Monovalent ions control proliferation of Ehrlich Lettre ascites cells

TY - JOUR

T1 - Monovalent ions control proliferation of Ehrlich Lettre ascites cells

AU - Klausen, Thomas Kjaer

AU - Preisler, Sarah

AU - Pedersen, Stine Helene Falsig

AU - Hoffmann, Else Kay

PY - 2010/9/1

Y1 - 2010/9/1

N2 - Channels and transporters of monovalent ions are increasingly suggested as putative anticarcinogenic targets. However, the mechanisms involved in modulation of proliferation by monovalent ions are poorly understood. Here, we investigated the role of K+, Na+, and Cl(-) ions for the proliferation of Ehrlich Lettre ascites (ELA) cells. We measured the intracellular concentration of each ion in G(0), G(1), and S phases of the cell cycle following synchronization by serum starvation and release. We show that intracellular concentrations and content of Na+ and Cl(-) were reduced in the G(0)-G(1) phase transition, followed by an increased content of both ions in S phase concomitant with water uptake. The effect of substituting extracellular monovalent ions was investigated by bromodeoxyuridine incorporation and showed marked reduction after Na+ and Cl(-) substitution. In spectrofluorometric measurements with the pH-sensitive dye BCECF, substitution of Na+ was observed to upregulate the activity of the Na+/H+ exchanger NHE1 as well as of Na+-independent acid extrusion mechanisms, facilitating intracellular pH (pH(i)) recovery after acid loading and increasing pH(i). Results using the potential sensitive dye DiBaC4(3) showed a reduced Cl(-) conductance in S compared with G(1) followed by transmembrane potential (E(m)) hyperpolarization in S. Cl(-) substitution by impermeable anions strongly inhibited proliferation and increased free, intracellular Ca2+ ([Ca2+]i), whereas a more permeable anion had little effect. Western blots showed reduced chloride intracellular channel CLIC1 and chloride channel ClC-2 expression in the plasma membrane in S compared with G(1). Our results suggest that Na+ regulates ELA cell proliferation by regulating intracellular pH while Cl(-) may regulate proliferation by fine-tuning of E(m) in S phase and altered Ca2+ signaling.

AB - Channels and transporters of monovalent ions are increasingly suggested as putative anticarcinogenic targets. However, the mechanisms involved in modulation of proliferation by monovalent ions are poorly understood. Here, we investigated the role of K+, Na+, and Cl(-) ions for the proliferation of Ehrlich Lettre ascites (ELA) cells. We measured the intracellular concentration of each ion in G(0), G(1), and S phases of the cell cycle following synchronization by serum starvation and release. We show that intracellular concentrations and content of Na+ and Cl(-) were reduced in the G(0)-G(1) phase transition, followed by an increased content of both ions in S phase concomitant with water uptake. The effect of substituting extracellular monovalent ions was investigated by bromodeoxyuridine incorporation and showed marked reduction after Na+ and Cl(-) substitution. In spectrofluorometric measurements with the pH-sensitive dye BCECF, substitution of Na+ was observed to upregulate the activity of the Na+/H+ exchanger NHE1 as well as of Na+-independent acid extrusion mechanisms, facilitating intracellular pH (pH(i)) recovery after acid loading and increasing pH(i). Results using the potential sensitive dye DiBaC4(3) showed a reduced Cl(-) conductance in S compared with G(1) followed by transmembrane potential (E(m)) hyperpolarization in S. Cl(-) substitution by impermeable anions strongly inhibited proliferation and increased free, intracellular Ca2+ ([Ca2+]i), whereas a more permeable anion had little effect. Western blots showed reduced chloride intracellular channel CLIC1 and chloride channel ClC-2 expression in the plasma membrane in S compared with G(1). Our results suggest that Na+ regulates ELA cell proliferation by regulating intracellular pH while Cl(-) may regulate proliferation by fine-tuning of E(m) in S phase and altered Ca2+ signaling.

KW - Animals

KW - Anions

KW - Calcium

KW - Carcinoma, Ehrlich Tumor

KW - Cations, Monovalent

KW - Cell Membrane

KW - Cell Membrane Permeability

KW - Cell Proliferation

KW - Cells, Cultured

KW - Chloride Channels

KW - Chlorides

KW - G0 Phase

KW - G1 Phase

KW - Hydrogen-Ion Concentration

KW - Meglumine

KW - Potassium

KW - Protein Transport

KW - S Phase

KW - Sodium

KW - Sodium-Hydrogen Antiporter

KW - Water

U2 - 10.1152/ajpcell.00445.2009

DO - 10.1152/ajpcell.00445.2009

M3 - Journal article

C2 - 20592244

SN - 0002-9513

VL - 299

SP - C714-25

JO - American Journal of Physiology

JF - American Journal of Physiology

IS - 3

ER -