Luciana V. Rossoni

Effects of aerobic exercise training on antioxidant enzyme activities and mRNA levels in soleus muscle from young and aged rats

The aim of this study was to investigate the effect of aerobic exercise training on activities and mRNA levels of catalase (CAT), glutathione peroxidase (GPX), Cu,Zn- and Mn-superoxide dismutases (SOD), TBARS content, and xanthine oxidase (XO) activity, in soleus muscle from young and aged rats. The antioxidant enzyme activities and mRNA levels were markedly increased in soleus muscle with aging. TBARS content of soleus muscle from the aged group was 8.3-fold higher as compared with that of young rats. In young rats, exercise training induced an increase of all antioxidant enzyme activities, except for Cu,Zn-SOD. XO also did not change. The TBARS content was also increased (2.9-fold) due to exercise training in soleus muscle from young rats. In aged rats, the activities of CAT, GPX and Cu,Zn-SOD in the soleus muscle did not change with the exercise training, whereas the activities of Mn-SOD (40%) and XO (27%) were decreased. The mRNA levels of Mn-SOD and CAT were decreased by 42% and 24%, respectively, in the trained group. Exercise training induced a significant decrease of TBARS content (81%) in the soleus muscle from aged rats. These findings support the proposition that exercise training presents an antioxidant stress effect on skeletal muscle from both young and aged rats.

Oxidative stress and inflammatory mediators contribute to endothelial dysfunction in high-fat diet-induced obesity in mice

Objective We investigated the effects of high-fat diet-induced obesity on vascular proinflammatory factors and oxidative stress on endothelium-dependent relaxation of the aorta. Methods Female Swiss mice were submitted to a high-fat diet for 16 weeks. At the end of the experimental period, we evaluated blood pressure, relaxation in response to acetylcholine in aortic rings in the absence and the presence of the superoxide anion scavenger, superoxide dismutase (SOD, 150 U/ml), and the nuclear factor (NF)-κB inhibitor, sodium salicylate (5 mmol/l). Aortic protein expression of endothelial nitric oxide synthase, Cu/Zn-SOD, NF-κB, IκB-α, and proinflammatory cytokines were also evaluated. Results Obese mice presented higher systolic and diastolic blood pressure than control mice (P < 0.05). The relaxation of aortas to acetylcholine, but not to sodium nitroprusside, was significantly decreased in obese mice and was corrected by both SOD and sodium salicylate (P < 0.05). The protein expression of endothelial nitric oxide synthase and Cu/Zn-SOD was significantly decreased in aorta from obese mice (P < 0.05). Total p65 NF-κB subunit protein expression was not affected by obesity, but the protein expression of NF-κB inhibitor IκB-α was lower in aorta from obese mice (P < 0.05). There were no significant differences in the interleukin (IL)-1β and IL-6 protein expression between groups. In contrast, the expression of TNF-α was significantly increased in aortas from obese mice. Conclusion Our results suggest that the reduced antioxidant defense and the local NF-κB pathway play an important role in the impairment of endothelium-dependent relaxation in aorta from obese mice.

Dipeptidyl peptidase IV inhibition attenuates blood pressure rising in young spontaneously hypertensive rats.

Objectives The present study aimed to assess the effect of the specific dipeptidyl peptidase IV (DPPIV) inhibitor sitagliptin on blood pressure and renal function in young prehypertensive (5-week-old) and adult spontaneously hypertensive rats (SHRs; 14-week-old). Methods Sitagliptin (40 mg/kg twice daily) was given by oral gavage to young (Y-SHR + IDPPIV) and adult (A-SHR + IDPPIV) SHRs for 8 days. Kidney function was assessed daily and compared with age-matched vehicle-treated SHR (Y-SHR and A-SHR) and with normotensive Wistar–Kyoto rats (Y-WKY and A-WKY). Arterial blood pressure was measured in these animals at the end of the experimental protocol. Additionally, Na+/H+ exchanger isoform 3 (NHE3) function and expression in microvilli membrane vesicles were assessed in young animals. Results Mean arterial blood pressure of Y-SHR + IDPPIV was significantly lower than that of Y-SHR (104 ± 3 vs. 123 ± 5 mmHg, P < 0.01) and was similar to Y-WKY (94 ± 4 mmHg, P > 0.05). Compared to Y-SHR, Y-SHR + IDPPIV exhibited enhanced cumulative urinary flow and sodium excretion and decreased NHE3 activity and expression in proximal tubule microvilli. In the A-SHR, sitagliptin treatment had no significant effect on either renal function or arterial blood pressure. Conclusion Our data suggest that DPPIV inhibition attenuates blood pressure rising in young prehypertensive SHRs, partially by inhibiting NHE3 activity in renal proximal tubule.

Exercise training improves relaxation response and SOD-1 expression in aortic and mesenteric rings from high caloric diet-fed rats

BackgroundObesity has been associated with a variety of disease such as type II diabetes mellitus, arterial hypertension and atherosclerosis. Evidences have shown that exercise training promotes beneficial effects on these disorders, but the underlying mechanisms are not fully understood. The aim of this study was to investigate whether physical preconditioning prevents the deleterious effect of high caloric diet in vascular reactivity of rat aortic and mesenteric rings.MethodsMale Wistar rats were divided into sedentary (SD); trained (TR); sedentary diet (SDD) and trained diet (TRD) groups. Run training (RT) was performed in sessions of 60 min, 5 days/week for 12 weeks (70–80% VO2max). Triglycerides, glucose, insulin and nitrite/nitrate concentrations (NOx-) were measured. Concentration-response curves to acetylcholine (ACh) and sodium nitroprusside (SNP) were obtained. Expression of Cu/Zn superoxide dismutase (SOD-1) was assessed by Western blotting.ResultsHigh caloric diet increased triglycerides concentration (SDD: 216 ± 25 mg/dl) and exercise training restored to the baseline value (TRD: 89 ± 9 mg/dl). Physical preconditioning significantly reduced insulin levels in both groups (TR: 0.54 ± 0.1 and TRD: 1.24 ± 0.3 ng/ml) as compared to sedentary animals (SD: 0.87 ± 0.1 and SDD: 2.57 ± 0.3 ng/ml). On the other hand, glucose concentration was slightly increased by high caloric diet, and RT did not modify this parameter (SD: 126 ± 6; TR: 140 ± 8; SDD: 156 ± 8 and TRD 153 ± 9 mg/dl). Neither high caloric diet nor RT modified NOx- levels (SD: 27 ± 4; TR: 28 ± 6; SDD: 27 ± 3 and TRD: 30 ± 2 μM). Functional assays showed that high caloric diet impaired the relaxing response to ACh in mesenteric (about 13%), but not in aortic rings. RT improved the relaxing responses to ACh either in aortic (28%, for TR and 16%, to TRD groups) or mesenteric rings (10%, for TR and 17%, to TRD groups) that was accompanied by up-regulation of SOD-1 expression and reduction in triglycerides levels.ConclusionThe improvement in endothelial function by physical preconditioning in mesenteric and aortic arteries from high caloric fed-rats was directly related to an increase in NO bioavailability to the smooth muscle mostly due to SOD-1 up regulation.

Toxic Effects of Mercury on the Cardiovascular and Central Nervous Systems

Environmental contamination has exposed humans to various metal agents, including mercury. This exposure is more common than expected, and the health consequences of such exposure remain unclear. For many years, mercury was used in a wide variety of human activities, and now, exposure to this metal from both natural and artificial sources is significantly increasing. Many studies show that high exposure to mercury induces changes in the central nervous system, potentially resulting in irritability, fatigue, behavioral changes, tremors, headaches, hearing and cognitive loss, dysarthria, incoordination, hallucinations, and death. In the cardiovascular system, mercury induces hypertension in humans and animals that has wide-ranging consequences, including alterations in endothelial function. The results described in this paper indicate that mercury exposure, even at low doses, affects endothelial and cardiovascular function. As a result, the reference values defining the limits for the absence of danger should be reduced.

Vasorelaxant effects of eugenol on rat thoracic aorta.

Eugenol is a natural pungent substance and the main component of clove oil, with vasorelaxant action. To elucidate some of the possible mechanisms involved in this action isometric tension was measured in aortic rings from male Wistar rats precontracted with phenylephrine (PHE, 10(-7) M) or KCl (75 mM). Responses to increasing concentrations of eugenol (10(-6)-10(-2) M) were obtained in the presence and absence of endothelium. In the presence of eugenol, dose-response curves to PHE (10(-9) to 10(-4) M) and KCl (5-125 mM) were displaced downwards. Concentration-dependent relaxation was observed in rings precontracted with PHE (10(-7) M) and KCl (75 mM). The tension increment produced by increasing external calcium concentration (0.25-3 mM) was also reduced by eugenol (300 microM) treatment. The inhibitory effects of eugenol (300 microM) were compared to those induced by nifedipine (0.01 microM), a selective Ca(2+) channel blocker, producing similar relaxant effects. Two other protocols were performed. After precontraction with PHE (10(-7) M), increasing concentrations of eugenol (10(-6)-10(-2) M) were used before and after N(w)-nitro-L-arginine (L-NAME, 10(-4) M) and methylene blue (10(-5) M) treatment. Eugenol-induced relaxation was reduced by endothelial damage (rubbing), L-NAME and methylene blue treatments. Results suggested that eugenol produces smooth muscle relaxation resulting from the blockade of both voltage-sensitive and receptor-operated channels that are modulated by endothelial-generated nitric oxide.

Alterations in phenylephrine-induced contractions and the vascular expression of Na+,K+-ATPase in ouabain-induced hypertension

Hypertension development, phenylephrine‐induced contraction and Na+,K+‐ATPase functional activity and protein expression in aorta (AO), tail (TA) and superior mesenteric (SMA) arteries from ouabain‐ (25 μg day−1, s.c., 5 weeks) and vehicle‐treated rats were evaluated. Ouabain treatment increased systolic blood pressure (127±1 vs 160±2 mmHg, n=24, 35; P<0.001) while the maximum response to phenylephrine was reduced (P<0.01) in AO (102.8±3.9 vs 67.1±10.1% of KCl response, n=12, 9) and SMA (82.5±7.5 vs 52.2±5.8%, n=12, 9). Endothelium removal potentiated the phenylephrine response to a greater extent in segments from ouabain‐treated rats. Thus, differences of area under the concentration‐response curves (dAUC) in endothelium‐denuded and intact segments for control and ouabain‐treated rats were, respectively: AO, 56.6±9.6 vs 198.3±18.3 (n=9, 7); SMA, 85.5±15.4 vs 165.4±24.8 (n=6, 6); TA, 13.0±6.1 vs 39.5±10.4% of the corresponding control AUC (n=6, 6); P<0.05. The relaxation to KCl (1 – 10 mM) was similar in segments from both groups. Compared to controls, the inhibition of 0.1 mM ouabain on KCl relaxation was greater in AO (dAUC: 64.8±4.6 vs 84.0±5.1%, n=11, 14; P<0.05), similar in SMA (dAUC: 39.1±3.9 vs 43.3±7.8%, n=6, 7; P>0.05) and smaller in TA (dAUC: 62.1±5.5 vs 41.4±8.2%, n=12, 13; P<0.05) in ouabain‐treated rats. Protein expression of both α1 and α2 isoforms of Na+,K+‐ATPase was augmented in AO, unmodified in SMA and reduced in TA from ouabain‐treated rats. These results suggest that chronic administration of ouabain induces hypertension and regional vascular alterations, the latter possibly as a consequence of the hypertension.

Aldosterone induces endothelial dysfunction in resistance arteries from normotensive and hypertensive rats by increasing thromboxane A2 and prostacyclin

The present study was designed to assess whether cyclooxygenase‐2 (COX‐2) activation is involved in the effects of chronic aldosterone treatment on endothelial function of mesenteric resistance arteries (MRA) from Wistar‐Kyoto (WKY) and spontaneously hypertensive rats (SHR).

Dehydroepiandrosterone protects against oxidative stress-induced endothelial dysfunction in ovariectomized rats

Non‐technical summary  It is well known that cardiovascular disease is more frequent in postmenopausal than in premenopausal women. Moreover, it has been shown that dehydroepiandrosterone (DHEA), a steroid hormone secreted by adrenal glands, reduces during ageing. Its reduced plasma level has been related to increased prevalence of obesity, insulin resistance and cardiovascular disease. We show that DHEA treatment in ovariectomized rats, an experimental model of menopause, reduces blood pressure and improves vascular function. Furthermore, DHEA reduced reactive oxygen species (ROS), correcting the reduced protein expression of Cu/Zn‐SOD, an antioxidant protein, and increased protein expression of NADPH oxidase, a pro‐oxidant protein. This work shows the potential effect of DHEA upon correction of endothelial dysfunction observed on oestrogen deprivation.

Time-dependent hyperreactivity to phenylephrine in aorta from untreated diabetic rats: role of prostanoids and calcium mobilization.

Diabetes alters vascular smooth muscle contractility. Changes in reactivity to phenylephrine (Phe) in aortas from controls and untreated 1- and 4-week streptozotocin (STZ)-induced diabetic rats were investigated. In 1-week diabetic (DB1) aortas, the maximum response (E(max)) and sensitivity (pD(2)) to Phe were similar to controls (CT1), but in 4-week diabetic (DB4) aortas, the E(max) for Phe was increased compared to CT4 aortas (E(max), DB4: 125+/-8.4% vs. CT4: 89.8+/-4.5%, P<.001). Endothelial denudation increased the response to Phe, and E(max) was increased in the DB4 aortas compared to CT4 (E(max), DB4: 156+/-4.2% vs. CT4: 125+/-3.8%, P<.001). Pretreatment of CT4 and DB4 aortas with indomethacin reduced E(max) and pD(2) for Phe. After indomethacin treatment, no differences in E(max) and pD(2) to Phe were observed in either group. SQ 29548 did not alter the Phe actions in CT4 aortas. However, in DB4 aortas, E(max) was reduced to control level. CT4 and DB4 aortas incubated in free-Ca(2+) solution plus Phe, contracted upon addition of CaCl(2), this response was increased in DB4 aortas. No changes were observed for acetylcholine (ACh) or sodium nitroprusside (SNP) responses. Nitric oxide (NO) release in response to Phe determined by acute L-NAME administration showed no differences in the percentage increase of the contraction in CT1 and DB1 aortas, but was enhanced in DB4 aortas. Results suggested that diabetes induces time-dependent changes in the vascular reactivity to Phe. This response is not related to a reduction of endothelium-derived NO but might be due to an increase in prostaglandin H(2) (PGH(2))/thromboxane A(2) (TxA(2)) and/or an enhanced extracellular Ca(2+) influx.