Human neutrophils do not express purinergic P2X7 receptors

Abstract

It has been reported that in human neutrophils, external ATP activates plasma membrane purinergic P2X 7 receptors (P2X 7 R) to elicit Ca 2+ entry, production of reactive oxygen species (ROS), processing and release of pro-inflammatory cytokines, shedding of adhesion molecules and uptake of large molecules. However, the expression of P2X 7 R at the plasma membrane of neutrophils has also been questioned since these putative responses are not always reproduced. In this work, we used electrophysiological recordings to measure functional responses associated with the activation of membrane receptors, spectrofluorometric measurements of ROS production and ethidium bromide uptake to asses coupling of P2X 7 R activation to downstream effectors, immunelabelling of P2X 7 R using a fluorescein isothiocyanateconjugated antibody to detect the receptors at the plasma membrane, RT-PCR to determine mRNA expression of P2X 7 R and Western blot to determine protein expression in neutrophils and HL-60 cells. None of these assays reported the presence of P2X 7 R in the plasma membrane of neutrophils and non-differentiated or differentiated HL-60 cells-a model cell for human neutrophils. We concluded that P2X 7 R are not present at plasma membrane of human neutrophils and that the putative physiological responses triggered by external ATP should be reconsidered.

Purinergic signalling and immune cells

“…Neutrophil accumulation in the skin during croton oil-induced irritant contact dermatitis was reduced in P2X 7 -deficient mice [ 97 ]. However, it was claimed more recently that human neutrophils do not express P2X 7 receptors [ 98 ]. In an RT-PCR study of human neutrophils, mRNA for P2X 1 was strongly expressed, while mRNA for P2X 4 and P2X 5 was weakly expressed and P2X 7 mRNA was not detected [ 99 ].…”

Significance of P2X7 Receptor Variants to Human Health and Disease

“…The relative amounts of this receptor, however, in these latter cell types in relation to other human hematopoietic cell types remain unknown. Despite the presence of P2X7 on eosinophils, human neutrophils appear to be devoid of P2X7 [26,27]. P2X7 is also present on other human cell types including osteoblasts [28], fibroblasts [29], endothelial cells [30], and epithelial cells residing in various tissues including the skin, cervix, pancreas and colon (see [31,32] and references therein).…”

Extracellular ATP protects against sepsis through macrophage P2X7 purinergic receptors by enhancing intracellular bacterial killing

“…The expression of P2X7Rs on neutrophils is controversial. Some studies have shown that it is present intracellularly but not on the cell surface (12, 13), whereas one study showed that it has antiapoptotic effects in neutrophils (14). Activation of macrophages is associated with increased expression of P2X7Rs (15).…”