Cooperative regulation of Mcl-1 by Janus kinase/STAT and phosphatidylinositol 3-kinase contribute to granulocyte-macrophage colony-stimulating factor-delayed apoptosis in human neutrophils

Polymorphonuclear neutrophils (PMN) are phagocytic cells constitutively pro grammed for apoptotic cell death. Exposure to GM-CSF delays apoptosis as me asured by annexin-V staining and cell morphological change. We found that S TAT5B, STAT1, and STAT3 DNA-binding activity was induced by GM-CSF. We also detected activation of the phosphatidylinositol 3-kinase (PI 3-kinase) pat hway after GM-CSF treatment which was inhibited by treatment with the PI 3- kinase inhibitors, wortmannin and LY294002. We investigated whether STAT or P1 3-kinase activity was necessary for the pro-survival response of GM-CSF in PMN. Exposure of PMN to GM-CSF in the presence of either AG-490, antise nse STAT3 oligonucleotides, or wortmannin resulted in a partial inhibition of GM-CSF-mediated pro-survival activity. GM-CSF induced a time-dependent i ncrease in the mRNA and protein expression of the anti-apoptotic Bcl-2-fami ly protein, Mcl-1. We examined the hypothesis that Janus kinase/STAT and PI 3-kinase regulation of Mcl-1 contributed to GM-CSF-delayed apoptosis. Usin g either AG-490 or wortmannin alone, we observed a dose-dependent inhibitio n of GM-CSF-induced Mcl-1 expression. Using suboptimal doses of AG-490 and wortmannin, we found that both drugs together had an additive effect on del ayed apoptosis and Mcl-1 expression. These data suggest that Cooperative re gulation of Mcl-1 by the Janus kinase/STAT and PI 3-kinase pathways contrib ute to GM-CSF-delayed apoptosis.