Stimulation of guanylate cyclase activity and reduction of adenylate cyclase activity by granulocyte-macrophage colony-stimulating factor in human blood neutrophils

Human neutrophils were incubated with granulocyte-macrophage (GM)-CSF and examined for changes in second messenger systems. Twofold increases in cGMP but not cAMP were measured after 5 to 20 min with 100 U/ml GM-CSF. Guanylate cyclase activities in membrane and cytosol fractions were increased to the same extent whether measured in the presence of Mg²⁺ or Mn²⁺, or in the cytosol with Mg²⁺ + N-methyl-N'-nitro-N-nitrosoguanidine. Kinetic studies of the cytosol enzyme showed no changes in the K(m) values for Mg²⁺ and Mn²⁺-dependent guanylate cyclase activities (0.91 and 0.022 mM, respectively), whereas V(m) values were increased after treating intact cells with GM-CSF. Two peaks of guanylate cyclase activity were observed, one at 10 and another at 60 min after adding 100 U/ml GM-CSF, whereas only one peak at 5 min occurred with 1 U/ml. Adenylate cyclase activity was reduced by nearly 50% after adding 100 U/ml GM-CSF for 10 to 30 min. These effects were also seen in the presence of several hormonal and nonhormonal adenylate cyclase stimulators. In contrast, small increases in adenylate cyclase activity occurred after adding 1 U/ml GM-CSF. In experiments to examine the pathway of guanylate cyclase activation by GM-CSF, we observed no changes in inositol phosphates, intracellular calcium ion, or cytosolic protein kinase C. The augmentation of chemotactic peptide-induced superoxide production by GM-CSF, which increases progressively with increasing GM-CSF concentrations, may be related to the effects of the higher levels of GM-CSF to stimulate late increases in guanylate cyclase or decreases in adneylate cyclase.