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1.
Proc Natl Acad Sci U S A ; 117(6): 2795-2804, 2020 02 11.
Artigo em Inglês | MEDLINE | ID: mdl-31980532

RESUMO

The human ether-á-go-go-related gene (hERG1) channel conducts small outward K+ currents that are critical for cardiomyocyte membrane repolarization. The gain-of-function mutation N629D at the outer mouth of the selectivity filter (SF) disrupts inactivation and K+-selective transport in hERG1, leading to arrhythmogenic phenotypes associated with long-QT syndrome. Here, we combined computational electrophysiology with Markov state model analysis to investigate how SF-level gating modalities control selective cation transport in wild-type (WT) and mutant (N629D) hERG1 variants. Starting from the recently reported cryogenic electron microscopy (cryo-EM) open-state channel structure, multiple microseconds-long molecular-dynamics (MD) trajectories were generated using different cation configurations at the filter, voltages, electrolyte concentrations, and force-field parameters. Most of the K+ permeation events observed in hERG1-WT simulations occurred at microsecond timescales, influenced by the spontaneous dehydration/rehydration dynamics at the filter. The SF region displayed conductive, constricted, occluded, and dilated states, in qualitative agreement with the well-documented flickering conductance of hERG1. In line with mutagenesis studies, these gating modalities resulted from dynamic interaction networks involving residues from the SF, outer-mouth vestibule, P-helices, and S5-P segments. We found that N629D mutation significantly stabilizes the SF in a state that is permeable to both K+ and Na+, which is reminiscent of the SF in the nonselective bacterial NaK channel. Increasing the external K+ concentration induced "WT-like" SF dynamics in N629D, in qualitative agreement with the recovery of flickering currents in experiments. Overall, our findings provide an understanding of the molecular mechanisms controlling selective transport in K+ channels with a nonconventional SF sequence.


Assuntos
Canal de Potássio ERG1/química , Canal de Potássio ERG1/metabolismo , Motivos de Aminoácidos , Canal de Potássio ERG1/genética , Mutação com Ganho de Função , Humanos , Cinética , Síndrome do QT Longo/genética , Síndrome do QT Longo/metabolismo , Mutação de Sentido Incorreto , Potássio/metabolismo , Domínios Proteicos , Estrutura Secundária de Proteína
2.
Biophys J ; 121(23): 4585-4599, 2022 12 06.
Artigo em Inglês | MEDLINE | ID: mdl-36815709

RESUMO

A cationic leak current known as an "omega current" may arise from mutations of the first charged residue in the S4 of the voltage sensor domains of sodium and potassium voltage-gated channels. The voltage-sensing domains (VSDs) in these mutated channels act as pores allowing nonspecific passage of cations, such as Li+, K+, Cs+, and guanidinium. Interestingly, no omega currents have been previously detected in the nonswapped voltage-gated potassium channels such as the human-ether-a-go-go-related (hERG1), hyperpolarization-activated cyclic nucleotide-gated, and ether-a-go-go channels. In this work, we discovered a novel omega current by mutating the first charged residue of the S4 of the hERG1, K525 to serine. To characterize this omega current, we used various probes, including the hERG1 pore domain blocker, dofetilide, to show that the omega current does not require cation flux via the canonical pore domain. In addition, the omega flux does not cross the conventional selectivity filter. We also show that the mutated channel (K525S hERG1) conducts guanidinium. These data are indicative of the formation of an omega current channel within the VSD. Using molecular dynamics simulations with replica-exchange umbrella sampling simulations of the wild-type hERG1 and the K525S hERG1, we explored the molecular underpinnings governing the cation flow in the VSD of the mutant. We also show that the wild-type hERG1 may form water crevices supported by the biophysical surface accessibility data. Overall, our multidisciplinary study demonstrates that the VSD of hERG1 may act as a cation-selective channel wherein a mutation of the first charged residue in the S4 generates an omega current. Our simulation uncovers the atomistic underpinning of this mechanism.


Assuntos
Canal de Potássio ERG1 , Humanos , Cátions , Simulação de Dinâmica Molecular , Mutação , Canal de Potássio ERG1/química , Canal de Potássio ERG1/genética
3.
Biophys J ; 120(4): 738-748, 2021 02 16.
Artigo em Inglês | MEDLINE | ID: mdl-33476597

RESUMO

The human-ether-a-go-go-related gene (hERG) encodes the voltage-gated potassium channel (KCNH2 or Kv11.1, commonly known as hERG). This channel plays a pivotal role in the stability of phase 3 repolarization of the cardiac action potential. Although a high-resolution cryo-EM structure is available for its depolarized (open) state, the structure surprisingly did not feature many functionally important interactions established by previous biochemical and electrophysiology experiments. Using molecular dynamics flexible fitting (MDFF), we refined the structure and recovered the missing functionally relevant salt bridges in hERG in its depolarized state. We also performed electrophysiology experiments to confirm the functional relevance of a novel salt bridge predicted by our refinement protocol. Our work shows how refinement of a high-resolution cryo-EM structure helps to bridge the existing gap between the structure and function in the voltage-sensing domain (VSD) of hERG.


Assuntos
Canais de Potássio Éter-A-Go-Go , Simulação de Dinâmica Molecular , Potenciais de Ação , Microscopia Crioeletrônica , Canal de Potássio ERG1/metabolismo , Canais de Potássio Éter-A-Go-Go/metabolismo , Humanos
4.
Circulation ; 141(6): 429-439, 2020 02 11.
Artigo em Inglês | MEDLINE | ID: mdl-31941373

RESUMO

BACKGROUND: Insight into type 5 long QT syndrome (LQT5) has been limited to case reports and small family series. Improved understanding of the clinical phenotype and genetic features associated with rare KCNE1 variants implicated in LQT5 was sought through an international multicenter collaboration. METHODS: Patients with either presumed autosomal dominant LQT5 (N = 229) or the recessive Type 2 Jervell and Lange-Nielsen syndrome (N = 19) were enrolled from 22 genetic arrhythmia clinics and 4 registries from 9 countries. KCNE1 variants were evaluated for ECG penetrance (defined as QTc >460 ms on presenting ECG) and genotype-phenotype segregation. Multivariable Cox regression was used to compare the associations between clinical and genetic variables with a composite primary outcome of definite arrhythmic events, including appropriate implantable cardioverter-defibrillator shocks, aborted cardiac arrest, and sudden cardiac death. RESULTS: A total of 32 distinct KCNE1 rare variants were identified in 89 probands and 140 genotype positive family members with presumed LQT5 and an additional 19 Type 2 Jervell and Lange-Nielsen syndrome patients. Among presumed LQT5 patients, the mean QTc on presenting ECG was significantly longer in probands (476.9±38.6 ms) compared with genotype positive family members (441.8±30.9 ms, P<0.001). ECG penetrance for heterozygous genotype positive family members was 20.7% (29/140). A definite arrhythmic event was experienced in 16.9% (15/89) of heterozygous probands in comparison with 1.4% (2/140) of family members (adjusted hazard ratio [HR] 11.6 [95% CI, 2.6-52.2]; P=0.001). Event incidence did not differ significantly for Type 2 Jervell and Lange-Nielsen syndrome patients relative to the overall heterozygous cohort (10.5% [2/19]; HR 1.7 [95% CI, 0.3-10.8], P=0.590). The cumulative prevalence of the 32 KCNE1 variants in the Genome Aggregation Database, which is a human database of exome and genome sequencing data from now over 140 000 individuals, was 238-fold greater than the anticipated prevalence of all LQT5 combined (0.238% vs 0.001%). CONCLUSIONS: The present study suggests that putative/confirmed loss-of-function KCNE1 variants predispose to QT prolongation, however, the low ECG penetrance observed suggests they do not manifest clinically in the majority of individuals, aligning with the mild phenotype observed for Type 2 Jervell and Lange-Nielsen syndrome patients.


Assuntos
Síndrome do QT Longo , Penetrância , Canais de Potássio de Abertura Dependente da Tensão da Membrana/genética , Sistema de Registros , Adolescente , Adulto , Morte Súbita Cardíaca , Cardioversão Elétrica , Eletrocardiografia , Feminino , Parada Cardíaca/genética , Parada Cardíaca/mortalidade , Parada Cardíaca/fisiopatologia , Parada Cardíaca/terapia , Humanos , Síndrome do QT Longo/genética , Síndrome do QT Longo/mortalidade , Síndrome do QT Longo/fisiopatologia , Síndrome do QT Longo/terapia , Masculino , Pessoa de Meia-Idade
5.
J Chem Inf Model ; 61(9): 4266-4279, 2021 09 27.
Artigo em Inglês | MEDLINE | ID: mdl-34420294

RESUMO

Psychostimulant drugs, such as cocaine, inhibit dopamine reuptake via blockading the dopamine transporter (DAT), which is the primary mechanism underpinning their abuse. Atypical DAT inhibitors are dissimilar to cocaine and can block cocaine- or methamphetamine-induced behaviors, supporting their development as part of a treatment regimen for psychostimulant use disorders. When developing these atypical DAT inhibitors as medications, it is necessary to avoid off-target binding that can produce unwanted side effects or toxicities. In particular, the blockade of a potassium channel, human ether-a-go-go (hERG), can lead to potentially lethal ventricular tachycardia. In this study, we established a counter screening platform for DAT and against hERG binding by combining machine learning-based quantitative structure-activity relationship (QSAR) modeling, experimental validation, and molecular modeling and simulations. Our results show that the available data are adequate to establish robust QSAR models, as validated by chemical synthesis and pharmacological evaluation of a validation set of DAT inhibitors. Furthermore, the QSAR models based on subsets of the data according to experimental approaches used have predictive power as well, which opens the door to target specific functional states of a protein. Complementarily, our molecular modeling and simulations identified the structural elements responsible for a pair of DAT inhibitors having opposite binding affinity trends at DAT and hERG, which can be leveraged for rational optimization of lead atypical DAT inhibitors with desired pharmacological properties.


Assuntos
Cocaína , Proteínas da Membrana Plasmática de Transporte de Dopamina , Éter , Humanos , Aprendizado de Máquina , Modelos Moleculares
6.
Mol Pharmacol ; 96(2): 259-271, 2019 08.
Artigo em Inglês | MEDLINE | ID: mdl-31182542

RESUMO

Abnormal cardiac electrical activity is a common side effect caused by unintended block of the promiscuous drug target human ether-à-go-go-related gene (hERG1), the pore-forming domain of the delayed rectifier K+ channel in the heart. hERG1 block leads to a prolongation of the QT interval, a phase of the cardiac cycle that underlies myocyte repolarization detectable on the electrocardiogram. Even newly released drugs such as heart-rate lowering agent ivabradine block the rapid delayed rectifier current IKr, prolong action potential duration, and induce potentially lethal arrhythmia known as torsades de pointes. In this study, we describe a critical drug-binding pocket located at the lateral pore surface facing the cellular membrane. Mutations of the conserved M651 residue alter ivabradine-induced block but not by the common hERG1 blocker dofetilide. As revealed by molecular dynamics simulations, binding of ivabradine to a lipophilic pore access site is coupled to a state-dependent reorientation of aromatic residues F557 and F656 in the S5 and S6 helices. We show that the M651 mutation impedes state-dependent dynamics of F557 and F656 aromatic cassettes at the protein-lipid interface, which has a potential to disrupt drug-induced block of the channel. This fundamentally new mechanism coupling the channel dynamics and small-molecule access from the membrane into the hERG1 intracavitary site provides a simple rationale for the well established state-dependence of drug blockade. SIGNIFICANCE STATEMENT: The drug interference with the function of the cardiac hERG channels represents one of the major sources of drug-induced heart disturbances. We found a novel and a critical drug-binding pocket adjacent to a lipid-facing surface of the hERG1 channel, which furthers our molecular understanding of drug-induced QT syndrome.


Assuntos
Canais de Potássio Éter-A-Go-Go/química , Canais de Potássio Éter-A-Go-Go/metabolismo , Ivabradina/farmacologia , Lipídeos de Membrana/metabolismo , Sítios de Ligação , Canais de Potássio Éter-A-Go-Go/genética , Humanos , Ivabradina/química , Modelos Moleculares , Simulação de Acoplamento Molecular , Simulação de Dinâmica Molecular , Mutagênese Sítio-Dirigida , Fenetilaminas/farmacologia , Ligação Proteica , Estrutura Terciária de Proteína , Sulfonamidas/farmacologia
7.
J Physiol ; 597(17): 4533-4564, 2019 09.
Artigo em Inglês | MEDLINE | ID: mdl-31278749

RESUMO

KEY POINTS: Induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs) capture patient-specific genotype-phenotype relationships, as well as cell-to-cell variability of cardiac electrical activity Computational modelling and simulation provide a high throughput approach to reconcile multiple datasets describing physiological variability, and also identify vulnerable parameter regimes We have developed a whole-cell model of iPSC-CMs, composed of single exponential voltage-dependent gating variable rate constants, parameterized to fit experimental iPSC-CM outputs We have utilized experimental data across multiple laboratories to model experimental variability and investigate subcellular phenotypic mechanisms in iPSC-CMs This framework links molecular mechanisms to cellular-level outputs by revealing unique subsets of model parameters linked to known iPSC-CM phenotypes ABSTRACT: There is a profound need to develop a strategy for predicting patient-to-patient vulnerability in the emergence of cardiac arrhythmia. A promising in vitro method to address patient-specific proclivity to cardiac disease utilizes induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs). A major strength of this approach is that iPSC-CMs contain donor genetic information and therefore capture patient-specific genotype-phenotype relationships. A cited detriment of iPSC-CMs is the cell-to-cell variability observed in electrical activity. We postulated, however, that cell-to-cell variability may constitute a strength when appropriately utilized in a computational framework to build cell populations that can be employed to identify phenotypic mechanisms and pinpoint key sensitive parameters. Thus, we have exploited variation in experimental data across multiple laboratories to develop a computational framework for investigating subcellular phenotypic mechanisms. We have developed a whole-cell model of iPSC-CMs composed of simple model components comprising ion channel models with single exponential voltage-dependent gating variable rate constants, parameterized to fit experimental iPSC-CM data for all major ionic currents. By optimizing ionic current model parameters to multiple experimental datasets, we incorporate experimentally-observed variability in the ionic currents. The resulting population of cellular models predicts robust inter-subject variability in iPSC-CMs. This approach links molecular mechanisms to known cellular-level iPSC-CM phenotypes, as shown by comparing immature and mature subpopulations of models to analyse the contributing factors underlying each phenotype. In the future, the presented models can be readily expanded to include genetic mutations and pharmacological interventions for studying the mechanisms of rare events, such as arrhythmia triggers.


Assuntos
Arritmias Cardíacas/fisiopatologia , Células-Tronco Pluripotentes Induzidas/fisiologia , Miócitos Cardíacos/fisiologia , Potenciais de Ação/fisiologia , Doença do Sistema de Condução Cardíaco/fisiopatologia , Simulação por Computador , Humanos , Armazenamento e Recuperação da Informação , Fenótipo
8.
J Am Soc Nephrol ; 29(4): 1165-1181, 2018 04.
Artigo em Inglês | MEDLINE | ID: mdl-29439156

RESUMO

Nonmicrobial inflammation contributes to CKD progression and fibrosis. Absent in melanoma 2 (AIM2) is an inflammasome-forming receptor for double-stranded DNA. AIM2 is expressed in the kidney and activated mainly by macrophages. We investigated the potential pathogenic role of the AIM2 inflammasome in kidney disease. In kidneys from patients with diabetic or nondiabetic CKD, immunofluorescence showed AIM2 expression in glomeruli, tubules, and infiltrating leukocytes. In a mouse model of unilateral ureteral obstruction (UUO), Aim2 deficiency attenuated the renal injury, fibrosis, and inflammation observed in wild-type (WT) littermates. In bone marrow chimera studies, UUO induced substantially more tubular injury and IL-1ß cleavage in Aim2-/- or WT mice that received WT bone marrow than in WT mice that received Aim2-/- bone marrow. Intravital microscopy of the kidney in LysM(gfp/gfp) mice 5-6 days after UUO demonstrated the significant recruitment of GFP+ proinflammatory macrophages that crawled along injured tubules, engulfed DNA from necrotic cells, and expressed active caspase-1. DNA uptake occurred in large vacuolar structures within recruited macrophages but not resident CX3CR1+ renal phagocytes. In vitro, macrophages that engulfed necrotic debris showed AIM2-dependent activation of caspase-1 and IL-1ß, as well as the formation of AIM2+ ASC specks. ASC specks are a hallmark of inflammasome activation. Cotreatment with DNaseI attenuated the increase in IL-1ß levels, confirming that DNA was the principal damage-associated molecular pattern in this process. Therefore, the activation of the AIM2 inflammasome by DNA from necrotic cells drives a proinflammatory phenotype that contributes to chronic injury in the kidney.


Assuntos
Proteínas de Ligação a DNA/fisiologia , DNA/metabolismo , Inflamassomos/fisiologia , Macrófagos/fisiologia , Insuficiência Renal Crônica/metabolismo , Animais , Transplante de Medula Óssea , Caspase 1/metabolismo , Proteínas de Ligação a DNA/deficiência , Proteínas de Ligação a DNA/genética , Nefropatias Diabéticas/metabolismo , Ativação Enzimática , Fibrose , Humanos , Interleucina-1beta/metabolismo , Glomérulos Renais/metabolismo , Túbulos Renais/metabolismo , Leucócitos/metabolismo , Masculino , Camundongos Endogâmicos C57BL , Camundongos Knockout , Necrose , Nefroesclerose/metabolismo , Fagocitose , Fenótipo , Quimera por Radiação , Células THP-1 , Obstrução Ureteral/metabolismo , Obstrução Ureteral/patologia
9.
Biochem J ; 473(21): 3951-3964, 2016 11 01.
Artigo em Inglês | MEDLINE | ID: mdl-27582498

RESUMO

Beat-to-beat alternations in the amplitude of the cytosolic Ca2+ transient (Ca2+ alternans) are thought to be the primary cause of cardiac alternans that can lead to cardiac arrhythmias and sudden death. Despite its important role in arrhythmogenesis, the mechanism underlying Ca2+ alternans remains poorly understood. Here, we investigated the role of cardiac ryanodine receptor (RyR2), the major Ca2+ release channel responsible for cytosolic Ca2+ transients, in cardiac alternans. Using a unique mouse model harboring a suppression-of-function (SOF) RyR2 mutation (E4872Q), we assessed the effect of genetically suppressing RyR2 function on Ca2+ and action potential duration (APD) alternans in intact hearts, and electrocardiogram (ECG) alternans in vivo We found that RyR2-SOF hearts displayed prolonged sarcoplasmic reticulum Ca2+ release refractoriness and enhanced propensity for Ca2+ alternans. RyR2-SOF hearts/mice also exhibited increased propensity for APD and ECG alternans. Caffeine, which enhances RyR2 activity and the propensity for catecholaminergic polymorphic ventricular tachycardia (CPVT), suppressed Ca2+ alternans in RyR2-SOF hearts, whereas carvedilol, a ß-blocker that suppresses RyR2 activity and CPVT, promoted Ca2+ alternans in these hearts. Thus, RyR2 function is an important determinant of Ca2+, APD, and ECG alternans. Our data also indicate that the activity of RyR2 influences the propensity for cardiac alternans and CPVT in an opposite manner. Therefore, overly suppressing or enhancing RyR2 function is pro-arrhythmic.


Assuntos
Coração/fisiopatologia , Miocárdio/metabolismo , Canal de Liberação de Cálcio do Receptor de Rianodina/metabolismo , Animais , Modelos Animais de Doenças , Eletrocardiografia , Coração/efeitos dos fármacos , Isoproterenol/farmacologia , Camundongos , Mutação/genética , Miócitos Cardíacos/efeitos dos fármacos , Miócitos Cardíacos/metabolismo , Canal de Liberação de Cálcio do Receptor de Rianodina/genética , Retículo Sarcoplasmático/efeitos dos fármacos , Retículo Sarcoplasmático/metabolismo , Taquicardia/genética , Taquicardia/metabolismo , Taquicardia Ventricular/genética , Taquicardia Ventricular/metabolismo
10.
Biophys J ; 108(6): 1414-1424, 2015 Mar 24.
Artigo em Inglês | MEDLINE | ID: mdl-25809254

RESUMO

Congenital and acquired (drug-induced) forms of the human long-QT syndrome are associated with alterations in Kv11.1 (hERG) channel-controlled repolarizing IKr currents of cardiac action potentials. A mandatory drug screen implemented by many countries led to a discovery of a large group of small molecules that can activate hERG currents and thus may act as potent antiarrhythmic agents. Despite significant progress in identification of channel activators, little is known about their mechanism of action. A combination of electrophysiological studies with molecular and kinetic modeling was used to examine the mechanism of a model activator (NS1643) action on the hERG channel and its L529I mutant. The L529I mutant has gating dynamics similar to that of wild-type while its response to application of NS1643 is markedly different. We propose a mechanism compatible with experiments in which the model activator binds to the closed (C3) and open states (O). We suggest that NS1643 is affecting early gating transitions, probably during movements of the voltage sensor that precede the opening of the activation gate.


Assuntos
Cresóis/farmacologia , Canais de Potássio Éter-A-Go-Go/metabolismo , Moduladores de Transporte de Membrana/farmacologia , Modelos Moleculares , Compostos de Fenilureia/farmacologia , Linhagem Celular , Canal de Potássio ERG1 , Canais de Potássio Éter-A-Go-Go/genética , Humanos , Cinética , Potenciais da Membrana/efeitos dos fármacos , Potenciais da Membrana/fisiologia , Mutação , Técnicas de Patch-Clamp , Transfecção
11.
Biophys J ; 108(6): 1400-1413, 2015 Mar 24.
Artigo em Inglês | MEDLINE | ID: mdl-25809253

RESUMO

Activators of hERG1 such as NS1643 are being developed for congenital/acquired long QT syndrome. Previous studies identify the neighborhood of L529 around the voltage-sensor as a putative interacting site for NS1643. With NS1643, the V1/2 of activation of L529I (-34 ± 4 mV) is similar to wild-type (WT) (-37 ± 3 mV; P > 0.05). WT and L529I showed no difference in the slope factor in the absence of NS1643 (8 ± 0 vs. 9 ± 0) but showed a difference in the presence of NS1643 (9 ± 0.3 vs. 22 ± 1; P < 0.01). Voltage-clamp-fluorimetry studies also indicated that in L529I, NS1643 reduces the voltage-sensitivity of S4 movement. To further assess mechanism of NS1643 action, mutations were made in this neighborhood. NS1643 shifts the V1/2 of activation of both K525C and K525C/L529I to hyperpolarized potentials (-131 ± 4 mV for K525C and -120 ± 21 mV for K525C/L529I). Both K525C and K525C/K529I had similar slope factors in the absence of NS1643 (18 ± 2 vs. 34 ± 5, respectively) but with NS1643, the slope factor of K525C/L529I increased from 34 ± 5 to 71 ± 10 (P < 0.01) whereas for K525C the slope factor did not change (18 ± 2 at baseline and 16 ± 2 for NS1643). At baseline, K525R had a slope factor similar to WT (9 vs. 8) but in the presence of NS1643, the slope factor of K525R was increased to 24 ± 4 vs. 9 ± 0 mV for WT (P < 0.01). Molecular modeling indicates that L529I induces a kink in the S4 voltage-sensor helix, altering a salt-bridge involving K525. Moreover, docking studies indicate that NS1643 binds to the kinked structure induced by the mutation with a higher affinity. Combining biophysical, computational, and electrophysiological evidence, a mechanistic principle governing the action of some activators of hERG1 channels is proposed.


Assuntos
Cresóis/metabolismo , Cresóis/farmacologia , Canais de Potássio Éter-A-Go-Go/metabolismo , Compostos de Fenilureia/metabolismo , Compostos de Fenilureia/farmacologia , Animais , Sítios de Ligação , Linhagem Celular , Canal de Potássio ERG1 , Canais de Potássio Éter-A-Go-Go/genética , Fluorometria , Humanos , Potenciais da Membrana/fisiologia , Simulação de Acoplamento Molecular , Simulação de Dinâmica Molecular , Mutação , Oócitos , Técnicas de Patch-Clamp , Estrutura Secundária de Proteína , Transfecção , Xenopus laevis
12.
J Mol Cell Cardiol ; 85: 71-8, 2015 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-25986146

RESUMO

In Europe, ivabradine has recently been approved to treat patients with angina who have intolerance to beta blockers and/or heart failure. Ivabradine is considered to act specifically on the sinoatrial node by inhibiting the If current (the funny current) to slow automaticity. However, in vitro studies show that ivabradine prolongs phase 3 repolarization in ventricular tissue. No episodes of Torsades de Pointes have been reported in randomized clinical studies. The objective of this study is to assess whether ivabradine blocked the hERG1 current. In the present study we discovered that ivabradine prolongs action potential and blocks the hERG current over a range of concentrations overlapping with those required to block HCN4. Ivabradine produced tonic, rather than use-dependent block. The mutation Y652A significantly suppressed pharmacologic block of hERG by ivabradine. Disruption of C-type inactivation also suppressed block of hERG1 by ivabradine. Molecular docking and molecular dynamics simulations indicate that ivabradine may access the inner cavity of the hERG1 via a lipophilic route and has a well-defined binding site in the closed state of the channel. Structural organization of the binding pockets for ivabradine is discussed. Ivabradine blocks hERG and prolongs action potential duration. Our study is potentially important because it indicates the need for active post marketing surveillance of ivabradine. Importantly, proarrhythmia of a number of other drugs has only been discovered during post marketing surveillance.


Assuntos
Benzazepinas/farmacologia , Canais de Potássio Éter-A-Go-Go/antagonistas & inibidores , Canais Disparados por Nucleotídeos Cíclicos Ativados por Hiperpolarização/antagonistas & inibidores , Miócitos Cardíacos/fisiologia , Bloqueadores dos Canais de Potássio/farmacologia , Potenciais de Ação , Animais , Benzazepinas/química , Sítios de Ligação , Relação Dose-Resposta a Droga , Canal de Potássio ERG1 , Canais de Potássio Éter-A-Go-Go/química , Humanos , Concentração Inibidora 50 , Ivabradina , Bicamadas Lipídicas/química , Camundongos , Simulação de Acoplamento Molecular , Miócitos Cardíacos/efeitos dos fármacos , Bloqueadores dos Canais de Potássio/química , Estrutura Secundária de Proteína , Estrutura Terciária de Proteína
13.
J Biol Chem ; 289(28): 19571-84, 2014 Jul 11.
Artigo em Inglês | MEDLINE | ID: mdl-24841199

RESUMO

Nucleotide-binding domain and leucine-rich repeat containing PYD-3 (NLRP3) is a pattern recognition receptor that is implicated in the pathogenesis of inflammation and chronic diseases. Although much is known regarding the NLRP3 inflammasome that regulates proinflammatory cytokine production in innate immune cells, the role of NLRP3 in non-professional immune cells is unclear. Here we report that NLRP3 is expressed in cardiac fibroblasts and increased during TGFß stimulation. NLRP3-deficient cardiac fibroblasts displayed impaired differentiation and R-Smad activation in response to TGFß. Only the central nucleotide binding domain of NLRP3 was required to augment R-Smad signaling because the N-terminal Pyrin or C-terminal leucine-rich repeat domains were dispensable. Interestingly, NLRP3 regulation of myofibroblast differentiation proceeded independently from the inflammasome, IL-1ß/IL-18, or caspase 1. Instead, mitochondrially localized NLRP3 potentiated reactive oxygen species to augment R-Smad activation. In vivo, NLRP3-deficient mice were protected against angiotensin II-induced cardiac fibrosis with preserved cardiac architecture and reduced collagen 1. Together, these results support a distinct role for NLRP3 in non-professional immune cells independent from the inflammasome to regulate differential aspects of wound healing and chronic disease.


Assuntos
Proteínas de Transporte/metabolismo , Inflamassomos , Proteínas Mitocondriais/metabolismo , Miocárdio/metabolismo , Miofibroblastos/metabolismo , Espécies Reativas de Oxigênio/metabolismo , Transdução de Sinais , Proteínas Smad Reguladas por Receptor/metabolismo , Angiotensina II/efeitos adversos , Angiotensina II/farmacologia , Animais , Proteínas de Transporte/genética , Colágeno Tipo I/biossíntese , Colágeno Tipo I/genética , Fibrose , Cardiopatias/induzido quimicamente , Cardiopatias/genética , Cardiopatias/metabolismo , Cardiopatias/patologia , Interleucina-18/genética , Interleucina-18/metabolismo , Interleucina-1beta/genética , Interleucina-1beta/metabolismo , Camundongos , Camundongos Knockout , Proteínas Mitocondriais/genética , Miocárdio/patologia , Miofibroblastos/patologia , Proteína 3 que Contém Domínio de Pirina da Família NLR , Proteínas Smad Reguladas por Receptor/genética , Fator de Crescimento Transformador beta/genética , Fator de Crescimento Transformador beta/metabolismo , Vasoconstritores/efeitos adversos , Vasoconstritores/farmacologia
14.
Am J Physiol Heart Circ Physiol ; 308(12): H1564-74, 2015 Jun 15.
Artigo em Inglês | MEDLINE | ID: mdl-25862829

RESUMO

Tetrandrine (TTD) is a calcium channel blocker with documented antifibrotic actions. In this study, for the first time, we identified that TTD can directly prevent in vitro human cardiac myofibroblast activation and limit in vivo myocardial fibrosis. In vitro, cardiac myofibroblasts from human atrial biopsies (N = 10) were seeded in three-dimensional collagen matrices. Cell-collagen constructs were exposed to transforming growth factor-ß1 (10 ng/ml), with or without TTD (1 and 5 µM) for 48 h. Collagen gel contraction, myofibroblast activation (α-smooth muscle actin expression), expression of profibrotic mRNAs, and rate of collagen protein synthesis were compared. TTD decreased collagen gel contraction (79.7 ± 1.3 vs 60.1 ± 8.9%, P < 0.01), α-smooth muscle actin expression (flow cytometry), collagen synthesis ([(3)H]proline incorporation), and collagen mRNA expression. Cell viability was similar between groups (annexin positive cells: 1.7 vs. 1.4%). TTD inhibited collagen gel contraction in the presence of T-type and L-type calcium channel blockers, and the intracellular calcium chelator BAPTA-AM (15 µM), suggesting that the observed effects are not mediated by calcium homeostasis. In vivo, Dahl salt-sensitive hypertensive rats were treated with variable doses of TTD (by intraperitoneal injection over 4 wk) and compared with untreated controls (N = 12). Systemic blood pressure was monitored by tail cuff. Myocardial fibrosis and left ventricular compliance were assessed by histology and passive pressure-volume analysis. Myocardial fibrosis was attenuated compared with untreated controls (%collagen area: 9.4 ± 7.3 vs 2.1 ± 1.0%, P < 0.01). Left ventricular compliance was preserved. In conclusion, TTD reverses human cardiac myofibroblast activation and myocardial fibrosis, independent of calcium channel blockade.


Assuntos
Apêndice Atrial/efeitos dos fármacos , Benzilisoquinolinas/farmacologia , Miofibroblastos/efeitos dos fármacos , Remodelação Ventricular/efeitos dos fármacos , Actinas/genética , Actinas/metabolismo , Animais , Apêndice Atrial/metabolismo , Apêndice Atrial/patologia , Cálcio/metabolismo , Bloqueadores dos Canais de Cálcio/farmacologia , Quelantes de Cálcio/farmacologia , Cardiomiopatias/metabolismo , Cardiomiopatias/patologia , Cardiomiopatias/fisiopatologia , Cardiomiopatias/prevenção & controle , Células Cultivadas , Colágeno/genética , Colágeno/metabolismo , Relação Dose-Resposta a Droga , Fibrose , Géis , Humanos , Hipertensão/tratamento farmacológico , Hipertensão/metabolismo , Hipertensão/patologia , Hipertensão/fisiopatologia , Masculino , Miofibroblastos/metabolismo , Miofibroblastos/patologia , Ratos Endogâmicos Dahl , Fatores de Tempo , Função Ventricular Esquerda/efeitos dos fármacos
15.
Circ Res ; 113(5): 517-26, 2013 Aug 16.
Artigo em Inglês | MEDLINE | ID: mdl-23856523

RESUMO

RATIONALE: Phospholamban (PLN) is an inhibitor of cardiac sarco(endo)plasmic reticulum Ca²âº ATPase. PLN knockout (PLN-KO) enhances sarcoplasmic reticulum Ca²âº load and Ca²âº leak. Conversely, PLN-KO accelerates Ca²âº sequestration and aborts arrhythmogenic spontaneous Ca²âº waves (SCWs). An important question is whether these seemingly paradoxical effects of PLN-KO exacerbate or protect against Ca²âº-triggered arrhythmias. OBJECTIVE: We investigate the impact of PLN-KO on SCWs, triggered activities, and stress-induced ventricular tachyarrhythmias (VTs) in a mouse model of cardiac ryanodine-receptor (RyR2)-linked catecholaminergic polymorphic VT. METHODS AND RESULTS: We generated a PLN-deficient, RyR2-mutant mouse model (PLN-/-/RyR2-R4496C+/-) by crossbreeding PLN-KO mice with catecholaminergic polymorphic VT-associated RyR2-R4496C mutant mice. Ca²âº imaging and patch-clamp recording revealed cell-wide propagating SCWs and triggered activities in RyR2-R4496C+/- ventricular myocytes during sarcoplasmic reticulum Ca²âº overload. PLN-KO fragmented these cell-wide SCWs into mini-waves and Ca²âº sparks and suppressed the triggered activities evoked by sarcoplasmic reticulum Ca²âº overload. Importantly, these effects of PLN-KO were reverted by partially inhibiting sarco(endo)plasmic reticulum Ca²âº ATPase with 2,5-di-tert-butylhydroquinone. However, Bay K, caffeine, or Li⁺ failed to convert mini-waves to cell-wide SCWs in PLN-/-/RyR2-R4496C+/- ventricular myocytes. Furthermore, ECG analysis showed that PLN-KO mice are not susceptible to stress-induced VTs. On the contrary, PLN-KO protected RyR2-R4496C mutant mice from stress-induced VTs. CONCLUSIONS: Our results demonstrate that despite severe sarcoplasmic reticulum Ca²âº leak, PLN-KO suppresses triggered activities and stress-induced VTs in a mouse model of catecholaminergic polymorphic VT. These data suggest that breaking up cell-wide propagating SCWs by enhancing Ca²âº sequestration represents an effective approach for suppressing Ca²âº-triggered arrhythmias.


Assuntos
Sinalização do Cálcio/fisiologia , Proteínas de Ligação ao Cálcio/deficiência , Taquicardia Ventricular/prevenção & controle , Éster Metílico do Ácido 3-Piridinacarboxílico, 1,4-Di-Hidro-2,6-Dimetil-5-Nitro-4-(2-(Trifluormetil)fenil)/farmacologia , Animais , Cafeína/farmacologia , Sinalização do Cálcio/efeitos dos fármacos , Proteínas de Ligação ao Cálcio/genética , Proteínas de Ligação ao Cálcio/fisiologia , ATPases Transportadoras de Cálcio/antagonistas & inibidores , Células Cultivadas/efeitos dos fármacos , Células Cultivadas/fisiologia , Modelos Animais de Doenças , Eletrocardiografia , Hidroquinonas/farmacologia , Isoproterenol/farmacologia , Cloreto de Lítio/farmacologia , Camundongos , Camundongos Knockout , Mutação de Sentido Incorreto , Miócitos Cardíacos/efeitos dos fármacos , Miócitos Cardíacos/enzimologia , Miócitos Cardíacos/fisiologia , Técnicas de Patch-Clamp , Canal de Liberação de Cálcio do Receptor de Rianodina/deficiência , Canal de Liberação de Cálcio do Receptor de Rianodina/genética , Canal de Liberação de Cálcio do Receptor de Rianodina/fisiologia , Retículo Sarcoplasmático/enzimologia , Retículo Sarcoplasmático/fisiologia , Taquicardia Ventricular/diagnóstico por imagem , Taquicardia Ventricular/fisiopatologia , Ultrassonografia
16.
J Immunol ; 190(3): 1239-49, 2013 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-23264657

RESUMO

Tubulointerstitial inflammation and fibrosis are strongly associated with the outcome of chronic kidney disease. We recently demonstrated that the NOD-like receptor, pyrin domain containing-3 (NLRP3) contributes to renal inflammation, injury, and fibrosis following unilateral ureteric obstruction in mice. NLRP3 expression in renal tubular epithelial cells (TECs) was found to be an important component of experimental disease pathogenesis, although the biology of NLRP3 in epithelial cells is unknown. In human and mouse primary renal TECs, NLRP3 expression was increased in response to TGF-ß1 stimulation and associated with epithelial-mesenchymal transition (EMT) and the expression of α-smooth muscle actin (αSMA) and matrix metalloproteinase (MMP) 9. TGF-ß1-induced EMT and the induction of MMP-9 and αSMA were significantly decreased in mouse Nlrp3(-/-) renal TECs, suggesting a role for Nlrp3 in TGF-ß-dependent signaling. Although apoptosis-associated speck-like protein containing a CARD domain(-/-) TECs demonstrated a phenotype similar to that of Nlrp3(-/-) cells in response to TGF-ß1, the effect of Nlrp3 on MMP-9 and αSMA expression was inflammasome independent, as IL-1ß, IL-18, MyD88, and caspase-1 were dispensable. Smad2 and Smad3 phosphorylation in response to TGF-ß1 was attenuated in Nlrp3(-/-) and apoptosis-associated speck-like protein containing a CARD domain(-/-) cells, accounting for the dampened EMT and TGF-ß1 responsiveness in these cells. Consistent with these findings, overexpression of NLRP3 in 293T cells resulted in increased Smad3 phosphorylation and activity. Taken together, these data support a novel and direct role for NLRP3 in promoting TGF-ß signaling and R-Smad activation in epithelial cells independent of the inflammasome.


Assuntos
Proteínas de Transporte/fisiologia , Células Epiteliais/imunologia , Transição Epitelial-Mesenquimal/fisiologia , Inflamassomos/fisiologia , Túbulos Renais Proximais/imunologia , Transdução de Sinais/imunologia , Fator de Crescimento Transformador beta1/fisiologia , Animais , Caspase 1/metabolismo , Células Cultivadas/efeitos dos fármacos , Células Cultivadas/metabolismo , Citocinas/metabolismo , Regulação da Expressão Gênica , Humanos , Interleucina-1beta/farmacologia , Túbulos Renais Proximais/metabolismo , Metaloproteinases da Matriz/biossíntese , Metaloproteinases da Matriz/genética , Camundongos , Camundongos Endogâmicos C57BL , Proteína 3 que Contém Domínio de Pirina da Família NLR , Nefrite Intersticial/imunologia , Nefrite Intersticial/patologia , Reação em Cadeia da Polimerase em Tempo Real , Proteínas Smad/metabolismo , Fator de Crescimento Transformador beta1/farmacologia
17.
BMC Cardiovasc Disord ; 14: 91, 2014 Jul 25.
Artigo em Inglês | MEDLINE | ID: mdl-25063541

RESUMO

BACKGROUND: Nationally, symptomatic heart failure affects 1.5-2% of Canadians, incurs $3 billion in hospital costs annually and the global burden is expected to double in the next 1-2 decades. The current one-year mortality rate after diagnosis of heart failure remains high at >25%. Consequently, new therapeutic strategies need to be developed for this debilitating condition. METHODS/DESIGN: The objective of the Alberta HEART program (http://albertaheartresearch.ca) is to develop novel diagnostic, therapeutic and prognostic approaches to patients with heart failure with preserved ejection fraction. We hypothesize that novel imaging techniques and biomarkers will aid in describing heart failure with preserved ejection fraction. Furthermore, the development of new diagnostic criteria will allow us to: 1) better define risk factors associated with heart failure with preserved ejection fraction; 2) elucidate clinical, cellular and molecular mechanisms involved with the development and progression of heart failure with preserved ejection fraction; 3) design and test new therapeutic strategies for patients with heart failure with preserved ejection fraction. Additionally, Alberta HEART provides training and education for enhancing translational medicine, knowledge translation and clinical practice in heart failure. This is a prospective observational cohort study of patients with, or at risk for, heart failure. Patients will have sequential testing including quality of life and clinical outcomes over 12 months. After that time, study participants will be passively followed via linkage to external administrative databases. Clinical outcomes of interest include death, hospitalization, emergency department visits, physician resource use and/or heart transplant. Patients will be followed for a total of 5 years. DISCUSSION: Alberta HEART has the primary objective to define new diagnostic criteria for patients with heart failure with preserved ejection fraction. New criteria will allow for targeted therapies, diagnostic tests and further understanding of the patients, both at-risk for and with heart failure. TRIAL REGISTRATION: ClinicalTrials.gov NCT02052804.


Assuntos
Diagnóstico por Imagem , Insuficiência Cardíaca/diagnóstico , Insuficiência Cardíaca/terapia , Projetos de Pesquisa , Alberta/epidemiologia , Biomarcadores/sangue , Diagnóstico por Imagem/métodos , Serviço Hospitalar de Emergência/estatística & dados numéricos , Recursos em Saúde/estatística & dados numéricos , Insuficiência Cardíaca/sangue , Insuficiência Cardíaca/etiologia , Insuficiência Cardíaca/mortalidade , Transplante de Coração/estatística & dados numéricos , Hospitalização , Humanos , Visita a Consultório Médico/estatística & dados numéricos , Valor Preditivo dos Testes , Estudos Prospectivos , Medição de Risco , Fatores de Risco , Volume Sistólico , Fatores de Tempo , Resultado do Tratamento , Função Ventricular Esquerda
18.
ACS Pharmacol Transl Sci ; 7(2): 515-532, 2024 Feb 09.
Artigo em Inglês | MEDLINE | ID: mdl-38357284

RESUMO

Currently, there are no FDA-approved medications for the treatment of psychostimulant use disorders (PSUD). We have previously discovered "atypical" dopamine transporter (DAT) inhibitors that do not display psychostimulant-like behaviors and may be useful as medications to treat PSUD. Lead candidates (e.g., JJC8-091, 1) have shown promising in vivo profiles in rodents; however, reducing hERG (human ether-à-go-go-related gene) activity, a predictor of cardiotoxicity, has remained a challenge. Herein, a series of 30 (([1,1'-biphenyl]-2-yl)methyl)sulfinylalkyl alicyclic amines was synthesized and evaluated for DAT and serotonin transporter (SERT) binding affinities. A subset of analogues was tested for hERG activity, and the IC50 values were compared to those predicted by our hERG QSAR models, which showed robust predictive power. Multiparameter optimization scores (MPO > 3) indicated central nervous system (CNS) penetrability. Finally, comparison of affinities in human DAT and its Y156F and Y335A mutants suggested that several compounds prefer an inward facing conformation indicating an atypical DAT inhibitor profile.

19.
Mol Metab ; 79: 101859, 2024 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-38142971

RESUMO

BACKGROUND: Dilated cardiomyopathy with ataxia (DCMA) is an autosomal recessive disorder arising from truncating mutations in DNAJC19, which encodes an inner mitochondrial membrane protein. Clinical features include an early onset, often life-threatening, cardiomyopathy associated with other metabolic features. Here, we aim to understand the metabolic and pathophysiological mechanisms of mutant DNAJC19 for the development of cardiomyopathy. METHODS: We generated induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs) of two affected siblings with DCMA and a gene-edited truncation variant (tv) of DNAJC19 which all lack the conserved DnaJ interaction domain. The mutant iPSC-CMs and their respective control cells were subjected to various analyses, including assessments of morphology, metabolic function, and physiological consequences such as Ca2+ kinetics, contractility, and arrhythmic potential. Validation of respiration analysis was done in a gene-edited HeLa cell line (DNAJC19tvHeLa). RESULTS: Structural analyses revealed mitochondrial fragmentation and abnormal cristae formation associated with an overall reduced mitochondrial protein expression in mutant iPSC-CMs. Morphological alterations were associated with higher oxygen consumption rates (OCRs) in all three mutant iPSC-CMs, indicating higher electron transport chain activity to meet cellular ATP demands. Additionally, increased extracellular acidification rates suggested an increase in overall metabolic flux, while radioactive tracer uptake studies revealed decreased fatty acid uptake and utilization of glucose. Mutant iPSC-CMs also showed increased reactive oxygen species (ROS) and an elevated mitochondrial membrane potential. Increased mitochondrial respiration with pyruvate and malate as substrates was observed in mutant DNAJC19tv HeLa cells in addition to an upregulation of respiratory chain complexes, while cellular ATP-levels remain the same. Moreover, mitochondrial alterations were associated with increased beating frequencies, elevated diastolic Ca2+ concentrations, reduced sarcomere shortening and an increased beat-to-beat rate variability in mutant cell lines in response to ß-adrenergic stimulation. CONCLUSIONS: Loss of the DnaJ domain disturbs cardiac mitochondrial structure with abnormal cristae formation and leads to mitochondrial dysfunction, suggesting that DNAJC19 plays an essential role in mitochondrial morphogenesis and biogenesis. Moreover, increased mitochondrial respiration, altered substrate utilization, increased ROS production and abnormal Ca2+ kinetics provide insights into the pathogenesis of DCMA-related cardiomyopathy.


Assuntos
Cardiomiopatia Dilatada , Ataxia Cerebelar , Células-Tronco Pluripotentes Induzidas , Maleatos , Erros Inatos do Metabolismo , Humanos , Trifosfato de Adenosina/metabolismo , Cardiomiopatia Dilatada/genética , Cardiomiopatia Dilatada/metabolismo , Cardiomiopatia Dilatada/patologia , Células HeLa , Células-Tronco Pluripotentes Induzidas/metabolismo , Mutação/genética , Miócitos Cardíacos/metabolismo , Espécies Reativas de Oxigênio/metabolismo , Respiração
20.
Exp Physiol ; 98(2): 462-72, 2013 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-22848083

RESUMO

Heart failure is associated with a low-grade and chronic cardiac inflammation that impairs function; however, the mechanisms by which this sterile inflammation occurs in structural heart disease remain poorly defined. Cardiac-specific heterozygous overexpression of the calcineurin transgene (CNTg) in mice results in cardiac hypertrophy, inflammation, apoptosis and ventricular dilatation. We hypothesized that activation of the Nlrp3 inflammasome, an intracellular danger-sensing pathway required for processing the pro-inflammatory cytokine interleukin-1ß (IL-1ß), may contribute to myocardial dysfunction and disease progression. Here we report that Nlrp3 mRNA was increased in CNTg mice compared with wild-type. Consistent with inflammasome activation, CNTg animals had increased conversion of pro-caspase-1 to cleaved and activated forms, as well as markedly increased serum IL-1ß. Blockade of IL-1ß signalling via chronic IL-1 receptor antagonist therapy reduced cardiac inflammation and myocyte pathology in CNTg mice, resulting in improved systolic performance. Furthermore, genetic ablation of Nlrp3 in CNTg mice reduced pro-inflammatory cytokine maturation and cardiac inflammation, as well as improving systolic performance. These findings indicate that activation of the Nlrp3 inflammasome in CNTg mice promotes myocardial inflammation and systolic dysfunction through the production of pro-inflammatory IL-1ß. Blockade of IL-1ß signalling with the IL-1 receptor antagonist reverses these phenotypes and offers a possible therapeutic approach in the management of heart failure.


Assuntos
Cardiomiopatias/imunologia , Proteínas de Transporte/metabolismo , Insuficiência Cardíaca/imunologia , Inflamassomos/metabolismo , Mediadores da Inflamação/metabolismo , Interleucina-1beta/metabolismo , Miocardite/imunologia , Miocárdio/imunologia , Animais , Calcineurina/genética , Calcineurina/metabolismo , Cardiomiopatias/tratamento farmacológico , Cardiomiopatias/genética , Cardiomiopatias/patologia , Cardiomiopatias/fisiopatologia , Proteínas de Transporte/genética , Caspase 1/metabolismo , Modelos Animais de Doenças , Ativação Enzimática , Precursores Enzimáticos , Insuficiência Cardíaca/genética , Insuficiência Cardíaca/patologia , Insuficiência Cardíaca/fisiopatologia , Insuficiência Cardíaca/prevenção & controle , Inflamassomos/deficiência , Inflamassomos/genética , Mediadores da Inflamação/sangue , Proteína Antagonista do Receptor de Interleucina 1/farmacologia , Interleucina-1beta/sangue , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Camundongos Transgênicos , Miocardite/genética , Miocardite/patologia , Miocardite/fisiopatologia , Miocardite/prevenção & controle , Miocárdio/patologia , Células NIH 3T3 , Proteína 3 que Contém Domínio de Pirina da Família NLR , Receptores de Interleucina-1/antagonistas & inibidores , Receptores de Interleucina-1/metabolismo , Recuperação de Função Fisiológica , Transdução de Sinais , Sístole , Fatores de Tempo , Função Ventricular Esquerda
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