The P2X7 receptor mediates the uptake of organic cations in canine erythrocytes and mononuclear leukocytes: comparison to equivalent human cell types

Abstract

We previously demonstrated that canine erythrocytes express the P2X 7 receptor, and that the function and expression of this receptor is greatly increased compared with human erythrocytes. Using 86 Rb + (K + ) and organic cation flux measurements, we further compared P2X 7 in erythrocytes and mononuclear leukocytes from these species. Concentration response curves of BzATP-and ATP-induced 86 Rb + efflux demonstrated that canine P2X 7 was less sensitive to inhibition by extracellular Na + ions compared to human P2X 7 . In contrast, canine and human P2X 7 showed a similar sensitivity to the P2X 7 antagonists KN-62 and Mg 2+ . KN-62 and Mg 2+ also inhibited ATPinduced choline + uptake into canine and human erythrocytes. BzATP and ATP but not ADP or NAD induced ethidium + uptake into canine monocytes, T-and B-cells. ATP-induced ethidium + uptake was twofold greater in canine T-cells compared to canine B-cells and monocytes. KN-62 inhibited the ATP-induced ethidium + uptake in each cell type. P2X 7 -mediated uptake of organic cations was 40-and fivefold greater in canine erythrocytes and lymphocytes (T-and B-cells), respectively, compared to equivalent human cell types. In contrast, P2X 7 function was threefold lower in canine monocytes compared to human monocytes.Thus, P2X 7 activation can induce the uptake of organic cations into canine erythrocytes and mononuclear leukocytes, but the relative levels of P2X 7 function differ to that of equivalent human cell types.

The P2X7 Receptor Channel: Recent Developments and the Use of P2X7 Antagonists in Models of Disease

“…In contrast, activation of P2X7 in canine erythrocytes identified that ATP, relative to BzATP, was a partial agonist of native canine P2X7 (Stevenson et al, 2009). This finding is similar to that of native human P2X7, in which ATP was also reported to be a partial agonist relative to BzATP .…”

“…However, study of native P2X7 in canine erythrocytes demonstrates that 2MeSATP and ATPgS, but not ADP or UTP, may also be (partial) agonists of canine P2X7 . NAD also failed to induce ethidium + uptake into canine lymphocytes and monocytes (Stevenson et al, 2009), suggesting that NAD is not an agonist of canine P2X7.…”

“…Functional P2X7 has been reported in erythrocytes, T cells, B cells, and monocytes Stevenson et al, 2009;Jalilian et al, 2012a), as well as in kidney epithelial cells (Jalilian et al, 2012b). Of note, P2X7 activation induces the release of interleukin (IL)-1b from canine monocytes (Jalilian et al, 2012a) and whole blood Spildrejorde et al, 2014).…”

P2X7 receptor activation induces reactive oxygen species formation in erythroid cells

“…P2X7 is present on mature red blood cells (erythrocytes) [13,14] where it participates in cation fluxes [13,[15][16][17], cell death [16,[18][19][20] and the release of lipid-derived mediators [21]. P2X7 is also present on erythroid precursors including murine erythroleukaemia (MEL) cells [22,23].…”

P2X7 receptor activation induces CD62L shedding from human CD4+ and CD8+ T cells

“…One of the most common P2X7 SNPs is rs3751143, which codes for a glutamic acid to alanine substitution at amino acid 496 (Glu496Ala) and leads to a near-complete loss of receptor function in homozygous dosage [9] . P2X7 is present on mononuclear leukocytes including T cells from various species [10][11][12] . P2X7 activation on T cells mediates several cell signaling events including the shedding of cell-surface CD62L [13,14] .…”