RESUMO
Leishmania spp., the causative agents of leishmaniasis, are intracellular parasites, transmitted to humans via the bite of their sand fly vectors. Once inoculated, the promastigotes are exposed to the dermis, which is composed of extracellular matrix (ECM), growth factors and its resident cells. Promastigote forms are phagocytosed by macrophages recruited to the site of the sand fly bite, either directly or after interaction with neutrophils. Since Leishmania is an intracellular parasite, its interaction with the host ECM has been neglected as well as the immediate steps after the sand fly bite. However, promastigotes must overcome the obstacles presented by the dermis ECM in order to establish the infection. Thus, the study of the interaction between Leishmania promastigotes and ECM components as well as the earliest stages of infection are important steps to understand the establishment of the disease, and could contribute in the future to new drug developments towards leishmaniasis.
Assuntos
Matriz Extracelular/patologia , Mordeduras e Picadas de Insetos/parasitologia , Leishmania/fisiologia , Macrófagos/fisiologia , Neutrófilos/fisiologia , Psychodidae/fisiologia , Animais , HumanosRESUMO
Cell migration is a multi-step process that involves the coordinated action of signaling networks, cytoskeletal dynamics and vesicular trafficking, leading to protrusion and adhesion at the leading edge of cells and contraction and detachment at their rear. In a recent paper in Cell Research, Ma et al. describe the biogenesis of a new exosome-like organelle--named migrasomes--that derive from retraction fibers at the rear of migrating cells and their potential roles in inter-cellular signaling.
Assuntos
Movimento Celular , Citoplasma/metabolismo , Organelas/metabolismo , Animais , HumanosRESUMO
Members of the genus Acanthamoeba are present in diverse environments, from freshwater to soil, and also in humans, causing serious brain and corneal infections. Their life cycle presents two stages: the dividing trophozoite and the quiescent cyst. The structures of these life stages have been studied for many years, and structural data have been used for taxonomy. The ultrastructural work on Acanthamoeba cysts was carried out previously by routine transmission electron microscopy (TEM), a process that requires the use of chemical fixation, a procedure that can cause serious artifacts in the ultrastructure of the studied material. In order to prevent fixation artifacts, we processed Acanthamoeba polyphaga cysts by ultrarapid freezing, followed by freeze-fracturing and deep-etching, in order to obtain a 3D visualization of the arrangements of the cyst wall. The exocyst presented an irregular surface, with vesicles located within or near this layer. The endocyst, instead, showed a biphasic arrangement with a more compact district in its innermost part, and a more loosened outer layer. For this reason, it was difficult to distinguish the filaments present in the intercyst space from those forming the endocyst. Surprisingly, the intercyst space was thinner when compared with samples processed by conventional TEM, evidencing the possible damage consequent to the use of chemical fixation.
Assuntos
Acanthamoeba/ultraestrutura , Parede Celular/ultraestrutura , Esporos de Protozoários/ultraestrutura , Microscopia CrioeletrônicaRESUMO
The recognition and binding of pathogens to extracellular matrix glycoproteins may determine the outcome of infective processes. The interaction between the bovine urogenital parasite Tritrichomonas foetus and the major basal membrane glycoprotein laminin-1 (LMN-1) was investigated. The chemical nature of parasite molecules involved in the attachment of T. foetus to immobilized LMN-1 and the influence of LMN-1 in the toxicity exerted by the parasite to HeLa cells was studied. Attachment of T. foetus to LMN-1 resulted in notable morphological alterations of the parasite, which became amoeboid. T. foetus recognized LMN-1 through specific amino acid sequences (AG73, C16, A208 and A13) in the LMN-1 molecule, and the protein nature of the parasite molecules involved in the recognition was demonstrated by dot-blot analyses. Such molecular recognition was cation-dependent and five LMN-1-binding molecules (220, 200, 130, 125 and 80 kDa) were identified in T. foetus. Binding of T. foetus to LMN-1 rendered the parasite toxic to HeLa cell monolayers. Thus, LMN-1 appears to provide signalling cues that mediate important cell functions in T. foetus concerning its interaction with host cells.
Assuntos
Doenças dos Bovinos/parasitologia , Laminina/metabolismo , Infecções Protozoárias em Animais , Tritrichomonas foetus/metabolismo , Sequência de Aminoácidos , Animais , Bovinos , Doenças dos Bovinos/metabolismo , Adesão Celular , Células HeLa , Interações Hospedeiro-Parasita , Humanos , Laminina/química , Laminina/genética , Masculino , Ligação Proteica , Infecções por Protozoários/metabolismo , Infecções por Protozoários/parasitologia , Proteínas de Protozoários/química , Proteínas de Protozoários/genética , Proteínas de Protozoários/metabolismo , Tritrichomonas foetus/genética , Tritrichomonas foetus/patogenicidadeRESUMO
Acanthamoeba spp. consists of free-living amoebae, widespread in nature, which occasionally can cause human infections including granulomatous amoebic encephalitis and amoebic keratitis. Acanthamoeba pathogenesis is not entirely known and correlations between pathogenic potential and taxonomy are complex issues. In order to decipher the definition of a pathogenic amoeba, the objective of this work was to decipher the definition of pathogenic amoeba by characterizing two isolates of Acanthamoeba polyphaga obtained from different origins (a keratitis patient and freshwater), looking for differences among them. The clinical isolate grew faster in Peptone-yeast extract-glucose (PYG) medium, transformed more rapidly from a trophozoite to cyst and exhibited increased cytopathic effect on cultured cells. Morphological differences were also noted, since freshwater amoebae presented more acanthopodia than the clinical isolate. Moreover, actin labeling demonstrated that microfilament organization varies between isolates, with the presence of locomotory structures as lobopodia and lamellipodia in the keratitis isolate, which were less adherent on plastic. Zymography demonstrated that the keratitis isolates presented higher proteolytic activity and also were more able to invade collagen matrices. Altogether, we conclude that a group of stable physiological characteristics exist in Acanthamoeba that can be related to pathogenicity.
Assuntos
Ceratite por Acanthamoeba/parasitologia , Acanthamoeba , Água Doce/parasitologia , Acanthamoeba/classificação , Acanthamoeba/isolamento & purificação , Acanthamoeba/patogenicidade , Acanthamoeba/fisiologia , Animais , Adesão Celular , Linhagem Celular , Células Epiteliais/parasitologia , Humanos , Microscopia Confocal , Microscopia Eletrônica de Varredura , FenótipoRESUMO
As observed in most of the investigated trichomonads, a strain of Tritrichomonas foetus includes different parasite subpopulations. Such population diversity might account for important properties such as the ability of the parasite to destroy host cells. The aim of this study was to characterize the cytotoxicity exerted by subpopulations (named as K1, K2, K3, K4 and K5) of an isolate of T. foetus on epithelial cultured cells. The five populations studied here destroyed epithelial monolayers at different rates (from 25% to 55%), even though the cytoadhesion level and whole-cell protease activity were closely related among them. We were also able to detect differences in contact-dependent and contact-independent cytotoxicity mechanisms among the five populations. An extracellular parasite protease had varying activity among the parasite populations. The intensity of contact-independent cytotoxicity was strictly related to the degree of enzyme activation, suggesting that such a protease might be involved in the cytotoxicity mediated by T. foetus.
Assuntos
Tritrichomonas foetus/classificação , Tritrichomonas foetus/patogenicidade , Animais , Adesão Celular , Células HeLa , Humanos , Peptídeo Hidrolases/metabolismo , Especificidade da Espécie , Tritrichomonas foetus/fisiologiaRESUMO
The aim of this work was to investigate the role played by iron during interaction of Tritrichomonas foetus with cultured epithelial cells. We have observed that the growth rate of T. foetus is influenced by the amount of iron available into culture medium. When organisms maintained for 24h in iron-depleted medium were transferred to an iron-rich one, many protozoan cells exhibited a cytokinesis blockage. Parasites maintained in iron-depleted medium exhibited a significant increase in cytoadhesion when compared with both controls and parasites that had been cultured in medium in which iron was replaced. T. foetus collected from iron-depleted medium also exhibited a reduction in its ability to destroy epithelial cell monolayers and a reduction in the activity of several cysteine proteases. Taken together, the results presented here demonstrate that iron may be an extracellular signal, which seems to modulate the ability of T. foetus to interact with host epithelial cells.