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Neutrophil activation by MNCF lectin results in gene transcription and secretion of cytokines, even in anti-inflammatory conditions

Abstract : Leukocytes are accumulated, in the inflammatory process, because to action of the wide array of stimuli. This event envolved several and coodenated steps whose inhibited by glucocoticoids, such as dexamethasone. Dexamethasone affects human neutrophils in different ways. It shows negative effects (on synthesis and secretion of pro-inflammatory mediators) and positive effects (for example, on annexin I). Among the inducers of leukocyte migration, MNCF, a galactose-binding lectin, has been described as an agonist and chemoattractant for neutrophils, both in vivo and in vitro. MNCF shows as peculiar activity the migration of neutrophils resistant to dexamethasone actions which awakes great interest in undertanding the mechanism of action on polymorphonuclears by this lectin. Our first step was study human MNCF-stimulated neutrophils pre-incubated with dexamethasone. In these conditions, MNCF, in the absence of F-actin polymerization: (a) protects neutrophils from spontaneous apoptosis, (b) induces tyrosine and p38 MAP quinases phosphorylation, (c) induces CD62L shedding, (d) degranulates secretory vesicles and secundary granules, but not azurophilic granules, in the dependent manner of tyrosine and MAP quinases and Src family, (e) translocates the transcription factor NF-kB and, (f) induces transcription and secretion of pro-inflammatory cytokines and chemokines. In parallel, human neutrophils pre-incubated with dexamethasone and stimulated with MNCF did not show CD62L shedding and F-actin polarization, but the in vitro migration was maintained. Besides, we already observe translocation of NF-kB from cytoplasm to nucleous which it activates the genic transcription and secretion of inflammatory mediators, such as CXCL8. The results, showed here, strengthens previous results, demonstranting that MNCF as a agonist to neutrophils, beyond increase the half life them. Although, dexamethasone modifies some effects of MNCF on neutrophis, this glucocorticoid does not inhibit the cellular response to the studied lectin. Thus, the maintenance of inflammatory mediators, dependents to NF-kB, during the inflammatory process, could explain, even parcialy, the break in the resitance to glucocorticoids actions by MNCF in the neutrophil migration.
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Karina Alves de Toledo. Neutrophil activation by MNCF lectin results in gene transcription and secretion of cytokines, even in anti-inflammatory conditions. Immunology. Université Pierre et Marie Curie - Paris VI, 2007. Portuguese. ⟨NNT : 2007PA066554⟩. ⟨tel-00809242⟩

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