RESUMO
The Renin-Angiotensin System (RAS) is expressed in the central nervous system and has important functions that go beyond blood pressure regulation. Clinical and experimental studies have suggested that alterations in the brain RAS contribute to the development and progression of neurodegenerative diseases. However, there is limited information regarding the involvement of RAS components in Huntington's disease (HD). Herein, we used the HD murine model, (BACHD), as well as samples from patients with HD to investigate the role of both the classical and alternative axes of RAS in HD pathophysiology. BACHD mice displayed worse motor performance in different behavioral tests alongside a decrease in the levels and activity of the components of the RAS alternative axis ACE2, Ang-(1-7), and Mas receptors in the striatum, prefrontal cortex, and hippocampus. BACHD mice also displayed a significant increase in mRNA expression of the AT1 receptor, a component of the RAS classical arm, in these key brain regions. Moreover, patients with manifest HD presented higher plasma levels of Ang-(1-7). No significant changes were found in the levels of ACE, ACE2, and Ang II. Our findings provided the first evidence that an imbalance in the RAS classical and counter-regulatory arms may play a role in HD pathophysiology.
Assuntos
Angiotensina I , Enzima de Conversão de Angiotensina 2 , Doença de Huntington , Fragmentos de Peptídeos , Receptor Tipo 1 de Angiotensina , Sistema Renina-Angiotensina , Angiotensina I/genética , Angiotensina I/metabolismo , Angiotensina II/metabolismo , Enzima de Conversão de Angiotensina 2/genética , Animais , Modelos Animais de Doenças , Humanos , Doença de Huntington/genética , Camundongos , Fragmentos de Peptídeos/genética , Fragmentos de Peptídeos/metabolismo , Peptidil Dipeptidase A/metabolismo , Receptor Tipo 1 de Angiotensina/genética , Receptor Tipo 1 de Angiotensina/metabolismo , Sistema Renina-Angiotensina/genética , Sistema Renina-Angiotensina/fisiologiaRESUMO
Huntington's disease (HD) is a genetic disorder marked by transcriptional alterations that result in neuronal impairment and death. MicroRNAs (miRNAs) are non-coding RNAs involved in post-transcriptional regulation and fine-tuning of gene expression. Several studies identified altered miRNA expression in HD and other neurodegenerative diseases, however their roles in early stages of HD remain elusive. Here, we deep-sequenced miRNAs from the striatum of the HD mouse model, BACHD, at the age of 2 and 8 months, representing the pre-symptomatic and symptomatic stages of the disease. Our results show that 44 and 26 miRNAs were differentially expressed in 2- and 8-month-old BACHD mice, respectively, as compared to wild-type controls. Over-representation analysis suggested that miRNAs up-regulated in 2-month-old mice control the expression of genes crucial for PI3K-Akt and mTOR cell signaling pathways. Conversely, miRNAs regulating genes involved in neuronal disorders were down-regulated in 2-month-old BACHD mice. Interestingly, primary striatal neurons treated with anti-miRs targeting two up-regulated miRNAs, miR-449c-5p and miR-146b-5p, showed higher levels of cell death. Therefore, our results suggest that the miRNAs altered in 2-month-old BACHD mice regulate genes involved in the promotion of cell survival. Notably, over-representation suggested that targets of differentially expressed miRNAs at the age of 8 months were not significantly enriched for the same pathways. Together, our data shed light on the role of miRNAs in the initial stages of HD, suggesting a neuroprotective role as an attempt to maintain or reestablish cellular homeostasis.
Assuntos
Sequenciamento de Nucleotídeos em Larga Escala/métodos , Doença de Huntington/genética , MicroRNAs/biossíntese , MicroRNAs/genética , Neuroproteção/fisiologia , Sintomas Prodrômicos , Animais , Células Cultivadas , Feminino , Doença de Huntington/metabolismo , Doença de Huntington/prevenção & controle , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Análise de Sequência de RNA/métodos , Regulação para Cima/fisiologiaAssuntos
Doença de Huntington/patologia , Neurônios Motores/patologia , Fibras Musculares de Contração Rápida/patologia , Junção Neuromuscular/patologia , Animais , Extremidade Inferior , Masculino , Camundongos , Camundongos Transgênicos , Músculo Esquelético/inervação , Músculo Esquelético/patologia , Transmissão Sináptica/fisiologiaAssuntos
Canais de Cálcio Tipo L/metabolismo , Doença de Huntington/metabolismo , Neurônios/metabolismo , Fármacos Neuroprotetores/farmacologia , Nifedipino/farmacologia , Animais , Bloqueadores dos Canais de Cálcio/farmacologia , Córtex Cerebral/metabolismo , Modelos Animais de Doenças , Camundongos , Camundongos Transgênicos , Neurônios/efeitos dos fármacosRESUMO
Huntington's disease (HD) is an autosomal dominant neurodegenerative disease characterized by chorea, incoordination and psychiatric and behavioral symptoms. The leading cause of death in HD patients is aspiration pneumonia, associated with respiratory dysfunction, decreased respiratory muscle strength and dysphagia. Although most of the motor symptoms are derived from alterations in the central nervous system, some might be associated with changes in the components of motor units (MU). To explore this hypothesis, we evaluated morphofunctional aspects of the diaphragm muscle in a mouse model for HD (BACHD). We showed that the axons of the phrenic nerves were not affected in 12-months-old BACHD mice, but the axon terminals that form the neuromuscular junctions (NMJs) were more fragmented in these animals in comparison with the wild-type mice. In BACHD mice, the synaptic vesicles of the diaphragm NMJs presented a decreased exocytosis rate. Quantal content and quantal size were smaller and there was less synaptic depression whereas the estimated size of the readily releasable vesicle pool was not changed. At the ultrastructure level, the diaphragm NMJs of these mice presented fewer synaptic vesicles with flattened and oval shapes, which might be associated with the reduced expression of the vesicular acetylcholine transporter protein. Furthermore, mitochondria of the diaphragm muscle presented signs of degeneration in BACHD mice. Interestingly, despite all these cellular alterations, BACHD diaphragmatic function was not compromised, suggesting a higher resistance threshold of this muscle. A putative resistance mechanism may be protecting this vital muscle. Our data contribute to expanding the current understanding of the effects of mutated huntingtin in the neuromuscular synapse and the diaphragm muscle function.
Assuntos
Diafragma/metabolismo , Doença de Huntington/metabolismo , Sinapses/metabolismo , Vesículas Sinápticas/metabolismo , Animais , Diafragma/patologia , Modelos Animais de Doenças , Humanos , Doença de Huntington/patologia , Junção Neuromuscular/metabolismo , Terminações Pré-Sinápticas/metabolismoRESUMO
Huntington's disease (HD) is an autosomal dominant neurodegenerative disorder caused by a polyglutamine expansion in the amino-terminal region of the huntingtin (htt) protein. In addition to facilitating neurodegeneration, mutant htt is implicated in HD-related alterations of neurotransmission. Previous data showed that htt can modulate N-type voltage-gated Ca2+ channels (Cav2.2), which are essential for presynaptic neurotransmitter release. Thus, to elucidate the mechanism underlying mutant htt-mediated alterations in neurotransmission, we investigated how Cav2.2 is affected by full-length mutant htt expression in a mouse model of HD (BACHD). Our data indicate that young BACHD mice exhibit increased striatal glutamate release, which is reduced to wild type levels following Cav2.2 block. Cav2.2 Ca2+ current-density and plasma membrane expression are increased in BACHD mice, which could account for increased glutamate release. Moreover, mutant htt affects the interaction between Cav2.2 and 2 major channel regulators, namely syntaxin 1A and Gßγ protein. Notably, 12-month old BACHD mice exhibit decreased Cav2.2 cell surface expression and glutamate release, suggesting that Cav2.2 alterations vary according to disease stage.
Assuntos
Canais de Cálcio Tipo N/fisiologia , Proteína Huntingtina/genética , Proteína Huntingtina/fisiologia , Doença de Huntington/genética , Doença de Huntington/fisiopatologia , Mutação , Transmissão Sináptica/genética , Animais , Modelos Animais de Doenças , Glutamatos/metabolismo , Camundongos Transgênicos , Neurotransmissores/metabolismo , Sinapses/metabolismo , Sintaxina 1/fisiologiaRESUMO
Involuntary choreiform movements are clinical hallmark of Huntington's disease, an autosomal dominant neurodegenerative disorder caused by an increased number of CAG trinucleotide repeats in the huntingtin gene. Involuntary movements start with an impairment of facial muscles and then affect trunk and limbs muscles. Huntington's disease symptoms are caused by changes in cortex and striatum neurons induced by mutated huntingtin protein. However, little is known about the impact of this abnormal protein in spinal cord motoneurons that control movement. Therefore, in this study we evaluated abnormalities in the motor unit (spinal cervical motoneurons, motor axons, neuromuscular junctions and muscle) in a mouse model for Huntington's disease (BACHD). Using light, fluorescence, confocal, and electron microscopy, we showed significant changes such as muscle fibers atrophy, fragmentation of neuromuscular junctions, axonal alterations, and motoneurons death in BACHD mice. Noteworthy, the surviving motoneurons from BACHD spinal cords were smaller than WT. We suggest that this loss of larger putative motoneurons is accompanied by a decrease in the expression of fast glycolytic muscle fibers in this model for Huntington's disease. These observations show spinal cord motoneurons loss in BACHD that might help to understand neuromuscular changes in Huntington's disease.
Assuntos
Doença de Huntington/patologia , Neurônios Motores/patologia , Atrofia Muscular/patologia , Animais , Vértebras Cervicais/patologia , Masculino , Camundongos , Músculo Esquelético/patologia , Junção Neuromuscular/patologia , Medula Espinal/patologiaRESUMO
Huntington's disease (HD) is a neurodegenerative disorder characterized by a progressive decline of motor and cognitive functions. It is caused by a polyglutamine expansion in the huntingtin (htt) protein, which then leads to neurodegeneration that span both the central and peripheral nervous system. Previous works have shown that htt interacts with several proteins from the neurotransmitter release machinery causing synaptic dysfunction. In this work, we looked for alterations in diaphragm neuromuscular junctions (NMJs) from 3 to 4 months old BACHD mouse model for HD. This model represents a new and robust in vivo paradigm for studying the pathogenesis of HD. For optical analysis, NMJs were stained with FM1-43fx and α-bungarotoxin to visualize both pre and postsynaptic elements, respectively. Confocal microscopy optical analysis showed a decrease in the number of synaptic elements and fluorescence intensity in NMJs from BACHD diaphragms compared to WT. We next analyzed presynaptic activity and we observed that synaptic vesicle exocytosis was impaired in NMJs from BACHD diaphragms. Ultrastructural analysis revealed significant changes in the form and sizes of the synaptic vesicles in BACHD diaphragm NMJs that could contribute to impaired exocytosis. Additionally, electrophysiology recordings revealed a decrease in the amplitude of miniature endplate potentials (MEPPs) from BACHD diaphragm NMJs. Our data suggest a dysfunction in BACHD diaphragm NMJs that might occur in other muscles and may aggravate the motor defects seen in HD. These results may contribute to a better understanding of peripheral cholinergic dysfunction in this neurodegenerative disease.