Human Recombinant Granulocyte-macrophage Colony Research Articles

Divergent regulation of cell surface protease expression in HL-60 cells differentiated into macrophages with granulocyte macrophage colony stimulating factor or neutrophils with retinoic acid.

Taking advantage of the recently demonstrated presence of N-aminopeptidases and the serine protease dipeptidyl aminopeptidase IV (DPP IV) at the surface of human myeloblastic HL-60 cells, the regulation of these protease activities in HL-60 cell differentiation has been assessed using combined spectrophotometric and flow cytometric assays. Addition of human recombinant granulocyte macrophage colony stimulating factor (rHu-GM-CSF) to HL-60 cells to induce differentiation into macrophages led to a time- and dose-dependent increase in both cell surface N-aminopeptidase and DPP IV activities. Protease up-regulation was due to an enhancement in cell surface protease number, associated with a slight rise in apparent affinities of the enzymes for their substrates. In contrast, in HL-60 cells induced to differentiate into neutrophils in the presence of retinoic acid, expression of cell surface N-aminopeptidases was almost completely abolished in a time- and dose-dependent fashion, and this down-regulation was accompanied by a weak but significant decrease in affinity. However, no noticeable difference was seen in serine DPP IV expression between retinoic acid-treated and untreated HL-60 cells. Retinoic acid treatment also reduced soluble protease activity in vitro indicating that down-regulation of membrane aminopeptidases was not due to their proteolytic clip. No modulation in the activity of any of the enzymes tested was seen with human recombinant tumor necrosis factor-alpha or retinol which do not induce HL-60 cell differentiation.(ABSTRACT TRUNCATED AT 250 WORDS)

Enhanced superoxide generation by eosinophils from asthmatic children.

In 21 asthmatic children, aged 2-19 years, and 11 age-matched controls purified (purity greater than 75%) peripheral blood eosinophils and neutrophils (purity greater than 95%) were stimulated with phorbol myristate acetate (44 ng/ml) for 30 min at 37 degrees C. The superoxide generation was determined as well as the superoxide dismutase inhibitable cytochrome c reduction. Eosinophils obtained from asthmatic patients displayed a significantly higher O2- generation (p less than 0.01) when compared to neutrophils from the same patients or to eosinophils and neutrophils from healthy controls. Preincubation with human recombinant granulocyte macrophage colony stimulating factor for 30 min or platelet-activating factor for 10 min resulted in augmented O2- generation by eosinophils from control, but not from asthmatic children, indicating a possible in vivo priming of eosinophils in asthma.

Enhancement of methotrexate cytotoxicity by modulation of proliferative activity in normal and neoplastic T lymphocytes and in a myeloid leukemia cell line.

Recent advances in the modulation of cell kinetics with growth factors suggest that the effect of cycle-specific cytostatic drugs can be enhanced by combination with such factors. The truth of this hypothesis was investigated by studying the effect of phytohemagglutinin and/or interleukin 2 on the sensitivity to methotrexate (MTX) of normal T lymphocytes and of lymphoblasts of a patient with acute T-cell lymphoid leukemia. In both cases, inhibition of proliferation by MTX was increased from less than 30% in resting cells or those suboptimally stimulated, in the case of leukemic blasts, to 68-83% in maximally stimulated cells. Similar results were observed when the AML 193 human myeloid leukemia line was stimulated with human recombinant granulocyte macrophage colony stimulation factor (GM-CSF). Under basal proliferation conditions, the addition of 1 microgram/ml and 10 micrograms/ml MTX was followed by 48% and 72% inhibition respectively. When 1 ng/ml GM-CSF (40 I.U./ml) was present, these figures rose to 89% and 91%. It is thus clear that growth factor-induced cell proliferation increases sensitivity to cycle-specific cytostatic agents. There is thus a biological premise for new perspectives in antineoplastic therapy.