Thyroid Hormone Increases TGF-β1 in Cardiomyocytes Cultures Independently of Angiotensin II Type 1 and Type 2 Receptors

Abstract

TH-induced cardiac hypertrophyin vivois accompanied by increased cardiac Transforming Growth Factor-β1 (TGF-β1) levels, which is mediated by Angiotensin II type 1 receptors (AT1R) and type 2 receptors (AT2R). However, the possible involvement of this factor in TH-induced cardiac hypertrophy is unknown. In this study we evaluated whether TH is able to modulate TGF-β1 in isolated cardiac, as well as the possible contribution of AT1R and AT2R in this response. The cardiac fibroblasts treated withT3did not show alteration on TGF-β1 expression. However, cardiomyocytes treated withT3presented an increase in TGF-β1 expression, as well as an increase in protein synthesis. The AT1R blockade prevented theT3-induced cardiomyocyte hypertrophy, while the AT2R blockage attenuated this response. TheT3-induced increase on TGF-β1 expression in cardiomyocytes was not changed by the use of AT1R and AT2R blockers. These results indicate that Angiotensin II receptors are not implicated inT3-induced increase on TGF-βexpression and suggest that the trophic effects exerted byT3on cardiomyocytes are not dependent on the higher TGF-β1 levels, since the AT1R and AT2R blockers were able to attenuate theT3-induced cardiomyocyte hypertrophy but were not able to attenuate the increase on TGF-β1 levels promoted byT3.