P2 receptor subtypes in human hematopoietic cells of peripheral and cord blood

P2 receptors have been found in several blood cells and their progenitors. However, most studies lack data about receptor subtypes and of receptors expression time in the process of cell differentiation. The aim of our study was to identify the subtypes of P2Y and P2X receptors on human CD34+ cells, c-kit+ cells, monocytes, lymphocytes of cord and peripheral blood. Expression of P2Y1, P2Y4, and P2Y6 receptors was the uniform in the cord and peripheral blood of all studied cells with the prevalence of monocytes expressing P2Y-receptors (up to 71%). At the same time, a significant difference was found between cells of cord and peripheral blood expressing subtypes of P2X2, P2X3, P2X4, P2X5, P2X6, P2X7 receptors. Cord blood lymphocytes contained a higher percentage of P2X receptors than peripheral blood lymphocytes. Similarly, the percentage of the peripheral blood monocytes, containing P2X receptors was significantly higher than the monocytes of cord blood

ATP-induced Ca2+ response mediated by P2U and P2Y purinoceptors in human macrophages: signalling from dying cells to macrophages

The activation of macrophages by various stimuli leading to chemotactic migration and phagocytosis is known to be mediated by an increase in intracellular Ca2+ concentration ([Ca2+]i). We measured changes in [Ca2+]i using a Ca2+ imaging method in individual human macrophages differentiated from freshly prepared peripheral blood monocytes during culture of 1–2 days. A transient rise in [Ca2+]i (duration 3–4 min) occurred in 10–15 macrophages in the vicinity of a single tumour cell that was attacked and permeabilized by a natural killer cell in a dish. Similar Ca2+ transients were produced in 90% of macrophages by application of supernatant obtained after inducing the lysis of tumour cells with hypo-osmotic treatment. Ca2+ transients were also evoked by ATP in a dose-dependent manner between 0·1 and 100 μm. The ATP-induced [Ca2+]i rise was reduced to less than one-quarter in Ca2+-free medium, indicating that it is mainly due to Ca2+ entry and partly due to intracellular Ca2+ release. UTP (P2U purinoceptor agonist) was more potent than ATP or 2-chloro-ATP (P2Y agonist). Oxidized ATP (P2Z antagonist) had no inhibitory effect. Both cell lysate- and ATP-induced Ca2+ responses were inhibited by Reactive Blue 2 (P2Y and P2U antagonist) to the same extent, but were not affected by PPADS (P2X antagonist). Sequential stimuli by cell lysate and ATP underwent long-lasting desensitization in the Ca2+ response to the second stimulation. The present study supports the view that macrophages respond to signal messengers discharged from damaged or dying cells to be ingested, and ATP is at least one of the messengers and causes a [Ca2+]i rise via P2U and P2Y receptors