Browsing by Author "Chaves, João"
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- Apolipoprotein E isoforms and susceptibility to genetic generalized epilepsiesPublication . Chaves, João; Martins-Ferreira, Ricardo; Carvalho, Cláudia; Bettencourt, Andreia; Brás, Sandra; Chorão, Rui; Freitas, Joel; Samões, Raquel; Lopes, João; Ramalheira, João; Silva, Berta; Costa, Paulo; Martins Da Silva, António; Leal, BárbaraBackground: Apolipoprotein E (ApoE) is the main lipoprotein secreted in brain. It has a critical immunomodulatory function, influences neurotransmission and it is involved in repairing damaged neurons. ApoE e4 is an isoform of ApoE with altered function, and was previously associated with early onset epilepsy and refractoriness, both in animal models and in patients with focal epilepsies. There is a limited knowledge on ApoE’s role in Genetic Generalized Epilepsies (GGE). Aim: To determine if ApoE isoforms are risk factors for GGE development. Methods: A group of 337 GGE patients (193 F, 144 M, 33.6 ± 14.2 years) was compared with a group of 342 healthy individuals in a case-control genetic association study. ApoE genotyping was performed using PCR-RFLP. Results: The genotypic frequency of ApoE e3/e2 was lower in GGE patients relative to controls (6.5% in GGE vs. 11.7% in controls, p = 0.019, OR (95% CI) = 0.53 (0.305–0.905). No associations with other clinical data such as photosensitivity or age at disease onset were observed. Conclusion: Our results show that ApoE e3/e2 genotype may be a protective factor for GGE development. There is evidence that this genotype could be neuroprotective, preventing oxidative damage and promoting neuronal survival. Although replication studies are warranted, our data suggest that ApoE isoforms have a role in epileptogenic mechanisms regardless of the specific epileptic manifestations.
- Brain expression of inflammatory mediators in Mesial Temporal Lobe Epilepsy patientsPublication . Leal, Bárbara; Chaves, João; Carvalho, Cláudia; Rangel, Rui; Santos, Agostinho; Bettencourt, Andreia; Lopes, João; Ramalheira, João; Silva, Berta M.; da Silva, António Martins; Costa, Paulo P.Neuroinflammation may be central in epileptogenesis. In this study we analysed inflammatory reaction markers in brain tissue of Mesial Temporal Lobe Epilepsy with Hippocampal Sclerosis (MTLE-HS) patients. TLR4, IL-1β and IL-10 gene expression as well as the presence of activated HLA-DR+ microglia was evaluated in 23 patients and 10 cadaveric controls. Inflammation characterized by the presence of HLA-DR+microglia and TLR4, IL-1β overexpression was evident in hippocampus and anterior temporal cortex of MTLE-HS patients. Anti-inflammatory IL-10 was also overexpressed in MTLE-HS patients. Our results show that hippocampal neuroinflammation extends beyond lesional limits, as far as the anterior temporal cortex.
- Cellular characterization of normal and mutant cystatin BPublication . Duarte, Ana Joana; Ribeiro, Diogo; Chaves, João; Amaral, OlgaUnverricht- Lundborg disease (ULD or EPM1, MIM 254800), is a myoclonic epilepsy, caused by mutations in the cystatin B gene (CSTB gene) which lead to impaired function of cystatin B compromising its function. The normal protein is an endogenous inhibitor of cysteine proteinases and has several cellular localizations, it is found in the nucleus, cytosol and lysosome. Identification of a rare molecular mechanism causal of Unverricht Lundborg disease in a unique Portuguese patient triggered research in this field. Skin fibroblasts were obtained with informed consent from a homozygous patient with a rare genotype and from a normal control (anonymized). Fibroblast cell cultures were expanded using standard methods. Western Blotting (WB) and immunofluorescence (IF) experiments were carried out following previous described methods (Pinto et al, 2012). For cell fractionation analysis, cells were collected by scraping and suspending in ice-cold phosphate buffer saline (PBS) and cell fractions where obtained using the methods described elsewhere (Suzuki et al, 2010). Immunofluorescence experimental results revealed consistency with the western blot analysis. Although with a decrease of about 4 fold, in relation to normal, cystatin B is clearly present in the cells’ total fraction and in the nuclear fraction. However, in the cytoplasm the decrease seems to be higher which could suggest a subsequent lower protective anti-protease function compromising cellular and lysosomal integrity. Discussion and future perspectives In patient’s fibroblasts the protein quantity is diminished. Although the nuclear location seems to be preserved in the patient´s cells, the cytoplasmic/lysosomal fraction is clearly decreased.
- Characterization of a rare Unverricht-Lundborg disease mutationPublication . Duarte, Ana Joana; Ribeiro, Diogo; Chaves, João; Amaral, OlgaCystatin B (CSTB) gene mutations cause Unverricht–Lundborg disease (ULD), a rare form of myoclonic epilepsy. The previous identification of a Portuguese patient, homozygous for a unique splicing defect (c.66GNA; p.Q22Q), provided awareness regarding the existence of variant forms of ULD. In this work we aimed at the characterization of thismutation at the population level and at the cellular level. The cellular fractionation studies here carried out showed mislocalization of the protein and add to the knowledge on this disease.
- Circulating cell-free DNA methylation mirrors alterations in cerebral patterns in epilepsyPublication . Martins-Ferreira, Ricardo; Leal, Bárbara; Chaves, João; Ciudad, Laura; Samões, Raquel; Martins da Silva, António; Pinho Costa, Paulo; Ballestar, EstebanBackground: DNA methylation profiling of circulating cell-free DNA (cfDNA) has rapidly become a promising strategy for biomarker identification and development. The cell-type-specific nature of DNA methylation patterns and the direct relationship between cfDNA and apoptosis can potentially be used non-invasively to predict local alterations. In addition, direct detection of altered DNA methylation patterns performs well as a biomarker. In a previous study, we demonstrated marked DNA methylation alterations in brain tissue from patients with mesial temporal lobe epilepsy with hippocampal sclerosis (MTLE-HS). Results: We performed DNA methylation profiling in cfDNA isolated from the serum of MTLE patients and healthy controls using BeadChip arrays followed by systematic bioinformatic analysis including deconvolution analysis and integration with DNase accessibility data sets. Differential cfDNA methylation analysis showed an overrepresentation of gene ontology terms and transcription factors related to central nervous system function and regulation. Deconvolution analysis of the DNA methylation data sets ruled out the possibility that the observed differences were due to changes in the proportional contribution of cortical neurons in cfDNA. Moreover, we found no overrepresentation of neuron- or glia-specific patterns in the described cfDNA methylation patterns. However, the MTLE-HS cfDNA methylation patterns featured a significant overrepresentation of the epileptic DNA methylation alterations previously observed in the hippocampus. Conclusions: Our results support the use of cfDNA methylation profiling as a rational approach to seeking non-invasive and reproducible epilepsy biomarkers.
- Circulating miR-134 in mesial temporal lobe epilepsy: implications in hippocampal sclerosis development and drug resistancePublication . Guerra Leal, Bárbara; Carvalho, Cláudia; Santos, Cristina; Samões, Raquel; Martins-Ferreira, Ricardo; Teixeira, Catarina; Rodrigues, Diana; Freitas, Joel; Lemos, Carolina; Chorão, Rui; Ramalheira, João; Lopes, João; Martins da Silva, António; Pinho E Costa, Paulo; Chaves, JoãoAim: miR-134 has been widely reported as upregulated in experimental and human studies of Mesial Temporal Lobe Epilepsy the most common drug-resistant epilepsy (DRE). Studies have shown that the use of antagomirs, anti-miR-134, may be a promising therapeutic approach to these epilepsies. However, data on miR-134 in other epileptic syndromes is scarce. In this study, we aimed to quantify serum levels of miR-134 in a cohort of patients with Mesial Temporal Lobe Epilepsy-Hippocampal Sclerosis (MTLE-HS) and with Genetic Generalized Epilepsies (GGE). Additionally, we explored the correlation between miR-134 serum levels and clinical parameters, such as age at onset or febrile seizures antecedents, to evaluate its potential as a biomarker and therapeutic target in epilepsy. Methods: miR-134 levels were evaluated in cell-free serum of 131 patients with epilepsy (75 women, 56 men; age 41.10 ± 13.12 years; 72 with DRE) and 42 healthy individuals (25 women, 17 men; age 42.40 ± 9.80 years). The epilepsy cohort included 77 MTLE-HS patients and 54 GGE patients. Results: Patients with elevated miR-134 circulating levels were at higher risk of drug-resistant epilepsy (OR [95% CI] = 2.246 [1.111–4.539], p = 0.021). Other risk factors included an older age (OR [95% CI] = 1.032 [1.004–1.061], p = 0.025), history of febrile seizures (OR [95% CI] = 2.994 [1.385–6.471], p = 0.005) and higher disease duration (OR [95% CI] = 1.038 [1.011–1.066], p = 0.006). The strongest predictor of DRE was hippocampal sclerosis (OR [95% CI] = 10.338 [4.566–23.404], p < 0.001). Circulating miR-134 levels were significantly higher in MTLE-HS patients compared to controls (p < 0.05) and GGE patients (p < 0.05). However, the clinical utility of miR-134 in discriminating MTLE-HS patients from controls was only moderated (AUC = 0.651 ± 0.051 95% CI 0.551–0.751, p = 0.007). Conclusion: We show that miR-134 circulating levels are associated with DRE, especially in MTLE-HS, a syndrome characterized by severe hippocampal damage, consistent with activity-regulated miR-134 expression. This overexpression likely contributes to disease progression and our results support the potential of targeting miR-134 as a novel therapeutic approach for refractory epilepsy.
- Correction of a Splicing Mutation Affecting an Unverricht-Lundborg Disease Patient by Antisense TherapyPublication . Matos, Liliana; Duarte, Ana Joana; Ribeiro, Diogo; Chaves, João; Amaral, Olga; Alves, SandraUnverricht-Lundborg disease (ULD) is a common form of progressive myoclonic epilepsy caused by mutations in the cystatin B gene (CSTB) that encodes an inhibitor of several lysosomal cathepsins. Presently, only pharmacological treatment and psychosocial support are available for ULD patients. To overcome the pathogenic effect of the ULD splicing mutation c.66G>A (exon 1), we investigated whether an antisense oligonucleotide therapeutic strategy could correct the defect in patient cells. A specific locked nucleic acid (LNA) antisense oligonucleotide was designed to block a cryptic 5′ss in intron 1. Overall, this approach allowed the restoration of the normal splicing pattern. Furthermore, the recovery was both sequence and dose-specific. In general, this work provides a proof of principle on the correction of a CSTB gene defect causing ULD through a mutation-specific antisense therapy. It adds evidence to the feasibility of this approach, joining the many studies that are paving the way for translating antisense technology into the clinical practice. The insights detailed herein make mutation-based therapy a clear candidate for personalized treatment of ULD patients, encouraging similar investigations into other genetic diseases.
- Epilepsy progression is associated with cumulative DNA methylation changes in inflammatory genesPublication . Martins-Ferreira, Ricardo; Leal, Bárbara; Chaves, João; Li, Tianlu; Ciudad, Laura; Rangel, Rui; Santos, Agostinho; Martins da Silva, António; Pinho Costa, Paulo; Ballestar, EstebanMesial temporal lobe epilepsy with hippocampal sclerosis (MTLE-HS) is the most common focal epilepsy in adults. It is characterized by alarming rates of pharmacoresistance. Epileptogenesis is associated with the occurrence of epigenetic alterations, and the few epigenetic studies carried out in MTLE-HS have mainly focused on the hippocampus. In this study, we obtained the DNA methylation profiles from both the hippocampus and anterior temporal neocortex of MTLE-HS patients subjected to resective epilepsy surgery and autopsied non-epileptic controls. We assessed the progressive nature of DNA methylation changes in relation to epilepsy duration. We identified significantly altered hippocampal DNA methylation patterns encompassing multiple pathways known to be involved in epileptogenesis. DNA methylation changes were even more striking in the neocortex, wherein pathogenic pathways and genes were common to both tissues. Most importantly, DNA methylation changes at many genomic sites varied significantly with epilepsy duration. Such progressive changes were associated with inflammation-related genes in the hippocampus. Our results suggest that the neocortex, relatively spared of extensive histopathological damage, may also be involved in epilepsy development. These results also open the possibility that the observed neocortical impairment could represent a preliminary stage of epileptogenesis before the establishment of chronic lesions or a consequence of prolonged seizure exposure. Our two-tissue multi-level characterization of the MTLE-HS DNA methylome suggests the occurrence of a self-propagating inflammatory wave of epigenetic dysregulation.
- Expression of Inflammation-Associated MicroRNAs in EpilepsyPublication . Leal, Bárbara; Carvalho, Cláudia; Chaves, João; Bettencourt, Andreia; Freitas, Joel; Lopes, João; Ramalheira, João; Silva, António M.; Costa, Paulo P.; Silva, Berta M.Background: Neuroinflammation appears as an important epileptogenic mechanism. MicroRNAs (miRNA) are small non-coding RNA molecules that function as post-transcriptional regulators of gene expression, controlling different biological process including immune system homeostasis and function. Evidences, both in patients and animal studies, have demonstrated an abnormal brain expression of miR-146a and miR-155 in Mesial Temporal Lobe Epilepsy (MTLE), the most refractory epilepsy type. Knowing that miR expression is very stable in biological fluids such as plasma or serum our aim was to characterize miR-146a and miR-155 expression in serum of MTLE and GGE patients. Methods: Expression levels of miR146a and RNU48 (reference gene) were quantified by Real-Time PCR in serum of 16 MTLE patients all with Hippocampal Sclerosis (6F, 8M, mean age= 44.1±11.7 years, age of onset= 13.5±10.6 years, 7 with Febrile Seizures antecedents). A group of 24 healthy individuals was used as control. Relative expression values were calculated using the 2-ΔΔCt method. Results: MTLE patients had a higher expression of miR-146a (6 fold) and miR-155 (2 fold) when compared to controls. Conclusion: Our results, although preliminary, show that miR-146a and miR-155 may be suitable biomarkers for epileptogenesis. It is thought that these miRNAs have role in fine-tuning the response to pro-inflammatory cytokines during epileptogenesis. Nevertheless its importance in epilepsy development it is yet not fully understood. The comprehension of this role may be relevant for the development of new therapeutic strategies.
- Immunogenetic predisposing factors for mesial temporal lobe epilepsy with hippocampal sclerosisPublication . Leal, Bárbara; Chaves, João; Carvalho, Cláudia; Bettencourt, Andreia; Brito, Cláudia; Boleixa, Daniela; Freitas, Joel; Brás, Sandra; Lopes, João; Ramalheira, João; Costa, Paulo; Silva, Berta; Martins Da Silva, AntónioPurpose: Neuroinflammation appears as an important epileptogenic mechanism. Experimental and clinical studies have demonstrated an upregulation of pro-inflammatory cytokines such as IL-1β and TNF-α, in mesial temporal lobe epilepsy with hippocampal sclerosis (MTLE-HS). Expression of these cytokines can be modulated by polymorphisms such as rs16944 and rs1800629, respectively, both of which have been associated with febrile seizures (FS) and MTLE-HS development. The human leukocyte antigen (HLA) system has also been implicated in diverse epileptic entities, suggesting a variable role of this system in epilepsy. Our aim was to analyse the association between immunogenetic factors and MTLE-HS development. For that rs16944 (-511 T>C, IL-1β), rs1800629 (-308 G>A, TNF-α) polymorphisms and HLA-DRB1 locus were genotyped in a Portuguese Population. Methods: We studied 196 MTLE-HS patients (108 females, 88 males, 44.7 ± 12.0 years, age of onset = 13.6 ± 10.3 years, 104 with FS antecedents) and 282 healthy controls in a case–control study. Results: The frequency of rs16944 TT genotype was higher in MTLE-HS patients compared to controls (14.9% in MTLE-HS vs. 7.7% in controls, p = 0.021, OR [95% CI] = 2.20 [1.13–4.30]). This association was independent of FS antecedents. No association was observed between rs1800629 genotypes or HLA-DRB1 alleles and MTLE-HS susceptibility. Also, no correlation was observed between the studied polymorphisms and disease age of onset. Conclusion: The rs16944 TT genotype is associated with MTLE-HS development what may be explained by the higher IL-1β levels produced by this genotype. High IL-1β levels may have neurotoxic effects or imbalance neurotransmission leading to seizures.