Lídia Piedrafita

Universitat de Lleida, Lleida, Catalonia, Spain

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Publications (10)30.83 Total impact

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    ABSTRACT: C boutons are large, cholinergic, synaptic terminals that arise from local interneurons and specifically contact spinal α-motoneurons (MNs). C boutons characteristically display a postsynaptic specialization consisting of an endoplasmic reticulum-related subsurface cistern (SSC) of unknown function. In the present work, by using confocal microscopy and ultrastructural immunolabeling, we demonstrate that neuregulin-1 (NRG1) accumulates in the SSC of mouse spinal MNs. We also show that the NRG1 receptors erbB2 and erbB4 are presynaptically localized within C boutons, suggesting that NRG1-based retrograde signaling may occur in this type of synapse. In most of the cranial nuclei, MNs display the same pattern of NRG1 distribution as that observed in spinal cord MNs. Conversely, MNs in oculomotor nuclei, which are spared in amyotrophic lateral sclerosis (ALS), lack both C boutons and SSC-associated NRG1. NRG1 in spinal MNs is developmentally regulated and depends on the maintenance of nerve-muscle interactions, as we show after nerve transection experiments. Changes in NRG1 in C boutons were also investigated in mouse models of MN diseases: i.e., spinal muscular atrophy (SMNΔ7) and ALS (SOD1(G93A)). In both models, a transient increase in NRG1 in C boutons occurs during disease progression. These data increase our understanding of the role of C boutons in MN physiology and pathology.-Gallart-Palau, X., Tarabal, O., Casanovas, A., Sábado, J., Correa, F. J., Hereu, M., Piedrafita, L., Calderó, J., Esquerda, J. E. Neuregulin-1 is concentrated in the postsynaptic subsurface cistern of C-bouton inputs to α-motoneurons and altered during motoneuron diseases.
    The FASEB Journal 05/2014; · 5.70 Impact Factor
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    ABSTRACT: Background / Purpose: Pioneering ultrastructural studies have defined different types of synapses (F-, S- and C-type boutons) on lower motoneurons (MNs). C-Type boutons are large nerve terminals characteristic of somatic alpha-MNs and display a subsynaptic cistern adjacent to postsynaptic membrane. The cholinergic nature of C-terminals has been established, and their origin from local interneurons has been deciphered. In a recent study concerning neuregulin-1 (NRG-1) on phrenic MNs, it has been reported that this trophic factor is expressed in cholinergic terminals synapsing these MNs and a presynaptic localization of this protein was suggested. Main conclusion: NRG-1 is concentrated at the subsynaptic cysterns of alpha-MN afferent cholinergic C-terminals.ALS-resistant MNs at the oculomotor nuclei show low NRG-1 expression. NRG-1 is developmentally regulated and depends on the maintenance of nerve muscle interactions.The transient increase in NRG-1-positive spots on MN somata during SMA or ALS progression is in concordance with the described sprouting of C-terminals in ALS.
    International Symposium on Amyotrophic Lateral Sclerosis and Motor Neurone Disease 2013; 01/2014
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    ABSTRACT: Amyotrophic lateral sclerosis (ALS) is an adult-onset progressive neurodegenerative disease affecting upper and lower motoneurons (MNs). Although the motor phenotype is a hallmark for ALS, there is increasing evidence that systems other than the efferent MN system can be involved. Mutations of superoxide dismutase 1 (SOD1) gene cause a proportion of familial forms of this disease. Misfolding and aggregation of mutant SOD1 exert neurotoxicity in a noncell autonomous manner, as evidenced in studies using transgenic mouse models. Here, we used the SOD1(G93A) mouse model for ALS to detect, by means of conformational-specific anti-SOD1 antibodies, whether misfolded SOD1-mediated neurotoxicity extended to neuronal types other than MNs. We report that large dorsal root ganglion (DRG) proprioceptive neurons accumulate misfolded SOD1 and suffer a degenerative process involving the inflammatory recruitment of macrophagic cells. Degenerating sensory axons were also detected in association with activated microglial cells in the spinal cord dorsal horn of diseased animals. As large proprioceptive DRG neurons project monosynaptically to ventral horn MNs, we hypothesise that a prion-like mechanism may be responsible for the transsynaptic propagation of SOD1 misfolding from ventral horn MNs to DRG sensory neurons.
    BioMed Research International 01/2014; 2014:852163. · 2.71 Impact Factor
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    ABSTRACT: Spinal muscular atrophy (SMA) is an autosomal recessive neuromuscular disorder caused by defective levels of the survival motor neuron (SMN) protein. SMA causes spinal motoneuron (MN) loss, and progressive muscle weakness and paralysis. Currently, there is no effective therapy to cure this disease. Although different strategies focused on increasing the expression of functional SMN protein have been assayed, numerous SMN-independent therapeutic approaches have been demonstrated to have potential effectiveness in improving SMA phenotype in mouse models and clinical trials. Recent works have shown that compounds which inhibit GSK-3β activity are effective in promoting MN survival and ameliorating lifespan in models of MN diseases including SMA. Taking into account the reported neuroprotective actions of lithium (Li) through the inhibition of GSK-3β in different studies, we tested here its potential efficiency as a therapeutic agent in a mouse model of severe SMA (SMNΔ7 mice). We show that the chronic treatment with Li initiated before the appearance of disease symptoms, although inhibited GSK-3β, did not improve the median survival, motor behavior, and spinal MN loss linked to SMA. Li administration did not either ameliorate the microglial and astroglial reaction in the spinal cord or the depletion of glutamatergic synapses on MNs observed in SMNΔ7 animals. Moreover, Li treatment did not mitigate muscle atrophy or calcitonin gene-related peptide (CGRP) downregulation in the neuromuscular junctions linked to the disease. However, a significant reduction in apoptotic cell death found in the skeletal muscle of SMA mice was observed after Li treatment.
    Neuroscience 07/2013; · 3.12 Impact Factor
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    ABSTRACT: We previously showed that some antipurinergic receptor P2X4 antibodies cross react with misfolded forms of amyotrophic lateral sclerosis (ALS)-linked mutant Cu/Zn superoxide dismutase (SOD1). Cross reactivity might be caused by abnormal exposure of an epitope in the inner hydrophobic region of SOD1 that shares structural homology with the P2X4-immunizing peptide. Here, we raised antibodies against the human SOD1 epitope mimicked by the P2X4 immunizing peptide. One of these antibodies, AJ10, is a recognized mutant/misfolded form of ALS-linked mutant SOD1. This was demonstrated in the hybrid motoneuron cell line NSC34 expressing enhanced green fluorescent protein-tagged G943A or A4V mutant SOD1. We also found AJ10 immunoreactivity to be selectively associated with degenerating neurons but not with glial cells in mice overexpressing either SOD1 or SOD1 mutants. Neurons with strongly positive AJ10 immunostaining were often associated with activated microglia displaying neuronophagic activity. AJ10-immunopositive SOD1 aggregates were also found in spinal cord tissue from a patient with a SOD1-linked familial ALS. AJ10-immunoreactive mutant SOD1 conformers were localized in large intracellular protein aggregates with a filamentous amyloid-like organization by ultrastructural immunolabeling and were also detected in neuronal organelles. These data are consistent with the ability of the AJ10 antibody to recognize misfolded conformations of SOD1 shared by different ALS-linked SOD1 mutations but not with the native protein. The neuronal mutant SOD1 conformers detected with AJ10 may promote neuroinflammation and may define a new epitope in SOD1 for ALS research.
    Journal of neuropathology and experimental neurology. 06/2013;
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    ABSTRACT: A detailed pathologic analysis was performed on Smn(-/-);SMN2 mice as a mouse model for human type I spinal muscular atrophy (SMA). We provide new data concerning changes in the spinal cord, neuromuscular junctions and muscle cells, and in the organs of the immune system. The expression of 10 synaptic proteins was analyzed in 3-dimensionally reconstructed neuromuscular junctions by confocal microscopy. In addition to defects in postsynaptic occupancy, there was a marked reduction in calcitonin gene-related peptide and Rab3A in the presynaptic motor terminals of some, but not all, of the skeletal muscles analyzed. Defects in the organization of presynaptic nerve terminals were also detected by electron microscopy. Moreover, degenerative changes in muscle cells, defective postnatal muscle growth, and prominent muscle satellite cell apoptosis were also observed. All of these changes occurred in the absence of massive loss of spinal cord motoneurons. On the other hand, astroglia, but not microglia, increased in the ventral horn of newborn SMA mice. In skeletal muscles, the density of interstitial macrophages was significantly reduced, and monocyte chemotactic protein-1 was downregulated. These findings raise questions regarding the primary contribution of a muscle cell defect to the SMA phenotype.
    Journal of Neuropathology and Experimental Neurology 06/2011; 70(6):444-61. · 4.35 Impact Factor
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    ABSTRACT: Massive programmed cell death (PCD) of developing chick embryo motoneurons (MNs) occurs in a well defined temporal and spatial sequence between embryonic day (E) 6 and E10. We have found that, when administered in ovo, either circulating immunoglobulins G (IgGs) or cerebrospinal fluid from patients with MN disease can rescue a significant number of chick embryo MNs from normally occurring PCD. An increase of branching of intramuscular nerves was also observed that may account for the rescuing effects of pathologic IgGs. Proteomic analysis and further analysis by ELISA indicated that these effects may be mediated by the interaction of circulating human immunoglobulins with proteins of the semaphorin family.
    Journal of neuroimmunology 12/2010; 229(1-2):157-68. · 2.84 Impact Factor
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    ABSTRACT: We recently reported that degenerating motor neurons of superoxide dismutase mutant 1 (SOD1) rodents exhibit immunoreactivity to P2X(4) antibodies. Neurons with strong P2X(4)-like immunoreactivity (P2X(4)-LIR) do not show an apoptotic phenotype and are often associated with microglial cells that display neuronophagic activity. Western blot analysis showed that P2X(4) antibodies recognize not only the P2X(4) adenosine triphosphate receptor protein but also a hitherto unidentified low-molecular weight band. Here, we identify the molecular counterpart of the strong P2X(4)-LIR observed in association with neuronal degeneration in SOD1 animals. After matrix-assisted laser desorption/ionization time-of-flight, we found that the low-molecular weight P2X(4)-immunoreactive protein was SOD1. Further analysis demonstrated that the P2X(4) antibody recognizes a form of misfolded mutant SOD1 that is expressed in neuronal cells undergoing degeneration but not in glial cells. Cross-reactivity could have been caused by the abnormal exposure of an epitope in the inner hydrophobic region of SOD1 that shared structural homology with the P2X(4)-immunizing peptide used for raising the antibody. No positive P2X(4) immunostaining was detected in mice overexpressing human wild-type SOD1. Intracerebral injections of affinity chromatography-isolated P2X(4)-immunoreactive SOD1 species promote microglial and astroglial activation. We conclude that neuronal SOD1 conformers with P2X(4)-LIR may have pathogenetic relevance in the promotion of neuroinflammation.
    Journal of Neuropathology and Experimental Neurology 02/2010; 69(2):176-87. · 4.35 Impact Factor
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    ABSTRACT: Several studies have reported the neuroprotective effects of lithium (Li) suggesting its potential in the treatment of neurological disorders, among of them amyotrophic lateral sclerosis (ALS). Although the cause of motoneuron (MN) death in ALS remains unknown, there is evidence that glutamate-mediated excitotoxicity plays an important role. In the present study we used an organotypic culture system of chick embryo spinal cord to explore the presumptive neuroprotective effects of Li against kainate-induced excitotoxic MN death. We found that chronic treatment with Li prevented excitotoxic MN loss in a dose dependent manner and that this effect was mediated by the inhibition of glycogen synthase kinase-3beta (GSK-3beta) signaling pathway. This neuroprotective effect of Li was potentiated by a combined treatment with riluzole. Nevertheless, MNs rescued by Li displayed structural changes including accumulation of neurofilaments, disruption of the rough endoplasmic reticulum and free ribosome loss, and accumulation of large dense core vesicles and autophagic vacuoles. Accompanying these changes there was an increase in immunostaining for (a) phosphorylated neurofilaments, (b) calcitonin gene-related peptide (CGRP) and (c) the autophagic marker LC3. Chronic Li treatment also resulted in a reduction in the excitotoxin-induced rise in intracellular Ca(2+) in MNs. In contrast to the neuroprotection against excitotoxicity, Li was not able to prevent normal programmed (apoptotic) MN death in the chick embryo when chronically administered in ovo. In conclusion, these results show that although Li is able to prevent excitotoxic MN death by targeting GSK-3beta, this neuroprotective effect is associated with conspicuous cytopathological changes.
    Neuroscience 11/2009; 165(4):1353-69. · 3.12 Impact Factor
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    ABSTRACT: Soluble proteins from normal, adult denervated, and developing rat muscles were studied in order to identify common molecular species undergoing developmental regulation and nerve dependence. Significant increases in 66- and 30-kDa proteins were found as a consequence of 14 days of denervation. Subsequent reinnervation restores normal adult levels. During development, high levels of the 66-kDa protein were found in neonatal muscles but slowly decreased concomitant with the following postnatal maturation period; the adult levels were reached at Postnatal Day (P) 21. From the immunocytochemical studies it is deduced that both proteins were concentrated mainly at the end-plate region in adult normal muscle. Following denervation, the proteins were found distributed over the entire cell. For the 66-kDa protein, a similar pattern of extensive distribution was seen in immature muscle. Although no data for functional implications for these proteins are available at present, the properties described here make them of interest in understanding nerve-muscle interactions.
    Experimental Neurology 09/1989; 105(2):211-8. · 4.65 Impact Factor