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Attenuation of apoptotic DNA fragmentation by amiloride
Author(s) -
Cobo José M.,
GarciaCañero Rafael,
Valdez Joseph G.,
Barrasso Anna M.,
Sailer Brian L.,
Crissman Harry A.
Publication year - 1998
Publication title -
journal of cellular physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.529
H-Index - 174
eISSN - 1097-4652
pISSN - 0021-9541
DOI - 10.1002/(sici)1097-4652(199804)175:1<59::aid-jcp7>3.0.co;2-b
Subject(s) - amiloride , apoptosis , intracellular , intracellular ph , dna damage , dna fragmentation , chemistry , microbiology and biotechnology , programmed cell death , biology , biochemistry , dna , sodium , organic chemistry
Amiloride is a K + ‐sparing diuretic that effectively inhibits the Na + /H + transporter in the plasma membrane of most mammalian cells. We have examined the effects of amiloride on the progression of apoptosis in HL‐60 cells induced by camptothecin (CAM), cycloheximide (CHX), and 20 Gy gamma irradiation. Spectrofluorometric measurements on cell populations showed an inhibition of Na + /H + transporter activity and a corresponding decrease in intracellular pH following treatment with amiloride alone, or in combination with the apoptosis‐inducing agents. Flow cytometric cell cycle analysis, in combination with DNA strand break analysis, indicated that amiloride diminished endonuclease‐mediated degradation of nuclear chromatin 3 h following treatment with CAM or CHX, and prevented degradation for 3 h following gamma radiation treatment. Apoptosis‐associated DNA degradation was significantly greater for all three agents in the absence of amiloride. Protection from radiation‐induced apoptosis was transient, since apoptotic subpopulations were observed, but still at a decreased level, 5 h following irradiation. Amiloride was as effective as zinc, an inhibitor of Ca 2+ /Mg 2+ ‐dependent endonucleases, in reducing or delaying the onset of endonuclease activity. Data presented show that effects of amiloride on membrane Na + /H + transporter activity and intracellular pH can potentially affect apoptotic signaling cascades, leading to a retardation in the rate of progression to an apoptotic cell death. Results also point to the involvement of intracellular pH and Ca 2+ in the regulation of apoptotic endonuclease activity, and the need for a functional Na + /H + exchanger for the induction of apoptosis. J. Cell. Physiol. 175:59–67, 1998. © 1998 Wiley‐Liss, Inc.