Induction of apoptotic DNA fragmentation and c-jun downregulation in human myeloid leukemia cells by the permeant Ca2+ chelator BAPTA/AM.

Abstract

The permeant Ca2+ chelator acetoxymethyl-1,2-bis(2-aminopheoxy)ethane- N,N,N',N'-tetraacetic acid (BAPTA/AM), an agent previously used to characterize drug-induced apoptosis in neoplastic cells, has been examined with respect to induction of DNA fragmentation and cytotoxicity in the human leukemia cell lines HL-60 and U937. Exposure of cells to various concentrations of BAPTA/AM for 6 h resulted in a biphasic induction of internucleosomal DNA cleavage, with maximal damage occurring at 10-microM concentrations. Higher BAPTA/AM concentrations were associated with the loss of internucleosomal cleavage products, but with the appearance of larger (i.e., 50-kilobase) fragments on pulsed-field gel electrophoresis. Cells exposed to 10 microM BAPTA/AM exhibited classic apoptotic morphology, whereas cells exposed to 50-microM concentrations displayed atypical features (e.g., cell swelling, chromatin clumping); in each case, substantial cytotoxicity was noted. The actions of BAPTA/AM did not depend upon the presence of extracellular Ca2+, nor were they affected by impermeant Ca2+ chelators. Measurement of cytosolic Ca2+ by Fura-2/AM or Indo-1 revealed late but not early increases in intracellular Ca2+ in BAPTA/AM-treated cells. Finally, BAPTA/AM-induced apoptosis was accompanied by the concentration-dependent downregulation of the immediate early response gene c-jun. These findings suggest a complex role for Ca2+ chelators such as BAPTA/AM in the regulation of human myeloid leukemic cell apoptosis, and indicate that this agent may selectively antagonize internucleosomal DNA fragmentation without interfering with other aspects of the apoptotic response and/or cell lethality.

• Authors: S Grant, A J Freemerman, P C Gregory, H A Martin, A J Turner, R Mikkelsen, J Chelliah, S Yanovich, W D Jarvis
• Journal: Oncology research (Oncol Res) Vol. 7 Issue 7-8 Pg. 381-92 ( 1995) ISSN: 0965-0407 [Print] United States
• PMID: 8747601 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't, Research Support, U.S. Gov't, P.H.S.)

Chemical References

• Chelating Agents
• 1,2-bis(2-aminophenoxy)ethane N,N,N',N'-tetraacetic acid acetoxymethyl ester
• Egtazic Acid
• Calcium

Topics

• Apoptosis (drug effects)
• Calcium (metabolism)
• Chelating Agents (pharmacology)
• DNA Damage (drug effects)
• Down-Regulation
• Egtazic Acid (analogs & derivatives, pharmacology)
• Gene Expression Regulation, Leukemic (genetics)
• Genes, jun (drug effects)
• Humans
• Leukemia, Myeloid (genetics, metabolism, pathology)