Inhibition of cPLA2 translocation and leukotriene C4 secretion by fluticasone propionate in exogenously activated human eosinophils.
We examined the effect of the highly lipophilic corticosteroid, fluticasone propionate (FP), in causing (1) inhibition of nuclear translocation of cytosolic phospholipase A2 (cPLA2), and (2) blockade of leukotriene C4 (LTC4) synthesis in isolated human eosinophils in vitro. Eosinophils were isolated from peripheral blood, treated with either buffer or 10(-)10 M to 10(-)6 M FP in the presence of 10 pg/ml human recombinant interleukin-5 (rhIL-5) and activated with formyl-met-leu-phe (FMLP) + cytochalasin B (CB). At 24 h, stimulated LTC4 secretion from eosinophils was unchanged; however, when corrected for cell viability, LTC4 secretion decreased from 1,429 +/- 327 pg/10(6) cells to 762 +/- 113 pg/10(6) cells for eosinophils treated for 48 h with >/= 10(-)8 M FP (p < 0.003). FMLP/CB-stimulated translocation of cPLA2 to the nuclear envelope assessed by specific immunohistochemical staining also was blocked by FP. By contrast, membrane expression of annexin-1, which was not minimal at 30 min, was substantial at 48 h for eosinophils treated with > 10(-)10 M FP, and inhibition of LTC4 synthesis was reversed by exogenous arachidonic acid (AA). We find that FP causes a decrease in stimulated eosinophil secretion of LTC4 that is regulated by phospholipase A2 (PLA2). Inhibition of LTC4 synthesis precedes the global cytotoxic effects of FP as indicated by the simultaneous upregulation of annexin-1 expression. Inhibited stimulated secretion corresponds to inhibited translocation of cPLA2 to the nuclear envelope during cellular activation.
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CHEMICAL CHEMICAL CHEMICAL CHEMICAL CHEMICAL CHEMICAL CHEMICAL CHEMICAL CHEMICAL CHEMICAL CHEMICAL CHEMICAL CHEMICAL CHEMICAL CHEMICAL CHEMICAL CHEMICAL GENE-Y GENE-Y GENE-Y GENE-Y CHEMICAL GENE-Y GENE-Y GENE-Y GENE-Y GENE-Y GENE-Y GENE-Y CHEMICAL CHEMICAL CHEMICAL CHEMICAL CHEMICAL CHEMICAL CHEMICAL
LTC4 FP formyl-met-leu-phe FMLP cytochalasin B CB LTC4 LTC4 fluticasone propionate FP FP FMLP CB FP FP leukotriene C4 fluticasone propionate phospholipase A2 PLA2 annexin-1 cytosolic phospholipase A2 LTC4 cPLA2 cPLA2 human recombinant interleukin-5 rhIL-5 cPLA2 annexin-1 cPLA2 arachidonic acid AA FP LTC4 LTC4 FP leukotriene C4