Thyroid hormones effects on oxidative stress and cardiac remodeling in the right ventricle of infarcted rats

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.

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.

Deiodinases and the Three Types of Thyroid Hormone Deiodination Reactions

Thyroid hormone (TH) signaling is strictly regulated by iodothyronine deiodinase activity, which both preserves the circulating levels of the biologically active triiodothyronine (T3) and regulates TH homeostasis at the local level, in a cell- and time-dependent manner. Three deiodinases have been identified-namely iodothyronine deiodinase 1 (DIO1), DIO2, and DIO3-that differ in their catalytic properties and tissue distribution. The deiodinases represent a dynamic system that changes in the different stages of life according to their functions and roles in various cell types and tissues. Deiodinase activity at the tissue level permits cell-targeted fine regulation of TH homeostasis, mediating the activation (DIO1 and DIO2) and inactivation (DIO3) of THs. Deiodinase homeostasis is the driving force that leads T3-target cells towards customized TH signaling, which takes into account both the hormonal circulating levels and the tissue-specific response. This review analyzes the complex role of deiodinases in physiological and pathological contexts, exploring new challenges and opportunities deriving from a deeper knowledge of the dynamics underlying their roles and functions.

Thyroid hormone mediates cardioprotection against postinfarction remodeling and dysfunction through the IGF-1/PI3K/AKT signaling pathway

AIMS

Severe cardiovascular diseases, such as myocardial infarction or heart failure, can alter thyroid hormone (TH) secretion and peripheral conversion, leading to low triiodothyronine (T3) syndrome. Accumulating evidence suggests that TH has protective properties against cardiovascular diseases and that treatment with TH can effectively reduce myocardial damage after myocardial infarction (MI). Our aim is to investigate the effect of T3 pretreatment on cardiac function and pathological changes in mice subjected to MI and the underlying mechanisms.

MAIN METHODS

Adult male C57BL/6 mice underwent surgical ligation of the left anterior descending coronary artery (LAD) (or sham operation) to establish MI model. T3, BMS-754807 (inhibitor of insulin-like growth factor-1 receptor (IGF-1R)) or vehicle was administered before surgery.

KEY FINDINGS

Compared with the MI group, the T3 pretreatment group exhibited significant attenuation of the myocardial infarct area, inhibition of cardiomyocyte apoptosis and fibrosis, and improved left ventricular function after MI. In addition, T3 exhibited an enhanced potency to stimulate angiogenesis and exert anti-inflammatory effects by reducing the levels of serum inflammatory cytokines after MI. However, all of these protective effects were inhibited by the IGF-1R inhibitor BMS-754807. Moreover, the protein expression of IGF-1/PI3K/AKT signaling-related proteins, such as IGF-1, IGF-1R, phosphorylated PI3K (p-PI3K) and p-AKT was significantly upregulated in MI mice that received T3 pretreatment, and BMS-754807 pretreatment blocked the upregulation of the expression of these signaling-related proteins.

SIGNIFICANCE

T3 pretreatment can protect the heart against dysfunction post-MI, which may be mediated by the activation of the IGF-1/PI3K/AKT signaling pathway.

Thyroid hormone treatment improved the response to maximum exercise test and preserved the ventricular geometry in myocardial infarcted rats

NEW FINDINGS

What is the central question of this study? Does thyroid hormone treatment given after myocardial infarction preserve left ventricular function and treadmill exercise performance, and improve parameters of oxidative stress in the right ventricle and lungs of Wistar rats? What is the main finding and its importance? Thyroid hormone treatment improved the performance of the maximum exercise test in infarcted rats and induced effects in the heart and lungs that were similar to those observed with exercise training. This suggests there is a significant value of thyroid hormones for preserving exercise tolerance after myocardial infarction.

ABSTRACT

Left ventricular myocardial infarction (MI) provokes damage in the heart and in other tissues, such as right ventricle and lungs. The present study elucidated whether thyroid hormone treatment (THT) may present positive effects in heart and lungs after MI, and whether or not these effects are similar to those of exercise training (ET). Male Wistar rats were divided into four groups: sham operated (SHAM), infarcted (MI), infarcted + exercise training (MIE), and infarcted + thyroid hormones (MIH). A maximum exercise test, left ventricle echocardiography, pulmonary histology, and oxidative stress in the right ventricle and lung were evaluated. THT and ET both reduced left ventricular dilatation and end-diastolic wall stress indexes to a similar extent. MI accentuated the content of macrophages and inflammatory infiltrate in the lungs, which was partially prevented in the MIH and MIE groups. THT and ET presented similar effects in the heart and lungs, and both improved the performance of the maximum exercise test in infarcted animals.

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.

Evaluating the Effect of Vitamin C on Myocardial Angiogenesis Under Oxidative Stress Induced by Exhaustive Exercise in Rat

Background: The main purpose of the present study was to assess the effects of exhaustive swimming with the consumption of a vitamin C supplement on indices of myocardial oxidative stress and gene expression related to angiogenesis. Methods: Wistar rats were randomly divided into six groups of normal (C), 100 and 200 mg/kg of vitamin C, (VC100 and VC200), exercise with 100 and 200 mg/kg of vitamin C (Ex+VC100 and Ex+VC200) and exercise without treatment (Ex). Finally, the serum activity of serum creatine phosphokinase (CK) and lactate dehydrogenase (LDH) and heart tissue oxidant/antioxidant parameters, besides gene expression of Vascular endothelial growth factor-B (VEGF-B), angiopoietin 1 (ANGPT-1) and matrix metalloproteinases 2 (MMP-2) was measured. Results: Significant increase in LDH level was seen in group Ex which was remarkably attenuated in group Ex+VC200 (p<0.001). The tissue oxidative stress was observed in group Ex where daily intake of vitamin C could remarkably regulate this property (p<0.01). Vitamin C could ameliorate significant upper gene expression of VEGF-B and MMP-2 remarkably (p<0.05). Conclusion: Oxidative condition in myocardial besides over expression of MMP-2, could be concluded as a detrimental condition resulting from exhaustive swimming that continued by the proteolytic release of CK and LDH from the muscle. Upper gene expression of VEGF-B and MMP-2 besides no changes of ANGPT-1 can be concluded as an early stage of angiogenesis. All these events were somehow attenuated by vitamin C which confirmed its beneficial effects as an antioxidant and the role of oxidation properties in the regulation of angiogenesis.

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.