MECHANISM OF ENHANCEMENT OF NEUTROPHIL SURVIVAL BY GRANULOCYTE-COLONY-STIMULATING FACTOR AND ADENINE

An in vitro study was performed on the effect of recombinant human gra nulocyte colony-stimulating factor (rhG-CSF) and adenine on the surviv al of purified human neutrophils. The addition of rhG-CSF (1 to 100 ng /mL) or adenine (100 mu M) enhanced the survival of neutrophils. The m aintenance of O-2(-) production in response to N-formylmethionyl-leucy l-phenylalanine (FMLP) suggested that these neutrophils were functiona lly alive. Neutrophils in cultures had shown two distinct biochemical changes during cell death: DNA fragmentation and depletion of cellular adenosine triphosphate (ATP) pools. Treatment with rhG-CSF (10 ng/mL) significantly delayed the appearance of DNA fragmentation as measured quantitatively by diphenylamine or by agarose gel electrophoresis. On the other hand, adenine had no effect on the generation of DNA fragme ntation. The decrease of ATP during incubation for 12 hours was simila r in control and rhG-CSF-treated neutrophils, while rhG-CSF prevented the further decline of ATP seen in control cultures. In contrast, aden ine (100 mu M)) preserved ATP at levels significantly higher than in c ontrols at both 12 hours and 24 hours of incubation. Our results sugge st that rhG-CSF and adenine promote the survival of neutrophils in vit ro by different mechanisms.