CIC   05421
CENTRO DE INVESTIGACIONES CARDIOVASCULARES "DR. HORACIO EUGENIO CINGOLANI"
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Acute glucocorticoid action promotes a reduction in cardiac NHE1 activity
Autor/es:
PRIETO DÍAZ JP; AMARILLO ME; PÉREZ NG; BARBIERI C; DIAZ RG
Lugar:
Rosario
Reunión:
Congreso; Reunión Anual de la Sociedad Argentina de Fisiología (SAFIS); 2019
Institución organizadora:
SAFIS
Resumen:
Background/Aims: Glucocorticoid receptor (GR) is highly expressed on cardiac tissue, but its specific activity remains unknown. After ischemia/reperfussion, GR activation ameliorates cardiac function by a mechanism that could include calcineurin pathway inactivation. Since NHE1 activity could increase calcineurin pathway, we seek if GR could regulate cardiac NHE1 activity.Methods: NHE1 activity was indirectly assessed by Na+-dependent pHi recovery induced by transient acidosis (TA) in isolated rat papillary muscles. AKT and NHE1 phosphorylation, expression and NHE1 dimerization were determined by western blot. Hydrocortisone (HC) was used to trigger GR activation. Experimental groups consist in control condition, TA, TA + HC 1nm and TA + HC 10nm.Results: Acute increasing concentrations of HC significantly blunted NHE1 activation triggered by TA. NHE1 expression remained invariant among the four experimental groups. Since a corticoid induced-membrane perturbation and a sensitivity of NHE1 dimerization after membrane lipid alteration were documented, we seek for dimerization status of NHE1. Non-reductor western blot was performed showing no differences between dimeric NHE1 vs. monomeric NHE1 among groups. In zebrafish, another rapid signaling pathway for GR involving AKT activation was described, then AKT phosphorylation as index of protein activation was explored in this experimental set. HC 10nm promotes a significant increase in AKT phosphorylation compared to control condition. Consequently, as NHE1 is an AKT substrate, we search for AKT phosphorylation consensus sequence (AKT-cs) in inmunoprecipitated NHE1 samples, finding a significant increase in AKT-cs as HC concentration increases. Conclusion: Our results shows an acute GR induced-negative regulation of NHE1 activity by hydrocortisone, and preliminary suggest that AKT phosphorylation/activation would be part of this signaling pathway.