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PLoS Pathogens Aug 2019Human respiratory syncytial virus (RSV) is the leading viral cause of acute pediatric lower respiratory tract infections worldwide, with no available vaccine or...
Human respiratory syncytial virus (RSV) is the leading viral cause of acute pediatric lower respiratory tract infections worldwide, with no available vaccine or effective antiviral drug. To gain insight into virus-host interactions, we performed a genome-wide siRNA screen. The expression of over 20,000 cellular genes was individually knocked down in human airway epithelial A549 cells, followed by infection with RSV expressing green fluorescent protein (GFP). Knockdown of expression of the cellular ATP1A1 protein, which is the major subunit of the Na+,K+-ATPase of the plasma membrane, had one of the strongest inhibitory effects on GFP expression and viral titer. Inhibition was not observed for vesicular stomatitis virus, indicating that it was RSV-specific rather than a general effect. ATP1A1 formed clusters in the plasma membrane very early following RSV infection, which was independent of replication but dependent on the attachment glycoprotein G. RSV also triggered activation of ATP1A1, resulting in signaling by c-Src-kinase activity that transactivated epidermal growth factor receptor (EGFR) by Tyr845 phosphorylation. ATP1A1 signaling and activation of both c-Src and EGFR were found to be required for efficient RSV uptake. Signaling events downstream of EGFR culminated in the formation of macropinosomes. There was extensive uptake of RSV virions into macropinosomes at the beginning of infection, suggesting that this is a major route of RSV uptake, with fusion presumably occurring in the macropinosomes rather than at the plasma membrane. Important findings were validated in primary human small airway epithelial cells (HSAEC). In A549 cells and HSAEC, RSV uptake could be inhibited by the cardiotonic steroid ouabain and the digitoxigenin derivative PST2238 (rostafuroxin) that bind specifically to the ATP1A1 extracellular domain and block RSV-triggered EGFR Tyr845 phosphorylation. In conclusion, we identified ATP1A1 as a host protein essential for macropinocytic entry of RSV into respiratory epithelial cells, and identified PST2238 as a potential anti-RSV drug.
Topics: A549 Cells; Cardiotonic Agents; Digitoxigenin; Epithelial Cells; ErbB Receptors; High-Throughput Screening Assays; Humans; Ouabain; Pinocytosis; RNA, Small Interfering; Respiratory Syncytial Virus Infections; Respiratory Syncytial Virus, Human; Respiratory System; Respiratory Tract Infections; Signal Transduction; Sodium-Potassium-Exchanging ATPase; Viral Proteins; Virus Internalization
PubMed: 31381610
DOI: 10.1371/journal.ppat.1007963 -
Cardiology 2019This study sought to assess the impact of treatment with digitalis on recurrences of ventricular tachyarrhythmias in implantable cardioverter defibrillator (ICD)... (Observational Study)
Observational Study
OBJECTIVE
This study sought to assess the impact of treatment with digitalis on recurrences of ventricular tachyarrhythmias in implantable cardioverter defibrillator (ICD) recipients with atrial fibrillation (AF) and heart failure (HF).
BACKGROUND
The data regarding outcomes of digitalis therapy in ICD recipients are limited.
METHODS
A large retrospective registry was used, including consecutive ICD recipients with episodes of ventricular tachyarrhythmia between 2002 and 2016. Patients treated with digitalis were compared to patients without digitalis treatment. The primary prognostic outcome was first recurrence of ventricular tachyarrhythmia at 5 years. Kaplan-Meier and multivariable Cox regression analyses were applied.
RESULTS
A total of 394 ICD recipients with AF and/or HF was included (26% with digitalis treatment and 74% without). Digitalis treatment was associated with decreased freedom from recurrent ventricular tachy-arrhythmias (HR = 1.423; 95% CI 1.047-1.934; p = 0.023). Accordingly, digitalis treatment was associated with decreased freedom from appropriate ICD therapies (HR = 1.622; 95% CI 1.166-2.256; p = 0.004) and, moreover, higher rates of rehospitalization (38 vs. 21%; p = 0.001) and all-cause mortality (33 vs. 20%; p = 0.011).
CONCLUSION
Among ICD recipients suffering from AF and HF, treatment with digitalis was associated with increased rates of recurrent ventricular tachyarrhythmias and ICD therapies. However, the endpoints may also have been driven by interactions between digitalis, AF, and HF.
Topics: Adult; Aged; Aged, 80 and over; Atrial Fibrillation; Defibrillators, Implantable; Digitoxin; Female; Germany; Heart Failure; Humans; Male; Middle Aged; Multivariate Analysis; Prognosis; Recurrence; Retrospective Studies; Survival Analysis; Tachycardia, Ventricular
PubMed: 31189160
DOI: 10.1159/000497271 -
Insects Apr 2019Cardiac glycosides, cardenolides and bufadienolides, are elaborated by several plant or animal species to prevent grazing or predation. Entomologists have characterized... (Review)
Review
Cardiac glycosides, cardenolides and bufadienolides, are elaborated by several plant or animal species to prevent grazing or predation. Entomologists have characterized several insect species that have evolved the ability to sequester these glycosides in their tissues to reduce their palatability and, thus, reduce predation. Cardiac glycosides are known to interact with the sodium- and potassium-activated adenosine triphosphatase, or sodium pump, through a specific receptor-binding site. Over the last couple of decades, and since entomologic studies, it has become clear that mammals synthesize endogenous cardenolides that closely resemble or are identical to compounds of plant origin and those sequestered by insects. The most important of these are ouabain-like compounds. These compounds are essential for the regulation of normal ionic physiology in mammals. Importantly, at physiologic picomolar or nanomolar concentrations, endogenous ouabain, a cardenolide, stimulates the sodium pump, activates second messengers, and may even function as a growth factor. This is in contrast to the pharmacologic or toxic micromolar or milimolar concentrations achieved after consumption of exogenous cardenolides (by consuming medications, plants, or insects), which inhibit the pump and result in either a desired medical outcome, or the toxic consequence of sodium pump inhibition.
PubMed: 30974764
DOI: 10.3390/insects10040102 -
European Journal of Heart Failure May 2019Despite recent advances in the treatment of chronic heart failure (HF), mortality and hospitalizations still remain high. Additional therapies to improve mortality and...
Rationale and design of the DIGIT-HF trial (DIGitoxin to Improve ouTcomes in patients with advanced chronic Heart Failure): a randomized, double-blind, placebo-controlled study.
AIMS
Despite recent advances in the treatment of chronic heart failure (HF), mortality and hospitalizations still remain high. Additional therapies to improve mortality and morbidity are urgently needed. The efficacy of cardiac glycosides - although regularly used for HF treatment - remains unclear. DIGIT-HF was designed to demonstrate that digitoxin on top of standard of care treatment improves mortality and morbidity in patients with HF and a reduced ejection fraction (HFrEF).
METHODS
Patients with chronic HF, New York Heart Association (NYHA) functional class III-IV and left ventricular ejection fraction (LVEF) ≤ 40%, or patients in NYHA functional class II and LVEF ≤ 30% are randomized 1:1 in a double-blind fashion to treatment with digitoxin (target serum concentration 8-18 ng/mL) or matching placebo. Randomization is stratified by centre, sex, NYHA functional class (II, III, or IV), atrial fibrillation, and treatment with cardiac glycosides at baseline. A total of 2190 eligible patients will be included in this clinical trial (1095 per group). All patients receive standard of care treatment recommended by expert guidelines upon discretion of the treating physician. The primary outcome is a composite of all-cause mortality or hospital admission for worsening HF (whatever occurs first). Key secondary endpoints are all-cause mortality, hospital admission for worsening HF, and recurrent hospital admission for worsening HF.
CONCLUSION
The DIGIT-HF trial will provide important evidence, whether the cardiac glycoside digitoxin reduces the risk for all-cause mortality and/or hospital admission for worsening HF in patients with advanced chronic HFrEF on top of standard of care treatment.
Topics: Humans; Cardiotonic Agents; Cause of Death; Chronic Disease; Digitoxin; Double-Blind Method; Heart Failure; Hospitalization; Mortality; Clinical Trials, Phase IV as Topic; Pragmatic Clinical Trials as Topic; Multicenter Studies as Topic; Randomized Controlled Trials as Topic
PubMed: 30892806
DOI: 10.1002/ejhf.1452 -
Tidsskrift For Den Norske Laegeforening... Oct 2018The withdrawal of digitoxin and subsequent substitution with digoxin around 2012 may have led to an increased health risk for patients. The aim of this study was to...
BACKGROUND
The withdrawal of digitoxin and subsequent substitution with digoxin around 2012 may have led to an increased health risk for patients. The aim of this study was to follow individual patients during the switch.
MATERIAL AND METHOD
Serum concentrations of digitoxin and digoxin, measured at the Department of Clinical Pharmacology at St Olavs University Hospital in the period 1 January 2011-31 December 2013 were reviewed. Patients who had switched from digitoxin to digoxin and whose serum concentrations of both drugs had been measured during this period were included.
RESULTS
A total of 304 patients, 1686 samples and 1858 serum concentration analyses were included in the study. Therapeutic serum concentrations were measured in 171 patients (56.3 %) before the switch and 176 (57.9 %) after this had taken place. Altogether 108 patients (35.5 %) had therapeutic concentrations both before and after the change. For 58.9 % of the patients, the change resulted in a reduction in serum concentration of digitalis, calculated as digoxin equivalents. The proportion of patients with assumed supratherapeutic concentrations fell from 43.1 % to 33.9 %; however, the proportion of patients with toxic serum concentrations rose from 0.3 % to 3.0 %.
INTERPRETATION
Although the switch led to a reduction in dose and serum concentration for many, a significant number of patients may have been put in harm's way.
Topics: Adult; Aged; Aged, 80 and over; Anti-Arrhythmia Agents; Digitoxin; Digoxin; Drug Monitoring; Drug Substitution; Drug and Narcotic Control; Female; Humans; Male; Middle Aged; Norway
PubMed: 30277048
DOI: 10.4045/tidsskr.18.0093 -
Tidsskrift For Den Norske Laegeforening... Oct 2018
Topics: Anti-Arrhythmia Agents; Digitoxin; Digoxin; Drug Substitution; Humans; Norway
PubMed: 30277041
DOI: 10.4045/tidsskr.18.0700 -
Biochimica Et Biophysica Acta.... Nov 2018Low concentrations of cardiac glycosides including ouabain, digoxin, and digitoxin block cancer cell growth without affecting Na,K-ATPase activity, but the mechanism...
Low concentrations of cardiac glycosides including ouabain, digoxin, and digitoxin block cancer cell growth without affecting Na,K-ATPase activity, but the mechanism underlying this anti-cancer effect is not fully understood. Volume-regulated anion channel (VRAC) plays an important role in cell death signaling pathway in addition to its fundamental role in the cell volume maintenance. Here, we report cardiac glycosides-induced signaling pathway mediated by the crosstalk between Na,K-ATPase and VRAC in human cancer cells. Submicromolar concentrations of ouabain enhanced VRAC currents concomitantly with a deceleration of cancer cell proliferation. The effects of ouabain were abrogated by a specific inhibitor of VRAC (DCPIB) and knockdown of an essential component of VRAC (LRRC8A), and they were also attenuated by the disruption of membrane microdomains or the inhibition of NADPH oxidase. Digoxin and digitoxin also showed anti-proliferative effects in cancer cells at their therapeutic concentration ranges, and these effects were blocked by DCPIB. In membrane microdomains of cancer cells, LRRC8A was found to be co-immunoprecipitated with Na,K-ATPase α1-isoform. These ouabain-induced effects were not observed in non-cancer cells. Therefore, cardiac glycosides were considered to interact with Na,K-ATPase to stimulate the production of reactive oxygen species, and they also apparently activated VRAC within membrane microdomains, thus producing anti-proliferative effects.
Topics: Cardiac Glycosides; Cell Line, Tumor; Cell Proliferation; Cyclopentanes; Fibroblasts; Gene Knockdown Techniques; HEK293 Cells; HT29 Cells; Humans; Indans; Membrane Microdomains; Membrane Proteins; Neoplasms; RNA, Small Interfering; Reactive Oxygen Species; Signal Transduction; Sodium-Potassium-Exchanging ATPase
PubMed: 30251696
DOI: 10.1016/j.bbadis.2018.09.014 -
PloS One 2018Diastolic dysfunction is increasingly prevalent in our ageing society and an important contributor to heart failure. The giant protein titin could serve as a therapeutic...
Diastolic dysfunction is increasingly prevalent in our ageing society and an important contributor to heart failure. The giant protein titin could serve as a therapeutic target, as its elastic properties are a main determinant of cardiac filling in diastole. This study aimed to develop a high throughput pharmacological screen to identify small molecules that affect titin isoform expression through differential inclusion of exons encoding the elastic PEVK domains. We used a dual luciferase splice reporter assay that builds on the titin splice factor RBM20 to screen ~34,000 small molecules and identified several compounds that inhibit the exclusion of PEVK exons. These compounds belong to the class of cardenolides and affect RBM20 dependent titin exon exclusion but did not affect RBFOX1 mediated splicing of FMNL3. We provide evidence that cardenolides do not bind to the RNA interacting domain of RBM20, but reduce RBM20 protein levels and alter transcription of select splicing factors that interact with RBM20. Cardenolides affect titin isoform expression. Understanding their mode of action and harnessing the splice effects through chemical modifications that suppress the effects on ion homeostasis and more selectively affect cardiac splicing has the potential to improve cardiac filling and thus help patients with diastolic heart failure, for which currently no targeted therapy exists.
Topics: Cardenolides; Connectin; Digitoxin; Drug Discovery; Genes, Reporter; HEK293 Cells; High-Throughput Screening Assays; Humans; Protein Isoforms; RNA Splicing; Transcription, Genetic
PubMed: 29889873
DOI: 10.1371/journal.pone.0198492 -
Deutsches Arzteblatt International Apr 2018
Topics: Digitoxin
PubMed: 29739499
DOI: 10.3238/arztebl.2018.0285b -
Deutsches Arzteblatt International Apr 2018
Topics: Chronic Disease; Digitoxin; Heart Failure; Humans
PubMed: 29739498
DOI: 10.3238/arztebl.2018.0285a