Effect of exercise training on structural cardiac adaptations in a genetic model of cardiomyopathy induced by sympathetic hyperactivity

Author(s)

Rodrigo da Silva Fermino de Oliveira

• Document type: Master's Dissertation
• Press: São Paulo.
• Institution: Universidade de São Paulo (USP). Faculdade de Medicina (FM/SBD)
• Defense date: 2009-03-12

Examining board members

Patricia Chakur Brum; Anselmo Sigari Moriscot; Paulo Rizzo Ramires

• Advisor: Patricia Chakur Brum

Abstract

I ntroduction: Heart failure (HF) is a clinical syndrome characterized by cardiac dysfunction associated with neuro-hormonal hyperactivity, which culminates in cardiac hypertrophy (CH). Among the intracellular pathways involved in CH associated with HF, the calcium-dependept calcineurin pathway has been demonstrated to take an important role. Exercise training has been used as adjuvant treatment of patients with IC, but its role on cardiac remodeling related with calcineurin pathway in CH of HF has not yet been studied yet. Therefore, in the present study we evaluated the effect of exercise training on the calcineurin pathway and on CH in a genetic model of sympathetic hyperactivity induced HF. Methods: A cohort of male congenic 2A/2C-ARKO mice in a C57BL6/J genetic background and their wild-type controls (WT) were studied from 5 to 7 months of age, and were randomly assigned into WT (n=19), 2A/2C-ARKO (n=26) and 2A/2C-ARKO trained (n=31) groups. Treadmill aerobic exercise training was performed over 8 wk, 5 times per wk for 1 hour. Exercise tolerance was evaluated by total distance covered in treadmill maximal test until exhaustion, fractional shortening by echocardiogram, cardiac structure by mass of cardiac cardiac mass, and cardiomyocyte cross-sectional diameter by optical microscopy. -MHC mRNA levels were evaluated by RT-PCR, and expression of calcineurin, NFATc3 and GATA-4 in cytoplasmatic and nuclear extracts were evaluated by Western blot. Indeed sub-cellular localization of NFATc3 and GATA-4 proteins were studied by confocal microscopy. Results: 2A/2C-ARKO mice displayed exercise intolerance, cardiac dysfunction and structural cardiac alterations, which included increased left ventricle mass, myocyte crosssectional diameter and increased -MHC expression when compared to WT group. In addition, we observed alteration in calcineurin pathway associated with CH of 2A/2C-ARKO mice, named increased NFATc3 and GATA-4 expression in nuclear extracts paralleled by increased nuclear localization of NFATc3 and GATA-4 by confocal microscopy when compared to WT group. Exercise training in 2A/2CARKO mice improved exercise tolerance and cardiac function with a partial reversion of CH associated with reduced nuclear expression and localization of NFATc3 and GATA-4 when compared with WT mice. Conclusions: These data provide evidences for the anticardiac remodeling effect of exercise training in HF associated with reduced activation of calcineurin intracellular pathway (AU)