Nuclear Inositol 1,4,5-Triphosphate is an Absolut Requirement for Cardiomyocyte Hypertrophy

Abstract

Ca2+ mediates a wide range of cellular responses and the release of this ion from inositol 1,4,5-triphosphate receptor (InsP3R) is known to play a critical role in transcription of genes involved in cardiac hypertrophy. The goal of this work is to investigate the relative role of nuclear InsP3 in hypertrophy response induced by endothelin-1 (ET-1). For that, we used an adenovirus construct that has the ability to act as selective InsP3 buffer in the nucleus (InsP3-sponge-NLS), inducing local changes in Ca2+ levels. We used a primary culture of neonatal cardiomyocytes, and cells were examined by confocal microscopy and immunofluorescence. We found that ET-1 increased cell surface area by 54.3 ± 6.87% compared to control (p<0.05), and that InsP3-sponge-NLS prevented hypertrophy induced by ET-1. We also found that ANP expression levels remained at control levels when ET-1 treated cardiomyocytes had InsP3 buffered in the nucleus. Then, we investigated whether buffering nuclear InsP3 would affect the signaling pathway as calcineurin (Cn)/ nuclear factor of activated T cells (NFAT) and histone deacetilase 5 (HDAC-5) preventing the activation of hypertrophic genes. We observed that buffering nuclear InsP3 decreased translocation of Cn, and NFAT (1.22 ± 0.13 and 0.46 ± 0.16 pixel/nuclear area for control and buffered cells, respectively, p<0.001) upon ET-1 stimulation. On the other hand, the HDAC-5 exportation to citosol was prevented by InsP3-sponge-NLS (2.965 ± 0.13 and 5.548 ± 0.25 pixel/nuclear area for ET-1 treated cells and InsP3-sponge-NLS infected plus ET-1 cardiomyocytes, respectively, p<0.001).Together, these results show that nuclear InsP3 plays a central role in the hypertrophic effect induced by ET-1. Suport:HHMI/CNPq/Fapemig/CAPES.