Rueda JO, Palomeque J, Mattiazzi A. Early apoptosis in different models of cardiac hypertrophy induced by high renin-angiotensin system activity involves CaMKII. J Appl Physiol 112: 2110 -2120, 2012. First published April 5, 2012 doi:10.1152/japplphysiol.01383.2011.-The objective of this study was to establish whether 1) hyperactivity of renin-angiotensin-aldosterone system (RAAS) produces apoptosis in early stages of cardiac disease; and 2) Ca 2ϩ -calmodulin-dependent protein kinase II (CaMKII) is involved in these apoptotic events. Two models of hypertrophy were used at an early stage of cardiac disease: spontaneously hypertensive rats (SHR) and isoproterenol-treated rats (Iso-rats). At 4 mo, SHR showed blood pressure, aldosterone serum levels, used as RAAS activity index, and left ventricular mass index, used as hypertrophy index, above control values by 84.2 Ϯ 2.6 mmHg, 211.2 Ϯ 25.8%, and 8.6 Ϯ 1.1 mg/mm, respectively. There was also an increase in apoptotis (Bax-to-Bcl-2 ratio and terminal deoxynucleotidyl transferase dUTP-mediated nick-end labeling positive cells) associated with an enhancement of CaMKII activity with respect to age-matched controls (phosphorylated-CaMKII, 98.7 Ϯ 14.1 above control). Similar results were observed in 4-mo-old Isorats. Cardiac function studied by echocardiography remained unaltered in all groups. Enalapril treatment significantly prevented hypertrophy, apoptosis, and CaMKII activity. Moreover, intracellular Ca 2ϩ handling in isolated myocytes was similar between SHR, Iso-rats, and their aged-matched controls. However, SHR and Iso-rats showed a significant increase in superoxide anion generation (lucigenin) and lipid peroxidation (thiobarbituric acid reactive substance). In transgenic mice with targeted cardiomyocyte expression of a CaMKII inhibitory peptide (AC3-I) or a scrambled control peptide (AC3-C), Iso treatment increased thiobarbituric acid reactive substance in both strains, whereas it increased CaMKII activity and apoptosis only in AC3-C mice. Endogenous increases in RAAS activity induce ROS and CaMKII-dependent apoptosis in vivo. CaMKII activation could not be associated with intracellular Ca 2ϩ increments and was directly related to the increase in oxidative stress.angiotensin II; Ca 2ϩ -calmodulin-dependent protein kinase II; reactive oxygen species; hypertrophy; apoptosis EXPERIMENTAL EVIDENCE INDICATES that a critical factor in the transition from compensated to noncompensated cardiac hypertrophy is myocyte cell loss by apoptosis and necrosis (42). The circulating levels of angiotensin II (ANG II) are increased in heart failure and may constitute one of the major causes of cell death in this transition (27). Moreover, activation of the multifunctional Ca 2ϩ -calmodulin protein kinase II (CaMKII), which ␦-isoform is largely predominant in mammalian myocardium (46), is a typical finding in heart failure from different etiologies. Activation of this kinase also constitutes a main step in the signaling cascade that leads to apoptosis following several cardiac insu...

Spontaneously hypertensive rat (SHR) constitutes a genetic model widely used to study the natural evolution of hypertensive heart disease. Ca2+-handling alterations are known to occur in SHR. However, the putative modifications of Ca2+-handling proteins during the progression to heart failure (HF) are not well established. Moreover, the role of apoptosis in SHR is controversial. We investigated intracellular Ca2+, Ca2+-handling proteins and apoptosis in SHR vs. control Wistar rats (W) from 3 to 15 months (mo). Changes associated with the transition to HF (i.e. lung edema and decrease in midwall fractional shortening), occurred at 15 mo in 38% of SHR (SHRF). In SHRF, twitch and caffeine-induced Ca2+ transients, significantly decreased relative to 6/9 mo and 15 mo without HF signs. This decrease occurred in association with a decrease in the time constant of caffeine-Ca2+ transient decay and an increase in Na+/Ca2+ exchanger (NCX) abundance (p<0.05) with no changes in SERCA2a expression/activity. An increased Ca2+-calmodulin-kinase II activity, associated with an enhancement of apoptosis (TUNEL and Bax/Bcl2) was observed in SHR relative to W from 3 to 15 mo. Conclusions: 1. Apoptosis is an early and persistent event that may contribute to hypertrophic remodeling but would not participate in the contractile impairment of SHRF. 2. The increase in NCX expression/activity, associated with an increase in Ca2+ efflux from the cell, constitutes a primary alteration of Ca2+-handling proteins in the evolution to HF. 3. No changes in SERCA2a expression/activity are observed when HF signs become evident.