Vascular non-endothelial nitric oxide induced by swimming exercise stress in rats

Effects of physical training on the metabolic profile of rats exposed to chronic restraint stress

INTRODUCTION

Despite strong evidences supporting the protective role of exercise against stress-induced repercussions, the literature remains inconclusive regarding metabolic aspects. Therefore, this study aimed to evaluate the effect of Physical Training (PT) by swimming on the metabolic parameters of rats subjected to restraint stress.

METHODS

Wistar rats (n = 40) were divided into four groups: Control (C), Trained (T), Stressed (S), and Trained/Stressed (TS). The restraint stress protocol involved confining the animals in PVC pipes for 60 minutes/day for 12 weeks. Concurrently, the swimming PT protocol was performed without additional load in entailed sessions of 60 minutes conducted five days a week for the same duration. The following parameters were analyzed: fitness progression assessed by the physical capacity test, body mass, serum level of glucose, triglyceride, cholesterol and corticosterone, as well as glycemic tolerance test, evaluated after glucose administration (2 g/kg, i.p.).

RESULTS

Trained groups (T and TS) exhibited enhanced physical capacity (169 ± 21 and 162 ± 22% increase, respectively) compared to untrained groups (C: 9 ± 5 and S: 11 ± 13% increase). Corticosterone levels were significantly higher in the S group (335 ± 9 nmoL/L) compared to C (141 ± 3 nmoL/L), T (174 ± 3 nmoL/L) and TS (231 ± 7 nmoL/L), which did not differ from each other. There were no significant changes in serum glucose, cholesterol, and triglyceride levels among the groups. However, the glycemic curve after glucose loading revealed increased glycemia in the S group (area under curve 913 ± 30 AU) but the TS group exhibited values (673 ± 12 AU) similar to the groups C (644 ± 10 AU) and T (649 ± 9 AU).

CONCLUSION

Swimming-based training attenuated stress-induced corticosterone release and prevented glucose intolerance in rats, reinforcing the importance of exercise as a potential strategy to mitigate the pathophysiological effects of stress.

Exercise training attenuates angiotensin II-induced vasoconstriction in the aorta of normotensive but not hypertensive rats

NEW FINDINGS

What is the central question of this study? What are the effects of exercise on Ang II-induced vasoconstriction in aortas of normotensive rats and how do these effects occur in two-kidney-one-clip hypertensive animals? What is the main finding and its importance? In two-kidney rats, exercise training improves the Ang II-induced vasoconstriction by endothelium-derived NO released through AT₂ R activation. This effect of exercise training on the Ang II-induced vasoconstriction is blunted in two-kidney-one-clip hypertensive animals, possibly as a consequence of oxidative stress.

ABSTRACT

This study investigated the effects of both acute exercise and training on the Ang II-induced vasoconstriction in aorta of normotensive (two-kidney; 2K) and two-kidney-one-clip (2K1C) hypertensive rats, focusing on endothelial mechanisms related to nitric oxide (NO) and prostanoids. Aorta rings of 2K and 2K1C male Wistar rats, sedentary and trained, killed at rest and after acute exercise, were challenged with Ang II in either the absence or the presence of PD 123,319, a selective angiotensin receptor subtype 2 (AT₂ R) antagonist; N^ω -nitro-l-arginine methyl ester (l-NAME), a non-selective inhibitor of nitric oxide synthase; indomethacin, a non-selective inhibitor of cyclooxygenase; or Tiron, an analogue of superoxide dismutase. Aortas of sedentary and trained animals studied at rest were also submitted to histomorphometric analysis. Exercise training reduced the Ang II-induced vasoconstriction in aorta of 2K but not of 2K1C animals. This reduction of Ang II response in aortas of 2K animals was not found after endothelial removal or treatment with PD 123,319 or l-NAME. These results suggest that exercise training improves the modulation of Ang II-induced vasoconstriction in aorta of 2K animals, by endothelium-derived NO released due to the activation of AT₂ R. No exercise-induced change of Ang II response occurred in 2K1C animals, except in the presence of Tiron, which was evidence for reduction of such responses only in resting trained 2K1C animals. In 2K1C animals, NO modulation of Ang II-induced vasoconstriction might be suppressed by local oxidative stress. Moreover, exercise training slightly reduced the media layer thickness in the aortas of the 2K1C, but not 2K animals, which may indicate cardiovascular protection of these animals.

Subchronic stress effects on vascular reactivity in C57BL/6 strain mice

BACKGROUND AND AIMS

There is a close relationship between psychosocial stress and the development of cardiovascular diseases. It has been reported that there are different alterations in endothelial function in this relationship. However, results obtained in different experimental stress models are controversial. Herein, we studied the effects of subchronic stress induced by movement restraint on several cardiovascular responses and plasma corticosterone concentration in male adult mice.

METHODS

Experiments were performed in adult male mice of C57BL/6 strain. Animals were allocated into three groups: Control group A, without manipulation; Control group B, with manipulation (quantitation of blood pressure); and Experimental group, with quantitation of blood pressure and exposure to movement restraint. In vivo, heart rate and blood pressure were registered. In vitro, in aortic rings, vascular reactivity was analyzed. Additionally, plasma corticosterone concentration was quantified.

RESULTS

In vivo, subchronic stress did not produce changes on heart rate either on blood pressure. In vitro, aortic rings with and without endothelium from control group B and experimental group showed: 1) a significant decrease in the maximal tension developed in response to phenylephrine; 2) this decrease was reverted by L-NAME. However, aortic rings from all groups, developed the same tension in response to high K⁺ solution. In aortic rings from animals of the experimental group, an increase in the maximal relaxation induced by carbachol was observed. This relaxation was prevented and/or reversed by L-NAME. Plasma corticosterone concentration was higher in the experimental group than that in the control group A.

CONCLUSIONS

Exposition to subchronic movement restraint did not produce alterations in neurovegetative responses in this strain mice. But according to vasomotor responses observed, the results suggest that this subchronic stress model induces an increase in the synthesis/release of nitric oxide, both from endothelial cells and vascular smooth muscle. In accordance with the aforementioned results, we propose that C57BL/6 mice strain is sensitive to subchronic movement restraint stress model.

Changes in histological structure and nitric oxide synthase expression in aorta of rats supplemented with bee pollen or whey protein

Various protein-based supplements are at least periodically consumed by 30%-40% of sportspeople. The current study compares cardiovascular effects of diet supplementation with 2 different protein-rich products: bee pollen and whey protein. Thirty Wistar rats were divided into 2 groups, one subjected to daily moderate physical activity and one not. Each group consisted of 3 subgroups: control, whey-protein-supplemented, and bee-pollen-supplemented. After 8 weeks, rats were decapitated, and proximal parts of thoracic aortas were collected and embedded in paraffin blocks. Histological slides were stained according to standard hematoxylin and eosin, Masson's trichrome, and Verhoeff - Van Gieson staining. Special immunohistochemical stains against neuronal nitric oxide synthase (nNOS), endothelial nitric oxide synthase (eNOS), and alpha smooth muscle actin were also prepared. Histological evaluation revealed noticeable changes in all supplemented groups: disturbances in elastic laminae, slight increase in collagen deposition, and significantly lowered nNOS and eNOS expression. The prevalence of small atherosclerotic plaques was the highest in non-running supplemented groups, while in running supplemented groups it resembled the prevalence in control groups. Both running groups had thinner tunica media than control. Both supplements exert visible effects on aortic structure, but the difference between them is far less evident. In some aspects, however, the bee pollen seems to be even slightly more harmful, which may be related to various possible contaminants like mycotoxins or pesticides.

Nandrolone administration with or without strenuous exercise increases cardiac fatal genes overexpression, calcium/calmodulin-dependent protein kinaseiiδ, and monoamine oxidase activities and enhances blood pressure in adult wistar rats

Misuse of anabolic androgenic steroids (AAS) increases prevalence of cardiovascular abnormalities in athletes, and the underlying molecular mechanism involved in those abnormalities continues to be investigated. The aim of this study was to investigate the effect of chronic nandrolone exposure on alpha and beta-myosin heavy chain (MHC) isoforms gene expression transition, blood pressure related parameters, calcium/calmodulin-dependent protein kinaseIIδ (CaMKIIδ), and monoamine oxidase (MAO) activities in rats' hearts. It was also planned to evaluate the effect of strenuous exercise on cardiac abnormalities induced by nandrolone. Thirty-two male wistar rats were assigned into four groups, namely control, nandrolone, nandrolone with strenuous exercise, and strenuous exercise groups. Nandrolone consumption significantly increased systolic, diastolic, pulse and dicrotic pressure, mean arterial pressure, as well as the amplitude of first peak (H1). Moreover, exercise combined with nandrolone completely masked this effect. The mRNA expression of β-MHC and the ratio of β -MHC/α -MHC showed a significant increase in the nandrolone and nandrolone with strenuous exercise groups compared to those in the control group. The values of heart tissue calcium/calmoldulin-dependent protein kinase IIδ (CaMKIIδ), and monoamine oxidase (MAO) in the nandrolone, nandrolone with strenuous exercise and exercise groups were significantly higher than those values in the control group. These findings indicate that nandrolone-induced heart and hemodynamic abnormalities may in part be associated with MHC isoform changes and Ca²⁺ homeostasis changes mediated by increased CaMKIIδ and MAO activities and that these effects can be provoked via strenuous exercise.

Blood pressure regulation in stress: focus on nitric oxide-dependent mechanisms

Stress is considered a risk factor associated with the development of various civilization diseases including cardiovascular diseases, malignant tumors and mental disorders. Research investigating mechanisms involved in stress-induced hypertension have attracted much attention of physicians and researchers, however, there are still ambiguous results concerning a causal relationship between stress and long-term elevation of blood pressure (BP). Several studies have observed that mechanisms involved in the development of stress-induced hypertension include increased activity of sympathetic nervous system (SNS), glucocorticoid (GC) overload and altered endothelial function including decreased nitric oxide (NO) bioavailability. Nitric oxide is well known neurotransmitter, neuromodulator and vasodilator involved in regulation of neuroendocrine mechanisms and cardiovascular responses to stressors. Thus NO plays a crucial role in the regulation of the stress systems and thereby in the BP regulation in stress. Elevated NO synthesis, especially in the initial phase of stress, may be considered a stress-limiting mechanism, facilitating the recovery from stress to the resting levels via attenuation of both GC release and SNS activity as well as by increased NO-dependent vasorelaxation. On the other hand, reduced levels of NO were observed in the later phases of stress and in subjects with genetic predisposition to hypertension, irrespectively, in which reduced NO bioavailability may account for disruption of NO-mediated BP regulatory mechanisms and accentuated SNS and GC effects. This review summarizes current knowledge on the role of stress in development of hypertension with a special focus on the interactions among NO and other biological systems affecting blood pressure and vascular function.

Chronic restraint stress increases angiotensin II potency in the rat carotid: role of cyclooxygenases and reactive oxygen species

OBJECTIVES

To investigate the mechanisms underlying the effects of chronic restraint stress on the vascular contractile response induced by angiotensin (Ang) II in rat carotid.

METHODS

Concentration-response curves for AngII were obtained in endothelium-intact or endothelium-denuded carotid rings, in the absence or presence of SC-560 (COX-1 inhibitor), SC-236 (COX-2 inhibitor), wortmannin (PI₃ K-Akt inhibitor), ML171 (NOX-1 inhibitor), VAS2870 (NOX-4 inhibitor), tiron (O2- scavenger) or PEG-catalase (H₂ O₂ scavenger). 6-ketoPGF_1α , TXB₂ , O2- or H₂ O₂ levels and superoxide dismutase and catalase activity or expression were also measured in rat carotid.

KEY FINDINGS

Stress increased AngII potency in rat carotid. Muscular COX-1 or COX-2-derived metabolites negatively modulated AngII-induced contraction in control rat carotid. Endothelial COX-1 or COX-2-derived metabolites positively modulated AngII-induced contraction in stressed rat carotid. PI₃ K-Akt, NOX-1, NOX-4, O2- and H₂ O₂ positively modulated AngII-induced contraction in stressed rat carotid. Stress increased 6-ketoPGF_1α or H₂ O₂ generation and reduced catalase activity in rat carotid. Protein expression of COX-1, NOX-4 or p-Akt was increased in stressed rat carotid.

CONCLUSIONS

Stress increases AngII potency in rat carotid by a mechanism that involves the increased generation of PGI₂ and H₂ O₂ and the activation of Akt pathway. Such mechanism could play a pathophysiological role in cardiovascular diseases correlated with stress.

Acute Aerobic Swimming Exercise Induces Distinct Effects in the Contractile Reactivity of Rat Ileum to KCl and Carbachol

Aerobic exercise promotes short-term physiological changes in the intestinal smooth muscle associated to the ischemia-reperfusion process; however, few studies have demonstrated its effect on the intestinal contractile function. Thus, this work describes our observations regarding the influence of acute aerobic swimming exercise in the contractile reactivity, oxidative stress, and morphology of rat ileum. Wistar rats were divided into sedentary (SED) and acutely exercised (EX-AC) groups. Animals were acclimated by 10, 10, and 30 min of swimming exercise in intercalated days 1 week before exercise. Then they were submitted to forced swimming for 1 h with a metal of 3% of their body weight attached to their body. Animals were euthanized immediately after the exercise section and the ileum was suspended in organ baths for monitoring isotonic contractions. The analysis of lipid peroxidation was performed in order to determinate the malondialdehyde (MDA) levels as a marker of oxidative stress, and intestinal smooth muscle morphology by histological staining. Cumulative concentration-response curves to KCl were altered in the EX-AC with an increase in both its efficacy and potency (E_max = 153.2 ± 2.8%, EC₅₀ = 1.3 ± 0.1 × 10⁻² M) compared to the SED group (E_max = 100%, EC₅₀ = 1.8 ± 0.1 × 10⁻² M). Interestingly, carbachol had its efficacy and potency reduced in the EX-AC (E_max = 67.1 ± 1.4%, EC₅₀ = 9.8 ± 1.4 × 10⁻⁷ M) compared to the SED group (E_max = 100%, EC₅₀ = 2.0 ± 0.2 × 10⁻⁷ M). The exercise did not alter the MDA levels in the ileum (5.4 ± 0.6 μ mol/mL) in the EX-AC compared to the SED group (8.4 ± 1.7 μ mol/mL). Moreover, neither the circular nor the longitudinal smooth muscle layers thickness were modified by the exercise (66.2 ± 6.0 and 40.2 ± 2.6 μm, respectively), compared to the SED group (61.6 ± 6.4 and 34.8 ± 3.7 μm, respectively). Therefore, the ileum sensitivity to contractile agents is differentially altered by the acute aerobic swimming exercise, without affecting the oxidative stress and the morphology of ileum smooth muscle.

Chronic aerobic swimming exercise promotes functional and morphological changes in rat ileum

In the present study, we evaluated the influence of chronic swimming aerobic exercise on the contractile reactivity, lipid peroxidation and tissue morphology of small intestine from rats. We showed that, accordingly to the time of exercise, the rat ileum has its contractile reactivity reduced, in addition to the increased lipid peroxidation followed by its reestablishment to basal levels, as well as the augmented longitudinal smooth muscle layer thickness together with the reduced circular thickness.

Several studies have reported the gastrointestinal (GI) effects promoted by the physical exercise. Thus, we aimed to evaluate the influence of swimming exercise on the contractile reactivity, lipid peroxidation and morphology of rat ileum. Wistar rats were divided into sedentary (SED) and groups exercised for two (EX2), four (EX4), six (EX6) or eight (EX8) weeks, 5 days/week. Animals were killed; the ileum was removed and suspended in organ baths where the isotonic contractions were recorded. Lipid peroxidation was evaluated by MDA (malondialdehyde) measurement with TBARS (thiobarbituric acid reactive substances) assay and morphology by histological staining. Cumulative concentration-response curves to KCl were attenuated, as the E_max values were changed from 100% (SED) to 63.1±3.9 (EX2), 48.8±3.8 (EX4), 19.4±1.8 (EX6) and 59.4±2.8% (EX8). Similarly, cumulative concentration-response curves to carbamylcholine hydrochloride (CCh) were attenuated, as the E_max values were changed from 100% (SED) to 74.1±5.4 (EX2), 75.9±5.2 (EX4) and 62.9±4.6 (EX6), but not in the EX8 (89.7±3.4%). However, CCh potency was increased in this latter, as the EC₅₀ was altered from 1.0±0.1×10⁻⁶ (SED) to 2.1±0.4×10⁻⁷ (EX8). MDA concentration was altered only in EX4 (44.3±4.4) compared with SED (20.6±3.6 μmol/l). Circular layer was reduced in SED when compared with the exercised groups. Conversely, longitudinal layer was increased. In conclusion, chronic swimming exercise reduces the ileum contraction, equilibrates the oxidative damage and promotes changes in tissue size to establish an adaptation to the exercise.

Exercise increases the angiotensin II effects in isolated portal vein of trained rats

Training in rats adapts the portal vein to respond vigorously to sympathetic stimuli even when the animal is re-exposed to exercise. Moreover, changes in the exercise-induced effects of angiotensin II, a potent venoconstrictor agonist, in venous beds remain to be investigated. Therefore, the present study aimed to assess the effects of angiotensin II in the portal vein and vena cava from sedentary and trained rats at rest or submitted to an exercise session immediately before organ bath experiments. We found that training or exposure of sedentary animals to a single bout of running exercise does not significantly change the responses of the rat portal vein to angiotensin II. However, the exposure of trained animals to a single bout of running exercise enhanced the response of the rat portal vein to angiotensin II. This enhancement appeared to be territory-specific because it was not observed in the vena cava. Moreover, it was not observed in endothelium-disrupted preparations and in preparations treated with N(omega)-nitro-l-arginine methyl ester hydrochloride, indomethacin, BQ-123 or BQ-788. These data indicate that training causes adaptations in the rat portal vein that respond vigorously to angiotensin II even upon re-exposure to exercise. This increased response to angiotensin II requires an enhancement of the vasocontractile influence of endothelin beyond the influence of nitric oxide and vasodilator prostanoids.

Phenylephrine-induced vasoconstriction of the rat superior mesenteric artery is decreased after repeated swimming

This study was performed to determine the effect of forced swimming on the vascular responsiveness of the rat superior mesenteric artery to phenylephrine, focusing on the involvement of locally produced substances. Repeated but not single sessions of forced swimming exercise reduced the vasoconstrictor potency of phenylephrine in the studied arteries, regardless of the presence of intact endothelium. No significant changes were observed in the maximal response to phenylephrine. Treatment with indomethacin (1 microM) did not affect the exercise-induced reduction in vascular responsiveness to phenylephrine. However, the reduction of vascular reactivity to phenylephrine due to repeated exercise was no longer observed after treatment with N(G)-monomethyl-L-arginine (L-NMMA, 100 microM). The results suggest that repeated exercise reduces vasomotor responses to phenylephrine in rat superior mesenteric arteries through a non-endothelial nitric oxide (NO)-related mechanism.