RESUMO
Stressful experience-induced cocaine-related behaviors are associated with a significant impairment of glutamatergic mechanisms in the Nucleus Accumbens core (NAcore). The hallmarks of disrupted glutamate homeostasis following restraint stress are the enduring imbalance of glutamate efflux after a cocaine stimulus and increased basal concentrations of extracellular glutamate attributed to GLT-1 downregulation in the NAcore. Glutamate transmission is tightly linked to microglia functioning. However, the role of microglia in the biological basis of stress-induced addictive behaviors is still unknown. By using minocycline, a potent inhibitor of microglia activation with anti-inflammatory properties, we determined whether microglia could aid chronic restraint stress (CRS)-induced glutamate homeostasis disruption in the NAcore, underpinning stress-induced cocaine self-administration. In this study, adult male rats were restrained for 2 h/day for seven days (day 1-7). From day 16 until completing the experimental protocol, animals received a vehicle or minocycline treatment (30 mg/Kg/12h i.p.). On day 21, animals were assigned to microscopic, biochemical, neurochemical or behavioral studies. We confirm that the CRS-induced facilitation of cocaine self-administration is associated with enduring GLT-1 downregulation, an increase of basal extracellular glutamate and postsynaptic structural plasticity in the NAcore. These alterations were strongly related to the CRS-induced reactive microglia and increased TNF-α mRNA and protein expression, since by administering minocycline, the impaired glutamate homeostasis and the facilitation of cocaine self-administration were prevented. Our findings are the first to demonstrate that minocycline suppresses the CRS-induced facilitation of cocaine self-administration and glutamate homeostasis disruption in the NAcore. A role of microglia is proposed for the development of glutamatergic mechanisms underpinning stress-induced vulnerability to cocaine addiction.
Assuntos
Cocaína , Animais , Cocaína/metabolismo , Ácido Glutâmico/metabolismo , Masculino , Microglia/metabolismo , Minociclina/metabolismo , Minociclina/farmacologia , Núcleo Accumbens/metabolismo , Ratos , Ratos Sprague-DawleyRESUMO
Innate immune activation and chronic neuroinflammation are characteristic features of many neurodegenerative diseases including Parkinson's disease (PD) and may contribute to the pathophysiology of the disease. The discovery of misfolded alpha-synuclein (αSYN) protein aggregates, which amplify in a "prion-like" fashion, has led us to consider that pathogenic αSYN might be hijacking the activation and mobilization mechanism of the peripheral immune system to reach and disseminate within the CNS. Furthermore, our lab and other groups have recently shown that αSYN can adopt distinct fibril conformations or "strains" with varying levels of pathogenic impact. Therefore, the aim of this study was to assess the impact of peripheral inflammation on αSYN spreading in order to better understand the participation of the immune system in the progression of PD. The results presented here show that intraperitoneal LPS injection prior to systemic intravenous recombinant administration of two different αSYN pathogenic strains (fibrils or ribbons) in wild type mice, induces an increase in brain resident microglia and promotes the recruitment of leukocytes toward the brain and the spinal cord. Our findings show for the first time that αSYN can be internalized by LPS-primed inflammatory monocytes, which in turn favors the dissemination from the periphery toward the brain and spinal cord. Further, we found a differential recruitment of CD4+ and CD8+ T cells after LPS priming and subsequent administration of the αSYN ribbons strain. Together, these data argue for a role of the peripheral immune system in αSYN pathology.
Assuntos
Encéfalo/imunologia , Vigilância Imunológica , Inflamação/imunologia , Monócitos/metabolismo , Medula Espinal/imunologia , alfa-Sinucleína/metabolismo , alfa-Sinucleína/farmacologia , Administração Intravenosa , Animais , Encéfalo/patologia , Linfócitos T CD4-Positivos/metabolismo , Linfócitos T CD8-Positivos/metabolismo , Modelos Animais de Doenças , Feminino , Injeções Intraperitoneais , Lipopolissacarídeos/administração & dosagem , Lipopolissacarídeos/farmacologia , Camundongos , Camundongos Endogâmicos C57BL , Microglia/efeitos dos fármacos , Doença de Parkinson/imunologia , Agregados Proteicos , Medula Espinal/patologia , alfa-Sinucleína/administração & dosagemRESUMO
Brain-resident microglia and peripheral migratory leukocytes play essential roles in shaping the immune response in the central nervous system. These cells activate and migrate in response to chemokines produced during active immune responses and may contribute to the progression of neuroinflammation. Herein, we addressed the participation of type I-II interferons in the response displayed by microglia and inflammatory monocytes to comprehend the contribution of these cytokines in the establishment and development of a neuroinflammatory process. Following systemic lipopolysaccharide (LPS) challenge, we found glial reactivity and an active recruitment of CD45hi leukocytes close to CD31+ vascular endothelial cells in circumventricular organs. Isolated CD11b+ CD45hi Ly6Chi Ly6G--primed inflammatory monocytes were able to induce T cell proliferation, unlike CD11b+ CD45lo microglia. Moreover, ex vivo re-stimulation with LPS exhibited an enhancement of T cell proliferative response promoted by inflammatory monocytes. These myeloid cells also proved to be recruited in a type I interferon-dependent fashion as opposed to neutrophils, unveiling a role of these cytokines in their trafficking. Together, our results compares the phenotypic and functional features between tissue-resident vs peripheral recruited cells in an inflamed microenvironment, identifying inflammatory monocytes as key sentinels in a LPS-induced murine model of neuroinflammation.
RESUMO
Autophagy is a fundamental cellular homeostatic mechanism, whereby cells autodigest parts of their cytoplasm for removal or turnover. Neurodegenerative disorders are associated with autophagy dysregulation, and drugs modulating autophagy have been successful in several animal models. Microglial cells are phagocytes in the central nervous system (CNS) that become activated in pathological conditions and determine the fate of other neural cells. Here, we studied the effects of autophagy on the production of pro-inflammatory molecules in microglial cells and their effects on neuronal cells. We observed that both trehalose and rapamycin activate autophagy in BV2 microglial cells and down-regulate the production of pro-inflammatory cytokines and nitric oxide (NO), in response to LPS and alpha-synuclein. Autophagy also modulated the phosphorylation of p38 and ERK1/2 MAPKs in BV2 cells, which was required for NO production. These actions of autophagy modified the impact of microglial activation on neuronal cells, leading to suppression of neurotoxicity. Our results demonstrate a novel role for autophagy in the regulation of microglial cell activation and pro-inflammatory molecule secretion, which may be important for the control of inflammatory responses in the CNS and neurotoxicity.
Assuntos
Autofagia , Morte Celular/efeitos dos fármacos , Citocinas/metabolismo , Lipopolissacarídeos/toxicidade , Neuroglia/fisiologia , Óxido Nítrico/metabolismo , alfa-Sinucleína/toxicidade , Animais , Linhagem Celular , Camundongos , Transdução de SinaisRESUMO
Hepatic mononuclear cells (HMC) are a heterogeneous population with innate immune properties involved in the response to several pathogens. Herein, during the primary infection with Candida albicans, we observed dynamic changes in CD3+, NK+ and NKT+ intrahepatic lymphoid subsets and a significant increase in the absolute number of antigen-presenting cells (APC). The liver tolerogenic microenvironment sustained by higher levels of IL-10, transforming growth factor-ß and IL-4 was severely modified upon the robust IFN-γ production after the fungal colonization. NKT cells purified from infected animals released significant amounts of IFN-γ and the production of this cytokine was exacerbated after a second contact with the fungus. Interestingly, C. albicans per se was unable to activate tolerogenic NKT cells from naive animals. In vitro experiments performed with HMC cells depleted of the CD11b/c+ population revealed that in the absence of APC, NKT cells are unable to produce IFN-γ in response to C. albicans. Our findings constitute the first evidence that this innate lymphocyte population is involved in the pathogenesis of C. albicans infection.