Chronic Treatment With P2-Purinergic Receptor Agonists Induces Phenotypic Modulation of the HL-60 and U937 Human Myelogenous Leukemia Cell Lines

Abstract

In previous studies we have demonstrated that extracellular ATP (and UTP), acting through P2-purinergic receptors, can stimulate the inositol phospholipid signaling system in neutrophils and monocytes, as well as in neutrophil/monocyte progenitor cells. In this study we have examined the ability of extracellular nucleotides to modulate the phenotype of myelomonocytic progenitor cells. As model systems, we utilized the established HL-60 promyelocytic and U937 promonocytic human cell lines which were cultured in the continuous presence of nucleotides known to be potent agonists for P2-purinergic receptors. When cultured for 5 days with ATP gamma S (a phosphatase resistant analog of ATP) plus 10% fetal bovine serum, both HL-60 cells and U937 cells expressed several (but not all) phenotypic characteristics of differentiated phagocytes. In HL-60 cells these characteristics were (1) increased intracellular calcium mobilization in response to formylated chemotactic peptides, (2) a reduction in cell size with a decreased nuclear/cytoplasmic ratio, (3) a sharply reduced rate of proliferation, (4) a reduction in the percentage of cells expressing surface transferrin receptors, and (5) an increase in the percentage of cells expressing the type 1 complement receptor (CR1). In U937 cells these characteristics were (1) increased intracellular calcium mobilization in response to formylated chemotactic peptides and platelet activating factor, (2) a reduced rate of proliferation, (3) a reduction in the percentage of cells expressing surface transferrin receptors, and (4) increases in the percentage of cells expressing both type 1 (CR1) and type 3 (CR3) complement receptors. During the first 12-24 hr after exposure to ATP gamma S, HL-60 cells showed no obvious changes in morphology, viability, or the levels of beta-actin mRNA, but did show (1) a 4-fold increase in chemotactic peptide-induced Ca2+ mobilization, and (2) a greater than 90% decrease in c-myc mRNA levels. Significantly, when HL-60 cells were treated under serum-free conditions, the ability of ATP to enhance expression of functional FMLP receptors could be dissociated from the inhibitory effects of adenine nucleotides on cell proliferation observed in serum containing media. Moreover, treatment of serum-free HL-60 cultures with UTP, another P2-purinergic receptor agonist, also resulted in enhanced expression of functional FMLP receptors.

Inhibition of H2 Histamine Receptor-Mediated Cation Channel Opening by Protein Kinase C in Human Promyelocytic Cells

“…At present, the action mechanism by which the [Ca 2ϩ ] i rise induces differentiation of promyelocytes was not yet completely understood. Some studies reported that expression of the proto-oncogene c-myc is dramatically regulated by the transient elevation of [Ca 2ϩ ] i in HL-60 cells (34,47). In those studies the induction of membrane tyrosine kinase activity also accompanied with a significant reduction of c-myc expression.…”

“…Granulocytic differentiation of HL-60 promyelocytes results in increased expression of formyl peptide receptors that can be readily monitored by observing the increased effectiveness of fMLP in inducing a rise in [Ca 2ϩ ] i (34). The responsiveness of HL-60 cells to fMLP was substantially increased when the cells were induced to differentiate by treatment with 1.25% DMSO, 100 M histamine, or 100 M dibutyryl cAMP (Fig.…”

The purinergic P2Z receptor of human macrophage cells. Characterization and possible physiological role.

“…The need for a better characterization of P2 purinergic receptors in human immune effector cells is stressed by the recent appreciation that the various and often contradictory responses triggered by ATPe, i.e., stimulation of cell proliferation (11) and differentiation (12), activation of the respiratory burst (7), inhibition of phagocytosis (8), and cytotoxicity (3,4), are due to an interaction with different P2 receptor subtypes expressed either by different immune cells or at different stages of maturation. One of the most intriguing effects of ATP, is reversible plasma membrane permeabilization to molecules of < 900 D ( 13,14), a response that is invariably associated with susceptibility to ATPe-mediated cytotoxicity ( 15 ).…”

CysLT1 receptor is a target for extracellular nucleotide-induced heterologous desensitization: a possible feedback mechanism in inflammation

“…Furthermore, purines are known to induce U937 phenotypic differentiation (Cowen et al, 1991), and to be involved in recruitment of neutrophils and monocytes to the site of injury (Kunapuli and Daniel, 1998). Thus, in addition to their intracellular functions in energy metabolism and nucleic acid synthesis, nucleotides are now recognized to have important roles as extracellular signaling molecules.…”