Posttranslational modifications of calcium/calmodulin-dependent protein kinase IIdelta and its downstream signaling in human failing hearts

BACKGROUND: In human failing hearts (HF) of different origin (coronary artery disease-CAD, dilated-DCM, restrictive and hypertrophic cardiomyopathy-OTHER), we investigated the active forms of Ca2+/calmodulin-dependent protein kinase IIdelta (p-Thr287-CaMKIIdelta, oxMet281/282-CaMKIIdelta) and their role in phenotypes of the disease. METHODS AND RESULTS: Although basic diagnostic and clinical markers indicating the attenuated cardiac contractility and remodeling were comparable in HF groups, CaMKIIdelta-mediated axis was different. P-Thr287-CaMKIIdelta was unaltered in CAD group, whereas it was upregulated in non-ischemic cardiomyopathic groups. No correlation between the upregulated p-Thr287-CaMKIIdelta and QT interval prolongation was detected. Unlike in DCM, oxMet281/282-CaMKIIdelta did not differ among HF groups. Independently of CaMKIIdelta phosphorylation/oxidation, activation of its downstreams-phospholamban and cardiac myosin binding protein-C was significantly downregulated supporting both diminished cardiac lusitropy and inotropy in all hearts. Content of sarcoplasmic reticulum Ca2+-ATPase 2a in all HF was unchanged. Protein phosphatase1beta was upregulated in CAD and DCM only, while 2A did not differ among groups. CONCLUSION: This is the first demonstration that the posttranslational activation of CaMKIIdelta differs in HF depending on etiology. Lower levels of downstream molecular targets of CaMKIIdelta do not correlate with either activation of CaMKIIdelta or the expression of major protein phosphatases in the HF. Thus, it is unlikely that these mechanisms exclusively underlie failing of the heart

P424Short-term ACE Inhibition upregulates cardiac expression of SERCA2a and protects against ventricular arrhythmias in healthy rats

Introduction: Chronic angiotensin converting enzyme inhibitor (ACEIs) treatment can suppress arrhythmogenesis. To examine whether the effect is more immediate and independent of suppression of pathological remodelling, we tested the antiarrhythmic effect of short-term ACE inhibition in healthy normotensive rats. Methods and results: Wistar rats were administered with enalaprilat (ENA, i.p., 5 mg/kg every 12 h) or vehicle (CON) for two weeks. Cellular shortening was measured in isolated, electrically paced cardiomyocytes. Standard 12-lead electrocardiography was performed and, hearts of anesthetized open-chest rats were subjected to 6-min ischemia followed by 10-minute reperfusion to examine susceptibility to ventricular arrhythmias. Expressions of calcium regulating proteins (SERCA2a, cardiac sarco/endoplasmic reticulum Ca2+-ATPase; CSQ, calsequestrin; TRD, triadin; PLB, phospholamban; FKBP12.6, FK506-binding protein) were measured by Western blot and mRNA levels of L-type calcium channel (Cacna1c), ryanodine receptor (Ryr2) and potassium channels Kcnh2 and Kcnq1 were measured by qRT-PCR. ENA decreased systolic as well as diastolic blood pressure (by 20%, and by 31%, respectively, for both P<0.05) but enhanced shortening of cardiomyocytes at basal conditions (by 34%, P<0.05) and under beta-adrenergic stimulation (by 73%, P<0.05). Enalaprilat shortened QTc interval duration (CON: 78±1 ms vs. ENA: 72±2 ms; P<0.05) and significantly decreased the total duration of ventricular fibrillations (VF) and the number of VF episodes (P<0.05). Reduction in arrhythmogenesis was associated with a pronounced upregulation of SERCA2a and increased Cacna1c mRNA levels. Conclusion: Short-term ACEI treatment can provide protection against I/R injury-induced ventricular arrhythmias in healthy myocardium and this effect is associated with increased SERCA2a expression. CON ENA Calcium regulating proteins SERCA2a 100±20 304±13* CSQ 100±6 105±7 TRD 100±16 117±10 PLB 100±9 109±16 FKBP12 100±12 93±

Prevention of salt-dependent cardiac remodeling and enhanced gene expression in stroke-prone hypertensive rats by the long-acting calcium channel blocker lacidipine.

OBJECTIVE: To analyze the effect of the long-acting calcium channel blocker lacidipine on cardiovascular remodeling induced by salt loading in a genetic model of hypertension. DESIGN: We examined the influence of threshold doses of lacidipine, with little blood-pressure lowering effect, on cardiac weight and gene expression in stroke-prone spontaneously hypertensive rats (SHRSP). METHODS: SHRSPs (8-week-old) were randomly allocated to four groups: control, salt-loaded SHRSP and salt-loaded SHRSP treated with lacidipine at 0.3 and 1 mg/kg per day. Systolic blood pressure was measured by the tail-cuff method. At the end of 6 weeks of treatment, ventricles were collected and weighed. Ventricular messenger RNA was extracted and subjected to Northern blot analysis. RESULTS: Lacidipine (0.3 mg/kg per day) not only prevented the salt-dependent cardiac hypertrophy and the slight increase in systolic blood pressure induced by salt, but also prevented, largely or completely, salt-dependent increases in ventricular levels of several gene products: skeletal and cardiac alpha-actin, beta-myosin heavy chain (beta-MHC), type I collagen, long-lasting (L)-type calcium channel and preproendothelin-1. At a higher dose of 1 mg/kg per day, lacidipine further decreased systolic blood pressure below the level of control SHRSP, completely prevented salt-dependent overexpression of the beta-MHC gene and markedly attenuated salt-dependent overexpression of the transforming growth factor-beta1 gene. CONCLUSIONS: Lacidipine prevents the cardiac remodeling and enhanced gene expression induced by salt loading in SHRSP at doses that only minimally affect the high systolic blood pressure