Changes in creatine kinase expression induced by exercise in borderline hypertensive rat hearts

Effects of concurrent training and N-acetylcysteine supplementation on cardiac remodeling and oxidative stress in middle-aged spontaneously hypertensive rats

BACKGROUND

This study evaluated the effects of concurrent isolated training (T) or training combined with the antioxidant N-acetylcysteine (NAC) on cardiac remodeling and oxidative stress in spontaneously hypertensive rats (SHR).

METHODS

Six-month-old male SHR were divided into sedentary (S, n = 12), concurrent training (T, n = 13), sedentary supplemented with NAC (SNAC, n = 13), and concurrent training with NAC supplementation (TNAC, n = 14) groups. T and TNAC rats were trained three times a week on a treadmill and ladder; NAC supplemented groups received 120 mg/kg/day NAC in rat chow for eight weeks. Myocardial antioxidant enzyme activity and lipid hydroperoxide concentration were assessed by spectrophotometry. Gene expression of NADPH oxidase subunits Nox2, Nox4, p22 phox, and p47 phox was evaluated by real time RT-PCR. Statistical analysis was performed using ANOVA and Bonferroni or Kruskal-Wallis and Dunn.

RESULTS

Echocardiogram showed concentric remodeling in TNAC, characterized by increased relative wall thickness (S 0.40 ± 0.04; T 0.39 ± 0.03; SNAC 0.40 ± 0.04; TNAC 0.43 ± 0.04 *; * p < 0.05 vs T and SNAC) and diastolic posterior wall thickness (S 1.50 ± 0.12; T 1.52 ± 0.10; SNAC 1.56 ± 0.12; TNAC 1.62 ± 0.14 * mm; * p < 0.05 vs T), with improved contractile function (posterior wall shortening velocity: S 39.4 ± 5.01; T 36.4 ± 2.96; SNAC 39.7 ± 3.44; TNAC 41.6 ± 3.57 * mm/s; * p < 0.05 vs T). Myocardial lipid hydroperoxide concentration was lower in NAC treated groups (S 210 ± 48; T 182 ± 43; SNAC 159 ± 33 *; TNAC 110 ± 23 *# nmol/g tissue; * p < 0.05 vs S, # p < 0.05 vs T and SNAC). Nox 2 and p22 phox expression was higher and p47 phox lower in T than S [S 1.37 (0.66-1.66); T 0.78 (0.61-1.04) *; SNAC 1.07 (1.01-1.38); TNAC 1.06 (1.01-1.15) arbitrary units; * p < 0.05 vs S]. NADPH oxidase subunits did not differ between TNAC, SNAC, and S groups.

CONCLUSION

N-acetylcysteine supplementation alone reduces oxidative stress in untreated spontaneously hypertensive rats. The combination of N-acetylcysteine and concurrent exercise further decreases oxidative stress. However, the lower oxidative stress does not translate into improved cardiac remodeling and function in untreated spontaneously hypertensive rats.

Combined Effects of Methyldopa and Baicalein or Scutellaria baicalensis Roots Extract on Blood Pressure, Heart Rate, and Expression of Inflammatory and Vascular Disease-Related Factors in Spontaneously Hypertensive Pregnant Rats

The aim of the study was to investigate the effect of baicalein or Scutellaria baicalensis root extract interaction with methyldopa in pregnant spontaneously hypertensive rats (SHR) at the pharmacodynamic, molecular, and biochemical levels. The rats, after confirming pregnancy, received baicalein (200 mg/kg/day, p.o.) and extract (1000 mg/kg/day, p.o.), in combination with methyldopa (400 mg/kg/day; p.o.), for 14 consecutive days, 1 h before blood pressure and heart rate measurements. In the heart and placenta from mothers after giving birth to their offspring, mRNA expression of factors related to inflammatory processes (TNF-α, Il-1β, IL-6) and vascular diseases (TGF-β, HIF-1α, VEGF, PlGF) was measured. Levels of markers of oxidative stress (superoxide dismutase and malondialdehyde) in the placenta and indicators of myocardial damage (troponin cTnC and cTnI, creatine kinase, myoglobin, and lactate dehydrogenase) in the heart were also assessed. Baicalein co-administered with methyldopa was associated with reduced blood pressure, especially during the first three days. The interactions were more pronounced for such factors as TGF-β, HIF-1α, VEGF, and PlGF than TNF-α, Il-1β, and IL-6. Combined application of baicalein and extract with methyldopa may be of value in the development of a new antihypertensive medication intended for patients suffering from preeclampsia or pregnancy-induced hypertension.

Exercise intensities modulate cognitive function in spontaneously hypertensive rats through oxidative mediated synaptic plasticity in hippocampus

Oxidative damage in the brain may lead to cognitive impairments. There was considerable debate regarding the beneficial effects of physical exercise on cognitive functions because exercise protocols have varied widely across studies. We investigated whether different exercise intensities alter performance on cognitive tasks. The experiment was performed on spontaneously hypertensive rats (6 months at the established phase of hypertension) distributed into 3 groups: sedentary, low-intensity exercise and high-intensity exercise. Systolic blood pressure measurements confirmed hypertension in spontaneously hypertensive rats. In comparison to normotensive Wistar-Kyoto rats, sedentary spontaneously hypertensive rats had similar escape latencies and a similar preference for the correct quadrant in the probe trial. Compared to the sedentary group, the low-intensity exercise group had significantly better improvements in spatial memory assessed by Morris water maze. Low-intensity exercise was associated with attenuated reactive oxygen species, as measured by dihydroethidine fluorescence and nitrotyrosine staining in the dentate gyrus of the hippocampus. This was coupled with increased numbers of neurons and dendritic spines as well as a significant upregulation of synaptic density. In contrast, the beneficial effects of low-intensity exercise are abolished in high-intensity exercise as shown by increased free radical levels and an impairment in spatial memory. We concluded that exercise is an effective strategy to improve spatial memory in spontaneously hypertensive rats even at an established phase of hypertension. Low-intensity exercise exhibited better improvement on cognitive deficits than high-intensity exercise by attenuating free radical levels and improving downstream synaptic plasticity.

Exercise-induced increases in the expression and activity of cardiac sarcoplasmic reticulum calcium ATPase 2 is attenuated in AMPKα2kinase-dead mice

Exercise enhances cardiac sarcoplasmic reticulum Ca2+-ATPase 2a (SERCA2a) function through unknown mechanisms. The present study tested the hypothesis that the positive effects of exercise on SERCA2a expression and function in the left ventricle is dependent on adenosine-monophosphate-activated protein kinase (AMPK) α2 function. AMPKα2kinase-dead (KD) transgenic mice, which overexpress inactivated AMPKα2subunit, and wild-type C57Bl/6 (WT) mice were randomized into sedentary groups or groups with access to running wheels. After 5 months, exercised KD mice exhibited shortened deceleration time compared with sedentary KD mice. In left ventricular tissue, the ratio of phosphorylated AMPKαThr172:total AMPKα was 65% lower (P < 0.05) in KD mice compared with WT mice. The left ventricle of KD mice had 37% lower levels of SERCA2a compared with WT mice. Although exercise increased SERCA2a protein levels in WT mice by 53%, this response of exercise was abolished in exercised KD mice. Exercise training reduced total phospholamban protein content by 23% in both the WT and KD mice but remained 20% higher overall in KD mice. Collectively, these data suggest that AMPKα influences SERCA2a and phospholamban protein content in the sedentary and exercised heart, and that exercise-induced changes in SERCA2a protein are dependent on AMPKα function.

Exercise training enhanced the expression of myocardial proteins related to cell protection in spontaneously hypertensive rats

Exercise training could potentially exert beneficial effects on the signaling events associated with cardiac cell apoptosis. Spontaneously hypertensive rats (SHR) were trained 5 days/week on a treadmill (18 m/min for 120 min/day) between the ages of 4 weeks and 1 week, corresponding to the hypertensive accelerating phase. The effect of exercise training on the expression of anti-apoptotic proteins HSP-72, Bcl-2 and protein kinase B (PKB), and the apoptotic proteins Bax and glycogen synthase kinase-3 (GSK-3) was examined. Exercise had a significant acute lowering effect on blood pressure, but this decrease did not attenuate the progressive increase in blood pressure. In the left ventricles of exercised SHR, PKB phosphorylation of both Ser473 and Thr308 residues was significantly increased by 166% and 120%, respectively, compared to sedentary SHR. PKB phosphorylation significantly correlated with GSK-3beta phosphorylation. HSP-72 and Bcl-2 protein expression were increased in the left ventricle of exercised SHR, and associated with the concomitant increased expression of the protein Bax. Thus, the Bcl-2/Bax ratio was not changed by exercise training, suggesting that the anti-apoptotic mechanism was effective in compensating the increase in the expression of the pro-apoptotic protein Bax in the myocardium of the SHR.

Effect of exercise training on liver antioxidant status of deoxycorticosterone acetate salt induced hypertensive rats

Several animal models have been developed to study the pathogenesis of hypertension. Deoxycorticosterone acetate (DOCA) salt induced hypertensive rats are adrenal models used to mimic human Conn's syndrome. Because previous studies showed a beneficial effect of chronic exercise (swimming) on the development of arterial hypertension in spontaneously hypertensive rats (which appears similar to human essential hypertension), we decided to evaluate the effects of swimming on DOCA-salt induced hypertension and liver antioxidant status. Therefore, the aim of this experiment was to study whether the swim training would improve hypertension and liver antioxidant status in DOCA-salt rats. DOCA-salt rats and control Sprague-Dawley rats were trained to swim 1 h/day, 5 days/week for 6 weeks and were sacrificed 48 h after the last exercise period. Systolic blood pressure was recorded before the sacrifice, and liver antioxidant status was evaluated in hepatic homogenates after the sacrifice. Swim exercise did not decrease systolic blood pressure in control and DOCA-salt rats but induced changes in liver activities of antioxidant enzymes, showing that exercise provoked liver oxidative stress in control and DOCA-salt rats. In comparison with our previous studies using spontaneously hypertensive rats, we conclude that the beneficial effects of chronic exercise on systolic blood pressure in rats are dependent on strain and the type of experimental hypertension.