Dysregulated IER3 Expression is Associated with Enhanced Apoptosis in Titin-Based Dilated Cardiomyopathy.

Apoptosis (type I programmed cell death) of cardiomyocytes is a major process that plays a role in the progression of heart failure. The early response gene IER3 regulates apoptosis in a wide variety of cells and organs. However, its role in heart failure is largely unknown. Here, we investigate the role of IER3 in an inducible heart failure mouse model. Heart failure was induced in a mouse model that imitates a human titin truncation mutation we found in a patient with dilated cardiomyopathy (DCM). Transferase dUTP nick end labeling (TUNEL) and ssDNA stainings showed induction of apoptosis in titin-deficient cardiomyocytes during heart failure development, while IER3 response was dysregulated. Chromatin immunoprecipitation and knock-down experiments revealed that IER3 proteins target the promotors of anti-apoptotic genes and act as an anti-apoptotic factor in cardiomyocytes. Its expression is blunted during heart failure development in a titin-deficient mouse model. Targeting the IER3 pathway to reduce cardiac apoptosis might be an effective therapeutic strategy to combat heart failure.

Apixaban versus Aspirin for Embolic Stroke of Undetermined Source.

BACKGROUND: Rivaroxaban and dabigatran were not superior to aspirin in trials of patients with embolic stroke of undetermined source (ESUS). It is unknown whether apixaban is superior to aspirin in patients with ESUS and known risk factors for cardioembolism. METHODS: We conducted a multicenter, randomized, open-label, blinded-outcome trial of apixaban (5 mg twice daily) compared with aspirin (100 mg once daily) initiated within 28 days after ESUS in patients with at least one predictive factor for atrial fibrillation or a patent foramen ovale. Cardiac monitoring was mandatory, and aspirin treatment was switched to apixaban in case of atrial fibrillation detection. The primary outcome was any new ischemic lesion on brain magnetic resonance imaging (MRI) during 12-month follow-up. Secondary outcomes included major and clinically relevant nonmajor bleeding. RESULTS: A total of 352 patients were randomly assigned to receive apixaban (178 patients) or aspirin (174 patients) at a median of 8 days after ESUS. At 12-month follow-up, MRI follow-up was available in 325 participants (92.3%). New ischemic lesions occurred in 23 of 169 (13.6%) participants in the apixaban group and in 25 of 156 (16.0%) participants in the aspirin group (adjusted odds ratio, 0.79; 95% confidence interval, 0.42 to 1.48; P=0.57). Major and clinically relevant nonmajor bleeding occurred in five and seven participants, respectively (1-year cumulative incidences, 2.9 and 4.2; hazard ratio, 0.68; 95% confidence interval, 0.22 to 2.16). Serious adverse event rates were 43.9 per 100 person-years in those given apixaban and 45.7 per 100 person-years in those given aspirin. The Apixaban for the Treatment of Embolic Stroke of Undetermined Source trial was terminated after a prespecified interim analysis as a result of futility. CONCLUSIONS: Apixaban treatment was not superior to cardiac monitoring-guided aspirin in preventing new ischemic lesions in an enriched ESUS population. (Funded by Bristol-Myers Squibb and Medtronic Europe; ClinicalTrials.gov number, NCT02427126.)

Resumption of Antiplatelet Therapy after Major Bleeding.

Major bleeding is a common threat in patients requiring antiplatelet therapy. Timing and intensity with regard to resumption of antiplatelet therapy represent a major challenge in clinical practice. Knowledge of the patient's bleeding risk, defining transient/treatable and permanent/untreatable risk factors for bleeding, and weighing these against thrombotic risk are key to successful prevention of major adverse events. Shared decision-making involving various disciplines is essential to determine the optimal strategy. The present article addresses clinically relevant questions focusing on the most life-threatening or frequently occurring bleeding events, such as intracranial hemorrhage and gastrointestinal bleeding, and discusses the evidence for antiplatelet therapy resumption using individual risk assessment in high-risk cardiovascular disease patients.

Biophysical properties of mutant KCNQ1 S277L channels linked to hereditary long QT syndrome with phenotypic variability.

Hereditary long QT syndrome (LQTS) is associated with ventricular torsade de pointes tachyarrhythmias and sudden cardiac death. Mutations in a cardiac voltage-gated potassium channel, KCNQ1, induce the most frequent variant of LQTS. We identified a KCNQ1 missense mutation, KCNQ1 S277L, in a patient presenting with recurrent syncope triggered by emotional stress (QTc=528ms). This mutation is located in the conserved S5 transmembrane region of the KCNQ1 channel. Using in vitro electrophysiological testing in the Xenopus oocyte expression system, the S277L mutation was found to be non-functional and to suppress wild type currents in dominant-negative fashion in the presence and in the absence of the regulatory ß-subunit, KCNE1. In addition, expression of S277L and wild type KCNQ1 with KCNE1 resulted in a shift of the voltage-dependence of activation by -8.7mV compared to wild type I(Ks), indicating co-assembly of mutant and wild type subunits. The electrophysiological phenotype corresponds well with the severe clinical phenotype of the index patient. However, investigation of family members revealed three patients that exhibit asymptomatic QT interval prolongation (QTc=493-518ms). In conclusion, this study emphasizes the value of biophysical testing to provide mechanistic evidence for pathogenicity of ion channel mutations identified in LQTS patients. The inconsistent association of the KCNQ1 S277L mutation with the clinical presentation suggests that additional genetic, epigenetic, or environmental factors play a role in defining the individual clinical LQTS phenotype.

Identification and functional characterization of the novel human ether-a-go-go-related gene (hERG) R744P mutant associated with hereditary long QT syndrome 2.

Mutations of the cyclic nucleotide binding domain (CNBD) may disrupt human ether-a-go-go-related gene (hERG) K(+) channel function and lead to hereditary long QT syndrome (LQTS). We identified a novel missense mutation located in close proximity to the CNBD, hERG R744P, in a patient presenting with recurrent syncope and aborted cardiac death triggered by sudden auditory stimuli. Functional properties of wild type (WT) and mutant hERG R744P subunits were studied in Xenopus laevis oocytes using two-electrode voltage clamp electrophysiology and Western blot analysis. HERG R744P channels exhibited reduced activating currents compared to hERG WT (1.48±0.26 versus 3.40±0.29µA; n=40). These findings were confirmed by tail current analysis (hERG R744P, 0.53±0.07µA; hERG WT, 0.97±0.06µA; n=40). Cell surface trafficking of hERG R744P protein subunits was not impaired. To simulate the autosomal-dominant inheritance associated with LQTS, WT and R744P subunits were co-expressed in equimolar ratio. Mean activating and tail currents were reduced by 32% and 25% compared to hERG WT (n=40), indicating that R744P protein did not exert dominant-negative effects on WT channels. The half-maximal activation voltage was not significantly affected by the R744P mutation. This study highlights the significance of in vitro testing to provide mechanistic evidence for pathogenicity of mutations identified in LQTS. The functional defect associated with hERG R744P serves as molecular basis for LQTS in the index patient.

Personalized Medicine Approach in a DCM Patient with LMNA Mutation Reveals Dysregulation of mTOR Signaling.

BACKGROUND: Mutations in the Lamin A/C (LMNA) gene are responsible for about 6% of all familial dilated cardiomyopathy (DCM) cases which tend to present at a young age and follow a fulminant course. METHODS: We report a 47-year-old DCM patient with severely impaired left ventricular ejection fraction and NYHA functional class IV despite optimal heart failure treatment. Whole-exome sequencing revealed an LMNA E161K missense mutation as the pathogenetic cause for DCM in this patient. We generated a patient-specific LMNA-knock in (LMNA-KI) in vitro model using mES cells. RESULTS: Beta adrenergic stimulation of cardiomyocytes derived from LMNA-KI mES cells resulted in augmented mTOR signaling and increased dysregulation of action potentials, which could be effectively prevented by the mTOR-inhibitor rapamycin. A cardiac biopsy confirmed strong activation of the mTOR-signaling pathway in the patient. An off-label treatment with oral rapamycin was initiated and resulted in an improvement in left ventricular ejection fraction (27.8% to 44.5%), NT-BNP (8120 ng/L to 2210 ng/L) and NYHA functional class. CONCLUSION: We have successfully generated the first in vitro model to recapitulate a patient-specific LMNA E161K mutation which leads to a severe form of DCM. The model may serve as a template for individualized and specific treatment of heart failure.

[Acquired immune thrombocytopenia: An update on aspects of diagnosis and management relevant for intensive care medicine]. / Erworbene immunvermittelte Thrombozytopenie in der Intensivmedizin: Ein Update über relevante Aspekte der Diagnostik und Therapie.

Acquired thrombocytopenias represent a group of bleeding diseases, which can be mediated by immune or non-immune factors. Acquired immune thrombocytopenia (AITP) leads to an accelerated decrease in platelet count by platelet reactive antibodies arising from several mechanisms. In AITP, autoantibodies, alloantibodies or drug-dependent antibodies are usually targeting platelet surface glycoproteins. The consequence of this is a significant decrease in the number of circulating platelets, leading to clinic pathological disorders including immune thrombocytopenia, heparin-induced thrombocytopenia or drug-induced thrombocytopenia, respectively. The aforementioned disorders are characterized by a severe reduction in platelet count (< 20 × 109/l), which is, with the exception of HIT, associated with high bleeding risk. In this review we provide current insight into recent achievements regarding diagnosis and management of AITP.

Autoimmune Heparin-Induced Thrombocytopenia after Transcatheter Aortic Valve Implantation: Successful Treatment with Adjunct High-Dose Intravenous Immunoglobulin.

We describe a rare case of autoimmune heparin-induced thrombocytopenia after transcatheter aortic valve implantation in which antibodies against platelet factor 4/heparin have led to platelet activation even after heparin cessation, causing a delayed drop in platelet count to below 20 × 10 9 /L. Most interestingly, platelet count rapidly improved after intravenous immunoglobulin treatment and no new thromboembolic complications were observed with further anticoagulation with rivaroxaban.

Inhibition of miR-208b improves cardiac function in titin-based dilated cardiomyopathy.

BACKGROUND: Dilated cardiomyopathy (DCM) is the result of maladaptive cardiac remodeling, which involves microRNA regulation. In turn, microRNAs can contribute to the remodeling process by post-transcriptional modulation of gene expression networks. The exact role of microRNAs in the pathogenesis of DCM is largely unknown. Here, we used an inducible DCM mouse model that carries a human truncation mutation in the sarcomeric protein titin to dissect microRNA pathways in DCM development. METHODS AND RESULTS: MicroRNA microarray studies revealed up-regulation of microRNA-208b in the myocardium of DCM mice and DCM patients (p<0.05 compared to controls). In order to investigate the effect of microRNA-208b on cardiac remodeling, loss-of-function and gain-of-function studies were performed by repetitive injections of LNA-modified microRNA-208b mimics and antimiR-208b. MiR-208b overexpression resulted in cardiac hypertrophy, whereas miR-208b antagonisation prevented transition of adaptive to maladaptive remodeling in the DCM mouse model. In vitro studies identified several pro-hypertrophic transcription factors as potential targets of miR-208b, suggesting that microRNA-208b plays an important role in cardiac development and growth. MiR-208b was also upregulated in DCM patients, but not in heart failure patients due to ischemic heart disease or myocarditis. CONCLUSION: Our data suggests that miR-208b is involved in the remodeling process and pathogenesis of DCM by post-transcriptional gene expression modulation. MicroRNA-208b might be a novel therapeutic target for DCM.

Pressure Overload by Transverse Aortic Constriction Induces Maladaptive Hypertrophy in a Titin-Truncated Mouse Model.

Mutations in the giant sarcomeric protein titin (TTN) are a major cause for inherited forms of dilated cardiomyopathy (DCM). We have previously developed a mouse model that imitates a TTN truncation mutation we found in a large pedigree with DCM. While heterozygous Ttn knock-in mice do not display signs of heart failure under sedentary conditions, they recapitulate the human phenotype when exposed to the pharmacological stressor angiotensin II or isoproterenol. In this study we investigated the effects of pressure overload by transverse aortic constriction (TAC) in heterozygous (Het) Ttn knock-in mice. Two weeks after TAC, Het mice developed marked impairment of left ventricular ejection fraction (p < 0.05), while wild-type (WT) TAC mice did not. Het mice also trended toward increased ventricular end diastolic pressure and volume compared to WT littermates. We found an increase in histologically diffuse cardiac fibrosis in Het compared to WT in TAC mice. This study shows that a pattern of DCM can be induced by TAC-mediated pressure overload in a TTN-truncated mouse model. This model enlarges our arsenal of cardiac disease models, adding a valuable tool to understand cardiac pathophysiological remodeling processes and to develop therapeutic approaches to combat heart failure.

Impaired ion channel function related to a common KCNQ1 mutation - implications for risk stratification in long QT syndrome 1.

Long QT syndrome (LQTS) 1 is the most common type of inherited LQTS and is linked to mutations in the KCNQ1 gene. We identified a KCNQ1 missense mutation, KCNQ1 G325R, in an asymptomatic patient presenting with significant QT prolongation (QTc, 448-600ms). Prior clinical reports revealed phenotypic variability ranging from the absence of symptoms to syncope among KCNQ1 G325R mutation carriers. The present study was designed to determine the G325R ion channel phenotype and its association with the clinical LQTS presentation. Electrophysiological testing was performed using the Xenopus oocyte expression system. KCNQ1 G325R channels were non-functional and suppressed wild type (WT) currents by 71.1%. In the presence of the native cardiac regulatory ß-subunit, KCNE1, currents conducted by G325R and WT KCNQ1 were reduced by 52.9%. Co-expression of G325R and WT KCNQ1 with KCNE1 shifted the voltage-dependence of I(Ks) activation by 12.0mV, indicating co-assembly of mutant and WT subunits. The dysfunctional biophysical phenotype validates the pathogenicity of the KCNQ1 G325R mutation and corresponds well with the severe clinical presentation revealed in some reports. However, the index patient and other mutation carriers were asymptomatic, highlighting potential limitations of risk assessment schemes based on ion channel data.