RESUMO
Background: Hyperpolarization-Activated Cyclic Nucleotide-Gated (HCN) ionic channels are known to play a key role in the control of neuron excitability and have been proposed as a molecular target of ethanol. Previous studies in rats have shown that gene-induced overexpression of the HCN2 channel in the ventral tegmental area (VTA) increases the rewarding effects of ethanol and its intake by the animals.Objective: The aim of this work was to study the effects of VTA HCN2 gene knockdown in the voluntary ethanol consumption of alcohol-preferring UChB rats.Methods: Two lentiviral vectors were generated; LV-siRNA-HCN2, coding for a siRNA that elicited >95% reduction of HCN2 protein levels in vitro, and a control vector coding for a scrambled siRNA sequence. Female UChB naïve rats (n = 14) were microinjected into the VTA with LV-siRNA-HCN2 or the scrambled control vector (n = 11). Four days after, animals were given a daily free access to 10% ethanol and water for 10 days.Results: Rats treated with the LV-siRNA-HCN2 vector showed a ~ 70% reduction (p < .001) in their ethanol preference and ethanol intake compared to control animals. No changes were observed in the total fluid intake of both groups. HCN2 levels in the VTA were measured by Western blot showing a reduction of 40% (p < .05) in the rats injected with LV-siRNA-HCN2, compared to control animals.Conclusion: These results show that knockdown of HCN2 ionic channels in the VTA of UChB rats markedly reduces their voluntary ethanol intake, supporting the idea that HCN2 channels may constitute a therapeutic target for alcohol use disorders.
Assuntos
Alcoolismo , Área Tegmentar Ventral , Consumo de Bebidas Alcoólicas/genética , Consumo de Bebidas Alcoólicas/metabolismo , Alcoolismo/genética , Animais , Etanol/farmacologia , Feminino , Técnicas de Silenciamento de Genes , Humanos , Canais Disparados por Nucleotídeos Cíclicos Ativados por Hiperpolarização/genética , Canais Disparados por Nucleotídeos Cíclicos Ativados por Hiperpolarização/metabolismo , Canais de Potássio/genética , Canais de Potássio/metabolismo , RNA Interferente Pequeno/genética , RNA Interferente Pequeno/metabolismo , RNA Interferente Pequeno/farmacologia , Ratos , Área Tegmentar Ventral/metabolismoRESUMO
Epilepsy is a chronic neurological disorder that affects 50 million people worldwide. The most common form of epilepsy is idiopathic, where most of the genetic defects of this type of epilepsy occur in ion channels. Hyperpolarization-activated cyclic nucleotide-gated (HCN) channels are activated by membrane hyperpolarization, and are mainly expressed in the heart and central and peripheral nervous systems. In humans, four HCN genes have been described, and emergent clinical data shows that dysfunctional HCN channels are involved in epilepsy. Danio rerio has become a versatile organism to model a wide variety of diseases. In this work, we used CRISPR/Cas9 to generate hcn2b mutants in zebrafish, and characterized them molecularly and behaviorally. We obtained an hcn2b mutant allele with an 89 bp deletion that produced a premature stop codon. The mutant exhibited a high mortality rate in its life span, probably due to its sudden death. We did not detect heart malformations or important heart rate alterations. Absence seizures and moderate seizures were observed in response to light. These seizures rarely caused instant death. The results show that mutations in the Hcn2b channel are involved in epilepsy and provide evidence of the advantages of zebrafish to further our understanding of the pathogenesis of epilepsy.
Assuntos
Comportamento Animal , Epilepsia/patologia , Canais Disparados por Nucleotídeos Cíclicos Ativados por Hiperpolarização/genética , Mutação , Neurônios/patologia , Convulsões/patologia , Proteínas de Peixe-Zebra/genética , Animais , Epilepsia/etiologia , Epilepsia/metabolismo , Canais Disparados por Nucleotídeos Cíclicos Ativados por Hiperpolarização/metabolismo , Neurônios/metabolismo , Convulsões/etiologia , Convulsões/metabolismo , Peixe-Zebra , Proteínas de Peixe-Zebra/metabolismoRESUMO
The kidney controls body fluids, electrolyte and acid-base balance. Previously, we demonstrated that hyperpolarization-activated and cyclic nucleotide-gated (HCN) cation channels participate in ammonium excretion in the rat kidney. Since acid-base balance is closely linked to potassium metabolism, in the present work we aim to determine the effect of chronic metabolic acidosis (CMA) and hyperkalemia (HK) on protein abundance and localization of HCN3 in the rat kidney. CMA increased HCN3 protein level only in the outer medulla (2.74 ± 0.31) according to immunoblot analysis. However, immunofluorescence assays showed that HCN3 augmented in cortical proximal tubules (1.45 ± 0.11) and medullary thick ascending limb of Henle's loop (4.48 ± 0.45) from the inner stripe of outer medulla. HCN3 was detected in brush border membranes (BBM) and mitochondria of the proximal tubule by immunogold electron and confocal microscopy in control conditions. Acidosis did not alter HCN3 levels in BBM and mitochondria but augmented them in lysosomes. HCN3 was also immuno-detected in mitoautophagosomes. In the distal nephron, HCN3 was expressed in principal and intercalated cells from cortical to medullary collecting ducts. CMA did not change HCN3 abundance in these nephron segments. In contrast, HK doubled HCN3 level in cortical collecting ducts and favored its basolateral localization in principal cells from the inner medullary collecting ducts. These findings further support HCN channels contribution to renal acid-base and potassium balance.
Assuntos
Acidose/etiologia , Acidose/metabolismo , Hiperpotassemia/etiologia , Hiperpotassemia/metabolismo , Canais Disparados por Nucleotídeos Cíclicos Ativados por Hiperpolarização/metabolismo , Néfrons/metabolismo , Canais de Potássio/metabolismo , Animais , Biomarcadores , Doença Crônica , Células Epiteliais/metabolismo , Imunofluorescência/métodos , Expressão Gênica , Canais Disparados por Nucleotídeos Cíclicos Ativados por Hiperpolarização/genética , Túbulos Renais Proximais/metabolismo , Alça do Néfron/metabolismo , Néfrons/ultraestrutura , Canais de Potássio/genética , RatosRESUMO
Human induced pluripotent stem cell derived cardiomyocytes (hiPSC-CMs) resemble fetal cardiomyocytes and electrical stimulation (ES) has been explored to mature the differentiated cells. Here, we hypothesize that ES applied at the beginning of the differentiation process, triggers both differentiation of the hiPSC-CMs into a specialized conduction system (CS) phenotype and cell maturation. We applied ES for 15 days starting on day 0 of the differentiation process and found an increased expression of transcription factors and proteins associated with the development and function of CS including Irx3, Nkx2.5 and contactin 2, Hcn4 and Scn5a, respectively. We also found activation of intercalated disc proteins (Nrap and ß-catenin). We detected ES-induced CM maturation as indicated by increased Tnni1 and Tnni3 expression. Confocal micrographs showed a shift towards expression of the gap junction protein connexin 40 in ES hiPSC-CM compared to the more dominant expression of connexin 43 in controls. Finally, analysis of functional parameters revealed that ES hiPSC-CMs exhibited faster action potential (AP) depolarization, longer intracellular Ca2+ transients, and slower AP duration at 90% of repolarization, resembling fast conducting fibers. Altogether, we provided evidence that ES during the differentiation of hiPSC to cardiomyocytes lead to development of cardiac conduction-like cells with more mature cytoarchitecture. Thus, hiPSC-CMs exposed to ES during differentiation can be instrumental to develop CS cells for cardiac disease modelling, screening individual drugs on a precison medicine type platform and support the development of novel therapeutics for arrhythmias.
Assuntos
Potenciais de Ação/fisiologia , Cálcio/metabolismo , Células-Tronco Pluripotentes Induzidas/fisiologia , Miócitos Cardíacos/fisiologia , Biomarcadores/metabolismo , Diferenciação Celular , Terapia Baseada em Transplante de Células e Tecidos/métodos , Conexinas/genética , Conexinas/metabolismo , Contactina 2/genética , Contactina 2/metabolismo , Estimulação Elétrica , Expressão Gênica , Sistema de Condução Cardíaco/citologia , Sistema de Condução Cardíaco/fisiologia , Proteína Homeobox Nkx-2.5/genética , Proteína Homeobox Nkx-2.5/metabolismo , Proteínas de Homeodomínio/genética , Proteínas de Homeodomínio/metabolismo , Humanos , Canais Disparados por Nucleotídeos Cíclicos Ativados por Hiperpolarização/genética , Canais Disparados por Nucleotídeos Cíclicos Ativados por Hiperpolarização/metabolismo , Células-Tronco Pluripotentes Induzidas/citologia , Proteínas Musculares/genética , Proteínas Musculares/metabolismo , Miócitos Cardíacos/citologia , Canal de Sódio Disparado por Voltagem NAV1.5/genética , Canal de Sódio Disparado por Voltagem NAV1.5/metabolismo , Canais de Potássio/genética , Canais de Potássio/metabolismo , Cultura Primária de Células , Fatores de Transcrição/genética , Fatores de Transcrição/metabolismo , Troponina I/genética , Troponina I/metabolismo , beta Catenina/genética , beta Catenina/metabolismo , Proteína alfa-5 de Junções ComunicantesRESUMO
The Ih is a mixed depolarizing current present in neurons which, upon activation by hyperpolarization, modulates neuronal excitability in the mesocorticolimbic (MCL) system, an area which regulates emotions such as pleasure, reward, and motivation. Its biophysical properties are determined by HCN protein expression profiles, specifically HCN subunits 1-4. Previously, we reported that cocaine-induced behavioral sensitization increases HCN2 protein expression in all MCL areas with the Ventral Tegmental Area (VTA) showing the most significant increase. Recent evidence suggests that HCN4 also has an important expression in the MCL system. Although there is a significant expression of HCN channels in the MCL system their role in addictive processes is largely unknown. Thus, in this study we aim to compare HCN2 and HCN4 expression profiles and their cellular compartmental distribution in the MCL system, before and after cocaine sensitization. Surface/intracellular (S/I) ratio analysis indicates that VTA HCN2 subunits are mostly expressed in the cell surface in contrast to other areas tested. Our findings demonstrate that after cocaine sensitization, the HCN2 S/I ratio in the VTA was decreased whereas in the Prefrontal Cortex it was increased. In addition, HCN4 total expression in the VTA was decreased after cocaine sensitization, although the S/I ratio was not altered. Together, these results demonstrate differential cocaine effects on HCN2 and HCN4 protein expression profiles and therefore suggest a diverse Ih modulation of cellular activity during cocaine addictive processes.
Assuntos
Córtex Cerebral/metabolismo , Cocaína/farmacologia , Canais Disparados por Nucleotídeos Cíclicos Ativados por Hiperpolarização/biossíntese , Sistema Límbico/metabolismo , Canais de Potássio/biossíntese , Animais , Córtex Cerebral/efeitos dos fármacos , Expressão Gênica , Canais Disparados por Nucleotídeos Cíclicos Ativados por Hiperpolarização/genética , Sistema Límbico/efeitos dos fármacos , Masculino , Canais de Potássio/genética , Subunidades Proteicas/biossíntese , Subunidades Proteicas/genética , Distribuição Aleatória , Ratos , Ratos Sprague-DawleyRESUMO
Hyperpolarization-activated cyclic nucleotide-gated (HCN) channels are highly regulated proteins which respond to different cellular stimuli. The HCN currents (Ih) mediated by HCN1 and HCN2 drive the repetitive firing in nociceptive neurons. The role of HCN channels in pain has been widely investigated as targets for the development of new therapeutic drugs, but the comprehensive design of HCN channel modulators has been restricted due to the lack of crystallographic data. The three-dimensional structure of the human HCN1 channel was recently reported, opening new possibilities for the rational design of highly-selective HCN modulators. In this review, we discuss the structural and functional properties of HCN channels, their pharmacological inhibitors, and the potential strategies for designing new drugs to block the HCN channel function associated with pain perception.
Assuntos
Canais Disparados por Nucleotídeos Cíclicos Ativados por Hiperpolarização/genética , Canais Disparados por Nucleotídeos Cíclicos Ativados por Hiperpolarização/metabolismo , Animais , Sistema Nervoso Central/metabolismo , Desenho de Fármacos , Descoberta de Drogas , Regulação da Expressão Gênica , Humanos , Canais Disparados por Nucleotídeos Cíclicos Ativados por Hiperpolarização/antagonistas & inibidores , Canais Disparados por Nucleotídeos Cíclicos Ativados por Hiperpolarização/química , Terapia de Alvo Molecular , Dor/tratamento farmacológico , Dor/genética , Dor/metabolismo , Manejo da Dor , Percepção da Dor , Transdução de Sinais , Relação Estrutura-AtividadeRESUMO
Psychostimulant addiction is associated with dysfunctions in frontal cortex. Previous data demonstrated that repeated exposure to methamphetamine (METH) can alter prefrontal cortex (PFC)-dependent functions. Here, we show that withdrawal from repetitive non-contingent METH administration (7 days, 1 mg/kg) depressed voltage-dependent calcium currents (ICa ) and increased hyperpolarization-activated cation current (IH ) amplitude and the paired-pulse ratio of evoked excitatory postsynaptic currents (EPSCs) in deep-layer pyramidal mPFC neurons. Most of these effects were blocked by systemic co-administration of the D1/D5 receptor antagonist SCH23390 (0.5 and 0.05 mg/kg). In vitroâ METH (i.e. bath-applied to slices from naïve-treated animals) was able to emulate its systemic effects on ICa and evoked EPSCs paired-pulse ratio. We also provide evidence of altered mRNA expression of (1) voltage-gated calcium channels P/Q-type Cacna1a (Cav 2.1), N-type Cacna1b (Cav 2.2), T-type Cav 3.1 Cacna1g, Cav 3.2 Cacna1h, Cav 3.3 Cacna1i and the auxiliary subunit Cacna2d1 (α2δ1); (2) hyperpolarization-activated cyclic nucleotide-gated channels Hcn1 and Hcn2; and (3) glutamate receptors subunits AMPA-type Gria1, NMDA-type Grin1 and metabotropic Grm1 in the mouse mPFC after repeated METH treatment. Moreover, we show that some of these changes in mRNA expression were sensitive D1/5 receptor blockade. Altogether, these altered mechanisms affecting synaptic physiology and transcriptional regulation may underlie PFC functional alterations that could lead to PFC impairments observed in METH-addicted individuals.