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Membrane depolarization and depletion of intracellular calcium stores are associated with delay of apoptosis in human neutrophils
Author(s) -
ChaconCruz Enrique,
Oelberg David G.,
Davis Paris,
Buescher E. Stephen
Publication year - 1998
Publication title -
journal of leukocyte biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.819
H-Index - 191
eISSN - 1938-3673
pISSN - 0741-5400
DOI - 10.1002/jlb.64.6.759
Subject(s) - depolarization , apoptosis , intracellular , thapsigargin , membrane potential , annexin , biology , cycloheximide , calcium in biology , microbiology and biotechnology , biophysics , biochemistry , protein biosynthesis
Apoptosis occurs rapidly in human polymorphonuclear leukocytes (PMN) after exposure to 1 mM cycloheximide (CHX). We examined whether this form of stimulated apoptosis altered either resting cytosolic free Ca 2+ concentrations ([free Ca]) or membrane potential (Ψ) in PMN and found no significant effects. However, manipulation of either PMN intracellular Ca 2+ stores or Ψ was found to delay CHX‐induced apoptosis. Depletion of PMN intracellular Ca 2+ stores with thapsigargin caused membrane depolarization and significantly delayed CHX‐induced apoptosis based on both morphological and annexin‐V‐fluorescein isothiocyanate binding criteria. Short‐term suspension (4 h) of PMN in Ca 2+ ‐free buffer depleted internal Ca 2+ stores, induced membrane depolarization at 2.5 h, and delayed spontaneous (24 h) apoptosis but had no effect on CHX‐induced apoptosis. Rapid membrane depolarization with 150 mM KCl buffer significantly delayed CHX‐induced apoptosis, suggesting that depolarization rather than Ca 2+ stores depletion was the crucial event. Timing experiments revealed that depolarization within 12 min of CHX exposure significantly delayed apoptosis. Collectively, these observations suggest an early Ψ‐sensitive step in the apoptosis pathway initiated by CHX. CHX exposure alone does not alter either resting PMN [free Ca] or Ψ; accompanying depolarization of plasma membrane (either electrochemically or via depletion of internal Ca 2+ stores) delays CHX‐induced apoptosis in a time‐dependent manner. J. Leukoc. Biol. 64: 759–766; 1998.