Center for Neuroscience and Cell Biology

Coimbra, Portugal

Center for Neuroscience and Cell Biology

Coimbra, Portugal
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Ribeiro M.,Center for Neuroscience and Cell Biology | Silva A.C.,Center for Neuroscience and Cell Biology | Rodrigues J.,Center for Neuroscience and Cell Biology | Naia L.,Center for Neuroscience and Cell Biology | And 3 more authors.
Toxicological Sciences | Year: 2013

Huntington's disease (HD) is a polyglutamine-expansion disease associated to degeneration of striatal and cortical neurons. Previously, we showed that oxidative stress occurs in HD knockin striatal cells, but little is known regarding cell antioxidant response against exogenous stimuli. Therefore, in the present study we analyzed cellular antioxidant profile following hydrogen peroxide (H2O2) and staurosporine (STS) exposure and tested the protective effect of cystamine and creatine in striatal cells expressing mutant huntingtin with 111 glutamines (STHdhQ111/Q111; mutant cells) versus wild-type cells (STHdhQ7/Q7). Mutant cells displayed increased mitochondrial reactive oxygen species (ROS) and decreased NADPH oxidase and xanthine oxidase (XO) activities, reflecting lower superoxide cytosolic generation, along with increased superoxide dismutases (SODs) and components of glutathione redox cycle. Exposure to H2O2 and STS enhanced ROS in mutant cells and largely increased XO activity; STS further boosted the generation of mitochondrial ROS and caspase-3 activity. Both stimuli slightly increased SOD1 activity, without affecting SOD2 activity, and decreased glutathione reductase with a consequent rise in oxidized glutathione or glutathione disulfide in mutant cells, whereas H2O2 only increased glutathione peroxidase activity. Additionally, creatine and cystamine increased mutant cells viability and prevented ROS formation in HD cells subjected to H2O2 and STS. These results indicate that elevation of the antioxidant systems accompanies mitochondrial-driven ROS generation in mutant striatal cells and that exposure to noxious stimuli induces a higher susceptibility to oxidative stress by increasing XO activity and lowering the antioxidant response. Furthermore, creatine and cystamine are efficient in preventing H2O2- and STSevoked ROS formation in HD striatal cells. © The Author 2013. Published by Oxford University Press on behalf of the Society of Toxicology. All rights reserved.

Saraiva C.,University of Beira Interior | Praca C.,Center for Neuroscience and Cell Biology | Praca C.,University of Coimbra | Praca C.,University of Artois | And 5 more authors.
Journal of Controlled Release | Year: 2016

The blood-brain barrier (BBB) is a vital boundary between neural tissue and circulating blood. The BBB's unique and protective features control brain homeostasis as well as ion and molecule movement. Failure in maintaining any of these components results in the breakdown of this specialized multicellular structure and consequently promotes neuroinflammation and neurodegeneration. In several high incidence pathologies such as stroke, Alzheimer's (AD) and Parkinson's disease (PD) the BBB is impaired. However, even a damaged and more permeable BBB can pose serious challenges to drug delivery into the brain. The use of nanoparticle (NP) formulations able to encapsulate molecules with therapeutic value, while targeting specific transport processes in the brain vasculature, may enhance drug transport through the BBB in neurodegenerative/ischemic disorders and target relevant regions in the brain for regenerative processes. In this review, we will discuss BBB composition and characteristics and how these features are altered in pathology, namely in stroke, AD and PD. Additionally, factors influencing an efficient intravenous delivery of polymeric and inorganic NPs into the brain as well as NP-related delivery systems with the most promising functional outcomes will also be discussed. © 2016 The Authors.

Domingues S.,University of Coimbra | Domingues S.,Center for Neuroscience and Cell Biology | Nielsen K.M.,Oslo University College | Nielsen K.M.,Innovation Norway
Current Opinion in Microbiology | Year: 2017

Membrane vesicles (MVs) are released from all living cells. MVs are lumen-containing spheres of lipid-bilayers derived from the cell surface. MVs are biologically active and contain various components, including genetic material. Both chromosomal and plasmid DNA, as well as different types of RNA have been detected in MVs. Vesicle-mediated transfer of genes coding for antibiotic resistance, virulence and metabolic traits has been reported in Gram-negative and Gram-positive bacteria and in Archaea. MVs can persist over time in natural environments. Here we review the characteristics of and the role of MVs in horizontal gene transfer (HGT) processes in prokaryotes. © 2017 Elsevier Ltd

Saraiva C.,University of Beira Interior | Paiva J.,Center for Neuroscience and Cell Biology | Santos T.,University of Beira Interior | Ferreira L.,Center for Neuroscience and Cell Biology | And 2 more authors.
Journal of Controlled Release | Year: 2016

Modulation of the subventricular zone (SVZ) neurogenic niche can enhance brain repair in several disorders including Parkinson's disease (PD). Herein, we used biocompatible and traceable polymeric nanoparticles (NPs) containing perfluoro-1,5-crown ether (PFCE) and coated with protamine sulfate to complex microRNA-124 (miR-124), a neuronal fate determinant. The ability of NPs to efficiently deliver miR-124 and prompt SVZ neurogenesis and brain repair in PD was evaluated. In vitro, miR-124 NPs were efficiently internalized by neural stem/progenitors cells and neuroblasts and promoted their neuronal commitment and maturation. The expression of Sox9 and Jagged1, two miR-124 targets and stemness-related genes, were also decreased upon miR-124 NP treatment. In vivo, the intracerebral administration of miR-124 NPs increased the number of migrating neuroblasts that reached the granule cell layer of the olfactory bulb, both in healthy and in a 6-hydroxydopamine (6-OHDA) mouse model for PD. MiR-124 NPs were also able to induce migration of neurons into the lesioned striatum of 6-OHDA-treated mice. Most importantly, miR-124 NPs proved to ameliorate motor symptoms of 6-OHDA mice, monitored by the apomorphine-induced rotation test. Altogether, we provide clear evidences to support the use of miR-124 NPs as a new therapeutic approach to boost endogenous brain repair mechanisms in a setting of neurodegeneration. © 2016 Elsevier B.V. All rights reserved.

Ferreira I.L.,Center for Neuroscience and Cell Biology | Cunha-Oliveira T.,Center for Neuroscience and Cell Biology | Nascimento M.V.,Center for Neuroscience and Cell Biology | Ribeiro M.,Center for Neuroscience and Cell Biology | And 6 more authors.
Experimental Neurology | Year: 2011

In this work we studied the mitochondrial-associated metabolic pathways in Huntington's disease (HD) versus control (CTR) cybrids, a cell model in which the contribution of mitochondrial defects from patients is isolated. HD cybrids exhibited an interesting increase in ATP levels, when compared to CTR cybrids. Concomitantly, we observed increased glycolytic rate in HD cybrids, as revealed by increased lactate/pyruvate ratio, which was reverted after inhibition of glycolysis. A decrease in glucose-6-phosphate dehydrogenase activity in HD cybrids further indicated decreased rate of the pentose-phosphate pathway. ATP levels of HD cybrids were significantly decreased under glycolysis inhibition, which was accompanied by a decrease in phosphocreatine. Nevertheless, pyruvate supplementation could not recover HD cybrids' ATP or phosphocreatine levels, suggesting a dysfunction in mitochondrial use of that substrate. Oligomycin also caused a decrease in ATP levels, suggesting a partial support of ATP generation by the mitochondria. Nevertheless, mitochondrial NADH/NADt levels were decreased in HD cybrids, which was correlated with a decrease in pyruvate dehydrogenase activity and protein expression, suggesting decreased tricarboxylic acid cycle (TCA) input from glycolysis. Interestingly, the activity of alpha-ketoglutarate dehydrogenase, a critical enzyme complex that links the TCA to amino acid synthesis and degradation, was increased in HD cybrids. In accordance, mitochondrial levels of glutamate were increased and alanine was decreased, whereas aspartate and glutamine levels were unchanged in HD cybrids. Conversely, malate dehydrogenase activity from total cell extracts was unchanged in HD cybrids. Our results suggest that inherent dysfunction of mitochondria from HD patients affects cellular bioenergetics in an otherwise functional nuclear background. © 2011 Elsevier Inc.

Melo S.A.,University of Houston | Melo S.A.,Beth Israel Deaconess Medical Center | Sugimoto H.,University of Houston | Sugimoto H.,Beth Israel Deaconess Medical Center | And 14 more authors.
Cancer Cell | Year: 2014

Exosomes are secreted by all cell types and contain proteins and nucleic acids. Here, we report that breast cancer associated exosomes contain microRNAs (miRNAs) associated with the RISC-Loading Complex (RLC) and display cell-independent capacity to process precursor microRNAs (pre-miRNAs) into mature miRNAs. Pre-miRNAs, along with Dicer, AGO2, and TRBP, are present in exosomes of cancer cells. CD43 mediates the accumulation of Dicer specifically in cancer exosomes. Cancer exosomes mediate an efficient and rapid silencing of mRNAs to reprogram the target cell transcriptome. Exosomes derived from cells and sera of patients with breast cancer instigate nontumorigenic epithelial cells to form tumors in a Dicer-dependent manner. These findings offer opportunities for the development of exosomes based biomarkers and therapies. © 2014 Elsevier Inc.

Guantes R.,Autonomous University of Madrid | Rastrojo A.,Centro Biologia Molecular Severo Ochoa | Neves R.,Weatherall Institute of Molecular Medicine | Neves R.,Center for Neuroscience and Cell Biology | And 4 more authors.
Genome Research | Year: 2015

Noise in gene expression is a main determinant of phenotypic variability. Increasing experimental evidence suggests that genome-wide cellular constraints largely contribute to the heterogeneity observed in gene products. It is still unclear, however, which global factors affect gene expression noise and to what extent. Since eukaryotic gene expression is an energy demanding process, differences in the energy budget of each cell could determine gene expression differences. Here, we quantify the contribution of mitochondrial variability (a natural source of ATP variation) to global variability in gene expression. We find that changes in mitochondrial content can account for ∼50% of the variability observed in protein levels. This is the combined result of the effect of mitochondria dosage on transcription and translation apparatus content and activities. Moreover, we find that mitochondrial levels have a large impact on alternative splicing, thus modulating both the abundance and type of mRNAs. A simple mathematical model in which mitochondrial content simultaneously affects transcription rate and splicing site choice can explain the alternative splicing data. The results of this study show that mitochondrial content (and/or probably function) influences mRNA abundance, translation, and alternative splicing, which ultimately affects cellular phenotype. © 2015 Guantes et al.

Melo C.A.,Netherlands Cancer Institute | Melo C.A.,Center for Neuroscience and Cell Biology | Drost J.,Netherlands Cancer Institute | Wijchers P.J.,University Utrecht | And 11 more authors.
Molecular Cell | Year: 2013

Binding within or nearby target genes involved in cell proliferation and survival enables the p53 tumor suppressor gene to regulate their transcription and cell-cycle progression. Using genome-wide chromatin-binding profiles, we describe binding of p53 also to regions located distantly from any known p53 target gene. Interestingly, many of these regions possess conserved p53-binding sites and all known hallmarks of enhancer regions. We demonstrate that these p53-bound enhancer regions (p53BERs) indeed contain enhancer activity and interact intrachromosomally with multiple neighboring genes to convey long-distance p53-dependent transcription regulation. Furthermore, p53BERs produce, in a p53-dependent manner, enhancer RNAs (eRNAs) that are required for efficient transcriptional enhancement of interacting target genes and induction of a p53-dependent cell-cycle arrest. Thus, our results ascribe transcription enhancement activity to p53 with the capacity to regulate multiple genes from a single genomic binding site. Moreover, eRNA production from p53BERs is required for efficient p53 transcription enhancement. © 2013 Elsevier Inc.

Melo C.A.,Netherlands Cancer Institute | Melo C.A.,Center for Neuroscience and Cell Biology | Leveille N.,Netherlands Cancer Institute | Agami R.,Netherlands Cancer Institute | Agami R.,Rotterdam University
Cell Research | Year: 2013

Recently, various studies shed light on the functional significance of enhancer RNAs. Two recent studies published in Nature by Li et al. and Lam et al. highlight the importance of these newly characterized RNA molecules and their key role in controlling transcriptional programs. © 2013 IBCB, SIBS, CAS.

Melo C.A.,Netherlands Cancer Institute | Melo C.A.,Center for Neuroscience and Cell Biology | Melo S.A.,University of Houston | Melo S.A.,University of Porto
Methods in Molecular Biology | Year: 2014

RNA-induced silencing complex is the cytoplasmic effector machine of the microRNA (miRNA) pathway and contains a single-stranded miRNA guiding it to its target mRNAs. The biogenesis of mature miRNAs is a regulatory process achieved by complex machinery composed of few protein components, among which the ribonuclease III Dicer plays a central role. Dicer is essential for miRNA maturation and catalyzes one of the rate-limiting steps of miRNA production. In this chapter, we describe a protocol to study the catalytic activity of Dicer in cell extracts by measuring their ability to process precursor RNA (pre-miRNAs) into functional mature miRNAs. Impairment of the miRNA biogenesis machinery due to loss-of-function mutations in effectors of the pathway such as Dicer has been demonstrated before. Dicing assay can be used in cancer to assess Dicer enzymatic activity compared with healthy controls. Therefore, this experimental approach is likely to be useful to researchers investigating the main steps of miRNA biogenesis and function in human health and diseases. © Springer Science+Business Media New York 2014.

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