Angiotensin receptor blockade improves the net balance of cardiac Ca 2+ handling-related proteins in sympathetic hyperactivity-induced heart failure Julio C.B. Ferreira, Jose B.N. Moreira, Juliane C. Campos, Marcelo G. Pereira, Katt C. Mattos, Marcele A. Coelho, Patricia C. Brum ⁎ School of Physical Education and Sport, University of Sao Paulo, SP, Brazil abstract article info Article history: Received 8 June 2010 Accepted 10 January 2011 Keywords: Ventricular dysfunction Cardiac remodeling Neurohumoral activation Renin angiotensin system Protein kinase A Ca 2+ /calmodulin-dependent protein kinase II Aims: The clinical benefits of angiotensin II type 1 (AT1) receptor blockers (ARB) in heart failure (HF) include cardiac anti-remodeling and improved ventricular function. However, the cellular mechanisms underlying the benefits of ARB on ventricular function need to be better clarified. In the present manuscript, we evaluated the effects of AT1 receptor blockade on the net balance of Ca 2+ handling proteins in hearts of mice lacking α 2A and α 2C adrenoceptors (α 2A /α 2C ARKO), which develop sympathetic hyperactivity (SH) induced-HF. Main methods: A cohort of male wild-type (WT) and congenic α 2A /α 2C ARKO mice in a C57BL6/J genetic background (5–7 mo of age) was randomly assigned to receive either placebo or ARB (Losartan, 10 mg/kg for 8wks). Ventricular function (VF) was assessed by echocardiography, and cardiac myocyte width and ventricular fibrosis by a computer-assisted morphometric system. Sarcoplasmic reticulum Ca 2+ ATPase (SERCA2), phospholamban (PLN), phospho-Ser 16 -PLN, phospho-Thr 17 -PLN, phosphatase 1 (PP1), Na + –Ca 2+ exchanger (NCX), Ca 2+ /calmodulin-dependent protein kinase II (CaMKII) and phospho-Thr 286 -CaMKII were analyzed by Western blot. Key findings: α 2A /α 2C ARKO mice displayed ventricular dysfunction, cardiomyocyte hypertrophy and cardiac fibrosis paralleled by decreased SERCA2 and increased phospho-Thr 17 -PLN, CaMKII, phospho-Thr 286 -CaMKII and NCX levels. ARB induced anti-cardiac remodeling effect and improved VF in α 2A /α 2C ARKO associated with increased SERCA2 and phospho-Ser 16 -PLN levels, and SERCA2:NCX ratio. Additionally, ARB decreased phospho-Thr 17 -PLN levels as well as reestablished NCX, CaMKII and phospho-Thr 286 -CaMKII toward WT levels. Significance: Altogether, these data provide new insights on intracellular Ca 2+ regulatory mechanisms underlying improved ventricular function by ARB therapy in HF. © 2011 Elsevier Inc. All rights reserved. Introduction Heart failure (HF) is a common leading cause of mortality worldwide. During HF progression, the heart is in constant peril of damage from pathological stresses, such as neurohumoral over- activation (Bacurau et al., 2009; Barki-Harrington et al., 2003; Brum et al., 2006). Several lines of evidence suggest that sustained renin angiotensin system (RAS) activation plays deleterious effects in the heart since increased cardiac angiotensin II levels lead to cardiomyocyte hypertrophy and myocardial fibrosis (Dostal, 2000; Ferreira et al., 2008a; Leenen et al., 2001), and further contribute to HF establish- ment (Palaniyandi et al., 2009). The benefit of RAS inhibition in HF has been demonstrated in several randomized clinical trials where ARB- treated HF patients displayed reduced morbidity and mortality (Pitt et al., 1995), and showed a wide range of desirable hemodynamic outcomes (Sweet and Rucinska, 1994). Besides the well-known cardiac anti-remodeling effect of ARB therapy, some clinical trials and experimental studies have shown that sustained ARB therapy also improves ventricular function in HF patients (Crozier et al., 1995; Qing and Garcia, 1992). However, the molecular mechanisms related to ARB therapy-mediated improved ventricular function in HF remains elusive. Considering that cardiac function is strongly coupled with Ca 2+ transient in the heart, a positive effect of ARB on cardiac Ca 2+ - handling proteins in HF might be a potential molecular mechanism involved in ARB improved ventricular function. The process involved in excitation–contraction coupling in the heart involves Ca 2+ release from the sarco/endoplasmic reticulum (SR) initiated by membrane depolarization and subsequent Ca 2+ influx via L-type Ca 2+ channels. This triggers further SR-Ca 2+ release channels (Ryanodine receptors, RyR) via Ca 2+ -induced Ca 2+ release and produces Ca 2+ sparks, triggering cardiomyocyte contraction. After contraction, sarcoplasmic reticulum Ca 2+ ATPase (SERCA) and Na + –Ca 2+ exchanger (NCX) Life Sciences 88 (2011) 578–585 ⁎ Corresponding author at: Escola de Educação Física e Esporte da Universidade de São Paulo, Departamento de Biodinâmica do Movimento do Corpo Humano, Av. Professor Mello Moraes, 65 - Butantã - São Paulo – SP, CEP 05508-900– Brazil. Tel.: +55 11 3091 3136; fax: +55 11 3813 5921. E-mail address: pcbrum@usp.br (P.C. Brum). 0024-3205/$ – see front matter © 2011 Elsevier Inc. All rights reserved. doi:10.1016/j.lfs.2011.01.009 Contents lists available at ScienceDirect Life Sciences journal homepage: www.elsevier.com/locate/lifescie