Exercise changes regional vascular control by commissural NTS in spontaneously hypertensive rats

Chemogenetic inhibition of Phox2-expressing neurons in the commissural NTS decreases blood pressure in anesthetized spontaneously hypertensive rats

Interruption of the activity of neurons in the commissural portion of the nucleus of the solitary tract (cNTS) decreases blood pressure (BP) in experimental models of hypertension, such as the spontaneously hypertensive (SH) rat. To examine whether PHOX2B expressing cNTS neurons are involved in maintaining the elevated BP, we used replication-deficient viruses with a modified Phox2 binding site promoter to express the inhibitory chemogenetic allatostatin receptor or green fluorescent protein in the cNTS. Following administration of allatostatin, we observed a depressor and bradycardic response in anesthetized SH rats that expressed the allatostatin receptor. Injection of allatostatin did not affect BP or heart rate (HR) in control SH rats expressing green fluorescent protein in the cNTS. Immunohistochemistry showed that the majority of transduced cNTS neurons were PHOX2B-immunoreactive and some also expressed tyrosine hydroxylase. We conclude that in anesthetized SH rat, the Phox2B expressing cNTS neurons maintain elevated BP.

Regularly swimming exercise modifies opioidergic neuromodulation in rostral ventrolateral medulla in hypertensive rats

Moderate exercise reduces arterial pressure (AP) and heart rate (HR) in spontaneously hypertensive rats (SHR) and changes neurotransmission in medullary areas involved in cardiovascular regulation. We investigated if regularly swimming exercise (SW) affects the cardiovascular adjustments mediated by opioidergic neuromodulation in the RVLM in SHR and Wistar-Kyoto (WKY) rats. Rats were submitted to 6 wks of SW. The day after the last exercise bout, α-chloralose-anesthetized rats underwent a cannulation of the femoral artery for AP and HR recordings, and Doppler flow probes were placed around the lower abdominal aorta and superior mesenteric artery. Bilateral injection of endomorphin-2 (EM-2, 0.4 mmol/L, 60 nL) into the RVLM increased MAP in SW-SHR (20 ± 4 mmHg, N = 6), which was lower than in sedentary (SED)-SHR (35 ± 4 mmHg, N = 6). The increase in MAP in SW-SHR induced by EM-2 into the RVLM was similar in SED- and SW-WKY. Naloxone (0.5 mmol/L, 60 nL) injected into the RVLM evoked an enhanced hypotension in SW-SHR (-66 ± 8 mmHg, N = 6) compared to SED-SHR (-25 ± 3 mmHg, N = 6), which was similar in SED- and SW-WKY. No significant changes were observed in HR after EM-2 or naloxone injections into the RVLM. Changes in hindquarter and mesenteric conductances evoked by EM-2 or naloxone injections into the RVLM in SW- or SED-SHR were not different. Mu Opioid Receptor expression by Western blotting was reduced in SW-SHR than in SED-SHR and SW-WKY. Therefore, regularly SW alters the opioidergic neuromodulation in the RVLM in SHR and modifies the mu opioid receptor expression in this medullary area.

Reduction of oxidative stress and inflammatory signaling in the commissural nucleus of the solitary tract (commNTS) and rostral ventrolateral medulla (RVLM) in treadmill trained rats

Inflammation has been associated with cardiovascular diseases and the key point is the generation of reactive oxygen species (ROS). Exercise modulates medullary neurons involved in cardiovascular control. We investigated the effect of chronic exercise training (Tr) in treadmill running on gene expression (GE) of ROS and inflammation in commNTS and RVLM neurons. Male Wistar rats (N = 7/group) were submitted to training in a treadmill running (1 h/day, 5 days/wk/10 wks) or maintained sedentary (Sed). Superoxide dismutase (SOD), catalase (CAT), neuroglobin (Ngb), Cytoglobin (Ctb), NADPH oxidase (Nox), cicloxigenase-2 (Cox-2), and neuronal nitric oxide synthase (NOS1) gene expression were evaluated in commNTS and RVLM neurons by qPCR. In RVLM, Tr rats increased Ngb (1.285 ± 0.03 vs. 0.995 ± 0.06), Cygb (1.18 ± 0.02 vs.0.99 ± 0.06), SOD (1.426 ± 0.108 vs. 1.00 ± 0.08), CAT (1.34 ± 0.09 vs. 1.00 ± 0.08); and decreased Nox (0.55 ± 0.146 vs. 1.001 ± 0.08), Cox-2 (0.335 ± 0.05 vs. 1.245 ± 0.02), NOS1 (0.51 ± 0.08 vs. 1.08 ± 0.209) GE compared to Sed. In commNTS, Tr rats increased SOD (1.384 ± 0.13 vs. 0.897 ± 0.101), CAT GE (1.312 ± 0.126 vs. 0.891 ± 0.106) and decreased Cox-2 (0.052 ± 0.011 vs. 1.06 ± 0.207) and NOS1 (0.1550 ± 0.03559 vs. 1.122 ± 0.26) GE compared to Sed. Therefore, GE of proteins of the inflammatory process reduced while GE of antioxidant proteins increased in the commNTS and RVLM after training, suggesting a decrease in oxidative stress of downstream pathways mediated by nitric oxide.

Impact of swimming exercise on inflammation in medullary areas of sympathetic outflow control in spontaneously hypertensive rats

Exercise reduces sympathetic activity (SA), arterial pressure and heart rate in spontaneously hypertensive rats (SHR). Exercise increases oxidative stress (OS) and inflammation is implicated in the generation of reactive oxygen species (ROS) and progression of hypertension. To unravel these effects of exercise and considering that SA is driven by medullary areas, we hypothesized that swimming exercise (SW) affects the gene expression (g.e.) of proteins involved in inflammation and OS in the commissural Nucleus of the Solitary Tract (cNTS) and Rostral ventrolateral medulla (RVLM), which control the sympathetic outflow in SHR. We used male SHR and Wistar rats (14-16wks-old) which were maintained sedentary (SED) or submitted to SW (1 h/day, 5 days/wk./6wks). The g.e. of cycloxygenase-2 (COX-2), interleukin 6 (IL-6), interleukin 10 (IL-10), AT-1 receptor (AT-1r), neuroglobin (Ngb) and cytoglobin (Ctb) in cNTS and RVLM was carried out by qPCR. We observed that COX-2 g.e. increased in SW-SHR in cNTS and RVLM compared to SED-SHR. The IL-6 g.e. reduced in RVLM in SW-SHR, whereas IL-10 g.e. increased in SW-SHR in comparison to SED-SHR. The AT-1r g.e. decreased in SW-SHR in cNTS and RVLM compared to SED-SHR. The Ngb and Ctb g.e. in cNTS neurons increased in SHR and Wistar rats submitted to SW compared to SED, but only Ctb g.e. increased in RVLM in SW-SHR and Wistar in comparison to SED. Therefore, the SW altered the g.e. in cNTS and RVLM for reducing the inflammation and ROS formation, which is increased particularly in SHR, consequently decreasing the OS.

Exercise training to reduce sympathetic nerve activity in heart failure patients. A systematic review and meta-analysis

OBJECTIVE

To determine the effects of exercise training on sympathetic nerve activity in heart failure patients.

METHODS

A systematic review was performed. An electronic search of MEDLINE, ProQuest, SciELO, SPORTDiscus, Rehabilitation and Sport Medicine Source, Cumulative Index to Nursing and Allied Health Literature, Tripdatabase, Science Direct and PEDrO was performed from their inception to February 2017. Clinical trials and quasi-experimental studies were considered for primary article selection. The studies should include patients diagnosed with chronic heart failure that performed exercise training for at least 4 weeks. Sympathetic nerve activity should be measured by microneurography before and after the intervention. The Cochrane Collaboration's Risk of Bias Tool was used to evaluate risk of bias, and the quality of evidence was rated following the GRADE approach. Standardized mean differences (SMD) were calculated for control and experimental groups. Meta-analysis was performed using the random effects model.

RESULTS

Five trials were included. Overall, the trials had moderate risk of bias. The experimental group indicated a significant decrease in the number of bursts per minute (SMD -2.48; 95% CI -3.55 to -1.41) when compared to the control group. Meanwhile, a significant decrease was also observed in the prevalence of bursts per 100 beats in the experimental group when compared to the control group (SMD -2.66; 95% CI -3.64 to -1.69).

CONCLUSION

Exercise training could be effective in reducing sympathetic nerve activity in patients with heart failure. The quality of evidence across the studies was moderate. Future studies are necessary to confirm these results.

Contribution of mitochondrial function to exercise-induced attenuation of renal dysfunction in spontaneously hypertensive rats

It is well known that exercise training exhibits renal protective effects in animal models of hypertension and chronic renal failure. However, the mechanisms regulating these effects of exercise training remain unclear. This study aimed to investigate the role of mitochondrial function in exercise-induced attenuation of renal injury in spontaneously hypertensive rats (SHR). The adult male SHR and age-matched normotensive Wistar-Kyoto rats (WKY) were given moderate-intensity exercise for 12 weeks or treated with MitoQ10 for 8 weeks. In this work, exercise training in SHR reduced blood pressure, and effectively attenuated renal dysfunction, marked by reduced creatinine excretion, albuminuria, blood urea nitrogen, and glomerular sclerosis. Exercise training in SHR reduced MDA levels in plasma and kidneys and suppressed formation of 3-nitrotyrosine in kidneys. Exercise training suppressed mitochondrial ROS and [Formula: see text] formation, enhanced ATP formation, reduced mitochondrial swelling, and restored electron transport chain enzyme activity in kidneys of SHR. Furthermore, exercise training upregulated protein expression of uncoupling protein 2 and manganese superoxide dismutase in kidneys of SHR. In addition, treatment with mitochondria-targeted antioxidant MitoQ10 exhibited similar renal protective effects in SHR. In conclusion, chronic aerobic exercise training preserved mitochondrial function and abated oxidative stress in the kidneys of SHR, which may in part explain the protective effect of exercise on renal function and structure in hypertensive individuals.

Contribution of receptor for advanced glycation end products to vasculature-protecting effects of exercise training in aged rats

The aim of present work was to investigate the underlying mechanism of vasculature-protecting effects of exercise training in aged rats. Experiment 1: aged rats were given moderate-intensity exercise for 12 weeks. Exercise training suppressed advanced glycation evidenced by reduced activity of aldose reductase, increased activity of glyoxalase 1, reduced levels of methylglyoxal and N(ε)-(carboxymethyl) lysine, and decreased expression of receptor for advanced glycation end products (RAGE) in aged aortas. Experiment 2: aged rats were given moderate-intensity exercise for 12 weeks or treated with FPS-ZM1, an inhibitor of RAGE. Exercise training attenuated aortic stiffening with age marked by reduced collagen levels, increased elastin levels and reduced pulse wave velocity (PWV), and prevented aging-related endothelial dysfunction marked by restored endothelium-mediated vascular relaxation of aortas in response to acetylcholine. Exercise training in aging aortas reduced formation of malondialdehyde, 3-nitrotyrosin and reactive oxygen species, increased GSH/GSSG ratio, suppressed activation of NFκB, and reduced levels of IL-6 and chemokine (C-C motif) ligand 2. Similar effects were demonstrated in aged rats treated with FPS-ZM1. Collectively, exercise suppressed advanced glycation in the aortas of aged rats, which, at least in part, explained the vasculature-protecting effects of exercise training in aged population.

Contribution of renin-angiotensin system to exercise-induced attenuation of aortic remodeling and improvement of endothelial function in spontaneously hypertensive rats

INTRODUCTION

It is well known that exercise alleviates aortic remodeling and preserves endothelial function in spontaneously hypertensive rats (SHRs). However, the underlying molecular mechanism remains unclear. This study aimed to investigate the role of renin-angiotensin system (RAS) components in exercise-induced attenuation of aortic remodeling and improvement of endothelial function in an animal model of human essential hypertension.

METHODS

The 10-week-old male SHR and age-matched normotensive Wistar-Kyoto rats were given moderate-intensity exercise for 12weeks (four groups, n=80-86 in each group).

RESULTS

In this work, exercise training reduced blood pressure and effectively attenuated aortic remodeling, marked by a reduction in aortic weight/length, wall thickness, and aortic levels of elastin and hydroxyproline, and improved endothelium-mediated vascular relaxations of aortas in response to acetylcholine. Exercise training in SHR reduced angiotensin II (AngII) levels and enhanced Ang-(1-7) levels in aortas. Exercise training in SHR suppressed aortic angiotensin-converting enzyme (ACE) and AngII type 1 receptor (AT1R) messenger RNA (mRNA) levels and protein expression and up-regulated ACE2, AngII type 2 receptor, and Mas mRNA levels and protein expression. In addition, exercise training in SHR increased levels of microRNA-27a (targeting ACE) and microRNA-155 (targeting AT1R) and decreased levels of microRNA-143 (targeting ACE2) in the aortas.

CONCLUSION

Chronic aerobic exercise training improved RAS balance in the aortas, which may in part explain the protective effect of exercise on aortic function and structure.

SUMMARY

Chronic aerobic exercise training improved RAS balance in the aortas, which may explain the protective effect of exercise on aortic function and structure, at least in part.

Chronic aerobic exercise training attenuates aortic stiffening and endothelial dysfunction through preserving aortic mitochondrial function in aged rats

Aging leads to large vessel arterial stiffening and endothelial dysfunction, which are important determinants of cardiovascular risk. The aim of present work was to assess the effects of chronic aerobic exercise training on aortic stiffening and endothelial dysfunction in aged rats and investigate the underlying mechanism about mitochondrial function. Chronic aerobic exercise training attenuated aortic stiffening with age marked by reduced collagen concentration, increased elastin concentration and reduced pulse wave velocity (PWV), and prevented aging-related endothelial dysfunction marked by improved endothelium-mediated vascular relaxation of aortas in response to acetylcholine. Chronic aerobic exercise training abated oxidative stress and nitrosative stress in aortas of aged rats. More importantly, we found that chronic aerobic exercise training in old rats preserved aortic mitochondrial function marked by reduced reactive oxygen species (ROS) formation and mitochondrial swelling, increased ATP formation and mitochondrial DNA content, and restored activities of complexes I and III and electron-coupling capacity between complexes I and III and between complexes II and III. In addition, it was found that chronic aerobic exercise training in old rats enhanced protein expression of uncoupling protein 2 (UCP-2), peroxisome proliferator-activated receptor γ co-activator 1α (PGC-1α), manganese superoxide dismutase (Mn-SOD), aldehyde dehydrogenase 2 (ALDH-2), prohibitin (PHB) and AMP-activated kinase (AMPK) phosphorylation in aortas. In conclusion, chronic aerobic exercise training preserved mitochondrial function in aortas, which, at least in part, explained the aorta-protecting effects of exercise training in aging.

Swimming exercise changes hemodynamic responses evoked by blockade of excitatory amino receptors in the rostral ventrolateral medulla in spontaneously hypertensive rats

Exercise training reduces sympathetic activity in hypertensive humans and rats. We hypothesized that the swimming exercise would change the neurotransmission in the rostral ventrolateral medulla (RVLM), a key region involved in sympathetic outflow, and hemodynamic control in spontaneously hypertensive rats (SHR) and Wistar-Kyoto (WKY) rats. Bilateral injections of kynurenic acid (KYN) were carried out in the RVLM in sedentary- (S-) or exercised- (E-) SHR and WKY rats submitted to swimming for 6 weeks. Rats were α-chloralose anesthetized and artificially ventilated, with Doppler flow probes around the lower abdominal aorta and superior mesenteric artery. Injections into the RVLM were made before and after i.v. L-NAME (nitric oxide synthase, NOS, inhibitor). Injections of KYN into the RVLM elicited a major vasodilation in the hindlimb more than in the mesenteric artery in E-SHR compared to S-SHR, but similar decrease in arterial pressure was observed in both groups. Injections of KYN into the RVLM after i.v. L-NAME attenuated the hindlimb vasodilation evoked by KYN and increased the mesenteric vasodilation in E-SHR. Swimming exercise can enhance the hindlimb vasodilation mediated by peripheral NO release, reducing the activation of neurons with EAA receptors in the RVLM in SHR.

Exercise training lowers the enhanced tonically active glutamatergic input to the rostral ventrolateral medulla in hypertensive rats

AIMS

It is well known that low-intensity exercise training (ExT) is beneficial to cardiovascular dysfunction in hypertension. The tonically active glutamatergic input to the rostral ventrolateral medulla (RVLM), a key region for control of blood pressure and sympathetic tone, has been demonstrated to be increased in hypertensive rats. The aim of this study was to determine the effect of ExT on the increased glutamatergic input to the RVLM in spontaneously hypertensive rat (SHR).

METHODS

Normotensive rats Wistar-Kyoto (WKY) and SHR were treadmill trained or remained sedentary (Sed) for 12 weeks and classed into four groups (WKY-Sed, WKY-ExT, SHR-Sed, and SHR-ExT). The release of glutamate in the RVLM and its contribution to cardiovascular activity were determined in WKY and SHR after treatment of ExT.

RESULTS

Blood pressure and sympathetic tone were significantly reduced in SHR after treatment with ExT. Bilateral microinjection of the glutamate receptor antagonist kynurenic acid (2.7 nmol in 100 nL) into the RVLM significantly decreased resting blood pressure, heart rate, and renal sympathetic nerve activity in SHR-Sed but not in WKY groups (WKY-Sed and WKY-ExT). However, the degree of reduction in these cardiovascular parameters evoked by KYN was significantly blunted in SHR-ExT compared with SHR-Sed group. The concentration of glutamate and the protein expression of vesicular glutamate transporter 2 in the RVLM were significantly increased in SHR-Sed compared with WKY-Sed, whereas they were reduced after treatment with ExT.

CONCLUSION

Our findings suggest that ExT attenuates the enhancement in the tonically acting glutamatergic input to the RVLM of hypertensive rats, thereby reducing the sympathetic hyperactivity and blood pressure.

Chronic exercise modulates RAS components and improves balance between pro- and anti-inflammatory cytokines in the brain of SHR

Recently, exercise has been recommended as a part of lifestyle modification for all hypertensive patients; however, the precise mechanisms of its effects on hypertension are largely unknown. Therefore, this study aimed to investigate the mechanisms within the brain that can influence exercise-induced effects in an animal model of human essential hypertension. Young normotensive WKY rats and SHR were given moderate-intensity exercise for 16 weeks. Blood pressure was measured bi-weekly by tail-cuff method. Animals were then euthanized; paraventricular nucleus (PVN) and rostral ventrolateral medulla (RVLM), important cardiovascular regulatory centers in the brain, were collected and analyzed by real-time RT-PCR, Western blot, EIA, and fluorescent microscopy. Exercise of 16-week duration attenuated systolic, diastolic, and mean arterial pressure in SHR. Sedentary SHR exhibited increased pro-inflammatory cytokines (PICs) and decreased anti-inflammatory IL-10 levels in the PVN and RVLM. Furthermore, SHR(sed) rats exhibited elevated levels of ACE, AT1R, and decreased levels of ACE2 and receptor Mas in the PVN and RVLM. Chronic exercise not only prevented the increase in PICs (TNF-α, IL-1β), ACE, and AT1R protein expression in the brain of SHR, but also dramatically upregulated IL-10, ACE2, and Mas receptor expression in SHR. In addition, these changes were associated with reduced plasma AngII levels, reduced neuronal activity, reduced NADPH-oxidase subunit gp91(phox) and inducible NO synthase in trained SHRs indicating reduced oxidative stress. These results suggest that chronic exercise not only attenuates PICs and the vasoconstrictor axis of the RAS but also improves the anti-inflammatory defense mechanisms and vasoprotective axis of the RAS in the brain, which, at least in part, explains the blood pressure-lowering effects of exercise in hypertension.

Involvement of the atrial natriuretic peptide in the reduction of arterial pressure induced by swimming but not by running training in hypertensive rats

The aim of this study was to compare, under resting conditions, the influence of chronic training in swimming or running on mean arterial pressure (MAP) and the involvement of the natriuretic peptide system in this response. Two-month-old male spontaneously hypertensive rats (SHR) were divided into three groups-sedentary (SD), swimming (SW) and running (RN)-and were trained for eight weeks under regimens of similar intensities. Atria tissue and plasma atrial natriuretic peptide (ANP) concentrations were measured by radioimmunoassay. ANP mRNA levels in the right and left atria as well as the natriuretic peptide receptors (NPR), NPR-A and NPR-C, mRNA levels in the kidney were determined by real-time PCR. Autoradiography was used to quantify NPR-A and NPR-C in mesenteric adipose tissue. Both training modalities, swimming and running, reduced the mean arterial pressure (MAP) of SHR. Swimming, but not running, training increased plasma levels of ANP compared to the sedentary group (P<0.05). Expression of ANP mRNA in the left atrium was reduced in the RN compared to the SD group (P<0.05). Expression of NPR-A and NPR-C in the kidneys of the SW group decreased significantly (P<0.05) compared to the SD group. Although swimming increased (125)I-ANP binding to mesenteric adipose tissue, displacement by c-ANF was reduced, indicating a reduction of NPR-C. These results suggest that the MAP reduction induced by exercise in SHR differs in its mechanisms between the training modalities, as evidenced by the finding that increased levels of ANP were only observed after the swimming regimen.

Exercise training attenuates acute hyperalgesia in streptozotocin-induced diabetic female rats

OBJECTIVES

We investigated the effects of chronic (eight weeks) low-to moderate-intensity swimming training on thermal pain sensitivity in streptozotocin-induced diabetic female rats.

METHODS

Female Wistar rats (n = 51) were divided into the following groups: trained streptozotocin-induced diabetic rats [hyperglycemic trained (HT)], sedentary streptozotocin-induced diabetic rats [hyperglycemic sedentary (HS)], normoglycemic trained rats (NT) and normoglycemic sedentary rats (NS). Diabetes was induced by a single injection of streptozotocin (50 mg/kg, i.p.). One day after the last exercise protocol (60 min/day, five days/week for eight weeks) in the trained groups or after water stress exposure (ten min/twice a week) in the sedentary groups, the rats were subjected to a hot plate test.

RESULTS

After eight weeks of swimming training, streptozotocin-induced diabetic rats presented a significantly lower body mass (trained: 219.5 ± 29 g, sedentary: 217.8 ± 23 g) compared with the normoglycemic groups (trained: 271 ± 24 g, sedentary: 275.7 ± 32 g). Interestingly, we did not find differences in blood glucose levels (mg/dl) between the trained and sedentary groups of the hyperglycemic or normoglycemic rats (HT: 360.2 ± 66.6, HS: 391.7 ± 66.7, NT: 83.8 ± 14.0, NS: 77.5 ± 10.1). In the hot plate test, the rats from the HT group presented a significantly lower latency than the other rats (HT: 11.7 ± 7.38 s, HS: 7.02 ± 7.38 s, NT: 21.21 ± 7.64 s, NS: 22.82 ± 7.82 s).

CONCLUSION

Low-to-moderate swimming training for a long duration reduces thermal hyperalgesia during a hot plate test in streptozotocin-induced diabetic female rats.