Publications by authors named "José Rodríguez-Alvarez"

34 Publications

microRNAs as Early Biomarkers of Alzheimer's Disease: A Synaptic Perspective.

Cells 2021 Jan 9;10(1). Epub 2021 Jan 9.

Department Bioquímica i Biologia Molecular, Institut de Neurociències, Universitat Autònoma de Barcelona, 08193 Cerdanyola del Vallès, Spain.

Pathogenic processes underlying Alzheimer's disease (AD) affect synaptic function from initial asymptomatic stages, long time before the onset of cognitive decline and neurodegeneration. Therefore, reliable biomarkers enabling early AD diagnosis and prognosis are needed to maximize the time window for therapeutic interventions. MicroRNAs (miRNAs) have recently emerged as promising cost-effective and non-invasive biomarkers for AD, since they can be readily detected in different biofluids, including cerebrospinal fluid (CSF) and blood. Moreover, a growing body of evidence indicates that miRNAs regulate synaptic homeostasis and plasticity processes, suggesting that they may be involved in early synaptic dysfunction during AD. Here, we review the current literature supporting a role of miRNAs during early synaptic deficits in AD, including recent studies evaluating their potential as AD biomarkers. Besides targeting genes related to Aβ and tau metabolism, several miRNAs also regulate synaptic-related proteins and transcription factors implicated in early synaptic deficits during AD. Furthermore, individual miRNAs and molecular signatures have been found to distinguish between prodromal AD and healthy controls. Overall, these studies highlight the relevance of considering synaptic-related miRNAs as potential biomarkers of early AD stages. However, further validation studies in large cohorts, including longitudinal studies, as well as implementation of standardized protocols, are needed to establish miRNA-based biomarkers as reliable diagnostic and prognostic tools.
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http://dx.doi.org/10.3390/cells10010113DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7827653PMC
January 2021

Sensing of nutrients by CPT1C controls SAC1 activity to regulate AMPA receptor trafficking.

J Cell Biol 2020 10;219(10)

Basic Sciences Department, Faculty of Medicine and Health Sciences, Universitat Internacional de Catalunya, Sant Cugat del Vallès, Spain.

Carnitine palmitoyltransferase 1C (CPT1C) is a sensor of malonyl-CoA and is located in the ER of neurons. AMPA receptors (AMPARs) mediate fast excitatory neurotransmission in the brain and play a key role in synaptic plasticity. In the present study, we demonstrate across different metabolic stress conditions that modulate malonyl-CoA levels in cortical neurons that CPT1C regulates the trafficking of the major AMPAR subunit, GluA1, through the phosphatidyl-inositol-4-phosphate (PI(4)P) phosphatase SAC1. In normal conditions, CPT1C down-regulates SAC1 catalytic activity, allowing efficient GluA1 trafficking to the plasma membrane. However, under low malonyl-CoA levels, such as during glucose depletion, CPT1C-dependent inhibition of SAC1 is released, facilitating SAC1's translocation to ER-TGN contact sites to decrease TGN PI(4)P pools and trigger GluA1 retention at the TGN. Results reveal that GluA1 trafficking is regulated by CPT1C sensing of malonyl-CoA and provide the first report of a SAC1 inhibitor. Moreover, they shed light on how nutrients can affect synaptic function and cognition.
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http://dx.doi.org/10.1083/jcb.201912045DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7659714PMC
October 2020

Proteasomal-Mediated Degradation of AKAP150 Accompanies AMPAR Endocytosis during cLTD.

eNeuro 2020 Mar/Apr;7(2). Epub 2020 Apr 16.

Institut de Neurociències and Dpt. Bioquímica i Biologia Molecular, Universitat Autònoma de Barcelona, Cerdanyola del Vallès 08193, Spain

The number and function of synaptic AMPA receptors (AMPARs) tightly regulates excitatory synaptic transmission. Current evidence suggests that AMPARs are inserted into the postsynaptic membrane during long-term potentiation (LTP) and are removed from the membrane during long-term depression (LTD). Dephosphorylation of GluA1 at Ser-845 and enhanced endocytosis are critical events in the modulation of LTD. Moreover, changes in scaffold proteins from the postsynaptic density (PSD) could be also related to AMPAR regulation in LTD. In the present study we analyzed the effect of chemical LTD (cLTD) on A-kinase anchoring protein (AKAP)150 and AMPARs levels in mouse-cultured neurons. We show that cLTD induces AKAP150 protein degradation via proteasome, coinciding with GluA1 dephosphorylation at Ser-845 and endocytosis of GluA1-containing AMPARs. Pharmacological inhibition of proteasome activity, but not phosphatase calcineurin (CaN), reverted cLTD-induced AKAP150 protein degradation. Importantly, AKAP150 silencing induced dephosphorylation of GluA1 Ser-845 and GluA1-AMPARs endocytosis while AKAP150 overexpression blocked cLTD-mediated GluA1-AMPARs endocytosis. Our results provide direct evidence that cLTD-induced AKAP150 degradation by the proteasome contributes to synaptic AMPARs endocytosis.
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http://dx.doi.org/10.1523/ENEURO.0218-19.2020DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7163082PMC
April 2020

Altered microRNAs related to synaptic function as potential plasma biomarkers for Alzheimer's disease.

Alzheimers Res Ther 2019 05 15;11(1):46. Epub 2019 May 15.

Institut de Neurociències and Dpt. Bioquímica i Biología Molecular, Universitat Autònoma de Barcelona, 08193, Cerdanyola del Vallès, Spain.

Background: Several evidences suggest that failure of synaptic function occurs at preclinical stages of Alzheimer's disease (AD) preceding neuronal loss and the classical AD pathological hallmarks. Nowadays, there is an urgent need to identify reliable biomarkers that could be obtained with non-invasive methods to improve AD diagnosis at early stages. Here, we have examined plasma levels of a group of miRNAs related to synaptic proteins in a cohort composed of cognitive healthy controls (HC), mild cognitive impairment (MCI) and AD subjects.

Methods: Plasma and brain levels of miRNAs were analysed in two different cohorts including 38 HC, 26 MCI, 56 AD dementia patients and 27 frontotemporal dementia (FTD) patients. D'Agostino and Pearson and Shapiro-Wilk tests were used to evaluate data normality. miRNA levels between groups were compared using a two-sided nonparametric Mann-Whitney test and sensitivity and specificity was determined by receiver operating characteristic curve analysis.

Results: Significant upregulation of miR-92a-3p, miR-181c-5p and miR-210-3p was found in the plasma of both MCI and AD subjects. MCI patients that progress to AD showed higher plasma levels of these miRNAs. By contrast, no changes in miR-92a-3p, miR-181c-5p or miR-210-3p levels were observed in plasma obtained from a cohort of FTD.

Conclusion: Our study shows that plasma miR-92a-3p, miR-181c-5p and miR-210-3p constitute a specific molecular signature potentially useful as a potential biomarker for AD.
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http://dx.doi.org/10.1186/s13195-019-0501-4DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6521366PMC
May 2019

Blood-brain barrier dysfunction underlying Alzheimer's disease is induced by an SSAO/VAP-1-dependent cerebrovascular activation with enhanced Aβ deposition.

Biochim Biophys Acta Mol Basis Dis 2019 09 30;1865(9):2189-2202. Epub 2019 Apr 30.

Biochemistry and Molecular Biology Department, Institute of Neurosciences (INc), Universitat Autònoma de Barcelona (UAB), Bellaterra, Barcelona, Spain. Electronic address:

Dysfunctions of the vascular system directly contribute to the onset and progression of Alzheimer's disease (AD). The blood-brain barrier (BBB) shows signs of malfunction at early stages of the disease. When Abeta peptide (Aβ) is deposited on brain vessels, it induces vascular degeneration by producing reactive oxygen species and promoting inflammation. These molecular processes are also related to an excessive SSAO/VAP-1 (semicarbazide-sensitive amine oxidase) enzymatic activity, observed in plasma and in cerebrovascular tissue of AD patients. We studied the contribution of vascular SSAO/VAP-1 to the BBB dysfunction in AD using in vitro BBB models. Our results show that SSAO/VAP-1 expression is associated to endothelial activation by altering the release of pro-inflammatory and pro-angiogenic angioneurins, most highly IL-6, IL-8 and VEGF. It is also related to a BBB structure alteration, with a decrease in tight-junction proteins such as zona occludens or claudin-5. Moreover, the BBB function reveals increased permeability and leukocyte adhesion in cells expressing SSAO/VAP-1, as well as an enhancement of the vascular Aβ deposition induced by mechanisms both dependent and independent of the enzymatic activity of SSAO/VAP-1. These results reveal an interesting role of vascular SSAO/VAP-1 in BBB dysfunction related to AD progression, opening a new window in the search of alternative therapeutic targets for fighting AD.
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http://dx.doi.org/10.1016/j.bbadis.2019.04.016DOI Listing
September 2019

CRTC1 Function During Memory Encoding Is Disrupted in Neurodegeneration.

Biol Psychiatry 2017 01 11;81(2):111-123. Epub 2016 Jul 11.

Institut de Neurociències, Department de Bioquímica i Biologia Molecular; and the; Centro de Investigación Biomédica en Red Enfermedades Neurodegenerativas, Universitat Autònoma de Barcelona, Barcelona, Spain. Electronic address:

Background: Associative memory impairment is an early clinical feature of dementia patients, but the molecular and cellular mechanisms underlying these deficits are largely unknown. In this study, we investigated the functional regulation of the cyclic adenosine monophosphate response element binding protein (CREB)-regulated transcription coactivator 1 (CRTC1) by associative learning in physiological and neurodegenerative conditions.

Methods: We evaluated the activation of CRTC1 in the hippocampus of control mice and mice lacking the Alzheimer's disease-linked presenilin genes (presenilin conditional double knockout [PS cDKO]) after one-trial contextual fear conditioning by using biochemical, immunohistochemical, and gene expression analyses. PS cDKO mice display classical features of neurodegeneration occurring in Alzheimer's disease including age-dependent cortical atrophy, neuron loss, dendritic degeneration, and memory deficits.

Results: Context-associative learning, but not single context or unconditioned stimuli, induces rapid dephosphorylation (Ser151) and translocation of CRTC1 from the cytosol/dendrites to the nucleus of hippocampal neurons in the mouse brain. Accordingly, context-associative learning induces differential CRTC1-dependent transcription of c-fos and the nuclear receptor subfamily 4 (Nr4a) genes Nr4a1-3 in the hippocampus through a mechanism that involves CRTC1 recruitment to CRE promoters. Deregulation of CRTC1 dephosphorylation, nuclear translocation, and transcriptional function are associated with long-term contextual memory deficits in PS cDKO mice. Importantly, CRTC1 gene therapy in the hippocampus ameliorates context memory and transcriptional deficits and dendritic degeneration despite ongoing cortical degeneration in this neurodegeneration mouse model.

Conclusions: These findings reveal a critical role of CRTC1 in the hippocampus during associative memory, and provide evidence that CRTC1 deregulation underlies memory deficits during neurodegeneration.
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http://dx.doi.org/10.1016/j.biopsych.2016.06.025DOI Listing
January 2017

Novel Regulation of the Synthesis of α-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid (AMPA) Receptor Subunit GluA1 by Carnitine Palmitoyltransferase 1C (CPT1C) in the Hippocampus.

J Biol Chem 2015 Oct 3;290(42):25548-60. Epub 2015 Sep 3.

From the Basic Sciences Department, Facultat de Medicina i Ciències de la Salut, Universitat Internacional de Catalunya, Sant Cugat del Vallès 08195, Spain, the Centro de Investigación Biomédica en Red de Fisiopatología de la Obesidad y la Nutrición (CIBEROBN), 15706 Santiago de Compostela, Spain

The regulation of AMPA-type receptor (AMPAR) abundance in the postsynaptic membrane is an important mechanism involved in learning and memory formation. Recent data suggest that one of the constituents of the AMPAR complex is carnitine palmitoyltransferase 1C (CPT1C), a brain-specific isoform located in the endoplasmic reticulum of neurons. Previous results had demonstrated that CPT1C deficiency disrupted spine maturation in hippocampal neurons and impaired spatial learning, but the role of CPT1C in AMPAR physiology had remained mostly unknown. In the present study, we show that CPT1C binds GluA1 and GluA2 and that the three proteins have the same expression profile during neuronal maturation. Moreover, in hippocampal neurons of CPT1C KO mice, AMPAR-mediated miniature excitatory postsynaptic currents and synaptic levels of AMPAR subunits GluA1 and GluA2 are significantly reduced. We show that AMPAR expression is dependent on CPT1C levels because total protein levels of GluA1 and GluA2 are decreased in CPT1C KO neurons and are increased in CPT1C-overexpressing neurons, whereas other synaptic proteins remain unaltered. Notably, mRNA levels of AMPARs remained unchanged in those cultures, indicating that CPT1C is post-transcriptionally involved. We demonstrate that CPT1C is directly involved in the de novo synthesis of GluA1 and not in protein degradation. Moreover, in CPT1C KO cultured neurons, GluA1 synthesis after chemical long term depression was clearly diminished, and brain-derived neurotrophic factor treatment was unable to phosphorylate the mammalian target of rapamycin (mTOR) and stimulate GluA1 protein synthesis. These data newly identify CPT1C as a regulator of AMPAR translation efficiency and therefore also synaptic function in the hippocampus.
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http://dx.doi.org/10.1074/jbc.M115.681064DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4646200PMC
October 2015

Delineating the factors and cellular mechanisms involved in the survival of cerebellar granule neurons.

Cerebellum 2015 Jun;14(3):354-9

Departament de Ciències Mèdiques, Facultat de Medicina, Universitat de Girona, C/ Emili Grahit, 77, 17071, Girona, Spain,

Cerebellar granule neurons (CGNs) constitute the most abundant neuronal population in the mammalian brain. Their postnatal generation and the feasibility to induce their apoptotic death in vitro make them an excellent model to study the effect of several neurotransmitters and neurotrophins. Here, we first review which factors are involved in the generation and proliferation of CGNs in the external granule layer (EGL) and in the regulation of their differentiation and migration to internal granule layer (IGL). Special attention was given to the role of several neurotrophins and the NMDA subtype of glutamate receptor. Then, using the paradigm of potassium deprivation in cultured CGNs, we address several extracellular factors that promote the survival of CGNs, with particular emphasis on the cellular mechanisms. The role of specific protein kinases leading to the regulation of transcription factors and recent data involving the small G protein family is also discussed. Finally, the participation of some members of Bcl-2 family and the inhibition of mitochondria-related apoptotic pathway is also considered. Altogether, these studies evidence that CGNs are a key model to understand the development and the survival of neuronal populations.
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http://dx.doi.org/10.1007/s12311-015-0646-zDOI Listing
June 2015

Endogenous XIAP, but not other members of the inhibitory apoptosis protein family modulates cerebellar granule neurons survival.

Int J Dev Neurosci 2014 Oct 21;37:26-35. Epub 2014 Jun 21.

División de Neurociencias, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, 04510 México City, Mexico. Electronic address:

Programmed cell death plays a critical role during cerebellar development. In particular, it has been shown in vivo and in vitro that developing cerebellar granule neurons (CGN) die apoptotically. Apoptosis involves a series of morphological changes and the activation of caspases. Inhibitor of apoptosis proteins (IAPs) is implicated in negative regulation of caspase activation and apoptotic cell death. Although apoptotic death of CGN has been extensively studied, there is no information about the role of IAPs in the developing cerebellum. Here, we studied the participation of some members of IAPs in the survival of the developing rat CGN in culture and under physiological conditions. Under these conditions, we found a differential expression pattern of cIAP-1, cIAP-2, XIAP and survivin during cerebellar development in an age-dependent manner, highlighting the significant increase of XIAP levels. We also detected an interaction between XIAP and caspase 3 at postnatal day (P) 12 and 16. On the other hand, we found a significant decrease of XIAP levels in cultured CGN maintained in chronic potassium deprivation, an apoptotic condition, suggesting a possible relationship between XIAP levels and neuronal viability. Under these conditions, we also detected the interaction of XIAP with active caspase-3. The down-regulation of XIAP in CGN cultured under survival conditions (chronic potassium depolarization) induced a reduction of cell viability and an increment of apoptotic cells. These findings support the idea that IAPs could be involved in the survival of CGN and that XIAP might be critical for neuronal survival in cerebellar development and during chronic depolarization in cultured CGN through a mechanism involving caspase inhibition.
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http://dx.doi.org/10.1016/j.ijdevneu.2014.06.006DOI Listing
October 2014

Crtc1 activates a transcriptional program deregulated at early Alzheimer's disease-related stages.

J Neurosci 2014 Apr;34(17):5776-87

Institut de Neurociències, Department de Bioquímica i Biologia Molecular, Universitat Autònoma de Barcelona, Barcelona 08193, Spain, and Centro de Investigación Biomédica en Red Enfermedades Neurodegenerativas (CIBERNED) and Institut de Neuropatologia, IDIBELL-Hospital Universitari de Bellvitge, Universitat de Barcelona, Barcelona 08907, Spain.

Cognitive decline is associated with gene expression changes in the brain, but the transcriptional mechanisms underlying memory impairments in cognitive disorders, such as Alzheimer's disease (AD), are largely unknown. Here, we aimed to elucidate relevant mechanisms responsible for transcriptional changes underlying early memory loss in AD by examining pathological, behavioral, and transcriptomic changes in control and mutant β-amyloid precursor protein (APPSw,Ind) transgenic mice during aging. Genome-wide transcriptome analysis using mouse microarrays revealed deregulation of a gene network related with neurotransmission, synaptic plasticity, and learning/memory in the hippocampus of APPSw,Ind mice after spatial memory training. Specifically, APPSw,Ind mice show changes on a cAMP-responsive element binding protein (CREB)-regulated transcriptional program dependent on the CREB-regulated transcription coactivator-1 (Crtc1). Interestingly, synaptic activity and spatial memory induces Crtc1 dephosphorylation (Ser151), nuclear translocation, and Crtc1-dependent transcription in the hippocampus, and these events are impaired in APPSw,Ind mice at early pathological and cognitive decline stages. CRTC1-dependent genes and CRTC1 levels are reduced in human hippocampus at intermediate Braak III/IV pathological stages. Importantly, adeno-associated viral-mediated Crtc1 overexpression in the hippocampus efficiently reverses Aβ-induced spatial learning and memory deficits by restoring a specific subset of Crtc1 target genes. Our results reveal a critical role of Crtc1-dependent transcription on spatial memory formation and provide the first evidence that targeting brain transcriptome reverses memory loss in AD.
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http://dx.doi.org/10.1523/JNEUROSCI.5288-13.2014DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6608295PMC
April 2014

Ras protein activation is a key event in activity-dependent survival of cerebellar granule neurons.

J Biol Chem 2014 Mar 12;289(12):8462-72. Epub 2014 Feb 12.

From the Institut de Neurociencies and Department of Bioquímica i Biología Molecular, Universitat Autònoma de Barcelona, 08193 Cerdanyola del Vallès, Spain.

Neuronal activity promotes the survival of cerebellar granule neurons (CGNs) during the postnatal development of cerebellum. CGNs that fail to receive excitatory inputs will die by apoptosis. This process could be mimicked in culture by exposing CGNs to either a physiological concentration of KCl (5 mm or K5) plus N-methyl-d-aspartate (NMDA) or to 25 mm KCl (K25). We have previously described that a 24-h exposure to NMDA (100 μm) or K25 at 2 days in vitro induced long term survival of CGNs in K5 conditions. Here we have studied the molecular mechanisms activated at 2 days in vitro in these conditions. First we showed that NMDA or K25 addition promoted a rapid stimulation of PI3K and a biphasic phosphorylation on Ser-473 of Akt, a PI3K substrate. Interestingly, we demonstrated that only the first wave of Akt phosphorylation is necessary for the NMDA- and K25-mediated survival. Additionally, we detected that both NMDA and K25 increased ERK activity with a similar time-course. Moreover, our results showed that NMDA-mediated activation of the small G-protein Ras is necessary for PI3K/Akt pathway activation, whereas Rap1 was involved in NMDA phosphorylation of ERK. On the other hand, Ras, but not Rap1, mediates K25 activation of PI3K/Akt and MEK/ERK pathways. Because neuroprotection by NMDA or K25 is mediated by Ras (and not by Rap1) activation, we propose that Ras stimulation is a crucial event in NMDA- and K25-mediated survival of CGNs through the activation of PI3K/Akt and MEK/ERK pathways.
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http://dx.doi.org/10.1074/jbc.M113.536375DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3961671PMC
March 2014

X-linked inhibitor of apoptosis protein negatively regulates neuronal differentiation through interaction with cRAF and Trk.

Sci Rep 2013 ;3:2397

Institut de Neurociències and Dpt. Bioquímica and Biología Molecular, Universitat Autònoma de Barcelona, 08193 Cerdanyola del Vallès, Spain.

X-linked Inhibitor of apoptosis protein (XIAP) has been classically identified as a cell death regulator. Here, we demonstrate a novel function of XIAP as a regulator of neurite outgrowth in neuronal cells. In PC12 cells, XIAP overexpression prevents NGF-induced neuronal differentiation, whereas NGF treatment induces a reduction of endogenous XIAP levels concomitant with the induction of neuronal differentiation. Accordingly, downregulation of endogenous XIAP protein levels strongly increases neurite outgrowth in PC12 cells as well as axonal and dendritic length in primary cortical neurons. The effects of XIAP are mediated by the mitogen-activated protein kinase (MEK)/extracellular signal-regulated kinases (ERKs) pathway since blocking this pathway completely prevents the neuritogenesis mediated by XIAP downregulation. In addition, we found that XIAP binds to cRaf and Trk receptors. Our results demonstrate that XIAP plays a new role as a negative regulator of neurotrophin-induced neurite outgrowth and neuronal differentiation in developing neurons.
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http://dx.doi.org/10.1038/srep02397DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3739015PMC
February 2014

Nurr1 protein is required for N-methyl-D-aspartic acid (NMDA) receptor-mediated neuronal survival.

J Biol Chem 2012 Mar 31;287(14):11351-62. Epub 2012 Jan 31.

Institut de Neurociencies and Departament de Bioquímica i Biología Molecular, Universitat Autònoma de Barcelona, 08193 Barcelona, Spain.

NMDA receptor (NMDAR) stimulation promotes neuronal survival during brain development. Cerebellar granule cells (CGCs) need NMDAR stimulation to survive and develop. These neurons differentiate and mature during its migration from the external granular layer to the internal granular layer, and lack of excitatory inputs triggers their apoptotic death. It is possible to mimic this process in vitro by culturing CGCs in low KCl concentrations (5 mm) in the presence or absence of NMDA. Using this experimental approach, we have obtained whole genome expression profiles after 3 and 8 h of NMDA addition to identify genes involved in NMDA-mediated survival of CGCs. One of the identified genes was Nurr1, a member of the orphan nuclear receptor subfamily Nr4a. Our results report a direct regulation of Nurr1 by CREB after NMDAR stimulation. ChIP assay confirmed CREB binding to Nurr1 promoter, whereas CREB shRNA blocked NMDA-mediated increase in Nurr1 expression. Moreover, we show that Nurr1 is important for NMDAR survival effect. We show that Nurr1 binds to Bdnf promoter IV and that silencing Nurr1 by shRNA leads to a decrease in brain-derived neurotrophic factor (BDNF) protein levels and a reduction of NMDA neuroprotective effect. Also, we report that Nurr1 and BDNF show a similar expression pattern during postnatal cerebellar development. Thus, we conclude that Nurr1 is a downstream target of CREB and that it is responsible for the NMDA-mediated increase in BDNF, which is necessary for the NMDA-mediated prosurvival effect on neurons.
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http://dx.doi.org/10.1074/jbc.M111.272427DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3322860PMC
March 2012

Soluble oligomers of amyloid-β peptide disrupt membrane trafficking of α-amino-3-hydroxy-5-methylisoxazole-4-propionic acid receptor contributing to early synapse dysfunction.

J Biol Chem 2011 Aug 10;286(31):27311-21. Epub 2011 Jun 10.

Institut de Neurociencies and Departament de Bioquímica i Biología Molecular, Universitat Autònoma de Barcelona, 08193 Cerdanyola del Vallès, Barcelona.

β-Amyloid (Aβ), a peptide generated from the amyloid precursor protein, is widely believed to underlie the pathophysiology of Alzheimer disease (AD). Emerging evidences suggest that soluble Aβ oligomers adversely affect synaptic function, leading to cognitive failure associated with AD. The Aβ-induced synaptic dysfunction has been attributed to the synaptic removal of α-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA) receptors (AMPARs). However, the molecular mechanisms underlying the loss of AMPAR induced by Aβ at synapses are largely unknown. In this study we have examined the effect of Aβ oligomers on phosphorylated GluA1 at serine 845, a residue that plays an essential role in the trafficking of AMPARs toward extrasynaptic sites and the subsequent delivery to synapses during synaptic plasticity events. We found that Aβ oligomers reduce basal levels of Ser-845 phosphorylation and surface expression of AMPARs affecting AMPAR subunit composition. Aβ-induced GluA1 dephosphorylation and reduced receptor surface levels are mediated by an increase in calcium influx into neurons through ionotropic glutamate receptors and activation of the calcium-dependent phosphatase calcineurin. Moreover, Aβ oligomers block the extrasynaptic delivery of AMPARs induced by chemical synaptic potentiation. In addition, reduced levels of total and phosphorylated GluA1 are associated with initial spatial memory deficits in a transgenic mouse model of AD. These findings indicate that Aβ oligomers could act as a synaptic depressor affecting the mechanisms involved in the targeting of AMPARs to the synapses during early stages of the disease.
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http://dx.doi.org/10.1074/jbc.M111.227504DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3149325PMC
August 2011

Short-term environmental enrichment rescues adult neurogenesis and memory deficits in APP(Sw,Ind) transgenic mice.

PLoS One 2011 Feb 9;6(2):e16832. Epub 2011 Feb 9.

Institut de Neurociències, Department de Bioquímica i Biologia Molecular, Centro de Investigación Biomédica en Red Enfermedades Neurodegenerativas, Universitat Autònoma de Barcelona, Barcelona, Spain.

Epidemiological studies indicate that intellectual activity prevents or delays the onset of Alzheimer's disease (AD). Similarly, cognitive stimulation using environmental enrichment (EE), which increases adult neurogenesis and functional integration of newborn neurons into neural circuits of the hippocampus, protects against memory decline in transgenic mouse models of AD, but the mechanisms involved are poorly understood. To study the therapeutic benefits of cognitive stimulation in AD we examined the effects of EE in hippocampal neurogenesis and memory in a transgenic mouse model of AD expressing the human mutant β-amyloid (Aβ) precursor protein (APP(Sw,Ind)). By using molecular markers of new generated neurons (bromodeoxiuridine, NeuN and doublecortin), we found reduced neurogenesis and decreased dendritic length and projections of doublecortin-expressing cells of the dentate gyrus in young APP(Sw,Ind) transgenic mice. Moreover, we detected a lower number of mature neurons (NeuN positive) in the granular cell layer and a reduced volume of the dentate gyrus that could be due to a sustained decrease in the incorporation of new generated neurons. We found that short-term EE for 7 weeks efficiently ameliorates early hippocampal-dependent spatial learning and memory deficits in APP(Sw,Ind) transgenic mice. The cognitive benefits of enrichment in APP(Sw,Ind) transgenic mice were associated with increased number, dendritic length and projections to the CA3 region of the most mature adult newborn neurons. By contrast, Aβ levels and the total number of neurons in the dentate gyrus were unchanged by EE in APP(Sw,Ind) mice. These results suggest that promoting the survival and maturation of adult generated newborn neurons in the hippocampus may contribute to cognitive benefits in AD mouse models.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0016832PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3036721PMC
February 2011

beta-Amyloid disrupts activity-dependent gene transcription required for memory through the CREB coactivator CRTC1.

J Neurosci 2010 Jul;30(28):9402-10

Institut de Neurociències, Universitat Autònoma de Barcelona, Barcelona, Spain.

Activity-dependent gene expression mediating changes of synaptic efficacy is important for memory storage, but the mechanisms underlying gene transcriptional changes in age-related memory disorders are poorly understood. In this study, we report that gene transcription mediated by the cAMP-response element binding protein (CREB)-regulated transcription coactivator CRTC1 is impaired in neurons and brain from an Alzheimer's disease (AD) transgenic mouse expressing the human beta-amyloid precursor protein (APP(Sw,Ind)). Suppression of CRTC1-dependent gene transcription by beta-amyloid (Abeta) in response to cAMP and Ca(2+) signals is mediated by reduced calcium influx and disruption of PP2B/calcineurin-dependent CRTC1 dephosphorylation at Ser151. Consistently, expression of CRTC1 or active CRTC1 S151A and calcineurin mutants reverse the deficits on CRTC1 transcriptional activity in APP(Sw,Ind) neurons. Inhibition of calcium influx by pharmacological blockade of L-type voltage-gated calcium channels (VGCCs), but not by blocking NMDA or AMPA receptors, mimics the decrease on CRTC1 transcriptional activity observed in APP(Sw,Ind) neurons, whereas agonists of L-type VGCCs reverse efficiently these deficits. Consistent with a role of CRTC1 on Abeta-induced synaptic and memory dysfunction, we demonstrate a selective reduction of CRTC1-dependent genes related to memory (Bdnf, c-fos, and Nr4a2) coinciding with hippocampal-dependent spatial memory deficits in APP(Sw,Ind) mice. These findings suggest that CRTC1 plays a key role in coupling synaptic activity to gene transcription required for hippocampal-dependent memory, and that Abeta could disrupt cognition by affecting CRTC1 function.
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http://dx.doi.org/10.1523/JNEUROSCI.2154-10.2010DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6632424PMC
July 2010

Bone morphogenetic protein-6 promotes cerebellar granule neurons survival by activation of the MEK/ERK/CREB pathway.

Mol Biol Cell 2009 Dec;20(24):5051-63

Institut de Neurociencies and Departament de Bioquímica i Biología Molecular, Universitat Autònoma de Barcelona, 08193 Cerdanyola del Valles, Barcelona, Spain.

Bone morphogenetic proteins (BMPs) have been implicated in the generation and postnatal differentiation of cerebellar granule cells (CGCs). Here, we examined the eventual role of BMPs on the survival of these neurons. Lack of depolarization causes CGC death by apoptosis in vivo, a phenomenon that is mimicked in vitro by deprivation of high potassium in cultured CGCs. We have found that BMP-6, but not BMP-7, is able to block low potassium-mediated apoptosis in CGCs. The neuroprotective effect of BMP-6 is not accompanied by an increase of Smad translocation to the nucleus, suggesting that the canonical pathway is not involved. By contrast, activation of the MEK/ERK/CREB pathway by BMP-6 is necessary for its neuroprotective effect, which involves inhibition of caspase activity and an increase in Bcl-2 protein levels. Other pathways involved in the regulation of CGC survival, such as the c-Jun terminal kinase and the phosphatidylinositol 3-kinase (PI3K)-Akt/PKB, were not affected by BMP-6. Moreover, failure of BMP-7 to activate the MEK/ERK/CREB pathway could explain its inability to protect CGCs from low potassium-mediated apoptosis. Thus, this study demonstrates that BMP-6 acting through the noncanonical MEK/ERK/CREB pathway plays a crucial role on CGC survival.
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http://dx.doi.org/10.1091/mbc.e09-05-0424DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2793283PMC
December 2009

Intraneuronal beta-amyloid accumulation in the amygdala enhances fear and anxiety in Alzheimer's disease transgenic mice.

Biol Psychiatry 2010 Mar 7;67(6):513-21. Epub 2009 Aug 7.

Institut de Neurociències, Universitat Autònoma de Barcelona, Bellaterra, Spain.

Background: Alzheimer's disease (AD) is characterized by progressive memory decline and neuropsychiatric symptoms. Despite common emotional symptoms in AD such as anxiety and fear are associated with a more rapid cognitive decline, the pathological mechanisms involved in these behavioral changes remain largely elusive. In this study, we examined the pathological mechanisms of emotional behavior in well-established AD transgenic mice expressing human mutant beta-amyloid (Abeta) precursor protein (APP(Ind) and APP(Sw,Ind)) and tau (3xTg-AD).

Methods: We evaluated unconditioned and conditioned fear-induced freezing behavior and spatial memory in APP(Ind), APP(Sw,Ind), and 3xTg-AD transgenic mice. The Abeta and tau pathologies and signaling pathways involved in emotional processing were studied by immunohistochemistry and immunoblotting analyses.

Results: The APP(Ind)/APP(Sw,Ind) and 3xTg-AD transgenic mice displayed at early ages enhanced innate and conditioned fear symptoms and spatial memory deficits coinciding with enhanced accumulation of Abeta in gamma-aminobutyric acid (GABA)ergic and glutamatergic neurons, respectively, of the basolateral amygdala (BLA). Similarly, the number of neurons with intraneuronal Abeta40 and Abeta42 was significantly increased in the BLA of human AD brains. Fear responses might reflect an influence of anxiety, because the anxiolytic compounds valproate, diazepam, and buspirone reduced efficiently unconditioned and conditioned fear responses in APP transgenic mice. In addition, phosphorylation of extracellular signal-regulated kinase (ERK)1/2, which is critical for acquisition and consolidation of fear conditioning, was increased in the amygdala of APP transgenic mice after cued conditioning.

Conclusions: We propose a deleterious role of intraneuronal Abeta on amygdala-dependent emotional responses by affecting the extracellular signal-regulated kinase/mitogen-activated protein kinase (ERK/MAPK) signaling pathway.
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http://dx.doi.org/10.1016/j.biopsych.2009.06.015DOI Listing
March 2010

Activation of caspase-8 by tumour necrosis factor receptor 1 is necessary for caspase-3 activation and apoptosis in oxygen-glucose deprived cultured cortical cells.

Neurobiol Dis 2009 Sep 23;35(3):438-47. Epub 2009 Jun 23.

Institut de Neurociencies, Departament de Bioquímica i Biología Molecular, Universitat Autònoma de Barcelona, Spain.

TNF-alpha has been reported to be relevant in stroke-induced neuronal death. However the precise function of TNF-alpha in brain ischemia remains controversial since there are data supporting either a detrimental or a protective effect. Here we show that TNF-alpha is released after oxygen-glucose deprivation (OGD) of cortical cultures and is a major contributor to the apoptotic death observed without affecting the OGD-mediated necrotic cell death. In this paradigm, apoptosis depends on TNF-alpha-induced activation of caspase-8 and -3 without affecting the activation of caspase-9. By using knock-out mice for TNF-alpha receptor 1, we show that the activation of both caspase-3 and -8 by TNF-alpha is mediated by TNF-alpha receptor 1. The pro-apoptotic role of TNF-alpha in OGD is restricted to neurons and microglia, since astrocytes do not express either TNF-alpha or TNF-alpha receptor 1. Altogether, these results show that apoptosis of cortical neurons after OGD is mediated by TNF-alpha/TNF-alpha receptor 1.
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http://dx.doi.org/10.1016/j.nbd.2009.06.005DOI Listing
September 2009

Noradrenergic modulation of the motor response induced by long-term levodopa administration in Parkinsonian rats.

J Neural Transm (Vienna) 2009 Jul 26;116(7):867-74. Epub 2009 May 26.

Laboratori de Neuropsicofarmacologia, Institut de Recerca de l'Hospital de la Santa Creu i de Sant Pau, Avgda Sant Antoni Maria Claret, 167, Barcelona 08025, Spain.

A decrease in noradrenergic activity in Parkinson's disease might play a critical role in long-term motor complications associated with chronic dopaminergic replacement. Using the rat model of parkinsonism with an additional noradrenergic degeneration induced by the N-(-2-chloroethyl)-N-ethyl-2-bromobenzylamine (DSP-4) toxin we evaluated whether the circling motor activity and dose-failure episodes induced by levodopa (L-DOPA) differ between single (6-OHDA) and double (6-OHDA + DSP-4) denervated animals challenged with a single daily dose of L-DOPA. While single-lesioned animals showed a sensitization-desensitization turning response with a significant increase on day 15 and a decrease on day 22, in double-lesioned animals, the turning activity was maximal from day 1 and did not decay on day 22. Double-lesioned rats exhibited significantly higher number of turns on days 15 and 22 and a significantly lower percentage of dose-failure episodes during treatment. Noradrenergic denervation appears to be associated with prolonged long-term dopaminergic sensitization. This type of response appears to be comparable to that in the clinical setting with intermittent L-DOPA administration where no desensitization occurs once the abnormal response is established.
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http://dx.doi.org/10.1007/s00702-009-0242-9DOI Listing
July 2009

Tetanus toxin H(C) fragment reduces neuronal MPP+ toxicity.

Mol Cell Neurosci 2009 Jul 31;41(3):297-303. Epub 2009 Mar 31.

Departament de Bioquímica i de Biologia Molecular, Institut de Neurociències, Universitat Autònoma de Barcelona, Cerdanyola del Vallès 08193, Spain.

The non-toxic carboxi-terminal domain of the heavy chain of tetanus toxin (H(C)) elicits neuroprotection of cerebellar granule neurons against apoptotic death induced by potassium deprivation. In this study we sought to determine whether H(C) also prevents the apoptosis induced by the mitochondrial poison 1-methyl-4-phenylpyridinium (MPP+), which induces a form of Parkinsonism. Pre-treatment of cultures with H(C) prevented MPP+-induced cell death, as well as impaired the MPP+-triggered apoptotic cascade. Cytochrome c release from the mitochondria, procaspase-3 activation and chromatin condensation, were significantly reduced in H(C)-pre-treated neurons. Moreover, H(C) induced Ser(112) and Ser(136) BAD phosphorylation, which correlated with the detachment of BAD from Bcl-X(L) and its association to 14-3-3. In turn, Bcl-X(L) remained bound to Bax, impairing its translocation to mitochondria of stressed neurons. The use of Wortmannin or PD98059 demonstrated the involvement of the PI3K/Akt as well as the ERK1/2 transduction pathways in the H(C) fragment effect. Interestingly, the H(C) fragment also induces an increase in the DNA binding activity of NF-kappaB, a well-established transcription factor involved in the prevention of neuronal death. Taken together, our results strongly suggest that the recombinant H(C) fragment of tetanus toxin can act as a neuroprotector in a model of MPP(+)-triggered apoptosis.
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http://dx.doi.org/10.1016/j.mcn.2009.03.006DOI Listing
July 2009

Estradiol facilitates neurite maintenance by a Src/Ras/ERK signalling pathway.

Mol Cell Neurosci 2008 Oct 14;39(2):143-51. Epub 2008 Jun 14.

Institut de Neurociències, Departament de Bioquímica i Biologia Molecular, Universitat Autònoma de Barcelona, Spain.

Different reports suggest the estrogens are involved in neuritic outgrowth, maintenance of dendritic morphology and spine formation in the CNS. However, the molecular mechanisms regulated by estrogens on neuronal integrity are not fully understood. We have addressed the relationship between 17beta-estradiol-dependent ERK pathway stimulation and the maintenance of neuritic morphology in cerebellar granule cell cultures (CGC). We report that 17beta-estradiol clearly activates ERK phosphorylation in CGC cultured in low potassium via ERalpha localized in the plasma membrane and without the activation of the insulin-like growth factor-I receptor. 17beta-estradiol activates the ERK pathway through Ras-dependent Src kinase activity. A concomitant activation of the cAMP-response element-binding protein (CREB) is observed. Moreover, we demonstrate that 17beta-estradiol-mediated ERK activation is involved in the maintenance of neuritic arborisation and neuronal morphology in proapoptotic conditions.
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http://dx.doi.org/10.1016/j.mcn.2008.06.001DOI Listing
October 2008

BCL-XL regulates TNF-alpha-mediated cell death independently of NF-kappaB, FLIP and IAPs.

Cell Res 2008 Oct;18(10):1020-36

Departament de Ciències Mèdiques Bàsiques, Universitat de Lleida, Lleida, Spain.

Upon activation, tumor necrosis factor alpha (TNF-alpha) receptor can engage apoptotic or survival pathways. Inhibition of macromolecular synthesis is known to sensitize cells to TNF-alpha-induced cell death. It is believed that this sensitization is due to the transcriptional blockade of genes regulated by NF-kappaB. Nevertheless, such evidence has remained elusive in the nervous system. Here, we show that TNF-alpha cannot normally induce apoptosis in PC12 cells or cortical neurons. However, cells treated with Actinomycin D (ActD) become susceptible to TNF-alpha-induced cell death through the activation of caspase-8, generation of tBid and activation of caspase-9 and -3. Analysis of several proteins involved in TNF-alpha receptor signaling showed no significant downregulation of NF-kappaB target genes, such as IAPs or FLIP, under such conditions. However, Bcl-x(L) protein levels, but not those of Bcl-2, Bax and Bak, are reduced by ActD or TNF-alpha/ActD treatments. Moreover, Bcl-x(L) overexpression fully protects cells against TNF-alpha/ActD-induced cell death. When endogenous levels of Bcl-x(L) are specifically downregulated by lentiviral-based RNAi, cells no longer require ActD to be sensitive to TNF-alpha-triggered apoptosis. Furthermore, Bcl-x(L) downregulation does not affect TNF-alpha-mediated NF-kappaB activation. Altogether, our results demonstrate that Bcl-x(L), and not Bcl-2, FLIP or IAPs, acts as the endogenous regulator of neuronal resistance/sensitivity to TNF-alpha-induced apoptosis in an NF-kappaB-independent manner.
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http://dx.doi.org/10.1038/cr.2008.76DOI Listing
October 2008

C2-ceramide mediates cerebellar granule cells apoptosis by activation of caspases-2, -9, and -3.

J Neurosci Res 2008 Jun;86(8):1734-47

Institut de Neurociencies and Department de Bioquímica i Biología Molecular, Universitat Autònoma de Barcelona, Barcelona, Spain.

Ceramide is able to induce the apoptotic death of cerebellar granule cells (CGC) in culture. However, previous reports did not agree on whether ceramide-induced apoptosis of CGC requires caspase activation. Here we have shown that addition of C2-ceramide is able to produce extensive death of cultured CGC, which is associated with chromatin condensation, ladder-like DNA fragmentation, and activation of caspases. Our results show that C2-ceramide activates caspases-3, -9, and -2 but not caspases-1 and -8. Caspase-9 activation was associated with cytochrome c release from mitochondria toward the cytosol and was followed by activation of caspases-2 and -3. PARP proteolysis was also observed after caspase-3 and -2 activation. The involvement of caspases-9, -3, and -2 in ceramide-mediated apoptotic death of CGC was further supported by the use of specific inhibitors.
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http://dx.doi.org/10.1002/jnr.21633DOI Listing
June 2008

The long form of Fas apoptotic inhibitory molecule is expressed specifically in neurons and protects them against death receptor-triggered apoptosis.

J Neurosci 2007 Oct;27(42):11228-41

Cell Signaling and Apoptosis Group, Departament de Ciències Mèdiques Bàsiques, Universitat de Lleida-Hospital Universitari Arnau de Vilanova, 25198 Lleida, Spain.

Death receptors (DRs) and their ligands are expressed in developing nervous system. However, neurons are generally resistant to death induction through DRs and rather their activation promotes neuronal outgrowth and branching. These results suppose the existence of DRs antagonists expressed in the nervous system. Fas apoptosis inhibitory molecule (FAIM(S)) was first identified as a Fas antagonist in B-cells. Soon after, a longer alternative spliced isoform with unknown function was identified and named FAIM(L). FAIM(S) is widely expressed, including the nervous system, and we have shown previously that it promotes neuronal differentiation but it is not an anti-apoptotic molecule in this system. Here, we demonstrate that FAIM(L) is expressed specifically in neurons, and its expression is regulated during the development. Expression could be induced by NGF through the extracellular regulated kinase pathway in PC12 (pheochromocytoma cell line) cells. Contrary to FAIM(S), FAIM(L) does not increase the neurite outgrowth induced by neurotrophins and does not interfere with nuclear factor kappaB pathway activation as FAIM(S) does. Cells overexpressing FAIM(L) are resistant to apoptotic cell death induced by DRs such as Fas or tumor necrosis factor R1. Reduction of endogenous expression by small interfering RNA shows that endogenous FAIM(L) protects primary neurons from DR-induced cell death. The detailed analysis of this antagonism shows that FAIM(L) can bind to Fas receptor and prevent the activation of the initiator caspase-8 induced by Fas. In conclusion, our results indicate that FAIM(L) could be responsible for maintaining initiator caspases inactive after receptor engagement protecting neurons from the cytotoxic action of death ligands.
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http://dx.doi.org/10.1523/JNEUROSCI.3462-07.2007DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6673028PMC
October 2007

Modulation of the motor response to dopaminergic drugs in a parkinsonian model of combined dopaminergic and noradrenergic degeneration.

Eur J Pharmacol 2007 Dec 25;576(1-3):83-90. Epub 2007 Aug 25.

Laboratori de Neuropsicofarmacologia, Institut de Recerca de l'Hospital de la Santa Creu i de Sant Pau, Avgda. St. Antoni M(a) Claret, 167, 08025 Barcelona, Spain.

Besides dopaminergic deficiency, other neurotransmitter systems such as noradrenergic nuclei are affected in Parkinson's disease. Locus coeruleus degeneration might influence the response to dopamine replacement and the presence of long-term complications such as dyskinesias. In this scenario of noradrenergic and dopaminergic neurodegeneration, behavioural effects induced by dopaminergic-interacting drugs are incompletely known. We investigated whether noradrenergic lesion modulates the levodopa (l-DOPA) response and modifies the response to adenosine antagonists and its interaction with l-DOPA. We examined the motor behaviour induced by: 1) subthreshold doses of l-DOPA (2mg/kg, i.p.), 2) the adenosine-receptor antagonist caffeine (10mg/kg), and 3) the combination of l-DOPA (2mg/kg) and caffeine (10mg/kg). Each study was done in two experimental conditions: a) rats with unilateral 6-OHDA lesion and b) rats with a lesion of the nigrostriatal pathway (6-OHDA) combined with selective denervation of locus coeruleus-noradrenergic terminal fields by N-(2-chloroethyl)-N-ethyl-2-bromobenzylamine (DSP-4). While only 28% of the 6-OHDA-lesioned animals presented circling behaviour after l-DOPA challenge, all (100%) double-denervated animals rotated after the same l-DOPA dose (p<0.05). No statistical differences in the percentage of rotating animals were observed between single- and double-denervated rats after caffeine challenge. Combined l-DOPA-caffeine challenge produced rotational behaviour in all (100%) single- and double-denervated rats. No differences in total turns were observed between single- and double-denervated animals in each treatment condition. These findings suggest that additional noradrenergic denervation selectively decreases the motor threshold to l-DOPA treatment without modifying the magnitude or the pattern of the motor response to adenosinergic antagonism.
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http://dx.doi.org/10.1016/j.ejphar.2007.08.024DOI Listing
December 2007

17beta-estradiol does not protect cerebellar granule cells from excitotoxicity or apoptosis.

J Neurochem 2007 Jul;102(2):354-64

Institut de Neurociencies i Department Bioquímica i Biología Molecular, Universitat Autònoma de Barcelona, Spain.

Mounting evidences have suggested that 17beta-estradiol (E2) could have a neuroprotective action in the CNS. In the present study, we wanted to study whether this estrogen was able to protect cerebellar granule cells (CGCs) from apoptosis or excitotoxicity. Our results suggest that E2 has no anti-apoptotic effect in CGCs cultures. The lack of phosphoinositide 3-kinase/Akt pathway activation in CGCs cultures could be on the basis of the failure of estradiol to protect CGCs from potassium-deprivation and ceramide-mediated apoptosis. Moreover, E2 does not protect CGCs from glutamate-mediated death despite activating the extracellular signal regulated kinase kinase/extracellular signal regulated kinase pathway, which suggests that extracellular signal regulated kinase kinase/extracellular signal regulated kinase pathway activation is not sufficient to sustain an estrogen-mediated neuroprotective effect in CGCs cultures. By contrast, we found that the estrogen had a significant neuroprotective effect against hydrogen peroxide-mediated neuronal death. This effect was due to the antioxidant properties of the chemical structure of estradiol, as the biological inactive isomer 17alpha-estradiol was also able to reduce hydrogen peroxide-mediated neuronal death.
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http://dx.doi.org/10.1111/j.1471-4159.2007.04475.xDOI Listing
July 2007

PACAP and C2-ceramide generate different AP-1 complexes through a MAP-kinase-dependent pathway: involvement of c-Fos in PACAP-induced Bcl-2 expression.

J Neurochem 2006 Nov 5;99(4):1237-50. Epub 2006 Oct 5.

INSERM U413, Laboratory of Cellular and Molecular Neuroendocrinology, European Institute for Peptide Research, University of Rouen, Mont-Saint-Aignan, France.

The neuropeptide pituitary adenylate cyclase-activating polypeptide (PACAP) inhibits C2-ceramide-induced cell death through blockade of the mitochondrial apoptotic pathway in rat cerebellar granule neurones. However, the gene induction processes and transcription factors involved in the anti-apoptotic effect of PACAP remain unknown. Here, we show that PACAP and C2-ceramide activate activator protein-1 (AP-1) DNA binding in a dose- and time-dependent manner, but generate different AP-1 dimers. Thus, PACAP increased the proportion of c-Fos and Jun D while C2-ceramide increased c-Jun and reduced c-Fos in AP-1 complexes. In addition, PACAP strongly activated c-Fos gene expression while C2-ceramide markedly increased c-Jun phosphorylation. The effect of PACAP on c-Fos expression was blocked by the mitogen-activated protein kinase/extracellular signal-regulated kinase (MEK) inhibitor, U0126, while phosphorylation of c-Jun induced by C2-ceramide was abrogated by the protein phosphatase 2A (PP2A) inhibitor, okadaic acid. Transfection of immature granule cells with c-Fos siRNA, which strongly reduced basal and PACAP-stimulated levels of the protein, totally prevented the stimulatory effect of PACAP on Bcl-2 expression. The present study demonstrates that AP-1 complexes containing c-Fos mediate the effect of PACAP on Bcl-2 gene expression in cerebellar granule neurones. Our data also indicate that different AP-1 dimers are associated with the pro-apoptotic effect of C2-ceramide and the anti-apoptotic effect of PACAP.
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http://dx.doi.org/10.1111/j.1471-4159.2006.04148.xDOI Listing
November 2006

N-methyl-D-aspartate blocks activation of JNK and mitochondrial apoptotic pathway induced by potassium deprivation in cerebellar granule cells.

J Biol Chem 2006 Mar 27;281(10):6801-12. Epub 2005 Dec 27.

Institut de Neurociencies i Dpt. Bioquímica i Biología Molecular, Universitat Autònoma de Barcelona, 08193 Cerdanyola del Vallès, Barcelona, Spain.

During the postnatal development of cerebellum, lack of excitatory innervation from the mossy fibers results in cerebellar granule cell (CGC) apoptosis during the migration of the cells toward the internal granule cell layer. Accordingly, CGCs die by apoptosis when cultured in physiological KCl concentrations (5 mm; K5), and they survive in the presence of depolarizing conditions such as high KCl concentration (25 mm; K25) or N-methyl-D-aspartate (NMDA). We have recently shown that NMDA is able to exert a long lasting neuroprotective effect when added to immature (2 days in vitro) CGC cultures by inhibition of caspase-3 activity. Here we show that NMDA- and K25-mediated neuroprotection is associated with an increase in the levels of Bcl-2, an inhibition of K5-mediated increase in Bax, and the inhibition of the release of apoptogenic factors from mitochondria such as Smac/DIABLO and cytochrome c. Moreover, we have shown that similar effects are observed when c-Jun N-terminal kinases (JNKs) are inhibited and that treatment of CGC cultures with NMDA blocks K5-mediated JNK activation. These results allow us to postulate that the inhibition of JNK-mediated release of apoptogenic factors from mitochondria is involved in the NMDA protection from K5-mediated apoptosis of CGCs.
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http://dx.doi.org/10.1074/jbc.M504571200DOI Listing
March 2006

Contribution of caspase-mediated apoptosis to the cell death caused by oxygen-glucose deprivation in cortical cell cultures.

Neurobiol Dis 2005 Oct;20(1):27-37

Institut de Neurociències i Dpt. Bioquímica i Biologia Molecular, Universitat Autònoma de Barcelona, 08193 Cerdanyola del Vallès, Barcelona, Spain.

Several evidences suggest that cell death after cerebral ischemia involves both necrosis and apoptosis. However, it is still unknown which is the relative contribution of both types of cell death. Exposing rat cortical cultures to oxygen-glucose deprivation (OGD), we show the simultaneous presence of necrotic and apoptotic cells. The relative contribution of necrosis and apoptosis was dependent on the duration of the OGD. OGD-mediated apoptotic cell death is caspase-dependent because the addition of a pan-caspase inhibitor specifically blocked the apoptotic component of the OGD-mediated cell death. Moreover, we observed the activation of caspase-3, -7, and -9 after OGD in neurons and microglial cells. No activation of these caspases was observed in GFAP positive cells. Our results also show that calpain is related to OGD-mediated proteolysis of caspase-3 and -9 but not of caspase-7. These data suggest that different pathways could be involved in OGD-mediated caspase activation.
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http://dx.doi.org/10.1016/j.nbd.2005.01.028DOI Listing
October 2005