Identificação de alterações estruturais e de vias de sinalização em corações de camundongos Knockout para o receptor Mas de Angiotensina-(1-7)

Abstract

Angiotensin(Ang)-(1-7) has been widely investigated due to its Ang II opposite effects in different organs. Consequently, Ang-(1-7) represents a potential target for new therapeutic approaches. Taking into consideration that its effects are mediated by the Mas receptor and that genetic ablation of the Mas causes cardiac dysfunction, the objective of this current study was to identify potential signaling proteins in hearts of Mas knockout mice that might be involved in the structural and functional alterations observed in these animals. We used C57BL/6 Mas knockouts (KO) mice and their controls Wild Type (WT). Using the data obtained in a microarray assay performed previously, we first selected 272 genes which the expression was up or down regulated in hearts of Mas deficient mice. To limit our search for specific genes involved in the cardiac alterations observed in KO mice, structural and ultra structural evaluations were performed using histological and transmission electron microscopy techniques, respectively. Mas deficient mice presented a lower body weight and cardiomyocyte diameter and a higher number of mitochondria in the heart when compared with WT mice. These findings allowed us to sort the genes into two groups: one related to the cardiac structure and another one related to the energy metabolism of the heart. Afterward, using the western blotting technique we identified two signaling proteins directly related to the energy metabolism (AMPK and AMPK1) and other two signaling proteins associated to the maintenance of the cardiac structure (ERK1/2 and p38). Knockout mice presented a lower expression of the catalytic isoform of the AMPK complex (AMPK) and a higher expression of the regulatory isoform of the AMPK complex (AMPK1), indicating an imbalance of the ATP levels and, consequently, disturbances in the energy metabolism of the cardiac cells of these animals. Furthermore, a higher expression of the MAPKs XVIII ERK1/2 and p38 were observed in hearts of Mas deficient mice. Thus, our study demonstrated that the Ang-(1-7)/Mas axis is directly involved in the maintenance of the cardiac structure and of the energy metabolism of the heart, likely by regulating the expression of the signaling proteins MAPK e AMPK.