RESUMO
Microglia (MG) play a crucial role as the predominant myeloid cells in the central nervous system and are commonly activated in multiple sclerosis. They perform essential functions under normal conditions, such as actively surveying the surrounding parenchyma, facilitating synaptic remodeling, engulfing dead cells and debris, and protecting the brain against infectious pathogens and harmful self-proteins. Extracellular vesicles (EVs) are diverse structures enclosed by a lipid bilayer that originate from intracellular endocytic trafficking or the plasma membrane. They are released by cells into the extracellular space and can be found in various bodily fluids. EVs have recently emerged as a communication mechanism between cells, enabling the transfer of functional proteins, lipids, different RNA species, and even fragments of DNA from donor cells. MG act as both source and recipient of EVs. Consequently, MG-derived EVs are involved in regulating synapse development and maintaining homeostasis. These EVs also directly influence astrocytes, significantly increasing the release of inflammatory cytokines like IL-1ß, IL-6, and TNF-α, resulting in a robust inflammatory response. Furthermore, EVs derived from inflammatory MG have been found to inhibit remyelination, whereas Evs produced by pro-regenerative MG effectively promote myelin repair. This review aims to provide an overview of the current understanding of MG-derived Evs, their impact on neighboring cells, and the cellular microenvironment in normal conditions and pathological states, specifically focusing on demyelination and remyelination processes.
Assuntos
Vesículas Extracelulares , Esclerose Múltipla , Remielinização , Humanos , Microglia/metabolismo , Citocinas/metabolismo , Vesículas Extracelulares/metabolismo , Esclerose Múltipla/metabolismoRESUMO
Nine-hundred-eighty-nine patients with lymphoma were studied. Fifty-three cases (5.3%) had lymphomatous craniocerebral infiltration. The principal factors of risk for this complication were: advanced stage of the lymphoma (III or IV), diffuse histiocytic, diffuse poorly differentiated lymphocytic, or mixed cellularity lymphoma histological type, bone marrow involvement, and previous systemic chemotherapy. Thirty-two per cent of the cases of meningeal lymphomatous infiltration were asymptomatic and represented autopsy findings. CT-scan was an useful test to detect brain focal parenchymatous infiltration, as opposed to meningeal infiltration. Mean survival time in patients with lymphomatous meningeal infiltration was 4.3 months, following the combined use of systemic chemotherapy, radiation therapy and intrathecal methotrexate. Two cases had primary cerebral lymphoma, although without associated immunodeficiency. Twenty patients (2%) had intracranial hemorrhage, in clear relationship with platelet alterations. Fifteen patients (1.5%) had CNS infection, caused by common bacteria or opportunistic agents. In 7 cases, the diagnosis was made at autopsy. Thirty-six autopsies were performed. In 8 cases (22%), pathologic findings such as, demyelination, microcalcifications, coagulative necrosis, or gliosis, suggested complications from treatment.