Palopegteriparatide Treatment Improves Renal Function in Adults with Chronic Hypoparathyroidism: 1-Year Results from the Phase 3 PaTHway Trial.

INTRODUCTION: Individuals with chronic hypoparathyroidism managed with conventional therapy (active vitamin D and calcium) have an increased risk for renal dysfunction versus age- and sex-matched controls. Treatments that replace the physiologic effects of parathyroid hormone (PTH) while reducing the need for conventional therapy may help prevent a decline in renal function in this population. This post hoc analysis examined the impact of palopegteriparatide treatment on renal function in adults with chronic hypoparathyroidism. METHODS: PaTHway is a phase 3 trial of palopegteriparatide in adults with chronic hypoparathyroidism that included a randomized, double-blind, placebo-controlled 26-week period followed by an ongoing 156-week open-label extension (OLE) period. Changes in renal function over 52 weeks (26 weeks blinded + 26 weeks OLE) were assessed using estimated glomerular filtration rate (eGFR). A subgroup analysis was performed with participants stratified by baseline eGFR < 60 or ≥ 60 mL/min/1.73 m2. RESULTS: At week 52, over 95% (78/82) of participants remained enrolled in the OLE and of those, 86% maintained normocalcemia and 95% achieved independence from conventional therapy (no active vitamin D and ≤ 600 mg/day of calcium), with none requiring active vitamin D. Treatment with palopegteriparatide over 52 weeks resulted in a mean (SD) increase in eGFR of 9.3 (11.7) mL/min/1.73 m2 from baseline (P < 0.0001) and 43% of participants had an increase ≥ 10 mL/min/1.73 m2. In participants with baseline eGFR < 60 mL/min/1.73 m2, 52 weeks of treatment with palopegteriparatide resulted in a mean (SD) increase of 11.5 (11.3) mL/min/1.73 m2 (P < 0.001). One case of nephrolithiasis was reported for a participant in the placebo group during blinded treatment; none were reported through week 52 with palopegteriparatide. CONCLUSION: In this post hoc analysis of the PaTHway trial, palopegteriparatide treatment was associated with significantly improved eGFR at week 52 in addition to previously reported maintenance and normalization of serum and urine biochemistries. Further investigation of palopegteriparatide for the preservation of renal function in hypoparathyroidism is warranted. TRIAL REGISTRATION: ClinicalTrials.gov NCT04701203.

Chronic hypoparathyroidism is caused by inadequate parathyroid hormone (PTH) levels. Hypoparathyroidism is managed with conventional therapy (active vitamin D and calcium), but over time the disease itself and conventional therapy can increase the risk of medical complications including kidney problems. This study looked at how a new treatment for chronic hypoparathyroidism, palopegteriparatide (approved in the European Union under the brand name YORVIPATH^®), affects kidney function in adults in the PaTHway clinical trial. Participants were randomly assigned to receive palopegteriparatide or a placebo injection once daily along with conventional therapy. For both groups, clinicians used a protocol to eliminate conventional therapy while maintaining normal blood calcium levels. After 26 weeks, participants on placebo switched to palopegteriparatide. Ninety-five percent of participants were still enrolled in the PaTHway trial after 52 weeks. Of those, 86% had normal blood calcium levels and 95% did not need conventional therapy (not taking vitamin D and not taking therapeutic doses of calcium [> 600 mg/day]). After 52 weeks of treatment with palopegteriparatide, significant improvements were seen in a measure of kidney function called estimated glomerular filtration rate (eGFR). Improvements in eGFR from the beginning of the trial to week 52 were considered clinically meaningful for over 57% of participants. In participants with impaired kidney function at the beginning of the trial, eGFR improvements were even greater, and 74% of participants had a clinically meaningful improvement. These results suggest that palopegteriparatide treatment may be beneficial for kidney function in adults with chronic hypoparathyroidism, especially those with impaired kidney function.

IncobotulinumtoxinA for Glabellar Frown Lines in Chinese Subjects: A Randomized, Double-blind, Active-Controlled Phase-3 Study.

This study evaluated the efficacy and safety of IncobotulinumtoxinA 20 U for treatment of glabellar frown lines in Chinese subjects. Methods: This was a prospective, randomized, double-blind, active-controlled, phase-3 study conducted in China. Subjects with moderate to severe glabellar frown lines at maximum frown were randomized to receive IncobotulinumtoxinA (N = 336) or OnabotulinumtoxinA (N = 167). Results: For the primary efficacy endpoint at day 30, response rates at maximum frown (score "none" or "mild") on the Merz Aesthetic Scales Glabella Lines - Dynamic were comparable between IncobotulinumtoxinA (92.5%) and OnabotulinumtoxinA (95.1%) per investigator's live rating. Noninferiority of IncobotulinumtoxinA versus OnabotulinumtoxinA was successfully demonstrated, as the two-sided 95% confidence interval of -0.97% to 0.43% for the difference in Merz Aesthetic Scales-based response rates (-0.27%) lay completely above the predefined noninferiority margin of -15%. For the secondary efficacy endpoints assessed at day 30, Merz Aesthetic Scales-based response rates (score "none" or "mild") at maximum frown were similarly comparable between both groups per subject (>85%) and independent review panel (>96%) rating. Per Global Impression of Change Scales, greater than 80% of subjects and greater than 90% of investigators in both groups rated treatment results as at least "much improved" at day 30 compared with baseline. Safety profiles were consistent between groups; IncobotulinumtoxinA was well tolerated, and no new safety concerns were identified in Chinese subjects. Conclusion: IncobotulinumtoxinA 20 U is safe and effective for treatment of moderate to severe glabellar frown lines at maximum frown in Chinese subjects and is noninferior to OnabotulinumtoxinA 20 U.

Relationship between alcohol consumption and adverse childhood experiences in college students-A cross-sectional study.

Background: Alcohol consumption is an important issue. Adverse childhood experiences (ACEs) can affect alcohol consumption later in life. Therefore, the main objective of this study was to test the association between ACE and the alcohol consumption in college students. Materials and methods: A cross-sectional study on college students was conducted during December 2021 and January 2022, Through the school web system, students received a standard questionnaire on alcohol consumption (AUDIT) and ACEs. The study involved 4,044 participants from three universities in Slovakia. Result: Compared to men, the incidence of emotional abuse by a parent, physical abuse by a parent, and sexual abuse was significantly higher in women (p < 0.001). Furthermore, women reported greater emotional and physical neglect (p < 0.001). The incidence of a high or very high AUDIT score in college students with ACE-0, ACE-1, ACE-2, ACE-3, and ACE-4+ was 3.8, 4.7, 4.1, 6.4, and 9.3%, respectively. Conclusion: More adverse childhood experiences were associated with increased alcohol consumption in both male and female university students. Baseline drinking was higher in male students, but increased drinking in relation to an increase in ACEs was higher in female students. These results point to gender-specific driving forces and targets for intervention.

HCV Elimination in Central Europe with Particular Emphasis on Microelimination in Prisons.

In 2016, the WHO announced a plan to eliminate viral hepatitis as a public health threat by 2030. In this narrative review, experts from Bulgaria, Croatia, the Czech Republic, Hungary, Latvia, Lithuania, Poland and Slovakia assessed the feasibility of achieving the WHO 2030 target for HCV infections in Central Europe. They focused mainly on HCV micro-elimination in prisons, where the highest incidence of HCV infections is usually observed, and the impact of the COVID-19 pandemic on the detection and treatment of HCV infections. According to the presented estimates, almost 400,000 people remain infected with HCV in the analyzed countries. Interferon-free therapies are available ad libitum, but the number of patients treated annually in the last two years has halved compared to 2017-2019, mainly due to the COVID-19 pandemic. None of the countries analyzed had implemented a national HCV screening program or a prison screening program. The main reason is a lack of will at governmental and prison levels. None of the countries analyzed see any chance of meeting the WHO targets for removing viral hepatitis from the public threat list by 2030, unless barriers such as a lack of political will and a lack of screening programs are removed quickly.

Altered Expression of Zonula occludens-1 Affects Cardiac Na+ Channels and Increases Susceptibility to Ventricular Arrhythmias.

Zonula occludens-1 (ZO-1) is an intracellular scaffolding protein that orchestrates the anchoring of membrane proteins to the cytoskeleton in epithelial and specialized tissue including the heart. There is clear evidence to support the central role of intracellular auxiliary proteins in arrhythmogenesis and previous studies have found altered ZO-1 expression associated with atrioventricular conduction abnormalities. Here, using human cardiac tissues, we identified all three isoforms of ZO-1, canonical (Transcript Variant 1, TV1), CRA_e (Transcript Variant 4, TV4), and an additionally expressed (Transcript Variant 3, TV3) in non-failing myocardium. To investigate the role of ZO-1 on ventricular arrhythmogenesis, we generated a haploinsufficient ZO-1 mouse model (ZO-1+/-). ZO-1+/- mice exhibited dysregulated connexin-43 protein expression and localization at the intercalated disc. While ZO-1+/- mice did not display abnormal cardiac function at baseline, adrenergic challenge resulted in rhythm abnormalities, including premature ventricular contractions and bigeminy. At baseline, ventricular myocytes from the ZO-1+/- mice displayed prolonged action potential duration and spontaneous depolarizations, with ZO-1+/- cells displaying frequent unsolicited (non-paced) diastolic depolarizations leading to spontaneous activity with multiple early afterdepolarizations (EADs). Mechanistically, ZO-1 deficient myocytes displayed a reduction in sodium current density (INa) and an increased sensitivity to isoproterenol stimulation. Further, ZO-1 deficient myocytes displayed remodeling in ICa current, likely a compensatory change. Taken together, our data suggest that ZO-1 deficiency results in myocardial substrate susceptible to triggered arrhythmias.

Is elimination of HCV in 2030 realistic in Central Europe.

According to the recent data presented by Central-European HCV experts, the estimated prevalence of HCV is between 0.2% and 1.7% in certain countries in this region. There are no financial limitations to access to treatment in most countries. Patients in these countries have access to at least one pangenotypic regimen. The most common barriers to the elimination of HCV in Central Europe are a lack of established national screening programmes and limited political commitment to the elimination of HCV. Covid-19 has significantly affected the number of patients who have been diagnosed and treated, thus, delaying the potential elimination of HCV. These data suggest that the elimination of HCV elimination projected by WHO before 2030 will not be possible in the Central Europe.

Abnormal myocardial expression of SAP97 is associated with arrhythmogenic risk.

Synapse-associated protein 97 (SAP97) is a scaffolding protein crucial for the functional expression of several cardiac ion channels and therefore proper cardiac excitability. Alterations in the functional expression of SAP97 can modify the ionic currents underlying the cardiac action potential and consequently confer susceptibility for arrhythmogenesis. In this study, we generated a murine model for inducible, cardiac-targeted Sap97 ablation to investigate arrhythmia susceptibility and the underlying molecular mechanisms. Furthermore, we sought to identify human SAP97 (DLG1) variants that were associated with inherited arrhythmogenic disease. The murine model of cardiac-specific Sap97 ablation demonstrated several ECG abnormalities, pronounced action potential prolongation subject to high incidence of arrhythmogenic afterdepolarizations and notable alterations in the activity of the main cardiac ion channels. However, no DLG1 mutations were found in 40 unrelated cases of genetically elusive long QT syndrome (LQTS). Instead, we provide the first evidence implicating a gain of function in human DLG1 mutation resulting in an increase in Kv4.3 current (Ito) as a novel, potentially pathogenic substrate for Brugada syndrome (BrS). In conclusion, DLG1 joins a growing list of genes encoding ion channel interacting proteins (ChIPs) identified as potential channelopathy-susceptibility genes because of their ability to regulate the trafficking, targeting, and modulation of ion channels that are critical for the generation and propagation of the cardiac electrical impulse. Dysfunction in these critical components of cardiac excitability can potentially result in fatal cardiac disease.NEW & NOTEWORTHY The gene encoding SAP97 (DLG1) joins a growing list of genes encoding ion channel-interacting proteins (ChIPs) identified as potential channelopathy-susceptibility genes because of their ability to regulate the trafficking, targeting, and modulation of ion channels that are critical for the generation and propagation of the cardiac electrical impulse. In this study we provide the first data supporting DLG1-encoded SAP97's candidacy as a minor Brugada syndrome susceptibility gene.

How close are we to hepatitis C virus elimination in Central Europe?

AIM OF THE STUDY: To collect and analyse data obtained from HCV opinion leaders/experts from central European countries, on factors which can affect the WHO target of HCV elimination by 2030. MATERIAL AND METHODS: Data were collected from opinion leaders/experts involved in management of HCV infections in Central European countries which participated in 9th Conference of the Central European Hepatologic Collaboration (Warsaw, 10-11 October 2019). A dedicated questionnaire collected current information related to HCV elimination in Bulgaria, Croatia, the Czech Republic, Hungary, Latvia, Lithuania, Poland and Slovakia. RESULTS: The HCV prevalence rate in particular countries varied from 0.2% to 1.7%. In most central European countries all the HCV infected population is eligible for reimbursement of treatment. However, in some countries there are still some limitations related to the stage of the disease and people who inject drugs. All countries have access to at least one pangenotypic regimen. The most common barrier to HCV elimination in all countries is insufficient political will to establish priority for HCV. None of the reporting countries has established a national screening programme. CONCLUSIONS: Access to therapy for HCV is similar and the majority of patients in Central Europe can be treated according to the current guidelines. Unfortunately there are still some limitations and a lack of political will to implement national screening programmes. According to collected data HCV elimination will not be possible in the region by 2030.

TASK-1 and TASK-3 channels modulate pressure overload-induced cardiac remodeling and dysfunction.

Tandem pore domain acid-sensitive K+ (TASK) channels are present in cardiac tissue; however, their contribution to cardiac pathophysiology is not well understood. Here, we investigate the role of TASK-1 and TASK-3 in the pathogenesis of cardiac dysfunction using both human tissue and mouse models of genetic TASK channel loss of function. Compared with normal human cardiac tissue, TASK-1 gene expression is reduced in association with either cardiac hypertrophy alone or combined cardiac hypertrophy and heart failure. In a pressure overload cardiomyopathy model, TASK-1 global knockout (TASK-1 KO) mice have both reduced cardiac hypertrophy and preserved cardiac function compared with wild-type mice. In contrast to the TASK-1 KO mouse pressure overload response, TASK-3 global knockout (TASK-3 KO) mice develop cardiac hypertrophy and a delayed onset of cardiac dysfunction compared with wild-type mice. The cardioprotective effects observed in TASK-1 KO mice are associated with pressure overload-induced augmentation of AKT phosphorylation and peroxisome proliferator-activated receptor-γ coactivator-1α (PGC-1α) expression, with consequent augmentation of cardiac energetics and fatty acid oxidation. The protective effects of TASK-1 loss of function are associated with an enhancement of physiologic hypertrophic signaling and preserved metabolic functions. These findings may provide a rationale for TASK-1 channel inhibition in the treatment of cardiac dysfunction.NEW & NOTEWORTHY The role of tandem pore domain acid-sensitive K+ (TASK) channels in cardiac function is not well understood. This study demonstrates that TASK channel gene expression is associated with the onset of human cardiac hypertrophy and heart failure. TASK-1 and TASK-3 strongly affect the development of pressure overload cardiomyopathies in genetic models of TASK-1 and TASK-3 loss of function. The effects of TASK-1 loss of function were associated with enhanced AKT phosphorylation and expression of peroxisome proliferator-activated receptor-γ coactivator-1 (PGC-1) transcription factor. These data suggest that TASK channels influence the development of cardiac hypertrophy and dysfunction in response to injury.

Novel Mechanistic Roles for Ankyrin-G in Cardiac Remodeling and Heart Failure.

Ankyrin polypeptides are intracellular proteins responsible for targeting cardiac membrane proteins. Here, the authors demonstrate that ankyrin-G plays an unexpected role in normal compensatory physiological remodeling in response to myocardial stress and aging; the authors implicate disruption of ankyrin-G in human heart failure. Mechanistically, the authors illustrate that ankyrin-G serves as a key nodal protein required for cardiac myofilament integration with the intercalated disc. Their data define novel in vivo mechanistic roles for ankyrin-G, implicate ankyrin-G as necessary for compensatory cardiac physiological remodeling under stress, and implicate disruption of ankyrin-G in the development and progression of human heart failure.

Pazopanib for renal cell carcinoma leads to elevated mean arterial pressures in a murine model.

BACKGROUND: In the setting of metastatic RCC (mRCC), pazopanib is approved as first line therapy. Unfortunately treatment may lead to cardiotoxicity such as hypertension, heart failure, and myocardial ischemia. OBJECTIVE: Define the in vivo role of pazopanib in the development of cardiotoxicity. METHODS: Wild type mice were dosed for 42 days via oral gavage, and separated into control and treatment (pazopanib) groups. Baseline ECG's, echocardiograms, and blood pressures were recorded. At the conclusion of the study functional parameters were again recorded, and animals were used for pathological, histological, and protein analysis. RESULTS: After 2 weeks of dosing with pazopanib, the treatment group exhibited a statistically significant increase in mean arterial pressure compared to control mice (119 ± 11.7 mmHg versus 108 ± 8.2 mmHg, p = 0.049). Treatment with pazopanib led to a significant reduction in the cardiac output of mice. CONCLUSION: Our findings in mice clearly demonstrate that treatment with pazopanib leads to a significant elevation in blood pressure after 2 weeks of dosing and this persists for the duration of dosing. The continued development of the cardio-oncology field will be paramount in providing optimal oncologic care while simultaneously improving cardiac outcomes through further investigation into the mechanisms of CV toxicity.

Gαi is required for carvedilol-induced ß1 adrenergic receptor ß-arrestin biased signaling.

The ß1 adrenergic receptor (ß1AR) is recognized as a classical Gαs-coupled receptor. Agonist binding not only initiates G protein-mediated signaling but also signaling through the multifunctional adapter protein ß-arrestin. Some ßAR ligands, such as carvedilol, stimulate ßAR signaling preferentially through ß-arrestin, a concept known as ß-arrestin-biased agonism. Here, we identify a signaling mechanism, unlike that previously known for any Gαs-coupled receptor, whereby carvedilol induces the transition of the ß1AR from a classical Gαs-coupled receptor to a Gαi-coupled receptor stabilizing a distinct receptor conformation to initiate ß-arrestin-mediated signaling. Recruitment of Gαi is not induced by any other ßAR ligand screened, nor is it required for ß-arrestin-bias activated by the ß2AR subtype of the ßAR family. Our findings demonstrate a previously unrecognized role for Gαi in ß1AR signaling and suggest that the concept of ß-arrestin-bias may need to be refined to incorporate the selective bias of receptors towards distinct G protein subtypes.

Neuronal Na+ Channels Are Integral Components of Pro-arrhythmic Na+/Ca2+ Signaling Nanodomain That Promotes Cardiac Arrhythmias During ß-adrenergic Stimulation.

BACKGROUND: Cardiac arrhythmias are a leading cause of death in the US. Vast majority of these arrhythmias including catecholaminergic polymorphic ventricular tachycardia (CPVT) are associated with increased levels of circulating catecholamines and involve abnormal impulse formation secondary to aberrant Ca2+ and Na+ handling. However, the mechanistic link between ß-AR stimulation and the subcellular/molecular arrhythmogenic trigger(s) remains elusive. METHODS AND RESULTS: We performed functional and structural studies to assess Ca2+ and Na+ signaling in ventricular myocyte as well as surface electrocardiograms in mouse models of cardiac calsequestrin (CASQ2)-associated CPVT. We demonstrate that a subpopulation of Na+ channels (neuronal Na+ channels; nNav) that colocalize with RyR2 and Na+/Ca2+ exchanger (NCX) are a part of the ß-AR-mediated arrhythmogenic process. Specifically, augmented Na+ entry via nNav in the settings of genetic defects within the RyR2 complex and enhanced sarcoplasmic reticulum (SR) Ca2+-ATPase (SERCA)-mediated SR Ca2+ refill is both an essential and a necessary factor for the arrhythmogenesis. Furthermore, we show that augmentation of Na+ entry involves ß-AR-mediated activation of CAMKII subsequently leading to nNav augmentation. Importantly, selective pharmacological inhibition as well as silencing of Nav1.6 inhibit myocyte arrhythmic potential and prevent arrhythmias in vivo. CONCLUSION: These data suggest that the arrhythmogenic alteration in Na+/Ca2+ handling evidenced ruing ß-AR stimulation results, at least in part, from enhanced Na+ influx through nNav. Therefore, selective inhibition of these channels and Nav1.6 in particular can serve as a potential antiarrhythmic therapy.

Cardiac Electrical and Structural Changes During Bacterial Infection: An Instructive Model to Study Cardiac Dysfunction in Sepsis.

BACKGROUND: Sepsis patients with cardiac dysfunction have significantly higher mortality. Although several pathways are associated with myocardial damage in sepsis, the precise cause(s) remains unclear and treatment options are limited. This study was designed to develop a new model to investigate the early events of cardiac damage during sepsis progression. METHODS AND RESULTS: Francisella tularensis subspecies novicida (Ft.n) is a Gram-negative intracellular pathogen causing severe sepsis syndrome in mice. BALB/c mice (N=12) were sham treated or infected with Ft.n through the intranasal route. Serial electrocardiograms were recorded at multiple time points until 96 hours. Hearts were then harvested for histology and gene expression studies. Similar to septic patients, we illustrate both cardiac electrical and structural phenotypes in our murine Ft.n infection model, including prominent R' wave formation, prolonged QRS intervals, and significant left ventricular dysfunction. Notably, in infected animals, we detected numerous microlesions in the myocardium, previously observed following nosocomial Streptococcus infection and in sepsis patients. We show that Ft.n-mediated microlesions are attributed to cardiomyocyte apoptosis, increased immune cell infiltration, and expression of inflammatory mediators (tumor necrosis factor, interleukin [IL]-1ß, IL-8, and superoxide dismutase 2). Finally, we identify increased expression of microRNA-155 and rapid degradation of heat shock factor 1 following cardiac Ft.n infection as a primary cause of myocardial inflammation and apoptosis. CONCLUSIONS: We have developed and characterized an Ft.n infection model to understand the pathogenesis of cardiac dysregulation in sepsis. Our findings illustrate novel in vivo phenotypes underlying cardiac dysfunction during Ft.n infection with significant translational impact on our understanding of sepsis pathophysiology.

Common human ANK2 variant confers in vivo arrhythmia phenotypes.

BACKGROUND: Human ANK2 (ankyrin-B) loss-of-function variants are directly linked with arrhythmia phenotypes. However, in atypical non-ion channel arrhythmia genes such as ANK2 that lack the same degree of robust structure/function and clinical data, it may be more difficult to assign variant disease risk based simply on variant location, minor allele frequency, and/or predictive structural algorithms. The human ankyrin-B p.L1622I variant found in arrhythmia probands displays significant diversity in minor allele frequency across populations. OBJECTIVE: The objective of this study was to directly test the in vivo impact of ankyrin-B p.L1622I on cardiac electrical phenotypes and arrhythmia risk using a new animal model. METHODS: We tested arrhythmia phenotypes in a new "knock-in" animal model harboring the human ankyrin-B p.L1622I variant. RESULTS: Ankyrin-B p.L1622I displays reduced posttranslational expression in vivo, resulting in reduced cardiac ankyrin-B expression and reduced association with binding-partner Na/Ca exchanger. Ankyrin-B(L1622I/L1622I) mice display changes in heart rate, atrioventricular and intraventricular conduction, and alterations in repolarization. Furthermore, ankyrin-B(L1622I/L1622I) mice display catecholamine-dependent arrhythmias. At the cellular level, ankyrin-B(L1622I/L1622I) myocytes display increased action potential duration and severe arrhythmogenic afterdepolarizations that provide a mechanistic rationale for the arrhythmias. CONCLUSION: Our findings support in vivo arrhythmogenic phenotypes of an ANK2 variant with unusual frequency in select populations. On the basis of our findings and current clinical data, we support classification of p.L1622I as a "mild" loss-of-function variant that may confer arrhythmia susceptibility in the context of secondary risk factors including environment, medication, and/or additional genetic variation.

Two-Pore K+ Channel TREK-1 Regulates Sinoatrial Node Membrane Excitability.

BACKGROUND: Two-pore K(+) channels have emerged as potential targets to selectively regulate cardiac cell membrane excitability; however, lack of specific inhibitors and relevant animal models has impeded the effort to understand the role of 2-pore K(+) channels in the heart and their potential as a therapeutic target. The objective of this study was to determine the role of mechanosensitive 2-pore K(+) channel family member TREK-1 in control of cardiac excitability. METHODS AND RESULTS: Cardiac-specific TREK-1-deficient mice (αMHC-Kcnk(f/f)) were generated and found to have a prevalent sinoatrial phenotype characterized by bradycardia with frequent episodes of sinus pause following stress. Action potential measurements from isolated αMHC-Kcnk2(f/f) sinoatrial node cells demonstrated decreased background K(+) current and abnormal sinoatrial cell membrane excitability. To identify novel pathways for regulating TREK-1 activity and sinoatrial node excitability, mice expressing a truncated allele of the TREK-1-associated cytoskeletal protein ßIV-spectrin (qv(4J) mice) were analyzed and found to display defects in cell electrophysiology as well as loss of normal TREK-1 membrane localization. Finally, the ßIV-spectrin/TREK-1 complex was found to be downregulated in the right atrium from a canine model of sinoatrial node dysfunction and in human cardiac disease. CONCLUSIONS: These findings identify a TREK-1-dependent pathway essential for normal sinoatrial node cell excitability that serves as a potential target for selectively regulating sinoatrial node cell function.

Dysfunction of the ß2-spectrin-based pathway in human heart failure.

ß2-Spectrin is critical for integrating membrane and cytoskeletal domains in excitable and nonexcitable cells. The role of ß2-spectrin for vertebrate function is illustrated by dysfunction of ß2-spectrin-based pathways in disease. Recently, defects in ß2-spectrin association with protein partner ankyrin-B were identified in congenital forms of human arrhythmia. However, the role of ß2-spectrin in common forms of acquired heart failure and arrhythmia is unknown. We report that ß2-spectrin protein levels are significantly altered in human cardiovascular disease as well as in large and small animal cardiovascular disease models. Specifically, ß2-spectrin levels were decreased in atrial samples of patients with atrial fibrillation compared with tissue from patients in sinus rhythm. Furthermore, compared with left ventricular samples from nonfailing hearts, ß2-spectrin levels were significantly decreased in left ventricle of ischemic- and nonischemic heart failure patients. Left ventricle samples of canine and murine heart failure models confirm reduced ß2-spectrin protein levels. Mechanistically, we identify that ß2-spectrin levels are tightly regulated by posttranslational mechanisms, namely Ca(2+)- and calpain-dependent proteases. Furthermore, consistent with this data, we observed Ca(2+)- and calpain-dependent loss of ß2-spectrin downstream effector proteins, including ankyrin-B in heart. In summary, our findings illustrate that ß2-spectrin and downstream molecules are regulated in multiple forms of cardiovascular disease via Ca(2+)- and calpain-dependent proteolysis.

Epidemiology of HCV infection in the Central European region.

Opinion leaders in each of four countries in the Central European region summarize the available data on hepatitis C virus (HCV) epidemiology. The overall prevalence of anti-HCV antibody reactivity in this region varies between 0.2% and 2.1%, the most prevalent HCV genotype is GT 1. The commonest route of transmission is intravenous drug abuse at present.

Protein phosphatase 2A regulatory subunit B56α limits phosphatase activity in the heart.

Protein phosphatase 2A (PP2A) is a serine/threonine-selective holoenzyme composed of a catalytic, scaffolding, and regulatory subunit. In the heart, PP2A activity is requisite for cardiac excitation-contraction coupling and central in adrenergic signaling. We found that mice deficient in the PP2A regulatory subunit B56α (1 of 13 regulatory subunits) had altered PP2A signaling in the heart that was associated with changes in cardiac physiology, suggesting that the B56α regulatory subunit had an autoinhibitory role that suppressed excess PP2A activity. The increase in PP2A activity in the mice with reduced B56α expression resulted in slower heart rates and increased heart rate variability, conduction defects, and increased sensitivity of heart rate to parasympathetic agonists. Increased PP2A activity in B56α(+/-) myocytes resulted in reduced Ca(2+) waves and sparks, which was associated with decreased phosphorylation (and thus decreased activation) of the ryanodine receptor RyR2, an ion channel on intracellular membranes that is involved in Ca(2+) regulation in cardiomyocytes. In line with an autoinhibitory role for B56α, in vivo expression of B56α in the absence of altered abundance of other PP2A subunits decreased basal phosphatase activity. Consequently, in vivo expression of B56α suppressed parasympathetic regulation of heart rate and increased RyR2 phosphorylation in cardiomyocytes. These data show that an integral component of the PP2A holoenzyme has an important inhibitory role in controlling PP2A enzyme activity in the heart.

Eps15 Homology Domain-containing Protein 3 Regulates Cardiac T-type Ca2+ Channel Targeting and Function in the Atria.

Proper trafficking of membrane-bound ion channels and transporters is requisite for normal cardiac function. Endosome-based protein trafficking of membrane-bound ion channels and transporters in the heart is poorly understood, particularly in vivo. In fact, for select cardiac cell types such as atrial myocytes, virtually nothing is known regarding endosomal transport. We previously linked the C-terminal Eps15 homology domain-containing protein 3 (EHD3) with endosome-based protein trafficking in ventricular cardiomyocytes. Here we sought to define the roles and membrane protein targets for EHD3 in atria. We identify the voltage-gated T-type Ca(2+) channels (CaV3.1, CaV3.2) as substrates for EHD3-dependent trafficking in atria. Mice selectively lacking EHD3 in heart display reduced expression and targeting of both Cav3.1 and CaV3.2 in the atria. Furthermore, functional experiments identify a significant loss of T-type-mediated Ca(2+) current in EHD3-deficient atrial myocytes. Moreover, EHD3 associates with both CaV3.1 and CaV3.2 in co-immunoprecipitation experiments. T-type Ca(2+) channel function is critical for proper electrical conduction through the atria. Consistent with these roles, EHD3-deficient mice demonstrate heart rate variability, sinus pause, and atrioventricular conduction block. In summary, our findings identify CaV3.1 and CaV3.2 as substrates for EHD3-dependent protein trafficking in heart, provide in vivo data on endosome-based trafficking pathways in atria, and implicate EHD3 as a key player in the regulation of atrial myocyte excitability and cardiac conduction.