RESUMO
Amyotrophic lateral sclerosis (ALS) is a devastating neurodegenerative disease affecting upper and lower motor neurons (MNs). Neuregulin-1 (NRG1) is a pleiotropic growth factor that has been shown to be potentially valuable for ALS when supplemented by means of viral-mediated gene therapy. However, these results are inconsistent with other reports. An alternative approach for investigating the therapeutic impact of NRG1 on ALS is the use of transgenic mouse lines with genetically defined NRG1 overexpression. Here, we took advantage of a mouse line with NRG1 type III overexpression in spinal cord α motor neurons (MN) to determine the impact of steadily enhanced NRG1 signalling on mutant superoxide dismutase 1 (SOD1)-induced disease. The phenotype of SOD1G93A-NRG1 double transgenic mice was analysed in detail, including neuropathology and extensive behavioural testing. At least 3 animals per condition and sex were histopathologically assessed, and a minimum of 10 mice per condition and sex were clinically evaluated. The accumulation of misfolded SOD1 (mfSOD1), MN degeneration, and a glia-mediated neuroinflammatory response are pathological hallmarks of ALS progression in SOD1G93A mice. None of these aspects was significantly improved when examined in double transgenic NRG1-SOD1G93A mice. In addition, behavioural testing revealed that NRG1 type III overexpression did not affect the survival of SOD1G93A mice but accelerated disease onset and worsened the motor phenotype.
Assuntos
Esclerose Lateral Amiotrófica , Doenças Neurodegenerativas , Camundongos , Animais , Esclerose Lateral Amiotrófica/genética , Esclerose Lateral Amiotrófica/terapia , Esclerose Lateral Amiotrófica/metabolismo , Superóxido Dismutase-1/genética , Neuregulina-1/genética , Doenças Neurodegenerativas/metabolismo , Superóxido Dismutase/genética , Superóxido Dismutase/metabolismo , Neurônios Motores/patologia , Camundongos TransgênicosRESUMO
Besides skeletal muscle wasting, sarcopenia entails morphological and molecular changes in distinct components of the neuromuscular system, including spinal cord motoneurons (MNs) and neuromuscular junctions (NMJs); moreover, noticeable microgliosis has also been observed around aged MNs. Here we examined the impact of two flavonoid-enriched diets containing either green tea extract (GTE) catechins or cocoa flavanols on age-associated regressive changes in the neuromuscular system of C57BL/6J mice. Compared to control mice, GTE- and cocoa-supplementation significantly improved the survival rate of mice, reduced the proportion of fibers with lipofuscin aggregates and central nuclei, and increased the density of satellite cells in skeletal muscles. Additionally, both supplements significantly augmented the number of innervated NMJs and their degree of maturity compared to controls. GTE, but not cocoa, prominently increased the density of VAChT and VGluT2 afferent synapses on MNs, which were lost in control aged spinal cords; conversely, cocoa, but not GTE, significantly augmented the proportion of VGluT1 afferent synapses on aged MNs. Moreover, GTE, but not cocoa, reduced aging-associated microgliosis and increased the proportion of neuroprotective microglial phenotypes. Our data indicate that certain plant flavonoids may be beneficial in the nutritional management of age-related deterioration of the neuromuscular system.
Assuntos
Envelhecimento , Catequina/farmacologia , Suplementos Nutricionais , Junção Neuromuscular/efeitos dos fármacos , Extratos Vegetais/farmacologia , Polifenóis/farmacologia , Animais , Cacau/química , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Neurônios Motores/efeitos dos fármacos , Músculo Esquelético/efeitos dos fármacos , Chá/químicaRESUMO
In an attempt to determine whether the rescue of developing motoneurons (MNS) from programmed cell death (PCD) in the chick embryo following reductions in neuromuscular function involves muscle or neuronal nicotinic acetylcholine receptors (nAChRs), we have employed a novel cone snail toxin alphaA-OIVA that acts selectively to antagonize the embryonic/fetal form of muscle nAChRs. The results demonstrate that alphaA-OIVA is nearly as effective as curare or alpha-bungarotoxin (alpha-BTX) in reducing neuromuscular function and is equally effective in increasing MN survival and intramuscular axon branching. Together with previous reports, we also provide evidence consistent with a transition between the embryonic/fetal form to the adult form of muscle nAChRs in chicken that involves the loss of the gamma subunit in the adult receptor. We conclude that selective inhibition of the embryonic/fetal form of the chicken muscle nAChR is sufficient to rescue MNs from PCD without any involvement of neuronal nAChRs.
Assuntos
Apoptose/fisiologia , Neurônios Motores/fisiologia , Junção Neuromuscular/citologia , Receptores Nicotínicos/fisiologia , Animais , Apoptose/efeitos dos fármacos , Axônios/efeitos dos fármacos , Axônios/fisiologia , Bungarotoxinas/farmacologia , Sobrevivência Celular , Embrião de Galinha , Conotoxinas/farmacologia , Curare/farmacologia , Neurônios Motores/citologia , Neurônios Motores/efeitos dos fármacos , Movimento/efeitos dos fármacos , Junção Neuromuscular/efeitos dos fármacos , Junção Neuromuscular/embriologia , Antagonistas Nicotínicos/farmacologia , Peptídeos Cíclicos/farmacologia , Tubulina (Proteína)/metabolismoRESUMO
In the chick embryo, in ovo application of NMDA from embryonic day (E) 5 to E9 results in selective damage to spinal cord motoneurons (MNs) that undergo a long-lasting degenerative process without immediate cell death. This contrasts with a single application of NMDA on E8, or later, which induces massive necrosis of the whole spinal cord. Chronic MN degeneration after NMDA implies transient incompetence to develop programmed cell death, altered protein processing within secretory pathways, and late activation of autophagy. Chronic NMDA treatment also results in an enlargement of thapsigargin-sensitive Ca(2+) stores. In particular MN pools, such as sartorius-innervating MNs, the neuropeptide CGRP is accumulated in somas, peripheral axons and neuromuscular junctions after chronic NMDA treatment, but not in embryos paralyzed by chronic administration of curare. Intramuscular axonal branching is also altered severely after NMDA: it usually increases, but in some cases a marked reduction can also be observed. Moreover, innervated muscle postsynaptic sites increase by NMDA, but to a lesser extent than by curare. Because some of these results show interesting homologies with MN pathology in human sporadic ALS, the model presented here provides a valuable tool for advancing in the understanding of some cellular and molecular processes particularly involved in this disease.