RESUMO
RATIONALE: Posttranslational phosphorylation of connexin43 (Cx43) has been proposed as a key regulatory event in normal cardiac gap junction expression and pathological gap junction remodeling. Nonetheless, the role of Cx43 phosphorylation in the context of the intact organism is poorly understood. OBJECTIVE: To establish whether specific Cx43 phosphorylation events influence gap junction expression and pathological remodeling. METHODS AND RESULTS: We generated Cx43 germline knock-in mice in which serines 325/328/330 were replaced with phosphomimetic glutamic acids (S3E) or nonphosphorylatable alanines (S3A). The S3E mice were resistant to acute and chronic pathological gap junction remodeling and displayed diminished susceptibility to the induction of ventricular arrhythmias. Conversely, the S3A mice showed deleterious effects on cardiac gap junction formation and function, developed electric remodeling, and were highly susceptible to inducible arrhythmias. CONCLUSIONS: These data demonstrate a mechanistic link between posttranslational phosphorylation of Cx43 and gap junction formation, remodeling, and arrhythmic susceptibility.
Assuntos
Arritmias Cardíacas/metabolismo , Conexina 43/metabolismo , Junções Comunicantes/metabolismo , Animais , Arritmias Cardíacas/genética , Arritmias Cardíacas/patologia , Conexina 43/genética , Junções Comunicantes/patologia , Camundongos , Camundongos Mutantes , Fosforilação/genéticaRESUMO
Sudden cardiac death is responsible for several hundred thousand deaths each year in the United States. Multiple lines of evidence suggest that perturbation of gap junction expression and function in the heart, or what has come to be known as cardiac gap junction remodeling, plays a key mechanistic role in the pathophysiology of clinically significant cardiac arrhythmias. Here we review recent studies from our laboratory using genetically engineered murine models to explore mechanisms implicated in pathologic gap junction remodeling and their proarrhythmic consequences, with a particular focus on aberrant posttranslational phosphorylation of connexin43.
Assuntos
Conexina 43/metabolismo , Junções Comunicantes/metabolismo , Animais , Animais Geneticamente Modificados , Arritmias Cardíacas/metabolismo , Humanos , Camundongos , Fosforilação , Processamento de Proteína Pós-TraducionalRESUMO
BACKGROUND: Innervation is a critical component of arrhythmogenesis and may present an important trigger/substrate modifier not used in current ventricular tachycardia (VT) ablation strategies. METHODS AND RESULTS: Fifteen patients referred for ischemic VT ablation underwent preprocedural cardiac (123)I- meta-iodobenzylguanidine ((123)I-mIBG) imaging, which was used to create 3-dimensional (3D) innervation models and registered to high-density voltage maps. 3D (123)I-mIBG innervation maps demonstrated areas of complete denervation and (123)I-mIBG transition zone in all patients, which corresponded to 0% to 31% and 32% to 52% uptake. (123)I-mIBG denervated areas were ≈2.5-fold larger than bipolar voltage-defined scar (median, 24.6% [Q1-Q3, 18.3%-34.4%] versus 10.6% [Q1-Q3, 3.9%-16.4%]; P<0.001) and included the inferior wall in all patients, with no difference in the transition/border zone (11.4% [Q1-Q3, 9.5%-13.2%] versus 16.6% [Q1-Q3, 12.0%-18.8%]; P=0.07). Bipolar/unipolar voltages varied widely within areas of denervation (0.8 mV [Q1-Q3, 0.3-1.7 mV] and 4.0 mV [Q1-Q3, 2.9-5.6 mV]) and (123)I-mIBG transition zones (0.8 mV [Q1-Q3, 0.4-1.8 mV] and 4.6 mV [Q1-Q3, 3.2-6.3 mV]). Bipolar voltages in denervated areas and (123)I-mIBG transition zones were <0.5 mV, 0.5 to 1.5 mV, and >1.5 mV in 35%, 36%, and 29%, as well as 35%, 35%, and 30%, respectively (P>0.05). Successful ablation sites were within bipolar voltage-defined scar (7%), border zone (57%), and areas of normal voltage (36%), but all ablation sites were abnormally innervated (denervation/(123)I-mIBG transition zone in 50% each). CONCLUSIONS: (123)I-mIBG innervation defects are larger than bipolar voltage-defined scar and cannot be detected with standard voltage criteria. Thirty-six percent of successful VT ablation sites demonstrated normal voltages (>1.5 mV), but all ablation sites were within the areas of abnormal innervation. (123)I-mIBG innervation maps may provide critical information about triggers/substrate modifiers and could improve understanding of VT substrate and facilitate VT ablation. CLINICAL TRIAL REGISTRATION: URL: http://www.clinicaltrials.gov. Unique Identifier: NCT01250912.
Assuntos
3-Iodobenzilguanidina , Ablação por Cateter , Ventrículos do Coração , Interpretação de Imagem Assistida por Computador , Imageamento Tridimensional , Compostos Radiofarmacêuticos , Sistema Nervoso Simpático/diagnóstico por imagem , Taquicardia Ventricular/diagnóstico por imagem , Taquicardia Ventricular/cirurgia , Potenciais de Ação , Idoso , Algoritmos , Baltimore , Ablação por Cateter/efeitos adversos , Técnicas Eletrofisiológicas Cardíacas , Estudos de Viabilidade , Feminino , Ventrículos do Coração/diagnóstico por imagem , Ventrículos do Coração/inervação , Ventrículos do Coração/cirurgia , Humanos , Masculino , Pessoa de Meia-Idade , Valor Preditivo dos Testes , Estudos Prospectivos , Cintilografia , Sistema Nervoso Simpático/fisiopatologia , Taquicardia Ventricular/fisiopatologia , Resultado do TratamentoRESUMO
Carboxylesterases are a broad class of enzymes important in the detoxification of many ester- or amide-bond containing xenobiotics. They also activate analgesics, anticancer prodrugs, and other biologically active compounds, such as cocaine and heroin. The objective of this work was to identify the CES2 gene structure, complex 5' untranslated regions and three potential promoters for the initiation of transcription in different human tissues. Using bioinformatics and progressive reverse transcriptase-polymerase chain reaction, we found that the 5' untranslated region is more than 1100 bases longer than previously reported. Rapid amplification of cDNA ends showed three distinctive transcription start sites at -74, -629 and -1187. DNA fragments upstream of each of the three transcription start sites were found to be transcriptionally active in HepG2 cells. The distal promoter is active in both orientations, suggesting its potential role in the transcription of another gene, CGI-128, located immediately upstream to the distal promoter in the opposite direction with respect to CES2. Hybridization analyses showed that CES2 is highly expressed in the heart, skeletal muscle, colon, spleen, kidney and liver, but considerably less expressed in fetal tissues (e.g. fetal heart, kidney, spleen, and liver) and cancer cells. It is also evident that the distal promoter is responsible for low level expression of the gene in many tissues, whereas the other two promoters are tissue specific. These findings shed some light on CES2 gene regulation, a gene important in the metabolism of many drugs.
Assuntos
Carboxilesterase/genética , Regiões Promotoras Genéticas , Regiões 5' não Traduzidas/química , Sequência de Aminoácidos , Sequência de Bases , Sítios de Ligação , Carboxilesterase/química , Carcinoma Hepatocelular/genética , Carcinoma Hepatocelular/metabolismo , Linhagem Celular Tumoral , Cromossomos Humanos Par 16 , Biologia Computacional , Éxons , Regulação Enzimológica da Expressão Gênica , Humanos , Íntrons , Dados de Sequência Molecular , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Homologia de Sequência de Aminoácidos , Distribuição Tecidual , Fatores de Transcrição/metabolismo , Sítio de Iniciação de Transcrição , Transcrição GênicaRESUMO
BACKGROUND: Modulation of the autonomic nervous system has been used to treat refractory ventricular tachycardia (VT). Renal artery denervation (RDN) is under investigation for the treatment of sympathetic-driven cardiovascular diseases. OBJECTIVE: The purpose of this study was to report the largest case series to date using RDN as adjunctive therapy for refractory VT in patients with underlying cardiomyopathy. METHODS: Four patients with cardiomyopathy (2 nonischemic, 2 ischemic) with recurrent VT despite maximized antiarrhythmic therapy and prior endocardial (n = 2) or endocardial/epicardial (n = 2) ablation underwent RDN ± repeat VT ablation. RDN was performed spirally along each main renal artery with either a nonirrigated (6 W at 50°C for 60 seconds) or an open irrigated ablation catheter (10-12 W for 30-60 seconds). Renal arteriography was performed before and after RDN. RESULTS: RDN was well tolerated acutely and demonstrated no clinically significant complications during follow-up of 8.8 ± 2.6 months (range 5.0-11.0 months). No hemodynamic deterioration or worsening of renal function was observed. The number of VT episodes was decreased from 11.0 ± 4.2 (5.0-14.0) during the month before ablation to 0.3 ± 0.1 (0.2-0.4) per month after ablation. All VT episodes occurred in the first 4 months after ablation (2.6 ± 1.5 months). The responses to RDN were similar for ischemic and nonischemic patients. CONCLUSION: This case series provides promising preliminary data on the safety and effectiveness of RDN as an adjunctive therapy in the treatment of patients with cardiomyopathy and VT resistant to standard interventions.
Assuntos
Denervação Autônoma , Cardiomiopatias/complicações , Rim/inervação , Taquicardia Ventricular/cirurgia , Idoso de 80 Anos ou mais , Denervação Autônoma/métodos , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Resultado do TratamentoRESUMO
The FOG family of transcriptional co-factors is composed of two members in mammals: FOG-1 and FOG-2. Both have been shown to bind to GATA factors and function as transcriptional co-repressors in specific cell and promoter contexts. We have previously defined a novel repression domain localized to the N-terminus of each FOG family member, the FOG repression motif, which is necessary for FOG-mediated transcriptional repression. In this report, we describe the identification and characterization of a novel isoform of FOG-2 lacking the FOG repression motif. In contrast to full-length FOG-2, this isoform is expressed predominately in the embryonic and adult heart. It can bind GATA4 avidly, but is unable to repress GATA4-mediated activation of cardiac-restricted gene promoters. Together, these results suggest that FOG-2 repressive activity may be modulated by the generation of isoforms of FOG-2 lacking the FOG repression motif.