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Doctoral Thesis
DOI
10.11606/T.42.2019.tde-18012019-135852
Document
Author
Full name
Caroline Antunes Lino
Institute/School/College
Knowledge Area
Date of Defense
Published
São Paulo, 2018
Supervisor
Committee
Chaves, Maria Luiza Morais Barreto de (President)
Akamine, Eliana Hiromi
Costa Neto, Claudio Miguel da
Lotfi, Claudimara Ferini Pacicco
Neves, Francisco de Assis Rocha
Title in Portuguese
Contribuição da sinalização dependente de beta-arrestinas, via receptor de angiotensina II do tipo 1, na hipertrofia cardiomiocítica induzida por T3.
Keywords in Portuguese
Beta-arrestinas
GPCR
Hipertrofia Cardíaca
Hormônios Tireoidianos
Internalização de Receptores
Receptor de Angiotensina II do tipo I
Abstract in Portuguese
Níveis elevados de hormônios tireoidianos (HTs) são comumente associados à ativação do sistema renina angiotensina local e ao desenvolvimento da hipertrofia cardíaca. O envolvimento do receptor de angiotensina II tipo 1 (AT1R) nos efeitos hipertróficos dos HTs fora descrito previamente. No entanto, os mecanismos subjacentes a essa interação ainda são desconhecidos. O AT1R pertence à família dos receptores acoplados à proteína G e, portanto, promove a transdução de sinal por mecanismos dependentes e independentes de proteína G. Recentemente, a sinalização dependente de beta-arrestinas (independente de proteína G) tem sido descrita por contribuir com a resposta hipertrófica em diferentes modelos experimentais. Assim, no presente estudo investigou-se o envolvimento da sinalização dependente de beta-arrestinas nos efeitos hipertróficos dos HTs, mediados pelo AT1R, bem como a participação de ERK½ nesse processo. Culturas primárias de cardiomiócitos foram estimuladas com T3 (triiodotironina; 15nM) para indução da hipertrofia. O tratamento dos cardiomiócitos com T3 por tempos rápidos (5-30 min) resultou na ativação transiente de ERK½, a qual foi parcialmente atenuada quando da administração de Losartan (1µM), antagonista do AT1R. A contribuição de ERK½ na hipertrofia dos cardiomiócitos foi verificada através do uso de PD98059 (20µM), inibidor de MEK½, o qual preveniu a transcrição de marcadores hipertróficos. Ensaios de imunoprecipitação revelaram o aumento da interação entre AT1R e beta-arrestina 2 sob estímulo do T3, sugerindo o recrutamento de beta-arrestina 2 e, possível, internalização do AT1R. Através de ensaios de imunofluorescência e fracionamento subcelular, foi demonstrado que o T3 estimula a translocação do AT1R, amentando sua expressão no núcleo dos cardiomiócitos. Além disso, tanto a ativação de ERK½ quanto a hipertrofia cardiomiocítica mostraram-se sensíveis à inibição da endocitose, a qual foi avaliada através de Concanavalina A (0,5µg/ml). Ensaios de silenciamento gênico por RNA de interferência foram eficientes em demonstrar o envolvimento de beta-arrestina 2 na ativação de ERK½ e na hipertrofia cardiomiocítica induzida por T3. Desta forma, os resultados evidenciam o envolvimento da sinalização dependente de beta-arrestina 2 na ativação de ERK½, através do AT1R, a qual contribui com a hipertrofia cardiomiocítica promovida pelo T3.
Title in English
Contribution of beta-arrestin signaling mediated by angiotensin II receptor type 1 in cardiomyocyte hypertrophy induced by T3.
Keywords in English
Angiotensin II Type 1 Receptor
Beta-arrestins
Cardiac hypertrophy
GPCR
Receptor Internalization
Thyroid Hormones
Abstract in English
Elevated levels of thyroid hormones (THs) are commonly associated with activation of the local renin angiotensin system and the development of cardiac hypertrophy. The involvement of the angiotensin II receptor type 1 (AT1R) in the hypertrophic effects of the THs was previously described. However, the mechanisms underlying this interaction are still unknown. AT1R belongs to the G-protein coupled receptor family and promotes its signal transduction by G-protein dependent and independent mechanisms. Recently, beta-arrestin signaling (G-protein independent) has been described as contributing to the hypertrophic response in different experimental models. Thus, the present study investigated the involvement of beta-arrestin signaling in the hypertrophic effects of THs mediated by AT1R, as well as the participation of ERK½ in this process. Primary cardiomyocytes cultures were stimulated with T3 (triiodothyronine; 15nM) for the induction of hypertrophy. Cardiomyocytes acutely treated with T3 (5-30 min) resulted in transient activation of ERK½, which was partially attenuated upon Losartan (1µM) administration, an AT1R antagonist. The contribution of ERK½ to cardiomyocyte hypertrophy was verified by using PD98059 (20µM), a MEK½ inhibitor, which prevented the transcription of hypertrophic markers. Immunoprecipitation assays revealed increased interaction between AT1R and beta-arrestin 2 under T3 stimulation, suggesting the recruitment of beta-arrestin 2 and, possibly, the internalization of AT1R. Through immunofluorescence and subcellular fractionation assays, T3 has been shown to stimulate AT1R translocation, enhancing its expression in the cardiomyocyte nucleus. In addition, both ERK½ activation and cardiomyocyte hypertrophy were sensitive to the inhibition of endocytosis, which was assessed by Concanavalin A (0.5µg/ml). Interfering RNA assays were efficient in demonstrating the involvement of beta-arrestin 2 in ERK½ activation and in T3-induced cardiomyocyte hypertrophy. Therefore, the results evidenced the involvement of beta-arrestin-2-dependent signaling in the activation of ERK½, through the AT1R, which contributes to the cardiomyocyte hypertrophy promoted by T3.
 
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Release Date
2021-01-17
Publishing Date
2019-01-28
 
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