48 h after first administration, 5 mg/kg/day DOX signi-ficantly increased expression levels of proapoptotic proteins: a)procaspase 3 and its cleaved form; b) procaspase 9 and itscleaved form; c) Bax/Bcl2 ratio. At the end of treatments, 5 mg/kg/day DOX significantly decreased expression levels oftroponin I and Myosin Heavy Chain (MHC) whereas increasedexpression levels of: a) procaspase 3 and its cleaved form; b)Bax/Bcl2 ratio; c) procaspase 8; d) procaspase 12 and itscleaved form; e) calpain I. 2.5 mg/kg/day DOX significantlyincreased expression levels of procaspase 12 at the end oftreatments only. In contrast, 1.25 mg/kg/day DOX did not affectexpression levels of pro- and antiapoptotic proteins. It isconcluded that 20 mg/kg DOX administered over a period of4 weeks induced minor apoptotic effects respect to the sameadministration in shorter period. This could be useful toestablish a treatment scheme with best efficacy and less toxicity.Further studies are in progress to elucidate these mechanisms.

Keywords: Apoptosis; Anthracyclines; Heart

doi:10.1016/j.yjmcc.2007.03.750

Regulation of the expression of ATF3 in cardiac myocytesin response to hypertrophic and apoptotic stimulationAlejandro Giraldo, Sampsa Pikkarainen, Peter H. Sugden,Angela Clerk. NHLI Division, Faculty of Medicine, ImperialCollege London, London, UK

The stress responses of cardiomyocytes are likely toconstitute a significant aspect of the development of cardiacpathologies. Oxidative stress is a common theme in the patho-physiology of ischaemic and non-ischaemic cardiomyopathy,and anticancer drugs (e.g. doxorubicin) induce cardiomyopathypotentially via oxidative stress. Microarray studies in cardiacmyocytes indicate that one of the genes most potently inducedby H2O2 (as an oxidative stress) or hypertrophic agonists (e.g.endothelin-1) is the transcription factor ATF3. The increase inexpression of ATF3 mRNA was confirmed in neonatal ratcardiac myocytes exposed to H2O2, endothelin-1 or doxorubicinusing RT-PCR. Using immunoblotting, it was confirmed thatH2O2 or endothelin-1 increased ATF3 protein expression,although endothelin-1 was the more potent. Inhibition of theextracellular signal-regulated kinase (ERK1/2) cascade withU0126 (10 μM) significantly decreased the expression of ATF3protein by endothelin, but had no effect on ATF3 mRNAexpression. ATF3 has an important role in the regulation of thecytokine interleukin-6 and the pro-apoptotic gene CHOP/GADD153 following oxidative stress, as demonstrated throughchromatin immunoprecipitation (ChIP) studies. We concludethat upregulation of ATF3 plays an important role in theregulation of cardiac myocyte hypertrophy and apoptosis.

Keywords: Cardiac hypertrophy; Apoptosis; Cardiomyocytes

doi:10.1016/j.yjmcc.2007.03.751

Transition from hypertrophy to heart failure in guinea pigsis associated with an increase in apoptosisAnita K. Sharma, Sanjiv Dhingra, Neelam Khaper, Pawan K.Singal. ICVS, Dept. of Physiology, Univ. of Manitoba,Winnipeg, Canada

Chronic pressure overload results in hypertrophy which cantransition into heart failure. In this study, hearts from maleGuinea pigs were examined at 10 and 20 weeks (W) after thebanding of their ascending aorta and compared with Shamcontrols. Echocardiography assessment, heart to body weightratio (H/BW), wet to dry weight ratios of lungs and liver,mitochondrial membrane potential, Cytochrome C release,caspase 3, apoptotic (Bax) and anti-apoptotic (Bcl-xl) proteins,apoptosis and oxidative stress were examined. The H/BW was66% and 88% higher in banded animals at 10 and 20W,respectively. There was no increase in wet to dry weight ratios forthe lungs and liver at 10W. However, at 20W, these ratios were19% and 31% higher. At 10W, left ventricle posterior wallthickness increased during diastole as well as systole with nofurther appreciable change at 20W. Fractional Shortening wassignificantly decreased at 20W (Sham 42.6%; Banded 28.7%).Mitochondrial membrane potential in the banded animals in boththe groups was significantly decreased. In the banded animals,Cytochrome C levels were higher in the cytosol as compared tothe mitochondria leading to a considerable increase in p17fragment expression of caspase 3. Oxidative stress was signi-ficantly higher in the 20W banded group. The ratio of Bax/Bcl-xlshowed an increase and this increasewasmore at 20W. Therewasan increase in apoptosis at 20W. It is suggested that increase inoxidative stress as well as apoptosis subsequent to banding maycontribute in the transition of heart hypertrophy to heart failure.

Acknowledgment

Supp. by CIHR.

Keywords: Heart failure; Apoptosis

doi:10.1016/j.yjmcc.2007.03.752

Human fetal cardiac myocyte growth is mediated byactivation of class 1A/1B pi 3-kinase, Akt, PKC, and ERKsignalingLakshman Sandirasegarane, Swarajit K. Biswas, Yan Zhao,Lawrence I. Sinoway. Penn State Heart and Vascular Institute,Coll of Medicine, Hershey, PA, USA

Numerous studies have employed terminally differentiatedneonatal/adult cardiac myocytes to demonstrate the critical rolesof phosphoinositide 3-kinase (PI 3-kinase)/Akt, PKC, and ERKsignalling toward physiological or pathological cardiac hyper-trophy. However, the regulatory effects of these key signallingcomponents on human fetal cardiac myocyte (HFCM) prolif-eration are not fully known. It is hypothesized that tyrosinekinase linked receptor (TKLR) vs. G protein-coupled receptor

S84 ABSTRACTS / Journal of Molecular and Cellular Cardiology 42 (2007) S80–S87