Leukotrienes (LT) constitute a group of potent biologically active arachidonic acid-derived metabolites (AA) that are implicated as mediators of immediate hypersensitivity reactions and inflammation. During the last years some researches about LT functions had restricted not only to their participation on inflammatory responses, but also as mediators able to modulate the synthesis and liberation of cytokines during adaptative immune response. The participation of LT in host defense mechanisms against infectious agents had been described, as Escherichia coli, Histoplasma capsulatum and Strongyloides venezuelensis. We shown in previous work that experimental infection with Mycobacterium tuberculosis induced enhancement of LTB4 in the lung and the pharmacological inhibition of LT leads to uncontrolled bacterial growth and mice succumb to the infection. Phagocytes, cytokines (Th1 and inflammatory) and reactive nitrogen intermediates are the major antimicrobial mechanisms against tuberculosis infection. Moreover, coupling of LTB4 to its receptor leads to intracellular activation that induces phagocytes and bacterial killing. In this sense, in the experimental infection with M. tuberculosis we will investigate the effects of LTB4 administration in vivo and in vitro. To protect the eicosanoid against extracellular degradation, LTB4 will be encapsulated in cationic liposomes, which ensure the intracellular delivery. For in vivo assay, 5-LO knockout and wild-type mice will be infected by intratracheal route with virulent strain of M. tuberculosis H37RV and treated with LTB4 formulation. Evaluation of the bacterial growth, analyze of some immunological parameters, as cytokine, lipid mediators and nitric oxide production will be performed. For in vitro assay, we will evaluate the effects of LTB4 addition in infected alveolar macrophage to investigate the phagocitosis and microbicidal activity, as well the intracellular signaling involved in this mechanisms and the cytokines and lipid mediators production. Considerable progress has been made on leukotriene research with regard to the characterization of the biological, pharmacological, and pathophysiological actions of these potent mediators and with this work, we intend to complement the knowledge about immune response in tuberculosis, as well provide understanding for the application of lipid mediators as therapeutic adjuvant against infectious diseases.
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