Background A hallmark of heart failure is impaired cytoplasmic Ca2+ handling of cardiomyocytes. It remains unknown whether specific alterations in nuclear Ca2+ handling – via altered excitation-transcription coupling – contribute to the development and progression of heart failure. Methods and Results Using tissue and isolated cardiomyocytes from non-failing and failing human hearts, as well as mouse and rabbit models of hypertrophy and heart failure, we provide compelling evidence for structural and functional changes of the nuclear envelope and nuclear Ca2+ handling in cardiomyocytes as remodeling progresses. Increased nuclear size and less frequent intrusions of the nuclear envelope into the nuclear lumen indicated altered nuclear structure that could have functional consequences. In the (peri)nuclear compartment there was also reduced expression of Ca2+ pumps and ryanodine receptors, and increased expression of inositol-1,4,5-trisphosphate receptors, and differential orientation among these Ca2+ transporters. These changes were associated with altered nucleoplasmic Ca2+ handling in cardiomyocytes from hypertrophied and failing hearts, reflected as increased diastolic Ca2+ levels with diminished and prolonged nuclear Ca2+ transients and slowed intranuclear Ca2+ diffusion. Altered nucleoplasmic Ca2+ levels were translated to higher activation of nuclear Ca2+/calmodulin-dependent protein kinase II and nuclear export of histone deacetylases. Importantly, the nuclear Ca2+ alterations occurred early during hypertrophy and preceded the cytoplasmic Ca2+ changes that are typical of heart failure. Conclusions During cardiac remodeling, early changes of cardiomyocyte nuclei cause altered nuclear Ca2+ signaling implicated in hypertrophic gene program activation. Normalization of nuclear Ca2+ regulation may, therefore, be a novel therapeutic approach for preventing adverse cardiac remodeling.
To conclude, the LFD test of BAL specimens is performed easily and provides accurate and rapidly available results in patients after SOT. Therefore, this new point-of-care test may be a promising diagnostic approach for detecting IPA using BAL specimens from SOT patients.
BACKGROUND AND PURPOSE Ca2+ leak from the sarcoplasmic reticulum (SR) via ryanodine receptors (RyR2s) contributes to cardiomyocyte dysfunction. RyR2 Ca 2+ leak has been related to RyR2 phosphorylation. In these conditions, JTV519 (K201), a 1,4-benzothiazepine derivative and multi-channel blocker, stabilizes RyR2s and decrease SR Ca 2+ leak. We investigated whether JTV519 stabilizes RyR2s without increasing RyR2 phosphorylation in mice and in non-failing human myocardium and explored underlying mechanisms. EXPERIMENTAL APPROACH SR Ca2+ leak was induced by ouabain in murine cardiomyocytes. [Ca 2+ ]-transients, SR Ca 2+ load and RyR2-mediated Ca 2+ leak (sparks/waves) were quantified, with or without JTV519 (1 mmol·L-1 ). Contribution of Ca 2+-/calmodulin-dependent kinase II (CaMKII) was assessed by KN-93 and Western blot (RyR2-Ser 2814 phosphorylation). Effects of JTV519 on contractile force were investigated in non-failing human ventricular trabeculae. ], Ca 2+ leak was significantly reduced by JTV519, but it had no effect on fractional Ca 2+ release or Ca 2+ wave propagation velocity. In human muscle, JTV519 was negatively inotropic at baseline but significantly enhanced ouabain-induced force and reduced its deleterious effects on diastolic function. 2+ removal varies among species between 7% (rats), 28% (rabbits) and up to about 50% (failing human hearts) (Dipla et al., 1999;Bers, 2001). KEY RESULTS Ouabain CONCLUSIONS AND IMPLICATIONSLeak of Ca 2+ from the SR through RyR2s during diastole has been implicated in arrhythmias and contractile dysfunction in heart failure (Marx et al., 2000;Lindner et al., 2002), myocardial ischaemia (Hirose et al., 2008), atrial fibrillation (Vest et al., 2005) and congenital arrhythmias (Mohamed et al., 2007). Several mechanisms have been proposed to explain RyR2 dysfunction, including altered RyR2 gating due to point mutations in the RyR2 molecule (Cerrone et al., 2005), alterations in RyR2 phosphorylation (Witcher et al., 1991;Wehrens et al., 2004b;Xiao et al., 2005) MethodsThe use of donor hearts and research protocols for human samples were approved by the local ethics committee (ref. nr. 20-277 ex 08/09). Investigations on human tissue conform with the principles outlined in the Declaration of Helsinki. All studies involving animals are reported in accordance with the ARRIVE guidelines for reporting experiments involving animals (McGrath et al., 2010). Animals were treated according to the Guidelines for the Care and Use of Laboratory Animals (National Institute of Health, USA). Cell isolationAdult FVB/N mice (11-16 weeks old; total = 43) provided by the Abt. f. Labortierkunde, Medical University of Vienna, Austria, were used for all experiments. Ventricular cardiomyocytes were isolated as previously described (Heinzel et al., 2002;Sedej et al., 2010). Mice were anesthetized with isoflu- . Only quiescent, rod-shaped ventricular cardiomyocytes were used for experiments. Confocal [Ca 2+ ] i measurementsCells were studied in a perfusion chamber mounted on the stage of an ...
BackgroundAs organ shortage is increasing, the acceptance of marginal donors increases, which might result in poor organ function and patient survival. Mostly, organ damage is caused during brain death (BD), cold ischemic time (CIT) or after reperfusion due to oxidative stress or the induction of apoptosis. The aim of this study was to study a panel of genes involved in oxidative stress and apoptosis and compare these findings with immunohistochemistry from a BD and living donation (LD) pig model and after cold ischemia time (CIT).MethodsBD was induced in pigs; after 12 h organ retrieval was performed; heart, liver and kidney tissue specimens were collected in the BD (n = 6) and in a LD model (n = 6). PCR analysis for NFKB1, GSS, SOD2, PPAR-alpha, OXSR1, BAX, BCL2L1, and HSP 70.2 was performed and immunohistochemistry used to show apoptosis and nitrosative stress induced cell damage.ResultsIn heart tissue of BD BAX, BCL2L1 and HSP 70.2 increased significantly after CIT. Only SOD2 was over-expressed after CIT in BD liver tissue. In kidney tissue, BCL2L1, NFKB, OXSR1, SOD2 and HSP 70.2 expression was significantly elevated in LD. Immunohistochemistry showed a significant increase in activated Caspase 3 and nitrotyrosine positive cells after CIT in BD in liver and in kidney tissue but not in heart tissue.ConclusionThe up-regulation of protective and apoptotic genes seems to be divergent in the different organs in the BD and LD setting; however, immunohistochemistry revealed more apoptotic and nitrotyrosine positive cells in the BD setting in liver and kidney tissue whereas in heart tissue both BD and LD showed an increase.
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