Publicação
Exploring the role of astrocytes in the pathophysiology of multiple sclerosis
| Resumo: | The presence of reactive astrocytes in multiple sclerosis (MS), a chronic inflammatory disease of the central nervous system, has been described for a long time, however its contribution for disease pathophysiology is still not fully understood. Therefore, in this work we proposed to further explore the contribution of astrocytes in MS using different experimental approaches. We started by performing a temporal transcriptomic analysis of astrocytes in the chronic experimental autoimmune encephalomyelitis (EAE) MS animal model. For that we isolated astrocytes from the cerebellum in 3 disease time points: before the symptom’s appearance (pre-symptomatic phase), at the onset/peak of the disease and at the chronic phase of EAE. Particularly at the onset phase of disease, astrocytes overexpressed genes associated with a neurotoxic phenotype (known as A1 phenotype), along with the overexpression of genes involved in metabolic pathways, like glycolysis and tricarboxylic acid cycle. This suggested that astrocytes could be undergoing metabolic reprogramming, similarly to what happens in macrophages/microglia in response to different inflammatory stimuli. On the second part of this work, we induced EAE in a model that presents “silent” astrocytes, i.e. astrocytes that present minimal calcium elevations in the soma and main processes, due to the ablation of the inositol 1,4,5-triphosphate receptor type 2 (IP3R2-null). IP3R2- null mice and wild-type littermates presented similar disease clinical scores, however IP3R2-null mice had decreased lesion burden in the cerebellum white matter, which could be associated with the increased astrocyte reactivity observed in these mice near the lesions, compared to the normal appearing white matter. Next, we studied the effects of a neuroprotective drug, dimethyl fumarate (DMF), on astrocyte activation and on the cognitive function in the EAE model. DMF treatment, started at the symptomatic phase of disease, was able to reduce astrocyte reactivity, evaluated by a decrease in the number of cells, and demyelination in the fimbria, which is the most important white matter pathway in the hippocampus, possibly contributing to the prevention of cognitive deficits observed in DMF-treated EAE animals. Finally, we focused our attention on a protein produced by astrocytes during EAE, lipocalin-2 (LCN2), an acute phase protein that was previously suggested as a possible disease biomarker. After the quantification of LCN2 concentration in cerebrospinal fluid samples from MS patients, we observed that increased LCN2 levels were associated with faster disease progression. However, this association was no longer statistically significant after controlling for the patients’ age and the presence of oligoclonal bands. |
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| Autores principais: | Neves, Sofia Pereira das |
| Assunto: | astrocytes dimethyl fumarate lipocalin-2 metabolic reprogramming multiple sclerosis astrócitos dimetil fumarato esclerose múltipla lipocalina-2 reprogramação metabólica |
| Ano: | 2021 |
| País: | Portugal |
| Tipo de documento: | tese de doutoramento |
| Tipo de acesso: | acesso aberto |
| Instituição associada: | Universidade do Minho |
| Idioma: | português |
| Origem: | RepositóriUM - Universidade do Minho |
| Resumo: | The presence of reactive astrocytes in multiple sclerosis (MS), a chronic inflammatory disease of the central nervous system, has been described for a long time, however its contribution for disease pathophysiology is still not fully understood. Therefore, in this work we proposed to further explore the contribution of astrocytes in MS using different experimental approaches. We started by performing a temporal transcriptomic analysis of astrocytes in the chronic experimental autoimmune encephalomyelitis (EAE) MS animal model. For that we isolated astrocytes from the cerebellum in 3 disease time points: before the symptom’s appearance (pre-symptomatic phase), at the onset/peak of the disease and at the chronic phase of EAE. Particularly at the onset phase of disease, astrocytes overexpressed genes associated with a neurotoxic phenotype (known as A1 phenotype), along with the overexpression of genes involved in metabolic pathways, like glycolysis and tricarboxylic acid cycle. This suggested that astrocytes could be undergoing metabolic reprogramming, similarly to what happens in macrophages/microglia in response to different inflammatory stimuli. On the second part of this work, we induced EAE in a model that presents “silent” astrocytes, i.e. astrocytes that present minimal calcium elevations in the soma and main processes, due to the ablation of the inositol 1,4,5-triphosphate receptor type 2 (IP3R2-null). IP3R2- null mice and wild-type littermates presented similar disease clinical scores, however IP3R2-null mice had decreased lesion burden in the cerebellum white matter, which could be associated with the increased astrocyte reactivity observed in these mice near the lesions, compared to the normal appearing white matter. Next, we studied the effects of a neuroprotective drug, dimethyl fumarate (DMF), on astrocyte activation and on the cognitive function in the EAE model. DMF treatment, started at the symptomatic phase of disease, was able to reduce astrocyte reactivity, evaluated by a decrease in the number of cells, and demyelination in the fimbria, which is the most important white matter pathway in the hippocampus, possibly contributing to the prevention of cognitive deficits observed in DMF-treated EAE animals. Finally, we focused our attention on a protein produced by astrocytes during EAE, lipocalin-2 (LCN2), an acute phase protein that was previously suggested as a possible disease biomarker. After the quantification of LCN2 concentration in cerebrospinal fluid samples from MS patients, we observed that increased LCN2 levels were associated with faster disease progression. However, this association was no longer statistically significant after controlling for the patients’ age and the presence of oligoclonal bands. |
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