Metabolismo de biomoléculas na embriogênese do carrapato Rhipicephalus (Boophilus) microplus
Guizzo, Melina GarciaAbreu, LeonardoMasuda, AoiLogullo, CarlosVaz Junior, Itabajara da Silva
Background: The hard tick Rhipicephalus (Boophilus) microplus is an hematophagous ectoparasite that causes important economic losses in the cattle raising. The control of the parasite is usually accomplished through the use of acaricides. Even though these chemicals substances present effectiveness, their continuous use can lead to the selection of resistant parasites. When not used properly acaricides can cause environmental damages in addition to risks for animal and human health. Because of these drawbacks there are efforts to the development of alternatives control methods. The immunological control is a promissing method due to target specifi city, which increases the environmental and animal safety. The development of such approach relies on the discovery and characterization of molecules involved in the metabolism of the parasite different life stages. The embryogenesis is the stage where the metabolites of maternal origin are mobilized through catabolic and anabolic pathways necessary for the development of the embryo. The study of the substrates and enzymes involved in metabolic pathways of the embryogenesis allows the directed search to potential antigens to the development of an anti-R. microplus vaccine. Review: The embryo, during its development, passes through the stages of a sincicial blastoderm, celular blastoderm and segmentation, and both morfological changes and energy sources mobilization are related. Lipids are the major energetic source to the cellular blastoderm formation. Up to cellularization stage and after embryo segmentation, sugars are the main metabolite required. It supports that tick embryogenesis occurs with two distinct phases regarding glucose utilization by the embryo. In the initial phase, until the formation of the celular blastoderm, there is the utilization of the maternal energetic source stored in oocytes, like glycogen. After segmentation, until larval hatching, the embryo performs gluconeogenesis through non-glucidic compounds to obtain the energy input required for its metabolism. Therewith occurs the activation of the glycolytic and gluconeogenic pathways to provide glucose to the developing embryo. Due to the high levels of glucose available, it is suggested that the insulin pathway is active and be conserved in R. microplus, as previously described for other organisms. Glycogen accumulation observed throughout tick embryogenesis could be a response to an endogenous insulin-like signal. During gluconeogenesi's amino acids stored in the storage proteins of the yolk granules are enzymatically mobilized to supply the metabolic energy required for the embryo development. In this context, three peptidases involved in the degradation of yolk proteins in eggs and one peptidase in larvae were characterized, and demonstrate the importance of the use of amino acids in this phase of the tick's life. Another metabolite involved in the development of the embryo is water, whose homeostasis must be mantained in the parasitic and environmental stages of the R. microplus's life. The function of water maintenance in eggs is particularly important for embryo development. Conclusion: The study of the energetic pathways important to the metabolism of R. microplus's embryo is a promissing way for development of control methods. In this context different enzymes involved in providing energetic substrates for the embryogenesis have been indentified, characterized and can be used as targets in the immunological control of the tick.Proteinases characterized from R. microplus eggs, BYC and VTDCE, were tested as antigens to immunize bovines and provided to be immunoprotective against the parasite. Other enzymes also showed a potential to be used as targets in an anti-R.microplus vaccine.
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