Redox-sensitive prosurvival and proapoptotic protein expression in the myocardial remodeling post-infarction in rats

Radical Oxygen Species, Oxidized Low-Density Lipoproteins, and Lectin-like Oxidized Low-Density Lipoprotein Receptor 1: A Vicious Circle in Atherosclerotic Process

Atherosclerosis is a complex condition that involves the accumulation of lipids and subsequent plaque formation in the arterial intima. There are various stimuli, cellular receptors, and pathways involved in this process, but oxidative modifications of low-density lipoprotein (ox-LDL) are particularly important in the onset and progression of atherosclerosis. Ox-LDLs promote foam-cell formation, activate proinflammatory pathways, and induce smooth-muscle-cell migration, apoptosis, and cell death. One of the major receptors for ox-LDL is LOX-1, which is upregulated in several cardiovascular diseases, including atherosclerosis. LOX-1 activation in endothelial cells promotes endothelial dysfunction and induces pro-atherogenic signaling, leading to plaque formation. The binding of ox-LDLs to LOX-1 increases the generation of reactive oxygen species (ROS), which can induce LOX-1 expression and oxidize LDLs, contributing to ox-LDL generation and further upregulating LOX-1 expression. This creates a vicious circle that is amplified in pathological conditions characterized by high plasma levels of LDLs. Although LOX-1 has harmful effects, the clinical significance of inhibiting this protein remains unclear. Further studies both in vitro and in vivo are needed to determine whether LOX-1 inhibition could be a potential therapeutic target to counteract the atherosclerotic process.

The Rising Use of E-Cigarettes: Unveiling the Health Risks and Controversies

The use of e-cigarettes has tremendously increased in recent times due to the widespread availability of e-cigarettes in diverse flavors, reduced cost compared to regular cigarettes, and misconception of being comparatively safe, which have led to around 2.55 million US middle and high school students smoking e-cigarettes. These devices use a nicotine-rich liquid, which is aerosolized electronically, producing vapors that may also include hazardous chemicals and heavy metals. E-cigarettes are associated with e-cigarette or vaping-associated lung injury, which presents as an acute respiratory ailment mirroring various pulmonary diseases. Additionally, it causes endothelial dysfunction, alters blood lipid profile by elevating circulating levels of low-density lipoprotein cholesterol, increases sympathetic tone, and is found to correlate with arterial stiffening, hence negatively affecting respiratory, cardiovascular, and overall health. We aim to provide a comprehensive analysis of the data on e-cigarettes and their harmful effects on health in comparison to conventional cigarette use by highlighting the pathophysiology of e-cigarette-induced adverse effects and critically analyzing the data both in favor and against its use. Our review concludes that no matter how much nicotine an e-cigarette contains, evidence shows that using it increases the risk of cardiovascular disease, albeit maybe not as much as smoking regular tobacco. Nonetheless, it is crucial to note that the long-term effects of e-cigarette usage are still not fully understood, and existing data have provided opposing viewpoints.

Influence of carvedilol and thyroid hormones on inflammatory proteins and cardioprotective factor HIF-1α in the infarcted heart

Inflammatory pathways of Toll-like receptor 4 (TLR4) and NLRP3 inflammasome contribute to acute myocardial infarction (AMI) pathophysiology. The hypoxia-inducible factor 1α (HIF-1α), however, is a key transcription factor related to cardioprotection. This study aimed to compare the influence of carvedilol and thyroid hormones (TH) on inflammatory and HIF-1α proteins and on cardiac haemodynamics in the infarcted heart. Male Wistar rats were allocated into five groups: sham-operated group (SHAM), infarcted group (MI), infarcted treated with the carvedilol group (MI + C), infarcted treated with the TH group (MI + TH), and infarcted co-treated with the carvedilol and TH group (MI + C + TH). Haemodynamic analysis was assessed 15 days post-AMI. The left ventricle (LV) was collected for morphometric and Western blot analysis. The MI group presented LV systolic pressure reduction, LV end-diastolic pressure elevation, and contractility index decrease compared to the SHAM group. The MI + C, MI + TH, and MI + C + TH groups did not reveal such alterations compared to the SHAM group. The MI + TH and MI + C + TH groups presented reduced MyD88 and NLRP3 and increased HIF-1α levels. In conclusion, all treatments preserve the cardiac haemodynamic, and only TH, as isolated treatment or in co-treatment with carvedilol, was able to reduce MyD88 and NLRP3 and increase HIF-1α in the infarcted heart.

Anti-Inflammatory Drug Candidates for Prevention and Treatment of Cardiovascular Diseases

Incidence and mortality rates for cardiovascular disease are declining, but it still remains a major cause of morbidity and mortality. Drug treatments to slow the progression of atherosclerosis focus on reducing cholesterol levels. The paradigm shift to consider atherosclerosis an inflammatory disease by itself has led to the development of new treatments. In this article, we discuss the pathophysiology of inflammation and focus attention on therapeutics targeting different inflammatory pathways of atherosclerosis and myocardial infarction. In atherosclerosis, colchicine is included in new recommendations, and eight randomized clinical trials are testing new drugs in different inflammatory pathways. After a myocardial infarction, no drug has shown a significant benefit, but we present four randomized clinical trials with new treatments targeting inflammation.

Cardioprotective doses of thyroid hormones improve NO bioavailability in erythrocytes and increase HIF-1α expression in the heart of infarcted rats

CONTEXT

Infarction leads to a decrease in NO bioavailability in the erythrocytes. Thyroid hormones (TH) present positive effects after infarction. However, there are no studies evaluating the effects of cardioprotective doses of TH in the erythrocytes after infarction.

OBJECTIVE

This study aimed to evaluate the effects of TH in NO bioavailability and oxidative stress parameters in the erythrocytes of infarcted rats.

MATERIAL AND METHODS

Wistar rats were allocated into the three groups: Sham-operated (SHAM), infarcted (AMI) and infarcted + TH (AMIT). AMIT rats received T4 and T3 for 12 days by gavage. Subsequently, the animals were evaluated by echocardiography and the LV and erythrocytes were collected.

RESULTS

TH improved NO bioavailability and increased catalase activity in the erythrocytes. Besides that, TH increased HIF-1α in the heart.

CONCLUSION

TH seems to be positive for erythrocytes preventing a decrease in NO bioavailability and increasing antioxidant enzymatic defense after infarction.

Cardiovascular Effects of Cydonia oblonga Miller (Quince)

Cydonia oblonga Miller (quince) is a monotypic genus in the Rosaceae family which used to treat or prevent many medical conditions such as diabetes, cancer, infections, and ulcer. This review will summarize the current state of knowledge available on botany, phytochemistry, and pharmacology of this plant with a focus on its effect on some cardiovascular risk factors such as diabetes, blood pressure, lipid profile, and body weight. Databases of Google Scholar, Web of Science, PubMed, Scopus, and SID were searched systematically for English published articles with no date limitation. There were no human studies found, and all of the studies were conducted on animals or in vitro models. Reviewing of all 12 included articles showed that different types of quince extract have positive effects on cardiovascular-related factors such as blood pressure, diabetes, glucose metabolism, lipid profile, ROS, body weight, liver dysfunction, and thrombosis. An antihypertensive effect of quince showed to be a magnitude that is comparable to captopril and the lipid-lowering effect of quince showed to be a magnitude that is comparable to simvastatin. However, two studies evaluated the effect of quince fruit extract on insulin levels; one of them reported no positive effect, and the other one reported a significant positive effect. It can be concluded that different parts of quince including leaf, seed, and fruit could be used for improving cardiovascular-related factors including blood pressure, glucose metabolism and diabetes, obesity, and lipid-adjusting purposes. Quince was also found to have strong anti-inflammatory and antioxidant capacity. This study paves the way for further studies on the cardiovascular effect of quince consumption as a beneficial nutraceutical in humans.

Pharmacological Inhibition of Mammalian Target of Rapamycin Attenuates Deoxycorticosterone Acetate Salt-Induced Hypertension and Related Pathophysiology: Regulation of Oxidative Stress, Inflammation, and Cardiovascular Hypertrophy in Male Rats

ABSTRACT

The present study aimed to explore the contribution of mammalian target of rapamycin (mTOR) in deoxycorticosterone acetate (DOCA) salt-induced hypertension and related pathophysiological changes in cardiovascular and renal tissues. DOCA salt loading resulted in an increase in systolic blood pressure, diastolic blood pressure, and mean blood pressure along with the activity of ribosomal protein S6, the effector protein of mTOR. Treatment with rapamycin, the selective inhibitor of mTOR, initiated at the fourth week of DOCA- salt administration normalized the systolic blood pressure and attenuated ribosomal protein S6 activity in the heart, aorta, and kidney. Cardiac and vascular hypertrophy, oxidative stress, and infiltration of macrophages (CD68+), the marker of inflammation, were also reduced in rapamycin-treated, DOCA-salt, hypertensive rats. In addition, renal hypertrophy and dysfunction were also reduced with rapamycin-treated hypertensive rats. Moreover, these pathophysiological changes in DOCA-salt hypertensive rats were associated with increased NADPH oxidase (NOX) activity, gp91phox (formerly NOX2) expression, ERK1/2, and p38 MAPK activities in the heart, aorta, and kidney were minimized by rapamycin. These data indicate that mTOR plays an important role in regulating blood pressure and the development of cardiovascular and renal pathophysiological changes, most likely due to increased NOX expression/activity, ERK1/2, and p38 MAPK activity with macrophages infiltration in the heart, kidney, and aorta. Pharmacological inhibition of mTOR and related signaling pathways could serve as a novel target for the treatment of hypertension.

The brief methylprednisolone administration is crucial to mitigate cardiac dysfunction after myocardial infarction

Acute myocardial infarction (AMI) is one of the major causes of heart failure and mortality. Glucocorticoids administration post-infarction has long been proposed, but it has shown conflicting results so far. This controversy may be associated with the glucocorticoid type and the period when it is administered. To elucidate these, the present aims to evaluate if the brief methylprednisolone acetate administration is determinant for heart adaptation after AMI. Male Wistar rats were divided into 3 groups: sham-operated (SHAM); infarcted (AMI); infarcted treated with methylprednisolone acetate (AMI+M). Immediately after surgery, the AMI+M group received a single dose of methylprednisolone acetate (40 mg/kg i.m.). After 56 days, the cardiac function was assessed and lungs, liver and heart were collected to determine rates of hypertrophy and congestion. Heart was used for oxidative stress and metalloproteinase activity analyses. Methylprednisolone acetate attenuated matrix metalloproteinase-2 activity, cardiac dilatation, and prevented the onset of pulmonary congestion, as well as avoided cardiac hypertrophy. Our data indicate that administration of methylprednisolone acetate shortly after AMI may be a therapeutic alternative for attenuation of detrimental ventricular remodeling.

Octreotide (somatostatin analog) attenuates cardiac ischemia/reperfusion injury via activating nuclear factor (erythroid-derived 2)-like 2 (Nrf2) signaling pathway in rat model of hyperthyroidism

Background

Hyperthyroidism is known to increase the risk of ischemic heart diseases. Octreotide has been reported to attenuate ischemia/reperfusion (I/R) injury. Whether it is useful when ischemic heart disease is accompanied with co-morbidities like hyperthyroidism needs more clarifying. So, this study aimed to explore the effect of octreotide on cardiac I/R injury in hyperthyroid rats and to clarify if Nrf2 activation is involved in this effect. Forty adult female Wistar rats were subdivided into control (euthyroid) (n = 10) and hyperthyroid (n = 30) groups. Rats in hyperthyroid group received l-thyroxine (12 mg/L) in drinking water for 35 days, then were randomly divided into three equal subgroups (n = 10): hyperthyroid control positive group, hyperthyroid octreotide treated group, and hyperthyroid octreotide + Nrf2 inhibitor (brusatol) treated group. Isolated hearts were submitted to I/R and evaluated for cardiac hemodynamics and infarct size. Serum T3 and T4, coronary efflux lactate dehydrogenase (LDH) and creatine kinase-myoglobin binding (CK-MB) and cardiac tissue malondialdehyde (MDA) were estimated. Nrf2- regulated gene expressions of HO-1, SOD, GPx, and catalase were assessed.

Results

Octreotide administration to hyperthyroid rats improved baseline and post-ischemic recovery of cardiac hemodynamics, decreased the high coronary efflux LDH and CK-MB and tissue MDA, reduced infarction size, and upregulated the decreased antioxidative enzymes HO-1, SOD, GPx, and catalase mRNA expressions in the hyperthyroid I/R rat hearts. The Nrf2 inhibitor brusatol reversed the cardioprotective effect of octreotide in hyperthyroid I/R rat hearts.

Conclusion

Octreotide can reduce oxidative stress to effectively alleviate I/R injury in the hyperthyroid rat hearts through upregulation of Nrf2-dependent antioxidative signaling pathways.

Stilbenoid pterostilbene complexed with cyclodextrin preserves left ventricular function after myocardial infarction in rats: possible involvement of thiol proteins and modulation of phosphorylated GSK-3β

Oxidative stress alters signalling pathways for survival and cell death favouring the adverse remodelling of postmyocardial remnant cardiomyocytes, promoting functional impairment. The administration of pterostilbene (PTS), a phytophenol with antioxidant potential, can promote cardioprotection and represents a therapeutic alternative in acute myocardial infarction (AMI). The present study aims to explore the effects of oral administration of PTS complexed with hydroxypropyl-β-cyclodextrin HPβCD (PTS:HPβCD complex) on the glutathione cycle, thiol protein activities and signalling pathways involving the protein kinase B (AKT) and glycogen synthase kinase-3β (GSK-3β) proteins in the left ventricle (LV) of infarcted rats. Animals were submitted to acute myocardial infarction through surgical ligation of the descending anterior branch of the left coronary artery and received over 8 days, by gavage, PTS:HPβCD complex at dose of 100 mg kg^-1 day^-1 (AMI + PTS group) or vehicle (aqueous solution with HPβCD) divided into Sham-operated (SHAM) and infarcted (AMI) groups. The results showed that the PBS: HPβCD complex decreased lipid peroxidation, prevented the decrease in thioredoxin reductase (TRxR) activity, and increased the activity of glutathione-S-transferase (GST) and glutaredoxin (GRx). Additionally, the expression of nuclear factor-erythroid two (Nrf2) and p-GSK-3β was increased, whereas the p-GSK-3β/GSK-3β ratio was reduced in the LV of the infarcted animals. Overall, the PTS:HPβCD complex modulates activity of thiol-dependent enzymes and induces to the expression of antioxidant proteins, improving systolic function and mitigating the adverse cardiac remodelling post infarction.

Thyroid hormones decrease the proinflammatory TLR4/NF-κβ pathway and improve functional parameters of the left ventricle of infarcted rats

Myocardial infarction leads to oxidative stress and promotes activation of the TLR4/NF-κβ proinflammatory pathway. Thyroid hormones (TH) are known to be cardioprotective after infarction. However, there are no studies evaluating whether TH could modulate this pathway in the heart. This study aimed to verify the effect of thyroid hormones on the TLR4/NF-κβ pathway after myocardial infarction. Male Wistar rats were allocated into the following groups: Sham-operated (SHAM), sham-operated + TH (SHAMT), infarcted (AMI) and infarcted + TH (AMIT). The treated rats received T4 and T3 (8 and 2 μg 100 g^-1 day^-1) for 12 days by gavage. Subsequently, the animals were evaluated by echocardiography and euthanized, and the left ventricle was collected for biochemical and molecular analyses. TH modulates TLR4/NF-κβ expression in the infarcted hearts of rats and decreases xanthine oxidase expression. These effects were related to cardiac functional improvement after infarction. The cardioprotective effects of T3 and T4 seem to involve an anti-inflammatory action.

DHEA Treatment Effects on Redox Environment in Skeletal Muscle of Young and Aged Healthy Rats

BACKGROUND

Dehydroepiandrosterone (DHEA) is an important precursor of active steroid hormone, produced abundantly by the adrenal cortex with an age-dependent pattern.

OBJECTIVE

We investigated whether chronic DHEA administration impacts on redox status and on Akt protein activation in skeletal muscle during the aging process (3 and 24 months-old rats).

METHODS

Rats received one weekly dose/5 weeks of DHEA (10 mg/kg) or vehicle. Gastrocnemius muscle was removed to evaluate glutathione system, hydrogen peroxide, antioxidant enzymes, and expression of Akt kinase protein.

RESULTS

In the 3-months-old rats DHEA induced an increase in hydrogen peroxide when compared both to its control (276%) and the 24-months-old DHEA group (485%). Moreover, in the 24- months-old rats DHEA caused an increase in GSSG (41 and 28%), a decrease in reduced-GSH (55 and 51%), and a more oxidized redox status (reduction in GSH/GSSG ratio, 47 and 65 %) when compared to 3-month-old DHEA and to 24-months-old control groups, respectively. Both older groups had increased G6PDH (2.7 fold) and GST (1.7 fold) activities when compared to younger groups, independently of any DHEA treatment. However, there was no modulation of Akt protein (phosphorylated/total isoform).

CONCLUSION

The results show that chronic DHEA administration to 3 and 24-months-old rats may not present positive effects regarding the redox environment in skeletal muscle without modulation of pro-survival Akt kinase. Due to the large-scale self-administration of DHEA as an "anti-aging" dietary supplement, it is crucial to investigate its molecular mechanisms over oxidative stressinduced related diseases.

Pterostilbene reduces oxidative stress, prevents hypertrophy and preserves systolic function of right ventricle in cor pulmonale model

BACKGROUND AND PURPOSE

In cor pulmonale, the increased afterload imposed on the right ventricle (RV) generates a maladaptive response, impairing the contractile cardiac function. Oxidative mechanisms play an important role in the pathophysiology and progression of this disease. The administration of pterostilbene (PTS), a phytophenol with antioxidant potential, may represent a therapeutic option. In the present study, we evaluated the effect of PTS complexed with hydroxypropyl-β-cyclodextrin (HPβCD) on hypertrophy, contractile function and oxidative parameters in the RV of rats with pulmonary hypertension, induced by the administration of monocrotaline (MCT).

EXPERIMENTAL APPROACH

The rats received daily doses of the PTS : HPβCD complex at 25, 50 or 100 mg·kg^-1 , p.o., for 14 days. The diastolic function, E/A ratio, and systolic function, shortening fraction, fractional area change (FAC) and tricuspid annular plane systolic excursion (TAPSE) of the RV were determined by echocardiography.

KEY RESULTS

The PTS : HPβCD complex reduced the production of NADPH oxidase-dependent superoxide anions and oxidative stress in the RV of MCT-treated rats in a dose-dependent manner. At higher doses it prevented the reduction in FAC and TAPSE in MCT-treated animals.

CONCLUSIONS AND IMPLICATIONS

The PTS : HPβCD complex prevented the maladaptative remodelling and protected systolic function in the RV of rats with pulmonary hypertension. These cardioprotective mechanisms may be related, in part, to the antioxidant potential of PTS, favoured by the increased p.o. bioavailability promoted by the presence of HPβCD in the complex.

The role of reactive oxygen species in the pathophysiology of cardiovascular diseases and the clinical significance of myocardial redox

Acute and chronic excessive intracellular increase of reactive oxygen species (ROS) is involved in the development and progression of cardiovascular diseases. ROS are by-products of various oxidative physiological and biochemical processes. Sources of ROS are mitochondrial respiration, NADH/NADPH oxidase, xanthine oxidoreductase or the uncoupling of nitric oxide synthase (NOS) in vascular cells. ROS mediate various signaling pathways that underlie cardiovascular pathophysiology. The delicate equilibrium between free-radical generation and antioxidant defense is altered in favor of the former, thus leading to redox imbalance, oxidative stress, and increased cellular injury. An understanding of the pathophysiological mechanisms mediated by oxidative stress is crucial to the prevention and treatment of cardiovascular diseases.

Insights for Oxidative Stress and mTOR Signaling in Myocardial Ischemia/Reperfusion Injury under Diabetes

Diabetes mellitus (DM) displays a high morbidity. The diabetic heart is susceptible to myocardial ischemia/reperfusion (MI/R) injury. Impaired activation of prosurvival pathways, endoplasmic reticulum (ER) stress, increased basal oxidative state, and decreased antioxidant defense and autophagy may render diabetic hearts more vulnerable to MI/R injury. Oxidative stress and mTOR signaling crucially regulate cardiometabolism, affecting MI/R injury under diabetes. Producing reactive oxygen species (ROS) and reactive nitrogen species (RNS), uncoupling nitric oxide synthase (NOS), and disturbing the mitochondrial quality control may be three major mechanisms of oxidative stress. mTOR signaling presents both cardioprotective and cardiotoxic effects on the diabetic heart, which interplays with oxidative stress directly or indirectly. Antihyperglycemic agent metformin and newly found free radicals scavengers, Sirt1 and CTRP9, may serve as promising pharmacological therapeutic targets. In this review, we will focus on the role of oxidative stress and mTOR signaling in the pathophysiology of MI/R injury in diabetes and discuss potential mechanisms and their interactions in an effort to provide some evidence for cardiometabolic targeted therapies for ischemic heart disease (IHD).

Maximal oxygen uptake and exercise tolerance are improved in rats with heart failure subjected to low-level laser therapy associated with resistance training

Exercise tolerance and maximal oxygen uptake (VO_2max) are reduced in heart failure (HF). The influence of combined resistance training (RT) and low-level laser therapy (LLLT) on exercise tolerance and VO_2max in HF has not yet been explored. The aim of this study was to evaluate the influence of combined RT and LLLT on VO_2max and exercise tolerance in rats with HF induced by myocardial infarction (MI). Rats were allocated to sedentary sham (Sed-Sham, n = 12), sedentary heart failure (Sed-HF, n = 9), RT heart failure (RT-HF, n = 7) and RT associated with LLLT heart failure (RT + LLLT-HF, n = 7) groups. After MI or sham surgery, rats underwent a RT and LLLT protocol (applied immediately after RT) for 8 weeks. VO_2max and exercise tolerance were evaluated at the end of protocol. HF rats subjected to LLLT combined with RT showed higher VO_2basal (41 %), VO_2max (40 %), VO_2reserve (39 %), run distance (46 %), time to exhaustion (30 %) and maximal velocity (22 %) compared with HF rats that underwent RT alone. LLLT associated with RT improved oxygen uptake and exercise tolerance compared with RT alone in HF rats.

Effects of thyroid hormones on aortic tissue after myocardial infarction in rats

Studies have shown a cardioprotective role of thyroid hormones (THs) in cardiac remodeling after acute myocardial infarction (MI). However, there is no data in the literature examining the influence of TH administration on the aortic tissue in an animal model of MI. This study aimed to evaluate the effects of thyroid hormones on the aorta after MI. Male Wistar rats were divided into a sham group (SHAM), infarcted group (AMI), sham+TH (SHAMT) and AMI+TH (AMIT). After MI, the animals received T3 and T4 (2 and 8μg/100g/day, respectively) by oral gavage for 12 days. Later, the animals underwent echocardiography and euthanasia and the aorta was collected for molecular and biochemical analysis. T3 and T4 administration increased the expression of the pro-angiogenic proteins vascular endothelial growth factor (VEGF) and hypoxia inducible factor 1α (HIF-1α) in the aorta of AMIT rats when compared with AMI. With respect to TH receptors, AMI rats presented a decrease in TRβ levels, which was prevented by the hormonal administration. In AMIT rats, both TRα and TRβ levels were increased when compared with the AMI group. Reactive oxygen species levels and NADPH oxidase activity were decreased in both treated groups when compared with the non-treated animals. TH administration after MI may improve angiogenic signaling in the aorta as well as the responsiveness of this vessel to T3 and T4. These positive effects in the aorta may result in additional protection for the cardiovascular system in the context of cardiac ischaemic injury.

Thyroid hormones improve cardiac function and decrease expression of pro-apoptotic proteins in the heart of rats 14 days after infarction

Apoptosis is a key process associated with pathological cardiac remodelling in early-phase post-myocardial infarction. In this context, several studies have demonstrated an anti-apoptotic effect of thyroid hormones (TH). The aim of this study was to evaluate the effects of TH on the expression of proteins associated with the apoptotic process 14 days after infarction. Male Wistar rats (300-350 g) (n = 8/group) were divided into four groups: Sham-operated (SHAM), infarcted (AMI), sham-operated + TH (SHAMT) and infarcted + TH (AMIT). For 12 days, the animals received T3 and T4 [2 and 8 µg/(100 g day)] by gavage. After this, the rats were submitted to haemodynamic and echocardiographic analysis, and then were sacrificed and the heart tissue was collected for molecular analysis. Statistical analyses included two-way ANOVA with Student-Newman-Keuls post test. Ethics Committee number: 23262. TH administration prevented the loss of ventricular wall thickness and improved cardiac function in the infarcted rats 14 days after the injury. AMI rats presented an increase in the pro-apoptotic proteins p53 and JNK. The hormonal treatment prevented this increase in AMIT rats. In addition, TH administration decreased the Bax:Bcl-2 ratio in the infarcted rats. TH administration improved cardiac functional parameters, and decreased the expression of pro-apoptotic proteins 14 days after myocardial infarction.

Diabetic hyperglycemia attenuates sympathetic dysfunction and oxidative stress after myocardial infarction in rats

Background

Previous research has demonstrated that hyperglycemia may protect the heart against ischemic injury. The aim of the present study was to investigate the association between hyperglycemia and myocardial infarction on cardiovascular autonomic modulation and cardiac oxidative stress profile in rats. Male Wistar rats were divided into: control (C), diabetic (D), myocardial infarcted (MI) and diabetic infarcted rats (DMI).

Methods

Diabetes was induced by streptozotocin (STZ, 50 mg/Kg) at the beginning of the protocol and MI was induced by left coronary occlusion 15 days after STZ. Thirty days after streptozocin-induced diabetes, cardiovascular autonomic modulation was evaluated by spectral analysis, and oxidative stress profile was determined by antioxidant enzyme activities and superoxide anion, together with protein carbonylation and redox balance of glutathione (GSH/GSSG).

Results

The diabetic and infarcted groups showed decreased heart rate variability and vagal modulation (p < 0.05); however, sympathetic modulation decreased only in diabetic groups (p < 0.05). Sympatho/vagal balance and vascular sympathetic modulation were increased only in the MI group (p < 0.05). Diabetes promoted an increase in catalase concentration (p < 0.05). Glutathione peroxidase activity was increased only in DMI when compared to the other groups (p < 0.05). Superoxide anion and protein carbonylation were increased only in MI group (p < 0.05). Cardiac redox balance, as evaluated by GSH/GSSG, was lower in the MI group (p < 0.05).

Conclusions

These data suggest that hyperglycemia promotes compensatory mechanisms that may offer protection against ischemia, as demonstrated by increased antioxidants, decreased pro-oxidants and protein damage, possibly related to the improvements in both redox balance and sympathetic modulation to the heart.

Cardioprotective effects of thyroid hormones in a rat model of myocardial infarction are associated with oxidative stress reduction

Reactive oxygen species (ROS) are involved with progression from infarction to heart failure. Studies show that thyroid hormones (TH) present cardioprotective effects. This study aims to evaluate whether TH effects after infarction are associated to redox balance modulation. Male Wistar rats were divided into four groups: Sham-operated (SHAM), infarcted (AMI), sham-operated+TH (SHAMT), and infarcted+TH (AMIT). During 26 days, animals received T3 (2 μg/100g/day) and T4 (8 μg/100g/day) by gavage. Echocardiographic parameters were assessed and heart tissue was collected to biochemical analysis. AMIT rats presented absence of lung congestion, less cardiac dilatation, and normalization in myocardial performance index, compared with AMI. AMI rats presented an increase in hydrogen peroxide levels and in lipid peroxidation and a decrease in GSH/GSSG. TH prevented these alterations in AMIT. In conclusion, TH seem to reduce the levels of ROS, preventing oxidative stress, and improving cardiac function in infarcted rats.

Adiponectin modulates oxidative stress-induced autophagy in cardiomyocytes

Diastolic heart failure (HF) i.e., "HF with preserved ejection fraction" (HF-preserved EF) accounts for up to 50% of all HF presentations; however there have been no therapeutic advances. This stems in part from an incomplete understanding about HF-preserved EF. Hypertension is the major cause of HF-preserved EF whilst HF-preserved EF is also highly associated with obesity. Similarly, excessive reactive oxygen species (ROS), i.e., oxidative stress occurs in hypertension and obesity, sensitizing the heart to the renin-angiotensin-aldosterone system, inducing autophagic type-II programmed cell death and accelerating the propensity to adverse cardiac remodeling, diastolic dysfunction and HF. Adiponectin (APN), an adipokine, mediates cardioprotective actions but it is unknown if APN modulates cardiomyocyte autophagy. We tested the hypothesis that APN ameliorates oxidative stress-induced autophagy in cardiomyocytes. Isolated adult rat ventricular myocytes were pretreated with recombinant APN (30 µg/mL) followed by 1mM hydrogen peroxide (H2O2) exposure. Wild type (WT) and APN-deficient (APN-KO) mice were infused with angiotensin (Ang)-II (3.2 mg/kg/d) for 14 days to induced oxidative stress. Autophagy-related proteins, mTOR, AMPK and ERK expression were measured. H2O2 induced LC3I to LC3II conversion by a factor of 3.4±1.0 which was abrogated by pre-treatment with APN by 44.5±10%. However, neither H2O2 nor APN affected ATG5, ATG7, or Beclin-1 expression. H2O2 increased phospho-AMPK by 49±6.0%, whilst pretreatment with APN decreased phospho-AMPK by 26±4%. H2O2 decreased phospho-mTOR by 36±13%, which was restored by APN. ERK inhibition demonstrated that the ERK-mTOR pathway is involved in H2O2-induced autophagy. Chronic Ang-II infusion significantly increased myocardial LC3II/I protein expression ratio in APN-KO vs. WT mice. These data suggest that excessive ROS caused cardiomyocyte autophagy which was ameliorated by APN by inhibiting an H2O2-induced AMPK/mTOR/ERK-dependent mechanism. These findings demonstrate the anti-oxidant potential of APN in oxidative stress-associated cardiovascular diseases, such as hypertension-induced HF-preserved EF.

Cardiac response to chronic intermittent hypoxia with a transition from adaptation to maladaptation: the role of hydrogen peroxide

Obstructive sleep apnea (OSA) is a highly prevalent respiratory disorder of sleep, and associated with chronic intermittent hypoxia (CIH). Experimental evidence indicates that CIH is a unique physiological state with potentially “adaptive” and “maladaptive” consequences for cardio-respiratory homeostasis. CIH is also a critical element accounting for most of cardiovascular complications of OSA. Cardiac response to CIH is time-dependent, showing a transition from cardiac compensative (such as hypertrophy) to decompensating changes (such as failure). CIH-provoked mild and transient oxidative stress can induce adaptation, but severe and persistent oxidative stress may provoke maladaptation. Hydrogen peroxide as one of major reactive oxygen species plays an important role in the transition of adaptive to maladaptive response to OSA-associated CIH. This may account for the fact that although oxidative stress has been recognized as a driver of cardiac disease progression, clinical interventions with antioxidants have had little or no impact on heart disease and progression. Here we focus on the role of hydrogen peroxide in CIH and OSA, trying to outline the potential of antioxidative therapy in preventing CIH-induced cardiac damage.

Homocysteine and its thiolactone-mediated modification of fibrinogen affect blood platelet adhesion

Homocysteine (Hcys) and homocysteine thiolactone (HTL) concentrations in organism are correlated with a number of serious pathologies. In the literature, there are few papers describing studies on the effects of homocysteine on proteins that participate in blood coagulation and fibrinolysis in human. However, mechanisms involved in the relationship between hyperhomocysteinemia and hemostatic process are still unclear. The role of N- or S-homocysteinylation (induced by Hcys and its derivatives) of different hemostatic proteins, including fibrinogen is also still poorly known. The aim of this study was to establish the functional changes of the fibrinogen molecule induced by Hcys (at final doses of 10-100 µM) and the most reactive form of Hcys - its cyclic thioester, homocysteine thiolactone (0.1-1 µM), and to examine the effects of these changes on the capability of fibrinogen to interact with human blood platelets (by measuring the platelet adhesion). Our present results demonstrated that Hcys-treated fibrinogen in comparison with native molecule had a distinct capability to mediate platelet adhesion. Both, unstimulated and thrombin-activated platelets showed a reduced ability to adhere to Hcys-mediated fibrinogen. HTL (at all tested concentrations) had similar properties when we used thrombin-activated platelets. In conclusion, the results reported in this study could be useful for a better understanding of changes in hemostasis during hyperhomocysteinemia.