An elevation in the concentration of free cytosolic calcium is sufficient to activate the oxidative burst of granulocytes primed with recombinant human granulocyte-macrophage colony-stimulating factor.
In granulocytes harvested from human blood, an elevation of the cytosolic concentration of Ca2+ ions is by itself insufficient to activate the cell's respiratory burst. We report herein that, when granulocytes are "primed" by a 90-min preincubation with the recombinant human hemopoietic growth factor granulocyte-macrophage colony-stimulating factor (GM-CSFrh), elevation of the concentration of cytosolic Ca2+ ions ([Ca2+]i) becomes a more effective transduction signal capable of triggering the generation of substantial quantities of superoxide (O2-) anions by the cell. In these studies, we used four separate and independent maneuvers to induce elevation of [Ca2+]i: 1) depolarization of the cell's electrical potential through obliteration of the transmembrane Na+ and K+ gradients; 2) acidification of the cytoplasm using propionic acid; 3) addition of the calcium ionophore ionomycin; and 4) treatment of the cells with the monoclonal antibody to the C3bi receptor, PMN7C3. In all cases, elevation of [Ca2+]i through these manipulations resulted in the release of substantially greater quantities of O2- by GM-CSFrh-primed granulocytes than by unprimed, control cells. The generation of O2- was in all cases markedly reduced by chelation of either intracellular Ca2+ with 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid or extracellular Ca2+ with [ethylene-bis(oxyethylenenitrilo)]tetraacetic acid. We conclude that during the process of GM-CSFrh priming, the metabolic assembly responsible for O2- anion production in the granulocyte becomes altered in such a way that a subsequent elevation in [Ca2+]i provides a potent signal for its activation.
Sullivan
R
R
Section of Hematology, Evans Memorial Department of Clinical Research, University Hospital, MA 02118.
Fredette
J P
JP
Griffin
J D
JD
Leavitt
J L
JL
Simons
E R
ER
Melnick
D A
DA
D000911:Antibodies, Monoclonal / Q000494:pharmacology; D002118:Calcium / Q000502:physiology*; D003115:Colony-Stimulating Factors / Q000494:pharmacology*; D004987:Ethers / Q000494:pharmacology; D016178:Granulocyte-Macrophage Colony-Stimulating Factor; D006098:Granulocytes / Q000502:physiology*; D006133:Growth Substances / Q000494:pharmacology*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D015759:Ionomycin; D008564:Membrane Potentials / Q000187:drug effects; D010084:Oxidation-Reduction; D011188:Potassium / Q000494:pharmacology; D011422:Propionates / Q000494:pharmacology; D011951:Receptors, Complement / Q000502:physiology; D011994:Recombinant Proteins / Q000494:pharmacology; D013481:Superoxides / Q000378:metabolism; D014634:Valinomycin / Q000494:pharmacology
D000911:Antibodies, Monoclonal; D003115:Colony-Stimulating Factors; D004987:Ethers; D006133:Growth Substances; D011422:Propionates; D011951:Receptors, Complement; D011994:Recombinant Proteins; D013481:Superoxides; D014634:Valinomycin; D015759:Ionomycin; D016178:Granulocyte-Macrophage Colony-Stimulating Factor; C029658:propionic acid; D011188:Potassium; D002118:Calcium