (-20.5%) and EDL (-20.0%) muscle mass. EDL atrophy was confirmed showing 43.8% decline in the fiber cross sectional area. Even though RET increased the lactate dehydrogenase protein content and fully restored phosphorylated form of 4EBP-1 to the control levels in skeletal muscle, it failed to rescue muscle morphology in tumor-bearing rats. Indeed, RET did not mitigated loss of muscle function, anorexia, tumor growth or mortality rate. However, loss of strength capacity (assessed by 1-RM test performance) demonstrated a negative correlation with rats' survival (p=0.02; r=0.40), suggesting that loss of strength capacity might predict cancer mortality. SIGNIFICANCE: These results demonstrated that bone marrow injection of Walker 256 tumor cells in rats induces cancer cachexia, strength capacity is associated with cancer survival and short-term RET promotes only modest effects during cachexia progression.

Exercise improves endothelial function: a local analysis of production of nitric oxide and reactive oxygen species.

This study aimed at investigating the acute effects of aerobic exercise on endothelium-dependent vasomotor function of rat aorta, as well as mechanisms involved in endothelial nitric oxide (NO) bioactivity. Wistar rats were assigned to either a resting control (C, n = 21) or acutely exercised (E, n = 21) groups (60 min, 55-60% of maximum speed). After exercise, thoracic aorta was excised and cut into rings. Two rings were promptly applied to evaluate vasomotor function and the rest of aorta was used for additional measurements. Acute exercise significantly improved maximum ACh-induced relaxation (C, 91.6 ± 1.2 vs. E, 102.4 ± 1.7%, p < 0.001) and sensitivity to ACh (C, -7.3 ± 0.06 vs. E, -7.3 ± 0.02 log M, p < 0.01), and was accompanied by significantly increases on serine1177 eNOS phosphorylation, reflecting its enhanced activation. However, acute exercise also enhanced both superoxide and hydrogen peroxide production, as assayed by dihydroethidium oxidation, lucigenin chemiluminescence and Amplex Red assays. We also provided evidence for Nox2 NADPH oxidase (Nox) activation through gp91dstat-mediated inhibition of superoxide signals. Enhanced arterial relaxations associated with acute exercise were nearly-completely prevented by catalase, suggesting a role for paracrine hydrogen peroxide. Despite increased detectable oxidant generation, cellular oxidative stress was not evident, as suggested by unaltered GSH:GSSG ratio and lipid hydroperoxides. Collectively, these results demonstrate that one bout of moderate aerobic exercise improves endothelial function by increasing NO bioavailability, while superoxide and hydrogen peroxide are generated in a controlled fashion.

NADPH oxidase hyperactivity induces plantaris atrophy in heart failure rats.

BACKGROUND: Skeletal muscle wasting is associated with poor prognosis and increased mortality in heart failure (HF) patients. Glycolytic muscles are more susceptible to catabolic wasting than oxidative ones. This is particularly important in HF since glycolytic muscle wasting is associated with increased levels of reactive oxygen species (ROS). However, the main ROS sources involved in muscle redox imbalance in HF have not been characterized. Therefore, we hypothesized that NADPH oxidases would be hyperactivated in the plantaris muscle of infarcted rats, contributing to oxidative stress and hyperactivation of the ubiquitin-proteasome system (UPS), ultimately leading to atrophy. METHODS: Rats were submitted to myocardial infarction (MI) or Sham surgery. Four weeks after surgery, MI and Sham groups underwent eight weeks of treatment with apocynin, a NADPH oxidase inhibitor, or placebo. NADPH oxidase activity, oxidative stress markers, NF-κB activity, p38 MAPK phosphorylation, mRNA and sarcolemmal protein levels of NADPH oxidase components, UPS activation and fiber cross-sectional area were assessed in the plantaris muscle. RESULTS: The plantaris of MI rats displayed atrophy associated with increased Nox2 mRNA and sarcolemmal protein levels, NADPH oxidase activity, ROS production, lipid hydroperoxides levels, NF-κB activity, p38 MAPK phosphorylation and UPS activation. NADPH oxidase inhibition by apocynin prevented MI-induced skeletal muscle atrophy by reducing ROS production, NF-κB hyperactivation, p38 MAPK phosphorylation and proteasomal hyperactivity. CONCLUSION: Our data provide evidence for NADPH oxidase hyperactivation as an important source of ROS production leading to plantaris atrophy in heart failure rats, suggesting that this enzyme complex plays key role in skeletal muscle wasting in HF.

Aerobic exercise training improves Ca2+ handling and redox status of skeletal muscle in mice.

Exercise training is known to promote relevant changes in the properties of skeletal muscle contractility toward powerful fibers. However, there are few studies showing the effect of a well-established exercise training protocol on Ca(2+) handling and redox status in skeletal muscles with different fiber-type compositions. We have previously standardized a valid and reliable protocol to improve endurance exercise capacity in mice based on maximal lactate steady-state workload (MLSSw). The aim of this study was to investigate the effect of exercise training, performed at MLSSw, on the skeletal muscle Ca(2+) handling-related protein levels and cellular redox status in soleus and plantaris. Male C57BL/6J mice performed treadmill training at MLSSw over a period of eight weeks. Muscle fiber-typing was determined by myosin ATPase histochemistry, citrate synthase activity by spectrophotometric assay, Ca(2+) handling-related protein levels by Western blot and reduced to oxidized glutathione ratio (GSH:GSSG) by high-performance liquid chromatography. Trained mice displayed higher running performance and citrate synthase activity compared with untrained mice. Improved running performance in trained mice was paralleled by fast-to-slow fiber-type shift and increased capillary density in both plantaris and soleus. Exercise training increased dihydropyridine receptor (DHPR) alpha2 subunit, ryanodine receptor and Na(+)/Ca(2+) exchanger levels in plantaris and soleus. Moreover, exercise training elevated DHPR beta1 subunit and sarcoplasmic reticulum Ca(2+)-ATPase (SERCA) 1 levels in plantaris and SERCA2 levels in soleus of trained mice. Skeletal muscle GSH content and GSH:GSSG ratio was increased in plantaris and soleus of trained mice. Taken together, our findings indicate that MLSSw exercise-induced better running performance is, in part, due to increased levels of proteins involved in skeletal muscle Ca(2+) handling, whereas this response is partially dependent on specificity of skeletal muscle fiber-type composition. Finally, we demonstrated an augmented cellular redox status and GSH antioxidant capacity in trained mice.

Sympathetic hyperactivity differentially affects skeletal muscle mass in developing heart failure: role of exercise training.

Sympathetic hyperactivity (SH) is a hallmark of heart failure (HF), and several lines of evidence suggest that SH contributes to HF-induced skeletal myopathy. However, little is known about the influence of SH on skeletal muscle morphology and metabolism in a setting of developing HF, taking into consideration muscles with different fiber compositions. The contribution of SH on exercise tolerance and skeletal muscle morphology and biochemistry was investigated in 3- and 7-mo-old mice lacking both alpha(2A)- and alpha(2C)-adrenergic receptor subtypes (alpha(2A)/alpha(2C)ARKO mice) that present SH with evidence of HF by 7 mo. To verify whether exercise training (ET) would prevent skeletal muscle myopathy in advanced-stage HF, alpha(2A)/alpha(2C)ARKO mice were exercised from 5 to 7 mo of age. At 3 mo, alpha(2A)/alpha(2C)ARKO mice showed no signs of HF and preserved exercise tolerance and muscular norepinephrine with no changes in soleus morphology. In contrast, plantaris muscle of alpha(2A)/alpha(2C)ARKO mice displayed hypertrophy and fiber type shift (IIA --> IIX) paralleled by capillary rarefaction, increased hexokinase activity, and oxidative stress. At 7 mo, alpha(2A)/alpha(2C)ARKO mice displayed exercise intolerance and increased muscular norepinephrine, muscular atrophy, capillary rarefaction, and increased oxidative stress. ET reestablished alpha(2A)/alpha(2C)ARKO mouse exercise tolerance to 7-mo-old wild-type levels and prevented muscular atrophy and capillary rarefaction associated with reduced oxidative stress. Collectively, these data provide direct evidence that SH is a major factor contributing to skeletal muscle morphological changes in a setting of developing HF. ET prevented skeletal muscle myopathy in alpha(2A)/alpha(2C)ARKO mice, which highlights its importance as a therapeutic tool for HF.

A single bout of moderate-intensity exercise increases vascular NO bioavailability and attenuates adrenergic receptor-dependent and -independent vasoconstrictor response in rat aorta.

The present study investigated the effect of one bout of moderate-intensity exercise on the adrenergic receptor-dependent and -independent vasoconstrictor response in rat aortas, and the role of nitric oxide (NO) bioavailability on these vasomotor responses. One group of rats was submitted to a 60 min of exercise at approximately 60% of maximal exercise capacity on a treadmill (exercise group) and the other one was placed in the treadmill without running (control group). Immediately after this period, both groups were euthanized and the thoracic aorta was removed to evaluate the vasoconstrictor response to norepinephrine and potassium chloride, and to evaluate the vascular nitrite and nitrate concentration. One bout of exercise attenuated the maximal contractile response to both norepinephrine and potassium chloride compared to control group. These differences on vascular reactivity were not observed in endothelium-denuded aortic rings and aortic rings pre-incubated with a nitric oxide synthesis inhibitor. Additionally, exercise group increased NO bioavailability (nitrite and nitrate concentration) as compared to control group. These results demonstrate that one bout of moderate-intensity exercise is able to attenuate adrenergic receptor-dependent and -independent vasoconstrictor response in rat aorta, mainly by increasing vascular NO bioavailability.

Moderate exercise training decreases aortic superoxide production in myocardial infarcted rats.

Myocardial infarction (MI) has been associated with increases in reactive oxygen species (ROS). Exercise training (ET) has been shown to exert positive modulations on vascular function and the purpose of the present study was to investigate the effect of moderate ET on the aortic superoxide production index, NAD(P)H oxidase activity, superoxide dismutase activity and vasomotor response in MI rats. Aerobic ET was performed during 11 weeks. Myocardial infarction significantly diminished maximal exercise capacity, and increased vasoconstrictory response to norepinephrine, which was related to the increased activity of NAD(P)H oxidase and basal superoxide production. On the other hand, ET normalized the superoxide production mostly due to decreased NAD(P)H oxidase activity, although a minor SOD effect may also be present. These adaptations were paralleled by normalization in the vasoconstrictory response to norepinephrine. Thus, diminished ROS production seems to be an important mechanism by which ET mediates its beneficial vascular effects in the MI condition.

Intracellular mechanisms of specific beta-adrenoceptor antagonists involved in improved cardiac function and survival in a genetic model of heart failure.

beta-blockers, as class, improve cardiac function and survival in heart failure (HF). However, the molecular mechanisms underlying these beneficial effects remain elusive. In the present study, metoprolol and carvedilol were used in doses that display comparable heart rate reduction to assess their beneficial effects in a genetic model of sympathetic hyperactivity-induced HF (alpha(2A)/alpha(2C)-ARKO mice). Five month-old HF mice were randomly assigned to receive either saline, metoprolol or carvedilol for 8 weeks and age-matched wild-type mice (WT) were used as controls. HF mice displayed baseline tachycardia, systolic dysfunction evaluated by echocardiography, 50% mortality rate, increased cardiac myocyte width (50%) and ventricular fibrosis (3-fold) compared with WT. All these responses were significantly improved by both treatments. Cardiomyocytes from HF mice showed reduced peak [Ca(2+)](i) transient (13%) using confocal microscopy imaging. Interestingly, while metoprolol improved [Ca(2+)](i) transient, carvedilol had no effect on peak [Ca(2+)](i) transient but also increased [Ca(2+)] transient decay dynamics. We then examined the influence of carvedilol in cardiac oxidative stress as an alternative target to explain its beneficial effects. Indeed, HF mice showed 10-fold decrease in cardiac reduced/oxidized glutathione ratio compared with WT, which was significantly improved only by carvedilol treatment. Taken together, we provide direct evidence that the beneficial effects of metoprolol were mainly associated with improved cardiac Ca(2+) transients and the net balance of cardiac Ca(2+) handling proteins while carvedilol preferentially improved cardiac redox state.

Exercício físico e disfunção endotelial / Exercise and endothelial dysfunction

A disfunção endotelial apresenta papel de destaque no desenvolvimento e na progressão da aterosclerose por estar diretamente relacionada a alterações na homeostase da parede vascular e no controle da circulação. Estudos clínicos e experimentais têm evidenciado efeitos benéficos do treinamento físico...

Efeitos do treinamento físico aeróbio sobre a bioatividade do óxido nítrico e a vasodilatação aórtica / Effects of aerobic exercise training opon nitric oxide bioactivity and aorta vasodilatation

O treinamento físico aeróbio (TF) é um importante meio para melhorar a função endotelial. Entretanto, como os vasos se adaptam ao TF ainda não está completamente esclarecido. Desta forma, o presente estudo teve por objetivo investigar, em ratos normotensos, os efeitos do TF sobre a via de produção de óxido nítrico (NO) e a defesa antioxidante vascular, e suas conseqüências sobre a resposta vasodilatadora em aorta isolada. Os ratos foram submetidos a um protocolo de TF aeróbio (esteira rolante, ~55%Veloc. Máx; cinco sessões/sem., 60 min/sessão, período de 11 semanas). Após o TF, foi avaliada a função vasomotora “in vitro” pela curva de concentração-efeito à acetilcolina (ACh) e ao nitroprussiato de sódio (NPS), e realizadas medidas bioquímicas na aorta. O programa de TF aumentou significativamente (P < 0,05) em 62% a expressão da enzima óxido nítrico sintase endotelial (eNOS). Entretanto, o TF não modificou significativamente a expressão e atividade da enzima antioxidante superóxido dismutase.Além disso, o TF não modificou o relaxamento individual e a sensibilidade à ACh. Por outro lado, o TF diminuiu significativamente a sensibilidade ao NPS (-8,26 ± 0,081 vs. -7,79 ± 0,099 Log [M], S vs T, respectivamente, P < 0,001). Os resultados apresentados demonstram que o TF aeróbio foi capaz de alterar um dos mecanismos envolvidos na bioatividade do NO, marcadamente o aumento da expressãoda eNOS. Entretanto, esta modificação não levou à melhora da responsividade vasodilatadora aórtica estimulada pela acetilcolina e provocou menor sensibilidade ao NPS.

Aerobic training (AT) is an important way to improve endothelial function. However, it is not completelyunderstood how the blood vessels adapt themselves to the AT. Therefore, the aim of this study was to investigate exercise training-induced adaptations on the nitric oxide (NO) production, antioxidant defense and aorta vasodilatation in normotensive rats. The rats were subjected to an AT protocol (treadmill,~55% Max Veloc., 5 bouts/week, 60 min/bout, 11 wks). After the AT, it was examined in vitro vasomotor function to acetylcholine (ACh) and sodium nitroprusside (SNP), and biochemical analysis in the aorta. Aerobic training significantly increased (P < 0.05) by 62% the expression of the endothelial nitric oxide synthase (eNOS). However, ET did not modify the relaxation response and sensitivity to ACh. In contrast, AT significantly reduced aortic sensitivity to SNP (-8.26 ± 0.081 vs. -7.79 ± 0.099 Log [M], Sed vs. AT,respectively, P < 0.001). These results demonstrate that aerobic AT was able to modify one important mechanism related to the NO bioactivity, which is the increase of eNOS expression. However, this response did not contribute to improve of the aortic vasodilatation response to acetylcholine and decreased the sensitivity to SNP.

Hemorragias digestivas bajas / Lower digestive hemorrhages

El diagnóstico exacto y precoz del origen de la hemorragia digestiva baja es la condición que nos permitirá considerar con resultados favorables un tratamiento acorde a la etiología de este episodio en donde podrán incluirse procedimientos médicos, endoscópicos o quirúrgicos. El colon es el lugar de mayor frecuencia de hallazgos (80 por ciento); se debe tener en cuenta que el 40 por ciento de estos tienen origen orificial, donde predomina la patología hemorroidaria. Menos frecuente (9 por ciento) se observan en patologías de intestino delgado. Se debe tener en cuenta que apróximadamente el 75 por ciento a 85 por ciento de las HDB dejan de sangrar en forma espontánea. Y que la hemorragia masiva o copiosa constituye el 1.5 por ciento de una emergencia quirúrgica. Existe también episodios de sangrado digestivo alto que puede manifestarse como HDB (11 por ciento). (AU)

Hemorragias digestivas bajas / Lower digestive hemorrhages

El diagnóstico exacto y precoz del origen de la hemorragia digestiva baja es la condición que nos permitirá considerar con resultados favorables un tratamiento acorde a la etiología de este episodio en donde podrán incluirse procedimientos médicos, endoscópicos o quirúrgicos. El colon es el lugar de mayor frecuencia de hallazgos (80 por ciento); se debe tener en cuenta que el 40 por ciento de estos tienen origen orificial, donde predomina la patología hemorroidaria. Menos frecuente (9 por ciento) se observan en patologías de intestino delgado. Se debe tener en cuenta que apróximadamente el 75 por ciento a 85 por ciento de las HDB dejan de sangrar en forma espontánea. Y que la hemorragia masiva o copiosa constituye el 1.5 por ciento de una emergencia quirúrgica. Existe también episodios de sangrado digestivo alto que puede manifestarse como HDB (11 por ciento).