a b s t r a c tThe tagitinins isolated of Tithonia diversifolia (Hemsl.) A. Gray, Asteraceae, are the most studied sesquiterpene lactones due to their wide spectrum of pharmacologic activities, especially related with nuclear factor-kappa B inhibition. Nevertheless, detailed studies about the mechanism of action of its active compounds are still lacking. Neutrophils perform a fundamental role in the inflammatory response to several etiologic factors. However, the effect of tagitinins on human neutrophil is not yet clearly known. We investigated the role of tagitinin C (1), tagitinin F (2) and tagitinin A (3) in activation and survival of human neutrophils to establish possible effects in their mechanisms of inflammation. Human neutrophils were purified from the peripheral blood and cultivated with tagitinins C (1), F (2) and A (3) in the presence or not of Escherichia coli lipopolysaccharide. The enzymatic activity, apoptosis and secretion of cytokines rate were determined after 18 h. Lipopolysaccharide-induced myeloperoxidase activity of human neutrophils was significantly inhibited only by tagitinin F (2). Apoptosis of neutrophils was increased in the presence of tagitinin C (1), and it occurred independently of the presence of lipopolysaccharide or dexamethasone. Tagitinins C (1), F (2) and A (3) decrease lipopolysaccharide-induced interleukin-6, interleukin-8 and Tumor necrosis factor alpha production by human neutrophils. Together, these results indicate that tagitinins exhibit anti-inflammatory action on human neutrophils. However, tagitinin F (2) was the only sesquiterpene lactone that decreased secretion of inflammatory products by neutrophils without inducing neutrophil apoptosis.
Fcγ receptors on aging neutrophilsObjective: Neutrophils are key effector cells of the innate immune system.They recognize antigens through membrane receptors, which are expressed during their maturation and activation. Neutrophils express FcγRII (CD32), FcγRIII (CD16), and FcγRI (CD64) after being activated by different factors such as cytokines and bacterial products. These receptors are involved with phagocytosis of IgG-opsonized microbes and enhance defense mechanisms.Based on that, our study seeks to compare the expression of FcγRII, FcγRIII, FcγRI, and CD11b on neutrophils from elderly and young subjects and their expression after in vitro activation with cytokines and LPS. Methodology: Neutrophils were isolated from human peripheral blood and from mice bone marrow by density gradient. After isolation, FCγRs expression was immediately analyzed by flow cytometry or after in vitro stimulation. Results:In freshly isolated cells, the percentage of FcγRIIIb + and CD11b + neutrophils were higher in samples from young individuals; FcγRIIIa expression was more prominent on aged neutrophils; FcγRIA expression was similar in all samples analyzed. Exposure to CXCL8 and LPS resulted in a higher percentage of FcγRIa + neutrophils on elderly individuals' samples but lower when compared with neutrophils from young donors. We observed that LPS caused an increase in FcγRIIa expression on aging human neutrophils. In contrast, FcγRIIIb expression in response to CXCL8 and LPS stimulation was not altered in the four groups. CD11b expression was lower in neutrophils from elderly individuals even in response to LPS and CXCL8. In mice, we observed differences only regarding CD11b expression, which was increased on aged neutrophils. LPS exposure caused an increase in all FcγRs. Conclusions:Our results suggest that, in humans, the overall pattern of FcγR expression and integrin CD11b are altered during aging and immunosenescence might contribute to age-related infection.
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