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

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 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.

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.