RESUMO
Purkinje-related ventricular arrhythmias have been increasingly reported, and with the development of catheter ablation techniques, intervention for Purkinje-related arrhythmias has been shown to be effective. The characteristics of Purkinje fibres orientation in the 12 canine left ventricles were observed at a gross level by staining the endocardium with Lugol's solution. Purkinje fibres were observed microscopically by HE, Masson's, PAS glycogen, and Cx40 immunohistochemical staining. Staining was successful, and the transverse orientation characteristics of Purkinje fibres were observed by Lugol's staining, and the longitudinal distribution was observed microscopically. The distribution of Purkinje fibres in the canine left ventricle is 'graded', 'layered', and 'networked', which can guide catheter ablation of Purkinje-related ventricular arrhythmia.
Assuntos
Ventrículos do Coração , Ramos Subendocárdicos , Animais , Cães , Ventrículos do Coração/metabolismo , Conexinas/metabolismo , Conexinas/genética , Masculino , Proteína alfa-5 de Junções Comunicantes , FemininoRESUMO
Omecamtiv mecarbil (OM) is a small molecule that has been shown to improve the function of the slow human ventricular myosin (MyHC) motor through a complex perturbation of the thin/thick filament regulatory state of the sarcomere mediated by binding to myosin allosteric sites coupled to inorganic phosphate (Pi) release. Here, myofibrils from samples of human left ventricle (ß-slow MyHC-7) and left atrium (α-fast MyHC-6) from healthy donors were used to study the differential effects of µmolar [OM] on isometric force in relaxing conditions (pCa 9.0) and at maximal (pCa 4.5) or half-maximal (pCa 5.75) calcium activation, both under control conditions (15 °C; equimolar DMSO; contaminant inorganic phosphate [Pi] ~170 µM) and in the presence of 5 mM [Pi]. The activation state and OM concentration within the contractile lattice were rapidly altered by fast solution switching, demonstrating that the effect of OM was rapid and fully reversible with dose-dependent and myosin isoform-dependent features. In MyHC-7 ventricular myofibrils, OM increased submaximal and maximal Ca2+-activated isometric force with a complex dose-dependent effect peaking (40% increase) at 0.5 µM, whereas in MyHC-6 atrial myofibrils, it had no effect or-at concentrations above 5 µM-decreased the maximum Ca2+-activated force. In both ventricular and atrial myofibrils, OM strongly depressed the kinetics of force development and relaxation up to 90% at 10 µM [OM] and reduced the inhibition of force by inorganic phosphate. Interestingly, in the ventricle, but not in the atrium, OM induced a large dose-dependent Ca2+-independent force development and an increase in basal ATPase that were abolished by the presence of millimolar inorganic phosphate, consistent with the hypothesis that the widely reported Ca2+-sensitising effect of OM may be coupled to a change in the state of the thick filaments that resembles the on-off regulation of thin filaments by Ca2+. The complexity of this scenario may help to understand the disappointing results of clinical trials testing OM as inotropic support in systolic heart failure compared with currently available inotropic drugs that alter the calcium signalling cascade.
Assuntos
Contração Miocárdica , Miofibrilas , Ureia , Humanos , Ureia/análogos & derivados , Ureia/farmacologia , Miofibrilas/metabolismo , Miofibrilas/efeitos dos fármacos , Contração Miocárdica/efeitos dos fármacos , Cálcio/metabolismo , Miocárdio/metabolismo , Isoformas de Proteínas/metabolismo , Miosinas/metabolismo , Ventrículos do Coração/efeitos dos fármacos , Ventrículos do Coração/metabolismo , Masculino , Miosinas Cardíacas/metabolismo , Feminino , AdultoRESUMO
PRDM16 is a transcription factor with histone methyltransferase activity expressed at the earliest stages of cardiac development. Pathogenic mutations in humans lead to cardiomyopathy, conduction abnormalities, and heart failure. PRDM16 is specifically expressed in ventricular but not atrial cardiomyocytes, and its expression declines postnatally. Because in other tissues PRDM16 is best known for its role in binary cell fate decisions, we hypothesized a similar decision-making function in cardiomyocytes. Here, we demonstrated that cardiomyocyte-specific deletion of Prdm16 during cardiac development results in contractile dysfunction and abnormal electrophysiology of the postnatal heart, resulting in premature death. By combined RNA+ATAC single-cell sequencing, we found that PRDM16 favors ventricular working cardiomyocyte identity, by opposing the activity of master regulators of ventricular conduction and atrial fate. Myocardial loss of PRDM16 during development resulted in hyperplasia of the (distal) ventricular conduction system. Hence, PRDM16 plays an indispensable role during cardiac development by driving ventricular working cardiomyocyte identity.
Assuntos
Diferenciação Celular , Proteínas de Ligação a DNA , Ventrículos do Coração , Miócitos Cardíacos , Fatores de Transcrição , Animais , Camundongos , Diferenciação Celular/genética , Linhagem da Célula/genética , Proteínas de Ligação a DNA/metabolismo , Proteínas de Ligação a DNA/genética , Regulação da Expressão Gênica no Desenvolvimento/genética , Ventrículos do Coração/metabolismo , Ventrículos do Coração/citologia , Camundongos Knockout , Miócitos Cardíacos/metabolismo , Miócitos Cardíacos/citologia , Análise de Célula Única , Fatores de Transcrição/metabolismo , Fatores de Transcrição/genética , Masculino , FemininoRESUMO
Right ventricular dysfunction is a key clinical issue for the viability of donation-after-circulatory-death (DCD) heart transplantation. DCD hearts with volume overload have the potential to exhibit aggravated right ventricular dysfunction following heart transplantation. The c-jun/c-fos mRNAs are genes that immediately respond to myocardial cell stretch. We assessed myocardial cell stretch during asphyxia-induced cardiac arrest by measuring c-jun/c-fos mRNA expression levels. The trachea was dissected and ligated to initiate asphyxiation in anesthetized Wistar rats under paralyzed ventilation. The hearts were harvested at 4 time points: 0, 15, 30, and 45 minutes after the termination of ventilation. Free walls of the right and left ventricles and the interventricular septum were sectioned. Total RNA was extracted from these tissues, and cDNA was synthesized using reverse transcription. The c-jun/c-fos mRNA expression levels were quantified using the droplet digital polymerase chain reaction method. In the left ventricle, c-jun/c-fos expression levels rapidly increased at 15 minutes, but the expression levels returned to the baseline level at 30 minutes after tracheal ligation. In contrast, in the right ventricle, c-jun/c-fos expression levels gradually increased and peaked 30 minutes after tracheal ligation. Myocardial cell stretching in the right ventricle is prolonged after asphyxia-induced cardiac arrest compared to that in the left ventricle, which may lead to right ventricular dysfunction after DCD heart transplantation.
Assuntos
Asfixia , Parada Cardíaca , Proteínas Proto-Oncogênicas c-fos , RNA Mensageiro , Animais , Masculino , Ratos , Asfixia/complicações , Asfixia/metabolismo , Modelos Animais de Doenças , Parada Cardíaca/metabolismo , Parada Cardíaca/genética , Transplante de Coração , Ventrículos do Coração/metabolismo , Ventrículos do Coração/fisiopatologia , Miocárdio/metabolismo , Proteínas Proto-Oncogênicas c-fos/metabolismo , Proteínas Proto-Oncogênicas c-fos/genética , Proteínas Proto-Oncogênicas c-jun/metabolismo , Proteínas Proto-Oncogênicas c-jun/genética , Ratos Wistar , RNA Mensageiro/metabolismo , RNA Mensageiro/genéticaRESUMO
Tissues undergo distinct morphogenetic processes to achieve similarly shaped structures. In the heart, cardiomyocytes in both the ventricle and atrium build internal structures for efficient contraction. Ventricular wall formation (trabeculation) is initiated by cardiomyocyte delamination. How cardiomyocytes build the atrial wall is poorly understood. Using longitudinal imaging in zebrafish, we found that at least 25% of the atrial cardiomyocytes elongate along the long axis of the heart. These cell shape changes result in cell intercalation and convergent thickening, leading to the formation of the internal muscle network. We tested factors important for ventricular trabeculation including Nrg/ErbB and Notch signaling and found no evidence for their role in atrial muscle network formation. Instead, our data suggest that atrial cardiomyocyte elongation is regulated by Yap, which has not been implicated in trabeculation. Altogether, these data indicate that distinct cellular and molecular mechanisms build the internal muscle structures in the atrium and ventricle.
Assuntos
Átrios do Coração , Ventrículos do Coração , Miócitos Cardíacos , Proteínas de Peixe-Zebra , Peixe-Zebra , Animais , Átrios do Coração/metabolismo , Átrios do Coração/citologia , Miócitos Cardíacos/metabolismo , Miócitos Cardíacos/citologia , Ventrículos do Coração/metabolismo , Ventrículos do Coração/citologia , Proteínas de Peixe-Zebra/metabolismo , Proteínas de Peixe-Zebra/genética , Transdução de Sinais , Forma Celular , Animais Geneticamente Modificados , Regulação da Expressão Gênica no Desenvolvimento , Morfogênese , Receptores Notch/metabolismoRESUMO
In rats decreased bioavailability of nitric oxide induces oxidative stress and right heart failure. Oxidative stress can activate matrix metalloproteinase-2 (MMP2). We addressed the question whether increasing oxidative defense by administration of the SOD mimetic Tempol or direct inhibition of MMP2 activity by SB-3CT mitigates right heart failure. Rats received l-NAME for four weeks and during week three and four treatment groups received either Tempol or SB-3CT in addition. After four weeks heart function was analyzed by echocardiography, organ weights and expression of NPPB and COL1A1 were analyzed, oxidative stress was monitored by DHE-staining and MMP2 activity was quantified by proteolytic auto-activation, zymography, and troponin I degradation. l-NAME induced oxidative stress and MMP2 activity stronger in the right ventricle than in the left ventricle. Troponin I, a MMP2 substrate, was degraded in right ventricles. Tempol reduced oxidative stress and preferentially affected the expression of fibrotic genes (i.e. COL1A1) and fibrosis. Tempol and SB-3CT mitigated right but not left ventricular hypertrophy. Neither SB-3CT nor Tempol alone strongly improved right ventricular function. In conclusion, both MMP2 activity and oxidative stress contribute to right ventricular failure but neither is MMP2 activation linked to oxidative stress nor does oxidative stress and MMP2 activity have common targets.
Assuntos
Óxidos N-Cíclicos , Insuficiência Cardíaca , Metaloproteinase 2 da Matriz , NG-Nitroarginina Metil Éster , Estresse Oxidativo , Marcadores de Spin , Animais , Metaloproteinase 2 da Matriz/metabolismo , Metaloproteinase 2 da Matriz/genética , Ratos , Insuficiência Cardíaca/tratamento farmacológico , Insuficiência Cardíaca/metabolismo , Insuficiência Cardíaca/induzido quimicamente , Insuficiência Cardíaca/patologia , Estresse Oxidativo/efeitos dos fármacos , Óxidos N-Cíclicos/farmacologia , NG-Nitroarginina Metil Éster/farmacologia , Masculino , Colágeno Tipo I/metabolismo , Fibrose , Cadeia alfa 1 do Colágeno Tipo I , Ventrículos do Coração/efeitos dos fármacos , Ventrículos do Coração/metabolismo , Troponina I/metabolismo , Inibidores de Metaloproteinases de Matriz/farmacologia , Modelos Animais de Doenças , Compostos Heterocíclicos com 1 Anel , SulfonasRESUMO
Objective. Myocardial fibrosis is a devastating condition causing millions of deaths yearly. Several factors, such as aging, cause myocardial fibrosis. The Wnt/ß-catenin pathway is one of the critical intracellular signaling for the development of cardiac fibrosis. Molecular and cellular mechanism of myocardial fibrosis induced by intensive exercise is not well-understood. The current study evaluates the effects of short- and long-term intensive exercise on the Wnt1 gene expression in a heart left ventricle in an animal model. Methods. Twenty-one male Wistar rats (mean weight 250±50 g) were divided into three groups (n=7): 1) control group (C); 2) short-term regular intensive exercise group (S-RIE, high-intensity exercise for one month six days weekly for 60 min with speed of 35 m/min), and 3) long-term regular intensive exercise group (L-RIE, high-intensity exercise for six months six days daily for 60 min with speed of 35 m/min). The heart left ventricle was isolated at the end of the experiment, and the relative gene expression of the Wnt1 gene was measured by the Real-Time PCR. Results. The L-RIE group showed a significant increase in the Wnt1 expression compared to the S-RIE and the control group. Although no difference was observed in the Wnt1 mRNA level in the S-RIE group compared to the control group, Wnt1 mRNA level increased in the L-RIE group compared to the S-RIE group. Conclusion. The exercise duration was of a great importance in the Wnt1 gene expression. Regular intensive exercise may be involved in the formation of the myocardial fibrosis by increasing the expression of the Wnt1 gene.
Assuntos
Ventrículos do Coração , Condicionamento Físico Animal , Ratos Wistar , Proteína Wnt1 , Proteína Wnt1/genética , Proteína Wnt1/metabolismo , Animais , Masculino , Ventrículos do Coração/metabolismo , Condicionamento Físico Animal/fisiologia , Ratos , Expressão Gênica , Fatores de Tempo , FibroseRESUMO
The molecular mechanisms of progressive right heart failure are incompletely understood. In this study, we systematically examined transcriptomic changes occurring over months in isolated cardiomyocytes or whole heart tissues from failing right and left ventricles in rat models of pulmonary artery banding (PAB) or aortic banding (AOB). Detailed bioinformatics analyses resulted in the identification of gene signature, protein and transcription factor networks specific to ventricles and compensated or decompensated disease states. Proteomic and RNA-FISH analyses confirmed PAB-mediated regulation of key genes and revealed spatially heterogeneous mRNA expression in the heart. Intersection of rat PAB-specific gene sets with transcriptome datasets from human patients with chronic thromboembolic pulmonary hypertension (CTEPH) led to the identification of more than 50 genes whose expression levels correlated with the severity of right heart disease, including multiple matrix-regulating and secreted factors. These data define a conserved, differentially regulated genetic network associated with right heart failure in rats and humans.
Assuntos
Insuficiência Cardíaca , Ventrículos do Coração , Animais , Humanos , Insuficiência Cardíaca/genética , Insuficiência Cardíaca/metabolismo , Ventrículos do Coração/metabolismo , Ratos , Modelos Animais de Doenças , Transcriptoma , Masculino , Perfilação da Expressão Gênica , Miócitos Cardíacos/metabolismo , Redes Reguladoras de Genes , Ratos Sprague-Dawley , Hipertensão Pulmonar/genética , Proteômica , Disfunção Ventricular Direita/genética , Disfunção Ventricular Direita/fisiopatologiaRESUMO
BACKGROUND: Cardiovascular disease remains one of the leading causes of death globally. Myocardial ischemia and infarction, in particular, frequently cause disturbances in cardiac electrical activity that can trigger ventricular arrhythmias. We aimed to investigate whether catestatin, an endogenous catecholamine-inhibiting peptide, ameliorates myocardial ischemia-induced ventricular arrhythmias in rats and the underlying ionic mechanisms. METHODS AND RESULTS: Adult male Sprague-Dawley rats were randomly divided into control and catestatin groups. Ventricular arrhythmias were induced by ligation of the left anterior descending coronary artery and electrical stimulation. Action potential, transient outward potassium current, delayed rectifier potassium current, inward rectifying potassium current, and L-type calcium current (ICa-L) of rat ventricular myocytes were recorded using a patch-clamp technique. Catestatin notably reduced ventricular arrhythmia caused by myocardial ischemia/reperfusion and electrical stimulation of rats. In ventricular myocytes, catestatin markedly shortened the action potential duration of ventricular myocytes, which was counteracted by potassium channel antagonists TEACl and 4-AP, and ICa-L current channel agonist Bay K8644. In addition, catestatin significantly increased transient outward potassium current, delayed rectifier potassium current, and inward rectifying potassium current density in a concentration-dependent manner. Catestatin accelerated the activation and decelerated the inactivation of the transient outward potassium current channel. Furthermore, catestatin decreased ICa-L current density in a concentration-dependent manner. Catestatin also accelerated the inactivation of the ICa-L channel and slowed down the recovery of ICa-L from inactivation. CONCLUSIONS: Catestatin enhances the activity of transient outward potassium current, delayed rectifier potassium current, and inward rectifying potassium current, while suppressing the ICa-L in ventricular myocytes, leading to shortened action potential duration and ultimately reducing the ventricular arrhythmia in rats.
Assuntos
Potenciais de Ação , Cromogranina A , Miócitos Cardíacos , Fragmentos de Peptídeos , Ratos Sprague-Dawley , Animais , Masculino , Miócitos Cardíacos/efeitos dos fármacos , Miócitos Cardíacos/metabolismo , Cromogranina A/farmacologia , Cromogranina A/metabolismo , Potenciais de Ação/efeitos dos fármacos , Fragmentos de Peptídeos/farmacologia , Canais de Cálcio Tipo L/metabolismo , Canais de Cálcio Tipo L/efeitos dos fármacos , Arritmias Cardíacas/fisiopatologia , Arritmias Cardíacas/prevenção & controle , Arritmias Cardíacas/metabolismo , Antiarrítmicos/farmacologia , Ventrículos do Coração/efeitos dos fármacos , Ventrículos do Coração/metabolismo , Ventrículos do Coração/fisiopatologia , Canais de Potássio Corretores do Fluxo de Internalização/metabolismo , Canais de Potássio Corretores do Fluxo de Internalização/efeitos dos fármacos , Modelos Animais de Doenças , Bloqueadores dos Canais de Potássio/farmacologia , Ratos , Técnicas de Patch-Clamp , Canais de Potássio de Retificação Tardia/metabolismo , Canais de Potássio de Retificação Tardia/efeitos dos fármacos , Canais de Potássio/metabolismo , Canais de Potássio/efeitos dos fármacosRESUMO
Unlike humans and other mammals, zebrafish demonstrate a remarkable capacity to regenerate their injured hearts throughout life. Mitochondrial fatty acid ß-oxidation (FAO) contributes to major energy demands of the adult hearts under physiological conditions; however, its functions in regulating cardiac regeneration and the underlying mechanisms are not completely understood. Different strategies targeting FAO have yield mixed outcomes. Here, we demonstrated that pharmacological inhibition of mitochondrial FAO with mildronate (MD) caused lipid accumulation in zebrafish larvae and suppressed ventricle regeneration. MD treatment impeded cardiogenic factor reactivation and cardiomyocyte (CM) proliferation, and impaired ventricle regeneration could be rescued by exogenous l-carnitine supplementation. Moreover, compared with the ablated hearts of wild-type fish, ventricle regeneration, cardiogenic factor reactivation and CM proliferation were significantly blocked in the ablated hearts of carnitine palmitoyltransferase-1b (cpt1b) knockout zebrafish. Further experiments suggested that NF-κB signaling and increased inflammation may be involved in the impediment of ventricle regeneration caused by systemic mitochondrial FAO inhibition. Overall, our study demonstrates the essential roles of mitochondrial FAO in zebrafish ventricle regeneration and reaffirms the sophisticated and multifaceted roles of FAO in heart regeneration with regard to different injury models and means of FAO inhibition.
Assuntos
Ácidos Graxos , Ventrículos do Coração , Oxirredução , Regeneração , Peixe-Zebra , Animais , Carnitina O-Palmitoiltransferase/genética , Carnitina O-Palmitoiltransferase/metabolismo , Proliferação de Células/efeitos dos fármacos , Ácidos Graxos/metabolismo , Ventrículos do Coração/metabolismo , Ventrículos do Coração/efeitos dos fármacos , Metilidrazinas/farmacologia , Mitocôndrias/metabolismo , Mitocôndrias/efeitos dos fármacos , Miócitos Cardíacos/metabolismo , Miócitos Cardíacos/efeitos dos fármacos , NF-kappa B/metabolismo , Oxirredução/efeitos dos fármacos , Regeneração/efeitos dos fármacos , Transdução de Sinais/efeitos dos fármacos , Proteínas de Peixe-Zebra/genética , Proteínas de Peixe-Zebra/metabolismoRESUMO
The Renin-Angiotensin-Aldosterone System (RAAS) has been implicated in systemic and neurogenic hypertension. The infusion of RAAS inhibitors blunted arterial pressure and efficacy of use-dependent synaptic transmission in sympathetic ganglia. The current investigation aims to elucidate the impact of RAAS-mediated receptors on left ventricular cardiomyocytes and the role of the sarcolemma-bound carrier system in the heart of the hypertensive transgene model. A significant increase in mRNA and the protein expression for angiotensin II (AngII) receptor subtype-1 (AT1R) was observed in (mREN2)27 transgenic compared to the normotensive rodents. Concurrently, there was an upregulation in AT1R and a downregulation in the MAS1 proto-oncogene protein receptor as well as the AngII subtype-2 receptor in hypertensive rodents. There were modifications in the expressions of sarcolemma Na+-K+-ATPase, Na+-Ca2+ exchanger, and Sarcoendoplasmic Reticulum Calcium ATPase in the transgenic hypertensive model. These observations suggest chronic RAAS activation led to a shift in receptor balance favoring augmented cardiac contractility and disruption in calcium handling through modifications of membrane-bound carrier proteins and blood pressure. The study provides insight into mechanisms underlying RAAS-mediated cardiac dysfunction and highlights the potential value of targeting the protective arm of AngII in hypertension.
Assuntos
Ventrículos do Coração , Hipertensão , Sistema Renina-Angiotensina , Animais , Hipertensão/metabolismo , Ventrículos do Coração/metabolismo , Miócitos Cardíacos/metabolismo , Receptor Tipo 1 de Angiotensina/metabolismo , Receptor Tipo 1 de Angiotensina/genética , Ratos , Proto-Oncogene Mas , Pressão Sanguínea , Masculino , Camundongos , Receptor Tipo 2 de Angiotensina/metabolismo , Receptor Tipo 2 de Angiotensina/genética , Sarcolema/metabolismo , ATPase Trocadora de Sódio-Potássio/metabolismo , ATPase Trocadora de Sódio-Potássio/genética , Trocador de Sódio e Cálcio/metabolismo , Trocador de Sódio e Cálcio/genética , Camundongos TransgênicosRESUMO
The goal of this study was to evaluate the intensity of autophagy and ubiquitin-dependent proteolysis processes occurring in myocardium of left ventricle (LV) in subsequent stages of pulmonary arterial hypertension (PAH) to determine mechanisms responsible for LV mass loss in a monocrotaline-induced PAH rat model. LV myocardium samples collected from 32 Wistar rats were analyzed in an early PAH group (n = 8), controls time-paired (n = 8), an end-stage PAH group (n = 8), and their controls (n = 8). Samples were subjected to histological analyses with immunofluorescence staining, autophagy assessment by western blotting, and evaluation of ubiquitin-dependent proteolysis in the LV by immunoprecipitation of ubiquitinated proteins. Echocardiographic, hemodynamic, and heart morphometric parameters were assessed regularly throughout the experiment. Considerable morphological and hemodynamic remodeling of the LV was observed over the course of PAH. The end-stage PAH was associated with significantly impaired LV systolic function and a decrease in LV mass. The LC3B-II expression in the LV was significantly higher in the end-stage PAH group compared to the early PAH group (p = 0.040). The measured LC3B-II/LC3B-I ratios in the end-stage PAH group were significantly elevated compared to the controls (p = 0.039). Immunofluorescence staining showed a significant increase in the abundance of LC3 puncta in the end-stage PAH group compared to the matched controls. There were no statistically significant differences in the levels of expression of all ubiquitinated proteins when comparing both PAH groups and matched controls. Autophagy may be considered as the mechanism behind the LV mass loss at the end stage of PAH.
Assuntos
Autofagia , Ventrículos do Coração , Proteólise , Hipertensão Arterial Pulmonar , Ratos Wistar , Ubiquitina , Animais , Ubiquitina/metabolismo , Ventrículos do Coração/metabolismo , Ventrículos do Coração/patologia , Ventrículos do Coração/fisiopatologia , Ratos , Masculino , Hipertensão Arterial Pulmonar/metabolismo , Hipertensão Arterial Pulmonar/patologia , Modelos Animais de Doenças , Miocárdio/metabolismo , Miocárdio/patologia , Ecocardiografia , Hipertensão Pulmonar/metabolismo , Hipertensão Pulmonar/patologia , Remodelação VentricularRESUMO
BACKGROUND: Mitochondria play a crucial role in adapting to fluctuating energy demands, particularly in various heart diseases. This study investigates mitochondrial morphology near intercalated discs in left ventricular (LV) heart tissues, comparing samples from patients with sinus rhythm (SR), atrial fibrillation (AF), dilated cardiomyopathy (DCM), and ischemic cardiomyopathy (ICM). METHODS: Transmission electron microscopy was used to analyze mitochondria within 0-3.5 µm and 3.5-7 µm of intercalated discs in 9 SR, 10 AF, 9 DCM, and 8 ICM patient samples. Parameters included mean size in µm2 and elongation, count, percental mitochondrial area in the measuring frame, and a conglomeration score. RESULTS: AF patients exhibited higher counts of small mitochondria in the LV myocardium, resembling SR. DCM and ICM groups had fewer, larger, and often hydropic mitochondria. Accumulation rates and percental mitochondrial area were similar across groups. Significant positive correlations existed between other defects/size and hydropic mitochondria and between count/area and conglomeration score, while negative correlations between count and size/other defects and between hydropic mitochondria and count could be seen as well. CONCLUSION: Mitochondrial parameters in the LV myocardium of AF patients were similar to those of SR patients, while DCM and ICM displayed distinct changes, including a decrease in number, an increase in size, and compromised mitochondrial morphology. Further research is needed to fully elucidate the pathophysiological role of mitochondrial morphology in different heart diseases, providing deeper insights into potential therapeutic targets and interventions.
Assuntos
Mitocôndrias Cardíacas , Humanos , Masculino , Feminino , Projetos Piloto , Pessoa de Meia-Idade , Idoso , Mitocôndrias Cardíacas/metabolismo , Mitocôndrias Cardíacas/ultraestrutura , Cardiomiopatia Dilatada/patologia , Cardiomiopatia Dilatada/metabolismo , Cardiopatias/metabolismo , Cardiopatias/patologia , Microscopia Eletrônica de Transmissão , Adulto , Ventrículos do Coração/patologia , Ventrículos do Coração/metabolismo , Ventrículos do Coração/ultraestrutura , Fibrilação Atrial/metabolismo , Fibrilação Atrial/patologia , Fibrilação Atrial/fisiopatologia , Miocárdio/metabolismo , Miocárdio/patologia , Miocárdio/ultraestruturaRESUMO
The sarcolemmal Ca2+ efflux pathways, Na+-Ca2+-exchanger (NCX) and Ca2+-ATPase (PMCA), play a crucial role in the regulation of intracellular Ca2+ load and Ca2+ transient in cardiomyocytes. The distribution of these pathways between the t-tubular and surface membrane of ventricular cardiomyocytes varies between species and is not clear in human. Moreover, several studies suggest that this distribution changes during the development and heart diseases. However, the consequences of NCX and PMCA redistribution in human ventricular cardiomyocytes have not yet been elucidated. In this study, we aimed to address this point by using a mathematical model of the human ventricular myocyte incorporating t-tubules, dyadic spaces, and subsarcolemmal spaces. Effects of various combinations of t-tubular fractions of NCX and PMCA were explored, using values between 0.2 and 1 as reported in animal experiments under normal and pathological conditions. Small variations in the action potential duration (≤ 2%), but significant changes in the peak value of cytosolic Ca2+ transient (up to 17%) were observed at stimulation frequencies corresponding to the human heart rate at rest and during activity. The analysis of model results revealed that the changes in Ca2+ transient induced by redistribution of NCX and PMCA were mainly caused by alterations in Ca2+ concentrations in the subsarcolemmal spaces and cytosol during the diastolic phase of the stimulation cycle. The results suggest that redistribution of both transporters between the t-tubular and surface membranes contributes to changes in contractility in human ventricular cardiomyocytes during their development and heart disease and may promote arrhythmogenesis.
Assuntos
Cálcio , Ventrículos do Coração , Miócitos Cardíacos , Sarcolema , Trocador de Sódio e Cálcio , Humanos , Miócitos Cardíacos/metabolismo , Cálcio/metabolismo , Trocador de Sódio e Cálcio/metabolismo , Ventrículos do Coração/metabolismo , Sarcolema/metabolismo , Potenciais de Ação , Sinalização do Cálcio , Membrana Celular/metabolismo , Modelos Biológicos , Modelos CardiovascularesRESUMO
BACKGROUND: Positron emission tomography/computed tomography (PET/CT) with 18F-florbetapir, a novel amyloid-targeting radiotracer, can quantify left ventricular (LV) amyloid burden in systemic light-chain (AL) amyloidosis. However, its prognostic value is not known. OBJECTIVES: The authors' aim was to evaluate the prognostic value of LV amyloid burden quantified by 18F-florbetapir PET/CT, and to identify mechanistic pathways mediating its association with outcomes. METHODS: A total of 81 participants with newly diagnosed AL amyloidosis underwent 18F-florbetapir PET/CT imaging. Amyloid burden was quantified using 18F-florbetapir LV uptake as percent injected dose. The Mayo stage for AL amyloidosis was determined using troponin T, N-terminal pro-B-type natriuretic peptide (NT-proBNP), and free light chain levels. Major adverse cardiac events (MACE) were defined as all-cause death, heart failure hospitalization, or cardiac transplantation within 12 months. RESULTS: Among participants (median age, 61 years; 57% males), 36% experienced MACE, increasing from 7% to 63% across tertiles of LV amyloid burden (P < 0.001). LV amyloid burden was associated with MACE (HR: 1.46; 95% CI: 1.16-1.83; P = 0.001). However, this association became nonsignificant when adjusted for Mayo stage. In mediation analysis, the association between LV amyloid burden and MACE was mediated by NT-proBNP (P < 0.001), a marker of cardiomyocyte stretch and heart failure, and a component of Mayo stage. CONCLUSIONS: In this first study to link cardiac 18F-florbetapir uptake to subsequent outcomes, LV amyloid burden estimated by percent injected dose predicted MACE in AL amyloidosis. This effect was not independent of Mayo stage and was mediated primarily through NT-proBNP. These findings provide novel insights into the mechanism linking myocardial amyloid deposits to MACE.
Assuntos
Compostos de Anilina , Etilenoglicóis , Amiloidose de Cadeia Leve de Imunoglobulina , Peptídeo Natriurético Encefálico , Fragmentos de Peptídeos , Tomografia por Emissão de Pósitrons combinada à Tomografia Computadorizada , Valor Preditivo dos Testes , Compostos Radiofarmacêuticos , Humanos , Feminino , Masculino , Pessoa de Meia-Idade , Idoso , Compostos Radiofarmacêuticos/administração & dosagem , Amiloidose de Cadeia Leve de Imunoglobulina/diagnóstico por imagem , Amiloidose de Cadeia Leve de Imunoglobulina/metabolismo , Amiloidose de Cadeia Leve de Imunoglobulina/mortalidade , Prognóstico , Peptídeo Natriurético Encefálico/sangue , Fragmentos de Peptídeos/metabolismo , Fragmentos de Peptídeos/sangue , Fatores de Risco , Função Ventricular Esquerda , Ventrículos do Coração/diagnóstico por imagem , Ventrículos do Coração/metabolismo , Fatores de Tempo , Insuficiência Cardíaca/diagnóstico por imagem , Insuficiência Cardíaca/metabolismo , Biomarcadores/sangue , Transplante de Coração/efeitos adversos , Medição de Risco , Cardiomiopatias/diagnóstico por imagem , Cardiomiopatias/metabolismo , Cardiomiopatias/mortalidade , Cadeias Leves de Imunoglobulina/metabolismoRESUMO
The cardiac extracellular matrix (cECM) is fundamental for organ morphogenesis and maturation, during which time it undergoes remodeling, yet little is known about whether mechanical forces generated by the heartbeat regulate this remodeling process. Using zebrafish as a model and focusing on stages when cardiac valves and trabeculae form, we found that altering cardiac contraction impairs cECM remodeling. Longitudinal volumetric quantifications in wild-type animals revealed region-specific dynamics: cECM volume decreases in the atrium but not in the ventricle or atrioventricular canal. Reducing cardiac contraction resulted in opposite effects on the ventricular and atrial ECM, whereas increasing the heart rate affected the ventricular ECM but had no effect on the atrial ECM, together indicating that mechanical forces regulate the cECM in a chamber-specific manner. Among the ECM remodelers highly expressed during cardiac morphogenesis, we found one that was upregulated in non-contractile hearts, namely tissue inhibitor of matrix metalloproteinase 2 (timp2). Loss- and gain-of-function analyses of timp2 revealed its crucial role in cECM remodeling. Altogether, our results indicate that mechanical forces control cECM remodeling in part through timp2 downregulation.
Assuntos
Matriz Extracelular , Coração , Inibidor Tecidual de Metaloproteinase-2 , Peixe-Zebra , Animais , Peixe-Zebra/embriologia , Peixe-Zebra/metabolismo , Matriz Extracelular/metabolismo , Inibidor Tecidual de Metaloproteinase-2/metabolismo , Inibidor Tecidual de Metaloproteinase-2/genética , Coração/embriologia , Proteínas de Peixe-Zebra/metabolismo , Proteínas de Peixe-Zebra/genética , Contração Miocárdica/fisiologia , Miocárdio/metabolismo , Morfogênese , Átrios do Coração/embriologia , Átrios do Coração/metabolismo , Fenômenos Biomecânicos , Regulação da Expressão Gênica no Desenvolvimento , Ventrículos do Coração/metabolismo , Ventrículos do Coração/embriologiaRESUMO
The exchange protein directly activated by cAMP (EPAC) has been implicated in cardiac proarrhythmic signaling pathways including spontaneous diastolic Ca2+ leak from sarcoplasmic reticulum and increased action potential duration (APD) in isolated ventricular cardiomyocytes. The action potential (AP) lengthening following acute EPAC activation is mainly due to a decrease of repolarizing steady-state K+ current (IKSS) but the mechanisms involved remain unknown. This study aimed to assess the role of EPAC1 and EPAC2 in the decrease of IKSS and to investigate the underlying signaling pathways. AP and K+ currents were recorded with the whole cell configuration of the patch-clamp technique in freshly isolated rat ventricular myocytes. EPAC1 and EPAC2 were pharmacologically activated with 8-(4-chlorophenylthio)-2'-O-methyl-cAMP acetoxymethyl ester (8-CPTAM, 10 µmol/L) and inhibited with R-Ce3F4 and ESI-05, respectively. Inhibition of EPAC1 and EPAC2 significantly decreased the effect of 8-CPTAM on APD and IKSS showing that both EPAC isoforms are involved in these effects. Unexpectedly, calmodulin-dependent protein kinase II (CaMKII) inhibition by AIP or KN-93, and Ca2+ chelation by intracellular BAPTA, did not impact the response to 8-CPTAM. However, inhibition of PLC/PKC and nitric oxide synthase (NOS)/PKG pathways partially prevents the 8-CPTAM-dependent decrease of IKSS. Finally, the cumulative inhibition of PKC and PKG blocked the 8-CPTAM effect, suggesting that these two actors work along parallel pathways to regulate IKSS upon EPAC activation. On the basis of such findings, we propose that EPAC1 and EPAC2 are involved in APD lengthening by inhibiting a K+ current via both PLC/PKC and NOS/PKG pathways. This may have pathological implications since EPAC is upregulated in diseases such as cardiac hypertrophy.NEW & NOTEWORHTY Exchange protein directly activated by cAMP (EPAC) proteins modulate ventricular electrophysiology at the cellular level. Both EPAC1 and EPAC2 isoforms participate in this effect. Mechanistically, PLC/PKC and nitric oxide synthase (NO)/PKG pathways are involved in regulating K+ repolarizing current whereas the well-known downstream effector of EPAC, calmodulin-dependent protein kinase II (CaMKII), does not participate. This may have pathological implications since EPAC is upregulated in diseases such as cardiac hypertrophy. Thus, EPAC inhibition may be a new approach to prevent arrhythmias under pathological conditions.
Assuntos
Potenciais de Ação , Fatores de Troca do Nucleotídeo Guanina , Ventrículos do Coração , Miócitos Cardíacos , Proteína Quinase C , Transdução de Sinais , Animais , Fatores de Troca do Nucleotídeo Guanina/metabolismo , Miócitos Cardíacos/metabolismo , Miócitos Cardíacos/efeitos dos fármacos , Miócitos Cardíacos/enzimologia , Proteína Quinase C/metabolismo , Ratos , Potenciais de Ação/efeitos dos fármacos , Ventrículos do Coração/metabolismo , Ventrículos do Coração/citologia , Proteínas Quinases Dependentes de GMP Cíclico/metabolismo , Óxido Nítrico Sintase/metabolismo , Óxido Nítrico Sintase/antagonistas & inibidores , Fosfolipases Tipo C/metabolismo , Fosfolipases Tipo C/antagonistas & inibidores , Masculino , Ratos Wistar , Potássio/metabolismo , AMP Cíclico/metabolismoRESUMO
Pulmonary arterial hypertension (PAH) is characterised by an increase in mean pulmonary arterial pressure and a compromised the right ventricle (RV), together with progression to heart failure and premature death. Studies have evaluated the role of melatonin as a promising therapeutic strategy for PAH. The objective of this study was to evaluate melatonin's effects on oxidative stress and on the TLR4/NF-kß inflammatory pathway in the RV of rats with PAH. Male Wistar rats were divided into the following groups: control, monocrotaline (MCT), and monocrotaline plus melatonin groups. These two last groups received one intraperitoneal injection of MCT (60 mg/kg) on the first day of experimental protocol. The monocrotaline plus melatonin group received 10 mg/kg/day of melatonin by gavage for 21 days. Echocardiographic analysis was performed, and the RV was collected for morphometric analysis oxidative stress and molecular evaluations. The main findings of the present study were that melatonin administration attenuated the reduction in RV function that was induced by monocrotaline, as assessed by TAPSE. In addition, melatonin prevented RV diastolic area reduction caused by PAH. Furthermore, animals treated with melatonin did not show an increase in ROS levels or in NF-kß expression. In addition, the monocrotaline plus melatonin group showed a reduction in TLR4 expression when compared with control and monocrotaline groups. To our knowledge, this is the first study demonstrating a positive effect of melatonin on the TLR4/NF-kß pathway in the RV of rats with PAH. In this sense, this study makes it possible to think of melatonin as a possible ally in mitigating RV alterations caused by PAH.
Assuntos
Ventrículos do Coração , Melatonina , Monocrotalina , Estresse Oxidativo , Ratos Wistar , Transdução de Sinais , Receptor 4 Toll-Like , Animais , Melatonina/farmacologia , Estresse Oxidativo/efeitos dos fármacos , Receptor 4 Toll-Like/metabolismo , Receptor 4 Toll-Like/genética , Masculino , Ventrículos do Coração/efeitos dos fármacos , Ventrículos do Coração/patologia , Ventrículos do Coração/metabolismo , Monocrotalina/toxicidade , Transdução de Sinais/efeitos dos fármacos , Hipertensão Arterial Pulmonar/tratamento farmacológico , Hipertensão Arterial Pulmonar/metabolismo , Hipertensão Arterial Pulmonar/patologia , NF-kappa B/metabolismo , Inflamação/patologia , Inflamação/tratamento farmacológico , Ratos , Hipertensão Pulmonar/tratamento farmacológico , Hipertensão Pulmonar/metabolismo , Hipertensão Pulmonar/patologia , Espécies Reativas de Oxigênio/metabolismoRESUMO
Aging is a risk factor for cardiovascular disease, the leading cause of death worldwide. Cardiac fibrosis is a harmful result of repeated myocardial infarction that increases risk of morbidity and future injury. Interestingly, both rates and outcomes of cardiac fibrosis differ between young and aged individuals, as well as men and women. Here, for the first time, we identify and isolate matrix-bound extracellular vesicles from the left ventricles (LVs) of young or aged males and females in both human and murine models. These LV vesicles (LVVs) show differences in morphology and content between these four cohorts in both humans and mice. LVV effects on fibrosis were also investigated in vitro, and aged male LVVs were pro-fibrotic while other LVVs were anti-fibrotic. From these LVVs, we could identify therapeutic miRNAs to promote anti-fibrotic effects. Four miRNAs were identified and together, but not individually, demonstrated significant cardioprotective effects when transfected. This suggests that miRNA synergy can regulate cell response, not just individual miRNAs, and also indicates that biological agent-associated therapeutic effects may be recapitulated using non-immunologically active agents. Furthermore, that chronic changes in LVV miRNA content may be a major factor in sex- and age-dependent differences in clinical outcomes of cardiac fibrosis.
Assuntos
Vesículas Extracelulares , Fibrose , MicroRNAs , MicroRNAs/metabolismo , MicroRNAs/genética , Animais , Masculino , Feminino , Humanos , Vesículas Extracelulares/metabolismo , Camundongos , Miocárdio/patologia , Miocárdio/metabolismo , Camundongos Endogâmicos C57BL , Envelhecimento , Fenótipo , Ventrículos do Coração/patologia , Ventrículos do Coração/metabolismo , Adulto , Idoso , Pessoa de Meia-IdadeRESUMO
The heart beats approximately 100,000 times per day in humans, imposing substantial energetic demands on cardiac muscle. Adenosine triphosphate (ATP) is an essential energy source for normal function of cardiac muscle during each beat, as it powers ion transport, intracellular Ca2+ handling, and actin-myosin cross-bridge cycling. Despite this, the impact of excitation-contraction coupling on the intracellular ATP concentration ([ATP]i) in myocytes is poorly understood. Here, we conducted real-time measurements of [ATP]i in ventricular myocytes using a genetically encoded ATP fluorescent reporter. Our data reveal rapid beat-to-beat variations in [ATP]i. Notably, diastolic [ATP]i was <1 mM, which is eightfold to 10-fold lower than previously estimated. Accordingly, ATP-sensitive K+ (KATP) channels were active at physiological [ATP]i. Cells exhibited two distinct types of ATP fluctuations during an action potential: net increases (Mode 1) or decreases (Mode 2) in [ATP]i. Mode 1 [ATP]i increases necessitated Ca2+ entry and release from the sarcoplasmic reticulum (SR) and were associated with increases in mitochondrial Ca2+. By contrast, decreases in mitochondrial Ca2+ accompanied Mode 2 [ATP]i decreases. Down-regulation of the protein mitofusin 2 reduced the magnitude of [ATP]i fluctuations, indicating that SR-mitochondrial coupling plays a crucial role in the dynamic control of ATP levels. Activation of ß-adrenergic receptors decreased [ATP]i, underscoring the energetic impact of this signaling pathway. Finally, our work suggests that cross-bridge cycling is the largest consumer of ATP in a ventricular myocyte during an action potential. These findings provide insights into the energetic demands of EC coupling and highlight the dynamic nature of ATP concentrations in cardiac muscle.