Coxsackie and adenovirus receptor is a modifier of cardiac conduction and arrhythmia vulnerability in the setting of myocardial ischemia

OBJECTIVES: The aim of this study was to investigate the modulatory effect of the coxsackie and adenovirus receptor (CAR) on ventricular conduction and arrhythmia vulnerability in the setting of myocardial ischemia. BACKGROUND: A heritable component in the risk of ventricular fibrillation during myocardial infarction has been well established. A recent genome-wide association study of ventricular fibrillation during acute myocardial infarction led to the identification of a locus on chromosome 21q21 (rs2824292) in the vicinity of the CXADR gene. CXADR encodes the CAR, a cell adhesion molecule predominantly located at the intercalated disks of the cardiomyocyte. METHODS: The correlation between CAR transcript levels and rs2824292 genotype was investigated in human left ventricular samples. Electrophysiological studies and molecular analyses were performed using CAR haploinsufficient (CAR(+/-)) mice. RESULTS: In human left ventricular samples, the risk allele at the chr21q21 genome-wide association study locus was associated with lower CXADR messenger ribonucleic acid levels, suggesting that decreased cardiac levels of CAR predispose to ischemia-induced ventricular fibrillation. Hearts from CAR(+/-) mice displayed slowing of ventricular conduction in addition to an earlier onset of ventricular arrhythmias during the early phase of acute myocardial ischemia after ligation of the left anterior descending artery. Expression and distribution of connexin 43 were unaffected, but CAR(+/-) hearts displayed increased arrhythmia susceptibility on pharmacological electrical uncoupling. Patch-clamp analysis of isolated CAR(+/-) myocytes showed reduced sodium current magnitude specifically at the intercalated disk. Moreover, CAR coprecipitated with NaV1.5 in vitro, suggesting that CAR affects sodium channel function through a physical interaction with NaV1.5. CONCLUSIONS: CAR is a novel modifier of ventricular conduction and arrhythmia vulnerability in the setting of myocardial ischemia. Genetic determinants of arrhythmia susceptibility (such as CAR) may constitute future targets for risk stratification of potentially lethal ventricular arrhythmias in patients with coronary artery disease

CYP2J2 Overexpression Protects against Arrhythmia Susceptibility in Cardiac Hypertrophy

<div><p>Maladaptive cardiac hypertrophy predisposes one to arrhythmia and sudden death. Cytochrome P450 (CYP)-derived epoxyeicosatrienoic acids (EETs) promote anti-inflammatory and antiapoptotic mechanisms, and are involved in the regulation of cardiac Ca²⁺-, K⁺- and Na⁺-channels. To test the hypothesis that enhanced cardiac EET biosynthesis counteracts hypertrophy-induced electrical remodeling, male transgenic mice with cardiomyocyte-specific overexpression of the human epoxygenase CYP2J2 (CYP2J2-TG) and wildtype littermates (WT) were subjected to chronic pressure overload (transverse aortic constriction, TAC) or β-adrenergic stimulation (isoproterenol infusion, ISO). TAC caused progressive mortality that was higher in WT (42% over 8 weeks after TAC), compared to CYP2J2-TG mice (6%). In vivo electrophysiological studies, 4 weeks after TAC, revealed high ventricular tachyarrhythmia inducibility in WT (47% of the stimulation protocols), but not in CYP2J2-TG mice (0%). CYP2J2 overexpression also enhanced ventricular refractoriness and protected against TAC-induced QRS prolongation and delocalization of left ventricular connexin-43. ISO for 14 days induced high vulnerability for atrial fibrillation in WT mice (54%) that was reduced in CYP-TG mice (17%). CYP2J2 overexpression also protected against ISO-induced reduction of atrial refractoriness and development of atrial fibrosis. In contrast to these profound effects on electrical remodeling, CYP2J2 overexpression only moderately reduced TAC-induced cardiac hypertrophy and did not affect the hypertrophic response to β-adrenergic stimulation. These results demonstrate that enhanced cardiac EET biosynthesis protects against electrical remodeling, ventricular tachyarrhythmia, and atrial fibrillation susceptibility during maladaptive cardiac hypertrophy.</p></div

Arrhythmia susceptibility after pressure overload-induced cardiac hypertrophy.

<p>(A) Representative original tracings showing the induction of ventricular tachyarrhythmia by programmed electrical stimulation in WT mice 4 weeks after TAC (upper panel) and the resistance of TAC operated CYP2J2-TG mice under the same conditions (lower panel). (B) Ventricular arrhythmia inducibility significantly increased in WT mice after TAC (n = 5) compared with the sham control (n = 7). Arrhythmias were not inducible in any of the CYP2J2-TG mice both after sham (n = 5) and TAC operation (n = 6). Each animal was subjected to three protocols of programmed electrical stimulation and statistical evaluation was performed as described in Materials and Methods. (C) The severity of ventricular tachyarrhythmias scored according to the length of induced episodes (number of consecutive ventricular extrasystoles; VES) increased in WT mice after TAC compared with the sham control, whereas neither non-sustained nor sustained arrhythmias were inducible in corresponding CYP2J2-TG mice. (D) Analysis of arrhythmia inducibility in Langendorff preparations of isolated perfused hearts (n = 4 per group). Comparison of the vehicle treated groups confirmed the contrasting vulnerabilities of hypertrophied WT and CYP2J2-TG hearts after TAC. Perfusion with the mitochondrial K_ATP-channel opener diazoxide (100 µM, 20 min prior to programmed electrical stimulation) reduced the arrhythmia inducibility of WT-TAC hearts to the levels of hearts isolated from sham WT mice as well as CYP2J2-TG mice after TAC. Pretreatment with the EET antagonist 14,15-EEZE-mSi (48.5 µM for 20 min) reversed the protection of hypertrophied CYP2J2-TG hearts towards arrhythmia inducibility. Results represent mean±SEM; ANOVA, Post-Hoc Tukey; *p<0.05 vs. WT-Sham (vehicle); ^‡p<0.05 vs. WT-TAC (vehicle); # p<0.05 vs. CYP-TAC (vehicle).</p

Coxsackie and adenovirus receptor is a modifier of cardiac conduction and arrhythmia vulnerability in the setting of myocardial ischemia.:Coxsackie and adenovirus receptor is a modifier of cardiac conduction and arrhythmia vulnerability in the setting of myocardial ischemia.

ObjectivesThe aim of this study was to investigate the modulatory effect of the coxsackie and adenovirus receptor (CAR) on ventricular conduction and arrhythmia vulnerability in the setting of myocardial ischemia.BackgroundA heritable component in the risk of ventricular fibrillation during myocardial infarction has been well established. A recent genome-wide association study of ventricular fibrillation during acute myocardial infarction led to the identification of a locus on chromosome 21q21 (rs2824292) in the vicinity of the CXADR gene. CXADR encodes the CAR, a cell adhesion molecule predominantly located at the intercalated disks of the cardiomyocyte.MethodsThe correlation between CAR transcript levels and rs2824292 genotype was investigated in human left ventricular samples. Electrophysiological studies and molecular analyses were performed using CAR haploinsufficient (CAR+/−) mice.ResultsIn human left ventricular samples, the risk allele at the chr21q21 genome-wide association study locus was associated with lower CXADR messenger ribonucleic acid levels, suggesting that decreased cardiac levels of CAR predispose to ischemia-induced ventricular fibrillation. Hearts from CAR+/− mice displayed slowing of ventricular conduction in addition to an earlier onset of ventricular arrhythmias during the early phase of acute myocardial ischemia after ligation of the left anterior descending artery. Expression and distribution of connexin 43 were unaffected, but CAR+/− hearts displayed increased arrhythmia susceptibility on pharmacological electrical uncoupling. Patch-clamp analysis of isolated CAR+/− myocytes showed reduced sodium current magnitude specifically at the intercalated disk. Moreover, CAR coprecipitated with NaV1.5 in vitro, suggesting that CAR affects sodium channel function through a physical interaction with NaV1.5.ConclusionsCAR is a novel modifier of ventricular conduction and arrhythmia vulnerability in the setting of myocardial ischemia. Genetic determinants of arrhythmia susceptibility (such as CAR) may constitute future targets for risk stratification of potentially lethal ventricular arrhythmias in patients with coronary artery disease

Induction of cardiac hypertrophy by chronic β-adrenergic stimulation.

<p>(A) Two weeks of chronic ISO infusion significantly increased the heart weight to tibia length-ratio in WT and CYP2J2-TG mice (n = 7 per group) compared with the vehicle controls (n = 7 and 5). The hypertrophic response was not different in CYP2J2-TG compared to WT mice. (B) Systolic function was not significantly altered upon chronic ISO infusion as indicated by preserved EF values compared to the respective vehicle controls. EF was slightly but significantly higher in CYP2J2-TG than WT mice two weeks after chronic ISO stimulation. Results represent mean±SEM; ANOVA, Post-Hoc Tukey; *p<0.05 vs. WT+Vehicle; †p<0.05 vs. CYP+Vehicle; ^‡p<0.05 vs. WT+ISO.</p

Arrhythmia susceptibility after chronic β-adrenergic stimulation-induced cardiac hypertrophy.

<p>(A) Representative original tracings showing the induction of atrial fibrillation by programmed electrical stimulation in WT mice 2 weeks after chronic ISO infusion (upper panel) and the resistance of CYP2J2-TG mice treated in the same manner (lower panel). (B) Atrial fibrillation inducibility significantly increased in WT mice after chronic ISO infusion (n = 9) compared with the vehicle control (n = 8) and was significantly higher than in CYP2J2-TG mice (n = 7 and n = 8 for the vehicle and ISO groups). (C) The relative percentage of inducible sustained atrial fibrillation was markedly higher in WT compared with CYP2J2-TG after chronic ISO infusion. For statistical evaluation of arrhythmia inducibilities and severity scoring compare <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0073490#pone-0073490-g002" target="_blank">Fig. 2</a>. Results represent mean±SEM; ANOVA, Post-Hoc Tukey; *p<0.05 vs. WT+Vehicle; †p<0.05 vs. CYP+Vehicle; ^‡p<0.05 vs. WT+ISO.</p