BACKGROUND:A structural, electrical and metabolic atrial remodeling is central in the development of atrial fibrillation (AF) contributing to its initiation and perpetuation. In the heart, HDACs ...(histone deacetylases) control remodeling associated processes like hypertrophy, fibrosis, and energy metabolism. Here, we analyzed, whether the HDAC class I/IIa inhibitor valproic acid (VPA) is able to attenuate atrial remodeling in CREM-IbΔC-X (cAMP responsive element modulator isoform IbΔC-X) transgenic mice, a mouse model of extensive atrial remodeling with age-dependent progression from spontaneous atrial ectopy to paroxysmal and finally long-lasting AF.
METHODS:VPA was administered for 7 or 25 weeks to transgenic and control mice. Atria were analyzed macroscopically and using widefield and electron microscopy. Action potentials were recorded from atrial cardiomyocytes using patch-clamp technique. ECG recordings documented the onset of AF. A proteome analysis with consecutive pathway mapping identified VPA-mediated proteomic changes and related pathways.
RESULTS:VPA attenuated many components of atrial remodeling that are present in transgenic mice, animal AF models, and human AF. VPA significantly (P<0.05) reduced atrial dilatation, cardiomyocyte enlargement, atrial fibrosis, and the disorganization of myocyte’s ultrastructure. It significantly reduced the occurrence of atrial thrombi, reversed action potential alterations, and finally delayed the onset of AF by 4 to 8 weeks. Increased histone H4-acetylation in atria from VPA-treated transgenic mice verified effective in vivo HDAC inhibition. Cardiomyocyte-specific genetic inactivation of HDAC2 in transgenic mice attenuated the ultrastructural disorganization of myocytes comparable to VPA. Finally, VPA restrained dysregulation of proteins in transgenic mice that are involved in a multitude of AF relevant pathways like oxidative phosphorylation or RhoA (Ras homolog gene family, member A) signaling and disease functions like cardiac fibrosis and apoptosis of muscle cells.
CONCLUSIONS:Our results suggest that VPA, clinically available, well-tolerated, and prescribed to many patients for years, has the therapeutic potential to delay the development of atrial remodeling and the onset of AF in patients at risk.
Understanding molecular mechanisms involved in atrial tissue remodeling and arrhythmogenesis in atrial fibrillation (AF) is essential for developing specific therapeutic approaches. Two-pore-domain ...potassium (K
2P
) channels modulate cellular excitability, and TASK-1 (K
2P
3.1) currents were recently shown to alter atrial action potential duration in AF and heart failure (HF). Finding animal models of AF that closely resemble pathophysiological alterations in human is a challenging task. This study aimed to analyze murine cardiac expression patterns of K
2P
channels and to assess modulation of K
2P
channel expression in murine models of AF and HF. Expression of cardiac K
2P
channels was quantified by real-time qPCR and immunoblot in mouse models of AF cAMP-response element modulator (CREM)-IbΔC-X transgenic animals or HF (cardiac dysfunction induced by transverse aortic constriction, TAC). Cloned murine, human, and porcine TASK-1 channels were heterologously expressed in
Xenopus laevis
oocytes. Two-electrode voltage clamp experiments were used for functional characterization. In murine models, among members of the K
2P
channel family, TASK-1 expression displayed highest levels in both atrial and ventricular tissue samples. Furthermore, K
2P
2.1, K
2P
5.1, and K
2P
6.1 showed significant expression levels. In CREM-transgenic mice, atrial expression of TASK-1 was significantly reduced in comparison with wild-type animals. In a murine model of TAC-induced pressure overload, ventricular TASK-1 expression remained unchanged, while atrial TASK-1 levels were significantly downregulated. When heterologously expressed in
Xenopus oocytes
, currents of murine, porcine, and human TASK-1 displayed similar characteristics. TASK-1 channels display robust cardiac expression in mice. Murine, porcine, and human TASK-1 channels share functional similarities. Dysregulation of atrial TASK-1 expression in murine AF and HF models suggests a mechanistic contribution to arrhythmogenesis.
Full text
Available for:
EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Teduglutide, a glucagon-like peptide 2 (GLP-2) analog, is an approved medication specific for short bowel syndrome patients with chronic intestinal failure (SBS-IF). Due to its intestinotrophic ...properties, it improves intestinal absorption of fluids and nutrients, which was shown to reduce the need for parenteral support in clinical trials. The present report aims to describe the experience of teduglutide's effects in routine medical care with focus on clinical and nutritional effects.
Data of adult SBS-IF patients, treated with teduglutide between Sept. 2014 and May 2017 within a structured multidisciplinary program to enhance intestinal rehabilitation, were analyzed retrospectively from a single university medical center.
In total, 27 patients were treated with teduglutide. Parenteral nutrition independency was achieved in 4/19 (21%) patients analyzed, with two remaining on intravenous fluids. A clinically significant reduction of parenteral volume was observed in 15/19 patients (79%) with onset between 1 and 45 weeks. Significant parenteral support reductions were observed, ranging from about −20% in patients treated for 3 months to about −45% in patients treated for 2 years. This was accompanied by an increase in parenteral nutrition-free days. We also report on a clinically relevant and significant effect of teduglutide-mediated improvement of stool frequency and consistency. Furthermore, nutritional status subgroup analysis revealed long-term stability in body weight, albumin levels and body composition albeit parenteral support reduction. Structural effects of teduglutide treatment were observed on small intestinal mucosa with significantly increased villus height, crypt depth and plasma citrulline levels.
Teduglutide can be applied to anatomically and clinically heterogeneous SBS-IF patients and results in an adaptive response with variable time and effect range in routine medical care. Teduglutide-induced functional and structural changes bring on a gradual reduction of parenteral support at no cost to body composition and suggest an improved intestinal function with compensatory effect on nutritional status.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
A detailed description of pathophysiological effects that viruses exert on their host is still challenging. For the first time, we report a highly controllable viral expression model based on an ...iPS-cell line from a healthy human donor. The established viral model system enables a dose-dependent and highly localized RNA-virus expression in a fully controllable environment, giving rise for new applications for the scientific community.
Full text
Available for:
IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
Abnormal intracellular calcium (Ca2+) handling contributes to the progressive nature of atrial fibrillation (AF), the most common sustained cardiac arrhythmia. Evidence in mouse models suggests that ...activation of the nuclear factor of activated T-cell (NFAT) signalling pathway contributes to atrial remodelling. Our aim was to determine the role of NFATc2 in AF in humans and mouse models.
Expression levels of NFATc1-c4 isoforms were assessed by quantitative reverse transcription-polymerase chain reaction in right atrial appendages from patients with chronic AF (cAF). NFATc1 and NFATc2 mRNA levels were elevated in cAF patients compared with those in normal sinus rhythm (NSR). Western blotting revealed increased cytosolic and nuclear levels of NFATc2 in AF patients. Similar findings were obtained in CREM-IbΔC-X transgenic (CREM) mice, a model of progressive AF. Telemetry ECG recordings revealed age-dependent spontaneous AF in CREM mice, which was prevented by NFATc2 knockout in CREM:NFATc2-/- mice. Programmed electrical stimulation revealed that CREM:NFATc2-/- mice lacked an AF substrate. Morphometric analysis and histology revealed increased atrial weight and atrial fibrosis in CREM mice compared with wild-type controls, which was reversed in CREM:NFATc2-/- mice. Confocal microscopy showed an increased Ca2+ spark frequency despite a reduced sarcoplasmic reticulum (SR) Ca2+ load in CREM mice compared with controls, whereas these abnormalities were normalized in CREM:NFATc2-/- mice. Western blotting revealed that genetic inhibition of Ca2+/calmodulin-dependent protein kinase II-mediated phosphorylation of S2814 on ryanodine receptor type 2 (RyR2) in CREM:RyR2-S2814A mice suppressed NFATc2 activation observed in CREM mice, suggesting that NFATc2 is activated by excessive SR Ca2+ leak via RyR2. Finally, chromatin immunoprecipitation sequencing from AF patients identified Ras and EF-hand domain-containing protein (Rasef) as a direct target of NFATc2-mediated transcription.
Our findings reveal activation of the NFAT signalling pathway in patients of Chinese and European descent. NFATc2 knockout prevents the progression of AF in the CREM mouse model.
Overexpression of the CREM (cAMP response element-binding modulator) isoform CREM-IbΔC-X in transgenic mice (CREM-Tg) causes the age-dependent development of spontaneous AF.
To identify key proteome ...signatures and biological processes accompanying the development of persistent AF through integrated proteomics and bioinformatics analysis.
Atrial tissue samples from three CREM-Tg mice and three wild-type littermates were subjected to unbiased mass spectrometry-based quantitative proteomics, differential expression and pathway enrichment analysis, and protein-protein interaction (PPI) network analysis.
A total of 98 differentially expressed proteins were identified. Gene ontology analysis revealed enrichment for biological processes regulating actin cytoskeleton organization and extracellular matrix (ECM) dynamics. Changes in ITGAV, FBLN5, and LCP1 were identified as being relevant to atrial fibrosis and structural based on expression changes, co-expression patterns, and PPI network analysis. Comparative analysis with previously published datasets revealed a shift in protein expression patterns from ion-channel and metabolic regulators in young CREM-Tg mice to profibrotic remodeling factors in older CREM-Tg mice. Furthermore, older CREM-Tg mice exhibited protein expression patterns reminiscent of those seen in humans with persistent AF.
This study uncovered distinct temporal changes in atrial protein expression patterns with age in CREM-Tg mice consistent with the progressive evolution of AF. Future studies into the role of the key differentially abundant proteins identified in this study in AF progression may open new therapeutic avenues to control atrial fibrosis and substrate development in AF.
Display omitted
•Atrial proteomics of CREM-Tg mice revealed protein expression changes linked to persistent AF.•Proteins involved in actin filaments and ECM remodeling were enriched in persistent AF.•AF disease progression causes a switch in atrial proteome changes in CREM-Tg mice.•Proteome alterations seen in older CREM-Tg mice mirror those in patients with persistent AF.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Adenosine can be released from the heart and may stimulate four different cardiac adenosine receptors. A receptor subtype that couples to the generation of cyclic adenosine monophosphate (cAMP) is ...the A
2A
-adenosine receptor (A
2A
-AR). To better understand its role in cardiac function, we studied mechanical and electrophysiological effects in transgenic mice that overexpress the human A
2A
-AR in cardiomyocytes (A
2A
-TG). We used isolated preparations from the left atrium, the right atrium, isolated perfused hearts with surface electrocardiogram (ECG) recording, and surface body ECG recordings of living mice. The hypothesized arrhythmogenic effects of transgenicity per se and A
2A
-AR stimulation were studied. We noted an increase in the incidence of supraventricular and ventricular arrhythmias under these conditions in A
2A
-TG. Moreover, we noted that the A
2A
-AR agonist CGS 21680 exerted positive inotropic effect in isolated human electrically driven (1 Hz) right atrial trabeculae carneae. We conclude that A
2A
-ARs are functional not only in A
2A
-TG but also in isolated human atrial preparations. A
2A
-ARs in A
2A
-TG per se and their stimulation can lead to cardiac arrhythmias not only in isolated cardiac preparations from A
2A
-TG but also in living A
2A
-TG.
Two-pore-domain potassium (K2P) channels modulate cellular excitability. The significance of stretch-activated cardiac K2P channels (K2P2.1, TREK-1, KCNK2; K2P4.1, TRAAK, KCNK4; K2P10.1, TREK-2, ...KCNK10) in heart disease has not been elucidated in detail. The aim of this work was to assess expression and remodeling of mechanosensitive K2P channels in atrial fibrillation (AF) and heart failure (HF) patients in comparison to murine models.
Cardiac K2P channel levels were quantified in atrial (A) and ventricular (V) tissue obtained from patients undergoing open heart surgery. In addition, control mice and mouse models of AF (cAMP-response element modulator (CREM)-IbΔC-X transgenic animals) or HF (cardiac dysfunction induced by transverse aortic constriction, TAC) were employed. Human and murine KCNK2 displayed highest mRNA abundance among mechanosensitive members of the K2P channel family (V > A). Disease-associated K2P2.1 remodeling was studied in detail. In patients with impaired left ventricular function, atrial KCNK2 (K2P2.1) mRNA and protein expression was significantly reduced. In AF subjects, downregulation of atrial and ventricular KCNK2 (K2P2.1) mRNA and protein levels was observed. AF-associated suppression of atrial Kcnk2 (K2P2.1) mRNA and protein was recapitulated in CREM-transgenic mice. Ventricular Kcnk2 expression was not significantly altered in mouse models of disease.
In conclusion, mechanosensitive K2P2.1 and K2P10.1 K+ channels are expressed throughout the heart. HF- and AF-associated downregulation of KCNK2 (K2P2.1) mRNA and protein levels suggest a mechanistic contribution to cardiac arrhythmogenesis.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Background
Sphingosine‐1‐phosphate plays vital roles in cardiomyocyte physiology, myocardial ischemia–reperfusion injury, and ischemic preconditioning. The function of the cardiomyocyte ...sphingosine‐1‐phosphate receptor 1 (S1P1) in vivo is unknown.
Methods and Results
Cardiomyocyte‐restricted deletion of S1P1 in mice (S1P1αMHCCre) resulted in progressive cardiomyopathy, compromised response to dobutamine, and premature death. Isolated cardiomyocytes from S1P1αMHCCre mice revealed reduced diastolic and systolic Ca2+ concentrations that were secondary to reduced intracellular Na+ and caused by suppressed activity of the sarcolemmal Na+/H+ exchanger NHE‐1 in the absence of S1P1. This scenario was successfully reproduced in wild‐type cardiomyocytes by pharmacological inhibition of S1P1 or sphingosine kinases. Furthermore, Sarcomere shortening of S1P1αMHCCre cardiomyocytes was intact, but sarcomere relaxation was attenuated and Ca2+ sensitivity increased, respectively. This went along with reduced phosphorylation of regulatory myofilament proteins such as myosin light chain 2, myosin‐binding protein C, and troponin I. In addition, S1P1 mediated the inhibitory effect of exogenous sphingosine‐1‐phosphate on β‐adrenergic–induced cardiomyocyte contractility by inhibiting the adenylate cyclase. Furthermore, ischemic precondtioning was abolished in S1P1αMHCCre mice and was accompanied by defective Akt activation during preconditioning.
Conclusions
Tonic S1P1 signaling by endogenous sphingosine‐1‐phosphate contributes to intracellular Ca2+ homeostasis by maintaining basal NHE‐1 activity and controls simultaneously myofibril Ca2+ sensitivity through its inhibitory effect on adenylate cyclase. Cardioprotection by ischemic precondtioning depends on intact S1P1 signaling. These key findings on S1P1 functions in cardiac physiology may offer novel therapeutic approaches to cardiac diseases.
Long-Term Results After Directional Atherectomy of Femoro-Popliteal Lesions
Thomas Zeller, Aljoscha Rastan, Sebastian Sixt, Uwe Schwarzwälder, Thomas Schwarz, Ulrich Frank, Karlheinz Bürgelin, ...Christian Müller, Uwe Rothenpieler, Peter-Christian Flügel, Gunnar Tepe, Franz-Josef Neumann
This study was designed to evaluate the long-term results after directional atherectomy of femoro-popliteal lesions using the Silverhawk device (FoxHollow Technologies, Redwood City, California). One hundred thirty-one included lesions consisted of de novo lesions (group 1, 34%), native vessel restenoses (group 2, 33%), and in-stent restenoses (group 3, 33%). Primary patency, secondary patency, and target lesion revascularization were significantly in favor for de novo lesions at 12 months and at 18 months, respectively. Independent predictor for restenosis was treated restenotic lesion. Clinical parameters significantly improved in all study cohorts.
Our objective in this research was the evaluation of the long-term results after directional atherectomy using the Silverhawk device (FoxHollow Technologies, Redwood City, California) of femoro-popliteal lesions.
Considering reports on stent fractures in femoro-popliteal arteries, atherectomy may be a valuable alternative to stenting.
Eighty-four patients with 100 legs and 131 lesions with peripheral occlusive disease Rutherford categories 2 to 5 were included in a prospective registry. Forty-five lesions were de novo lesions (group 1; 34%), 43 lesions native vessel restenoses (group 2; 33%), and 43 lesions in-stent restenoses (group 3; 33%). Additional low pressure balloon angioplasty was used in 78 of 131 lesions (59%) and stenting in 8 lesions (6%).
Technical success rate was 86% for atherectomy only and 100% after additional therapy. Mean lesion length was 43 ± 54 mm, 105 ± 122 mm, and 131 ± 111 mm for group 1, group 2, and group 3, respectively (p < 0.001). Primary patency, defined as freedom of a >50% restenosis detected by duplex, was 84%, 54%, and 54% at 12 months (p = 0.002) and 73%, 42%, and 49%, at 18 months (p = 0.008); secondary patency rates were 100%, 93%, and 91% at 12 months (p = NS) and 89%, 67%, and 79% at 18 months (p = 0.001), respectively; and target lesion revascularization rate was 16%, 44%, and 47% at 12 months and 22%, 56%, and 49% at 18 months (p = 0.003 each) for group 1, group 2, and group 3, respectively. The only independent predictor for restenosis was treatment of restenotic lesions. Ankle-brachial index was significantly improved after 12 months and 18 months in all groups.
Long-term technical and clinical results after directional atherectomy of femoro-popliteal lesions are in favor of de novo lesions compared with restenotic lesions.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
PDF
