RESUMO
Naegleria fowleri causes a fatal disease known as primary amoebic meningoencephalitis. This condition is characterized by an acute inflammation that originates from the free passage of peripheral blood cells to the central nervous system through the alteration of the blood-brain barrier. In this work, we established models of the infection in rats and in a primary culture of endothelial cells from rat brains with the aim of evaluating the activation and the alterations of these cells by N. fowleri. We proved that the rat develops the infection similar to the mouse model. We also found that amoebic cysteine proteases produced by the trophozoites and the conditioned medium induced cytopathic effect in the endothelial cells. In addition, N. fowleri can decrease the transendothelial electrical resistance by triggering the destabilization of the tight junction proteins claudin-5, occludin, and ZO-1 in a time-dependent manner. Furthermore, N. fowleri induced the expression of VCAM-1 and ICAM-1 and the production of IL-8, IL-1ß, TNF-α, and IL-6 as well as nitric oxide. We conclude that N. fowleri damaged the blood-brain barrier model by disrupting the intercellular junctions and induced the presence of inflammatory mediators by allowing the access of inflammatory cells to the olfactory bulbs.
Assuntos
Barreira Hematoencefálica/parasitologia , Infecções Protozoárias do Sistema Nervoso Central/metabolismo , Células Endoteliais/metabolismo , Naegleria fowleri/metabolismo , Naegleria fowleri/patogenicidade , Proteínas de Junções Íntimas/metabolismo , Animais , Infecções Protozoárias do Sistema Nervoso Central/parasitologia , Infecções Protozoárias do Sistema Nervoso Central/patologia , Claudina-5/metabolismo , Cisteína Proteases/metabolismo , Citocinas/metabolismo , Modelos Animais de Doenças , Inflamação , Molécula 1 de Adesão Intercelular/metabolismo , Interleucina-1beta/metabolismo , Interleucina-8/metabolismo , Masculino , Meningoencefalite/parasitologia , Meningoencefalite/patologia , Camundongos , Mucosa/parasitologia , Mucosa/patologia , Ocludina/metabolismo , Ratos , Ratos Wistar , Trofozoítos/metabolismo , Fator de Necrose Tumoral alfa/metabolismo , Conchas Nasais/patologia , Molécula 1 de Adesão de Célula Vascular/metabolismo , Proteína da Zônula de Oclusão-1/metabolismoRESUMO
Naegleria fowleri causes acute and fulminant primary amoebic meningoencephalitis. This microorganism invades its host by penetrating the olfactory mucosa and then traveling up the mesaxonal spaces and crossing the cribriform plate; finally, the trophozoites invade the olfactory bulbs. During its invasion, the protozoan obtains nutrients such as proteins, lipids, carbohydrates, and cationic ions (e.g., iron, calcium, and sodium) from the host. However, the mechanism by which these ions are obtained, particularly iron, is poorly understood. In the present study, we evaluated the ability of N. fowleri to degrade iron-binding proteins, including hololactoferrin, transferrin, ferritin, and hemoglobin. Zymography assays were performed for each substrate under physiological conditions (pH 7 at 37°C) employing conditioned medium (CM) and total crude extracts (TCEs) of N. fowleri. Different degradation patterns with CM were observed for hololactoferrin, transferrin, and hemoglobin; however, CM did not cause ferritin degradation. In contrast, the TCEs degraded only hololactoferrin and transferrin. Inhibition assays revealed that cysteine proteases were involved in this process. Based on these results, we suggest that CM and TCEs of N. fowleri degrade iron-binding proteins by employing cysteine proteases, which enables the parasite to obtain iron to survive while invading the central nervous system.
Assuntos
Infecções Protozoárias do Sistema Nervoso Central/metabolismo , Cisteína Proteases/metabolismo , Interações Hospedeiro-Patógeno , Ferro/metabolismo , Proteólise , Animais , Infecções Protozoárias do Sistema Nervoso Central/parasitologia , Infecções Protozoárias do Sistema Nervoso Central/patologia , Proteínas de Ligação ao Ferro/metabolismo , Lactoferrina/metabolismo , Naegleria fowleri/enzimologia , Naegleria fowleri/patogenicidade , Bulbo Olfatório/metabolismo , Bulbo Olfatório/patologia , Transferrina/metabolismo , Trofozoítos/metabolismoRESUMO
Central nervous system (CNS) damage can occur during Trypanosoma cruzi infection, especially in immunosuppressed patients. The enhanced susceptibility of C3H/He mice to CD8-mediated acute meningoencephalitis is associated with higher up-regulation of vascular cell adhesion molecule-1 (VCAM-1) on CNS vascular endothelia than in the less susceptible C57BL/6. Further, in vitro adhesion of activated peripheral blood cells to CNS blood vessels was abrogated by anti-VLA-4 antibodies that also inhibited cell migration into the CNS of T. cruzi-infected mice. Lastly, the reactivation of meningoencephalitis in immunosuppressed chronically infected mice was associated with VCAM-1 up-regulation. Therefore, we hypothesize that VLA-4/VCAM-1 pathway plays a pivotal role in the establishment of T. cruzi-elicited encephalitis.