Increased cytosol Ca2+ and type 1 programmed cell death in Bcl-2-positive U937 but not in Bcl-2-negative PC-3 and Panc-1 cells induced by the 5-lipoxygenase inhibitor MK 886

• DOI: 10.1054/plef.2001.0372
• Publication Date: 2002-09-19T15:33:28Z
• Authors: K.M. Anderson; W.A. Alrefai; P.K. Dudeja; S. Jadko; P. Bonomi; Y. Hu; D. Ou; J.E. Harris
• Keywords: 0303 health sciences; Arachidonate 5-Lipoxygenase; Indoles; Reverse Transcriptase Polymerase Chain Reaction; Apoptosis; HL-60 Cells; U937 Cells; Membrane Potentials; Mitochondria; Oxidative Stress; 03 medical and health sciences; Cytosol; Proto-Oncogene Proteins c-bcl-2; Tumor Cells, Cultured; Humans; Calcium; Calcium Signaling; Lipoxygenase Inhibitors; RNA, Messenger; Fluorescent Dyes

MK 886, an arachidonic acid-related analog which inhibits the enzyme, 5-lipoxygenase by an indirect mechanism involving the 5-lipoxygenase activating protein, rapidly increased U937 cytosol Ca(2+), much of which localized around the cell nuclei. Five-lipoxygenase activity was not directly involved since the direct redox-dependent 5-LPOx inhibitor, SC-41661A did not increase Ca(2+). U937 cells subsequently undergo classic type 1 programmed cell death. At least initially the ionized calcium originates from internal stores. Coincident with the rise in U937 ionized calcium, MK 886 rapidly increased reactive oxygen species and reduced mitochondrial membrane potential, as judged by several fluorescent probes. The Ca(2+) response of myeloid leukemia-derived HL-60 cells to MK 886 was similar and both cell lines express Bcl-2 protein. Bcl-2-negative Panc-1 and PC-3 cells did not respond to MK 886 with a Ca(2+) signal but did develop oxidative stress and a decline in mitochondrial membrane potential; these events are thought to contribute to the inhibition of cell proliferation and induction of a type 2 PCD. In addition to its marked inhibition of Bcl-2 mRNA synthesis, an interesting hypothesis is that MK 886, serving as a low molecular weight ligand, either by direct or indirect inhibition of U937 Bcl-2 protein function, possibly related to an ion channel activity, alters the distribution of intracellular, possibly nuclear Ca(2+), thereby promoting the development of type 1 programmed cell death.