RESUMO
Congenital Myasthenic Syndromes (CMS) are a set of genetic diseases that affect the neuromuscular transmission causing muscular weakness. The standard pharmacological treatment aims at ameliorating the myasthenic symptom by acetylcholinesterase inhibitors. Most patients respond well in the short and medium term, however, over time the beneficial effects rapidly fade, and the efficacy of the treatment diminishes. Increasing evidence shows that ß2-adrenergic agonists can be a suitable choice for the treatment of neuromuscular disorders, including CMS, as they promote beneficial effects in the neuromuscular system. The exact mechanism on which they rely is not completely understood, although patients and animal models respond well to the treatment, especially over extended periods. Here, we report the use of the long-lasting specific ß2-adrenergic agonist formoterol in a myasthenic mouse model (mnVAChT-KD), featuring deletion of VAChT (Vesicular Acetylcholine Transporter) specifically in the α-motoneurons. Our findings demonstrate that formoterol treatment (300 µg/kg/day; sc) for 30 days increased the neuromuscular junction area, induced skeletal muscle hypertrophy and altered fibre type composition in myasthenic mice. Interestingly, ß2-adrenergic agonists have shown efficacy even in the absence of ACh (acetylcholine). Our data provide important evidence supporting the potential of ß2-adrenergic agonists in treating neuromuscular disorders of pre-synaptic origin and characterized by disruptions in nerve-muscle communication, through a direct and beneficial action within the motor unit.
Assuntos
Agonistas de Receptores Adrenérgicos beta 2 , Modelos Animais de Doenças , Fumarato de Formoterol , Síndromes Miastênicas Congênitas , Junção Neuromuscular , Proteínas Vesiculares de Transporte de Acetilcolina , Animais , Síndromes Miastênicas Congênitas/tratamento farmacológico , Síndromes Miastênicas Congênitas/genética , Fumarato de Formoterol/farmacologia , Fumarato de Formoterol/uso terapêutico , Agonistas de Receptores Adrenérgicos beta 2/farmacologia , Junção Neuromuscular/efeitos dos fármacos , Camundongos , Proteínas Vesiculares de Transporte de Acetilcolina/metabolismo , Proteínas Vesiculares de Transporte de Acetilcolina/genética , Camundongos Endogâmicos C57BL , MasculinoRESUMO
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
Abnormal calcium influx and glutamatergic excitotoxicity have been extensively associated with neuronal death in Huntington's disease (HD), a genetic movement disorder. Currently, there is no effective treatment for this fatal condition. The neurotoxin Phα1ß has demonstrated therapeutic effects as a calcium channel blocker, for example during pain control. However, little is known about its neuroprotective effect in HD. Herein, we investigated if Phα1ß is effective in inhibiting neuronal cell death in the BACHD mouse model for HD. We performed intrastriatal injection of Phα1ß in WT and BACHD mice. No side effects or unusual behaviors were observed upon Phα1ß administration. Using three different motor behavior tests, we observed that injection of the toxin in BACHD mice greatly improved the animals' motor-force as seen in the Wire-hang test, and also the locomotor performance, according to the Open field test. NeuN labeling for mature neuron detection revealed that Phα1ß toxin promoted neuronal preservation in the striatum and cortex, when injected locally. Intrastriatal injection of Phα1ß was not able to preserve neurons from the spinal cord and also not revert muscle atrophy in BACHD mice. Finally, we observed that Phα1ß might, at least in part, exert its protective effect by decreasing L-glutamate, measured in cerebrospinal fluid. Our data provide evidence of a novel neuroprotector effect of Phα1ß, paving a path for the development of new approaches to treat HD motor symptoms.
Assuntos
Doença de Huntington/tratamento farmacológico , Fármacos Neuroprotetores/administração & dosagem , Venenos de Aranha/administração & dosagem , Animais , Modelos Animais de Doenças , Ácido Glutâmico/metabolismo , Doença de Huntington/patologia , Camundongos , Camundongos Transgênicos , Músculo Esquelético/efeitos dos fármacos , Músculo Esquelético/patologia , Neurônios/efeitos dos fármacos , Medula Espinal/efeitos dos fármacos , Medula Espinal/patologiaRESUMO
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.