CELL ACIDIFICATION IN APOPTOSIS - GRANULOCYTE-COLONY-STIMULATING FACTOR DELAYS PROGRAMMED CELL-DEATH IN NEUTROPHILS BY UP-REGULATING THE VACUOLAR H+-ATPASE

Neutrophils in tissue culture spontaneously undergo programed cell death (apoptosis), a process characterized by well-defined morphological alterations affecting the cell nucleus. We found that these morphological changes were preceded by intracellular acidification and that acidification and the apoptotic changes in nuclear morphology were both delayed by granulocyte colony-stimulating factor (G-CSF). Among the agents that defend neutrophils against intracellular acidification is a vacuolar H+-ATPase that pumps protons out of the cytosol. When this proton pump was inhibited by bafilomycin At G-CSF no longer protected the neutrophils against apoptosis. We conclude that G-CSF delays apoptosis in neutrophils by up-regulating the cells' vacuolar H+-ATPase and that intracellular acidification is an early event in the apoptosis program.