title: Effects of Na+/H+ antiport and intracellular pH in the regulation of HL-60 cell apoptosis.
abstract: The roles of Na+/H+ antiport and intracellular pH in apoptosis of HL-60 cells were investigated here. We found that dimethyl amiloride, a specific Na+/H+ antiport inhibitor, induced intracellular acidification but not apoptosis; while sodium ionophore, monensin caused intracellular alkalinization as well as apoptosis in HL-60 cells. Br-A23187 and thapsigargin could induce a various degree of intracellular alkalinization through the stimulation of Na+/H+ antiport. Dimethyl amiloride blocked the intracellular alkalinization and inhibited apoptosis induced by Br-A23187 and thapsigargin. PMA also stimulated Na+/H+ antiport and induced intracellular alkalinization which was completely blocked by dimethyl amiloride and partially attenuated by PKC inhibitors. PMA could inhibit apoptosis in HL-60 cells. PMA-induced suppression of apoptosis was, however, not interfered by dimethyl amiloride, but could be abolished by PKC inhibitors. These results indicate that pHi alkalinization and/or the stimulation of Na+/H+ antiport, instead of intracellular acidification, are contributory to the induction of apoptosis. PMA-induced inhibition of apoptosis is not necessarily associated with intracellular alkalinization, but primarily due to activation of PKC. We suggest that stimulation of Na+/H+ antiport and pHi alkalinization act as facilitating factors in the induction of apoptosis.
mesh_terms: D000584:Amiloride / Q000031:analogs & derivatives / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology*; D004249:DNA Damage; D004791:Enzyme Inhibitors / Q000494:pharmacology; D018922:HL-60 Cells; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007211:Indoles / Q000494:pharmacology; D007476:Ionophores / Q000494:pharmacology; D008301:Maleimides / Q000494:pharmacology; D008985:Monensin / Q000494:pharmacology; D011493:Protein Kinase C / Q000037:antagonists & inhibitors; D017923:Sodium-Hydrogen Exchangers / Q000037:antagonists & inhibitors / Q000378:metabolism*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
chemical_list: D004791:Enzyme Inhibitors; D007211:Indoles; D007476:Ionophores; D008301:Maleimides; D017923:Sodium-Hydrogen Exchangers; C039465:5-dimethylamiloride; D000584:Amiloride; D008985:Monensin; D011493:Protein Kinase C; C070515:bisindolylmaleimide I; D013755:Tetradecanoylphorbol Acetate