The role of triiodothyronine (T3) on the regulation of rat cardiomyocyte genes expression: in vivo and in vitro studies.

Author(s)

Erika Lia Brunetto Ract

• Document type: Doctoral Thesis
• Press: São Paulo.
• Institution: Universidade de São Paulo (USP). Instituto de Ciências Biomédicas (ICB/SDI)
• Defense date: 2011-11-22

Examining board members

Maria Tereza Nunes; Maria Luiza Morais Barreto de Chaves; Rodrigo Antonio Peliciari Garcia; Ubiratan Fabres Machado; Célia Regina Nogueira

• Advisor: Maria Tereza Nunes

Abstract

Through nuclear actions, thyroid hormones (TH) control the expression of several cardiac genes, but there are several evidences that TH also promotes effects that occur in a short time (few minutes), and which are independent of its interaction with specific nuclear receptors attached to the TH-responsive elements, known as non-genomic or extranuclear actions. In heart failure, there are a lower expression of nuclear T3 receptors, which reduce the cardiostimulating effects of the hormone, which is extremely advantageous in an energy contention. Thus, this study aims to evaluate the acute (nongenomic) administration of T3 on the expression and translocation of GLUT4, and key proteins of the cardiac activity, such as GLUT1, Mb, SERCa2a, <font face=\"Symbol\">&#945; and <font face=\"Symbol\">b myosin in: ( 1) rats with or without heart failure after aortic stenosis surgery, as well as (2) primary cultured cardiomyocytes neonates and adults. In the vivo model, after 30 min of the administration of T3 in the group with CHF, there is an increased in the mRNA expression in GLUT1, GLUT4 and Mb. Their proteins had an increase after 30 min (GLUT1 and GLUT4) and after 60 min (Mb). As for genes related to cardiac function, Atp2a2, Myh6 and MYH7, we observed that, the treatment with T3 for 30 min in rats with CHF promoted a decrease of the mRNA of three genes as well as the beta MHC protein. The content of alpha-MHC and SERCa2a did not change in 30 min, but increased after T3 treatment for 60 min. In the in vitro model of neonatal cardiomyocytes, we had evidence of modulation of mRNA and protein content after 30 and 45 min after the addition of T3 in different doses (from 10-9 to 10-6 M). When evaluating the effect of T3 on the mRNA content in adult cardiomyocytes in culture, we also observed a random response, not dependent on dose. All the data obtained so far points to the existence of a post-transcriptional control of T3 on the expression of target genes of this study, which could induce an improvement in cardiac function in the presence of an CHF, since these actions are elicited and fleeting, preventing cardiostimulating effects persist, which could be deleterious. (AU)