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

Melatonin improves nitric oxide bioavailability in isoproterenol induced myocardial injury

Isoproterenol administration is associated with cardiac inflammation and decreased NO availability. Melatonin has been reported to have cardioprotective effect. The aim of this study was to investigate the effect of melatonin on NO bioavailability and inflammation in myocardial injury induced by isoproterenol. Isoproterenol was administrated in male Wistar rats for 7 days to induce cardiac injury. The animals were divided into 3 groups: Control, Isoproterenol, Isoproterenol + Melatonin. Animals received melatonin for 7 days. Echocardiographic analysis was performed and the hearts were collected for molecular analysis. Animals that received isoproterenol demonstrated a reduction in left ventricle systolic and diastolic diameter, indicating the presence of concentric hypertrophy. Melatonin was able to attenuate this alteration. Melatonin also improved NO bioavailability and decreased NF-κβ, TNFα and IL-1β expression. In conclusion, melatonin exhibited a cardioprotective effect which was associated with improving NO bioavailability and decreasing the pro-inflammatory proteins.

Melatonin effects on oxidative stress and on TLR4/NF-kβ inflammatory pathway in the right ventricle of rats with pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is characterised by an increase in mean pulmonary arterial pressure and a compromised the right ventricle (RV), together with progression to heart failure and premature death. Studies have evaluated the role of melatonin as a promising therapeutic strategy for PAH. The objective of this study was to evaluate melatonin's effects on oxidative stress and on the TLR4/NF-kβ inflammatory pathway in the RV of rats with PAH. Male Wistar rats were divided into the following groups: control, monocrotaline (MCT), and monocrotaline plus melatonin groups. These two last groups received one intraperitoneal injection of MCT (60 mg/kg) on the first day of experimental protocol. The monocrotaline plus melatonin group received 10 mg/kg/day of melatonin by gavage for 21 days. Echocardiographic analysis was performed, and the RV was collected for morphometric analysis oxidative stress and molecular evaluations. The main findings of the present study were that melatonin administration attenuated the reduction in RV function that was induced by monocrotaline, as assessed by TAPSE. In addition, melatonin prevented RV diastolic area reduction caused by PAH. Furthermore, animals treated with melatonin did not show an increase in ROS levels or in NF-kβ expression. In addition, the monocrotaline plus melatonin group showed a reduction in TLR4 expression when compared with control and monocrotaline groups. To our knowledge, this is the first study demonstrating a positive effect of melatonin on the TLR4/NF-kβ pathway in the RV of rats with PAH. In this sense, this study makes it possible to think of melatonin as a possible ally in mitigating RV alterations caused by PAH.

Effects of Pterostilbene on Heart and Lung Oxidative Stress Parameters in 2 Experimental Models of Cardiovascular Disease: Myocardial Infarction and Pulmonary Arterial Hypertension

ABSTRACT

Myocardial infarction (MI) and pulmonary arterial hypertension (PAH) are 2 prevalent cardiovascular diseases. In both conditions, oxidative stress is associated with a worse prognosis. Pterostilbene (PTE), an antioxidant compound, has been studied as a possible therapy for cardiovascular diseases. This study aims to evaluate the effect of PTE on oxidative stress in the hearts of animals with MI and in the lungs of animals with PAH. Male Wistar rats were used in both models. In the MI model, the experimental groups were sham, MI, and MI + PTE. In the PAH model, the experimental groups were control, PAH, and PAH + PTE. Animals were exposed to MI through surgical ligation of the left coronary artery, or to PAH, by the administration of monocrotaline (60 mg/kg). Seven days after undergoing cardiac injury, the MI + PTE animals were treated with PTE (100 mg/kg day) for 8 days. After this, the heart was collected for molecular analysis. The PAH + PTE animals were treated with PTE (100 mg/kg day) for 14 days, beginning 7 days after PAH induction. After this, the lungs were collected for biochemical evaluation. We found that PTE administration attenuated the decrease in ejection fraction and improved left ventricle end-systolic volume in infarcted animals. In the PAH model, PTE improved pulmonary artery flow and decreased reactive oxygen species levels in the lung. PTE administration promoted protective effects in terms of oxidative stress in 2 experimental models of cardiac diseases: MI and PAH. PTE also improved cardiac function in infarcted rats and pulmonary artery flow in animals with PAH.

Nrf2-Mediated Antioxidant Defense and Thyroid Hormone Signaling: A Focus on Cardioprotective Effects

Thyroid hormones (TH) perform a plethora of actions in numerous tissues and induce an overall increase in metabolism, with an augmentation in energy demand and oxygen expenditure. Oxidants are required for normal thyroid-cell proliferation, as well as for the synthesis of the main hormones secreted by the thyroid gland, triiodothyronine (T3) and thyroxine (T4). However, an uncontrolled excess of oxidants can cause oxidative stress, a major trigger in the pathogenesis of a broad spectrum of diseases, including inflammation and cancer. In particular, oxidative stress is implicated in both hypo- and hyper-thyroid diseases. Furthermore, it is important for the TH system to rely on efficient antioxidant defense, to maintain balance, despite sustained tissue exposure to oxidants. One of the main endogenous antioxidant responses is the pathway centered on the nuclear factor erythroid 2-related factor (Nrf2). The aim of the present review is to explore the multiple links between Nrf2-related pathways and various TH-associated conditions. The main aspect of TH signaling is described and the role of Nrf2 in oxidant-antioxidant homeostasis in the TH system is evaluated. Next, the antioxidant function of Nrf2 associated with oxidative stress induced by TH pathological excess is discussed and, subsequently, particular attention is given to the cardioprotective role of TH, which also acts through the mediation of Nrf2. In conclusion, the interaction between Nrf2 and most common natural antioxidant agents in altered states of TH is briefly evaluated.

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.

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.

Thyroid disorders and cardiovascular manifestations: an update

Cardiovascular disease (CVD) remains the leading cause of death worldwide, representing a major health, social, and economic issue. Thyroid disorders are very common and affect >10% of the adult population in total. The aim of this review is to describe the physiologic role of thyroid hormones on cardiovascular system, to present cardiovascular manifestations in patients with thyroid disorders, emphasizing in molecular mechanisms and biochemical pathways, and to summarize current knowledge of treatment options. Thyroid hormone receptors are located both in myocardium and vessels, and changes in their concentrations affect cardiovascular function. Hyperthyroidism or hypothyroidism, both clinical and subclinical, without the indicated therapeutical management, may contribute to the progression of CVD. According to recent studies, even middle changes in thyroid hormones levels increase cardiovascular mortality from 20% to 80%. In more details, thyroid disorders seem to have serious effects on the cardiovascular system via plenty mechanisms, including dyslipidemia, hypertension, systolic and diastolic myocardial dysfunction, as well endothelial dysfunction. On top of clinical thyroid disorders management, current therapeutics focus on younger patients with subclinical hypothyroidism and elderly patients with subclinical hyperthyroidism.

Pterostilbeno Reduz o Estresse Oxidativo no Pulmão e no Ventrículo Direito Induzido por Infarto do Miocárdio Experimental

Fundamento

O pterostilbeno (PS), um composto polifenólico natural e antioxidante, surge como uma intervenção promissora para minimizar danos do infarto agudo do miocárdio (IAM).

Objetivo

Este estudo teve como objetivo avaliar o desempenho do PS na promoção da homeostase redox nos pulmões e no ventrículo direito (VD) de animais infartados.

Métodos

Ratos Wistar machos (60 dias de idade) foram randomizados em três grupos: SHAM, IAM (infarto) e IAM+PS (IAM + pterostilbeno). Sete dias após o procedimento de IAM, os ratos foram tratados com PS (100 mg/kg/dia) por gavagem por oito dias. Os animais foram depois sacrificados e os pulmões e VD foram coletados para análise do balanço redox (diferenças foram consideradas significativas quando p<0,05).

Resultados

Nossos resultados mostram que o IAM desencadeia a interrupção redox no VD e nos pulmões, o que pode contribuir para danos induzido pelo IAM nesses órgãos. Consistentemente, o PS mitigou o estresse oxidativo e restaurou as defesas antioxidantes (Glutationa – GSH nos pulmões: SHAM = 0,79 ± 0,07; IAM = 0,67 ± 0,05; IAM + PS = 0,86 ± 0,14; p<0,05), indicando seu papel protetor neste cenário.

Conclusão

Nosso trabalho evidencia o potencial do uso de PS como abordagem terapêutica adjuvante após IAM para proteção dos tecidos pulmonares e cardíacos direitos.

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.

Hypothyroidism is associated with clinical outcomes in patients with acute myocardial infarction: subgroup analysis of China PEACE study

PURPOSE

Thyroid dysfunction contributes to adverse events in several types of cardiovascular diseases. The aim of the present study is to determine whether thyroid status is associated with the prognosis of patients with acute myocardial infarction (AMI).

METHODS

The present cohort arose from the China PEACE‑Prospective AMI study. Based on the evaluation of thyroid status, participants were divided into euthyroid, hypothyroid, and hyperthyroid groups. A total of 2569 AMI patients met the inclusion criteria of our present study. The primary outcomes were the 12-month composite cardiovascular endpoint (CCVE, a composite of all-cause death, myocardial infarction, revascularization, and heart failure) and the composite cardio-cerebral vascular endpoint (CCCVE, comprising CCVE and stroke).

RESULTS

Of the entire cohort, 431 patients (16.8%) confirmed hypothyroid status and 102 (4.0%) were at hyperthyroid status. There were total 594 CCVEs (23.1%) and 687 CCCVEs (26.7%) in the general population. After adjusting conventional risk factors, AMI patients from the hypothyroid status group were at increased risk of the two composite endpoints, compared with euthyroid individuals (CCVE, HR:1.337, 95%CI: 1.097-1.630; CCCVE, HR:1.336, 95%CI: 1.111-1.607). However, no significant increased trends of the two composite endpoints could be observed in hyperthyroid group. Furthermore, hypothyroid status was also independently associated with a higher risk of revascularization (HR: 1.648, 95%CI: 1.047-2.595) and heart failure (HR: 1.382, 95%CI: 1.066-1.792).

CONCLUSION

Compared with euthyroid status, hypothyroid status has an independent predicting value for adverse cardiovascular events in AMI patients. Further investigations are required to illustrate whether treatment of thyroid dysfunction could improve the prognosis of AMI patients.

Effects of Carvedilol and Thyroid Hormones Co-administration on Apoptotic and Survival Proteins in the Heart After Acute Myocardial Infarction

Cellular death and survival signaling plays a key role in the progress of adverse cardiac remodeling after acute myocardial infarction (AMI). Therapeutic strategies, such as co-treatment with beta-blocker carvedilol and thyroid hormones (THs), give rise to new approaches that can sustain the cellular homeostasis after AMI. Therefore, we sought to investigate the effects of carvedilol and TH co-administration on apoptosis and survival proteins and on cardiac remodeling after AMI. Male Wistar rats were distributed in 5 groups as follows: sham-operated group (SHAM), infarcted group (MI), infarcted plus carvedilol group (MI+C), infarcted plus TH group (MI+TH), and infarcted plus carvedilol and TH co-treatment group (MI+C+TH). Echocardiographic analysis was performed, and hearts were collected for western blot evaluation. The MI group presented systolic posterior wall thickness loss, an increase in the wall tension index, and an increase in atrial natriuretic peptide tissue levels than the SHAM group. However, in the MI+C+TH group, these parameters were equally to the SHAM group. Moreover, whereas the MI group showed Bax protein expression elevated in relation to the SHAM group, the MI+C+TH group presented Bax reduction and also Akt activation compared with the MI group. In addition, the MI+TH group revealed beta-1 adrenergic receptor (β1AR) upregulation compared with the MI and MI+C groups, whereas the MI+C+TH group presented lower levels of β1AR in relation to the SHAM and MI+TH groups. In conclusion, we suggest that carvedilol and TH co-administration may mediate its cardioprotective effects against adverse cardiac remodeling post-AMI through the Bax reduction, Akt activation, and β1AR decrease.

Downregulation of Caveolin-1 and Upregulation of Deiodinase 3, Associated with Hypoxia-Inducible Factor-1α Increase, Are Involved in the Oxidative Stress of Graves' Orbital Adipocytes

Background: Even though the clinical features of Graves' orbitopathy (GO) are well known, its exact pathogenesis remains controversial. The imbalance of redox homeostasis in the connective tissue could play a crucial role leading to an inflammatory state and edema of soft orbital tissues, thus contributing to orbital hypoxia and increase in hypoxia-inducible factor (HIF)-1α. This oxidative stress appears to target the orbital cells such as fibroblasts and also adipocytes. This study aims to explore which pathways can lead to the aforementioned oxidative stress in GO adipose cells and therefore offers new plausible therapeutic targets. Methods: Orbital fat samples were obtained from patients with GO (Western blot [WB]: n = 8, immunohistochemistry [IHC]: n = 8) and from control patients (WB: n = 5, IHC: n = 3-5). They were processed for WB analysis and IHC of the antioxidants (catalase, superoxide dismutase 1) and for HIF-1α. The expression of caveolin-1 (Cav-1) and deiodinase 3 (DIO3), known to be regulated by HIF-1α, was also analyzed by WB and IHC, as well as the targets of Cav-1: glucose transporter type 4 (Glut-4), NADPH oxidase (NOX)-2, and endothelial nitric oxide synthase (eNOS). Triiodothyronine (T3) expression was also analyzed by IHC. Results: In GO adipocytes, the expression of catalase was reduced, whereas that of HIF-1α was strongly increased. A decreased local T3 supply was associated with DIO3 upregulation. The low expression of Cav-1 in GO adipocytes was associated not only with low expression of Glut-4 but also with an increased expression of NOX-2 and active eNOS phosphorylated on serine 1177. Conclusions: Cav-1 and DIO3, both sensitive to hypoxia and to the increase of HIF-1α, play a pivotal role in the oxidative stress in GO adipocytes. DIO3 regulates the cellular supply of T3, which is essential for the cell homeostasis. Cav-1 determines the cellular glucose supply through Glut-4 and regulates the activity of NOX-2 generating superoxide anions and that of eNOS generating nitric oxide (NO).

Prospective role of thyroid disorders in monitoring COVID-19 pandemic

COVID-19 pandemic has affected more than 200 countries and 1.3 million individuals have deceased within eleven months. Intense research on COVID-19 occurrence and prevalence enable us to understand that comorbidities play a crucial role in spread and severity of SARS-CoV-2 infection. Chronic kidney disease, diabetes, respiratory diseases and hypertension are among the various morbidities that are prevalent in symptomatic COVID-19 patients. However, the effect of altered thyroid-driven disorders cannot be ignored. Since thyroid hormone critically coordinate and regulate the major metabolism and biochemical pathways, this review is on the potential role of prevailing thyroid disorders in SARS-CoV-2 infection. Direct link of thyroid hormone with several disorders such as diabetes, vitamin D deficiency, obesity, kidney and liver disorders etc. suggests that the prevailing thyroid conditions may affect SARS-CoV-2 infection. Further, we discuss the oxidative stress-induced aging is associated with the degree of SARS-CoV-2 infection. Importantly, ACE2 protein which facilitates the host-cell entry of SARS-CoV-2 using the spike protein, are highly expressed in individuals with abnormal level of thyroid hormone. Altogether, we report that the malfunction of thyroid hormone synthesis may aggravate SARS-CoV-2 infection and thus monitoring the thyroid hormone may help in understanding the pathogenesis of COVID-19.

Management of Hypothyroidism in Patients with Acute Myocardial Infarction

Background and Objectives: Thyroid hormones (TH) affect cardiac function through effects on cardiac contractility and systemic vascular resistance. While TH replacement for patients with hypothyroidism might be necessary for restoration of cardiac output after an acute myocardial infarction (AMI), it could theoretically lead to excessively rapid restoration of the metabolic rate. The appropriate management of hypothyroidism in patients with AMI is unknown. We describe the practice patterns in the management of hypothyroidism in the setting of AMI as well as patients’ clinical outcomes. Material and Methods: Retrospective study of patients that were admitted to a tertiary care hospital with AMI and newly diagnosed or uncontrolled hypothyroidism (TSH ≥ 10 mIU/L) between 2011–2018. Eligible patients were identified using diagnosis codes for AMI and laboratory values, followed by medical record review. We categorized patients according to treatment status with TH and by degree of hypothyroidism. Clinical outcomes included: 30-day mortality/readmission, bleeding, stroke, arrhythmia, sudden cardiac death, and new or worsening heart failure. Summary statistics and group comparisons are presented. Results: Sixty-four patients were included, their median age was 64 years and 61% (n = 39) were women. Most of the patients (59%) had a documented history of hypothyroidism. Of these, all were restarted on levothyroxine (LT4) during the index admission when compared to patients without a history of hypothyroidism, of which 54% received LT4 treatment (p = 0.001). The median TSH in those treated with LT4 was higher (25 mIU/L) when compared to those who were not (12 mIU/L), (p = 0.007). Patients who received intravenous LT4 had higher TSH levels and other variables suggesting worse clinical presentation, but these differences were not statistically significant. No statistically significant differences were noted on clinical outcomes according to LT4 treatment status. Conclusion: A history of hypothyroidism and the degree of TSH elevation seem to guide the management of hypothyroidism in patients with AMI. The clinical effect of correcting hypothyroidism in this setting requires further evaluation.

Protective Effects of Euthyroidism Restoration on Mitochondria Function and Quality Control in Cardiac Pathophysiology

Mitochondrial dysfunctions are major contributors to heart disease onset and progression. Under ischemic injuries or cardiac overload, mitochondrial-derived oxidative stress, Ca²⁺ dis-homeostasis, and inflammation initiate cross-talking vicious cycles leading to defects of mitochondrial DNA, lipids, and proteins, concurrently resulting in fatal energy crisis and cell loss. Blunting such noxious stimuli and preserving mitochondrial homeostasis are essential to cell survival. In this context, mitochondrial quality control (MQC) represents an expanding research topic and therapeutic target in the field of cardiac physiology. MQC is a multi-tier surveillance system operating at the protein, organelle, and cell level to repair or eliminate damaged mitochondrial components and replace them by biogenesis. Novel evidence highlights the critical role of thyroid hormones (TH) in regulating multiple aspects of MQC, resulting in increased organelle turnover, improved mitochondrial bioenergetics, and the retention of cell function. In the present review, these emerging protective effects are discussed in the context of cardiac ischemia-reperfusion (IR) and heart failure, focusing on MQC as a strategy to blunt the propagation of connected dangerous signaling cascades and limit adverse remodeling. A better understanding of such TH-dependent signaling could provide insights into the development of mitochondria-targeted treatments in patients with cardiac disease.

The impact of thyroid hormone dysfunction on ischemic heart disease

Thyroid hormones have a central role in cardiovascular homeostasis. In myocardium, these hormones stimulate both diastolic myocardial relaxation and systolic myocardial contraction, have a pro-angiogenic effect and an important role in extracellular matrix maintenance. Thyroid hormones modulate cardiac mitochondrial function. Dysfunction of thyroid axis impairs myocardial bioenergetic status. Both overt and subclinical hypothyroidism are associated with a higher incidence of coronary events and an increased risk of heart failure progression. Endothelial function is also impaired in hypothyroid state, with decreased nitric oxide-mediated vascular relaxation. In heart disease, particularly in ischemic heart disease, abnormalities in thyroid hormone levels are common and are an important factor to be considered. In fact, low thyroid hormone levels should be interpreted as a cardiovascular risk factor. Regarding ischemic heart disease, during the late post-myocardial infarction period, thyroid hormones modulate left ventricular structure, function and geometry. Dysfunction of thyroid axis might even be more prevalent in the referred condition since there is an upregulation of type 3 deiodinase in myocardium, producing a state of local cardiac hypothyroidism. In this focused review, we summarize the central pathophysiological and clinical links between altered thyroid function and ischemic heart disease. Finally, we highlight the potential benefits of thyroid hormone supplementation as a therapeutic target in ischemic heart disease.

Cardioprotection and Thyroid Hormones in the Clinical Setting of Heart Failure

Ischemic heart disease is the main cause of morbidity and mortality worldwide and is becoming more widespread with population aging. Cardioprotection is a dynamic process characterized by mechanisms related to myocardial damage and activation of protective factors. Targeting these processes could be attractive as a new therapeutic strategy in the evolution of post-ischemic heart failure (HF). In this context, the role of thyroid hormone (TH)-mediated cardioprotection is supported by a number of findings regarding the modulation of neuroendocrine systems, inflammatory and oxidative stress status, pro-survival intracellular pathways, and epigenetic factors, its effects on cardiac angiogenesis, structure, and function and on the preservation of mitochondrial function and morphology, and its beneficial effects on cell growth and redifferentiation. Moreover, the numerous effects of TH on the heart involve genomic mechanisms, which include cardiac differentiation during the perinatal period and non-genomic action, directed toward the maintenance of cardiovascular homeostasis. This evidence suggests that there is an opportunity to treat HF patients with TH. This review is mainly focused on the clinical evidence of the role of the thyroid system in the complex setting of HF.

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.

Association between Low Free Triiodothyronine Levels and Poor Prognosis in Patients with Acute ST-Elevation Myocardial Infarction

Background

Low free triiodothyronine (fT3) levels are generally associated with poor prognosis in patients with heart diseases, but this is controversial and there is a lack of data about ST-elevation myocardial infarction (STEMI) in Chinese patients.

Objective

To assess the association between fT3 levels and the prognosis of patients with STEMI.

Methods

This was a prospective observational study of 699 consecutive patients with STEMI treated at the Xinqiao Hospital between January 1, 2013, and December 31, 2014. The patients were divided into the low fT3 (fT3 < 3.1 pmol/L; n = 179, 27.5%) and normal fT3 (fT3 ≥ 3.1 pmol/L; n = 473, 72.5%) groups according to fT3 levels at admission. Patients were followed up at 1, 3, 6, and 12 months for all-cause death and major adverse cardiac events (MACE).

Results

During the 1-year follow-up, there were 70 all-cause deaths (39.1%) in the low fT3 group and 40 (8.5%) in the normal fT3 group (P < 0.001). MACE occurred in 105 patients (58.7%) in the low fT3 group and 74 (15.6%) in the normal fT3 group (P < 0.001). Multivariate Cox proportional hazards regression analysis indicated that fT3 levels were independently associated with 30-day and 1-year all-cause death [30-day: hazard ratio (HR) = 0.702, 95% confidence interval (95% CI): 0.501–0.983, P = 0.04; 1-year: HR = 0.557, 95% CI: 0.411–0.755, P < 0.001] and MACE (30-day: HR = 0.719, 95% CI: 0.528–0.979, P = 0.036; 1-year: HR = 0.557, 95% CI: 0.445–0.698, P < 0.001).

Conclusion

Low fT3 levels were strongly associated with poor prognosis in patients with STEMI. Measurement of fT3 levels may be a valuable and simple way to identify high-risk STEMI patients.

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.

Exercise training versus T3 and T4 hormones treatment: The differential benefits of thyroid hormones on the parasympathetic drive of infarcted rats

AIMS

This study aimed to investigate whether beneficial effects of thyroid hormones are comparable to those provided by the aerobic exercise training, to verify its applicability as a therapeutic alternative to reverse the pathological cardiac remodeling post-infarction.

MATERIALS AND METHODS

Male rats were divided into SHAM-operated (SHAM), myocardial infarction (MI), MI subjected to exercise training (MIE), and MI who received T3 and T4 treatment (MIH) (n = 8/group). MI, MIE and MIH groups underwent an infarction surgery while SHAM was SHAM-operated. One-week post-surgery, MIE and MIH groups started the exercise training protocol (moderate intensity on treadmill), or the T3 (1.2 μg/100 g/day) and T4 (4.8 μg/100 g/day) hormones treatment by gavage, respectively, meanwhile SHAM and MI had no intervention for 9 weeks. The groups were accompanied until 74 days after surgery, when all animals were anesthetized, left ventricle echocardiography and femoral catheterization were performed, followed by euthanasia and left ventricle collection for morphological, oxidative stress, and intracellular kinases expression analysis.

KEY FINDINGS

Thyroid hormones treatment was more effective in cardiac dilation and infarction area reduction, while exercise training provided more protection against fibrosis. Thyroid hormones treatment increased the lipoperoxidation and decreased GSHPx activity as compared to MI group, increased the t-Akt2 expression as compared to SHAM group, and increased the vascular parasympathetic drive.

SIGNIFICANCE

Thyroid hormones treatment provided differential benefits on the LV function and autonomic modulation as compared to the exercise training. Nevertheless, the redox unbalance induced by thyroid hormones highlights the importance of more studies targeting the ideal duration of this treatment.

Aerobic training prior to myocardial infarction increases cardiac GLUT4 and partially preserves heart function in spontaneously hypertensive rats

We assessed cardiac function (echocardiographic) and glucose transporter 4 (GLUT4) expression (Western blot) in response to 10 weeks of aerobic training (treadmill) prior to acute myocardial infarction (AMI) by ligation of the left coronary artery in spontaneously hypertensive rats. Animals were allocated to sedentary+sham, sedentary+AMI, training+sham, and training+AMI. Aerobic training prior to AMI partially preserves heart function. AMI and/or aerobic training increased GLUT4 expression. However, those animals trained prior to AMI showed a greater increase in GLUT4 in cardiomyocytes.

Free Triiodothyronine Level Correlates with Myocardial Injury and Prognosis in Idiopathic Dilated Cardiomyopathy: Evidence from Cardiac MRI and SPECT/PET Imaging

Thyroid dysfunction is associated with poor prognosis in heart failure, but theories of mechanisms are mainly based on animal experiments, not on human level. We aimed to explore the relation between thyroid function and myocardial injuries in idiopathic dilated cardiomyopathy (IDCM) using cardiac magnetic resonance imaging (MRI), single-photon emission computed tomography (SPECT) and positron emission tomography (PET). Myocardial fibrosis was detected by late gadolinium enhancement (LGE) MRI, and myocardial perfusion/metabolism was evaluated by ^99mTc-MIBI SPECT /¹⁸F-FDG PET imaging. Across the quartiles of FT3, decreased percentage of segments with LGE and perfusion/metabolism abnormalities were found. As for FT4 and TSH levels, no significant distribution trend of myocardial injuries could be detected. In logistic analysis, FT3 was independently associated with the presence of LGE (OR: 0.140, 95% CI: 0.035-0.567), perfusion abnormalities (OR: 0.172, 95% CI: 0.040-0.738) and metabolism abnormalities (OR: 0.281, 95% CI: 0.081-0.971). After a median follow-up of 46 months, LGE-positive and FT3 < 2.77 pg/mL was identified as the strongest predictor of cardiac events (HR: 8.623, 95% CI: 3.626-16.438). Low FT3 level is associated with myocardial fibrosis and perfusion/metabolism abnormalities in patients with IDCM. The combination of FT3 level and LGE provides useful information for assessing the prognosis of IDCM.

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.

Upregulation of rat liver PPARα-FGF21 signaling by a docosahexaenoic acid and thyroid hormone combined protocol

Prevention of ischemia-reperfusion liver injury is achieved by a combined omega-3 and thyroid hormone (T₃ ) protocol, which may involve peroxisome-proliferator activated receptor-α (PPAR-α)-fibroblast growth factor 21 (FGF21) signaling supporting energy requirements. Combined docosahexaenoic acid (DHA; daily doses of 300 mg/kg for 3 days) plus 0.05 mg T₃ /kg given to fed rats elicited higher hepatic DHA contents and serum T₃ levels, increased PPAR-α mRNA and its DNA binding, with higher mRNA expression of the PPAR-α target genes for carnitine-palmitoyl transferase 1α, acyl-CoA oxidase, and 3-hydroxyl-3-methylglutaryl-CoA synthase 2, effects that were mimicked by 0.1 mg T₃ /kg given alone or by the PPAR-α agonist WY-14632. Under these conditions, the mRNA expression of retinoic X receptor-α (RXR-α) is also increased, with concomitant elevation of the hepatic mRNA and protein FGF21 levels and those of serum FGF21. It is concluded that PPAR-α-FGF21 induction by DHA combined with T₃ may involve ligand activation of PPAR-α by DHA and enhanced expression of PPAR-α by T₃ , with consequent upregulation of the FGF21 that is controlled by PPAR-α. Considering the beneficial effects of PPAR-α-FGF21 signaling on carbohydrate and lipid metabolism, further investigations are required to clarify its potential therapeutic applications in human metabolic disorders. © 2016 BioFactors, 42(6):638-646, 2016.

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.

Antioxidant therapy improves non-thyroidal illness syndrome in uremic rats

BACKGROUND

The roles of antioxidant therapy on non-thyroidal illness syndrome (NTIS) in uremic rats is still unclear.

MATERIALS AND METHODS

Twenty-four Sprague-Dawley (SD) rats were randomly divided into blank, 5/6 nephrectomy (Nx), pyrrolidine dithiocarbamate (PDTC, 10 mg/100 g), sodium bicarbonate (SB, 0.1 g/100 g), N-acetylcysteine (NAC, 80 mg/100 g) and thyroid hormones (TH, levothyroxine 2 μg/100 g) groups. The serum levels of malondialdehyde (MDA), superoxide dismutase (SOD), advanced oxidation protein products (AOPP), interleukin (IL)-1β, free triiodothyronine (FT3), and thyroid stimulating hormone (TSH) were detected in the sixth week. The expressions of IL-1β and deiodinase type 1 (DIO1) were assessed by western blotting. The nuclear factor kappa B (NF-κB) inflammatory signal pathway was confirmed by electrophoretic mobility shift assay (EMSA).

RESULTS

Compared with 5/6 Nx group, PDTC and NAC significantly reduced the levels (p < 0.01, respectively) of serum MDA, AOPP, TSH, and elevated levels of serum SOD (p < 0.01, respectively) and FT3 (p = 0.016 and p < 0.01). Neither had significant effects on serum IL-1β content (p = 0.612 and p = 0.582). PDTC and NAC markedly decreased the protein expression of IL-1β (p < 0.01) and increased the protein expression of DIO1 (p < 0.01), respectively. Both had been considerably blunted NF-κB activity (p < 0.01).

CONCLUSIONS

In uremic rat model, PDTC and NAC can effectively improve oxidative stress level and NTIS. In terms of improving oxidative stress level, NAC is probably superior to PDTC.

Molecular and biochemical evidences on the protective effects of triiodothyronine against phosphine-induced cardiac and mitochondrial toxicity

AIM

Aluminum phosphide (AlP) is a widely used fumigant and rodenticide. While AlP ingestion leads to high mortality, its exact mechanism of action is unclear. There are ample evidences suggesting cardioprotective effects of triiodothyronine (T3). In this study, we aimed to examine the potential of T3 in the protection of a rat model of AlP induced cardiotoxicity.

MAIN METHODS

In order to induce AlP intoxication animals were intoxicated with AlP (12 mg/kg; LD50) by gavage. In treatment groups, T3 (1, 2 and 3 μg/kg) was administered intra-peritoneally 30 min after AlP administration. Animals were connected to the electronic cardiovascular monitoring device simultaneously after T3 administration. Then, electrocardiogram (ECG), blood pressure (BP), and heart rate (HR) were monitored for 180 min. Additionally, 24h after AlP intoxication, rats were deceased and the hearts were dissected out for evaluation of oxidative stress, cardiac mitochondrial function (complexes I, II and IV), ATP/ADP ratio, caspases 3 & 9, and apoptosis by flow cytometry.

KEY FINDINGS

The results demonstrated that AlP intoxication causes cardiac toxicity presenting with changes in ECG patterns such as decrement of HR, BP and abnormal QRS complexes, QTc and ST height. T3 at a dose of 3 μg/kg significantly improved ECG and also oxidative stress parameters. Furthermore, T3 administration could increase mitochondrial function and ATP levels within the cardiac cells. In addition, administration of T3 showed a reduction in apoptosis through diminishing the caspase activities and improving cell viability.

SIGNIFICANCE

Overall, the present data demonstrate the beneficial effects of T3 in cardiotoxicity of AlP.

Thyroid hormone in the frontier of cell protection, survival and functional recovery

Thyroid hormone (TH) exerts important actions on cellular energy metabolism, accelerating O2consumption with consequent reactive oxygen species (ROS) generation and redox signalling affording cell protection, a response that is contributed by redox-independent mechanisms. These processes underlie genomic and non-genomic pathways, which are integrated and exhibit hierarchical organisation. ROS production led to the activation of the redox-sensitive transcription factors nuclear factor-κB, signal transducer and activator of transcription 3, activating protein 1 and nuclear factor erythroid 2-related factor 2, promoting cell protection and survival by TH. These features involve enhancement in the homeostatic potential including antioxidant, antiapoptotic, antiinflammatory and cell proliferation responses, besides higher detoxification capabilities and energy supply through AMP-activated protein kinase upregulation. The above aspects constitute the molecular basis for TH-induced preconditioning of the liver that exerts protection against ischemia-reperfusion injury, a strategy also observed in extrahepatic organs of experimental animals and with other types of injury, which awaits application in the clinical setting. Noteworthy, re-adjusting TH to normal levels results in several beneficial effects; for example, it lengthens the cold storage time of organs for transplantation from brain-dead donors; allows a superior neurological outcome in infants of <28 weeks of gestation; reduces the cognitive side-effects of lithium and improves electroconvulsive therapy in patients with bipolar disorders.

Mitochondria as key targets of cardioprotection in cardiac ischemic disease: role of thyroid hormone triiodothyronine

Ischemic heart disease is the major cause of mortality and morbidity worldwide. Early reperfusion after acute myocardial ischemia has reduced short-term mortality, but it is also responsible for additional myocardial damage, which in the long run favors adverse cardiac remodeling and heart failure evolution. A growing body of experimental and clinical evidence show that the mitochondrion is an essential end effector of ischemia/reperfusion injury and a major trigger of cell death in the acute ischemic phase (up to 48–72 h after the insult), the subacute phase (from 72 h to 7–10 days) and chronic stage (from 10–14 days to one month after the insult). As such, in recent years scientific efforts have focused on mitochondria as a target for cardioprotective strategies in ischemic heart disease and cardiomyopathy. The present review discusses recent advances in this field, with special emphasis on the emerging role of the biologically active thyroid hormone triiodothyronine (T3).