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Interleukin (IL)-4 is a cytokine known mainly for its anti-inflammatory activity. Using the in vivo murine air pouch model, we found that IL-4 significantly increased the number of leukocytes after 9 hours of treatment, consisting mainly of neutrophil (60%) and monocytic (40%) cell populations. Using an antibody array, we found that the expression of several analytes (predominantly CCL2) was increased by IL-4 before the arrival of leukocytes. The IL-4-induced expression of CCL-2 was confirmed by ELISA. Air pouch resident lining cells were harvested and were found to express IL-4Rα. CCL2 mRNA expression was monitored in lining cells, cells isolated from the air pouch skin, in RAW264.7 macrophage and in epithelial Mode-K cells and its expression was increased in response to IL-4 in all conditions. We conclude that IL-4 can attract leukocytes in vivo by an indirect mechanism involving the production of several analytes by, at least, resident cells.

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Inflammation is one of the major toxic effects reported in the literature following nanoparticle (NP) exposure. Knowing the importance of neutrophils to orchestrate inflammation, it is surprising that the direct role of NPs on neutrophil biology is poorly documented. Here, we investigated if ZnO NPs can alter neutrophil biology. We found that ZnO NPs increased the cell size, induced cell shape changes, activated phosphorylation events, enhanced cell spreading onto glass, but did not induce the generation of reactive oxygen species (ROS). Treatment of neutrophils with ZnO NPs markedly and significantly inhibited apoptosis and increased de novo protein synthesis, as demonstrated by gel electrophoresis of metabolically [(35)S]-labeled cells. Utilization of the protein synthesis inhibitor, cycloheximide, reversed such antiapoptotic effect. We conclude that ZnO NPs are activators of several human neutrophil functions and that they inhibit apoptosis by a de novo protein synthesis-dependent and ROS-independent mechanism. This is the first example that a NP acts on the neo-synthesis of polypeptides.