4 research outputs found
Autophagic Balance Between Mammals and Protozoa: A Molecular, Biochemical and Morphological Review of Apicomplexa and Trypanosomatidae Infections
Participação da autofagia na interação Toxoplasma gondii-célula hospedeira
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Previous issue date: 2014-11-18Fundação Oswaldo Cruz. Instituto Oswaldo Cruz. Rio de Janeiro, RJ, BrasilToxoplasma gondii é um protozoário parasito intracelular obrigatório, agente causador da toxoplasmose, uma das zoonoses mais difundidas no mundo, podendo ser transmitido por via transplacentária, fecal-oral ou por carnivorismo. Durante a resposta imune do hospedeiro, ocorre a formação de cistos teciduais, possibilitando assim a manutenção do parasito no interior da célula hospedeira, sem ocorrência da fusão fagolisossomal. A autofagia, processo de degradação de componentes celulares, é crucial para a homeostase celular. Recentemente, vem sendo proposta a participação da via autofágica na interação de diferentes patógenos, como o T. gondii, com suas células hospedeiras. Assim, o presente trabalho teve como objetivo avaliar o papel da via autofágica na interação de T. gondii com macrófagos e células musculares esqueléticas (CME e C2C12), células envolvidas na infecção natural in vivo. A autofagia nas células hospedeiras foi avaliada na presença ou na ausência de indutores autofágicos (rapamicina ou estresse nutricional), durante a infecção pelo T. gondii. Ambos os estímulos foram capazes de inibir a infecção e a proliferação intracelular do parasito nos diferentes tipos celulares
Foi observado ainda que a infecção na presença ou na ausência de estímulo induziu a autofagia em macrófagos e CME, indicando que este processo possa regular naturalmente a manutenção intracelular do parasito, auxiliando-o, por exemplo, na captação de nutrientes da célula hospedeira. Adicionalmente, os aspectos morfológicos das culturas de macrófagos e CME infectadas tratadas com rapamicina ou submetidas a estresse nutricional sugerem a eliminação do T. gondii por mecanismos que envolvem tanto a autofagia da célula hospedeira quanto a do parasito. Dessa forma, os resultados do presente trabalho sugerem a indução da autofagia da célula hospedeira como um mecanismo regulador importante durante a infecção, representando, no entanto, a sua exacerbação, uma via de eliminação desse parasito. Além disso, os nossos resultados encorajam a utilização da rapamicina como modelo para o estudo da autofagia in vivo durante a infecção aguda pelo T. gondiiToxoplasma gondii is an obligate intracellular protozoan parasite, the causative agent of toxoplasmosis, one of the most widespread zoonoses in the world and can be transmitted by transplacental, fecal-oral or carnivorism routes. During the host immune response, there is the formation of tissue cysts, thus enabling the maintenance of parasite within the host cell without occurrence of phagolysosomal fusion. Autophagy, the degradation process of cellular components, is critical for cellular homeostasis. Recently, the autophagy has been proposed to participate during the interaction between different pathogens, such as T. gondii, with their host cell. Thus, the present study aimed to evaluate the role of the autophagic pathway in the interaction of T. gondii with macrophages and skeletal muscle cells (C2C12 and CME), cells involved in natural infection in vivo. Host cells autophagy was assessed in the presence or absence of autophagic inductors (rapamycin or nutritional stress) during the infection with T. gondii. Both stimuli were able to inhibit infection and proliferation of the intracellular parasite in different cell types. It was also observed that the infection in the presence or absence of stimulation induced autophagy in macrophages and CME, indicating that this process may naturally regulate the maintenance of intracellular parasites, assisting him, for example, in the nutrients uptake from the host cell. Additionally, the morphological aspects of cultures of infected macrophages and CME treated with rapamycin or subjected to nutritional stress suggest the elimination of T. gondii by mechanisms involving both, host cell and parasite autophagy. Thus, the present results suggest the induction of host cell autophagy as an important regulatory mechanism during the infection, however its exacerbation can represent one route of parasite elimination. Furthermore, our results encourage the use of rapamycin as a model for in vivo autophagic studies during acute infection of T. gondii
Trypanosoma cruzi nucleoside triphosphate diphosphohydrolase 1 (TcNTPDase-1) biochemical characterization, immunolocalization and possible role in host cell adhesion.
Previous work has suggested that Trypanosoma cruzi diphosphohydrolase 1 (TcNTPDase-1) may be involved in the infection of mammalian cells and serve as a potential target for rational drug design. In this work, we produced recombinant TcNTPDase-1 and evaluated its nucleotidase activity, cellular localiza- tion and role in parasite adhesion to mammalian host cells. TcNTPDase-1 was able to utilize a broad range of triphosphate and diphosphate nucleosides. The enzyme’s Km for ATP (0.096mM) suggested a capabil-ity to influence the host’s ATP-dependent purinergic signaling. The use of specific polyclonal antibodies allowed us to confirm the presence of TcNTPDase-1 at the surface of parasites by confocal and electron microscopy. In addition, electron microscopy revealed that TcNTPDase-1 was also found in the flagellum, flagellum insertion region, kinetoplast, nucleus and intracellular vesicles. The presence of this enzyme in the flagellum insertion region and vesicles suggests that it may have a role in nutrient acquisition, and the widespread distribution of TcNTPDase-1 within the parasite suggests that it may be involved in other biological process. Adhesion assays using anti-TcNTPDase-1 polyclonal antibodies as a blocker or purified recombinant TcNTPDase-1 as a competitor revealed that the enzyme has a role in parasite–host cell adhesion. These data open new frontiers to future studies on this specific parasite–host interaction and other unknown functions of TcNTPDase-1 related to its ubiquitous localization