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

Abstract

We have investigated responses of human monocyte/macrophage cells to extracellular ATP (ATPe). Freshly isolated peripheral blood monocytes showed responses linked to P2Y but not P2Z purinergic receptors; however, during in vitro macrophage differentiation, these cells also exhibited responses suggestive of the presence of the membrane-permeabilizing P2z receptor. In fact, in human macrophages a brief (15-min) exposure to ATPe, but not other nucleotides, caused (1) a rapid and long-lasting plasma membrane depolarization; (2) a large increase in intracellular Ca2+ concentration followed by efflux of the Ca2+ indicator; (3) uptake of low molecular weight hydrophilic molecules such as Lucifer yellow and ethidium bromide; and (4) cell rounding, swelling, and eventual release of the cytoplasmic enzyme lactate dehydrogenase. rIFN-y enhanced both membranepermeabilizing and cytotoxic ATPe effects. Membrane permeabilization and cytotoxicity were fully blocked by pretreatment of the cells with oxidized ATP, a compound recently shown to block P2z receptors covalently in macrophages. Blocking of the P2z receptor by oxidized ATP also inhibited multinucleated giant cell generation stimulated by concanavalin A or rIFN-y without decreasing monocyte migration or membrane adhesion molecule expression. These data suggest that human macrophages express rIFN-ymodulated purinergic P2z receptors in vitro and hint at a role for these plasma membrane molecules in the generation of macrophage polykarions. (J. Clin. Invest. 1995Invest. . 95:1207Invest. -1216

ATP receptors and giant cell formation

“…oATP, at the optimal concentration of 300 µM, was a potent blocker of macrophage fusion. It demonstrated no effects on cell motility, as assessed by measuring random locomotion of chemotaxis, or on expression of adhesion molecules thought to partake in cell fusion such as CD11a, CD18, and CD54 [17]. However, as is the case with other purinergic antagonists, we could not exclude that other membrane molecules in addition to P2X 7 are also ligated and blocked by oxATP.…”

Involvement of P2X receptors in the NAD+-induced rise in [Ca2+]i in human monocytes

“…Although the expression of P2X 7 receptors on monocytes and their contribution to the Ca 2+ peak is rather low, one would assume that monocytes would become permeable to ethidium when stimulated with high concentrations of ATP. However as described earlier, monocytes, in contrast to monocyte-derived macrophages, do not form pores in [46,47]. Considering the crucial role of ionic compositions of the extracellular medium in P2X 7 receptor activation by ATP [48][49][50][51], Gudipaty et al [37] showed that replacement of extracellular Na + and Cl − with K + and nonhalide anions strongly facilitated ATP-dependent pore formation in monocytes.…”

Neuronal death induced by endogenous extracellular ATP in retinal cholinergic neuron density control

“…However, a number of non neuronal cell populations, ranging from human macrophages (Falzoni et al, 1995) and keratynocytes (Girolomoni et al, 1993) to colonies of fungi (Koshlukova et al, 1999) undergo cell death induced by ATP through the P2X 7 receptors, suggesting that the cholinergic neurons are a new example of an ancient mechanism of cell death control.…”

“…A conserved mechanism of cell death activation has been described in non-neuronal cells (Falzoni et al, 1995;Girolomoni et al, 1993;Koshlukova et al, 1999), whereby extracellular ATP (e-ATP) triggers cell death by binding the P2X 7 receptors. Upon sustained or repeated activation, the P2X 7 receptors induce large non-selective membrane pores, which eventually lead to cell death (Di Virgilio et al, 1998;North, 2002).…”