title: Inhibition of the Na+/H+ antiporter induces cell death in TF-1 erythroleukemia cells stimulated by the stem cell factor.
abstract: Leukemia cells produce acidic metabolites due to their high metabolic condition. An alkaline pHi (intracellular pH) shift, caused by activation of the Na+/H+ exchange, is an important event in the mechanism of growth factor activity. However, the role of the Na(+)/H(+) exchanger in the survival of erythroleukemia TF-1 cells has not yet been studied in detail. The aim of this study was to identify the effects of 5-(N-ethyl-N-isopropyl) amiloride (EIPA), a highly specific blocker of the Na(+)/H(+) exchanger, on the survival of SCF-dependent TF-1 cells. The effects of EIPA on survival and mitochondrial membrane potential were studied when exposing wild type TF-1 cells and TF-1 cells expressing bcl-2 to EIPA for 48h. Ectopic expression of the bcl-2 gene maintained a mildly alkaline pH and prevented the simultaneous appearance of apoptosis and autophagy (typically displayed by TF-1 cells) in the presence of EIPA. Consistent with Stem Cell Factor (SCF) function, we found that this molecule rescued TF-1 cells during autophagy but not apoptosis, allowing these cells to subsequently respond to GM-CSF. Serum deprivation or SCF withdrawal induced cell death at 36h in TF-1 and TF-1 neo cells, whereas TF-1/bcl-2 cells tended to undergo apoptosis and show acidic vacuoles after 96h, pointing to a transient anti-apoptotic effect. The present study shows the suppressive effect of EIPA on the proliferation of leukemia cell line stimulated with SCF, apparently by decreasing the mitochondria membrane potential and averting alkalinization. Through the constitutive expression of bcl-2, TF-1 cells were survival factor independent. Proliferation in these cells was not affected by EIPA at the concentrations used against parental TF-1 cells, indicating that the inhibitory effect in SCF-stimulated cells can be attributed to specific blocking of the Na(+)/H(+) exchanger.
authors.affiliation: Laboratorio de Cáncer y Hematopoyesis, Sección de Estudios de Posgrado e Investigación, Escuela Superior de Medicina, Instituto Politécnico Nacional, 11340, Mexico.
authors.forename: Leonardo Fermin
authors.initials: LF
authors.lastname: Acevedo-Olvera
authors.affiliation: Laboratorio de Cáncer y Hematopoyesis, Sección de Estudios de Posgrado e Investigación, Escuela Superior de Medicina, Instituto Politécnico Nacional, 11340, Mexico.
authors.forename: Hector
authors.initials: H
authors.lastname: Diaz-Garcia
authors.affiliation: Laboratorio de Cáncer y Hematopoyesis, Sección de Estudios de Posgrado e Investigación, Escuela Superior de Medicina, Instituto Politécnico Nacional, 11340, Mexico.
authors.forename: Alberto
authors.initials: A
authors.lastname: Parra-Barrera
authors.affiliation: Laboratorio de Cáncer y Hematopoyesis, Sección de Estudios de Posgrado e Investigación, Escuela Superior de Medicina, Instituto Politécnico Nacional, 11340, Mexico.
authors.forename: Alejandro Arturo
authors.initials: AA
authors.lastname: Caceres-Perez
authors.affiliation: Laboratorio de Cáncer y Hematopoyesis, Sección de Estudios de Posgrado e Investigación, Escuela Superior de Medicina, Instituto Politécnico Nacional, 11340, Mexico.
authors.forename: Gisela
authors.initials: G
authors.lastname: Gutierrez-Iglesias
authors.affiliation: Laboratorio de Cáncer y Hematopoyesis, Sección de Estudios de Posgrado e Investigación, Escuela Superior de Medicina, Instituto Politécnico Nacional, 11340, Mexico.
authors.forename: Rosalva
authors.initials: R
authors.lastname: Rangel-Corona
authors.affiliation: Laboratorio de Cáncer y Hematopoyesis, Sección de Estudios de Posgrado e Investigación, Escuela Superior de Medicina, Instituto Politécnico Nacional, 11340, Mexico. Electronic address: cortesj@unam.mx.
authors.forename: Julio Roberto
authors.initials: JR
authors.lastname: Caceres-Cortes
mesh_terms: D000584:Amiloride / Q000031:analogs & derivatives / Q000737:chemistry; D017209:Apoptosis; D001343:Autophagy; D002453:Cell Cycle; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D002469:Cell Separation; D002470:Cell Survival; D005456:Fluorescent Dyes / Q000737:chemistry; D015973:Gene Expression Regulation, Leukemic; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007938:Leukemia / Q000188:drug therapy* / Q000378:metabolism; D004915:Leukemia, Erythroblastic, Acute / Q000378:metabolism* / Q000473:pathology; D008564:Membrane Potentials; D051336:Mitochondrial Membranes / Q000378:metabolism; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D017923:Sodium-Hydrogen Exchangers / Q000037:antagonists & inhibitors* / Q000737:chemistry*; D019089:Stem Cell Factor / Q000378:metabolism*
chemical_list: D005456:Fluorescent Dyes; D019253:Proto-Oncogene Proteins c-bcl-2; D017923:Sodium-Hydrogen Exchangers; D019089:Stem Cell Factor; D000584:Amiloride; C039614:ethylisopropylamiloride
keywords: Apoptosis; Autophagy; Na(+)/H(+) exchanger; Stem cell factor; TF-1 cells