RESUMO
Myeloid-derived suppressor cells (MDSC) are a heterogeneous cell population with high immunosuppressive activity that proliferates in infections, inflammation, and tumor microenvironments. In tumors, MDSC exert immunosuppression mainly by producing reactive oxygen species (ROS), a process triggered by the NADPH oxidase 2 (NOX2) activity. NOX2 is functionally coupled with the Hv1 proton channel in certain immune cells to support sustained free-radical production. However, a functional expression of the Hv1 channel in MDSC has not yet been reported. Here, we demonstrate that mouse MDSC express functional Hv1 proton channel by immunofluorescence microscopy, flow cytometry, and Western blot, besides performing a biophysical characterization of its macroscopic currents via patch-clamp technique. Our results show that the immunosuppression by MDSC is conditional to their ability to decrease the proton concentration elevated by the NOX2 activity, rendering Hv1 a potential drug target for cancer treatment.
Assuntos
Canais Iônicos , Células Supressoras Mieloides , Prótons , Linfócitos T , Animais , Canais Iônicos/genética , Canais Iônicos/metabolismo , Camundongos , Células Supressoras Mieloides/imunologia , NADPH Oxidase 2/metabolismo , Espécies Reativas de Oxigênio/metabolismo , Linfócitos T/imunologiaRESUMO
The mechanisms underlying atrial-selective prolongation of effective refractory period (ERP) and suppression of atrial fibrillation (AF) by NS8593 and UCL1684, small conductance calcium-activated potassium (SK) channel blockers, are poorly defined. The purpose of the study was to confirm the effectiveness of these agents to suppress AF and to probe the underlying mechanisms. Transmembrane action potentials and pseudoelectrocardiograms were recorded from canine isolated coronary-perfused canine atrial and ventricular wedge preparations. Patch clamp techniques were used to record sodium channel current (INa) in atrial and ventricular myocytes and human embryonic kidney cells. In both atria and ventricles, NS8593 (3-10 µM) and UCL1684 (0.5 µM) did not significantly alter action potential duration, suggesting little to no SK channel inhibition. Both agents caused atrial-selective: (1) prolongation of ERP secondary to development of postrepolarization refractoriness, (2) reduction of Vmax, and (3) increase of diastolic threshold of excitation (all are sodium-mediated parameters). NS8593 and UCL1684 significantly reduced INa density in human embryonic kidney cells as well as in atrial but not in ventricular myocytes at physiologically relevant holding potentials. NS8593 caused a shift of steady-state inactivation to negative potentials in atrial but not ventricular cells. NS8593 and UCL1684 prevented induction of acetylcholine-mediated AF in 6/6 and 8/8 preparations, respectively. This anti-AF effect was associated with strong rate-dependent depression of excitability. The SK channel blockers, NS8593 and UCL1684, are effective in preventing the development of AF due to potent atrial-selective inhibition of INa, causing atrial-selective prolongation of ERP secondary to induction of postrepolarization refractoriness.
Assuntos
1-Naftilamina/análogos & derivados , Alcanos/farmacologia , Antiarrítmicos/farmacologia , Fibrilação Atrial/prevenção & controle , Átrios do Coração/efeitos dos fármacos , Frequência Cardíaca/efeitos dos fármacos , Miócitos Cardíacos/efeitos dos fármacos , Canal de Sódio Disparado por Voltagem NAV1.5/efeitos dos fármacos , Compostos de Quinolínio/farmacologia , Bloqueadores dos Canais de Sódio/farmacologia , 1-Naftilamina/farmacologia , Potenciais de Ação/efeitos dos fármacos , Animais , Fibrilação Atrial/metabolismo , Fibrilação Atrial/fisiopatologia , Cães , Feminino , Células HEK293 , Átrios do Coração/metabolismo , Átrios do Coração/fisiopatologia , Ventrículos do Coração/efeitos dos fármacos , Ventrículos do Coração/metabolismo , Ventrículos do Coração/fisiopatologia , Humanos , Masculino , Miócitos Cardíacos/metabolismo , Canal de Sódio Disparado por Voltagem NAV1.5/genética , Canal de Sódio Disparado por Voltagem NAV1.5/metabolismo , Bloqueadores dos Canais de Potássio/farmacologia , Período Refratário Eletrofisiológico/efeitos dos fármacos , Canais de Potássio Ativados por Cálcio de Condutância Baixa/antagonistas & inibidores , Canais de Potássio Ativados por Cálcio de Condutância Baixa/metabolismoRESUMO
El síndrome de Brugada es una enfermedad hereditaria caracterizada por una anormalidad electrocardiográfica y un aumento del riesgo de muerte súbita cardiaca. El síndrome de Brugada puede ser causado por la presencia de mutaciones en el gen SCN5A en aproximadamente el 20% de los casos familiares. El gen SCN5A codifica la subunidad a del canal iónico de sodio en las células cardiacas. Estudios realizados durante la última década en genética molecular han permitido identificar 11 nuevos genes con susceptibilidad para síndrome de Brugada además del SCN5A, lo que lleva a pensar que es una enfermedad con heterogeneidad genética y compleja de identificar en la clínica y a nivel molecular en el laboratorio. Una manera de heredar el síndrome de Brugada es por medio de un patrón de transmisión hereditaria autosómica dominante. Esta breve revisión se enfoca a describir el proceso de diagnóstico de marcadores genéticos en un caso reportado de síndrome de Brugada guiando al lector a través del proceso de identificación de las variantes genéticas responsables del síndrome y a determinar la consecuencia funcional de las mutaciones del canal de sodio sobre la alteración electrocardiográfica.
Brugada syndrome is a genetic disease that is characterized by abnormal electrocardiogram findings and an increased risk of sudden cardiac death. This syndrome is linked to mutations in the SCN5A gene in approximately 20% of Brugada syndrome probands. SCN5A encodes the a subunit of the cardiac sodium channel. Studies conducted over the past decade have identified 11 other Brugada syndrome susceptibility genes besides to SCN5A, pointing to genetic heterogeneity of the syndrome. Transmission of the disease shows an autosomal dominant inheritance pattern. This brief review focuses on a reported case of sodium channel-mediated Brugada syndrome, guiding the reader through the process of identification of the genetic variants responsible for the clinically-diagnosed syndrome, mutagenesis to clone SCN5A with and without the 2 variants identified and transfection of the 2 variants into TSA201 cells to determine the functional consequence of these genetic variants on sodium channel expression and function.
Assuntos
Humanos , Masculino , Síndrome de Brugada/genética , /genética , Síndrome de Brugada/diagnóstico , Mutação , LinhagemRESUMO
Brugada syndrome is a genetic disease that is characterized by abnormal electrocardiogram findings and an increased risk of sudden cardiac death. This syndrome is linked to mutations in the SCN5A gene in approximately 20% of Brugada syndrome probands. SCN5A encodes the α subunit of the cardiac sodium channel. Studies conducted over the past decade have identified 11 other Brugada syndrome susceptibility genes besides to SCN5A, pointing to genetic heterogeneity of the syndrome. Transmission of the disease shows an autosomal dominant inheritance pattern. This brief review focuses on a reported case of sodium channel-mediated Brugada syndrome, guiding the reader through the process of identification of the genetic variants responsible for the clinically-diagnosed syndrome, mutagenesis to clone SCN5A with and without the 2 variants identified and transfection of the 2 variants into TSA201 cells to determine the functional consequence of these genetic variants on sodium channel expression and function.
Assuntos
Síndrome de Brugada/genética , Canal de Sódio Disparado por Voltagem NAV1.5/genética , Síndrome de Brugada/diagnóstico , Humanos , Masculino , Mutação , LinhagemRESUMO
The present work is a thorough investigation of the degree of reproductive isolation between Meccus mazzottii and Meccus longipennis, Meccus picturatus, Meccus pallidipennis and Meccus bassolsae, as well as between M. longipennis and M. picturatus. We examined fertility and segregation of morphological characteristics in two generations of hybrids derived from crosses between these species. The percentage of pairs with (fertile) offspring was highest in the set of crosses between M. longipennis and M. picturatus, and lowest between M. mazzottii and M. picturatus. Most first-generation (F1) individuals from crosses involving M. mazzottii were morphologically similar to this species, while only F1 x F1 progeny of parental crosses between M. mazzottii and M. longipennis had offspring second generation that looked like M. mazzottii. The results indicate that different degrees of reproductive isolation apparently exist among the species of the Phyllosoma complex examined in this study. The biological evidence obtained in this study does not support the proposal that M. longipennis and M. picturatus are full species. It could indicate on the contrary, that both could be considered as subspecies of a single polytypic species. On the other hand, biological evidence supports the proposal that M. mazzottii is a full species.
Assuntos
Quimera/genética , Cruzamentos Genéticos , Triatominae/genética , Animais , Feminino , Masculino , México , Fenótipo , Reprodução/fisiologia , Triatominae/classificação , Triatominae/fisiologiaRESUMO
The present work is a thorough investigation of the degree of reproductive isolation between Meccus mazzottii and Meccus longipennis, Meccus picturatus, Meccus pallidipennis and Meccus bassolsae, as well as between M. longipennis and M. picturatus. We examined fertility and segregation of morphological characteristics in two generations of hybrids derived from crosses between these species. The percentage of pairs with (fertile) offspring was highest in the set of crosses between M. longipennis and M. picturatus, and lowest between M. mazzottii and M. picturatus. Most first-generation (F1) individuals from crosses involving M. mazzottii were morphologically similar to this species, while only F1 x F1 progeny of parental crosses between M. mazzottii and M. longipennis had offspring second generation that looked like M. mazzottii. The results indicate that different degrees of reproductive isolation apparently exist among the species of the Phyllosoma complex examined in this study. The biological evidence obtained in this study does not support the proposal that M. longipennis and M. picturatus are full species. It could indicate on the contrary, that both could be considered as subspecies of a single polytypic species. On the other hand, biological evidence supports the proposal that M. mazzottii is a full species.