Acute arrhythmogenesis after myocardial infarction in normotensive rats: Influence of high salt intake

Intermittent exposure to chlorpyrifos results in cardiac hypertrophy and oxidative stress in rats

Forbidden in some countries due to its proven toxicity to humans, chlorpyrifos (CPF) still stands as an organophosphate pesticide (OP) highly used worldwide. Cardiotoxicity assessment is an unmet need in pesticide regulation and should be deeply studied through different approaches to better inform and generate an appropriate regulatory response to OP use. In the present study, we used our 4-week intermittent OP exposure model in rats to address the CPF effects on cardiac morphology allied with cardiovascular functional and biomolecular evaluation. Rats were intermittently treated with CPF at doses of 7 mg/kg and 10 mg/kg or saline (i.p.) and assessed for cardiac morphology (cardiomyocyte diameter and collagen content), cardiopulmonary Bezold-Jarisch reflex (BJR) function, cardiac autonomic tone, left ventricle (LV) contractility, cardiac expression of NADPH oxidase (Nox2), catalase (CAT), superoxide dismutase 1 (SOD1), superoxide dismutase 2 (SOD2) and cardiac levels of advanced oxidation protein products (AOPP) and thiobarbituric acid reactive substances (TBARS). Plasma butyrylcholinesterase (BuChE) and brainstem acetylcholinesterase (AChE) were also measured. Intermittent exposure to CPF induced cardiac hypertrophy, increasing cardiomyocyte diameter and collagen content. An impairment of cardioinhibitory BJR responses and an increase in cardiac vagal tone were also observed in CPF-treated animals without changes in LV contractility. CPF exposure increased cardiac Nox-2, CAT, SOD1, and TBARS levels and inhibited plasma BuChE and brainstem AChE activities. Our data showed that intermittent exposure to CPF induces cardiac hypertrophy together with cardiovascular reflex impairment, imbalance of autonomic tone and oxidative stress, which may bring significant cardiovascular risk to individuals exposed to OP compounds seasonally.

Ellagic Acid Prevents Myocardial Infarction-induced Left Ventricular Diastolic Dysfunction in Ovariectomized Rats

Estrogen deficiency is associated with increased oxidative stress, which can contribute to left ventricular diastolic dysfunction (LVDD). We hypothesized that oral treatment with ellagic acid (EA), a potent and natural antioxidant compound, can improve MI-induced LVDD in ovariectomized rats, by reducing the formation of reactive oxygen species (ROS). Ovariectomized rats MI-induced LVDD followed by treatment with vehicle (DD) or EA (DD+EA) for 4 weeks. Non-LVDD-induced rats treated with vehicle (S) or EA (S+EA) were used as controls. Left ventricular systolic pressure: LVSP; left ventricular end-diastolic pressure: LVEDP; maximum rate of pressure rise: +dP/dt and fall: -dP/dt) were evaluated in all animals after treatment. Left ventricle superoxide anion formation was quantified in situ by fluorescence. Phospho-CAMKII, SOD2, catalase and gp91-phox abundances were evaluated by Western blot analyses. SOD and catalase activities were measured by spectrophotometry. The results showed that the LVEDP was significantly increased in both DD and DD+EA groups compared to S and S+EA. However, LVEDP in the DD+EA group was significantly decreased compared to DD, indicating an EA-mediated effect. In the DD group, superoxide production and gp91-phox protein abundance were increased while SOD2 abundance was decreased when compared to the S and S+EA groups. An increase in SOD activity was also observed in the DD+EA group. EA treatment reduced CaMKII phosphorylation in the DD+EA group compared to the DD. We concluded that EA treatment attenuated diastolic dysfunction in our experimental model, via reduction of ROS and CaMKII activity, indicating EA as a promising natural therapeutic option for cardiac dysfunction.

Discrepant acute effect of saline loading on blood pressure, urinary sodium and potassium according to salt intake level: EpiSS study

Acute dietary salt intake may cause an elevation in blood pressure (BP). The study aimed to assess the acute effect of saline loading on BP in subjects with different levels of salt intake. This study is based on the baseline survey of systemic epidemiology of salt sensitivity study. The sodium excretion in the 24-hour urine was calculated for estimating the level of salt intake. Subjects were performed an acute oral saline loading test (1 L), and data of 2019 participants were included for analyses. Multivariate linear regression and stratified analyses were performed to identify associations between 24-hour urinary sodium (24hUNa) with BP changes. Due to saline loading, systolic BP (SBP), pulse pressure, and urinary sodium concentration were significantly increased, while diastolic BP, heart rate, and urinary potassium concentration were significantly decreased. The SBP increments were more significant in subjects with lower salt intake, normotensives, elders, males, smokers, and drinkers. There was a significant linear negative dose-response association between SBP increment with 24hUNa (β = -0.901, 95% CI: -1.253, -0.548), especially in lower salt intake individuals (β = -1.297, 95% CI: -2.338, -0.205) and hypertensive patients (β = -1.502, 95% CI: -2.037, -0.967). After excluding patients who received antidiabetic or antihypertensive medicines, the effects of negative associations weakened but remained significantly. In conclusion, acute salt loading leads to an increment in SBP, and the increased SBP was negatively related with 24hUNa. This study indicated avoiding acute salt loading was important for escaping acute BP changes, especially in lower salt intake populations.

Estrogen Therapy Worsens Cardiac Function and Remodeling and Reverses the Effects of Exercise Training After Myocardial Infarction in Ovariectomized Female Rats

There is an increase in the incidence of cardiovascular events such as myocardial infarction (MI) after menopause. However, the use of estrogen therapy (E2) remains controversial. The aim of this study was to evaluate the effects of E2, alone and combined with exercise training (ET), on cardiac function and remodeling in ovariectomized (OVX) rats after MI. Wistar female rats underwent ovariectomy, followed by MI induction were separated into five groups: S; MI; MI+ET; MI+E2; and MI+ET+E2. Fifteen days after MI or sham surgery, treadmill ET and/or estrogen therapy [17-β estradiol-3-benzoate (E2), s.c. three times/week] were initiated and maintained for 8 weeks. After the treatment and/or training period, the animals underwent cardiac hemodynamic evaluation through catheterization of the left ventricle (LV); the LV systolic and diastolic pressures (LVSP and LVEDP, respectively), maximum LV contraction and relaxation derivatives (dP/dt+ and dP/dt−), and isovolumic relaxation time (Tau) were assessed. Moreover, histological analyses of the heart (collagen and hypertrophy), cardiac oxidative stress [advanced oxidation protein products (AOPPs)], pro- and antioxidant protein expression by Western blotting and antioxidant enzyme activity in the heart were evaluated. The MI reduced the LVSP, dP/dt+ and dP/dt− but increased the LVEDP and Tau. E2 did not prevent the MI-induced changes in cardiac function, even when combined with ET. An increase in the dP/dt+ was observed in the E2 group compared with the MI group. There were no changes in collagen deposition and myocyte hypertrophy caused by the treatments. The increases in AOPP, gp91-phox, and angiotensin II type 1 receptor expression induced by MI were not reduced by E2. There were no changes in the expression of catalase caused by MI or by the treatments, although, a reduction in superoxide dismutase (SOD) expression occurred in the groups subjected to E2 treatment. Whereas there were post-MI reductions in activities of SOD and catalase enzymes, only that of SOD was prevented by ET. Therefore, we conclude that E2 therapy does not prevent the MI-induced changes in cardiac function and worsens parameters related to cardiac remodeling. Moreover, E2 reverses the positive effects of ET when used in combination, in OVX infarcted female rats.

Development of pharmacological screening method for evaluation of effect of drug on elevated pulse pressure and arterial stiffness

INTRODUCTION

Elevated pulse pressure (PP) and amplification of arterial stiffness (AS) are responsible for various cardiovascular disease and deaths. Numerous investigations have identified that different antihypertensive agents influence PP and AS differently. None of the previous studies described any reliable animal model particularly to screen drugs having effects on PP and AS. In present study, we developed an animal model to screen such drugs particularly affecting PP and AS.

METHODS

Elevation of PP and amplification of AS were induced in rats by uninephrectomy along with high salt intake (NaCl 4% w/v) for a period of six weeks, and weekly changes in body weight, PP, systolic, diastolic, mean pressure and pulse wave velocity (PWV) were estimated. After six weeks, collagen elastin ratio of aortic segment was estimated. Histomorphometry of abdominal aortic section of rats was done using trinocular microscope.

RESULTS

After six weeks, uninephrectomized rats that were kept on high salt drinking water shown significant increase (P < 0.001) in MAP, PP and PWV indicates that hypertension along with elevated PP developed in rats, and increase in collagen/elastin ratio (P < 0.001) as well as PWV as compared to normal rats indicates the increase in AS.

CONCLUSION

The development of condition of hypertension in conjunction with increase in PP and AS in rats can be used as in-vivo screening model to determine the potency of drugs for the treatment of hypertension or other cardiovascular diseases associated with high PP and AS.

Chronic fructose intake accelerates non-alcoholic fatty liver disease in the presence of essential hypertension

BACKGROUND

The growing epidemic of metabolic syndrome has been related to the increased use of fructose by the food industry. In fact, the use of fructose as an ingredient has increased in sweetened beverages, such as sodas and juices. We thus hypothesized that fructose intake by hypertensive rats would have a worse prognosis in developing metabolic disorder and non-alcoholic fatty liver disease.

METHODS

Male Wistar and SHR rats aged 6weeks were given water or fructose (10%) for 6weeks. Blood glucose was measured every two weeks, and insulin and glucose sensitivity tests were assessed at the end of the follow-up. Systolic blood pressure was measure by plethysmography. Lean mass and abdominal fat mass were collected and weighed. Liver tissue was analyzed to determine interstitial fat deposition and fibrosis.

RESULTS

Fasting glucose increased in animals that underwent a high fructose intake, independent of blood pressure levels. Also, insulin resistance was observed in normotensive and mostly in hypertensive rats after fructose intake. Fructose intake caused a 2.5-fold increase in triglycerides levels in both groups. Fructose intake did not change lean mass. However, we found that fructose intake significantly increased abdominal fat mass deposition in normotensive but not in hypertensive rats. Nevertheless, chronic fructose intake only increased fat deposition and fibrosis in the liver in hypertensive rats.

CONCLUSIONS

We demonstrated that, in normotensive and hypertensive rats, fructose intake increased triglycerides and abdominal fat deposition, and caused insulin resistance. However, hypertensive rats that underwent fructose intake also developed interstitial fat deposition and fibrosis in liver.

High salt intake does not produce additional impairment in the coronary artery relaxation of spontaneously hypertensive aged rats

The effect of a salt-based diet on the coronary responsiveness in aged hypertensive rats (SHR) still is unclear. We investigated the effects of high salt intake on the relaxation properties of coronary arteries of aged SHRs. Male SHR (32 week-old) received drinking water (SHR) or 1% NaCl solution (SHR-Salt) for 8 weeks. Isolated coronary segments were subjected to concentration-response curves to acetylcholine (ACh) in the presence or absence of L-NAME (100 μM), enalaprilate (10 μM), losartan (10 μM), and spironolactone (100 μM). Salt intake did not increase blood pressure in old SHRs, but caused ventricular hypertrophy. The endothelium-dependent relaxation in SHRs was lower than in Wistar rats. However, salt intake did not add further impairment. Both enalaprilate and losartan reduced the vasodilator response in coronary arteries from Wistar, but did not affect SHR-salt rats. Conversely, losartan attenuated the impaired ACh relaxation observed in SHR. Spironolactone reduced the relaxation induced by ACh in coronary arteries from Wistar rats but not in SHR. The renin-angiotensin-aldosterone system participates in the impaired coronary relaxation in aged SHR, but does not partake in this deleterious effect under increased salt intake, indicating that age could differentiate the effects of high sodium intake in coronary arteries of SHR.